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Expanding with a Lofty Goal
Computer-Aided Civil and Infrastructure Engineering (Wiley InterScience) - Sun, 01/01/2012 - 12:00am
Categories: Computing in Civil Engineering (Journal)
A Decentralized Control Algorithm for Large-Scale Building Structures
Computer-Aided Civil and Infrastructure Engineering (Wiley InterScience) - Sun, 01/01/2012 - 12:00am
Abstract: Decentralized control strategy is more suitable for structural control of large-scale structural systems as it increases in the feasibility of control implementation and decreases the risk on the failure of the control system compared with the conventional centralized control approach. In this article, a decentralized control algorithm is proposed for large-scale linear building structures. A large-scale building structure is divided into a set of smaller substructures based on its finite element model. Interconnections between adjacent substructures are treated as disturbances to the individual substructure. Each substructure is controlled by its own local controller using linear quadratic Gaussian control scheme with acceleration measurements as feedback signals. A computational procedure is developed for the recursive estimation of the unknown disturbances to each substructure. Two cases, with substructure interface measurement and without substructure interface measurement respectively, are considered. A numerical example of the decentralized control of the 20-story Structural Engineers Association of California (SAC) benchmark linear building under seismic excitation is studied to evaluate the performance of the proposed algorithm. Simulation results demonstrate that the decentralized control algorithm has quite good control performance compared with the conventional centralized control approach. Therefore, the proposed decentralized control algorithm is viable for structural control of large-scale linear structural systems.
Categories: Computing in Civil Engineering (Journal)
Comparing Ant Colony Optimization and Genetic Algorithm Approaches for Solving Traffic Signal Coordination under Oversaturation Conditions
Computer-Aided Civil and Infrastructure Engineering (Wiley InterScience) - Sun, 01/01/2012 - 12:00am
Abstract: This article proposes to solve the oversaturated network traffic signal coordination problem using the Ant Colony Optimization (ACO) algorithm. The traffic networks used are discrete time models which use green times at all the intersections throughout the considered period of oversaturation as the decision variables. The ACO algorithm finds intelligent timing plans which take care of dissipation of queues and removal of blockages as opposed to the sole cost minimization usually performed for undersaturation conditions. Two scenarios are considered and results are rigorously compared with solutions obtained using the genetic algorithm (GA), traditionally employed to solve oversaturated conditions. ACO is shown to be consistently more effective for a larger number of trials and to provide more reliable solutions. Further, as a master-slave parallelism is possible for the nature of ACO algorithm, its implementation is suggested to reduce the overall execution time allowing the opportunity to solve real-time signal control systems.
Categories: Computing in Civil Engineering (Journal)
Concrete Crack Detection by Multiple Sequential Image Filtering
Computer-Aided Civil and Infrastructure Engineering (Wiley InterScience) - Sun, 01/01/2012 - 12:00am
Abstract: This article presents a new robust automated image processing method for detecting cracks in surface images of concrete structures. This method involves two steps: (1) development of an image filter for detecting major cracks using genetic programming (GP), and (2) elimination of residual noise after filtering and detection of indistinct cracks by iterative applications of the image filter to the local regions surrounding the cracks. The proposed method can be used for the accurate detection of cracks in surface images recorded under various conditions. Moreover, the widths of the detected cracks can be quantified on the basis of the spatial derivatives of the brightness patterns. The estimated crack widths are in good agreement with those measured manually.
