• 제목/요약/키워드: Pure-integration

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천연가스 액화공정의 최적설계 (Optimal Design of Natural Gas Liquefaction Processes)

  • 조현준;여영구;김진국
    • Korean Chemical Engineering Research
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    • 제51권1호
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    • pp.25-34
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    • 2013
  • 본 총설에서는 천연가스 액화공정의 최적설계에서 에너지 효율을 높이기 위해 고려해야 하는 주요 공정설계 인자들에 대한 논의와 상용 LNG 플랜트에서 이러한 인자들이 어떻게 적용되고 있는지에 대하여 살펴보았다. 압축기에서 소모되는 축일의 양을 최소화하기 위한 방법으로서 단일 냉매를 사용하는 냉각 사이클을 다단, 혹은 중첩 구조로 설계하여 온도 범위가 넓은 영역에서 운용하는 방법과 혼합냉매를 사용하여 단순한 사이클 구조를 유지하면서 최적 냉각공급 곡선을 유지하는 방법을 다루었고, 천연가스 액화조건에 맞추어 이러한 구조들의 최적 조합을 구성하는 원리를 소개하였다. 열 통합(heat integration) 기법을 활용하여 상용화 공정들의 특징을 도식적으로 고찰하였으며 아울러 에너지 효율 및 경제성에 대한 분석을 수행하였다. 또한 액화 공정 설계에서 사용되는 대용량의 압축기들을 구동하는 에너지 시스템에 대한 설계 문제를 살펴보았으며 최적설계를 위한 여러 가지 요소들을 고찰하여 보았다.

사업 포트폴리오의 기술시너지 효과 : 50대 재벌의 패널자료분석

  • 김태유;박경민
    • 기술혁신연구
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    • 제5권1호
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    • pp.15-43
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    • 1997
  • This paper investigates empirically the relationship between various business portfolio properties (particularly technological properties) and chaebol's performance using data on the 50largest chaebols in Korea. In addition to the traditional indexes to measure diversification such as entropy index, we calculated inter-industry technological similarity using R'||'&'||'D expenditure data by industry and 1990 Input-output Table in korea, and obtained chaebol-level technological relatedness and internal transaction proportion from chaebols' business profile, inter-inustry technological similarity and 1990 input-output table. We applied factor analysis on 13 business portfolio property indexes and showed that they could be grouped into 3 dimensions. diversification scope, inter-business relatedness and degree of vertical integration. In this paper, using 50 largest chaebols' financial data (1989-1994), we analyzed empirically the effect of business portfolio properties on ROS(Return On Sales) which is conventional index for firm performance and on TFP(Total Factor Productivity) growth which is a pure measure of firm performance. To utilize the advantage of panel data, FEM(Fixed Effect Model) and REM(Random Effect Model) were used. The empirical result shows that the entropy index as a measurement of inter-business relatedness in not significant but technological relatedness index is significant. OLS estimates on pooled data were considerably different from FEM or REM estimates on panel data. By introducing interaction effect among the three variables for business portfolio properties, we obtained three findings. First, only VI(Vertical integration) has a significant positive correlation with ROS. Second, when using TFP growth as an dependent variable, both TR(Technological Relatedness) and VI are significant and positively related to the dependent variable. Third, the interaction term between TR and VI is significant and negatively affects TFP growth, meaning that TR and VI are substitutes. These results suggest strategic directions on restructuring business portfolio. As VI is increased, chaebols will get more profit. A higher level of either TR or VI will increase TFP growth rate, but increase in both TR and VI will have a negative effect on TFP growth. To summarize, certain business portfolio properties such as VI and TR can be considered "resources" themselves since they can affect profit rate and productivity growth. VI and TR have a synergy effect of change in profit rate and productivity growth. VI increases ROS and productivity growth, while TR increases productivity growth representing a technological synergy effect.t.

