Price Faculty of Engineering Scholarly Works

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http://hdl.handle.net/1993/36351

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Open Access
A decoding-based fusion rule for cooperative spectrum sensing with nonorthogonal transmission of local decisions
(2013-07-08) Bokharaiee, Simin; Nguyen, Ha H; Shwedyk, Ed
Abstract Cooperative spectrum sensing in cognitive radio (CR) networks is studied in which each CR performs energy detection to obtain a binary decision on the absence/presence of the primary user. The problem of interest is how to efficiently report and combine the local decisions to/at the fusion center under fading channels. In order to reduce the required transmission bandwidth in the reporting phase, the paper examines nonorthogonal transmission of local decisions by means of on-off keying. Proposed and analyzed is a novel decoding-based fusion rule that essentially performs in three steps: (1) estimating minimum mean-square error of the transmitted information from cognitive radios, (2) making hard decisions of the transmitted bits based on the estimated information, and (3) combining the hard decisions in a linear manner. Simulation results support the theoretical analysis and show that the added complexity of the decoding-based fusion rule leads to a considerable performance gain over the simpler energy-based fusion rule when the reporting links are reasonably strong.
Open Access
A discrete single server queue with Markovian arrivals and phase type group services
(1995-1-1) Alfa, Attahiru Sule; Dolhun, K. Laurie; Chakravarthy, S.
We consider a single-server discrete queueing system in which arrivals occur according to a Markovian arrival process. Service is provided in groups of size no more than M customers. The service times are assumed to follow a discrete phase type distribution, whose representation may depend on the group size. Under a probabilistic service rule, which depends on the number of customers waiting in the queue, this system is studied as a Markov process. This type of queueing system is encountered in the operations of an automatic storage retrieval system. The steady-state probability vector is shown to be of (modified) matrix-geometric type. Efficient algorithmic procedures for the computation of the rate matrix, steady-state probability vector, and some important system performance measures are developed. The steady-state waiting time distribution is derived explicitly. Some numerical examples are presented.
Open Access
A finite capacity queue with Markovian arrivals and two servers with group services
(1994-1-1) Chakravarthy, S.; Alfa, Attahiru Sule
In this paper we consider a finite capacity queuing system in which arrivals are governed by a Markovian arrival process. The system is attended by two exponential servers, who offer services in groups of varying sizes. The service rates may depend on the number of customers in service. Using Markov theory, we study this finite capacity queuing model in detail by obtaining numerically stable expressions for (a) the steady-state queue length densities at arrivals and at arbitrary time points; (b) the Laplace-Stieltjes transform of the stationary waiting time distribution of an admitted customer at points of arrivals. The stationary waiting time distribution is shown to be of phase type when the interarrival times are of phase type. Efficient algorithmic procedures for computing the steady-state queue length densities and other system performance measures are discussed. A conjecture on the nature of the mean waiting time is proposed. Some illustrative numerical examples are presented.
Open Access
A new diagnostic vestibular evoked response
(2015-04-11) Dastgheib, Zeinab A; Lithgow, Brian; Blakley, Brian; Moussavi, Zahra
Abstract Objective To describe the development of a new clinically applicable method for assessing vestibular function in humans with particular application in Meniere’s disease. Study design Sophisticated signal-processing techniques were applied to data from human subject undergoing tilts stimulating the otolith organs and semicircular canals. The most sensitive representatives of vestibular function were extracted as “features”. Methods After careful consideration of expected response features, Electrovestibulography, a modified electrocochleography, recordings were performed on fourteen Meniere’s patients and sixteen healthy controls undergoing controlled tilts. The data were subjected to multiple signal processing techniques to determine which “features” were most predictive of vestibular responses. Results Linear discriminant analysis and fractal dimension may allow data from a single tilt to be used to adequately characterize the vestibular system. Conclusion Objective, physiologic assessment of vestibular function may become realistic with application of modern signal processing techniques.
