• 한국해양공학회지
• /
• 제13권2호통권32호
• /
• pp.83-89
• /
• 1999

In this paper an experimental study on the development of the shielded metal are welding(SMAW) optimization technique for the dissimilar materials SS41 and STS304 of Auto-Lifting Magnet core plate was carried out. It was confirmed that the optimum welding heat input range was 37.5 to 45 kj/cm by considering on the strength and fatigue life of the welded joints more than 100% joint efficiency. And the quantitative relationship empirical wquation between the strength toughness adn fatigue life and the weld heat input was obtained.

• 한국멀티미디어학회논문지
• /
• 제18권1호
• /
• pp.71-80
• /
• 2015

Many researches have been studied to overcome the weak points in authentication schemes of mobile devices such as pattern-authentication that is vulnerable for smudge-attack. Since random-pattern-lock authenticates users by drawing figure of predefined-shape, it can be a method for robust security. However, the authentication performance of random-pattern-lock is influenced by input noise and individual characteristics sign pattern. We introduce an optimization method of user input direction to increase the authentication accuracy of random-pattern-lock. The method uses the likelihood of each direction given an data which is angles of line drawing by user. We adjusted recognition range for each direction and achieved the authentication rate of 95.60%.

• International Journal of Korean Welding Society
• /
• 제1권1호
• /
• pp.44-50
• /
• 2001

A genetic algorithm was applied to the arc welding process as to determine the near-optimal settings of welding process parameters that produce the good weld quality. This method searches for optimal settings of welding parameters through the systematic experiments without the need for a model between the input and output variables. It has an advantage of being capable to find the optimal conditions with a fewer number of experiments rather than conventional full factorial designs. A genetic algorithm was applied to the optimization of the weld bead geometry. In the optimization problem, the input variables were wire feed rate, welding voltage, and welding speed. The output variables were the bead height bead width, and penetration. The number of levels for each input variable is 16, 16, and 8, respectively. Therefore, according to the conventional full factorial design, in order to find the optimal welding conditions,2048 experiments must be performed. The genetic algorithm, however, found the near optimal welding conditions in less than 40 experiments.

• 한국지능시스템학회논문지
• /
• 제11권4호
• /
• pp.325-330
• /
• 2001

최적화문제에 사용되는 신경회로망을 회로레벨에서 시뮬레이션을 해보면, 알고리즘레벨에서 시뮬레이션한 결과와 많이 다름을 체험한다. 즉, 이런 신경회로망의 출력값들은 시간이 흐름에 따라 점근적으로 수렴하나, 입력단의 값들은 입력단에 부수적으로 연결되어 있는 컨덕턴스의 값에 따라 수렴여부도 달라지고, 또한 시스템의 성능도 변함을 안다. 이 논문에서는 입력단에 시스템의 안정도를 위해 부수적으로 연결된 컨덕턴스의 값에 따라 시스템의 수렴여부를 입력단과 출력단에서 분석하였으며, 에너지함수의 수렴점들이 이들 컨덕턴스의 값에 따라 성분이 변함을 분석하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
• /
• pp.204-206
• /
• 2007

In this study, we introduce the optimization method of fuzzy inference systems that is based on Hierarchical Fair Competition-based Parallel Genetic Algorithms (HFCGA) and information data granulation, The granulation is realized with the aid of the Hard C-means clustering and HFCGA is a kind of multi-populations of Parallel Genetic Algorithms (PGA), and it is used for structure optimization and parameter identification of fuzzy model. It concerns the fuzzy model-related parameters such as the number of input variables to be used, a collection of specific subset of input variables, the number of membership functions, the order of polynomial, and the apexes of the membership function. In the optimization process, two general optimization mechanisms are explored. The structural optimization is realized via HFCGA and HCM method whereas in case of the parametric optimization we proceed with a standard least square method as well as HFCGA method as well. A comparative analysis demonstrates that the proposed algorithm is superior to the conventional methods. Particularly, in parameter identification, we use the UNDX operator which uses multiple parents and generate offsprings around the geographic center off mass of these parents.

