I run a pair of Schoeps mics into one of my stereo preamps, which is run in front of my D100. From the preamp I have a stereo cable that goes from two female XLRs to a single stereo right angle 1/8 mini-connector. The 1/8 mini connector is plugged into the line-in jack. For loud music I use the 20db pad on the left side of the of the D100. It all works great.
Since this is a taper forum ... I don't record music all that much (as a percentage of all my recording work). But when I do I use the Soundman binaural mics or the Church CA-14s. Both are stereo but end in a mini-jack. Both work just fine with the D100. But for me the real "test case" is when using mics that need a lot more gain. If I were only taping music and relying only on something like the Church CA-14s (or something more expensive) with a mobile pre-amp, then I'd probably mainly use a Sony M10. Smaller, cheaper, and given all the various factors would work as well as the D100.
So in some cases the M10 might be the better choice, for my usage the D100 rocks, and in other cases the SD 702 would definitely be the best choice.
That helps and your patience is appreciated.
There must be ten or twenty other handheld portable recorders that cost much less than the D100, some with XLR inputs and some with more channels. For you guys to bypass all the other recorder options and spend so much extra money on the D100, you must see some advantages that I haven't quite yet grasped or figured out on my own. That's where I need help understanding what you see as advantageous and worth the extra money?
In my own situation, I figure I could get a used SD702 for $1000-$1300 and either use my Rode NT45 omnis or Line Audio CM3s unless I also upgrade mics. Now the SD has been out for a while and uses CF cards. It's also a firewire unit. The D100 is newer technology and no firewire is involved. The SD100 is also smaller and uses AAs. The SD has the reputation of being extremely reliable under harsh operating conditions and has an aluminum case. If one tried to use the external mics on the D100, it wouldn't be the easiest thing to put on a stand. You can tell I'm going back and forth in my mind here.
So what pros/cons do you see between the two options?
I'm with 2manyrocks - for pure 2-channel, I would buy a 702 in a heartbeat over a D100 for the reasons he mentioned. I'm sure the D100 is a great recorder based on my great experience with the M10 and D50, but the SD recorders are in another class entirely, and you're getting top-quality preamps built in also. I suppose if you own good external pres already then you wouldn't feel so inclined to get one of their recorders. As much as I wish I could afford a 702, I wonder how much improvement I would really see (hear?) over my current chain of FP24 > M10.
To H2O's statement: I still do not see the advantages of DSD at all - can someone please enlighten me? To me, unless you're making SACDs or keeping your DSD recording entirely in the DSD domain and using a DSD-capable DAC to listen to it, there's no point. What am I missing?
Simple. Better sound quality. Period. ...and yes you leave your files in DSD format and play them back in DSD format either on your D100, on a portable X3 or X5 player like I have, or connected to your computer through a DAC. I'm still deciding how I ultimately want to archive, but at minimum it will be saving the master DSD files. Right now I'm also saving the converted 24/48 files.
If you have no desire to bother with the higher quality files, then forget it, you get no benefit from DSD. If you want to record music and squeeze another layer of great sound out of your live recordings...another layer of realism, then IMHO paying the extra $400 or $500 is probably worth it and you'll love DSD. But keep in mind I've already got five grand in my bag, so adding another 10% for that extra layer of realism is definitely money well spent for my rig. No it's not a black and white difference, but it's a definite step up.
I was a bit skeptical, but the korg users were pretty universal. Now I'm a believer as well. This absolutely isn't snake oil.
Anyway, I'm playing most of my recordings on my Fiio X3 and I'm absolutely in love with it.
I wonder if the high quality you are hearing has more to do with the D100 itself and its improved ADC / DAC rather than the DSD format. I think I remember seeing a comp somewhere of the D100 at 24/192 vs. DSD, but I didn't bother listening as my DAC doesn't decode DSD - again, the DSD files would have to be converted by software to PCM to pass to my PCM-only DAC, so it wouldn't be a fair comparison.
Very valid questions. Trying to answer the same questions when I first got the D100, I posted a comp. Not too many people posted their impressions. The samples compared an m10 at 24/48 against a d100 at 24/48. Then I compared the m10 24/48 against the d100 at DSD but with the files converted back to 24/48. Really not much difference could be heard, though there was some consensus that the converted DSD file had a very slightly better sound. The main difference I could hear was in playing back the DSD file directly on my players.
I recently bought a great priced D50. I'm going to record multiple stages this summer. I'm kinda curious to see if the D50 sounds exactly like the M10. I'm sure they've been comped here before...gotta do a search to see what I find.
There's the rub I guess - unless you have a DAC that directly decodes DSD you really can't make a true comparison between formats. For instance, I'm pretty sure the X3 doesn't decode DSD, but the X5 does, so there could theoretically be a difference in sound between the original DSD played on the X5 and the converted PCM played on the X3. I have downloaded some DSD / DFF files and listened on my computer using Foobar, and they sound no different than high-rate PCM. But Foobar is just decoding and resampling to 24/96 PCM to pass to my DAC so unless I shell out for a much more expensive DAC, I'll never hear true DSD.
Having used both the D50 for quite a while and then the M10, I think they sound pretty much the same, at least for line-in. The D50 has far superior built-in mics, but the M10 beats it in size, weight, battery usage, etc. The D50 is a really great unit though.
Comparisons between m10, d50 and d100 with the same external preamp would be interesting.
Ahh, didn't know they did that - good to know. B&H was showing the X3 as discontinued and didn't mention anything about DSD, but I knew the X5 supported it.
Apparently still in stock at Adorama.
How do you edit DSD? Looks Reaper, for example, won't work with DSD.
Korg's free version of Audiogate has some basic functionality for normalizing files and converting to PCM. There are a number of high end software packages out there, such as Pyramix. Older unlicensed versions are floating around.


