text:
Track behaviour
A railway bridge may support a load of several hundred tons in mid air. The load is transmitted through various parts of the structure to the foundations, where it dissipates into the ground. You might not think of the track itself as a 'structure' but in fact it does a similar job on a smaller scale. Here, the structure consists of three main elements: rails, sleepers and road bed. They work together to support the wheels of a moving train, and spread out the load so the ground underneath doesn't give way. Their behaviour determines the maximum weight per axle of the train and the speed at which it can travel. The engineer's task is to work out the cheapest possible configuration that meets two requirements. First, the rails mustn't break, and second, any deflection under the wheels of a train should fall within an acceptable range: too much and a train may jump the rails, too little and the track will provide a rough ride and wear out prematurely.
Effect of static loading
A wheel can exert a force in any of several different directions on the rail, but here we are interested mainly in the vertical load. On a freight line, a wheel load can be as much as 20 tonnes, [21], but on the passenger network in Europe, it is rather less: the maximum permitted values are set out in table 1. For mainline traffic the greatest load per axle (two wheels together) is 22.5 tonnes, roughly twice the equivalent for a heavy lorry. To estimate the impact of wheel loads on the track, we need first to consider what happens when the train is standing still.
Maximum wheelset loads on European railways (data compiled from [3])
Axle load
Wheel load
(tonnes) (tonnes)
Mainline 17.0 8.5
Mainline Other 22.5 11.25
Metro 10.0 5.0
Tram 6.0 3.0
The Winkler beam model
The track is a complex structure. Several methods have been devised to predict the stresses and strains within each of its components (see for example [26]), of which the most sophisticated involve computer simulation. But much can be learned by visualising the rail as a simple beam that rests on a springy surface, rather like a broomstick resting on a mattress. If you press down in the middle of the broomstick it will bend, sagging in the centre and compressing the mattress (figure 1). As the mattress deflects it provides increased resistance, and the reaction that supports the broomstick varies along the length of the broomstick in proportion to the deflection at each point. Expressed in mathematical terms, this idealised structure is known as a Winkler beam, after the German pioneer of structural theory Emil Winkler (1835 - 1888), who first conceived the 'elastic foundation' as a tool for analysing and explaining the interaction between structures and the ground on which they stand. When applied in a railway context, the broomstick represents the rail while the mattress represents the sleepers and roadbed as if they formed a continuous body that flexes slightly under load. Although in reality the sleepers are discrete objects, the model yields quite good predictions of the deflection at different points along the rail, and it uses only three numerical parameters: Young's modulus \(E\) for the steel rail, the moment of inertia \(I\) for the rail cross-section [39], and a stiffness parameter \(k\) that represents the force per unit length required to produce unit deflection of the roadbed.
A broomstick pressing on a mattress
The details can be found in a classic work on structural engineering [40] and specifically in a railway context in [7] and [27]. Each uses a different notation and we shall largely follow [7]. Without trying to prove them, we will set out here the most important formulae that describe the behaviour of the track in response to a single wheel load, and use them to map out the deflections and stresses in the rail nearby. For a wheel considered as a point load \(P\), the deflection \(w(x)\) of the track at a point located at a distance \(x\) downstream is the product of a constant term \(P/2kL\) and a dimensionless 'shape function' \(\eta (x)\) thus:
\[\begin{equation} w(x) \quad = \quad \frac{P}{2kL} \eta (x) \end{equation}\]
where \(L\) is the characteristic length given by
\[\begin{equation} L \quad = \quad \left( \frac{4EI}{k} \right)^\frac{1}{4} \end{equation}\]
and the shape function by
\[\begin{equation} \eta (x) \quad = \quad e^{- x/L} \left[ \cos \left( \frac{x}{L} \right) \; + \; \sin \left( \frac{x}{L} \right) \right] \end{equation}\]
The result is a sine curve of wavelength \(2 \pi L\) whose amplitude decays with distance away from the origin. The greatest deflection occurs immediately under the wheel at \(x = 0\). Here, the shape function takes on the value 1, and the deflection is given by
\[\begin{equation} w_{\max } \quad = \quad w(0) \quad = \quad \frac{P}{2kL} \end{equation}\]
A typical profile is shown in figure 2 for a wheel load of 125 kN on a track with a good quality roadbed and a stiff rail (\(k = 0.09\) kN mm\(^{-2}\) and \(L = 700\) mm). If you just look at the right hand part of the curve, you may find the shape familiar. It is mathematically identical to the deflection profile traced out by a car bouncing freely on its suspension after a sudden impact as shown in the upper diagram of Figure 5 in Section G1115, except of course that the deflections of the car body vary over time, whereas the deflections in the rail vary over distance. Both are damped, and the motion decays rapidly from one cycle to the next. Figure 2 shows that the maximum deflection of the rail is around 1 mm, and also that the deflection is negative a little distance away on either side, where the rail actually rises above its normal level. The model as presented here does not take into account the weight of the track, which presents an additional load to be superimposed on the system. While the weight of modern concrete sleepers is usually enough to prevent them from lifting clear of the ground [9], nevertheless, the rail surface does in fact rise. It seems that the wheel drags along with it a depression or valley in the track together with a small hill fore and aft.
Track deflection under a wheel load (exaggerated vertical scale)
So much for the deflections, but what about the stresses? First, we must determine the bending moment in the rail, which is related directly to the profile of deflections. For readers not familiar with structural analysis, we obtain the bending moment at any point in a beam by cutting the beam at that point in our imagination. Let's assume the beam is horizontal. Then ignoring the left-hand piece we work out the couple exerted at the severed cross-section by the various loads and reactions acting on the right-hand piece. As a check, we can then take the left-hand piece and work out the couple acting at the severed cross-section in the same way. Since the beam is in equilibrium, the two couples should be equal, and opposite in sign. The convention among structural engineers is to register a sagging moment as negative and a hogging moment (which produces an upward bulge) as positive. For the Winkler beam model, it can be shown that the value of the bending moment is given by the expression
\[\begin{equation} M(x) \quad = \quad - \frac{PL}{4} \mu (x) \end{equation}\]
where the shape function \(\mu (x)\) is given by
\[\begin{equation} \mu (x) \quad = \quad e^{- x / L} \left[ \cos \left( \frac{x}{L} \right) \; - \; \sin \left( \frac{x}{L} \right) \right] \end{equation}\]
Bending moment profile for the same track
figure 3 shows the shape of the curve given the parameters specified earlier. The bending moment is negative in the neighbourhood of the wheel, indicating a sagging mode as one might expect. On either side it rises to a positive value that can be shown to peak at a distance \(d_{p}\) given by \(\pi L/2\) which in this case comes to a little over a metre [8]. This is an important point and we'll return to it later. The largest numerical value of the bending moment is negative in sign and it occurs directly under the wheel at \(x = 0\), where the shape function \(\mu(0) = 1\). Its value is given by
\[\begin{equation} M_{\min } \quad = \quad M(0) \quad = \quad - \frac{PL}{4} \end{equation}\]
Stresses and strains
The first requirement of a railway track is that it shouldn't break. Nor should it distort in such a way as to derail the train. Let's look at the possibility of a broken rail first. Using a model such as the Winkler beam, or a computer simulation package, one can estimate the stresses in the rail that arise from bending under a wheel load in the vertical plane. As we saw earlier in Section R1605, the stress induced by the bending moment varies over the rail cross-section. The maximum compressive stress occurs at the upper surface, and the maximum tensile value at the lower surface (figure 4). Mathematically, we picture this as a negative stress at the top of the rail head that changes linearly to a positive value at the foot, passing through zero at the neutral axis near the centre. For the above example with UIC 54 rail, the peak stresses turn out to be nearly -90 MPa at the top and nearly 80 MPa at the bottom.
Bending stresses on the rail cross-section
Superposition of other stresses on the rail cross-section
To the bending stresses must be added the thermal stresses in the rail: tensile in cold weather when the rail tends to shrink, and compressive in hot weather when it expands. Both act more-or-less uniformly over the whole cross-section. And on a curve, the train wheels push the outside rail sideways so that it bends in the horizontal plane, creating extra tension on the outside edge and compression on the inside. If we superimpose these on the bending stresses as shown schematically in figure 5, we can then judge whether the total at any point in the cross-section exceeds the allowable stress for the rail material used. Sample calculations are set out in [10]. So far, we have ignored the additional loads associated with the impact of the wheel on irregularities in the rail alignment, which we'll look into later. For the moment, it's worth making two general points.
Failure of a steel bar under a tensile load
The first is about the failure of the rail. How does a rail break, and what are the possible causes? The wheel load produces a large vertical stress within the contact patch. This is complemented by the longitudinal stresses caused by bending and thermal loads. But none of these stresses will cause a metal to yield or crack, at least not directly. Metals don't fail in compression or tension as such. But a tensile or compressive force will set up a shear stress within the material, and it is in the plane of maximum shear stress, often around \(45^\circ\) to the applied load, that the failure occurs, because the atoms slide over one another more easily than they pull apart (figure 6). But there's another factor at work. If there were no longitudinal stresses, the loading pattern would be symmetrical with a vertical contact stress only, and any plane at \(45^\circ\) to the vertical contact stress would serve as a plane of failure. But in the case of a railway track, the longitudinal stresses destroy the symmetry, effectively reducing the shear in the \(xz\) plane and leaving the shear in the lateral \(yz\) plane dominant [6]. Hence we would expect the material to yield and crack laterally across the rail from side to side rather than in a longitudinal direction, which seems to agree with the predominant fatigue cracking modes referred to in Section R2020. This doesn't mean that the bending stresses are benign. With the passage of each wheel, the material goes through a loading cycle, and it is the rise and fall that puts energy into the rail, encouraging cracks to propagate and potentially leading to failure over time.
The effect of adding a second axle
The second point is related to the first because it, too, is concerned with bending moment reversals. But here we are dealing with the bending moment profile in space rather than time. So we must step back and view what happens along an appreciable length of track, and in particular, the way in which the bending moment switches from negative to positive, peaking at a distance \(d_{p}\) on either size of the wheel load (figure 3). The point is that no railway vehicle can balance on a single axle - there must be at least two. If we can choose the spacing between axles, where do we put the second one? A sensible place might be at the point P of the profile shown in the upper part of figure 7. If we add a second wheel load here of equal magnitude to the first, the profile of bending moment along the rail changes. To find it, we simply add the profile for the original wheel and the profile for the second wheel, which is shifted along the rail by a distance \(d_{p}\). The trough in the first wheel load is partly cancelled by one of the peaks in the first, and vice versa, so that overall, the maximum stresses are reduced. You can see in the lower part of figure 7 that with the additional wheel load the size of the bending moment 'trough' under each wheel is significantly reduced. It's worth pausing to take in the significance of what is going on here. It may seem paradoxical at first sight, but we can double the load at the same time as relieving the stress in the rail - a case of adding more weight to ease the burden as it were. Or to put it another way, we can take a twin-axle freight wagon and convert it into a four-axle bogie vehicle and thereby reduce the rail stresses by more than a half. If the Winkler beam theory is accurate, then the optimum bogie wheelbase will be \(\pi L/2\). With modern track, whose characteristic length L is typically less than 1 metre, the optimum works out at 1.5 m. In practice, a modern bogie needs a longer wheelbase of around 2.5 m for safe running at high speeds, so the benefit is not as large as it might be.
Now for the deflections. In the past, rails used to move up and down quite a lot, and if you stood by a level crossing gate and watched what happened, you would have noticed them sink then rise again under the weight of each wheel. During the steam era, the deflection at a rail joint could be more than 10 mm [41] but with modern continuously welded rail it is barely noticeable: typically around 2 mm, and less for concrete slab track [30]. Thinking about the deflections leads one to question how 'stiff' the track should be. A degree of flexibility helps to reduce the dynamic impacts, but we don't want the rail to deflect more than a millimetre or two on a high-speed track, especially on a curve or a switch where there is a real possibility of derailing the train. If we want to increase the stiffness, there are two ways of doing it: (a) make the roadbed deeper, or (b) use a heavier rail. Which works best? Here again, the Winkler beam model can help. It turns out that a one percent increase in the roadbed stiffness parameter \(k\) reduces the deflection by about 0.75%. An alternative is to stiffen the rail itself by choosing one with a larger cross-section, but it seems that a 1% increase in area produces a more modest fall in deflection of 0.5%. On the other hand, a heavier rail helps to relieve the bending stresses. Further details about the effects of varying each of the parameters referred to earlier on rail stress and deflection are set out in the Appendix at the end of this Section.
Dynamic behaviour
So what happens when the train moves? The depression or valley in the rail is carried along with the wheel, and provided the track is straight and the train doesn't go too fast, the bending moment profile and the profile of stresses in the track are carried along too, almost unchanged. But on a curve, the inertia of the vehicle comes into play. The vehicle undergoes centripetal forces acting on the outside wheels, which constrain its motion, pushing it sideways towards the centre of curvature. From the point of view of the rail, the outside wheels react laterally outwards against the railhead which adds a horizontal component to the wheel load (figure 8). There is also a transfer of vertical load from the inner wheels to the outer wheels. In principle, for a curve of constant radius one can work out these extra loads and treat them as static forces that don't change while the vehicle is travelling round the curve. Less easy to deal with are the irregularities in the track alignment - both on curved and on straight track - that create shock loads that can't be predicted in terms of track geometry.
Additional components of wheel load
Shock loads
The rail surface is not as smooth as one might think. On older tracks, there are gaps at the fishplates where the rail sections are bolted together, and each gap delivers a jolt to the suspension of a moving train. Even a continuously welded rail will produce shock loads at the joints. When heated during the welding process, the surface will deform slightly on either side of each weld, so the rails meet at a shallow angle rather than a straight line. There may also be a slight discontinuity if the butt ends aren't perfectly aligned. So the joints can be a problem, but what about the rail itself? The rail is never perfectly smooth because over time, particles flake away from the surface, and material is gouged out by loose particles and grit from the ballast that gets caught between the wheel and the rail. Since there are no rubber tyres, each bump injects a disturbance into the vehicle suspension: that's why you can feel the wheels rumbling along the rails when you ride in a tram. People who live close to a railway feel it too because the process works both ways. The wheels generate vibrations that propagate along the rails and in turn radiate noise into the surrounding environment. Vibrations are propagated through the ground to buildings nearby and along the track ahead of the train (which leads to the interesting question, which we'll come to later, of what happens if a train catches up with its own waves).
Let's stay with the wheel tread for the moment. When the wheel tread encounters small irregularities in the rail surface, the reaction between the wheel and the rail varies over a considerable range on either side of the static load. The difference between the static load and the dynamic load is rather like the difference between the weight of a milk bottle resting on a table, and the force it generates momentarily when you knock it over. How should one extrapolate from the one to the other? In practice, engineers do what they often do in such circumstances: they assume the two are in direct proportion and express the dynamic element through an empirical factor, a multiplier which in this case is not a fixed ratio for all circumstances - its value depends on vehicle speed. For conventional track the maximum dynamic load is taken as about 50% greater than the static wheel load, so the multiplication factor is 1.5. Experience with the TGV system operating at 300 km/h suggests a 'dynamic impact factor' \(\eta\) of about 2.0, meaning that the maximum stresses are about twice the static ones for a vehicle moving on high-quality track at that speed [28].
Such factors can be incorporated into Winkler-type formulae and used to predict dynamic forces on the sleepers and track. But a more 'scientific' way to get to grips with shock impacts is to represent the various elements of the track as springs, masses and dampers in the same way as one might represent a vehicle suspension. Because there are so many interacting elements, it isn't possible to work out explicit formulae for the track response, and the problem must be solved numerically using computer software.
Track deterioration
So what are the consequences of a rough rail surface from the railway operator's point of view? They are worse perhaps than you might expect. Whenever the rail jolts the wheel, the wheel reciprocates by jolting the rail, which increases the rate of wear and tear on the track as a whole. The wear and tear results in more irregularities that in turn exacerbate the shock loads - it is a circular process, or if you like, a spiral of deterioration. A smooth track will stay smooth for a considerable time while a rough track will get worse at an accelerating rate [12]. That's why modern high-speed track is aligned very precisely and irregularities kept within narrow limits through intensive maintenance. High-precision track requires (a) a smooth and uniform ballast layer profile and (b) straight rails with a smooth running surface, all at wavelengths ranging from a few centimeters to many metres. At the longest wavelengths, an error of 1 or 2 mm can have significant effects, while at the shortest wavelengths, microns matter [13].
While irregularities in the vertical profile are the ones that most concern railway engineers, irregularities in the horizontal profile matter too. The Tokaido Shinkansen railway provides a good example. Before the line was opened, a high-speed test was carried out with a 4-car electric train at 240 km/h. During the test, one car developed a zig-zag 'hunting' motion, and in subsequent runs, other cars began to hunt at the same point along the track. It turned out that the track had deformed laterally, 'snaking' from side to side, and the engineers concluded that one particular bogie in poor condition had caused the problem by exerting a lateral force of about 10 tonnes at intervals along the track. The displaced track then triggered hunting in the other bogies. After the service was launched, the railway operator decided to measure the vibrational acceleration daily, and where necessary, to adjust the track overnight [42].
Frequent re-alignment is of course expensive, and in the case of a conventional ballasted track, it's not very efficient, because as we saw in Section R1602, the ballast is relatively unstable for some time after tamping. It may even have a 'memory' of its former state [11] and will settle towards the irregular profile that the adjustment was intended to correct. It has been suggested that for this reason, 'rough' or poor sections of track deteriorate more quickly after treatment than smooth sections, not because of any underlying weakness in the subgrade but because the track inherits irregularities that have been worsened by dynamic wheel loads early in the life of the track.
The rail vibrates like a xylophone bar
Passengers waiting on a station platform know when a train is coming because vibrations propagate along the rails for some distance ahead. The track 'sings'. The train sings too, because as we saw in Section R1610 each wheel shares many of the characteristics of a church bell.
The resonating track
If the wheel is a church bell, the rail is a tuning fork, or perhaps more aptly, a xylophone: like the bars of a xylophone, successive segments of rail can vibrate between their supports (figure 9). When stimulated by a train wheel rolling over small imperfections in the rail surface, each resonates with a natural frequency \(f_N\) whose value depends on the distance \(S\) between its supporting sleepers together with the mass and stiffness of the rail thus [5]:
\[\begin{equation} f_N \quad = \quad \frac{\pi}{2} \sqrt {\frac{EI}{m S^{4}}} \end{equation}\]
where \(m\) is the mass per unit length of rail, \(E\) is Young's modulus for the rail material, and \(I\) is the moment of inertia of the rail cross-section. Hence for a UIC60 rail with \(E = 210\) GPa, \(I = 3.055 \times 10^{-5}\) m4, \(m = 60.34\) kg/m and \(S = 0.65\)m, this comes to 1212 Hz, which is close to the note Eb6 on a piano, a little over two octaves above middle C. In practice this particular mode of vibration plays a minor role among many others that together produce a mixture of frequencies in concert with other track components such as the sleepers [34] [38].
