• The Journal of Korean Association of Computer Education
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• v.11 no.1
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• pp.23-32
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• 2008

In this paper, we have investigated the education effect of a web-based virtual laboratory for digital logic circuits which consists of multimedia contents about the usages of equipments for logic circuit experiments and the experimental logic circuits. In case of the engineering experiment of the lower grades in universities, preunderstanding about the usages of experimental equipments and the experimental circuits is necessary for the learners to conduct the experiments well. But it is impossible for the learners to have access to the real experimental equipments earlier due to the lack of equipments and the difficulty in management of the equipments. We have implemented the digital logic circuit virtual laboratory which provides the same experimental environment as a real experimental lab, and the learner can conduct the same experiments as the real ones before the real laboratory class. The learners using the laboratory have reduced the experiment completion time by the average of about 8.2% during a term, compared with the learners not using the lab.

• Journal of Korea Multimedia Society
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• v.2 no.3
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• pp.265-276
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• 1999

Video on Demand (VOD) system is definitely one of main applications in upcoming multimedia era. In this research, we have designed and implemented a host-based scalable VOD system (SVOD) which is composed of low cost PC servers and runs on Linux kernel that is currently spotlighted in enterprise and research domains. Our contribution is as follows: first, the previous Ext2 file system was modified to efficiently support continuous media like MPEG stream. Second, the storage server features a host-based scalable architecture. Third, a software MPEG decoder was implemented using Microsoft's DirectShow$\circledR$COM. Finally, flow control between client and server is provided to suppress overflow and underflow of client circular buffer and supports FF VCR operation. We have known that it is possible to develop a thread-based and scalable VOD system on low cost PC servers and free Linux kernel.

• The Transactions of the Korea Information Processing Society
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• v.7 no.7
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• pp.2149-2160
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• 2000

Recently many efforts on the development of automatic processing system for delivery sequence sorting have been performed in ETRI, which requires the use of postal4-state bar code system to encode delivery points. The 4-state bar code called postal 4-state barcode for high speed processing that has been specifically designed for information processing of logistics and automatic processing of he mail items. The Information of 4-state bar code indicates mail data such as post code, delivery sequence number, error correction code worked, customer information, and a unique ID. This appear addresses the issue on he reduction of reading error in postal 4-state raster beam based bar code reader. The raster beam scanning features are the unequally distributed number of spots per each unit, which cause reading errors. We propose a method for reducing the bar code reading error by adjusting measured values of bar code width to its average value over each interval. The test results show that the above method reduces the average reading error rate approximately by 99.88%.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.374-379
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• 2004

H-브릿지 멀티레벨 인버터는 여러 개의 단상 Power Cell을 직렬로 연결함으로써 저전압 전력용 반도체를 사용하여 고전압을 얻을 수 있고, 정현파에 가까운 출력전압 파형을 얻을 수 있는 멀티레벨 인버터 토폴로지이다. 본 토폴로지는 출력전압 레벨에 비례하여 Power Cell의 수가 증가하므로, 주제어기의 연산능력에 대한 부담증가와 신호선의 많아지는 단점이 있다. 따라서 Power Cell제어를 직접적인 PWM 신호가 아닌 통신을 사용함으로써 이러한 단점을 극복할수 있으며, 신뢰성 측면이나 보수/유지 측면에서도 유리하다. 본 논문은 산업현장에서 신뢰성을 인정받아 많이 사용되고 있는 직렬통신 방식의 일종인 CAN통신 인터럽터를 이용한 H-브릿지 멀티레벨 인버터 Power Cell의 PWM 동기화 및 위상 전이 방법에 관한 것이다. 제안된 방법의 주요 장점은 주제어기와 셀 제어기 사이에 직렬통신(CAN)을 사용함으로써 주제어기와 셀 제어기의 신호선의 단순화, 주제어기의 부담 감소, Power Cell의 모듈화, 셀 단위의 보호동작 용이, 확장성 향상 그리고 제어 신호 및 Power Cell의 신뢰성을 향상에 있다. 13레벨로 구성된 H-브릿지 멀티레벨 인버터 시험을 통해 제안된 방법의 타당성과 신뢰성을 입증하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.6
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• pp.620-627
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• 2004

