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2014

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Articles 1231 - 1260 of 12299

Full-Text Articles in Physical Sciences and Mathematics

Incoherent Scatter Radar Observations Of Dynamic Ion Composition Changes At High Latitudes During Geomagnetic Storms, Bryan C. Wright Nov 2014

Incoherent Scatter Radar Observations Of Dynamic Ion Composition Changes At High Latitudes During Geomagnetic Storms, Bryan C. Wright

Doctoral Dissertations and Master's Theses

Two new methods are developed for estimating F region ion composition from field-aligned incoherent scatter radar (ISR) measurements. These methods address incoherent scatter spectra temperature-mass ambiguities by self-consistently modeling ion temperature profiles as a function of electric fields and plasma interactions with the neutral atmosphere. These two new methods improve on previous, similar work developed in Zettergren et al. [2010,2011] by incorporating more accurate physical models and improving the estimation procedures. These techniques enable studies of ionospheric composition during highly disturbed conditions and are suitable for data collected with short integration times (2-10 minutes). The improved models incorporate the effects …

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Learning About Being A Scientist From The Vitamin B-12 Structure Collaboration, Susan White Nov 2014

Learning About Being A Scientist From The Vitamin B-12 Structure Collaboration, Susan White

Chemistry Faculty Research and Scholarship

This historical note reviews the work that resulted in the publication of the structure of Vitamin B12. The collaborations and resulting friendships that developed during this time made a strong impression on the author and encouraged her to pursue a scientific career.

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Particle Moment Canting In Cofe2o4 Nanoparticles, K. Hasz, Yumi Ijiri, Kathryn L. Krycka, Julie A. Borchers, R.A. Booth, S. Oberdick, S.A. Majetich Nov 2014

Particle Moment Canting In Cofe2o4 Nanoparticles, K. Hasz, Yumi Ijiri, Kathryn L. Krycka, Julie A. Borchers, R.A. Booth, S. Oberdick, S.A. Majetich

Faculty & Staff Scholarship

Polarization-analyzed small-angle neutron scattering methods are used to determine the spin morphology in high crystalline anisotropy, 11 nm diameter CoFe2O4 nanoparticle assemblies with randomly oriented easy axes. In moderate to high magnetic fields, the nanoparticles adopt a uniformly canted structure, rather than forming domains, shells, or other arrangements. The observed canting angles agree quantitatively with those predicted from an energy model dominated by Zeeman and anisotropy competition, with implications for the technological use of such nanoparticles.

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Imagespirit: Verbal Guided Image Parsing, Ming-Ming Cheng, Shuai Zheng, Wen-Yan Lin, Vibhav Vineet, Paul Sturgess, Nigel Crook, Niloy J. Mitra, Philip Torr Nov 2014

Imagespirit: Verbal Guided Image Parsing, Ming-Ming Cheng, Shuai Zheng, Wen-Yan Lin, Vibhav Vineet, Paul Sturgess, Nigel Crook, Niloy J. Mitra, Philip Torr

Research Collection School Of Computing and Information Systems

Humans describe images in terms of nouns and adjectives while algorithms operate on images represented as sets of pixels. Bridging this gap between how humans would like to access images versus their typical representation is the goal of image parsing, which involves assigning object and attribute labels to pixels. In this article we propose treating nouns as object labels and adjectives as visual attribute labels. This allows us to formulate the image parsing problem as one of jointly estimating per-pixel object and attribute labels from a set of training images. We propose an efficient (interactive time) solution. Using the extracted …

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Rapid: A Toolkit For Reliability Analysis Of Non-Deterministic Systems, Lin Gui, Jun Sun, Yang Liu, Truong Khanh Nguyen, Jin Song Dong Dong Nov 2014

Rapid: A Toolkit For Reliability Analysis Of Non-Deterministic Systems, Lin Gui, Jun Sun, Yang Liu, Truong Khanh Nguyen, Jin Song Dong Dong