Propagation of vibrations along the rail
Of course each bar on a xylophone is physically separate so that when you strike it, only the one bar resonates. But a rail is continuous, and successive segments are connected to one another, so that when a train wheel impacts any given segment, its neighbours vibrate too (figure 10). The result is that vibrations propagate along the rail and noise is radiated over a wide area, damped down to some degree by the rail fastenings, sleepers and ballast. But the damping is less effective when the rails are bedded on a concrete slab, where the fastenings are 'softer' and the rail can vibrate over a longer length [35]. And the frequency depends on speed, so a slow- moving vehicle causes the track to oscillate at a relatively low frequency. In the case of a freight train, this is typically below 10 Hz, which is perceived as vibration rather than noise. It can be felt in buildings over 100 m from the track [36].
Broadly, there are three ways to reduce track noise radiated to the surrounding environment. The first is to ensure that the wheel and rail surfaces are smooth. The second is to build in some form of mechanical damping such as resilient rail pads. The third is to make a barrier of some kind between the track and its surroundings. Let's look at each of these in turn.
To begin with, a rough rail surface produces more noise, and as we saw earlier in Section R1605, a corrugated surface is particularly noisy. It helps if the rail surface is as smooth as possible when it is first installed - experiments carried out by British Rail at Rugby showed that corrugations developed less quickly on rails whose surface was first treated to remove the tiny irregularities associated with the manufacturing process [15], that along with uneven rail welds tend to stimulate the wheel and rail into resonance.
Measures in the second category involve tinkering with the structure of the system itself. Some are based on the principle of a resilient material in the form of pads or mats that at some level isolate the rail from the ground. Resilient pads between the rail and sleeper reduce the stiffness of the rail structure as presented to the wheel and thereby inhibit the growth of corrugations [14] [18], but once corrugations have begun, the only remedy is to grind the rails. This was pioneered in Germany as a routine maintenance procedure [16], although it's not as good as a new rail because the impact of a wheel on a corrugation peak produces local yielding together with residual stresses that are locked into the material below the surface and persist after the corrugations themselves are removed. These can trigger re-growth after treatment [17]. Bearing pads also reduce the level of energy injected into the sleepers. In this way, ground vibration caused by the UK Channel Tunnel Rail Link was reduced by an estimated 3 - 5 dB [2]. However, if the pads are too soft, the wave travels further along the rail, and therefore a compromise may be necessary, especially in the case of a concrete slab track, where softer rail fasteners are needed to reduce the impact forces between wheel and rail. The result is to increase the noise level by 2 - 4 dBA [35]. An ingenious way round this - at least in principle - is to space the rail supports at irregular intervals, which interrupts the natural mode of vibration of the rail. This approach recalls the irregular spacing of the cooling fan blades in a passenger car, which reduces the noise generated within the engine compartment. Another form of damping is provided by the tuned absorber, in this case blocks of steel or continuous strips of steel glued to the side of the rail. Experiments have shown that they can reduce noise by around 6 dBA, and a brief description appears in [34]. The problem is that unlike other noise emitters such as a motor car engine, a steel rail propagates energy away from the source. This energy can't be intercepted by a single damping device at just one location; it has to be applied over the whole length of the track [32].
The third option is to prevent the noise from escaping into the surroundings. In fact the most effective measure is to put the railway in a cutting [29], and failing that, to install a barrier by the side of track [19]. Although a conventional barrier can reduce noise emissions by about 10 dBA [31], its performance depends on the geometry. Most barriers work by reflecting noise back towards the source, and the sides of a train can reflect the noise once more, this time over the barrier crest (figure 11). Barriers that actually absorb noise have been installed along viaducts on the Channel Tunnel Rail Link in the UK. They are placed quite close to the track so the height and weight can be reduced in comparison with conventional designs [1].
Noise reflected between a train and a noise barrier
Ground waves
It is easy to imagine ground-borne vibrations as a kind of noise: waves travelling through the ground rather than through the air. When generated by a railway they can make buildings shake or tremble, and although the buildings are rarely damaged, the experience is not a pleasant one for the occupants. It is usual therefore to shield nearby buildings with trenches and walls [33]. But like air waves, ground-borne waves travel at a finite speed. This affects the motion of the train itself, and it is the effect on the train that we shall take up here. We've already seen that each axle produces in the track a shallow trough or depression. When the wheel is stationary, the trough is stationary too, centred underneath the point of contact. When the train starts to move, the trough responds by moving with it. But the response is not instantaneous. Track deflection is conveyed as a wave radiating away from the point of contact, and carrying energy like a sea wave excited during a storm. The disturbance needs time to propagate along the track and the underlying soil, and because there is a delay, the trough lags slightly behind the wheel. The result is that the wheel always seems to be climbing uphill, so that a horizontal component of its reaction with the rail adds to the resistance that the engine must overcome to keep the train rolling at constant speed (figure 12). Under normal conditions it doesn't add very much, but as we shall later, this is not always the case.
The depression lags behind the wheel
Ground-borne waves move in a distinctive way. They are made up of two components (figure 13): dilatational waves and shear waves. The dilatational wave is a pressure wave or 'P-wave': it alternately squeezes and stretches the ground in the direction of motion, in much the same way as the air is squeezed and relaxed in a sound wave. The second component consists of shear waves or 'SV waves' (the V stands for vertical), which shake the ground up and down at right angles to the direction of motion. The P-wave travels several times faster than the SV wave. There are also SH waves in which the ground moves horizontally from side-to-side at right-angles to the direction of motion, but these are much less intensive. Sooner or later, hysteresis in either the track or the ground will damp down the waves: stones and other material rub against one another, and energy is lost irretrievably in the form of heat (Section G2116). This heat loss drains energy from the vehicle, which is another way of explaining the element of rolling resistance we referred to earlier.
Different types of ground wave
In reality, the behaviour of ground waves is quite complicated, not least because they interact with waves in the track itself, which acts as a springy structure that flexes up and down in its own characteristic way. The 'critical track velocity' depends on both, and a brief resume can be found in [37]. What matters here is that when a train approaches the critical track velocity the vibration can reach dangerously high levels.
Superseismic trains
Waves travel through the ground at a speed that varies according to the nature of the rock or soil through which they are travelling. In harder materials it is often around 240 km/h, but it falls to 150 km/h (42 m/s) in soft, peaty soil [20]. When a train's speed approaches this critical velocity, the train becomes superseismic [25]. It catches up with its own waves, which pile up underneath the leading bogie and grow rapidly in size rather like the bow wave of a ship. And as with a ship, wave-like oscillations trail behind [23]. Simulation studies indicate that should a train actually exceed the critical speed like an aircraft as it passes through the sound barrier, the wave amplitude should decrease, but no-one has so far dared to try it. Waves of this kind can theoretically derail the train, and they represent greatly increased resistance, drawing energy from the power unit. To make matters worse, an embankment can act as a wave guide, reducing the effect on the surrounding environment but increasing the amplitude of deflections in the track.
The first documented case of near-superseismic rail deflections arose at Ledsgård on the newly-constructed Swedish west coast line built on soft soil, which was opened in 1997. It was designed to operate with the X2000 tilting train. At low speeds, the train rode with each axle close to the bottom of its trough, with track deflections of the order of 5 mm that were carried along with the wheels [22]. But at a speed of 185 km/h, each axle climbed to approximately half way between the trough and the crest, and track vibrations of around 20 - 25 mm were recorded. It seems that the train was approaching critical track velocity, which has since been estimated at around 235 km/h [24]. The operators were forced to impose a temporary 70 km/h speed restriction. In the light of experience gained, more recent projects have been designed with a stiffened track structure. For example, a 7 km section of the Channel Tunnel Rail Link crossing the West London marshes is supported on concrete piles designed to limit track deflections to 5 mm at a train speed of 270 km/h [4].
Over the last hundred years one can see a fundamental change in the way railway tracks are built. Until about 1960, the first consideration was resilience, so tracks were laid on ballast that provided a springy foundation. This minimised the damage arising from the shock loads that occurred whenever a train wheel jolted over any roughness in the rail surface or over a gap in the rail. As long as the rails were kept the right distance apart, and didn't break, the train would not be in danger. But modern trains run at higher speeds and to avoid derailment, we no longer want the rail to move up or down by more than a millimetre or so. Logic dictates a more stable foundation - the concrete slab. To make this work, the engineer must align the rail accurately and ensure that the surface is kept smooth, so that the track injects fewer impacts into the wheel, and vice versa. The high-speed railway has become a high-precision railway with millimetre tolerances that are an order of magnitude smaller than the nineteenth century railway engineer would have thought possible.
Appendix: Strengthening the track
Two priorities are high on the railway engineer's list: (a) reducing the stresses in the rails so they don't break, and (b) reducing deflections in the track so the train doesn't come off the rails. Both require the track in some sense to be made more robust, and there are two possible ways of doing this. The first is to increase the track bed stiffness, embodied in the parameter \(k\). The second is to increase the rail stiffness, embodied in the two parameters \(E\) and \(I\). Using the Winkler beam model, in this Appendix we aim to work out the sensitivity of rail stress and track deflection to each of these parameters in turn, as a basis for judging which of the alternatives is likely to have the most effect.
A sensitivity measure
A good way to judge the sensitivity of a target variable to a change in any one of the variables on which its value depends is to work out the ratio \(\rho \;\)of a proportional change in the one to a proportional change in the other, assuming that both changes are small. Suppose that the target or 'output' variable is \(Y\) and the input variable, whose effect we are trying to judge, is \(X\). Imagine that \(X\) changes by a small amount \(\delta X\); we can express this as a proportional change \(\delta X / X\). Suppose this leads to small change \(\delta Y\) in the target variable \(Y\). The proportional change in the target is then \(\delta Y / Y\). The ratio \(\rho\) of the two is given by
\[\begin{equation} \rho \quad = \quad \frac{X}{\delta X} . \frac{\delta Y}{Y} \end{equation}\]
which in the limit as \(\delta X\) and \(\delta Y\) both tend to zero becomes
\[\begin{equation} \rho \quad = \quad \frac{X}{Y} . \frac{dY}{dX} \end{equation}\]
Now, if \(X\) and \(Y\) are connected by a power relationship, this expression for \(\rho\) takes on a simple form. If
\[\begin{equation} Y \quad = \quad C X^p \end{equation}\]
where the exponent \(p\) is a constant, then by differentiating both sides with respect to \(X\) we get
\[\begin{equation} \frac{dY}{dX} \quad = \quad p C X^{p - 1} \end{equation}\]
We can now substitute \(C X^{p}\) for \(Y\) and \(p C X^{p-1}\) for \(dY/dX\) in equation 10 to get
\[\begin{equation} \rho \quad = \quad \frac{X}{CX^p} . p C X^{p-1} \end{equation}\]
and most of the terms on the terms on the right-hand side cancel out to leave
\[\begin{equation} \rho \quad = \quad p \end{equation}\]
Hence, a small change in \(X\) produces a change in \(Y\)that is \(p\) times as great, both changes being expressed in proportional terms. In everyday language, a 1% change in \(X\) produces a \(p\%\)change in \(Y\).
Stiffening the track bed
We can now get to grips with the problem of strengthening a railway track. We'll start by looking at the effect of varying the track bed stiffness parameter \(k\) on track deflection \(w_{\max}\) while keeping \(E\) and \(I\) fixed. If we substitute the right hand side of equation 2 for \(L\) in equation 4, we get
\[\begin{equation} w_{\max} \quad = \quad \frac{1}{2 \sqrt 2} P (EI)^{- 1/4} k^{-3/4} \end{equation}\]
This can be written in the form
\[\begin{equation} w_{\max } \quad = \quad C_{1} k^{- 3/4} \end{equation}\]
where \(C_1\) is a (positive) constant. This is a power relationship of the same form as equation 11, and it follows that \(\rho\) is -3/4, so a one percent rise in \(k\) produces approximately a 0.75% reduction in deflection.
A similar line of reasoning can be applied to the effect of \(k\) on the bending moment \(M\). The value of the bending moment is given by equation 7. The negative sign on the right hand side is purely a convention; what we are interested in is the numerical magnitude, and therefore we'll work in terms of the absolute value of \(M_{\min}\), which we'll denote here by \(M_{a}\) thus:
\[\begin{equation} M_a \quad = \quad \left| M_{\min} \right| \quad = \quad \frac{1}{4} P L \end{equation}\]
If we substitute the right hand side of equation 2 for \(L\) in this equation, we get
\[\begin{equation} M_a \quad = \quad \frac{1}{2 \sqrt 2} P \left( E I \right)^{1/4} k^{ - 1/4} \end{equation}\]
\[\begin{equation} M_a \quad = \quad C_2 k^{-1/4} \end{equation}\]
where \(C_2\) is a (positive) constant. Hence \(\rho\) = -1/4. Since for any given rail cross-section the maximum stress due to bending is proportional to \(M_a\), it follows that a one percent increase in \(k\) reduces the maximum stress in the rail by only 0.25%. This seems a relatively meagre gain.
Stiffening the rail
Now let's see what can be gained by stiffening the rail instead. The rail stiffness is embodied in the two parameters \(E\) and \(I\), respectively Young's modulus for steel, and the moment of inertia of the rail cross-section. Let's deal with \(E\) first. To find how it affects deflection, we write equation 15 in the form
\[\begin{equation} w_{\max} \quad = \quad \frac{1}{2\sqrt 2} P (EI)^{- 1/4} k^{- 3/4} \quad = \quad C_{3} E^{- 1/4} \end{equation}\]
and the ratio \(\rho\) is now -1/4, so that a one percent increase in Young's modulus yields only a 0.25% reduction in deflection. To find its effect on the bending moment, we write equation 18 in the form
\[\begin{equation} M_a \quad = \quad \frac{1}{\sqrt 2} P \left( EI \right)^{1/4} k^{- 1/4} \quad = \quad C_{4} E^{1/4} \end{equation}\]
Therefore \(\rho = 1/4\), and a one percent increase in Young's modulus doesn't reduce the bending moment at all, but rather causes it to increase by 0.25%, and the maximum stress on the rail cross-section will increase by 0.25% as well. This is not quite the paradox it seems, because we are dealing with a composite structure in which the rail and the track bed interact. A stiffer rail doesn't flex so easily and therefore spreads the load along a greater length of track bed. In structural terms, it is working harder than would a more flexible rail.
It remains to look at the parameter \(I\). Its effect on deflections can be judged immediately from equation 15, because the parameter \(I\) plays the same role in this equation as the parameter \(E\). In other words, a one percent increase in the moment of inertia of the rail cross-section yields only a 0.25% decrease in track deflection. But we can't apply the same trick to determine its effect on rail stress, because the assumption that we relied on earlier, that the maximum stress in the rail is proportional to the bending moment, no longer holds: the parameter \(I\) is a geometrical property of the rail cross-section, and if you change the cross-section the relationship between maximum stress and bending moment changes too.
According to the assumptions made in classical bending theory, the stress within the cross-section of a beam subjected to a bending moment \(M\) varies linearly from the upper surface to the lower surface, passing through zero at the neutral axis. Its value \(\sigma\) at any point P within the cross-section is given by
\[\begin{equation} \sigma \quad = \quad \frac{Mz}{I} \end{equation}\]
where \(z\) is the distance measured vertically from the neutral axis to P, which for the sake of argument we'll take here as positive downwards. Hence there are two peaks in the stress, one at the upper surface of the rail and one at the foot (see figure 4). In general terms we can say that the maximum absolute stress \(\sigma_a\) is proportional to \(M\)and to the rail height \(h\), and inversely proportional to \(I\) thus:
\[\begin{equation} \sigma _a \quad = \quad \text{constant} \times \frac{Mh}{I} \end{equation}\]
Let's assume that when we substitute a stronger rail, its cross-section will have the same shape with all dimensions scaled up in the same proportion, which is approximately the case in practice. The moment of inertia \(I\) is defined as the sum of each small area of the cross-section multiplied by the square of its vertical distance from the neutral axis, and for any given shape of cross-section scaled up or down in size is proportional to \(h^{4}\). Conversely, \(h\) must be proportional to \(I^{1/4}\). Also from equation 18, \(M_{a}\) is proportional to \(I^{1/4}\). It follows from equation 23 that
\[\begin{equation} \sigma _a \quad = \quad C_{5} \frac{I^{1/4} I^{1/4}}{I} \quad = \quad C_{5} I^{-1/2} \end{equation}\]
where \(C_{5}\) is a constant. Hence a one percent increase in \(I\) reduces the maximum stress in the rail by about 0.5%.
But knowing the effect of changing the parameter \(I\) doesn't help very much. The railway engineer classifies alternative rail stock in terms of weight, which is proportional to the cross-sectional area. If the height of the rail is \(h\), the area \(A\) will be proportional to \(h^{2}\). Thus \(I\) is proportional to \(A^{2}\), and in equation 15 we can replace the quantity \(I\) by \(K A^{2}\) where \(K\) is a constant. We get
\[\begin{equation} w_{\max} \quad = \quad \frac{1}{2 \sqrt 2} P E^{-1/4} \left( K A^2 \right)^{- 1/4} k^{- 3/4} \end{equation}\]
and if we hold \(P\), \(E\) and \(k\) fixed this can be written
\[\begin{equation} w_{\max} \quad = \quad {C_6} A^{- 1/2} \end{equation}\]
It follows that a one percent increase in cross-sectional area yields a half percent decrease in deflection. Beefing up the rail has a modest effect. But what about the stresses? If we substitute \(KA^{2}\) for \(I\) in equation 24 we get:
\[\begin{equation} \sigma_a \quad = \quad C_{7} A^{- 1} \end{equation}\]
where \(C_{7}\) is a constant. So a one percent increase in cross-sectional area yields a one percent decrease in stress, which puts the option of strengthening the rail in a more favourable light.
Sensitivity of track deflection and rail stress to various stiffness parameters
All these results are summarised in figure 14, which shows that if we consider a given percentage reduction in deflection as the target, and a percentage increase in one or other of the parameters \(k\), \(E\), \(I\) or \(A\) as the means of achieving it, then stiffening the track bed, i.e., increasing the value of the parameter \(k\), is the most effective solution. (It may not be the cheapest.) On the other hand if we consider a given percentage reduction in the rail stress as the target, then subject to the proviso that all the dimensions are scaled up in the same ratio, increasing the weight of the rail is the most effective solution.
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Boca Raton: CRC Press, 279-325.
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We are delighted to announce the publication of a new eBook presenting cutting edge themes on weather systems: "Circulation Weather types as a tool in atmospheric, climate and environmental research", published under Frontiers in Environmental Science, hosted by: Alexandre M. Ramos, David Barriopedro, Emanuel Dutra.
We hope this achievement serves as a stepping stone to inspire future research topics in our journal.
Topic Description: Classifications of circulation weather systems have a long history in meteorology and climatology. Starting with manual classifications over specific regions of the globe, these tools (generally called "catalogs of synoptic types") were restricted mainly to weather forecasting and historical climate variability studies.
In the last decades, the advance of computing resources and the availability of datasets have fostered the development of fast and objective methods that process large amount of data. In recent years numerous methods of circulation type classification have been designed, showing their usefulness on a wide range of applications in scientific domains related to weather, climate, and environment.
This Research Topic highlights methodological advances in circulation weather types and also their applications to different research areas. The articles included in this research topic show that circulation weather types can be used not only in Europe, where they have been always more frequent, but also applied to other regions of the world.
If you have an idea for a new Research Topic, contact our team: researchtopics@frontiersin.org. A list of the most popular Research Topics can be found here.
If you are interested in becoming either an Associate Editor or Review Editor for Environmental Science please contact environmentalscience.editorial.office@frontiersin.org for more information. We look forward to hearing from you!
Good one! When it comes to future, we don't have enough tools to predict it with precision. But we can always prepare for it. This holds true in the case of climate change.


