• 한국멀티미디어학회논문지
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• 제8권6호
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• pp.744-752
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• 2005

When the multiple video sources are transmitted together through the channel of fixed bandwidth, an efficient picture quality control is necessary. This paper presents a joint picture quality control method to satisfy the user requirement by priority among the video sources. The better picture quality is assigned to the source of higher priority compared to lower priority. We obtain the bitrate for each source to have a required distortion level among the sources by using an approximate distortion-bitrate model for simple implementation. It is shown by simulation that the proposed bandwidth allocation method can keep almost the user-required picture quality among the sources in comparison to an independent bandwidth allocation method.

• 한국기계연구소 소보
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• 통권19호
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• pp.81-92
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• 1989

This paper presents a simple identification method of the actual kinematic parameters for the robot with parallel joints. It is known that Denavit-Hartenberg's coordinate system is not useful for nearly parallel joints. In this paper, the coordinate frames are reassigned to model the kinematic parameter between nearly parallel joints by four parameters. The proposed identification method uses a straight ruler about 1m long. A robot hand is placed by using a teaching pendant at the prescribed points on the ruler, and corresponding error function is defined. The identified kinematic parameters which make the error function zero are obtained by iterative least square error method based on the singular value decomposition. In the compensation of joint angles, only the position is considered because the usual applications of robot do not require a precise orientation control.

• 한국군사과학기술학회지
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• 제13권3호
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• pp.461-469
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• 2010

In this paper, we have proposed an improved fusion method of detection features which can enhance the detection probability under the given false alarm rate in the prescreening stage of SAR ATR(Synthetic Aperture Radar Automatic Target Recognition) system. Since the detection features have the positive correlation, the detection performance can be improved if the joint probability distribution of detection features is considered in the fusion process. The detection region is designed as a simple piecewise linear function which can be represented by few parameters. The parameters for the detection region can be derived by training the sample SAR images to maximize the detection probability with the given false alarm rate. Simulation result shows that the detection performance of the proposed method is improved for all combinations of detection features.

• 한국항공운항학회지
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• 제18권4호
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• pp.44-50
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• 2010

Structural vibration is a significant problem in many multi-part or multi-component assemblies. In aircraft industry, structures are composed of various fasteners, such as bolts, snap, hinge, weld or other fastener or connector (collectively "fasteners"). Due to these, prediction and design involving dynamic characteristics is quite complicated. However, the current state of the art does not provide an analytical tool to effectively predict structure's dynamic characteristics, because consideration of structural uncertainties (i.e. material properties, geometric tolerance, dimensional tolerance, environment and so on) is difficult and very small fasteners in the structure cause a huge amount of analysis time to predict dynamic characteristics using the FEM (finite element method). In this study, to resolve the current state of the art, a new approach is proposed using the FEM and probabilistic analysis. Firstly, equivalent elements are developed using simple element (e.g. bar, beam, mass) to replace fasteners' finite element model. Developed equivalent elements enable to explain static behavior and dynamic behavior of the structure. Secondly, probabilistic analysis is applied to evaluate the PDF (probability density function) of dynamic characteristics due to tolerance, material properties and so on. MCS (Monte-Carlo simulation) is employed for this. Proposed methodology offers efficiency of dynamic analysis and reality of the field as well. Simple plates joined by fasteners are taken as an example to illustrate the proposed method.

• Journal of Trauma and Injury
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• 제36권4호
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• pp.451-453
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• 2023

We introduce a convenient method of urethrography before catheterization for patients with pelvic trauma that can be used in a resuscitation area. A 10-mL syringe without a needle was used. X-ray contrast medium (Iohexol, 300 mg I/mL) was administered through the urethral orifice using a 10-mL syringe without needle and a simple pelvic anteroposterior film was taken (70 kilovolt [peak], 50 mAs). A 36-year-old soldier with a saddle injury from a gun barrel was taken to a trauma center. He had a pelvic fracture and complained of hematuria. Bedside urethrography above described was performed. The anterior urethra showed nonspecific findings, but dye leaked from the posterior urethra. Bedside Foley catheter insertion was attempted, but the catheter could not be advanced past the membranous urethra. Thereafter, suprapubic catheterization was performed. On the day of the injury, iliac artery embolization was carried out. The dislocated sacroiliac joint was also treated using open reduction and internal fixation. On hospital day 7, guidewire Foley insertion was performed. This bedside urethrography technique is simple and useful for pelvic fractures in which urethral injury is suspected.

