Engineering Commons^™

การศึกษาปัจจัยที่ก่อให้เกิดตามดในกระบวนการหล่อฉีดแรงดันสูง, แพรวดี แก้วคงคา

Chulalongkorn University Theses and Dissertations (Chula ETD)

วัตถุประสงค์ของงานวิจัยนี้คือการศึกษาปัจจัยที่ส่งผลต่อตามดในกระบวนการหล่อฉีดแรงดันสูงอลูมิเนียม R14 สำหรับคอมเพรสเซอร์ของชิ้นส่วนยานยนต์ ที่แรงดันในการฉีด 75 ถึง 85 เมกกาปาสคาล ความเร็วในการเคลื่อนที่ของลูกสูบที่ความเร็วต่ำ 0.16 ถึง 0.30 เมตรต่อวินาที ความเร็วในการเคลื่อนที่ของลูกสูบที่ความเร็วสูง 1.8 ถึง 3.0 เมตรต่อวินาที ระยะที่ลูกสูบเคลื่อนที่ด้วยความเร็วสูง 320 ถึง 340 มิลลิเมตร และแรงดันสุญญากาศ -93.0 ถึง -100.0 กิโลปาสคาล โดยการตรวจสอบการวิเคราะห์พื้นผิวตอบสนองกับวิธีบ็อกซ์-เบหน์เคน การออกแบบเพื่อศึกษาปัจจัยและความสัมพันธ์ของพารามิเตอร์และหาสภาวะที่เหมาะสมเพื่อลดสัดส่วนตามดให้เกิดขึ้นน้อยที่สุด จากผลการทดลองพบว่าทั้ง 5 ปัจจัยมีอิทธิพลต่อการเกิดข้อบกพร่องประเภทตามดอย่างมีนัยสำคัญที่ระดับความเชื่อมั่น 95 เปอร์เซ็นต์ ส่งผลให้สัดส่วนของเสียตามดลดลงเหลือ 5.18 เปอร์เซ็นต์จากการตั้งค่าสภาวะที่เหมาะสมจากการทดลองได้แก่ แรงดันในการฉีดคือ 85 เมกกะปาสกาล การเคลื่อนที่ของลูกสูบที่ความเร็วต่ำคือ 0.30 เมตรต่อวินาที การเคลื่อนที่ของลูกสูบที่ความเร็วสูงคือ 2.49 เมตรต่อวินาที ระยะที่ลูกสูบเคลื่อนที่ด้วยความเร็วสูงคือ 326.81 มิลลิเมตร และแรงดันสุญญากาศที่ -97.28 กิโลปาสกาล

Effect Of Additives In Lubricant On Cobalt-Iron Alloy Lapping, Wiraya Anamnart

Chulalongkorn University Theses and Dissertations (Chula ETD)

To maintain this flying height of read-write head (called slider) at 12 nm across the disk, read and writer elements will be lapped to meet designed surface roughness, surface topography, as well as magnetic property. The writer element was made from cobalt-iron alloy (CoFe). Final lapping process of sliders uses lubricant to control surface morphology and to avoid corrosion. The aim of this study was to determine the effect of additives on corrosion protection of CoFe. The corrosion was studied by potentiostat technique and atomic force microscopy (AFM). Water content was determined by Karl Fischer method. Thin film passivation was …

Measuring And Modelling The Thermal Performance Of The Tamar Suspension Bridge Using A Wireless Sensor Network, Nicholas De Battista, James M. W. Brownjohn, Hwee-Pink Tan, Ki Young Koo

Research Collection School Of Computing and Information Systems

A study on the thermal performance of the Tamar Suspension Bridge deck in Plymouth, UK, is presented in this paper. Ambient air, suspension cable, deck and truss temperatures were acquired using a wired sensor system. Deck extension data were acquired using a two-hop wireless sensor network. Empirical models relating the deck extension to various combinations of temperatures were derived and compared. The most accurate model, which used all the four temperature variables, predicted the deck extension with an accuracy of 99.4%. Time delays ranging from 10 to 66 min were identified between the daily cycles of the air temperature and …

Assembly And Mechanical Characterization Of Suspended Boron Nitride Nanotubes, Rachel Waxman

Theses and Dissertations

This study details the dielectrophoretic assembly and mechanical characterization of boron nitride nanotubes on silicon chips with gold electrodes. The chips were fabricated from 4in round silicon wafers with a 100nm-thick low stress silicon nitride insulating layer on the top and bottom. The electrodes were patterned using photo- and electron-beam lithography and dry etching, and the wafers were cut into 4 x 6mm chips. The boron nitride nanotubes studied were obtained from NIA and were synthesized via a unique pressurized vapor/condensor method, which produced long, small-diameter BNNTs without the use of a catalyst. These nanotubes were studied due to their …

