• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.2059-2066
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• 2018

This study explored the feasibility of utilizing an SWCNT-coated fabric sensor for the development of a wearable motion sensing device. The extent of variation in electric resistance of the sensor material was evaluated by varying the fiber composition of the SWCNT-coated base fabrics, attachment methods, number of layers, and sensor width and length. 32 sensors were fabricated by employing different combinations of these variables. Using a custom-built experimental jig, the amount of voltage change in a fabric sensor as a function of the length was measured as the fabric sensors underwent loading-unloading test with induced strains of 30 %, 40 %, and 50 % at a frequency of 0.5 Hz. First-step analysis revealed the following: characteristics of the strain-voltage curves of the fabric sensors confirmed that 14 out of 32 sensors were evaluated as more suitable for measuring human joint movement, as they yield stable resistance values under tension-release conditions; furthermore, significantly stable resistance values were observed at each level of strain. Secondly, we analyzed the averaged maximum, minimum, and standard deviations at various strain levels. From this analysis, it was determined that the two-layer sensor structure and welding attachment method contributed to the improvement of sensing accuracy.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.713-716
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• 2000

In this study, we present a mobile robot for ultrasonic scanning of weldment. magnetic Caterpillar mechanism is selected in order to travel on the inclined surface and vertical wall. A motion control board and motor driver are developed to control four DC-servo motors. A virtual device driver is also developed for the purpose of communicating between the control board and a host PC with Dual 'port ram. To provide the mobile robot with stable and accurate movement, PID control algorithm is applied to the mobile robot control. And a vision system for detecting the weld-line are developed with laser slit beam as a light source. In the experiments, movement of the mobile robot is tested inclined on a surface and a vertical wall.

• 영어어문교육
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• 제12권4호
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• pp.31-68
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• 2006

The present research investigates the acquisition of the English locative alternation by Korean EFL learners, which poses a learnability paradox, taking Pinker's framework of learnability theory as its basis. It addresses two questions (1) how lexical knowledge is represented initially and at different levels of interlanguage development and (2) what kinds of difficulty Korean learners find in the acquisition of English locative verbs and their constructions. Three groups of learners at different proficiency levels with a control group of English native speakers are examined by two instruments: elicited production task and grammaticality judgment task. According to different levels of proficiency, the learners exhibit gradual sensitivity to a change-of-state meaning and obtain complete perception of the meanings of locative verbs (manner-of-motion and change-of-state) and their constructions. Overgeneralization errors are observed in their performance. The errors are due to misinterpretations of particular lexical items in conjunction with the universal linking rules. More fundamental cause of difficulty is accounted for by partial use of learning mechanisms, caused by insufficient L2 input.

• IEIE Transactions on Smart Processing and Computing
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• 제5권4호
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• pp.274-282
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• 2016

This paper proposes code optimization techniques to reduce energy consumption of complex multimedia applications in a hybrid memory system with volatile dynamic random access memory (DRAM) and non-volatile spin-transfer torque magnetoresistive RAM (STT-MRAM). The proposed approach analyzes read/write operations for variables in an application. Based on the profile, variables with a high read operation are allocated to STT-MRAM, and variables with a high write operation are allocated to DRAM to reduce energy consumption. In this paper, to optimize code for real-life complicated applications, we develop a profiler, a code modifier, and compiler/link scripts. The proposed techniques are applied to a Fast Forward Motion Picture Experts Group (FFmpeg) application. The experiment reduces energy consumption by up to 22%.

• 천문학회보
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• 제36권1호
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• pp.45.1-45.1
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• 2011

Shock waves form in the intergalactic medium as a consequence of accretion, merger, and turbulent motion during the structure formation of the universe. They not only heat gas but also govern non-thermal processes through the acceleration of cosmic rays (CRs), production of magnetic fields, and generation of vorticity. We examine diffusive shock acceleration of the pre-existing as well as freshly injected populations of nonthermal, CR particles at weak cosmological shocks. Since the injection is extremely inefficient at weak shocks, the pre-existing CR population dominates over the injected population. If the pressure due to pre-existing CR protons is about 5 % of the gas thermal pressure in the upstream flow, the downstream CR pressure can absorb typically a few to 10 % of the shock ram pressure at shocks with the Mach number M<3. Yet, the re-acceleration of CR electrons can result in a substantial synchrotron emission behind the shock. The implication of our findings for observed bright radio relics is discussed.