text:
TIME.BUSINESS
TIME.KEEPER
EUROPA STAR CHANNEL
EUROPA STAR PREMIÈRE
L'ambitieux plan de Chrono24
12 RUPTURES DE L'INDUSTRIE HORLOGERE
Serge Maillard
Avec environ un million d'utilisateurs enregistrés pour des transactions annuelles qui se montent à un milliard d'euros, Chrono24 est à la tête d'un véritable « trésor » de data - c'est à dire une liste de clients actuels de l'horlogerie.
Cette interview est disponible uniquement en anglais.
ith around one million registered users making transactions worth a billion euros annually, Chrono24 is sitting on a gold mine of data – meaning actual buyers of watches – to try to win their hearts and minds.
Among the main new actors that appeared with the advent of the internet era, Chrono24 has established itself as a leading global marketplace for buyers and sellers of vintage, pre-owned and, increasingly, new watches. Brands as diverse as Frédérique Constant, Porsche Design and Louis Moinet have indeed opened their own selling platforms on Chrono24. More brands will follow, says the company.
Is it the beginning of a closer relationship between the pre-owned market, which has been booming online this last decade, and the contemporary market, which has been struggling over the last three years and is now rushing to develop e-commerce solutions? More than 2,000 dealers already sell watches online on the platform, which is hoping to gain more leverage with global watch collectors.
This is why Chrono24, which employs more than 150 people from Germany to New York and Hong Kong, for yearly transactions of a billion euros thus organised a first "get-together" last January at its headquarters in Karlsruhe, Germany. "The event attracted more than 30 collectors, some of them from as far away as London or New York. We will now move forward with organising these kinds of meetings in other parts of the world and on a more frequent basis," says Tim Stracke, co-CEO of Chrono24. Europa Star met him in order to better understand how the platform works, and what it hopes to achieve.
Tim Stracke, co-CEO of Chrono24
« We are not only a marketplace. We are also a platform that knows a lot of information and data about its users. »
Could you share with us a few numbers about Chrono24, to give us a clearer picture of the platform? Such as the volume of transactions by year, the number of unique users, number of dealers, etc
We assume that one out of three watch lovers worldwide uses Chrono24 from time to time. And we assume that almost all collectors that use the internet also use Chrono24. When we talk to dealers, it almost never happens that they don't know us. We attract between 10 and 12 million visits per month on our platform. In 2017, the transaction volume generated through Chrono24 was one billion euros. And it is growing by around 25% per year.
What is the profile of the watch buyers, on one side, and the sellers, on the other?
Almost all watch acquisitions are made by private individuals. People use Chrono24 for inspiration, to compare prices, to get information and ultimately to buy or sell watches. On the sales side, more than 90% of sellers are professional dealers. They include established names like Govberg in the USA. We have 2,400 dealers registered and active on Chrono24.
What is the average price of the timepieces traded on the platform?
It lies between 7,000 and 9,000 euros. The prices start at a few hundred euros, up to more than one million euros. Watches that are really expensive are usually not transacted directly through Chrono24. They still use our platform find the watch and communicate, and then operate the transaction on their own.
How does your business model work?
It is a mix of listing fees and transaction fees. Our current goal, however, is much less about generating revenue than about increasing the user base and expanding the platform through partnerships with brands and the sales of new watches. The main benefit for brands who join us is that they have access to a global user base through Chrono24, and can convey their very own message to these users.
Could you tell us more about the growth of the business of selling pre-owned watches online since you started, just a few years ago?
Chrono24 was founded in 2003. We have always focused on listing as many watches as possible, and this has attracted many sellers and subsequently buyers onto the platform. It has made us the global player for buying and selling luxury watches online.
But we are not only a marketplace. We are also a platform that holds a lot of information and data about its users. We want to use this information to help our users find the best watches. Now, we know pretty well what the users like, looking at their search profile and what they have bought. We have also introduced a feature where buyers can upload their existing watch collection so that we can make tailor-made suggestions to them.
Do you share this data with brands?
First of all, we take private data protection very seriously. We do share metadata with brands, to give them deeper insights into their industry. We also help them to get access to watch lovers and collectors worldwide – but we won't and are not allowed to hand over any personal data to them. For instance, we know that when someone is looking for a certain model, he might also like another model.
Imagine you go to a store and you say that you are interested in an Omega Speedmaster, and the seller presents you some Speedmasters, as well as, based on our research, watches from other brands with the highest proximity. It is purely based on data. It gets increasingly interesting for the watch brands, even though they might not publicly work with us on our platforms.
How do you intend to convince them to move to an official partnership?
More and more established watch brands do want to work directly with us, because of our global reach to potential buyers, but they also realise that it is sometimes easier to convey the brand message via the internet than in the store.
A lot of brands have a strong heritage and the question is: are all salesmen able to talk about it to potential buyers? In many cases, the founder or the watchmaker of the brand can do it much better and more emotionally, using videos and images. It is sometimes better than talking to a seller, who might not know the brand very well.
But will buyers of pre-owned or vintage watches convert to buyers of new watches?
Chrono24 already has the categories of vintage, preowned and new watches. The biggest by far is the vintage and pre-owned watch segment, but we are trying to develop the new watch segment as well. We are already working with brands that want to directly sell to our users.
Some brands do it openly in our newly established brand boutiques; other brands just advertise on our platform or work with us in other ways to build a direct bridge with the potential customer. For example, if a really exclusive brand wants to host a collectors' dinner in Dubai or Tokyo, we can easily invite 20 to 30 people in the city, who have a very strong tendency to buy this brand or who have bought similar brands in the past.
Watch brands are very cautious about the pre-owned market, which may look like a "parallel market" jungle… What kind of relationship are you trying to establish with them?
We are in talks with almost all brands and are discussing potential ways of working together. Some brands are already openly selling on Chrono24, others use a partnership to connect to potential buyers worldwide, and we are just opening discussions with yet other brands. But there are very few brands that are ignoring us, and not looking for a discussion at all. We are open to discuss with all brands. But maybe we still need a few big names working openly with us, to overcome the psychological barrier.
You know the watch buying habits of millions of people around the world. How do you collect this data?
We know from our users what their core interest is by looking at their search behavior, and we use this to make better suggestions. We also gather data when users upload their existing watch collections.
But the brands that join your platform would also get access to data… and what about other brands that are not on your platform but which are interested in your data?
We are open to all kinds of partnerships.
MOST POPULAR BRANDS BY CLICKS ON CHRONO24
What measures do you take to avoid counterfeits, a phenomenon that we see a lot online?
We do careful due diligence on all the dealers that join the platform, in order to be sure we keep only the best ones. In addition, when you buy a watch on Chrono24, we hold the money in an escrow account until the watch is safely delivered to your home. Only when you say that you are happy with the watch do we release the money.
Otherwise, you get your money back. It is very rare that a watch is really fake: there have been fewer than five returns over the last few years because of authenticity issues. And more than 100,000 watches are being transacted through Chrono24 per year. We would rather kick a dealer off the platform than risking having a single fake watch.
Another issue is when watches are not in the promised condition…
That is also part of our policy. You can return any watch that has been bought on Chrono24, no questions asked. But very few watches are actually returned: very low single digits. The most common reason for returns is that the watch is not as it was described on the platform. Only around 1% are returned without a specific reason, just because the buyer does not want it anymore, mostly because the watch is a bit smaller than expected, not because it is fake or damaged! Our total return rate is less than 5%.
Indeed, the "touch and feel" experience remains important when it comes to watches, to avoid the situation where you don't realise until it has been delivered to your home that the watch is too small. Have you thought about ways of displaying the watches or organising meeting places for the buyers and sellers, like physical "lounges" in major cities?
We are indeed considering all kinds of measures to bring people together and to build trust during the transactions. Chrono24 is a lot more than a digital market place. We are also considering developing logistics services. There are a lot of developments to come yet.
KEY NUMBERS ABOUT CHRONO24
• 10-12 million visits per month
• 1 billion euros in transaction volume generated in 2017
• 2,400 professional dealers registered
• More than 90% of sellers are professional dealers
• 100,000 watches bought/sold through Chrono24 in 2017
• The most expensive watch ever sold through Chrono24: a Patek Philippe Sky Moon Tourbillon, for more than one million dollars
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Cancer treatments can lead to a change in taste.
Cancer treatments have many effects on patients – some apparent and some less so. One of the most noticeable changes is a change in taste.
Changes in taste are a "very common nutritional change" for patients undergoing cancer treatment, says Catherine Carpenter, professor of clinical nutrition at the David Geffen School of Medicine at UCLA. The reason: chemotherapy, radiation therapy, and cancer type can each affect a person's sense of taste and dietary preferences.
When food tastes different, it an also affect the types of foods that patients want to eat.


