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2017

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Articles 7381 - 7410 of 8353

Full-Text Articles in Engineering

Low Complexity Link Level Performance Prediction For Simo Systems, Asif Khan, Alam Zaib, Shahid Khattak Jan 2017

Low Complexity Link Level Performance Prediction For Simo Systems, Asif Khan, Alam Zaib, Shahid Khattak

Turkish Journal of Electrical Engineering and Computer Sciences

In this paper a low-cost link level performance prediction technique is proposed for a single input and multiple output system. Receiver link level abstraction is used in system level simulations of large networks in order to reduce their complexity. Usually, a single lookup table is employed in link level abstraction to predict a receiver's performance under different channel conditions. In the presented work, the mean frame error rate curve of different diverse channels is proposed as the reference for performance prediction in single input multiple output systems. Its generation involves compression of the received code word into a single quality …

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A Predictive Modeling Approach For Improving Paddy Crop Productivity Using Data Mining Techniques, Anitha Arumugam Jan 2017

A Predictive Modeling Approach For Improving Paddy Crop Productivity Using Data Mining Techniques, Anitha Arumugam

Turkish Journal of Electrical Engineering and Computer Sciences

Agriculture has a great impact on the economy of developing countries. To provide food security for people, there is a need for improving the productivity of major crops. Rapidly changing climatic conditions and the cost of investment in agriculture are major barriers for small-holder farmers. The proposed research aims to develop a predictive model that provides a cultivation plan for farmers to get high yield of paddy crops using data mining techniques. Unlike statistical approaches, data mining techniques extract hidden knowledge through data analysis. The data set used in this research for mining process is real data collected from farmers …

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Development Of Metal Oxide Arrester Block Using A Rare Earth Element For Very Fast Transient Overvoltage Applications, Kannadasan Raju, Valsalal Prasad, Jayavel Ramasamy Jan 2017

Development Of Metal Oxide Arrester Block Using A Rare Earth Element For Very Fast Transient Overvoltage Applications, Kannadasan Raju, Valsalal Prasad, Jayavel Ramasamy

Turkish Journal of Electrical Engineering and Computer Sciences

The protection ability of metal oxide arresters against switching, lightning, and steep current surges has been well proven. On the contrary, during the invasion of very fast transients, the existing arrester fails to operate due to delay in its initial response. In order to decrease the delay, it is imperative to improve the electrical properties of the arrester such as nonlinearity and voltage gradient with reduced capacitive effect. In this context, new arrester blocks are developed with the addition of a rare earth element, namely scandium trioxide (Sc$_{2}$O$_{3})$, and then sintered with a microwave sintering process. Owing to the uniform …

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New Patterson-Wiedemann Type Functions With 15 Variables In The Generalized Rotation-Symmetric Class, Selçuk Kavut Jan 2017

New Patterson-Wiedemann Type Functions With 15 Variables In The Generalized Rotation-Symmetric Class, Selçuk Kavut

Turkish Journal of Electrical Engineering and Computer Sciences

Recently, it was shown that there is no Boolean function on 15 variables with nonlinearity greater than 16276 in the class of functions that are invariant under the action of GF(2$^{3})^{\ast }\times GF(2^{5})^{\ast }$. In this study, we consider some important subsets of this class and perform an efficient enumeration of the 15-variable Patterson-Wiedemann (PW) type functions with nonlinearity greater than the bent concatenation bound 16256 in the generalized classes of both 3-RSBFs and 5-RSBFs for which the corresponding search spaces are 2$^{28.2}$ and 2$^{47.85}$, respectively. For the case of 3-RSBFs, we find that there are 32 functions with nonlinearity …

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Effects Of Nonaerated Circulation Water Velocity On Nutrient Release From Aquaculture Pond Sediments, Xiangju Cheng, Dantong Zhu, Xixi Wang, Deguang Yu, Jun Xie Jan 2017

Effects Of Nonaerated Circulation Water Velocity On Nutrient Release From Aquaculture Pond Sediments, Xiangju Cheng, Dantong Zhu, Xixi Wang, Deguang Yu, Jun Xie