• 한국ITS학회 논문지
• /
• 제15권4호
• /
• pp.143-152
• /
• 2016

본 논문에서는 이동통신대역에 사용 가능한 MMIC(Monolithic Microwave Integrated Circuits) 이중평형 주파수 혼합기(Double Balanced Mixer)를 설계하고 LO 전력 최적화에 관한 연구를 다룬다. 본 논문에서 제안한 MMIC 이중평형 주파수 혼합기의 칩 크기는 $4{\times}4$[$mm^2$]이며, GaAs 기판을 사용한다. LO power에 대한 최적화 연구는 입력신호의 선형성에 대한 Input IP3(IIP3)에 대해서 진행하며, LO power+16 dBm을 인가했을 때 IIP3성분이 약 23.2dBm을 보여 가장 우수한 특성을 나타내었다.

• Composites Research
• /
• 제32권5호
• /
• pp.243-248
• /
• 2019

As demand of light weight in the automotive industry has increased, the cowl cross member has been investigated using various methods to change the material. Conventionally, a cowl cross member has been made of steel and aluminum, but recently researchers tested multi-material such as aluminum and plastic. We studied a new model of the cowl cross member made of composite and non ferrous materials. For products with a high degree of freedom in design, generally, the method of topology optimization is advantageous and for the partial bracket part of the cowl cross member had a degree of freedom in the design, a topology optimization is appropriate. Considering the characteristics of the cowl cross members, we need research to minimize the weight while having the performance of noise, vibration and harshness(NVH). Taking the mounting status of the product into consideration, we used an assembly model to optimize the cowl cross member. But this method took too much time so we considered simple cowl cross member assemble conditions using the direct matrix input method(DMI) with the Craig-Bampton Nodal Method. This method is capable of considering the status of the assembly without assembling the model, which reduced the solving time and increased the accuracy comparison with a cowl cross member without DMI.

• Journal of Electrical Engineering and Technology
• /
• 제11권6호
• /
• pp.1863-1871
• /
• 2016

This paper presents an application of fractional order controller for the control of multi input multi output twin rotor aerodynamic system. Dynamics of the considered system are highly nonlinear and there exists a significant cross-coupling between the horizontal and vertical axes (pitch & yaw). In this paper, a fractional order model of twin rotor aerodynamic system is identified using input output data from nonlinear system. Based upon identified fractional order model, a fractional order PID controller is designed to control the angular position of level bar of twin rotor aerodynamic system. The parameters of controller are tuned using Nelder-Mead optimization and compared with particle swarm optimization techniques. Simulation results on the nonlinear model show a significant improvement in the performance of fractional order PID controller as compared to a classical PID controller.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제9권12호
• /
• pp.5015-5027
• /
• 2015

Transceiver optimization in multiple input multiple output (MIMO) cognitive systems is studied in this paper. The joint transceiver beamformer design is introduced to minimize the transmit power at secondary base station (SBS) while simultaneously controlling the interference to primary users (PUs) and satisfying the secondary users (SUs) signal-to-interference-plus-noise ratio (SINR) based on the convex optimization method. Due to the limited cooperation between SBS and PUs, the channel state information (CSI) usually cannot be obtained perfectly at the SBS in cognitive system. In this study, both perfect and imperfect CSI scenarios are considered in the beamformer design, and the proposed method is robust to CSI error. Numerical results validate the effectiveness of the proposed algorithm.

• 전기학회논문지
• /
• 제57권6호
• /
• pp.915-923
• /
• 2008

This paper focuses on optimal tuning of nonlinear parameters of a dual-input power system stabilizer(dual-input PSS), which can improve the system damping performance immediately following a large disturbance. Until recently, various PSS models have developed to bring stability and reliability to power systems, and some of these models are used in industry applications. However, due to non-smooth nonlinearities from the interaction between linear parameters(gains and time constants of linear controllers) and nonlinear parameters(saturation output limits), the output limit parameters cannot be determined by the conventional tuning methods based on linear analysis. Only ad hoc tuning procedures('trial and error' approach) have been used. Therefore, the steepest descent method is applied to implement the optimal tuning of the nonlinear parameters of the dual-input PSS. The gradient required in this optimization technique can be computed from trajectory sensitivities in hybrid system modeling with the differential-algebraic-impulsive-switched(DAIS) structure. The optimal output limits of the dual-input PSS are evaluated by time-domain simulation in both a single machine infinite bus(SMIB) system and a multi-machine power system in comparison with those of a single-input PSS.