• Journal of the Korean Society of Clothing and Textiles
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• v.34 no.11
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• pp.1880-1888
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• 2010

This study was a preliminary investigation of the influence of surface characteristics of substrates on the detergency of particulate soil. A PET film was surface modified with NaOH and DMF for different times. The surface morphology of the film was scanned by AFM and the surface energies were calculated from the measured contact angles between several solutions and film based on a geometric mean and the Lewis acid base method. The surface morphology of the PET film treated with NaOH and DMF became more etched and swelled with an increased treatment time, respectively. The surface roughness and surface area of film treated with NaOH enlarged with increased treatment time. However, the coefficient of friction of film treated with NaOH and coefficient of friction, surface roughness, and surface area of film treated with DMF increased and then decreased with increased treatment time. The contact angle of film treated with DMF decreased with increased treatment time in water and surfactant solution; however, the effect of treatment time on the contact angle was different in both solutions for film treated with NaOH. By the treatment of PET film with NaOH and DMF, the polar group of the surface energy increased and the nonpolar group decreased; however, the change of total surface energy was not significant.

• Research in Community and Public Health Nursing
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• v.13 no.1
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• pp.171-181
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• 2002

Purpose: To provide the basic data for nursing intervention to improve the psychosocial adaptation of unemployed homeless by examining the degree of self-esteem, depression. and hope, and the relation of these variables. Method: The subjects were a volunteer sample of 218 unemployed homeless residing at 2 shelters in Seoul and Suwon, Korea. The instruments for this study were Rosenberg's self-esteem scale, Beck's depression inventory, and Miller and Powers's hope scale. Using the SPSS program, the data were analysed by frequency, percentage, t-test, ANOVA, Duncan test and Pearson Correlation Coefficient. Result: 1) The degree of self-esteem is, on average, 23.72 points, depression is 24.41 points, and hope is 124.72 points. 2) The degree of self-esteem in the general characteristics of the subjects showed a significant difference by age, marital status, and contact with family. 3) The degree of depression in the general characteristics of the subjects showed a significant difference by age, marital status, and contact with family. 4) The degree of hope in the general characteristics of the subjects showed a significant difference by contact with family. 5) There was a significant positive correlation between the variables of self-esteem and hope, while there was a significant negative correlation between the variables of self-esteem and depression, and hope and depression. Conclusion: 1) The study identifies psychological characteristics of the homeless. 2) It is required not only to develop nursing intervention programs to improve the degree of self-esteem and hope, and alleviate depression but also to testify the effect of the program. 3) It is needed to develop nursing intervention programs to prevent chronic homelessness.

• Journal of the Korean Vacuum Society
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• v.21 no.3
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• pp.151-157
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• 2012

The two dimensional electron gas system based on GaAs/$Al_xGa_{1-x}As$ heterostructure is widely used for fabricating quantum structures such as quantum dot, quantum point contact, electron interferometer and so on. However the conductance of the device is usually unstable due to the presence of random telegraph noise in the device. To overcome such problem, we have studied the effect of surface state on the stability of the device by altering the surface state of the device with oxygen plasma. The dramatic improvement of the device stability has been observed after cleaning the device surface with oxygen plasma (by 50 W~120 W plasma power) for 30 sec followed by etching in HCl : $H_2O$ (1 : 3) solution.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.1
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• pp.17-22
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• 2010

The enhancement of adhesion for Cr film on polycarbonate (PC) substrate with electron irradiation treatment was considered. The electron treatment changes the contact angle of the PC substrates. As increase the electron energy from 300 eV to 900 eV, the contact angle decreases from $90^{\circ}$ to $60^{\circ}C$. It is supposed that electron treatment changes the chemical property of PC substrate into hydrophilic one. The micro surface roughness was also affected by electron treatment. The PC substrates irradiated with intense electron beam of 900 eV show the rougher surface than those of other PC substrates. Cr thin films deposited on the PC substrate treated with electron irradiation at 900 eV show the higher adhesion than that of the Cr thin film deposited untreated bare PC substrates.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.98-106
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• 2016

Measurements of the elastic modulus and hardness using a nano indentation machine rely on the equation for the fitted contact area, which is valid for only sink-in materials. For most soft engineering materials that involve pile-up behavior rather than sink-in, the contact area equation underestimates the contact area and thus overestimates the elastic modulus and hardness. This study proposes a correction method to amend erroneous hardness measurements in pile-up situations. The method is a supplemental derivation to the original hardness measurement with the known value of the elastic modulus. The method was examined for soft engineering metals, Al 6061 T6 and C 12200, via tensile tests, nano indentation tests, impression observations, and finite element analysis. The proposed technique shows reasonable agreement with the analytical results accounting for strain gradient plasticity from a previous study.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.36.1-36.1
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• 2010

