• Structural Engineering and Mechanics
• /
• 제26권3호
• /
• pp.231-250
• /
• 2007

The influence of masonry infills with eccentric openings on the seismic performance of reinforced concrete (r/c) frames that were designed in accordance with current code provisions are investigated. Eight 1/3-scale, single-story, single-bay frame specimens were tested under cyclic horizontal loading up to a drift level of 4%. In all examined cases the shear strength of columns was higher than the cracking shear strength of solid infill. The parameters investigated include the shape and the location of the opening. Assessment of the behavior of the frames is also attempted, based on the observed failure modes, strength, stiffness, ductility, energy dissipation capacity and degradation from cycling loading. Based on these results there can be deduced that masonry infills with eccentrically located openings has been proven to be beneficial to the seismic capacity of the bare r/c frames in terms of strength, stiffness, ductility and energy dissipation. The location of the opening must be as near to the edge of the infill as possible in order to provide an improvement in the performance of the infilled frame.

• 전기학회논문지
• /
• 제63권5호
• /
• pp.719-725
• /
• 2014

Transient of Electric railway vehicle occurs when change to another state. The duration of the transient phenomenon only takes a few second. During this time is considered, the present of short circuit current and the normal state, the energy is present in the form of a magnetic field. Recognized by the vibration of the transient voltage or transient current at witch energy is present in the field. This paper is presented the result of transient characteristics by transformer % impedance at the time of opening and closing of the main circuit Breaker on the electric railway vehicle.

• 한국태양에너지학회 논문집
• /
• 제31권6호
• /
• pp.1-7
• /
• 2011

Sound waves and acoustic energy generated by two identical TA (ThermoAcoustic) lasers were analyzed and studied. One end of the ceramic stack was heated by a thin NiCr wire wound around that end. The other end of the stack was cooled by natural convection of atmospheric air. The wavelength of the sound waves generated by a single TA laser was four times the tube length and the amplitude of the waves increased with the heating rate. SPL (SoundPressure Level) meters and microphones were employed to measure and study the sound waves at different distances from the glass tube opening and at the focusing point of the TA laser pair for different laser position arrangements. The sound waves of the two TA lasers at the focusing point were found to be almost 180 degrees out of phase when the openings of the two lasers were very close to each other and the angle between the laser axes was small. When the two TA lasers were placed far apart, the sound wave amplitudes and the phase difference between the two laser outputs varied periodically with time. The frequencies of the sound waves changed when the openings of the two TA lasers were in close vicinity and the angle between the laser axes exceeded a certain value. In this case, the glass tube opening was no longer a pressure anti-node and the wavelength of the fundamental mode was not equal to four times the tube length.

• 한국수소및신에너지학회논문집
• /
• 제28권1호
• /
• pp.106-112
• /
• 2017

The present study describes flow induced noise generated from a ball valve used for a gas pipeline. Noise generation from a ball valve mainly induces by interference between unstable(or fluctuating) leakage flow and pipe wall when the ball valve is working closed or opened. To measure the positions of the noise source and the amplitude of noise with respect to measuring frequencies, a commercial acoustic camera is introduced. Noise characteristics generated by the ball valve have been performed by four valve opening rates: 30, 50, 70 and 100 percents. It is noted that 100 percent opening rate means that the valve is fully opened. Throughout the experimental measurements using the acoustic camera, the location of the noise source and the noise amplitude with respect to the frequencies for the test ball valve are clearly evaluated. It is found that the dominant frequencies come from the fluctuating flow at the downstream of the ball valve for four opening rates are observed between 3,000Hz and 3,200Hz. Maximum noise amplitude comes from the ball valve reaches 75dB at the valve opening rate of 50 percent.

• 터널과지하공간
• /
• 제28권5호
• /
• pp.457-475
• /
• 2018

본 연구에서는 갱내채광장의 발파현상을 보다 현실적으로 수치해석상에서 반영하기 위하여 현장에서의 발파를 통해 획득한 발파진동 파형을 발파지점의 진동속도로 변환하여 이를 동적수치해석의 입력 자료로 직접 활용하였다. 석회석 갱내채광장의 지질특성과 채광단계를 반영한 수치모델을 구성하였으며, 이를 바탕으로 동적수치해석을 수행하여 석회석 갱내광산의 발파작업이 채광장의 안정성에 미치는 영향을 분석하였다. 해석결과와 현장에서 계측된 발파진동의 비교를 통하여 실측발파진동의 적정성을 확인하였으며, 연속되는 채광작업은 응력의 교란에 의한 천반붕락 및 채굴공동 주변의 활동성 파괴영역의 발생을 야기할 수 있는 것으로 분석되었다. 이로부터 연구대상 광산에서의 안정적인 채광활동을 위해서는 추가적인 보강대책이 필요할 것으로 판단된다.

• 폴리머
• /
• 제33권5호
• /
• pp.458-462
• /
• 2009

본 연구에서는 순차적 음이온 및 개환중합반응을 통해 ABC 형태의 폴리스티렌-폴리에틸렌옥사이드-폴리락티드 블록공중합체를 성공적으로 합성하였다. 우선, 첫번째 블록인 폴리스티렌을 합성하기 위해서, 사이클로헥산 용매에서 스티렌/이차-부틸리튬을 각각 단량체/개시제로 사용하여 음이온중합(anionic polymerization)을 수행하였고, 이후 고분자 말단을 수산기로 전환시키기 위해, 에틸렌옥사이드를 첨가하였다. 다음 단계로 포타슘 나프탈레나이드(potassium naphthalenide)를 이용하여 폴리스티렌 말단 수산기의 수소를 제거하여, 거대개시제인 PS-$O^-K^+$를 제조하였다. 준비된 거대 개시제에 정량된 에틸렌옥사이드를 첨가하여, 음이온중합을 수행하였다. 폴리락티드 블록을 도입시키는 개환중합의 경우, THF 용매에서 트리에틸알루미늄(triethylaluminum)/피리딘(pyridine)시스템을 이용하여 PS-b-PEO-$AlEt_2$ 형태의 거대개시제를 형성한 후, $90^{\circ}C$에서 중합을 수행하였다. 합성된 블록공중합체를 수소핵자기공명법 및 겔침투크로마토그래피 방법을 통해 조사한 결과, 잘 정의된 분자량 및 낮은 분자량 분포를 나타냄을 확인할 수 있었다.