Several years ago The Guardian wrote a lovely big article about me under the headline "The Spielberg of Hereford". I had just completed Soul Searcher, a feature-length fantasy-action movie shot in this sleepy backwater of the rural West Midlands. The project had not been without its challenges – from a malfunctioning camera to a striking stunt team – but shooting in the provinces wasn't one of them.
Yes, on the face of it, basing yourself away from the vast majority of actors, crew and facilities is inconvenient. I have long since accepted that my casting calls mentioning a shoot far outside the M25 will get a limited response, and that I will have to travel to London to hold auditions.
Crewing can seem similarly problematic, but in fact there are many excellent TV and film technicians hidden away in rural areas, constantly driving to London to work, but keen to be involved in anything more local if they get half a chance. It's a novelty, and that's an advantage.
Londoners can often be cynical about filming; it's a business like any other. Most locations in the capital will whip out a rate card at the first whiff of a scouting crew. But out in the sticks, many property owners will let you shoot on their premises free of charge for the rare glamour of a brush with the film business. On Soul Searcher I only had to pay for a single location. At least two others told me they would charge me, but never did. Their accounts departments presumably had no procedure or precedent for raising an invoice for location fees, and so overlooked it.
The savings a regional producer makes on locations are often countered by an increased travel and accommodation budget. But there are benefits to this accommodation that, to my mind, outweigh the financial burden. A cast and crew staying away from home together will bond far more than one that scatters to the four corners of the tube map every night. This means improved morale and more realistic on-screen relationships between actors.
Regional filmmaking has more potential now than it's ever had. Established networks like Talent Circle may remain London-centric, but social media enables us to connect quickly with others in our area – Shooting People's regional "Shooters in the Pub" Facebook pages, for example, or Herefordshire Media Network, through which I found the editor for my last short film, Stop/Eject. And in an age when everyone's looking for a hook for their crowdfunding campaign, the declaration "shooting in YOUR home town" can help you connect to potential sponsors.
Finally, regional press will often jump on local film projects, providing great free advertising for your crowdfunding campaign, cast/crew call or screening. I've appeared on BBC Midlands Today on three separate occasions, but I can't imagine BBC London News covering yet another struggling filmmaker. And would "The Spielberg of Hackney" have been so newsworthy to The Guardian? I suspect not.
If you're interested in the potential of regional film and TV production, the Herefordshire Media Network will be hosting a panel discussion on this subject at the Borderlines Film Festival next month.
I've just finished reading the classic thesping manual An Actor Prepares, by Konstantin Stanislavski. Don't worry, I'm not planning a career switch to the other side of the camera, just endeavouring to become a better director by deepening my understanding of acting.
Despite being 80 years old and translated from Russian, the book is surprisingly accessible. It takes the form of a fictional diary in which an eager drama student, Kostya – whom Stanislavski apparently based on his younger self – records his lessons with teacher and director Tortsov, representing the author's older, wiser self.
The first instalment of a trilogy which continues with Building a Character and Creating a Role, An Actor Prepares outlines the mental processes which Stanislavski believed are required in order to stimulate the subconcious inspiration from which all truly great acting springs. As such, the book focuses on work that would be done by an actor on their own, before beginning their relationship with a director.
Elsewhere in the book, there is a great tip regarding objectives (read: motivation). "You should not try to express the meaning of your objectives in terms of a noun… The objective must always be a verb." The author suggests that powerful objectives often start with "I wish…" It seems to me that if a scene is going off-track, sitting down with the actor and formulating a suitable objective beginning with "I wish" might be a constructive way to get back to the heart of the narrative and characterisation.
Perhaps one of the best-known elements of Stanislavski's system is the "magic if". The theory is that by asking "if" questions, maybe as basic as, "What if I was in the same situation as my character?" a performer – or indeed a director – can very quickly get to the truth of a role, a scene, or a script. By probing scenarios that don't even occur in the script, for example, "What would my character have done if such-and-such an event happened?" we can start to build a more nuanced character.
Stanislavski also stresses the importance of the "super-objective", the over-arching motivation which drives the character through the piece, and "counteraction", forces working against the super-objective, which are often embodied by the antagonist or villain. This is a good reminder for directors and writers not to lose sight of what the hero is ultimately trying to achieve, and to derive the maximum dramatic conflict from the hero's clash with the people and obstacles in their way.
Aside from these nuggets of wisdom, the principle thing I've come away with is an increased understanding of and respect for the craft of acting. It must require an extraordinary level of mental discipline to control your every thought and action – or rather, to immerse yourself in the character to such a degree that your every thought and action naturally become those of the character – while simultaneously hitting your marks, finding your light, delivering the lines put in your mouth by someone else, remembering your continuity, executing the director's notes, and ignoring all the crew and equipment in your face.
Which I knew already, of course, but reading An Actor Prepares very much brought it home to me.
Following our positive recce of Newstead Abbey last month, we returned there yesterday, this time with new crew members Benjamin Maier (director of photography), Tom Walsh (first assistant director) and designer Amy Nicholson's assistants Anya and Charlotte. It was an opportunity for Ben to assess the power, lighting, lens and grip requirements, for Tom to consider the logistics of working in the place, and for the art department to take measurements.
Amy and her team are sinking their teeth into the project. Initial ideas of a single feature wall which would be re-wallpapered for each of the film's four time periods have expanded into full-blown redecoration of the room. This will create a whole different mood and palette for each period and really up the production values.
After leaving the gatekeeper's cottage, we drove up to the lake to show Ben where the waterside scenes would take place. His immediate observation, which had escaped me on the previous recce because I was wearing my director's hat, was that it was in the worst possible orientation to the sun: the actors would be flatly lit. We walked around the lake to a cool Victorian folly that looked like part of a miniature castle. Here the light would strike from a better angle, and indeed it was a better location in every respect except for one. I can't tell you what that one is because it would give away the ending of the film.
This recce was my first chance to use Artemis, a virtual director's viewfinder app which I recently purchased. At £20.99 it's very pricey, but where it scores over other, cheaper viewfinder apps is in its vast array of cameras you can choose from. You don't have to worry about calculating crop factors; you simply select your camera from the menu, along with the lenses you have available, and Artemis shows you the field of view you'll get with each one. On the wide end it's limited by the iPad camera's lens length, which in terms of a Super-35mm sensor at 16:9 is equivalent in height to a 22mm lens and in width to about 25mm, but you can purchase an optional wide angle lens adaptor to get around this. I have yet to use the app's more advanced features, but it's certainly cheaper than a real director's viewfinder, and much more convenient than carting a DSLR and lenses around, which is what I did on the first recce.
In other areas of preproduction, I've had initial Skype chats with the two lead actors, which led to some suggestions for little additions to the script, and I've been continuing to watch genre films for inspiration, taking in The Silence of the Lambs, The Woman in Black (2012) and The Innocents lately.


Enrolled with Home Advisor effective 8/30/2018 - annual fee of $347.98 deducted from our account. We Requested only Alarm and Camera Job leads . During a two week period we were billed an additional $518.68 for leads, of the $518.68 only two of the leads were for Alarm and/or Camera jobs. The billing for those two was $33.75 leaving a balance of $484.93 for job leads in field/area not requesting. We have requested our account closed with them. Emailed Home Advisor several times to correct the issue, no response. We have since closed our credit card so Home Advisor would not continue to charge our credit card. Spent over an hour on the phone 9/28/2018 with one of the supervisors from Home Advisor, who acknowledge we were billed in error, but that Home Advisor would NOT refund us for their error of charging us for Lead Types we had not requested We have requested a refund of our money several times, but as of today we have not received any refunds for their errors.


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android Apps TOP VIDEOS
Best Free Video Sharing Apps For Android
December 23, 2021 December 25, 2021 Yasha Jackson 0 Comments
A Free video sharing App is a software component for your android device that allows you to share your videos and content all around the world today. For a business, this means that you can use your cell phone to make and share fantastic visual content of your products.
Online video-sharing services have been increasingly popular as internet connections have become fast and more reliable, especially as user engagement has increased. Videos easily account for the vast bulk of the material we consume nowadays on the internet. With the emergence of augmented and virtual reality, demand is only expected to grow much more.
It might be tough to select the best video-sharing app when there are so many available. As a result, we'll go through the top 12 Best Video Sharing applications for Android 2021
Here are the Top 12 Best Video Sharing Apps download with the latest version 2021–
YouTube is a multimedia and streaming platform that allows users to watch videos and submit their own. Since its launch in 2005, it has risen in popularity due to its tremendous performance and simplicity. It was bought by Google the following year, and it is currently the most well-known and widely used video platform among the numerous comparable sites on the internet.
YouTube is mostly used for watching videos, despite the fact that it is a video-sharing site. As a consequence, the app has been set to produce a pleasurable viewing experience. On YouTube, you may watch videos by just clicking on them from the main screen, and they will start playing right away.
Except for YouTube Premium and YouTube TV, most content, including music, is available for free. Music, entertainment, education, and everything in between can be found on the video base, thus you can discover anything important or fascinating there.
TikTok is regarded as one of the greatest short video apps for creating and sharing short films. TikTok provided a massive platform for content providers to demonstrate their abilities.
Tik Tok is a popular short-video platform that is compatible with both Android and iOS smartphones. It has been utilized by a wide user base from many nations since it was initially made accessible in 2016.
Tik Tok, which is owned by the Chinese business ByteDance, lets users create short and exciting, hilarious, lip-sync, and dance videos. Millions of people have used the built-in capabilities to edit, change, merge numerous movies, and make them more entertaining.
TikTok is a popular platform for fashionistas and influencers to earn money, and marketers utilize it to reach a larger audience. This short video app was recently prohibited by Indian councils in 2020 owing to privacy concerns and security dangers.
Instagram is a photo and video-sharing app that allows users to edit, share, and post photographs and short films. With 180 million users as of July 2021, Instagram is a popular short video app in India.
Instagram is enjoyed and utilized all around the world, with the majority of users in the United States. Professional content producers utilize it to engage, network and communicate with their followers. In 2012, Facebook-owned it.
It has features like sharing brief films as profile stories, adding highlights, and posting eye-candy photos that are completely customizable. Because of this, the short video platform has gained popularity in recent years.
The video platform's long-held supremacy was threatened by Facebook's fickle algorithm adjustments, fake news controversies, and video metric miscalculations. Facebook Watch is flourishing, despite the fact that Lasso, Facebook's response to TikTok, failed to compete. With 140 million daily users and 720 million monthly users, Facebook Watch nearly quadrupled its viewership six months after its inception in 2017.
On series like "The Red Table" and MTV's "The Real World," Facebook has previously partnered with significant personalities and networks, like Jada Pinkett Smith.
Facebook Watch also emphasizes social interaction and features that bring people together. Their Watch Parties are a big hit.
Snapchat, which has been in use since 2011, is accessible in 37 languages and allows for simple and captivating video sharing. According to the research, as of July 2021, this short video app had 105.25 million users in India.
It allows you to share live and recorded moments. It has become popular among teenagers due to the great filters that offer some exciting effects. Maintaining streak features with friends has recently increased the user base by multiple folds.
It offers a fun discovery area where you may look at tales from public accounts to learn about what's up with your friends and celebs.
Vimeo.com is a rapidly expanding platform with significant traffic. Unlike YouTube, Vimeo focuses on professional-looking films and offers three types of accounts to its users: a free account with limits and two subscription accounts with more features and storage.
Vimeo pays Its premium content producers 90% of the money generated by their own films and supports uploads in numerous file formats. Uploading files to different platforms is a wonderful way to promote and market them, and Vimeo is one such site that should be at the top of a content creator's priority list.
Triller is an entertainment and music portal. For a community of creators, a social video editor was created. Where you can capture great films and share them in seconds to show the world who you are.
Triller is the video app you need to add music to videos, apply filters and effects, post your films on Triller and other platforms, and discover the next great star! With the aid of our innovative auto-editing technology, you can create great videos in minutes. With over 100 video filters, you'll always look your best.
You can listen to the most popular songs or your own music from your collection.
View live video feeds from our most talented producers.
Pinterest launched a mobile video ad platform for advertisers and publishers in response to their newly identified market segment.
Promoted Videos give marketers a one-of-a-kind opportunity to reach customers where they shop, where they've previously expressed an interest in purchasing a product, and where it simply takes one click to do so.
Pinterest has also improved its video uploader, allowing companies and users to post video straight to the platform. The player allows users to interact with their audiences as well as see their most recent analytics.
The newly updated Flipgrid video platform enables educational and commercial customers to integrate video to improve corporate learning results.
Microsoft bought Flipgrid in 2018 and made it free for schools to use. Microsoft tools such as Teams and One Note are integrated with the video platform. Flipgrid is now used by around one-third of all U.S. schools, and students and teachers can respond to prompts by generating one to five-minute movies ranging from instructional videos to peer review.
In addition, Flipgrid unveiled additional capabilities for 2020, such as automated closed captioning that may be modified to smooth out transcription glitches.
WeChat is for you if you enjoy versatile applications with short video features. It serves as a platform for communications, video production, financial gateways, and social media entertainment. It can be utilized by Android and iOS users and includes voice, picture, and video chatting modes.
WeChat is a Chinese application developed by Tencent that has over one billion users globally. WeChat is also facing a ban by the Indian government in 2020 due to its integrated privacy and security requirements. As a result, Indian users are unable to access it.
Twitch is a gaming-focused video platform. People can stream themselves playing or chatting about games, and others can view them live or via archived video. You can also record or broadcast your games, interact with other players, and join other gaming communities.
Advertising on videos is included with the free account. Consider going Turbo if you want to eliminate it. Free users, unlike Turbo users, can only save their live footage for 14 days on Twitch. Even though Twitch's broadcasting method is difficult, using it to share your game videos is a good idea.
12. TED Talks
TED Talks is a popular video-sharing platform. It includes approximately 2,300 speeches on a wide range of subjects, including technology, business, design, science, and global challenges.
Some of the chats are lighthearted, while others are heartfelt. Some speeches are intended to teach how the brain works, while others are only intended to entertain. The one thing you can count on from all of the TED Talks videos is that you'll remember something from each one.
If you're short on time, the TED Talks website is useful. If a video is less than six minutes long, it is marked with a visible red circle on the menu.
There are so many amazing Video Sharing Platforms that it may be overwhelming at times. To locate the best free video-sharing apps for 2021 for you, think about what you want to achieve first, and then try out a few different video-sharing apps until you find the one that's ideal for you.
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redpajama_set_name: RedPajamaCommonCrawl