Android-Based Smartphone Application Simulation And Systematic Design To Reduce Medication Administration Error In Prehospital Emergency Care., Natalie Vazquez

Theses and Dissertations

Since 1999 when the report To Err is Human: Building a Safer Health System was released, medical errors have come into focus (Kohn, 2000). In an effort to reduce medication administration errors in prehospital emergency care, an android-based smartphone application simulation was created. The app has components including QR barcode scanning, text to speech for medication cross-checking, weight-based medication dose calculations, and time stamped medication data wirelessly transferring to a database in real-time. Color standard identification was implemented, aiding to a designed systematic process for patient treatment to reduce medication errors. Direct observation was performed of emergency patient calls with …

Capillarity And Two-Phase Fluid Transport In Media With Fibers Of Dissimilar Properties, Thomas M. Bucher Jr.

Theses and Dissertations

Capillarity is a physical phenomenon that acts as a driving force in the displacement of one fluid by another within a porous medium. This mechanism operates on the micro and nanoscale, and is responsible for countless observable events. This can include applications such as absorption in various hygiene products, self-cleaning surfaces such as water beading up and rolling off a specially-coated windshield, anti-icing, and water management in fuel cells, among many others.

The most significant research into capillarity has occurred within the last century or so. Traditional formulations for fluid absorption include the Lucas–Washburn model for porous media, which is …

Optical Characterization Of Ingan Heterostructures For Blue Light Emitters And Vertical Cavity Lasers: Efficiency And Recombination Dynamics, Serdal Okur

Theses and Dissertations

OPTICAL CHARACTERIZATION OF INGAN HETEROSTRUCTURES FOR BLUE LIGHT EMITTERS AND VERTICAL CAVITY LASERS: EFFICIENCY AND RECOMBINATION DYNAMICS

By Serdal Okur, Ph.D.

A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Virginia Commonwealth University.

Virginia Commonwealth University, 2014.

Major Director: Ümit Özgür, Associate Professor, Electrical and Computer Engineering

This thesis explores radiative efficiencies and recombination dynamics in InGaN-based heterostructures and their applications as active regions in blue light emitters and particularly vertical cavities. The investigations focus on understanding the mechanism of efficiency loss at high injection as well as developing designs to mitigate …

Cfd Assessment Of Respiratory Drug Delivery Efficiency In Adults And Improvements Using Controlled Condensational Growth, Ross L. Walenga

Theses and Dissertations

Pharmaceutical aerosols provide a number of advantages for treating respiratory diseases that include targeting high doses directly to the lungs and reducing exposure of other organs to the medication, which improve effectiveness and minimize side effects. However, difficulties associated with aerosolized drug delivery to the lungs include drug losses in delivery devices and in the extrathoracic region of human upper airways. Intersubject variability of extrathoracic and thoracic drug deposition is a key issue as well and should be minimized. Improvements to respiratory drug delivery efficiency have been recently proposed by Dr. P. Worth Longest and Dr. Michael Hindle through the …

Molecular Dynamics Simulations Of Pure Polytetrafluoroethylene Near Glassy Transition Temperature For Different Molecular Weights, Rawan Al-Nsour

Theses and Dissertations

Fluoropolymers are employed in countless end-user applications across several industries. One such fluoropolymer is polytetrafluoroethylene. This research is concerned with studying and understanding the thermal behavior of polytetrafluoroethylene. Such understanding is critical to predict its behavior in diverse service environments as the polymer ages and for allowing bottom up design of improved polymers for specific applications.

While a plethora of experiments have investigated the thermal properties of polytetrafluoroethylene, examining these properties using molecular dynamics simulations remains in its infancy. In particular, the current body of molecular dynamics research on polytetrafluoroethylene has primarily focused on studying polytetrafluoroethylene phases, its physical nature, …

Design And Validation Of A Computational Model For Study Of Scapholunate Joint Kinematics, Edward J. Tremols

Theses and Dissertations

As computational power has increased, computational modeling has become a very promising tool to model the biomechanics of complex joint systems. Musculoskeletal computational models have become more complex when compared to original iterations which utilized a number of simplifications. This thesis utilized a three-dimensional computational model of the wrist joint structure to investigate scapholunate kinematics. The model accurately represented the bony anatomy of the wrist and hand and represented soft tissue structures such as ligaments, tendons, and other surrounding tissues. Creation of the model was done using commercially available computer-aided design and medical image processing software, and utilized the rigid …

Streaming Computations With Precise Control, Peng Li, Kunal Agrawal, Jeremy Buhler, Roger Chamberlain

All Computer Science and Engineering Research

No abstract provided.