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광화학-궤적 모델에 의한 여름철 맑은 날 서울지방의 지상 오존 농도 추정 (Estimate of Surface Ozone Concentration on Sunny Summer Days in Seoul Area by the Photochemical-Trajectory Model)

  • 이시우;이광목
    • 한국환경과학회지
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    • 제11권6호
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    • pp.497-506
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    • 2002
  • A Photochemical-Trajectory model was used to understand the production of ozone in the atmospheric boundary layer. This model was composed of the trajectory and the photochemical models. To calculate trajectories of air parcels, winds were obtained from the three-dimensional nonhydrostatic mesoscale model (PSU/NCAR MM5V2), and the results were interpolated into constant height surfaces. Numerical integration in the trajectory model was performed by the Runge-Kutta method. The photochemical model consisted of chemical reactions and photodissociation processes. Chemical equations were integrated by the semi-implicit Bulirsch-Stoer method. We performed our experiments from 21 July to 23 July 1994 during the summer time for Seoul area. During the time of maximum ozone concentration in Seoul, four trajectories of air parcels which traveled from Inchon to Seoul were selected. Ozone concentrations estimated by two models are compared with observed one in Seoul area and the photochemical-trajectory model is better fitted than pure photochemical model. During the selected period, high ozone concentrations in Seoul area were more influenced by transferred pollutants from Inchon than emitted pollutants in Seoul.

과학로켓 2호(KSR-II) 준비행 모델의 지상 진동 시험 (Ground Vibration Test for Korea Sounding Rocket - II PFM)

  • 우성현;김홍배;문상무;이상설;문남진
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2001년도 춘계학술대회논문집
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    • pp.546-551
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    • 2001
  • Space Test Department at KARI(Korea Aerospace Research Institute) plans to carry out the GVT(Ground Vibration Test) for the KSR(Korea Sounding Rocket)-III FM(Flight Model) which is being developed by Space Technology R&D Division. KSR-III will be an intermediate to the launch vehicle capable of carrying satellites to their orbits. GVT offers very important information to predict the behavior of KSR in its operation, and to develop the flight control and aerodynamic analysis. For development of test facilities, testing and analysis methods which can be used for the future test, Space Test Department has performed the GVT with KSR-II PFM(Proto-Flight Model) at Satellite Integration & Test Center of KARl This paper discusses the procedures, techniques and the results of it. In this test, to simulate free-free condition, test object hung in the air by 4 bungee cords specially devised. The GVT was carried out using pure random excitation technique with MIMO(Multi-Input-Multi-Output) method with three electromagnetic shakers, and poly-reference parameter estimation was used to identify the modal parameters. As the result of the test, 11 mode shapes and modal parameters below 200㎐ were identified and compared with analytical results.

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천측 항법 시스템의 수직 방향 결정 (Determination of Local Vortical in Celestial Navigation Systems)

  • 석병석;유준
    • 제어로봇시스템학회논문지
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    • 제13권1호
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    • pp.72-78
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    • 2007
  • Determination of the local vertical is not trivial for a moving vehicle and in general will require corrections for the Earth geophysical deflection. The vehicle's local vertical can be estimated by INS integration with initial alignment in SDINS(Strap Down INS) system. In general, the INS has drift error and it cause the performance degradation. In order to compensate the drift error, GPS/INS augmented system is widely used. And in the event that GPS is denied or unavailable, celestial navigation using star tracker can be a backup navigation system especially for the military purpose. In this celestial navigation system, the vehicle's position determination can be achieved using more than two star trackers, and the accuracy of position highly depends on accuracy of local vertical direction. Modern tilt sensors or accelerometers are sensitive to the direction of gravity to arc second(or better) precision. The local gravity provides the direction orthogonal to the geoid and, appropriately corrected, toward the center of the Earth. In this paper the relationship between direction of center of the Earth and actual gravity direction caused by geophysical deflection was analyzed by using precision orbit simulation program embedded the JGM-3 geoid model. And the result was verified and evaluated with mathematical gravity vector model derived from gravitational potential of the Earth. And also for application purpose, the performance variation of pure INS navigation system was analyzed by applying precise gravity model.

