ace Scurry: A Race-To-Finish Scavenger Hunt App By feedproxy.google.com Published On :: Thu, 26 Mar 2020 13:58:00 -0400 We have a lot of traditions here at Viget, many of which you may have read about - TTT, FLF, Pointless Weekend. There are others, but you have to be an insider for more information on those. Pointless Weekend is one of our favorite traditions, though. It’s been around over a decade and some pretty fun work has come out of it over the years, like Storyboard, Baby Bookie, and Short Order. At a high level, we take 48 hours to build a tool, experiment, or stunt as a team, across all four of our offices. These projects are entirely separate from our client work and we use them to try out new technologies, explore roles on the team, and stress-test our processes. The first step for a Pointless Weekend is assembling the teams. We had two teams this year, with a record number of participants. You can read about TrailBuddy, what the other team built, here. The Scurry team was split between the DC and Durham offices, so all meetings were held via Hangout. Once we were assembled, we set out to understand the constraints and the goals of our Pointless Project. We went into this weekend with an extra pep in our step, as we were determined to build something for the upcoming Viget 20th anniversary TTT this summer. Here’s what we knew we wanted: An activity all Vigets could do together, where they could create memories, and share broadly on socialSomething that we could use in a spotty network at C Lazy U Ranch in ColoradoA product we can share with others: corporate groups, families and friends, schools, bachelor/ette parties We landed on a scavenger hunt native app, which we named Scurry (Scavenger + Hurry = Scurry. Brilliant, right?). There are already a few scavenger apps available, so we set out to create something that was Quick and easy to set up huntsFree and intuitive for usersA nice combination of trivia and activitiesSocial! We wanted to enable teams to share photos and progress One of the main reasons we have Pointless Weekends is to test out new technologies and processes. In that vein, we tried out Notion as our central organizing tool - we used it for user journeys, data modeling, and even writing tickets, which we typically use Github for. We tested out Notion as our primary tool, writing tickets and tracking progress. When we built the app, we needed to prepare for spotty network service, as internet connectivity isn’t guaranteed at C Lazy U Ranch – where our Viget20 celebration will be. A Progressive Web Application (PWA) didn't make sense for our tech requirements, so we chose the route of creating a native application. There are a number of options available to build native applications. But, as we were looking to make as much progress as possible in 48-hours, we chose one of our favorite frameworks: React Native. React Native allows developers to build true, cross-platform native applications, using some of our favorite technologies: javascript, the React framework, and a native-specific variant of CSS. We decided on the turn-key solution Expo. Expo has extra tooling allowing for easy development, deployment, and debugging. This is a snap shot of our app and Expo. Our frontend developers were able to immediately dive in making screens and styling components, and quickly made the mockups in Whimsical a reality. On the backend, we used the supported library to connect to the backend datastore, Firebase. Firebase is a hosted solution for data storage, with key features built-in like authentication, realtime updates, and offline support. Our backend developer worked behind the frontend developers hooking those views up to live data. Both of these tools, Expo and Firebase, were easy to use and allowed us to focus on building a working application quickly, rather than being mired in setup or bespoke solutions to common problems. Whimsical is one of our favorite tools for building out mockups of an app. We made impressive progress in our 48-hour sprint, but there’s still some work to do. We have some additional features we hope to add before TTT, which will require additional testing and refining. For now, stay tuned and sign up for our newsletter. We’ll be sure to share when Scurry is ready for the world! Full Article News & Culture
ace Meet the Remote Workplaces of the WPZOOM Team By feedproxy.google.com Published On :: Thu, 26 Mar 2020 15:55:21 +0000 The world turned upside down lately, forcing the majority of people to work from their homes. For the WPZOOM team, working remotely is not something new. Some of our team members have been working remotely since they joined us, others had the experience of both working from home and from the office (hello, Pavel). However, we’ve gone completely remote, without […] Full Article News
ace TTT in SPAAACE By feedproxy.google.com Published On :: Mon, 24 Feb 2020 09:33:00 -0500 By now, you’ve probably heard of TTT, our quarterly team events. If you haven’t, you should read all about their history. TTT, or Third Third Thursday, is a time for us to look back and look ahead. Twice a year, all four offices come together for an all-hands, conference-style experience. The other two TTTs are celebrated locally and casually. Each office meets for a round-table discussion followed by a fun activity out of the office. In these meetings, we discuss team and industry changes and review business health metrics. Additionally, at each TTT, both our President, Andy Rankin, and CEO Brian Williams, directly field questions from any member of our team. At our TTTs we’ve talked about team diversity and tech ethics, celebrated our victories, and worked through our failures. The conversations have sparked new understanding, new initiatives, new processes, and have truly shaped the company over time. We come together in the spirit of “progress, not perfection.” While each office is unique, and the conversation is tailored to and shaped by each audience, the People Team finds ways to make everyone’s TTT similar, particularly our afternoon activity, so we can bond over shared experiences, even miles apart. This summer, we all tried our hands at ax throwing, and just a few weeks ago each of our offices got to venture into Space.Well, sort of. After a morning meeting, Boulder visited the Fiske Planetarium at CU Boulder. Durham visited UNC’s Morehead Planetarium. And since the Smithsonian is refurbishing the Einstein Planetarium, our Falls Church office made our way to the Udvar Hazy center to catch an Imax show and fly a few jets, via simulator. Each office also got a taste of space food trying Astronaut ice cream, to mixed reviews. TTTs are more than fun snacks and field trips. They are about finding common ground with colleagues, challenging each other to grow, and re-connecting with folks you don’t work with day-to-day. They are about setting aside time for frank discussion across disciplines and experience levels, and getting outside the office for new perspectives. They are just a little part of what makes Viget so unique. Are you ready to join us for our next big TTT adventure? It’s Viget20, and it’s going to be a good one. We're hiring. Full Article News & Culture
