• 한국환경과학회지
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• 제19권9호
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• pp.1161-1167
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• 2010

The effects of addition of non degradable polymers, polystyrene (PS) and poly(methyl methacrylate) (PMMA) on the rate of enzymatic degradation of biodegradable poly(l-lactide) (PLLA) have been studied in term of surface structure. Since a component in multicomponent polymeric system has shown surface enrichment, PS and PMMA which have lower surface energy than PLLA were selected as a minor blend component (5 wt%). Enzymatic degradation was carried out at $37^{\circ}C$ and pH 8.5 in the aqueous solution of Proteinase K. Two blend systems, partially miscible (PS/PLLA) and immiscible (PMMA/PLLA), showed the surface enrichment of 4 and 2 times of PS and PMMA, respectively. From the weight loss profile data, the slow degradation rate of both blend films was observed. This indicates that PS or PMMA domains which exist at surface act as a retardant of enzymatic attack.

• 한국정보통신학회논문지
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• 제9권6호
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• pp.1316-1322
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• 2005

인터넷을 통한 전자상거래와 전자서명기술이 대두되면서 부각된 기술이 PKI(Public Key Ifrastructure)이다. PKI는 암호화기반기술에 있어서 여러 가지 새로운 표준들을 가져왔다. 그러나 이 같은 표준화가 활발히 진행되고 있음에도 PKI를 응용한 솔루션들은 가격이 비싸고 느린 단점들이 지적되고 있다. 현재 PKI를 포함한 암호화기술의 주된 관심이 빠른 속도와 보다 향상된 보안성이라고 한다면 이 같은 문제들은 심각한 문제들이라고 할 수 있다. 본 논문은 기존의 PKI구조에서 가지는 몇 가지 문제를 개선하여 짧은 메시지 통신이나 단순 방식 암호화 통신에 단순하고 쉽게 사용될 수 있는 통신 컴포넌트를 설계하고 구현하였다.

• 한국기계가공학회지
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• 제4권3호
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• pp.32-38
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• 2005

Electrical discharge machining is the method of using thermal energy by electrical discharge. Generally, if the material of workpiece has conductivity even though very hard materials and complicated shape which are difficult to cut such as quenching steel, cemented carbide, diamond and conductive ceramics, the EDM process is favorable one of possible machining processes. But, the process is necessarily required of finish cut and heat treatment because of slow cutting speed, no mirror surface, brittleness and crack due to the residual stress for manufactured goods. In this experimental thesis, the super EDM drilling was developed for high precision semiconductor die steel and for minimization of leadframe width. It was possible to development of EDM drilling machine for high precision semiconductor die with the electrode guide and its modelling and stress analysis. The development of electrode with the copper pipe type was conducted to drill the hole from the diameter of 0.1mm to 3.0mm with the error of from 0.02mm to 0.12mm. From the SEM and EDX analysis, the entrance of the EDM drill was found the resolidification of not only the component of tungsten but also the component of copper.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권7호
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• pp.3076-3092
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• 2020

An IKPCA-ELM-based intrusion detection method is developed to address the problem of the low accuracy and slow speed of intrusion detection caused by redundancies and high dimensions of data in the network. First, in order to reduce the effects of uneven sample distribution and sample attribute differences on the extraction of KPCA features, the sample attribute mean and mean square error are introduced into the Gaussian radial basis function and polynomial kernel function respectively, and the two improved kernel functions are combined to construct a hybrid kernel function. Second, an improved particle swarm optimization (IPSO) algorithm is proposed to determine the optimal hybrid kernel function for improved kernel principal component analysis (IKPCA). Finally, IKPCA is conducted to complete feature extraction, and an extreme learning machine (ELM) is applied to classify common attack type detection. The experimental results demonstrate the effectiveness of the constructed hybrid kernel function. Compared with other intrusion detection methods, IKPCA-ELM not only ensures high accuracy rates, but also reduces the detection time and false alarm rate, especially reducing the false alarm rate of small sample attacks.

