MSCS Faculty Research and PublicationsCopyright (c) 2014 Marquette University All rights reserved.
http://epublications.marquette.edu/mscs_fac
Recent documents in MSCS Faculty Research and Publicationsen-usThu, 28 Aug 2014 01:48:12 PDT3600Statistical Image Reconstruction of Two Simultaneously Excited fMRI Slices
http://epublications.marquette.edu/mscs_fac/202
http://epublications.marquette.edu/mscs_fac/202Tue, 26 Aug 2014 13:44:41 PDT
In functional MRI, each slice in a volume is traditionally excited individually, measuring enough data in a single k-space array to reconstruct an image for that slice. However, simultaneously exciting multiple slices that make up a volume can produce sufficient data in a single k-space array to represent multiple slices. This single array of k-space data can be reconstructed into a single image representing the aliased slices, and then separated into individual images for each slice. A statistical description of an image representing two aliased slices using a single channel coil is presented. Image separation, utilizing calibration reference scans of each slice, through both an existing magnitudeonly approach and a new complex-valued approach are described, and the statistical properties of these two image separation approaches are presented. Through examining the expected mean image and covariance matrix of the separated images, it is theoretically shown that correlations remain between images of slices through both approaches. Since the image separation process is not the inverse of the image aliasing process, the separated images have different statistical properties than slices excited individually. Through both theoretical and experimental data, the complex-valued approach is shown to out-perform the magnitude-only approach.
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Daniel B. Rowe et al.Topological Extensions and Subspaces of ηα-sets
http://epublications.marquette.edu/mscs_fac/201
http://epublications.marquette.edu/mscs_fac/201Tue, 12 Aug 2014 10:27:48 PDT
The η_{x}-sets of Hausdorff have large compactifications (of cardinality ≽ exp(α); and of cardinality ≽ exp(exp(2^{<}^{α})) in the Stone-Čech case). If Q_{α} denotes the unique (when it exists) η_{α }-set of cardinality α, then Q_{α} can be decomposed (= partitioned) into homeomorphs of any prescribed nonempty subspace; moreover the subspaces of Q_{α} can be characterized as those which arc regular T_{1}, of cardinality and weight ≼ α, whose topologies are closed under < α intersections.
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Paul BankstonA System Implementation of Interruption Management for Mobile Devices
http://epublications.marquette.edu/mscs_fac/200
http://epublications.marquette.edu/mscs_fac/200Thu, 07 Aug 2014 14:08:27 PDT
As the number of worldwide cellular subscriptions approaches the world's population, the negative effects of cell phone disruption have become increasingly apparent. With advances in mobile phones, specifically their sensor technology, mobile phones are now capable of moderating interruptions based on whether or not the user would want an interruption. Research into the area of interruption management has provided models and architectures for the creation of such an application. However, to our knowledge, there are no interruption management systems currently available in the Android or iPhone app stores that utilize a probabilistic model to moderate cell phone interruptions. A probabilistic model would be an improvement over current binary decision models as the user would not need to predetermine every possible outcome. In this project, we have used a probabilistic model to implement an interruption management system for Android OS 4.0 which utilizes five contexts: schedule, time of day, location, caller relationship, and driving. Our system intercepts the call, calculates the probability of interruption, and then changes the phone's audio profile to vibrate, silent, or ring based on our model. Our performance evaluations indicate minor application foot print size, reasonable battery consumption, and very little time overhead for the application.
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William Vilwock et al.A2E: Adaptively Aggressive Energy Efficient DVFS Scheduling for Data Intensive Applications
http://epublications.marquette.edu/mscs_fac/199
http://epublications.marquette.edu/mscs_fac/199Thu, 07 Aug 2014 13:39:51 PDT
Featured by high portability and programmability, Dynamic Voltage and Frequency Scaling (DVFS) has been widely employed to achieve energy efficiency for high performance applications on distributed-memory architectures nowadays through various scheduling algorithms. Generally, different forms of slack from load imbalance, network latency, communication delay, memory and disk access stalls, etc. are exploited as energy saving opportunities where peak CPU performance is not necessary, with little or limited performance loss. The deployment of DVFS for communication intensive applications is straightforward due to the explicit boundary between Energy Saving Blocks (ESBs) at source code level, while for data (e.g., memory and disk access) intensive applications it is difficult for applying DVFS since ESB boundary is implicit due to mixed types of workloads. We propose an adaptively aggressive DVFS scheduling strategy to achieve energy efficiency for data intensive applications, and further save energy via speculation to mitigate DVFS overhead for imbalanced branches. We implemented and evaluated our approach using five memory and disk access intensive benchmarks with imbalanced branches against another two energy saving approaches. The experimental results indicate an average of 32.6% energy savings were achieved with 6.2% average performance loss compared to the original executions on a power-aware 64-core cluster.