• 한국해양공학회지
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• 제29권1호
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• pp.45-55
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• 2015

Because of the high stress concentration near the toe of a welded joint, the calculation of local stress using the finite element method which is relevant to the fatigue strength of the weld toe crack, is a challenging task. This is mainly caused by the sensitivity of finite element analysis, which usually occurs near the area of a dramatically changing stress field. This paper presents a novel numerical method through which a less mesh-sensitive local stress calculation can be achieved based on the 3D solid finite element, strictly sticking to the original definition of hot spot stress. In order to achieve the goal, a traction stress, defined at 0.5t and 1.5t away from the weld toe, was calculated using either a force-equivalent or work-equivalent approach, both of which are based on the internal nodal forces on the imaginary cut planes. In the force-equivalent approach, the traction stress on the imaginary cut plane was calculated using the simple force and moment equilibrium, whereas the equivalence of the work done by both the nodal forces and linearized traction stress was employed in the work-equivalent approach. In order to confirm the validity of the proposed method, five typical welded joints widely used in ships and offshore structures were analyzed using five different solid element types and four different mesh sizes. Finally, the performance of the proposed method was compared with that of the traditionally used surface stress extrapolation method. It turned out that the sensitivity of the hot spot stress for the analyzed typical welded joints obtained from the proposed method outperformed the traditional extrapolation method by far.

• 지질공학
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• 제12권2호
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• pp.167-178
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• 2002

서울시 북동부의 서울화강암에 대한 불연속면의 특성을 수락산과 불암산 지역으로 구분하여 비교, 분석하였다. 본 연구에서는 암석의 공학적 특성 중 터널과 도로 건설시 중요하게 취급하여 측정된 요소는 다음과 같다: 1) 절리의 방향성, 2) 절리간격, 3) 절리밀도, 4) 암석의 일축압축강도. 이 중 절리의 방향성, 절리간격과 절리밀도는 선조사법, 원형조사법, 그리고 면적조사법을 이용하여 야외에서 직접 측정될 수 있는 요소이나, 암석의 일축압축강도의 측정에는 원래 암석의 시추코아 표본이 필요하지만 이번 연구에서는 간단히 응용할 수 있는 대비공식을 이용하여 계산하였다. 측정된 대표적인 절리의 방향성은 두 지역에서 모두 3조의 방향성이 나타났다. 즉 2조의 수직정방절리와 저각으로 경사하는 1조의 판상절리이었으며, 서로 매우 유사한 방향성을 갖는다. 측정된 절리밀도는 0.039-0.066/cm 이었으며, 면적조사법으로 측정된 평균절리길이는 1.30-4.52m, 평균절리간격은 10.3cm에서 최대 59,6cm로 측정된 조사선의 방향에 따라 변화가 심하다. 또한 슈미트해머 타격값에 근거한 절리면의 일축압축강도는 217 MPa에서 335 MPa로 강한 암체로 판명되었다.

