• Journal of Powder Materials
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• v.9 no.1
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• pp.19-24
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• 2002

This paper reports the results of an investigation into the effect of Cu additions upon the nano-crystallization behaviour of an Al-Y-Ni alloy. 1 at.% Cu was added to a base alloy of Al/sub 88/Y₄Ni/sub 8/ either by substitution for Al to form Al/sub 87/Y₄Ni/sub 8/Cu₁, or by substitution for Ni to form Al/sub 88/Y₄Ni/sub 7/Cu₁. Consistent with previous findings in the literature, the substitution of Cu for Al was found to increase the thermal stability of the amorphous phase whereas the substitution of Cu for Ni was found to decrease its thermal stability. Comparing the microstructures of these alloys after heat treatment to produce equivalent volume fractions of Al nanocrystals showed average grain sizes of 14 nm, 12 nm and 9 nm for the alloys Al/sub 88/Y₄Ni/sub 8/, Al/sub 87/Y₄Ni/sub 8/Cu₁respectively. The effect of Cu in refining the size of the nanocrystals was attributed to enhanced nucleation increasing the number density of the nanocrystals, rather than diffusion limited or interface limited growth.

• Journal of Pharmaceutical Investigation
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• v.19 no.1
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• pp.1-7
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• 1989

Coprecipitates of ibuprofen (IPF)-sodium deoxycholate (DC-Na) were prepared at various mixing ratios of IPF to DC-Na. X-ray diffraction measurments indicated that IPF in 1:3 and 1:5 IPF-DC-Na coprecipitate did not exist in the crystal form, however in the 1:8 coprecipitate, IPF remained its crystalline form. The dissolution rate was tested in pH 7.4 phosphate buffer by the paddle method of dissolution test of KP V. The dissolution rates of IPF from 1:1, 1:3, 1:5, 1:8 and 1:10(w/w) IPF-DC-Na coprecipitates and physical mixtures were compared with that of IPF alone. It was found that the dissolution rate of 1:5(w/w) coprecipitate was greater than that of pure IPF, coprecipitate and physical mixture at any other ratios of the two components. The concentration of IPF released from the IPF-DC-Na coprecipitates reached a plateau within 10 min, and thereafter gradually decreased indicating that IPF released from the coprecipitate was recrystallized due to the transient supersaturation.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.459-459
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• 2000

The purpose of this paper is the application of the techniques for the new estimation of robustness for the aircraft systems having structured uncertainties. The basic ideas to analyze the system which is the originally nonlinear is Lyapunov direct theorems. The nonlinear systems have various forms of terms inside the system equations and this investigation is confined in the form of bounded uncertainties. The number of uncertainties will be the degree of freedoms in the calculation of the robust stability regions called the robustness bounds. This proposition adopts the theoretical analysis of the Lyapunov direct methods, that is, the sign properties of the Lyapunov function derivative integrated along finite intervals of time, in place of the original method of the sign properties of the time derivative of the Lyapunov function itself. This is the new sufficient criteria to relax the stability condition and is used to generate techniques for the robust design of control systems with structured perturbations. Using this relaxing stability conditions, in this paper, the quadratic form of Lyapunov function is utilized. In this paper, the practical system of vertical take-off and landing (VTOL) aircraft is analyzed with the proposed stability criteria based upon the Lyapunov direct method. The application of numerical procedures can prove the improvements in estimations of robustness with structured uncertainties. The applicable aircraft system is assumed to be linear with time-varying with nonlinear bounded perturbations.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.271-271
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• 2010

Using ab initio density functional theory, we investigate the dimerization and one-dimensional (1-D) polymerization of metal-encapsulated gold nanoclusters, M@$Au_{12}$ (M=W, Mo) and their structural and electronic properties. M@$Au_{12}$ clusters with a magic number 13 can form icosahedral and cuboctahedral structures. We consider various dimer configurations with different compounds and symmetries to find the most stable dimer structure in each case. Au atoms in the one cluster, which participate directly in dimerization, tend to form triangular bonds together with counterpart Au atoms in the other. It is found that both M@$Au_{12}$ and M@$Au_{12}$ clusters are stabilized by about 3 eV due to dimerization. We also calculate and compare the electronic and magnetic properties of different dimerized clusters. Based on our investigation on dimerization, we further study on 1-D polymerization of M@$Au_{12}$ with different compounds and symmetries. We will also discuss their formation energies as well as their electronic and magnetic properties.

• Journal of Pharmaceutical Investigation
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• v.30 no.1
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• pp.33-37
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• 2000

One of the methods to increase the solubility of a drug is to use complexation with a cyclodextrin. Due to the hydrophobic nature of the interior cavity of the cyclodextrin, it has been known that undissociated lipophilic drugs can be included within the cyclodextrin by hydrophobic interaction. Recently, inclusion of hydrophilic or dissociated form of a drug has been investigated. In this study, the synergism of pH and complexation with $hydroxypropy-{\beta}-cyclodextrin\;(HP\;{\beta}\;CD)$ to increase the solubility of two oxicam derivatives was investigated. In addition, the effect of partition coefficient of dissociated and undissociated form of the drug on the extent of complexation with HP ${\beta}$ CD was studied. The solubility was measured by equilibrium solubility method. The solubility of tenoxicam and piroxicam increased exponentially with an increase in solution pH above the pKa of the drug in the presence and absence of HP ${\beta}$ CD. The solubility of the drugs increased linearly as a function of HP ${\beta}CD$ concentration at fixed pH. Although the stability constant of ionized species is less than that of the unionized species, the concentration of the ionized drug complex is greater than that of the unionized drug complex due to higher concentration of ionized species at pH 7.3.