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B1G Basketball Diaries: Minnesota's Freefall Continues
Since beating the Illini the Gophers have dropped four straight.
By Apollo Forza Jan 27, 2013, 10:00am CST
Share All sharing options for: B1G Basketball Diaries: Minnesota's Freefall Continues
WE HAVE TO GET CLOSER
Wisconsin 45 Minnesota 44
We know how it feels, Minnesota, we do. You started out the season with a 15-1 record and that lone loss coming against Duke. Still, after you started the Big Ten season with impressive wins over Michigan State and Illinois things were looking really good.
But that's no longer the case.
Minnesota dropped its fourth straight on Saturday thanks to a 15-foot jumper from Traevon Jackson with 4 seconds left. It was an ugly game, one that saw Minnesota's Andre Hollins score 20 points by himself. That's 22% of the points scored in the entire game, as no other Gopher scored more than 8 points and only two Badgers reached double-digits. Making matters worse for Minnesota, Trevor Mbakwe aggravated a wrist injury.
Nebraska 64 Northwestern 49
See, this is why Northwestern is always going to be Northwestern when it comes to basketball. The Wildcats win consecutive games against both Illinois and Minnesota and then hit the road and lose by 15 to a Nebraska team that the Illini had no trouble with. Dylan Talley finished with 20 points and 8 rebounds and Brandon Ubel finished with 14 and 12 for the Cornhuskers.
Ohio State 65 Penn State 51
"Why the fuck are we showing this game," asked an ESPN executive Saturday morning when trying to figure out why the fuck ESPN was broadcasting an Ohio State game against Penn State.


My client is looking for a Product Manager/Director in charge of leading the development and delivery of one or several products in the OSS Service Assurance domain for the Digital world.
You are passionate and have been actively involved in the Telco transformation journey: of the OSS/BSS or in the development of NFV ecosystem (MANO, Policy Manager, Open Source initiatives) or in leading and applying AI/ML technics for Telco processes automation. You are currently working as a Product Manager or Solution/Software architect with Business insights, in a similar transformation project. You are looking for new challenges and making direct impact on Company's business results. You will be interacting with Tier 1 CSP/DSP worldwide, capturing their NFV/SDN journey, understating their Service Assurance strategies & blueprint and making recommendations for the company vision and blueprint.
· Be a team player with strong communications, interpersonal, negotiation and the ability to persuade people to your point of view.
· Demonstrated ability to effectively communicate with, tactfully collaborate with, and compellingly convince people in diverse functional areas.
· Ability to structure and present qualitative data in a compelling and convincing fashion; strong writing, and presentation.
· Intellectual curiosity with a purpose is essential.


Found Festival Roundup Culture Music. What to Expect from iOS 10 Culture. This look combines the weight of a full beard with the definition too often lacking from a hipster thatch. A great option for striking this balance is the circle beard. So to combat this, you need to work the angles. Like hairstyles and glasses, face hair can be utilized to compliment your face shape by enhancing your best features, while minimizing the rest. The diamond face shape is widest at the cheekbones, with a narrow forehead and jawline that are approximately symmetrical in width.
Very angular, with a prominent square chin, broad forehead and jawline. What Face Shape Am I? But first, take a look in the mirror and use our guide below to identify your face shape and make all future grooming decisions clean-cut. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Multiply. With this hybrid style, avoid anything too full and thick on the cheeks, which will give the unwanted impression of an even wider jawline. The chin is pointed. So, have fun and try the various styles on for size.
Ideally, you want to square off a prominent chin, to create the illusion of having more balanced bone structure. Try one, or try all 15, and tweet us Gillette to let us know which beard style is your favorite. Then, take the following measurements, recording each as you go: Top 15 Beard Styles For Men. With this hybrid style, avoid anything too full and thick on the cheeks, which will give the unwanted impression of an even wider jawline.
Description: Get all the latest must-read FashionBeans content direct to your inbox weekly:. Credits will be awarded for each unique subscription plan and value equal to the lowest of previous 3 subscription orders incl. Make sure you have the right tools for the job. The angle of the jaw is rounded rather than sharp. Is Beard Oil a Waste of Money?


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Manqoba "Shakes" Ngwenya (born 23 March 1981 in Soweto, Gauteng) is a South African football (soccer) midfielder currently playing for Township Rollers in Botswana.