Open Access
A QCT-Based Nonsegmentation Finite Element Head Model for Studying Traumatic Brain Injury
(2015-1-29) Liang, Zhaoyang; Luo, Yunhua
In the existing finite element head models (FEHMs) that are constructed from medical images, head tissues are usually segmented into a number of components according to the interior anatomical structure of the head. Each component is represented by a homogenous material model. There are a number of disadvantages in the segmentation-based finite element head models. Therefore, we developed a nonsegmentation finite element head model with pointwise-heterogeneous material properties and corroborated it by available experiment data. From the obtained results, it was found that although intracranial pressures predicted by the existing (piecewise-homogeneous) and the proposed (pointwise-heterogeneous) FEHM are very similar to each other, strain/stress levels in the head tissues are very different. The maximum peak strains/stresses predicted by the proposed FEHM are much higher than those by the existing FEHM, indicating that piecewise-homogeneous FEHM may have underestimated the stress/strain level induced by impact and thus may be inaccurate in predicting traumatic brain injuries.
Open Access
A Stand-Alone Magnetic Bubble Memory
(1981-1-1) Kinsner, W.; Joll, B. S.
Open Access
A Theory of Bubbles in Ion-implanted Structures
(1981-1-1) Kinsner, W.
Open Access
An Investigation into the Response of GFRP-Reinforced Glue-Laminated Tudor Arches
(2012-5-15) Alshurafa, S.; Alhayek, H.; Taheri, F.
This paper presents the results of an experimental and computational investigation tailored to examine the response of glass fiber-reinforced-plastic-(GFRP-) reinforced glue-laminated curved beams and arches. The main objective was to ascertain the viability of GFRP as an effective reinforcement for enhancing the load carrying capacity and stiffness of such curved structures. The study included optimization of the length and thickness of the GFRP reinforcement. In doing so, first a parametric finite element study was conducted to evaluate the influence of unidirectional GFRP reinforcement applied onto the arch using eleven possible configurations and different thicknesses. Subsequently, an experimental investigation was conducted to verify the results established by the finite element method as well as the integrity of actual GFRP-reinforced glue-laminated curved structures. The results indicate that GFRP can be considered as an effective and economically viable solution for strengthening and stiffening glulam arches, without adding any appreciable weight to the structure.
Open Access
Analysis of wind speed data and wind energy potential in three selected locations in south-east Nigeria
(2012-05-25) Oyedepo, Sunday O; Adaramola, Muyiwa S; Paul, Samuel S
Abstract In this study, the wind speed characteristics and energy potential in three selected locations in the southeastern part of Nigeria were investigated using wind speed data that span between 24 and 37 years and measured at a height of 10 m. It was shown that the annual mean wind speed at a height of 10 m for Enugu, Owerri and Onitsha are 5.42, 3.36 and 3.59 m/s, respectively, while the annual mean power densities are 96.98, 23.23 and 28.34 W/m2, respectively. It was further shown that the mean annual value of the most probable wind speed are 5.47, 3.72 and 3.50 m/s for Enugu, Owerri and Onitsha, respectively, while the respective annual value of the wind speed carrying maximum energy are 6.48, 4.33 and 3.90 m/s. The performance of selected commercial wind turbine models (with rated power between 50 and 1,000 kW) designed for electricity generation and a windmill (rated power, 0.36 kW) for water pumping located in these sites was examined. The annual energy output and capacity factor for these turbines, as well as the water produced by the windmill, were determined. The minimum required design parameters for a wind turbine to be a viable option for electricity generation in each location are also suggested.
Open Access
Arthritic Hand-Finger Movement Similarity Measurements: Tolerance Near Set Approach
(2011-4-5) Henry, Christopher; Peters, James F.
The problem considered in this paper is how to measure the degree of resemblance between nonarthritic and arthritic hand movements during rehabilitation exercise. The solution to this problem stems from recent work on a tolerance space view of digital images and the introduction of image resemblance measures. The motivation for this work is both to quantify and to visualize differences between hand-finger movements in an effort to provide clinicians and physicians with indications of the efficacy of the prescribed rehabilitation exercise. The more recent introduction of tolerance near sets has led to a useful approach for measuring the similarity of sets of objects and their application to the problem of classifying image sequences extracted from videos showing finger-hand movement during rehabilitation exercise. The approach to measuring the resemblance between hand movement images introduced in this paper is based on an application of the well-known Hausdorff distance measure and a tolerance nearness measure. The contribution of this paper is an approach to measuring as well as visualizing the degree of separation between images in arthritic and nonarthritic hand-finger motion videos captured during rehabilitation exercise.
