• 터널과지하공간
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• 제30권4호
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• pp.417-431
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• 2020

이 연구에서는 라이다(LiDAR) 반사강도를 이용하여 암반 풍화도 및 변질도를 산정하는 작업의 기초연구를 진행하였다. 실내 시험을 통하여 라이다 반사강도에 직접적으로 영향을 미치는 인자와 그 영향 정도를 정량적으로 고찰하고자 하였다. 영향 인자로는 주사거리, 입사각, 표면거칠기, 표면색상, 암석물성, 광물조성, 포화도를 선정하였다. 실험에서는 FARO 라이다 장비와 12가지 종류의 시험편을 사용하였다. 실험 결과 반사강도는 표면색상, 입사각, 주사거리, 암석물성, 포화도 혹은 표면습윤상태, 표면거칠기 순으로 영향을 크게 미치는 것으로 나타났다.

• 상하수도학회지
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• 제25권4호
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• pp.471-478
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• 2011

A series of laboratory experiments carried out to investigate the particle separation efficiency and flotation characteristics using $CO_2$ bubbles. The primary objective of this study was to find out the feasibility of $CO_2$ bubbles as an applicable unit of flotation process in tap-water and wastewater treatment plant. The fundamental measurements were conducted to characterize the $CO_2$ bubble from the physical viewpoint in water including bubble size distribution and rising velocity under various operational conditions. In addition, the removal efficiency of solid was experimented using the lab scale plant applied $CO_2$ bubbles, namely the dissolved carbon dioxide flotation (DCF) process. The DCF process using carbon dioxide bubble, which is an advantage as the decrease and the reuse of Green-House gas, can be a promising technology as an water treatment process. On the other hand, the further research to decrease the bubble size distribution of $CO_2$ is required to enhance the particle separation efficiency.

• 한국국방경영분석학회지
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• 제30권2호
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• pp.96-107
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• 2004

This paper deals with $\ulcorner$Requirement Decision Model for Repair Parts supplied by the Government$\lrcorner$ which is to reduce Aircraft Contract Maintenance Cost. It aims to find solutions to the fundamental problems of the Aircraft Contract Maintenance System. Under the current Aircraft Contract Maintenance System, it is hard to forecast the exact demand of repair parts, so support rate of Repair Parts supplied by the Government is restricted under 50 percent. It is inevitable to purchase Repair Parts from the firm with much higher price than those of Government source. However, absence of fixed demand pattern makes it difficult to improve accuracy of demand forecast. As a solution to these problems, this model prevents a cost increase due to the unit price difference between Repair Parts supplied by the Government and Repair Parts purchased by the Firm. It also reflects demand characteristics of each repair part, and prevents continual stock increase by setting an upper limit on the amount of Repair Parts supplied by the Government. The effectiveness of this model is verified by empirical analysis using the latest raw data. By applying this model to real situation, we expect to reduce about 4 billion won every year.

• Journal of Biosystems Engineering
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• 제16권1호
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• pp.27-36
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• 1991

This study was carried out getting basic data for developing a new combine which is suitable for the cultivating situation in Korea or Southeast Asia. The relation of the amount of unthreshed grains and the axial displacement of crop in threshing process was attempted to formulate mathematically in a threshing chamber of axial-flow threshing unit. It was found that unthreshed grain is an exponetially-decaying functon of axial displacement of grains based on available data. Threshing experiments were performed to validate the mathematical model by changing various levels of pertinent variables for malting barley. Good correlation were obtained between the theoretical calculation and observed data for various test conditions, such as inclination, vane pitch, concave length, drum speed, feeding velocity, stream weight, moisture content. Therefore the model can be used for general purpose to find the amount of unthreshed grain if the mean rate of occurence of threshing of kernels(${\lambda}_{\tau}$) is properly calibrated considering some other operating conditions and crop conditions which are not involved in this analysis.

• 융합신호처리학회논문지
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• 제3권2호
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• pp.45-52
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• 2002

EMI(전자파간섭)은 전기/전자제품의 이상동작을 야기할수 있는 장치로부터 방사되는 10KHz에서 3GHz대역의 전자파를 말한다. 본 연구에서는 안정적이고 정상적인 동작을 위해 2.5Gbps SDH시스템에서 전자파발생원인 STGU유니트에 대하여 전자파간섭을 시뮬레이션하였으며 On-Site Test를 통하여 조화주파수에 대한 전자파 세기를 측정하였다. 또한 소자들간의 EMI를 최소화하기 위하여 2GHz의 Cut-off주파수에서 저역통과필터를 설계하였다. 저역통과필터를 STGU유니트에 적용한 결과 전자파는 약 20dBm이상 감소되었으며 동기기준클럭의 품질을 결정하는 TIE와 MTIE를 측정한 결과 ITU-T G8l3을 만족하였다.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2002년도 추계학술대회
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• pp.227-232
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• 2002