Easter, April 21, 2019 Sunrise Service-6:30a.m lead by the youth of the church Easter Breakfast serving 7:00-10:00a.m. Traditional Worship – 8:00 & 10:30a.m. Contemporary Worship – 9:15a.m. Hope you will be able to join us to celebrate the resurrection of our Savior!


text:
A bitter, grumpy "Heh!"
Courtesy of Ninety Miles from Tyranny: Given the Uranium One scandal, that's all too accurate. Peter
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That's a big plane . . .
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The Electronic Frontier Foundation (EFF) has spoken out against the proposed Allow States and Victims to Fight Online Sex Trafficking Act (FOSTA). FOSTA would undermine Section 230, the law protecting online platforms from some types of liability for their users' speech. As we've explained before, the modern Internet is only possible thanks to a strong Section 230. Without Section 230, most of the online platforms we use would never have been formed—the risk of liability for their users' actions would have simply been too high. Section 230 strikes an important balance for when online platforms can be held liable for their users'
Would you pay $100 for a meatball???
Even this meatball? Meatball lovers unite. The humble meatball is being transformed for one day only — on March 9, for National Meatball Day. (Who knew?!) The $100 meatball will be available at Davio's Northern Italian Steakhouse at 447 Lexington Ave. Created by executive chef Juan Tourn, it's made with Wagyu beef, truffle Caciocavallo cheese, foie gras, winter truffles — and topped with a creamy shallot and champagne sauce. There's more at the link, including a photograph of the gonzo gargantua meatball. Sorry. I'll be darned if I pay $100 for any meatball, no matter how good its ingredients –
So when does an adult become an adult?
Calls by several groups and individuals (including President Trump) to raise the legal age for purchasing a firearm to 21 are making headlines at present. The problem is, buying a gun is just one part of being an adult, and it's neither the most risky nor the most politically awkward one. At the same time, some are calling for the voting age to be reduced to 16. Tell me; if someone's not mature enough to own a gun until they're 21, what makes you think they'll be mature enough to vote – arguably a far graver responsibility – when they're
Cowardice and betrayal of trust in Broward County
By now, I'm sure most of my readers are aware that four Broward County deputy sheriffs – including the school security officer – cowered outside the Parkwood school buildings and refused to go in to confront the shooter as he was murdering 17 of his former classmates. (I won't name him. He doesn't deserve to be remembered as a human being. Let his name be forgotten.) When it comes to the deputies' conduct, I don't think anyone has said it better than my friend and comrade Lawdog. I'll go so far as to say that there is no dishonour in
So true it hurts
Courtesy of Mr. B. (for the quote) and Aesop (for the meme graphic). Says it all, doesn't it? Peter