Civil & Environmental Engineering Faculty Publications

Sustaining good water quality in aquaculture ponds is vital. Without an aerator, the dissolved oxygen in ponds comes primarily from mass transfer at the water-ambient atmosphere interface. As sediment can seriously affect water quality, this study used indoor experiments to examine the nutrient (nitrogen and phosphorus) release mechanisms and fluxes from sediment in aquaculture ponds with moving water but no aeration. The results showed that the ammonia nitrogen (NH3-N) concentration in the overlying water was inversely proportional to flow velocity and that a higher flow velocity tended to result in a lower concentration in the overlying water, a …

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Upscaling Stem To Community-Level Transpiration For Two Sand-Fixing Plants: Salix Gordejevii And Caragana Microphylla, Limin Duan, Yang Li, Xue Yan, Tingxi Liu, Xixi Wang Jan 2017

Upscaling Stem To Community-Level Transpiration For Two Sand-Fixing Plants: Salix Gordejevii And Caragana Microphylla, Limin Duan, Yang Li, Xue Yan, Tingxi Liu, Xixi Wang

Civil & Environmental Engineering Faculty Publications

The information on transpiration is vital for sustaining fragile ecosystem in arid/semiarid environment, including the Horqin Sandy Land (HSL) located in northeast China. However, such information is scarce in existing literature. The objectives of this study were to: (1) measure sap flow of selected individual stems of two sand-fixing plants, namely Salix gordejevii and Caragana microphylla, in HSL; and (2) upscale the measured stem-level sap flow for estimating the community-level transpiration. The measurements were done from 1 May to 30 September 2015 (i.e., during the growing season). The upscaling function was developed to have one dependent variable, namely sap …

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Modeling Algae Powered Neighborhood Through Gis And Bim Integration, Florina Dutt, Steven Jige Quan, Erik Woodworth, Daniel Castro-Lacouture, Ben J. Stuart, Perry Pei-Ju Yang Jan 2017

Modeling Algae Powered Neighborhood Through Gis And Bim Integration, Florina Dutt, Steven Jige Quan, Erik Woodworth, Daniel Castro-Lacouture, Ben J. Stuart, Perry Pei-Ju Yang

Civil & Environmental Engineering Faculty Publications

This paper aims to propose a modeling method for algae powered neighborhoods through GIS-BIM integration. In the first part of the paper, the applicability of different types of algae systems in an urban neighborhood are studied. The various systems of algae provide different strengths and weakness that affect their performance and suitability for given urban scenarios. Through extensive literature review, the variables that affect the performance of the micro-algae in the built environment are identified, with a focus on flat-panel photo bio-reactors and tubular photobioreactors. A previous GIS model for data management, performance analysis and design of the algae systems …

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Dynamic Model To Predict Ac Critical Flashover Voltage Of Nonuniformly Polluted Insulators Under Thermal Ionization Conditions, Saeed Shahabi, Ahmad Gholami Jan 2017

Dynamic Model To Predict Ac Critical Flashover Voltage Of Nonuniformly Polluted Insulators Under Thermal Ionization Conditions, Saeed Shahabi, Ahmad Gholami

Turkish Journal of Electrical Engineering and Computer Sciences

This paper presents a theoretical dynamic model based on the Hampton criterion and Mayr's equation for predicting the critical values of flashover on the surface of nonuniformly polluted cap and pin porcelain insulators. The nonuniform pollution layer on the surface of the insulator, the number of disk insulator units, and the geometry of the insulator such as diameter and ribs are the important factors used for prediction. Two types of pollution layer configuration, linear and graded, are introduced as nonuniform pollution layers. The influences of the nonuniform pollution layer on critical flashover voltage are investigated. Furthermore, a random value is …

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Automatic Reduction Of Periodic Noise In Images Using Adaptive Gaussian Star Filter, Seni̇ha Ketenci̇, Ali̇ Gangal Jan 2017

Automatic Reduction Of Periodic Noise In Images Using Adaptive Gaussian Star Filter, Seni̇ha Ketenci̇, Ali̇ Gangal