Categories: Computing in Civil Engineering (Journal)
Active and Semi-active Adaptive Control for Undamaged and Damaged Building Structures Under Seismic Load
Computer-Aided Civil and Infrastructure Engineering (Wiley InterScience) - Sun, 01/01/2012 - 12:00am
Abstract: During the lifetime of a structural system, many severe events such as earthquakes and strong winds may impact the system and result in potential damage. To mitigate the structural vibration and damage during these extreme events, control devices such as active and semi-active devices have received considerable attention because of their attractive characteristics. Active control devices are adaptable to any change and semi-active devices have the capability of offering the reliability of passive devices and the versatility and adaptability of active devices. In this research, a direct-adaptive-control method is used to control the behavior of an undamaged and a damaged structure using semi-active and active devices. In the adaptive control method, the controlled system is forced to behave like the model system which exhibits the desired behavior. The model of the adaptive control method is defined in a way to optimize the response of the controlled structure. The controller developed using this method can deal with changes that occur in the characteristics of the structure because it can modify its parameters during the control process. A magnetorheological (MR) damper is used as the semi-active device in this study, whereas a hydraulic actuator is utilized as the active device to control the behavior of the structure. The performance of a three-story building from the SAC project for the third generation of the control benchmark problem is studied by performing time–history analyses. The structure is subjected to different earthquakes and controlled by the direct adaptive control method. In the analysis of the structure, some stiffness reduction is assumed as a result of potential damage in the first story of the building. Also, the direct adaptive control strategy is used to optimize the response of the undamaged structure and to mitigate the damage impact on the performance of the controlled structure in the presence of noise for output measurements. The results of adaptive control method are compared with those of other control strategies. It is shown that the performance of the three-story building is improved using the adaptive control method. By assessing the results of different control approaches, it is found that the adaptive control method works more effectively than other methods and semi-active devices can provide reliable results.
Categories: Computing in Civil Engineering (Journal)
Using Numerical Simulations and Engineering Reasoning under Uncertainty: Studying the Collapse of WTC-1
Computer-Aided Civil and Infrastructure Engineering (Wiley InterScience) - Sun, 01/01/2012 - 12:00am
Abstract: A series of numerical aircraft crash simulations and thermal behavior analyses were made at Purdue University to study the response of the World Trade Center Tower 1 (WTC-1) on September 11, 2001. The process included accuracy verification for the computational tools using available experiment data. Numerical models for the Boeing 767–200ER aircraft and the structural system for the top 20 stories of WTC-1 were developed for the simulations. A second aircraft model, simpler yet comparable in effect, was developed and used for a parametric sensitivity analysis. Results from these simulations and published by other researchers indicate that while the observed impact damage to tower exterior framing can be estimated accurately, the unseen impact damage to the core structure of the tower could not be estimated with high confidence. Although the computational tools helped in developing an understanding as to what might have happened as the aircraft penetrated and disintegrated into the structure, they were not able to reduce the uncertainty in the core damage estimate. However, reflecting insight from the behavior of the Pentagon building under the impact loads it received on the same day and studying the effects of elevated temperature on mechanical properties of steel in light of experimental data, the uncertainty in the core structural damage estimate was found to be of negligible importance with regards to the ultimate fate of the tower. It is demonstrated that through use of numerical simulations and engineering reasoning, a dominant factor in the collapse of the tower could be proposed with confidence. It was the loss of fire-proofing in the tower core during aircraft impact that left the core vulnerable to ensuing thermal loads and resulted in the eventual collapse of the tower.
Categories: Computing in Civil Engineering (Journal)
Dead Kennedys
Visual Complexity - Sat, 31/12/2011 - 9:18am
A visual overview of Dead Kennedys' five studio albums including quotes of the lyrics, track titles, album titles and their release years, soundwaves, track lengths, song writers and the lyrical themes and their relations.
Categories: Visualizations
Musical Nodes
Visual Complexity - Sat, 31/12/2011 - 9:18am
MusicalNodes is a visualization system for digital music collections. Artists, albums, songs and genres are represented as nodes in a network, where musically similar items are connected with each other. A force based graph determines the positions of the nodes, based on data like song tempo, genre and similar artists. It provides a good overview of your music at a glance and offers new insights into your collection.
Categories: Visualizations
Health InfoScape
Visual Complexity - Sat, 31/12/2011 - 9:18am
Designed by the team at MIT SENSEable City Lab, Health InfoScape is a disease network that combines 7.2 million patient records from General Electric's proprietary database in an effort to illustrate relationships between various conditions that commonly affect Americans today. It essentially tries to answer questions like: When you have heartburn, do you also feel nauseous? Or if you're experiencing insomnia, do you tend to put on a few pounds, or more? By investigating how different ailments are related, one may gain various insights about condition associations.
Categories: Visualizations
Circle of Trust
Visual Complexity - Sat, 31/12/2011 - 9:18am
The Circle of Trust is an interface data-visualization experiment using Google+ API and HTML5. In an effort to understand how asymmetric relationship networks are at Google Plus, the authors made a simple algorithm to visualize who are the people inside your circle of trust and who are the people outside.
