text:
\section{Introduction}

Around 25 per cent of all binary stars are born close enough that they will
eventually interact with each other when the more massive member of the binary
evolves off the main-sequence and becomes a giant star
\citep{willems04}. Very often this results in material flowing from the
expanding giant onto the lower mass star, which cannot incorporate
it fast enough and therefore the material overflows the lower-mass star's
Roche lobe, leading to the entire binary being engulfed in what is known as a
common envelope (CE, \citealt{paczynski76,webbink84}). Inside this
envelope the stars are subject to strong frictional forces leading to a loss
of angular momentum and orbital energy, hence the two stars spiral inward
towards each other, ejecting the envelope as they do so. What emerges from the
CE is a close binary, known as a post common-envelope binary (PCEB),
containing the core of the giant star (which will become a white dwarf) and
its main-sequence star companion. Depending upon the stellar masses and final
separation after the CE stage, the binary may go on to experience a second CE
stage when the main-sequence star evolves, resulting in a double degenerate
binary system \citep{webbink84,nelemans01,toonen12}. Alternatively, the stars
may have emerged from the CE close enough to each other that angular momentum
loss will drive them in to contact before the main-sequence star has evolved,
often leading to the formation of a cataclysmic variable (CV) system.

PCEBs are important objects since they are likely the progenitors of supernova
Ia (SN\,Ia). While it is generally established that SN\,Ia are the result of
the thermonuclear ignition of a carbon-oxygen core white dwarf, there is not
yet a consensus on the pathway leading to the explosion. In the classic double
degenerate scenario the merger of two white dwarfs with a combined mass above
the Chandrasekhar limit leads to a SN\,Ia explosion
\citep{tutukov79,webbink84}. This channel has the advantage that it can
produce systems with both long and short time delays and explain the lack of
hydrogen and helium lines in most SN\,Ia spectra \citep{branch95}. Moreover,
there is both theoretical and observational evidence for a large population of
close double white dwarf binaries
\citep{yungelson94,nelemans05,napiwotzki01}. However, there is some
uncertainty as to whether the merger leads to an explosion or
rather a core collapse and the formation of a neutron star instead
\citep{nomoto91} and at present the situation remains uncertain
\citep{yoon07}. Moreover, a range of explosion masses are possible with
  the merger of two white dwarfs of arbitrarily mass, which would cause a
  spread in the luminosities of SN\,Ia, affecting their use as standard
  candles. In the alternative scenario, known as the single degenerate
channel, a white dwarf stably accretes material from a non-degenerate
companion star until it grows to the Chandrasekhar mass and explodes
\citep{iben84}. In this case the progenitor systems are thought to be white
dwarfs accreting from main-sequence or giant stars at a sufficiently high rate
that hydrogen is stably burnt on the surface of the white dwarf, avoiding nova
explosions \citep{shara77,iben82}. Such systems are observed in the Galaxy and
Magellanic Clouds \citep{vdheuvel92,kahabka97} and are known as supersoft X-ray
sources (SSSs). However, in order to sufficiently grow the white dwarf, models
often require fine-tuning many uncertain input parameters such as the
accretion rate \citep{hillebrandt00,wang12}. Furthermore, the single
degenerate channel has difficulty in creating SN\,Ia with time delays larger
than a few Gyr due to the short main-sequence lifetimes of their
  progenitors \citep[e.g.][]{claeys14}.

In recent years the idea of sub-Chandrasekhar or
double-detonation models have become popular. In this model the white dwarf
has accumulated a substantial surface layer of helium. When this layer ignites
it can send a strong shock wave into the core of the white dwarf, compressing
it and triggering a secondary detonation of the core, leading to a SN\,Ia
explosion \citep{fink07,sim10,kromer10}. This can be achieved via the double
degenerate route, with the merger of a carbon-oxygen core and a helium core
white dwarf, or the single degenerate route, with the white dwarf accreting
material from a helium-rich companion star. This idea has the advantage that
there are a sufficient number of such binaries to explain the birthrate of
SN\,Ia \citep{ruiter09}, although it is difficult to explain the observed
similarities in most SN\,Ia via this model \citep[e.g.][]{branch95}. In
virtually every model for the formation of SN\,Ia the progenitor systems are
binaries that have passed through at least one CE event (two in the case of
the double degenerate channel), hence PCEBs are a valuable population for
testing the ideas of SN\,Ia formation. In particular, PCEBs containing white
dwarfs with massive FGK-type main-sequence star companions are both potential
SN\,Ia progenitors (via the single degenerate channel) and an intermediate
stage (via the double degenerate channel) and therefore are a particularly
useful population. A large sample of such systems can even be used to estimate
the relative number of systems evolving through the double degenerate and the
single degenerate channels.

The number of PCEBs with late-type companions has rapidly increased in the
last few years thanks mainly to the Sloan Digital Sky Survey (SDSS) and its
spectroscopic database
\citep{raymond03,silvestri06,rebassa07,rebassa12,li14}. With
optical spectra alone it is possible to detect even very cool white dwarfs
next to M-type stars \citep[e.g.][]{parsons12} and hotter white dwarfs are
still detectable with companions up to very-late K ($\sim$5 per cent of SDSS
white dwarf plus main-sequence star binaries contain K star components,
\citealt{rebassa16}). However, detecting PCEBs with earlier-type companions is
more chalenging because these hotter, larger main-sequence stars completely
outshine white dwarfs in the optical, implying that a combination of
ultraviolet (UV) and optical data is required.

Several attempts have been made to identify white dwarfs with FGK-type
main-sequence star companions \citep[e.g.][]{maxted09}, which have succeeded
in finding these systems, but have failed to produce large numbers of
them. For example, SDSS FGK stars are generally located at large enough
  distances that all but the very hottest white dwarfs will go undetected in
  UV surveys, severely reducing the sample size. Previous studies of the
far-UV and soft X-ray spectra of main-sequence stars have revealed the
presence of white dwarf companions
\citep{landsman93,barstow94,vennes95,christian96,landsman96,vennes97,burleigh97,burleigh98,burleigh98b,burleigh99},
but the vast majority of these systems are visually resolved binaries that
were formed far enough apart that they avoided a CE event. To
date, only 7 PCEBs with early-type main-sequence star companions have been
identified and had their orbital periods measured
\citep{nelson70,simon85,berghofer00,vennes98,kruse14,parsons15}. The
difficulty in detecting white dwarf companions to FGK stars is not only due to
the extreme optical contrast between the two stars (typically the white dwarf
will only contribute $\sim$1 per cent of the potical light), but also due to
the fact that many of the largest samples of FGK stars (e.g. from the SDSS)
are lacking in bright (V<12) members because they saturate in modern survey
data. This means that these samples contain fainter stars that are located at
large distances. For example, the saturation limits for SDSS (about 14 mag in
$g$, $r$ and $i$ and about 12 mag in $u$ and $z$, \citealt{chonis08}) mean
that main-sequence FGK stars are generally located at more than 0.5\,kpc from
Earth \citep{bilir09}. At these large distances only the hottest (hence
youngest and most short-lived) white dwarf companions will be bright enough to
be detected in the UV, severely limiting the sample size (only $\sim$2 per
cent of UV-excess FGK stars in SDSS are the result of a white dwarf companion,
\citealt{smith14}). Therefore, searching for PCEBs with early-type companions
requires a sample of bright, nearby FGK stars with UV data.

To this end, we have started a project that uses data from surveys that
target bright FGK stars in combination with UV data from the Galaxy Evolution
Explorer (GALEX) database in order to detect main-sequence stars with
substantial UV-excess colours that we interpret as the result of a nearby
white dwarf companion. Follow-up ground-based spectroscopic observations can
then be used to distinguish between the close PCEBs and wide systems that
avoided a CE event. The final aim of this project is to establish the first
large sample of PCEBs with early-type components, suitable for population
synthesis studies and useful for testing models of SN\,Ia formation. The first
result from this project \citet{parsons15} was the identification of
TYC\,6760-497-1 as a white dwarf plus F-star in a 12 hour binary, which is the
first known progenitor of a SSS, i.e. the white dwarf will grow in mass in its
future evolution. In this paper we present the initial step in our project, the
selection process and sample of UV-excess FGK stars. The spectroscopic
follow-up data and identification of PCEB/wide systems will be presented in a
future paper. We have also obtained Hubble Space Telescope (\textit{HST}) UV
spectroscopy of 9 of these stars that unambiguously prove that the excesses
are indeed due to white dwarfs and we present these data in this paper.

\section{Sample selection}

In this section we outline the methods we used to select our sample of FGK
main-sequence stars with UV-excesses. Note that these stars may be close,
short-period PCEBs (the main targets of this project), or
they may be wide\footnote{Throughout this paper, the term \textit{wide
    binaries} refers to systems that did not undergo CE evolution. Such
  systems may have orbital separations of as little as $\sim$10 AU, and can
  therefore remain unresolved in the available imaging, hence we note that
  \textit{wide} should not be mistaken for \textit{spatially resolved}.} white
dwarf plus FGK binaries, or they may be a chance alignment of an FGK star with
a foreground or background white dwarf. Other potential sources of
contamination are discussed in Section~\ref{sec:contam}.

We used data from two surveys, the Radial Velocity Experiment (RAVE) survey in
the southern hemisphere and the Large Sky Area Multi-Object Fiber
Spectroscopic Telescope (LAMOST) survey in the northern hemisphere. We begin
by discussing these two samples separately.

