• Journal of applied mathematics & informatics
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• 제16권1_2호
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• pp.125-142
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• 2004

We analyze the convergence properties of Powell's UOBYQA method. A distinguished feature of the method is its use of two trust region radii. We first study the convergence of the method when the objective function is quadratic. We then prove that it is globally convergent for general objective functions when the second trust region radius p converges to zero. This gives a justification for the use of p as a stopping criterion. Finally, we show that a variant of this method is superlinearly convergent when the objective function is strictly convex at the solution.

• 제어로봇시스템학회논문지
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• 제17권12호
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• pp.1210-1218
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• 2011

GA (Genetic Algorithms) are efficient for searching for global optima but may have some problems such as premature convergence, convergence to local extremum and divergence. These phenomena are related to the evolutionary operators. As population diversity converges to low value, the search ability of a GA decreases and premature convergence or converging to local extremum may occur but population diversity converges to high value, then genetic algorithm may diverge. To guarantee that genetic algorithms converge to the global optima, the genetic operators should be chosen properly. In this paper, we analyze the effects of the selection operator, crossover operator, and mutation operator on convergence properties, and propose the sweeping method of mutation probability and elitist propagation rate to maintain the diversity of the GA's population for getting out of the premature convergence. Results of simulation studies verify the feasibility of using these sweeping operators to avoid premature convergence and convergence to local extrema.

• 융복합기술연구소 논문집
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• 제5권2호
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• pp.43-48
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• 2015

Deep eutectic solvents (DESs) are now broadly understood as a new kind of ionic liquid (IL) because they exhibit many characteristics and properties similar with ILs. The DESs made of quaternary ammonium salt blended with one of hydrogen bonding donor (HBD) compounds behave as ILs even at very low temperature. In this study, properties such as density, viscosity, surface tension, conductivity, and electrochemical behavior of DESs were reported and their applications were reviewed. Study on DESs has been drawn attention on application in metal finishing, but these solvents can be used in a variety of synthesis, and their potentials have been demonstrated in various areas. DESs are expected to offer applicability by extending the types of salts and hydrogen bond donor mixtures.

• 한국산업융합학회 논문집
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• 제8권3호
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• pp.149-154
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• 2005

The purpose of this study was to develop the High Functional Stretch Yarns and Woven Fabrics to produce the high value added textile goods and to meet the consumer's needs. For the study 8 yarns and 10 fabrics were made with three develop machine and the thermal-stress properties of the sample were tested and analysed. The result indicated that the sample fabrics kept their stretch performance regardless of conventional process. EDY(elastic DTY) had higher stretch than that of DTY(drawn textured yarn). Especially Macel yarn had higher stretch than that of DTY compared with the same condition of yarn. With time course behavior the elongation of DTY and EDY had stabled tendency without variation. The above results show that wearing sensation and comfort properties of fabrics are changed depending on the end-use. and thus, above results can be used to manufacture of fabrics for specific end-use with high comfort properties.

• 한국산업융합학회 논문집
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• 제12권1호
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• pp.5-10
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• 2009

The Nylon/clay nanocomposite were prepared with Cloisite25A and Cloisite30B. And mechanical properties and thermal properties of Nylon/clay nanocomposites on the amount of MMT have been investigated. From the results of XRD and TEM, we found that mono layered silicates were dispersed in polymer matrix and those resultants were exfoliated nanocomposites. When Cloisite30B was used as an intercalant in the Nylon/Clay nanocomposites, the mechanical and thermal properties of Nylon were higher than those with Cloisite25A.

• 한국전기전자재료학회논문지
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• 제30권6호
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• pp.349-355
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• 2017

Zinc sulphide (ZnS) nanoparticles were fabricated by hydrothermal synthesis at $180^{\circ}C$ for 12 h. Two kinds of ZnS powder (hydrothermal synthesized ZnS and commercial ZnS) were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) for phase and microstructure, respectively. The XRD patterns showed that all ZnS nanoparticles have a sphalerite (cubic) structure. The nanoparticles of two different ZnS powders were sintered by spark plasma sintering. The sintered ZnS were analyzed by XRD, SEM, and FT-IR. We found that the transmittance of the infrared region is highly dependent on the density and crystal structure of sintered ZnS and the purity of the starting ZnS powder.

