In this paper it is explained how most of asteroids can avoid very close approach to Jupiter, to the earth for earth orbit crossing asteroids, and to Neptune for Kuiper-belt asteroids by mechanisms which work also for Neptune-Pluto system. In fact the mutual distance of the planets cannot become very small as the critical argument librates around 180° because of 2:3 mean motion resonance and the argument of perihelion of Pluto librates around 90°. And it is found that among nearly 40 Kuiper-belt asteroids discovered in recent years 40% have orbits similar to Pluto. For main-belt asteroids the distribution with respect to the semi-major axes has peculiar characteristics and the author tries to explain how their peaks and gaps are created. It is also found that 30% of 80 earth orbit crossing asteroids which have minimum perihelion distances less than 1.04AU have no chance to collide with the earth. Still 30% of them have a few probability to collide with the earth as they have dynamical characteristics of short-periodic comets.

고진공하에서 벽개된 GaAs를 대기중 노출시킨후, 결합상태 및 조성의 변화를 정량적으로 연구하여 Ga의 우선적 산화경향 및 결합의 붕괴에 기인한 원소상태 Ga 및 As의 생성을 관찰하였다. 대기중 노출시, 초기 Ga/As 비(=0.01)는 Ga의 우선적 산화에 의해 증가하였으며 원소상태 As의 증가와 더불어 일정값(=1.25)으로 유지되었다. 습식세정된 GaAs와 유황처리된 (S-passivated)GaAs를 각각 대기중에 노출시켜, 각각의 표면상태 변화를 비교, 관찰하였다. 유황처리된 GaAs는 습식세정처리만한 GaAs에 비해 산화막 성장이 크게 억제되었고, 이는 (NH4)2Sx 용액 처리로 형성된 Ga-S 및 As-S 겹합의 표면보호 효과에 기인한 것이다. 특히 대기중 노출에 따른 유황처리된 GaAs 표면조성 및 결합상태 변화의 정량적 관찰을 통하여, 유황보호막(S-passivation layer) 및 GaAs 표면과 대기중 산소와의 반응 기구를 규명할 수 있었다. 대기중 노출에 따라, 표면의 Ga-S 및 As-S 결합은 대기중 산소와 반응하여 점차 붕괴, 감소하는 경향을 나타냈으며, 이와 동시에 unpassivated 상태의 GaAs가 산소와 반응하여 Ga-O 결합을 형성함을 관찰할 수 있었다. 본 연구에서는 X-선 광전자 분광기를 사용하여 GaAs 표면 조성 및 결합상태의 변화를 관찰하였다.

본 논문의 목적은 단충래티스 돔의 안정해석 기법을 제안하고， 다양한 조건하에서 단충래티스 폼이 갖는 좌 굴특성을규명하는데 있다. 기하학적 비선형 평형경로의 탐색 및 좌굴점 그리고분기경로의 방향퉁올수치적 으로 계산하기 위하여 孤長法(Arc-Length Method) 을 이용하였으며， 부재의 좌굴가능성올 판단하기 위하여 에너지밀도함수를 제안하였다. 강절점을 갖는 구조물의 거동 특성을 규명하기 위하여 3 종류의 비선형 강성 행렬을 유도하여 해석하였으며， semi-rigid 절점올 갖는 구조울올 해석하기 위하여 스프링모델을 제안하고， 부재의 세장비， 반개각(半開角)， 경계조건 및 다양한 하중조건을 파라메터로 하여 좌굴특성올 규명하였다.

