• 한국유기농업학회지
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• 제6권2호
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• pp.127-140
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• 1998

Organic farming excludes any use of the herbicide. The present paper reviews what can be done for effective weed control with existing weed control technology by farmers crop-ping paddy rice, field crops, vegetables, and fruit trees. If condition of the crop-land-al-lows diversified rotational use of the paddy land as paddy and upland field would minimize weed problem. Practising this is limited in acreage due to extremely limited governmental investment to the land for the purpose. Secondly, rotation of crops in the upland field breaking life cycles of various weeds adapted to each crop should reduce the weed problem. This is also limited as only a few crops are making the farmer profitable. In addition climate and tolerance of crops to high and low temperature. Monsoon rains and poor drainage restrict the freedom of choice. For any crop land year-round multiple cropping in denser planting shall lessen the weed problem, this multiple cropping practiced by 1960s has been abandoned due to laborshortage and increased production cost. Deep flooding the rice is impractical at present in Korean. Mulching crop with transparent, black , or combinated polyethylene sheet, hs been in-creasingly used. Progresses in development and use of mulch with allelopathic crop residues. inexpensive paper mulch, allelopathic crop residues, inexpensive paper mulch, allelopathic crop cultivar development, recently developed ex-perimental weeding machinaries, flamers, microbial herbicides, biological control organisms, soil sterilization techniques have been critically reviewed for their adoption into existing in-tegrated weeding system. Unfortunately, information on cost-benifit, and labor-benefit, for the various methods above mentioned are lacking. Urgent need for the research on rational weeding in organic farming, and herbicide low-input farming is emphasized.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 1994년도 추계학술발표회 및 정기총회
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• pp.1-2
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• 1994

With the prevalence of computers in modern organizations, simulation is receiving more atention as an effectvie decision -making tool. Simualtion is a computer-based numerical technique which uses mathmatical and logical models to approximate the behaviror of a real-world system. However, iptimization of synamic stochastic systems often defy analytical and algorithmic soluions. Although a simulation approach is often free fo the liminting assumption s of mathematical modeling, cost and time consiceration s make simulation the henayst's last resort. Therefore, whenever possible, analytical and algorithmica solutions are favored over simulation. This paper discussed the issues and procedrues for using simulation as a tool for optimization of stochastic complex systems that are dmodeled by computer simulation . Its emphasis is mostly on issues that are speicific to simulation optimization instead of consentrating on the general optimizationand mathematical programming techniques . A simulation optimization problem is an optimization problem where the objective function. constraints, or both are response that can only be evauated by computer simulation. As such, these functions are only implicit functions of decision parameters of the system, and often stochastic in nature as well. Most of optimization techniqes can be classified as single or multiple-resoneses techniques . The optimization of single response functins has been researched extensively and consists of many techniques. In the single response category, these strategies are gradient based search techniques, stochastic approximate techniques, response surface techniques, and heuristic search techniques. In the multiple response categroy, there are basically five distinct strategies for treating the responses and finding the optimum solution. These strategies are graphica techniqes, direct search techniques, constrained optimization techniques, unconstrained optimization techniques, and goal programming techniques. The choice of theprocedreu to employ in simulation optimization depends on the analyst and the problem to be solved. For many practival and industrial optimization problems where some or all of the system components are stochastic, the objective functions cannot be represented analytically. Therefore, modeling by computersimulation is one of the most effective means of studying such complex systems. In this paper, after discussion of simulation optmization techniques, the applications of above techniques will be presented in the modeling process of many flexible manufacturing systems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권7호
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• pp.2972-2991
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• 2016

WLAN is the best choice in the place where complex network is hard to set up. Intelligent terminals are more and more assembled in some areas now. However, according to IEEE 802.11n/802.11ac, the access-point (AP) can only serve one user at a single frequency channel. The spectrum efficiency urgently needs to be improved. In theory, AP with multi-antenna can serve multiple users if these users do not interfere with each other. In this paper, we propose a user clustering scheme that could achieve multi-user selection through the mutual cooperation among users. We focus on two points, one is to achieve multi-user communication with multiple antennas technique at a single frequency channel, and the other one is to use a way of distributed users' collaboration to determine the multi-user selection for user clustering. Firstly, we use the CSMA/CA protocol to select the first user, and then we set this user as a source node using users' cooperation to search other proper users. With the help of the users' broadcast cooperation, we can search and select other appropriate user (while the number of access users is limited by the number of antennas in AP) to access AP with the first user simultaneously. In the network node searching, we propose a maximum degree energy routing searching algorithm, which uses the shortest time and traverses as many users as possible. We carried out the necessary analysis and simulation to prove the feasibility of the scheme. We hope this work may provide a new idea for the solution of the multiple access problem.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.354-359
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• 2006

The analysis of large-scale water resources systems is often complicated by the presence of multiple reservoirs and diversions, the uncertainty of unregulated inflows and demands, and conflicting objectives. Reinforcement learning is presented herein as a new approach to solving the challenging problem of stochastic optimization of multi-reservoir systems. The Q-Learning method, one of the reinforcement learning algorithms, is used for generating integrated monthly operation rules for the Keum River basin in Korea. The Q-Learning model is evaluated by comparing with implicit stochastic dynamic programming and sampling stochastic dynamic programming approaches. Evaluation of the stochastic basin-wide operational models considered several options relating to the choice of hydrologic state and discount factors as well as various stochastic dynamic programming models. The performance of Q-Learning model outperforms the other models in handling of uncertainty of inflows.