Enormous flocks by the reduced life cycle of products caused by the technological innovation if later 20 century, development of new materials and diversified demands of customers appeared as the pressing element causing the trouble in management of companies, and when considering the logistic costs that are imposed to companies in terms of function, the costs related to the stock topped the list of costs, followed by the transportation ones, and for pallet pool system, inventory of stocks is very difficult by the number of companies. Reducing the logistic cost may be accomplished by numbers of logistic management methods, but the most fundamental and essential one is the accomplishment of the consistent pallet system that is the core of unit load system, and the purpose of consistent pallet system is the treatment of logistic functions such as transportation, storage and unloading with consistent pallet system, and increasing the turnover ratio is required for the improvement of the system. As the turnover ratios is increased, more pallets will be used so, numbers of empty pallets will be increased accordingly by returning the pallet. Therefore, in this study, we will establish the effective stock management system by comparing with the other existing stock management system after looking at the concept and examples of pallet full system in order to resolved this kind of problem.

• 한국초등과학교육학회지:초등과학교육
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• 제18권2호
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• pp.103-117
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• 1999

The importance of pedagogical content knowledge(PCK) has been recognized in learning science teaching. PCK is based partly on the essence of subject matter knowledges. Therefore, the effective teaching of science content knowledges is fundamental in preservice education of student teachers. But, particularly the science curriculum of primary teachers' colleges is composed of less lessons than needed. This research was executed to identify the content and context of earth science which were contained in questions by student teachers These questions which were written by the students about the earth science content in elementary science texts and teachers' guide books were collected and analyzed. Frequency and context concentration of questions about the themes of contents were obtained. In each unit of the text books, scatter diagrams of question frequency and context concentration of themes showed various features. The main results were as follows. first, in case of the units which contents ate composed of themes expected to be experienced in everyday life, the question frequency and context concentration showed positive correlation between them. But, other units, which everyday life experiences are not expected to influence, did not show distinct correlation.

• 한국농공학회지
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• 제38권6호
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• pp.74-82
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• 1996

In this study, the characteristics of antiwashout underwater concrete according to the using types of admixture were experimentally investigated. Especially, the comparison on the performance of seven types(CO-A, B, C, D, E, F, G) of the manufactured admixtures was carried out in the same mixing condition and proportions. Based on the results of experiments, the conclusions were summarized as follows : (1) The slump flow on most of specimens except by CO-F type were progressed very well. (2) In most of products, the measured values of suspensions, pH's and air contents were lower than their reference values. However, CO-B, CO-F and CO-G types exceeded the reference ones in suspension and pH. (3) The time lags between initial and final setting were about three hours in most of tests, however, the maximum difference of total setting time was ten hours in comparing with the admixture types. The unit weights were mostly lower than $2300kg/m^3$ and the compressive strengths cured by salt water were about 80% of the ones by fresh water. (4) Finally, in spite of some problems, most of the manufactured admixtures may be performed well their functions in antiwashout under-water concrete if the using quantities are properly controlled by the site experiments.

• Journal of Advanced Marine Engineering and Technology
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• 제13권2호
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• pp.78-88
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• 1989

The fundamental objective of this paper has been to develop a means for incoporating the concept of the linear fractional transformation more generally and easily into multivariable feedback design procedure. When we design a continuous system, generally, we are constrained by design methods which arise specifically for the system. Also, in the design of descrete systems, it is the same concept. But the approach developed in this paper is very flexible in the view that in spite of being the continuous or discrete, the design can be done using a well known design method in both cases. That is, when we design a contnuous system or discrete system, the design can be done by a standard design method of continuous systmes or discrete ones, depending on the choice of the linear fractional transformation. Therefore, it is noted that this concept has broken the unflexibility of the conventional design rules for multivariable control system. In essence, the concept shows that if a given system is controllable, some desirable design, for examples, pole assignment within prespecified region, optimal controllers with poles within prespecified region etc., could be done easily by transforming a desirable region into a standard region, such as the complex left-half plane or the unit disk, by the chosen linear fractional transformation, and then by designing the transformed system using the well known standard results.

• 대한안전경영과학회지
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• 제5권1호
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• pp.33-43
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• 2003

Enormous stocks by the reduced life cycle of products caused by the technological innovation in later 20 century, development of new materials and diversified demands of customers appeared as the pressing element causing the trouble in management of companies, and when considering the logistic costs that are imposed to companies in terms of function, the costs related to the stock topped the list of costs, followed by the transportation ones, and for pallet pool system, inventory of stocks is very difficult by the number of companies. Reducing the logistic cost may be accomplished by numbers of logistic management methods, but the most fundamental and essential one is the accomplishment of the consistent pallet system that is the core of unit load system, and the purpose of consistent pallet system is the treatment of logistic functions such as transportation, storage and unloading with consistent pallet system, and increasing the turnover ratio is required for the improvement of the system. As the turnover ratios is increased, more pallets will be used so, numbers of empty pallets will be increased accordingly by returning the pallet. Therefore, in this study, we will establish the effective stock management system by comparing with the other existing stock management system after looking at the concept and examples of pallet full system in order to resolved this kind of problem.