• Korean Journal of Materials Research
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• v.14 no.3
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• pp.203-210
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• 2004

Effects of various pretreatments on the adhesion of copper-coated polymer films were investigated. Copper-coated polymer films were prepared by an electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) coupled with a DC bias system at room temperature. PET(polyethylene terephthalate) film was employed as a substrate material and it was pretreated by industrially feasible methods such as chromic acid, sand-blasting, oxygen plasma and ion-implantation treatment. Surface characterization of the copper-coated polymer film was carried out by AFM(Atomic Force Microscopy) and FESEM(Field Emission Scanning Electron Microscopy). Surface energy was calculated by based on the value of the contact angle measured. The adhesion of copper/PET films was determined by a pull-off test according to ASTM D-5179. It was found that suitable pretreatment of the PET substrate was required for obtaining good adhesion property between copper films and the substrate. In this study the highest adhesion was observed in sand-blasting, and then followed by those of acid and oxygen plasma treatment. However, the effect of surface energy was insignificant in our experimental range. This is probably due to compensating the difference in surface energy from various pretreatments by exposing substrate to ECR plasma for 5 min or longer at the early stage of the copper deposition. Therefore, it can be concluded that surface roughness of the polymer substrate plays an important role to determine the adhesion of copper-coated polymer for the deposition of copper by ECR-MOCVD.

• Journal of the Korean Electrochemical Society
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• v.16 no.1
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• pp.39-45
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• 2013

The water management is one of the key issues in low operating temperature proton exchange membrane fuel cells (PEMFCs). The gas diffusion layer (GDL) allows the reactant gases flow to the reaction sites of the catalyst layer (CL). At high current density, generated water forms droplets because the normal operating temperature is $60{\sim}80^{\circ}C$. If liquid water is not evacuated properly, the pores in the GDL will be blocked and the performance will be reduced severely. In this study, the microchannel GDL was proposed to solve the flooding problem. The liquid water transport through 3-D constructed conventional GDL and microchannel GDL was analyzed varying air velocity, water velocity, and contact angle. The simulation results showed that the liquid water was evacuated rapidly through the microchannel GDL because of the lower flow resistance. Therefore, the microchannel GDL was efficient to remove liquid water in the GDL and gas channels.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.3
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• pp.347-353
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• 2012

Recently, multi-functionalization (as in smart phones) has been in demand, and the connectors connecting the electrical signals of each board in a cellular phone have become key components. The miniaturization of these connectors is required to achieve a finer pitch design and enhance the electrical signal transfer capacity. However, the miniaturization of connectors reduces the structural safety, and a finer pitch design may cause contact problems under external impact. In this paper, a preliminary design for miniaturized, finer-pitch connectors is suggested for a product with 50 pins and a thickness of 0.2 mm. The assembly process of the FPCB (Flexible Printed Circuit Board) and connector was simulated to ensure the holding force between the two components and avoid overstressing. The design optimization process was performed with the Taguchi method. Fatigue analysis was also conducted to predict the fatigue life of the terminal, and the theoretical and experimental results were compared.

• Journal of Korean Society on Water Environment
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• v.20 no.2
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• pp.126-131
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• 2004

This research sought to compare chlorine, chlorine dioxide and ozone as chemical disinfectants of drinking water, with inactivation of total coliform as the indicator. The inactivation of total coliform was tested against several variables, including the dose of disinfectant, contact time, pH, temperature and DOC. A series of batch processes were performed on water samples taken from the outlet of a settling basin in a conventional surface water treatment system that is provided with the raw water drawn from the mid-stream of the Han River. Injection of 1 mg/L of chlorine, chlorine dioxide and ozone resulted in nearly 2.4, 3.0 and 3.9 log inactivation, respectively, of total coliform at 5 min. To achieve 99.9 % the inactivation, the disinfectants were required in concentrations of 1.70, 1.00 and 0.60 mg/L for chlorine, chlorine dioxide and ozone, respectively. Bactericidal effects generally decreased as pH increased in the range of pH 6 to 9. The influence of pH change on the killing effect of chlorine dioxide was not strong, but that on ozone and free chlorine was sensitive. The activation energies of chlorine, chlorine dioxide and ozone were 36,053, 29,822 and 24,906 J/mol for coliforms with inactivation effects being shown in the lowest orders of these.