Meet Kyle George, 28, of Hattiesburg, USM's associate athletics director of marketing and communications.
Meet Kyle George, 28, of Hattiesburg, associate athletics director of marketing and communications for the University of Southern Mississippi, where he is involved in marketing, promotions and storytelling for all Southern Miss sports.
"I get to work in college athletics for a living, and I love every minute of it," the Hoover, Alabama, native said in an email.
George earned a bachelor's degree in history in 2011 from Samford University and a master's degree in sport management in 2013 from Southern Miss. George's parents, David and Allyson George, and younger sister, Katelyn George, live in Hoover.
What advice would you give people who want to get into the same line of work as you? Take the time to volunteer and make connections with individuals working in the sports industry. I spent my entire undergraduate career volunteering with the Sports Marketing Department at Samford University and had the opportunity to learn and grow. I also had the opportunity to volunteer with the Southeastern Conference. This is a relationship-based industry, and it is imperative to have mentors to guide you along the way. Never be afraid to reach out to individuals who you believe do great work in this industry as you can always learn something and create a new connection.
Why did you choose to live and work in the Hattiesburg area? I had the opportunity to come to Hattiesburg as a graduate assistant for Sports Marketing in August 2011, and I've been fortunate to be at Southern Miss in various roles ever since. I love Hattiesburg and Southern Miss. The people of this community and campus make this such a special place.
What do you do in your free time? Free time? Ha — don't have much of that! My dad always told me that if you love what you do, you'll never work a day in your life. And I can say that is true for me. I love being in college athletics and the fast-paced atmosphere where every day brings a new challenge. And when I do have free time, you'll probably find me at one of our sporting events. What can I say? I'm a sports fanatic.
If you could meet anyone, living or dead, who would it be and why? Peyton Manning. I've looked up to him as a role model ever since I was a little kid. The way he approached the game and how he continually gives back to others has always been something that I have admired about him. Plus, my grandfather always told me that we are distant cousins — maybe one of these days I'll get an invite to a family reunion.
If you could go back 10 years and give a younger you tips or advice on life, work or anything in general, what would it be? Never take for granted the little moments you get to spend with your family. Because in those moments and memories, I can say I've learned more about life and how to handle myself as an adult than I ever thought possible back when I was a teenager.