Turkish Journal of Electrical Engineering and Computer Sciences

The reduction of noise in images is a crucial issue and an inevitable preprocessing step in image analysis. Many diverse noise sources, which disrupt source images, exist in nature and through manmade devices. Periodic noise is one such disruption that has a periodic pattern in the spatial domain, causing hills in the image spectrum. In practice, quasiperiodic noise is commonly encountered instead of periodic noise. It has a more complex frequency spectrum, such as a star shape, in place of a pure delta shape in the frequency amplitude spectrum. In this study, we consider designing a star shape Gaussian filter …

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Design And Realization Of A Novel Planar Array Antenna And Low Power Lna For Ku-Band Small Satellite Communications, Lida Kouhalvandi, Osman Ceylan, Selçuk Paker, Hasan Bülent Yağci Jan 2017

Design And Realization Of A Novel Planar Array Antenna And Low Power Lna For Ku-Band Small Satellite Communications, Lida Kouhalvandi, Osman Ceylan, Selçuk Paker, Hasan Bülent Yağci

Turkish Journal of Electrical Engineering and Computer Sciences

This article presents both a four-element novel microstrip array antenna and a low noise amplifier (LNA) for a Ku-band small satellite receiver. It includes all design details with measurement results of the fabricated array antenna and LNA. Measured minimum and maximum gains of the proposed antenna are 10.1 and 10.9 dBi in 11.9-12.9 GHz band frequency. The designed LNA has a noise figure lower than 1.5 dB and gain higher than 8 dB (at 2 V, 10 mA biasing). In order to reduce the design period and cost, discrete components are chosen and a hetero-junction FET is used as the …

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Threshold Distance-Based Cluster Routing Protocols For Static And Mobile Wireless Sensor Networks, Padmavati Khandnor, Trilok Aseri Jan 2017

Threshold Distance-Based Cluster Routing Protocols For Static And Mobile Wireless Sensor Networks, Padmavati Khandnor, Trilok Aseri

Turkish Journal of Electrical Engineering and Computer Sciences

In cluster-based wireless sensor network routing protocols, when the cluster head transfers data based on single hop transmission to the sink node, then the cluster heads that are farther away deplete more energy as compared to nearby cluster heads. This condenses load balancing in the network. If the cluster heads collaborate with each other and transfer data based on multihop transmission, then the cluster heads nearer to the sink node are burdened with significant relay traffic and deplete energy much faster, which causes a network coverage problem also known as a hot spot problem. To avoid both of the above …

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Optimal Determination Of Island Boundaries Besides The Optimal Placement Of D-Statcom Devices And Dg Units, Sadeq Rabie, Hossein Afrakhte Jan 2017

Optimal Determination Of Island Boundaries Besides The Optimal Placement Of D-Statcom Devices And Dg Units, Sadeq Rabie, Hossein Afrakhte

Turkish Journal of Electrical Engineering and Computer Sciences

In this study, integration of three important concepts of distributed generation, D-FACTS devices, and microgrids are evaluated. The performance of a microgrid is dependent on its location, capacity, and placement of DG units and D-FACTS devices. In this paper a new method is proposed to simultaneously determine the optimal number, location, and capacity of DG units and D-STATCOM devices and optimal boundaries of electrical islands in the independent mode of microgrids. The main objective is to minimize the economic costs. The optimal locations of DG units and D-STATCOM devices should be determined to maximize the DG capacities with minimum loss …

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Design And Implementation Of A Modified Communication Disturbance Observer For Teleoperation Systems, Zahra Zeinaly, Amin Ramezani, Sadjaad Ozgoli Jan 2017

Design And Implementation Of A Modified Communication Disturbance Observer For Teleoperation Systems, Zahra Zeinaly, Amin Ramezani, Sadjaad Ozgoli

Turkish Journal of Electrical Engineering and Computer Sciences

In this paper, a novel structure for a communication disturbance observer in teleoperation systems is proposed to achieve robust stability. A time delay compensation method based on the concept of network disturbance and a communication disturbance observer (CDOB) has been proposed in past research. Unlike model-based approaches, it works without a time delay model. Therefore, it can be implemented in teleoperation systems with unknown and time-varying delay. However, it has been observed that the system model errors and external disturbances seriously affect the steady-state characteristics. Hence, in this paper, to achieve robustness against disturbance and model uncertainty, the structure of …

