• International Journal of Automotive Technology
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• 제5권3호
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• pp.215-219
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• 2004

A vehicle structure needs to be more precisely analyzed because of complexities and varieties. Structural fatigue which is generated by fluctuations of stresses during the service life of a mechanical system is the primary concern in the structural design for safety. A fatigue life is difficult to obtain in structural components during the service life of mechanical systems since the fluctuating stress contributes to fatigue. This study introduces new procedures to measure the lethargy coefficient and to predict the fatigue life of a mechanical structure by using molecular dynamic simulation. A lethargy coefficient is the total defect-estimating coefficient, which was obtained by using the results of a simple tensile test in this study. With this lethargy coefficient, fatigue life was estimated. The proposed method will be useful in predicting the fatigue life of a structurally-modified vehicle design. The effectiveness of the proposed method using lethargy coefficient measurement to predict the fatigue life of a structure was examined by applying this method to predict the fatigue life of SS41 steel, used extensively as material of vehicle structures. Two types of specimen such as pre-cracked plate and simple plate is discussed. equation of fatigue life using the lethargy coefficient and failure time, both obtained from a simple tensile test, will be useful in engineering. This measurement and prediction technology will be extended for use in analysis of any geometric shapes of modified automotive structures.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.106-113
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• 2004

Most of mechanical structures are composed of many substructures connected to one another by various types of mechanical joints. In automotive engineering, it is important to study these connected structures under various dynamic forces for the evaluations of fatigue life and stress concentration exactly. In this study, the dynamic response of vehicle structure to external forces is classified an inverse problem involving strains from the experiment and the analysis. The practical dynamic forces are determined by the combination of the analytical and experimental method with analyzed strain by quasi-static finite element analysis under unit force and with measured strain by a strain gage under driving load, respectively. In a stressed body, inter-molecular chemical bonds are failed beyond the certain magnitude. The failure of molecular structure in material is considered as a time process of which rate is determined by mechanical stress. That is, the failure of inter-molecular chemical bonds is the fatigue lift of material. This kinetic concept is expressed as lethargy coefficient. And S-N curve is obtained with the lethargy coefficient from quasi-static tensile test. Equivalent practical dynamic force is obtained from the identification of practical dynamic force for one loading point. Using the practical dynamic force and S-N curve, fatigue life of a window pillar is analyzed with FEM under the identified force by the procedure of above mentioned.

• 한국공작기계학회논문집
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• 제12권1호
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• pp.32-37
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• 2003

Evaluation of fatigue strength on the spot welded part is very important for strength design of spot welded steel structures. In this paper, we could get the life cycle of the spot welded part using the lethargy coefficient obtained through the quasi-static tensile shear test for the specimen welded by current 10kA. The reliability evaluation of the life cycle is completed by comparing the life cycle calculated under the constant loading rate with the life cycle obtained by dynamic fatigue test. And then the result calculated by the lethargy coefficient is verified through the lift cycle calculated using the dynamic final tensile stress formula under the increased loading speed. This way can make save the time and cost in processing of predicting the life cycle of a structure.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.269-273
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• 1998

The failure of material structures or mechanical system is considered as a direct or indirect result of fatigue. In the design of mechanical structure for estimating of reliability, the prediction of failure life is the most important failure mode to be considered. However, because of a complicated behavior of fatigue in mechanical structure, the analysis of fatigue is in need of much researches on life prediction. This document presents a prediction of fatigue life of the SAPH45 steel, which is extensively for vehicle frame. The method using lethargy coefficient and stress distribution factor at pediction of fatigue life based on the consideration of the failure characteristics from the tensile test should be provided in this study.

• 대한기계학회논문집A
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• 제35권2호
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• pp.157-162
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• 2011

발전설비 및 자동차의 엔진에서 고온과 응력이 발생하므로 안전을 위하여 제품을 생산하기 전에 재료의 수명설계가 필요하다. 본 연구에서는 온도, 응력, 파단 시간으로 이루어진 무기력계수를 이용하여 수명설계를 수식화하였다. 통합수명식을 이용하여 SP-Creep 시험 데이터와 계산된 데이터를 비교하였다. SP-Creep 시험은 X20CrMoV121강의 파단시간을 획득하기 위하여 수행하였고 수명설계식을 통해 하중, 온도, 하중-온도가 작용하는 3가지 경우를 고려하였다. 첫째로, 무기력계수는 SP-Creep 시험에서 획득한 파단응력과 시간에 의해 계산하였다. 두 번째로, 온도 조건을 주어 수명을 예상하였다. 세 번째로, 부재는 피로와 크리프가 동시에 작용할 때 커플링 효과 때문에 더 열악한 상태에 놓이게 된다. 수명은 커플링 효과 때문에 현저하게 감소하는 것으로 나타났다.