• 한국콘텐츠학회논문지
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• 제6권11호
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• pp.258-265
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• 2006

DEVS 형식론은 이산사건 시스템의 구조를 계층적으로 나타낼 수 있기 때문에 복잡한 시스템을 모델링 하기에 적합하며, 가독성이 좋기 때문에 유지 보수에 유리한 장점이 있다. 반면에, 계층적인 모델의 구조는 시뮬레이션 실행 시에 빈번한 메시지 전달을 야기 시켜 시뮬레이션 속도가 저하되는 단점이 있다. 본 논문에서는 계층적인 DEVS 모델들을 하나로 합성하여 빈번한 메시지 전달을 방지하고 시뮬레이션 실행 속도를 개선할 수 있는 모델 합성법을 제안한다. 제안한 방법은 시뮬레이터 실행코드를 생성하기 이전에 구성 모델들 간의 메시지 전달 관계를 해석하여 실행시간에는 모델 해석과정을 생략하도록 하는 기법으로 기존의 모델 수평화 기법보다 훨씬 뛰어난 속도 향상 결과를 보인다. 제안한 방법의 효용성을 보이기 위해 실험을 통하여 시뮬레이션 속도가 18배 정도 개선될 수 있음을 보인다.

• 설비공학논문집
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• 제5권3호
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• pp.217-225
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• 1993

Nonflammable mixtures of flammable and nonflammable refrigerants are possible as substitute refrigerants for use in domestic heat pumps and refrigerators. Refrigerant leakage from such a system is of paramount concern since it is possible that the resulting mixture composition remaining in system will reside in the flammable range. This paper presents a simulation of a leakage process of refrigerant mixtures. Idealized cases of isothermal leakage process are considered in this study representing a slow leak. Simulation is performed for selected composition of binary and ternary refrigerant mixture; R-32/134a and R-32/125/134a. Mixture compositions with respect to percentage leak of original charge are presented. In isothermal leakage process, both vapor and liquid compositions of more volatile refrigerant decrease during vapor and liquid leak, but the total composition of this component decreases during vapor leak and increases during liquid leak. Vapor and liquid compositions are determined depending on the vapor-liquid equilibrium relation of the refrigerant mixture. The refrigerant mixture left in the system can go to a nonflammable direction relying on which component in the mixture is flammable.

• 약학회지
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• 제35권5호
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• pp.416-426
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• 1991

The effects of an irreversible or a reversible $\alpha_1$-adrenoceptor antagonist (dibenamine or prazosin) on $\alpha_1$-adrenoceptor-mediated vasoconstrictions were studied in the endothelium-denuded rat aorta. In these experiments, the mobilization of intracelluier calcium and translocation of extracellular calcium were also studied. To exclude the modulation of endothelium releasing EDRF and EDCF, the endothelium was removed in all rat aortas. Contraction induced by phenylephrine (a full $\alpha_1$-adrenoceptor agonist) was separated into a fast phasic component of the response due to the release of intracellular calcium and a slow tonic one due to the influx of extracellular calcium. Pretreatments with increasing doses of reversible $\alpha_1$-adrenoceptor antagonist prazosin, as well as irreversible $\alpha_1$-adrenoceptor antagonist dibenamine, inhibited the phasic component of phenylephrine-induced contraction more effectively than the tonic one. Pretreatment of dibenamine (0.2 $\mu{M}$) or prazosin (10 nM) to the rat aorta abolished phasic response but remained tonic one about 41% and 51%, respectively. These results suggest that as the efficiency of phenylephrine was progressively reduced by pretreatments with increasing doses of an irreversible or a reversible $\alpha_1$-adrenoceptor antagonist (dibenamine or prazosin), the contraction induced by phenylephrine became progressively more dependent on the influx of extracellular calcium.

• 한국자동차공학회논문집
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• 제11권4호
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• pp.58-67
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• 2003

An automotive engine cooling system is closely related with overall engine performances, such as reduction of fuel consumption, decrease of air pollution, and increase of engine life. Because of complex reaction between each component, the direct experiment, using a vehicle, takes high cost, long time, and slow response to the system change. Therefore, a computer simulation would provide the designer with an inexpensive and effective tool for design, development, and optimization of the engine cooling system over a wide range of operating conditions. In this work, it has been predicted the thermal performance of the engine cooling system in cases of stationary mode, constant speed mode, and city-drive mode by mathematical modelling of each component and numerical analysis. The components are engine, radiator, heater, thermostat, water pump, and cooling fans. Since the engine model is the most important, that is divided into eight sub-sections. The volume mean temperature of eight sub-sections are simultaneously calculated at a time. For detail calculation, the radiator and heater are also divided into many sub-sections like control volumes in finite difference method. Each sub-section is assumed to consist of three parts, coolant, tube with fin, and air. Hence it has been developed the simulation program that can be used in case of design and system configuration changes. The overall performance results obtained by the program were desirable and the time-traced tendencies of the results agreed fairly well with those of actual situations.

