• Title/Summary/Keyword: 경사각

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Distribution of X-ray Strength in Exposure Field Caused by Heel Effect (양극의 경사각 효과에 따른 조사야 X-선 강도 분포)

  • Jang, Keun-Jo;Kim, Nam-Hun;Lee, Jun-Haeng;Lee, Sang-Bock
    • Journal of the Korean Society of Radiology
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    • v.5 no.5
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    • pp.223-229
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    • 2011
  • When negative electron in x-ray tube is accelerated in to a high speed and then the currency of the electron is blocked by the target, x-ray happens by the conversion of the energy. The real area where the fast accelerated electron collides to a target area is called actual focal spot. When the string focused size is observed at the central ray side, where the direction x-ray comes out, the size seems to be reduced. This focus is called effective focal spot. According to radiation angle of x-rays tube, the degree of the negative pole side presents higher value than inclination, the amount of exposed radiation that patient receives differs by the angle of positive pole, which means effective focal spot is the variable. This paper presents the correlation between size of effective focal spot and amount of exposed radiation to the patient by it, and effective research for homogenized dose dispersion by the size of effective focal spot. In conclusion, following the focal size, effective range which was -8cm ~ 0 cm on average, was found and average dose rate was 0.019 R/min. Through this range, for patients with small radiation exposure, image with good density and resolution in aspect of diagnosing will be able to be obtained.

Stress Analysis in Multiple Isotropic Elliptical Fibers of Arbitrary Orientation (다수의 임의로 경사진 등방성 타원형 장섬유를 포함하는 복합재료에서의 응력 해석)

  • Lee, Jung-Ki;Oh, Sang-Min
    • Composites Research
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    • v.26 no.4
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    • pp.235-244
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    • 2013
  • A volume integral equation method (VIEM) is introduced for the solution of elastostatic problems in an unbounded isotropic elastic solid containing multiple isotropic elliptical fibers of arbitrary orientation subject to uniform stress at infinity. The fibers are assumed to be long parallel elliptical cylinders composed of isotropic elastic material perfectly bonded to the isotropic matrix. The solid is assumed to be under plane strain on the plane normal to the cylinders. A detailed analysis of the stress field at the matrix-fiber interface for square and hexagonal packing of the fibers is carried out for different values of the number, orientation angles and concentration of the elliptical fibers. The accuracy and efficiency of the method are examined through comparison with results obtained from analytical and finite element methods.

Structural Analysis and Failure Prediction of Tape-Wrapped Structures (테이프래핑 구조물의 구조 해석 및 파단 예측)

  • Goo, Nam-Seo;Park, Hoon-Cheol;Yoon, Kwang-Joon;Lee, Yeol-Hwa
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.32 no.3
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    • pp.17-21
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    • 2004
  • Tape-wrapped structures have been generally used in nozzle parts of guided missiles. A continuous band of woven composite material is wrapped around a mandrel that is designed to produce real products. After going through a vacuum bagging process, this woven composite material is cured in a high-pressure autoclave or hydroclave. However, tape-wrapped structures are difficult to analyze because of its large thickness and inclined lay-up. The present study investigates the method of analysis and failure prediction of tape-wrapped structures. The four-point bending test and its finite element analysis were performed to study how to model tape-wrapped structures and investigate their failure characteristics.

A Study on the Oil/Water Separation Efficiency of Laminated Plate Type Oily water Separator with Inclined Angle (경사각을 갖는 적층판식 유수분리기의 유수분리 효율에 관한 연구)

