• 한국운동역학회지
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• 제29권3호
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• pp.185-196
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• 2019

Objective: The aim of this study was to suggest correct and effective way of squat through biomechanical analysis variables on the change of the toe-out angle. Method: 7 high school male weightlifter (age: $17.57{\pm}0.53yrs$, height: $174.0{\pm}3.93cm$, weight: $81.0{\pm}9.17kg$, 1RM: $164.29{\pm}20.7kg$) participated in this study. Results: Angle of the hip joint at E2 was smaller than toe-out angle was in $20^{\circ}$ than in $0^{\circ}$ (p<.05). Angular velocity of the foot joint at E1 and E3 was quicker that in $10^{\circ}$ than in $30^{\circ}$ (p<.05). Anterior-posterior stability index was greater that toe-out angle was in $30^{\circ}$ than in $0^{\circ}$ (p<.05). In average iEMG of flexion phase, VM of right, left leg showed high activity at toe-out angle $30^{\circ}$. In average iEMG of flexion phase, extension phase and in peak iEMG, RF of right leg, VM and VL of left leg showed high activity at all of the toe-out angles. In average iEMG of flexion phase, extension phase and in peak iEMG, all of the muscles activity of right leg showed high in $10^{\circ}$ and low in $0^{\circ}$, $30^{\circ}$. Conclusion: It is judged that setting the toe-out angle $10^{\circ}$ in squat help to efficiently use muscles and ensure stability.

• Journal of Veterinary Science
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• 제25권1호
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• pp.2.1-2.14
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• 2024

Background: Sufficient surgical resection is necessary for effective tumor control, but is usually limited for vertebral tumors, especially in the cervical spine in small animal neurosurgery. Objective: To evaluate the primary stability and safety of customized three-dimensional (3D)-printed implants for cervical spine reconstruction after total vertebrectomy. Methods: Customized guides and implants were designed based on computed tomography (CT) imaging of five beagle cadavers and were 3D-printed. They were used to reconstruct C5 after total vertebrectomy. Postoperative CT images were obtained to evaluate the safety and accuracy of screw positioning. After harvesting 10 vertebral specimens (C3-C7) from intact (group A) and implanted spines (group B), implant stability was analyzed using a 4-point bending test comparing with groups A and C (reconstituted with plate and pins/polymethylmethacrylate after testing in Group A). Results: All customized implants were applied without gross neurovascular damage. In addition, 90% of the screws were in a safe area, with 7.5% in grade 1 (< 1.3 mm) and 2.5% in grade 2 (> 1.3 mm). The mean entry point and angular deviations were 0.81 ± 0.43 mm and 6.50 ± 5.11°, respectively. Groups B and C significantly decreased the range of motion (ROM) in C3-C7 compared with intact spines (p = 0.033, and 0.018). Both groups reduced overall ROM and neutral zone in C4-C6, but only group B showed significance (p = 0.005, and 0.027). Conclusion: Customized 3D-printed implants could safely and accurately replace a cervical vertebra in dog cadavers while providing primary stability.

• International Journal of Aeronautical and Space Sciences
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• 제8권1호
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• pp.10-20
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• 2007

