• Computers and Concrete
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• 제5권1호
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• pp.21-36
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• 2008

Steel fiber reinforced concrete is increasingly used day by day in various structural applications. An extensive experimentation was carried out with w/cm ratio ranging from 0.25 to 0.40, and fiber content ranging from zero to1.5 percent by volume with an aspect ratio of 80 and silica fume replacement at 5%, 10% and 15%. The influence of steel fiber content in terms of fiber reinforcing index on the compressive strength of high-performance fiber reinforced concrete (HPFRC) with strength ranging from 45 85 MPa is presented. Based on the test results, equations are proposed using statistical methods to predict 28-day strength of HPFRC effecting the fiber addition in terms of fiber reinforcing index. A strength model proposed by modifying the mix design procedure, can utilize the optimum water content and efficiency factor of pozzolan. To examine the validity of the proposed strength model, the experimental results were compared with the values predicted by the model and the absolute variation obtained was within 5 percent.

• 한국수학사학회지
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• 제30권5호
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• pp.289-304
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• 2017

The interdisciplinary study explores the discussion of actual infinity between Georg Cantor and Roman Catholic Church. Regarding the actual infinity, we first trace the theological background of Cantor by interpreting his correspondence and major works including ${\ddot{U}}ber$ die verschiedenen Standpunkte in bezug auf das aktuelle Unendliche(1885) and Mitteilungen zur Lehre vom Transfiniten (1887), and then investigate his argumentation for two points at issue: (1) pantheism and (2) inconsistency of the necessity with freedom of God. In terms of mathematics and theology, Cantor defined the actual infinity(aphorismenon) as characterized by (1) the transfinite infinity(Transfinitum) and (2) the absolute infinity(Absolutum). Transfinitum is conceptualized here in mathematical terms as a multipliable actual infinity, whereas Absolutum is not as a multipliable actual infinity. The results imply that Cantor's own concept of Transfinitum and Absolutum is adequate for Roman Catholic theology as well as mathematics including the reflection principle.

• Structural Engineering and Mechanics
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• 제70권3호
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• pp.367-380
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• 2019

The paper concerns topology and geometry optimization of statically determinate beams with arbitrary number of supports. The optimization problem is treated as a bi-criteria one, with the objectives of minimizing the absolute maximum bending moment and the maximum deflection for a uniform gravity load. The problem is formulated and solved using the Pareto optimality concept and the lexicographic ordering of the objectives. The non-dominated sorting genetic algorithm NSGA-II and the local search method are used for the optimization in the Pareto sense, whereas the genetic algorithm and the exhaustive search method for the lexicographic optimization. Trade-offs between objectives are examined and sets of Pareto-optimal solutions are provided for different topologies. Lexicographically optimal beams are found assuming that the maximum moment is a more important criterion. Exact formulas for locations and values of the maximum deflection are given for all lexicographically optimal beams of any topology and any number of supports. Topologies with lexicographically optimal geometries are classified into equivalence classes, and specific features of these classes are discussed. A qualitative principle of the division of topologies equivalent in terms of the maximum moment into topologies better and worse in terms of the maximum deflection is found.

• 방송공학회논문지
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• 제12권2호
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• pp.177-184
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• 2007

본 논문에서는 멀티미디어 응용을 위한 동영상의 주관적 품질평가방법으로 널리 사용되는 DSCQS(Double Stimulus Continuous Quality Scale method) 및 ACR(Absolute Category Rating)방법을 비교분석하였다. 두 가지 방법을 비교 실험한 결과 MOS (Mean Opinion Score) 값의 경우 DSCQS와 ACR의 평가치가 매우 높은 상관도를 보이는 것을 확인할 수 있었다. 또한 DMOS (Difference Mean Opinion Score)값의 경우에는 DSCQS와 ACR 방법이 MOS 값의 경우보다 약간 낮은 정도의 상관도를 보였다. 이 같은 결과는 ACR 방식이 DSCQS에 필적하는 성능을 제공하며 많은 수의 영상을 평가 할 수 있는 효율적인 주관적 품질평가 방법임을 보여주고 있다.

• 국제지역연구
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• 제17권4호
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• pp.89-106
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• 2013

본 연구의 대상지역은 대한민국 16개 광역시도이며, 분석기간은 2000년부터 2009년의 제조업 10개년도 시계열 데이터를 이용하여 지역총생산(GRDP)에 큰 영향을 미치는 제조업의 노동생산성을 분석대상으로 설정하여 지역패널회귀분석을 이용한 절대적 및 조건부 수렴여부 및 제조업 생산성 결정요인을 분석 하였다.분석결과를 살펴보면, 절대적 수렴 및 조건부 수렴가설 모두 귀무가설(H0)를 기각함에 따라 수렴가설이 성립하고 있으며, 전국의 제조업 생산성은 수렴하고 있음을 확인할 수 있었다. 수렴속도를 살펴보면 절대적 수렴모형에서 수렴속도는 연간 4.4%가 나왔고, 조건부 수렴에서는 연간 0.73%인 것으로 나타났다. 또한 지역별 제조업의 생산성 결정요인에 대한 분석결과, 종속변수를 1인당 부가가치로 이용했을 때, 인적자본 변수와 제조업 입지계수변수가 정(+)의 관계로 나타났고, 1인당 정부지출 변수가 부(-)의 관계로 나타났다. 연구개발변수의 경우 지식재산권변수만 정(+)의 관계로 나타났다. 총요소생산성의 경우 1인당 정부지출과 1인당 고정자본형성변수가 정(+)의 관계로 유의하였으며, 연구개발변수는 통계적으로 유의하지 않는 것으로 나타났다.

