16,537 results
Search Results
2. Effect of temperature on space charge characteristics of oil-paper insulation and its numerical simulation.
- Author
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Zhang, Jinfeng, Chen, Qingguo, Chi, Minghe, Tan, Peng, Sun, Wenxin, and Cao, Jinming
- Subjects
- *
SPACE charge , *TEMPERATURE effect , *COMPUTER simulation , *HEAVY oil - Abstract
In this study, the space charge in oil-impregnated thick pressboard and Kraft paper were measured by the pulsed electroacoustic (PEA) method from -20 to +60 °C. A bipolar charge transport model was used to simulate the transport processes of homocharge and heterocharge, and the acoustic attenuation process in the samples. The test results show that space charge accumulates in the thick pressboard and Kraft paper increases first and then decreases with temperature, and its maximum appears at 40°C, while little space charge accumulates at -20°C. The space charge near the lower electrode shrinks in the oil-impregnated thick pressboard at high temperature and the shrinkage is larger at 60°C. In the oil-impregnated Kraft paper, the accumulation and charge density of positive charge is different from negative charge. The ion transport process model simulates the charge shrinkage near the electrode, and disappears at the upper electrode after the acoustic attenuation simulation. The model established in this paper can well simulate the space charge distribution of oil-impregnated thick pressboard and Kraft paper under different temperatures. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
3. Simulation Study on the FDS Characteristics of Non-uniform Dampened Oil-paper Bushing
- Author
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Zhao Haoxiang, Hai-Bao Mu, Daning Zhang, Haotian Zhang, Yanhua Han, and Lu Zhang
- Subjects
010302 applied physics ,Materials science ,Moisture ,Computer simulation ,business.industry ,020208 electrical & electronic engineering ,02 engineering and technology ,Dielectric ,Structural engineering ,01 natural sciences ,law.invention ,Core (optical fiber) ,Capacitor ,Electric power system ,law ,Bushing ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Dielectric loss ,business - Abstract
Oil-paper insulation high-voltage bushings are one of the most important power equipment in substations, and their insulation status is critical to the safety and the stabilization of the power system operation. During the production and operation, the bushing may be dampened because of the insufficient drying and impregnation or the intrusion of external moisture, which leads to the deterioration of oil paper insulation and threatens the reliability of bushing. Due to the special insulation structure of the bushing capacitor core, the distribution of moisture inside the bushing is usually non-uniform, especially when the moisture is intruded from the external environment. In this paper, a numerical simulation model of dual-unit laminated oil-paper and 110kV capacitor bushing is established. Then the frequency domain dielectric spectrum (FDS) characteristics of oil-paper insulation with different non-uniform moisture distribution are obtained by simulation. Different types of non-uniform moisture distribution include: non-uniform moisture distribution in different directions of the bushing, and different degrees of non-uniform moisture distribution. When the non-uniform moisture distribution of bushing is along the axial direction, different degrees of non-uniformity of moisture distribution have little effect on the FDS results; when the non-uniform moisture distribution of bushing is along the radial direction, the $\text{tan}\delta-f$ curve shows a clear dielectric loss peak, the characteristics of which are closely related to the degree of non-uniformity of the moisture distribution. Partial damping at the outermost side of the bushing or the end screen are more common in practice, and the FDS results of these two different types of damped bushing show different characteristic. This paper carried out a comprehensive FDS simulation study of different types of non-uniform dampened oil-paper insulation, which is of great significance for the evaluation of the insulation status of the oil-paper bushing.
- Published
- 2020
4. Investigation on the Improvement of the Performance of Modified Savonius Rotor Based on Numerical Study Paper Title
- Author
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Wenlong Tian, Zhaoyong Mao, Guo Fen, and Baowei Song
- Subjects
Impeller ,Offset (computer science) ,Electricity generation ,Computer simulation ,Maximum power principle ,Control theory ,020209 energy ,B-spline ,0202 electrical engineering, electronic engineering, information engineering ,Torque ,02 engineering and technology ,Fixed point ,Mathematics - Abstract
Savonius rotor is a very popular vertical shaft power generation impeller, with the advantage of small starting torque and low cost. In order to improve the maximum power coefficient of the impeller, this paper presents a method using B spline optimization to get the best solution. The new design of the blades' shape is controlled by three variable points and two threefold fixed points. With the decrease of vertical height, the best power coefficient shows the trend of increasing first and then decreasing. With the increase of the horizontal offset, the optimal power coefficient shows a tendency of increasing first and then decreasing. By comparing all simulation data, the case H1 is the best blade curve. Its maximum power coefficient of 0.288 is 3.2% greater than the original blade.
- Published
- 2018
5. Interface charge behvaiors in the composite insulation of oil immersed paper
- Author
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Kai Wu and Chuanhui Cheng
- Subjects
010302 applied physics ,Materials science ,Computer simulation ,business.industry ,020209 energy ,Composite number ,Electrical engineering ,Mechanical engineering ,02 engineering and technology ,Acoustic wave ,01 natural sciences ,Space charge ,law.invention ,law ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Transformer ,business ,Surface states - Abstract
In the insulation of converter transformers for HVDC transmission, the effect of space charges on field distortion is an important factor. Multilayers of oil immersed papers and oil gaps that compose paper/paper and paper/oil interfaces are used in converter transformers. The interface charge behaviors may not follow traditional Maxwell-WagnarSillars polarization law. In this report, the measurement techniques and the phenomena of space charge behaviors at the paper/paper and paper/oil interfaces are summarized. It is indicated that surface states are necessary to be included in the numerical simulation on the charge and field distributions.
- Published
- 2016
6. An approach for economic assessment on oil-paper insulation diagnosis through accelerated aging experiments.
- Author
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Cao, Wen, He, Baosheng, Shen, Wei, Shi, Xuetao, Wu, Kai, Okamoto, Tatsuki, and Suzuoki, Yasuo
- Subjects
- *
ELECTRIC insulators & insulation , *ACCELERATED life testing , *THERMAL analysis , *STRENGTH of materials , *FAULT tolerance (Engineering) , *COMPUTER simulation - Abstract
In this paper the accelerated aging experiments of oil-paper insulation are carried out to simulate the oil-paper aging process under normal thermal aging process. On the basis of the results of accelerated aging experiments, how the deviation degree of aging status change under the same aging factors is studied, and a method to calculate the failure probability due to the loss of mechanical strength of the insulation is put forward. This paper presents an approach for economic assessment on insulation diagnosis through accelerated aging experiments. The foundation of this approach for economic assessment on insulation diagnosis is to establish condition simulation method of triple relationships between condition status, aging time and failure probability according to data from accelerated aging experiments. The conclusions are made that the economic and technical factors can affect the optimum life cycle cost of each maintenance strategy, which consequently affects the economic feasibility of condition-based maintenance strategies. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
7. Magic Paper: Sketch-Understanding Research.
- Author
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Davis, Randall
- Subjects
- *
PATTERN recognition systems , *TOUCH screen interfaces , *COMPUTER-aided design , *COMPUTER simulation , *FEATURE extraction , *COMPUTER science research , *TECHNOLOGICAL innovations - Abstract
The article reports on research into sketch-understanding systems for tablet personal computers (tablet PC). It discusses the work of the Sketch Understanding Group, of which the author is a member, at the Massachusetts Institute of Technology (MIT) on developing a "magic paper," or "intelligent paper," a paper-like surface that can convert sketches of physical systems into animated computer graphics. Sketch-understanding systems go beyond traditional computer-aided design (CAD) programs that produce diagrams, and beyond handwriting recognition systems.