External links

1981 births
South African soccer players
Living people
Mamelodi Sundowns F.C. players
Bidvest Wits F.C. players
Association football midfielders
Association football forwards
Sportspeople from Soweto
South Africa international soccer players
Mpumalanga Black Aces F.C. players
Thanda Royal Zulu F.C. players
Notwane F.C. players
Township Rollers F.C. players
South African expatriate soccer players
Expatriate footballers in Botswana
South African expatriate sportspeople in Botswana

redpajama_set_name: RedPajamaWikipedia


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Keira Davidson
eCommerce SEO Consultant
You are here: Home / International SEO / Beginners Guide to Hreflang
Beginners Guide to Hreflang
4th June 2020 By Keira Davidson Leave a Comment
For every client a different SEO strategy is needed and that could be in the form of local SEO, national SEO or international SEO. Depending on what you're wanting to target determines what elements of SEO will be necessary.
What Is Hreflang?
Hreflang is a snippet of HTML code which is added to a webpage(s) to specify the language and/or geographical targeting which is displayed to search engines in order for them to present the correct variations to users. The most common ways to implement hreflang are:
Content with regional variations like en-us and en-gb.
Content in different languages like en, de and fr.
A mixture of different languages and regional variations.
E.g an international website targeting different languages and/or regions may use hreflang tags as each URL used for the website can have the same content in a different language, or the same language but targeted at a different region.
Hreflang is only a signal to search engines and therefore there are many SEO factors that could potentially override hreflang attributes resulting in a different version of the page to rank higher.
Why Is Hreflang So Important?
If you have spent your time/resources using native copywriter to produce the content then you'll want to maximise the performance by using hreflang tags to ensure users are presented with the most appropriate content. In turn by doing this it often enhances the users experience which can indirectly lead to a lower bounce rate and a higher average time on site, all of which is thought to have a positive impact on rankings and organic performance.
The other key reason for including hreflang tags is that as there are multiple URLs for the same website which all consist of the same content it could result in duplicated content. E.g URLs targeting the UK, US and Australia will all have localised English copy which is why hreflang is needed so that the search engines understand that it's almost the same content just optimised for each targeted audience.
When implementing hreflang tags it's important to remember that they are only used on Google and Yandex. Currently Bing and Baidu don't refer to hreflang tags as they use content language HTML attributes.
When Should Hreflang Be Used?
Hreflang tags should be added to your website if the content used is near enough identical on one or multiple domains even though it's displayed in several languages or if you have content which targets different regions but in the same language.
What Does A Hreflang Tag Look Like?
Typically a hreflang tags is shown like below:
<link rel="alternate" hreflang="x" href="https://www.domain.com/location-or-language-targeted-page" />
How Can Hreflang Be Implemented?
There are three main ways in which people can add hreflang tags to their websites.
HTML hreflang link elements – This method of adding the hreflang snippet of code into the <head> tag of your web page. This way of adding hreflang tags to a site is thought to be the easiest way for people who are new to international SEO as you can use a hreflang tag generator to produce the HTML code for you to then upload.A drawback to using this method is that if you're having to do this for a massive site it can be very time consuming and mistakes can easily be made.
Hreflang HTTP headers – Not all pages on a website are coded in HTML such as PDFs and because of this it's not possible to add in hreflang attributes to the <head> tags. In instances where this is the case it's possible to use HTTP headers to outline which version you'd like displaying.
Sitemaps – XML sitemaps are often the best method to use for adding in hreflang tags for large websites due to them often having many languages/countries which can sometimes end up being too complicated to specify in the header as it would require lots of additional code being uploaded.
Sometimes it may not be possible to to use a single hreflang implementation method across all web pages due to them having different characteristics and therefore it's important to establish clear rules for when each method is used as it becomes increasingly difficult to avoid errors between each method.
What Is A X-Default Tag?
X-default tags are only used to help Google understand that when a targeted version of the website doesn't exist for a certain region to present users the default version of the website. It's important to recognise that x-default tags do not replace hreflang tags and therefore they should be used together.So for example, if you have a UK and French version of the website but someone in Spain searches for the related terms you'd x-default them to the preferred version.
What Does A X-Default Tag Look Like?
The snippet of code below contains 3 example hreflang tags (displayed in blue) along with the final like of code outlining the x-default version (displayed in red).
<link rel="alternate" href="http://example.com/en-gb" hreflang="en-GB" />
<link rel="alternate" href="http://example.com/en-us" hreflang="en-US" />
<link rel="alternate" href="http://example.com/en-au" hreflang="en-AU" />
<link rel="alternate" href="http://example.com/" hreflang="x-default" />
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Home Tech Tech News
Sony PlayStation 5 Pre-Orders Restarts in India; Here are details
by Afaan Dalvi
Growing up we are all excited about when would the new PlayStation arrive. The experience Sony provides with its PlayStation is totally unmatchable. Over time it has become such a big thing that you might have not used it or bought it in your own life but you surely would have heard about it. And that excitement brought you here to read this article. More such excitement would be seen among the PlayStation fans as the stocks of PlayStation 5 are back!
Yeah, you read the right thing! PlayStation 5's stocks would again be available in India and no one thought that it would happen so soon! Sony has declared on its official website that the PlayStation 5 will now be available in India for pre-order. The pre-order will start from May 27, 12 noon sharp.
Sony has also said that the orders might take time to reach their destinations depending upon the local restrictions in a particular state due to Covid- 19. Also, the people who ordered the PS5 from its website previously wouldn't be able to order it again. The restriction of buying only one unit will also be seen in the upcoming pre-order of May 27.
Here are the specifications of PlayStation 5 and PlayStation 5 Digital Edition:
As of now only the official website shopAtSC has only declared their pe orders on their official websites. But with time, other giants like Amazon, Reliance Digital, and Flipkart might also come into the picture.
Just after 10 days of the previous set of orders completed the PlayStation 5 is back. Again this time it's clear that the stocks will get sold much faster. The last time the stock of Sony PlayStation was sold out in seconds. The restock has been done so soon that it clearly implies that the craze of PS5 is going to crazy heights and its demand seems to go continuously.
Tags: playstationPlaystation Digital EditionPS5


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Solway Investment Group files three defamation civil lawsuits against Le Monde
October 3, 2019, Zug. The biggest Swiss investor in Guatemala Solway Investment Group, represented by Burguburu Blamoutier Charvet Gardel & Associés (BCG&A), has filed three complaints of public defamation with the Tribunal de Grande Instance in Paris against the newspaper Le Monde.
On 19 June 2019, the newspaper Le Monde published on its website (https://www.lemonde.fr) two articles entitled "In Guatemala, the Deaths of Lake Izabal" and "Carlos Choc, clandestine journalist in Guatemala: Here freedom has a price, and that's the price I am paying", both written by Anne Michel. The next day, June 20, 2019, an article entitled "From Switzerland to Guatemala, the organized opacity of the Solway mining group " was also published on the same website.
The three articles were a part of a series featuring the results of a journalistic investigation conducted by the team of 30 journalists, published as a collection under the name "Forbidden Stories". The group of journalists conducted research, referred to as "Green Blood", on practices presented as opaque in the mining sector in three countries. The purpose of this research was to continue investigations initiated by local journalists who would be threatened, prosecuted or even murdered because of their investigations. The stated mission of Forbidden Stories is to take over some of this reporting and ultimately publish their findings.
Various passages in the articles published by Le Monde contained extremely grave accusations against Solway Group and two of its subsidiaries. Solway considers all of these allegations and imputations to be neither vague nor general.
All these contentious remarks are, moreover, seriously damaging to the reputation of the Solway Group, as they, in essence, accuse the Group of extreme attacks on the integrity of people working in its locations or those living nearby, as well as of voluntarily, consciously seeking to hide these morally reprehensible behaviors.
Dan Bronstein, Chairman of the Board of Solway Investment Group said: "Living in a democratic society, we respect the freedom of speech and acknowledge the right of journalists to their private opinions. We are always happy to enter into fair discussions and deliver arguments to oppose criticism. What we cannot tolerate is when this criticism is based on purposely misrepresented facts and manipulative assumptions. Since the early days of the investigation, we have been working with the Forbidden Stories team to provide them with explanations and factual evidence. Most media outlets came out with relatively balanced coverage, and we can certainly take their criticism into consideration to further perfect the Group's performance.
When the borderline is crossed, however, we can only go to court in the hope that our counterarguments will be heard and judged fairly. Solway's primary responsibility is to promote and protect the health, safety and well-being of all its employees, contract staff, and members of Solway's host communities. We regret that we have been forced into defending our reputation through legal institutions instead of building a bilateral, productive dialogue, but we cannot step aside when the Group's reputation is under attack."


text:
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\section{Introduction}
\label{S:1}

A thermionic energy converter (TEC) is a solid-state heat engine that directly generates electric power from heat by thermionic emission of electrons \cite{Hatsopoulos1973,Hatsopoulos1979}. A vacuum TEC consists of emitter and collector electrodes separated by a vacuum gap, such that electrons vaporized from a hot emitter can be collected by a relatively cold collector. When the two electrodes are connected by an electrical load, electric current flows through the load due to the potential difference to generate electric power. TEC is beneficial because of its pollution-free and noise-free power generation. However, a TEC device needs a very high operating temperature and yet suffers from low energy conversion efficiency due to a high vacuum energy barrier \cite{Hatsopoulos1973,Hatsopoulos1979}. To mitigate these challenges, \citet{Schwede2010} proposed photon-enhanced thermionic emission (PETE) that utilizes photoexcitation of electrons for thermionic power generation by replacing a metallic emitter with a $p$-doped semiconductor. When the $p$-doped semiconductor emitter is illuminated by photons having energies above the band gap, photoexcitation of electrons increases the electron population in the conduction band, reducing the effective energy barrier for electron emission \cite{nelson2003physics,Green2003333}. In addition, thermalization of excessive photon energy increases the emitter temperature to facilitate thermionic emission of electrons. As a result, PETE is expected to generate power with a much higher energy conversion efficiency than a conventional TEC even at lower operating temperatures \cite{Schwede2010}.

