• 대한인간공학회지
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• 제34권4호
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• pp.313-326
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• 2015

Objective: The objective of this research is to quantitatively analyze muscle activities of arm and shoulder, according to direction in various types of one-handed manual material handling, based on surface electromyography. Background: Workers in industrial sites frequently carry out one-handed manual material handling using arm and shoulder muscles. Therefore, chronic load and accumulated fatigue occur to arm and shoulder muscles, which becomes a main cause of upper arm and shoulder musculoskeletal disorders. The shoulder muscles have widely range of motion, and complex interactions take place among various muscles including rotator cuff muscles. In this regard, research on interactions among should muscles, according to such various dynamic motions, is required. Method: Ten male subjects in their 20s participated in this research. This research considered upward, downward, leftward, rightward, forward and backward directions and fourteen muscles around arm and shoulder (biceps brachii and trapezius, etc.) as independent variables. The mean muscle activity was set as the dependent variable. This research extracted $4^{th}{\sim}7^{th}$ repetition signals according to ten times of repetitive muscle contraction, and analyzed the muscle activity concerned using the envelope detection technique. Results: The mean muscle activity of upward direction was analyzed highly statistically significant. The reason is that the effect of gravity works to arm and shoulder muscles. Also, it is conjectured that deformation of coracoacromial ligament was caused, and its contact pressure increased, due mainly to the shoulder flexion, and therefore load was analyzed high. Muscle activity was analyzed significantly low, according to concentric ballistic motion used in the concentric contraction phase by storing elastic energy in the eccentric contraction phase with a motion to bring the weight to the front of subject's body as to downward, leftward and backward directions. Because, elbow joint's flexion-extension motions mainly occurred, biceps brachii was analyzed high muscle activity as the prime mover. Conclusion: The information on the quantitative load of muscles can be applied to ergonomic work design for one-handed manual material handling to minimize muscle load. Application: This research has effectively identified muscle activity according to dynamic contraction by applying an envelope detection technique. The results can be used for ergonomic work design to minimize muscle load during the one-handed manual material handling, according to each direction. The research results are expected to be used for musculoskeletal disorder prevention and physiotherapy in the rehabilitation medical field, based on the muscle load of arm and shoulder in various directions.

• 대한의용생체공학회:의공학회지
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• 제30권1호
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• pp.79-88
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• 2009

A harmonic quadrature demodulation method to extract the second harmonic component from focused ultrasound signals after a single transmit-receive event is proposed. In the proposed method, the focused ultrasound signal is converted into baseband inphase and quadrature components by multiplying with sine and cosine signals both having twice the center frequency of the transmitted signal and filtering the two modulated signals. The quadrature component is then passed through a Hilbert filter to be added to the inphase component, which leaves only the envelope of the second harmonic component. A novel phase estimation technique is employed in the proposed method to avoid the phase mismatch between the focused signal and the two modulating signals. The proposed method is verified through both theoretical analysis and computer simulations. It is shown that compared to the pulse inversion scheme the proposed method provides almost the same results for stationary targets and significantly improved harmonic to fundamental ratio for moving targets.

• 한국항공우주학회지
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• 제39권1호
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• pp.33-41
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• 2011

내삽형 부스터의 분리 운동 수학모델을 소개하였다. 부스터 분리 운동을 시뮬레이션 하기 위하여 3자유도 2물체 운동모델을 정립하였다. 유도탄과 공기중에 노출되는 부스터 영역의 공력모델을 개발하였다. 그리고, 부스터를 밀어내는 가스발생기도 모델링하였다. 이 모델을 시뮬레이션하기 위하여 유도탄이 부스터 분리과정에서 계속 1g 수평비행 조건을 유지한다는 가정을 세우고, 이를 기반으로 유도탄과 부스터간의 작용력을 분리 단계별로 정의 할 수 있었다. 단계 0: 초기, 단계 1: 선형이동, 단계 2: 자유운동. 이 시뮬레이션을 통하여 부스터를 안전하게 분리할 수 있는 유도탄의 마하수 및 고도의 범위를 제안할 수 있었다.

• International Journal of Aeronautical and Space Sciences
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• 제12권4호
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• pp.365-370
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• 2011

This paper presents the air-to-air missile autopilot design for a $180^{\circ}$ heading reversal maneuver during boost-phase. The missile's dynamics are linearized at a set of operating points for which angle of attack controllers are designed to cover an extended flight envelope. Then, angle of attack controllers are designed for this set of points, utilizing a pole-placement approach. The controllers' gains in the proposed configuration are computed from aerodynamic coefficients and design parameters in order to satisfy designer-chosen criteria. These design parameters are the closed-loop frequency, damping ratio, and time constant; these represent the characteristics of the control system. To cope with highly nonlinear and rapidly time varying dynamics during boost-phase, the global gain-scheduled controller is obtained by interpolating the controllers' gains over variations of the angle of attack, Mach number, and center of gravity. Simulation results show that the proposed autopilot design provides satisfactory performance and possesses good [ed: or "sufficient" or "excellent"] capabilities.