  • 한원희;김준효;최민선
    • Journal of Advanced Marine Engineering and Technology
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    • v.25 no.2
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    • pp.365-374
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    • 2001
  • Its a tendency to strengthen related international was as the importance on marine oil pollution recently becomes the issue. According to the regulation of IMO, oil discharge from ships is allowed under 15PPM only and oil filtering equipment is essential. Oily water separator of laminated plate type which is one of gravity type separator can be use as assistant equipment for the oil filtering system to meet the present IMO standard, because it fits well to process large amount of rich oil with high specific gravity. The purpose of this paper is to investigate an efficiency of oil/water separation with the characteristics of laminated plate arrangement. The analyse of oil contents for oil-water mixture were carried out in order to find an efficiency of oil/water separation and an experimental study was simultaneously carried out to investigate internal flow characteristics of separator by visualization method and PIV(Particle Image Velocimetry) measurement at three spaces of plates for 5, 10 and 15 mm with variation of inlet flow rates of $0.25m^3$/h and $0.5m^3$/h. The experimental results showed that the space of the plates acts a significant role in the separating process.

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shear Tests on female-to-female Type Joint between Precast Concrete Bridge Decks (프리캐스트 콘크리트 교량바닥판 female-female이음부의 전단실험)

  • 김영진;김영진;김종희
    • Magazine of the Korea Concrete Institute
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    • v.10 no.6
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    • pp.161-168
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    • 1998
  • Increase of traffic volume in recent years results in deterioration of the bridge slab, which is directly subjected ot vehicle loads. Where extensive repair is necessary, replacement or enhancement of load carrying capacity using full depth precast concrete deck is often the most practical solution. Precast deck system has transverse joints between adjacent precast decks. Vertical shear forces occur when a vehicle wheel load is carried by precast decks and the joints are used to transfer the load to an adjacent deck. Effective load transfer between precast decks is critical for integral behavior. Finite element analysis and tests were run on the proposed femal-to-female type joint. 18 joint specimens were tested to investigate the effects of angle. D/H, and confining stress under static load. Results indicate joint with angle of 60$^{\circ}$ and D/H of 1/4 shows the improved load carrying capacity on crack. It is effective in protecting the cracking of joints to keep the joint in compression using confining stress.

Fabrication of 3-dimensional magnetic sensor by anisotropic etching in TMAH (TMAH에 의한 이방성 식각을 이용한 3차원 자기센서의 제작)

  • Jung, Woo-Chul;Nam, Tae-Chul
    • Journal of Sensor Science and Technology
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    • v.8 no.4
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    • pp.308-313
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    • 1999
  • This paper will present an anisotropic etching in TMAH technique used in the fabrication of three-dimensional magnetic field vector sensor based on angled Hall plate structure. This sensor design relies on simultaneously detecting all magnetic field vector components using Hall plates that are imbedded into the silicon [111] sloped-surface of bulk micromachined cavity by the anisotropic etching of [100] silicon. The fabricated Hall elements has relatively improved sensitivity compare to convensional Hall elements for three-dimensional magnetic field sensing. The product sensitivity of 547V/AT at the supply current of 1.0mA was achived. The corresponding limit in the detection of magnrtic field is 0.07G that calculated by measured power spectral density(PSD) in magnetic sensor output.

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The Returning Force Analysis of Working Fluid and the Heat Transfer Characteristics in Revolving Heat Pipe Heat Exchanger (회전형 히트파이프 열교환기의 작동유체 귀환력 해석 및 열전달특성에 관한 연구)

  • 이기우;박기호;전원표
    • Journal of Energy Engineering
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    • v.10 no.3
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    • pp.214-222
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    • 2001
  • The purpose of this research it to develop gas-air rotary heat exchanger using heat pipe and the performances were examined by way of the theoretical analysis and the experiment. Centrifugal force to return the working fluid in heat pipe elements with different radius was evaluated as a function of the revolution speed and inclination angle, and a rotary heat exchanger with 60 heat pipes in 3 rows was designed and manufactured. The inclination angle of a heat pipe relative to the revolving axis was designed to be 2$^{\circ}$and water was used as a working fluid. Experimental result showed the heat exchange rate was enhanced by 16% with compared to the calculated value.

