• 한국수소및신에너지학회논문집
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• 제5권2호
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• pp.73-79
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• 1994

The hydrogenation behavior of Ti-Ni powders prepared by mechanical alloying in a high energy ball mill have been investigated by P-C isotherm curves, DSC(differential scanning calorimetry), X-ray diffractometer, SEM(scanning electron microscope). Amorphous TiNi phase was formed after 10 milling hours. The hydrogen storage capacity gradually decreased as a function of mechanical alloying time. There appears the DSC endothermic peak due to hydrogen evolution of amorphous hydride phase.

• 전자공학회논문지CI
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• 제41권2호
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• pp.87-94
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• 2004

특징 집합 선택은 학습 알고리즘의 전처리 과정으로 사용되기도 한다. 수집된 자료가 문제와 관련이 없다거나 중복된 정보를 갖고 있는 경우, 이를 학습 모델생성 이전에 제거함으로써 학습의 성능을 향상시킬 수 있다. 또한 탐색 공간을 감소시킬 수 있으며 저장 공간도 줄일 수 있다. 본 논문에서는 특징 집합의 추출과 추출된 특징 집합의 성능 평가를 위하여 엔트로피를 기반으로 한 휴리스틱 함수를 사용하는 새로운 특징 선택 알고리즘을 제안하였다. 탐색 방법으로는 ACS 알고리즘을 이용하였다. 그 결과 학습에 사용될 특징의 차원을 감소시킴으로써 학습 모델의 크기와 불필요한 계산 시간을 감소시킬 수 있었다.

• 한국응용과학기술학회지
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• 제15권2호
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• pp.25-32
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• 1998

The emulsion stability of W/O emulsion prepared by D phase emulsification during storage and handling is studied by using phase diagrams. The process of D phase emulsification begins with the formation of isotropic surfactant solution, followed by formation of oil-in-surfactant (O/D) gel emulsion by dispersion of octamethylcyclotetrasiloxane(OMCS) in the surfactant solution. Polyols were essential components for this purpose. To understand the function of polyols, the solution behavior of nonionic surfactant/oil/water/polyol systems were investigated by the ternary phase diagrams of polyoxyethylene oleyl ether/OMCS/propylene glycol(PG) aqueous solutions. The addition of PG increased the solubility of oil in the isotropic surfactant phase. D phase emulsification method has been applied to a new type of cosmetics. By using this emulsification technique, O/W emulsion were formed without a need for adjust of HLB. Fine and stable W/O emulsions were prepared by D phase emulsion.

• Archives of Pharmacal Research
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• 제29권9호
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• pp.795-799
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• 2006

Peptides, although high efficacy and specificity in their physiological function, usually have low therapeutical activities due to their poor bioavailability when administrated orally. Nanoparticles have been regarded as a useful vector for targeted drug delivery system because they can protect drug from being degraded quickly and pass the gastrointestinal barriers. Here we described a novel oral N-trimethyl chitosan nanoparticles formulation containing thymopentin (Tp5-TMC-NP). N-trimethyl chitosan (TMC) was synthesized and then used to prepare Tp5-TMC-NP by ionotropic gelation. A three-factor, five-level CCD (Central Composite Design) design was used in the optimization procedure, with HPLC as the analyzing method. The resulting Tp5-TMC-NP had a regular spherical surface and a narrow particle size range with a mean diameter of 110.6 nm. The average entrapment efficiency was 78.8%. The lyophilized Tp5-TMC-NP formulation was stable in $4^{\circ}C\;or\;-20^{\circ}C$ after storage of 3 months without obvious changes in morphology, particle size, pH and entrapment ratio. The results of the flow cytometer determination showed that the ratio of $CD4^+/CD8^+$ of Wistar female rat given Tp5-TMC-NP (ig) was 2.59 time that of the group given Tp5 (ig).

• 대한기계학회논문집A
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• 제26권7호
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• pp.1416-1425
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• 2002

In this study, the effects of combined environmental factors on mechanical and thermal analysis properties of graphite/epoxy composites were evaluated by the use of an accelerated aging test. Environmental factors such as temperature, moisture. and ultraviolet were considered. A xenon-arc lamp was utilized for ultraviolet light. and exposure times of up to 3000 hours were applied. Several types of specimens - tensile. bending, and shear specimens those are transverse to the fiber direction, and bending specimens those are parallel to the tiber direction - were used to investigate the effects of environmental factors on mechanical properties of the composites. Also, glass transition temperature, storage shear modulus, loss shear modulus, and tan ${\delta}$ were measured as a function of exposure times through a dynamic mechanical analyzer. In addition. a suitable testing method for determining the effect of environmental factors on mechanical properties is suggested by comparing the results from using two different types of strain measuring sensors. Finally, composite surfaces exposed to environmental factors were examined using a scanning electron microscope.