• Journal of Oral Medicine and Pain
• /
• 제22권1호
• /
• pp.95-109
• /
• 1997

The purpose of this research is to investigate the influence on mandibular movements and TMJ sounds with changes of head and neck posture. For the research, twenty patients who had complained of TMJ sounds without any other symptoms of cranio-mandibular disorders, were selected as subjects for measurements of TMJ sounds, and radiographs on transcranial view of TMJ were taken on ten of the subjects. From NHP, UHP, DHP and FHP, aspects of mandibular movement and TMJ sound were investigated from each posture. Aspects of mandibular movement and TMJ sound were observed by measuring total vibration energy(Integral), peak amplitude, maximum amound of mouth opening, and TMJ sound-emitting point using Sonopak for windows (version 1.33) and Bio-EGN(Bioresearch Inc. WI. U.S.A.). Head and neck movement-measuring instrument, CROM(perfomance attainment Inc. U.S.A.) was to maintain even head posture. Degrees of inclination of UHP and DHP were determined at 30' and distance of FHP was 4cm. The results obtained were as follows. 1. Total vibration energy and peak amplitude of TMJ sounds were decreased more on UHP and on UHP and increased more on DHP and FHP than that on NHP. 2. At the maximum mouth opening, distance of TMJ sound-emitting point were decreased more on UHP and increased more on DHP and FHP than that on NHP. 3. The amounts of the maximum mouth opening were increased more on UHP and decreased more on DHP and FHP than that on NHP. 4. For the changes of the head posture with mouth opening observed in radiograph, condylar head was positioned more lower-anteriorly on UHP, and more upper-posteriorly on DHP and FHP than that on NHP. From the results obtained as above, considering positive influence of the change of head and neck posture, avoiding down-head and forward-head posture, and recommending upper- head posture can prevent the progress of temporomandibular disorder and lead to successful treatment for the patients with temporomandibular joint sounds.

• 터널과지하공간
• /
• 제29권1호
• /
• pp.64-74
• /
• 2019

지하공동의 굴착 과정에서 암반 절리로 인해 생성되는 암석블록의 거동 여부는 지하공동의 역학적 안정성에 있어서 중요한 요소이다. 본 연구에서는 대심도 지하공동 조건 하에서 지체응력 및 절리물성 조건에 따른 암석블록의 거동 안정성을 정량적으로 분석하였다. 이론적으로 계산된 암석블록의 거동조건과 3DEC 수치해석을 통해 분석된 암석블록의 거동양상을 비교하여, 이론값과 수치해석 결과간의 오차를 지체응력 및 절리물성 조건에 따라 분석하였다. 암석블록의 거동 안정성 분석을 수행한 결과는 수치해석 결과와 비교할 때 약 5% 이하의 오차를 보여 본 연구에서 제시한 이론적 방법론의 적용가능성을 검증하였다.

• 한국기계가공학회지
• /
• 제21권9호
• /
• pp.78-84
• /
• 2022

An air circuit breaker (ACB) is an electrical protection device that interrupts abnormal fault currents that result from overloads or short circuits in a low-voltage power distribution line. The ACB consists of a main circuit part for current flow, mechanism part for the opening and closing operation of movable conductors, and arc-extinguishing part for arc extinction during the breaking operation. The driving mechanism of the ACB is a spring energy charging type. The faster the contact opening speed of the movable conductors during the opening process, the better the breaking performance. However, there is a disadvantage that the durability of mechanism decreases in inverse proportion to the use of a spring capable of accumulating high energy to configure the breaking speed faster. Therefore, to simultaneously satisfy the breaking performance and mechanical endurance of the ACB, its driving mechanism must be optimized. In this study, a dynamic model of the ACB was developed using the MDO(Mechanism Dynamics Option) module of CREO, which is widely used in multibody dynamics analysis. To improve the opening velocity, the Taguchi design method was applied to optimize the design parameters of an ACB with many linkages. In addition, to evaluate the improvement in the operating characteristics, the simulation and experimental results were compared with the MDO model and improved prototype sample, respectively.

• The Korean Journal of Ecology
• /
• 제20권2호
• /
• pp.83-94
• /
• 1997

Stomatal closing by ozone and water stress could reduce further ozone injury by inhibition of ozone influx to the tissue. Direct effect of ozone on stomata can be explained from two aspects which are a stimulation of stomatal closing and an inhibition of stomatal opening. An increase of $Ca^{2+}$ influx into cytoplasm by ozone could stimulate potassium efflux ion channel and inhibits inward potassium ion channels. By this mechanism ozone could induce stomatal closing. On the other hand, ozone could inhibit stomatal opening by affecting the activity of $H^{+}$ dependent ATPase of the membrane in guard cells. This would inhibit proton efflux which precede stomatal opening. It is also possible that ozone could reduce the activity of photosynthesis in guard cells which lead to affect the production of osmotically active sugars and energy. Indirect effect of ozone to stomata is through the effect of $CO_2$ elevation as a result of damage of the photozynthetic machinery. This indirect effect is slower than the direct effect.