The liposomes have been developed in many drugs and cosmetics fields. The liposomes prepared with main compounds of the intercellular lipids and lecithin. Amphiphile nonionic surfactants used for (PEG) n-sitosterol(n=5), diethanolamine cetylphosphate. The effect of gelation for liposomes have been on swelling reaction which have been mixed phospholipid with polyol-group at the high temperature. There were very good encapsulated properties of the active ingredients whether hydrophilic-group(magnesium ascorbyl phosphate, allantoin, sodium hyaluronate) and hydrophobic-group(vitamin-E acetate, vitamin-A palmitate). Optimum condition of liposomes were passed five times in the microfluidizer(700bar), wetting reaction temperature was at 95±5℃ for a hours. Particle size distribution of the vesicles should be within range 50-560nm(mean 200nm). The stability of liposomes for the course of time was stabilized for six months at 45℃. Application of the cosmetic was prepared moisturizing cream with liposomes of the phospholipid base.

This paper considers robust stability and transient behavior of the Two - Degree - of - Freedom(2DOF) servosystem. A class of uncertainties allowed in the plant model is obtained, to which the servosystem is robustly stable for any gain of the integral compensator. This result implies that if the plant uncertainty is the allowable set defined by the condition, a high - gain compensation can be carried out preserving stability to achieve a high - speed tracking response. The transient behavior attainable by the limit of the high - gain compensation is calculated using the singular perturbation approach.

Microwave용 GaAs MESFET 소자에 적용가능한 Schottky 접합구조로서 Au/Nb/WNx(Si) 다층박막의 특성을 평가하였다. WNx 증착시 co-sputtering에 의하여 첨가된 실리콘은 열처리 과정 동안 GaAs/Schottky 계면으로 확산되며 이 과정은 sputtering damage의 회복이 활성화되는 700˚C이상에서 활발해진다. 계면으로 축적된 실리콘은 Ga와 As의 유효한 확산 경로를 차단함으로서 Ga의 확산으로 인한 GsAs 내의 carrier 농도 증가를 최소화 할 수 있어서 WNx와 같은 Schottky 접합재료의 열적 안정특성의 향상을 기대할 수 있다. Au/Nb의 층을 적층시 Nb는 탈탈륨 등의 고융점 금속과 같이 sacrificial 형태의 확산방지막으로 작용하여 열적으로 안정하며 microwave용 소자에서 요구되는 낮은 비저항치(-10-5Ω-cm)를 유지할 수 있다.

기계적합금화한 Al-8wt.%(Ti+Zr)합금의 열적안정성에 미치는 Zr첨가의 영향에 대하여 조사하였다. Ti에 대한 Zr의 첨가비가 증가함에 따라 고온에서 장시간 노출에 따른 합금의 경도감소가 저하되어 합금의 열적안정성이 향상된 결과를 나타내었는데 이는 TEM 관찰결과 분산입자의 조대화가 억제되었기 때문이었다. XRD, SAD 및 EDS 분석결과 이러한 분산입자들은 DO2+와 DO23구조를 갖는 Al3(Ti+Zr)삼원계 금속간화합물이었으며 특히 DO23Al3(Ti+Zr)은 Zr의 첨가비가 증가함에 따라 보다 작은 Al기지와의 격자간불일치도를 갖는 방향으로 격자상수가 변화하여 합금의 열적안정성 향상에 주된 기여를 한 것으로 생각된다

The theoretical optimum quaternary composition for improving the thermal stability of Al-Ti alloy was recently proposed. On the basis of the suggestion, quaternary Al-Ti-V-Zr alloy powders corresponding to the optimum compositions, one of which belongs to the region of the smallest lattice misfit between the matrix and the precipitates and the other belongs to the region of the smallest rate constant of coarsening, were prepared by mechanical alloying and the powders were vacuum-hot-pressed at under the pressure of 800 MPa. The thermal stability of the specimens was evaluated by hardness testing after isothermal aging up to 400 hrs at various temperatures. The decrease of hardness of Al-Ti-V-Zr alloys was smaller than that of Al-Ti alloys. It was considered to be due to the formation of type and type quaternary precipitates having smaller lattice misfit than and the increase of volume fraction of All0v during the isothermal aging. The quaternary Al-Ti-V-Zr alloys corresponding to the smallest lattice misfit showed the most improved thermal stablilty and it was mainly considered to be due to the formation of All0v.