For spacecraft attitude control, reaction wheel (RW) steering laws with more than three wheels for three-axis attitude control can be derived by using a control allocation (CA) approach.1-2 The CA technique deals with a problem of distributing a given control demand to available sets of actuators.3-4 There are many references for CA with applications to aerospace systems. For spacecraft, the control torque command for three body-fixed reference frames can be constructed by a combination of multiple wheels, usually four-wheel pyramid sets. Multi-wheel configurations can be exploited to satisfy a body-axis control torque requirement while satisfying objectives such as minimum control energy.1-2 In general, the reaction wheel steering laws determine required torque command for each wheel in the form of matrix pseudo-inverse. In general, the attitude control command is generated in the form of a feedback control. The spacecraft body angular rate measured by gyros is used to estimate angular displacement also.⁵ Combination of the body angular rate and attitude parameters such as quaternion and MRPs(Modified Rodrigues Parameters) is typically used in synthesizing the control command which should be produced by RWs.¹ The attitude sensor signals are usually corrupted by noise; gyros tend to contain errors such as drift and random noise. The attitude determination system can estimate such errors, and provide best true signals for feedback control.⁶ Even if the attitude determination system, for instance, sophisticated algorithm such as the EKF(Extended Kalman Filter) algorithm⁶, can eliminate the errors efficiently, it is quite probable that the control command still contains noise sources. The noise and/or other high frequency components in the control command would cause the wheel speed to change in an undesirable manner. The closed-loop system, governed by the feedback control law, is also directly affected by the noise due to imperfect sensor characteristics. The noise components in the sensor signal should be mitigated so that the control command is isolated from the noise effect. This can be done by adding a filter to the sensor output or preventing rapid change in the control command. Dynamic control allocation(DCA), recently studied by Härkegård, is to distribute the control command in the sense of dynamics⁴: the allocation is made over a certain time interval, not a fixed time instant. The dynamic behavior of the control command is taken into account in the course of distributing the control command. Not only the control command requirement, but also variation of the control command over a sampling interval is included in the performance criterion to be optimized. The result is a control command in the form of a finite difference equation over the given time interval.⁴ It results in a filter dynamics by taking the previous control command into account for the synthesis of current control command. Stability of the proposed dynamic control allocation (CA) approach was proved to ensure the control command is bounded at the steady-state. In this study, we extended the results presented in Ref. 4 by adding a two-step dynamic CA term in deriving the control allocation law. Also, the strict equality constraint, between the virtual and actual control inputs, is relaxed in order to construct control command with a smooth profile. The proposed DCA technique is applied to a spacecraft attitude control problem. The sensor noise and/or irregular signals, which are existent in most of spacecraft attitude sensors, can be handled effectively by the proposed approach.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제34권6호
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• pp.404-412
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• 2012

Purpose: The purpose of this study was to evaluate postsurgical facial hard tissue stability after orthognathic surgery with/without posterior impaction in skeletal class III malocclusion patients, and to evaluate the horizontal relapse tendency, according to changes in anteroposterior discrepancy and occlusal planes. Methods: Ninety patients, who had undergone orthognathic surgery in Pusan National University Dental Hospital, were enrolled in this study. Three main groups were classified as follows: Thirty patients underwent mandibular setback bilateral sagittal split ramus osteotomy (BSSRO) only (BSSRO group, BG); another thirty patients underwent mandibular setback BSSRO and Le Fort I osteotomy with posterior impaction (posterior impaction group, PG); and another thirty patients underwent mandibular setback BSSRO and Le Fort I osteotomy without posterior impaction (non-posterior impaction group, NPG). Preoperative (T0), immediate postoperative (T1) and six-month follow-up period (T2) lateral cephalograms were taken, and various parameters were measured. The analyses were done by linear and angular measurements between T0-T1 and T1-T2, to evaluate postsurgical facial hard tissue stability. Results: Mean horizontal relapse rates were distributed from 11.81% to 19.08%, and there were significant postsurgical changes (0.52 mm~2.44 mm) at the B point in all 3 groups. But, there were no statistical differences on relapse rate among BG, PG and NPG patients. Conclusion: In this study, the postsurgical stabilities of BSSRO and Le Fort I osteotomy with/without posterior impaction in skeletal class III malocclusion patients were acceptable. There were no significant statistical differences in mandibular stability according to changes in anteroposterior discrepancy and occlusal planes.

• 한국식품과학회지
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• 제46권5호
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• pp.593-600
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• 2014