\subsection{The southern hemisphere sample}

In order to identify main-sequence FGK stars with UV-excesses in the southern
hemisphere sky, we used data from the RAVE
survey\footnote{https://www.rave-survey.org} data release 4
\citep{kordopatis13}. RAVE is a magnitude limited survey of
randomly selected southern hemisphere stars spanning 9$<I<$12. It has
collected spectra for over 425,000 stars covering the infrared calcium triplet
(8410$-$8795\AA) with a resolution of $R\sim7500$ using the 6dF facility on
the 1.2m Schmidt Telescope at Anglo-Australian Observatory in Siding Spring,
Australia. The data are then used to determine atmospheric parameters
(effective temperature, surface gravity, metallicity) as well as a measurement
of the radial velocity of the star. For a more detailed description of the
RAVE survey we refer the reader to \citet{kordopatis13} and references
therein.

We selected all the main-sequence (non-giant, $\log{g}>3.5$) stars in the RAVE
survey with effective temperatures between 4,000\,K and 7,000\,K
(corresponding to F, G and K stars) and cross correlated them with UV data
from the GALEX survey \citep{martin05}, selecting all the sources with both
far-UV (FUV) and near-UV(NUV) measurements (with errors below 0.2 mag and no
artifacts associated to their photometry), resulting in 23,484 main-sequence
stars with good UV photometry. The distribution of effective temperatures and
FUV$-$NUV colours of these stars are shown in Figure~\ref{fig:ravedis}.

\begin{figure}
\begin{center}
 \includegraphics[width=\columnwidth,bb=10 10 500 400,clip]{RAVE_cut.eps}
 \caption{Distribution of the 23,484 RAVE dwarf stars ($\log{g}>3.5$) with
   both a GALEX FUV and NUV detection. The temperatures are taken directly
   from the RAVE DR4 catalogue. Shown in blue are two theoretical tracks
   computed from PHOENIX atmospheric models, one with a high metallicity and
   high surface gravity ($\log{Z}=+1$ $\log{g}=5.0$, top curve) and one with a
   low metallicity and low surface gravity ($\log{Z}=-3$ $\log{g}=3.5$, bottom
   curve). These represent extreme limits on the colours of main-sequence
   stars. The vast majority of RAVE stars fall within these extreme models, as
   expected. The red points mark the 430 targets that fall within our cut
   (FUV$-$NUV$<$4, T$>$4000\,K and FUV$-$NUV at least 1.5 magnitudes bluer than
   the bottom model).}
 \label{fig:ravedis}
 \end{center}
\end{figure}

We used the extensive library of PHOENIX stellar synthetic spectra from
\citet{husser13} to determine the UV colours of single main-sequence stars
over a range of temperatures by convolving the synthetic spectra with the
GALEX FUV and NUV filter profiles. We used synthetic spectra spanning surface
gravities of 3.5$<\log{g}<$5.0 and metallicities of -3.0$<\log{Z}<$1.0, but
did not include any alpha element enhancement or depletion. We found that the
UV colours of main-sequence stars are strongly affected by both their surface
gravity (due to the surface gravity dependence in the strength of the Balmer
jump, and the associated suppression of NUV flux) and their metallicity (which
causes variations in the UV opacity), leading to a spread in the FUV$-$NUV
colour of almost 3 magnitudes for stars with the same effective
temperature\footnote{activity is likely to further increase the intrinsic
  scatter, particularly for the lower mass stars}. In Figure~\ref{fig:ravedis}
we plot two tracks showing the UV colours of the bluest and reddest
main-sequence stars within our parameter range. We expect single FGK
main-sequence star from RAVE to have UV colours somewhere between these two
tracks. Indeed, Figure~\ref{fig:ravedis} shows that the FUV$-$NUV colours of
the vast majority of FGK stars in RAVE fall within these two extremes
($\simeq$99 per cent). However, there are also a small number of
stars with substantially bluer UV colours which may be caused by the
presence of a nearby white dwarf companion. We flag a star as having a
UV-excess if it has a FUV$-$NUV colour at least 1.5 magnitudes bluer than the
bluest main-sequence star models for its effective temperature(the bottom
curve in Figure~\ref{fig:ravedis}). We also place an upper limit on the
FUV$-$NUV colour of 4, to avoid including any stars with erroneous RAVE
temperatures.

In total our sample contains 430 stars with UV-excesses, these
are highlighted in Figure~\ref{fig:ravedis} as red points and are detailed in
Table~\ref{tab:ravetargs} in the appendix. The completeness and any
  sources of bias in our sample will be addressed in a future paper.

We checked our sample of UV-excess FGK stars against the list of white dwarf's
with early-type companions from \citet{holberg16}. We found that only 4 of
the 98 objects from the \citet{holberg16} catalogue are in the RAVE survey,
and only one of these, WD\,0354-368 (53,000K white dwarf plus G2 star with
a sky projected separation of $\sim$0.5\arcsec), has GALEX FUV and NUV
measurements (most objects in the \citet{holberg16} catalogue are too bright
for GALEX). However, this star did make it into our cut.

\subsection{The northern hemisphere sample}

\begin{figure}
\begin{center}
 \includegraphics[width=\columnwidth,bb=10 10 500 400,clip]{LAMOST_cut.eps}
 \caption{The UV colours and temperatures of LAMOST main-sequence FGK
   stars. We plot the same two PHOENIX models shown in
   Figure~\ref{fig:ravedis}, which represent the most extreme colours for
   main-sequence stars. Stars flagged as having UV-excesses are shown as red
   points and have UV colours at least 1.5 magnitudes bluer than the bottom
   model. The LAMOST sample does not suffer from the same discretisation
     issue seen in the RAVE sample, hence why it appers smoother.}
 \label{fig:lamostdis}
 \end{center}
\end{figure}

The Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST)
is a $\simeq$4 meter effective aperture Meridian reflecting Schmidt
telescope with a 5 degrees diameter field of view
\citep{cuietal12-1, luoetal12-1, yuanetal15-2}. As a dedicated-survey
telescope, LAMOST makes use of spectral plates to observe 4,000
spectroscopic plus calibration targets in one single exposure, equally
distributed among 16 fiber-fed spectrographs. The spectra cover the
entire optical wavelength range ($\simeq$3,700$-$9,000$\AA$) at
a resolving power of $\sim$2,000. The two main surveys carried out
by LAMOST are LEGAS (the LAMOST Extra-Galactic Survey of
galaxies), that aims at studying the large scale structure of the
Universe \citep{zhaoetal12-1}, and LEGUE (the LAMOST Experiment for
Galactic Understanding and Exploration), that aims at obtaining millions
of main-sequence star spectra to study the structure and evolution of
the Milky Way \citep{dengetal12-1}. Unlike the SDSS, the LEGUE survey
follows a target selection algorithm that is not restricted by a lower
magnitude limit \citep{zhaoetal12-1, carlinetal12-1}, thus allowing
collection of a large number of main-sequence star spectra that are bright
enough to search for white dwarf companions. This, together with the
fact that the LAMOST is located in the Xinglong observing station of
China, allows us to complement our search of white dwarf plus FGK
binaries in the northern hemisphere.

From 2012 September, the LAMOST has been performing a five-year
regular survey. Before that there was a one-year pilot survey followed
by a two-year commissioning survey. The current data product of the
LAMOST that is publicly available is data release 1 (DR1). DR1
contains a total of 2,204,696 spectra, 1,944,392 of which are
catalogued as main-sequence stars by the LAMOST pipeline
\citep{luo15}. Of these, 794,371 are flagged as F, G or K
main-sequence stars and all of them have effective
temperature, surface gravity and metallicity values derived via the
LAMOST stellar parameter pipeline \citep{wuetal14-1, xiangetal15-1}. We
selected only those objects having spectra with a signal-to-noise ratio
of greater than 10, to ensure that the stellar parameters are robust.

\begin{figure}
\begin{center}
 \includegraphics[width=\columnwidth]{tdist.eps}
 \caption{The distribution of temperatures of the UV-excess stars in our
   combined RAVE+LAMOST sample. The approximate temperature ranges for
   standard ($\log{g}=5$) F, G and K type main-sequence stars are indicated at
   the top of the plot.}
 \label{fig:tdist}
 \end{center}
\end{figure}

We cross-correlated the $\sim$800,000 LAMOST FGK main-sequence stars
with GALEX and found NUV and FUV detections for 4632
objects. In all cases the ultraviolet magnitude errors were below
0.2\,mag and no artifacts were associated to their photometry. As for the RAVE
sample, we selected white dwarf plus FGK binary candidates based on the
detection of an ultraviolet excess, defined as being, for a given temperature,
1.5 magnitudes bluer than the bluest PHOENIX main-sequence colour track (see
Figure~\ref{fig:lamostdis}). The total number of LAMOST FGK stars with
UV-excesses selected in this way is 504. These objects are detailed in
Table~\ref{tab:lamosttargs} in the appendix. As with the RAVE sample, there
was only one previously known system from the \citet{holberg16} catalogue
in the LAMOST database with good UV photometry, WD\,1024+326 (an unresolved
41,000K white dwarf plus G5 system) and this system made it into our cut.

