• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.206-211
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• 2015

Recently, for UHPC (Ulta High Performance Concrete) which is researched actively, as the tensile strength is absolutely influenced on the content of steel fiber, in this paper, experiments of compressive strength, elasticity modulus and tensile strength were performed according to compressive strength and content of steel fiber as variables. By the test results, compressive strength, elasticity modulus and tensile strength are proportioned and have a good correlation and according to content of steel fiber, compressive and tensile strength are also proportioned and have a good correlation. In case of elasticity modulus, the difference between test and present design code is not large, so it is possible to adapt to present design code. On the other hand, in case of tensile strength, as there is no specification of present design code, new prediction equation is proposed by using nonlinear regression analysis and the proposed equation have a good correlation to test results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1C
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• pp.41-51
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• 2008

The load distribution and deformation of single piles which is embedded in Jumunjin sand and Kimhae clay are investigated, based on small scale model tests. Special attention is given to the consideration of flexural rigidity in laterally loaded piles. To consider the flexural rigidity of the pile, tests are performed with the aluminium piles of three different length under different relative densities and undrained shear strength. The test results indicate that the initial slope from the results of tests is proportional to the depth and pile-soil rigidity in both soils. But the increasing rate of the initial slope in the clay is less than in the sand. In addition, the soil resistance is more related to the depth and soil condition than the pile rigidity. Base on the test results, an empirical formula is proposed, which is good agreement with previously published small scale model test and field lateral load test.

• Communications for Statistical Applications and Methods
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• v.19 no.1
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• pp.23-32
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• 2012

This paper deals with the bias and variance of regression coefficient estimators in a finite population. We derive approximate formulas for the bias, variance and mean square error of two estimators when we select a fixed-size inclusion probability proportional to the size sample and then estimate regression coefficients by the ordinary least square estimator as well as the weighted least square estimator based on the selected sample data. Necessary and sufficient conditions for the comparison of the two estimators in terms of variance and mean square error are suggested. In addition, a simple example is introduced to numerically compare the variance and mean square error of the two estimators.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.182-190
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• 2017

All liquids contain a small amount of gaseous components and the amount of gases dissolved in a liquid is in accordance with Henry's Law. In a multi-stage thermal-type seawater desalination plant, as the supplied seawater undergoes variations in temperature and pressure in each evaporator, the gases dissolved in the seawater are discharged from the liquid. The discharged gases are carbon dioxide, nitrogen, oxygen, and argon, and these emitted gases are non-condensable. From the viewpoint of convective heat transfer, the evaluation of non-condensable gas released during a vacuum evaporation process is a very important design factor because the non-condensable gases degrade the performance of the cooler. Furthermore, in a thermal-type seawater desalination plant, most evaporators operate under vacuum, which maintained through vacuum system such as a steam ejector or a vacuum pump. Therefore, for the proper design of a vacuum system, estimating the non-condensable gases released from seawater is highly crucial. In the study, non-condensable gases released in a thermal-type seawater desalination plant were calculated quantitatively. The calculation results showed that the NCG releasing rate decreased as the stage comes getting a downstream and it was proportional to the freshwater production rate.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.12-23
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• 1995

Currents driven by irregular waves are modelled using numerical model with various empirical relations improved. Kitaigorodskii's equilibrium equation is refined to account for shoaling effect and used for checking the breaking condition. In order to compute the bottom friction realistically. equivalent roughness blights are estimated considering the ripple shape and bed load transport which may be significant the surf zone. Two sets of equations are employed to evaluate the ripple shape: one is suggested by Nielsen and the other by Madsen and Rogengaus. Both equations give similar shape of ripples. but Madsen et al. give lower value of ripple factor than Swart suggesting that the equivalent roughness becomes relatively small. Optimization technique is used to determine the proper values for the empirical parameters of $\kappa$-ι equations, and the longshore current velocity is computed using the values of empirical parameters determined by the optimization technique.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.331-336
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• 1995

In this past decade, industrial robot have substituted human workers successfully in certain areas, however, the applications are limited due to the shortcoming in their mechanism and control strategies. Many researchers, therefore, have focused on improving the mechanical and sensory capabilities. Developing mult-degree-of-freedom end effectors, in other words robot hands, is one of the topics that researchers have begun to improve the limitation. A set of direct drive type servo-pneumatic finger joint has been developed for a dexterous robot hand. To control the pneumatic finger joints, a prototype 4/3-way proportional control valve has been designed and tested as a preliminary, research for the control of the pneumatic finger joints. A series of experiments have been conducted to verify the performance characteristics of the valve and the conventional proportional error contral with minor-loop compensation has been used to control the anguar position of the finger joints.

• Journal for History of Mathematics
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• v.17 no.3
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• pp.23-32
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• 2004

In this paper, Ive investigated algebraic concepts which are contained in Euclid's Elements. In the Books II, V, and VII∼X of Elements, there are concepts of quadratic equation, ratio, irrational numbers, and so on. We also analyzed them for mathematical meaning with modem symbols and terms. From this, we can find the essence of the genesis of algebra, and the implications for students' mathematization through the experience of the situation where mathematics was made at first.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.5
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• pp.33-38
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• 2013

This paper presents a simpler calculation of the generator load sharing according to the change of system frequency and the droop setting of turbine-generator governor. The author firstly draws a graph based on the generator operation at rated MW output and normal frequency, and secondly, builds a proportional expression using the graph in order to obtain the solution in a simpler way rather than using conventional mathematical calculation, to provide the readers with an easier understanding of the droop setting of turbine-generator governor.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.107-108
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• 2016

Our study proposes the methods of distinguishing vehicle types using the interval and size of the car. The car videos converts the basic RGB model to Gray model for use and through Canny Edge Direction, it eliminates the background of the car while obtaining feature points through the detection of contours.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.52-57
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• 2007

The control characteristics for radiant panel heating system with automatic thermostatic valves were researched by computer simulation and experiment. The unsteady energy analysis using equivalent R-C circuit method and radiation heat transfer analysis of enclosure analysis method with simple structured rooms was performed. The results of flow rate changes of the simulation study are good fit with the ones of experimental one.