The photon-enhancement of thermionic emission has been verified experimentally for different semiconducting materials  \cite{schwede2013photon,sun2014thermally,Tang2014,Zhuravlev2014,Zhuravlev2017}. Theoretical models have also been developed to understand the underlying physics of the PETE process and applied to predict the performance of a PETE device for concentrated solar power (CSP) \cite{Varpula2012a,Sahasrabuddhe2012,varpula2015,YANG2015410,FENG2018,yang2020temperature}. However, they handled the emitter temperature as an independent input variable without considering the energy balance of the system. Several works have conducted the energy balance analysis of the PETE device to calculate the dependence of the emitter temperature on incident solar radiation and its effect on the performance of PETE power generation \cite{Segev2012,Segev2013b, Su2013,su2014material, Segev2015,su2016photon,Kribus2016,sandovsky2016,xiao2018thermodynamic}. However, the obtained results are not consistent to each other, revealing that the accuracy of the energy balance analysis stringently depends on the adequate modeling of charge and thermal transports due to photothermal interactions of solar energy with electrode materials. Lack of rigor in the modeling of transport processes based on unrealistic material properties could lead to an overprediction of the PETE performance.

In the present article, we report the comprehensive energy balance analysis of a PETE device when concentrated solar radiation is incident onto the device. Instead of assuming perfect solar absorption by the thermionic emitter \cite{Segev2012,Segev2013b,Su2013,Segev2015,Segev2015a,sandovsky2016,Wang2016,WANG2019}, real material properties are implemented to calculate the locally distributed spectral solar absorption in the emitter structure.
Energy balance analysis is rigorously applied to the emitter structure to calculate its temperature distribution upon the illumination of solar radiation with different concentration factors. For accurate calculation of charge transport for a wide range of the interelectrode vacuum gap distance, we take into account the negative space charge effect \cite{ito2012optically,SU2014137,Reck2014a,Segev2015a,Buencuerpo2015,Kribus2016} and the image charge effect \cite{Wang2016} to the potential barrier profile. In addition to the energy transfer by electrons, radiative heat transfer should be considered as another energy transport mechanism between the electrodes. Particularly when the interelectrode vacuum gap is set within the single-digit micrometer or smaller range, a PETE device would suffer from significant radiative heat loss due to the near-field interactions of thermally induced evanescent electromagnetic (EM) waves in the vacuum space \cite{Park2013,liu2019effects,WANG2019}. Near-field radiative heat loss from the emitter structure to the collector is calculated by implementing the multi-layer dyadic Green's function within the fluctuational electrodynamics framework \cite{Park2008c}. Our study also presents optimal design and operating parameters for photon-enhanced thermionic concentrated solar power generation, along with the expected power output and the energy conversion efficiency.

\section{Modeling}
\label{S:2}
Fig. \ref{Fig1} illustrates the schematic diagram of the modeled PETE device under concentrated solar irradiation. The emitter electrode is configured as a boron-doped single crystalline silicon (Si) layer on a soda-lime glass substrate. Si is selected as an emitter material in the present study because it can withstand a higher operational temperature compared to other candidate materials, such as GaAs and InP, which start decomposing above 870 K for GaAs and above 750 K for InP \cite{varpula2015}. The glass substrate is required to structurally supports the Si emitter layer while transmitting high-energy photons to the Si emitter for photoexcitation of electrons. In addition, it absorbs some low-energy photons below the bandgap of Si, which is beneficially used to heat the emitter for thermalization. On the other hand, a phosphorus-doped diamond film deposited on tungsten by chemical vapor deposition (CVD) is considered as a thermionic collector due to its lowest work function measured to date (i.e., 0.9 eV) \cite{Koeck2009}.

For the energy balance analysis of the PETE device upon the concentrated solar irradiation, the emitter structure is discretized into $N$ layers for the glass substrate, each at temperature $T_{i}$ ($i=1,2,3 ... N$), and the Si emitter layer at $T_\mathrm{E}$ ($i=\mathrm{E}$). When the collector temperature is assumed to be uniform at $T_\mathrm{C}$, the energy balance equation for each layer of the emitter structure can be written as
\begin{subequations}
    \label{Eq:energy_S}
    \begin{IEEEeqnarray}{rCl}
        Q^{1}_\mathrm{abs}- Q^\mathrm{ S\rightarrow\infty}_\mathrm{rad}-Q^{1\rightarrow2}_\mathrm{con}&= 0& ~~~\mathrm{for}~~ i=1 \\

         Q^{i}_\mathrm{abs}+Q^{(i-1)\rightarrow i}_\mathrm{con}-Q^{i\rightarrow (i+1)}_\mathrm{con} &= 0& ~
         ~~\mathrm{for}~~ 2\le i \le N-1 \\

        Q^{N}_\mathrm{abs}+Q^{(N-1)\rightarrow N}_\mathrm{con}-Q^{N\rightarrow \mathrm{E}}_\mathrm{con}- Q^\mathrm{ S\rightarrow C}_\mathrm{rad} &= 0& ~~~\mathrm{for}~~ i = N
    \end{IEEEeqnarray}
\end{subequations}
for the glass substrate and
    \begin{equation}
        Q^\mathrm{E}_\mathrm{abs}+Q^{N\rightarrow \mathrm{E}}_\mathrm{con}- Q^\mathrm{ E\rightarrow C}_\mathrm{rad}- Q_e = 0
    \label{Eq:energy_E}
    \end{equation}
for the Si emitter. Here, $Q^{i}_\mathrm{abs}$ is the total solar irradiance absorbed in the $i$-th layer, $Q_\mathrm{rad}$ is the radiative heat flux, $Q^{i\rightarrow (i+1)}_\mathrm{con}$ is the conduction heat flux from the $i$-th to ($i+1$)-th layer, and $Q_e$ is the net energy flux carried by electrons. It should be noted that the convection heat loss from the top surface of the glass substrate is ignored by assuming that the PETE device is vacuum-packaged. The solar absorption per unit area in the $i$-th layer ($Q^{i}_\mathrm{abs}$) can be calculated by $Q^{i}_\mathrm{abs} = \int_0^\infty [G_\lambda(z_{i-1},\omega)-G_\lambda(z_{i},\omega)]d\omega$, where $G_\lambda (z_i,\omega)$ is the spectral solar irraidance (or flux) at interface $z_i$ and $\omega=2\pi c_0/\lambda$ is the angular frequency with $c_0$ and $\lambda$ being the speed of light in free space and the wavelength of solar radiation, respectively. In the present study, the spectral solar irradiance at each interface of the multi-layered emitter structure is calculated by the scattering-matrix method \cite{ Francoeur2009ay,Deparis:11}.