\section{Properties of the sample}

In total we have found 934 (430 from RAVE, 504 from LAMOST) main-sequence FGK
stars that show a UV-excess that may be indicative of the presence of a nearby
white dwarf companion. In Figure~\ref{fig:tdist} we show the distribution of
temperatures (and approximate spectral types) for these stars. Approximately
half our sample consists of K-type stars (471 objects), whilst one third
are G-type stars (307 objects) and the remainder are F-type stars(156
objects).

\begin{figure}
\begin{center}
 \includegraphics[width=\columnwidth]{wdtempeff.eps}
 \caption{The effect of a white dwarf companion on the UV colours of
   main-sequence stars. The dashed line shows the FUV$-$NUV of $\log{g}=4.5$,
   solar metallicity main-sequence stars as computed from PHOENIX models. The
   solid lines show how the colours of these stars are changed due to the
   presence of a $\log{g}=8.0$ white dwarf companion at the same distance. The
   white dwarf temperatures increase in steps of 5000\,K from right to
   left. The gray points correspond to our RAVE/LAMOST UV-excess objects and
   the red points are those for which we have obtained \textit{HST} UV
   spectra.}
 \label{fig:wdtemp}
 \end{center}
\end{figure}

To estimate the range of white dwarf parameters that our sample can probe, we
combined the PHOENIX model spectra of main-sequence stars with synthetic
spectra of white dwarfs from \citet{koester10}. We used the Torres relation
\citep{torres10} to estimate the radius of the main-sequence star, and the
cooling models of \citet{holberg06} to estimate the radius of the white
dwarf. We then combined the spectra of both stars and computed the resulting
NUV$-$FUV colour. In Figure~\ref{fig:wdtemp} we show the effects on the
NUV$-$FUV colour of varying the temperature of the white dwarf, while keeping
its surface gravity fixed at $\log{g}=8.0$. The figure shows that our sample
could potentially contain systems with white dwarfs as cool as 10,000K next to
K stars, 15,000K next to G stars and 20,000K next to F stars, hence covering a
large range of cooling times. However, the effects of surface gravity are also
important. Figure~\ref{fig:wdlogg} shows the results of keeping the
temperature of the white dwarf fixed at 20,000K and varying it's surface
gravity. The figure shows that surface gravity only has a very minor effect on
the detectability of a white dwarf next to a K star and only a moderate effect
next to a G star. However, when placed next to an F star the surface gravity
of the white dwarf is important for its detectability. High surface gravity
(hence more massive and smaller) white dwarfs only contribute a small fraction
of the overall UV flux against an F star and hence these binaries would not be
detected in our cut. The situation is better at higher temperatures, above
$\sim$25,000K any white dwarf should be detected, regardless of its surface
gravity. Therefore, our sample of systems with F stars likely contains only
the younger members. Fortunately, given the shorter main-sequence lifetimes of
F stars (compared to later spectral types), there is unlikely to be a large
population of these stars with cool ($T_\mathrm{eff}<20,000$K) white dwarf
companions.

\begin{figure}
\begin{center}
 \includegraphics[width=\columnwidth]{wdlogg.eps}
 \caption{Same as Figure~\ref{fig:wdtemp} but placing 20,000K white dwarfs
   with varying surface gravity next to $\log{g}=4.5$, solar metallicity
   main-sequence stars. The white dwarf surface gravity increases from left
   to right in steps of 0.5 dex.}
 \label{fig:wdlogg}
 \end{center}
\end{figure}

To reinforce this point we simulated the evolution of a population of binaries
with FGK-type secondary stars in order to see the distribution of white dwarf
temperatures in the resulting population. The simulations were performed
in the same way as in \citet{zorotovic14b} assuming a flat initial-mass-ratio
distribution, a common envelope efficiency of 0.25, solar metallicity and
without any contribution from recombination energy. Our results include all
type of detached white dwarf plus FGK systems, not only PCEBs, but also wide
system. The binary star evolution code from \citet{hurley02} uses very old
models \citep{mestel52} to calculate the white dwarf effective
temperature. Therefore, more accurate values were calculated following
\citet{zorotovic16} i.e. by using the cooling tracks from \citet{althaus97}
and from \citet{fontaine01} for helium-core or carbon/oxygen-core white dwarf
respectively. Figure~\ref{fig:simu} clearly shows that there is a lack of
systems containing white dwarfs with temperatures below $\sim$15,000K with
F-type companions (which would be found in the top-left of the plot), because
the F stars have also evolved and these systems are now double white dwarf
binaries. Figure~\ref{fig:simu} does suggest that we are missing a small number
of F stars with 15,000-25,000K white dwarf companions. Note that it is
possible for main-sequence stars with a large range of masses to all have
temperatures close to 6,200K (stars between 1.0 and 1.5{\mbox{$\mathrm{M_{\odot}}$}} can have
temperatures close to 6,200K depending upon their surface gravity) and hence
there is a peak in the distribution shown in Figure~\ref{fig:simu} for stars
of this temperature.

\begin{figure}
\begin{center}
 \includegraphics[width=\columnwidth]{simul.eps}
 \caption{Simulated distribution of white dwarf and main-sequence star
   temperatures. Our sample of UV-excess objects does not cover systems
   containing cool ($T_\mathrm{eff}<20,000$K) white dwarfs and hot (F-type,
   $T_\mathrm{eff}>=6,500$K) main-sequence stars. However, this plot shows
   that the population of systems of this type is very minor and therefore we
   are not missing a large number of systems. The intensity of the grey-scale
   represents the density of simulated objects in each bin, on a linear scale,
   and normalized to one for the bin that contains most systems.}
 \label{fig:simu}
 \end{center}
\end{figure}

\begin{figure}
\begin{center}
 \includegraphics[width=\columnwidth]{wdtempeff_ex.eps}
 \caption{Same as Figure~\ref{fig:wdtemp} but with a $\log{g}=3.5$ metal poor
   ($\log{Z}=-3.0$) main-sequence star.}
 \label{fig:wdtemp2}
 \end{center}
\end{figure}

\begin{figure}
\begin{center}
 \includegraphics[width=\columnwidth]{wdlogg_ex.eps}
 \caption{Same as Figure~\ref{fig:wdlogg} but with a $\log{g}=3.5$ metal poor
   ($\log{Z}=-3.0$) main-sequence star.}
 \label{fig:wdlogg2}
 \end{center}
\end{figure}

Finally, the parameters of the main-sequence star (beyond its surface
temperature) also have an effect on the detectability of a white dwarf
companion. In Figure~\ref{fig:wdtemp2} and Figure~\ref{fig:wdlogg2} we show
the same plots as before, but with low surface gravity, metal poor
main-sequence stars, which have the bluest UV colours. In this case the
detectability is reduced in all circumstances and is particularly challenging
in the case of F stars, where even the hottest white dwarfs only produce an
excess of one magnitude, hence our sample is likely to contain only very few
such stars. Only 5 per cent of our UV-excess stars are metal poor
($\log{Z}<-1$) and all of these are K stars. Likewise, only 25 per cent of our
sample are low surface gravity stars ($\log{g}<4$), of which the majority
(65 per cent) are K stars and most of the rest (30 per cent) are G stars.

\section{Hubble Space Telescope UV observations} \label{sec:hst}

\subsection{Observations and their reduction}

We spectroscopically observed 9 UV-excess objects with \textit{HST} in order
to confirm that the excess is due to a white dwarf companion. Depending upon
the brightness of the target we either used the Space Telescope Imaging
Spectrograph (STIS) or the Cosmic Origins Spectrograph (COS). All observations
we obtained within program GO 13704 between October 2014 and July 2015 and
are summarised in Table~\ref{tab:hstobs}. For the STIS observations we used
the G140L grating centered on 1425{\AA} and for the COS observations we used
the G130M grating centered on 1291{\AA}. Each target was observed for one
spacecraft orbit. The data were processed using {\sc calstis} V3.4 and
{\sc calcos} V3.1.

\begin{table}
 \centering
  \caption{Log of \textit{HST} observations.}
  \label{tab:hstobs}
  \begin{tabular}{@{}llll@{}}
  \hline
  Target             & Instrument & JD start & Exp (s) \\
  \hline
  CD-68\,2365        & STIS       & 2457182.2344 & 2712 \\
  LAMOST\,J1122+5236 & COS        & 2457015.3989 & 2309 \\
  LAMOST\,J1445+1236 & STIS       & 2457131.3753 & 2362 \\
  LAMOST\,J1528+4305 & COS        & 2456961.7038 & 2109 \\
  TYC\,6760-497-1    & STIS       & 2457031.7870 & 2381 \\
  TYC\,6917-654-1    & COS        & 2456987.8214 & 1977 \\
  TYC\,6996-449-1    & STIS       & 2457001.6869 & 2418 \\
  TYC\,7218-934-1    & COS        & 2457151.5144 & 2175 \\
  TYC\,7218-934-1    & COS        & 2457150.4747 & 2175 \\
  TYC\,9151-303-1    & COS        & 2457233.8558 & 2440 \\
  \hline
\end{tabular}
\end{table}