Research Collection School Of Computing and Information Systems

Non-determinism in concurrent or distributed software systems (i.e., various possible execution orders among different distributed components) presents new challenges to the existing reliability analysis methods based on Markov chains. In this work, we present a toolkit RaPiD for the reliability analysis of non-deterministic systems. Taking Markov decision process as reliability model, RaPiD can help in the analysis of three fundamental and rewarding aspects regarding software reliability. First, to have reliability assurance on a system, RaPiD can synthesize the overall system reliability given the reliability values of system components. Second, given a requirement on the overall system reliability, RaPiD can distribute …

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Semantics-Aware Android Malware Classification Using Weighted Contextual Api Dependency Graphs, Mu Zhang, Yue Duan, Heng Yin, Zhiruo Zhao Nov 2014

Semantics-Aware Android Malware Classification Using Weighted Contextual Api Dependency Graphs, Mu Zhang, Yue Duan, Heng Yin, Zhiruo Zhao

Research Collection School Of Computing and Information Systems

The drastic increase of Android malware has led to a strong interest in developing methods to automate the malware analysis process. Existing automated Android malware detection and classification methods fall into two general categories: 1) signature-based and 2) machine learning-based. Signature-based approaches can be easily evaded by bytecode-level transformation attacks. Prior learning-based works extract features from application syntax, rather than program semantics, and are also subject to evasion. In this paper, we propose a novel semantic-based approach that classifies Android malware via dependency graphs. To battle transformation attacks, we extract a weighted contextual API dependency graph as program semantics to …

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Online Transfer Learning, Peilin Zhao, Steven C. H. Hoi, Jialei Wang, Bin Li Nov 2014

Online Transfer Learning, Peilin Zhao, Steven C. H. Hoi, Jialei Wang, Bin Li

Research Collection School Of Computing and Information Systems

This paper investigates a new machine learning framework of Online Transfer Learning (OTL), which aims to attack an online learning task on a target domain by transferring knowledge from some source domain. We do not assume data in the target domain follows the same distribution as that in the source domain, and the motivation of our work is to enhance a supervised online learning task on a target domain by exploiting the existing knowledge that had been learnt from training data in source domains. OTL is in general a challenging problem since data in both source and target domains not …

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Developer Involvement Considered Harmful? An Empirical Examination Of Android Bug Resolution Times, Subhajit Datta, Proshanta Sarkar, Subhashis Majumder Nov 2014

Developer Involvement Considered Harmful? An Empirical Examination Of Android Bug Resolution Times, Subhajit Datta, Proshanta Sarkar, Subhashis Majumder

Research Collection School Of Computing and Information Systems

In large scale software development ecosystems, there is a common perception that higher developer involvement leads to faster resolution of bugs. This is based on conjectures around more ``eyeballs" making bugs "shallow" -- whose validity and applicability are not without dispute. In this paper, we posit that the level of developer attention as well as its extent of diversity influence how quickly bugs get resolved. We report results from a study of 1,000+ Android bugs. We find statistically significant evidence that attention and diversity have contrasting relationships with the resolution time of bugs, even after controlling for factors such as …

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Linguistic Analysis Of Toxic Behavior In An Online Video Game, Haewoon Kwak, Telefonica Nov 2014

Linguistic Analysis Of Toxic Behavior In An Online Video Game, Haewoon Kwak, Telefonica

Research Collection School Of Computing and Information Systems

In this paper we explore the linguistic components of toxic behavior by using crowdsourced data from over 590 thousand cases of accused toxic players in a popular match-based competition game, League of Legends. We perform a series of linguistic analyses to gain a deeper understanding of the role communication plays in the expression of toxic behavior. We characterize linguistic behavior of toxic players and compare it with that of typical players in an online competition game. We also find empirical support describing how a player transitions from typical to toxic behavior. Our findings can be helpful to automatically detect and …

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Vireo @ Trecvid 2014: Instance Search And Semantic Indexing, Wei Zhang, Hao Zhang, Ting Yao, Yijie Lu, Jingjing Chen, Chong-Wah Ngo Nov 2014

Vireo @ Trecvid 2014: Instance Search And Semantic Indexing, Wei Zhang, Hao Zhang, Ting Yao, Yijie Lu, Jingjing Chen, Chong-Wah Ngo

