• 제목/요약/키워드: conduction model

검색결과 525건 처리시간 0.033초

화재시 터널내 열유동 시뮬레이션 모델 연구 (A Study on the Heat and Gas Flow for Fire Simulation in a Tunnel)

  • 우경범;김원갑;한화택
    • 설비공학논문집
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    • 제14권7호
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    • pp.584-591
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    • 2002
  • The objective of the present study is to develop a model to predict heat and gas flow movement by fire in a tunnel. The model includes component models such as turbulence model, combustion model, fire model, jet fan model, etc. It has been validated using the data from Memorial Tunnel Fire Ventilation Test Program. The predictions are in good quantitative agreement with the experimental data in the far-field region of the tunnel. It should be further investigated to develop models for radiation between surfaces, for composite boundary conditions for conduction and convection, and for vigorous turbulent mixing in a tunnel especially for a large size of fire.

Improved DC Model and Transfer Functions for the Negative Output Elementary Super Lift Luo Converter

  • Wang, Faqiang
    • Journal of Electrical Engineering and Technology
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    • 제12권3호
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    • pp.1082-1089
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    • 2017
  • Negative output elementary super lift Luo converter (NOESLLC), which has the significant advantages including high-voltage transfer gain, high efficiency, high power density, and reduced output voltage/inductor current ripples when compared to the traditional DC-DC converters, is an attractive DC-DC converter for the field of negative DC voltage applications. In this study, in consideration of the voltage across the energy transferring capacitor changing abruptly at the beginning of each switching cycle, the improved averaged model of the NOESLLC operating in continuous conduction mode (CCM) is established. The improved DC model and transfer functions of the system are derived and analyzed. The current mode control is applied for this NOESLLC. The results from the theoretical calculations, the PSIM simulations and the circuit experiments show that the improved DC model and transfer functions here are more effective than the existed ones of the NOESLLC to describe its real dynamical behaviors.

하악 이공부에 조사된 Nd:YAG 레이저가 감각신경전도변화에 미치는 영향 (Effect of Nd:YAG Laser Irradiation to Mental Region for Sensory Nerve Conduction Change)

  • 전재우;김경희;고명연;안용우;박준상
    • Journal of Oral Medicine and Pain
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    • 제30권4호
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    • pp.447-455
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    • 2005
  • 이 연구의 목적은 하악 이공부에 Nd:YAG 레이저 조사시 통증의 전달과 관련하여 감각신경전도 변화에 영향을 미치는지 조사하는 것이다. 각각 10 Hz와 20 Hz에 100 mJ/pulse의 조건으로 Nd:YAG 레이저를 하악 이공부에 비접촉식으로 5분간 조사하였다. 조사부위는 하악 이공부의 30 mm 지름을 가지는 원으로 설정하였고 조사부와 레이저 팁사이의 거리는 10 mm로 유지하여 원을 그리듯 움직이며 조사하였다. 이때의 출력밀도는 각각 $212\;mW/cm^2$$424\;mW/cm^2$이었다. Nd:YAG 레이저 조사 전과 후의 감각신경전도는 $Neurometer^{(R)}$ CPT/C를 이용하여 평가하였다. 그 결과 레이저 조사 전과 후 이공부에서의 전류인지역치(CPT)와 통증내성역치(PTT)를 얻었으며 통계처리를 거쳐 다음의 결과를 얻었다. 1. 2 W, 20 Hz 조건과 1 W, 10 Hz 조건으로 Nd:YAG 레이저를 조사한 경우 레이저 조사 전과 조사 후의 유의한 전류인지역치의 차이는 없었다. 2. 2 W, 20 Hz 조건과 1 W, 10 Hz 조건으로 Nd:YAG 레이저를 조사한 경우 레이저 조사 전과 조사 후의 유의한 통증내성역치의 차이는 없었다. 3. 1 W, 10 Hz 조건과 2 W, 20 Hz 조건으로 Nd:YAG 레이저를 조사하였을 때 두 군 사이 전류인지역치와 통증내성역치의 유의한 차이는 없었다. 따라서 우리는 하악 이공부에 Nd:YAG 레이저 조사가 이신경의 감각신경전도에 유의한 변화를 보이지 않음을 확인하였다.

Thermo-mechanical damage of tungsten surfaces exposed to rapid transient plasma heat loads

  • Crosby, Tamer;Ghoniem, Nasr M.
    • Interaction and multiscale mechanics
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    • 제4권3호
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    • pp.207-217
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    • 2011
  • International efforts have focused recently on the development of tungsten surfaces that can intercept energetic ionized and neutral atoms, and heat fluxes in the divertor region of magnetic fusion confinement devices. The combination of transient heating and local swelling due to implanted helium and hydrogen atoms has been experimentally shown to lead to severe surface and sub-surface damage. We present here a computational model to determine the relationship between the thermo-mechanical loading conditions, and the onset of damage and failure of tungsten surfaces. The model is based on thermo-elasticity, coupled with a grain boundary damage mode that includes contact cohesive elements for grain boundary sliding and fracture. This mechanics model is also coupled with a transient heat conduction model for temperature distributions following rapid thermal pulses. Results of the computational model are compared to experiments on tungsten bombarded with energetic helium and deuterium particle fluxes.

d-q 동기좌표 변환 개념을 이용한 BLDC 전동기의 센서리스 (Sensorless Control of BLDC Motor using d-q Synchronously Rotating Reference Frame Concept)

  • 문종주;허홍준;김장목
    • 전력전자학회논문지
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    • 제20권3호
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    • pp.232-238
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    • 2015
  • A sensorless control algorithm of brushless DC (BLDC) motors with a model current based on 120 degree conduction mode is proposed in this paper. The rotor speed and position can be estimated using the current model of BLDC motor, which is a modified version of the conventional current model of permanent magnet synchronous motor. The rotor speed and position can be obtained using the difference of the actual current and the model current. The position error caused by the parameter errors of the model current is compensated using a PI controller and the feedback loop of the real current. The validity of the proposed sensorless control algorithm is verified through simulation.