Cloudpowercap: Integrating Power Budget And Resource Management Across A Virtualized Server Cluster, Yong Fu, Anne Holler, Chenyang Lu

All Computer Science and Engineering Research

In many datacenters, server racks are highly underutilized. Rack slots are left empty to keep the sum of the server nameplate maximum power below the power provisioned to the rack. And the servers that are placed in the rack cannot make full use of available rack power. The root cause of this rack underutilization is that the server nameplate power is often much higher than can be reached in practice. To address rack underutilization, server vendors are shipping support for per-host power caps, which provide a server-enforced limit on the amount of power that the server can draw. Using this …

Strategic Decision Support System Using Heuristic Algorithm For Practical Outlet Zones Allocation To Dealers In A Beer Supply Distribution Network, Michelle Lee Fong Cheong

Research Collection School Of Computing and Information Systems

We consider a two-echelon beer supply distribution network with the brewer replenishing the dealers and the dealers serving the outlet zones directly, for multiple product types. The allocation of the outlet zones to the dealers will determine the quantity of products the brewer replenishes each dealer, which will in turn impact the total warehousing and transportation costs. The non-linear optimization model formulated is difficult to solve to optimality, and the model itself does not include practical business considerations in the distribution business. A heuristics algorithm is designed and easily implemented using spreadsheets with Visual Basic programming to effectively and efficiently …

Risk Minimization Of Disjunctive Temporal Problem With Uncertainty, Hoong Chuin Lau, Tuan Anh Hoang

Research Collection School Of Computing and Information Systems

The Disjunctive Temporal Problem with Uncertainty (DTPU) is a fundamental problem that expresses temporal reasoning with both disjunctive constraints and contingency. A recent work (Peintner et al, 2007) develops a complete algorithm for determining Strong Controlla- bility of a DTPU. Such a notion that guarantees 100% confidence of execution may be too conservative in practice. In this paper, following the idea of (Tsamardinos 2002), we are interested to find a schedule that minimizes the risk (i.e. probability of failure) of executing a DTPU. We present a problem decomposition scheme that enables us to compute the probability of failure efficiently, followed …

A Performance Comparison Of Linear And Nonlinear Control Of A Scig-Wind Farm Connecting To A Distribution Network, Mohamed Benchagra, Mohamed Maaroufi, Mohammed Ouassaid

Turkish Journal of Electrical Engineering and Computer Sciences

This study presents a comparison of linear and nonlinear control to regulate the DC-link voltage and power factor correction of a wind farm equipped with squirrel cage induction generators (SCIGs), connecting to a 22-kV distribution network. Both active and reactive powers are employed in 2 independent control laws. The proposed control strategies are derived from the Lyapunov approach. The aim of the control is to maximize the generated power with the lowest possible impact in the grid voltage and frequency during normal operation and under the occurrence of faults. The nonlinear backstepping controller to be used for the control of …

Statistical Approach For Determining Impulse Breakdown Voltage Distribution Under Dc Sweep Voltage, Mehmet Demi̇r, Celal Koraşli

Turkish Journal of Electrical Engineering and Computer Sciences

This paper presents a comprehensive approach to the statistical characterization of impulse breakdown voltage under the effect of a DC sweep voltage. Several goodness-of-fit tests are applied to up-and-down test results obtained in the air-insulated rod-plane gap. Three distributions, normal, logistic, and Gumbel, are compared by means of the Kolmogorov--Smirnov goodness-of-fit test, and logistic distribution is also compared to 3-parameter Weibull distributions using the likelihood ratio test. Logistic distribution is found to be a possible alternative to normal and 3-parameter Weibull distributions.

A Learning Method To Evaluate A Generation Company's Bidding Strategy In The Electricity Market, Shengjie Yang, Jiangang Yao

Turkish Journal of Electrical Engineering and Computer Sciences

In the electricity market, generation companies (GenCos) are usually faced with the problem of choosing a better bidding strategy. They often have to evaluate each possible strategy according to its potential reward. In a competitive market environment, the electricity price is stochastic and volatile, and the GenCo's mixed strategies also make the problem more complicated. In this paper, we model the market price with a Markov regime-switching model and propose the temporal difference learning method in the Markov decision process to approximate the expected reward over an infinite horizon. The simulations based on this method have achieved the evaluation of …

Coherence Analysis On Thermal Effect For Power Cables Under Different Environmental Conditions, Sezai̇ Taşkin, Şahi̇n Serhat Şeker, Özcan Kalenderli̇, Murat Karahan