- Published
- 2007
- Full Text
- View/download PDF
8. 2015 International Symposium on Computer Architecture Influential Paper Award.
- Author
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Albonesi, David H.
- Subjects
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COMPUTER architecture , *ENERGY consumption , *ELECTRONIC circuit design software , *COMPUTER simulation , *COMPUTER hardware description languages , *CONFERENCES & conventions - Abstract
This column discusses the 2015 ISCA Influential Paper Award, which recognized "Wattch: A Framework for Architectural-Level Power Analysis and Optimizations" by David Brooks, Vivek Tiwari, and Margaret Martonosi. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
9. A New Edge-based Intra-field Interpolation Method for Deinterlacing Using Locally Adaptive-thresholded Binary Image.
- Author
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Dong-Ho Lee
- Subjects
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NUMERICAL analysis , *PAPER , *COMPUTER simulation , *SIMULATION methods & models , *ELECTROMECHANICAL analogies , *COMPUTERS , *MATHEMATICAL models , *DEFECT correction methods (Numerical analysis) , *MATHEMATICAL analysis - Abstract
This paper proposes a new method to improve re performance of intra-field interpolation which is the mos~ important element of deinterlacing method. Traditional edge- based methods were poor at determining accurate edge iirection which decides interpolation performance. The 7roposed method decides the direction and slope of edge based on locally adaptive-thresholded binary image to mprove efficiency and accuracy, and it also increased the ~orizontal size of search window to 15 for better direction ietermination at gentle slope. Compared to traditional edge- based methods, interpolation based on binary image, which is ,`enerated using the proposed method, leads to great erformance improvement. With computer simulations for a ~`ariety of images, this paper shows the new approach is much ~etter than traditional methods.. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
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10. A Hands-Free Unit with Noise Reduction by Using Adaptive Beamformer.
- Author
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Kobayashi, Kazunori, Haneda, Yoichi, Furuya, Ken'ichi, and Kataoka, Akitoshi
- Subjects
- *
NOISE , *PAPER , *NUMERICAL analysis , *COMPUTER simulation , *SIMULATION methods & models , *ELECTROMECHANICAL analogies , *COMPUTERS , *MATHEMATICAL models , *SOUND - Abstract
This paper presents an implementation of an ~daptive beamformer in a hands-free unit. The proposec~ ~daptive beamformer suppresses stationary noise an~ nterference sound. The adaptive beamformer and acoustic `cho canceller were implemented in a compact hands-free mit with a low-cost DSP. Experimental results demonstrate he noise reduction performance of the hands-free unit'. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
11. Letter.
- Subjects
DIELECTRIC measurements ,DIELECTRICS ,LIQUID dielectrics ,LETTERS ,ELECTRIC fields - Abstract
Beginning with the June issue of the Transactions, papers will be separated into two categories; Part A — Dielectric Fundamentals and Part B — Dielectric Applications. Professor Huseyin Hiziroglu of Kettering University is the co-editor of Part A papers and Professor Giovanni Mazzanti of Bologna University is the co-editor of Part B papers. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
12. A Study on Overvoltages in Windfarm Caused by Direct Lightning Stroke.
- Author
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Sekioka, Shozo, Otoguro, Hitomi, and Funabashi, Toshihisa
- Subjects
WIND turbines ,ELECTRIC generators ,WIND power plants ,CABLES ,LIGHTNING ,COMPUTER simulation - Abstract
Wind turbine generators in a windfarm are connected by underground cables. Lightning sometimes strikes a nacelle or a blade. Lightning overvoltages due to a direct lightning strike to the system cause damages in the underground cable. Many parameters should be investigated to establish a rational lightning protection design for wind power generation system. Numerical simulation is a useful method to discuss the influence of the parameters on the lightning overvoltages. This paper uses an Electro-Magnetic Transients Program for the lightning surge analysis. This paper discusses the influence of grounding method of metallic sheath of the cable and grounding resistance on the lightning overvoltages for the direct lightning strike to the generation system. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
13. Fuzzy Neural-Network Friction Compensation-Based Singularity Avoidance Energy Swing-Up to Nonequilibrium Unstable Position Control of Pendubot.
- Author
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Xia, Deyin, Chai, Tianyou, and Wang, Liangyong
- Subjects
EQUILIBRIUM ,MACHINE theory ,ALGORITHMS (Physics) ,COMPUTER simulation ,ELECTRIC motors ,ELECTRIC drives ,ELECTRIC machinery - Abstract
This paper mainly researches the swing-up control of Pendubot. Comparing with the uppermost unstable equilibrium position, it is more difficult to make the Pendubot swing up to the unstable nonequilibrium position. In order to complete the control target, the energy-based controller incorporated with fuzzy neural network compensation (ECFNNC) is designed in this paper. In addition, numerical simulations and experimental results of the Pendubot actuated by a dc servo motor are given in this paper. By comparing the results with other algorithms, it is found that the ECFNNC proposed in this paper has better performance under the same conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
14. Message from the VR Paper Chairs and Guest Editors.
- Subjects
VIRTUAL reality ,COMPUTER simulation - Abstract
The papers in this special issue were presented at the 2016 IEEE Virtual Reality Conference (IEEE VR 2016) that was held March 19?23, 2016 in Greenville, South Carolina. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
15. Call for papers and special issues IEEE Transactions on Computational Social.
- Subjects
- *
COMPUTER simulation , *SOCIAL systems - Abstract
The article presents information on the topics such as modeling, simulation, and analysis of social systems covered by the journal IEEE Transactions on Computational Social Systems and the names of the websites where the papers can be submitted.
- Published
- 2015
- Full Text
- View/download PDF
16. Call for papers and special issues IEEE Transactions on Computational Social.
- Subjects
- *
COMPUTATIONAL sociology , *SOCIAL systems , *COMPUTER simulation , *SYSTEMS design , *MATHEMATICAL models - Abstract
Describes the above-named upcoming special issue or section. May include topics to be covered or calls for papers. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
17. Numerical Simulations and Experimental Study of Magneto-Acousto-Electrical Tomography With Plane Transducer.
- Author
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Li, Yuanyuan, Liu, Guoqiang, Xia, Hui, and Xia, Zhengwu
- Subjects
TRANSDUCERS ,MAGNETOACOUSTIC effects ,SEPARATION (Technology) ,ELECTRIC properties of solids ,COMPUTER simulation - Abstract
This paper presents new results on a novel coupled-physics modality called magneto-acousto-electrical tomography (MAET). With static magnetic field, a beam of ultrasound is applied to the sample to be imaged; the ultrasonic vibration can lead to the separation of the charges due to the Lorentz force and produces the current distributed in the object. In this paper, simulations were conducted on biological tissue model, and the electrical properties were reconstructed, which could reflect the state of physiological or pathological. We also conducted experiments to detect the voltage signal of microvolt level by the electrodes placed around the sample. The series of experiments were conducted on low-conductivity (0.2 S/m) animal gelatin phantom and real biological tissue, successively placed in a 260 mT magnetic field and sonicated with a plane ultrasonic transducer of central frequency 2.25 MHz. In this paper, we obtained axis resolution of 1 mm, much more significant improvement than the previous reports. More importantly, the experimental result does also demonstrate the feasibility of MAET to image the electrical properties of biological tissue. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
