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Dynamic Analysis of Effect of Number of Balls on Rotor-Bearing System
황평,Hwang, Pyung,Nguyen, Van Trang Korean Tribology Society 2013 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.8 No.1
This paper presents a numerical model for investigating the structural dynamic response of an unbalanced rotor system supported on deep groove ball bearings. The aim of this work is to develop a numerical model for investigating the effect of the number of balls on the dynamic characteristics of the rotor ball bearing system. The fourth-order Runge-Kutta numerical integration technique has been applied. The results are presented in the form of time displacement responses and frequency spectra. The analysis demonstrates that the model can be used as a tool for predicting the nonlinear dynamic behavior of the rotor ball bearing system under different operating conditions. Moreover, the study may contribute to a further understanding of the nonlinear dynamics of rotor bearing systems.
가족 내 발생을 보인 Wolff-Parkinson-White 증후군 2례
주찬웅,임소희,황평한,Joo, Chan Uhng,Lim, So Hee,Hwang, Pyung Han 대한소아청소년과학회 2002 Clinical and Experimental Pediatrics (CEP) Vol.45 No.9
WPW 증후군은 발작성 상실성 빈맥을 유발할 수 있는데 매우 드물게 가족 내 동시 발생이 보고되고 있다. 그런데 최근 유전자 연구에 의해 가족 내 동시 발생된 WPW 증후군의 경우 PRKAG2 유전자의 변이가 보고된 바 있다. 저자들은 빈맥 등 특이할 만한 임상증상을 보이지 않았던 한가족에서 3명의 자녀 중 남매 간에 WPW 증후군의 심전도 소견을 동시에 나타낸 증례를 보고하면서 PRKAG2 유전자 검사 소견을 분석하였는데 이 유전자의 변이 소견이 환아와 가족 내에서 관찰되지 않아 본 증례의 원인으로 다른 유전자의 변이 가능성을 보고하는 바이다. Wolff-Parkinson-White(WPW) syndrome is characterized by electrographic evidence of ventricular preexcitation, which predisposes to supraventicular arrhythmias. Familial occurrence of WPW syndrome is uncommon. We observed two affected siblings in a family. Five members of the family underwent 12-lead electrocardiography and echocardiography. Although known genetic abnormality of the 7q34-q36(PRKAG2) for the familial WPW syndrome was evaluated, the mutation was not detected in this family. Other unknown mutations responsible for this familial WPW syndrome were suggested.
유전자 돌연변이 분석을 이용하여 진단된 Glycogen storage disease type Ia 1례
유가영(Ka Young Yu),노성훈(Sung Hoon Noh),황평한(Pyung Han Hwang),김선준(Sun Jun Kim) 대한소아신경학회 2009 대한소아신경학회지 Vol.17 No.1
저자들은 혈뇨와 관절 구축 및 발달 지연으로 내원한 의료적 방임 상태의 14세 여자 환자에서 간종대로 인한 복부팽만, 성장발육부전, 다발성 병적 골절에 의한 관절 구축 등의 임상 양상과 저혈당, 고 지혈증, 고 뇨산혈증, 혈뇨 및 요 결석, 고칼슘뇨증 등의 생화학 검사 소견과 함께 유전자 돌연변이 분석을 이용하여 진단된 당원병 제 Ia 환자 1례를 보고하는 바이다. Glycogen storage disease(GSD) type Ia is an autosomal recessive disease, caused by the absence or deficiency of glucose-6-phosphatase activity in the liver, kidney, and intestinal mucosa. Glucose-6-phosphatase is an essential enzyme necessary for gluconeogenesis and glycogenolysis. GSD type Ia is characterized by hypoglycemia, lactic acidosis, hepatomegaly, seizures, doll-like faces with fat cheeks, thin extremities, short stature, protuberant abdomen, easy bruising and epistaxis, delayed puberty, early gout, pancreatitis, kidney stone, and other metabolic derangements such as hyperlipidemia. The most important complications of GSD-Ia are focal segmental glomerulosclerosis and hepatic adenomas. Various mutations have been reported. The most common mutation sites are g727t, G122D, and T255I and also P178A and Y128X muations have been reported. We experienced a female patient showing typical clinical characteristics, laboratory findings such as hypoglycemia, hyperuricemia, and hyperlipidemia, and g727t mutation confirmed by DNA analysis. We present this case with a brief review of related articles.
교란 유한요소법을 이용한 하드 디스크 슬라이더의 동특성 해석
황평(Pyung Hwang),콴폴리냐(Polina V. Khan) 한국트라이볼로지학회 2004 한국트라이볼로지학회 학술대회 Vol.39 No.-
The numerical analysis of the hard disk drive slider is presented. The pressure distribution was calculated using the finite element method. The generalized Reynolds equation was applied in order to include the gas rarefaction effect. The balance of the air bearing force and preload force was considered. The characteristics of the small vibrations near the equilibrium were studied using the perturbation method. Triangular mesh with variable element size was employed to model the two-rail slider. The flying height, pitching angle, rolling angle, stiffness and damping of the two-rail slider were calculated for radial position changing from the inner radius to the outer radius and for a wide range of the slider crown values. It was found that the flying height, pitching angle and rolling angle were increased with radial position while the stiffness and damping coefficients were decreased. The higher values of crown resulted in increased flying height, pitching angle and damping and decreased stiffness.
Pyung Hwang(황평),Van Trang Nguyen(트랑뉴엔) 한국자동차공학회 2013 한국자동차공학회 부문종합 학술대회 Vol.2013 No.5
In recent years with continuing demands for increased performance, most of electric motors are now being designed for operation at high speed, a trend which has resulted in increased mechanical vibration and noise problems. Dynamic analysis of rotor system need to be done to predict vibration behavior in rotating structures to improve the design and decrease the possibility of failure. For this work, nonlinear dynamics of rotor system will be considered with the effect of internal radial clearance. The aim of this work is to develop a numerical model for investigation of the influence of nonlinear source on the dynamic characteristic of rotor ball bearing system. The numerical integration technique 4th order Runge-Kutta method is used to solve the system of nonlinear differential equations iteratively. The result presents here have been achieve from huge number of numerical integrations; mainly presented in form of time displacement response, frequency spectra, and Poincare map. Analyses have been carried out to observe that the characteristic of the dynamic behavior of the system is sensitive to small variation of the system parameters and the effect of radial internal clearance on the dynamic characteristics of a rotor-ball bearing system.
Load/Unload 하드 디스크 드라이브 시스템에의 Fold Bifurcations 의 교란 유한욧 해석
황평 ( Pyung Hwang ),콴폴리냐 ( Polina V. Khan ) 정보저장시스템학회 2005 추계학술대회논문집 Vol.2005 No.-
The load/unload behavior of the hard disk drive slider is studied in terms of the air bearing static characteristics. The numerical continuation methods are applied to calculate suspension force - equilibrium position curve. The critical preloads of the femto size slider are analyzed. The bi-stability conditions are depicted on the skew angle - preload diagram. The perturbation method is used to check the stability of the solution branches.