어항/어제$\cdot$오늘$\cdot$내일 - 거점항 개발 촉진

김시문 한국어촌어항협회 1987 어항어장 Vol.1 No.-

열시스템에 대한 새로운 엑서지 비용계산방법 ( A New Approach of Exergoeconomic Analysis of Thermal Systems )

김시문,곽호영,오시덕 대한기계학회 1995 대한기계학회 춘추학술대회 Vol.- No.-

물질전달을 고려한 기포의 이동 ( Bubble Behavior with Mass Transfer )

김시문,곽호영 대한기계학회 1995 대한기계학회 춘추학술대회 Vol.- No.-

순환유동층 반응기에서 벽면의 마모 특성 고찰

김시문,이종민,김재성,김종진,김의현 한국화학공학회 2002 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.40 No.2

순환유동층(0.25m-L×0.62m-W×10m-H) 반응기에서 조업조건에 따른 상승관 벽면에서의 마모특성을 고찰하였다. 상승관에서의 기체유속(1.9-3.8m/s), 전체 고체량(100-200㎏) 그리고 일-이차 공기비(0.8-1.0) 변화에 따른 상승관 높이 및 위치별 마모율을 고찰한 결과, 고체 체류량 및 고체 순환량, 그리고 입자의 유속 혹은 유동화 속도의 변화가 마모율에 영향을 미치는 것으로 나타났다. 순환유동층 희박상에서는 유동화 속도 증가 및 일-이차 공기비의 증가에 따른 고체 체류량의 증가로 인해 벽면에서의 마모율이 증가되었으며, 반면 농후상에서는 고체 체류량보다는 유동화 속도의 증가 혹은 이차 공기 주입에 따른 유동변화에 의해 마모율이 크게 영향을 받는 것으로 나타났다. 전이영역에 대한 마모율은 대부분의 조업조건에 대해 농후상과 희박상 영역의 중간 정도의 마모율을 갖는 것으로 나타났다. 한편, 순환유동층내의 유속 증가에 따른 고체 순환량 증가에 따라 상승관 천장부위에서의 마모율은 크게 증가하는 것으로 고찰되었다. 특히 가운데 부위가 가장 큰 마모율을 보였다. 또한 상승관 상부 벽면의 마모 경향은 입자의 하향흐름이 가장 많이 생성되는 사이클론 주입부 벽면에서 가장 큰 마모율을 보이는 것으로 나타났다. The wall erosion characteristics of a circulating fluidized bed reactor(0.25m-L×0.62m-W×10m-H) was observed with various operating conditions, such as fluidizing velocity, total solid inventory and primary to secondary air ratio. The erosion rate was affected by solid hold-up and solid circulation rate as well as fluidizing velocity which were varied due to operating conditions. The wall erosion in dilute phase of the CFB riser increased with increasing solid hold up resulted from increasing of the fluidizing velocity and the primary to secondary air ratio. The erosion of the wall in dense phase increased with increasing fluidizing velocity although the solid hold up decreased with fluidizing velocity. The extent of erosion in the transition phase was somewhere in between the dense and the dilute phases. The erosion of the roof of the CFB riser increased with increasing solid circulation rate resulted from increasing the fluidizing velocity, total solid inventory and primary to secondary air ratio. The middle part of the roof where the solid circulation rate was higher than that of the side part of the roof, showed the highest erosion rate. The erosion seemed to be serious at the area around the cyclone inlet duct due to the enlarged down flow of the solid particles at this area.

소나 플랫폼의 운동 파라미터에 따른 합성개구소나 영상 왜곡의 정량적 분석

김시문,변성훈,Kim, Sea-Moon,Byun, Sung-Hoon 한국음향학회 2021 韓國音響學會誌 Vol.40 No.4

Synthetic aperture sonars as well as side scan sonars or multibeam echo sounders have been commercialized and are widely used for seafloor imaging. In Korea related research such as the development of a towed synthetic aperture sonar system is underway. In order to obtain high-resolution synthetic aperture sonar images, it is necessary to accurately estimate the platform motion on which it is installed, and a precise underwater navigation system is required. In this paper we are going to provide reference data for determining the required navigation accuracy and precision of navigation sensors by quantitatively analyzing how much distortion of the sonar images occurs according to motion characteristics of the platform equipped with the synthetic aperture sonar. Five types of motions are considered and normalized root mean square error is defined for quantitative analysis. Simulation for error analysis with parameter variation of motion characteristics results in that yaw and sway motion causes the largest image distortion whereas the effect of pitch and heave motion is not significant.