• 대한핵의학회지
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• 제38권5호
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• pp.331-337
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• 2004

Cardiac neurotransmission imaging allows in vivo assessment of presynaptic reuptake, neurotransmitter storage and postsynaptic receptors. Among the various neurotransmitter, I-123 MIBG is most available and relatively well-established. Metaiodobenzylguanidine (MIBG) is an analogue of the false neurotransmitter guanethidine. It is taken up to adrenergic neurons by uptake-1 mechanism as same as norepinephrine. As tagged with I-123, it can be used to image sympathetic function in various organs including heart with planar or SPECT techniques. I-123 MIBG imaging has a unique advantage to evaluate myocardial neuronal activity in which the heart has no significant structural abnormality or even no functional derangement measured with other conventional examination. In patients with cardiomyopathy and heart failure, this imaging has most sensitive technique to predict prognosis and treatment response of betablocker or ACE inhibitor. In diabetic patients, it allow very early detection of autonomic neuropathy. In patients with dangerous arrhythmia such as ventricular tachycardia or fibrillation, MIBG imaging may be only an abnormal result among various exams. In patients with ischemic heart disease, sympathetic derangement may be used as the method of risk stratification. In heart transplanted patients, sympathetic reinnervation is well evaluated. Adriamycin-induced cardiotoxicity is detected earlier than ventricular dysfunction with sympathetic dysfunction. Neurodegenerative disorder such as Parkinson's disease or dementia with Lewy bodies has also cardiac sympathetic dysfunction. Noninvasive assessment of cardiac sympathetic nerve activity with I-123 MIBG imaging nay be improve understanding of the pathophysiology of cardiac disease and make a contribution to predict survival and therapy efficacy.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
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• pp.222-228
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• 2012

This paper presents a design and simulation of bi-directional DC/DC boost converter for a fuel cell system. In this paper, we analyze the equivalent model of both a boost converter and a buck converter. Also we propose the controller of bi-directional DC-DC converter, which has buck mode of charging a capacitor and boost mode of discharging a capacitor. In order to design a controller, we draw bode plots of the control-to-output transfer function using specific parameters and incorporate 3pole-2zero compensator in a closed loop. As a result, it has increased PM(Phase Margin) for better dynamic performance. The proposed bi-directional DC-DC converter's 3pole-2zero compensation method has been verified with computer simulation and simulation results obtained demonstrates the validity of the proposed control scheme.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1991년도 수공학논총 제33권
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• pp.88-101
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• 1991

충주댐 및 소양강댐 유역에 대해 현재 한국수자원공사에서 개발 사용되고 있는 저류함수 유출모형에 최적화 기법을 적용하여 모형을 효율적으로 자동보정 하기위함이 본 연구의 목적이다. 최적화 기법으로는 다양한 조건하에서도 해의 안정성이 Gradient-Based 방법보다 우수한 직접 탐색법(Direct Search Method)의 하나인 Pattern-Search법으로 선정하였으며 목적함수로는 산정된 유출과 관측치의 편차의 제곱에 대한 누계치로 정의하였다. 합성유입량(Synthetic Inflow)을 이용한 민감도 분석에 의해 매개변수 5개(유역 저류상수 및 지체시간, 포화우량, 하도의 지체시간)를 결정변수로 선정하였다. 또한 실시간 모형의 보정을 위하여 최적화 모형의 수렴조건을 분석한 결과 P-S 법의 증분 감소횟수 2회가 합리적으로 나타났다. 본 모형을 충주댐 및 소양강댐의 과거 홍수사상에 대해 적용하였으며 댐지점에서 전체유역을 일괄 보정하는 방법과 댐 상류 수위국을 기준으로 나눈 중유역별로 일괄 보정하는 방법을 채택하여 분석하였다. 실시간 보정된 모형의 예측기능을 시험한 결과 상당한 오차발생의 여지가 충분하며 중유역별 매개변수의 보정은 대유역 일괄보정에 비해 예측에 따른 오차를 줄일 수 있는 방법의 하나이다. 또한 최적화 기법에 의한 매개변수의 자동 보정은 시행착오에 의한 수동보정의 경우보다 시간 및 노력면에서 효율적이며 보다 신뢰성 있는 보정을 실시 할 수 있다.

• 한국환경복원기술학회지
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• 제7권1호
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• pp.97-109
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• 2004

The disposal of stormwater is one of the major problems in urban water management. One method of reducing peak runoff rates and other detrimental impacts of stormwater is detention storage. Detention ponds as a water quality control alternatives have been investigated by a number of researchers. Recognizing multiple roles such as flood peak attenuation, pollution removal and aesthetic enhancement, the design and management of detentions ponds deserve more research. The purpose of this research is to establish design criteria wet detention ponds to improve water quality. Water quality in detention pond discharge might be improve with physical, chemical and biological alterations. Physical alteration was focused in this study. There are several methods for estimating the suspended solid control capability of wet detention ponds. Existing models of suspended solids removal are based on sedimentation and gravity settling theory. The pollutant trap efficiency of pond is a function of several interrelating factors. Detention time is the most important factor, because it determine gravity settling quantities of pollutants. Desirable modification of physical factors for improvement of water quality in wet detention ponds are volume ratio, area ratio, length to width ratio, depth, out let location, bottom soil type. In order to apply design procedure in actual site, Namak new town development area was selected.

• 한국수자원학회논문집
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• 제30권2호
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• pp.131-141
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• 1997

본 연구에서는 저류함수법과 Loopnet(부정류해석모형) 모형으로 홍수예측 시스템을 구성하여 대청댐의 방루에 따른 하류지역의 홍수영향을 에측하여 보았다. 대청댐 하류부에 지역빈도 분석방법(L-모멘트)으로 강우량을 산정하고, 홍수예측시스템으로 금강 하류부의 홍수추적을 실시하여 빈도별 홍수량을 산정하였다. 또한 대청댐의 방류에 따른 금강 하루 주요지점의 홍수량, 홍수위 및 방류량 도달시간을 산정하여 홍수발생시 대청댐 운영의 지표포 활동할 수 있도록 하였다.