Full-Range Analytic Drain Current Model for Depletion-Mode Long-Channel Surrounding-Gate Nanowire Field-Effect Transistor

  • Yu, Yun Seop
    • JSTS:Journal of Semiconductor Technology and Science
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    • 제13권4호
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    • pp.361-366
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    • 2013
  • A full-range analytic drain current model for depletion-mode long-channel surrounding-gate nanowire field-effect transistor (SGNWFET) is proposed. The model is derived from the solution of the 1-D cylindrical Poisson equation which includes dopant and mobile charges, by using the Pao-Sah gradual channel approximation and the full-depletion approximation. The proposed model captures the phenomenon of the bulk conduction mechanism in all regions of device operation (subthreshold, linear, and saturation regions). It has been shown that the continuous model is in complete agreement with the numerical simulations.

자동차 전자식 조향장치용 PMSM 구동 시스템의 신속한 동적해석을 위한 비선형 인버터 모델 개발 (Development of Nonlinear Inverter Model for Fast Dynamic Analysis of Electric Power Steering with PMSM Drive System)

  • 최진철;이우택;홍정표
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2007년도 제38회 하계학술대회
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    • pp.1132-1133
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    • 2007
  • A circuit-domain model of PWM inverter provides accurate simulation results in consideration of detail switching characteristics. Although, a huge amount of computation time is demanded for the simulation results of several ten seconds, which is the required time to analyze system behaviors or control performances of Electric Power Steering(EPS) on real drive condition. This paper describes the nonlinear inverter model for fast dynamic simulation of EPS without the PWM concept through analyzing the effect of nonlinear switching characteristics like dead time, forward voltage drop and conduction resistance. Some inverter models including proposed model are compared from two standpoints which are computation time and accuracy. The comparison results show the usefulness of the developed model in order to develop the control algorithm through the fast prediction of system behaviors.

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전자-포논 상호작용 모델을 이용한 실리콘 박막 소자의 포논 평균자유행로 스펙트럼 열전도 기여도 수치적 연구 (A Numerical Study on Phonon Spectral Contributions to Thermal Conduction in Silicon-on-Insulator Transistor Using Electron-Phonon Interaction Model)

  • 강형선;고영하;진재식
    • 대한기계학회논문집B
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    • 제41권6호
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    • pp.409-414
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    • 2017
  • 본 연구의 목적은 실제 실리콘 박막 트랜지스터 내 포논 전달 특성을 이해하는 것이다. 이를 위해 박막 소자 내 열해석 예측 정확성이 검증된 전자-포논 상호작용 모델을 이용하여 반도체 산업에서 중요한 Silicon-on-Insulator(SOI) 시스템에 대한 다양한 조건에서 전자-포논 산란에 의한 Joule 가열 메커니즘의 고려하여 포논 전달 해석을 수행했다. 소자 장치 전원(device power)과 실리콘 층 두께 변화에 따른 포논의 평균자유행로(mean free path) 스펙트럼에 대한 열적 특성을 조사하여, 실제 SOI 소자 내 포논 전달을 이해했다. 이 결과는 SOI 소자의 신뢰성 설계 및 고효율 열소산(heat dissipation) 설계전략에 필요한 포논 전달 특성 이해에 활용될 수 있다.

평판형 히트 파이프 내의 유체 유동 및 열전달 특성에 관한 연구 (Study on Fluid Flow and Heat Transfer Characteristics in a Flat Heat Pipe)

  • 도규형;김성진
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2007년도 춘계학술대회B
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    • pp.2113-2118
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    • 2007
  • In this study, a mathematical model for a thermal analysis of a flat heat pipe with a grooved wick structure is presented. The effects of the liquid-vapor interfacial shear stress, the contact angle, and the amount of liquid charge have been included in the proposed model. In particular, the axial variations of the wall temperature and the evaporation/condensation rates are considered by solving the one-dimensional conduction and the augmented Young-Laplace equations, respectively. In order to verify the model, the results obtained from the model are compared to existing experimental data.

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승화 건조모델에 대한 운전방법별 건조시간의 예측 (Prediction of the Drying Time under the Various Operational Conditions using a Sublimation Model)

  • 박노현;배신철
    • 대한기계학회논문집
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    • 제17권8호
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    • pp.2088-2098
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    • 1993
  • A mathematical model of freeze drying by sublimation was suggested and used to estimate the drying time. Under the various conditions, the drying time of pure water and carrot was numerically calculated for the suggested model. Optimal policies of freeze drying were investigated experimentally in a laboratory freeze dryer. It was found that the shortest drying times could be obtained when the chamber pressure and condenser temperature were kept at their lowest values and the best method of heat transfer for sublimation was the conduction involving radiation. The sublimation drying period was finished when the bottom temperature of material could be reached at near $0^{\circ}C$ from frozen temperature.