Diglycidyll ether of bisphenol A(DGEBA)/4, 4'-methylene dianiline(MDA)계에 반응성 첨가제 malononitrile(MN)을 첨가하면 내충격성은 크게 향상되나 반응속도는 감소하게 된다. 에폭시 수지의 경화반응은 에폭시기가 개환되어 생성되는 히드록시기가 촉매로 작용하는 자촉매 반응이며, 외부에서도입된 히드록시기도 같은 효과를 나타낸다. 따라서 본 연구에서는 DGEBA/MDA/MN 계의경화 반응속도를 증가시키기 위해 히드록시기를 가진 촉매로서 hydroquinone(HQ)을 도입하였고 이들 계의경화특성 및 열적성질을 고찰하였다. HQ가 첨가됨으로 인해 활성화 에너지는 감속하고 속도상수는 증가하였으며, 발열곡선에서 반응 시작온도가 낮아졌다. 이 결과로부터 HQ가 반응 가속제로 작용하고 있음을 알 수 있다.

Hexyltriphenylphosphonium-TCNQ(HTPP-TCNQ) complex for preparing organic thin film by Langmuir-Blodgett technique was synthesized from LiTCNQ and Hexyltriphenylphosphonium bromide. The structure of the new complex was confirmed by 1H NMR, 31P NMR, IR, UV spectroscopies, TGA and elemental analysis. A stability to spreading solvent, which is acetonitrile, ethylacetate, ethanol and acetonitrile-ethylacetate(1:1 v/v), of HTPP-TCNQ complex was investigated by UV-visible spectrophotometer. The complex was stabilized in acetonitrile, ethylacetate, aceton, acetonitrile-ethylacetate (1:1 v/v) for 6 h.

The Synthesis of long chain fatty acid containing azobenzene and (Cn-Azo) was optimized, starting from p-(p'-hydroxy phenyl azo)-benzoic acid and the product of reaction containing azobenzene chromophores was investigated by ultraviolet spectrophotometery in chloroform solvent at the various temperature. In addition, Reversibility and stability of azo compounds have been measured by means of Ultraviolet and the structure of these compound were ascertained by means of FT-IR and NMR. Recrystallization of reaction product in the solvent results the experimental yield obtained about 62.93% p-(p'-octadecyloxy phenyl azo)-benzoic acid. Long chain azobenzene derivatives in chloroform solution are induced photoisomerization by u. v. and visible light irradiation. The solution of long chain fatty acids(Cn-Azo) containing azobenzene are possible of being applied to functional molecular devices such as photomemory and light switching.

In this outline, the stability of solid/liquid dispersion was theoretically investigated the matter from all angles by using the modified DLVO theory. The stability was handled various considerations such as a production and characteristics of electrical double layer, total interaction(VT) that consisting of attractive force(VA) and repulsion(VR). coagulation, the stability ratio(W), critical flocculation concentration (cfc) and zeta potential(ξ) etc. It was possible for us to examine with the stability ratio(W), critical flocculation concentration (cfc) and zeta potential(ξ) that may estimation of stability of solid/liquid dispersion experimentally.

The stability of the geometrically thin, two-temperature hot accretion disk is studied. The general criterion for thermal instability is derived from the linear local analyses, allowing for advective cooling and dynamics in the vertical direction. Specifically, classic unsaturated Comptonization disk is analysed in detail. We find five eigen-modes: (1) Heating mode grows in thermal time scale, (5/3)(αω)-1, where alpha is the viscosity parameter and w the Keplerian frequency. (2) Cooling mode decays in time scale, (2/5)(Te/Ti)(αω)-1, where Te and Ti are the electron and ion temperatures, respectively. (3) Lightman-Eardley viscous mode decays in time scale, (4/3)(Λ/H)2(αω)-1, where Λ is the wavelength of the perturbation and H the unperturbed disk height. (4) Two vertically oscillating modes oscillate in Keplerian time scale, (3/8)1/2ω-1 with growth rate ∝(H/Λ)2. The inclusion of dynamics in the vertical direction does not affect the thermal instability, adding only the oscillatory modes which gradually grow for short wavelength modes. Also, the advective cooling is not strong enough to suppress the growth of heating modes, at least for geometrically thin disk. Non-linear development of the perturbation is followed for simple unsaturated Compton disk: depending on the initial proton temperature perturbation, the disk can evolve to decoupled state with hot protons and cool electrons, or to one-temperature state with very cool protons and electrons.