Turkish Journal of Electrical Engineering and Computer Sciences

There are 2 important aspects of this research; these are the experimental study and the data analysis, which are based on coherence analysis. In this study, a low-voltage power cable is tested under 2 different environments, air and water, and the variations in temperature are measured for the conductor, the sheath parts of the cable, and the environment. The recorded test data are analyzed using such as coherence analysis. This in turn provides the means to determine the relationship among the sheath, conductor, and the environment. In conclusion, high correlated peaks in the frequency domain are used to determine the …

Modeling And Simulation Of Deadbeat-Based Pi Controller In A Single-Phase H-Bridge Inverter For Stand-Alone Applications, Tow Leong Tiang, Dahaman Ishak

Turkish Journal of Electrical Engineering and Computer Sciences

This paper presents a deadbeat-based proportional-integral (PI) controller for a stand-alone single-phase voltage source inverter using a battery cell as the primary energy source. The inverter system is simulated in MATLAB/Simulink. It consists of a lead acid battery, third-order Butterworth low-pass DC filter and AC filter, H-bridge inverter, step-up transformer, and a variety of loads, as well as its sinusoidal pulse-width modulation (SPWM) deadbeat-based PI controller. In this paper, 2 simulation case studies are carried out, which are the abrupt load changes from a 400 W resistive load to a 500 W resistive load, and from a 400 W resistive …

Inverse Covariance Principal Component Analysis For Power System Stability Studies, Abdullah Alodienat, Tauseef Gulrez

Turkish Journal of Electrical Engineering and Computer Sciences

The dominant poles (eigenvalues) of system matrices are used extensively in determining the power system stability analysis. The challenge is to find an accurate and efficient way of computing these dominant poles, especially for large power systems. Here we present a novel way for finding the system stability based on inverse covariance principal component analysis (ICPCA) to compute the eigenvalues of large system matrices. The efficacy of the proposed method is shown by numerical calculations over realistic power system data and we also prove the possibility of using ICPCA to determine the eigenvalues closest to any damping ratio and repeated …

Hd-Mr: A New Algorithm For Number Recognition In Electrical Meters, Miguel Rodriguez, Geovanni Berdugo, Daladier Jabba, Maria Calle, Miguel Jimeno

Turkish Journal of Electrical Engineering and Computer Sciences

Utility companies in developing countries employ analog electrical meters to determine consumption and bill their customers accordingly. Obtaining an accurate reading is an expensive and time-consuming process. High consumption levels of water, energy, or gas are fined by the government; thus, it is necessary to develop tools that allow users to be informed about their consumption in real time. This paper proposes a new number recognition algorithm named the Hausdorff distance for meter reading (HD-MR). Experiments prove that HD-MR can achieve a 99.9% recognition rate, even when recognized numbers are under rotation. The maximum recognition time is 31 ms; hence, …

A Novel Sms Application With Gsm Control On Numerator Systems, Ali̇ Sarikaş, Zi̇ya Ekşi̇, Cüneyt Yücelbaş, Ali̇ Buldu

Turkish Journal of Electrical Engineering and Computer Sciences

Numerator systems are widely used in various fields, sorting, and structures to ensure regular functioning. They are used today in places such as banks and hospitals to minimize the time spent waiting in a queue, and various studies have been undertaken to achieve efficiency in the workplace. At the beginning of these studies, numerator systems, which have been integrated into the short message service (SMS) application, have been used efficiently. With this application, to supply the required information to the user in the fastest way, a numerator system is developed by utilizing radio frequency communications and the SMS message structure. …

Rfid And Communication Technologies For An Intelligent Bus Monitoring And Management System, Mahammad Abdul Hannan, Aishah Mustapha, Abdulla Al Mamun, Aini Hussain, Hassan Basri

Turkish Journal of Electrical Engineering and Computer Sciences

This paper highlights the implementation of an intelligent bus monitoring system based on current challenges and problems. In this system, radio frequency identification and integrated sensing technologies, such as a global positioning system, general packet radio service, and geographic information system, are used to monitor the movement of a bus. A new theoretical framework and ruled-based decision algorithms are developed for the system. An experimental setup is developed for the prototype implementation. The results show that the choice of integrated technologies used in the system is suitable to monitor and manage a vehicle transportation system.