As h-bridge multilevel inverter is connected with series of single phase power cell, so it obtain high voltage using low voltage power semi-conductor and output voltage similar to sine wave. In this topology, the number of power cell increases in proportion to the output voltage level. Therefore, there are drawbacks that are responsibility against operating ability of main controller and signal wire increase. However, we can overcome this problems by the substitution of serial communication for the PWM signal in power cell control. Additionally, it has merits of reliability and maintenance. This paper deals with the synchronization and phase-shift method of power cell PWM using CAN(Controller Area Network) communication interrupt in H-bridge multilevel inverter. The advantages of proposed method are signal-line simplification using serial communication between main controller and cell controller, burden reduction in main controller, modularization of power cell, easy protection of each power cell, expandability improvement and reliability increase of control signal and power cell. This paper establishes propriety and reliability of proposed method through experiment of 13-level H-bridge multilevel inverter.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.389-392
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• 2008

Electric-furnace-slag has the expansion, due to the reaction with water and free Cao. So compared with the blast-furnace-slag, the recycling range of EFS is subject to restriction. But the expansive reaction of EFS is removed, the it is possible to use aggregate for concrete. This study is the basic properties of concrete to used stabilized EFS(oxidized EFS). The EFS is used fine aggregate in concrete, and replaced by sea-sand(natural sand). The replacement ratio are 0%, 25%, 50%, 75%, 100%. The result of study, to used oxidized EFS-sand, the flowability and the compressive strength is increased. Also it is possible to reduce the Bleeding. It is necessary more study about using the EFS aggregate, like the durability, the mechanical property for concrete

• Journal of the Korean Ceramic Society
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• v.40 no.2
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• pp.159-166
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• 2003

The preparation method for composite membranes of high temperature operation above $100^{\circ}C$ for Polymer Electrolyte Membrane Fuel Cells (PEMFCs ) was presented, using perfluorosulfonylfluoride Nafion resin and mordenite, in addition to the physical properties, proton conductivity and single cells performance for it. The composite membranes were fabricated via melting of Nafion resin with various mordenite content. As the increase of mordenite content, at high temperature range, proton conductivity of the composite membrane increased due to the late dehydration rate of existent water in the mordenite. Also, from the result of the current-voltage relationship for single cells under $130^{\circ}C$ operation condition, the composite membrane cell with l0 wt% mordenite content showed better performance than that of the others over the entire current density range. This result indicated that the existent water in the composite membrane with l0 wt% mordenite content was higher than that with the others, thereby maintains its conductivity. Based upon the results of experiments, therefore, a Nafion/mordenite composite membrane prepared by this work is thought to be a satisfactory polymer electrolyte membrane for PEMFC operation above $100^{\circ}C$.

• The Korean Journal of Ecology
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• v.22 no.5
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• pp.255-263
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• 1999

Entomopathogenic nematodes were isolated through the investigation of soil samples from various biotopes in south Korea, the efficiency of isolation for highly pathogenic nematodes to silkworms (Bombyx mori) was as high as 28 %. Twenty-eight strains of nematodes, selected among 100 samples by silkworms were confirmed the pathogenicity, multiplicity, and tolerance against various condition of preservation. Pathogenicity of the nematode isolates to agricultural and environmental pests such as Calliphora vomitoria, Pseufaletia separata, Palomena angulosa, and Melolontha incana were high. Mortality was varied from 20 to 100% by the pest insects and nematode strains. The high detectablity of entomopathogenic nematodes resulted from the methods of collection for soil samples within 10 cm depth after eliminating dried soil surface and the use of silkworm trap. High population of entomopathogenic nematodes represented the strong activity and broad action radius in the environment. Most of the nematode isolates were successfully cultured on the silkworm host as well as on artificial media, and proved their potential for the use of biological control agent.