• KSBB Journal
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• v.13 no.5
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• pp.577-584
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• 1998

A sensitive membrane strip assay for plasma lipoprotein cholesterol that can be performed without handling reagents has been investigated. We previously developed an assay system with immobilized enzymes (cholesterol esterase and cholesterol oxidase) on the surfaces of nitrocellulose membrane(1). In such a case, the amount of enzymes present on the membrane was limited by its surface area and, thus, the detection capability was relatively poor (> 50 mg/dL cholesterol). To overcome this problem, we devised a new system with non-immobilized enzymes by placing them within interstitial spaces of a celullose membrane pad in a dry state. Upon contact with sample medium, the enzymes were immediately dissolved and participated in the reactions with cholesterol in a liquid phase. We constructed a user-friendly system consisting of four membrane pads fro sample application, cholesterol decomposition, color development as signal, and medium absorption to invoke a continuous flow (sequential location from the bottom). A sample containing lipoproteins was added into the application pad by capillary action and transferred to the next pad for decomposition. The decomposition pad (namely, enzyme pad) contained a detergent (sodium cholate) for the destruction of lipoprotein particles, the two enzymes for cholesterol decomposition, and a chromogen (3,3'-diaminobenzidine). As a consequence of the enzyme reactions, hydrogen peroxide was produced, and then reacted in the presence of the chromogen with horseradish peroxidase immobilized on the signal generation pad. Finally, a colorimetric signal directly proportional to the cholesterol concentration was produced. The detection limit determined from this system under optimal conditions was at least 2 times lower than of the enzyme-immobilized system.

• Journal of the Korea Convergence Society
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• v.9 no.8
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• pp.301-309
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• 2018

The aim of this study was to investigate the relationship between the neurocognitive ability and the risk factors of non-contact anterior cruciate ligament injuries during landing in female recreational athletes. Thirty-two female athletes participated in computerized neurocognition test and motion analysis for drop vertical jump. Pearson's linear correlation analysis was performed to analyze the relationship between the raw scores of neurocognition test and biomechanical variables including 3D joint angle, moment, power, vertical ground reaction force, loading rate, and support time. There were correlations between the scores of neurocognition test and biomechanical variables as high the neurocognition score, it also increase landing strategies were used to maintain posture of the lower extremity. Therefore, the neurocognitive test might be used as a good screening method to detect the risk factors before injury.

• Journal of Korean Public Health Nursing
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• v.14 no.1
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• pp.26-40
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• 2000

This study was conducted to find out residential environment, mood states, ADL(Activity Daily Living) and nursing need of the elderly who live alone. The questionnaire survey was conducted on 154 single household elderly over 65years who live n D-city, Kangwon Province. The data were collected between September 1. 1999 and October 17, 1999 and analyzed by means of SPSS package. The results were as follows; 1. The percentage of the subjects who owned their house was no were than $13\%$., which showed that they still belonged to the economically vulnerable class. As for their residential environment, the average indoor temperature and humidity level were $16.45^{\circ}C\;and\;44.62\%$ respectively during the daytime between September and October, which proved to range within the standard scope. The average indoor illumination level was, however, 43.61 Lux, which showed that their illumination environment was very poor. 2. The average score of their mood states was 3.31. which turned out to be rather low. 3. The mean score of ADL was 1.69, which showed that they didn't have any serious inconveniences in their ordinary lives. 4. The mean score of their nursing need was 275, which proved to be close to the normal level. 5. The higher the room humidity was, the higher their nursing need increased. The higher the degree of illumination level was, the lower the degree of their nursing need was and the higher the level of ADL was. 6. The major factors influencing their moon status were the frequency of their contact with children and room humidity. These two factors could account for $22\%$ of the total mood status. These results suggest that the residential environment should be necessarily considered in the psychological nursing intervention for the elderly who live alone and they should be urgently supported in terms of health policy so that they can maintain the optimum level of illumination during the daytime.

