• 제목/요약/키워드: Rational Function Model

검색결과 132건 처리시간 0.025초

상관도 분석을 통한 RFM의 위치 정확도 분석 및 수치표고모형의 제작 (Positional Precision Improvement of RFM by the correlation analysis and Production of DEMs)

  • 손홍규;손덕재;박정환;유형욱;피문희
    • 한국지형공간정보학회:학술대회논문집
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    • 한국지형공간정보학회 2002년도 춘계학술대회 논문집
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    • pp.27-33
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    • 2002
  • 최근 들어 다항식비례모형(RFM: Rational Function Model)은 비전문가에게 있어서 지형보정을 위한 정확도 문제를 해결함과 동시에 센서 종류에 상관없이 적용 가능한 범용적인 센서모델링 기법으로 각광을 받고 있다. 그러나 엄밀(physical) 모델이 없는 센서 혹은 위성의 궤도력 자료를 제공하지 않는 센서의 경우 다항식비례모형의 적용을 위해서는 다수의 매개변수 사용으로 인한 계수들 간의 상관성을 고려해야 한다. 이에 본 연구에서는 2차 다항식비례모형에 기초하여 전방 다항식비례모형(Forward RFM)과 상관도 분석을 통한 전방 다항식비례모형의 이른 및 위치정확도에 관한 연구를 수행하였다. 대상연구지역은 KOMPSAT(Korea Multi-Purpose Satellite)과 SPOT으로 촬영한 대전광역시와 그 주변지역으로 SPOT과 KOMPSAT 모두 상관성 분석 전에는 대략 50% 정도의 검사점에 대해 과대오차(>100m)가 얻어졌으며, 이 점들을 제외한 검사점에 대해서도 SPOT은 평균수평오차 20-24m, 평균표고오차 25m, KOMPSAT은 평균수평오차 15-24m, 평균표고오차 30m를 나타내었다. 전방 다항식비례모형에 대하여 상관성 분석을 수행한 후에는 검사점에 대한 모든 과대오차 조정결과가 소거되었고 검사점에 대해서 SPOT은 평균수평오차 8.8m, 평균표고오차 25.2m, KOMPSAT은 평균수평오차 8.4m, 평균표고오차 14.5m를 나타내었다. 최종적으로 연구지역에 대한 수치표고모형의 제작을 통해 상관도 분석을 통한 다항식비례모형의 실제 적용 가능성을 보여주었다.

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A topology optimization method of multiple load cases and constraints based on element independent nodal density

  • Yi, Jijun;Rong, Jianhua;Zeng, Tao;Huang, X.
    • Structural Engineering and Mechanics
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    • 제45권6호
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    • pp.759-777
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    • 2013
  • In this paper, a topology optimization method based on the element independent nodal density (EIND) is developed for continuum solids with multiple load cases and multiple constraints. The optimization problem is formulated ad minimizing the volume subject to displacement constraints. Nodal densities of the finite element mesh are used a the design variable. The nodal densities are interpolated into any point in the design domain by the Shepard interpolation scheme and the Heaviside function. Without using additional constraints (such ad the filtering technique), mesh-independent, checkerboard-free, distinct optimal topology can be obtained. Adopting the rational approximation for material properties (RAMP), the topology optimization procedure is implemented using a solid isotropic material with penalization (SIMP) method and a dual programming optimization algorithm. The computational efficiency is greatly improved by multithread parallel computing with OpenMP to run parallel programs for the shared-memory model of parallel computation. Finally, several examples are presented to demonstrate the effectiveness of the developed techniques.