ace Scurry: A Race-To-Finish Scavenger Hunt App By feedproxy.google.com Published On :: Thu, 26 Mar 2020 13:58:00 -0400 We have a lot of traditions here at Viget, many of which you may have read about - TTT, FLF, Pointless Weekend. There are others, but you have to be an insider for more information on those. Pointless Weekend is one of our favorite traditions, though. It’s been around over a decade and some pretty fun work has come out of it over the years, like Storyboard, Baby Bookie, and Short Order. At a high level, we take 48 hours to build a tool, experiment, or stunt as a team, across all four of our offices. These projects are entirely separate from our client work and we use them to try out new technologies, explore roles on the team, and stress-test our processes. The first step for a Pointless Weekend is assembling the teams. We had two teams this year, with a record number of participants. You can read about TrailBuddy, what the other team built, here. The Scurry team was split between the DC and Durham offices, so all meetings were held via Hangout. Once we were assembled, we set out to understand the constraints and the goals of our Pointless Project. We went into this weekend with an extra pep in our step, as we were determined to build something for the upcoming Viget 20th anniversary TTT this summer. Here’s what we knew we wanted: An activity all Vigets could do together, where they could create memories, and share broadly on socialSomething that we could use in a spotty network at C Lazy U Ranch in ColoradoA product we can share with others: corporate groups, families and friends, schools, bachelor/ette parties We landed on a scavenger hunt native app, which we named Scurry (Scavenger + Hurry = Scurry. Brilliant, right?). There are already a few scavenger apps available, so we set out to create something that was Quick and easy to set up huntsFree and intuitive for usersA nice combination of trivia and activitiesSocial! We wanted to enable teams to share photos and progress One of the main reasons we have Pointless Weekends is to test out new technologies and processes. In that vein, we tried out Notion as our central organizing tool - we used it for user journeys, data modeling, and even writing tickets, which we typically use Github for. We tested out Notion as our primary tool, writing tickets and tracking progress. When we built the app, we needed to prepare for spotty network service, as internet connectivity isn’t guaranteed at C Lazy U Ranch – where our Viget20 celebration will be. A Progressive Web Application (PWA) didn't make sense for our tech requirements, so we chose the route of creating a native application. There are a number of options available to build native applications. But, as we were looking to make as much progress as possible in 48-hours, we chose one of our favorite frameworks: React Native. React Native allows developers to build true, cross-platform native applications, using some of our favorite technologies: javascript, the React framework, and a native-specific variant of CSS. We decided on the turn-key solution Expo. Expo has extra tooling allowing for easy development, deployment, and debugging. This is a snap shot of our app and Expo. Our frontend developers were able to immediately dive in making screens and styling components, and quickly made the mockups in Whimsical a reality. On the backend, we used the supported library to connect to the backend datastore, Firebase. Firebase is a hosted solution for data storage, with key features built-in like authentication, realtime updates, and offline support. Our backend developer worked behind the frontend developers hooking those views up to live data. Both of these tools, Expo and Firebase, were easy to use and allowed us to focus on building a working application quickly, rather than being mired in setup or bespoke solutions to common problems. Whimsical is one of our favorite tools for building out mockups of an app. We made impressive progress in our 48-hour sprint, but there’s still some work to do. We have some additional features we hope to add before TTT, which will require additional testing and refining. For now, stay tuned and sign up for our newsletter. We’ll be sure to share when Scurry is ready for the world! Full Article News & Culture
ace Teamstack: Everything You Need, All in One Place By webdesignledger.com Published On :: Fri, 10 Apr 2020 14:17:08 +0000 You know what sucks? Having to navigate through dozens of tools, all on separate dashboards, just to get one job done. Nowadays, there’s a tool for everything, and while that’s amazing, it’s very overwhelming sometimes. Oftentimes, some tools are forgotten about completely. How on earth do we tackle this situation? I mean, as time goes […] Read More at Teamstack: Everything You Need, All in One Place Full Article Editors Pick Featured News Resources Tools
ace Track Your Keyword Placement with Ranktrackify (Sponsored) By feedproxy.google.com Published On :: Mon, 27 Apr 2020 16:17:10 +0000 I don’t need to tell you how important search engine placement is. You either earn it with quality content, loads of SEO work, paying for placement, or all of the above. And even we you achieve best placement, you need to be wary of your content becoming stale or someone else coming along with a […] The post Track Your Keyword Placement with Ranktrackify (Sponsored) appeared first on David Walsh Blog. Full Article Sponsored
ace Is Zero UI The Key Factor For The Future Of Interfaces? By icanbecreative.com Published On :: Tue, 10 Mar 2020 05:54:37 PDT Zero UI is about removing everything that comes between users and their devices, about making the interaction easier, seamless, more direct. Does it sound to you like a concept from a science-fiction... Full Article Technology
ace TTT in SPAAACE By feedproxy.google.com Published On :: Mon, 24 Feb 2020 09:33:00 -0500 By now, you’ve probably heard of TTT, our quarterly team events. If you haven’t, you should read all about their history. TTT, or Third Third Thursday, is a time for us to look back and look ahead. Twice a year, all four offices come together for an all-hands, conference-style experience. The other two TTTs are celebrated locally and casually. Each office meets for a round-table discussion followed by a fun activity out of the office. In these meetings, we discuss team and industry changes and review business health metrics. Additionally, at each TTT, both our President, Andy Rankin, and CEO Brian Williams, directly field questions from any member of our team. At our TTTs we’ve talked about team diversity and tech ethics, celebrated our victories, and worked through our failures. The conversations have sparked new understanding, new initiatives, new processes, and have truly shaped the company over time. We come together in the spirit of “progress, not perfection.” While each office is unique, and the conversation is tailored to and shaped by each audience, the People Team finds ways to make everyone’s TTT similar, particularly our afternoon activity, so we can bond over shared experiences, even miles apart. This summer, we all tried our hands at ax throwing, and just a few weeks ago each of our offices got to venture into Space.Well, sort of. After a morning meeting, Boulder visited the Fiske Planetarium at CU Boulder. Durham visited UNC’s Morehead Planetarium. And since the Smithsonian is refurbishing the Einstein Planetarium, our Falls Church office made our way to the Udvar Hazy center to catch an Imax show and fly a few jets, via simulator. Each office also got a taste of space food trying Astronaut ice cream, to mixed reviews. TTTs are more than fun snacks and field trips. They are about finding common ground with colleagues, challenging each other to grow, and re-connecting with folks you don’t work with day-to-day. They are about setting aside time for frank discussion across disciplines and experience levels, and getting outside the office for new perspectives. They are just a little part of what makes Viget so unique. Are you ready to join us for our next big TTT adventure? It’s Viget20, and it’s going to be a good one. We're hiring. Full Article News & Culture
