• 한국생산제조학회지
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• 제25권4호
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• pp.301-306
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• 2016

High speed polishing can kinematically increase the polishing removal rate by using the conventional Preston equation, especially for hard substrates such as sapphire or diamond. However, high speed effects should be clarified beforehand considering the lubrication state and process parameter variations. In this paper, we developed a polishing experimental method and apparatus to determine the lubrication state by measuring the real time friction coefficient using two load cells. Through experiments, we obtained a boundary lubrication state above 0.35 of the friction coefficient by using low table speed and high polishing load, indicating a synchronized stable behavior in polishing head rotation. However, larger Stribeck indexes by a high speed above 200 rpm can generate a hydrodynamic lubrication state below 0.25 of the low friction coefficient. This causes the polishing head rotation to stop. A forced and synchronized head rotation is required for high speed polishing.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.985-990
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• 1995

Recently, the development of high speed and high precision NC-lathe for piston head machining is needed for the complexity and diversity of the piston head shape used in automobile reciprocating engine. THe piston head has many complex shapes in the aspect of fuel economy, such as ovality, profile, double ovality and recess. Among them, for the maching of the over shape of 0.1~1mm the cutting tool should move periodically symchronized with the rotation of piston workpiece. The cutting tool feeed system must have high positioning accuracy for the precise machining, high speed for the fast maching and high dynamic stiffness for the cutting force. The linear brushless DC motor is used for satisfying these coditions. The ballbush guide and supporting guide using turcite is used for the guidance of the feed drive system. Linear encoder, digital servo ampllifer and controller are used for driving the motor. THis paper presents the design and simulation of the new tool feed system for noncircular machining.

• 대한간호학회지
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• 제22권2호
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• pp.127-142
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• 1992

The purpose of this study was to identify relationships between the nursing performance of staff nurses and the leadership styles of head as perceived by the head nurses and the staff nurses. The subject consisted of 33 head nurses and 200 staff nurses who were working at SNUH between July 1, and July 31, 1991. Leadership styles as perceived by head nurses and staff nurses were measured using an instrument adapted by Park (1988) . Evaluations of the nursing performance of staff nurses were done by head nurses utilizing a questionnaire adopted by Park(1988). Data were analysed using percentage distribution, ANOVA, Scheffe test and Pearson Correlation Coefficient. The results are summarized as follows : 1. The majority of the head nurses and staff nurses perceived the head nurse as having a tendency to exercise high level authority and benevolence oriented leadership. 2. The majority of the staff nurses carried out their nursing performance in a highly skilled manner. 3. There were significant differences in perceptions of leadership style between head nurses and staff nurses. 4. “Authority” and “Benevolence” in leadership style as perceived by the head nurses were related very weakly to the nursing performance of the staff nurse. 5. “Benevolence” of leadership style as perceived by the staff nurses was related very weakly to the nursing performance of the staff nurse. 6. Group comparisons of nursing performance and leadership style found that high nursing performance by the staff nurse was related in the group with high “Authority” as perceived by the head nurse and low “Authority” as perceived by the staff nurse. From the above findings, this study suggests the following : 1) Further studies are needed to control extraneous variables. 2) Efforts in leadership development are needed to enhance nursing performance. 3) Factor exploration study are needed to seek factors that contribute to the perception gap between the head nurse and the staff nurse.

• 대한청각학회지
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• 제25권2호
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• pp.80-88
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• 2021