• Korean Journal of Materials Research
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• v.18 no.5
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• pp.272-276
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• 2008

In submicron MOSFET devices, maintaining the ratio between the channel length (L) and the channel depth (D) at 3 : 1 or larger is known to be critical in preventing deleterious short-channel effects. In this study, n-type SOI-MOSFETs with a channel length of $0.1\;{\mu}m$ and a Si film thickness (channel depth) of $0.033\;{\mu}m$ (L : D = 3 : 1) were virtually fabricated using a TSUPREM-4 process simulator. To form functioning transistors on the very thin Si film, a protective layer of $0.08\;{\mu}m$-thick surface oxide was deposited prior to the source/drain ion implantation so as to dampen the speed of the incoming As ions. The p-type boron doping concentration of the Si film, in which the device channel is formed, was used as the key variable in the process simulation. The finished devices were electrically tested with a Medici device simulator. The result showed that, for a given channel doping concentration of $1.9{\sim}2.5\;{\times}\;10^{18}\;cm^{-3}$, the threshold voltage was $0.5{\sim}0.7\;V$, and the subthreshold swing was $70{\sim}80\;mV/dec$. These value ranges are all fairly reasonable and should form a 'magic region' in which SOI-MOSFETs run optimally.

• Journal of architectural history
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• v.1 no.1 s.1
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• pp.49-67
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• 1992

This study is an architectural investigation paper which has been investigated for 5 years from 1986 about commoner's traditional houses and village in southwestern island area of Korea. Man has lived in this area form the prehistoric age. But from 13C to 14C and in 16C most of people had left this islands by external invasion (Japan) and from 17C many people have lived in real earnest. This area did not have cultural interchange easily than inland area because of geographical conditions, Therefore, so far, many traditional factors have been handed down and especially, a good many commoner's traditional houses exist. The time of builging of these houses is mainly 19C and building shape of those days remains nearly as it is. About 450 houses have been investigated for 5 years. The composition of the houses is composed of Anchae (a centeral house), Sarangchae (an attached house of anchae) and Chukganchae (It has rest room and stores barnyard manure). Somtimes, Sarangchae was ommitted according to the circumstance of the house. Generally, the form of arrangement of house is divided into two shapes; One is 'ㅡ'shape which has only Anchae and the other is 'ㄱ' shape which has Anchae and Sarangchae. In the scale of the house, Anchae averages $41m^2$ and Sarangchae averages $27m^2$.

• Journal of Auto-vehicle Safety Association
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• v.12 no.2
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• pp.47-55
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• 2020

In this case study, the brake line failure of air over hydraulic(AOH) brake system is described. AOH brake system is applied to commercial vehicles between 5 to 8 tons. It consists of a hydraulic system using compressed air and operates the air master to form hydraulic pressure to transfer braking power to the wheels. When the brake lines of the system applied to vehicles with high load capacity are damaged, the braking force of one shaft is lost, and the braking distance increases rapidly, leading to a big accident. Failure of the brake line occurs due to various causes such as road surface fragmentation, corrosion of the line, and aged deterioration of air brake hose. The braking force could be decreased even when a very small break in the form of a pin-hole occurs. However, it is difficult to find a part where the thickness of the line is thin due to stone pecking or corrosion generated in the pin-hole formed on the brake line located under the lower part of the vehicle by the sensory evaluation or the conventional braking force test. Accordingly, it is necessary to analyze the condition and cause of the failure of the brake line more precisely when the accident investigation of the heavy vehicles, and also to examine the necessity of the advanced test for the aged brake line.

• Structural Engineering and Mechanics
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• v.12 no.3
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• pp.249-266
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• 2001

Current seismic design provisions allow structures to deform into inelastic range during design level earthquakes since the chance to meet such event is quite rare. For this purpose, design base shear is defined in current seismic design provisions as the value of elastic seismic shear force divided by strength reduction factor, R (${\geq}1$). Strength reduction factor generally consists of four different factors, which can account for ductility capacity, overstrength, damping, and redundancy inherent in structures respectively. In this study, R factor is assumed to account for only the ductility rather than overstrength, damping, and redundancy. The R factor considering ductility is called "ductility factor" ($R_{\mu}$). This study proposes ductility factor with correction factor, C, which can account for dynamic P-${\Delta}$ effect. Correction factor, C is established as the functional form since it requires computational efforts and time for calculating this factor. From the statistical study using the results of nonlinear dynamic analysis for 40 earthquake ground motions (EQGM) it is shown that the dependence of C factor on structural period is weak, whereas C factor is strongly dependant on the change of ductility ratio and stability coefficient. To propose the functional form of C factor statistical study is carried out using 79,920 nonlinear dynamic analysis results for different combination of parameters and 40 EQGM.

• Wind and Structures
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• v.1 no.4
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• pp.317-336
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• 1998

In this paper the appraisal of a folding dome structure under the influence of wind loading is discussed. The foldable structure considered is constructed from an assembly of interconnected elements, together with a flexible membrane, all of which are initially store in a compact form and on deployment expand, like an umbrella, into a dome structure. Loading on the dome was obtained from a wind tunnel analysis of the pressure distribution over the roof of a 1:10 scale model of the structure. The critical loading obtained from the wind tunnel investigation was used, together with individual member and material tests, to form a series of numerical non-linear finite element models which were, in turn, used to investigate the forces within the structure. The numerical analysis was used to determine the critical wind loading that the structure can sustain, as well as providing a method by which to investigate the failure modes of the structure. In order to enhance the load carrying capacity of the dome it was found that both the strength and stiffness of the structural nodes needed to be enhanced and in addition, changes were necessary to substantially increase the stiffness of the individual member and caps.