Open Access
Biomaterials and tissue engineering for scar management in wound care
(2017-01-21) Rahimnejad, Maedeh; Derakhshanfar, Soroosh; Zhong, Wen
Abstract Scars are a natural and unavoidable result from most wound repair procedures and the body’s physiological healing response. However, they scars can cause considerable functional impairment and emotional and social distress. There are different forms of treatments that have been adopted to manage or eliminate scar formation. This review covers the latest research in the past decade on using either natural agents or synthetic biomaterials in treatments for scar reduction.
Open Access
Case study scenarios in site selection of hazardous material facilities based on transportation preferences
(2019-06-08) Mehran, Babak; Khan, Musharraf A; Mehran, Mina; Roh, Hyukjae; Sharma, Satish
Abstract A methodology is proposed to evaluate and rank potential sites for facilities dealing with hazardous materials (HAZMAT). The proposed methodology incorporates HAZMAT route planning into facility siting while considering transportation preferences and challenges. The area of interest is divided into smaller zones representing potential sites for a HAZMAT facility. A multimodal transportation network including railways and roads is considered for transportation of HAZMAT. Each zone is evaluated based on its accessibility from a set of selected points of interests (POIs), which are defined as potential origin/destination points for transportation of HAZMAT. The shortest routes between each POI and potential zones are evaluated based on a cost function which can accommodate multiple criteria to determine the associated disutility for each potential zone. Finally, zones are ranked based on their cumulative disutility scores. The proposed analysis method is quantitative, and at the same time it is adequately flexible to allow inclusion of subjective criteria. Application of the proposed methodology is demonstrated for identifying optimal locations for a HAZMAT facility (e.g., a nuclear facility) using the Canadian province of Saskatchewan as an example. Three scenarios were evaluated including (1) all network segments and POIs were treated equally, (2) network segments were rank ordered based on their functional classification while POIs were treated equally and (3) network segments were rank ordered based on their functional classification with preferences given to specific POI(s).
Open Access
Collagen morphology and texture analysis: from statistics to classification
(Nature, 2013-07-12) Mostaço-Guidolin, Leila B.; Ko, Alex C.-T.; Wang, Fei; Xiang, Bo; Hewko, Mark; Tian, Ganghong; Major, Arkady; Shiomi, Masashi; Sowa, Michael G.
In this study we present an image analysis methodology capable of quantifying morphological changes in tissue collagen fibril organization caused by pathological conditions. Texture analysis based on first-order statistics (FOS) and second-order statistics such as gray level co-occurrence matrix (GLCM) was explored to extract second-harmonic generation (SHG) image features that are associated with the structural and biochemical changes of tissue collagen networks. Based on these extracted quantitative parameters, multi-group classification of SHG images was performed. With combined FOS and GLCM texture values, we achieved reliable classification of SHG collagen images acquired from atherosclerosis arteries with >90% accuracy, sensitivity and specificity. The proposed methodology can be applied to a wide range of conditions involving collagen re-modeling, such as in skin disorders, different types of fibrosis and muscular-skeletal diseases affecting ligaments and cartilage.
Open Access
Computational Procedures for a Class of GI/D/k Systems in Discrete Time
(2009-11-5) Rahman, Md. Mostafizur; Alfa, Attahiru Sule
A class of discrete time GI/D/ systems is considered for which the interarrival times have finite support and customers are served in first-in first-out (FIFO) order. The system is formulated as a single server queue with new general independent interarrival times and constant service duration by assuming cyclic assignment of customers to the identical servers. Then the queue length is set up as a quasi-birth-death (QBD) type Markov chain. It is shown that this transformed GI/D/1 system has special structures which make the computation of the matrix R simple and efficient, thereby reducing the number of multiplications in each iteration significantly. As a result we were able to keep the computation time very low. Moreover, use of the resulting structural properties makes the computation of the distribution of queue length of the transformed system efficient. The computation of the distribution of waiting time is also shown to be simple by exploiting the special structures.