• The Journal of the Acoustical Society of Korea
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• v.19 no.1
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• pp.4-10
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• 2000

The work presented in this paper is about a postprocessor, which improves the performance of automatic speech segmentation system by correcting the phoneme boundary errors. We propose a postprocessor that reduces the range of errors in the auto labeled results that are ready to be used directly as synthesis unit. Starting from a baseline automatic segmentation system, our proposed postprocessor trains the features of hand labeled results using multi-layer perceptron(MLP) algorithm. Then, the auto labeled result combined with MLP postprocessor determines the new phoneme boundary. The details are as following. First, we select the feature sets of speech, based on the acoustic phonetic knowledge. And then we have adopted the MLP as pattern classifier because of its excellent nonlinear discrimination capability. Moreover, it is easy for MLP to reflect fully the various types of acoustic features appearing at the phoneme boundaries within a short time. At the last procedure, an appropriate feature set analyzed about each phonetic event is applied to our proposed postprocessor to compensate the phoneme boundary error. For phonetically rich sentences data, we have achieved 19.9 % improvement for the frame accuracy, comparing with the performance of plain automatic labeling system. Also, we could reduce the absolute error rate about 28.6%.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.179-179
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• 2011

근래 농촌지역에서의 하천 및 저수지의 수질오염에 관하여 관심이 고조됨에 따라 비오염원에 대한 파악과 대책을 세우기 위해 관련분야에서 많은 연구가 진행 되고 있다. 비점오염원은 주로 강우나 유출에 의해 배출되기 때문에 배출 장소와 경로가 불분명하고 다양하다. 비점오염의 관리를 위한 유역모델로 SWAT (Soil and Water Assessment Tool) 모델을 이용한 연구가 광범위하게 사용되고 있다. 그러나 SWAT 모델은 유역모델로써 농촌지역에 논, 밭에서의 비점오염원 기작을 표현하기에는 공간적 범위의 한계가 있다. 이에 본 연구에서는 예당저수지 유역(465.12 km2)을 대상으로 유역규모의 SWAT 모델과 유역-필드규모에 적용 가능한 SWAT-APEX (Agricultural Policy/Environmental eXtender) 모델의 수질(T-N, T-P) 모의결과를 비교하여 SWAT-APEX 모델의 적용성을 평가하고자 하였다. 모형의 적용을 위한 입력자료로 기상자료와 지형자료를 구축하였으며 기상자료로 예당저수지유역 3개의 강우관측소 자료를 수집하여 구축하였으며, 지형자료로 격자크기 30m의 DEM (Digital Elevation Model)과 농촌진흥청에서 제공하는 1:25,000 정밀토양도와 토지이용도는 환경부로부터 1:25,000 중분류 토지이용도를 이용하였다. 또한 환경부에서 제공하는 월단위 하천수질 자료(기간)를 구축하여 모형의 검증을 실시하였다. 분석과정으로 SWAT 모델에서의 유역차원 수문, 수질 모의를 한 후, APEX 모델을 이용하여 소유역별 논, 밭에 대한 필드단위에 오염물질 모의 후 각각 소유역 출구에서 APEX 모델에 결과를 반영한 SWAT-APEX 모의를 거쳐 최종 유역출구에서의 유출량과 수질항목을 분석하였다. 모의 결과 유출량에 대해 Nash와 Sutcliffe (1970)가 제안한 모델효율성계수 (Model Efficient, ME)는 0.67, 결정계수는 0.69 그리고 수질항목의 결정계수는 각각 0.77, 0.75으로 분석되었다. 또한, SWAT-APEX 모의 결과 수질항목의 결정계수는 각각 0.80, 0.72이었다. 따라서, 본 연구에서 농촌지역의 비점오염원 모의는 필드모의를 반영한 SWAT-APEX 모델 결과가 SWAT 모델만 적용한 결과보다 정확한 비점오염 모의가 이루어졌다고 판단 할 수 있다.