• Journal of Ship and Ocean Technology
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• 제6권1호
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• pp.1-15
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• 2002

A new concept for launching free-fall lifeboats, proposed by Yokohama National University is described in this paper. It has been pointed out that, using the conventional single-skid free-fall system, the potential for dangerous lifeboat motions (in which the lifeboat moves backward or jerks on the surface after entering the water) increases with the fall height of the lifeboat. One of the principal causes of this undesirable motion is vertical rotation of the lifeboat during its restricted fall at the edge of the launching skid. Thus a new "double-skid"launching concept is proposed to effectively eliminate the rotation of the lifeboat at the skid end and to enable the lifeboat to move smoothly after entering the water. In order to evaluate the performance of the proposed method, a series of model experiments and numerical simulations is carried out in which two lifeboat models with overall lengths of 1 meter and 6 meters are used. The effects of design parameters such as skid angle and skid height are investigated, and an example of the implementation of this new system at the stern of a large merchant ship is illustrated.

• 전자공학회논문지
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• 제54권3호
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• pp.15-21
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• 2017

능동 소나시스템에서 수신 신호의 해상도를 높이기 위한 방법은 다양하게 연구되어 왔다. 본 논문에서는 착저 물체의 탐지 해상도를 높이기 위한 방법으로 소나의 평면 배열 (planar array) 설계를 수행하였다. 해상력이 높은 좁은 형태의 빔 패턴을 얻기 위해서는 평면 형태의 어레이를 고려하는 것이 필요하다. 어레이를 구성하는 개별 음향 트랜스듀서의 송신 주파수는 13 kHz를 사용하였다. 비대칭 크기를 갖는 목표물의 효율적인 탐지를 위해 어레이 디자인에서 방위각(azimuth angle)과 고도각(elevation angle)에 따른 해상도를 동시에 고려하기 위해 areal angle 개념을 사용하였다. 그에 따라 목표 해상도를 만족하는 areal angle을 먼저 구하고 이를 역산하여 각각 목표 방위각과 고도각을 계산하여 어레이의 설계를 진행하였다.

• 대한족부족관절학회지
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• 제9권1호
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• pp.13-19
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• 2005

Purpose: To determine the radiographic changes in forefoot geometry with weight-bearing. Materials and Methods: The forefoot radiographs of 100 normal Korean adults, 50 male and 50 female volunteers, were evaluated both in nonweight-bearing and weight-bearing. The mean age was 27 years with range of 21-39 years. Those with normal feet were selected from volunteers having no history of foot problems or other musculoskeletal diseases. Results: The changes of measured angle between phalanges and metatarsals with weight-bearing were as follows; Hallux valgus angle was noted to increase in 20% of the feet, decrease in 59%, and remained unchange in 21%. Intermetatarsal angle $1{\sim}2$ was noted to increase in 76% of the feet, decrease in 3%, and remained unchange in 21%. Intermetatarsal angle $1{\sim}5$ was noted to increase in 95% and remained unchange in 5%. Shift in medial sesamoid on weight-bearing was also not consistent. Lateral shift was noted in 27%, no shift in 66%, medial shift in 7%. Conclusion: The generalized concept that the angles between bones and shift of medial sesamoid in the forefoot will change consistently with weightbearing was not found.

• 한국산학기술학회논문지
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• 제16권10호
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• pp.6917-6924
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• 2015

인간의 시각구조는 시야각과 가시거리에 의해 형성된다. 그러나 시지각에 기반한 대다수의 공간구조분석이론은 시야각을 반영하고 있지 않거나 평면적인 시야각만을 고려하고 있다. 일부 반영하는 이론들도 시야각에 포함된 부분과 제외된 부분을 이분법적으로 분리시킨 이론으로서 인간의 보편적 주시특성이 배제되어 있다. 본 연구는 아이트래킹 실험을 통하여 시야각의 한계를 실증적으로 파악하고 시야각별 주시확률을 도출하여, 이를 3차원 가시성 분석이론에 적용하였다. 그리고 시야각체 제한이 가능한 공간 시지각 분석어플리케이션을 제작하고 여기에 시야각별 Multiple frustum culling의 개념을 적용하여 그 가능성을 파악하였다. 주시특성 파악은 33명을 대상으로 이동형 아이트래커를 이용하여 임의의 공간에 대한 3분간의 보행과정을 측정한 데이터를 수집하였으며, 각도별로 주시고정 빈도 확률을 분석하여 데이터를 마련하였다.

• 한국추진공학회지
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• 제23권1호
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• pp.24-32
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• 2019

유체 추력벡터 제어에서 이중목 노즐 개념의 이용 가능성을 조사하기 위하여, 초음속 노즐에서 수치해석을 수행하였다. 수치해석 검증에서 SST $k-{\omega}$ 난류모델을 사용하여 실험결과를 잘 구현하였다. 광범위한 노즐 압력비와 분사 압력비에서 편향각도, 시스템의 전체 추력비 및 추력 효율을 조사하였다. 본 연구에서 이중목 노즐의 추력벡터제어 시스템의 성능 변화는 2차원 계산영역에서 명확하게 설명되었다. 본 연구에서 얻어진 결과들은 유체추력벡터제어 분야에 중요한 기초자료를 제공할 것이다.

