• Composites Research
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• v.35 no.5
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• pp.322-327
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• 2022

Composite lap joints have been extensively used due to their excellent properties and the demand for light structures. However, due to the weak mechanical properties in the thickness direction, the lap joint is easily fractured. various reinforcement methods that delay fracture by dispersing stress concentration have been applied to overcome this problem, such as z-pinning and conventional stitching. The Z-pinning is reinforcement method by inserting metal or carbon pin in the thickness direction of prepreg, and the conventional stitching process is a method of reinforcing the mechanical properties in the thickness direction by intersecting the upper and lower fibers on the preform. I-fiber stitching method is a promising technology that combines the advantages of both z-pinning and the conventional stitching. In this paper, the static and fatigue strengths of the single-lap joints reinforced by the I-fiber stitching process were evaluated. The single-lap joints were fabricated by a co-curing method using an autoclave vacuum bag process and I-fiber reinforcing effects were evaluated according to adherend thickness and stitching angle. From the experiments, the thinner the composite joint specimen, the higher the I-fiber reinforcement effect, and Ifiber stitched single lap joints showed a 52% improvement in failure strength and 118% improvement in fatigue strength.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.6
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• pp.251-261
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• 2022

This paper describes the finite element analysis and die design change of spring retainer forging process to reduce the cold forging load and plastic forming stress concentration. Plastic deformation analysis was carried out in order to understand the forming process of workpieces and elastic stress analysis of the die set was performed in order to get basic data for the die fatigue life estimation. Cold forging die design was set up to each process with different four types analysis progressing, the upper and lower dies shapes with combination of fillets and chamfers shapes of cold forging dies. This study suggested optimal cold forging die geometry to reduce cold forging load. The design parameters of fillets and chamfers are selected geometry were selected to apply optimization with the DoE (design of experiment) and Taguchi method. DoE and Taguchi method was performed to optimize the workpiece preform shape for spring retainer forging process, it was possible to expect an increase in cold forging die life due to the 20 percentage forging load reduction.

• Korean Journal of Optics and Photonics
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• v.33 no.2
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• pp.74-83
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• 2022

The entire process, from the raw material to the final system qualification test, has been developed to fabricate a large-diameter, lightweight reflective-telescope system for a satellite observation. The telescope with 3 anastigmatic mirrors has an aperture of 700 mm and a total mass of 66 kg. We baked a silicon carbide substrate body from a carbon preform using a reaction sintering method, and tested the structural and chemical properties, surface conditions, and crystal structure of the body. We developed the polishing and coating methods considering the mechanical and chemical properties of the silicon carbide (SiC) body, and we utilized a chemical-vapor-deposition method to deposit a dense SiC thin film more than 170 ㎛ thick on the mirror's surface, to preserve a highly reflective surface with excellent optical performance. After we made the SiC mirrors, we measured the wave-front error for various optical fields by assembling and aligning three mirrors and support structures. We conducted major space-environment tests for the components and final assembly by temperature-cycling tests and vibration-shock tests, in accordance with the qualifications for the space and launch environment. We confirmed that the final telescope achieves all of the target performance criteria.

• Journal of Preventive Medicine and Public Health
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• v.21 no.1 s.23
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• pp.10-20
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• 1988

This study was conducted to compare the maternal charactristics, and birth weight of infants delivered at five different categories of medical facility in Taegu to examine the risk level of pregnant women and children by the medical facility for delivery. The study population included 1,410 pregnant women who delivered a baby at one of nine medical facilities (3 university hospitals, 2 general hospitals, 2 private clinics, 1 midwife clinic, 1 MCH center) in Taegu in April, 1987(April and May, 1987 for K university hospital), Pregnant women were interviewed to ask the age and educational level of woman, payment of medical fee, birth order, delivery method. Birth weight of infant was obtained from medical record. Mean ages of the women delivering at the university hospitals(27.5 years) and at general hospitals(26.7 years) were higher than those at midwife clinic(25.4 years) and at MCH center(26.1 years). Also, mean years of school education were higher in women of university hospitals(12.7 years) and general hospitals (12.2 years) than in women of midwife clinic(9.2 years) and MCH center (9.3 years). The percentages of women covered by the medical insurance were far greater in the university hospitals(78.1%) and general hospitals(82.9%) than in private clinics(44.3%) , midwife clinic(29.1%) and MCH center (5.4%). Infants born at the MCH center were mostly the second birth (47.3%) while 56.0% to 61.7% of infants born at all the other medical facilities were the first birth more women delivering at the university hospitals had history of spontaneous abortion as well as still birth than the women delivering at the other medical facilities. The preform birth rate (11.4%) and low birthweight incidence rates(5.8-13.0%) in university hospitals were significantly higher than those of other medical facilities. Accordingly, c-section rates showed a wide variation among the medical facilities. Study findings revealed that most of women delivering at the university hospitals and general hospitals are in the middle of or upper socio-economic class and obstetrically high risk group regardless of socioeconomic class while the wome delivering at the midwife clinic and MCH center are low risk group of low socioeconomic class. Therefore, the data of a specific medical facility are highly limited in interpretation and can not be generalized.

