• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1078-1084
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• 2005

The relationship between fatigue crack opening behavior and the reversed plastic zone sizes is studied. An elastic-plastic finite element analysis (FEA) is performed to examine the opening behavior of fatigue crack, where the contact elements are used in the mesh of the track tip area. The smaller element size than reversed plastic zone size is used fer evaluating the distribution of reversed plastic zone. In the author's previous results the FEA could predict the crack opening level, which crack tip elements were in proportion to the theoretical reversed plastic zone size. It is found that the calculated reversed plastic zone size is related to the theoretical reversed plastic zone size and crack opening level. The calculated reversed plastic zone sizes are almost equal to the reversed plastic zone considering crack opening level obtained by experimental results. It can be possible to predict the crack opening level from the reversed plastic zone size calculated by finite element method. We find that the experimental crack opening levels correspond with the opening values of contact nodes on the calculated reversed plastic zone of finite element simulation.

• Korean Journal of Human Ecology
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• v.24 no.6
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• pp.811-827
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• 2015

The purpose of this study was to explore the factors related to depression of female elderly living alone by region. Data for this study was based on the 2011 National Survey on Elderly. Total of 1,684(689 rural elderly, 995 urban) community samples of female elderly living alone participated in this study. Even though there was no difference of depression score by region, this study found that the effects of factors on depression were significantly different by region. Yearly income, subjective health, balanced exchange of emotional support and satisfaction with their children were significantly associated with depression of both rural and urban female elderly living alone. For rural female elderly living alone, average daily television viewing time, number of close friends and frequency of contact with friends/neighbors were significant predictors to their depression. In the case of urban female elderly living alone, exercise, frequency of message, email or telephone contact with friends/ neighbors and balanced exchange of economic support contributed significantly to the prediction of depression. Subjective health had the strongest effect on depression for both rural and urban female elderly living alone.

• Journal of the Korean Magnetic Resonance Society
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• v.19 no.3
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• pp.149-155
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• 2015

Acyl carrier protein is related with fatty acid biosynthesis in which specific enzymes are involved. Especially, acyl carrier protein (ACP) is the key component in the growing of fatty acid chain. ACP is the small, very acidic protein that covalently binds various intermediates of fatty acyl chain. Acylation of ACP is mediated by holo-acyl carrier protein synthase (ACPS), which transfers the 4'PP-moiety of CoA to the 36th residue Ser of apo ACP. Acyl carrier protein P (ACPP) is one of ACPs from Helicobacter plyori. The NMR structure of ACPP consists of four helices, which were reported previously. Here we show how acylation of ACPP can affect the overall structure of ACPP and figured out the contact surface of ACPP to acyl chain attached during expression of ACPP in E. coli. Based on the chemical shift perturbation data, the acylation of ACCP seems to affect the conformation of the long loop connecting helix I and helix II as well as the second short loop connecting helix II and helix III. The significant chemical shift change of Ile 54 upon acylation supports the contact of acyl chain and the second loop.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11A
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• pp.1091-1096
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• 2010

Stiction in microelectromechanical systems (MEMS) has been a major failure mechanism. Especially, in RF MEMS switches, moving parts often suffered in-use and release related stiction problems. Some materials and methods have been used to prevent this problem. Diamond-like carbon (DLC) has not only been used as a protective material owing to its good mechanical properties but also has been used as a hydrophobic material. Its properties could be controlled by post annealing treatment in various conditions. We synthesized DLC films using a radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method on silicon substrates using methane ($CH_4$) and hydrogen ($H_2$) gas. Then, the change of the hydrophobic property of the films was investigated undervarious annealing temperatures in nitrogen and in oxygen ambient. The films, that were annealed above $700^{\circ}C$ in nitrogen ambient, showed a high contact angle of water (> $90^{\circ}$) even though their mechanical property was sacrificed to some degree. The structural variation and the changes of the hydrophobic and mechanical properties of the DLC films were analyzed by Raman spectrum, contact angle measurement, surface profiler, and a nanoindentation test.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.9
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• pp.967-972
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• 2004

Hardness and surface property of coated gel materials are considerably different according to kinds(particle size/stabilized ion) of colloidal silica(CS), kinds of silanes, content ratio of silane versus CS, and reaction degree in sol solution. We report the properties of sol-gel coating materials in which the factors of reaction are kinds of CS, contents ratio of CS and MTMS, and reaction time of sol. The contact angles of the coated films obtained from the mixed CS system showed a little good relationship with MTMS content increase to those from HSA CS reaction system and the change of contact angle didn't have much effect on reaction time of sol. In the coating films obtained from HSA CS reaction system, the surface was much rough in case of that the content MTMS decreased and the reaction of sol kept long. The surface roughness of films obtained from the mixed CS reaction system showed similar tendency, though its degree was a little different. In synthesis of sol-gel coating materials, we could identify that choice of CS kinds and content ratio of CS and silane were important and it was desirable the reaction time of sol is not long.