Batch the multiplied ingredients in a large measuring cup or pitcher and pour into the individual bottles. Cap the bottles using crown bottle caps and a capper.
Store the Wheatley Shandy in the refrigerator Saturday night to be ready to go by Sunday.


text:
Kitchen Assistant @ Deliveroo
restaurant food delivery
London Posted: Tuesday, June 11, 2019
Why Deliveroo?
When you first think about Deliveroo, you probably think of getting great food to your house in less than half an hour. Awesome right? But behind the scenes is the real story. This story is one of high growth, huge challenges & an enormous opportunity ahead of us. It began with our founder Will, arriving in London over 5 years ago & finding it almost impossible to order great food, despite the wealth of incredible restaurants in the city. Fast forward 5 years & we operate in 13 countries with over 50,000 riders who deliver orders from 50,000 restaurants in over 200 cities worldwide.
We want to be the definitive food company - the app you go to any time you have a hunger pang. We are transforming the way people think about food. We are providing people with limitless access to different cuisines & restaurants, turning cooking from a chore to a choice, & giving people the freedom to eat what they want, when they want, where they want it.
We work with riders, restaurants & consumers. We operate one of the most complex three sided marketplaces in the world & we do this in real time. Millions of customers & thousands of restaurants & riders rely on us to match them within milliseconds. The algorithms behind that marketplace are the secret sauce that allow us to deliver our orders in under 30 minutes.
And were just getting started
The scale of the opportunity ahead of us is immense. The global food market is valued at 7.7 trillion but only 1% of it is currently online. Contrast that with the digital disruption of countless other industries - from banking & travel to retail & communications - its clear that our journey in the food sector has only just begun.
We are already a multi-billion dollar company that is more than doubling in size every year. Deliveroo came top in the FTs list of Europes fastest growing 1000 companies in 2018, & we were the first company ever to win Deloittes UK Top 50 two years in a row. Yet most of the extraordinary value this company will generate lies ahead of us.
The Kitchen Assistant will work at one of our original content sites & will be responsible for:
Cleaning the Editions site (Including; kitchen, cooking equipment & site facilities)
Adhering to the highest level of food safety (5 stars from EHO)
Assisting the Site Manager with general duties
The ideal candidate will have the following;
A Passion for food & customer excellence
Ability to work with a large team
Previous experience working in a high volume environment
Previous kitchen experience an advantage
Flexibility with availability for evening & weekend shifts
We're always on the look out for new talent & would love to hear from you if you're interested in joining the team. We will be in touch when a Kitchen Assistant vacancybecomes available.
Life at Deliveroo
We are a growing team, with very large impact, seeking to answer some of the most interesting questions out there. We move fast, were always looking for new ideas & were very transparent about the decisions we make & why we make them.
There are so many questions we need to answer & plenty more we havent even encountered. How do data & technology help restaurants to grow as consumer habits change? How can we predict what someone wants to order for dinner long before the idea has even crossed their mind? At Deliveroo these are just some of the tough problems we are solving - & there is no challenge that cannot be yours. No solution is owned by a particular team, which means the scope for growth & personal impact is enormous.
Benefits & Diversity
At Deliveroo we know that people are the heart of the business & we prioritise their welfare. We offer a wide range of competitive benefits in areas including health, family, finance, community, convenience, growth, time away & relocation.
In 2018 we announced our decision to give every employee equity in the company. We did this because we wanted all of our employees, regardless of location, level or role to be owners & because we believe that this is the right thing to do. We believe this helps build a culture where everyone is committed & able to share in the companys success.
We believe a great workplace is one that represents the world we live in & how beautifully diverse it can be. That means we have no judgement when it comes to any one of the things that make you who you are - your gender, race, sexuality, religion or a secret aversion to coriander. All you need is a passion for (most) food & a desire to be part of one of the fastest growing start-ups around.