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Communications Protocol For Power Management In Smart Homes, Milan Bjelica, Mirjana Simic Pejovic Jan 2017

Communications Protocol For Power Management In Smart Homes, Milan Bjelica, Mirjana Simic Pejovic

Turkish Journal of Electrical Engineering and Computer Sciences

Emergency situations, incentives for energy efficiency, new pricing plans, and distributed electricity market jointly require home automation systems that would conform an instantaneous load to a dynamically set limit. In this paper, a novel machine-to-machine communications protocol that interconnects a smart grid and smart house is described. ''Intelligent'' domestic appliances use it to coordinate their switch-on times so that the assigned power quota will not be exceeded. In this way, the end-user experience can be improved by reducing the electricity bills, conveniently conforming to prepaid pricing plans, or even by providing continued service at possibly reduced consumption levels during power …

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Investigation Of Secondary Cooling Design Enhancements In Thermally Limited Compact Notebooks, Muhammad Azhar Ali Khan, Eray Uzgören, Ali̇ Muhtaroğlu Jan 2017

Investigation Of Secondary Cooling Design Enhancements In Thermally Limited Compact Notebooks, Muhammad Azhar Ali Khan, Eray Uzgören, Ali̇ Muhtaroğlu

Turkish Journal of Electrical Engineering and Computer Sciences

Thermal design enhancements in a thermally limited compact notebook system are investigated in this paper. System temperature, power, and fan speed are characterized under a range of activity levels. A finite element model is developed, and validated against measurements. Design enhancements improve cooling with minimum intrusion to the existing mechanical design. A passive secondary heat pipe in the system reduces the CPU temperature by 5 $^{\circ}$C, and improves the system performance through increased CPU + Graphics and Memory Controller Hub (GMCH) thermal design power (TDP) by 6.4%. When such a secondary heat pipe is considered with an integrated off-the-shelf Peltier …

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A Neural Network Approach To Navigation Of A Mobile Robot And Obstacle Avoidance In Dynamic And Unknown Environments, Farhad Shamsfakhr, Bahram Sadeghi Bigham Jan 2017

A Neural Network Approach To Navigation Of A Mobile Robot And Obstacle Avoidance In Dynamic And Unknown Environments, Farhad Shamsfakhr, Bahram Sadeghi Bigham

Turkish Journal of Electrical Engineering and Computer Sciences

Mobile robot navigation and obstacle avoidance in dynamic and unknown environments is one of the most challenging problems in the field of robotics. Considering that a robot must be able to interact with the surrounding environment and respond to it in real time, and given the limited sensing range, inaccurate data, and noisy sensor readings, this problem becomes even more acute. In this paper, we attempt to develop a neural network approach equipped with statistical dimension reduction techniques to perform exact and fast robot navigation, as well as obstacle avoidance in such a manner. In order to increase the speed …

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Erp: An Efficient Reactive Routing Protocol For Dense Vehicular Ad Hoc Networks, Thandapany Sivakumar, Rajendiran Manoharan Jan 2017

Erp: An Efficient Reactive Routing Protocol For Dense Vehicular Ad Hoc Networks, Thandapany Sivakumar, Rajendiran Manoharan

Turkish Journal of Electrical Engineering and Computer Sciences

A vehicular ad hoc network (VANET) is a type of mobile ad hoc network (MANET) that provides an exchange of messages between vehicles. VANETs encourage researchers to create safety and comfort applications that will lead to intelligent transport systems. Conventional ad hoc routing methods may cause flooding of packets to find routes in a VANET. Hence, finding a route from the source to the destination vehicle by local broadcast techniques in densely populated urban areas may create a broadcast storm and network bandwidth is unnecessarily wasted to discover routes between source and destination vehicles. In this paper, an efficient routing …