철도 전자연동장치의 고신뢰화를 위한 실시간 전문가 시스템 (A Real-Time Expert System for the High Reliability of Railway Electronic Interlocking System)

  • 고윤석;최인선;권용훈
    • 대한전기학회논문지:전력기술부문A
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    • 제48권11호
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    • pp.1457-1463
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    • 1999
  • This paper develops an real-time expert system for the electronic interlocking system. it obtains the higher safety by determining the railway interlocking strategy in order to prevent trains from colliding, and derailing in the viewpoint of veteran expert, considering the situation of station in real-time. The expert system determines the real-time interlocking strategy by confirming the interlocking relationships among signal facilities based on the interlocking knowledge base from input information such as signal, points, and it is implemented as the rule-based system in order to represented accurately and effectively the interlocking relationships. Especially in case of emergency the function which determines the rational route coordinating with IIKBAG on the workstation is designed in order to minimize the spreading effect. It is implemented in C computer language for the purpose of the implementation of the inference engine using the dynamic memory allocation technique, the build and interface of the station structure database. And, the validity of the built expert system is proved by simulating the diversity cases which may occur in the real system for the typical station model.

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Dynamic properties of a building with viscous dampers in non-proportional arrangement

  • Suarez, Luis E.;Gaviria, Carlos A.
    • Structural Engineering and Mechanics
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    • 제55권6호
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    • pp.1241-1260
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    • 2015
  • Any rational approach to define the configuration and size of viscous fluid dampers in a structure should be based on the dynamic properties of the system with the dampers. In this paper we propose an alternative representation of the complex eigenvalues of multi degree of freedom systems with dampers to calculate new equivalent natural frequencies. Analytical expressions for the dynamic properties of a two-story building model with a linear viscous damper in the first floor (i.e. with a non-proportional damping matrix) are derived. The formulas permit to obtain the equivalent damping ratios and equivalent natural frequencies for all the modes as a function of the mass, stiffness and damping coefficient for underdamped and overdamped systems. It is shown that the commonly used formula to define the equivalent natural frequency is not applicable for this type of system and for others where the damping matrix is not proportional to the mass matrix, stiffness matrix or both. Moreover, the new expressions for the equivalent natural frequencies expose a novel phenomenon; the use of viscous fluid dampers can modify the vibration frequencies of the structure. The significance of the new equivalent natural frequencies is expounded by means of a simulated free vibration test. The proposed approach may offer a new perspective to study the effect of viscous dampers on the dynamic properties of a structure.

Guyed Tower의 신뢰성 해석 (A Reliability Analysis of a Guyed Tower)

  • 하태범;최항순
    • 대한조선학회지
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    • 제24권2호
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    • pp.29-35
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    • 1987
  • As offshore activities move into deeper ocean, conventional fixed-base platforms drastically increase in size and cost, One of alternatives available is a guyed tower, in which environmental loads are supported by guylines instead of structural members. The guying system of the guyed tower is designed on one hand to be stiff enough to limit the structural displacement in normal operations, but on the other hand to be soft enough to permit large slow sways during the presence of design-level storms. This compliancy provides an efficient means of withstanding harsh environment so that the disproportionate increase in size of deep water platforms can be kept to a rational limit. Novel configurations contain always some degrees of potential risks mainly due to the lack of experience. The most critical hazard inherent to a guyed tower may be the pullout of anchor piles. Once it happens, the guyline fails to function and it may eventually lead to the total collapse of the system. It is the aim of this paper to discuss and quantify the anchor-pullout risk of a guyed tower. A stochastic analysis is made for evaluating the first-upcrossing probability of the tension acting on anchor piles over the uplift capacity. Nonlinearities involved in the mooring stiffness and hydrodynamics are taken into account by using time-domain analysis. A simplified two dimensional dynamic model is developed to exemplify the underlying concept. Real hurricane data in the Gulf of Mexico spanning over 70 years are incorporated in a numerical example of which result clearly indicates highly potential risk of anchor pullout.