Green are the people you have circled and they have circled you back, yellow is for people that you cared to circle but they didn't, and red is for people that have circled you but you didn't care to circle back.
You can map your network directly here.
Categories: Visualizations
Sense of Patterns
Visual Complexity - Sat, 31/12/2011 - 9:18am
Sense of Patterns is an on-going project, a series of printed data visualizations aiming to depict the behaviors of masses in different public spaces. The visualizations have a focus on the patterns of moving entities in public like commuters, cars and public transportation vehicles as well as the interaction between these entities and physical structures like roads, sidewalks, buildings and parks. The project intends to provide strong visuals on what we all experience in our daily lives in different cities.
The first image maps 915.353 single entries (unique trip id, timestamps, longitude and latitude coordinates) of taxi trips during the 25th of July, 2011, in the city of Vienna, Austria. The second shows the same data mapped at different periods of the day.
Categories: Visualizations
Max Planck Research Networks
Visual Complexity - Sat, 31/12/2011 - 9:18am
This multi-touch installation, on display at the Max Planck Science Gallery, explores how the various Max Planck Institutes collaborate with each other, and with their international partners. Max Planck Society for the Advancement of Science (MPG) comprises nearly 80 research institutes covering different areas, such as natural sciences, life sciences, social sciences, arts and humanities. With 32 Nobel Prizes amongst its associated scientists, MPG is one of the most respected scientific institutions in Germany and Europe.
For this graph visualization, the authors analysed data from SciVerse Scopus for over 94,000 publications over the last ten years. The dynamic network provides a high-level map of the Max Planck Institutes and their connections. The size of the institute icons represents the number of scientific publications, and the width of the connecting lines the number of jointly published papers between two institutes.
The network visualization is also accompanied by a map of Max Planck institutes showing their respective locations, and a world map disclosing the locations of external collaboration partners.
Touching an institute icon on the multitouch screen centers the view around it and highlights its most important collaboration partners, both in the network as well as on the maps. Visitors can move and zoom all views by touching and "pinching" (moving two fingers together or apart). The international flow of ideas is represented metaphorically by streams of energy particles, being continuously exchanged between the institutions.
Categories: Visualizations
Global Pulse
Visual Complexity - Sat, 31/12/2011 - 9:18am
Twitter is a remarkable tool to analyze information diffusion, and investigate social patterns and trends. In June 2011, Abdur Chowdhury and his team at Twitter posted a few visualization experiments covering the volume and worldwide scale of Twitter messages during the devastating earthquake in Japan on March 11.
As they stated on the original post: "During major events, people use Twitter to share news and thoughts with friends, family and followers around the world. Messages originating in one place are quickly spread across the globe through Retweets, @replies and Direct Messages. We see this behavior during everything from sporting events like the World Cup to widely-televised news events like the royal wedding, and also in the face of major disasters like the March 11 earthquake in Japan, where the volume of Tweets sent per second spiked to more than 5,000 TPS five separate times after the quake and ensuing tsunami."
To better understand this diffusion process, Abdur and his team created two video clips. The first image is from a clip showing the volume of @replies traveling into and out of Japan in a one-hour period just before and then after the earthquake. Replies directed to users in Japan are shown in pink; messages directed at others from Japan are shown in yellow.
The second one is from a clip displaying worldwide retweets of Tweets originating in Japan for one hour after the earthquake. Senders' original Tweets are shown in pink; Tweets retweeted by their followers in the hour after the event are displayed in green.
Categories: Visualizations
Wikipedia Edits During the Middle-East Protests
Visual Complexity - Sat, 31/12/2011 - 9:18am
The images shown here are from a short, dynamic visualization of edits to Wikipedia pages from December 1st to February 20th, 2011. It focuses on pages about nations where protests and revolutions occurred as well as pages about the protests themselves. Edits are color-coded by type, with orange-red lines indicating changes that added to a page whereas purple indicates changes that removed text from a page.
Each pulse is a day, but the graph actually displays the current day plus any edits that occurred that day or during the prior six days, so it's actually showing a week of edits at a time.