Open Access
Data for: An experimental and numerical study for salt dissolution and density-driven flow in porous media
(2018-08) Moore, Kayla; Holländer, Hartmut
The data was collected during laboratory experiments in a 2-D porous media, in a 0.9 m x 0.3 m x 0.12 m box. Sand hydraulic conductivity was 2.3E-3 m/s. A salt core was placed along the bottom third of the tank. A constant head boundary was applied at the top left and top right corners of the tank. Gradients of 2%, 5% and 10% were used. Salt concentrations were collected using resistance measurements which were calibrated against standards.
Open Access
Data mining and machine learning approaches for the integration of genome-wide association and methylation data: methodology and main conclusions from GAW20
(2018-09-17) Darst, Burcu; Engelman, Corinne D; Tian, Ye; Lorenzo Bermejo, Justo
Abstract Background Multiple layers of genetic and epigenetic variability are being simultaneously explored in an increasing number of health studies. We summarize here different approaches applied in the Data Mining and Machine Learning group at the GAW20 to integrate genome-wide genotype and methylation array data. Results We provide a non-intimidating introduction to some frequently used methods to investigate high-dimensional molecular data and compare the different approaches tried by group members: random forest, deep learning, cluster analysis, mixed models, and gene-set enrichment analysis. Group contributions were quite heterogeneous regarding investigated data sets (real vs simulated), conducted data quality control and assessed phenotypes (eg, metabolic syndrome vs relative differences of log-transformed triglyceride concentrations before and after fenofibrate treatment). However, some common technical issues were detected, leading to practical recommendations. Conclusions Different sources of correlation were identified by group members, including population stratification, family structure, batch effects, linkage disequilibrium and correlation of methylation values at neighboring cytosine-phosphate-guanine (CpG) sites, and the majority of applied approaches were able to take into account identified correlation structures. The ability to efficiently deal with high-dimensional omics data, and the model free nature of the approaches that did not require detailed model specifications were clearly recognized as the main strengths of applied methods. A limitation of random forest is its sensitivity to highly correlated variables. The parameter setup and the interpretation of results from deep learning methods, in particular deep neural networks, can be extremely challenging. Cluster analysis and mixed models may need some predimension reduction based on existing literature, data filtering, and supplementary statistical methods, and gene-set enrichment analysis requires biological insight.
Open Access
Decoding of Turbo Codes in Symmetric Alpha-Stable Noise
(2011-3-29) Shafieipour, Mohammad; Lim, Heng-Siong; Chuah, Teong-Chee
This paper investigates the decoding of turbo codes in impulsive symmetric α-stable (SαS) noise. Due to the nonexistence of a closed-form expression for the probability density function (pdf) of α-stable processes, numerical-based SαS pdf is used to derive branch transition probability (btp) for the maximum a posteriori turbo decoder. Results show that in Gaussian noise, the turbo decoder achieves similar performance using both the conventional and the proposed btps, but in impulsive channels, the turbo decoder with the proposed btp substantially outperforms the turbo decoder utilizing the conventional btp. Results also confirm that the turbo decoder incorporating the proposed btp outperforms the existing Cauchy-based turbo decoder in non-Cauchy impulsive noise, while the two decoders accomplish similar performance in Cauchy noise.
Open Access
Design Around Bundle Patent Portfolio Based on Technological Evolution
(2019-10-25) Li, Hui; Yuan, Jiefeng; Tan, Runhua; Peng, Qingjin
Abstract Product innovation can be achieved by analyzing leading products patents in the market. Different methods have been proposed for design around patent, commonly using the elimination or replacement of a single patent element. However, the existing research fails to restore the position and function of the design around object in the original patent portfolio of enterprises, which often leads to the phenomenon of evading one patent and violating another. This paper proposes a method for design around patent through using the fusion of technologies of the evolution theory and bundle-type patent portfolio analysis in the initial stage of product development. The object system is analyzed to select technical opportunities through the evolutionary path of technologies and functional trimming methods to achieve circumvent barriers of bundle-type patents. The bundle patent portfolio is analyzed for the product evolution with a radar map. The technological evolution path is combined with the TRIZ innovation method to identify and solve the design problem. Patentability of the new design is evaluated using the patent system rules for innovative scheme difference from the original patent portfolio. The method is verified in a case study for the design of a glass-wiping robot. The design solution has been patented.