Research Collection School Of Computing and Information Systems

This paper summarizes the following two tasks participated by VIREO group: instance search and semantic indexing. We will present our approaches and analyze the results obtained in TRECVID 2014 benchmark evaluation

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K-Sketch: Digital Storytelling With Animation Sketches, Richard Christopher Davis, Nur Camellia Binte Zakaria Nov 2014

K-Sketch: Digital Storytelling With Animation Sketches, Richard Christopher Davis, Nur Camellia Binte Zakaria

Research Collection School Of Computing and Information Systems

K-Sketch gives novice animators an easy way to tell stories with animation sketches. It relies on users’ intuitive sense of space and time, and makes animation easy through the use of sketching and demonstration. Our studies have shown that people take naturally to telling stories with K-Sketch, and it is particularly helpful for exploring the timing of events. We also found that K-Sketch is a good collaborative medium for telling stories. In this demonstration we will show how K-Sketch works and explain how these advantages are realized in practice.

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Stopwatch: A Cloud Architecture For Timing Channel Mitigation, Peng Li, Debin Gao, Michael K Reiter Nov 2014

Stopwatch: A Cloud Architecture For Timing Channel Mitigation, Peng Li, Debin Gao, Michael K Reiter

Research Collection School Of Computing and Information Systems

This article presents StopWatch, a system that defends against timing-based side-channel attacks that arise from coresidency of victims and attackers in infrastructure-as-a-service clouds. StopWatch triplicates each cloud-resident guest virtual machine (VM) and places replicas so that the three replicas of a guest VM are coresident with nonoverlapping sets of (replicas of) other VMs. StopWatch uses the timing of I/O events at a VM’s replicas collectively to determine the timings observed by each one or by an external observer, so that observable timing behaviors are similarly likely in the absence of any other individual, coresident VMs. We detail the design and …

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Grumon: Fast And Accurate Group Monitoring For Heterogeneous Urban Spaces, Rijurekha Sen, Youngki Lee, Kasthuri Jayarajah, Rajesh Krishna Balan, Archan Misra Nov 2014

Grumon: Fast And Accurate Group Monitoring For Heterogeneous Urban Spaces, Rijurekha Sen, Youngki Lee, Kasthuri Jayarajah, Rajesh Krishna Balan, Archan Misra

Research Collection School Of Computing and Information Systems

Real-time monitoring of groups and their rich contexts will be a key building block for futuristic, group-aware mobile services. In this paper, we propose GruMon, a fast and accurate group monitoring system for dense and complex urban spaces. GruMon meets the performance criteria of precise group detection at low latencies by overcoming two critical challenges of practical urban spaces, namely (a) the high density of crowds, and (b) the imprecise location information available indoors. Using a host of novel features extracted from commodity smartphone sensors, GruMon can detect over 80% of the groups, with 97% precision, using 10 minutes latency …

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Cama: Efficient Modeling Of The Capture Effect For Low Power Wireless Networks, Behnam Dezfouli, Marjan Radi, Kamin Whitehouse, Shukor Abd Razak, Hwee-Pink Tan Nov 2014

Cama: Efficient Modeling Of The Capture Effect For Low Power Wireless Networks, Behnam Dezfouli, Marjan Radi, Kamin Whitehouse, Shukor Abd Razak, Hwee-Pink Tan

Research Collection School Of Computing and Information Systems

Network simulation is an essential tool for the design and evaluation of wireless network protocols, and realistic channel modeling is essential for meaningful analysis. Recently, several network protocols have demonstrated substantial network performance improvements by exploiting the capture effect, but existing models of the capture effect are still not adequate for protocol simulation and analysis. Physical-level models that calculate the signal-to-interference-plus-noise ratio (SINR) for every incoming bit are too slow to be used for large-scale or long-term networking experiments, and link-level models such as those currently used by the NS2 simulator do not accurately predict protocol performance. In this article, …

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Generative Modeling Of Entity Comparisons In Text, Maksim Tkachenko, Hady W. Lauw Nov 2014

Generative Modeling Of Entity Comparisons In Text, Maksim Tkachenko, Hady W. Lauw

