• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.310-312
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• 2005

An out-of-step condition results from the loss of the synchronism of the generators. A disturbance in a power system causes the generator angle to oscillate. When there is a severe disturbance such as a heavy current fault loss of major generation or loss of a large block of load the oscillation can be severe and even increase largely and finally the out-of-step condition may occur During the power swing and out-of-step conditions, the a apparent impedance at a relay location changes, and the power flow also changes as the angle difference is varied. This paper presents a method to analyze the trajectory of complex power during a power swing and out-of-step condition. The trajectory of the complex power is analyzed when a power swings and a fault occurs. Moreover, the complex power is analyzed when the ratios between the voltages at both sides and the line impedances are changed. These methods are verified through simulation using the ATP/EMTP MODELS.

• Journal of Radiation Protection and Research
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• v.38 no.4
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• pp.208-213
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• 2013

The suitability of the site criteria is a basic requirement for securing safety of nuclear power plants. The suitability should be confirmed through the estimation of environmental radiation effects at the exclusion area boundary under the severe weather conditions. In this study, field tracer experiments over short range of 1 km radius under severe weather conditions were conducted at flat area in Daejeon. Severe weather conditions are represented with stable atmospheric condition and low wind speed. In general, the condition is appeared at clean night time with weak wind. The analysis of the measured distribution of the released tracer gas shows two big differences between the results of the past experiments conducted under the favorable weather conditions. One is the difficulty of finding the typical distribution of the released tracer gas with peak concentration in the downwind direction. The other one is the appearance of the contour of the concentration of tracer gas at several hundred meters even though the gas released at 10 m height over the ground.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.32 no.2
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• pp.116-128
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• 2022

Objectives: The aim of this study was to examine the association of working posture with headache/eye strain in Korean waged workers. Methods: Data were collected from the 5th Korean Working Condition Survey. A total of 30,955 workers participated in this study. A four-items of working postures were measured using a 7-point Likert scale, and we categorized them into three groups ('normal', 'moderate', and 'severe') each 4 items. Headache/eye strain were measured using a self-administrative questionnaire ('yes' vs. 'no'). To examine the relationship between the total working postures score and headache/eye strain, we summed a 4-items of working postures. It was categorized into five groups according to the severity of exposures('normal', 'mild', 'moderate', 'severe', and 'very severe'). The multivariate logistic regression analysis was performed using the IBM SPSS(Ver. 25), and a p<.05 was considered significant. Results: The results show that 'fatiguing and painful posture' and 'posture repetitively using hands or arms' were associated with headache/eye strain after controlling for control variables. The total working posture score was positively associated with headache/eye strain. People with higher levels of the total working posture score were more likely to increase the risk of headache/eye strain compared to those of normal(OR: 1.844, 95% CI: 1.549~2.195 for 'mild'; OR: 2.564, 95% CI: 2.152~3.503 for 'moderate'; OR: 4.140, 95% CI: 3.432~4.994 for 'severe'; OR: 7.613, 95% CI: 5.625~10.304 for 'very severe') (p<.05 for trend). Conclusions: These results indicate that inappropriate working postures might play a crucial role in developing headache/eye strain. It is needed to improve the working environment, especially focusing on reducing inappropriate working posture at the organizational level.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.433-436
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• 2009

This study is concerned with an effect of frictional condition in a forward/backward combined extrusion process. Generally, the material flow of the billet is influenced by the corners of the die cavity, the ratio in reduction in area, and thickness ratio of backward can thickness to forward can thickness. In addition, the frictional condition in contact area between the billet and the punch/die also affect the material flow. This paper investigated the effect of frictional condition for variable friction factors. The FEM simulation has been carried out in order to examine the effect of frictional condition. Deformation patterns and flow characteristics were examined in terms of design parameters such as extruded length ratio etc. Die pressure exerted on the die-workpiece interface is calculated by the simulation results and analyzed for safe tooling. Therefore the numerical simulation works provide a combined extrusion process of stable cold forging process planning to avoid the severe damage on the tool.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.218-223
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• 2001

Many research of elastohydrodynamic lubrication (EHL) has been performed under the condition of steady state loding. However, mechanical elements undergo severe high loads that are fluctuating in general. Conventional numerical method for the circular contact of EHL study has a difficulty in converging the film pressure and thickness especially in high load of steady state. In this work, multigrid multilevel method expels the convergence problem under the condition of high load and very stable convergence is obtained under the dynamic loading condition over 1.0GPa. Several results of dynamic loading condition are shown and compared with those of steady state condition.