• 한국소음진동공학회논문집
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• 제24권7호
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• pp.537-548
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• 2014

In this paper, horn loudspeaker modeling was suggested, investigated and verified through comparison of test results and simulation ones based on input electrical impedance curves and acoustic sensitivity ones. First, Thiele Small parameters of horn driver were identified by using pseudo loudspeaker model concept and verified in case of both closed and open horndriver. Second, cone-shaped horn models were investigated and compared with input acoustic impedance curves for real horn(cone angle $6.6^{\circ}$) and short horn(cone angle $27.9^{\circ}$). It showed that Leach model for cone horn was well described to test results, which were electrical impedance and acoustic sensitivity, compared to Lemaitre one. To represent horn system model good approximation in wide frequency range, mass correction filter and lowpass filter were adopted and consequently showed good fitted to test results.

• 대한두개안면성형외과학회지
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• 제21권6호
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• pp.351-356
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• 2020

Background: We have devised a novel surgical method, termed as temporalis muscle tendonperiosteum (T-P) compound surgical method, by modifying pre-existing techniques. Our method is characterized by elevation of temporalis muscle tendon and the periosteum of the mandibular ramus as a single compound. Here, we describe the concept and clinical outcomes of our method. Methods: We conducted both a cadaveric study and a clinical study. First, we used four human cadavers (two males and two females) to confirm the anatomy of the temporalis muscle tendon and availability of sufficient length extension through the elevation of the T-P compound. Moreover, we obtained measurements of the mouth angle and the philtrum angle from a total of six patients (two males and four females) and compared them between preoperatively and postoperatively. Results: The mean length of the periosteal portion was measured as 2.43± 0.15 cm (range, 2.2-2.6 cm). There was an improvement in the mouth angle postoperatively as compared with preoperatively (7.2°± 3.0° vs. 14.5°± 4.7°, respectively). Moreover, there was also an improvement in the philtrum angle postoperatively as compared with preoperatively (7.2°± 3.4° vs. 17.2°± 6.5°, respectively). Conclusion: Our method is a simple, minimally-invasive modality that is effective in achieving good clinical outcomes. Its advantages include an ability to achieve a firm extension of the temporalis muscle tendon as well as a lack of requirement for a donor site that may cause complications.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.463-467
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• 2005

In this paper, the guidance law applicable to formation flight of UAV in three-dimensional space is proposed. The concept of miss distance, which is commonly used in the missile guidance laws, and Lyapunov stability theorem are effectively combined to obtain the guidance commands of the wingmen. The propose guidance law is easily integrated into the existing flight control system because the guidance commands are given in terms of velocity, flight path angle and heading angle to form the prescribed formation. In this guidance law, communication is required between the leader and the wingmen to achieve autonomous formation. The wingmen are only required the current position and velocity information of the leader vehicle. The performance of the proposed guidance law is evaluated using the complete nonlinear 6-DOF aircraft system. This system is integrated with nonlinear aerodynamic and engine characteristics, actuator servo limitations for control surfaces, various stability and control augmentation system, and autopilots. From the nonlinear simulation results, the new guidance law for formation flight shows that the vehicles involved in formation flight are perfectly formed the prescribed formation satisfying the several constraints such as final velocity, flight path angle, and heading angle.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1998년도 제10회 학술강연회논문집
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• pp.13-13
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• 1998

A simple model of the tip leakage flow models of the rotor downstream flow is developed, based on Lakshminarayana's theoretical concept on the tip clearance flow and the experimental data published in open literature. And new spanwise distribution models of deviation angle and pressure loss coefficient due to the tip leakage flow are formulated for use in association with the streamline curvature method as a through flow analysis. Combining these new models and previous deviation and loss models due to secondary flow, a robust streamline curvature method is established for flow analysis of single-stage, subsonic axial turbines with wide ranges of turning angle, aspect ratio and blading type. At the exit from rotor rows, the flow variables are mixed radially according to a spanwise transport equation. The proposed streamline curvature method is tested against a forced vortex type turbine as well as a free vortex type one. The results show that the spanwise variations of flow angle, axial velocity and loss coefficients at rotor exit are predicted with good accuracy, being comparable to a steady three-dimensional Navier-Stokes analysis. This simple and fast flow analysis is found to be very useful for the turbine design at the initial design phase.

• 대한기계학회논문집B
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• 제29권4호
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• pp.425-434
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• 2005

In order to analyze pulsating flows in elastic blood vessels, a method based on the ALE concept and finite volume method was reformed and modulated to include wall motion of elastic vessels and impedance phase angle(phase difference between wall motion and blood flow). Our study indicated wall shear rates(WSR) were significantly influenced by the wall motion and the impedance phase angle. For larger wall motion more than $5{\%},$ the computed WSR started to deviate from the results of the perturbation theory that assumed smaller wall motion. The study showed that oscillatory shear index increased as the impedance phase angle became more negative like $-70{\circ}\;or\;-80{\circ}$ due to reduced mean WSR and increased amplitude of WSR. This result indicated that hypertensive patients are more vulnerable to atherosclerosis than normal persons because of the role of more negative impedance phase angles usually observed in these patients.