독립, 비독립 음원이 동시에 존재할 경우 선형 마이크로폰 어레이를 이용한 소음원 탐지 방법

김시문,김양한 한국소음진동공학회 1996 소음 진동 Vol.6 No.6

To identify the locations and strengths of acoustic sources, one may use a microphone line array. Apparent advantage of the source identification method utilizing a line array is that it requires less measurement points than intensity method and holography. This method is based on the information of magnitude and phase difference between pressure signals at each microphone. Since those differences are dependent on the source model, we have to assume them such as plane, monopole, etc. In this paper the conventional source identification methods such as beamforming method and MUSIC method are briefly reviewed by modeling a source as plane and spherical wave, then a modified method is introduced. This can be applied to sound field which may by either coherent or incoherent. Typical simulations and experiment are performed to confirm this identification method.

네 가지 음향 홀로그래피의 특성 및 오차

김시문,김양한 대한기계학회 1995 대한기계학회논문집 Vol.19 No.4

Acoustic holography makes it possible to reconstruct the acoustic field based on the measurement of the pressure distribution on the hologram surface. Because of the merit that one can obtain an entire three-dimensional wave field from the data recorded on a two-dimensional surface, the holographic method has been widely studied. Being an experimental method, holography has an unavoidable error which is generate by sampling in space and frequency domain and finite aperture size. Its magnitude is dependent on the space and frequency domain and finite aperture size. Its magnitude is dependent on the shape of hologram surface, acoustic holography may be classified into four types of holography : rectangular type planeholography, circular type plane holography, cylindrical holography and spherical holography. In this paper, four types of holography are studied by modal summation method. Numerical simulation is performed using a monopole source with varying parameters to find out effects to the estimation error in each holography. Experiments of circular type plane holography and cylindrical holography explain strong relation between the shape of hologram surface and the acoustic field.

농촌순례 : 각국농촌의 새로운 경향 : 내가 본 대만의 농업

김시문 대한지방행정공제회 1965 地方行政 Vol.14 No.140

원통형 음향 홀로그래피를 이용하여 구성한 유도전동기의 방사 음장

김시문,김양한 한국소음진동공학회 1997 소음 진동 Vol.7 No.6

Induction motors are used in many areas to transform electrical energy to mechanical energy. In the design of an induction motor, not only energy efficiency but also noise becomes an important factor. To effectively address the noise problem, it will be convenient if one can see where and how noise is generated and propagated. In this study sound radiation by an induction motor is visualized using cylindrical acoustic holography. To minimize the bias error by window effect Minimum Error Window(MEW) is used. Its performance is verified by numerical simulations. Based on these theoretical understanding, sound pressure measurement with an induction motor are performed. Not only sound radiation are visualized but sound pressure level and sound power level are also estimated. Results show that the main source is located at nearly bottom part of the motor and the total sound pressure level is 49dB, which satisfies the guideline value suggested by the KS C 4202.

원통면 음향 홀로그래피를 이용한 음장예측의 오차 해석 및 적용 방법

김시문,권휴상,김양한 한국소음진동공학회 1995 소음 진동 Vol.5 No.1

The prediction of sound pressure using acoustic holography has been recognized as a useful tool for the visualization of sound field. Cylindrical acoustic holography amongst acoustic holographic methods planar, spherical, and cylindrical ones-has a wide range of application since its rather simple construction and easy implementation for the sources. To utilize the propery of cylindrical holographic method, estimation errors associated with holographic parameters such as aperture size and sampling space must be envisaged. In this these errors have been studied by numerical simulation and the relation between the errors and the spectrum in wavenumber domain is described. The results are also confirmed by simple experiments.