• 제목/요약/키워드: surface integral method

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전자유압 비례밸브와 경사센서를 이용한 농용 프론트 로더 버켓 능동수평유지 시스템 개발 (Development of a self-leveling system for the bucket of an agricultural front-end loader using an electro hydraulic proportional valve and a tilt sensor)

  • 이창주;하종우;최덕수;김학진
    • 드라이브 ㆍ 컨트롤
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    • 제12권4호
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    • pp.60-70
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    • 2015
  • A front-end loader (FEL) mounted on an agricultural tractor is one of the most commonly used implements for farm work. However, when the tractor carries material using the bucket attached to the FEL on a sloping ground, the materials can spill or roll back over the operator due to the tilted body, thereby requiring the bucket surface to remain level at a constant value regardless of varying slopes. In this study, an active system for controlling the angle of the FEL bucket on a tractor based on the real-time measurement of ground slopes was developed to enable the bucket to constantly remain level. A FEL simulator operated based on an electro hydraulic proportional valve (EHPV) was constructed in the laboratory to develop a proportional-integral-derivative (PID) controller forming a virtual electronic control unit (ECU) on the computer, which could automatically adjust the bucket angles depending on varying input angles while sending SAE-J1939 associated messages via CAN BUS to the EHPV. The different parameter values for the PID controller due to the gravity effect of the bucket were determined using a manual PID tuning method while assuming that the tractor travels on either an ascending slope or a descending slope. The developed PID control-based self-leveling system showed a mean of steady-state errors of within $1^{\circ}$ and a mean of delayed times of ~ 0.8s when the step input of $+20^{\circ}$ was given, implying that the developed system and control algorithm would be effective in maintaining the bucket angle at a certain value. Future studies include the improvement of the control algorithm to reduce such a time delay as well as the application of the developed algorithm to the FEL mounted on a tractor tested at a testing ground.

인프라사운드 관측을 통한 2004년 울진해역지진의 지반운동 특성 분석 (Analysis of Ground-Motion Characteristics of the 2004 Offshore Uljin Earthquake through Atmospheric Infrasound Observation)

  • 제일영;윤여웅;임인섭
    • 한국지구과학회지
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    • 제41권6호
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    • pp.647-657
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    • 2020
  • 2004년 5월 29일 발생한 울진해역지진(Mw 5.1)과 관련된 대기 인프라사운드 신호가 철원(진앙 거리 321 km) 및 대전(256 km) 관측소에 기록되었다. 신호의 지속시간은 수 분 이상이며, 음원 방향을 지시하는 후방-방위각은 28°이상의 큰 변화를 보였다. 역-투사 방법과 신호 감쇄 보정 결과, 인프라사운드 신호는 삼척-울진-포항까지 연결되는 약 4,600 ㎢ 면적의 지반운동으로 발생하였으며, 음원 최대 크기(BSP)는 11.1 Pa로 계산되었다. 이 결과는 최대지반가속도(PGA) 자료로 계산한 음원 최대 크기(PSP)와도 부합하고 있으며, 지진 발생 당시 인프라사운드 신호 탐지를 가능케 했던 최소 지반운동은 ~3.0 cm s-2 이상으로 확인되었다. 울진해역지진이 비록 동해 해역에서 발생하였지만, 진앙과 가까운 강원도 남부-경상북도의 고지대를 따라 전파한 표면파의 지반운동으로 회절 인프라사운드가 효과적으로 발생한 것으로 해석된다. 인프라사운드 관측을 통한 원거리 지진 지반운동 특성 추정 방법은 지진관측망이 설치되어 있지 않거나 관측소 수가 적은 지역을 대상으로 활용이 가능할 것이다.