• Journal of Surface Science and Engineering
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• v.45 no.1
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• pp.8-14
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• 2012

The effects of the alkali surface modification process on the adhesion strength between electroless-plated Cu and polyimide films were investigated. The polyimide surfaces were effectively modified by alkali surface treatments from the hydrophobic to the hydrophilic states, and it was confirmed by the results of the contact angle measurement. The surface roughness increased by alkali surface treatments and the adhesion strength was proportional to the surface roughness. The adhesion strength of Cu/polyimide interface treated by KOH + EDA (Ethylenediamine) was 874 gf/cm which is better than that treated by KOH and KOH + $KMnO_4$. The results of XPS spectra revealed that the alkali treatment formed oxygen functional groups such as carboxyl and amide groups on the polyimide films which is closely related to the interfacial bonding mechanism between electroless-plated Cu and polyimide films. It could be suggested that the species and contents of functional group on polyimide films, surface roughness and contact angle were related with the adhesion strength of Cu/polyimide in combination.

• The KSFM Journal of Fluid Machinery
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• v.17 no.2
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• pp.30-34
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• 2014

Membrane distillation (MD) is a thermal driven separation process in which separation a hydrophobic membrane is a barrier for the liquid phase, letting the vapor phase pass through the membrane pores. Therefore, a porous and hydrophobic membrane should be used in membrane distillation. MD cannot work if water penetrates into the pores of the membrane (membrane wetting). Accordingly, it is necessary to prevent wetting of MD membranes and to remove water inside the pores of the wetted membranes if possible. In this context, our study aimed to develop methods to recover wetted membranes in MD processes. Poly-vinylidene fluoride (PVDF) membranes were used in this study. A laboratory-scale direct contact MD (DCMD) system was used to examine the effect of operating parameters on wetting. For dewetting the wetted membranes, specific techniques including the use of high temperature air were applied. The performances of the membranes before and after dewetting were compared in terms of flux, salt rejection and liquid entry pressure(LEP). The surface morphology of dewetted membrane was confirmed by scanning electron microscope (SEM).

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.60-67
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• 2014

The battery cells in lithium-ion battery pack assembled with high-capacity and high-power pouch cells, are commonly cooled with thin aluminum cooling plates in contact with the cells. For HEV/EV lithium-ion battery systems assembled with high-capacity, high-power pouch cells, the cells are commonly cooled with thin aluminum cooling plates in contact with the cells. Thin aluminum cooling plates are cooled by cold plate with coolant flow paths. In this study, the effect of the battery cooling system design including aluminum cooling plate thickness and various position of cold plate on the cooling performance are investigated by using finite element methods (FEM). Optimal cooling plate and cold plate design are proposed for improving the uniformity in temperature distributions as well as lowering average temperature for the cells with large capacities based on the simulation results.

• KSTLE International Journal
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• v.5 no.1
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• pp.1-6
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• 2004

Nano-scale studies on adhesion and friction were conducted in Si-wafer (100) using Atomic Force Microscopy (AFM). Glass (Borosilicate) balls of radii 0.32$\mu\textrm{m}$, 1.25$\mu\textrm{m}$, and 2.5$\mu\textrm{m}$, mounted on cantilever (Contact Mode type NPS) were used as tips. Adhesion and friction between Si-wafer and glass tips were measured at ambient temperature (24${\pm}$1$^{\circ}C$) and humidity (45${\pm}$5%). Friction was measured as a function of applied normal load in the range of 0-160 nN. Results showed that, both adhesion and friction increased with the tip radii. Also, friction increased linearly as a function of applied normal load. The effect of tip size on adhesion and friction was explained as the influence of the capillary force exerted by meniscus and that of the contact area on these parameters respectively. The coefficient of friction was estimated in two different ways, as the slope from the plot of friction force against the applied normal load and as the ratio between the friction force and the applied normal load. Both these estimates showed that the coefficient of friction increased with the tip size. Further, the influence of the adhesion force on the coefficient of friction was also discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.123-124
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• 2006

Usually, hydraulic cylinder is widely used as the actuator in the equipment of construction machines, airplane and military machines. In case of these devices, due to use under severe environment such as water, $SiO^2$ and dust, etc. seal which has high packing ability and long service life has been required. These characteristics are largely influenced by material and geometries of seal such as approach angle, withdrawal angle and interference. Recently, many a study about seal material has been performed so that many materials have been developed. But the concrete studies including the relationships between geometry of seal and sealing performance have hardly been performed yet. Therefore, in this study, we predicted the deformation behavior and contact normal distribution of dust seal with the variation of geometries of seal lip using finite element analysis. And based on the results of analyses, we discussed the effects of the design variables fur sealing performance of the dust seal.