The editing was visualized in Gephi, an open-source network analysis package.
Categories: Visualizations
Discovr
Visual Complexity - Sat, 31/12/2011 - 9:18am
After releasing the great Discovr Music app for the iPad, Filter Squad recently launched Discovr, a visualization app that behaves as a recommendation engine for Apple's large repository of apps.
Discovr provides an interactive map of the App Store and makes its easy to discover new apps for the iPhone & iPad. It has been a Number 1 app in 17 countries including the US, Japan, Australia, and Germany.
Categories: Visualizations
Nike+ City Runs
Visual Complexity - Sat, 31/12/2011 - 9:18am
Nike+ involves the placement of a sensor underneath the footbed of your Nike running shoe in order to collect data about where you've run, how long it took and where you can improve over time - since each individual run becomes part of a collective historical database. Even though Nike+ website already gives individual users a variety of features to make sense of their personal data, the collective analysis of this growing database is remarkably promising.
The interactive collective YesYesNo developed an installation for Nike's retail stores to visualize a year's worth of runs uploaded to the Nike+ website. With custom software, the installation plays back runs throughout three cities: New York, London and Tokyo. The runs showed tens of thousands of peoples' runs animating the city and bringing it to life. The software visualizes and follows individual runs, as well as showing the collective energy of all the runners, defining the city by the constantly changing paths of the people running in it.
Categories: Visualizations
Visualising traffic on img.ly
Visual Complexity - Sat, 31/12/2011 - 9:18am
During Nodecamp 2011, the members of 9elements - a small company dedicated to web applications - were eager to present a live tracker built with node.js. Inspired by Paul Butler's Facebook Map, the team decided to go with data from img.ly, a popular social photo sharing service that happens to be the image service of Twitterrific.
The visualization they ended up creating shows the live activity of visitors on img.ly as a series of dynamic arcs across the globe. Each arc starts with the location of the visitor and ends with the location of the image the visitor is looking at.
As the authors explain, they were particularly interested in disclosing hidden connections within img.ly: "There are already many apps plotting visitors on a map, so obviously this was not very interesting. We were interested in connections, and basically there is already a very important type of connection on img.ly. Whenever you call a picture on img.ly, you create a connection to the user who posted it. We can apply this idea to location, thus all we had to do was to connect the location of visitors with the location of the picture they're viewing. That's the idea."
Categories: Visualizations
Opinion Cloud
Visual Complexity - Sat, 31/12/2011 - 9:18am
It's always fascinating to see network visualization being embraced by mainstream media in a prominent way. This has lately been the case of The Economist, which now features an advanced form of interconnected tag cloud in many of its online articles. This "opinion cloud" aggregates all user commentary by readers of The Economist and creates relevant connections between emergent topics, regions, and countries. It was made possible by a collaboration between Appinions opinion extraction technology and Infomous text visualization.
Categories: Visualizations
See something or say something
Visual Complexity - Sat, 31/12/2011 - 9:18am
Eric Fischer, who has been previously featured in VC, produced a new set of striking visualizations mapping Flickr and Twitter against each other.
The maps from different cities and areas around the globe depict geotagged photos uploaded to Flickr (orange) versus geotagged tweets to Twitter (blue). In case an image and a tweet originate from the same location, it appears as a white dot. The first image is a map of Europe using the described visualization method, while the second one is a map of New York City.
You can read more about the project at a Fast Company's Co.Design article on Fischer's work.
Categories: Visualizations
Visualizing Databases
Visual Complexity - Sat, 31/12/2011 - 9:18am
Using the visualization tool Gephi, Elijah Meeks has produced a series of experiments depicting databases in diverse styles. The images show here are mapping the top contributors to the Catalogue of Life and their associated species, references and databases.
As Elijah states: "While it could be argued that all databases can be devolved into graph databases, and as such all databases are graphs and therefore networks in the most pure sense, I think that there's something more practical at play here: the importance of network visualization for database aesthetics. Summaries and statistics drawn from within the structure of the database are not enough. If there is to be any real grappling with the database as an culturally-embedded construct, then it has to be done in a manner that reveals the data, the model and the population simultaneously."
Categories: Visualizations