내압을 받는 복합 적층 파이프(GFRP) 구조의 유한요소 해석 (Finite Element Analysis of Glass Fiber Reinforced Plastic Pipes Under Internal Pressure)

  • 조병완
    • 전산구조공학
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    • 제7권2호
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    • pp.101-109
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    • 1994
  • 내압을 받는 섬유강화 복합적층 파이프 구조를 해석하기 우해 감절점 원통형 쉘 유한요소를 이용하였다. 이요소는 lockintg현상을 제거하고, 수렴성을 개선하기 위해 감차적분기법, 변위형의 추가, 가정된 전단 변형 도장을 사용한 9절점의 3차원 쉘 유한요소이다. 이 유한요소를 이용하여 여러개의 예제를 해석하고, 결과를 이론식 및 다른 구조해석 프로그램과 비교하였다. 비교결과 유한요소의 수렴도 양호하였고, 섬유강과 복합적층 파이프 구조의 섬유 배향 각도를 증가시킴에 따라 파이프의 처짐은 감소하면서 파이프의 강성이 증가함을 알 수 있고 이는 또한 90.deg.적층 각도가 내압을 받는 파이프 구조의 hoop tension을 유효하게 받을 수 있음을 보여주고 있다.

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경사안내면 상에서 이송되는 볼나사-슬라이드 이송계의 마찰기인 진동해석 (Analysis of Friction-Induced Vibrations in a Ball Screw Driven Slide on Skewed Guideway)

  • 최영휴
    • 한국기계가공학회지
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    • 제13권6호
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    • pp.88-98
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    • 2014
  • A moving mass on a skewed linear guideway model to analyze the friction-induced stick-slip behavior of ball-screw-driven slides is proposed. To describe the friction force, a friction coefficient function is modelled as a third-order polynomial of the relative velocity between the slide mass and a guideway. A nonlinear differential equation of motion is derived and an approximate solution is obtained using a perturbation method for the amplitudes and base frequencies of both pure-slip and stick-slip oscillations. The results are presented with time responses, phase plots, and amplitude plots, which are compared adequately with those obtained by Runge Kutta 4th-order numerical integration, as long as the difference between the static and kinematic friction coefficients is small. However, errors in the results by the approximate solution increase and are not negligible if the difference between the friction coefficients exceeds approximately 40% of the static friction coefficient.

Fast 웹 서비스를 위한 Fast Infoset 알고리즘 구현 (Implementation of Fast Infoset Algorithm for Fast Web Services)

  • 조태범;박연식;정회경
    • 한국정보통신학회논문지
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    • 제11권1호
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    • pp.131-138
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    • 2007
  • 기존의 웹 서비스(Web Services)는 운영환경에 독립적인 문서 형식을 정의할 수 있는 XML(Extensible Markup Language)을 기본 문서 형식으로 사용함으로서 서비스의 통합을 실현하였다. 그러나 텍스트 데이터로 이루어져 있는 XML 문서는 네트워크 환경이나 임베디드 시스템과 같이 상대적으로 느린 통신 매체에 자주 접속하거나 모바일과 같이 자원이 한정된 소형기기에서 사용 할 경우 전체 응용 프로그램의 성능을 저하시키는 요소로 작용한다. 이에 본 논문은 Fast Infoset 방식과 ASN.1의 PER 인코딩 기법을 사용하여 XML 문서를 Fast XML으로 변환 할 수 있는 Fast Infoset 알고리즘을 구현하였고, 테스트 베드(Test Bed)를 구축하였다. 또한, 웹 서비스 구축 시 전송 프로토콜로 사용되는 XML 기반의 SOAP 메시지를 인코딩하여 기존의 순수 XML 메시지 방식과의 처리 성능 차이를 비교 분석하였다.

브로일러계열화 생산조직에 관한 고찰 - 미국의 예를 중심으로 - (Integrated Broiler Production System - As a Means of Stabilizing Whole Industry with Particular Reference to U.S. Experience -)