• Journal of the Korean Society for Precision Engineering
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• v.3 no.3
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• pp.40-71
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• 1986

By developing a computer program for the systematic design of worm gears, the design formulae and tables of AGMA, JGMA, BS and DIN are analized and compared. The computer program can be used on micro-computers. According to the input data of the reduction ratio, the center distance. the driving torque and the material as design parameters, the program calculate the most efficient worm gear dimension. The variation of the design parameters and other empirical coefficients in case of resulting an inadequate design gear dimension can be easily modified throuth the way of interactive method between the user and the monitoring system of computer. A proposal of the standardization of worm gears was made in which a standard module according to the DIN 323 standard series number was applied. For the more exact and effective calculation of the stress concentration and the deformation of gear teeth, a computer program using the boundary element method is also developed. Even the strength of the special gear shape such as Niemann's "Cavex" gear can be calculated in a short CPU-time. The most effort of this study has been layed on the developing a computer program for the correction of a tooth profile and face width which is most important design factor for an exact and wide teeth contacts under loads, especially by great and wide gears. For this purpose were investigated the tooth stiffness, the mesh interferences and the kinematics and the dynamics of gear mesh. The deflection and the deformation of the gear shaft due to the loads acting on gear and shaft were aslo considered. Some examples have shown the sufficient good status of teeth contact in which the correction of the tooth profile and face width were accomplished due to the calculated results.d results.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.956-960
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• 1998

Cu-Zn and Cu-Zn-Ti catalysts for the steam reforming of methanol were prepared. This reaction was carried out at atmospheric pressure, $250^{\circ}C$, steam/methanol molar ratio 1.5, and contact time 0.1 g-cat.hr/mL-feed. In case of the catalyst with 3 mol% of $TiO_2$, the activity was superior to that of catalysts without $TiO_2$. The reaction products were mainly hydrogen and carbon dioxide. It was found that catalytic activity was not related to specific surface area but affected by metallic copper area which was measured by $N_2O$ decomposition and increased with the addition of $TiO_2$ content. XPS and XRD showed that the oxidation state of zinc was not changed during reaction, but oxidation states of copper existed in Cu(0) or Cu(I).

• Journal of Pharmaceutical Investigation
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• v.38 no.3
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• pp.157-162
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• 2008

The aim of the study was to formulate the stable amlodipine maleate tablet by selecting and combining of suitable ingredients. Amlodipine tablets were designed by using different manufacturing methods or formulations. Dissolution rate at 30 min of newly formulated tablets was over 98% in 0.1 M HCl medium. After 4 months storage under accelerated condition, the changes of appearance, loss on drying, content and total impurity were investigated. For long-term stability tests, two formulations of K017 (direct compressed tablets consisting of microcrystalline cellulose and pregelatinized starch) and K018 (wet granulated tablets by OpadryAMB) were stored under $25^{\circ}C$, 60% RH for 24 months. Under the accelerated condition, moisture content in K017 formulation was increased as 5.96% for 4 months, while other formulations with anhydrous monobasic phosphoric potassium or by wet granulation showed higher increase in moisture content compared to K017. In addition, K017 formulation showed a low decrease in contents and total relative substance as 0.8% and 0.7%, respectively. Similar stability of amlodipine in K017 was obtained under the long-term stability test. These results indicate that the K017 combined with microcrystalline cellulose and pregelatinized starch as ingredients is very stable formulation to protect active substance from moisture contact and sustain stability. Therefore, suitable combination of ingredients such as microcrystalline cellulose and pregelatinized starch could attribute to enhance the stability of moisture-labile drug such as amlodipine maleate.