opencomputeproject/Project-Zipline: Defines a lossless compressed data format that is independent of CPU type, operating system, file system, and character set, and is suitable for compression using the XP10 algorithm.
This Day in Tech History - The History of Technology in a Daily Blog!
Gotenberg · A Docker-powered stateless API for converting HTML, Markdown and Office documents to PDF.
portabletext/portabletext: Portable Text is a JSON based rich text specification for modern content editing platforms.
bevry/cson: CoffeeScript-Object-Notation. Same as JSON but for CoffeeScript objects.
hashicorp/hcl: HCL is the HashiCorp configuration language.
sed-seyedi/mset: Mset is a user friendly configuration file format with a parser that is only 50 lines of code.
thosakwe/t2b: A wicked-powerful text macro language for building binary files.
SVG to raster - convert vector SVG images to PNG, JPEG or TIFF images.


text:
Home Industry News Electric Motorcycles ARC VECTOR – A NEO CAFÉ RACER IN SEARCH OF FRESH TERRAIN...
ARC VECTOR – A NEO CAFÉ RACER IN SEARCH OF FRESH TERRAIN AND NEW FRONTIERS
Newly announced motorcycle maker Arc has launched its first model, the Vector, at Milan's EICMA Motorcycle show today; a machine which tears up convention, just as it tears up the tarmac. The Arc Vector is the most advanced electric motorcycle ever brought to market, utilising exotic materials, thoroughbred componentry and cutting-edge architecture, wrapped in a futuristic body with post-modern nods to café racers past.
Human Machine Interface (HMI) has been taken to a new level, comprising an intelligent rider jacket packed with haptic sensory technology and a Heads-Up Display (HUD) helmet inspired by those of fighter pilots, giving the user important information and enhancing the freedom and wellbeing of their riding experience.
As big on soul as it is technology, the hand-built Vector has a lightweight carbon-composite structure and ingeniously elegant battery-module monocoque, which is as clean and efficient as it is beautiful to behold. Its featherweight solves one of the headaches normally attributed to brick battery EVs, and it has MotoGP levels of stiffness so that there's zero compromise on ride. Vector utilises carbon swingarms front and rear, custom-made Ohlins dampers for telepathic handling and feedback, and meaty Brembo brakes on anorexic BST wheels. The entire package tips the scales at 220kg, which is almost 60kg lighter than comparable machines. Vector has the best power-to-weight ratio of any electric motorcycle of its class by a considerable margin.
In raw pace, Vector rivals fossil-fuelled superbikes, sprinting from standstill to 60mph in 3.1 seconds and carrying on to 120mph.
The battery cells are the absolute cutting-edge. Their packaging has been developed to be completely modular, flexible, and legacy-free, maximised for simplicity, space and mass- reduction. The power cell produces 399 units of voltage, giving a realistic range of about 200 miles in urban use and 120 miles on the highway. That's about 30% more than any comparable EV. Arc will install a personal electric charger at the owner's desired premises. Away from home, the Vector can be charged in 45 minutes at a quick charge point or service station.
The key to the bike is the Zenith helmet, which has been designed in collaboration with Hedon. Its connected HUD projects speedo, sat-nav and ancillary graphics onto the rider's visor so they can keep their eyes affixed to the road, Iron Man-style. A live rear-view camera is encased in the calfskin-trimmed helmet, giving the user the ability to see what's behind them.
The bespoke jacket, Origin, represents a game-changing advance in intelligent technology, making motorcycling even more immersive. HMI has been applied to the armoured ride-wear by packing the jacket with audio-type haptic amplifiers – like a smart phone's vibration notifications, but a lot more advanced. These may vibrate to alert of a potential hazard, provide dynamic performance-based feedback, or enhance the senses when on a stimulating ride.
The Origin jacket, which is tailored in collaboration with style gurus Knox, has three settings. Urban Mode focuses on safety, alerting the rider to dangers such as vehicles in their blind spot with a polite tap on the shoulder. Sports Mode gives the rider feedback on the bike's dynamic position and parameters by taking G-Force related data from the Vector's carefully nuanced sensors and providing a graduated level of feedback. This tells the rider how close to the limit of the motorcycle's capabilities the rider is. For example, the harder you brake the more feedback you receive. Euphoric Mode lets you play music through the haptics as you ride and simulates the bass through the jacket's amplifiers, making your hairs stand on end. It communicates with the Vector bike and the Zenith helmet wirelessly, emboldening freedom by enhancing the senses.
Recognising the Vector's ingenuity and enormous potential, financial backing has been obtained from a number of blue-chip beneficiaries, including Jaguar Land Rover's venture capital fund InMotion Ventures, Mercia Fund Managers and the Midlands Engine Investment Fund.
The Arc Vector, which includes the custom-made Zenith and Origin ride-wear, is priced at £90,000. Production is targeting 399 motorcycles in year one, the same figure as the batteries' total voltage.
Mark Truman, Founder and CEO, Arc Vehicle Ltd: "We felt that there was more one could get out of motorcycling which no one was tapping into. This is about using technology to strip back the experience of riding a bike, through the use of haptics and HUD. The helmet and jacket work in tandem with the Vector to remove distractions and emphasise the joy of riding."
"With Vector, we've set out to build the best performance electric motorcycle. With electric vehicles in general, the powertrain weighs a lot. This really can't be avoided if you want capacity, distance and performance. So, it was about stripping everything back and using a lot of exotic, lightweight materials, such as carbon-fibre. The chassis and battery module had to be one, and because of this approach we've been able to reduce the weight as much as possible to achieve the performance we wanted. The design brief was; if the term 'cafe racer' was going to be coined in ten years' time, what would that look like?"
"Arc Vector satisfies those of us who are rarely satisfied, who are always looking for a different road, a different view. We understand the need to be different, to be better, and challenge the norm."
Sebastian Peck, Managing Director, InMotion Ventures: "For Jaguar Land Rover's venture capital fund, this is about being a technology leader in a disruptive environment. Our mission is to develop an expanded footprint for Jaguar Land Rover in the brave new world of premium mobility. We understand the power of emotional connection and creating really desirable objects, so we see natural synergy with Arc. The Vector is an incredible development in the next generation of motorcycle travel."
Based in Coventry, in the centre of the UK's automotive high-tech industry, Arc is on a mission to explore Earth in state-of-the-art style, combined with a promise to protect it. Vector is a catalyst; a transformative vehicle that will challenge the rider's way of seeing and thinking, and one that shapes the world around it.
In addition to revolutionary tech, Arc promises a sales and ownership experience as individual, luxurious and highly-detailed as the Vector machine itself.
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Q: Disqus universal code for Django I try to install disqus in my site, but nothing is displayed on the page. Site url - djaway.net
This is my code:
views.py
def detail(request, slug):
    url = (reverse('content:detail', args=[slug]))
    content_info = Post.objects.get(slug =  slug)
    return render(request, 'detail.html', {'content_info':content_info, 'url':url})

template.html

Please enable JavaScript to view the comments powered by Disqus.

Tag {{ url }} return right links, for example /content/slug/

A: You are missing the https:// in the URL for loading the disqus javascript:
s.src = 'https://djaway.disqus.com/embed.js';

It might be a good idea to include http:// or https:// (depending on whether your site uses https):
this.page.url = 'https://djaway.net{{ url }}';

redpajama_set_name: RedPajamaStackExchange


text:
Q: "Install Xcode" in Applications, necessary after I've installed Xcode? Do I need the Install Xcode after Xcode is installed?
Do you know of any reason it installed an installer to Applications?

A: You may want to keep it in order to be able to download delta updates instead of the full version when updating via the Mac App Store.
If you don't care about that or care more about disk space, you can delete it (you'll be asked for the administrator password) and continue to use Xcode.

A: It's not necessary to keep the XCode installer file after XCode is installed. However, you may wish to consider keeping it stored somewhere as the XCode download is relatively large.
It's probably in the Applications folder because this is where the App Store puts downloaded packages by default.

A: The Mac App Store is setup to install in /Applications, but some applications, like Xcode, are way more complicated to be contained in an .app file.
So they need to use an installer, which is going to add the /Developer folder which itself contains multiple applications (Xcode, Dashcode, the iOS simulator, etc.).

