• School Mathematics
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• v.4 no.2
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• pp.205-222
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• 2002

In school mathematics, the negative numbers have been instructed using the intuitive models such as the number line model, the counting model, and inductive-extrapolation on the additionand multiplication and using inverse operation on the subtraction and division. Theseinstructions on the negative numbers did not present their formal nature and caused the difficulty for students to understand their operations because of the incomplete function of the intuitive models. In this study, we tried to improve such problems of the instructions of the negative numbers on the basis of the didactical phenomenological analysis. First of all, we analysed the nature of the negative numbers and the cognitive obstructions through the examination about the historic process of them. Second, we examined hew the nature of the negative numbers were analysed and described in mathematics. Third, we explored the improving directions for them on the ground of the didactical phenomenological analysis. In school mathematics, the rules of operations using the intuitive models of the negative numbers have been Instructed rather than approaching toward the nature of them. The negative numbers have been developed from the necessity to find the general solution of equations. The study tries to approach the operations instructions of the negative numbers formative]y to overcome the problems of those that are using the intuitive models and to reflect the formative Furthermore of the negative numbers. Furthermore, we examine the way of the instruction of the negative numbers in real context so that the algebraic feature and the real context should be Interactive.

• Journal of Power Electronics
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• v.10 no.2
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• pp.155-164
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• 2010

This paper presents a voltage control algorithm for a hybrid multilevel inverter based on a staged-perception of the inverter voltage vector diagram. The algorithm is applied to control a three-stage eighteen-level hybrid inverter, which has been designed with a maximum number of symmetrical levels. The inverter has a two-level main stage built using a conventional six-switch inverter and medium- and low- voltage three-level stages constructed using cascaded H-bridge cells. The distinctive feature of the proposed algorithm is its ability to avoid the undesirable high switching frequency for high- and medium- voltage stages despite the fact that the inverter's dc sources voltages are selected to maximize the number of levels by state redundancy elimination. The high- and medium- voltage stages switching algorithms have been developed to assure fundamental switching frequency operation of the high voltage stage and not more than few times this frequency for the medium voltage stage. The low voltage stage is controlled using a SVPWM to achieve the reference voltage vector exactly and to set the order of the dominant harmonics. The inverter has been constructed and the control algorithm has been implemented. Test results show that the proposed algorithm achieves the desired features and all of the major hypotheses have been verified.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.359-364
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• 2004

In this paper, we implemented real-time speaker undependent speech recognizer that is robust in noise environment using DSP(Digital Signal Processor). Implemented system is composed of TMS320C32 that is floating-point DSP of Texas Instrument Inc. and CODEC for real-time speech input. Speech feature parameter of the speech recognizer used robust feature parameter in noise environment that is transformed feature space of MFCC(met frequency cepstral coefficient) using ICA(Independent Component Analysis) on behalf of MFCC. In recognition result in noise environment, we hew that recognition performance of ICA feature parameter is superior than that of MFCC.

• Journal of KIISE:Information Networking
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• v.30 no.2
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• pp.199-206
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• 2003

one of the representative micropayment protocols. The original PayWord system is designed for a user who generates paywords by performing hash chain operation for payment to an only designated vendor. In other words, a user has to create new hash chain values in order to establish commercial transactions with different vendors on the Internet. Therefore, we suggest an efficient scheme that is able to deal with business to different vendors by using only one hash chain operation to supplement this drawback. In this proposed system, a broker creates a new series of hash chain values along with a certificate for the user's certificate request. This certificate is signed by a broker to give authority enabling a user to generate hash chain values. hew hash chain values generated by a broker provide means to a user to do business with multiple vendors.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.1
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• pp.49-57
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• 2011

This paper concentrate on the passengers' perception of risks by analyzing data gathered through a field survey in the South Korean air market. Twenty two Koreans were killed in the accident of PMT Air in the Kingdom of Cambodia on June 25th 2007 and This has caused customers to be more concerned about the safety of airline. Three hundred forty-two samples were collected from field survey at Kimpo International Airport in Seoul and Jeju International Airport on Jeju island and the findings are based on 316 questionnaires. The multiple regression analysis, Analysis of variance (ANOVA), Correlation analysis, T-test were carried out to examine the effect, relationship and difference of data set. The results show that there are differences between passengers' perceived risks in LCC's and those in FSC's. Passengers of LCC's took serious consideration of the type of fleet and feeling physical risk, whereas those of FSC's only took consideration of financial risk.

• Korean journal of food and cookery science
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• v.27 no.1
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• pp.21-31
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• 2011

The purposes of this study were to investigate the gap in perceived importance-performance between dietitians and food service workers regarding school food service sanitation and to analyze items that should be given priority for improvement. Data were collected by 440 food service workers and 71 dietitians in Gyeongbuk province. All statistical analyses were conducted using the SAS package program (version 8.2 for Windows) for descriptive analysis, t-test, and importance-performance analysis (IPA). According to the performance analysis, there were significant differences between dietitians and food service workers in 18 out of the 20 items. In all of 18 items, the evaluated performance scores according to the food service workers were higher than those of the dietitians. In addition, the results of IPA confirmed the following areas as improvement priorities: proper hand washing of food service workers, cleanliness of trays and utensils, monitoring of temperature of refrigerated/frozen foods and quality of the food materials during inspection, proper washing and disinfection of raw vegetables and fruits and maintenance of CCP records, and control of food holding temperature and methods. In conclusion, dietitians should perform education about sanitation management items that have low perceived importance and should make a plan to improve sanitation management after understanding the gap in perceived importance-performance between dietitians and food service workers.

