• 한국항공우주학회지
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• 제49권8호
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• pp.637-648
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• 2021

본 논문에서는 한국형 우주비행기(KSP)에 대한 새로운 재진입 유도를 제안하고자 한다. 제안된 방법은 우주 왕복선 유도 개념과 유사하게 다양한 비행경로 제약조건과 경계조건을 만족시키는 기준 항력 프로파일을 미리 결정하고, 결정된 기준 항력 프로파일을 추종하는 방식으로 유도명령이 구현된다. 이를 위해 본 연구에서는 항력 동역학을 조사하였으며, 그 결과 항력과 비행경로각의 동역학적 응답 특성이 상당히 다르다는 사실이 밝혀졌다. 이 사실을 바탕으로 제안한 유도명령은 시간분리 기법과 궤환선형화 방법을 사용하여 결정된다. 제안한 유도기법의 주요 특징은 간단한 구조와 명확한 작동 메커니즘에 있다. 따라서 제안된 방법은 기존 방법에 비해 구현이 간단하다. 본 논문에서는 제안된 방법의 성능을 조사하기 위해 수치 시뮬레이션을 수행한다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1998년도 제13차 학술회의논문집
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• pp.47-52
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• 1998

This study deals with guidance and control laws for an optimal reentry trajectory of a vertical landing reusable launch vehicle (RLV) in the future. First, a guidance law is designed to create the reference trajectory which minimizes propellant consumption. Then, a nonlinear feedback controller based on a linear quadratic regulator is designed to make the vehicle follow the predetermined reference trajectory, The proposed method is simulated for the first stage of the H-II scale rocket.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1228-1233
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• 2005

In this paper, we present a new guidance law for a reusable launch vehicle (RLV) that lands vertically after reentry. In our past studies, a guidance law was developed for a vertical/soft landing to a target point. The guidance law, which is analytically obtained, can regenerate a trajectory against disturbances because it is expressed in the form of state feedback. However, the guidance law does not necessarily guarantee a vertical/soft landing when a dynamical system such as an RLV includes a nonlinear phenomenon owing to the atmosphere of the earth. In this study, we introduce a design of the guidance law for a nonlinear system to achieve a vertical/soft landing on the ground using the exact linearization method and solving the two-point boundary-value problem for the derived linear system. Numerical simulation confirmed the validity of the proposed guidance law for an RLV in an atmospheric environment.

• Clinical and Experimental Pediatrics
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• 제60권12호
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• pp.390-394
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• 2017

Purpose: Atrioventricular nodal reentry tachycardia (AVNRT) is less common in pediatric patients than in adult patients. Thus, data for pediatric AVNRT patients are insufficient. Hence, we aimed to analyze the patient characteristics, treatment, and any recurrences in pediatric AVNRT patients. Methods: We reviewed the records of 50 pediatric AVNRT patients who had undergone radiofrequency catheter ablation (RFCA) between January 1998 and December 2016 at a single regional center. The patients were aged ${\leq}18years$. Results: Among 190 pediatric patients who underwent RFCA for tachyarrhythmia, 50 (26.3%; mean age, $13.4{\pm}2.6years$) were diagnosed as having AVNRT by electrophysiological study. Twenty-five patients (25 of 50, 50%) were male. Twenty patients (20 of 50, 40%) used beta-blockers before RFCA. All patients had no structural heart disease except 1 patient with valvular aortic stenosis and coarctation of the aorta. RFCA was performed using the anatomic approach under fluoroscopic guidance. The most common successfully ablated region was the midseptal region (25 of 50, 50%). Slow pathway (SP) ablation and SP modulation were performed in 43 and 6 patients, respectively. Complication occurred in 1 patient with complete atrioventricular block. During follow-up, 6 patients had recurrence of supraventricular tachycardia, as confirmed by electrocardiography. Among them, 5 underwent successful ablation at the first procedure. In 1 patient, induction failed during the first procedure. Conclusion: RFCA is safe and effective in pediatric AVNRT patients. However, further research is needed for establishing the endpoints of ablation in pediatric AVNRT patients and for identifying risk factors by evaluating data on AVNRT recurrence after RFCA.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• 제24권3호
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• pp.141-150
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• 2013

Objectives : The objective of this report is to identify the utilization of hospital school service during hospitalization among patients in their childhood and adolescence with psychiatric disorders. Methods : We retrospectively reviewed the medical record of child and adolescent psychiatric who were hospitalized during March 2009 through October 2012. We compared the one-year successful schooling and outpatient follow up rate between users and nonusers of the inpatient hospital school service. The hospital schooling experiences of the users were investigated upon follow-up visits to the outpatient clinic. Results : Sixty-three students received hospital school service during hospitalization among total 122 child and adolescent inpatients. Hospital school participants showed a significantly higher school reentry rate (61.9%) than non-participants (40.7%). However, there was no difference on follow up rate between the two groups. More than 60% of the 22 interviewed participants expressed an above-average level of satisfaction about hospital school service. Conclusion : Many patients with mental illness experience difficulty in receiving school education during treatment. That induces deterioration in disease, academic failure, poor social skills, low self-esteem, economic difficulties, and future job opportunities. The results of this study emphasize the importance of hospital school service and offer useful guidance for hospital school operation.