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Li Tan et al.Using Intelligent Prefetching to Reduce the Energy Consumption of a Large-scale Storage System
http://epublications.marquette.edu/mscs_fac/198
http://epublications.marquette.edu/mscs_fac/198Thu, 07 Aug 2014 13:30:40 PDT
Many high performance large-scale storage systems will experience significant workload increases as their user base and content availability grow over time. The U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) center hosts one such system that has recently undergone a period of rapid growth as its user population grew nearly 400% in just about three years. When administrators of these massive storage systems face the challenge of meeting the demands of an ever increasing number of requests, the easiest solution is to integrate more advanced hardware to existing systems. However, additional investment in hardware may significantly increase the system cost as well as daily power consumption. In this paper, we present evidence that well-selected software level optimization is capable of achieving comparable levels of performance without the cost and power consumption overhead caused by physically expanding the system. Specifically, we develop intelligent prefetching algorithms that are suitable for the unique workloads and user behaviors of the world's largest satellite images distribution system managed by USGS EROS. Our experimental results, derived from real-world traces with over five million requests sent by users around the globe, show that the EROS hybrid storage system could maintain the same performance with over 30% of energy savings by utilizing our proposed prefetching algorithms, compared to the alternative solution of doubling the size of the current FTP server farm.
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Brian Romoser et al.Regularization of Multivariate Regression Models with Skew Errors
http://epublications.marquette.edu/mscs_fac/197
http://epublications.marquette.edu/mscs_fac/197Thu, 07 Aug 2014 07:51:43 PDT
We consider regularization of the parameters in multivariate linear regression models with the errors having a multivariate skew-t distribution. An iterative penalized likelihood procedure is proposed for constructing sparse estimators of both the regression coefficient and inverse scale matrices simultaneously. The sparsity is introduced through penalizing the negative log-likelihood by adding L_{1}-penalties on the entries of the two matrices. Taking advantage of the hierarchical representation of skew-t distributions, and using the expectation conditional maximization (ECM) algorithm, we reduce the problem to penalized normal likelihood and develop a procedure to minimize the ensuing objective function. Using a simulation study the performance of the method is assessed, and the methodology is illustrated using a real data set with a 24-dimensional response vector.
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Lianfu Chen et al.Bayesian Decision Theoretic Approach to Directional Multiple Hypotheses Problems
http://epublications.marquette.edu/mscs_fac/196
http://epublications.marquette.edu/mscs_fac/196Wed, 06 Aug 2014 11:28:35 PDT
A multiple hypothesis problem with directional alternatives is considered in a decision theoretic framework. Skewness in the alternatives is considered, and it is shown that this skewness permits the Bayes rules to possess certain advantages when one direction of the alternatives is more important or more probable than the other direction. Bayes rules subject to constraints on certain directional false discovery rates are obtained, and their performances are compared with a traditional FDR rule through simulation. We also analyzed a gene expression data using our methodology, and compare the results to that of a FDR method.
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Naveen Bansal et al.H-Enrichments and Their Homeomorphism Groups
http://epublications.marquette.edu/mscs_fac/195
http://epublications.marquette.edu/mscs_fac/195Wed, 23 Jul 2014 13:56:44 PDTPaul BankstoniPrevention: Towards a Novel Real-Time Smartphone-Based Fall Prevention System
http://epublications.marquette.edu/mscs_fac/194
http://epublications.marquette.edu/mscs_fac/194Thu, 17 Jul 2014 12:52:12 PDT
Falling remains one of the leading causes of hospitalization and death for the elderly all around the world. The considerable risk of falls and the substantial increase of the elderly population have stimulated scientific research on smartphone-based fall detection systems recently. Even though these systems are helpful for fall detection, the best way to reduce the number of falls and their consequences is to prevent them from happening in the first place. Therefore, our focus is on fall prevention rather than fall detection. To address the issue of fall prevention, in this paper, we propose a smartphone-based fall prevention system that can alert the user about their abnormal walking pattern. Most current systems merely detect a fall whereas our approach attempts to identify high-risk gait patterns and alert the user to save them from an imminent fall. Our system uses a gait analysis approach that couples cycle detection with feature extraction to detect gait abnormality. We validated our approach using a decision tree with 10-fold cross validation and found 99.8% accuracy in gait abnormality detection. To the best of our knowledge, we are the first to use the built-in accelerometer and gyroscope of the smartphone to identify abnormal gaits in users for fall prevention.