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Using Latent Semantic Analysis For Automated Keyword Extraction From Large Document Corpora, Tuğba Önal Süzek Jan 2017

Using Latent Semantic Analysis For Automated Keyword Extraction From Large Document Corpora, Tuğba Önal Süzek

Turkish Journal of Electrical Engineering and Computer Sciences

In this study, we describe a keyword extraction technique that uses latent semantic analysis (LSA) to identify semantically important single topic words or keywords. We compare our method against two other automated keyword extractors, Tf-idf (term frequency-inverse document frequency) and Metamap, using human-annotated keywords as a reference. Our results suggest that the LSA-based keyword extraction method performs comparably to the other techniques. Therefore, in an incremental update setting, the LSA-based keyword extraction method can be preferably used to extract keywords from text descriptions from big data when compared to existing keyword extraction methods.

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Eccentricity Fault Diagnosis In A Permanent Magnet Synchronous Motor Under Nonstationary Speed Conditions, Mustafa Eker, Mehmet Akar Jan 2017

Eccentricity Fault Diagnosis In A Permanent Magnet Synchronous Motor Under Nonstationary Speed Conditions, Mustafa Eker, Mehmet Akar

Turkish Journal of Electrical Engineering and Computer Sciences

Electric motor faults decrease production capacity and increase maintenance costs. Today, predictive detection based on real-time monitoring and fault detection is taking the place of periodic applications. In this study, a new method is presented for the detection of eccentricity faults in permanent magnet synchronous motors. The motor current and the rotor speed were monitored under stationary and nonstationary speed and different load conditions, after which the fault detection was carried out via angular domain-order tracking method. The obtained results were compared with traditional fast Fourier transform results. It was observed that the suggested method can successfully detect the fault …

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High-Pass/Low-Pass Section Design For 0$^{\Circ}$-360$^{\Circ}$ Lumped-Element Phase Shifters Via The Real Frequency Technique, Meti̇n Şengül Jan 2017

High-Pass/Low-Pass Section Design For 0$^{\Circ}$-360$^{\Circ}$ Lumped-Element Phase Shifters Via The Real Frequency Technique, Meti̇n Şengül

Turkish Journal of Electrical Engineering and Computer Sciences

In this paper, an algorithm based on the real frequency technique (RFT) is proposed to design high-pass and low-pass sections of a 0$^{\circ}$-360$^{\circ}$ wide range lumped-element phase shifter. The switching process, however, is not considered in this work. In the algorithm, it is enough to define the section type (high-pass or low-pass) and the number of elements in the sections; there is no need to select the exact circuit topologies for the high-pass and low-pass sections. This is a natural consequence of the proposed approach. Unlike in the methods described in the literature, there is also no need to derive …

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New Use Of The Hits Algorithm For Fast Web Page Classification, Mohamed Nadjib Meadi, Mohamed Chaouki Babahenini, Abdelmalik Taleb Ahmed Jan 2017

New Use Of The Hits Algorithm For Fast Web Page Classification, Mohamed Nadjib Meadi, Mohamed Chaouki Babahenini, Abdelmalik Taleb Ahmed

Turkish Journal of Electrical Engineering and Computer Sciences

The immense number of documents published on the web requires the utilization of automatic classifiers that allow organizing and obtaining information from these large resources. Typically, automatic web pages classifiers handle millions of web pages, tens of thousands of features, and hundreds of categories. Most of the classifiers use the vector space model to represent the dataset of web pages. The components of each vector are computed using the term frequency inversed document frequency (TFIDF) scheme. Unfortunately, TFIDF-based classifiers face the problem of the large-scale size of input data that leads to a long processing time and an increase in …

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Intellimote: A Hybrid Classifier For Classifying Learners' Emotion In A Distributed E-Learning Environment, Lopa Mandal, Rohan Das, Samar Bhattacharya, Pramatha Nath Basu Jan 2017

Intellimote: A Hybrid Classifier For Classifying Learners' Emotion In A Distributed E-Learning Environment, Lopa Mandal, Rohan Das, Samar Bhattacharya, Pramatha Nath Basu

