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DC 전동기 구동시스템을 위한 자기동조 속도제어기의 설계
지준근,차응석 순천향대학교 부설 산업기술연구소 1999 순천향 산업기술연구소논문집 Vol.5 No.2
This parer describes the design of self-tuning speed controller for DC motor drive system using RLS(Recursive Least Squares) algorithm and thole-P1acement method. The model parameters, related to inertia and damping coefficient of motor, are estimated on-line by using RLS estimation algorithm. And a control signal is calculated by using pole placement method. Simulation and experimental results show that the proposed controller possesses excellent adaptation capability than a conventional PI/IP controller under parameter change.
DC 전동기 구동시스템을 위한 자기동조 속도제어기의 설계
차응석(Eung-seok Cha),지준근(Jun-Keun Ji) 전력전자학회 1999 전력전자학술대회 논문집 Vol.- No.-
This paper describes the design of a self<br/> tuning speed controller for DC motor drive system using PWM To get a better transient response than conventional Proportional Integral (PI) and/or Integral Proportional(IP) speed control in the presence of parameter variances, the model parameters, relative to inertia and damping coefficient of motor, is estimated on-line by using Recursive Least Squares (RLS) estimation algorithm On the basis of the estimated model parameters and a pole placement design, a control signa1 is calculated. Experimental result show that the proposed controller possesses excellent adaptation capability than a conventional PI/IP controller under parameter change
모래의 수분함유량에 따른 비저항 및 비유전율의 주파수 의존성
이복희(Bok-Hee Lee),차응석(Eung-Suk Cha),최종혁(Jong-Hyuk Choi),최영철(Young-Chul Choi),유양우(Yang-Woo Yoo),안창환(Chang-Hwan Ann) 한국조명·전기설비학회 2009 한국조명·전기설비학회 학술대회논문집 Vol.2009 No.5월
In order to evaluate the performance of a grounding system against lightning or fault currents including high frequency components, the grounding impedance should be considered rather than its ground resistance. Recently, some researches on the evaluation and modeling of the grounding impedances have been carried out, but the results have not been yet sufficient. This paper deals with the frequency dependence of the resistivity and relative dielectric constant of sand associated with water contents. As a result, the resistivity of sand is getting lower with increasing water content, and it is nearly independent on the frequency in the range of less than 1㎒, and is decreased over the frequency range of above 1㎒. Also, the relative dielectric constant is rapidly decreased with the frequency in the range of less than 10㎑, but it is nearly not dependent on the frequency over the frequency range of 10㎑. It was found from this work that the frequency dependance of resistivity and relative dielectric constant of soil should be considered in designing the grounding systems for protection against lightning or surges.
수분함유량에 따른 토양의 저항률 및 비유전율의 주파수의존성
최종혁(Jong-Hyuk Choi),차응석(Eung-Suk Cha),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.1
고주파수성분을 포함하는 뇌격전류나 또는 고장전류에 대한 접지시스템의 성능을 평가하기 위해 접지저항보다는 접지임피던스에 대한 고려가 필요하다. 접지임피던스를 평가하기 위해서는 토양의 저항률과 비유전율의 주파수의존성이 규명되어야 한다. 본 논문은 3가지 다른 토양에 대하여 수분함유량에 따른 저항률과 비유전율의 주파수의존성을 나타낸다. 결론적으로 토양의 저항률은 수분함유량이 증가함에 따라서 작아지게 되고, 1[㎒]보다 낮은 주파수에서 거의 변화하지 않으며 1[㎒]이상의 주파수에서는 감소한다. 반면에 비유전율은 1[㎒]이하의 주파수에서 매우 급격하게 감소하며, 1[㎒]이상의 주파수에서는 거의 변화하지 않는 것으로 나타났다. 본 실험 결과로 부터 낙뢰 또는 개폐서지에 대한 보호를 목적으로하는 접지시스템의 설계시 토양의 저항률과 비유전율을 고려하는 것이 바람직한 것으로 밝혀졌다. In order to evaluate the performance of a grounding system against lightning or fault currents including high frequency components, the grounding impedance should be considered rather than the steady state ground resistance. To evaluate the ground impedance, the frequency dependence of resistivity and relative dielectric constant of the soil have to be analyzed. This paper deals with the frequency dependence of the resistivity and relative dielectric constant of three types of soil on water content. As a result, the resistivity of soil is getting lower with increasing of water content. It is nearly independent of the frequency in the range less than 1[㎒], and is decreased over the frequency range above 1[㎒]. On the other hand, the relative dielectric constant is rapidly decreased with the frequency in the range less than 1[㎒], but it is nearly independent on the frequency over the range of 1[㎒]. It was found from the experiments that the frequency-dependant resistivity and relative dielectric constant of soil should be considered when designing the grounding systems for protection from lightning or switching surges.
