• Computers and Concrete
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• v.32 no.2
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• pp.185-206
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• 2023

This article aimed to explore the optimization of mineral admixtures and retarding admixture for high-performance concrete. In essence, fresh concrete can be regarded as a mixture in which both coarse and fine aggregates are suspended in a cement-based matrix paste. Based on this view, the test procedure was divided into three progressive stages of binder paste, mortar, and concrete to explore their rheological behavior and mechanical properties respectively. At each stage, there were four experimental control factors, and each factor had three levels. In order to reduce the workload of the experiment, the Taguchi method with an L9(3⁴) orthogonal array and four controllable three-level factors was adopted. The test results show that the use of the Taguchi method effectively optimized the composition of high-performance concrete. The slump of the prepared concrete was above 18 cm, and the slump flow was above 50 cm, indicating that it had good workability. On the other hand, the 28-day compressive strength of the hardened concretes was between 31.3-59.8 MPa. Furthermore, the analysis of variance (ANOVA) results showed that the most significant factor affecting the initial setting time of the fresh concretes was the retarder dosage, and its contribution percentage was 62.66%. On the other hand, the ANOVA results show that the most significant factor affecting the 28-day compressive strength of the hardened concretes was the water to binder ratio, and its contribution percentage was 79.05%.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.830-837
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• 2010

Since it started the researches on a maglev train on 1960, Germany and Japan arrived to putting to practical use level and accomplished most tests from their test-line. Korea is in progress the preparation for a practical use of low-speed maglev train in 110 [km/h] class and Korea Railroad Research Institute(KRRI) is in progress of a research about core technology of maglev system for high-speed tube train of 700 [km/h] class. In this paper, authors suggest an effective design method of Linear Synchronous Motor(LSM) for high-speed tube train of 700 [km/h] class which has a wound type electro-magnet. Then, authors calculate a variety of properties by changing speed of the LSM model which is designed by a method based on some theoretical equations. Then, authors verify the validity of the method based on some theoretical equations through a verification of property values by Finite Element Method(FEM) analysis method. Finally, in order to design a shape of pole-shoe part of LSM electro-magnet which is hard to design with a basic design method, authors analyze a transition of property values by changing a pole-shoe width and current of the electro-magnet through an analytical method by FEM.

• Women's Health Nursing
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• v.12 no.2
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• pp.156-167
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• 2006

Purpose: The purpose of this study was to investigate the stress caused by having a senior in high school preparing for the college entrance examination, and coping methods of middle aged women in order to have a high quality of life. Method: The subjects of this study were 410 middle aged women. The data were collected by a structured questionnaire during September 5 to October 26, 2005. Result: The respondents' scores of stress were relatively low. The scores of stress perception related to 'studies record inactivity', 'a bad feeling because their sons and daughters are lazy', and worries about fatigue and health of their sons and daughters' were relatively high. The scores of the coping method related to 'affirmative thought and conduct', and 'sincerity it in the senior in high school student' were relatively high. In subjects with a higher degree(score$\geq$3) of stress caused by the senior student in high school the scores of coping methods related to 'projection', 'evasion', and 'perseverance' were relatively higher than the scores of coping methods of subjects with a lower degree (score<3) of stress. Conclusion: Based on the findings of this study, we should develop an integrated support program for middle-aged women. A place must be made where mothers will be able to discuss the education of their children such as on-line group community by mothers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.5789-5794
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• 2015

Recently, thin and light-weight production technologies are needed in IT industry in accordance with increase of the smart phones and mobile PC products. In order to make light and high rigidity products, engineering plastic and aluminum materials are frequently used in products appearance and frame hat support structure. Especially aluminum extrusion and CNC Brick processes are widely used for high strength and high rigidity technology. But extrusion method has constraints to apply exterior design and CNC Brick process has relatively high production cost and low speed of manufacturing. In this research, a new process method is introduced in order to reduce material cost and to improve manufacturing speed dramatically. Plate forging process means basically that thickening of local wall area thickness after deform exterior shape by deep drawing and bending process. Therefore, it is possible to minimize the waste of material and the manufacturing time. In this study the process of plate forging is designed using finite element program AFDEX-2D and the thickness and the width of initial deformed blank. And it is verified as a sample which is a part of laptop developed through the proposed plate forging method.