  • 박영인
    • 한국가금학회지
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    • 제6권2호
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    • pp.91-102
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    • 1979
  • The basic problem of the broiler industry is that of fluctuating prices, mainly thanks to unstable supply of and inelastic demand for products as usually indicated as a peculiarity of agricultural commodities. This particularly brings the producer to a great economic risk, because he has to sell products under the condition of pure competition, whereas others from whom he has to buy deal under the condition of oligopoly or even monopoly. Therefore, producers economic position is generally placed in the worst comparing others dealing with, which results in unbalanced economic status of elements involved in broiler operation and further obstruction of industry development as a whole. A certain type of business coordination to overcome such a problem should be measured in order to improve the efficiency of entire operation and thus assure the balanced industry development. The concept of the economic integration developed in modern business system had been adapted to U.S. poultry industry which became common later around the world as a means of stabilizing producers price and whole industry as well. There are two main typos of integration; horizontal and vertical The former refers to the general grouping of similar business units, eg. a hatchery tying with other hatchery, while the latter refers to the knitting together of two or more stages of economic activities, eg. tying together among units of hatching, fled milling, production, processing and marketing. By having the industry integrated, risk and uncertainty involved in various stages of operation could be diversified. The typo of integrating contract between producers and integrators include the share of profits, flat fee payment, feed conversion payment and salary basis. In the U.S., extensive changes in production, processing, and marketing during the last few decades have changed the thicken broiler industry from one of small, widely scattered farms to one that is largo, concentrated and efficient. More than 99 percent of all broilers produced are grown under contract and by integrated firms which vary in size of operation and complexity. About 84 percent of all production is concentrated in 10 States. Some of the other factors ;hat contributed to these choses arc costs, energy use, prices, processing, marketing and demand. No integrated broiler production system has yet been applied in Korea's poultry industry, thus all stages all broiler operation run independently seeking for its own profit. Consequently, producers price fluctuate very widely around the year even more than 50 percent in a few months. This also leads to disadvantages of material supplies, processors and distributors and enforce the industry unstable. The current economic environment in Korea seems that the time for broiler integration comes and as an ideal integrator, feed millers, food processors and producers group may be considered.

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중학교 과학 교과서의 국제 비교 (International Comparison of Junior High School Science Textbooks)

  • 박윤배
    • 한국과학교육학회지
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    • 제18권1호
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    • pp.19-34
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    • 1998
  • 본 연구는 한국, 미국, 호주, 일본의 중학교 ($7{\sim}9$학년) 과학 교과서를 한 종류씩 선택하여, 포함하고 있는 지식, 과정기능, 활동, 상황, 과학의 본성, 그리고 사용된 통합주제의 양과 형태를 국가별, 학년별, 내용별로 각각 비교해 보는 것을 목적으로 하고 있다. 연구결과는 다음과 같다. 교과서의 분량은 미국의 경우가 가장 많아 한국의 두배 정도나 되었고, 한국을 제외한 세 나라의 교과서에는 색채인쇄가 많았고, 편집은 2단으로 되어 있었다. 내용별로는 한국과 일본의 교과서에서는 물리, 화학, 생물, 지학의 네 영역이 같은 분량을 차지하고 있었고, 미국의 교과서에는 생물과 지학이, 호주에서는 환경과 STS를 강조하고 있었다. 모든 나라의 교과서에서 '개념'올 가장 많이 사용하고 있었고, 학년이 올라갈수록 '법칙'을 점차 강조하고 있었다. 한국의 교과서는 다른 나라의 교과서에 비해 '법칙'을 많이 다루고 있었다. 한국의 교과서에서 가장 많은 과정기능이 사용되었다. 나라별로는 한국의 교과서에는 비례와 변인통제가, 일본의 교과서에는 상관/인과와 비례가, 미국과 호주의 교과서에는 변인통제와 자료변환이 많이 사용되었다. 미국과 한국의 교과서가 호주나 일본의 교과서보다 훨씬 많은 수의 활동들을 다루고 있었다. 한국, 일본, 호주의 교과서에서는 실험과 관찰 활동이 대부분을 차지하였고, 미국의 교과서에는 관찰, 실험, 조사, 실습, 측정 활동들이 고루 다루어지고 있었다. 한국과 일본, 호주의 교과서에서는 순수과학 상황이 가장 많이 사용되었고, 미국의 교과서에는자연환경 상황이 가장 많았으나, 미국과 호주의 교과서에서는 나머지 상황들이 골고루 사용되고 있었다. 과학의 본성을 상당한 정도로 다루고 있는 호주와 미국에 비해, 한국과 일본의 교과서에서는 이에 관한 부분이 극히 적거나 전혀 없었다. 과학과 기술 간의 통합소재가 가장 많이 사용되었으며, 과학내 소재는 가장 적게 사용되었다. 한국과 일본의 교과서에서는 다른 나라에 비해 적게 사용하고 있었다.

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