• Title/Summary/Keyword: Optimum Algorithm

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Shape Optimization of Cavitator for a Supercavitating Projectile Underwater (초공동(超空洞) 하의 수중 주행체 캐비데이터 형상최적설계)

  • Grandhli Ramana V.;Choi JooHo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.10
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    • pp.1566-1573
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    • 2004
  • When a projectile travels at high speed underwater, supercavitating flow arises, in which a huge cavity is generated behind the projectile so that only the nose, i.e., the cavitator, of the projectile is wetted, while the rest of it should be surrounded by the cavity. In that case, the projectile can achieve very high speed due to the reduced drag. Furthermore if the nose of the body is shaped properly, the attendant pressure drag can be maintained at a very low value, so that the overall drag is also reduced dramatically. In this study, shape optimization technique is employed to determine the optimum cavitator shape for minimum drag, given certain operating conditions. Shape optimization technique is also used to solve the potential flow problem fur any given cavitator, which is a free boundary value problem having the cavity shape as unknown a priori. Analytical sensitivities are derived for various shape parameters in order to implement a gradient-based optimization algorithm. Simultaneous optimization technique is proposed for efficient cavitator shape optimization, in which the cavity and cavitator shape are determined in a single optimization routine.

An Improved Particle Swarm Optimization Adopting Chaotic Sequences for Nonconvex Economic Dispatch Problems (개선된 PSO 기법을 적용한 전력계통의 경제급전)

  • Jeong, Yun-Won;Park, Jong-Bae;Cho, Ki-Seon;Kim, Hyeong-Jung;Shin, Joong-Rin
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.6
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    • pp.1023-1030
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    • 2007
  • This paper presents a new and efficient approach for solving the economic dispatch (ED) problems with nonconvex cost functions using particle swarm optimization (PSO). Although the PSO is easy to implement and has been empirically shown to perform well on many optimization problems, it may easily get trapped in a local optimum when solving problems with multiple local optima and heavily constrained. This paper proposes an improved PSO, which combines the conventional PSO with chaotic sequences (CPSO). The chaotic sequences combined with the linearly decreasing inertia weights in PSO are devised to improve the global searching capability and escaping from local minimum. To verify the feasibility of the proposed method, numerical studies have been performed for two different nonconvex ED test systems and its results are compared with those of previous works. The proposed CPSO algorithm outperforms other state-of-the-art algorithms in solving ED problems, which consider valve-point and multi-fuels with valve-point effects.

A PTV Applied to Measuring the Solid Particle Velocity of Slurry Flow in a Vertical Pipe (PTV를 이용한 수직관 내 슬러리유동의 고체입자 속도계측 연구)

  • Yang, Chan-Kyu;Choi, Jong-Su;Hong, Sup
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2001.10a
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    • pp.213-219
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    • 2001
  • In this paper, particle velocity of slurry flow, a kind of solid-particle two phase flow, was measured by using a particle tracking velocimetry. Particles are modeled by sphere-shaped glass whose diameters are 3mm, 5mm, and 7mm At first, a particle which is falling in the water is captured and analyzed to give their free falling velocity. The falling velocity was very high up to about 4m/sec in the air, which needs special algorithm for the accurate measurement. For the upwelling slurry flow in the straight duct, there are some noises caused by cavity. However, the effect was so small that it does not affect the measurement of large particles. From the preliminary study of applying the PTV to measurement of particle movement in slurry flow, we could find out the optimum value of parameters: threshold value., searching area radius and correlation area size.

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Application of Blind Deconvolution with Crest Factor for Recovery of Original Rolling Element Bearing Defect Signals (볼 베어링 결함신호 복원을 위한 파고율을 이용한 Blind Deconvolution의 응용)

  • Son, Jong-Duk;Yang, Bo-Suk;Tan, A.C.C.;Mathew, J.
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.585-590
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    • 2004
  • Many machine failures are not detected well in advance due to the masking of background noise and attenuation of the source signal through the transmission mediums. Advanced signal processing techniques using adaptive filters and higher order statistics have been attempted to extract the source signal from the measured data at the machine surface. In this paper, blind deconvolution using the eigenvector algorithm (EVA) technique is used to recover a damaged bearing signal using only the measured signal at the machine surface. A damaged bearing signal corrupted by noise with varying signal-to-noise (s/n) was used to determine the effectiveness of the technique in detecting an incipient signal and the optimum choice of filter length. The results show that the technique is effective in detecting the source signal with an s/n ratio as low as 0.21, but requires a relatively large filter length.

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Design and Performance Analysis of SOAP based ebXML Cryptography Systems (SOAP기반의 ebXML 암호화 설계 및 성능분석)

  • Kang, Min-Goo
    • The Journal of the Korea Contents Association
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    • v.6 no.11
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    • pp.1-7
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    • 2006
  • In this paper, a SOAP based ebXML cryptography system is proposed for the optimum XML document encryption using RSA algorithm in e-Marketplace. And ciphering algorithms of DES, 3DES, RSA, and proposed RSA were used for the performance analysis of ebXML cryptography system. The network performance of ciphering and deciphering times is evaluated for its enhancement of SOAP based ebXML ciphering e-Marketplace systems using the same block and document sizes by computer simulations.