• Research in Community and Public Health Nursing
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• v.7 no.2
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• pp.294-312
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• 1996

Relatively young widows, who are left with young children by a sudden death of their husbands, will be faced with not only psychological troubles such as individual anxiety and frustration but also the dual burden of playing both father and mother roles in a family, Also, family members have difficulty in adapting themselves to new circumstances of the family system, the training and raising of family members, and management of the family economy. In this study, the realistic resources on the experience of middle-aged women who are bereaved of their husbands by accidents were explored. The purpose of this study is to help widows adapt to life in society and live a more positive life by setting a new goals and recovering from a lost and twisted life. 11 women, who have experienced the loss their husbands and live in the Seoul metropolitan area were studied. The research took 116 days from December 15, 1995 to April 8, 1996. The method of research was direct interviews. While having interviews with them, the contents were recorded with their consent. The ground theory was that used by Strauss & Corbin(1990) in the analysis of the data. 81 concepts were analyzed and they were subdirided into 22 subordinate categories through the course of the analysis. These were then classified into 9 general categories. In the course of being categorized, 'absurdity' was showed as a core category. The subordinate categories 'surprise', 'gloom', 'grudge', 'helplessness', 'emptiness', and 'loss' were united in the core category 'absurdity'. Ominous presentiment, belated notice, death, surprise, gloom, grudge, helplessness, emptiness, loss, the situation of the children, lack of support from neighbors, support from neighbors, mulling over ways to live, choosing a job, strengthening, reinforcement, burden, sadness, smoldering, yearning, overcoming these 22 subordinate categories were re-composed into 9 general ones the husband's death, absurdity, presence of children, existence of support, self-support ability, preparation of countermeasures, self-reinforcement, toilsomeness, and overcoming. 'Absurdity' widows experience was shown in the results of 'toilsomeness' and 'overcoming' through reaction, confrontation, and adaptation. According to the analysis the central phenomenon was absurdity, the causal condition of the death of a husband, the presence of children and the existence of support, and the meditated situation of self-support. To solve absurdity, the preparation of countermeasures and self-reinforcements were shown resulting in toilsomeness and overcoming. Through the contrast in the data, the following statements were deduced: (1) If the death of the husband is expected, the more a widow will feel absurdity. (2) The more children she has and the younger she is, the more a widow will feel absurdity. (3) The lower support she is given, the more a widow will feel absurdity. (4) The larger self-ability she has, the more actively she will prepare countermeasures. (5) The smaller self-ability she has, the more passively she will prepare countermeasures. (6) The larger self-ability she has, the weaker self-reinforcement she will preform. (7) The smaller self-ability she has, the stronger self-reinforcement she will perform. (8) The more actively she prepares countermeasures for absurdity, the better she will overcome. (9) The more passively she prepares counter measure for absurdity, the worse she will overcome. (10) The stronger self-reinforcement for absurdity she performs, the better she will overcome. (11) The weaker self-reinforcement for absurdity she performs, the worse she will overcome. Through the results in this study, the following suggested: 1) A study whose object is all family members, and a comparative study on the case of a husband who has lost his wife should be done. These studies can be expected to develop a more refined theory. 2) Because of the collapse of the extended family system and the changes of family culture in Korea, a widow's status and position are apt to be ambiguous between her husband's home and her parent's. Therefore a new study on family culture should be made. 3) A continuous study on growing social Self Help Groups should be requested for the widows of this study to re-establish and recover from their twisted and scattered lives.