ace Scurry: A Race-To-Finish Scavenger Hunt App By feedproxy.google.com Published On :: Thu, 26 Mar 2020 13:58:00 -0400 We have a lot of traditions here at Viget, many of which you may have read about - TTT, FLF, Pointless Weekend. There are others, but you have to be an insider for more information on those. Pointless Weekend is one of our favorite traditions, though. It’s been around over a decade and some pretty fun work has come out of it over the years, like Storyboard, Baby Bookie, and Short Order. At a high level, we take 48 hours to build a tool, experiment, or stunt as a team, across all four of our offices. These projects are entirely separate from our client work and we use them to try out new technologies, explore roles on the team, and stress-test our processes. The first step for a Pointless Weekend is assembling the teams. We had two teams this year, with a record number of participants. You can read about TrailBuddy, what the other team built, here. The Scurry team was split between the DC and Durham offices, so all meetings were held via Hangout. Once we were assembled, we set out to understand the constraints and the goals of our Pointless Project. We went into this weekend with an extra pep in our step, as we were determined to build something for the upcoming Viget 20th anniversary TTT this summer. Here’s what we knew we wanted: An activity all Vigets could do together, where they could create memories, and share broadly on socialSomething that we could use in a spotty network at C Lazy U Ranch in ColoradoA product we can share with others: corporate groups, families and friends, schools, bachelor/ette parties We landed on a scavenger hunt native app, which we named Scurry (Scavenger + Hurry = Scurry. Brilliant, right?). There are already a few scavenger apps available, so we set out to create something that was Quick and easy to set up huntsFree and intuitive for usersA nice combination of trivia and activitiesSocial! We wanted to enable teams to share photos and progress One of the main reasons we have Pointless Weekends is to test out new technologies and processes. In that vein, we tried out Notion as our central organizing tool - we used it for user journeys, data modeling, and even writing tickets, which we typically use Github for. We tested out Notion as our primary tool, writing tickets and tracking progress. When we built the app, we needed to prepare for spotty network service, as internet connectivity isn’t guaranteed at C Lazy U Ranch – where our Viget20 celebration will be. A Progressive Web Application (PWA) didn't make sense for our tech requirements, so we chose the route of creating a native application. There are a number of options available to build native applications. But, as we were looking to make as much progress as possible in 48-hours, we chose one of our favorite frameworks: React Native. React Native allows developers to build true, cross-platform native applications, using some of our favorite technologies: javascript, the React framework, and a native-specific variant of CSS. We decided on the turn-key solution Expo. Expo has extra tooling allowing for easy development, deployment, and debugging. This is a snap shot of our app and Expo. Our frontend developers were able to immediately dive in making screens and styling components, and quickly made the mockups in Whimsical a reality. On the backend, we used the supported library to connect to the backend datastore, Firebase. Firebase is a hosted solution for data storage, with key features built-in like authentication, realtime updates, and offline support. Our backend developer worked behind the frontend developers hooking those views up to live data. Both of these tools, Expo and Firebase, were easy to use and allowed us to focus on building a working application quickly, rather than being mired in setup or bespoke solutions to common problems. Whimsical is one of our favorite tools for building out mockups of an app. We made impressive progress in our 48-hour sprint, but there’s still some work to do. We have some additional features we hope to add before TTT, which will require additional testing and refining. For now, stay tuned and sign up for our newsletter. We’ll be sure to share when Scurry is ready for the world! Full Article News & Culture
ace Beards and Face Masks from the CDC By feedproxy.google.com Published On :: Tue, 03 Mar 2020 16:09:29 +0000 Back in 2017, the U.S. Center for Disease Control and Prevention (CDC) published this infographic on the Facial Hairstyles and Filtering Facepiece Respirators to help men understand that beards can make facemasks ineffective. With the daily news about the Coronavirus (Covid-19) bordering on panic, this infographic has resurfaced, and is being widely republished.NOTE: The CDC does not recommend that people who are well wear a facemask to protect themselves from COVID-19.From the CDC FAQ:Does the CDC recommend the use of facemask to prevent COVID-19?CDC does not recommend that people who are well wear a facemask to protect themselves from respiratory illnesses, including COVID-19. You should only wear a mask if a healthcare professional recommends it. A facemask should be used by people who have COVID-19 and are showing symptoms. This is to protect others from the risk of getting infected. The use of facemasks also is crucial for health workers and other people who are taking care of someone infected with COVID-19 in close settings (at home or in a health care facility).From the original CDC blog post on November 2, 2017:The month of November is full of fun, interesting, and thought-provoking observances. November is National Raisin Bread Month, Historic Bridge Awareness Month, and Inspirational Role Models Month among so much more. November is also the host month to campaigns like No-Shave November and Movember. Campaigns such as these are working hard to raise money for important causes such as cancer research, education, and awareness. These increasingly popular campaigns are a great way to demonstrate your support … unless you need to wear a tight-fitting respirator for your job.Don’t despair! We will not completely ruin your plans to compete for facial hair bragging rights. But we’re going to have to get creative about it…I do love that the CDC is using infographics to spread valuable information in a fun, easy-to-digest way that informs people using visual explanations. They also specifically call out the designer of the beard and moustache vector art they used from ShutterStock, fredrisher Full Article
ace What is cognitive load and why does it matter in web and interface design? By feedproxy.google.com Published On :: Thu, 27 Jun 2019 15:25:28 +0000 Successful design manages cognitive load. Cognitive load is a technical term for “mental effort,” more specifically it’s the total amount of mental effort required for a given task. Completing any task requires some level of mental effort. This includes learning new information, analyzing stimuli, and working with short and long-term memory. Mental energy which has […] The post What is cognitive load and why does it matter in web and interface design? appeared first on Psychology of Web Design | 3.7 Blog. Full Article Psychology of Design User Experience Web Design
ace Everything I Know In One Place By feedproxy.google.com Published On :: Wed, 17 Jul 2019 13:15:58 +0000 It was surreal to sit down at the mic and record this show after spending the last few years (5 a.m. mornings, late, late nights, and many long weekends hunkered down) writing a book that I’m proud and beyond excited to share with YOU and the world. It’s called CREATIVE CALLING and it’s officially available for pre-order TODAY! In this episode, you get the little sneak peek at the book (yes, I read a little from it) and a little background on why I needed to write it. After all, life isn’t about “finding” fulfillment and success – it’s about creating it. Creativity is a force inside every person that, when unleashed, transforms our lives and delivers vitality to everything we do. Establishing a creative practice is therefore our most valuable and urgent task – as important to our well-being as exercise or nutrition. The good news? Creativity isn’t a skill—it’s a habit available to everyone: beginners and lifelong creators, entrepreneurs to executives, astronauts to zookeepers, and everyone in between. It’s only through small, daily actions that we can supercharge our innate creativity and (re-)discover our personal power in life. Everything you need is inside you right now. Whether your ambition is a creative career, completing a creative […] The post Everything I Know In One Place appeared first on Chase Jarvis Photography. Full Article chasejarvisLIVE Inspiration Podcast