Radiative heat loss is another key feature for the accurate energy balance analysis. Radiative heat loss from the glass substrate to the environment is expressed as $Q^\mathrm{ S\rightarrow\infty}_\mathrm{rad}=\varepsilon \sigma( {T^4_1}-{T^4_\infty})$, where $\varepsilon$ is the total emissivity of glass, $\sigma$ is the Stefan-Boltzmann constant, and $T_\infty$ is the surrounding temperature \cite{gubareff1960thermal}. Near-field radiative heat losses from the glass substrate and the Si emitter to the collector are calculated within the fluctuational electrodynamics framework:
\begin{subequations}
    \label{Eq:energy_S}
    \begin{IEEEeqnarray}{rCl}
    Q^\mathrm{ S\rightarrow C}_\mathrm{rad}=\int_\mathrm{0}^\infty {S^\mathrm{ S\rightarrow C}_z(T_N,\omega)} d\omega \\
    \nonumber \\
    Q^\mathrm{ E\rightarrow C}_\mathrm{rad}=\int_\mathrm{0}^\infty {S^\mathrm{ E\rightarrow C}_z(T_\mathrm{E},\omega)} d\omega,
\end{IEEEeqnarray}
\end{subequations}
where superscripts S, E, and C represent the glass substrate, the emitter, and the collector, respsctively, and $S_\mathrm{z}$ is the time-averaged Poynting vector in the $z$-direction between layers as indicated by the arrow, which can be calculated using the multi-layer dyadic Green's function \cite{Park2008c}. For the calculation of the near-field radiative heat transfer, we assume that the collector is composed of a thin CVD diamond film on top of a semi-infinite tungsten at the uniform temperature, $T_\mathrm{C}$. In addition, $S_z^\mathrm{ S\rightarrow C}$ is calculated by assuming that the glass substrate is semi-infinite at $T_N$, which is an adequate assumption due to a short penetration depth of near-field thermal radiation \cite{Basu2009c}.
The conduction heat flux from the $i$-th to ($i+1$)-th layer in the emitter structure can be approximated as $Q^{i\rightarrow (i+1)}_\mathrm{con}= k_\mathrm{eff} \left(T_{i}-T_{i+1}\right)/\Delta z$, where $k_\mathrm{eff}$ is the effective thermal conductivity and $\Delta z$ is the distance between the center points of the $i$-th and ($i+1$)-th layers \cite{patankar2018numerical}. For the present study, dielectric functions were taken from literature for soda-lime glass \cite{RUBIN1985275}, boron-doped Si \cite{Fu2006a}, CVD diamond \cite{Dore:98}, and tungsten \cite{Lee2012j}. Among them, the temperature dependences of dielectric functions were considered for boron-doped Si and tungsten. The temperature-dependent thermal conductivities were also found from Ref. \cite{sergeev1982thermophysical} for soda-lime glass and Ref. \cite{Shank1963} for Si. It should be noted that the thermal conductivity of intrinsic Si is used for the present study due to the lack of available data for $p-$doped Si at high temperatures. However, we believe that this approximation would not significantly alter the result as the conduction thermal resistance of the Si emitter is three orders of magnitude smaller than that of the glass substrate.

The net energy flux transported by electrons from the emitter to the collector is expressed as \cite{Ghashami2017,WANG2019}
\begin{equation}
    \label{Eq:Qe}
    Q_{e}=\frac{1}{q}\left[(J_\mathrm{E}-J_\mathrm{C})W_\mathrm{max} + 2k_\mathrm{B}(J_\mathrm{E}T_\mathrm{E}-J_\mathrm{C}T_\mathrm{C})\right],
\end{equation}
where $J_\mathrm{E(C)}$ is the current density of the emitter (collector), $W_\mathrm{max}$ is the maximum potential barrier, $k_\mathrm{B}$ is the Boltzmann constant, and $q$ is the electron charge. It should be noted that a portion of the electron-carried energy is used to generate electric power while the remainder is lost as heat.
Solar radiation whose energy is greater than the energy bandgap of Si photoexcites electrons to the conduction band, which greatly enhances the concentration of electrons in the conduction band ($n$) over the equilibrium value ($n_\mathrm{eq}$). The thermionic current density from the emitter due to photoexcited electrons can be written as \cite{Wang2016}
\begin{equation}
\label{Eq:J_E}
    J_\mathrm{E}=\left(\frac{n}{n_\mathrm{eq}}\right)A_\mathrm{E} T_\mathrm{E}^2  \exp\left(-\frac{W_\mathrm{max}}{k_\mathrm{B} T_\mathrm{E}}\right),
\end{equation}
where $A_\mathrm{E}=120~\mathrm{A/cm^2K^2}$ is the Richardson constant of the Si emitter \cite{Schwede2010}. It should be noted that $J_\mathrm{E}^0 = A_\mathrm{E} T_\mathrm{E}^2  \exp(-W_\mathrm{max}/k_\mathrm{B} T_\mathrm{E})$ denotes the conventional thermionic current density, indicating that $n/n_\mathrm{eq}$ can be defined as \textit{the (photon-)enhancement ratio}. Similarly, the collector current density is expressed as $J_\mathrm{C}=A_\mathrm{C} T_\mathrm{C}^2  \exp[-({W_\mathrm{max}}-qV_\mathrm{op})/{k_\mathrm{B} T_\mathrm{C}}]$, where $A_\mathrm{C}=120~\mathrm{A/cm^2K^2}$ is the Richardson constant of the diamond collector \cite{Koeck2009,Schwede2010} and $V_\mathrm{op}$ is the operational voltage drop across the electrical load.

The carrier concentration in the conduction band of the Si emitter under photoexcitation ($n$) is calculated by the following equation \cite{Schwede2010,Ghashami2017}:
\begin{equation}
\label{Eq:Gamma_Balance}
    \Gamma_\mathrm{gen}-\Gamma_\mathrm{rec}-\Gamma_e=0,
\end{equation}
which balances the photogeneration rate of electron-hole pairs due to solar absorption ($\Gamma_\mathrm{gen}$), the recombination rate of electron-hole pairs ($\Gamma_\mathrm{rec}$), and the thermionic emission rate of photoexcited electrons from the emitter ($\Gamma_e$). The photogeneration rate of electron-hole pairs can be expressed as $\Gamma_\mathrm{gen}=(1/d_\mathrm{E})\int_{\hbar\omega\geq E_\mathrm{g}} \left[Q_\mathrm{abs,\lambda}^\mathrm{E}(\omega)/\hbar\omega\right] d\omega$,
where $d_\mathrm{E}$ is the emitter thickness, $\hbar$ is the reduced Plank constant, $E_\mathrm{g}$ is the energy bandgap of the emitter, and $Q_\mathrm{abs,\lambda}^\mathrm{E}$ is the spectral absorption of the solar irradiance in the emitter.
In the present study, the temperature-dependence of the Si bandgap is considered by $E_\mathrm{g}=1.170-(4.73\times 10^{-4})T_\mathrm{E}^2/(T_\mathrm{E}+636)$ eV \cite{sze2006physics}. The recombination rate ($\Gamma_\mathrm{rec}$) is determined by considering the near-field radiative recombination ($\Gamma_\mathrm{rad}$), Auger recombination ($\Gamma_\mathrm{Aug}$), Shockley-Read-Hall recombination ($\Gamma_\mathrm{SRH}$) and surface recombination ($\Gamma_\mathrm{surf}$) mechanisms, i.e., $\Gamma_\mathrm{rec}=\Gamma_\mathrm{rad}+\Gamma_\mathrm{Aug}+\Gamma_\mathrm{SRH}+\Gamma_\mathrm{surf}$. Detailed formulation of each type of recombination can be found in other works \cite{Segev2013b,Ghashami2017} and will not be repeated here. Finally, the thermionic emission rate of photoexcited electrons ($\Gamma_e$) can be calculated by $\Gamma_e=\left(J_\mathrm{E}-J_\mathrm{E}^0\right)/qd_\mathrm{E}$.

$W_\mathrm{max}$ can be determined from the potential energy barrier profile $W(x)$ in the inter-electrode gap space. $W(x)$ is written as
\begin{equation}
\label{eq12}
    W(x) = W_\mathrm{\mathrm{sc}}(x) +  W_\mathrm{\mathrm{ic}}(x)
\end{equation}
based on the potential barrier profile due to electron accumulation in the inter-electrode space, $W_\mathrm{\mathrm{sc}}(x)$, and the image charge perturbation, $W_\mathrm{\mathrm{ic}}(x)$. When electrons accumulate in the inter-electrode vacuum space and build up negative space charges, it hinders further emission of electrons from the emitter surface. Under the assumption that electrons traveling in the inter-electrode gap are collisionless, the space charge potential can be calculated by numerically solving Poisson's equation \cite{Langmuir1923,Hatsopoulos1973,Hatsopoulos1979,WANG2019}:
\begin{equation}
\label{Eq:Poisson}
\frac{d^2W_\mathrm{sc}(x)}{dx^2}=-\frac{q^2N_\mathrm{e}(x)}{\epsilon_{0}},
\end{equation}
where $x$ is the location between the emitter ($x= 0$) and the collector $(x=d_\mathrm{G})$, $N_e(x)$ is the local electron number density, and $\epsilon_{0}$ is the permittivity of vacuum. Boundary conditions for Eq. (\ref{Eq:Poisson}) are $W_\mathrm{sc}(0)=\Phi_\mathrm{E}$ and $W_\mathrm{sc}(d_\mathrm{G})=\Phi_\mathrm{C}$ while $dW_\mathrm{sc}/dx=0$ at $x=x_\mathrm{max}$ ($0\leq x_\mathrm{max} \leq d_\mathrm{G}$), where $\Phi_\mathrm{E(C)}$ is the work function of the emitter (collector). For a semiconductor emitter, the work function can be expressed as $\Phi_\mathrm{E}=\chi+E_g-E_F$, where $\chi$ and $E_F$ are the electron affinity and the Fermi energy of the emitter, respectively. The numerical framework to calculate $W_\mathrm{sc}$ has been discussed in detail in Ref. \cite{Hatsopoulos1973,Hatsopoulos1979,WANG2019}.
On the other hand, the image charge potential $W_{\mathrm{ic}}(x)$ is calculated by considering the electrostatic forces between image charges formed in the electrodes and the electrons in the vacuum gap \cite{Simmons1963a,Hishinuma2001,Baldea2012a,Wang2016}:
\begin{equation}
\label{eq15}
  W_{\mathrm{ic}}(x) = \frac{q^2}{16\pi \epsilon_0 d_\mathrm{G}}\left[-2\Psi(1)+\Psi\left( \frac{x}{d_\mathrm{G}}\right)+\Psi\left(1-\frac{x}{d_\mathrm{G}}\right)\right]
\end{equation}
where $\Psi$ is the digamma function. It should be noted that the image charge effect competes with the space charge effect in modifying the potential barrier. For a larger inter-electrode vacuum gap, the space charge effect plays a dominant role to increase the potential barrier. However, as the inter-electrode gap distance decreases, the image charge effect becomes important to lower the potential barrier while the space charge effect is suppressed due to the sweep of electrons under the stronger electric field between the electrodes \cite{Jensen2017b}.