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디지털 게임의 부분유료화 모델에 관한 연구 (A Study on the Free-to-Play Model for Digital Games)

  • 이동은;이유호
    • 한국게임학회 논문지
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    • 제15권6호
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    • pp.107-120
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    • 2015
  • 디지털 게임의 부분유료화 모델은 플레이어로 하여금 신규 게임 유입의 장벽을 낮추고 동시에 소액 결제를 통해 소비를 유도하여 안정적인 수익을 촉발한다는 점에서 게임 업계의 대표적인 수익모델로 평가받고 있다. 하지만 부분유료화를 통해 제공되는 서비스들의 종류와 적용 대상, 적용 양상이 다양해지면서 있는 플레이어들의 게임 플레이 경험에 불균형을 양산하는 문제를 만들고 있다. 이에 본 논문은 부분유료화의 개념과 특징을 정리하고, 획득방법, 지속성, 기능 발현 대상에 따라 2가지 유형, 7가지 세분류를 진행하였다. 이 과정을 통해 부분유료화 모델이 가지는 세 가지 문제점을 도출할 수 있었는데 첫째, 게임 플레이 경험의 불평등 유발, 둘째, 게임 세계 경제의 불균형 양산, 셋째 게임 플레이 지속성 파괴가 바로 그것이다. 본 논문에서는 이 세 가지 문제점을 구체적인 사례를 중심으로 설명하고 그 해결책을 제언하는 것을 목적으로 한다. 이러한 연구는 앞으로의 부분유료화 모델이 한국 게임 시장에 어떤 방식으로 적용되어야 하는지에 대한 지표를 제공한다는 점에서 의의를 찾을 수 있다.

Analysis of Ship Groundings on Soft Sea Beds

  • Simonsen, B. Cerup;Redersen, P. Terndrup
    • Journal of Ship and Ocean Technology
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    • 제1권1호
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    • pp.35-47
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    • 1997
  • The consequences associated with ships running aground depend very much on the soil characteristics of the sea bed and the geometrical shape of the ship bow. The penetration into the sea bed depends on these factors and the penetration is an important factor for the ship motion because it influences the ship heave and pitch motions as well as the friction between the ship and the soil. In this paper a rational calculation model is presented for the sea bed soil reaction forces on the ship bottom. The model is based on the assumption that the penetration of the ship bow generates a flow of pore water through the grain skeleton of the soil. The flow is governed by Darcy\`s law and it is driven by the pressure of the pore water at the bow. In addition to this pore water pressure, the bow is subjected to the effective stresses in the grain skeleton at the bow surface. These stresses are determined by the theory of frictional soils in rupture. Frictional stresses on the bow surface are assumed to be related to the normal pressure by a simple Coulomb relation. The total soil reaction as a function of velocity and penetration is found by integration of normal pressure and frictional stresses over the surface of the bow. The analysis procedure is implemented in a computer program for time domain rigid body analysis of ships running aground and it is verified in the paper through a comparison of calculated stopping lengths, effective coefficients of friction, and sea bed penetrations with corresponding experimental results obtained by model tests as well as large, scale tests.

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Harris-Todaro 모형에 의한 국가간 잠재적 노동인구 이동에 관한 실증분석: 한-중-일 3국을 중심으로 (Empirical Analysis on Potential Labor Migration between Countries Implemented by Harris-Todaro Model: Result from Korea, China, and Japan)

  • 이현재
    • 한국콘텐츠학회논문지
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    • 제15권6호
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    • pp.421-431
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    • 2015
  • 본 연구는 합리적기대에 의한 기대소득 격차를 반영한 Harris-Todaro 모형에 의해 한-중-일 3국간 잠재적 노동인구 이동을 분석하였다. 실증분석 결과에 의하면 한국의 노동시장은 노동인구 유입의 영향력이 약하고, 중국과 일본으로 양방향성의 노동인구 유출이 있는 것으로 나타났다. 중국의 노동시장은 노동인구의 유출입에 미치는 영향력은 약하지만, 한국뿐만 아니라 일본과의 관계에 있어서 노동인구가 유출에서 유입으로 전환되었다. 일본의 노동시장은 일관성 있게 노동인구를 유입시키는 영향력이 있으며, 한국과는 노동인구의 유입, 중국과는 노동인구 유출로 나타났다. 결과적으로 한-중-일 3국간 노동시장은 상호 보완적이기 보다는 대체성이 강한 형태를 유지하고 있다.