\subsection{Results}

We show the STIS and COS spectra in Figure~\ref{fig:stis} and
Figure~\ref{fig:cos} respectively. We confirm the presence of a white dwarf in
8 of the 9 observed systems. The analysis of TYC\,6760-497-1, which also
contains a white dwarf, was previously presented in \citet{parsons15} and is
not shown again. One system, LAMOST\,J1528+4305, appears to contain a
pre-white dwarf object. In this case the narrow Ly$\alpha$ line implies that
this object has a low surface gravity ($\log{g}\sim5$), which is too low for a
typical white dwarf. However, the blue continuum slope shows that the UV flux
originates from a hot star and is clearly not from the 4,700\,K main-sequence
star seen in the optical. Therefore, this hot object is fainter than the
main-sequence star in the optical and hence must be smaller. Therefore, we
suspect that this object could be either a hot subdwarf star or a pre-helium
white dwarf (similar to the objects seen in EL\,CVn type binaries
\citealt{maxted14}). The spectra of LAMOST\,J1122+523, LAMOST\,J1528+4305 and
TYC\,6917-654-1 also show narrow metal lines that may either be interstellar
or due to the white dwarf accreting wind material from the main-sequence star,
which may be an indication that some of these systems are close binaries
\citep[e.g.][]{parsons15}. All the spectra also show some geocoronal emission
in the core of the Ly$\alpha$ line and most of the COS spectra show geocoronal
airglow of O{\sc i} at 1310\AA. In at least one case, CD-68\,2365 in
Figure~\ref{fig:stis}, the main-sequence star appears to contribute a
noticeable flux towards the red end of the spectrum.

\begin{figure}
\begin{center}
 \includegraphics[width=\columnwidth]{stis.eps}
 \caption{\textit{HST} STIS UV spectra of three of our UV-excess objects, clearly
   showing that the excess is the result of a nearby white dwarf. Also shown
   are the best fit white dwarf model spectra assuming a mass of
   0.6\mbox{$\mathrm{M_{\odot}}$}.}
 \label{fig:stis}
 \end{center}
\end{figure}

\begin{figure}
\begin{center}
 \includegraphics[width=\columnwidth]{cos.eps}
 \caption{\textit{HST} COS UV spectra of five of our UV-excess objects, clearly
   showing that the excess is the result of a nearby white dwarf. Also shown
   are the best fit white dwarf model spectra assuming a mass of
   0.6\mbox{$\mathrm{M_{\odot}}$}, with the exception of LAMOST\,J1528+4305, that cannot be fitted
   with a standard white dwarf model (see text). A $log{g}=5$ model is shown
   instead.}
 \label{fig:cos}
 \end{center}
\end{figure}

We fitted TLUSTY/SYNSPEC \citep{hubeny95} white dwarf model spectra to each
of our \textit{HST} observations. With the UV data alone it is not possible to
simultaneously solve for the surface gravity, temperature and distance of the
white dwarf. Therefore, we fix the mass of the white dwarf at 0.6\mbox{$\mathrm{M_{\odot}}$} (close
to the mean observed value for DA white dwarfs, \citealt{liebert05, falcon10})
and fitted the spectrum to get an estimate of the temperature and distance for
the white dwarf. The best fit models are overplotted in red in
Figure~\ref{fig:stis} and Figure~\ref{fig:cos} and detailed in
Table~\ref{tab:dists}. Note that in the case of LAMOST\,J1528+4305, where the
nature and hence radius of the compact star are unknown, we were unable to
determine a reliable distance estimate.We also estimated the distance to the
corresponding main-sequence stars in these systems by fitting their spectral
energy distributions (SEDs) using the virtual observatory SED analyzer (VOSA;
\citealt{bayo08}). We used archival optical data from the TYCHO and NOMAD
catalogues and infrared data from the 2MASS and WISE databases. We fitted the
SED with BTSettl models \citep{allard12} and kept the physical parameters of
the stars (effective temperature, surface gravity and metallicity) fixed at
the values from the RAVE and LAMOST databases and scaled the models to best
fit the SED, then used the resulting scale factor to determine the distance to
the star. The results are listed in Table~\ref{tab:dists}.

\begin{figure*}
  \begin{center}
    \includegraphics[width=0.95\textwidth]{all_sed.eps}
    \caption{Spectral energy distributions for 8 UV-excess objects observed
    with \textit{HST}. Photometric measurements are shown in red (errors
    smaller than the symbol size) and are taken from GALEX (UV), TYCHO and
    NOMAD (optical) and 2MASS (near-infrared). The \textit{HST} spectra are
    shown in black. We also plot the best fit model spectra for the white
    dwarfs (blue lines) and main-sequence stars (green lines). For
    TYC\,6996-449-1 there is a substantial difference between the \textit{HST}
    flux and GALEX UV measurements. We believe that this is due to the white
    dwarf and main-sequence star being a spatially resolved binary (or the
    white dwarf is a background source) separated by a few tenths of an
    arcsecond. Since the \textit{HST} acquisition for STIS observations is
    done in the optical the slit may not have been properly centred on the
    white dwarf (but rather on the main-sequence star) resulting in slit
    losses.}
  \label{fig:seds}
  \end{center}
\end{figure*}

\begin{table*}
 \centering
  \caption{Distance and physical parameter estimates to the white dwarfs
    (assuming $\log{g}=8.0$) and main-sequence stars in the systems observed
    with \textit{HST}. Typical uncertainties in the white dwarf temperatures
    are $\pm500$K. The main-sequence star parameters are taken from the
    RAVE/LAMOST pipelines. A reliable estimate of the distance to the hot
    component in LAMOST\,J1528+4305 is not currently possible as the nature
    of the star (and hence its radius) is unknown.}
  \label{tab:dists}
  \begin{tabular}{@{}lcccccc@{}}
  \hline
  Target & White dwarf & White dwarf & MS star & MS star & MS star & MS star \\
         & T$_\mathrm{eff}$ (K) & distance (pc) & T$_\mathrm{eff}$ (K) & $\log{g}$ & $\log{Z}$ & distance (pc) \\
  \hline
  CD-68\,2365        & $17,500$              & $271$          & $6159 \pm 66$  & $3.91 \pm 0.13$ & $ 0.00 \pm 0.10$ & $235 \pm 20$  \\
  LAMOST\,J1122+5236 & $26,000$              & $430$          & $4437 \pm 86$  & $3.95 \pm 0.34$ & $-0.71 \pm 0.39$ & $505 \pm 60$  \\
  LAMOST\,J1445+1236 & $24,000$              & $726$          & $6225 \pm 159$ & $4.20 \pm 0.46$ & $-0.61 \pm 0.40$ & $945 \pm 100$ \\
  LAMOST\,J1528+4305 & $24,000$              & -              & $4734 \pm 47$  & $2.99 \pm 0.45$ & $-0.09 \pm 0.20$ & $480 \pm 55$  \\
  TYC\,6917-654-1    & $25,000$              & $170$          & $6503 \pm 127$ & $4.01 \pm 0.21$ & $-0.25 \pm 0.13$ & $190 \pm 20$  \\
  TYC\,6996-449-1    & $16,500$              & $1400$         & $5937 \pm 95$  & $3.96 \pm 0.15$ & $-0.24 \pm 0.10$ & $425 \pm 40$  \\
  TYC\,7218-934-1    & $16,500$              & $165$          & $5746 \pm 95$  & $3.97 \pm 0.15$ & $-0.01 \pm 0.10$ & $190 \pm 15$  \\
  TYC\,9151-303-1    & $16,500$              & $151$          & $6161 \pm 95$  & $4.63 \pm 0.18$ & $ 0.13 \pm 0.11$ & $205 \pm 25$  \\
  \hline
\end{tabular}
\end{table*}

In Figure~\ref{fig:seds} we plot the UV to infrared SEDs of all eight systems
observed with \textit{HST} and the best fit white dwarf and main-sequence star
models. We do not show the RAVE spectra, since they cover a very small
wavelength range (near the Ca{\sc ii} infrared triplet), or the LAMOST
spectra, since the flux calibration of LAMOST spectra is relative
\citep{song12}. We found that in all but one case the distance derived for the
white dwarf and main-sequence star in reasonable agreement and therefore the
stars are likely in a physically associated binary, some of which may be
PCEBs, which we are aiming to identify in this sample (although additional
data are required to confirm this). However, we note that the distance
estimates to both stars are subject to systemic uncertainties. For determining
the distances to the white dwarfs, we fixed their masses at 0.6\mbox{$\mathrm{M_{\odot}}$}, however,
if their actual masses are higher (lower) then their radii will be smaller
(larger) and hence they will be closer (further) than our estimates. Likewise,
the uncertainties on the physical parameters of the main-sequence stars lead
to a relatively large spread of possible distances. More accurate and precise
distances to the main-sequence stars will soon be available once the results
of the \textit{Gaia} mission are published. Only in one system,
TYC\,6996-449-1, is there is a clear discrepancy between the distance
estimates of the two stars, where the implied distance to the white dwarf is
more than three times that of the main-sequence star's. Forcing this white
dwarf to the same distance as the main-sequence star would require it to have
a mass in excess of the Chandrasekhar mass. However, inspection of
Figure~\ref{fig:seds} reveals that the flux of the \textit{HST} spectrum for
this object falls substantially below its measured GALEX magnitudes. We
believe that this is due to slit losses during the \textit{HST} observations,
caused by the fact that acquisition for STIS observations are done in the
optical, meaning that the slit is centered on the main-sequence star. If
there is a small offset between the main-sequence star and white dwarf
(i.e. if this system is a spatially resolved  binary or chance alignment),
then the 0.2{\arcsec} slit will not be properly centred on the white dwarf
component. This renders the white dwarf distance estimate unreliable and also
implies that this system is not a PCEB. However, re-scaling the COS spectrum
to fit the GALEX measurements reduces the distance to the white dwarf and
brings it into agreement with that of the main-sequence star, therefore, this
is likely to be a spatially resolved binary. Despite the fact that the
optical and GALEX  positional information for this target are coincident to
within 0.25\arcsec, the resolution and precision of the GALEX astrometry means
that we cannot exclude a spatial resolution of a few tenths of an arcsecond
between the main-sequence component and the white dwarf in any of our
systems. This means that, with the current data, we cannot easily distinguish
between PCEBs and main-sequence stars with nearby foreground/background white
dwarfs or wide binaries.

