• KCI Concrete Journal
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• 제11권3호
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• pp.153-164
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• 1999

The objective of this research is to observe the actual response of a low-rise nonseismic moment-resisting masonry-infilled reinforced concrete frame subjected to varied levels of earthquake ground motions. The reduction scale for the model was determined as 1 : 5 considering the capacity of the shaking table to be used. This model was, then, subjected to the shaking table motions simulating Taft N2IE component earthquake ground motion, whose peak ground acceleration(PGA) was modified to 0.12g, 0.2g, 0.3g, and 0.4g. The g1oba1 behavior and failure mode were observed. The lateral accelerations and displacements at each story and local deformations at the critical portions of the structure were measured. Before and after each earthquake simulation test, free vibration tests and white noise tests were performed to find the changes in the natural period of the model. When the results of the masonry-infilled frame are compared with those of the bare frame, it can be recognized that masonry infills contribute to the large increase in the stiffness and strength of the g1oba1 structure whereas it also accompanies the increase of earthquake inertia forces. However, it is judged that masonry infills may be beneficial to the performance of the structure since the rate of increase in strength appears to be greater than that of the induced earthquake inertia forces.

• Earthquakes and Structures
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• 제27권1호
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• pp.57-67
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• 2024

To assess the seismic performance of Plate-Shell Integrated Concrete Liquid-Storage Structure (PSICLSS), a scaled test model was constructed. This model incorporated a hybrid isolation system, which combined shape memory alloy (SMA), lead-cored rubber isolation bearing (LRB) and sliding isolation bearing (SB). By conducting shaking table test, the dynamic responses of both non-isolated and hybrid-isolated PSICLSS were analyzed. The results show that the hybrid isolation system can effectively reduce the acceleration and displacement responses of the structure. However, it also results in an increase in local hydrodynamic pressure and liquid sloshing height. Under extreme earthquake action, the displacement of isolation layer is small. When vertical ground motion is taken into account, the shock absorption rate of horizontal acceleration decreases. The peak hydrodynamic pressure increases significantly, and the peak hydrodynamic pressure position also changes. The maximum displacement of isolation layer increases, the residual displacement decreases.

• 방송공학회논문지
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• 제15권3호
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• pp.426-433
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• 2010

H.264/AVC 비디오 압축 표준은 압축 효율을 높이기 위해 다양한 크기의 블록을 사용하여 화면 사이의 움직임 예측을 수행한다. H.264/AVC는 가변적인 블록 크기의 움직임 보상을 통해 세밀한 영역의 움직임까지 예측할 수 있어 잔여 영상을 나타내는 정보량을 효과적으로 줄일 수 있다. 복호를 위해서는 각 블록의 움직임 벡터를 전송해야 하는데, 저비트율 환경에서는 움직임 벡터 정보가 전체 비트스트림의 약 40%를 차지한다. 움직임 벡터 정보량을 줄이기 위해 비디오 부호화 전문가 그룹(VCEG)에서는 다양한 움직임 벡터 예측(Motion Vector Competition) 방법을 제안하였다. 다양한 예측 움직임 벡터를 사용하여 실제 전송해야 할 움직임 벡터 차분값(Motion Vector Difference, MVD)의 크기를 줄이기 때문에 압축 효율을 높일 수 있다. 그러나 다양한 예측 움직임 벡터를 사용하기 때문에 선택된 예측 움직임 벡터의 인덱스 정보를 복호기로 전송해야 한다. 이 논문에서는 인덱스 정보를 효율적으로 전송하기 위해 Phased-in 코드를 기반으로 한 새로운 코드워드 표를 제안했다. 실험을 통해 제안한 방법을 이용하여 동일한 화질에서 평균 약 7.24%의 비트율을 절감할 수 있었고, 동일한 비트율에서는 평균 약 0.36dB의 화질을 향상시킬 수 있었다.

• 대한인간공학회지
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• 제35권6호
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• pp.595-609
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• 2016