18. Guest Editorial: Network science.
- Author
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Basu, Prithwish, Gibbens, Richard, La Porta, Thomas, Lin, Ching-Yung, Swami, Ananthram, and Yoneki, Eiko
- Subjects
SOCIAL network theory ,NETWORK performance ,INFORMATION storage & retrieval systems ,LITERATURE reviews ,COMPUTER simulation - Abstract
A recent topic of research in the network science community is combined or composite networks ? these are two or more interacting networks that must be characterized jointly rather than individually. For example, a social network and a communication network sharing some nodes (corresponding to users) may be modeled together as a composite network. This may be useful since the aggregate performance of a composite network may often depend on how the individual networks influence each other. Information may travel faster or slower through composite networks depending on how they are coupled. The above vision was captured in the Call for Papers for this special issue in the IEEE Journal On Selected Areas In Communications, and it was published in June 2012. As a result of this solicitation, we received 62 submissions by the deadline of August 15, 2012. Papers were selected after two rigorous rounds of review. The first round of notifications were sent out on December 17, 2012 to the authors whose papers passed the first round of review. Revised versions of the papers were submitted on January 31, 2013. Finally, after a second round of review, the Guest Editorial board decided on March 12, 2013 to accept 16 high quality papers for publication in this competitive special issue. Papers appearing in this special issue belong to five broad themes, which are not necessarily mutually exclusive: (1) fundamental principles in network science, (2) information propagation models in networks, (3) bringing insights from other genres of networks, (4) economic and game theoretic models, and (5) application of network science principles to communications networking problems. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
19. Advancing Constrained Ranking and Selection With Regression in Partitioned Domains.
- Author
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Gao, Fei, Gao, Siyang, Xiao, Hui, and Shi, Zhongshun
- Subjects
RESOURCE allocation ,COMPUTER simulation ,CONSTRAINED optimization ,REGRESSION analysis ,CLOUD computing - Abstract
Ranking and selection (R&S) procedures are powerful tools to enhance the efficiency of simulation-based optimization. In this paper, we consider the R&S problem subject to stochastic constraints and seek to improve the selection efficiency by incorporating the information from across the domain into quadratic regression metamodels. To better fulfill the quadratic assumption of the regression metamodel used in this paper, we divide the solution space into adjacent partitions such that the underlying functions of both the objective and constraint measures in each partition are approximately quadratic with homogeneous noise. Using the large deviations theory, we characterize the asymptotically optimal allocation rule by maximizing the rate at which the probability of false selection tends to zero. Numerical experiments demonstrate that our approach dramatically improves the selection efficiency by 50%–90% on some typical selection examples compared with the existing approaches. Note to Practitioners—Simulation is widely used for designing and analyzing complex discrete-event systems such as manufacturing production systems, transportation systems, and supply chain operations. However, efficiency is still a significant concern when using simulation for stochastic optimization problems, especially in the presence of stochastic constraints. This paper was motivated by the problem of selecting the best feasible design (solution) from a finite set of alternatives given anobjective and stochastic constraints, where the performances of the objective and constraint measures can be estimated via simulation. Different from the existing approaches in the literature, in this paper, we propose a new R&S procedure using regression metamodels. Given a fixed amount of computing budget, our approach determines the asymptotic optimal number of simulation replications for each design. It can be shown through numerical experiments that the proposed approach can significantly improve the selection efficiency by more than 50% over the existing methods on some typical benchmark examples. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
20. Stabilization of Canonical Systems via Adaptive Chattering Free Sliding Modes With No Singularity Problems.
- Author
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Aghababa, Mohammad P.
- Subjects
SLIDING mode control ,MANIPULATORS (Machinery) ,COMPUTER simulation - Abstract
In the system and control community, the sliding mode control technology has been known as a tool which is able to handle system uncertainties and external disturbances. Simplicity in implementation and good stability performance are the other interesting features of the sliding modes. However, traditional sliding mode controllers exhibit two weaknesses, as follows: 1) generally, they have asymptotic stability in sliding mode dynamics which results in a slow speed system and 2) the so-called chattering phenomenon exists, which produces undesirable high frequency oscillations in the control signal. In this paper, the former problem is solved using a twofold terminal sliding manifold displaying desired transient and steady state behavior. The latter issue is responded to by a twofold sliding mode technology which leads to a continuous sliding control rule instead of a discontinuous switching control. The effects of uncertain terms as well as external perturbations with unknown bounds are fully compensated using updated parameters. The values of the updated parameters approach fixed values as the system trajectories converge to the equilibrium states. The analytical results of this paper are theoretically proved using the Lyapunov technique and the finite-time control strategy. Comparative computer simulations on a robotic manipulator confirm the fast convergence attribute and robust performance of the introduced adaptive robust nonsingular terminal sliding control algorithm. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
21. Call for papers and special issues IEEE Transactions on Computational Social.
- Subjects
- *
COMPUTER simulation , *COMPUTATIONAL statistics , *SOCIAL networks , *SOCIAL intelligence , *SIMULATION methods & models - Abstract
The article offers information on the publication of "IEEE Transactions on Computational Social System" and topics covered under the publication which include modeling, simulation and understanding of social system from computational perspectives. The article covered in the publication include social network dynamics, social intelligence and cognition, and computational behavior modeling.
- Published
- 2015
- Full Text
- View/download PDF
22. Parkinsonian Tremor as Unstable Feedback in a Physiologically Consistent Control Framework.
- Author
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Kelley CR and Kauffman JL
- Subjects
- Humans, Models, Neurological, Motor Cortex physiopathology, Thalamus physiopathology, Algorithms, Feedback, Physiological, Cerebellum physiopathology, Movement physiology, Tremor physiopathology, Tremor etiology, Basal Ganglia physiopathology, Parkinson Disease physiopathology, Parkinson Disease complications, Computer Simulation
- Abstract
Parkinson's disease (PD) is characterized by decreased dopamine in the basal ganglia that causes excessive tonic inhibition of the thalamus. This excessive inhibition seems to explain inhibitory motor symptoms in PD, but the source of tremor remains unclear. This paper investigates how neural inhibition may change the closed-loop characteristics of the human motor control system to determine how this established pathophysiology could produce tremor. The rate-coding model of neural signals suggests increased inhibition decreases signal amplitude, which could create a mismatch between the closed-loop dynamics and the internal models that overcome proprioceptive feedback delays. This paper aims to identify a candidate model structure with decreased-amplitude-induced tremor in PD that also agrees with previously recorded movements of healthy and cerebellar patients. The optimal feedback control theory of human motor control forms the basis of the model. Key additional elements include gating of undesired movements via the basal ganglia-thalamus-motor cortex circuit and the treatment of the efferent copy of the control input as a measurement in the state estimator. Simulations confirm the model's ability to capture tremor in PD and also demonstrate how disease progression could affect tremor and other motor symptoms, providing insight into the existence of tremor and non-tremor phenotypes. Altogether, the physiological underpinnings of the model structure and the agreement of model predictions with clinical observations provides support for the hypothesis that unstable feedback produces parkinsonian tremor. Consequently, these results also support the associated framework for the neuroanatomy of human motor control.