Turkish Journal of Electrical Engineering and Computer Sciences

A huge collection of textual, graphical, audio, and video contents are readily available on the Internet to be used for the purpose of learning. Sentimental feedbacks of learners posted at the end of many of these contents may be considered as genuine reactions of the learners who have gone through the contents. Such learners' sentiments are important inputs for judging the acceptability of a learning material. Analyzing such feedbacks using sentiment analysis techniques can identify the best reusable learning contents that may be used for developing new courseware. This can significantly reduce the time and effort of authoring, which is …

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Electrocardiogram Signal Analysis For R-Peak Detection And Denoising With Hybrid Linearization And Principal Component Analysis, Harjeet Kaur, Rajni Rajni Jan 2017

Electrocardiogram Signal Analysis For R-Peak Detection And Denoising With Hybrid Linearization And Principal Component Analysis, Harjeet Kaur, Rajni Rajni

Turkish Journal of Electrical Engineering and Computer Sciences

In the areas of biomedical and healthcare, electrocardiogram (ECG) signal analysis is one of the major aspects of research. The accuracy in the detection of subtle characteristic features in ECG is of great significance. This paper deals with an algorithm based on hybrid linearization and principal component analysis for ECG signal denoising and R-peak detection. The ECG data have been taken from the MIT-BIH Arrhythmia Database for performance evaluation. The signal is denoised by applying the hybrid linearization method, which is an arrangement of the extended Kalman filter along with discrete wavelet transform, and then principal component analysis is employed …

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Offset-Free Adaptive Nonlinear Model Predictive Control With Disturbance Observer For Dc-Dc Buck Converters, Bahareh Vatankhah, Mohammad Farrokhi Jan 2017

Offset-Free Adaptive Nonlinear Model Predictive Control With Disturbance Observer For Dc-Dc Buck Converters, Bahareh Vatankhah, Mohammad Farrokhi

Turkish Journal of Electrical Engineering and Computer Sciences

The aim of this paper is to design a nonlinear model predictive control for DC-DC buck converters to track constant reference signals with zero steady-state error. The online trained neural network (NN) model is employed as the predictor and the steady-state error, which is called the offset, is studied in the presence of the changes in system parameters and the external disturbances. The stability of the closed-loop system is investigated using the Lyapunov direct theory. The proposed method can provide offset-free behavior in the presence of constant disturbances. For rejecting nonconstant disturbances, a nonlinear disturbance observer based on the NN …

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Modified Control Of The Matrix Converter-Based Drive For Voltage Sag Impact Reduction, Gytis Petrauskas, Gytis Svinkunas Jan 2017

Modified Control Of The Matrix Converter-Based Drive For Voltage Sag Impact Reduction, Gytis Petrauskas, Gytis Svinkunas

Turkish Journal of Electrical Engineering and Computer Sciences

Faults in transmission and distribution networks often cause voltage sags. Direct matrix converter (DMC)-based drives are a new generation of electrical drives. Unlike the conventional two-stage diode supply-side inverter drive, the DMC drive has no direct current (DC) link capacitor and no capacitor charging-time delay before operation. The absence of a DC link makes the DMC-based drive more sensitive to voltage sags. The above-mentioned faults in transmission and distribution networks could degrade the DMC drive's performance and reliability. This paper investigates possible kinds and levels of voltage sags, dependency on network configuration, and the behavior of the DMC-based drive under …

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Biomimetic Devices To Drive A Thermodynamically Uphill Reaction Using Light And To Degrade Industrial Waste Stream Components, Madison Joanne Sloan Jan 2017

Biomimetic Devices To Drive A Thermodynamically Uphill Reaction Using Light And To Degrade Industrial Waste Stream Components, Madison Joanne Sloan

Theses and Dissertations--Chemistry

Given the amount of industrial waste produced each year, as well as the accruing amount of greenhouse gases in our atmosphere produced by the burning of fossil fuels, it is imperative that humanity develop environmentally-sustainable sources of energy and methods of remediation. Nature achieves both of these by use of enzymes as catalysts, inspiring interest in designing biomimetic systems capable of harnessing clean energy and remediating industrial waste. This study examined the ability of enzymes in electrochemical and convective flow systems to achieve these tasks. The first portion studied the incorporation of enzymes into an electrochemical system to drive the …