• 한국재료학회지
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• 제34권5호
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• pp.242-246
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• 2024

La modified lead zirconate titanate ceramics (Pb_0.92La_0.08)(Zr_0.95Ti_0.05)O₃ = PLZT-8/95/5 were prepared using the conventional solid state reaction method in order to investigate the complex impedance characteristics of the PLZT-8/95/5 ceramic according to temperature. The complex impedance in the PLZT-8/95/5 ceramic was measured over a temperature range of 30~550 ℃ at several frequencies. The complex dielectric constant anomaly of the phase transition was observed near T_U1 = 179 ℃ and T_U2 = 230 ℃. A remarkable diffuse dielectric constant anomalous behaviour of the complex dielectric constant was found between 100 ℃ and 550 ℃. The complex impedance spectra below and above T_U1 and T_U2 were fitted by the superposition of two Cole-Cole types of impedance relaxations. The fast component in the higher frequency region may be due to ion migration in the bulk, and the slow component in the lower frequency region is interpreted to be the formation and migration of ions at the grain boundary or electrode/crystal interfacial polarization.

• 한국작물학회지
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• 제49권3호
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• pp.160-166
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• 2004

벼 M/G RIL 162 계통에 대한 초기급속등숙율에 대한 이화학적특성 및 색차색도특성 변이에 대한 주성분분석 및 유전력분석의 결과를 요약하면 다음과 같다. 1. 초기급속등숙율이 41％ 이하인 계통군은 164계통중 74계통이었으며, 41∼60％의 계통군에는 32계통이 있었다. 또한, 초기급속등숙율이 빠른 계통군에 속하는 61∼80％사이에는 24계통이 있었으며, 초기급속등숙율이 매우 빠른 계통군으로 분류되는 81％ 이상인 계통은 32계통이 있었다. 2. 벼 M/G RIL 164계통에 대한 품종군별 이화학적특성을 보면, 초기급속등숙을이 40％ 이하인 계통군이 단백질 함량이 9.1％로 가장 높았으며, 지방산함량은 초기급속등숙율이 61∼80％의 계통군에서 26.5KOHmg/100g으로 가장 높게 나타났다. 또한, 곡립형태에 있어서 현미길이는 41∼60％사이의 초기급속등숙율을 보인 계통군이 5.40mm로 가장 짧았으며, 81％ 이상인 계통군이 1.80mm로 현미두께가 가장 두꺼웠으며, 현미의 형태를 나타내는 현미 길이/넓이 비에 있어서는 41∼60％사이의 계통군이 2.18로 나타났다. 3. 호화온도와 깊은 관련이 있는 알카리붕괴도에 있어서는 초기급속등숙율이 61∼80％사이가 3.40으로 가장 붕괴가 되지않는 계통군으로 나봤으며, 81％이상인 계통군은 4.31로서 붕괴가 가장 잘 되는 것으로 나타나 81％의 계통군이 호화온도가 낮은 것으로 나타났다. 4. 화학적특성, 색차색도특성 및 알카리붕괴도를 이용한 벼M/G RIL 164 계통에 대한 주성분분석의 결과 제 1주성분은 약 3.6개의 형질을 포함하고 있었으며, 제 2주성분은 약 2.1개의 형질을 포함하고 있는 것으로 밝혀졌다. 또한, 제 1주성분은 전체 변동에 대한 기여율은 약 36％이었으며, 제 4주성분까지의 전체 변동에 대한 누적 기여율은 86.4％로서 설명이 가능함을 알 수 있었다. 5. 벼 M/G RIL 164 계통의 품질평가치, 단백질함량, 아밀로오스함량, 지방산함량, 명도, a-value, b-value, 채도, 색상 및 알카리붕괴도 등의 형질에 대한 유전력 검정의 결과, 품질평가치의 유전력은 87.89％로 가장 높은 유전력을 나타내었으며, 단백질함량 ＞ 알카리붕괴도 ＞ 지방산함량 ＞ 아밀로오스함량 ＞ 색상 ＞ 명도 ＞ a-value ＞ b-value의 순으로 나타났으며, 채도의 유전력은 30.62％로 가장 낮음을 알 수 있었다.