찹쌀 전분과 검(XAT, LBG, 및 XAT:LBG) 혼합물의 페이스팅 특성과 이들 페이스트의 점탄특성 및 냉해동 안정성을 조사하여 일반 쌀 전분(20% 수준의 아밀로오스 함유)의 물성을 대체할 수 있으며 낮은 냉해동 안정성을 개선할 수 있는 찹쌀 전분-검 혼합물의 조성을 제시하고자 하였다. 찹쌀 전분은 검(XAT 및 LBG) 및 검 혼합물(XAT:LBG)에 의해 건조중량 대비 19:1의 비율로 대체하여(총 고형분 함량 5%, w/w) 페이스팅 점도 특성을 조사하였을 때 찹쌀 전분-검 혼합물 내의 XAT 농도가 낮아질수록 찹쌀 전분의 페이스팅 온도에 근접하였다. 최고점도는 찹쌀 전분-XAT 혼합물에서 가장 낮았으며 XAT와 LBG를 75:25의 비율의 검 혼합물로 찹쌀 전분을 대체하였을 때(X075L025)가 가장 높았다. 또한 찹쌀 전분-XAT:LBG의 최고점도에서 최종점도 사이의 온도 프로파일 범위에서 찹쌀 전분만을 이용하였을 때보다 높은 수준의 페이스팅 점도를 나타내었다. 찹쌀 전분-검 혼합물 페이스트의 점탄특성은 찹쌀 전분-XAT:LBG (X050L050 및 X025L050) 페이스트들에 한해 5 rad/s의 높은 진동수에서 일반 쌀 전분 페이스트의 저장탄성률과 유사해졌다. 손실탄성률은 모든 찹쌀 전분-검 혼합물 페이스틀이 찹쌀 전분과 일반 쌀 전분들 보다 높은 수준을 나타내었다. 냉해동 안정성과 관련하여 일반 쌀 전분 페이스트에 비해 찹쌀 전분 및 찹쌀 전분-검 혼합물들이 높은 냉해동 안정성을 나타내었다. 이 중 찹쌀 전분-XAT와 찹쌀 전분-XAT:LBG (X075L025)가 7회의 냉해동 순환처리에도 syneresis 현상이 관찰되지 않았다. 모든 결과들을 고려할 때 일반 쌀 전분을 대체할 수 있는 찹쌀 전분-검 혼합물은 XAT와 LBG를 건조중량 비율로 50:50으로 혼합한 검 혼합물을 찹쌀 전분의 건조중량의 5% 수준으로 대체하는 것으로 판단되었다.

• Archives of Plastic Surgery
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• 제38권6호
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• pp.821-828
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• 2011

Purpose: The authors applied Bilhaut-Cloquet procedure to Wassel type III and IV duplicated thumb, which was limited to patients with Wassel type I, II. This procedure was applied in order to improve the growth potential, range of joint motion, joint stability and cosmetic outcome. Methods: Sixteen patients received Bilhaut-Cloquet procedures to correct duplicated thumbs from May, 2005 to December, 2010. Seven patients were Wassel type III, nine patients were type IV. This procedure was applied not only to balanced type, but also unbalanced type or convergent type. Five patients were balanced type and eleven patients were unbalanced type. Convergent type of Wassel type IV was three. Sex ratio was the same, mean age at the operation was 20.1 months old (8~52 months old). Angular deformity, joint stability and range of joint motion and cosmetic outcome were considered together and estimated in Tada score. Also, postoperative subjective satisfaction score of the parents was evaluated by a 100-points scale. Results: Mean subjective satisfaction scored 75 points at 28 months after the operation. Radiologic study showed bony union of proximal phalangeal bone and stable joint in all patients. Range of motion was mean 20 degrees in interphalangeal joint and mean 73 degrees in metacarpophalangeal joint. Tada score showed 'good' in eleven patients (68.8%), 'fair' in three patients (18.7%) and 'poor' in two patients (12.5%). In seven patients those who were able to follow up for a long term showed no significant difference in length of proximal and distal phalangeal bones compared to the opposite thumb. Conclusion: Bilhaut-Cloquet procedure can be applied not only to balanced type of Wassel type III, IV duplicated thumb, but also to unbalanced type or convergent type that focused on functional reconstruction and cosmetic improvement.