• 한국전자파학회논문지
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• 제22권2호
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• pp.182-190
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• 2011

진폭 변조를 이용한 거리 측정 시스템은 반송파를 진폭 변조하여 송수신한 신호의 진폭 변조 신호의 위상차를 사용하여 거리를 측정하게 된다. 진폭 변조 거리 측정 시스템에서 문제가 되는 안테나 간의 누설 신호 및 불요 신호에 의한 측정 오차를 최소화하기 위해 능동반사기를 사용하여 주파수 대역을 바꾸어 송신하는 방식이 제안되었다. 본 논문에서는 모호성이 없는 측정 거리를 확장하면서도 정밀한 측정을 가능하게 하는 새로운 위상측정부의 구현에 대해 설명하고 있다. 즉, 8 MHz 및 1 MHz의 두 개의 변조 주파수를 교차적으로 선택하여 변조함으로써, 150 m까지의 거리를 2 cm 이하의 오차로서 측정할 수 있게 하였다. 위상측정부는 정밀한 위상 측정을 위하여 높은 변조 주파수는 JK 플립플롭 위상차 측정기를 사용하고, 낮은 변조 주파수일 경우는 XOR 위상차 측정기를 사용하였다.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.162-167
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• 2011

Thermal storage plays an important role in building energy saving, which is greatly assisted by the incorporation of latent heat storage in building materials. A phase change material is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, can be storing and releasing large amount of energy. Heat is stored or released when the material changes from solid to liquid. Integration of building materials incorporating PCMs into the building envelope can result in increased efficiency of the built environment. The aim of this research is to identify thermal performance of PCMs impregnated building materials which is applied to interior of building such as gypsum and red clay. In order to analyze thermal performance of phase change materials, test-cell experiments and simulation analysis were carried out. The results show that micro-encapsulated PCM has an effect to maintain a constant indoor temperature using latent heat through the test-cell experiments. PCM wallboard makes it possible to reduce the fluctuation of room temperature and heating and cooling load by using EnergyPlus simulation program. Phase change material can store solar energy directly in buildings. Increasing the heat capacity of a building is capable of improving human comfort by decreasing the frequency of indoor air temperature swings so that the interior air temperature is closer to the desired temperature for a long period of time.

• 대한전자공학회논문지
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• 제21권3호
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• pp.66-72
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• 1984

본 논문에서는 동일 채널 간섭과 잡음 환경하에서의 L레벨 ASK 및 다상 PSK, APK 시스템의 성능을 오율의 관점에서 구명하였다. ASK 신호와 PSK 신호에 대한 오율식을 이용하여 반송파대 잡음 전력비, 반송파대 간섭파 전력비 및 간섭파의 포락선 분포의 함수로서 APK 시스템의 오율 특성을 밝히고 PSK시스템 및 ASK 시스템, QAM 시스템, APK시스템의 성능을 비교 검토하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.687-692
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• 2008

In a nuclear power plant, loose part monitoring and its diagnostic technique is one of the major issues for ensuring the structural integrity of the reactor system. Typically, accelerometers are mounted on the surface of a reactor vessel to localize impact location caused by the impact of metallic substances on the reactor system. However, in some cases, the number of the accelerometers is not enough to estimate the impact location precisely. In such a case, one of alternative plan is to utilize another type sensors that can measure the vibration of the reactor structure even though the measuring frequency ranges are different from each others. The AE sensors installed on the reactor structure can be utilized as additional sensors for loose part monitoring. In this paper, we proposed a new method to estimate impact location by using both accelerometer signal and AE signal, simultaneously. The feasibility of the proposed method is verified by an experiment. The experimental results demonstrate that we can enhance the reliability and precision of the loose part monitoring.

• Architectural research
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• 제20권3호
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• pp.93-102
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• 2018

With the change in Earth's ecosystems due to climate change, a number of studies on zero energy buildings have been conducted globally, due to the depletion of energy and resources. However, most studies have concentrated on residential and office buildings and the performance predictions were made only in the design phase. This study verifies the zero-energy performance in the operational phase by acquiring and analyzing data after the completion of an exhibition building. This building was a retention building, in which a renewable energy system using a passive house building envelope, solar photovoltaic power generation panels, as well as fuel cells were adopted to minimize the maintenance cost for future energy-zero operations. In addition, the energy performance of the building was predicted through prior simulations, and this was compared with actual measured values to evaluate the energy performance of the actual operational records quantitatively. The energy independence rate during the measurement period of the target building was 123% and the carbon reduction due to the energy production on the site was 408.07 tons. The carbon reduction exceeded the carbon emission (331.5 tons), which verified the carbon zero and zero-energy performances.

• 한국통신학회논문지
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• 제26권12B호
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• pp.1637-1647
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• 2001

Multi-Code CDMA (MC-CDMA) 방식은 송신 시 여러 채널의 신호를 동시에 선형적으로 합하여 전송하므로 채널수가 증가할수록 신호의 PAPR(Peak to Average Power Ratio)가 증가하게 되어 증폭기의 비선형 특성에 의해 시스템 성능이 변화한다. 본 논문에서는 다중 레벨 신호에 대한 증폭기의 비선형 왜곡 특성을 분석하고, 증폭기의 비선형 특성에 의한 영향을 최소화하기 위해 다중 레벨 신호를 constant envelope 신호로 변환하는 Multi-Phase CDMA (MP-CDMA) 방식을 제안한다. 또한 다중 레벨 신호의 일정 레벨 이상은 잘라버리는 clipping 방식을 적용함으로써 레벨수의 증가에 따른 성능 저하 및 시스템의 복잡화를 줄이며 이로 인한 시스템 성능의 변화와 요구 전송 속도에 따른 최적의 clipping level을 연구한다.