While the substrate-type solar cells with Cu(In,Ga)Se2 absorbers yield conversion efficiencies of up 20%[1], the highest published efficiency of Cu(In,Ga)Se2 superstrate solar cell is only 12.8% [2]. The commerciallized Cu(In,Ga)Se2 solar cells are made in the substrate configuration having the stacking sequence of substrate (soda lime glass)/back contact (molybdenum)/absorber layer (Cu(In,Ga)Se2)/buffer layer (cadmium sulfide)/window layer (transparent conductive oxide)/anti reflection layer (MgF2) /grid contact. Thus, it is not possible to illuminate the substrate-type cell through the glass substrate. Rather, it is necessary to illuminate from the opposite side which requires an elaborate transparent encapsulation. In contrast to that, the configuration of superstrate solar cell allows the illumination through the glass substrate. This saves the expensive transparent encapsulation. Usually, the high quality Cu(In,Ga)Se2 absorber requires a high deposition temperature over 550C. Therefore, the front contact should be thermally stable in the temperature range to realize a successful superstrate-type solar cell. In this study, it was tried to make a decent superstrate-type solar cell with the thermally stable ZnO:Al layer obtained by adjusting its deposition parameters in magnetron sputtering process. The effect of deposition condition of the layer on the cell performance will be discussed together with hall measurement results and current-voltage characteristics of the cells.

• Journal of Welding and Joining
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• v.26 no.2
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• pp.75-84
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• 2008

With the development of surface roughness textured steel for automotive body-in-white assemble, one of key issues is to understand the role of the surface roughness in textured steel sheets. To investigate effect of surface roughness on weldability in prepared steels, electrode force was varied. Steel sheets (T-H) with high surface roughness ($Ra\;=\;1.94\;{\mu}m$) reduced electrode life. It was attributed to the higher contact resistance at the electrode-sheet interface in the presence of the high surface roughness. The increased electrode diameter decreased current density, therefore reducing weld electrode life due to small weld button size. When an increased electrode force was used, a significant increase in the electrode life was observed in welding of high surface roughness steel sheet. This study suggested that contact resistance at the electrode-sheet interface was the dominant factor, as compared to the sheet-sheet interface for determining electrode life in welding of surface roughness textured steel.

• Korean Journal of Food Science and Technology
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• v.27 no.2
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• pp.176-180
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• 1995

Direct contact heat exchange (DCHE) method has been employed to investigate the separation of ethanol from dilute aqueous solutions. Bubbles at high temperature were dispersed into a continuous liquid phase, generating temperature gradient in air-liquid interface, which causes heat and mass transfer accordingly. The experiments were performed in the ranges of jet regime air flow. The air-water stripping coefficient increased $5{\sim}10,\;and\;1{\sim}1.5$ times as temperature and air flow rate increased, respectively. The recovery ratio based on the initial ethanol concentration reached into 80% at the air flow rate of 84.88 m/min. The initial ethanol concentration showed little effect on the stripping coefficient and the recovery ratio.

• The Journal of Korean Physical Therapy
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• v.23 no.6
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• pp.15-22
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• 2011

Purpose: This research investigated falls due to obstacles that occur among elderly people by assessing changes in the values of plantar foot force, peak force, and plantar foot pressure in elderly subjects while they were stepping over obstacles of different heights. Methods: The subjects were 20 elderly people aged 70-80 years; Pressure was measured on flat ground(0 cm), and after installing obstacles of 8 cm and 12 cm using the F-scan system, which is a resistance-type pressure sensor. A one-way analysis of variance was performed to compare pressure on each part of the foot according to various heights after collecting data using the Tekscan program. The least significant difference test was used for the post-hoc analysis, A p-value <0.05 was considered significant. Results: The force value for the toe area (parts 1, and 2) and contact pressure increased significantly with the 12 cm obstacle (p<0.05). The peak force value and the peak contact pressure for part 1 increased significantly with the 12 cm obstacle (p<0.05). Conclusion: Larger changes appeared in the functions and structure of the foot while subjects walked over obstacles of different heights compared to flatland walking. This result suggests that people have safety strategies to prevent falls, and that there is a need for a more realistic approach through practice to overcome obstacles of various heights to prevent falls.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.313-323
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• 2003

The sliding wear behaviors of Zircaloy-4 nuclear fuel rod were investigated using two support springs with convex and concave shapes in room temperature air and water. The main focus is to compare the wear behavior of various test variables such as slip amplitude, environment, contact contours with different spring shape and a number of cycles. The results indicated that wear volume and maximum wear depth increased with slip amplitude in both air and water, but their trends tended to change according to the spring shapes and test environments. In air condition, the wear volume was controlled by wear debris behavior generated on worn surface. As a result, final wear volume and maximum wear depth decreased if a ratio of protruded wear volume to worn area $(D_p)$ would be saturated to specific value. This is because wear particle layer could accommodate large strain by accumulating and transforming wear particle layer. However, in water condition, metal-to metal contact was more dominant and wear volume was greatly affected by changed mechanical behavior between contact surfaces since wear debris should be generated after repeated plastic deformation and fracture. After wear test, worn surfaces were examined using optical microscope and SEM and details of wear mechanism were discussed using a ratio of wear volume to worn area $(D_e)$ at each test condition.