Objective: The purpose of this study was to develop and validate the guidelines for Medic Work Table (MWT) based on the anthropometric data of medical technologists. Background: Users' anthropometric data such as sitting height, sitting elbow height, knee height, and so on are significant factors for designing comfortable and useful furniture. Thus, many guidelines for different types of desks and chairs based on the users' anthropometric data have been suggested to many researchers. However, few researches have been conducted to provide design guidelines for MWT for blood collecting task. Medical technologists often use their upper extremities to perform blood collecting task with high repetitions. These repeated motions could be a critical factor in the prevalence rate of Work-related Musculoskeletal Disorders (WMSDs). Therefore, a study on ergonomic design of MWT would be essential in preventing the WMSDs and improving the quality of the working environment of medical technologists. Method: This study suggested design guidelines for ergonomic MWT by focusing on the heights of the upper side and underside, depths of the inside and outside, and width of MWT through anthropometric studies and literature reviews. Afterwards, a new MWT was made using the suggested design guidelines for this study. Five healthy medical technologists participated to evaluate the original MWT and new MWT. All participants took part in the range of motion (ROM) test, electromyography (EMG) muscle activity test, and usability test to validate the suggested guidelines in this study. EMG signals of related muscles (Flexor Carpi Ulnaris, Extensor Carpi Ulnaris, Deltoid Anterior, and Biceps Branchii) were recorded through the surface electromyography system from both the original MWT and the new MWT. The ROM test of the shoulder and elbow flexion was also assessed using motion sensors. Results: The newly designed MWT showed decreased ROMs of the shoulder and elbow up to 22% and 18% compared to the original MWT. The muscle activities in the new MWT also showed a decrease of 13% in Anterior Deltoid, 6% in Biceps Brachii, 5% in Flexor Carpi Ulnaris, and 8% in Extensor Carpi Ulnaris muscle groups, compared to the original MWT. In the usability test, the satisfaction score of the new MWT was also 56.1% higher than that of the original MWT. Conclusion: This study suggested guidelines for designing MWT and validating the guidelines through qualitative and quantitative analyses. The results of motion analysis, muscle activity, and usability tests demonstrated that the newly designed MWT may lead to less physical stress, less awkward posture, and better physical user interface. Application: The recommended guidelines of the MWT would be helpful information for designing an ergonomic MWT that reduces physical loads and improves the performance of many medical technologists.

• 제어로봇시스템학회논문지
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• 제15권5호
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• pp.496-504
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• 2009

This paper presents a recognition performance of VOR (Vestibular-Ocular Reflex) based vision tracking system for mobile robot. The VOR is a reflex eye movement which, during head movements, produces an eye movement in the direction opposite to the head movement, thus maintaining the image of interested objects placed on the center of retina. We applied this physiological concept to the vision tracking system for high recognition performance in mobile environments. The proposed method was implemented in a vision tracking system consisting of a motion sensor module and an actuation module with vision sensor. We tested the developed system on an x/y stage and a rate table for linear motion and angular motion, respectively. The experimental results show that the recognition rates of the VOR-based method are three times more than non-VOR conventional vision system, which is mainly due to the fact that VOR-based vision tracking system has the line of sight of vision system to be fixed to the object, eventually reducing the blurring effect of images under the dynamic environment. It suggests that the VOR concept proposed in this paper can be applied efficiently to the vision tracking system for mobile robot.

• 한국항공우주학회지
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• 제34권5호
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• pp.81-87
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• 2006

본 논문에서는 전투기 조종석과 같은 제한된 공간에서 사용 가능한 광학 방식의 헤드 트랙커 시스템을 설계하고 그 성능을 시험하였다. 이 시스템은 다른 빛의 간섭을 차단하기 위해 적외선 발광다이오드와 두 대의 적외선 CCD 카메라를 사용하였다. 그리고 광학 방식의 헤드 트랙커 알고리즘은 특징점 추출 알고리즘과 3차원 움직임 추정 알고리즘으로 구성하였다. 카메라 이미지 평면 위에서 특징점의 2차원 위치 좌표를 획득하기 위한 특징점 추출 알고리즘은 디지털 영상 처리 기술인 문턱치 (thresholding)와 마스킹 (masking) 기법을 사용하였다. 특징점의 위치 변화로부터 조종사의 머리 움직임을 추정하는 3차원 움직임 추정 알고리즘은 확장 칼만 필터 (EKF)를 사용하였다. 또한, 정밀한 레이트 테이블을 사용하여 시스템 성능을 검증하고 회전 성능에 대해 관성 센서와 비교하였다.

• Geomechanics and Engineering
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• 제34권6호
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• pp.665-681
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• 2023

Liquefaction is one of the most devastating geotechnical phenomena that severely damage vital structures and lifelines. Before constructing structures on problematic ground, it is necessary to improve the site and solve the geotechnical problem. Among ground improvement methods dealing with liquefaction, gravel drain (GD) columns and deep soil mixing (DSM) columns are popular. In this study, the results of a series of seismic experiments in a 1g environment on a structure located over liquefiable ground with different thicknesses reinforced with GD and DSM techniques were presented. The dynamic response of the reinforced ground system was investigated based on the parameters of subsidence rate, excess pore water pressure ratio, and maximum acceleration. The time history of the input acceleration was applied harmonically with an acceleration range of 0.2g and at frequencies of 1, 2, and 3 Hz. The results show that the thickness of the liquefiable layer and the frequency of the input motion have a significant impact on the effectiveness of the improvement method and all responses. Among the two techniques used, DSM in thick liquefied layers was much more efficient than GD in controlling the subsidence and rupture of the soil under the foundation. Maximum settlement values, settlement rate, and foundation rotation in the thicker liquefied layer at the 1-Hz input frequency were higher than at other frequencies. At low thicknesses, the dynamic behavior of the GD was closer to that of the DSM.

