• Archives of Plastic Surgery
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• 제33권1호
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• pp.53-60
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• 2006

The current authors performed two-stage ear reconstruction of microtia using autogenous costal cartilage combined with canaloplasty of the acoustic meatus in a team approach. In the first stage, lobule transposition, fabrication of the cartilage framework, and implantation of the framework were peformed. In the second stage, elevation of the auricle, cartilage graft for posterior auricular sulcus, coverage with the mastoid fascia flap and skin graft, and concha excavation were performed. The canaloplasty was combined simultaneously in patients with radiologic and audiometric evidence of cochlear function in the second stage. A total of 36 consecutive patients with congenital microtia were treated from 1998 to 2003. Among them, 27 patients(male: 18, female: 9) ranging from 7 to 43 years old were combined with canaloplasty. The follow-up period was one year to 5 years. Thirteen patients exhibited improved hearing over 30 dB PTA(pure tone average), 9 patients below 30 dB, and 5 patients with no improvement. Complications related to the canaloplasty were chronic drainages of the auditory meatus and meatal stenosis. Lobule type deformity combined with the canaloplasty showed higher complications than concha type. Therefore, in the lobule type, meticulous manipulation is necessary to reduce complications after the canaloplasty.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.309-317
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• 2011

비행 마하수 6으로 운용되며, 지상 정지 추력으로부터 사용이 가능하도록 2단 추진체 개념이 적용된 스크램제트 엔진 비행체에 대한 개념설계를 수행하였다. 1단은 로켓을 적용되었으며, 2단은 탄화수소 계열의 연료를 사용하는 스크램제트 엔진이 적용되었다. 개념설계를 위하여 반경 2,000km의 운용거리와 0.2톤의 탑재체 무게를 가정하였다. 개념설계의 첫 번째 단계로 3-DOF 코드를 이용하여 비행궤도를 계산하였으며, 계산된 비행계도를 바탕으로 일차원-비평형 유동 코드와 NASA의 HASA 데이터베이스를 이용하여 스크램제트 엔진에 대한 개념설계를 수행하였다.

• 한국정밀공학회지
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• 제23권2호
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• pp.43-50
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• 2006

Recently, with rapid development of semiconductor and flat panel display, the manufacturing equipments are required to have large travel range, high productivity, and high accuracy. In this paper, an ultra precision decoupled dual servo (DDS) system is proposed to meet these requirements. And a control scheme for the DDS is studied. The proposed DDS consists of a $XY{\Theta}$ fine stage for handling work-pieces precisely and a XY coarse stage for large travel range. The fine stage consists of four voice coil motors (VCM) and air bearing guides. The coarse stage consists of linear motors and air bearing guides. The DDS is mechanically decoupled between coarse stage and fine stage. Therefore, both stages must be controlled independently and the performance of the DDS is mainly determined by the fine stage. For high performance tracking, the controller of fine stage consists of time delay control (TDC) and perturbation observer while the controller of coarse stage is TDC alone. With these individual controllers, two kinds of dual-servo control strategies are suggested: master-slave type and parallel type. By simulations and experiments, the performances of two dual-servo control strategies are compared.

• 대한전기학회논문지:전력기술부문A
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• 제50권9호
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• pp.424-430
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• 2001

A multi-level optimal power flow(OPF) algorithm has been evolved from a simple two stage optimal Power flow algorithm for constrained power economic dispatch control. In the proposed algorithm, we consider various constraints such as ower balance, generation capacity, transmission line capacity, transmission losses, security equality, and security inequality constraints. The proposed algorithm consists of four stages. At the first stage, we solve the aggregated problem that is the crude classical economic dispatch problem without considering transmission losses. An initial solution is obtained by the aggregation concept in which the solution satisfies the power balance equations and generation capacity constraints. Then, after load flow analysis, the transmission losses of an initial generation setting are matched by the slack bus generator that produces power with the cheapest cost. At the second stage we consider transmission losses. Formulation of the second stage becomes classical economic dispatch problem involving the transmission losses, which are distributed to all generators. Once a feasible solution is obtained from the second stage, transmission capacity and other violations are checked and corrected locally and quickly at the third stage. The fourth stage fine tunes the solution of the third stage to reach a real minimum. The proposed approach speeds up the two stage optimization method to an average gain of 2.99 for IEEE 30, 57, and 118 bus systems and EPRI Scenario systems A through D testings.