Research Collection School Of Computing and Information Systems

Users frequently rely on online reviews for decision making. In addition to allowing users to evaluate the quality of individual products, reviews also support comparison shopping. One key user activity is to compare two (or more) products based on a specific aspect. However, making a comparison across two different reviews, written by different authors, is not always equitable due to the different standards and preferences of individual authors. Therefore, we focus instead on comparative sentences, whereby two products are compared directly by a review author within a single sentence. We study the problem of comparative relation mining. Given a set …

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Pulsar J0453+1559, The 10th Double Neutron Star System In The Universe, Jose Guadalupe Martinez Nov 2014

Pulsar J0453+1559, The 10th Double Neutron Star System In The Universe, Jose Guadalupe Martinez

Theses and Dissertations - UTB/UTPA

Pulsars are neutron stars that spin rapidly, are highly magnetized, and they emit beams of electromagnetic radiation like a lighthouse out in space. These beams of radiation are only observed when the beams face towards Earth and can be measured by a radio telescope. Pulsar studies have an abundance of scientific implementations in solid state physics, general relativity, galactic astronomy, astronomy, planetary physics and have even opened windows in cosmology. This thesis reports the results of a study of pulsar (PSR) J0453+1559, a new binary pulsar discovered in the Arecibo All-Sky 327 MegaHertz Drift Pulsar Survey. The recorded observations of …

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Isotope Shifts In Francium Isotopes Fr206-213 And Fr-221, R. Collister, G. Gwinner, M. Tandecki, Seth Aubin Nov 2014

Isotope Shifts In Francium Isotopes Fr206-213 And Fr-221, R. Collister, G. Gwinner, M. Tandecki, Seth Aubin

Arts & Sciences Articles

We present the isotope shifts of the 7s(1/2) to 7p(1/2) transition for francium isotopes Fr206-213 with reference to Fr-221 collected from two experimental periods. The shifts are measured on a sample of atoms prepared within a magneto-optical trap by a fast sweep of radio-frequency sidebands applied to a carrier laser. King plot analysis, which includes literature values for 7s(1/2) to 7p(3/2) isotope shifts, provides a field shift constant ratio of 1.0520(10) and a difference between the specific mass shift constants of 170(100) GHz amu between the D-1 and D-2 transitions, of sufficient precision to differentiate between ab initio calculations.

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Galaxy And Mass Assembly (Gama) : Galaxy Close Pairs, Mergers And The Future Fate Of Stellar Mass., A. S. G. Robotham, S. P. Driver, L. J. M. Davies, A. M. Hopkins, I. K. Baldry, N. K. Agius, A. E. Bauer, J. Bland-Hawthorn, S. Brough, M. J. I. Brown, M. Cluver, R. De Propis, M. J. Drinkwater, Benne W. Holwerda, L. S. Kelvin, M. A. Lara-Lopez, J. Liske, Angel R. Lopez-Sanchez, J. Loveday, S. Mahajan, T. Mcnaught-Roberts, A. Moffett, P. Norberg, D. Obreschkow, M. S. Owers, S. J. Penny, K. A. Pimbblet, M. Prescott, E. N. Taylor, E. Van Kampen, S. M. Wilkins Nov 2014

Galaxy And Mass Assembly (Gama) : Galaxy Close Pairs, Mergers And The Future Fate Of Stellar Mass., A. S. G. Robotham, S. P. Driver, L. J. M. Davies, A. M. Hopkins, I. K. Baldry, N. K. Agius, A. E. Bauer, J. Bland-Hawthorn, S. Brough, M. J. I. Brown, M. Cluver, R. De Propis, M. J. Drinkwater, Benne W. Holwerda, L. S. Kelvin, M. A. Lara-Lopez, J. Liske, Angel R. Lopez-Sanchez, J. Loveday, S. Mahajan, T. Mcnaught-Roberts, A. Moffett, P. Norberg, D. Obreschkow, M. S. Owers, S. J. Penny, K. A. Pimbblet, M. Prescott, E. N. Taylor, E. Van Kampen, S. M. Wilkins