• The Korean Journal of Pain
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• v.12 no.2
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• pp.253-257
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• 1999

Hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome, a variant presentation of severe preeclampsia/eclampsia is associated with high maternal morbidity and mortality. Despite several advantages to the use of epidural analgesia for the management of labor pain in preeclamptic parturients, this procedure is relatively contraindicated in the presence of severe thrombocytopenia. Determining the pain management of choice depends on the parturient's condition, fetal well-being, and the urgency of the situation. We report a safe case of epidural analgesia in a HELLP syndrome parturient with severe thrombocytopenia for labor pain management without any neurologic complications or epidural hematoma.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.10
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• pp.1894-1899
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• 2010

This note is concerned with a robust sliding mode control(SMC) for a class of unmatched uncertain system with severe commensurate state time delay. The suggested method is extended to the control of severe state time delay systems with unmatched uncertainties except the matched input matrix uncertainty. A transformed sliding surface is proposed and a stabilizing control input is suggested. The closed loop stability together with the existence condition of the sliding mode on the proposed sliding surface is investigated through one Lemma and two Theorems by using the Lyapunov direct method with the concept of the control Lyapunov function instead of complex Lyapunov-Kravoskii functionals. Through an illustrative example and simulation study, the usefulness of the main results is verified.

• Journal of Yeungnam Medical Science
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• v.38 no.3
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• pp.235-239
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• 2021

Accessory cavitated uterine mass (ACUM) is a rare and unique condition seen in young women. We report cases of ACUMs in two patients, a 14-year-old girl and a 25-year-old woman, both with complaints of severe dysmenorrhea that had started at menarche and had progressively worsened since. A large cystic lesion was localized in the anterolateral wall of the myometrium separate from the endometrium, which was difficult to distinguish from congenital uterine anomalies. Laparoscopic excision of the ACUMs was successful and completely resolved the dysmenorrhea. Early investigation of severe dysmenorrhea in young women can provide appropriate management and relieve symptoms.

• Journal of Medicine and Life Science
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• v.17 no.3
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• pp.103-106
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• 2020

Bone marrow failure, such as aplastic or myelophthisic anemia, can occur due to an underlying lymphoid malignancy and cause life-threatening events. A 58-year-old man diagnosed with angioimmunoblastic T-cell lymphoma had recently visited the emergency department because of an altered level of consciousness caused by acute severe anemia. The laboratory findings were strongly suggestive of bone marrow failure syndrome. Bone marrow examination was immediately performed and, subsequently, dexamethasone was initiated to control the underlying lymphoma. Intravenous immunoglobulin was also administered in combination due to combined immune hemolytic anemia and thrombocytopenia. Bone marrow examination revealed a packed marrow with marked fibrosis and lymphoma involvement. A diagnosis of secondary myelofibrosis related to the underlying lymphoma was made, and sequential combination chemotherapy was introduced despite the presence of severe anemia and thrombocytopenia. After combination chemotherapy, his hematologic profile and underlying lymphoma improved. Better understanding of various hematologic manifestations and knowledge of the rare condition of lymphoma are essential for appropriate diagnostic approaches and treatment.

• Journal of Chest Surgery
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• v.55 no.3
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• pp.239-242
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• 2022

Papillary muscle rupture with severe acute mitral regurgitation is a rare complication of acute myocardial infarction (AMI) that causes pulmonary congestion and cardiogenic shock. Moreover, it has a poor prognosis. Surgical intervention, including revascularization, is indicated; however, surgical mortality remains high. We report the case of an 85-year-old woman with cardiogenic shock from severe acute mitral regurgitation, in whom a hybrid intervention, combining percutaneous coronary intervention with mitral valve replacement via minithoracotomy, was performed after post-infarction papillary muscle rupture. She was discharged in a favorable clinical condition. We describe a novel hybrid intervention for treating a rare complication of AMI, which could minimize surgical invasion in elderly patients, prevent disuse syndrome after the intervention, and improve prognosis. However, mitral valve surgery via minithoracotomy for emergency cases requires technical proficiency, as well as collaboration with other healthcare professionals, and the choice to perform this procedure requires careful consideration.