점박이응애(Tetranychus urticae Koch)의 감수성계통(S)과 dicofol 저항성계통(R)을 공시하여 dicofol저항성의 안정성을 조사하였다. Dicofol 저항성계통(저항성비 23.0)의 약제도태없는 조건하에서 사육된 암컷성충의 dicofol에 대한 저항성 수준은 1년이 경과된 후에도 변화가 없었다. 그러나 1년 이후부터는 감소하기 시작하여 2년째에는 저항성비가 15.8배, 3년째에는 10.7배로 감수성쪽으로 기울었다. 점박이응애의 dicofol 저항성계통과 감수서계통의 상호교배 에서 얻어진 세대별 약제 감수성도 세대가 경과됨에 따라 감수성쪽으로 기울었다.

대두유를 튀김유로 사용하여 french fried potato를 185℃에서 제조하면서 84시간 튀김한 후 aluminium alloy (물, silicone, manganese, porous aluminium carrier을 함유)를 처리한 감자튀김유와 대조구의 물리화학적변화를 측정하였다. 물리화학적 변화의 척도로는 극성지질, 중합체의 함량, 공액이중산가 및 유리지방산가를 사용하였다. Aluminium alloy를 처리한 시료는 대조구에 비해 극성지질 및 중합체 형성을 크게 억제하였으며 공액이중산가 및 유리지방산가의 증가 억제에는 영향을 주지 않았으며 유리지방산가의 경우 오히려 촉진되는 결과를 보였다 따라서 튀김유에 대한 aluminium alloy의 처리는 유리지방산이나 공액이중산의 형성억제보다는 극성지질 및 중합체의 형성억제에 효과적임을 알 수 있었다.

The objective of this study was to determine effects of soybean oil(SO), cottonseed oil(CO) and ricebran oil(RO) on stability and flavor of yackwa. This study consisted of yackwa fried in 3 differnet oils, then stored for 0, 3, 6 weeks in normal wrap at room temp. or vaccum package at 4℃. The moisture, oil contents, Hunter color values(L, 'a' and 'b'), % free fatty acid(FFA), thiobarbituric acid(TBA) value and sensory scores for color, flavor and acceptability were analyzed. The foam height of the oil after frying was also determined. Yackwa fried in RO was more red('a'=11.43) than yackwa fried in SO(10.64) or CO(10.51). TBA value of yackwa showed no difference among frying oils. Yackwa fried in SO showed better acceptability than those fried in CO. Yackwa fried in RO showed similar acceptability to yackwa fried in SO. The % FFA and TBA value of yackwa averaged across oil and package showed increasing tendency during 6 weeks storage.

A stability to the spreading solvent, which is acetonitrile, benzene, chloroform and acetonitrile-benzene(1:1, v/v) of (3-Alkyl benzimidazdium)-TCNQ(1:2) complex was investigated by UV-visible spectrometer and was confirmed stabilized on acetonitrile, acetonitrile-benzene (1:1, v/v) for five hours. Using Ultra pure water as subphase for Langmuir-Blodgett(LB) films, it was achived successively to fabricate the Y-type LB films of (3-Alkyl benzimidazolium)-TCNQ(1:2) complex. For the identification of (3-Alkyl benzimidazolium)-TCNQ(1:2) complex, UV-visible spectra was recorded on HP 8452A spectrometer.