Since charge and thermal transport processes are strongly coupled, the energy balance analysis should be carefully conducted through iterations. After the initial calculation of $Q_\mathrm{abs}^i$ in each layer, the temperature distribution of the emitter structure is calculated iteratively until the incoming and outgoing energy fluxes of the Si emitter in Eq. (\ref{Eq:energy_E}) are balanced within the convergence criterion of 0.001\%. From the energy balance analysis and the thermionic current density calculation, the electric power density can be determined by
\begin{equation}
    P_\mathrm{net}=(J_\mathrm{E}-J_\mathrm{C})V_\mathrm{op},
    \label{Eq:P_net}
\end{equation}
In addition, the energy conversion efficiency is defined as
\begin{equation}
    \eta=\frac{P_\mathrm{net}}{C\times Q_s},
\end{equation}
where $C$ is the concentration factor and $Q_s$ is the total solar irradiance with the global standard spectrum (AM1.5D). Therefore, when the concentration factor is fixed, the energy conversion efficiency should be linearly proportional to the generated power density.
Table \ref{table:1} summarizes input and geometrical parameters that are optimized through the energy balance analysis. More discussions about the optimization process will be provided in the following section. Unless otherwise mentioned, these parameters are used to calculate the PETE power generation. The collector temperature ($T_\mathrm{C}$) is set to 540 K by satisfying the optimal collector condition, i.e., $T_\mathrm{C}=600\times\Phi_\mathrm{C}$ \cite{Hatsopoulos1973,Lee2012j,WANG2019}. The effect of the collector temperature onto the PETE performance is further discussed in Fig. \ref{Fig7}.

\section{Results and Discussion}
\label{S:3}
When concentrated solar radiation is incident on the PETE device, part of the solar energy is absorbed as it interacts with each of the layers. Fig. \ref{Fig2}(a) shows the solar absorption spectra in the glass substrate ($Q_\mathrm{abs,\lambda}^\mathrm{S}$) and the Si emitter layer ($Q_\mathrm{abs, \lambda}^\mathrm{E}$). In the figure, the shaded region denotes the above-bandgap spectrum of Si at 925 K, which is the calculated temperature of the Si emitter at the default operation conditions (Table \ref{table:1}). It should be noted that the temperature dependence of the Si bandgap was considered here (i.e., $E_g =$ 0.91 eV at 925 K) as described in the Modeling section. For this particular case, 57.2 \% of the above-bandgap solar energy is absorbed by the Si emitter to photoexcite electrons, while 25.3 \% of the above-bandgap energy is absorbed by the glass substrate. In addition, sub-bandgap energy is also absorbed by the Si emitter (50.5\%) and the glass substrate (32.6 \%). All absorbed solar energy not used for photoexcitation is converted to heat the emitter structure, which is in fact beneficial for thermalization of electrons. Fig. \ref{Fig2}(b) shows the resultant local temperature profile of the emitter structure. The top surface of the emitter assembly ($z=0$) has a lower temperature (864 K) due to radiative heat loss to the environment. While strong absorption of sub-bandgap energy in the glass substrate is desired to increase the emitter layer temperature for thermionic emission, it also induces substantial radiavie heat loss to the environment. Although the present study considers glass as a readily available and cost-effective substrate material, an optically engineered substrate can be implemented to maximize thermionic emission by making a good balance between photoexcitation and thermalization of electrons in the emitter.

The net PETE current density ($J_\mathrm{net}=J_\mathrm{E}-J_\mathrm{C}$) as a function of the operational voltage is shown in Fig. \ref{Fig3}(a) for different electron affinities of Si. Other design parameters still remain the same as provided in Table \ref{table:1}. The general trend of the calculated $J-V$ curve is similar to the conventional thermionic emission, which shows a nearly constant current density up to the flat-band voltage ($V_\mathrm{FB}=(\Phi_\mathrm{E}-\Phi_\mathrm{C})/q$) and decays in the Boltzmann regime ($V_\mathrm{op}>V_\mathrm{FB}$) \cite{Hatsopoulos1979}. As a result, the PETE power density and the efficiency reach the maxima at the optimal operating voltage around $V_\mathrm{FB}$: see Fig. \ref{Fig3}(b). However, the PETE power density ($P_\mathrm{net}$) and the efficiency ($\eta$) will be kept and used to denote the maximum values at the optimal operating voltage for simplicity in the remaining results and discussion. Figs. \ref{Fig3}(a) and (b) also show the effect of the electron affinity to the PETE current and the power densities. Previous studies have demonstrated that the electron affinity of Si can be tuned over a wide range even to a negative value by cesium deposition or oxygen-potassium co-adsorption \cite{goldstein1973leed,martinelli1974thermionic,morikawa1995further,smestad2004conversion}. The obtained results demonstrate that PETE power generation is benefited by lowing the electron affinity of the emitter. A low electron affinity leads to a low potential barrier within the inter-electrode vacuum space, allowing more electron emission from the emitter in the flat-band regime. However, the maximum power output (the efficiency) only increases from 1.56 W/cm$^2$ (17.3 \%) to 1.62 W/cm$^2$ (18.0 \%) when the electron affinity changes from 0.9 eV to 0.6 eV. Particularly, the power density curves for $\chi=0.6$ eV and $0.7$ eV are almost identical, suggesting that the electron affinity of the Si emitter should be optimized at 0.7 eV for the best cost-effectiveness. The electron affinity also affects the emitter temperature as can be seen in Fig. \ref{Fig3}(c). A low electron affinity facilitates the emission of hot electrons by lowing the potential barrier, resulting in a decrease of the emitter temperature. When optimized at $\chi=0.7$ eV, the emitter temperature at the maximum power output is calculated to be 925 K, which is much lower than an operational temperature of conventional thermionic power generation.

The thickness of the semiconducting emitter layer may be one of the most important factors that govern PETE power generation. As shown in Fig.\ref{Fig4}(a), almost $57\%$ of the total incident solar radiation can be absorbed by the Si layer when its thickness becomes $\sim 50$ $\mu$m. However, further increase of the Si layer thickness does not help increase the solar absorption. On the other hand, the glass substrate absorbs $\sim$26\% of the incident solar radiation, although its value is slightly affected by the Si layer thickness. For a sub-micron Si layer, solar radiation is reflected back from the bottom surface of the Si layer and absorbed by the substrate again. The remaining $\sim17\%$ is reflected from the top surface of the glass substrate, which is considered as the optical loss. Fig. \ref{Fig4}(b) shows the PETE power output as a function of the Si layer thickness. The increasing electric power output for $d_\mathrm{E} \lesssim 50$ $\mu$m is consistent with the solar absorption trend in the Si emitter, indicating that photoexcited electrons drive thermionic power generation. However, the power output begins to slightly decrease with the further increase of the Si layer thickness because more electron-hole pairs start recombining than being photogenerated as the emitter becomes thicker than the optimal value \cite{YANG2015410}. Therefore, the Si emitter thickness is optimized to $50$ $\mu$m that suppresses the recombination of electron-hole pairs while the solar absorption by the Si emitter is fully secured.