- Published
- 2024
- Full Text
- View/download PDF
23. Compact Quad-Mode Planar Phased Array With Wideband for 5G Mobile Terminals.
- Author
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Syrytsin, Igor, Zhang, Shuai, Pedersen, Gert Frolund, and Morris, Arthur S.
- Subjects
BROADBAND communication systems ,5G networks ,BANDWIDTHS ,PHASED array antennas ,COMPUTER simulation - Abstract
In this paper, a quad-mode endfire planar phased antenna array with wide scan angle and 1.2 mm clearance is proposed for 5G mobile terminals. The proposed antenna can obtain over 8 GHz of impedance bandwidth. In this paper, it is suggested to efficiently combine a multimode array element with different radiation patterns for each mode into a phased antenna array. In the array, similar and wide embedded radiation patterns are obtained for the all four modes. Furthermore, a coaxial to differential stripline transition is designed in this paper. The differential feeding structure is very compact and utilizes only MMPX connector and vias. The total scan pattern and coverage efficiency of the measured and simulated phased array antenna are calculated in the range from 25 to 33 GHz, and good agreement between measured and simulated results is observed. The mean coverage efficiency along the frequency range is very similar, but minor difference in variance of coverage efficiency is observed in the measurements. The coverage efficiency of around 50% for the threshold gain of 5 dBi is achieved in the chosen frequency range. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
24. Modeling and Performance Diagnostics of Composite Work Cells With Gantries.
- Author
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Ou, Xinyan, Chang, Qing, Zou, Jing, Arinez, Jorge, and Xiao, Guoxian
- Subjects
GANTRIES ,MATERIALS handling ,IMPACT (Mechanics) ,COMPUTER simulation ,IMAGE segmentation - Abstract
In this paper, the performance of a typical composite work cell structure that includes multiple machines and a material handling gantry is studied. A mathematic model is established to analyze the performance of such gantry systems. Due to the unique features of the gantry system, cycle time and waiting time of the gantry and machines are discussed and formulated based on two basic scenarios. To measure the impact of disruption events, permanent production loss is evaluated by using the sensor data collected from plant floors. Data-driven diagnostic methods are developed to identify the bottleneck machine and to evaluate permanent production loss attribution of each machine. The results provide a solid base to efficiently and effectively improve the performance of a composite work system. Performance diagnostics of gantry systems provides a theoretical and practical basis for production improvement. A gantry system for composite lay-up processes is used for numerical simulation case studies, by which the performance diagnostic methodologies and improvements are demonstrated. Note to Practitioners—Accurate performance diagnostics and effective improvement methods are critical to manufacturing operation and management. Most existing efforts are devoted to analyzing the performance of a whole production line rather than considering the complexity of each station/work cell in the line. This paper zooms into a composite work cell with a material handling gantry and focuses on the performance diagnostics of the lay-up station in a composite work center. The methods presented in this paper can be extended and applied to other manufacturing work cells comprising the similar gantry structure. We build a mathematical model to analyze the characteristics of the gantry system such as gantry cycle and waiting time. The evaluation of system production loss, which directly adopts sensor data from the factory floors, provides a quantitative tool for production engineers to monitor and control the system in real-time operation. In addition, the performance diagnostic methods based on production loss attribution and bottleneck identification are developed to guide the decision makers to improve the production system under different resource conditions. The methods are developed based on a work cell with only one gantry under a fixed gantry moving sequence. In the future research, we will extend the study to the systems with more gantries and more complex gantry moving policies. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
25. Experimental and Numerical Study of the Behavior of a Multilayer for Active Magnetic Refrigerator Based on La-Fe-Co-Si.
- Author
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Chiba, Younes
- Subjects
MAGNETIC cooling ,COMPUTER simulation ,MAGNETOCALORIC effects ,EXERGY ,MAGNETIC materials - Abstract
This paper is dedicated to study the experimental validation of a numerical model based on La-Fe-Co-Si layered operating near room temperature. For the purpose of this paper, a numerical simulation based on the transient energy equations is proposed for modeling the heat exchange between the multilayer material and the carrier fluid in the regenerator bed with an applied magnetic field of 1.5 T. The main findings of the simulation show a comparison between the numerical model and experimental setup including the magnetocaloric effect of La-Fe-Co-Si, pressure drop, and exergy and exergetic efficiency. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
26. CORDIC-Based Architecture for Computing Nth Root and Its Implementation.
- Author
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Luo, Yuanyong, Wang, Yuxuan, Sun, Huaqing, Zha, Yi, Wang, Zhongfeng, and Pan, Hongbing
- Subjects
DIGITAL computer simulation ,ALGORITHMS ,HARDWARE ,COMPUTER simulation ,DIGITAL signal processing - Abstract
This paper presents a COordinate Rotation Digital Computer (CORDIC)-based architecture for the computation of Nth root and proves its feasibility by hardware implementation. The proposed architecture performs the task of Nth root simply by shift-add operations and enables easy tradeoff between the speed (or precision) and the area. Technically, we divide the Nth root computation into three different subtasks, and map them onto three different classes of the CORDIC accordingly. To overcome the drawback of narrow convergence range of the CORDIC algorithm, we adopt several innovative methods to yield a much improved convergence range. Subsequently, in terms of convergence range and precision, a flexible architecture is developed. The architecture is validated using MATLAB with extensive vector matching. Finally, using a pipelined structure with fixed-point input data, we implement the example circuits of the proposed architecture with radicand ranging from zero to one million, and achieve an average mean of approximately 10−7 for the relative error. The design is modeled using Verilog HDL and synthesized under the TSMC 40-nm CMOS technology. The report shows a maximum frequency of 2.083 GHz with $197421.00~{\mu }\text{m}^{2}$ area. The area decreases to $169689.98~{\mu }\text{m}^{2}$ when the frequency lowers to 1.00 GHz. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
27. An MILP Optimization Problem for Sizing Port Rail Networks and Planning Shunting Operations in Container Terminals.
- Author
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Caballini, Claudia, Fioribello, Simone, Sacone, Simona, and Siri, Silvia
- Subjects
RAILROAD management ,LINEAR programming ,LOGISTICS management ,LOGISTICS software ,COMPUTER simulation - Abstract
This paper proposes an optimization approach for sizing port rail networks and planning railway shunting operations by adopting a discrete-time model of the overall system. First, a mixed-integer linear mathematical programming problem is defined in order to optimize shunting operations to be performed on the considered network by satisfying certain arrivals and departures of import and export flows. Moreover, the proposed procedure can be used to evaluate the capacity of a port rail network, in terms of maximum number of trains that can be managed over a certain time horizon, and to carry out what-if analyses aimed at testing different scenarios. The effectiveness of the proposed approach is shown by applying the optimization problem to a real case study referred to the port rail network of La Spezia Container Terminal located in Northern Italy. A computational analysis realized by varying the dimension and complexity of the problem instances is also reported in this paper to discuss the computational performance of the proposed model. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
28. Efficient Computation of Feedback-Based Control System Equations for Electromagnetic Transients.
- Author
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Mugombozi, C. F., Mahseredjian, J., and Saad, O.