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Formulation And Characterization Of Poly(Β-Amino Ester) Networks For Controlled Delivery Of Antioxidants In Pharmaceutical Applications, Vinod Shivaji Patil Jan 2017

Formulation And Characterization Of Poly(Β-Amino Ester) Networks For Controlled Delivery Of Antioxidants In Pharmaceutical Applications, Vinod Shivaji Patil

Theses and Dissertations--Chemical and Materials Engineering

Oxidative stress, which reflects an imbalance between oxidants and endogenous antioxidants, is known to be a cause as well as an effect of health conditions such as cancer, diabetes, Alzheimer’s disease, Parkinson’s disease and ischemia-reperfusion injury. Antioxidants have shown promising results in vitro in controlling oxidative stress. However, years of in vitro studies have failed to translate into effective clinical interventions for controlling oxidative stress in the disease conditions. This has been due to low bioavailability and lower stability of antioxidants. Poly(antioxidant β-amino esters) (PABAE) are a recently-developed class of biodegradable polymeric hydrogels that have shown promise in their ability …

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Understanding Glycoside Hydrolase Processivity For Improved Biomass Conversion, Suvamay Jana Jan 2017

Understanding Glycoside Hydrolase Processivity For Improved Biomass Conversion, Suvamay Jana

Theses and Dissertations--Chemical and Materials Engineering

In nature, organisms secrete synergistic enzyme cocktails to deconstruct crystalline polysaccharides, such as cellulose and chitin, to soluble sugars. The cocktails consist of multiple classes of processive and non-processive glycoside hydrolases (GH) that aid in substrate accessibility and reduce product inhibition. Processive GHs attach to chain ends and hydrolyze many glycosidic linkages in sequence to produce disaccharide units before dissociation, and as such, are responsible for the majority of hydrolytic bond cleavages. Accordingly, processive GHs are targets for activity improvements towards efficient and economical biomass conversion. However, the mechanism and factors responsible for processivity are still not understood completely at …

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The Effect Of Pore Density And Distribution On Fatigue Weak Links In An A713 Cast Aluminum Alloy, Rami A. Almatani Jan 2017

The Effect Of Pore Density And Distribution On Fatigue Weak Links In An A713 Cast Aluminum Alloy, Rami A. Almatani

Theses and Dissertations--Chemical and Materials Engineering

The effects of pore density and distribution were investigated on the fatigue crack initiation behavior in an A713 sand cast aluminum alloy plate of 12 mm thickness. The applied stress- the number of cycles to failure (S-N) curves of the samples taken from 2 mm and 5 mm from the free surface were obtained using four-point bend fatigue testing at room temperature, frequency of 20 Hz, stress ratio of 0.1, sinusoidal waveform, and in ambient air. The fatigue strengths of both, the 2 mm and 5 mm samples were 60% of the yield strength (σy=171.9 MPa) of the …

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Utilization Of Bio-Renewable Lignin In Building High Capacity, Durable, And Low-Cost Silicon-Based Negative Electrodes For Lithium-Ion Batteries, Tao Chen Jan 2017

Utilization Of Bio-Renewable Lignin In Building High Capacity, Durable, And Low-Cost Silicon-Based Negative Electrodes For Lithium-Ion Batteries, Tao Chen

Theses and Dissertations--Chemical and Materials Engineering

Silicon-based electrodes are the most promising negative electrodes for the next generation high capacity lithium ion batteries (LIB) as silicon provides a theoretical capacity of 3579 mAh g-1, more than 10 times higher than that of the state-of-the-art graphite negative electrodes. However, silicon-based electrodes suffer from poor cycle life due to large volume expansion and contraction during lithiation/delithiation. In order to improve the electrochemical performance a number of strategies have been employed, such as dispersion of silicon in active/inactive matrixes, devising of novel nanostructures, and various coatings for protection. Amongst these strategies, silicon-carbon coating based composites are one …

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