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AKM Jahangir Alam Majumder et al.On the Distributions of Certain Spacings
http://epublications.marquette.edu/mscs_fac/193
http://epublications.marquette.edu/mscs_fac/193Mon, 14 Jul 2014 09:57:49 PDT
A characterization of the uniform distribution based on distributions of spacings is presented which extends the existing result in this direction. Also, a result on the distribution of spacings for distributions close to the uniform one is discussed.
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Gholamhossein Hamedani et al.Conditional Moments, Sub-Independence and Independence II
http://epublications.marquette.edu/mscs_fac/192
http://epublications.marquette.edu/mscs_fac/192Mon, 14 Jul 2014 09:48:09 PDT
We recall a concept called sub-independence, which is defined in terms of the convolution of the distributions of random variables, providing a stronger sense of dissociation between random variables than that of uncorrelatedness. In risk and decision analysis, the investigator may encounter a stochastic model whose components are uncorrelated dependent random variables. The marginal distributions of the components are known but not their joint distribution. The investigator, however, is interested in (or in need of) the distribution of the sum of some or all of the components. The concept of sub-independence will allow the determination of the distribution of the sum of the components based on the marginal distributions of the summands. This concept is much weaker than that of independence and yet can be employed to determine the distribution of the sum of random variables from their marginal distributions. We shall mention some possible applications of the concept of sub-independence to risk and decision analysis.
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Gholamhossein Hamedani et al.Characterizations of Continuous Univariate Distributions Based on the Truncated Moments of Functions of Order Statistics
http://epublications.marquette.edu/mscs_fac/191
http://epublications.marquette.edu/mscs_fac/191Mon, 14 Jul 2014 09:31:07 PDT
Most of the well-known continuous univariate distributions are characterized based on a truncated moment of a function of the 1^{st} order statistic or of the n^{th} order statistic.
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Gholamhossein HamedaniCharacterizations of Distributions of Ratio of Rayleigh Random Variables
http://epublications.marquette.edu/mscs_fac/190
http://epublications.marquette.edu/mscs_fac/190Fri, 11 Jul 2014 11:13:17 PDT
Various characterizations of the distribution of the ratio of two independent Rayleigh random variables are presented. These characterizations are based, on a truncated moment; on hazard function; and on certain functions of order statistics.
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Gholamhossein HamedaniMicro-Environment Causes Reversible Changes in DNA Methylation and mRNA Expression Profiles in Patient-Derived Glioma Stem Cells
http://epublications.marquette.edu/mscs_fac/189
http://epublications.marquette.edu/mscs_fac/189Mon, 07 Jul 2014 09:52:28 PDTIn vitro and in vivo models are widely used in cancer research. Characterizing the similarities and differences between a patient's tumor and corresponding in vitro and in vivo models is important for understanding the potential clinical relevance of experimental data generated with these models. Towards this aim, we analyzed the genomic aberrations, DNA methylation and transcriptome profiles of five parental tumors and their matched in vitro isolated glioma stem cell (GSC) lines and xenografts generated from these same GSCs using high-resolution platforms. We observed that the methylation and transcriptome profiles of in vitro GSCs were significantly different from their corresponding xenografts, which were actually more similar to their original parental tumors. This points to the potentially critical role of the brain microenvironment in influencing methylation and transcriptional patterns of GSCs. Consistent with this possibility, ex vivo cultured GSCs isolated from xenografts showed a tendency to return to their initial in vitro states even after a short time in culture, supporting a rapid dynamic adaptation to the in vitro microenvironment. These results show that methylation and transcriptome profiles are highly dependent on the microenvironment and growth in orthotopic sites partially reverse the changes caused by in vitro culturing.