ace Finding Stillness in a Fast Paced World with Ryan Holiday By feedproxy.google.com Published On :: Wed, 30 Oct 2019 15:35:14 +0000 Ryan Holiday is described by the New York Times as popularizing stoicism, a philosophy of personal ethics which has been practiced by Kings, presidents, artists, writers, and entrepreneurs. His career started at 19 when he dropped out of college at 19 to work with author Robert Greene. Today, he’s a NYT Bestselling author, with 9 books under his belt, including his latest book: Stillness Is the Key which hit #1 on its first week. In this episode: Stillness isn’t a monk-like existence only reserved for the enlightened. Stillness is the idea of being still in a chaotic world and where our best work will come from. Ryan’s personal habits and process during the creation process to find stillness and it doesn’t include meditation. How to say no and build a practice around managing your time. Enjoy! FOLLOW RYAN: instagram | twitter | website Listen to the Podcast Subscribe Watch the Episode This podcast is brought to you by CreativeLive. CreativeLive is the world’s largest hub for online creative education in photo/video, art/design, music/audio, craft/maker, money/life and the ability to make a living in any of those disciplines. They are high quality, highly curated classes taught by the world’s top […] The post Finding Stillness in a Fast Paced World with Ryan Holiday appeared first on Chase Jarvis Photography. Full Article chasejarvisLIVE Podcast creativity meditation mindfulness ryan holiday stoicism
ace Workplace Revolution with Amy Nelson By feedproxy.google.com Published On :: Wed, 19 Feb 2020 16:25:13 +0000 Amy Nelson is the founder and CEO of The Riveter. If you’re not familiar with The Riveter, it’s a modern day union of women and their allies. It’s a community, a workspace and resource that supports women in building business and careers. The Riveter has locations all throughout the US and is growing rapidly. I cannot wait for you to hear this story. Amy Nelson practiced corporate litigation for over a decade in New York City and Seattle and worked in politics under several presidents. But it wasn’t until she was a mother that she started noticing something. Conversations no longer were about her career, but how motherhood would impact her career. Why was it not possible to “have it all”: be the best lawyer, the best wife, and mother? Looking for inspiration, she discovered a telling statistic: 43% of highly trained professional women “off-ramp” after having kids. It was then an idea started to form. In this episode we explore: How a bold concept can go from idea to reality. How Amy raised money and grew a national company in 2.5 years Being a vulnerable leader + the emotional journey of exploring and building something new How can we all […] The post Workplace Revolution with Amy Nelson appeared first on Chase Jarvis Photography. Full Article chasejarvisLIVE Podcast entrepreneurship fear gender gap mother startup the riveter Transition women
ace Start in a Place That’s True with IN-Q By feedproxy.google.com Published On :: Thu, 02 Apr 2020 13:15:09 +0000 Storytelling is one of the oldest art forms. It connects us. Our brains our wired for it. Story is not only a way for us to share and connect with others, but a path to deeper understanding and vulnerability. That’s why I’m very excited to have on the show award winning Poet, Author, and Performer, IN-Q. In addition to his poetry, live performances and storytelling workshops, IN-Q is a multi-platinum songwriter having worked with Selena Gomez, Aloe Black, Miley Cyrus, Mike Posner, and Foster the People. Oprah named him on her SuperSoul 100 list of the world’s most influential thought leaders. He’s been featured all over the place including A&E, ESPN, HBO, and companies such as Nike, Instagram, Spotify, and many more. In our conversation, we get into his new book, Inquire Within. In fact, he reads a bit of it on the show. It’s an awe-inspiring rhythmic exploration of transforming love, loss, and forgiveness into growth. Super excited for you to hear it. We also get into: Developing your own voice by focusing on what’s moving and meaningful for you How to find calm in the chaos Using vulnerability to short-cut and deepen relationships in our lives and much, […] The post Start in a Place That’s True with IN-Q appeared first on Chase Jarvis Photography. Full Article chasejarvisLIVE Podcast grief growth hip hop loss love pain poet self development spoken word writer
ace TTT in SPAAACE By feedproxy.google.com Published On :: Mon, 24 Feb 2020 09:33:00 -0500 By now, you’ve probably heard of TTT, our quarterly team events. If you haven’t, you should read all about their history. TTT, or Third Third Thursday, is a time for us to look back and look ahead. Twice a year, all four offices come together for an all-hands, conference-style experience. The other two TTTs are celebrated locally and casually. Each office meets for a round-table discussion followed by a fun activity out of the office. In these meetings, we discuss team and industry changes and review business health metrics. Additionally, at each TTT, both our President, Andy Rankin, and CEO Brian Williams, directly field questions from any member of our team. At our TTTs we’ve talked about team diversity and tech ethics, celebrated our victories, and worked through our failures. The conversations have sparked new understanding, new initiatives, new processes, and have truly shaped the company over time. We come together in the spirit of “progress, not perfection.” While each office is unique, and the conversation is tailored to and shaped by each audience, the People Team finds ways to make everyone’s TTT similar, particularly our afternoon activity, so we can bond over shared experiences, even miles apart. This summer, we all tried our hands at ax throwing, and just a few weeks ago each of our offices got to venture into Space.Well, sort of. After a morning meeting, Boulder visited the Fiske Planetarium at CU Boulder. Durham visited UNC’s Morehead Planetarium. And since the Smithsonian is refurbishing the Einstein Planetarium, our Falls Church office made our way to the Udvar Hazy center to catch an Imax show and fly a few jets, via simulator. Each office also got a taste of space food trying Astronaut ice cream, to mixed reviews. TTTs are more than fun snacks and field trips. They are about finding common ground with colleagues, challenging each other to grow, and re-connecting with folks you don’t work with day-to-day. They are about setting aside time for frank discussion across disciplines and experience levels, and getting outside the office for new perspectives. They are just a little part of what makes Viget so unique. Are you ready to join us for our next big TTT adventure? It’s Viget20, and it’s going to be a good one. We're hiring. Full Article News & Culture