• KIPS Transactions on Software and Data Engineering
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• v.5 no.8
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• pp.361-368
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• 2016

While dimension reduction methods on high dimensional data have been widely studied, research on dimension reduction methods for high dimensional streaming data with concept drift is limited. In this paper, we review incremental dimension reduction methods and propose a method to apply dimension reduction efficiently in order to improve classification performance on high dimensional streaming data with concept drift.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.561-566
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• 2016

In this paper, effective design method of linear induction motor(LIM) for Maglev is proposed in order to maximize system efficiency of Maglev. For the high system efficiency of Maglev, it is important to minimize weight of traction motor. Light weight design by changing materials of core and winding is conducted without changing volume of LIM. For the silicon steel core of primary part for magnetic flux path, iron-cobalt alloy steel with high magnetic saturation characteristic compared to silicon steel is suggested. Moreover, aluminium winding with light weight instead of copper winding is wounded in the widen slot area due to the high magnetic saturation level. For the verification of performance of proposed model, the characteristics are analyzed by using finite element method(FEM).

• Journal of Power System Engineering
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• v.9 no.4
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• pp.143-147
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• 2005

Graphites is well known to have superior advantages to high-temperature, high-pressured, and strong acid-state gas or liquid because it is very stable and chemical structure. Nowadays the new plant with high performance is developed in field of chemical industries, so the need of graphites is increasing rapidly. In this paper, newly developed graphite products with high density is investigated by the mechanical properties of that. I introduced the graphite material which developed for this experiment by the forming process in order to compare to the commercial graphite sheet from expanded graphite which made by the rolling process. Through measuring density and hardness test also tensile test, I investigated the characteristics of these materials. It is verified that the newly developed graphite products forming method is able to make graphite products which have superior mechanical properties than that of commercial graphite sheet.

• Journal of Korean Academy of Nursing
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• v.31 no.4
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• pp.610-618
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• 2001

Purpose: This study attempted to grasp the significance of high school boys smoking experiences, and to define its structure, then utilizing the results to create effective nursing intervention in order to protect students from smoking habit. Method: This study is based on a phenomenological approach. A group of eight male high school students who had experience in smoking were selected as the subject of this study. Intimate interview with participatory observation were carried out from them and the resulted data were analyzed by Giorgi's method as below. Result: The male high school students’smoking experiences were found to be a direct result from the environments around them and misty curiosity, masculinity, maintenance of close relations with peers, habitualness, stress relief, and concealment from the family. Conclusion: The result indicates that the male high school students' smoking, especially in an aspect from its starting point, motivational perspective, from the early stage of childhood as possible.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.3
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• pp.145-156
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• 2000

In this paper, we propose a new methodology which includes the optimal design procedure of Polynomial Neural Networks(PNN) structure for model identification of complex and nonlinear system. The proposed PNN algorithm is based on GMDA(Group Method of Data handling) method and its structure is similar to Neural Networks. But the structure of PNN is not fixed like in conventional Neural Networks and can be generated. The each node of PNN structure uses several types of high-order polynomial such as linear, quadratic and cubic, and is connected as various kinds of multi-variable inputs. In other words, the PNN uses high-order polynomial as extended type besides quadratic polynomial used in GMDH, and the number of input of its node in each layer depends on that of variables used in the polynomial. The design procedure to obtain an optimal model structure utilizing PNN algorithm is shown in each stage. The study is illustrated with the aid of pH neutralization process data besides representative time series data for gas furnace process used widely for performance comparison, and shows that the proposed PNN algorithm can produce the model with higher accuracy than previous other works. And performance index related to approximation and prediction capabilities of model is evaluated and also discussed.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.956-959
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• 2004

Recently the monitoring system of tool setting in high speed precision machining center is required for manufacturing products that have highly complex and small shape, high precision and high function. It is very important to reduce time to setup tool in order to improve the machining precision and the productivity and to protect the breakage of cutting tool as the shape of product is smaller and more complex. Generally, the combination of errors that geometrical clamping error of fixing tool at the spindle of machining tool and the asynchronized error of driving mechanism causes that the run-out of tool reaches to 3$^{\sim}$20 times of the thickness of cutting chip. And also the run-out is occurred by the misalignment between axis of tool shank and axis of spindle and spindle bearing in high speed rotation. Generally, high speed machining is considered when the rotating speed is more than 8,000 rpm. At that time, the life time of tool is reduced to about 50% and the roughness of machining surface is worse as the run-out is increased to 10 micron. The life time of tool could be increased by making monitoring of tool-setup easy, quick and precise in high speed machining tool. This means the consumption of tool is much more reduced. And also it reduces the manufacturing cost and increases the productivity by reducing the tool-setup time of operator. In this study, in order to establish the concept of tool-setup monitoring the measuring method of the geometrical error of tool system is studied when the spindle is stopped. And also the measuring method of run-out, dynamic error of tool system, is studied when the spindle is rotated in 8,000${\sim}$60,000 rpm. The dynamic phenomena of tool-setup are analyzed by implementing the monitoring system of rotating tool system and the non-contact measuring system of micro displacement in high speed.