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The Optimal Design of Air Bearing Sliders of Optical Disk Drives by Using Simulated Annealing Technique (SA 기법을 이용한 광디스크 드라이브 공기베어링 슬라이더의 최적설계)

  • Chang, Hyuk;Kim, Hyun-Ki;Kim, Kwang-Sun;Rim, Kyung-Hwa
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.8
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    • pp.1545-1551
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    • 2002
  • The optical storage device has recently experienced significant improvement, especially for the aspects of high capacity and fast transfer rate. However, it is necessary to study a new shape of air bearing surface for the rotary type actuator because the optical storage device has the lower access time than that of HDD (Hard Disk Drives). In this study, we proposed the air bearing shape by using SA (Simulated Annealing) algorithm which is very effective to achieve the global optimum instead of many local optimums. The objective of optimization is to minimize the deviation in flying height from a target value 100nm. In addition, the pitch and roll angle should be maintained within the operation limits.

A Study on Generator Maintenance Scheduling Considering Renewable Energy Generators (신재생에너지 발전원을 고려한 발전기 예방정비계획수립에 관한 연구)

  • Lee, Yeonchan;Oh, Ungjin;Choi, Jaeseok;Jung, Myeunghoon
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.67 no.5
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    • pp.601-610
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    • 2018
  • The purpose of this paper is to establish a new optimum Generator Maintenance Scheduling(GMS) considering renewable energy generator. In this paper, the total renewable energy generation is estimated using hourly capacity factor of renewable energy generator. The GMS was optimized with the objective function of maximizing the minimum reserve rate, minimizing the probabilistic production cost, minimizing the loss of load expectation, and minimizing $CO_2$ emissions. In the case study of this paper, GMS considering renewable energy and GMS not considering renewable energy are shown by each objective function. And it shows scenarios of the reliability, the environmental and economical factors when two nuclear power plants inputted and ten coal thermal power plants shut downed respectively.

Compensation Mechanism of Cell Delay Variation by Optimum Partial Timestamps on the ATM-to-Satellite Interface (위성 TDMA 와 ATM 접속에서 최적의 부분 타임스탬프에 의한 CVD 보상 기법)

  • Chung, Ha-Jae;Kim, Jeong-Ho;Oh, Chang-Suk
    • The Transactions of the Korea Information Processing Society
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    • v.7 no.9
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    • pp.2980-2993
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    • 2000
  • In order to achieve the rapid deployment of services. B-ISON network is being combined with terrestrial ATM and satellite network. Cell delay variation (CDV) generated by the difference of transfer mode between TOMA and ATM deteriorates transmission quality of the network system. We proposed the Partial Timestamps algorithm to supplement the problems of existing COV compensation methods. To minimize CDV and to utilize the satellite channels efficiently. only the optimized timestamps of a few cells within a control unit time of TDMA are selected and transmitted to the receiving earth station. The COV compensating efficiency of Partial Timestamps is evaluated by simulation. It is confirmed that CDV compensation capability of the proposed mechanism is superior to the other methods.

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Advanced Field Weakening Control for Maximum Output Power Operation of Seawater Cooling Pump Induction Motor in a Limited Environment (제한된 환경에서의 해수냉각펌프용 유도전동기 최대출력 운전을 위한 약계자 제어)

  • Son, Yung-Deug;Seo, Yong-Joo;Jung, Jun-Hyung;Kim, Jang-Mok
    • The Transactions of the Korean Institute of Power Electronics
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    • v.18 no.6
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    • pp.540-546
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    • 2013
  • The induction motor is used for driving the special equipments such as warship and submarine pump due to robust structure and simple maintenance. Domestic and foreign warships use a wide range of voltages and the DC voltage sources mainly from battery. In the low voltage level, the ${\Delta}$-connection operation of induction motor can be used for the maximum power. However, the temperature of the inverter increases because of the high input current. On the other hand, Y-connection operation of the induction motor does not cause a problem of temperature because of the low input current compared to the ${\Delta}$-connection. But the lack of the supply voltage can not be avoided. Therefore, this paper suggests the algorithm of the optimum field weakening control to extend the operating range of the induction motor with maximum power in a limited thermal and DC voltage condition.

Optimal Voltage and Reactive Power Scheduling for Saving Electric Charges using Dynamic Programming with a Heuristic Search Approach

  • Jeong, Ki-Seok;Chung, Jong-Duk
    • Journal of Electrical Engineering and Technology
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    • v.11 no.2
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    • pp.329-337
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    • 2016
  • With the increasing deployment of distributed generators in the distribution system, a very large search space is required when dynamic programming (DP) is applied for the optimized dispatch schedules of voltage and reactive power controllers such as on-load tap changers, distributed generators, and shunt capacitors. This study proposes a new optimal voltage and reactive power scheduling method based on dynamic programming with a heuristic searching space reduction approach to reduce the computational burden. This algorithm is designed to determine optimum dispatch schedules based on power system day-ahead scheduling, with new control objectives that consider the reduction of active power losses and maintain the receiving power factor. In this work, to reduce the computational burden, an advanced voltage sensitivity index (AVSI) is adopted to reduce the number of load-flow calculations by estimating bus voltages. Moreover, the accumulated switching operation number up to the current stage is applied prior to the load-flow calculation module. The computational burden can be greatly reduced by using dynamic programming. Case studies were conducted using the IEEE 30-bus test systems and the simulation results indicate that the proposed method is more effective in terms of saving electric charges and improving the voltage profile than loss minimization.