• 대한방사선치료학회지
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• 제23권1호
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• pp.13-19
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• 2011

목 적: 체부 정위방사선치료 시 치료 효과 향상을 위해서는 병소 부위의 정확한 위치 파악과 함께 호흡에 의한 종양의 움직임을 최소화하는 것이 필수적이다. 이에 본 연구에서는 기존에 자체 개발하여 사용 중인 호흡운동 감소기구를 보다 사용이 편리하고 효과적이도록 개선하여, 체부 정위방사선치료에 있어서 임상 적용의 유용성을 평가하였다. 대상 및 방법: 자체 개발하여 사용 중이던 기존 호흡운동 감소기구의 장단점을 분석하여 재현성과 사용 정확도를 개선하였다. 그리고 개선된 호흡운동 감소기구를 체부 정위방사선치료에 활용하기 위한 유용성 평가 방법으로 첫째, 8명의 폐종양 환자에 대해 들숨(inhalation)과 날숨(exhalation) 상태에서 획득한 고속(spiral) 전산화단층촬영 영상을 통해, 호흡에 따른 종양 움직임을 3차원적으로 정량 분석하였다. 둘째, 선량 평가를 위해 EBT2 필름(Gafchromic, ISP, USA)을 장착할 수 있는 폴리에틸렌 팬텀과 3차원적 종양 움직임을 재현하기 위한 2축의 직교좌표 로봇(Cartesian Robot-2Axis, FARA RCM4H, Samsung Mechatronics, Korea)을 제작하였다. 그리고 전산화단층촬영에서 획득한 결과를 바탕으로 호흡운동을 재현하여, 등선량 곡선 및 2차원 등선량 프로파일을 분석하였다. 결 과: 벨크로 벨트로 제작된 사용이 편리하고 재현성이 우수한 호흡운동 감소기구를 개발하였다. 전산화단층촬영 영상으로 분석한 폐암환자의 호흡에 따른 3차원적인 종양의 움직임은 좌우, 전후, 두미측 방향에 따라 평균 3.2 mm, 4.3 mm, 13.0 mm로 나타났다. 팬텀과 직교좌표 로봇을 이용한 호흡에 의한 선량분포 특성변화의 결과로는, 치료계획 선량보다 방사선을 적게 받은 영역은 두미측 방향으로 각각 8.0%와 16.8%, 좌우측 방향으로 각각 8.1%와 10.9%로 후미측 방향의 선량 왜곡이 가장 크게 나타났고, 길이는 평균 4.2 mm이었다. 호흡주기에 따른 선량 왜곡의 변화는 크게 나타나지 않았다. 결 론: 본 연구를 통해 장기의 움직임을 최소화할 수 있는 사용이 편리하고 효과적인 호흡운동 감소기구를 개발하였다. 개발된 기구를 사용할 경우 평균 6 mm 정도의 CTV-PTV 마진을 사용하면 호흡에 따른 과소선량(underdose)을 극복할 수 있을 것으로 결과를 통해 확인하였다. 이로서 개발된 호흡운동 감소기구는 체부 정위방사선치료에 있어서 호흡동조 방법을 병행할 수 있는, 임상 적용이 용이한 효과적인 보조기구로 활용할 수 있을 것으로 사료된다.

• 한국전문물리치료학회지
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• 제18권3호
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• pp.26-37
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• 2011

Although there have been various studies related to the body's movement from a sitting to a standing position (sit-to-stand task), there is limited information on the kinematic changes on the frontal and transverse planes. The purpose of this study was to ascertain how pelvic tilt affects kinematic changes in the frontal and transverse planes in the hip and knee joints during a sit-to-stand task. For this study, 33 healthy participants (13 female) were recruited. Each participant rose from a sitting to a standing posture at his or her preferred speed for each of three different pelvic tilt trials (anterior, posterior, and neutral), and the measured angles were analyzed using a 3-D motion analysis system. A one-way repeated measure analysis of variance was performed with Bonferroni's post hoc test. In addition, an independent t-test was carried out to determine the sex differences in hip and knee joint kinematic changes during the sit-to-stand tasks. The results were as follows: 1) The hip and knee joint angle in the frontal and transverse planes showed a significant difference between the different pelvic tilt postures during sitting in the pre-buttock lift-off phase (pre-LO) (p<.05). Compared to the posterior pelvic tilt posture, the anterior pelvic tilt posture involved significantly greater hip joint adduction and internal rotation, knee joint adduction, and reduced internal rotation of the knee joint. 2) Sex differences were found with significant differences for males in the initial and maximal angles in the frontal plane of the hip and knee joint (p<.05). Females had a significantly smaller initial abduction angle of the hip joint and a significantly greater maximal angle of the hip adduction joint. These results suggest that selecting a sit-to-stand exercise for pelvic tilt posture should be considered to control abnormal movement in the lower extremities.

