• 한국안전학회지
• /
• 제24권2호
• /
• pp.83-88
• /
• 2009

The objective of this paper was to evaluate the effectiveness of horizontal, vertical, asymmetric and coupling multipliers for manual material handling. Lifting tasks with 5 different horizontal distances ($30{\sim}70cm$) for 6 vertical distances(ankle, knee, waist, elbow, shoulder and head height) were experimented. The muscle activity and muscle exertion level during asymmetric load handling(without trunk flexion) was experimented. Lifting tasks with and without handle tote box for three postures(straight, bending, right angle posture) were experimented. The degrading tendency did not appeared almost in $60{\sim}70cm$ interval's horizontal distance. As a result of ANOVA, MVC paid attention to horizontal and vertical distance but cross effect was insignificant(p<0.01). The change of the MVC according to the horizontal, vertical distance appeared similar from of RWL. The results of normalized MVC measurement were decreased about 16%, 24%, 34% respectively as the asymmetry angle was $30^{\circ}$, $60^{\circ}$, $90^{\circ}$. RMS EMG values of right erector spinae muscles were decreased as the work posture went to $90^{\circ}$ and those of left erector spinae muscles were increased until the asymmetry angle was $40^{\circ}$ but decreased continually over $40^{\circ}$. 7 subjects, activities of left and right latissimus dorsi muscles were maintained constantly, while for remainer, those were irregular. MVC reduced maximum 23% by type of handle. MVC was highest in straight posture, but was lowest in right angle posture. As a result of ANOVA, MVC paid attention to posture, coupling(p<0.01). To all handle types, biceps brachii activity was increased in right angle posture, but reduced in straight posture. Based on the results of this study, it is suggested that the NIOSH guideline should not be directly applied to Korean without reasonable reexamination. In addition, we need to afterward study through an age classification.

• Nuclear Engineering and Technology
• /
• 제56권1호
• /
• pp.19-33
• /
• 2024

In nuclear thermal-hydraulic system codes, most correlations used for vertical pipes, under downward two-phase flow, have been developed considering small pipes or pool systems. This suggests that there could be uncertainties in applying the correlations to accident scenarios involving large vertical pipes owing to the difference in the characteristics of two-phase flows, or flow conditions, between large and small pipes. In this study, we modified the Multi-dimensional Analysis of Reactor Safety KINS Standard (MARS-KS) code using correlations, such as the drift-flux model and two-phase multiplier, developed in a plant-scale air-inflow experiment conducted for a pipe of diameter 600 mm under downward two-phase flow. The results were then analyzed and compared with those based on previous correlations developed for small pipes and pool conditions. The modified code indicated a good estimation performance in two plant-scale experiments with large pipes. For the siphon-breaking experiment, the maximum errors in water flow for modified and original codes were 2.2% and 30.3%, respectively. For the air-inflow accident experiment, the original code could not predict the trend of frictional pressure gradient in two-phase flow as / increased, while the modified MARS-KS code showed a good estimation performance of the gradient with maximum error of 3.5%.

• 융합신호처리학회논문지
• /
• 제10권4호
• /
• pp.267-273
• /
• 2009

본 논문은 WDR(Wide Dynamic Range)의 구현을 위한, 나눗셈기를 사용하지 않은 가변적 평균기의 설계에 관한 것이다. 이전에 제안하였던 평균기 [5]는 나눗셈기를 곱셈기로 대체함으로써 하드웨어의 복잡도 및 하드웨어 자원의 효율성을 향상시켰다. 하지만 기존에 제안한 구조는 가로와 세로의 길이를 측정하고, 사용자에 의해 Mode에 설정되어 있는 기본 영상의 크기와 정확히 일치할 경우에만 동작이 가능하다는 단점이 있었다. 본 논문은 이러한 기존 평균기의 단점을 보완하기 위하여, 영상의 전체 크기를 이용하여 Mode를 선택하도록 하였다. 또한 특정 크기의 영상에만 적용되는 것이 아니라 다양한 크기의 영상에 대해서도 적용 가능하도록 제안한다. 특히, 보다 정확한 평균값을 구하기 위하여 외부 보상 값을 추가하였다. Verilog-HDL을 이용하여 설계하였으며, 합성결과를 통해 Serial multiplier의 구조가 좀 더 하드웨어 크기와 자원의 효율성이 높은 것을 확인하였다.