\section{Discussion}

\subsection{Sources of contamination} \label{sec:contam}

Our sample of UV excess FGK stars contains close PCEBs (at least one has been
identified already, \citealt{parsons15}), wide binaries (with spatial
separations $\lesssim$0.25\arcsec) and chance alignments between FGK stars and
foreground or background UV bright sources (this includes white dwarfs, but
also hot subdwarfs and quasars).

Several other types of object that could potentially contaminate our sample.
The hot chromospheres of active stars can result in them possessing quite blue
UV colours. Additionally, any active star that flared during GALEX
observations may make it into our sample. Previous investigations of FGK stars
in SDSS determined that the strong chromospheres of some stars was likely the
cause of most UV excesses, particularly at later spectral types
\citep{smith14}. Recall that SDSS FGK stars are generally too distant to
detect any white dwarf companions and therefore the sample is dominated by
other types of UV-bright sources. Indeed, several stars in our sample are
known to be active and are listed as such in the SIMBAD database. However, the
vast majority of these are at the cooler end of our sample and hence are K
stars.

As well as isolated active main-sequence stars, stars in close binary systems
can be spun-up and become active. Therefore, its possible that our sample is
contaminated by some active binaries. These are FGK plus M dwarf
binaries in which the unseen M dwarf has been spun-up and a flare from this
stars, or its strong chromosphere, is detected by GALEX. Since it appears that
most, if not all, M dwarfs in close binaries are active \citep{rebassa13},
this may be a source of contamination across our entire sample. Indeed,
several objects in our sample are listed as binary stars in SIMBAD (either
W\,UMa or RS\,CVn type variables). However, the fact that none of the systems
we observed with \textit{HST} were these types of binaries implies that the
contamination is relatively low.

Finally, we note that RR\,Lyrae stars can have NUV$-$FUV colours of between
$\sim$3$-$5 \citep{kinman14}, which places them within our cut. Generally,
most RR\,Lyrae stars are too faint to make it into our sample. However, while
there were no known RR\,Lyrae stars in our RAVE sample, there were 3 in our
LAMOST sample (since the LAMOST sample goes $\sim$2 mag deeper than RAVE), all
of which are at the fainter end of the sample (V>12).

Given that all our \textit{HST} observations confirmed the presence of hot,
compact companions we conclude that there are few contaminating sources.
However, we note that our \textit{HST} observations mainly cover the
  larger UV excess objects and therefore more detailed observations are
required to better quantify this.

\subsection{Testing compact binary evolution}

This large sample of white dwarf plus FGK star binaries has the potential to
address several important questions relating to the evolution of compact
binaries and SN\,Ia formation. An initial step is to use spectroscopic data to
identify the PCEBs within the sample and measure their orbital
periods, a task that we have begun. High-resolution imaging can also be used
to identify the wide binaries and chance alignments.

One of the most interesting results from the handful of known PCEBs with
early-type components is that they can have a much larger range of orbital
periods after the CE stage \citep{zorotovic14}. While PCEBs containing M
dwarfs generally have periods below $\sim$10 days \citep{nebot11}, several
PCEBs containing early type stars have much longer periods. For example, the
white dwarf plus G5 binary KOI-3278 has a period of 88.2 days
\citep{kruse14}, while the white dwarf plus A8 binary IK\,Peg has a period of
21.7 days \citep{vennes98}. Conversely, there are still systems with very short
periods such as the 12.5 hour white dwarf plus K2 binary V471\,Tau
\citep{nelson70} or the 12 hour white dwarf plus F8 binary TYC\,6760-497-1
\citep{parsons15}. This suggests an additional source of energy is
  required during the CE phase in order to expel the envelope quickly enough
to prevent the two stars getting too close \citep{zorotovic10,rebassa12b},
although it is not clear what the source of this energy is
\citep{ivanova15}. This is particularly relevant to the
evolution of double white dwarf binaries, since the two stars must emerge from
the first CE far enough apart to survive the second CE phase. So far, models
of the CE phase have struggled to simultaneously replicate the observed
populations of very close white dwarf plus M dwarf binaries and the population
of double white dwarf binaries, requiring two different formalisms to create
each population \citep{nelemans00,toonen13}. Therefore, a large,
well-characterised set of PCEBs with FGK components would be an extremely
valuable population for formulating a more complete description of the CE
phase itself, since it contains systems that emerged from the CE phase with
both very short and long orbital periods.

This is also a particularly important subject for determining the progenitors
of SN\,Ia. Constraining the orbital period distribution of white dwarfs with
FGK companions (which will require additional spectroscopic observations)
will allow us to determine the fraction of systems following
the single and double degenerate formation channels. Moreover, our project has
already uncovered one system that will undergo a phase of thermal timescale
mass-transfer in the future \citep{parsons15} and hence, in this case, the
white dwarf will grow in mass. Given that it may be possible for
sub-Chandrasekhar mass white dwarfs to explode as SN\,Ia via the
double-detonation model it may even be that our sample contains some genuine
SN\,Ia progenitors.

\section{Conclusions}

We have presented a large population of 934 bright main-sequence F, G and K
type stars with UV excess colours that are likely the result of nearby white
dwarf companions. \textit{HST} spectra of nine of these objects has confirmed
that these are white dwarf plus main-sequence star binaries (in one case the
companion is likely a hot subdwarf star or pre-helium white dwarf) and there
appears to be very little contamination, at least among the larger UV
  excess objects. This previously undetected group of objects has the
potential to address a number of key questions relating to binary star
evolution and improve our understanding of the common-envelope
stage. Moreover, it will also constrain the ratio of binaries that undergo a
single common-envelope event to those that will undergo two, with clear
implications for the study of type Ia supernovae.

\section*{Acknowledgements}

We thank the referee for helpful comments and suggestions. SGP and MZ
acknowledge financial support from FONDECYT in the form of grant numbers
3140585 and 3130559. This research was partially funded by MINECO grant
AYA2014-59084-P, and by the AGAUR. The research leading to these results
has received funding from the European Research Council under the European
Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement
n. 320964 (WDTracer). MRS thanks for support from FONDECYT (1141269) and
Millennium Science Initiative, Chilean ministry of Economy: Nucleus
P10-022-F. JJR acknowledges support by National Key Basic Research Program of
China 2014CB845700. Funding for RAVE has been provided by institutions of the
RAVE participants and by their national funding agencies. Guoshoujing
Telescope (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope,
LAMOST) is a National Major Scientific Project built by the Chinese Academy of
Sciences. Funding for the project has been provided by the National
Development and Reform Commission. LAMOST is operated and managed by the
National Astronomical Observatories, Chinese Academy of Sciences.

\bibliographystyle{mnras}

redpajama_set_name: RedPajamaArXiv


Back in 2012, I wrote about the Cross-State Air Pollution Rule (CSAPR) and the impacts of pollution that traveled via wind from one state to another. It was a look at the effects of dirty air from "upwind" states on "downwind" states.
Now, 5 years later, a study released December 2017 by Muzhe Yang (Associate Professor in the Economics Department) and Shin-yi Chou (Professor of Economics) of Lehigh University has proven the validity of the "cross-state" air pollution premise. They have authored the paper, The Impact of Environmental Regulation on Fetal Health: Evidence from the Shutdown of a Coal-Fired Power Plant Located Upwind of New Jersey.
Ozone pollution, or smog, is carried by the wind. This pollution has decreased over time, in part thanks to mandates to reduce dangerous emissions. Yet, climate change exacerbates air pollution, as heat makes ozone pollution and smog worse. Increased heat waves that are expected to come with climate change could mean ozone pollution won't fall as fast as it would under normal conditions.
The analysis of this study examines a specific coal-fired power plant situated on the state borderline between Pennsylvania and New Jersey.
The facility in question was the Portland Generating Station, which was on the Pennsylvania side of the Delaware River. Its shut down in 2014 had a major ramification for the downwind residents of New Jersey. Data revealed a 15 percent reduction in the numbers of low birth weight babies, and a decrease in the occurrence of preterm births by 28 percent.
The results emphasized potential accomplishments when the power of federal law, under the Clean Air Act, supersedes state regulatory directives.
The ruling from the EPA categorized the installation as "a sole pollution source" harming the air quality of New Jersey. The state counties included Warren, Sussex, Morris, and Hunterdon.
The research drilled down on a look at the pollution coming from plant eighteen months prior to its termination. It showed sulfur dioxide emissions at 2,596.648 tons monthly. In the same time span (eighteen months) after the closing, the emissions measured almost zero.
The information was collected from zip codes covering downwind areas within sixty miles of the plant.
Earlier in 2017, a related report by Yang and Chou, with two other writers, showed that infants born during 1990-2006 had a 6.5 percent greater risk of low birth weight and a 17.12 percent greater risk of a very low birth rate (less than 5.50 pounds). This applied to mothers residing within a twenty to thirty-mile radius.
The creators of the reports believe that the EPA should be more proactive in taking individual states to task when their actions affect the health and well-being of their neighbors.
They also noted that when studies have been done to gauge the connection between public health and the Cross-State Air Pollution Rules, fetal health concerns have been overlooked. In light of the fact that there has been ongoing evidence to show that fetal health is a benchmark for outcomes in later life — from physical health to education and earnings — it seems like an obvious oversight.
And a refresher for those who don't remember the actions of current EPA head, Scott Pruitt, back in 2011 when he was the Attorney General of Oklahoma…he sued the EPA over the Cross-State Air Pollution Rule.
The impacts of emissions from coal-fired power plants directly affect the fetal health of our babies. Please take a look at this WIND MAP and you can see how the children in your state share the air with other states.