A: I found the App Store download put an xcode installer into /Applications. I then had to run that installer. Situation complicated by recent upgrade/fix to App Store installer [ itunes error message ]. So had to repeat process using upgrade [ 4.1.1 ]. This way only way I could get g++ to run.


text:
Dunkirk Little Ship to set sail again
A model of the Skylark IX floating at Dunkirk shore on the 75th anniversary of Operation Dynamo
A Dunkirk Little Ship that saved 600 lives is itself going to be rescued thanks to National Lottery funding and the passion of a local community group. The restoration project will allow recovering drug addicts to learn new skills by working with a specialist boatbuilding team.
Skylark IX was built as a passenger cruiser for 75 people in 1927. But in 1940 she was called to the aid of the stranded Allied troops in Dunkirk as part of Operation Dynamo. She, and the ordinary seamen that sailed her, saved hundreds of lives.
However, due to disrepair, the Dunkirk Little Ship sank on Loch Lomond in 2010.
Anne Dyer, advisor to the Skylark IX Recovery Trust, said: "Skylark's first mission was to save Second World War Allied forces stranded on the shores at Dunkirk and today she will continue to save lives by allowing recovery clients from Alternatives to bring her to life again."
Creating a floating museum
Skylark IX was raised by the Royal Navy following following a campaign involving veterans and the local community, and is currently located at the Scottish Maritime Museum in Irvine. She will be restored thanks to £404,400 National Lottery funding to create a floating museum which will sail on the River Clyde telling the fascinating story of her role in the Second World War.
The project will include paid traineeships leading to recognised qualifications in woodworking skills. The traineeships will be undertaken by clients of Alternatives Community Drugs Service, who are partners in the project.
[quote=Lucy Casot, Head of the Heritage Lottery Fund in Scotland]"The Skylark IX is a part of Scotland's Second World War history and we are delighted she will be saved to share her incredible story."[/quote]
Anne continued: "When we started this venture, we never really knew the climb we had in front of us but in our hearts, we had a sense that if we set out our vision and gather like-minded people then we would get there in the end.
"Funding from the Heritage Lottery Fund has made this mission real. They have supported and encouraged us every step of the way and with them and many others, we now can bring our dream to the fore."
Lucy Casot, Head of the Heritage Lottery Fund in Scotland, added:"The Skylark IX is a part of Scotland's Second World War history and we are delighted she will be saved to share her incredible story. As part of her recovery, others will recover too, learning skills that will help secure them a better future too."
Skylark IX honouring the past, uniting communities, continuing to save lives of those in need
Moving the Skylark IX
Modern-day rescue for Second World War heritage
A Dunkirk Little Ship, which saved 600 lives, and a camp of Nissen huts are to be brought back to life thanks to HLF.


A 50-year marriage deserves a celebration that will be remembered by friends and family for 50 more. Let the staff of Ko'olau Ballrooms ensure every last detail is in place. We'll provide everything you need for a truly grand celebration.
At Ko'olau Ballrooms, we believe every successful year of marriage is cause for celebration. Put your anniversary celebration in the hands of our professional staff, and know that the party will be a gift unto itself.


Over 90% of property sourcing by Buyers is from the internet, and the internet can be informative – or not – depending on the information sourced, it's timeliness, ease of use, relevance and accuracy. For Buyers, they want ease of use, they want to access all available properties, and increasingly, do it mobility. Unfortunately, not all property search platforms give the Buyer these features. Some corporate brokerages try to use their site(s) to drive business just to their listings, a more profitable transaction from the corporate perspective. Likewise, the two big commercial sites, Trulia and Zillow, have had issues with inaccurate information and are designed to drive properties to agents who pay for their exposure on the site, and sometimes this can get misleading.
The answer is to use a property site that includes all listings to help you search, like our website. We designed it to specifically be easy to use, have all the listings, current information, plus interesting information about the neighborhoods we serve along with other aspects of our communities. The other non-excluding sites like ours are fed unfiltered MLS data and include Realtor.com, movoto.com or redfin.com; that said, these are typically paid for by being a lead source for Realtors so you may get some phone calls.
Allied with these sites designed to show you what properties are available, one should be researching schools, and other appropriate community information to help one get to know the area get out an see some open houses to learn the nuances of the market.
Going to Open Houses is one of the best ways for learning neighborhoods and what drives values…Is it views? Remodeling? Privacy? Light? Sun and exposure? Prestige of the street? Ease of access? Parking? How much does lack of updating effect value? Is it priced to the market? Many of the attributes of residential properties are qualitative and even subjective, and walking through homes on the market can be informative and educational and give you the confidence about the market.
Once you have been Pre-Approved for a loan (if you are using one…) with the amount your bank has approved you for, it's time to find your home! Work together with your Realtor, use him as your source of background information and experience and answers to the following: How is this particular market? Any neighborhood nuances? What drives value in this location? Who are we negotiating with? What are their goals? Disclosures? Obvious issues? Potential issues and solutions? Anything about escrow that needs to be known now? A well seasoned Realtor often times has seen many of the homes in your area on the market before and can be a tremendous resource in helping manage the myriad of activities that go into finding and buying your home..
There is an art to making an offer on a home. Typically, sellers place their home's value a little higher than their desired price. A buyer will send in their offer at a reasonable range, and the seller will counter. The issues that have come up in the inspection process may factor into the process, as your Realtor, I will be watching for signs of problems in the home and will make suggestions to you regarding solutions and costs to be considered with the offer. This is our business and we see a lot of houses and deal with this stuff every day. Most Buyer's only buy a home once every 7 years or so, sometimes longer, particularly in our area where the lifestyle, weather and quality of life are hard to supersede. As an experienced Realtor, our job is to protect you, our client, in the contract.
Getting a home inspection is a vital part of the home buying process. These inspections ensure that the home's foundation, ceiling, heating, electrical system, walls, plumbing and entryways are up to certain standards. Sometimes the bank will require a home inspection however; many times they leave it to the buyer to purchase their own. It is extremely important to protect yourself by getting a home inspection right away. You typically have 10 days from an accepted offer to get the home inspected. Many buyers have been saved from disaster by taking the time to spend the extra $400 – $900 to get a home inspection only to find out the house has major problems allowing them to back out of the contract before it is too late.
Before the home is legally transferred to you, the closing process must occur. During this phase, you will sign all of the mortgage documents, pay closing costs, and sign various other legal documents. Once all of the papers are signed, the keys to your new home are yours! The only thing left to do is get the keys and move into your new home after the closing or at the date set in the closing documents.


text:
Yves Saint Laurent's Oasis-Like Museum by Studio KO
June 8, 2020 by jpacheco
A museum dedicated to the life and work of French fashion icon Yves Saint Laurent is situated in the Moroccan city of Marrakech. Designed by the Top Architects Studio KO, the building sits a short distance away from Jardin Majorelle – the home acquired by Saint Laurent and Pierre Bergé in 1980.
With a large permanent exhibition space designed by scenographer Christophe Martin, showcasing the collections of its namesake, the contemporary museum also features temporary exhibition spaces, a research library and archives, an auditorium, bookstore, and a terrace café.
Informed by the archives of Yves Saint Laurent, Studio KO was "struck by curves running alongside straight lines; by the succession of delicate and bold forms." As a result, the façade of the building appears as "an intersection of cubes with a lace-like covering of bricks," forging patterns that "recall the weft and warp of the fabric."
The modern museum's 400-square-metre permanent exhibition space is designed by scenographer Christophe Martin and showcases 50 couture creations.
"It is not a retrospective, but rather a voyage to the heart of his work," said Christophe Martin.
More than 50 garments, most never before seen, are displayed in an understated environment, one without affectation, which accompanies and underscores the work. An immense, luminous and radiating portrait of Yves Saint Laurent envelopes the garments.
See Also: The Most Iconic Fashion Designers Of All Time
"Musée Yves Saint Laurent Marrakech combines two worlds that we are very familiar with and that are dear to our hearts: fashion and Morocco," said Studio KO.
"It is with great joy that we have worked on this ambitious project, and contributed in our way to the history and prestige of the most influential fashion designer of the 20th century," the architects continued.
Stay with us to discover more about Yves Saint Laurent
Tags: Architectural Building, architecture, contemporary design, exclusive design, french fashion, Modern Museum, Studio KO, Top Architect, Yves Saint Laurent
Modern Sofas With Exceptional Designs
Discover Carpenters Workshop Gallery's Handmade Cabinets


text:
Q: octopress's date_format not working I comment the original data_format in _config.yml  and have set the date format to another one(I tried several date format):
date_format: "%F %a"        #2012-01-01
#date_format: "ordinal"

I rake generate and rake preview/or rake deploy, I still saw the date format is showing like "OCT 18TH, 2014 7:37 PM"  , why is that?
Thank you!

A: First solution:
As far as I found the date_format parameter from _config.yml file is obsolete (I reported it in https://github.com/imathis/octopress/issues/1697) because the previous Octopress date plugin was replaced with Jekyll Date Format. The parameter is no longer used.
To change date format on your blog you have to edit source/_includes/post/date.html file. You just need to replace two occurrences of
{{ page.date_time_html }}
with the
{{ post.date | date: "%F" }}
Of course you can change the %F as you want. More about Jekyll Date Format you can find at: http://alanwsmith.com/jekyll-liquid-date-formatting-examples

Second solution:
I have checked the issue once again and now it works as it should. You do not need replace {{ page.date_time_html }} any more. Just follow the configuration of the Octopress Date Format plugin: https://github.com/octopress/date-format#configuration.
You need to add second option - time_format - for time formatting and everything should works properly.
Example:

date_format: "%Y-%m-%d"  # e.g. 2014-07-03
time_format: "%H:%M"     # 24 hour time

Summary:
Octopress is constantly developed project and the date format issue will probably be different on different commits at GitHub.