• 한국자동차공학회논문집
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• 제14권1호
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• pp.48-53
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• 2006

A methodology is described for predicting the fatigue life of the resistance spot weldment including strain rate effect. Because it is difficult to perform a physical failure test with high strain rate, an analytical method is necessary to get the mechanical properties of various strain rate, To this end, quasi-static tensile-shear tests at several strain rate were performed on spot weldments of SPC. These test provided the empirical data with the strain rate. With these results, we formulated the function of fatigue life prediction using the lethargy coefficient which is the global material property from tensile test. And, we predicted the fatigue life of spot weldment at dynamic strain rate. To confirm this method for fatigue life prediction, analytical results were compared with the experimental fatigue data.

• 셀메드
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• 제14권3호
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• pp.69.1-69.3
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• 2024

Objective: A Case of improvement of hyperlipidemia through the use of OCNT. Methods: A Korean female in her 40s has been suffering from a wide range of symptoms due to hyperlipidemia. Results: Hyperlipidemia was improved following implementation of OCNT. Conclusion: Application of OCNT on hyperlipidemia can be helpful in alleviation of symptoms.

• 대한한방부인과학회지
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• 제22권4호
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• pp.157-172
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• 2009

Purpose: The purpose of this study is to analyze the status of cooperative treatment of western-oriental medicine in post gynecological surgery. Methods: This study is conducted by investigating the hospitalized patient's medical chart and OCS dated from March 2008 to May 2009 in obstetrics and gynecology of oriental medicine department in Dong-Eui medical center. The total patient number was 58. Results: Out of 58 women, 74.1% complained abdominal pain and discomfort, 24.1% complained headache and dizziness, 22.4% complained lumbago, 22.4% complained lethargy and fatigue. There were 63.8% women in the age group between 41 to 50 and 20.7% women in the age group between 31 to 40. 53.4% women hospitalized for less than 7 days, 43.1% women hospitalized for 8 to 14 days. 53.4% had uterine myoma, 20.7% had more than two types of complex diseases and 19.0% had adenomyosis uterine. 60.3% had total hysterectomy and 27.6% had simple hysterectomy. 64.9% had abdominal surgery, 17.5% had laparoscope surgery and 15.8% had hysteroscope surgery. 62.8% of 43 women complained abdominal pain and discomfort, 78.6% of 14 women complained headache and dizziness, 46.2% of 13 women complained lumbago, 84.6% of 13 women complained lethargy and fatigue improved to VAS 0-3. Conclusion: The results has shown that it is necessary to have cooperative treatment of both western-oriental medicine for the effective treatment in managing post gynecological surgery. The further study in data collection and manual development is needed.

• 대한한방소아과학회지
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• 제24권1호
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• pp.57-64
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• 2010

Objectives This study is to examine case that has an significant result on treating Polyarticular Type Juvenile Idiopathic Arthritis(JIA) the patient who did not response to DMARDs and NSAIDs with oriental medicine. JIA is the most common form of persistent arthritis in children before age 16. The symptoms of JIA is pain and edema of joints, fever, lethargy, reduced physical activity, and poor appetite. But the symptoms vary. Methods The patient felt pain and had limitation of mobility on his joints, but the DMARDs and NSAIDs were not effective. Therefore, he was treated with oriental medicine and withdrew from DMARDs and NSAIDs. The patient took DMARDs and NSAIDs from May 2007 to November 2008(He did not took DMARDs and NSAIDs from December 2007 to June 2008), and took oriental medicine from November 2008 until now. Results The patient's pain and limited mobility on his joints, edema, morning stiffness, fatigue was gone, and could maintain the condition. He doesn't have DMARDs or any other western medicine anymore. Conclusions This study shows that a Polyarticular Type Juvenile Idiopathic Arthritis patient who had ineffective response to DMARDs and NSAIDs can reach to the clinical remission by oriental medicine treatment. His morning stiffness, fatigue, pain of joints, edema was gone and ESR was in normal range with Oriental medicine treatment.

• 대한치과마취과학회지
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• 제13권3호
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• pp.139-143
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• 2013

The patient who has congenital hypothyroidism and pseudohypoparathyroidism could have mental retardation even though adequate hormone treatment and cannot endure conventional dental treatment. In this case, general anesthesia is selected to administer effective dental treatment. But, there could be symptoms such as anemia, neuropathy, associated pituitary or adrenal hypofunction, cardiac failure even in euthyroid state. And, bradycardia, mental dullness, hypothermia, slow reflexes can appear in case of inadequate thyroid hormone replacement. Especially, macroglosssia, slow drug metabolism, exaggerated responses to anesthetic agents and decreased ventilatory responses could be problem during general anesthesia. The presentation of hypoparathyroidism also varies depending on the chronicity of the result of hypocalcemia. Muscle spasms/tetany, paresthesias, and seizures may occur in an acute onset. Chronic hypocalcaemia causes fatigue, muscle cramps, lethargy, personality changes, and cerebration defects.