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Mehmet Baysan et al.When Hausdorff Continua Have No Gaps
http://epublications.marquette.edu/mscs_fac/188
http://epublications.marquette.edu/mscs_fac/188Thu, 26 Jun 2014 13:51:21 PDT
An interpretation of betweenness on a set is gap free if each two distinct points of the set have a third point between them. In this paper we are interested in gap free betweenness relations naturally induced by the topology of Hausdorff continua. In particular, we say c lies between a and b in the K-interpretation precisely when every subcontinuum that contains both a and b also contains c. We explore the connection between K-gap freeness and hereditary unicoherence.
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Paul BankstonTopological Reduced Products and the GCH
http://epublications.marquette.edu/mscs_fac/187
http://epublications.marquette.edu/mscs_fac/187Thu, 26 Jun 2014 13:42:10 PDT
Since its inception in the late fifties, the theory of reduced products in model theory and algebra has developed into an active field of research with increasingly many participants. In particular the theory of ultraproducts has provided "algebraic" proofs of the compactness theorem of first order logic, the existence of saturated models of certain kinds; as well as a characterization of the notion of elementary equivalence between models. Copious details can be found in [BS] and [CK]. In our paper [B] we attempted to translate the notion of reduced product into the context of general topology and found, not too surprisingly, that here was a vast untapped source of research problems, many of the type already encountered in the theory of box products. In [B] several parallel problems involving box products and "topological" ultraproducts are explored; and it turns out that the ultraproduct theorems are often either easier than their counterparts to prove or can be proved directly in ZFC without recourse to extra set-theoretic axioms. Topological reduced products are formed as certain quotients of box products where the equivalence relations in question derive from filters on the index set. In this note ~N'e present a result about paracompactness in topological ultraproducts (i.e. where the filter is maximal) and show how this result relates to a known theorem about paracompactness in box products (trivially reduced products via the singleton filter). Both of these results relate directly with the Generalized Continuum Hypothesis (GCH).
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Paul BankstonTopological Measures of Systems of Sets
http://epublications.marquette.edu/mscs_fac/186
http://epublications.marquette.edu/mscs_fac/186Wed, 25 Jun 2014 09:15:34 PDT
If X is an infinite set, we may topologize the power set of X naturally so that systems of subsets of X can be described in the language of Baire category. Systems we consider include: subalgebra lattices of algebraic structures; topologies; filters; and families of almost disjoint sets.
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Paul BankstonContinua and the Co-elementary Hierarchy of Maps
http://epublications.marquette.edu/mscs_fac/185
http://epublications.marquette.edu/mscs_fac/185Wed, 25 Jun 2014 08:52:41 PDT
The co-elementary hierarchy is a nested ordinal-indexed sequence of classes of mappings between compacta, with each successor level being defined inductively from the previous one using the topological ultracopower construction. The lowest level is the class of continuous surjections; and the next level up, the coexistential maps, is already a much more restricted class. Co-existential maps are weakly confluent, and monotone when their images are locally connected. These maps also preserve important topological properties, such as: being infinite, being of covering dimensions ≤ n, and being a (hereditarily decomposable, indecomposable, hereditarily indecomposable) continuum.
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Paul BankstonCharacterizations of Certain Continuous Univariate Distributions Based on the Conditional Distribution of Generalized Order Statistics
http://epublications.marquette.edu/mscs_fac/184
http://epublications.marquette.edu/mscs_fac/184Tue, 24 Jun 2014 14:45:44 PDT
The problem of characterizing probability distributions is an interesting problem which has recently attracted the attention of many researchers. Various characterization results have been established in different directions as reported in the literature. We present here, various characterizations of certain univariate continuous distributions based on the conditional distribution of generalized order statistics.
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M. Ahsanullaha et al.Feature Extraction Method for Real Time Human Activity Recognition on Cell Phones
http://epublications.marquette.edu/mscs_fac/183
http://epublications.marquette.edu/mscs_fac/183Mon, 19 May 2014 08:30:20 PDT
In this paper we contribute a novel linear-time method for extracting features from acceleration sensor signals in order to identify human activities. We benchmark this method using a standard acceleration-based activity recognition dataset called SCUT-NAA. The results show that the described method performs best when the training and testing data are from the same person. In this context, a linear kernel based support vector machine (SVM) classifier and a radial basis function (RBF) based one produced similar levels of accuracy. Finally we demonstrate an application of the proposed method for realtime activity recognition on a cell phone with a single triaxial accelerometer. This feature extraction method can be used for realtime activity recognition on resource constrained devices.
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Mridul Khan et al.