Faculty and Staff Scholarship

We use a highly complete subset of the Galaxy And Mass Assembly II (GAMA-II) redshift sample to fully describe the stellar mass dependence of close pairs and mergers between 108 and 1012 M⊙. Using the analytic form of this fit we investigate the total stellar mass accreting on to more massive galaxies across all mass ratios. Depending on how conservatively we select our robust merging systems, the fraction of mass merging on to more massive companions is 2.0–5.6 per cent. Using the GAMA-II data we see no significant evidence for a change in the close pair fraction between redshift z …

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Spitzer/Infrared Array Camera Near-Infrared Features In The Outer Parts Of S4g Galaxies., Seppo Laine, Johan H. Knapen, Juan Carlos Munoz-Mateos, Taehyun Kim, Sebastien Comeron, Marie Martig, Benne W. Holwerda, E. Athanassoula, Albert Bosma, Peter H. Johansson, Santiago Erroz-Ferrer, Dimitri A. Gadotti, Armando Gil De Paz, Joannah Hinz, Jarkko Laine, Eija Laurikainen, Karin Menendez-Delmestre, Trisha Mizusawa, Michael Regan, Heikki Salo, Kartik Sheth, Mark Seibert, Ronald J. Buta, Mauricio Cisternas, Bruce G. Elmegreen, Debra M. Elmegreen, Luis C. Ho, Barry F. Madore, Dennis Zaritsky Nov 2014

Spitzer/Infrared Array Camera Near-Infrared Features In The Outer Parts Of S4g Galaxies., Seppo Laine, Johan H. Knapen, Juan Carlos Munoz-Mateos, Taehyun Kim, Sebastien Comeron, Marie Martig, Benne W. Holwerda, E. Athanassoula, Albert Bosma, Peter H. Johansson, Santiago Erroz-Ferrer, Dimitri A. Gadotti, Armando Gil De Paz, Joannah Hinz, Jarkko Laine, Eija Laurikainen, Karin Menendez-Delmestre, Trisha Mizusawa, Michael Regan, Heikki Salo, Kartik Sheth, Mark Seibert, Ronald J. Buta, Mauricio Cisternas, Bruce G. Elmegreen, Debra M. Elmegreen, Luis C. Ho, Barry F. Madore, Dennis Zaritsky

Faculty and Staff Scholarship

We present a catalogue and images of visually detected features, such as asymmetries, extensions, warps, shells, tidal tails, polar rings, and obvious signs of mergers or interactions, in the faint outer regions (at and outside of R25) of nearby galaxies. This catalogue can be used in future quantitative studies that examine galaxy evolution due to internal and external factors. We are able to reliably detect outer region features down to a brightness level of 0.03 MJy sr−1 pixel−1 at 3.6 μm in the Spitzer Survey of Stellar Structure in Galaxies (S4G). We also tabulate companion galaxies. We find asymmetries …

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Evidence For The Concurrent Growth Of Thick Discs And Central Mass Concentrations From S4g Imaging., S. Comeron, B. G. Elmegreen, H. Salo, E. Laurikainen, Benne W. Holwerda, J. H. Knapen Nov 2014

Evidence For The Concurrent Growth Of Thick Discs And Central Mass Concentrations From S4g Imaging., S. Comeron, B. G. Elmegreen, H. Salo, E. Laurikainen, Benne W. Holwerda, J. H. Knapen

Faculty and Staff Scholarship

We have produced 3.6 μm + 4.5 μm vertically integrated radial luminosity profiles of 69 edge-on galaxies from the Spitzer Survey of Stellar Structure in Galaxies (S4G). We decomposed the luminosity profiles into a disc and a central mass concentration (CMC). These fits, combined with thin/thick disc decompositions from our previous studies, allow us to estimate the masses of the CMCs, the thick discs, and the thin discs (ℳCMC, ℳT, and ℳT). We obtained atomic disc masses (ℳg) from the literature. We then consider the CMC and the thick disc to be dynamically hot components and the thin …

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Using Variations Of Shape And Appearance In Alignment Methods For Classifying Human Actions, Sultan Mohammad Almotairi Nov 2014