text:
Reverse Engineering the Boeing E-3 Sentry's Secondary Flight Controls
By Scott KnocheNews
Reverse Engineering the Boeing E-3
Sentry's Secondary Flight Controls
Read this article on the Aerospace & Defense Technology site HERE
The Boeing E-3 Sentry has stood the test of time. The E-3 Airborne Early Warning and Control System (AWACS) was first carried aboard militarized 707 commercial aircraft with the first E-3 entering U.S Air Force service in 1977.
Reverse Engineering Aircraft Components
Amplify Technical Solutions was contracted to reverse engineer and manufacture a first article assembly of the secondary flight controls, focusing on the throttle quadrant and console configuration, for a NATO E-3 AWACS. Reverse engineering aircraft components is one of the specialties of Amplify. The finished deliverables were part of a sophisticated flight simulator controls system being produced by Simulation and Control Technologies for an E-3 AWACS Full Flight Simulator program. The project presented challenges due to the vintage and highly evolved state of the aircraft, which required creative engineering to accurately capture and replicate the control assemblies.
The NATO E-3 AWACS has stood the test of time. The E-3 Airborne Early Warning and Control System (AWACS) was first carried aboard militarized Boeing 707 commercial aircraft with the first E-3 entering U.S Air Force service in 1977.
Government Furnished Equipment (GFE), non-working throttle quadrant from an earlier configuration was made available for dissection and reference.
Throughout its history, the AWACS fleet has undergone extensive enhancements, including upgrades to radar, avionic suites, satellite communications and air traffic management. But under it all is still the old reliable 707 built between 1958 and 1979.
With many upgraded E-3s still in service, it is important to provide comprehensive pilot training based on new standards and techniques developed over the years, which includes foremost, flight simulator training. Today's modern flight simulators, or trainers as they are
called, are about as real as it gets, providing a safe learning environment without the costs and risks of putting planes in the air. Pilots can train on the latest innovations and have capabilities assessed in a controlled situation, with presentation, review, and playback. The challenge with legacy platforms like the 707 is getting ergonomic and tactile features and controls of an old aircraft into a new trainer. For this project, Government Furnished Equipment (GFE) would typically be provided to work from, but in this case, there was not much available – no spare assemblies, and the boneyards had been picked clean.
Original throttle configuration: final was re-engineered to support the current model.
In order to recreate an exact replica of the controls for the current E-3 configuration, our team was given one-time access for three days to an existing trainer. We were also provided a single, non-working throttle quadrant from an earlier configuration that could be dissected, referenced, and re-engineered to match current specs. This meant that literally every component needed to be reverse-engineered and then re-engineered using photos, hand measurements, 3D scans, and measurement software.
REVERSE ENGINEERING AND RE-ENGINEERING THE THROTTLE QUADRANT
The most complex assembly of the project was the throttle quadrant containing over 300 components. The entire assembly needed to be reverse engineered, then re-engineered for design and simulator performance, within .005″ tolerance or better across the entire unit. The redesigned quadrant was manufactured and given a single part number to directly replace the GFE part number referenced within the drawing package. The production package requirement for the throttle quadrant included:
Detailed CAD model
Drawing package in Native CAD format
Separate parts list in PDF and Excel format
Drawings in PDF and DWG (AutoCAD)
Complete drawing trees
Drawing delivery list
Fabrication and assembly support for first article assembly
THE REVERSE ENGINEERING TOOLSET USED ACROSS THE PROJECT INCLUDED:
Verisurf software for 3D scanning, touch-probing, and reverse engineering
Mastercam software for re-engineering and final CAD modeling
Creaform HandySCAN Black 3D scanner
Master3DGage, portable Coordinate Measuring Machine (CMM)
Manual measurement instruments for capturing simple geometry, friction, and lever forces
FORM, FIT AND FUNCTION REQUIRED
When reverse engineering and re-engineering the throttle quadrant, form, fit, and function were required. The geometry and surface profile of every part had to be exact. When aviating, controls are often identified by touch and feedback. Everything needs to look right, feel right, and move right.
3D PROFILE SCAN
Using Verisurf software and a Creaform HandySCAN Black 3D scanner, key control elements, including the throttle quadrant installed in the reference trainer, were scanned in high-resolution. Verisurf software was then used to convert captured point cloud data to a triangular mesh model. From there, individual parts relative to the assembly could be isolated, extracted, measured, and modeled to CAD, within the software. Reference entities such as points, lines, and circles, as well as geometric features including planes, cylinders, slots, cones, and spheres, could be extracted and applied as individual features of reverse-engineered parts.
The software's ability to measure and compare centricity illustrated variations up to .030″ – which in this project is like a football field – across the barrel-shaped base that guides the throttle levers. Each of the throttle levers also had unique geometry that had to be taken into consideration, including the profile of each throttle guide plate relative to the curved base. Every nuance of the controls had to be exact. The form, features, and functions of the trainer, compared to the actual cockpit, needed to fit like an old glove.
Point cloud data image from complex profile scan.
Verisurf software used to measure centricity of the base and to capture mounting surface profile for throttle guide plates.
Each of the captured parts making up the overall profile was committed to CAD and any design variations added to comply with the E-3 version the trainer was meant to emulate. The challenge now was to make the quadrant move and feel right while providing input to the actuators interfacing with the simulation software.
RE-ENGINEERING FOR FUNCTIONALITY AND PERFORMANCE
Verisurf software used to isolate throttle levers and guide plates from the original surface profile scan. Note planes and edges highlighted for capture of geometry and conversion to CAD.
Having fully dissected the scan data from the reference trainer and committed the visible features to CAD, it was now time to get inside the supplied legacy throttle quadrant and reverse engineer its movements. Bear in mind, aircraft controls are not made to come apart; trainers must have the same integrity and durability but must be field serviceable and be easily taken apart and put back together to minimize trainer downtime over the expected 15- to 20-year life cycle. This was a critical objective of the re-engineering process.
The throttle quadrant was completely disassembled; along the way, each component was measured and documented to understand the assembly of the original GFE. This was to ensure everything was accurately represented in the CAD model to help alleviate issues between the reused components and the re-engineered components. Areas that needed acute attention for the design included where components connect, touch, or interact during the throttle movement. Forces and positions were accounted for, including pulley sizes, cable diameters, detents, stops, and connections to actuators.
Throttle levers and sub assembly under development in CAD. Exposed profile of throttle levers was captured and converted to CAD using Verisurf software.
A force gauge, calipers, and a digital inclinometer were all used to measure and determine range of movement, mechanical friction, and applied forces. Also noted were special areas and envelopes that need to be off-limits during re-engineering. During disassembly, parts that could be used in the re-manufacturing of the quadrant were identified, including the original throttle knobs, speed brake, and flap position levers.
When re-engineering the throttle quadrant, it was critical that the system looked and behaved exactly like the legacy unit. As long as those two criteria were met, design modifications could be implemented inside the unit. This was important as the legacy assembly was completely mechanical and the re-engineered assembly would serve as a mechanical interface to a digitally controlled trainer.
Typically, reverse engineering processes are applied to a part or individual component, removed from an assembled system. This allows the entire geometry to be captured using measurement software and CMMs with touch probes or non-contact scanners. Using Verisurf software, the process is fast, accurate, and very comprehensive. Isolated parts are quickly converted from point clouds to intelligent CAD models.
REVERSE ENGINEERING SOFTWARE
Finished profile of the throttle quadrant reverse engineered using Verisurf software. Captured and defined geometry was exported to Mastercam software for re-engineering and assembly of an intelligent 3D CAD model.
In the case of the E-3 throttle quadrant, the value of the Verisurf software took on an increased level of importance, especially given the stated overall profile tolerances of .005″ all around.
The software was able to capture high-resolution point cloud data and create a watertight mesh model, effectively connecting all the assembled components and features as they relate to the overall assembly;
Verisurf software was able to isolate features, extracting only selected geometry to be converted into intelligent CAD files;
After converting scan data to CAD models, Mastercam was used to assemble all parts into a final CAD assembly file.
Finished throttle quadrant – reverse engineered, re-engineered, and assembled.
A project such as this cannot be done using "just" CAD. Most CAD systems can handle small scan data files imported directly into their system as an STL mesh surface and converted to a usable model file. In this case, the scan included many parts scanned as an assembly, which creates a very complex data set. A CAD system would be able to open this data file eventually, with enough power, but all the data points would be converted into a polygon mesh, giving you an approximation of the surfaces scanned. CAD systems see this polygon mesh as geometry/surfaces, which bogs the system down to a crawl and only allows data points to be taken from exterior/intersecting mesh points of the polygon. This greatly reduces the precision of the measurement and anyone who has done it knows that it can take hours to get very little data from these files.
Verisurf software can manipulate that same data with ease, allowing captured features to be accurately extracted and converted to intelligent CAD. Individual points can be completely isolated from the main scan. Measurements can be taken, and edges and planes can be referenced, before exporting the feature to CAD. This ability of Verisurf software to break down complex scan data to individual components was instrumental in reverse engineering the throttle quadrant and console.
When reverse engineering complex assemblies, it is important to have tool options. For some components, hand measuring and 3D modeling is all that is necessary, but in the case of recreating complex surface profiles and extracting features to CAD, the right measurement and reverse engineering software can be invaluable.
This article was written by David Fleury, President, Amplify Technical Solutions LLC (Leonardtown, MD).
Verisurf Software, Inc.
Verisurf Software, Inc. is an advanced three-dimensional measurement solutions company committed to delivering advanced computer-aided inspection and reverse engineering solutions. Verisurf software helps manufacturers of all sizes and industries produce higher quality products in less time and at a lower cost with automated, Model-Based Inspection processes. For more information, visit the Verisurf website at https://verisurf.com.
3D Scan-to-CAD3D ScanningCAD/CAMReverse Engineering