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Studils on Micro Fibril Angle of Woody Plant Cell Wall(1) - Variation of Micro Fibril Angle on Tree Stem - (목재세포벽(木材細胞壁)의 MICRO FIBRIL 경사각(傾斜角)에 관(關)한 연구(硏究)(1) - 수간내(樹幹內) MICRO FIBRIL 경사각(傾斜角)의 변이(變異) -)

  • Chun, Su-Kyung;Lee, Won-Yong
    • Journal of the Korean Wood Science and Technology
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    • v.11 no.1
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    • pp.5-11
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    • 1983
  • This paper aims at gaining the informations atout the fibril angle at secondary walls of tracheids. The test specimens were taken from disks on stem wood of "Pinus koraiensis Sieb. et zucc". The method of measuring the fibirl angle was selected so-called "iodine method" that crystalline aggregates of iodine may be induced to form within the elongated interstices of the cellulose matrix of the secondary wall and that these elongated crystals are oriented parallel to the long axies of the fibrills of cellulose. The following conclusions may be drawn from the results of this investigation. 1) Gross average fibril angle was about $17.6^{\circ}$ on stem wood. 2) Its values seem to be greater for earlywood (avg.$19.8^{\circ}$) than for latewood tracheids (avg.$15.3^{\circ}$) in normal wood. 3) According to the increase of annual ring from pith to barks the orientation of fibril angle seems to be decrease gradually in normal wood. 4) In the case of height variation in trees the sample trees have a tendency to increase the orientation fibril angle to the increase of tree height in stem.

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다목적실용위성 3호 초기 궤도조정 결과 분석

  • Jeong, Ok-Cheol;Kim, Dong-Gyu;Jeong, Dae-Won;Kim, Hak-Jeong
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.2
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    • pp.163.2-163.2
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    • 2012
  • 다목적실용위성 3호는 2012년 5월 발사되어, 위성 기능점검을 위한 시험을 성공적으로 완료하였다. 위성이 발사체로부터 분리된 이후 임무궤도(고도 685km, 승교점 지방시 13시 30분을 갖는 태양동기궤도)를 획득하기 위해서는 궤도조정이 필요하다. 본 논문에서는 다목적실용위성 3호의 초기운영 기간 동안 수행한 총 10번의 궤도조정 계획 및 결과에 대해 기술하였다. 궤도조정 1 단계에서는 궤도조정 절차 및 기능을 점검하기 위해 6번의 시험 궤도조정을 순차적으로 수행하였고 이후 2 단계에서는 임무궤도 진입을 위해 4번의 궤도조정을 실시하였다. 궤도조정을 위해서는 원하는 추력분사 방향을 맞추기 위해 롤 방향 또는 피치 방향의 자세제어가 필요한데, 추력기를 사용하여 자세를 기동하는 모드(Del-V Mode)와 휠을 사용하여 자세를 기동하는 모드(Fine Del-V Mode)로 구분된다. 시험 궤도조정에서는 우선적으로 두 가지 모드에 대한 모드전환 시험을 실시하여 위성체 및 지상국 운영절차에 대한 이상 유무를 점검하였고, 이후 추력기 분사량을 10초로 설정하여 예측 대비 실제 궤도변경 결과값을 확인하였다. 시험 궤도조정의 결과를 토대로 본 궤도조정에서는 임무궤도를 획득하기 위한 경사각 조정 및 고도 조정을 수행하였다. 경사각 조정 시에는 승교점 지방시의 변화량을 줄이고, 이후 자연 교란력에 의한 궤도변화를 고려하여 목표궤도를 계획하였다. 또한, 고도 조정 단계에서는 연료 사용량 및 이심률 변화를 최소화 할 수 있도록 전형적인 호만 궤도천이 방식을 적용하였다. 궤도조정 결과 당초 목표한 값을 정확하게 달성하였고, 궤도조정 이후 궤도변화도 장기간 동안 임무궤도 범위를 유지함을 확인할 수 있었다.

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