• 한국멀티미디어학회논문지
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• 제9권12호
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• pp.1560-1571
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• 2006

In order to transmit multimedia streams over the network with a timely changing channel bandwidth such as Internet, scalable video coding schemes have been studied to represent video in flexible bitstream. Much research has been made on how to represent encoded media(such as video) bitstream in scalable ways. In this paper, rte propose an optimal selection of the objects for MPEG-4 bitstream adaptation to meet a given constraint. We adopt a multiple choice knapsack problem with multi-step selection for the MPEG-4 objects with different bit-rate scaling levels in the MPEG-4 bitstream. The bitstream adaptation based on the optimal selection result is then to fetch the necessary parts of the MPEG-4 bitstream to constitute an adapted version of the original MPEG-4 binary resource. The experiment results show that the optimal selection of MPEG-4 objects for a given constraint can promisingly be made which meets the given constraint.

• 영어어문교육
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• 제5호
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• pp.149-189
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• 1999

Assessment can be defined as any method used to understand the current knowledge that a student possesses. Assessment may influence decisions about grades, placement, instructional needs, and curriculum. Therefore, the purpose of assessment is to identify how the students think and know, to diagnose the difficulties they face, and to reflect the result of assessment on teaching. But the traditional multiple-choice test failed to evaluate and teach higher-level thinking and problem-solving skills. In this context, performance assessment is being required as an alternative assessment to get better understanding about what the students can do as well as what they know. This article points out some weaknesses of traditional assessments, and comments on the theoretical background and necessity of performance assessment. And it presents more specific information about performance assessment and some examples. It is certain that performance assessment is student-centered and future-oriented. But performance assessment can't be the surest and best way of evaluating the students' abilities. We are just on the way of another experimental stage for improving teaching methodology. More supplementary analyses and further improvements are needed.

• 한국경영과학회지
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• 제30권1호
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• pp.55-74
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• 2005

Bankruptcy prediction has drawn a lot of research interests in previous literature, and recent studies have shown that machine learning techniques achieved better performance than traditional statistical ones. This paper employs a relatively new machine learning technique, support vector machines (SVMs). to bankruptcy prediction problem in an attempt to suggest a new model with better explanatory power and stability. To serve this purpose, we use grid search technique using 5-fold cross-validation to find out the optimal values of the parameters of kernel function of SVM. In addition, to evaluate the prediction accuracy of SVM. we compare its performance with multiple discriminant analysis (MDA), logistic regression analysis (Logit), and three-layer fully connected back-propagation neural networks (BPNs). The experiment results show that SVM outperforms the other methods.

• 영재교육연구
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• 제14권4호
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• pp.113-123
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• 2004

The concern with scientific mode1s has been growing in science education, and schematic models are frequently used to teach science concepts in secondary schools. The aim of this study is to investigate how well the scientifically gifted students understand scientific concepts through activities of modifying scientific models which we developed. Thirty 8th-grade students participated in the study, 15 in a control group and 15 in an experimental group. For the students in the experimental group, teaching material with activities of modifying models, while for the students in the control group, the teaching material with traditional activities such as explanation, problem solving, and reading. The teaching contents in physics for both groups were linear momentum. We used multiple-choice test and essay-type test to evaluate students' achievements after lessons, and then compared their achievements of both groups. Through the research, we could find a clue that model-modifying activities are helpful for the gifted students to enhance their understanding of physics concepts, although the statistics does not show meaningful difference between experimental and control groups.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.1359-1363
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• 2009

The object of this research is to develop a simulation system for earthmoving operations in consideration of the impact of congestion in-between equipment and existing traffic flow around the site. The congestion in-between equipment and traffic flow affect work productivity. The conventional discrete event simulation, however, has limitations in simulating the flow of construction equipment. To consider the impact of congestion in-between equipment and existing traffic flow, in this paper, a multi-agent based simulation model that can realize characteristics of truck behavior more accurately to consider the impact of congestion was proposed. In this simulation model, multiple agents can identify environmental changes and adapt themselves to the new environment. This modeling approach is a better choice for this problem since it describes behavioral characteristics of each agent by sensing changes in dynamic surroundings. This study suggests a detailed system design of the multi-agent based simulation system.

• 한국학교수학회논문집
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• 제15권4호
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• pp.699-718
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• 2012

학생들이 문장으로 이루어진 문제를 해결과정에서 발생하는 오류의 유형을 분류하고, 각각의 오류 유형을 보인 학생들의 면담(인터뷰)을 통하여 오류를 범하게 된 요인을 분석하였다. 연구결과에 따라 나타난 대표적인 오류 유형은 '문항 이해의 부족', '풀이과정의 오류', '정리나 정의에 대한 왜곡된 이해', '이기과정의 오류', '기술적 오류', '풀이과정 생략' 등으로 나타났다. 또한 일부 학생들은 문장제에 대한 부담감으로 문제를 해결하기보다는 포기하는 현상이 나타났으며, 학생들은 문장으로 이루어진 문제를 해결을 하기 위해서 무엇보다 문제에 대한 이해가 필요한데, 이 부분이 절대적으로 부족하여 문제에서 주어진 자료를 자의적으로 판단하고 활용하는 경향이 짙게 보였다. 교사는 학생들이 문장제 문제 해결과정에서 발생하는 오류를 미리 파악하고 이를 보안할 수 있는 교수-학습방법으로 학생들을 지도한다면 오류를 사전에 예방하여 발생빈도를 줄일 수 있고, 학생들로 하여금 효과적인 학습이 이루어 질 수 있을 것이다.