redpajama_set_name: RedPajamaCommonCrawl


The web is a wonderful thing, brimming with resources and inspiration for people wanting to present information in an exciting and dynamic way. But, sometimes, too much choice can be confusing, so we've picked 10 top sites that will really help you get to grips with it.
If you're after infographics and data visualization inspiration, Visual.ly is a brilliant starting point. Featuring over 33,000 examples, this site describes itself as 'the world's largest community of infographics and data visualization'. Artwork is helpfully organised into specific topics for easy navigation. Each piece also features details of the artist behind it, as well as a short description and link to the original source.
Featuring thousands of inspirational images, Pinterest is full of beautiful examples of data visualization. Simply use the keyword search tool and watch the screen fill up with awesome infographics in every subject you can imagine from artists all over the world!
Artists all over the world have a Behance portfolio, which makes it a great resource for finding brilliant examples of data visualization. Use they keyword search tool to find exactly what you're looking for, then organise the work by most recently posted, most appreciated, featured and more. A brilliant place to find new, undiscovered artwork.
This site does exactly what it says on the tin, or title. Delivering a new infographic each day, the team behind Daily Infographic spend countless hours searching the web for the most interesting, stimulating, mind-blowing infographics. They then curate their findings and choose one infographic to publish every week-day.
Submit Infographics by Killer Infographics is a user generated gallery, in which artists everywhere can submit their infographic to be featured on the site. Work featured comes complete with a review, link back and an audience that loves data visualization. It's all free, all the team behind the site ask for in return is a like on the site's Facebook page.
This blog is run by London-based author, writer and designer David McCandless. Being a lover of data visualisation, McCandless uses the site to celebrate beautiful information design and infographics.
OK, so we could spend all day looking at this cool blog that collects awesome infographics and data visualizations from all over the web. No matter what you're into, you'll find a topic on this site of interest. Cool Infographics is run by Randy Krum, president of data visualization company InfoNewt.
Visual complexity showcases a huge range of visualizations and infographics, with over 750 projects submitted to the site. In order to help find what you're looking for among the extensive portfolio, graphics have categorised - including art, biology and music - with each image accompanied by informative text.
Flowing Data explores how designers and computer scientists are using data to understand things better through data visualization. The site showcases some awesome infographics and visualizations, all with accompanied commentary.
If it's inspiration you're looking for then Many Eyes is a fantastic starting point. The data visualization site features literally thousands of inforgraphics for you to browse through, as well as a tool for creating your own visualizations.


text:
Q: How to set first value of plus button click as default value to save in my TextView? The problem is to display the first value as default value in TextView for the + Button click which increases the value. These are the variables in which
mInteger` is -
int minteger =0;
int count=0;

These are 2 functions which is increaseInteger(View view) function is for Plus button click and decreaseInteger(View view) function is for Decrease button click. Below is the code for plus and minus button clicks
public void increaseInteger(View view) {
            minteger++; //for increasing value
            display(minteger);
        }public void decreaseInteger(View view) {
            if(minteger>0)
            {
                minteger--;  //for decreasing value
                display(minteger);
            }
        }

Below code is to show the changes in TextViews according to the mInteger which is changed by button clicks. The display() function uses button click integer but how to set the default value in TextView as 1 and other values changes accordingly as default values when the activity opens.
    private void display(int number) {
        TextView displayInteger = (TextView) findViewById(R.id.quantityPerTeam);
        displayInteger.setText("" + number);
        int total=count*minteger;
        quantityTeam.setText((String.valueOf(total))+" "+"Images@$2.49/print");
        float total1=total;
        total1= (float) (total*2.49);
        totalprint.setText("Total: $" +(String.valueOf(total1)));
    }

How to set the default value as 1 of mInteger when the activity first loads? and show the calculated values accordingly.

A: you can set Text of the displayInteger When the Activity is loaded
Inside the onCreate method add the following
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        int minteger =1;
        TextView displayInteger = (TextView) findViewById(R.id.quantityPerTeam);
        displayInteger.setText("" + minteger);

}

A: In the xml file,set text to '1' in TextView in android by default.
Try this
int count=1;
increaseButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View arg0) {
               ++count;
            }
        });
displayInteger.setText(Integer.toString(count));

redpajama_set_name: RedPajamaStackExchange


A witness, in the sense that I am using the word, is a man whose life and faith are so completely one that when the challenge comes to step out and testify for his faith, he does so, disregarding all risks, accepting all consequences.
My children, as long as you live, the shadow of the Hiss Case will brush you. In every pair of eyes that rests on you, you will see pass, like a cloud passing behind a woods in winter, the memory of your father - dissembled in friendly eyes, lurking in unfriendly eyes.
I see in Communism the focus of the concentrated evil of our time.
It is popular to call it a crisis of the Western world. It is in fact a crisis of the whole world. Communism, which claims to be a solution of the crisis, is itself a symptom and an irritant of the crisis.
Political freedom is a political reading of the Bible.
A man is not primarily a witness against something. That is only incidental to the fact that he is a witness for something.
For in this century, within the next decades, will be decided for generations whether all mankind is to become Communist, whether the whole world is to become free, or whether, in the struggle, civilization as we know it is to be completely destroyed or completely changed.
On that road of the informer, it is always night. I cannot ever inform against anyone without feeling something die within me. I inform without pleasure, because it is necessary.
At issue in the Hiss Case was the question whether this sick society, which we call Western civilization, could in its extremity still cast up a man whose faith in it was so great that he would voluntarily abandon those things which men hold good, including life, to defend it.
When you understand what you see, you will no longer be children. You will know that life is pain, that each of us hangs always upon the cross of himself. And when you know that this is true of every man, woman and child on earth, you will be wiser.
I do not know any way to explain why God's grace touches a man who seems unworthy of it.
A nation's life is about as long as its reverential memory.
Every man is crucified upon the cross of himself.
The chief fruit of the First World War was the Russian Revolution and the rise of Communism as a national power.
On a scale personal enough to be felt by all, but big enough to be symbolic, the two irreconcilable faiths of our time - Communism and Freedom - came to grips in the persons of two conscious and resolute men.
Human societies, like human beings, live by faith and die when faith dies.
I know that I am leaving the winning side for the losing side, but it is better to die on the losing side than to live under Communism.


This is cute. I have a faithful follower who wants to start a fan club for Addie Acres. I told her it would probably only have two members…me and her. Then I thought, no it will have at least 14! My animals! But before they sign up, I can just see Linda Williams advertising with posters on every phone pole to rally up the troops, stand on the street corner with Super Farmer and his bullhorn demanding people to join the fan club, handing out fliers, giving away candy, selling raffle tickets (you win a free 8 x 10 pic with Sammie or Remi), pleading with folks to just look at the site…you know, ways to make us popular among folks who dont really care for farmers.
They would be out in the hot heat shaking hands, making promises, like the fan club would be fun…exciting…complete with perks like free farm fresh eggs!
Then I thought, they would probably only get 3.5 people to sign up, only because they felt sorry for them yelling on the street corner in 100° weather pleading with people. I can see Linda and Chad dragging themselves through the gate with one wrinkled sign up sheet that has less than 4 people on it. That's when my faithful, devoted, loves me to the ends of the earth and back animals, would line up to sign the fan club form that offers perks (the chickens wouldn't be thrilled with it). Chad and Linda would get a second wind, pull up a table and chairs, spread out the 'I promise to be a fan forever and ever' form and let those barn yard animals sign away! Of course they cant really use a pencil so Chippie will leave a paw print, Biscuit wont be able to get near his because chippie will be growling at him, Dunkay would sneeze on his, Laci will drool on hers, the llamas will spit on their papers, Dillion the old goat will blankly stare at it (so Super Farmer will sign it for him) Remi will eat hers, the birds will leave a feather or 10, and the barn kitties with scratch their forms into tiny shreds! I predict that by the end of the day, we will have close to 30 fans! Of course 25 will be animals and 5 will be real people! Heck, I'm in! Let's do this!!