- Subjects
RELAY control systems ,ELECTRIC relays ,ELECTROMAGNETISM ,ELECTRIC transients ,COMPUTER simulation ,JACOBIAN matrices ,NEWTON-Raphson method - Abstract
This paper contributes to the accurate and efficient computation of control system equations in electromagnetic-transient simulation tools. The proposed approach is based on the formulation of a reduced rank Jacobian matrix in a fully iterative Newton method. In addition, this paper compares the accuracy and efficiency for the proposed method's variants, including a hybrid approach with a fixed-point solution. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
29. Numerical Simulations of Dust Dynamics Around Small Asteroids.
- Author
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Yu, Wiliam, Han, Daoru, and Wang, Joseph
- Subjects
ASTEROIDS ,DUST ,RADIATION pressure ,COMPUTER simulation ,SOLAR radiation ,GRAVITATION ,SURFACE charges - Abstract
This paper presents a simulation study of the dynamics of dust grains around a small asteroid. Plasma-asteroid interactions and asteroid charging are obtained from fully kinetic particle-in-cell simulations. Dust transport simulation takes into account the electrostatic force, solar radiation pressure, and the gravitational force. Both the result derived from laboratory measurements of regolith surface charging and the single dust charging model are considered for dust charging. For the small asteroid considered in this paper, we find that dust transport is mostly determined by the competition between the electrostatic force and the solar pressure and dust distribution is sensitive to both dust charging and dust grain size. For dust grains in the tens of micrometer size range, the solar radiation pressure dominates dust transport at small dust charge-to-mass ratio, whereas the electrostatic force dictates dust transport at large dust charge-to-mass ratio. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
30. Numerical Simulations of Temperature Stability Limits in High-Voltage Direct Current Cable Insulations.
- Author
-
Jorgens, Christoph, Kasolis, Fotios, and Clemens, Markus
- Subjects
DIRECT currents ,ELECTRIC conductivity ,COMPUTER simulation ,FINITE difference method ,ELECTRIC fields ,ELECTRIC conduits - Abstract
The high-voltage direct current cable insulations consist of polymeric or mass-impregnated paper materials. Their electric conductivities depend on the electric field and the temperature. Losses inside the conductor and in the insulation increase the temperature, resulting in increased losses and in a possible thermal runaway process. In this paper, coupled electro-thermal field simulations including nonlinear field-dependent conductivities are carried out. With a varying applied voltage and a current in the conductor, the condition for a thermal breakdown is computed. To compute the losses inside a 1-D insulation model, the finite-difference method is used. The simulation results conform well to experimental measurements. An approximation of the condition for a thermal breakdown is developed and show equal results in comparison to the coupled electro-thermal field simulations. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
31. Distortion Characterization of Exponential Signal Reconstructed by Low-Chirp Signal.
- Author
-
Carni, Domenico Luca, Grimaldi, Domenico, and Lamonaca, Francesco
- Subjects
SIGNAL processing ,COMPUTER simulation ,MATHEMATICAL models ,EXPONENTIAL functions ,ELECTRIC potential - Abstract
This paper is an extension of the procedure pointed out to evaluate the distortion of the exponential signal, modeled as multiexponential signal with different amplitudes and time constants. This procedure evaluates the distortion by applying the Prony-like method to the signal reconstructed by zero-crossing time evaluated on the difference between the exponential original signal and the reference sinusoidal one. The extension proposed in this paper concerns with the use of the low-chirp signal as reference instead of the sinusoidal signal. The low-chirp signal permits to increase the number of the zero-crossing time in the section of exponential signal with the higher slope and decreasing in the section with the lower slope. This setting permits to estimate the distortion of the exponential signal with higher accuracy and precision. The parameters’ amplitude, phase, and start frequency of the reference low-chirp signal are used to reconstruct the exponential signal in the zero-crossing time in order to overcome the problem of the high-resolution sampling. Their estimation is carried out by the time-varying sine-fitting algorithm that processes the resulting signal that is the difference between the exponential original signal and the low-chirp signal. Advantages of the proposed extended procedure regard the direct estimation of the reference low-chirp signal parameters from the resulting signal over-sampled at low resolution, and the use of only one input acquisition channel that permits to overcome the synchronization problem between the reference and the resulting signal. The numerical and experimental tests validate the extended procedure. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
32. Experimental Investigation of Drawing Vacuum Arc Under Different TMF Contacts in Vacuum Interrupter.
- Author
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Shi, Weixin, Wang, Lijun, Lin, Renjie, Wang, Yuan, Ma, Jinwei, and Jia, Shenli
- Subjects
VACUUM circuit breakers ,VACUUM arcs ,COMPUTER simulation ,MAGNETIC fields ,VACUUM chambers - Abstract
Vacuum interrupter is widely used in the medium-voltage power system. Controlling the arc by the magnetic field is an effective method to improve the breaking capacity. The transverse magnetic field (TMF) forces the constricted arc to rotate to reduce local overheating. In this paper, three kinds of TMF contacts, which are Swastika-type contact, cup-shaped contact, and double-TMF contact that combines Swastika-type and cup-shaped contacts coaxially, are investigated in a demountable vacuum chamber with a high-speed camera. The arc voltage and current are also recorded. The experiments were conducted with circuit currents from 5 to 20 kA (root mean square) with a frequency of 50 Hz. There are four current levels in the experiment, which are 5, 10, 15, and 20 kA, and at least three tests are taken for each current level. The results showed that under low current (I = 10 kA), the arc of the three TMF contacts did not rotate. Under high current (I = 20 kA), it was observed that the arc of Swastika-type and double-TMF contacts rotated in the gap. The arc speed of double-TMF contacts is higher than that of Swastika-type contacts. The cup-shaped contacts have the highest arc voltage and noise among the three TMF contacts. The Swastika-type contacts were eroded most seriously. The simulation results show the force distribution of the arc on different locations. The resultant force makes the arc rotate counterclockwise. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
33. Dual-Polarized Faster-Than-Nyquist Transmission Using Higher Order Modulation Schemes.
- Author
-
Jana, Mrinmoy, Lampe, Lutz, and Mitra, Jeebak
- Subjects
DATA transmission systems ,POLARIZATION spectroscopy ,CODING theory ,COMPUTER simulation ,MICROWAVE communication systems - Abstract
Faster-than-Nyquist (FTN) transmission employing antenna polarization multiplexing and higher order modulation (HoM) schemes can significantly increase the spectral efficiency (SE) of the existing wireless backhaul links. However, the benefits of each of these SE enhancement techniques come with a price. While FTN introduces inter-symbol interference, a dual-polarized (DP) transmission suffers from cross-polarization interference (XPI), and HoM makes a communication system vulnerable to phase-noise (PN) distortions. In this paper, we investigate, for the first time, a DP-FTN HoM transmission system. We propose a XPI cancellation and PN mitigation structure, coupled with adaptive decision-feedback equalization or linear precoding, to jointly mitigate interference and accomplish carrier-phase tracking. The DP systems combined with the FTN signaling presented in this paper offer more than 150% increase in SE compared with a single-polarized Nyquist transmission. The effectiveness of the proposed algorithms is demonstrated through computer simulations of a coded DP-FTN microwave communication system in the presence of PN. Numerical results suggest that with the proposed interference cancellation methods, a DP-FTN transmission can yield a 3–5.5-dB performance improvement over an equivalent DP-Nyquist system that employs a higher modulation order to achieve the same data rate. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