A Methodology For Memristance Calculation, Reşat Mutlu, Ertuğrul Karakulak

Turkish Journal of Electrical Engineering and Computer Sciences

A memristor is a newly found fundamental circuit element whose behavior can be predicted using either the charge-dependent function called memristance or the flux-dependent function called memductance. Therefore, it is important to find the memristance or memductance function of a memristor. To the best of our knowledge, there is no methodology describing how to obtain the memristance function or memristor characteristic in the literature for this purpose as of yet. In this work, a methodology is suggested to find the memristance or memductance functions. The methodology suggests first doing several experiments with a memristor using a square-wave signal to acquire …

M-Fdbscan: A Multicore Density-Based Uncertain Data Clustering Algorithm, Atakan Erdem, Taflan İmre Gündem

Turkish Journal of Electrical Engineering and Computer Sciences

In many data mining applications, we use a clustering algorithm on a large amount of uncertain data. In this paper, we adapt an uncertain data clustering algorithm called fast density-based spatial clustering of applications with noise (FDBSCAN) to multicore systems in order to have fast processing. The new algorithm, which we call multicore FDBSCAN (M-FDBSCAN), splits the data domain into c rectangular regions, where c is the number of cores in the system. The FDBSCAN algorithm is then applied to each rectangular region simultaneously. After the clustering operation is completed, semiclusters that occur during splitting are detected and merged to …

Increasing Key Space At Little Extra Cost In Rfid Authentications, Gökhan Dalkiliç, Mehmet Hi̇lal Özcanhan, Hafi̇ze Şen Çakir

Turkish Journal of Electrical Engineering and Computer Sciences

Traditional authentication and key establishment protocols utilize nonce parameters as a means for message freshness, recent aliveness, and key derivation. Improving identity verification, increasing key space, or making secret updates more complex through nonces are not goals. Generating random numbers as nonces and not making the most out of them can be considered as a loss in resource stricken radio frequency identification (RFID) tags. By increasing the shared secrets slightly, a new functionality for the nonces is introduced, which makes the authentication and key establishment protocols of RFID systems more secure, in general. The proposed method contributes to the security …

A Web Laboratory Using Matlab Builder Ne For Computer Image Processing, Sezgi̇n Kaçar, Cüneyt Bayilmiş, Özdemi̇r Çeti̇n

Turkish Journal of Electrical Engineering and Computer Sciences

Many various instruments are needed for computer image processing. These instruments are used for image restoration, analysis, etc. This paper presents a novel web laboratory based on MATLAB Builder NE with Web Figure, called ImageWeb, to facilitate computer image processing without needed technical information for users. The developed ImageWeb provides fundamental principles of image processing, including basic, compression, edge detection, filtering, optimization, and histogram processes, and so on. In addition, the usage of MATLAB Builder NE with MATLAB Web Figure provides high flexibility with visualization means such as zoom, rotate, and 3-dimensional view. Users can easily access ImageWeb using only …

Analysis Of A Rule-Based Curriculum Plan Optimization System With Spearman Rank Correlation, Di̇dem Abi̇di̇n, Hafi̇ze Şen Çakir

Turkish Journal of Electrical Engineering and Computer Sciences

In corporations, accurate planning should be applied to manage the in-service training task within an optimum time period and without hindering the working tempo of the employees. For this reason, it is better to consider the curriculum planning task as a timetabling problem. However, when the timetables are prepared manually, it may turn out to be a complicated and time-consuming problem. In this study, it is aimed to evaluate the results of software introduced previously, which seeks to find a solution to the curriculum planning problem of in-service training programs in corporations using a rule-based genetic algorithm (GA). The input …

Effects Of A Current Transformer's Magnetizing Current On The Driving Voltage In Self-Oscillating Converters, Güngör Bal, Seli̇m Öncü

Turkish Journal of Electrical Engineering and Computer Sciences

Magnetizing inductance is one of the parameters that affect the phase and amplitude error of the output current of current transformers (CTs). In this study, the linear circuit model of a CT is developed to be used for driving purposes in power electronics applications. A simulation of the CT and its linear model is achieved. In the model circuit, the effect of the magnetizing inductance on the driving voltage can be examined. The equivalent circuit simulation results and the linear model simulation results along with the calculated results show agreement with each other. These results are compared with experimental results.

A Low-Memory Intensive Decoding Architecture For Double-Binary Convolutional Turbo Code, Ming Zhan, Liang Zhou, Jun Wu

Turkish Journal of Electrical Engineering and Computer Sciences

Memory accesses take a large part of the power consumption in the iterative decoding of double-binary convolutional turbo code (DB-CTC). To deal with this, a low-memory intensive decoding architecture is proposed for DB-CTC in this paper. The new scheme is based on an improved maximum a posteriori probability algorithm, where instead of storing all of the state metrics, only a part of these state metrics is stored in the state metrics cache (SMC), and the memory size of the SMC is thus reduced by 25%. Owing to a compare-select--recalculate processing (CSRP) module in the proposed decoding architecture, the unstored state …