text:
What is FiraTàrrega
Artistic programming
Professional meeting point
Fira 2020
Map of spaces and services
Stallholders Market
Support for creation
History of selected companies
FiraTàrrega TV
The City: Art, Thought and Society
Introductory theoretical module
A working area where students will familiarize themselves with the main content of the Master's degree. A panoramic perspective of the city and public space from the standpoint of anthropology, urban planning, philosophy, and historical, social and artistic viewpoints.
Art and Community (12h) Eva Marichalar
Creation in public space can become an activity of public interest, not just from an artistic and cultural point of view. From a social, educational and investigative standpoint, street arts are presented here as a possible context for the promotion of collaborative practices from different points of view. Taking contact with the territory as an essential premise, this course will analyze the possibilities of the discipline as a space intended for each and every inhabitant of a territory as a possible setting for relationships, transformations and social protest. We will also focus on defending a semantic usage that is coherent with a vision of the arts as one of the opportunities available to a community for creating narratives. We will work with and debate about different contemporary examples in relation to the introductory theoretical material analyzed previously. The nuances and meanderings within the course structure will be influenced by the specificities of the participating students.
Art and Public Space (8h) Paco González
Public spaces - squares, streets - are the platform for formal and informal cultural expression in the city. These spaces have changed with the advent of the Internet and its social adoption - the so-called web 2.0 - allowing for contemporary spatial practices to be described and documented, making them accessible to the majority. Residents and citizens, artists and practitioners are both producers and consumers, actors and spectators at the same time. The aim of this course is to debate and engage in a critical evaluation of the changes in public space and its cultural practices.
Organization and design of projects I (4h) Pep Salazar
The final project is a compulsory exercise that must be completed by postgraduate students as the culmination of their studies. From a content point of view, they must apply all the knowledge acquired throughout the three modules but from an organizational point of view. They must also rigorously apply the knowledge gained in this course.
How can a final project be approached formally that in turn may well be a real artistic project? Strategic management, design and organization of content and tools for analysis and planning are key elements for tackling an ambitious project that today can be a work and tomorrow a professional project. It is necessary to display the contents of the project in a logical and orderly way so that they are well understood by the recipients of the message.
This course will be held over the three modules with the goal of being able to face the final project continuously throughout the course.
The City and Contemporary Thought (8h). Maria Buhigas
Students will describe and analyze the principal characteristics of the current urban phenomenon in the Western world, society and trends in the policies applied to urban space. Special attention will be paid to the privatization of public space and its ties to social and cultural change.
Discussion topics: The city and the urban phenomenon. Toward building a world of cities. 21st century urban society. From producer cities to consumer cities. Recent history of the Western city. Urban characteristics of contemporary urban space in Europe. The lived city and the planned city. How do we use, conceive and plan cities? The crisis of public space in the contemporary city. Western urban society. Characteristics and trends. City and culture. The role of culture in current urban policy. The city and the commons. Action and citizen participation.
Urban Anthropology (8h) Manuel Delgado
An introduction to urban anthropology, not in the framework the city per se but in urban spaces, where there is a particular system of social ties, characterized by a proliferation of relational fabrics involving uses, impositions, rectifications and mutual adjustments in a setting that is suited to democratic equality as well as conflicts, inequalities, struggles and social catharsis. It serves as the framework for all kinds of theater arts, the surface where the aesthetics of the present and the rhetoric of taste can be seen, and the landscape where the limits between the concrete and the imaginary blend together.
The Graduate Diploma
Objectives and skills
Pl. de St. Antoni, 1
ES-25300 Tàrrega
info(ELIMINAR)@firatarrega.com
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In the wake of Australia sweltering through its hottest month on record, academics and environmental advocates are calling for urgent changes to the country's building codes. Poorly designed homes are ill-equipped to handle sustained heat, leading to soaring energy bills and contributing to global warming, University of South Australia Professor of Environmental Mathematics John Boland said. "Our increasing reliance on air conditioning is causing untold damage to the environment, emitting greenhouse gases and warming the globe even more," Professor Boland said. "What's needed are brand new building codes which make things like wall insulation, double glazing and restrictions on window placement mandatory for all new homes." Given Ballarat's cool winter and warm summer climate and growing housing estates, local environmentalists have advocated for stricter regulations for builders for more than 10 years. READ MORE: Sustainable house design achievable for the everyday homeowner Ballarat Renewable Energy and Zero Emissions president Ian Rossiter said the lack of state and federal government leadership to change uniform building codes was frustrating. "In the absence of good policy it really has come down to consumer preference driving change which we are starting to see more and more of," he said. "But for people renting properties, they don't have the purchasing power to decide how their buildings are constructed. It is important all constructions are sustainably designed and built. "What we would hope is we can see some of the volume builders moving to normalise energy efficiency in their homes as a prime selling point. In the past when electricity and gas were reasonably cheap, the extra expense of investing in thermal efficiency often wasn't top of mind to home buyers, whereas today people are really aware of ever rising energy costs and the impacts extreme heat and cold is having on peak demand." Professor Boland said simple things like ensuring houses have less than a quarter of their windows on the west-facing side, installing wall as well as roof insulation and double or even triple glazing windows should be considered in designs – and energy savings would offset upfront costs. "Simply complying with a 6-star rating (the current requirement) is useless because not only is that energy rating rarely checked; it does not consider climate change," he said. "Moreover, since the star rating is done on total energy use over the year, a design can be highly rated based on its energy use in winter. The house can still cause a lot of heat stress in summer. "We need to get away from this idea that everything is voluntary in relation to building codes. Alternative energy sources like solar are great, but nothing beats a good design." Michael Robinson and Jo Taylor built a house following sustainable design principles in Mollongghip and share a vision that all builders and architects will follow sustainable building practices. The household is completely self-sufficient, powered by an 11kW PV system with battery storage, water harvesting and storage for all water requirements and wood heating. READ MORE: Sustainable design thinkers driving the housing revolution Other sustainable design elements help them live in comfort, including northern orientation to maximise sun exposure, air lock entry to prevent heat loss and gain, a thick 200 mm of insulation and double glazed windows. Mr Robinson said building sustainable houses "just makes sense" and reassured those interested that it was "completely doable". Mr Rossiter said there were changes consumers could make to existing houses too, by considering how to improve shading, reduce solar penetration, stop drafts and leakages and treating windows with double glazing. READ MORE: This Beaufort house is completely recyclable The Smart Building and Living Expo held in Buninyong on February 24 will feature information on sustainable building and design features, as well as tips for sustainable living. BREAZE will be set up at the festival to assist with inquiries and provide information on its residential energy scorecard program – some BREAZE members are now accredited to assess energy efficiency in homes and provide a rating and a list of changes that can be made to improve efficiency. Visit smartbuildingandlivingexpo.com.au for more information about the Buninyong event.
In the wake of Australia sweltering through its hottest month on record, academics and environmental advocates are calling for urgent changes to the country's building codes.
PASSIVE HOUSE: Sustainable homes in Beaufort, Buninyong and Hepburn use design principles focused on reducing environmental impact.
Poorly designed homes are ill-equipped to handle sustained heat, leading to soaring energy bills and contributing to global warming, University of South Australia Professor of Environmental Mathematics John Boland said.
What's needed are brand new building codes which make things like wall insulation, double glazing and restrictions on window placement mandatory for all new homes.
"Our increasing reliance on air conditioning is causing untold damage to the environment, emitting greenhouse gases and warming the globe even more," Professor Boland said.
Given Ballarat's cool winter and warm summer climate and growing housing estates, local environmentalists have advocated for stricter regulations for builders for more than 10 years.
Ballarat Renewable Energy and Zero Emissions president Ian Rossiter said the lack of state and federal government leadership to change uniform building codes was frustrating.
"In the absence of good policy it really has come down to consumer preference driving change which we are starting to see more and more of," he said.
"But for people renting properties, they don't have the purchasing power to decide how their buildings are constructed. It is important all constructions are sustainably designed and built.
Professor Boland said simple things like ensuring houses have less than a quarter of their windows on the west-facing side, installing wall as well as roof insulation and double or even triple glazing windows should be considered in designs – and energy savings would offset upfront costs.
"Simply complying with a 6-star rating (the current requirement) is useless because not only is that energy rating rarely checked; it does not consider climate change," he said.
Michael Robinson and Jo Taylor built a house following sustainable design principles in Mollongghip and share a vision that all builders and architects will follow sustainable building practices.
The household is completely self-sufficient, powered by an 11kW PV system with battery storage, water harvesting and storage for all water requirements and wood heating.
Other sustainable design elements help them live in comfort, including northern orientation to maximise sun exposure, air lock entry to prevent heat loss and gain, a thick 200 mm of insulation and double glazed windows.
Mr Robinson said building sustainable houses "just makes sense" and reassured those interested that it was "completely doable".
Mr Rossiter said there were changes consumers could make to existing houses too, by considering how to improve shading, reduce solar penetration, stop drafts and leakages and treating windows with double glazing.
The Smart Building and Living Expo held in Buninyong on February 24 will feature information on sustainable building and design features, as well as tips for sustainable living.
BREAZE will be set up at the festival to assist with inquiries and provide information on its residential energy scorecard program – some BREAZE members are now accredited to assess energy efficiency in homes and provide a rating and a list of changes that can be made to improve efficiency.
Visit smartbuildingandlivingexpo.com.au for more information about the Buninyong event.


Aerial photo of Morgan Meadows Monolithic dome rental community south of Italy, Texas.
Morgan Meadows is upon completion of it's 48 single Cottages of 314 square feet each in a garden type setting. The cottages will provide a private, secluded feel — each set off with plantings, walks, fences and canopies. A single carport is included with additional parking for guests. The structures are Io-20 Monolithic Domes as developed by Monolithic Dome Institute.
The Io-20 is an ideal size. It comfortably fits a single person, two people, or two adults and a small child or one adult and two small children. This is our favorite size. It is affordable for those who are renting and profitable for those who are managing them.
The prototype for Morgan Meadows consists of 15 cottages located on Dome Park Lane built by the Monolithic Dome Institute. The second project is a group of four cottages called Secret Garden located on a small commercial lot in Italy, Texas. Each of these projects have served as successful prototypes for determining efficient floor plans, appliances, window selection and storage capacity.