ace Scurry: A Race-To-Finish Scavenger Hunt App By feedproxy.google.com Published On :: Thu, 26 Mar 2020 13:58:00 -0400 We have a lot of traditions here at Viget, many of which you may have read about - TTT, FLF, Pointless Weekend. There are others, but you have to be an insider for more information on those. Pointless Weekend is one of our favorite traditions, though. It’s been around over a decade and some pretty fun work has come out of it over the years, like Storyboard, Baby Bookie, and Short Order. At a high level, we take 48 hours to build a tool, experiment, or stunt as a team, across all four of our offices. These projects are entirely separate from our client work and we use them to try out new technologies, explore roles on the team, and stress-test our processes. The first step for a Pointless Weekend is assembling the teams. We had two teams this year, with a record number of participants. You can read about TrailBuddy, what the other team built, here. The Scurry team was split between the DC and Durham offices, so all meetings were held via Hangout. Once we were assembled, we set out to understand the constraints and the goals of our Pointless Project. We went into this weekend with an extra pep in our step, as we were determined to build something for the upcoming Viget 20th anniversary TTT this summer. Here’s what we knew we wanted: An activity all Vigets could do together, where they could create memories, and share broadly on socialSomething that we could use in a spotty network at C Lazy U Ranch in ColoradoA product we can share with others: corporate groups, families and friends, schools, bachelor/ette parties We landed on a scavenger hunt native app, which we named Scurry (Scavenger + Hurry = Scurry. Brilliant, right?). There are already a few scavenger apps available, so we set out to create something that was Quick and easy to set up huntsFree and intuitive for usersA nice combination of trivia and activitiesSocial! We wanted to enable teams to share photos and progress One of the main reasons we have Pointless Weekends is to test out new technologies and processes. In that vein, we tried out Notion as our central organizing tool - we used it for user journeys, data modeling, and even writing tickets, which we typically use Github for. We tested out Notion as our primary tool, writing tickets and tracking progress. When we built the app, we needed to prepare for spotty network service, as internet connectivity isn’t guaranteed at C Lazy U Ranch – where our Viget20 celebration will be. A Progressive Web Application (PWA) didn't make sense for our tech requirements, so we chose the route of creating a native application. There are a number of options available to build native applications. But, as we were looking to make as much progress as possible in 48-hours, we chose one of our favorite frameworks: React Native. React Native allows developers to build true, cross-platform native applications, using some of our favorite technologies: javascript, the React framework, and a native-specific variant of CSS. We decided on the turn-key solution Expo. Expo has extra tooling allowing for easy development, deployment, and debugging. This is a snap shot of our app and Expo. Our frontend developers were able to immediately dive in making screens and styling components, and quickly made the mockups in Whimsical a reality. On the backend, we used the supported library to connect to the backend datastore, Firebase. Firebase is a hosted solution for data storage, with key features built-in like authentication, realtime updates, and offline support. Our backend developer worked behind the frontend developers hooking those views up to live data. Both of these tools, Expo and Firebase, were easy to use and allowed us to focus on building a working application quickly, rather than being mired in setup or bespoke solutions to common problems. Whimsical is one of our favorite tools for building out mockups of an app. We made impressive progress in our 48-hour sprint, but there’s still some work to do. We have some additional features we hope to add before TTT, which will require additional testing and refining. For now, stay tuned and sign up for our newsletter. We’ll be sure to share when Scurry is ready for the world! Full Article News & Culture
ace Cute Collection of 210 User Interface Icons By feedproxy.google.com Published On :: Wed, 16 Aug 2017 18:54:12 +0000 Did you remember how was your life before Freepik and Flaticon. No I can’t remember the dark ages either. To celebrate this golden times, they are giving away once more an incredible package of 210 User Interface Icons in 3 versions: Flat, filled and lineal. Download This work is licensed under a Creative Commons Attribution 3.0 License … Cute Collection of 210 User Interface Icons Read More » Full Article Freebies
ace Non-associative Frobenius algebras for simply laced Chevalley groups. (arXiv:2005.02625v1 [math.RA] CROSS LISTED) By arxiv.org Published On :: We provide an explicit construction for a class of commutative, non-associative algebras for each of the simple Chevalley groups of simply laced type. Moreover, we equip these algebras with an associating bilinear form, which turns them into Frobenius algebras. This class includes a 3876-dimensional algebra on which the Chevalley group of type E8 acts by automorphisms. We also prove that these algebras admit the structure of (axial) decomposition algebras. Full Article
ace Almost invariant subspaces of the shift operator on vector-valued Hardy spaces. (arXiv:2005.02243v2 [math.FA] UPDATED) By arxiv.org Published On :: In this article, we characterize nearly invariant subspaces of finite defect for the backward shift operator acting on the vector-valued Hardy space which is a vectorial generalization of a result of Chalendar-Gallardo-Partington (C-G-P). Using this characterization of nearly invariant subspace under the backward shift we completely describe the almost invariant subspaces for the shift and its adjoint acting on the vector valued Hardy space. Full Article
ace Some Quot schemes in tilted hearts and moduli spaces of stable pairs. (arXiv:2005.02202v2 [math.AG] UPDATED) By arxiv.org Published On :: For a smooth projective variety $X$, we study analogs of Quot functors in hearts of non-standard $t$-structures of $D^b(mathrm{Coh}(X))$. The technical framework is that of families of $t$-structures, as studied in arXiv:1902.08184. We provide several examples and suggest possible directions of further investigation, as we reinterpret moduli spaces of stable pairs, in the sense of Thaddeus (arXiv:alg-geom/9210007) and Huybrechts-Lehn (arXiv:alg-geom/9211001), as instances of Quot schemes. Full Article
ace Automorphisms of shift spaces and the Higman--Thomspon groups: the one-sided case. (arXiv:2004.08478v2 [math.GR] UPDATED) By arxiv.org Published On :: Let $1 le r < n$ be integers. We give a proof that the group $mathop{mathrm{Aut}}({X_{n}^{mathbb{N}}, sigma_{n}})$ of automorphisms of the one-sided shift on $n$ letters embeds naturally as a subgroup $mathcal{h}_{n}$ of the outer automorphism group $mathop{mathrm{Out}}(G_{n,r})$ of the Higman-Thompson group $G_{n,r}$. From this, we can represent the elements of $mathop{mathrm{Aut}}({X_{n}^{mathbb{N}}, sigma_{n}})$ by finite state non-initial transducers admitting a very strong synchronizing condition. Let $H in mathcal{H}_{n}$ and write $|H|$ for the number of states of the minimal transducer representing $H$. We show that $H$ can be written as a product of at most $|H|$ torsion elements. This result strengthens a similar result of Boyle, Franks and Kitchens, where the decomposition involves more complex torsion elements and also does not support practical extit{a priori} estimates of the length of the resulting product. We also give new proofs of some known results about $mathop{mathrm{Aut}}({X_{n}^{mathbb{N}}, sigma_{n}})$. Full Article
ace The Shearlet Transform and Lizorkin Spaces. (arXiv:2003.06642v2 [math.FA] UPDATED) By arxiv.org Published On :: We prove a continuity result for the shearlet transform when restricted to the space of smooth and rapidly decreasing functions with all vanishing moments. We define the dual shearlet transform, called here the shearlet synthesis operator, and we prove its continuity on the space of smooth and rapidly decreasing functions over $mathbb{R}^2 imesmathbb{R} imesmathbb{R}^ imes$. Then, we use these continuity results to extend the shearlet transform to the space of Lizorkin distributions, and we prove its consistency with the classical definition for test functions. Full Article