Using Variations Of Shape And Appearance In Alignment Methods For Classifying Human Actions, Sultan Mohammad Almotairi

Theses and Dissertations

In this dissertation, we address the problem of recognizing human-action from videos. The recognition aims at recovering action information from the image sequences using different features such as variations of the human shape. Approaches based on such features often use sequence-alignment methods. We propose two novel methods for human-action recognition. We also propose an elliptical-shaped band for the Dynamic Time Warping (DTW) that provides a good compromise between alignment accuracy and computational speed. First, we study the applicability of the pairwise shape-similarity measurements for human-action recognition. Since action can be seen as a sequence of shapes of silhouette poses, there …

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A Privacy Risk Scoring Framework For Mobile, Jedidiah Spencer Montgomery Nov 2014

A Privacy Risk Scoring Framework For Mobile, Jedidiah Spencer Montgomery

Theses and Dissertations

Protecting personal privacy has become an increasingly important issue as computers become a more integral part of everyday life. As people begin to trust more personal information to be contained in computers they will question if that information is safe from unwanted intrusion and access. With the rise of mobile devices (e.g., smartphones, tablets, wearable technology) users have enjoyed the convenience and availability of stored personal information in mobile devices, both in the operating system and within applications.For a mobile application to function correctly it needs permission or privileges to access and control various resources and controls on the mobile …

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Client/Server Data Synchronization In Ios Development, Dmitry Tumanov Nov 2014

Client/Server Data Synchronization In Ios Development, Dmitry Tumanov

Undergraduate Honors Theses

Electronic gadgets such as touchpads and smartphones are becoming more popular in business and everyday life. The main advantage of mobile devices over personal computers is their portability. Cellular data plans allow Internet access without having permanent access point. There is a number of web-based applications available for gadgets. The primary goal of these apps is to provide their services through constant Internet access. However, it may affect the operation of both devices and applications. The objective of this thesis is to find a better way of client/server data synchronization in iOS development that can reduce the negative consequences of …

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Limit Distributions Of Random Walks On Stochastic Matrices, Santanu Chakraborty, Arunava Mukherjea Nov 2014

Limit Distributions Of Random Walks On Stochastic Matrices, Santanu Chakraborty, Arunava Mukherjea

School of Mathematical and Statistical Sciences Faculty Publications and Presentations

Problems similar to Ann. Prob. 22 (1994) 424–430 and J. Appl. Prob. 23 (1986) 1019–1024 are considered here. The limit distribution of the sequence XnXn−1 ··· X1, where (Xn)n≥1 is a sequence of i.i.d. 2 × 2 stochastic matrices with each Xn distributed as μ, is identified here in a number of discrete situations. A general method is presented and it covers the cases when the random components Cn and Dn (not necessarily independent), (Cn, Dn) being the first column of Xn, have the same (or different) Bernoulli distributions. Thus (Cn, Dn) is valued in {0, r}2, where r is …

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Exploiting Geographical Neighborhood Characteristics For Location Recommendation, Yong Liu, Wei Wei, Aixin Sun, Chunyan Miao Nov 2014

Exploiting Geographical Neighborhood Characteristics For Location Recommendation, Yong Liu, Wei Wei, Aixin Sun, Chunyan Miao

Research Collection School Of Computing and Information Systems

Geographical characteristics derived from the historical check-in data have been reported effective in improving location recommendation accuracy. However, previous studies mainly exploit geographical characteristics from a user’s perspective, via modeling the geographical distribution of each individual user’s check-ins. In this paper, we are interested in exploiting geographical characteristics from a location perspective, by modeling the geographical neighborhood of a location. The neighborhood is modeled at two levels: the instance-level neighborhood defined by a few nearest neighbors of the location, and the region-level neighborhood for the geographical region where the location exists. We propose a novel recommendation approach, namely Instance-Region Neighborhood …

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Online Passive Aggressive Active Learning And Its Applications, Jing Lu, Peilin Zhao, Steven C. H. Hoi Nov 2014