• 한국콘텐츠학회논문지
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• 제11권12호
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• pp.619-628
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• 2011

일반적으로 비전기반 3차원 인체 포즈 인식 기술은 HCI(Human-Computer Interaction)에서 인간의 제스처를 전달하기 위한 방법으로 사용된다. 특수한 환경에서 단순한 2차원 움직임 포즈만 인식할 수 있는 2차원 포즈모델 기반 인식 방법에 비해 3차원 관절을 묘사한 포즈모델은 관절각에 대한 정보와 신체 부위의 모양정보를 선행지식으로 사용할 수 있어서 좀 더 일반적인 환경에서 복잡한 3차원 포즈도 인식할 수 있다는 장점이 있다. 이 논문은 인체의 3차원 관절 정보를 이용한 포즈 인식 기술을 인터페이스로 활용한 상호작용 게임 콘텐츠 개발에 관해 기술한다. 제안된 시스템에서 사용되는 포즈는 인체 관절 중 14개 관절의 3차원 위치정보를 이용해서 구성한 포즈 템플릿과 현재 사용자의 포즈를 비교해 인식된다. 이 방법을 이용하여 제작된 시스템은 사용자가 부가적인 장치의 사용 없이 사용자의 몸동작만으로 자연스럽게 게임 콘텐츠를 조작할 수 있도록 해준다. 제안된 3차원 인식 기술을 게임 콘텐츠에 적용하여 성능을 평가한다. 향후 다양한 환경에서 더욱 강건하게 포즈를 인식할 수 있는 연구를 수행할 계획이다.

• 한국전문물리치료학회지
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• 제26권3호
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• pp.99-105
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• 2019

Background: Although magnetic resonance imaging is accurate, it is expensive to measure the movement of temporomandibular joint. The three-dimensional (3D) motion analysis system is an inexpensive measurement tool. Objects: This study examined the reliability of quantifying the mouth opening and lateral mandibular shift and differences between individuals with and without temporomandibular disorder (TMD) using the hygienic method of surface markers on the skin with 3D ultrasound-based motion analysis. Methods: This study included 24 subjects (12 with and 12 without TMD). Temporomandibular joint motion during mouth opening was recorded using two surface markers with 3D ultrasound-based motion analysis. An intraclass correlation coefficient [ICC (3,k)] was used to confirm the intrarater reliability of quantifying kinematic temporomandibular joint motion, and an independent t-test was used to evaluate differences in maximal mouth opening and lateral mandibular shift between the two groups. Results: Assessment of mouth opening and lateral mandibular shift showed excellent test-retest reliability with low standard error of measurement. The lateral mandibular shift and opening-lateral mandibular shift ratio were significantly increased in the TMD group during maximum mouth opening (p<.05). However, no significant difference in maximal mouth opening was observed between the groups with and without TMD (p>.05). Conclusion: This hygienic and simple surface marker method can be used to quantify the mouth opening and lateral mandibular shift at the end-range of mouth opening. The TMD group showed an increased lateral mandibular shift movement at the end-range of mouth opening. The lateral mandibular shift movement can be regarded as a symptom in the diagnosis and treatment of TMD.

• 한국컴퓨터그래픽스학회논문지
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• 제27권1호
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• pp.1-8
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• 2021

본 논문에서는 캐릭터의 걷기 동작 데이터를 변형하는 방법을 제안한다. 이를 위하여 주 관절(root joint)의 이동 경로를 그래프로 분석하고 라플라스 연산자를 이용해 변형하는 방법을 사용한다. 주 관절의 경로는 동작 데이터의 각 프레임별 위치와 방향을 정점으로 하고 이를 인접 프레임의 정점과 연결한 그래프 형태로 나타낸다. 주 관절 경로를 라플라스 연산자를 이용하여 좌표계를 변환하고 이를 목표 위치 및 방향에 맞도록 반복적인 방법으로 해를 구하여 변형한다. 이 방법을 이용하여 동작 데이터의 걷기 스타일을 유지하면서 다양한 경로의 걷기 동작을 얻을 수 있게 되며 많은 비용이 드는 동작 데이터 취득을 최소화할 수 있다. 최종 모션은 변형된 주 관절 경로를 기준으로 기존 모션의 다른 관절을 위치시키고 후처리하여 생성한다. 본 논문에서 제안한 방법을 응용함으로써 적은 모션 데이터로도 복잡한 환경에서 캐릭터의 걷는 동작을 생성하는 것을 보인다.