• Fire Science and Engineering
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• v.15 no.1
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• pp.47-54
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• 2001

Similar patterned fire incidents such as, Inchon Live-Hof Pub Restaurant as, Sea-land Children Resort have proven that serious loss of lives were caused by hazardous gas generated from a combustion of interior finish and decorative materials. Therefore, comparing Korean fire regulation with other countries fire code, e.g. UK, USA, France about limitation of interior finish and decorative materials in premises as assemblies, differences & problems have been int estimated and analyzed on hew serious they may affect on fire spread and smoke development based on analyze facts. It is suggested that Korean fire code would be revised in order to reduce hazardous interior finish materials from special occupancy and adapted new test methods to verify proper fire performance in premises as assembles which require a fire certificate. Finally, detailed code alternatives will be suggested in order to set up effective fire regulation, which could promote preventing serious loss of lives in future.

• Ocean and Polar Research
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• v.25 no.4
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• pp.607-615
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• 2003

Many organisms are known to survive in icy environments. These include both over wintering terrestrial insects and plants as well the marine fish inhabiting high latitudes. The adaptation of these organisms is both a fascinating and important topic in biology. Marine teleosts in particular, can encounter ice-laden seawater that is approximately $1^{\circ}C$ colder than the colligative freezing point of their body fluids. These animals produce a unique group of proteins, the antifreeze proteins (AFPs) or antifreeze glycoproteins (AFGPs) that absorb the ice nuclei and prevent ice crystal growth. Presently, there are at least four different AFP types and one AFGP type that are isolated from a wide variety of fish. Despite their functional similarity, there is no apparent common protein homology or ice-binding motifs among these proteins, except that the surface-surface complementarity between the protein and ice are important for binding. The remarkable diversity of these proteins and their odd phylogenetic distribution would suggest that these proteins might have evolved recently in response to sea level glaciations just 1-2 million years ago in the northern hemisphere and 10-30 million years ago around Antarctica. Winter flounder, Pleuronectes americanus, has been used as a popular model to study the regulation of AFP gene expression. It has a built-in annual cycle of AFP expression controlled negatively by the growth hormone. The signal transduction pathways, transcription factors and promoter elements involved in this process have been studied in our laboratory and these studies will be presented.

• Journal of radiological science and technology
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• v.18 no.2
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• pp.61-73
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• 1995

For the managements of the diagnostic X-ray equipments, the authors examined the output of single phase rectification assembly, Three phase rectification assembly and serial radiographic appartus, and got the following conclusions. 1. When the tube voltages in X-ray control panels ware compared to the measured values on the kVp pulse meter, only little differences were detected in all the X-ray equipments. And most of the equipments were all well managed within the internationally permitted limits, excepting the 12.02 % error at 120 kVp in three phase rectifying assembly. 2. As for the X-ray qualities affecting the X-ray images, the serial radiographic apparatus showed excellence, while the single phase rectification assembly were somewhat inferior to the others only maining the internationally recommended limits. 3. The tube voltage ranges where the X-ray output showed excellence were $100{\sim}200\;mA$ in serial radiographic apparatus, $200{\sim}350\;mA$ in three phase rectification assembly and $350{\sim}400\;mA$ in single phase rectification assembly respectively. 4. In the repeatability test of the X-ray equipments, CVs were in the range of $0.0029{\sim}0.049$, which is within the HEW or KS standards. Consequently all the equipments are thought to be well-manage. 5. This study on characteristics and output of the X-ray equipments was accomplished within a limited short time. Long-time researches on the function managements for the X-ray equipments should be followed along with the periodical checking the output for reduction of X-ray exposures to the patients or radio-technologists, and for maintanance and prediction of trouble of the equipments.

• Journal of the Korean Society for Railway
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• v.12 no.3
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• pp.376-381
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• 2009

While applying the systems engineering (SE) in systems development, a series of technical reviews play a critical role and is intended to monitor the status of the progress and outcomes of the project for which appropriate technical plans prepared earlier should be executed. It is noted however that during the technical review executed as planned, a lot of problems usually come out. Included are the ambiguity in the reports of the progress status and outcomes, discrepancies among the opinions from different participants, and the delay in carrying out the tasks. To solve those problems in an early stage, informal reviews are usually adopted before the formal technical reviews are held. A type of the informal reviews is the peer review. This paper is concerned with the peer review process model to make the later technical reviews more effective. Specifically, we first review the necessity and meaning of the peer reviews. We then study a model for the peer review process. To model the process, the methods of an IDEF modeling and schema definition have been applied using a computer-aided SE tool, Cradle(R), in the environment of the national research and development project. As a result, the implemented process model can show hew the peer review process is designed and managed to be utilized in the technical review. The documents related with the peer review process can also be generated automatically from the developed model Database. Finally, a general misunderstanding about the peer review and its improvement plan have also been mentioned.