• Journal of The Korean Association For Science Education
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• v.31 no.1
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• pp.32-47
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• 2011

The purpose of this study was to analyze the ability to control variables and the ways by which variables are controlled. First, the assessment criteria for evaluating the students' ability to control variables were developed for 8th grade students. Second, the ways variables are controlled were classified from student activity reports. These students' answers were categorized into six types (type A~ type F). Type A is defined as the group that excelled in recognizing the importance of controlling variables, eliminating unnecessary variables and identifying manipulated, dependent and controlled variables. Third, the scores of ability to control variables (CV score) and the classroom test of scientific reasoning (Lawson SRT) scores were measured. The results indicated that the CV score was highly correlated with Lawson SRT scores (r=.67, p<.01). Therefore, the assessment criteria developed in this study was used to evaluate the ability to control variables (CV score) and to measure the students' scientific reasoning.

• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.519-528
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• 2011

The main purpose of this study was to develop a teaching program, especially designed to improve the skills of control variables. The secondary purpose was to investigate the effect of the program on enhancing students' scientific reasoning and understanding. The program was designed based on the 3-step learning model: i.e. students recognize the necessity of controlling the variables (step 1), perform their own experiments (step 2), and reflect on their variables control process (step 3). The program included 9 topics of increasing difficulty. In results, Lawson's SRT scores increased in both experimental and control groups after application of the program, but the difference was not statistically significant. After the application, there was an increase in type A and type B which implied that students' skills of control variables was improved. In addition, responses of students in the experimental group to the open-ended items showed that it was challenging for them to think scientifically and critically when controling variables, but they ended up feeling proud of their achievement after the program.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.8
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• pp.711-716
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• 2000

A fuzzy defrost control algorithm for the multi-type heat pump system was developed. In the fuzzy defrost control algorithm, the air temperature difference at the outdoor unit and the refrigerant pressure difference at the compressor were used as input variables, and the defrost starting time and the defrost time interval were used as output variables. This fuzzy algorithm was applied to the multi-type heat pump system and tested in the five dynamic environmental chambers. Test results show that the newly developed control algorithm is more effective than the conventional control algorithm in the removal of frost formed at the outdoor unit of the heat pump.

• Journal of Information Processing Systems
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• v.3 no.1
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• pp.26-32
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• 2007

Although the Java bytecode has numerous advantages, it also has certain shortcomings such as its slow execution speed and difficulty of analysis. In order to overcome such disadvantages, a bytecode analysis and optimization must be performed. The control flow of the bytecode should be analyzed; next, information is required regarding where the variables are defined and used to conduct a dataflow analysis and optimization. There may be cases where variables with an identical name contain different values at different locations during execution, according to the value assigned to a given variable in each location. Therefore, in order to statically determine the value and type, the variables must be separated according to allocation. In order to achieve this, variables can be expressed using a static single assignment form. After transformation into a static single assignment form, the type information of each node expressed by each variable and expression must be configured to perform a static analysis and optimization. Based on the basic type information, this paper proposes a method for finding the related equivalent nodes, setting nodes with strong connection components, and efficiently assigning each node type.

• Journal of the Korean Data and Information Science Society
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• v.28 no.4
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• pp.937-945
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• 2017

The purpose of using a control chart is to detect any change that occurs in the process. When control charts are used to monitor processes, we want to identify this changes as quickly as possible. Many problems in quality control involve a vector of observations of several characteristics rather than a single characteristic. Multivariate CUSUM or EWMA charts have been developed to address the problem of monitoring covariance matrix or the joint monitoring of mean vector and covariance matrix. However, control charts tend to work poorly when we use the highly correlatted variables. In order to overcome it, Hawkins (1991) proposed the use of regression adjustment variables. In this paper, to monitor covariance matrix, we investigate the performance of MEWMA-type control charts with and without the use of regression adjusted variables.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.2
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• pp.163-171
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• 2006

In order to control multi-zone temperatures, a multi-type air-conditioning system may be used. In this study, control algorithms for the compressor and the electronic expansion valve of a multi-type air-conditioning system were developed by using fuzzy logics. The compressor control algorithm was composed of a compressor pressure setpoint algorithm, a compressor pressure setpoint reset algorithm, and a compressor frequency setpoint algorithm. The electronic expansion valve control algorithm was composed of an indoor temperature control algorithm, and a superheat control algorithm. These algorithms were applied to a multi-type air-conditioning system. Test showed good results for the control of a multi-type air-conditioning system.

• Nonlinear Functional Analysis and Applications
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• v.28 no.3
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• pp.613-622
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• 2023

In this paper, finite element method is applied to solve boundary control problem governed by elliptic variational inequality with an infinite number of variables. First, we introduce some important features of the finite element method, boundary control problem governed by elliptic variational inequalities with an infinite number of variables in the case of the control and observation are on the boundary is introduced. We prove the existence of the solution by using the augmented Lagrangian multipliers method. A triangular type finite element method is used.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.32 no.6
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• pp.211-218
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• 1983

In this paper, an attempt is made to match the continuous state trajectory of the digital control system with that of its continuous data model. Matching the state trajectories instead of the output responses assures that the performances of the internal variables of the plant as well as the output variables are preserved in the discretization. The mathematical tool used in this research is an extended maximum principle of the Pontryagin type, which enables one to synthesize a staircase type of optimal control signals, such as the output signal of a zero-order hold asociated with a digital controller. A general mathematical expression of the digital controller which may be used to replace the analog controller of a general system while preserving as mauch as possible the performance characteristics of the original continuous-data control system is derived in this paper.

• Journal of the Korean Mathematical Society
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• v.37 no.4
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• pp.625-643
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• 2000

In this paper we formulate an optimal control problem governed by time-delay Volterra integral equations; the problem includes control constraints as well as terminal equality and inequality constraints on the terminal state variables. First, using a special type of state and control variations, we represent a relatively simple and self-contained method for deriving new necessary conditions in the form of Pontryagin minimum principle. We show that these results immediately yield classical Pontryagin necessary conditions for control processes governed by ordinary differential equations (with or without delay). Next, imposing suitable convexity conditions on the functions involved, we derive Mangasarian-type and Arrow-type sufficient optimality conditions.

• The Journal of the Korea Contents Association
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• v.6 no.2
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• pp.117-126
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• 2006

Although the Java bytecode has numerous advantages, there are also shortcomings such as slow execution speed and difficulty in analysis. In order to overcome such disadvantages, bytecode analysis and optimization must be performed. First control flow of the bytecode should be analyzed, after which information is required regarding where the variables are defined and used to conduct data flow analysis and optimization. There may be cases where variables with an identical name contain different values at a different location during the execution according to the value assigned to a variable in each location. Therefore, in order to statically determine the value and type, the variables must be separated according to allocation. In order to do so, the variables can be expressed using a static single assignment form. After the transformation into a static single assignment form, the type information of each node expressed by each variable and expression must be configured to perform static analysis and optimization. Based on the basic type information, this paper proposes a method for finding related equivalent nodes, setting the nodes with strongly connection components and efficiently assigning each node the type.