• 융합신호처리학회논문지
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• 제12권1호
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• pp.20-25
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• 2011

부밴드 구조에서 투사차원이 P인 전밴드 인접투사 적응필터는 최대 군위상 분해와 노블아이덴티티를 적용함으로써 P개의 적응 부필터로 분해된다. 각각의 적용 부필터는 투사차원이 1인 간단한 계수 갱신식을 갖게 된다. 이러한 부밴드 분해기법은 구현관점에서 가장 실용적인 해법 중 하나이다. 많은 응용에서 활용을 위해 MPDSAP 적응 필터의 최적 스텝사이즈 해석이 필요하다. 본 논문은 MPDSAP 적응 필터의 MSE에 대한 개선된 해석 모델을 제안하고 초기 최적 스텝사이즈를 유도한다. 컴퓨터 시뮬레이션을 통해 MSE의 개선된 해석 모텔과 유도된 최적 초기 스텝사이즈에 대해 이론과 실험적 결과 사이의 일치함을 확인하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.121-124
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• 2000

In IMT-2000 systems, the outer loop dynamically adjusts the target SIR so that adequate performance in terms of the frame error rate(FER) and the true quality measure is achieved. This paper utilizes an analytic model lot outer loop power control(OLPC) adjusting the target SIR in IMT-2000. The analytic model is based on the discrete-time Markov chain as voice traffic SIR. It is described that the model can be used to find the optimum step size in voice traffic for fast fading environments. The optimum step size influences the performance of OLPC： As the step size decreases, the average target SIR increases and average FER decreases.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권6호
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• pp.602-614
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• 2016

It is necessary to develop an efficient optimization technique to perform optimum designs which have given design spaces, discrete design values and several design goals. As optimization techniques, direct search method and stochastic search method are widely used in designing of ship structures. The merit of the direct search method is to search the optimum points rapidly by considering the search direction, step size and convergence limit. And the merit of the stochastic search method is to obtain the global optimum points well by spreading points randomly entire the design spaces. In this paper, Pareto Strategy (PS) multi-objective function method is developed by considering the search direction based on Pareto optimal points, the step size, the convergence limit and the random number generation. The success points between just before and current Pareto optimal points are considered. PS method can also apply to the single objective function problems, and can consider the discrete design variables such as plate thickness, longitudinal space, web height and web space. The optimum design results are compared with existing Random Search (RS) multi-objective function method and Evolutionary Strategy (ES) multi-objective function method by performing the optimum designs of double bottom structure and double hull tanker which have discrete design values. Its superiority and effectiveness are shown by comparing the optimum results with those of RS method and ES method.

• 한국전자파학회논문지
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• 제14권1호
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• pp.8-13
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• 2003

본 논문에서는 이동통신 품질 보호를 위한 주파수 1 GHz CISPR 허용기준 설정의 적정성을 조사하였으며, 주파수 1 GHz 이상의 장해파 측정에 있어 최대값 추출의 정확성을 높이기 위해 사전 시험에 이용될 수 있는 피시험체의 최적 회전 스텝 분해능에 대해 조사하였다. 마이크로 프로세스의 클럭속도 500 MHz 및 1.7 GHz인 퍼스널 컴퓨터를 피시험체로 측정한 결과, 클럭속도 500 MHz의 경우, 미국 표준과학연구원 Koepke 방식에 의해 추출된 최적 스텝 분해능은 40 개이었으며, 클럭속도 1.7 GHz 퍼스널 컴퓨터의 경우 스텝 분해능은 36개로 평가되었다. 완전 스캔(fully scan) 방식의 측정이 요구되는 기가헤르쯔 측정에서 회전 스텝 분해능에 대한 예측은 측정의 정확성뿐만 아니라 측정 시간을 상당히 단축시켜 줄 것이다.

• 한국전기전자재료학회논문지
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• 제14권4호
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• pp.289-296
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• 2001

The piezoelectric transformers of 2.0x10x48 ㎣ size were fabricated with PSN-PMN-PZT(T10 and PNW-PMN-PZT(T2) composition ceramics. Effects of micro structural and piezoelectric properties on the electrical characteristics of the piezoelectric transformers were investigated. Under the fixed output power of 6 W, temperature rise of T1 transformer at the optimum load was smaller than T2 one because of fine grain size effect. Voltage step-up ratio of T1 transformer showed higher value than T2 one T1 transformer showed an excellent properties with voltage step-up ratio of 12.41, efficiency of 95.23% and temperature rise of 7.2$^{\circ}C$ at 200㏀ load resistance. And also, T2 transformer showed an excellent properties with voltage step up ratio of 9.81, efficiency of 95.51% and temperature rise of 9$^{\circ}C$ at 150㏀ load resistance.

• ETRI Journal
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• 제45권6호
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• pp.996-1006
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• 2023

Renewable energy is promoted massively to overcome problems that fossil fuel power plants generate. One popular renewable energy type that offers easy installation is a photovoltaic (PV) system. However, the energy harvested through a PV system is not optimal because influenced by exposure to solar irradiance in the PV module, which is constantly changing caused by weather. The maximum power point tracking (MPPT) technique was developed to maximize the energy potential harvested from the PV system. This paper presents the MPPT technique, which is operated on a new high-gain voltage DC/DC converter that has never been tested before for the MPPT technique in PV systems. Fuzzy logic (FL) was used to operate the MPPT technique on the converter. Conventional and adaptive perturb and observe (P&O) techniques based on variables step size were also used to operate the MPPT. The performance generated by the FL algorithm outperformed conventional and variable step-size P&O. It is evident that the oscillation caused by the FL algorithm is more petite than variables step-size and conventional P&O. Furthermore, FL's tracking speed algorithm for tracking MPP is twice as fast as conventional P&O.