ace The $kappa$-Newtonian and $kappa$-Carrollian algebras and their noncommutative spacetimes. (arXiv:2003.03921v2 [hep-th] UPDATED) By arxiv.org Published On :: We derive the non-relativistic $c oinfty$ and ultra-relativistic $c o 0$ limits of the $kappa$-deformed symmetries and corresponding spacetime in (3+1) dimensions, with and without a cosmological constant. We apply the theory of Lie bialgebra contractions to the Poisson version of the $kappa$-(A)dS quantum algebra, and quantize the resulting contracted Poisson-Hopf algebras, thus giving rise to the $kappa$-deformation of the Newtonian (Newton-Hooke and Galilei) and Carrollian (Para-Poincar'e, Para-Euclidean and Carroll) quantum symmetries, including their deformed quadratic Casimir operators. The corresponding $kappa$-Newtonian and $kappa$-Carrollian noncommutative spacetimes are also obtained as the non-relativistic and ultra-relativistic limits of the $kappa$-(A)dS noncommutative spacetime. These constructions allow us to analyze the non-trivial interplay between the quantum deformation parameter $kappa$, the curvature parameter $eta$ and the speed of light parameter $c$. Full Article
ace Surface Effects in Superconductors with Corners. (arXiv:2003.00521v2 [math-ph] UPDATED) By arxiv.org Published On :: We review some recent results on the phenomenon of surface superconductivity in the framework of Ginzburg-Landau theory for extreme type-II materials. In particular, we focus on the response of the superconductor to a strong longitudinal magnetic field in the regime where superconductivity survives only along the boundary of the wire. We derive the energy and density asymptotics for samples with smooth cross section, up to curvature-dependent terms. Furthermore, we discuss the corrections in presence of corners at the boundary of the sample. Full Article
ace Willems' Fundamental Lemma for State-space Systems and its Extension to Multiple Datasets. (arXiv:2002.01023v2 [math.OC] UPDATED) By arxiv.org Published On :: Willems et al.'s fundamental lemma asserts that all trajectories of a linear system can be obtained from a single given one, assuming that a persistency of excitation condition holds. This result has profound implications for system identification and data-driven control, and has seen a revival over the last few years. The purpose of this paper is to extend Willems' lemma to the situation where multiple (possibly short) system trajectories are given instead of a single long one. To this end, we introduce a notion of collective persistency of excitation. We will then show that all trajectories of a linear system can be obtained from a given finite number of trajectories, as long as these are collectively persistently exciting. We will demonstrate that this result enables the identification of linear systems from data sets with missing data samples. Additionally, we show that the result is of practical significance in data-driven control of unstable systems. Full Article
ace New ${cal N}{=},2$ superspace Calogero models. (arXiv:1912.05989v2 [hep-th] UPDATED) By arxiv.org Published On :: Starting from the Hamiltonian formulation of ${cal N}{=},2$ supersymmetric Calogero models associated with the classical $A_n, B_n, C_n$ and $D_n$ series and their hyperbolic/trigonometric cousins, we provide their superspace description. The key ingredients include $n$ bosonic and $2n(n{-}1)$ fermionic ${cal N}{=},2$ superfields, the latter being subject to a nonlinear chirality constraint. This constraint has a universal form valid for all Calogero models. With its help we find more general supercharges (and a superspace Lagrangian), which provide the ${cal N}{=},2$ supersymmetrization for bosonic potentials with arbitrary repulsive two-body interactions. Full Article
ace Nonlinear stability of explicit self-similar solutions for the timelike extremal hypersurfaces in R^{1+3}. (arXiv:1907.01126v2 [math.AP] UPDATED) By arxiv.org Published On :: This paper is devoted to the study of the singularity phenomenon of timelike extremal hypersurfaces in Minkowski spacetime $mathbb{R}^{1+3}$. We find that there are two explicit lightlike self-similar solutions to a graph representation of timelike extremal hypersurfaces in Minkowski spacetime $mathbb{R}^{1+3}$, the geometry of them are two spheres. The linear mode unstable of those lightlike self-similar solutions for the radially symmetric membranes equation is given. After that, we show those self-similar solutions of the radially symmetric membranes equation are nonlinearly stable inside a strictly proper subset of the backward lightcone. This means that the dynamical behavior of those two spheres is as attractors. Meanwhile, we overcome the double roots case (the theorem of Poincar'{e} can't be used) in solving the difference equation by construction of a Newton's polygon when we carry out the analysis of spectrum for the linear operator. Full Article
ace Effective divisors on Hurwitz spaces. (arXiv:1804.01898v3 [math.AG] UPDATED) By arxiv.org Published On :: We prove the effectiveness of the canonical bundle of several Hurwitz spaces of degree k covers of the projective line from curves of genus 13<g<20. Full Article
ace Local mollification of Riemannian metrics using Ricci flow, and Ricci limit spaces. (arXiv:1706.09490v2 [math.DG] UPDATED) By arxiv.org Published On :: We use Ricci flow to obtain a local bi-Holder correspondence between Ricci limit spaces in three dimensions and smooth manifolds. This is more than a complete resolution of the three-dimensional case of the conjecture of Anderson-Cheeger-Colding-Tian, describing how Ricci limit spaces in three dimensions must be homeomorphic to manifolds, and we obtain this in the most general, locally non-collapsed case. The proofs build on results and ideas from recent papers of Hochard and the current authors. Full Article
ace Surjective endomorphisms of projective surfaces -- the existence of infinitely many dense orbits. (arXiv:2005.03628v1 [math.AG]) By arxiv.org Published On :: Let $f colon X o X$ be a surjective endomorphism of a normal projective surface. When $operatorname{deg} f geq 2$, applying an (iteration of) $f$-equivariant minimal model program (EMMP), we determine the geometric structure of $X$. Using this, we extend the second author's result to singular surfaces to the extent that either $X$ has an $f$-invariant non-constant rational function, or $f$ has infinitely many Zariski-dense forward orbits; this result is also extended to Adelic topology (which is finer than Zariski topology). Full Article
ace Continuity properties of the shearlet transform and the shearlet synthesis operator on the Lizorkin type spaces. (arXiv:2005.03505v1 [math.FA]) By arxiv.org Published On :: We develop a distributional framework for the shearlet transform $mathcal{S}_{psi}colonmathcal{S}_0(mathbb{R}^2) omathcal{S}(mathbb{S})$ and the shearlet synthesis operator $mathcal{S}^t_{psi}colonmathcal{S}(mathbb{S}) omathcal{S}_0(mathbb{R}^2)$, where $mathcal{S}_0(mathbb{R}^2)$ is the Lizorkin test function space and $mathcal{S}(mathbb{S})$ is the space of highly localized test functions on the standard shearlet group $mathbb{S}$. These spaces and their duals $mathcal{S}_0^prime (mathbb R^2),, mathcal{S}^prime (mathbb{S})$ are called Lizorkin type spaces of test functions and distributions. We analyze the continuity properties of these transforms when the admissible vector $psi$ belongs to $mathcal{S}_0(mathbb{R}^2)$. Then, we define the shearlet transform and the shearlet synthesis operator of Lizorkin type distributions as transpose mappings of the shearlet synthesis operator and the shearlet transform, respectively. They yield continuous mappings from $mathcal{S}_0^prime (mathbb R^2)$ to $mathcal{S}^prime (mathbb{S})$ and from $mathcal{S}^prime (mathbb S)$ to $mathcal{S}_0^prime (mathbb{R}^2)$. Furthermore, we show the consistency of our definition with the shearlet transform defined by direct evaluation of a distribution on the shearlets. The same can be done for the shearlet synthesis operator. Finally, we give a reconstruction formula for Lizorkin type distributions, from which follows that the action of such generalized functions can be written as an absolutely convergent integral over the standard shearlet group. Full Article
