• 터널과지하공간
• /
• 제17권1호
• /
• pp.66-74
• /
• 2007

석회암 용식지역 상부에 위치한 주거지역에 대하여 지반침하 안정성을 분석하였다. 석회암지역에 분포한 공동을 조사하기 위하여 전기비저항 토모그래피, 전자탐사를 실시하였으며 지반특성을 규명하기 위하여 시추조사를 포함한 지반공학적인 조사를 실시하였다. 조사 결과를 바탕으로 공동의 형상과 지하수 조건에 대하여 지반침하 분석 및 예측을 위한 수치해석을 실시하였다. 지반침하를 일으키는 주요인은 지하수위의 하강으로 예측되었는데 이는 표토 하부의 지하수위가 감소함으로써 지반의 역학적 평형상태가 교란되고 공동이나 지표면의 침하가 발생해 표토 토양층이 유실되기 때문이다. 석회암 용식지역에서의 지반침하를 방지하기 위하여서는 천부 공동 상부의 지하수위를 지속적으로 유지시키는 것이 필수불가결한 것으로 보인다.

• 대한기계학회논문집A
• /
• 제38권5호
• /
• pp.475-482
• /
• 2014

유압밸브 구동용 서보 액추에이터는 항공기, 자동차의 유압시스템 그리고 산업용 유압시스템의 정밀한 작동에 중요한 장치이다. 서보 액추에이터의 신뢰성 있는 동작은 전체 유압시스템의 정밀한 제어에 큰 영향을 미친다. 서보 액추에이터의 주파수 응답특성, 스텝 응답특성과 같은 응답특성은 액추에이터의 성능을 판단하는 중요한 기준이 된다. 본 논문에서는 신뢰성해석을 통해 신뢰성 있는 동작과 응답특성을 만족시키기 위한 구성 부품에 대한 분석을 실시하였다. 또한 신뢰성 있는 동작과 빠른 응답성을 구현하기 위해 현장의 경험적 지식과 문헌 및 전문가의 전자기 이론을 통해 유압밸브 구동용 서보 액추에이터의 설계 파라미터를 도출하였다. 보빈, 요크, 플런저의 설계값, 그리고 코일의 감긴 수와 같은 서보 액추에이터의 설계값들을 결정하는 설계 파라미터를 제안하고, 설계방정식을 통해 산출한 설계값을 유한요소해석을 통해 타당성을 검증하였다. 또한 서보 액추에이터가 장착된 유압밸브의 성능시험을 통해 제안한 설계 방안의 타당성을 검증하였다.

• 한국측량학회지
• /
• 제21권3호
• /
• pp.237-243
• /
• 2003

도시의 집중화로 인하여 도시미관이 중요시되면서 복잡한 지상시설물들을 지하에 매설하게 되었다 그러나 다양한 종류의 시설물들이 좁은 공간에 집중적으로 매설되면서 이들 시설물들에 대한 유지관리의 어려움과 부정확한 확인으로 인하여 빈번한 사고를 유발하고 있다. 따라서 본 연구에서는 우선 지하매설물의 탐사법을 비교평가하기 위해 현장실험모형을 구성하여 전자유도탐사법과 지중탐사법이 지하매설관거의 자료취득에 유용한 방법임을 확인할 수 있었다. RTK-GPS를 이용하여 지하매설물에 대해 실시간 평면 위치정보를 획득하여 재래적인 측량방법과 비교한 뒤 지하시설물도의 위치 정확도를 분석하였다. 또한, ArcView를 이용하여 지하시설물의 3차원위치와 매설심도를 DB화하고 지하매설물 정보 체계(UIS)에 활용하므로써 지하시설물에 대한 효과적인 유지관리, 재해방지에 기여하고자 한다.

• Progress in Superconductivity
• /
• 제4권1호
• /
• pp.86-89
• /
• 2002

In this paper, the design of a IMVA single-phase high temperature superconducting(HTS) power transformer with BSCCO-2223 HTS tapes is presented. The rated voltages of each sides of the transformer are 22.9 ㎸ and 6.6 ㎸, respectively The winding of 1MVA HTS transformer is consisted of double pancake type HTS windings, which have advantages of insulation and distribution of high voltage, and are cooled by subcooled liquid nitrogen of 65K. Four HTS tapes were wound in parallel for the windings of low voltage side and the four parallel conductors are transposed. The design of 1MVA HTS transformer, a shell type core made of laminated silicon steel plate is chosen, and the core is separated with the windings by a cryostat with a room temperature bore. The cryostat made of non-magnetic and non-conducting material and a liquid nitrogen sub-cooling system is designed in order to maintain the coolant's temperature of 65K. For electromagnetic analysis of 1MVA HTS transformer, a finite element method of an axis of symmetry is used. The maximum perpendicular component of magnetic flux density of pancake windings is about 0.15T. And through analyzing the magnetic field distribution, an optimal winding arrangement of 1MVA HTS transformer is obtained.