Background and Objectives: Non-linear frequency compression (NLFC) technology compresses and shifts higher frequencies into a lower frequency area that has better residual hearing. Because consonants are uttered in the high-frequency area, NLFC could provide better speech understanding. The aim of this study was to investigate the clinical effectiveness of NLFC technology on the perception of speech and music in patients with high-frequency hearing loss. Subjects and Methods: Twelve participants with high-frequency hearing loss were tested in a counter-balanced order, and had two weeks of daily experience with NLFC set on/off prior to testing. Performance was repeatedly evaluated with consonant tests in quiet and noise environments, speech perception in noise, music perception and acceptableness of sound quality rating tasks. Additionally, two questionnaires (the Abbreviated Profile of Hearing Aid Benefit and the Korean version of the International Outcome Inventory-Hearing Aids) were administered. Results: Consonant and speech perception improved with hearing aids (NLFC on/off conditions), but there was no significant difference between NLFC on and off states. Music perception performances revealed no notable difference among unaided and NLFC on and off states. The benefits and satisfaction ratings between NLFC on and off conditions were also not significantly different, based on questionnaires, however great individual variability preferences were noted. Conclusions: Speech perception as well as music perception both in quiet and noise environments was similar between NLFC on and off states, indicating that real world benefits from NLFC technology may be limited in Korean adult hearing aid users.

• Journal of Audiology & Otology
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• 제25권2호
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• pp.80-88
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• 2021

Background and Objectives: Non-linear frequency compression (NLFC) technology compresses and shifts higher frequencies into a lower frequency area that has better residual hearing. Because consonants are uttered in the high-frequency area, NLFC could provide better speech understanding. The aim of this study was to investigate the clinical effectiveness of NLFC technology on the perception of speech and music in patients with high-frequency hearing loss. Subjects and Methods: Twelve participants with high-frequency hearing loss were tested in a counter-balanced order, and had two weeks of daily experience with NLFC set on/off prior to testing. Performance was repeatedly evaluated with consonant tests in quiet and noise environments, speech perception in noise, music perception and acceptableness of sound quality rating tasks. Additionally, two questionnaires (the Abbreviated Profile of Hearing Aid Benefit and the Korean version of the International Outcome Inventory-Hearing Aids) were administered. Results: Consonant and speech perception improved with hearing aids (NLFC on/off conditions), but there was no significant difference between NLFC on and off states. Music perception performances revealed no notable difference among unaided and NLFC on and off states. The benefits and satisfaction ratings between NLFC on and off conditions were also not significantly different, based on questionnaires, however great individual variability preferences were noted. Conclusions: Speech perception as well as music perception both in quiet and noise environments was similar between NLFC on and off states, indicating that real world benefits from NLFC technology may be limited in Korean adult hearing aid users.

• 한국의류산업학회지
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• 제4권6호
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• pp.534-543
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• 2002

The purpose of this study was to identify the body proportions of girls in middle and high school who have been a major sales target of clothing manufacturers and thus to provide the basic information on the proportion of human body, which is essential for manufacturer to produce clothing and for individual consumers to select right apparels to wear and purchase. The subjects were 133 girls in middle school and 141 girls in high school. As measuring instruments, the Martin's anthropometer, tapelines, and belts for marking waistline were used. In order to analyze the data, t-test and factor analysis were used. The measurement of vertical distance between vertex and measuring points, showed a significant difference between the high school group and middle school group in every item. In the comparison of eight head proportion between the two groups, middle school students had 7.2 head proportion while girls in high school had 6.9 head proportion in detail. The factor analysis of major divided body parts of the two groups indicated that waist-hip and hip-crotch, constituting lower trunk together, vertex-apex nasi, and apex nasi-back neck point, constituting head together, back neck point-spina scapula and spina scapula-waist, constituting posterior of upper body together, and mentum-bust point and bust point-waist, constituting anterior of upper body together, were in inverse proportion.

• 한국잠사곤충학회지
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• 제39권2호
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• pp.174-179
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• 1997

The larval head capsule width, larval weight and length of mulberry longicorn beetle, Apriona germari Hope were measured when the larvae were exuviated in artificial diet rearing. The larval head capsule width from the 1st to the 12th instar was ranged from 0.12 to 0.69 cm, and growth ratio of each instar was significantly high between the 1st and the 2nd instars. The fitness to Dyar's law for the larval head capsule width was 87.6%. When the logarithum of the larval head capsule width is plotted against the number of instars, the calculated regression line was LogY=0.12086+0.06998X and Dyar's constant was 1.18. The larval weight was increased with larval developmental stages, and the coefficient of variation of larval weight was apparently high. But the calculated regression line was LogY=-0.91592+0.25959X and Dyar's constant was 1.25. The growth ration of the larval length was clearly high between the 2nd and the 3rd instars, and that of larvae from the 4th instar was decreased. The calculated regression line was LogY=-0.16932+0.09841X and Dyar's constant was 1.25. In conclusion, our results suggested that the larvae growth of mulberry longicorn beetle appeared to be highly related in the larval head capsule width, larval weight and length.