Online Passive Aggressive Active Learning And Its Applications, Jing Lu, Peilin Zhao, Steven C. H. Hoi

Research Collection School Of Computing and Information Systems

We investigate online active learning techniques for classification tasks in data stream mining applications. Unlike traditional learning approaches (either batch or online learning) that often require to request the class label of each incoming instance, online active learning queries only a subset of informative incoming instances to update the classification model, which aims to maximize classification performance using minimal human labeling effort during the entire online stream data mining task. In this paper, we present a new family of algorithms for online active learning called Passive-Aggressive Active (PAA) learning algorithms by adapting the popular Passive-Aggressive algorithms in an online active …

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Traccs: Trajectory-Aware Coordinated Urban Crowd-Sourcing, Cen Chen, Shih-Fen Cheng, Aldy Gunawan, Archan Misra, Koustuv Dasgupta, Deepthi Chander Nov 2014

Traccs: Trajectory-Aware Coordinated Urban Crowd-Sourcing, Cen Chen, Shih-Fen Cheng, Aldy Gunawan, Archan Misra, Koustuv Dasgupta, Deepthi Chander

Research Collection School Of Computing and Information Systems

We investigate the problem of large-scale mobile crowd-tasking, where a large pool of citizen crowd-workers are used to perform a variety of location-specific urban logistics tasks. Current approaches to such mobile crowd-tasking are very decentralized: a crowd-tasking platform usually provides each worker a set of available tasks close to the worker's current location; each worker then independently chooses which tasks she wants to accept and perform. In contrast, we propose TRACCS, a more coordinated task assignment approach, where the crowd-tasking platform assigns a sequence of tasks to each worker, taking into account their expected location trajectory over a wider time …

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Historical Traffic-Tolerant Paths In Road Networks, Pui Hang Li, Man Lung Yiu, Kyriakos Mouratidis Nov 2014

Historical Traffic-Tolerant Paths In Road Networks, Pui Hang Li, Man Lung Yiu, Kyriakos Mouratidis

Research Collection School Of Computing and Information Systems

Historical traffic information is valuable for transportation analysis and planning, as well as for route search services. In view of these applications, we propose the k traffic-tolerant paths problem (TTP) on road networks, which takes a source-destination pair and historical traffic information as input, and returns k paths that minimize the aggregate (historical) travel time. Unlike the shortest path problem, the TTP problem has a combinatorial search space that renders the optimal solution expensive to compute. We propose an exact algorithm and a heuristic algorithm for this problem. Experiments on real traffic data demonstrate the effectiveness of TTP paths and …

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Dynamic Clustering Of Contextual Multi-Armed Bandits, Trong T. Nguyen, Hady W. Lauw Nov 2014

Dynamic Clustering Of Contextual Multi-Armed Bandits, Trong T. Nguyen, Hady W. Lauw

Research Collection School Of Computing and Information Systems

With the prevalence of the Web and social media, users increasingly express their preferences online. In learning these preferences, recommender systems need to balance the trade-off between exploitation, by providing users with more of the "same", and exploration, by providing users with something "new" so as to expand the systems' knowledge. Multi-armed bandit (MAB) is a framework to balance this trade-off. Most of the previous work in MAB either models a single bandit for the whole population, or one bandit for each user. We propose an algorithm to divide the population of users into multiple clusters, and to customize the …

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An Ecological Model For Digital Platforms Maintenance And Evolution, Paolo Rocchi, Paolo Spagnoletti, Subhajit Datta Nov 2014

An Ecological Model For Digital Platforms Maintenance And Evolution, Paolo Rocchi, Paolo Spagnoletti, Subhajit Datta

Research Collection School Of Computing and Information Systems

The maintenance of software products has been studied extensively in both software engineering and management information systems. Such studies are mainly focused on the activities that take place prior to starting the maintenance phase. Their contribution is either related to the improvement of software quality or to validating contingency models for reducing maintenance efforts. The continuous maintenance philosophy suggests to shift the attention within the maintenance phase for better coping with the evolutionary trajectories of digital platforms. In this paper, we examine the maintenance process of a digital platform from the perspective of the software vendor. Based on our empirical …

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