Open Access
Development of an ultra low noise, miniature signal conditioning device for vestibular evoked response recordings
(2014-01-27) Kumaragamage, Chathura L; Lithgow, Brian J; Moussavi, Zahra
Abstract Background Inner ear evoked potentials are small amplitude (<1 μVpk) signals that require a low noise signal acquisition protocol for successful extraction; an existing such technique is Electrocochleography (ECOG). A novel variant of ECOG called Electrovestibulography (EVestG) is currently investigated by our group, which captures vestibular responses to a whole body tilt. The objective is to design and implement a bio-signal amplifier optimized for ECOG and EVestG, which will be superior in noise performance compared to low noise, general purpose devices available commercially. Method A high gain configuration is required (>85 dB) for such small signal recordings; thus, background power line interference (PLI) can have adverse effects. Active electrode shielding and driven-right-leg circuitry optimized for EVestG/ECOG recordings were investigated for PLI suppression. A parallel pre-amplifier design approach was investigated to realize low voltage, and current noise figures for the bio-signal amplifier. Results In comparison to the currently used device, PLI is significantly suppressed by the designed prototype (by >20 dB in specific test scenarios), and the prototype amplifier generated noise was measured to be 4.8 nV / Hz @ 1 kHz (0.45 μVRMS with bandwidth 10 Hz-10 kHz), which is lower than the currently used device generated noise of 7.8 nV / Hz @ 1 kHz (0.76 μVRMS). A low noise (<1 nV / Hz ) radio frequency interference filter was realized to minimize noise contribution from the pre-amplifier, while maintaining the required bandwidth in high impedance measurements. Validation of the prototype device was conducted for actual ECOG recordings on humans that showed an increase (p < 0.05) of ~5 dB in Signal-to-Noise ratio (SNR), and for EVestG recordings using a synthetic ear model that showed a ~4% improvement (p < 0.01) over the currently used amplifier. Conclusion This paper presents the design and evaluation of an ultra-low noise and miniaturized bio-signal amplifier tailored for EVestG and ECOG. The increase in SNR for the implemented amplifier will reduce variability associated with bio-features extracted from such recordings; hence sensitivity and specificity measures associated with disease classification are expected to increase. Furthermore, immunity to PLI has enabled EVestG and ECOG recordings to be carried out in a non-shielded clinical environment.
Open Access
Distributed joint source-channel code design for GMAC using irregular LDPC codes
(2014-01-09) Shahid, Iqbal; Yahampath, Pradeepa
Abstract Separate source and channel coding is known to be sub-optimal for communicating correlated sources over a Gaussian multiple access channel (GMAC). This paper presents an approach to designing distributed joint source-channel (DJSC) codes for encoding correlated binary sources over a two-user GMAC, using systematic irregular low-density parity check (LDPC) codes. The degree profile defining the LDPC code is optimized for the joint source probabilities using extrinsic information transfer (EXIT) analysis and linear programming. A key issue addressed is the Gaussian modeling of log-likelihood ratios (LLRs) generated by nodes representing the joint source probabilities in the combined factor graph of the two LDPC codes, referred to as source-channel factor (SCF) nodes. It is shown that the analytical expressions based on additive combining of incoming LLRs, as done in variable nodes and parity check nodes of the graph of a single LDPC code, cannot be used with SCF nodes. To this end, we propose a numerical approach based on Monte-Carlo simulations to fit a Gaussian density to outgoing LLRs from the SCF nodes, which makes the EXIT analysis of the joint decoder tractable. Experimental results are presented which show that LDPC codes designed with the proposed approach outperforms previously reported DJSC codes for GMAC. Furthermore, they demonstrate that when the sources are strongly dependent, the proposed DJSC codes can achieve code rates higher than the theoretical upper-bound for separate source and channel coding.