34. Decentralized Optimal Control of Distributed Interdependent Automata With Priority Structure.
- Author
-
Stursberg, Olaf and Hillmann, Christian
- Subjects
DISCRETE systems ,COMPUTER simulation ,PROCESS control systems ,SUPERVISORY control systems ,PROCESS optimization - Abstract
For distributed discrete-event systems (DESs), which are specified by a set of coupled automata, the centralized synthesis for a composed plant model is often undesired due to a high computational effort and the need to subsequently split the result into local controllers. This paper proposes modeling and synthesis procedures to obtain optimal decentralized controllers in state-feedback form for distributed DES. In particular, this paper addresses the DES with priority structures, in which subsystems with high priorities are supplied with the output of subsystems with lower priority. If the subsystem dependencies have linear or treelike structures, the synthesis of the subsystem controllers can be accomplished separately. Any local controller is computed by algebraic computations, it communicates with controllers of adjacent subsystems, and it aims at transferring the corresponding subsystem into goal states with a minimal sum of transfer costs. As is shown for an example, the computational effort can be significantly reduced compared with the synthesis of centralized controllers following the composition of all subsystem models. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
35. Design and Validation of Polarity-Changeable Magnetizer for Encoding Patterns on Ring-Like Rotary Encoders.
- Author
-
Liu, Yu-Chen, Hsiao, Heng-Sheng, and Chang, Jen-Yuan James
- Subjects
COMPUTER simulation ,MAGNETIC flux density ,MAGNETIZATION transfer ,CALIBRATION ,POLARITY (Physics) - Abstract
Through numerical simulations and calibrated experiments, the aim of the work presented in this paper is placed on the development of a polarity changeable magnetizing platform for a rotary magnetic encoder using a permanent magnet and thin silicon steel plate. Parameter studies are conducted via finite-element analyses to obtain optimized geometric design parameters for the magnetizer, leading to desirable magnetic flux density and effective magnetized patterns on the magnetic media. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
36. Performance Evaluation of Leader–Follower-Based Mobile Molecular Communication Networks for Target Detection Applications.
- Author
-
Nakano, Tadashi, Okaie, Yutaka, Kobayashi, Shouhei, Koujin, Takako, Chan, Chen-Hao, Hsu, Yu-Hsiang, Obuchi, Takuya, Hara, Takahiro, Hiraoka, Yasushi, and Haraguchi, Tokuko
- Subjects
NANONETWORKS ,TARGETED drug delivery ,COMPUTER simulation ,MAGNETIC particles ,ACYL-homoserine lactones - Abstract
This paper proposes a leader–follower-based model of mobile molecular communication networks for target detection applications. The proposed model divides the application functionalities of molecular communication networks into two types of mobile bio-nanomachine: leader and follower bio-nanomachines. Leader bio-nanomachines distribute in the environment to detect a target and create an attractant gradient around the target. Follower bio-nanomachines move according to the attractant gradient established by leader bio-nanomachines; they approach the target and perform necessary functionalities, such as releasing drug molecules. This paper develops mathematical expressions for the proposed model, describes wet laboratory experiments designed to estimate model parameters, and performs biologically realistic computer simulation experiments to evaluate the performance of the proposed model. The main contributions of this paper are to demonstrate the functional division of molecular communication networks, which will facilitate the design and development of molecular communication networks. Furthermore, insight into the application-level performance of molecular communication networks will be provided based on the proposed model. [ABSTRACT FROM PUBLISHER]
- Published
- 2017
- Full Text
- View/download PDF
37. Guest Editorial Special Issue on GaN Electronic Devices.
- Author
-
Ghione, Giovanni, Chen, Kevin J., Egawa, Takashi, Meneghesso, Gaudenzio, Palacios, Tomas, and Quay, Ruediger
- Subjects
ELECTRONICS ,COMPUTER simulation ,SEMICONDUCTOR characterization ,DIGITAL Object Identifiers ,ELECTRONIC amplifiers ,ELECTRIC resistors - Abstract
Due to the rapid advances taking place in the development and application of GaN electronics, there is an immediate need to take cognizance of the recent technological improvements and bring the potential and opportunities that exist in the area to a wider device community. The primary goal of this special issue is, therefore, to put together works in different aspects, including modeling, design, technology, characterization and applications so that this special issue will not only be of great archival value but also attract new researchers into this area for Digital Object Identifier 10.1109/TED.2013.2278653 further accelerating the application of III-N devices in building reliable, cheaper, and high-performance electronic systems. The papers collected in this special issue have been grouped into six topics. They are: 1) Fabrication and characterization of GaN-based devices. 2) High power GaN HEMTs for power switching applications. 3) High speed GaN HEMTs for RF applications. 4) Reliability and parasitic issues in GaN HEMTs. 5) Simulation-based development of GaN HEMTs devices. 6) GaN-based low noise amplifiers and gate drive circuits. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
38. Strapped Magnetron Performance Affected by Dielectric Material Filling.
- Author
-
Vyas, Sandeep Kumar, Maurya, Shivendra, Verma, Rajendra Kumar, and Singh, Vindhyavasini Prasad
- Subjects
DIELECTRIC materials ,MAGNETRONS ,COMPUTER simulation ,RESONATORS ,ELECTROMAGNETISM - Abstract
This paper describes the output performance of a strapped vane type 2.450 ± 0.030-GHz magnetron in the presence of a dielectric material. A 3-D particle in cell software computer simulation technology has been used for this study. The side resonators (cavities) of the magnetron are partially filled with a low-loss dielectric material ( \varepsilon r=11.7 and tan \delta =3.5\times 10^-6 ). The efficiency and output power of the magnetron have been increased by 2% and 10%, respectively, by dielectric material filling. It has been found that oscillation start-up time of magnetron is not directly affected by dielectric material filling as described in previous research papers. In addition, it has also been found that magnetron output performance remains almost the same for the lossless and the low-loss dielectric material. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
39. Enhanced Energy Management System With Corrective Transmission Switching Strategy—Part I: Methodology.
- Author
-
Li, Xingpeng and Hedman, Kory W.