• 대한인간공학회지
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• 제29권4호
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• pp.495-503
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• 2010

The packing and sorting processes of grape are required repetitive movements to need considerable physical load for a long time. And thereby, there is strong possibility to cause musculoskeletal disorders. In this study, ergonomically designed convenience equipments of worktable and handcart are introduced for improvement of the working movements and less physical load to increase the work efficiency. For objective analysis of the movements and the workload between the ones before and after the improvement, we measured heart rate, OWAS, RULA, REBA, LMM, moving Line and work time. Also, we used a checklist of physical fatigue regions to confirm the subjective evaluation of physical load of workers. As the result of study, it showed lower heart rate, value of Working Postures (OWAS, RULA, REBA) and LMM in the work after introduction of those convenient equipments than the work of before the introduction. The work time and moving Line were shortened and the number of grape boxes packed within the same work time was increased, too. Also the overall load as the subjective evaluation was reduced.

• 한국산업보건학회지
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• 제8권1호
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• pp.36-49
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• 1998

The purpose of this study is to investigate the relationship between the work postures and upper extremity cumulative trauma disorders(CTDs) in female medical insurance bill reviewers(n=448). This study included diagnosis for CTDs, anthropometry and job analysis (workstations and posture). The characteristics of subject were 33.6 years of average age and 8.7 years of average work duration. The results were as fallows. Ergonomic conditions of workstation were unsuitable compared with anthropometry result. The height of work surface(79.5 cm) and chair(43.0 cm)were high. work space was small, and legs space under the table was limited. Work postures were awkward compared with recommended neutral postures. Neck flexion($21.0-36.0^{\circ}$), elbow elevation, shoulder abduction ($46.0-47.0^{\circ}$). wrist radial and ulnar deviation, forearm supination and pronation, and wrist repeated motion(12.7-21.5 freq./min) were analyzed as hazardous risk factors by job analysis. The prevalence of CTDs was 32.8 % by medical diagnosis. The prevalence rate of CTDs in hazardous work posture group was significantly greater than safe work posture group both neck-shoulder (relative prevalence = 5.2, p<0.001) and wrist-hand (relative prevalence = 2.5, p<0.05).

• The Korean Journal of Physiology
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• 제1권1호
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• pp.121-130
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• 1967

Determination of weekly and daily energy expenditure was made on 62 Republic of Korea Army cadets who were selected at random in order to estimate the weekly and daily ealorie expenditure. Basal metabolic rate (B.M.R.), and energy cost of various military and daily activities were measured by indirect calorimetry using open circuit method. Time-motion studies were also carried on using a stop-watch. The total weekly energy expenditure was calculated by summation of data using energy cost per minute, and the time spent on each activity. Determination of daily energy expenditure was deduced from each data of weekly energy expenditure. Food survey was also carried on for a week, and daily calorie intake was determined by a weekly average discounting loss in cooking. All measurements were determined from the Standard Table of Food Composition published by the Ministry of National Defense (1961). Following data were observed. 1. Physical status of cadets are as follows. Please note that the height and weight averages are 1-2cm and 4-5kg respectively over that of the Seoul National University students. First year Height 167.92 cm $(S.D.{\pm}4.09)$ Weight 61.72 kg $(S.D.{\pm}4.53)$ Second year Height 167.89 cm $(S.D.{\pm}3.46)$ Weight 63.01 kg $(S.D.{\pm}4.61)$ Third year Height 168.15 cm $(S.D.{\pm}4.24)$ Weight 43.48 kg $(S.D.{\pm}5.03)$ Fourth year Height 168.10 cm $(S.D.{\pm}3.70)$ Weight 64.02kg $(S.D.{\pm}5.10)$ 2. The B.M.R. of cadets averaged $36.57\;Cal./m^2/hr.(S.D.{\pm}3.63\;Cal./m^2/hr.)$ is almost equal with data on the same ages of civilians and the Japanese, but a lower average of $5.1\;Cal./m^2/hr.$ than that of a common soldier. 3. The energy expenditure during various military activities is close agreement with Consolazio. Passmore and Durnin, and Japanese reports.