유통업체의 부실예측모형 개선에 관한 연구 (Performance Evaluation and Forecasting Model for Retail Institutions)

  • 김정욱
    • 유통과학연구
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    • 제12권11호
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    • pp.77-83
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    • 2014
  • Purpose - The National Agricultural Cooperative Federation of Korea and National Fisheries Cooperative Federation of Korea have prosecuted both financial and retail businesses. As cooperatives are public institutions and receive government support, their sound management is required by the Financial Supervisory Service in Korea. This is mainly managed by CAEL, which is changed by CAMEL. However, NFFC's business section, managing the finance and retail businesses, is unified and evaluated; the CAEL model has an insufficient classification to evaluate the retail industry. First, there is discrimination power as regards CAEL. Although the retail business sector union can receive a higher rating on a CAEL model, defaults have often been reported. Therefore, a default prediction model is needed to support a CAEL model. As we have the default prediction model using a subdivision of indexes and statistical methods, it can be useful to have a prevention function through the estimation of the retail sector's default probability. Second, separating the difference between the finance and retail business sectors is necessary. Their businesses have different characteristics. Based on various management indexes that have been systematically managed by the National Fisheries Cooperative Federation of Korea, our model predicts retail default, and is better than the CAEL model in its failure prediction because it has various discriminative financial ratios reflecting the retail industry situation. Research design, data, and methodology - The model to predict retail default was presented using logistic analysis. To develop the predictive model, we use the retail financial statements of the NFCF. We consider 93 unions each year from 2006 to 2012 to select confident management indexes. We also adapted the statistical power analysis that is a t-test, logit analysis, AR (accuracy ratio), and AUROC (Area Under Receiver Operating Characteristic) analysis. Finally, through the multivariate logistic model, we show that it is excellent in its discrimination power and higher in its hit ratio for default prediction. We also evaluate its usefulness. Results - The statistical power analysis using the AR (AUROC) method on the short term model shows that the logistic model has excellent discrimination power, with 84.6%. Further, it is higher in its hit ratio for failure (prediction) of total model, at 94%, indicating that it is temporally stable and useful for evaluating the management status of retail institutions. Conclusions - This model is useful for evaluating the management status of retail union institutions. First, subdividing CAEL evaluation is required. The existing CAEL evaluation is underdeveloped, and discrimination power falls. Second, efforts to develop a varied and rational management index are continuously required. An index reflecting retail industry characteristics needs to be developed. However, extending this study will need the following. First, it will require a complementary default model reflecting size differences. Second, in the case of small and medium retail, it will need non-financial information. Therefore, it will be a hybrid default model reflecting financial and non-financial information.

등가강도 개념에 의한 탄소섬유 복합재료의 이축강도 및 피로수명 예측 (Prediction of Biaxial Strength and Fatigue Life using the Concept of Equivalent Strength)

  • 이창수;황운봉
    • Composites Research
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    • 제12권2호
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    • pp.53-61
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    • 1999
  • 복합재료의 파단식은 강도계수의 산정이 쉽고, 형상이 유연하며, 논리적인 단순성을 유지하기 위하여 각 파단모드와 하중조건을 고려하는 것이 바람직하다. 본 연구에서는 인장 및 비틀림의 이축하중에 대한 등가강도를 도입함으로써 새로운 파단식을 유도하였다. 이축 실험 결과는 등가이축강도가 cos($tan^{-1}R_b$)의 지수함수로 표현됨을 보였다. 이축하중의 파단강도는 일방향 인장강도 및 비틀림강도와 이축비의 함수로 예측할 수 있다. 실험 데이터의 산포성은 Weibull 분포함수와 등가이축강도 개념을 이용하여 분석하였다. 또한, 일방향 인장 및 비틀림 S-N 선도로부터 복합하중하의 S-N 선도를 구할 수 있는 피로해석법을 평면 응력 모델을 기반으로 개발하였다. 예측결과는 적층복합재료의 이축강도와 피로수명의 실험 데이터와 잘 일치하였다.

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