• 한국산학기술학회논문지
• /
• 제17권4호
• /
• pp.474-479
• /
• 2016

친환경에너지에 대한 요구가 높아지면서 전기에너지의 사용은 계속 증가하고 있다. 최근 친환경, 에너지 절약을 위해서 유도가열을 이용한 여러 가지 가열방식에 대한 관심이 높아지고 있다. 본 논문에서는 전자유도현상을 이용한 유도가 열방식을 이용하여 보다 친환경적이고 에너지 절약이 가능한 전기온풍기를 설게 제작하였다. 온풍기는 송풍부, 유도가열부 및 전력변환부 등 3부분으로 구성하였다. 유도가열부는 송풍부에 결합되어 송풍부로부터 발생된 바람이 가열되어 분출되며, 전력변환부는 고주파를 인가하여 자속을 발생시킴으로써 유도가열부의 내부를 가열시킨다. 발열방식은 유도가열의 원리를 적용하고, 전력변환효율성을 높이기 위해 공진형 인버터를 사용하였다. 공진형 인버터는 풀브리지 전압형 직렬부하 공진형 인버터를 사용하였다. 유도가열부는 세라믹 계열의 절연체와 SUS40계열의 금속체를 사용했으며, 전력변환부는 정류부, 필터부 및 공진형 인버터부 등으로 구성 하였다. 본 연구에서 제안한 전기온풍기는 기존의 전기히터와 가스히터 등과 비교한 결과, 온도 상승속도가 빠르고, 사용에너지 비용이 절감되는 등 경제성도 있음을 보였다. 개발된 전기온풍기는 가정용, 상업용 및 농업용 등 여러 분야에 친환경 에너지절감형 온풍기로의 적용 가능성이 있다.

• Journal of Biosystems Engineering
• /
• 제39권1호
• /
• pp.21-33
• /
• 2014

Background: Significant technological development and changes happened in the tractor industries. Contrariwise, the test procedures of the major standard development organizations (SDO's) remained unchanged or with a little modification over the years, demanding new tractor test standards or improvement of existing ones for tractor performance, safety, and comfort. Purpose: This study focuses on reviewing the research trends regarding performance, safety and comfort evaluation of agricultural tractors. Based on this review, few recommendations were proposed to revise or improve the current test standards. Review: Tractor power take-off power test using the DC electric dynamometer reduced human error in the testing process and increased the accuracy of the test results. GPS signals were used to determine acceleration and converted into torque. High capacity double extended octagonal ring dynamometer has been designed to measure drawbar forces. Numerical optimization methodology has been used to design three-point hitch. Numerous technologies, driving strategies, and transmission characteristics are being considered for reducing emissions of gaseous and particulate pollutants. Engine emission control technology standards need to be revised to meet the exhaust regulations for agricultural tractors. Finite Element Analysis (FEA) program has been used to design Roll-Over Protective Structures (ROPS). Program and methodology has been presented for testing tractor brake systems. Whole-body vibration emission levels have been found to be very dependent upon the nature of field operation performed, and the test track techniques required development/adaptation to improve their suitability during standardized assessment. Emphasizes should be given to improve visibility and thermal environment inside the cab for tractor operator. Tractors need to be evaluated under electromagnetic compatibility test conditions due to large growing of electronic devices. Research trends reviewed in this paper can be considered for possible revision or improvement of tractor performance, safety, and comfort test standards.

• 한국에너지공학회:학술대회논문집
• /
• 한국에너지공학회 1995년도 춘계학술발표회 초록집
• /
• pp.185-198
• /
• 1995

This is an experimental study conducted to visualize the nucleate boiling phenomena and flow regimes occurring inside the liquid pool in a closed two-phase thermosyphon. To meet this purpose, an annular-type thermosyphon was designed and manufactured using a glass tube and a stainless steel tube, being assembled axisymmetrically. The heat to be supplied to the working fluid is generated within a very thin layer of stainless steel tube wall by applying a high frequency electromagnetic field through the induction coil, axisymmetrically set around the evaporator zone. Some important results were as follows ; 1) Considering the structural complexity of the tested thermosyphon, it showed good performance for the range of heat flux 2＜ q" ＜25kW/$m^2$ and saturation vapor pressure, 0.1＜Pv＜1.1bar 2) different type of nucleating boiling regimes were observed as described below, -Pulse boiling regime : Flow pattern changed cyclically with time during 1 cycle of pulse boiling process. The onset of Nucleation was followed by expulsive growing of vapor bubble, resulting in the so called blow-up phenomenon, massive expulsion of large amount of liquid around the bubble. -Transient : Some spherical vapor bobbles were observed growing out from 2~3 nucleating sites, that was dispersed at the lower part of the heated tube wall in the liquid pool. But the rest upper region above the nucleating sites were filled with churns or bubbles of vapor. -Continuous nucleate boiling regime : The whole zone of evaporator was filled with lots of spherical vapor bubbles, and the bubbles showed tendency to decrease in diameter as the heat flux increased.ased.

