• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.1
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• pp.42-48
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• 2003

To get a periodic trim solution from Level II helicopter flight dynamic equations, DAE based PPT A (partial Periodic Trimming Algorithm) has been proposed. Iterative update of state variables from PPT A can cause a numerical instability in DAE solver which needs compatible initial conditions. By simply adjusting the order of DAE solver a periodic trim can be obtained with good accuracy. Application for CBM (Common Baseline Model) helicopter showed the same trim result as harmonic balance method and the effective elimination of unrealistic initial responses at the start of flight simulation.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.8 no.2
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• pp.67-80
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• 1998

논문에서는 프레임릴레이 프로토콜을 사용하는 암호 통신 시스템에 적합한 키 스트림 동기 방식을 제안하였다. 제안된 주소영역의 확장 비트를 이용한 키 스트림 동기 방식은 단위 측정 시간 동안 측정된 프레임릴레이 프로토콜의 주소영역의 확장 비트 정보와 플래그 패턴의 수신률을 이용하여 문턱값보다 적은 경우에 동기 신호와 세션 키를 전송하므로써 종래의 주기적인 동기 방식에서 전송 효율성 저하와 주기적인 상이한 세션 키 발생, 다음 주김까지 동기 이탈 상태로 인한 오류 확산 등의 단점을 해결하였다. 제안된 알고리즘을 데이터 링크 계층의 처리기능을 최소화하여 패킷 망의 고속화가 가능하도록 설계된 프레임릴레이 프로토콜에서 서비스되는 동기식 스트림 암호 통신 시스템에 적용하여 slip rate $10^{-7}$의 환경에서 주기가 Isec인 주기적인 동기 방식에서 요구되는 9.6*10/ sup 6/비트에 비해 6.4*$10^{5}$비트가 소요됨으로써 전송율 측면에서의 성능 향상과 오복호율과 오복호율과 오복호 데이터 비트 측면에서 성능 향상을 얻었다.다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.4
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• pp.25-32
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• 2006

An advanced method of Relaxed Static Stability (RSS) is utilized for improving the aerodynamic performance of modern version supersonic jet fighter aircraft. The flight control system utilize RSS criteria in both longitudinal and lateral-directional axes to achieve performance enhancements and improve stability. The T-50 advanced trainer employs the RSS concept in order to improve the aerodynamic performance and the flight control law in order to guarantee aircraft stability. The longitudinal two modes are the short period with high frequency and the phugoid mode with low frequency. The design goals of longitudinal control laws is concerned with the short period damping and frequency optimization using lower order equivalent system and utilizing the requirement of MIL-F-8785C. Analysis of short period mode has been and continues to be performed This paper addresses the analysis of aircraft phugoid node characteristics such as damping, natural frequency, and analysis of aircraft pitch motion that impacted by angle of attack limiter and auto pitch attitude control law.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.4
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• pp.297-305
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• 2011

In this study, the aeroelastic analysis of rotorcraft in forward flight has been performed using dynamic inflow model to handle unsteady aerodynamics. The quasi-steady airload model based on the blade element method has been coupled with dynamic inflow model developed by Peters and He. The nonlinear steady response to periodic motion is obtained by integrating the full finite element equation in time through a coupled trim procedure with a vehicle trim for stability analysis. The aerodynamic and structural characteristics of dynamic inflow model are validated against other numerical analysis results by comparing induced inflow and blade tip deflections(flap, lag). In order to validate aeroelastic stability of dynamic inflow model, lag damping are also compared with those of linear inflow model.

• The Journal of the Korea Contents Association
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• v.8 no.4
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• pp.86-91
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• 2008

To present the design procedure of discretized 8-bit tent map executing the transformation of tent function which is one of the chaotic functions, first, the truth table of discretized tent map was written, and then according to the simplified Boolean algebra equations obtained from the truth table, the discretized map is implemented with the exclusive logic gate as a real hardware. The discretized tent map circuit which provides the feedback circuit for generating the period-8 states relevant to the 8-bit finite precision is also designed and presented in this paper. Furthermore, it might be used stream cipher system with a new key-stream circuit for generate of chaotic binary sequence.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.6
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• pp.503-508
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• 2007

In this study, the aeroelastic response and stability of bearingless rotors are investigated using a large deflection beam theory. The outboard main blade, flexbeam, and torque tube are all assumed to be an elastic beam undergoing arbitrary large displacements and rotations. The finite element equations of motion obtained from Hamilton's principle. Two-dimensional quasi-steady strip theory is used to evaluate aerodynamic forces. In hover, the modal approach method based on coupled rotating natural modes is used for the stability analysis. In forward flight, the nonlinear periodic blade steady response is obtained by integrating the full finite element equation in time through a coupled trim procedure with a vehicle trim. The results of the full finite element analysis using the large deflection beam theory are compared with those of a previously published modal analysis using the moderate deflection-type beam theory.

• Korean Journal of Veterinary Research
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• v.34 no.4
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• pp.745-757
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• 1994

Superovulatory treatment with exogenous gonadotropins adversely affects the uterus through the disruption of the delicate balance of ovarian steroids (estrogens, progestins, androgens). To examine the uterine effects of this treatment, 189 rats were given 4IU, 20IU or 40IU pregnant mare',s serum gonadotropin(PMSG) at 28 days of age and sacrificed every 24h until day 10(D10) post injection. Long term uterine effects were examined in 12 rats treated with 4IU or 40IU PMSG and killed on D30. Adult rat uteri were examined to provide a reference for comparisons. Morphological and histological changes of control (4IU) uteri mimicked those of the adult on a comparable time-course form D2 to D5. Administration of superovulatory doses(20IU, 40IU) of PMSG produced stromal hypertrophy by D2 and focal papillary hyperplasia of the luminal epithelia by D3. Levels of $17{\beta}$-estradiol following 20IU and 40IU PMSG treatment were significantly(p<0.05, p<0.005) elevated above those of controls after D1. Androgen levels of both groups(20IU, 40IU) significantly p<0.05, p<005 increased from baseline on D1 and were maximum between D2 and D3. In the 20IU PMSG group, the hyperplasia gradually regressed after D3 and was absent by D10. The hyperplasia in the 40IU PMSG group, however, had become extensive by D6. It is suspected that preceding elevated levels of estrogen may be responsible for this progressive change. On D 4, the levels of $17{\beta}$-estradiol reached a maximum, which was significantly(p<0.001) greater than both the controls and 20IU PMSG-treated rats. Between D6 and D10, the hyperplasia in 40IU PMSG-treated rats partially regressed. Examination of uteri from D30 revealed no evidence of the hyperplasia. It is suggested that previous exposure to high levels of estrogen and androgens, secondary to superovulation, is possible cause for the observed hyperplasia.