• 한국항행학회논문지
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• 제18권2호
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• pp.170-177
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• 2014

유전 알고리즘은 강인한 탐색과 최적화 기술이기는 하나 조기 수렴과 국부 최적해에 수렴하는 문제점들을 내포하고 있다. 모집단의 다양성이 작은 값으로 수렴할수록 탐색능력이 감소하고, 국부 최적해에 수렴하지만, 모집단의 다양성이 높은 값으로 수렴할수록 탐색능력이 증가하고 전역 최적해에 수렴할 수 있으나 유전 알고리즘은 발산할 수도 있다. 유전 알고리즘이 전역 최적해에 수렴하는 것을 보장하기 위해서는 유전 연산자가 적절하게 선정되어야 한다. 본 논문에서는 조기 수렴으로부터 벗어나기 위하여 모집단의 다양성을 유지하도록 평균해밍거리와 적합도 값을 혼합한 함수를 이용한 유전 연산자들을 제안하였다. 모의실험을 통하여 다양성의 유지를 위한 돌연변이 연산자와 수렴 특성의 향상을 위한 다른 유전자들의 효과를 확인할 수 있었으며, 본 논문에서 제안한 유전 연산자들이 조기 수렴이나 국부 최적해에 수렴하는 경우를 피하는데 유용한 방법임이 확인되었다.

• ETRI Journal
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• 제31권6호
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• pp.660-666
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• 2009

We investigate the effects of interfacial dielectric layers (IDLs) on the electrical properties of top-gate In-Ga-Zn-oxide (IGZO) thin film transistors (TFTs) fabricated at low temperatures below $200^{\circ}C$, using a target composition of In:Ga:Zn = 2:1:2 (atomic ratio). Using four types of TFT structures combined with such dielectric materials as $Si_3N_4$ and $Al_2O_3$, the electrical properties are analyzed. After post-annealing at $200^{\circ}C$ for 1 hour in an $O_2$ ambient, the sub-threshold swing is improved in all TFT types, which indicates a reduction of the interfacial trap sites. During negative-bias stress tests on TFTs with a $Si_3N_4$ IDL, the degradation sources are closely related to unstable bond states, such as Si-based broken bonds and hydrogen-based bonds. From constant-current stress tests of $I_d$ = 3 ${\mu}A$, an IGZO-TFT with heat-treated $Si_3N_4$ IDL shows a good stability performance, which is attributed to the compensation effect of the original charge-injection and electron-trapping behavior.

• Nuclear Engineering and Technology
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• 제42권2호
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• pp.193-202
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• 2010

In order to study the cladding properties of zirconium after a loss-of-coolant accident (LOCA)-simulation oxidation and water quenching test, commercial Zircaloy-4 and two kinds of HANA claddings were oxidized at temperatures ranging from $900^{\circ}C$ to $1250^{\circ}C$ and exposed for 300 s, and then cooled to $700^{\circ}C$ before quenching. Microstructural observations were made to evaluate the matrix characteristics with the chemical compositions after the LOCA-simulation test. Ring compression testing was then performed to compare the ductile behaviour of the HANA and Zircaloy-4 claddings. An X-ray diffraction (XRD) analysis was carried out for temperatures ranging from room temperature to $1250^{\circ}C$ for the oxide layer to verify the oxide crystal structure at each oxidation temperature.

• 디지털융복합연구
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• 제11권4호
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• pp.267-271
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• 2013

우리사회는 점점 더 융/복합 현상이 가속화되고, 광범위한 영역으로 확대되고 있다. 이러한 중심축에는 정보통신 기술이 자리잡고 있음은 당연한 일이다. 일례로 정보통신기술과 의료산업의 융합의 결과로 스마트 헬스케어 산업이 등장하였으며, 모든 분야에 정보통신 기술을 접목하고자 하는 노력들이 계속되고 있다. 이로 인해 우리주변에는 수많은 디지털 데이터들이 만들어지고 있다. 또 다른 한편으로는 대중화 되고 있는 스마트폰, 태블릿PC와 카메라, 게임기기등을 통하여 다양한 데이터들이 생성되고 있다. 본 연구에서는 광범위하게 발생하고 있는 빅데이터에 대한 활용 상태를 알아보고 빅데이터 플랫폼의 한 축인 처리 프로세스들에 대해 비교, 분석하였다.