• 소성∙가공
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• 제32권5호
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• pp.268-275
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• 2023

ISO 21029 cryogenic vessel is used to transport cryogenic fluids. High-manganese steel (High-Mn steel) is widely regarded as suitable for use at cryogenic temperatures. The conventional way of manufacturing an ellipsoidal vessel head involves incremental stretching, followed by a spinning process. In this study, an alternative method for forming an ellipsoidal vessel head was proposed. Finite element analysis (FEA) was used to theoretically examine the strain evolution during a multi-stage forming process, which involved progressive stretching, deep drawing, and spinning of High-Mn steel. The distribution of effective strain and strain components were analyzed at different regions of the formed part. The FEA results revealed that only normal strains were evident in the dished region of the vessel head due to the stretching process. However, the flange region experienced complex strain evolution during the subsequent deep drawing and spinning process.

• 대한치과교정학회지
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• 제17권1호
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• pp.55-62
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• 1987

Diagnosis and treatment plans of patients are depended on cephalogram in most case. However, conventional cephalogram may change diagnosis because it ignores a conception of natural head position. The purpose of this study was to investigate the difference of head positions between conventional X-ray taking and x-ray taking in natural head position, and correlation between above results and craniofacial morphology, 60 male students in dental college, Yon sei Univ. were selected, and every cephalogram is studied by comparison of the change of head position. The results are as follows. 1. When taking X-ray by using conventional method, external auditary meatus FH was more tilted than ear rod FM by $2.1^{\circ}{\pm}1.8$ in forward and downward direction. 2. As facial form becomes concave, natural head position and head position, appeared in X-ray taking by using conventional method, become more similiar. 3. Change in head position had showed high correlations with facial form (N-A-Pog angle), and there was high significance to concave group when compared with average group, but significance to convex group was not found. 4. Multiple regression equation concerning change of head position was solved. ${\Delta}FH=24.5\;+\;0.31$ NAPog + 0.43 Prominence of Chin + 0.13 Facial length -0.32 Anterior facial height.

• 한국전산구조공학회논문집
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• 제25권2호
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• pp.163-173
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• 2012

이 연구에서는 프리스트레싱용 고강도 강연선의 정착장치 중 강연선을 직접 정착하는 앵커헤드(anchor head)에 대해 거동특성을 분석하고, 앵커헤드의 제원을 결정하는 단계에 있어서 해석적 검토에 요구되는 프로세스에 대해 정립하였다. 앵커헤드는 쐐기와의 접촉(contact)을 통해 강연선으로부터의 힘이 전달되고 거동변화에 따라 접촉상태 또한 변하게 된다. 이를 고려한 상세 거동분석을 위해 쐐기와 헤드 사이의 접촉(contact)조건을 설정하였으며, 앵커헤드의 비선형 재료모델을 적용하여 기하 및 재료 비선형성을 고려한 구조해석을 수행하였다. 해석결과로부터 다음의 결과를 얻을 수 있었다. 앵커헤드의 거동은 앵커헤드와 쐐기 간의 상호거동에 크게 영향을 받기 때문에 초기 설계단계부터 상대 영향을 고려해야 한다. 쐐기홀(wedge hole)의 배치는 층배열(layered) 보다는 원형배열(circular)이 보다 응력분배에 효과적이고, 쐐기홀의 간격을 증가시키고 헤드 하면 구멍의 크기를 줄여 구멍사이 강재의 두께를 다소 늘이는 것이 구조거동에 효과적이다.