ace Continuity in a parameter of solutions to boundary-value problems in Sobolev spaces. (arXiv:2005.03494v1 [math.CA]) By arxiv.org Published On :: We consider the most general class of linear inhomogeneous boundary-value problems for systems of ordinary differential equations of an arbitrary order whose solutions and right-hand sides belong to appropriate Sobolev spaces. For parameter-dependent problems from this class, we prove a constructive criterion for their solutions to be continuous in the Sobolev space with respect to the parameter. We also prove a two-sided estimate for the degree of convergence of these solutions to the solution of the nonperturbed problem. Full Article
ace Derivatives of normal Jacobi operator on real hypersurfaces in the complex quadric. (arXiv:2005.03483v1 [math.DG]) By arxiv.org Published On :: In cite{S 2017}, Suh gave a non-existence theorem for Hopf real hypersurfaces in the complex quadric with parallel normal Jacobi operator. Motivated by this result, in this paper, we introduce some generalized conditions named $mathcal C$-parallel or Reeb parallel normal Jacobi operators. By using such weaker parallelisms of normal Jacobi operator, first we can assert a non-existence theorem of Hopf real hypersurfaces with $mathcal C$-parallel normal Jacobi operator in the complex quadric $Q^{m}$, $m geq 3$. Next, we prove that a Hopf real hypersurface has Reeb parallel normal Jacobi operator if and only if it has an $mathfrak A$-isotropic singular normal vector field. Full Article
ace Characteristic Points, Fundamental Cubic Form and Euler Characteristic of Projective Surfaces. (arXiv:2005.03481v1 [math.DG]) By arxiv.org Published On :: We define local indices for projective umbilics and godrons (also called cusps of Gauss) on generic smooth surfaces in projective 3-space. By means of these indices, we provide formulas that relate the algebraic numbers of those characteristic points on a surface (and on domains of the surface) with the Euler characteristic of that surface (resp. of those domains). These relations determine the possible coexistences of projective umbilics and godrons on the surface. Our study is based on a "fundamental cubic form" for which we provide a closed simple expression. Full Article
ace The formation of trapped surfaces in the gravitational collapse of spherically symmetric scalar fields with a positive cosmological constant. (arXiv:2005.03434v1 [gr-qc]) By arxiv.org Published On :: Given spherically symmetric characteristic initial data for the Einstein-scalar field system with a positive cosmological constant, we provide a criterion, in terms of the dimensionless size and dimensionless renormalized mass content of an annular region of the data, for the formation of a future trapped surface. This corresponds to an extension of Christodoulou's classical criterion by the inclusion of the cosmological term. Full Article
ace Semiglobal non-oscillatory big bang singular spacetimes for the Einstein-scalar field system. (arXiv:2005.03395v1 [math-ph]) By arxiv.org Published On :: We construct semiglobal singular spacetimes for the Einstein equations coupled to a massless scalar field. Consistent with the heuristic analysis of Belinskii, Khalatnikov, Lifshitz or BKL for this system, there are no oscillations due to the scalar field. (This is much simpler than the oscillatory BKL heuristics for the Einstein vacuum equations.) Prior results are due to Andersson and Rendall in the real analytic case, and Rodnianski and Speck in the smooth near-spatially-flat-FLRW case. Similar to Andersson and Rendall we give asymptotic data at the singularity, which we refer to as final data, but our construction is not limited to real analytic solutions. This paper is a test application of tools (a graded Lie algebra formulation of the Einstein equations and a filtration) intended for the more subtle vacuum case. We use homological algebra tools to construct a formal series solution, then symmetric hyperbolic energy estimates to construct a true solution well-approximated by truncations of the formal one. We conjecture that the image of the map from final data to initial data is an open set of anisotropic initial data. Full Article
ace Type space functors and interpretations in positive logic. (arXiv:2005.03376v1 [math.LO]) By arxiv.org Published On :: We construct a 2-equivalence $mathfrak{CohTheory}^ ext{op} simeq mathfrak{TypeSpaceFunc}$. Here $mathfrak{CohTheory}$ is the 2-category of positive theories and $mathfrak{TypeSpaceFunc}$ is the 2-category of type space functors. We give a precise definition of interpretations for positive logic, which will be the 1-cells in $mathfrak{CohTheory}$. The 2-cells are definable homomorphisms. The 2-equivalence restricts to a duality of categories, making precise the philosophy that a theory is `the same' as the collection of its type spaces (i.e. its type space functor). In characterising those functors that arise as type space functors, we find that they are specific instances of (coherent) hyperdoctrines. This connects two different schools of thought on the logical structure of a theory. The key ingredient, the Deligne completeness theorem, arises from topos theory, where positive theories have been studied under the name of coherent theories. Full Article
ace Smooth non-projective equivariant completions of affine spaces. (arXiv:2005.03277v1 [math.AG]) By arxiv.org Published On :: In this paper we construct an equivariant embedding of the affine space $mathbb{A}^n$ with the translation group action into a complete non-projective algebraic variety $X$ for all $n geq 3$. The theory of toric varieties is used as the main tool for this construction. In the case of $n = 3$ we describe the orbit structure on the variety $X$. Full Article
ace A Chance Constraint Predictive Control and Estimation Framework for Spacecraft Descent with Field Of View Constraints. (arXiv:2005.03245v1 [math.OC]) By arxiv.org Published On :: Recent studies of optimization methods and GNC of spacecraft near small bodies focusing on descent, landing, rendezvous, etc., with key safety constraints such as line-of-sight conic zones and soft landings have shown promising results; this paper considers descent missions to an asteroid surface with a constraint that consists of an onboard camera and asteroid surface markers while using a stochastic convex MPC law. An undermodeled asteroid gravity and spacecraft technology inspired measurement model is established to develop the constraint. Then a computationally light stochastic Linear Quadratic MPC strategy is presented to keep the spacecraft in satisfactory field of view of the surface markers while trajectory tracking, employing chance based constraints and up-to-date estimation uncertainty from navigation. The estimation uncertainty giving rise to the tightened constraints is particularly addressed. Results suggest robust tracking performance across a variety of trajectories. Full Article
ace Non-relativity of K"ahler manifold and complex space forms. (arXiv:2005.03208v1 [math.CV]) By arxiv.org Published On :: We study the non-relativity for two real analytic K"ahler manifolds and complex space forms of three types. The first one is a K"ahler manifold whose polarization of local K"ahler potential is a Nash function in a local coordinate. The second one is the Hartogs domain equpped with two canonical metrics whose polarizations of the K"ahler potentials are the diastatic functions. Full Article