- Subjects
CHARITIES ,COST control ,COMPUTER simulation ,RELIABILITY in engineering ,SUCCESSIVE approximation analog-to-digital converters - Abstract
The flexibility in transmission networks is not fully utilized in existing energy management systems (EMSs). Corrective transmission switching (CTS) is proposed in this two-part paper to enable EMS to take advantage of the flexibility in transmission systems in a practical way. This paper proposes the following two EMS procedures: first, Procedure-A connects real-time security-constrained economic dispatch (RT SCED) with real-time contingency analysis (RTCA), which is consistent with industrial practice; and second, Procedure-B, an enhanced version of Procedure-A, includes CTS in EMS with the proposed concept of branch pseudo limit used in RT SCED. Part-I of this paper presents the methodology, whereas Part-II includes detailed results analysis. It is demonstrated that Procedure-A can effectively eliminate the base case overloads and the potential post-contingency overloads identified by RTCA, and Procedure-B can achieve significant congestion cost reduction with consideration of CTS in RT SCED. Numerical simulations also illustrate that integrating CTS into RT SCED would improve social welfare. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
40. Feedback Stabilization of Switched Linear Systems: A Quantization and Triggering Joint Event-Triggered Mechanism.
- Author
-
Wang, Xiaomei and Zhao, Jun
- Subjects
LINEAR systems ,LYAPUNOV functions ,SYMMETRIC matrices ,COMPUTER simulation - Abstract
This paper adopts a quantization-dependent Lyapunov function to study the output feedback stabilization problem of a switched system subject to output event-triggered sampling and quantization. First, a new event-triggered mechanism related to quantization parameters is proposed, which can obtain a trade-off between the event-triggered frequency and quantization density on the premise of ensuring asymptotic stability of the switched system. Moreover, sufficient conditions are obtained to ensure asymptotic stability of the switched system by a quantization-dependent Lyapunov function. Lastly, through a numerical simulation and PWM-driven boost converter system, we demonstrate the availability of the proposed quantization-dependent Lyapunov function and event-triggered mechanism methods based on quantization parameters, respectively. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
41. A Basic Signal Analysis Approach for Magnetic Flux Leakage Response.
- Author
-
Huang, Song Ling, Peng, Lisha, Wang, Shen, and Zhao, Wei
- Subjects
MAGNETIC flux leakage ,COMPUTER simulation ,POINT defects ,FINITE element method ,SIGNAL processing - Abstract
Magnetic flux leakage (MFL) response predicting is important for defect estimation. This paper first proposes a concept of basic signal by discovering the combination property of the MFL response. The basic signal can be used to predict the MFL response conveniently by a basic signal combination method (BSCM), which is also innovatively put forward in this paper. In this method, the basic signal is calculated in advance, and the MFL response can be calculated by several transformation and combination operations. Both the simulation and experimental results demonstrate the feasibility of BSCM. Compared with other traditional methods (magnetic dipole method and finite-element method), BSCM shows a good performance on both the computational speed and accuracy. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
42. Minimizing Expected Cycle Time of Stochastic Customer Orders Through Bounded Multi-Fidelity Simulations.
- Author
-
Zhao, Yaping, Xu, Xiaoyun, and Li, Haidong
- Subjects
STOCHASTIC models ,MATHEMATICAL optimization ,SIMULATION methods & models ,COMPUTER simulation ,SYNCHRONIZATION - Abstract
This paper considers the scheduling of stochastic customer orders to minimize expected cycle time. Customer orders dynamically arrive at a machine station, and each order consists of multiple product types. Random workloads are required by each product type, and the workloads are assigned to a set of unrelated parallel machines in the station to be processed. The objective is to obtain the minimal long-run expected order cycle time through proper workload assignments. In view of the difficulty in evaluating the objective function, this paper models the targeted problem as a simulation optimization problem and proposes to solve it under the multifidelity model framework. To improve the efficiency in evaluating candidate solutions, a low-fidelity model is constructed to select solutions with better performances for high-fidelity simulations. The effectiveness of this low-fidelity model is demonstrated through a series of theoretical evidences. A simulation optimization algorithm, named Bound-Multi-fidelity Optimization with Ordinal Transformation and Optimal Sampling Bound-(MO2TOS), is developed by taking advantage of the properties of the low-fidelity model. Numerical experiments are conducted to evaluate the performance of the proposed algorithm against three other well-known simulation optimization algorithms in the literature. Results indicate that the Bound-MO2TOS outperforms all the other tested algorithms, and its performance is robust against changes in problem scale. Note to Practitioners—Customer order scheduling models have wide applications in industries where every single order may contain multiple product types and the entire order requires one shipment delivery. In many applications, such as pigments dyes manufacturing, auto repair, and grocery, consideration of customer orders rather than individual jobs is often preferred. Given the stochastic nature and the synchronization constraints of the problem, a multifidelity simulation algorithm named Bound-Multi-fidelity Optimization with Ordinal Transformation and Optimal Sampling Bound-(MO2TOS) is proposed. Experimental results suggest that the proposed algorithm outperforms three other popular simulation optimization algorithms under a variety of scenarios. It is admitted that further improvement can be made in refining the computation resource distribution process of Bound-MO2TOS. In the future research, such an improvement will be more thoroughly elaborated so that practitioners can utilize it to coordinate their productions better. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
43. Distributed Estimation and Control for Leader-Following Formations of Nonholonomic Mobile Robots.
- Author
-
Miao, Zhiqiang, Liu, Yun-Hui, Wang, Yaonan, Yi, Guo, and Fierro, Rafael
- Subjects
MOBILE robots ,NONHOLONOMIC dynamical systems ,ESTIMATION theory ,COMMAND & control systems ,COMPUTER simulation - Abstract
The problem of the leader-following formation control of nonholonomic mobile robots is addressed in this paper. A distributed formation control strategy using explicitly the coordination errors among robots is proposed without assuming that each follower robot knows the full state of the leader. First, a distributed estimation law is proposed for each follower robot to estimate the states, including the position, orientation, and linear velocity of the leader. The distributed formation control law is then designed based on the estimated states of the leader, and the neighborhood formation tracking error. Under some mild assumptions on the interaction graph among the leader and the follower robots, and the velocity of the leader, asymptotic convergence of formation tracking errors to zero can be achieved. Finally, some numerical simulations and experiments on a group of nonholonomic mobile robots are presented to demonstrate the effectiveness of the proposed strategy. Note to Practitioners—The motivation of this paper is to investigate a practical control strategy for the leader-following formation of multiple autonomous mobile robots subjected to nonholonomic constraints. In most of the existing leader-following formation control schemes for nonholonomic mobile robots, having access to the full state of the leader is a requirement. However, due to limitations in communication bandwidth and range, it is reasonable to assume that the information of the leader is available only to a subset of followers. Hence, this paper suggests a new distributed leader-following formation control strategy based on the distributed estimation of the leader’s states. Moreover, the coordination error between a pair of interacting robots is explicitly used in the control design to weaken the dependence on the estimated state of the leader, and enhance the decentralized nature of the proposed control scheme. The stability and convergence of the system are analyzed mathematically and the experiment using unicycles provides promising results. In ongoing research, we are addressing the issues of collision avoidance and communication delays to provide more realistic setup for the industrial applications of multivehicle systems. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
44. Exact Timing Analysis for Asynchronous Systems.
- Author
-
Hua, Wenmian and Manohar, Rajit
- Subjects
INTEGRATED circuits ,COMPUTER simulation ,DELAY lines ,DISCRETE systems ,SYNCHRONIZATION - Abstract
Analyzing the timing properties of asynchronous systems is essential for characterizing their performance and power. Previous work on timing showed that such systems under and-causality and fixed delay exhibit periodicity properties. We give a different graph-based rigorous proof of the exact timing behavior of more general classes of such systems, and conclude their exact periodicity property, where each of the signal transition will occur with the same period after finite occurrences. We established our results under weaker assumption about system connectivity/topology, and this paper provides the theoretical foundation, for the exact periodicity property to be applied and exploited in circuits containing a combination of synchronous and asynchronous components. We provide simulation-based results for several typical asynchronous circuit topologies to quantify this time period in practical circuits. We also provide an extension of our analysis and methods to the case of bounded delay systems. A key result that is a consequence of our analysis is that asynchronous circuits can be integrated with synchronous logic via a metastability-free interface, thereby eliminating the high-overhead synchronizers when an asynchronous circuit is fully surrounded by synchronous logic. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
- Full Text
- View/download PDF
45. Evaluation of Preventive Maintenance Segregation: A Multi Factorial Study.
- Author
-
Kalir, Adar A., Rozen, Kosta, and Morrison, James R.