• 한국농림기상학회지
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• 제14권4호
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• pp.269-276
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• 2012

작물모형 평가에 사용되거나 사용할 수 있는 9가지 지표를 소개하였으며 이들의 특징은 다음과 같다. efficiency of model (EF)와 index of agreement (d)은 dimension이 없고 관측수(n)에 의존적이지 않았으며, dimension에 대해서만 자유로운 것은 relative root mean square error (RRMSE), bias factor (Bf)와 accuracy factor (Af)이다. Root mean sqruar, mean error, mean absolute error들은 관측수와 dimension에 영향을 받기 때문에 판단 시 주의가 필요하다. 따라서 이들의 특징을 파악하여 목적에 맞게 모형의 성능을 파악하여야 한다.

• 대한전자공학회논문지SP
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• 제38권5호
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• pp.453-463
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• 2001

본 논문에서는 하이브리드 항법변수 추정 시스템의 일부분인 IRS 위성영상을 이용한 절대위치 추정기법을 다룬다. 빠른 에지 기반 정합을 위하여 accumulator cell로 이루어진 accumulated buffer (AB)를 이용한 정합방법을 제안하였다. 항공기에서 촬영한 두 가지 실제 연속 영상들을 이용한 실험 결과로부터 제안한 AB 정합 방법의 성능을 분석하고, 거리 오차 측면에서 전체 항법변수 추정 시스템에서의 절대위치 추정기법의 효율성을 보였다.

• Computers and Concrete
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• 제3권6호
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• pp.389-400
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• 2006

This paper presents the investigations towards developing a better understanding on the contribution of steel fibers on the tensile strength of high-performance fiber reinforced concrete (HPFRC). An extensive experimentation was carried out with w/cm ratios ranging from 0.25 to 0.40 and fiber content ranging from zero to 1.5 percent with an aspect ratio of 80. For 32 concrete mixes, flexural and splitting tensile strengths were determined at 28 days. The influence of fiber content in terms of fiber reinforcing index on the flexural and splitting tensile strengths of HPFRC is presented. Based on the test results, mathematical models were developed using statistical methods to predict 28-day flexural and splitting tensile strengths of HPFRC for a wide range of w/cm ratios. The expressions, being developed with strength ratios and not with absolute values of strengths and are applicable to wide range of w/cm ratio and different sizes/shapes of specimens. Relationship between flexural and splitting tensile strengths has been developed using regression analysis and absolute variation of strength values obtained was within 3.85 percent. To examine the validity of the proposed model, the experimental results of previous researchers were compared with the values predicted by the model.

• 한국도로학회논문집
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• 제20권2호
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• pp.127-135
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• 2018

PURPOSES : This study develops various models that can estimate the pattern of road surface temperature changes using machine learning methods. METHODS : Both a thermal mapping system and weather forecast information were employed in order to collect data for developing the models. In previous studies, the authors defined road surface temperature data as a response, while vehicular ambient temperature, air temperature, and humidity were considered as predictors. In this research, two additional factors-road type and weather forecasts-were considered for the estimation of the road surface temperature change pattern. Finally, a total of six models for estimating the pattern of road surface temperature changes were developed using the MATLAB program, which provides the classification learner as a machine learning tool. RESULTS : Model 5 was considered the most superior owing to its high accuracy. It was seen that the accuracy of the model could increase when weather forecasts (e.g., Sky Status) were applied. A comparison between Models 4 and 5 showed that the influence of humidity on road surface temperature changes is negligible. CONCLUSIONS : Even though Models 4, 5, and 6 demonstrated the same performance in terms of average absolute error (AAE), Model 5 can be considered the optimal one from the point of view of accuracy.

• International Journal of Control, Automation, and Systems
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• 제4권4호
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• pp.438-447
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• 2006

Fuzzy controller's design depends mainly on the rule base and membership functions over the controller's input and output ranges. This paper presents two different approaches to deal with these design issues. A simple and efficient approach; namely, Fuzzy Subtractive Clustering is used to identify the rule base needed to realize Fuzzy PI and PD type controllers. This technique provides a mechanism to obtain the reduced rule set covering the whole input/output space as well as membership functions for each input variable. But it is found that some membership functions projected from different clusters have high degree of similarity. The number of membership functions of each input variable is then reduced using a similarity measure. In this paper, the fuzzy subtractive clustering approach is shown to reduce 49 rules to 8 rules and number of membership functions to 4 and 6 for input variables (error and change in error) maintaining almost the same level of performance. Simulation on a wide range of linear and nonlinear processes is carried out and results are compared with fuzzy PI and PD type controllers without clustering in terms of several performance measures such as peak overshoot, settling time, rise time, integral absolute error (IAE) and integral-of-time multiplied absolute error (ITAE) and in each case the proposed schemes shows an identical performance.