• 지구물리와물리탐사
• /
• 제5권4호
• /
• pp.316-322
• /
• 2002

단일 시추공 환경에서 얻어지는 전자기장을 해석하기 위해 확장 Born 혹은 국소비선형 근사를 이용한 계산시간이 짧고 효율적인 역산법을 만들었다. 매질은 시추공에 관해 축대칭이라 가정하였으며 그 대칭성을 유지하기 위해 수직 자기 쌍극자원을 사용하였다. 역산법의 효율성과 안정성은 적절한 라그랑지계수의 사용에 크게 의존하지만 이는 일반적으로 원하는 수렴성을 달성하기 위해 수작업으로 결정된다. 본 연구에서는 현장 자료를 다루는 역산법의 효율을 향상하기 위해 라그랑지계수의 자동결정법을 개발하였다. 그 역산법의 안정성과 효율성은 이론모델링 자료를 사용하여 검토되었다.

• 한국항해학회지
• /
• 제12권2호
• /
• pp.23-32
• /
• 1988

This paper offers a method of magnetic compass adjustment for the vessel alongside the wharf using newly designed magnetic north former, which makes the same magnetic field-change as the turning vessel does. The characteristics of the magnetic north former was examined by observing the deviation curves of the magnetic compass installed on the compass deviascop at laboratory. The magnetic north former consists of A and B arms which hold the permanent bar magnets at the both ends of each arm. The arm is to rotae in the horizontal plane about the vertical axis fixed at the center boss of the magnetic compass and it is to compensate the horizontal plane about the vertical axis fixed at the center boss of the magnetic compass and it is to compensate the horizontal component of the earth's field. The B arm makes the artificial magnetic north around the magnetic compass for every ship's heading. The results of investigation are summarized as follows ; 1. The observation and correction of magnetic compass deviation can be done without swinging the ship, of the effect of D coefficient is negligible. 2. The residual deviation curve of the magnetic compass depends on the accuracy of deduced value of ship's multplier($\lambda$). 3. The errors due to the inaccuracy of deduced value of ship's multiplier change in the same way as the B and C coefficient do.

• Carbon letters
• /
• 제13권1호
• /
• pp.17-22
• /
• 2012

Currently, graphene is a topic of very active research in fields from science to potential applications. For various radio-frequency (RF) circuit applications including low-noise amplifiers, the unique ambipolar nature of graphene field-effect transistors can be utilized for high-performance frequency multipliers, mixers and high-speed radiometers. Potential integration of graphene on Silicon substrates with complementary metal-oxide-semiconductor compatibility would also benefit future RF systems. The future success of the RF circuit applications depends on vertical and lateral scaling of graphene metal-oxide-semiconductor field-effect transistors to minimize parasitics and improve gate modulation efficiency in the channel. In this paper, we highlight recent progress in graphene materials, devices, and circuits for RF applications. For passive RF applications, we show its transparent electromagnetic shielding in Ku-band and transparent antenna, where its success depends on quality of materials. We also attempt to discuss future applications and challenges of graphene.