• 한국지능시스템학회논문지
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• 제22권5호
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• pp.639-645
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• 2012

본 논문에서는 모바일 로봇이 자연스러운 손동작을 은닉 마르코프 모델(HMM: hidden markov model)을 이용하여 인식해 원하는 명령을 수행하는 방법을 제안한다. 기존의 손동작 기반 로봇 제어 방식은 정해진 몇 종류의 제스처를 사용했었고, 따라서 지시동작이 자연스럽지 않았다. 또한 정해진 제스처를 미리 공부해야하여 불편했었다. 이러한 문제를 해결하기 위해 손동작을 인식하는 방법에 대한 많은 연구가 활발히 진행되고 있다. 본 논문에서는 3차원 카메라를 사용해 색상 데이터와 깊이 데이터를 얻어서, 사람의 손을 검색하고 그 동작을 인식한다. 여기서 동작을 인식하는 방법으로 HMM을 사용하였으며, 인식된 결과를 로봇에게 전달하여 원하는 방향으로 이동시킨다.

• 대한의용생체공학회:의공학회지
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• 제40권6호
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• pp.223-229
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• 2019

The number of knee-related disease patients and knee joint surgeries is steadily increasing every year, and for knee rehabilitation training for these knee joint patients, it is necessary to strengthen the muscle of vastus medialis and quadriceps femoris. However, because of the cost and time-consuming difficulties of receiving regular hospital treatment in the course of knee rehabilitation, we developed knee exoskeleton using rapid prototype for knee rehabilitation with feedback from the electromyogram (EMG) and inertia motion unit (IMU) sensor. The modules was built on the basis of EMG and an IMU sensor applied complementary filter, measuring muscle activity in the vastus medialis and the range of joint operation of the knee, and then performing the game based on this measurement. The IMU sensor performed up to 97.2% accuracy in experiments with ten subjects. The functional game contents consisted of an exergaming platform based on EMG and IMU for the real-time monitoring and performance assessment of personalized isometric and isotonic exercises. This study combined EMG and IMU-based functional game with knee rehabilitation training to enable voluntary rehabilitation training by providing immediate feedback to patients through biometric information, thereby enhancing muscle strength efficiency of rehabilitation.

• 한국운동역학회지
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• 제28권1호
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• pp.37-43
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• 2018

Objective: The aim of this study was to analyze muscle activation of the lower extremities as a function of changes of the center of pressure (CoP) of the foot during squats in order to provide quantitative information to trainers who would like to teach correct movements for developing muscles. Method: Ten men with over three years of weight training experience participated in this study (age: $26.1{\pm}0.8yrs$, height: $171.2{\pm}3.9cm$, body mass: $71.1{\pm}5.7kg$, 60%RM: $84{\pm}9kg$, career: $4.0{\pm}0.7yrs$). The participants were instructed to perform a squat in each of 3 conditions, with different CoP's (the front, middle, and rear of the foot). Results: The position of the CoP showed significant differences according to instructions in both the eccentric and concentric contraction phases (p < .05). The range of movement of the hip and ankle joints showed significant differences corresponding to changes of the CoP position (p < .05). The rectus femoris and gluteus maximus muscle showed significant differences for different CoP positions only in the concentric contraction phase, while the gastrocnemius and anterior tibialis were significantly different in both the concentric and eccentric contraction phase (p < .05). Conclusion: When the target muscle of squat training is the gastrocnemius, the CoP should be located in the front of the foot for effective muscle training. When the target muscles of squat training are the gluteus maximus and quadriceps femoris, the CoP should be located on the rear of the foot.