• Smart Structures and Systems
• /
• 제9권5호
• /
• pp.393-410
• /
• 2012

Conventional geotechnical instrumentation techniques available for monitoring of slopes, especially soil-nailed slopes have limitations such as electromagnetic interference, low accuracy, poor longterm reliability and difficulty in mounting a series of strain sensors on a soil nail bar with a small-diameter. This paper presents a slope monitoring system based on fibre Bragg grating (FBG) sensing technology. This monitoring system is designed to perform long-term monitoring of slope movements, strains along soil nails, and other slope reinforcement elements. All these FBG sensors are fabricated and calibrated in laboratory and a trial of this monitoring system has been successfully conducted on a roadside slope in Hong Kong. As part of the slope stability improvement works, soil nails and a toe support soldier-pile wall were constructed. During the slope works, more than 100 FBG sensors were installed on a soil nail, a soldier pile, and an in- place inclinometer. The paper presents the layout and arrangement of the instruments as well as the installation procedures adopted. Monitoring data have been collected since March 2008. This trial has demonstrated the great potential of the optical fibre monitoring system for long-term monitoring of slope performance. The advantages of the slope monitoring system and experience gained in the field implementation are also discussed in the paper.

• Restorative Dentistry and Endodontics
• /
• 제26권2호
• /
• pp.134-140
• /
• 2001

The polymerization shrinkage of composite resins is an important drawback although the composites have many advantages-more esthetic and conservative than metallic restoratives etc. The purposes of this research were to develop a new measurement method and to manufacture an instrument that can measure the initial dynamic volumetric shrinkage of composite resins during polymerization. The instrument was basically an electromagnetic balance that constructed with a force transducer using position sensitive photo detector(PSPD) and a negative feedback servo amplifier of proportional-derivative(PD) controller. The volumetric change of composites during polymerization was detected continuously as buoyancy change in distilled water by means of Archimedes's principle. It was converted to continuous electrical voltage signal in real time. The signal was properly conditioned and filtered and then it was stored in computer by a data acquisition(DAQ) board. By using this electronic instrument. the dynamic patterns of the polymerization shrinkage of eight commercial(Z-100, DenFil, AeliteFil, Z-250, P-60, SureFil, Synergy compact, and Tetric ceram) composite resins were measured and compared. The results were as follows. 1. From this project of developing instrument, the ability has been achieved that can acquire and process data of electrical signal transformed from various physical phenomenon by using temperature, displacement. photo. and force transducer. As a consequence, the instrumentation and measurement system used to analyze the physical characteristics of various dental materials in dental research field can be designed, manufactured and implemented in lab. 2. This instrument has some advantages. It was insensible to temperature change and could measure true dynamic volumetric shrinkage in real time without complicated process. It showed accuracy and high precision results with small standard deviation. 3. The polymerization shrinkage of composites was significantly different between brands and ranged from 2.47％ to 3.89％, The order of polymerization shrinkage was as follows, in order of increasing shrinkage, SureFil, P60, Z250, Z100, Synergy compact. DenFil, Tetric ceram, and AeliteFil. 4. The polymerization shrinkage rate per unit time, dVol％/dt, showed that the instrument can provide an indirect research method for polymerization reaction kinetics.

• 폴리머
• /
• 제30권6호
• /
• pp.572-575
• /
• 2006

사회적 관심이 되고 있는 전력선과 휴대폰의 전자파 영향에 의한 인체 유해성 문제에 대한 상대적 개념으로 암 치료에 있어서 보조요법의 일환으로 제시될 수 있는 전자파를 이용한 온열치료법 개발을 위한 기초연구로서 고분자계의 젤리팬텀을 제작하였다. 폴리에틸렌을 비롯한 다양한 구성비를 가지는 팬텀 재료의 조합을 통해 CDMA와 PCS 대역에 적용되는 인체 두뇌의 젤리팬텀을 제작한 후 전기적 특성을 분석하였다. 본 연구는 향후 제조된 젤리팬텀을 비롯한 각종 장기의 모의인체에 대한 전기적 특성 값을 분석한 다음, 자성유체를 젤리팬텀에 주입시킨 후 실제 온도상승을 온도감지 적외선 카메라로 촬영하여 확인, 젤리팬텀의 전자기적 특성 분석을 통한 암 치료에 있어서의 새로운 방법론을 제시할 수 있을 것으로 기대된다.