ace Generalized Cauchy-Kovalevskaya extension and plane wave decompositions in superspace. (arXiv:2005.03160v1 [math-ph]) By arxiv.org Published On :: The aim of this paper is to obtain a generalized CK-extension theorem in superspace for the bi-axial Dirac operator. In the classical commuting case, this result can be written as a power series of Bessel type of certain differential operators acting on a single initial function. In the superspace setting, novel structures appear in the cases of negative even superdimensions. In these cases, the CK-extension depends on two initial functions on which two power series of differential operators act. These series are not only of Bessel type but they give rise to an additional structure in terms of Appell polynomials. This pattern also is present in the structure of the Pizzetti formula, which describes integration over the supersphere in terms of differential operators. We make this relation explicit by studying the decomposition of the generalized CK-extension into plane waves integrated over the supersphere. Moreover, these results are applied to obtain a decomposition of the Cauchy kernel in superspace into monogenic plane waves, which shall be useful for inverting the super Radon transform. Full Article
ace Continuation of relative equilibria in the $n$--body problem to spaces of constant curvature. (arXiv:2005.03114v1 [math.DS]) By arxiv.org Published On :: We prove that all non-degenerate relative equilibria of the planar Newtonian $n$--body problem can be continued to spaces of constant curvature $kappa$, positive or negative, for small enough values of this parameter. We also compute the extension of some classical relative equilibria to curved spaces using numerical continuation. In particular, we extend Lagrange's triangle configuration with different masses to both positive and negative curvature spaces. Full Article
ace On the notion of weak isometry for finite metric spaces. (arXiv:2005.03109v1 [math.MG]) By arxiv.org Published On :: Finite metric spaces are the object of study in many data analysis problems. We examine the concept of weak isometry between finite metric spaces, in order to analyse properties of the spaces that are invariant under strictly increasing rescaling of the distance functions. In this paper, we analyse some of the possible complete and incomplete invariants for weak isometry and we introduce a dissimilarity measure that asses how far two spaces are from being weakly isometric. Furthermore, we compare these ideas with the theory of persistent homology, to study how the two are related. Full Article
ace Homotopy invariance of the space of metrics with positive scalar curvature on manifolds with singularities. (arXiv:2005.03073v1 [math.AT]) By arxiv.org Published On :: In this paper we study manifolds $M_{Sigma}$ with fibered singularities, more specifically, a relevant space $Riem^{psc}(X_{Sigma})$ of Riemannian metrics with positive scalar curvature. Our main goal is to prove that the space $Riem^{psc}(X_{Sigma})$ is homotopy invariant under certain surgeries on $M_{Sigma}$. Full Article
ace Teaching Cameras to Feel: Estimating Tactile Physical Properties of Surfaces From Images. (arXiv:2004.14487v2 [cs.CV] UPDATED) By arxiv.org Published On :: The connection between visual input and tactile sensing is critical for object manipulation tasks such as grasping and pushing. In this work, we introduce the challenging task of estimating a set of tactile physical properties from visual information. We aim to build a model that learns the complex mapping between visual information and tactile physical properties. We construct a first of its kind image-tactile dataset with over 400 multiview image sequences and the corresponding tactile properties. A total of fifteen tactile physical properties across categories including friction, compliance, adhesion, texture, and thermal conductance are measured and then estimated by our models. We develop a cross-modal framework comprised of an adversarial objective and a novel visuo-tactile joint classification loss. Additionally, we develop a neural architecture search framework capable of selecting optimal combinations of viewing angles for estimating a given physical property. Full Article
ace Optimal Adjacent Vertex-Distinguishing Edge-Colorings of Circulant Graphs. (arXiv:2004.12822v2 [cs.DM] UPDATED) By arxiv.org Published On :: A k-proper edge-coloring of a graph G is called adjacent vertex-distinguishing if any two adjacent vertices are distinguished by the set of colors appearing in the edges incident to each vertex. The smallest value k for which G admits such coloring is denoted by $chi$'a (G). We prove that $chi$'a (G) = 2R + 1 for most circulant graphs Cn([[1, R]]). Full Article
ace Transfer Learning for EEG-Based Brain-Computer Interfaces: A Review of Progress Made Since 2016. (arXiv:2004.06286v3 [cs.HC] UPDATED) By arxiv.org Published On :: A brain-computer interface (BCI) enables a user to communicate with a computer directly using brain signals. Electroencephalograms (EEGs) used in BCIs are weak, easily contaminated by interference and noise, non-stationary for the same subject, and varying across different subjects and sessions. Therefore, it is difficult to build a generic pattern recognition model in an EEG-based BCI system that is optimal for different subjects, during different sessions, for different devices and tasks. Usually, a calibration session is needed to collect some training data for a new subject, which is time consuming and user unfriendly. Transfer learning (TL), which utilizes data or knowledge from similar or relevant subjects/sessions/devices/tasks to facilitate learning for a new subject/session/device/task, is frequently used to reduce the amount of calibration effort. This paper reviews journal publications on TL approaches in EEG-based BCIs in the last few years, i.e., since 2016. Six paradigms and applications -- motor imagery, event-related potentials, steady-state visual evoked potentials, affective BCIs, regression problems, and adversarial attacks -- are considered. For each paradigm/application, we group the TL approaches into cross-subject/session, cross-device, and cross-task settings and review them separately. Observations and conclusions are made at the end of the paper, which may point to future research directions. Full Article
ace Subgraph densities in a surface. (arXiv:2003.13777v2 [math.CO] UPDATED) By arxiv.org Published On :: Given a fixed graph $H$ that embeds in a surface $Sigma$, what is the maximum number of copies of $H$ in an $n$-vertex graph $G$ that embeds in $Sigma$? We show that the answer is $Theta(n^{f(H)})$, where $f(H)$ is a graph invariant called the `flap-number' of $H$, which is independent of $Sigma$. This simultaneously answers two open problems posed by Eppstein (1993). When $H$ is a complete graph we give more precise answers. Full Article
ace Maximal Closed Set and Half-Space Separations in Finite Closure Systems. (arXiv:2001.04417v2 [cs.AI] UPDATED) By arxiv.org Published On :: Several problems of artificial intelligence, such as predictive learning, formal concept analysis or inductive logic programming, can be viewed as a special case of half-space separation in abstract closure systems over finite ground sets. For the typical scenario that the closure system is given via a closure operator, we show that the half-space separation problem is NP-complete. As a first approach to overcome this negative result, we relax the problem to maximal closed set separation, give a greedy algorithm solving this problem with a linear number of closure operator calls, and show that this bound is sharp. For a second direction, we consider Kakutani closure systems and prove that they are algorithmically characterized by the greedy algorithm. As a first special case of the general problem setting, we consider Kakutani closure systems over graphs, generalize a fundamental characterization result based on the Pasch axiom to graph structured partitioning of finite sets, and give a sufficient condition for this kind of closures systems in terms of graph minors. For a second case, we then focus on closure systems over finite lattices, give an improved adaptation of the greedy algorithm for this special case, and present two applications concerning formal concept and subsumption lattices. We also report some experimental results to demonstrate the practical usefulness of our algorithm. Full Article