• 한국재료학회지
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• 제11권10호
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• pp.869-878
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• 2001

Alumina $(Al_2O_3)$ green bodies were fabricated by gel-casting using three kinds of alumina with different particle size (mean particle size: 4.6 $\mu\textrm{m}$, 0.32 $\mu\textrm{m}$, 10nm). The effects of particle size on gel-casting process and green microstructure were investigated. The optimum dispersion conditions using ammonium salt (D-3019) as dispersant were 0.2 wt% (4.63 $\mu\textrm{m}$), 0.5 wt% (0.32 $\mu\textrm{m}$), and 5.0 wt% (10 nm), in high solid loading. The optimum solid loading of each starting material for gel-casting was obtained as 59 vol% (4.63 $\mu\textrm{m}$), 57 vol% (0.32 $\mu\textrm{m}$), 15 vol% (10 nm), depending on particle size, indicating that nano-size particle (10 nm) represent lower solid loading as high specific surface area than those of other two starting materials. The drying at ambient conditions (humidity; $\thickapprox$90%) was performed more than 48hrs to enable ejection of the part from the mold and then at $120^{\circ}C$ for 2hrs in an air oven, showing no crack and flaw in the dried green bodies. The pore size and distribution of the gelcast green bodies showed the significant decrease with decreasing particle size. Green microstructure was dependent on the pore size and distribution due to the particle size, and on the deairing step. The green density maximum obtained was 58.9% (4.63 $\mu\textrm{m}$), 60% (0.32 $\mu\textrm{m}$), 47% (10 nm) theoretical density (TD), and the deairing step applied before gel-casting did not affect green density.

• 공업화학
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• 제19권4호
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• pp.370-375
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• 2008

비수계 분산(NAD : non-aqueous dispersion) 중합을 이용하여 친환경적인 아크릴 수지를 합성시 최적의 중합조건에 대해 연구하였다. 중합된 고분자 입자들 간의 응집을 방지하기 위한 안정제의 적정량은 20 wt%로 나타났고 안정된 NAD 상태를 유지하기 위한 혼합 용매의 적정 혼합비는 지방족과 방향족 용매의 비율이 80 : 20인 것으로 나타났다. NAD 수지의 점도는 반응시간뿐만 아니라 개시제의 양 및 교반 속도 등에 의해 영향을 받는 것으로 나타났다. 또한 NAD 수지의 입자 크기 및 분포도, 안정제의 양, 개시제의 농도 등에 의해 영향을 받는 것을 확인하였다. 단량체의 투입시기는 단량체를 초기에 모두 투입하면 용매의 극성이 증가하여 입자의 크기가 커져서 입자의 안정성이 저하되므로 단계별로 지속적으로 투입할 필요가 있는 것으로 관찰되었다.

• 한국통신학회논문지
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• 제41권9호
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• pp.995-1000
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• 2016

무작위 발생된 심볼 집합과 최대 상호 코렌트로피 (maximum cross-correntropy) 로 설계된 MCC 알고리듬은 최소자승평균 (MSE) 기반 알고리듬과 달리, 충격성 잡음 하에서 최적 가중치가 동요 없이 안정을 유지하며 그 요인이 오차 전력에 따라 입력의 세기를 조절하는 입력 크기 조정기 (input magnitude controller, IMC)에 있음이 밝혀졌다. 이 논문에서는 스텝사이즈를 정규화한 알고리듬 (normalized MCC, NMCC)를 제안하였으며 여기서 IMC 통과된 신호 전력은 1-pole 저역 통과 필터로 반복적 추정한다. 두 가지 다중경로 채널 모델과 충격성 잡음 환경에서 시행된 시뮬레이션 결과, 정규화된 NMCC알고리듬은 MCC알고리듬에 비해 정상상태 MSE에서 1 dB 정도의 성능 향상을, 수렴 속도에서도 500 샘플 정도 빠른 성능을 나타냈다.

• 대한조선학회논문집
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• 제42권2호
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• pp.175-182
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• 2005

It is necessary to develop an efficient optimization technique to optimize the engineering structures which have given design spaces, discrete design values and several design goals. As optimization techniques, direct search method and stochastic search method are widely used in designing of engineering structures. The merit of the direct search method is to search the optimum points rapidly by considering the search direction, step size and convergence limit. And the merit of the stochastic search method is to obtain the global optimum points by spreading point randomly entire the design spaces. In this paper, a Pareto optimal based multi-objective function method (PMOFM) is developed by considering the search direction based on Pareto optimal points, step size, convergence limit and random search generation . The PMOFM can also apply to the single objective function problems, and can consider the discrete design variables such as discrete plate thickness and discrete stiffener spaces. The design results are compared with existing Evolutionary Strategies (ES) method by performing the design of double bottom structures which have discrete plate thickness and discrete stiffener spaces.