• Bulletin of the Korean Mathematical Society
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• v.25 no.2
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• pp.185-194
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• 1988

In [2], we have shown that the optimal boundary controls for hyperbolic systems in L$^{2}$-spaces can be attained in a feedback form via Riccati operators. A number of authors [1, 5, 7 and 10] have investigated approximations of Riccati operators arising in distributed parameter systems. They assumed bounded controls for parabolic systems. However, we in this paper study Galerkin approximations of Riccati operators and feedback controls for hyperbolic systems with unbounded control actions. Let us briefly introduce some results of [2]. Let .ohm. be an open bounded region in R$^{n}$ with smooth boundary .GAMMA. where n is a fixed positive integer. We consider a strictly hyperbolic differential operator H(x) of order 1 on .ohm. with noncharacteristic boundary on .GAMMA.

• Speech Sciences
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• v.12 no.1
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• pp.15-25
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• 2005

The purpose of the present study was to investigate the characteristics of metalinguistic awareness of children with specific language impairment. Forty-five children participated in this study; 15 children with specific language impairment (SLI group) whose range of the language age was 4;6-6;6, 15 normal children chronological age matched (CA controls) and 15 normal children language age matched with the SLI group (CA controls). A metalinguistic task involving the identification and revision of syntactic, semantic, and phonologic errors was used. The SLI group performed significantly poorer than CA controls as well as LA controls in identifying and correcting error sentences, especially sentences with syntactic error. These results revealed the relation between language problems of children with SLI and metalinguistic abilities.

• Journal of the Korean Home Economics Association
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• v.45 no.4
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• pp.87-96
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• 2007

The purpose of this study was to investigate the relationship between the father's emotional expressiveness and verbal controls, and his children's social competency depending on gender. Subjects were 156 five-year-old children and their fathers in 4 private kindergarten in Gyeongi province. The data obtained were analyzed by frequencies, percentiles, means, standard deviations, Cronbach's alpha, t-test, and Pearson's correlations. The major findings of this study were as follows: 1) A significant difference was found between the children's gender in terms of children's external behavioral problems in social competency. 2) There was a negative correlation between the fathers' negative emotional expressiveness and their male children's social competency. 3) There was a negative correlation between the fathers' imperative control under verbal controls and their male children's social competency.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.7
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• pp.943-951
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• 1995

In this paper the projective controls, previously derived to preserve the dynamic modes of a state-feedback reference system, are extended to allow the preservation of the modes of a general output-feedback reference system. In general, the extension allows projective controls to be used as a controller approximation technique, where a reduced-order controller is designed to approximate the closed-loop behavior of the higher-order reference controller. This extension is useful if the best available reference control for the system is an output-feedback control. An example shows that the increased design freedom of proposed design method allows the stabilization of a given plant using a lower-order controller than the projective controls with state-feedback reference.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.4 no.4
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• pp.25-34
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• 1981

Recently there has been a marked increase in concern for security in computerized operations. The purposes of computer security controls are to protect against the unauthorized access to and modification of data processing resources, unauthorised access to and modification of data files and software, and the misuse of authorized activities. The controls relate to the physical security of the data processing department and of the areas within the data processing department : to the security of the data files, programs, and system software : and to the human interaction with the data files, programs, and system software. The controls that will be discussed in this paper include : I. Risk on the computer use. II. Methods of risk counter measure. III. Role of system auditing.

• Journal of the Korean Operations Research and Management Science Society
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• v.25 no.1
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• pp.1-13
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• 2000

Electronic Data Interchange (EDI) has a significant impact on business practices by eliminating paper related adult trails and enabling transactions to be processed at high speed without human intervention. Major advantages advangtages and benefits derived from EDI, however, depend upon the usage of EDI controls. Management must determine whether their investment on EDI controls is appropriate, as the establishment of EDI controls demandds much resources and high skills. This study proposes data envelopment analysis model to identify efficient and inefficient EDI control systems in various context of input (formal and automated EDI controls) and output (EDI implementation and performance). DEA can also determine the factors that are significantly different between efficient and inefficient groups. The model is tested using data collected form EDI adopters.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.128-129
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• 2012

This paper proposed the wind turbine simulator for comparative study of the MPPT controls. The development of this wind turbine simulator is based on the torque controlled induction motor. The torque reference is obtained from a mathematical model of wind turbine whereas the inputs are rotor speed, wind speed and fixed-value of pitch angle. By using this wind turbine simulator, the real wind is not needed. Wind speed information can be stored and regenerated anytime. Hence it is possible to apply the same wind speed condition to different MPPT controls. With the same wind speed condition, it can fairly compare the advantages and disadvantages of the MPPT controls. The proposed wind turbine simulator is verified through PSIM simulation.

• ETRI Journal
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• v.40 no.6
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• pp.813-823
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• 2018

In existing mobile computing environments, users need to choose between their privacy and the services that they can receive from an application. However, existing mobile platforms do not allow users to perform such trade-offs in a fine-grained manner. In this study, we investigate whether users can effectively make utility-privacy trade-offs when they are provided with a multilevel privacy control method that allows them to recognize the different quality of service that they will receive from an application by limiting the disclosure of their private information in multiple levels. We designed a research model to observe users' utility-privacy trade-offs in accordance with the privacy control methods and other factors such as the trustworthiness of an application, quality level of private information, and users' privacy preferences. We conducted a user survey with 516 participants and found that, compared with the existing binary privacy controls, both the service utility and the privacy protection levels were significantly increased when the users used the multilevel privacy control method.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.3
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• pp.147-152
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• 2019

With the recent emphasis on the importance of energy conservation, studies on high-efficiency elevator systems are being continuously conducted. Therefore, pulse width modulation converters are commonly used in traction drives on elevator systems. Wide bandgap devices have been increasingly commercialized, and their application to power conversion systems, such as renewable and energy storage system, has been gradually increasing. In this study, a SiC inverter for an elevator traction drive is investigated. In particular, an inverter is designed to minimize stray and parasitic inductance. Input and output filters are designed by considering switching frequency. The designed SiC inverter reduces volume by approximately 32% compared with that of a Si inverter, and power converter efficiency is over 98.8%.

• YAKHAK HOEJI
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• v.57 no.5
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• pp.348-356
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• 2013

The present study investigated the effects of Hovenia Dulcis (HD) fruit extract powder on the improvement of physical activity, especially exercise capacity. Forty mice were divided into 4 groups including normal controls, negative controls, 100 (HD-100) and 200 (HD-200) mg/kg HD fruit extract powder groups for 5-times exercises using treadmill. Normal control did not performed treadmill running but others did 5-times for 10 days. HD fruit extract powders were administrated orally one-times per day for 10 days before treadmill exercise and normal and negative controls were fed with excipient water. After 5-times exercise, blood biochemical analysis showed that aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and creatine phosphokinase (CK) activities and blood lactate concentration were statistically increased in negative controls than in normal controls. They were decreased in HD fruit extract powder groups, compared with negative controls. These results were considered as the effects of HD fruit extract powders on reduced tissue damages during exercise. Other measured indices did not reveal remarkable differences. All together, these results suggest that HD fruit extract powders may enhance the exercise performance by recovering the exercise-fatigue via blood lactate concentration by reducing blood LDH activity and via reduction of blood CK and AST activity.