설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제26권12호
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

토끼 뇌종양 모델에서의 관류 CT 영상에 관한 연구 (Research on Perfusion CT in Rabbit Brain Tumor Model)

  • 하본철;곽병국;정지성;임청환;정홍량
    • 대한방사선기술학회지:방사선기술과학
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    • 제35권2호
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    • pp.165-172
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    • 2012
  • VX2 암종을 이식한 토끼 뇌종양 모델에서, perfusion CT(computed tomography, CT)를 이용하여 종양과 정상 뇌조직의 혈류 특성을 알아보고자 하였다. 체중 2.4~3.0kg(평균 2.6kg)의 토끼(New Zealand white rabbit) 수놈 9마리를 대상으로, 토끼 뇌에 VX2 세포 현탁액 $1{\times}10^7$ cells/ml, 0.1 ml을 이식하고 종양이 5mm 정도 크기로 자라면 perfusion CT를 시행 하였다. GE사의 AW(advantage windows workstation, version 4.2)로 종양의 용적과 perfusion 값을 산출 하였다. 뇌종양의 평균 용적은 $316{\pm}181mm^3$ 이었고, 가장 큰 종양은 497 $mm^3$, 가장 작은 종양은 195 $mm^3$ 이었 이식된 종양 모두 단일 결절형으로 만들어졌고, 두개강 내로 전이는 발견되지 않았다. perfusion CT에서 종양 중심부의 혈류량(cerebral blood volume, CBV)은 $74.40{\pm}9.63$ 이었고, 종양쪽 정상 뇌조직에서는 $16.08{\pm}0.64$ 이었으며, 종양 반대쪽 정상 뇌조직에서는 $15.24{\pm}3.23$이었다. 혈류 속도(cerebral blood flow, CBF)는 종양 중심부에서 $962.91{\pm}75.96$ 이였고, 종양쪽 정상 뇌조직에서는 $357.82{\pm}12.82$ 이었으며, 종양 반대쪽 정상 뇌조직에서는 $323.19{\pm}83.24$ 이었다. 평균 통과시간(mean transit time, MTT)은 종양 중심부에서 $4.37{\pm}0.19$ 이었고, 종양쪽 정상 뇌조직에서는 $3.02{\pm}0.41$ 이었으며, 종양 반대쪽 정상 뇌조직에서는 $2.86{\pm}0.22$ 이었다. 투과성 표면적(permeability surface, PS)은 종양 중심부에서 $47.23{\pm}25.45$ 이었고, 종양쪽 정상 뇌조직에서는 $14.54{\pm}1.60$ 이었으며, 종양 반대쪽 정상 뇌조직에서는 $6.81{\pm}4.20$이었다. 또한, 종양 중심부에서 최고치 도달 시간(time to peak, TTP)은 $19.33{\pm}0.42$ 이었고, 종양쪽 정상 뇌조직에서는 $16.43{\pm}1.72$ 이었으며, 종양 반대쪽 정상 뇌조직에서는 $15.14{\pm}0.88$이었지만 통계적으로 유의하지 않았다. PEI(positive enhancement integral, PEI)은 종양 중심부에서 $61.56{\pm}16.07$ 이었고, 종양쪽 정상 뇌조직에서는 $12.58{\pm}2.61$ 이었으며, 종양 반대쪽 정상 뇌조직에서는 $8.26{\pm}5.55$ 이었다. 최대 증가 기울기(maximum slope of increase, MSI)는 종양 중심부에서 $13.18{\pm}2.81$ 이었고, 종양쪽 정상 뇌조직에서는 $6.99{\pm}1.73$ 이었으며, 종양 반대쪽 정상 뇌조직에서는 $6.41{\pm}1.39$ 이었다. 최대 감소 기울기(maximum slope of decrease, MSD)는 종양 중심부에서 $4.02{\pm}1.37$ 이었고, 종양쪽 정상 뇌조직에서는 $4.66{\pm}0.83$ 이었으며, 종양 반대쪽 정상 뇌조직에서는 $6.47{\pm}1.53$ 으로 나타났다. 결과적으로 정위적(stereotactic)으로 이식된 종양은 단일 결절형으로 두개강 내에 전이가 없어 정상 조직과 종양 조직의 비교 연구에 적합하며, perfusion CT 에서 얻어진 매개 변수(parameter)들은 종양과 정상 조직의 혈관 관류 상태 차이를 잘 반영해 주었다.