• 조명전기설비학회논문지
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• 제14권3호
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• pp.49-58
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• 2000

본 논문에서는 FACTS(Flexible AC Transnission System)로 분류되는 여라 기기중 기존의 전압제어 및 무효 전력보상기들이 가지고 있는 바속응성과 불연속성 문제를 해결해줄 수 있는 정지형 무효전력 보상가(Static Var Compensator : SVC)를 포함한 전력계통에 신경회로망 제어기를 적용하여 안정화에 관하여 연구하였다. 제안된 신경회로망 제어기는 오차와 오차변화량을 입력하는 오차역전과 학습 알고리즘을 사용하고, 학습시간올 단축하기 위해 모멘텀 방법을 사용하였다. 제안된 방법의 강인섬을 입증하기 위해 중부하시 및 정상부하시에 초기 전력을 변동시킨 경우와 초기에 회천자각을 변동시킨 경우에 대하여 시스렘의 회전자각, 각속도 편차 특성 및 단 자전압의 동특성을 고찰하여 다른 시스템보다 응답특성이 우수합을 보였다.

• Journal of Astronomy and Space Sciences
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• 제20권3호
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• pp.205-216
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• 2003

회전안정화 로켓 모터를 이용하는 upper stage 위성체의 자세 불안정 현상을 연구하였다. 이 위성체는 대칭형의 본체와 내장된 유동질량으로 구성되며, 유동질량은 구진자로 모델링되었다. 종래의 선형모델이 갖는 단점을 보완하기 위해 정확한 시변 비선형 방정식을 사용하고, 본체 및 구진자 모두 회전 대칭축에 대해 정상상태에 있다고 가정하였다. 본 논문에서는 진자에 대한 준정상해(quasi-stationary solution) 및 공진조건을 파라미터의 함수로 결정하였다. 공진조건의 분석결과 유동질량은 계수자극 및 외부자극을 동시에 받으며, 자극을 받은 유동질량으로부터 에너지가 본체에 유입되면서 위성체는 불안정한 장동운동을 일으키는 것으로 확인되었다. 본 논문에서는 수치시뮬레이션 예시를 통하여 주어진 위성체 모델에 대해 발생가능한 공진조건에서 진자의 운동, 위성체 각 운동량 및 섭동모멘트의 관계 규명과 로켓모터 추진 후에 자세운동이 어떻게 변화하는가를 설명하였다.

• 한국항공우주학회지
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• 제41권2호
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• pp.98-106
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• 2013

본 논문에서는 슬라이딩 모드 제어와 간단한 적응 법칙을 이용하여 반작용 휠 고장에 대한 고장 허용 제어 법칙을 제안한다. 위성의 동역학식에 시스템 파라미터 오차와 고장 불확실성을 고려하여 자세 제어 법칙을 설계하였다. 고장은 구동기 고장인 반작용 휠 고장만을 고려하였으며, 반작용 휠 고장은 곱 형태로 반영된다. 제안된 자세 제어 법칙은 르야프노프 안정성 이론을 통해 안정성을 확인하였고, 수치 시뮬레이션을 통하여 기존의 슬라이딩 모드 제어기와 비교하였으며 위성의 자세 각속도가 안정화되지 않은 경우 제안된 적응 슬라이딩 자세 제어기가 고장에 더욱 빠른 응답 속도를 갖는 것을 확인하였다.

• 한국터널지하공간학회 논문집
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• 제23권6호
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• pp.485-502
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• 2021

터널 굴착으로 인해 필연적으로 발생되는 지반침하 및 상부 구조물 영향 평가를 수행하기 위해 지표침하와 구조물 건전도 저감의 총 7개의 주요 영향 인자들을 설정하고 수치해석을 이용한 Parameter Study를 수행하였다. 그 결과를 통해 Boscardin and Cording 구조물 손상도표를 이용한 안정성 분석, 최대침하량과 각변위를 이용한 안정성 분석을 수행하고 각각의 주요 영향 인자들에 대한 상관성 분석을 실시하였다. 또한, 매개변수 해석을 통한 지반 및 구조물 상호거동 양상을 이용하여 경기도 화성시에 위치한 𐩒𐩒𐩒터널 현장에 적용하고 현장 적용성을 분석하였다. 그 결과 오차가 약 1.0%로 나타나 설계단계에서의 터널 굴착에 따른 구조물 안정성 평가 시 다양한 조건에서 적합한 노선 결정을 위한 기초 자료로 활용될 수 있도록 하였다.