- Subjects
MAINTENANCE ,METALLURGICAL segregation ,SEMICONDUCTOR manufacturing ,COMPUTER simulation ,FACTOR analysis - Abstract
Recently, several papers on preventive maintenance (PM) have shown that segregation of PM’s can be beneficial when it comes to improving factory performance. However, these were limited to either cases of equal PM segregation and/or without consideration of other factors and operating conditions such as incurred setup or the number of tools in the toolset. In this paper, we extend previous work in this area in two major respects. First, we consider the more realistic case of PM segregation into equal or unequal portions and second, we evaluate the impact of PM segregation under various operating conditions via simulation. Our simulation experiments provide insight and guidelines for practitioners in planning the PM activity such that the overall performance is improved. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
46. Upper and Lower Bounds for the Maximum Number of Frequencies That Can Be Generated by a Class of Fractional Oscillators.
- Author
-
Tavazoei, Mohammad Saleh
- Subjects
NONLINEAR oscillators ,INTEGRATORS ,COMPUTER simulation ,OSCILLATIONS ,HARMONIC analysis (Mathematics) ,HEURISTIC algorithms - Abstract
This paper deals with investigating the maximum number of frequencies generated by an oscillator in the case that a half number of integrators in the conventional dynamic structure of this oscillator are replaced by fractional integrators with an identical order. First, an upper bound for the maximum number of frequencies, which can exist in a steady state response of the oscillator, with respect to the number of integrators, is obtained. Then, on the basis of the recent advances in the field of determinant-based representations of bivariate polynomials, a lower bound is found for the maximum number of sinusoidal components in the steady state oscillations generated by the oscillator. A systematic algorithm is also introduced to find a dynamic structure and its dynamic matrices for realization of an oscillator, such that the number of distinct frequencies in its steady state oscillations is equal to the obtained lower bound. Numerical simulation results are presented to validate the introduced algorithm. Moreover, an idea for improving the lower bound is proposed. Finally, the paper is closed by describing some related open problems that invite future research works. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
47. Understanding Phase Error and Jitter: Definitions, Implications, Simulations, and Measurement.
- Author
-
Galton, Ian and Weltin-Wu, Colin
- Subjects
PHASE noise ,COMPUTER simulation ,ERROR analysis in mathematics - Abstract
Precision oscillators are ubiquitous in modern electronic systems, and their accuracy often limits the performance of such systems. Hence, a deep understanding of how oscillator performance is quantified, simulated, and measured, and how it affects the system performance is essential for designers. Unfortunately, the necessary information is spread thinly across the published literature and textbooks with widely varying notations and some critical disconnects. This paper addresses this problem by presenting a comprehensive one-stop explanation of how oscillator error is quantified, simulated, and measured in practice, and the effects of oscillator error in typical oscillator applications. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
48. Method for Assessing the Risk of Subsynchronous Oscillations in DFIG-Based Wind Parks.
- Author
-
Arguello, Andres, Torquato, Ricardo, and Freitas, Walmir
- Subjects
ELECTRIC transients ,ELECTRIC lines ,COMPUTER simulation ,ENGINEERS ,OSCILLATIONS - Abstract
The risk of unstable subsynchronous oscillations (SSO) in DFIG-based wind parks radially connected to transmission lines with series capacitive compensation is typically assessed with numerous electromagnetic transient (EMT) simulations, which is a time-consuming process. However, not all operating scenarios present risk of SSO and require such a detailed investigation. This paper proposes two charts based on impedance equivalents of wind generators obtained through frequency scans to quickly map which combinations of parameters can create unstable SSOs and which combinations are risk-free. With the information, engineers can immediately filter out scenarios with no risk of instability and conduct detailed studies on fewer scenarios that are truly critical. These charts can be obtained with simple equations that use only information readily available in practice to engineers, without the need to run any computer simulation. The charts also reveal the key operating conditions that can increase the risk of an unstable SSO and provide real-time quantitative insights into how close a wind park is to an instability. Application examples are provided to illustrate how this approach can help engineers speed up studies to identify the risk of SSO. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
49. On the Convergence of Orthogonal/Vector AMP: Long-Memory Message-Passing Strategy.
- Author
-
Takeuchi, Keigo
- Subjects
SIGNAL reconstruction ,COMPRESSED sensing ,SPARSE matrices ,ORTHOGONAL matching pursuit ,HEURISTIC algorithms ,COMPUTER simulation ,MESSAGE passing (Computer science) - Abstract
Orthogonal/vector approximate message-passing (AMP) is a powerful message-passing (MP) algorithm for signal reconstruction in compressed sensing. This paper proves the convergence of Bayes-optimal orthogonal/vector AMP in the large system limit. The proof strategy is based on a novel long-memory (LM) MP approach: A first step is a construction of LM-MP that is guaranteed to converge systematically. A second step is a large-system analysis of LM-MP via an existing framework of state evolution. A third step is to prove the convergence of state evolution recursions for Bayes-optimal LM-MP via a new statistical interpretation of existing LM damping. The last is an exact reduction of the state evolution recursions for Bayes-optimal LM-MP to those for Bayes-optimal orthogonal/vector AMP. The convergence of the state evolution recursions for Bayes-optimal LM-MP implies that for Bayes-optimal orthogonal/vector AMP. Numerical simulations are presented to show the verification of state evolution results for damped orthogonal/vector AMP and a negative aspect of LM-MP in finite-sized systems. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
50. CAWSAC: Cost-Aware Workload Scheduling and Admission Control for Distributed Cloud Data Centers.
- Author
-
Yuan, Haitao, Bi, Jing, Tan, Wei, and Li, Bo Hu
- Subjects
CLOUD computing ,DISTRIBUTED databases ,SERVER farms (Computer network management) ,PRODUCTION scheduling ,COMPUTER simulation - Abstract
Multiple heterogeneous applications concurrently run in distributed cloud data centers (CDCs) for better performance and lower cost. There is a highly challenging problem of how to minimize the total cost of a CDCs provider in a market where the bandwidth and energy cost show geographical diversity. To solve the problem, this paper first proposes a revenue-based workload admission control method to judiciously admit requests by considering factors including priority, revenue and the expected response time. Then, this paper presents a cost-aware workload scheduling method to jointly optimize the number of active servers in each CDC, and the selection of Internet service providers for the CDCs provider. Finally, trace-driven simulation results demonstrate that the proposed methods can greatly reduce the total cost and increase the throughput of the CDCs provider in comparison to existing methods. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
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