국소성 분질성 사구체경화증에서 Cyclosporin A의 치료효과
김병길,이재승,최인준,권민중,차응석 대한신장학회 1996 Kidney Research and Clinical Practice Vol.15 No.4
It is difficult to differentiate focal segmental glomerulosclerosis(FSGS) from MCNS clinically. However, FSGS is characterized by higher incidence of hematuria, poor selective protein index(SPI), resistance to steroid and progression to end stage renal failure. This study was designed to evaluated the clinical manifestation and the possible better management in FSGS. 31 cases of children who were diagnosed as FSGS on renal biopsies were studied retrospectively. Male to female ratio was 2.4 to l. The mean age at onset was 6 6/12 years(range 1 1/12-13 11/12 years). Proteinuria was detected in all cases and edema(87%), hematuria(45%), hypertension (35%), renal failure(26%) were also found. SPI was 0.31(?0.16). As management, steroid alone was used in 6 cases, cyclosporin A with steroid in 17 cases and cyclophosphamide with steroid in 2 cases. Patients were followed up for average 18 months and 7 cases progressed to chronic renal failure. There was no significant difference in the clinical and laboratoy findings between remission and no-remission group, and between CRF and non-CRF group at diagnosis. Remission rate was 33.4% with the regimen steroid alone and 58.8% with cydospo- rin A with steroid. In condusion, the renal biopsy should be performed for the patients with nephrotic syndrome resistant to steroid as soon as possible for the detection of FSGS. Cyclosporin A with steroid was more effective than steroid alone, even though no statistical difference between the two groups.
선천성 신증후군(Congenital Nephrotic Syndrome) 의 임상적 고찰
김병길,이연경,이재승,정현주,권민중,차응석 대한신장학회 1997 Kidney Research and Clinical Practice Vol.16 No.1
Congenital nephrotic syndrome(CNS) is a rare disease defined by nephrotic syndrome at birth or within the 1st year of life. This study is performed to investigate a classification based on clinicopathology and to evaluate the clinical course and prognosis according to types of CNS. We performed retrospective clinical study with chart review in 8 patients who were diagnosed as CNS from 1980 to 1995. The results were as follows; Their ages at the onset of illness ranged from birth to 7 months (median 2.2 months) and there were 7 males and 1 female. There were proteinuria, hypoalbuminemia and edema in all cases, accompanied with ascites(7cases), hematuria(5cases), hepatosplenomegaly(2cases), umbilical hernia(lcase) and inguinal hernia(lcase). A classification of these based on clinicopathology showed CNS of Finnish type in 2 patients, congenital syphilitic nephrotic syndrome in 2, mesangial glomerulosclerosis, minimal change disease, Drash syndrome and undefined CNS in 1 each. Of the 8 patients with CNS, 3 died of sepsis and renal failure, 1 responded to steroid and cyclosporin therapy and is alive at 20 months, 1 responded to penicillin, 1 discharged voluntarily, and 2 were lost to follow-up. In conclusion, it had been considered that all forms of CNS except the secondary ones have a very poor prognosis. But if the appropriate management including early renal transplantation is established under the definite diagnosis which is based on clinicopathology, we can expect long term sur- vival, normal growth and development for the child of CNS.