• Journal of Mechanical Science and Technology
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• 제15권11호
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• pp.1548-1554
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• 2001

Flow patterns and dynamic properties of two-stage Weis-Fogh type ship propulsion mechanism are studied by a discrete vortex method. To study mutual interference between two wings, two cases are con sidered - wing motions with the same and reverse phases. The predicted flow patterns correspond to the available flow visualization results. Time histories of thrust and drag coefficients are also calculated, and the interference between the two wings are numerically clarified.

• Journal of information and communication convergence engineering
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• 제14권1호
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• pp.1-8
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• 2016

Spectrum sensing in cognitive radio networks allows secondary users to sense the unused spectrum without causing interference to primary users. Cognitive radio requires more accurate sensing results from unused portions of the spectrum. Accurate spectrum sensing techniques can reduce the probability of false alarms and misdetection. In this paper, a two-stage spectrum sensing scheme is proposed for cooperative spectrum sensing in cognitive radio networks. In the first stage, spectrum sensing is executed for each secondary user using energy detection based on double adaptive thresholds to determine the spectrum condition. If the energy value lies between two thresholds, a fuzzy logic scheme is applied to determine the channel conditions more accurately. In the second stage, a fusion center combines the results of each secondary user and uses a fuzzy logic scheme for combining all decisions. The simulation results show that the proposed scheme provides increased sensing accuracy by about 20% in some cases.

• Communications for Statistical Applications and Methods
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• 제15권5호
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• pp.727-735
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• 2008

Consider a clinical trial in which the main end-point is survival. Suppose after the start of the study an intermediate event occurs which may be influenced by a covariate(or treatment). In many clinical studies the occurrence of an intermediate event may change the survival distribution. This investigation develops two-stage model which, in the first stage, models the effect of covariate on the intermediate event and models the relationship between survival time and covariate as well as the intermediate event. In this paper, the two-stage model is presented in order to model intermediate event and a test based on this model is also provided. A numerical simulations are carried out to evaluate its overall significance level.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.611-616
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• 2001

This paper analyzed PFC of active clamp ZVS flyback converter by adding two methods PFC (power Factor Correction) circuit - two-stage and single-stage. The addition of active clamp circuit also provides a mechanism for achieving ZVS of both the primary and auxiliary switches. ZVS also limits the turn off di/dt of the output rectifier, reducing rectifier-switching loss and switching noise, due to diode reverse recovery. As a result, the proposed converters have characteristics of the reduced switching noise and high efficiency in comparison to conventional flyback converter. The simulation and experimental results show that the proposed converter improve the input PF of 300W ZVS flyback converter by adding single-stage, two-stage PFC circuit.

• 전자공학회논문지B
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• 제33B권5호
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• pp.102-108
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• 1996

Adaptive resonance theory (ART2) characterized by its built-in mechanism of handling the stability-plasticity switching and by the adaptive learning without forgetting informations learned in the past, is based on an unsupervised template matching. We propose an improved tow-stage learning algorithm for aRT2: the original unsupervised learning followed by a new supervised learning. Each of the output nodes, after the unsupervised learning, is labeled according to the category informations to reinforce the template pattern associated with the target output node belonging to the same category some dominant classes from exhausting a finite number of template patterns in ART2 inefficiently. Experimental results on a set of 2545 FLIR images show that the ART2 trained by the two-stage learning algorithm yields better accuracy than the original ART2, regardless of th esize of the network and the methods of evaluating the accuracy. This improvement shows the effectiveness of the two-stage learning process.

• 응용통계연구
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• 제1권2호
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• pp.27-33
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• 1987

감마분포에 따르는 K($\geq$2)개의 처리들 중에서 최대 척도모수를 갖는 처리를 선택하는 제거형 이단 선택방법을 제안하고 주어진 $(\delta^*, p^*)$에 대하여 Kim(1985)이 제안한 선택확률의 하한을 만족할때 설계상수(nr, mr, c)와 총실험횟수의 평균을 Monte Carlo 방법으로 구하였다. 또한 총실험횟수를 작게한다는 점에서 일단 선택방법보다 유용함을 밝혔다.