Another key parameter for PETE power generation is the inter-electrode vacuum gap distance. The gap-dependent PETE behaviors shown in Fig. \ref{Fig5} demonstrate strongly coupled charge and thermal transport processes across the vacuum gap.  For large gap distances above 2 $\mu$m, the negative charge effect plays a dominant role in the PETE process. The buildup of the potential barrier (or $W_\mathrm{max}$) as a result of the negative charge effect inhibits thermionic emission of electrons, which is manifested by the drastic decrease of the PETE power density ($P_\mathrm{net}$) and the thermionic heat loss (i.e., $Q_\mathrm{e}-P_\mathrm{net}$): see Figs. \ref{Fig5}(a) and (b). The inhibition of thermionic emission also results in the significant increase of the emitter temperature, as shown in Fig. \ref{Fig5}(c). However, reducing the inter-electrode vacuum gap into the sub-micron regime does not improve PETE performance as well. Although electrons may travel more freely in a sub-micron vacuum space due to the image charge effect and the suppression of the space charge effect, near-field radiative heat transfer increases with the decreasing vacuum gap distance: see Fig. \ref{Fig5}(b). As a result, the emitter temperature cools down for a sub-micron vacuum gap, which ultimately reduces the PETE power output. The optimal gap distance for the best PETE power generation is determined at 2 $\mu$m for the present study, which produces the power density of 1.61 W/cm$^2$ with 17.9 \% energy conversion efficiency for 100$\times$ solar concentration. Fig. \ref{Fig5}(c) also shows the decreasing trend of the photon-enhancement ratio ($n/n_\mathrm{eq}$) as a function of the inter-electrode gap distance. The dependence of $n_\mathrm{eq}$ on the emitter temperature is expressed as $n_\mathrm{eq}=N_C\exp{\left[-(E_g - E_F)/k_B T_\mathrm{E}\right]}$ with $N_C=2\left(m_e^* k_BT_\mathrm{E}/2\pi\hbar^2\right)^{3/2}$ being the effective density of states in the conduction band of Si \cite{sze2006physics}. When the gap distance increases to $d=10$ $\mu$m (i.e., $T_\mathrm{E}=1119$ K), thermally excited electrons ($n_\mathrm{eq}$) greatly outnumber photoexcited electrons ($n-n_\mathrm{eq}$) in the conduction band to make the enhancement ratio close to the unity ($n \approx n_\mathrm{eq}$).

Fig. \ref{Fig6} presents the effect of the solar concentration factor onto the PETE performance. As expected, both the PETE power output and the efficiency monotonically increase with the increasing solar concentration factor. However, a high concentration factor drastically decreases the photon-enhancement ratio, indicating that the thermal excitation of electrons should play a more dominant role than photoexcitation in thermionic power generation for high solar concentration. The transition of the electron excitation mechanism is supported by the monotonic increase of the emitter temperature plotted in Fig. \ref{Fig6}(b). Although the photoexcitation rate of electrons in the Si emitter is proportional to the solar concentration factor, most of the absorbed solar energy is converted to heat to increase the emitter temperature. At 150$\times$ suns, for example, the enhancement ratio decreases to $\sim$1.5 while the emitter temperature exceeds 1000 K, suggesting that PETE may be a better energy conversion process for low to mid-scale CSP (e.g., $C\lesssim100$). Unstable semiconducting behaviors at high temperatures (e.g., $\gtrsim1000$ K for Si) are another potential issue of implementing a PETE device for high CSP. It should be noted that the obtained enhancement ratio is much smaller than the previous work \cite{WANG2019}, which predicted the enhancement ratio in the range of several thousand at 100$\times$ suns. We believe that this discrepancy may be due to the aforementioned exponential dependence of $n_\mathrm{eq}$ on the bandgap and temperature of the emitter. While the present study considers the temperature-dependent narrowing of the Si bandgap, which is reduced from 1.12 eV at 300 K to 0.88 eV at 1000 K, \citet{WANG2019} used a constant bandgap (1.4 eV) for calculation. In addition, they did not consider the Auger and Shockley-Read-Hall recombinations, which may lead to an inaccurate prediction of $n$.

Although the collector temperature is set to 540 K to meet the optimal operating condition in the present study, Fig. \ref{Fig7} presents the effect of the collector temperature onto the PETE performance when all other parameters are optimized as given in Table \ref{table:1}. As the collector temperature increases, the PETE performance deteriorates as a result of the increase of the back emission from the collector to the emitter. The back emission becomes more significant when the collector temperature surpasses $\sim$550 K, leading to the drop of the power output and efficiency. Although it seems beneficial to cool the collector below the optimal temperature, it should be noted that lowering the collector temperature requires additional cooling power that is not considered for the calculation of Fig. \ref{Fig7}. The slight gain of the PETE power output by cooling the collector would not be sufficient enough to cover the required cooling load to maintain the collector temperature.

Table \ref{table:2} summarizes the distribution of incident solar energy into the power output and various losses under the determined geometric configuration and operating conditions as tabulated in Table \ref{table:1}. A portion of incident solar energy that is not absorbed in the device (17.3 \%) accounts for the optical loss. This loss is mostly due to the reflection of solar radiation at the top surface of the glass substrate. Another substrate-related loss is the far-field radiative heat loss to the environment, which takes 27.3 \% of the incoming solar energy. These two loss factors emphasize the importance of substrate material for PETE power generation. Since a substrate is an essential structure that supports a thin semiconducting emitter layer, a substrate material should be carefully selected or engineered to minimize solar reflection in the visible range and thermal emission in the mid-IR range while being transparent in the above-bandgap solar spectrum for effective photoexcitation of electrons in the emitter layer. The optimal design of a substrate material and structure is one of the key requirements to maximize the PETE performance and should be studied in the near future. Thermionic energy transport ($Q_\mathrm{e}$) is the most important mechanism that carries more than 50\% of the incoming solar energy to the collector. Although $\sim$65\% of the thermionic energy is lost as waste heat, this loss is inevitable as far as $P_\mathrm{net}$ is to be maximized: see Eqs. (\ref{Eq:Qe}) and (\ref{Eq:P_net}). The obtained energy conversion efficiency (17.9 \%) is much lower than those predicted in the previous studies \cite{Schwede2010,liu2019effects,WANG2019}. For example, \citet{liu2019effects} predicted the efficiency of 30.2 \% when the PETE device is configured by 0.55$\mu$m inter-electrode gap and operated at $T_\mathrm{E}=1000$ K under 1000$\times$ suns. Their overestimation mainly comes from the fixed temperature assumption without the rigorous energy balance analysis. They also ignored the optical loss and the far-field radiative heat loss to the environment, both of which take a substantial portion of the wasted energy. Assuming the constant emitter bandgap at 1.11 eV without non-radiative recombination processes is another reason of their overprediction of the PETE power output. However, our results show that PETE is still competitive when compared with other CSP technologies \cite{ju2017review,islam2018comprehensive}, and has a room for further improving its performance by implementing novel engineered materials and optimizing the operating conditions.

\section{Conclusion}
\label{S:d}
The present study reports a rigorous energy balance analysis of a PETE device for the evaluation of its performance when the device is to be used for CSP. Instead of assuming ideal materials and operating conditions, we have considered a PETE device configured with real materials (i.e., a boron-doped Si thermionic emitter on top of a glass substrate and a phosphorus-doped CVD diamond collector on top of a tungsten substrate) and accounted for all major energy loss mechanisms occurring in the device under solar irradiation. The dependences of the PETE process on several key parameters, such as the Si emitter thickness, the inter-electrode vacuum gap, the solar concentration factor, and the collector temperature, have been carefully examined to find an optimal design point that would provide the best PETE power output and the energy conversion efficiency. The predicted performance turns out to be not as remarkable as the earlier studies mainly due to the optical and far-field radiative heat losses from the glass substrate, which could be reduced by optically engineering a substrate material and structure to balance the photoexcitation and thermalization processes of electrons in the emitter layer. Although we have considered only one specific PETE device configuration, the developed energy balance analysis and the obtained results can help better understand a realistic feature of the photon-enhanced thermionic energy conversion process for CSP.

\section*{Acknowledgement}
This research has been supported by National Science Foundation (NSF: ECCS 1611320) and U.S. Department of Energy Solar Energy Technologies Office (DE: EE0008531). The authors greatly acknowledge Dr. Mathieu Francoeur from the University of Utah for fruitful discussions and his valuable comments.

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