• Earthquakes and Structures
• /
• 제8권1호
• /
• pp.205-224
• /
• 2015

A new method for designing moment resisting concrete frames failing in a global mode is presented in this paper. Starting from the analysis of the typical collapse mechanisms of frames subjected to horizontal forces, the method is based on the application of the kinematic theorem of plastic collapse. The beam section properties are assumed to be known quantities, because they are designed to resist vertical loads. As a consequence, the unknowns of the design problem are the column sections. They are determined by means of design conditions expressing that the kinematically admissible multiplier of the horizontal forces corresponding to the global mechanism has to be the smallest among all kinematically admissible multipliers. In addition, the proposed design method includes the influence of second-order effects. In particular, second-order effects can play an important role in the seismic design and can be accounted for by means of the mechanism equilibrium curves of the analysed collapse mechanism. The practical application of the proposed methodology is herein presented with reference to the design of a multi-storey frame whose pattern of yielding is validated by means of push-over analysis.

• 한국지반공학회논문집
• /
• 제17권6호
• /
• pp.193-205
• /
• 2001

본 연구에서는 수직 및 수평하중을 받는 군말뚝의 배열 및 중심간격을 고려한 실내모형실험을 수행하여 군말뚝기초의 거동특성을 분석하였다. 모형말뚝은 PVC말뚝을 사용하였으며 모형지반은 주문진표준사를 이용해 조밀한 사질토 지반(Dr=73%)으로 조성하였다. 말뚝의 배열은 $2\times2,\; 3\times3$ 배열, 말뚝중심간격은 말뚝직경의 2.5, 5.0, 7.5 배인 경우를 고려하였다. 실험결과 수직하중을 받는 말뚝에서는 두부에서의 수직하중-침하량곡선, 하중전이함수인 주면마찰락력-변위곡선(t-z 곡선)과 선단지지력-변위곡선(q-z 곡선)을 구하였으며, 수평하중을 받는 말뚝에서는 두부에서의 수평하중-수평변위곡선, 하중전이함수인 지반반력-변위곡선(p-y곡선)을 구하였고 이를 토대로 말뚝의 배열 및 중심간격에 따른 군말뚝계수를 제안하였다. 또한 수평하중을 받는 군말뚝의 각 열에 대해 상호작용계수(P-multiplier)를 산정하였다.

• Journal of Radiation Protection and Research
• /
• 제28권2호
• /
• pp.97-108
• /
• 2003

복잡한 지형상에서 바람장 분포를 산정하기 위해 변분기법에 근거한 3차원 바람장 모델을 개발하였다. Lagrangian multiplier와 조정된 바람장 분포를 얻기 위하여 직각 및 지형을 따르는 좌표계상에서 3차원 타원형 편미분 방정식이 수립되었다. 반구, 반 실린더 및 안장 형태의 지형상에서 바람장의 변화를 추정하기 위해 계산이 수행되었고, 또한 지형을 따르는 좌표계상에서 바람장 모델이 Gauss precision moduli의 변화에 따른 바람장 특성을 평가하기 위하여 적용되었다. 산정결과 수평 및 수직 바람 성분은 Gauss precision moduli값의 선정에 강하게 영향을 받고 있음이 확인되었다.

• 대한전자공학회논문지SD
• /
• 제41권11호
• /
• pp.97-104
• /
• 2004

본 논문은 JPEG2000의 손실 압축 또는 무손실 압축에 사용되어지는 9-7/5-3 리프팅 DWT필터에 대한 효율적인 VLSI 구조를 제안한다. 제안된 구조는 리프팅 DWT 연산을 위해 내부 라인 메모리만을 사용하며, 내부 처리 유닛은 1개의 곱셈기와 1개의 덧셈기의 임계경로를 갖는다. 특히 본 논문에서는 처리유닛의 수를 감소하기 위해 1레벨의 열방향을 담당하는 필터로 하여금 2레벨 이상의 행방향과 열방향 연산 모두를 처리하도록 하였다. 결과적으로 제안된 구조는 기존의 구조에 비해 작은 하드웨어 크기를 갖는다. 제안된 리프팅 DWT구조는 RTL 수준에서 VHDL로 모델링되었으며, 기능 검증 후 Altera APEX 20K FPGA로 구현되었다.