• 한국안전학회지
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• 제24권2호
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• pp.17-22
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• 2009

Thermal stress and elastic creeping stress analysis was conducted by finite element method to simulate start-up process of a boiler header of 500MW standard fossil power plant. Start-up temperature and operating pressure history were simplified from the real field data and they were used for the thermal stress analysis. Two kinds of thermal stress analysis were considered. In the first case only temperature increase was considered and in the second case both of temperature and operating pressure histories were considered. In the first analysis peak stress was occurred during the temperature increase from the room temperature. Hence cracking or fracture may occur at the temperature far below the operating maximum temperature. In the results of the second analysis von Mises stress appeared to be higher after the second temperature increase. This is due to internal pressure increase not due to the thermal stress. When the stress components of radial(r), hoop($\theta$) and longitudinal(z) stress were investigated, compression hoop stress was occurred at inner surface of the stub tube when the temperature increased from room temperature to elevated temperature. Then it was changed to tension hoop stress and increased because of the operating pressure. It was expected that frequent start-up and shut-down operations could cause thermal fatigue damage and cracking at the stub tube hole in the header. Elastic-creeping analysis was also carried out to investigate the stress relaxation due to creep and stabilized stress after considerable elapsed time. The results could be used for assessing the creep damage and the residual life of the boiler header during the long-tenn service.

• 한국수소및신에너지학회논문집
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• 제22권6호
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• pp.765-771
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• 2011

This study was conducted to investigate the effect of heat treatment on the start-up performance for anaerobic hydrogen fermentation of food waste. The result showed that hydrogen production was $0.61{\pm}0.31$ mol $H_2$/mol hexose with heat-treatment of food waste at $70^{\circ}C$ for 60 min whereas it was $0.36{\pm}0.31$ mol $H_2$/mol hexose without heat-treatment of one. The heat treatment of food waste enhanced hydrogen yield due probably to the increase of hydrolysis as well as the decrease of non-hydrogen fermentation microorganisms. The removal efficiency of carbohydrate in reactors regardless of heat treatment of food waste maintained over 90%. The hydrogen conversion efficiency from food waste was 1.7-6.3% with heat-treatment whereas it was 0.7-4.5% without heat-treatment. At the time of switchover from batch to continuous operation, lactate concentration was high compared to the n-butyrate concentration in anaerobic hydrogen fermentation reactor without heat-treatment. Anaerobic hydrogen fermentation of food waste with heat treatment was stable in start-up periods because lactate concentration could be maintained at a relatively low compared to n-butyrate concentration due to the decrease of non-hydrogen fermentation microorganisms.

• 한국자동차공학회논문집
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• 제23권1호
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• pp.122-129
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• 2015

Excessive overheating to a manual transmission clutch system under operating conditions can be considered the main reason of its performance degradation. The clutch system has to be ensured with its service life by showing that it passes the extreme tests called anti-fade test and hill start test in a certain design step. In general, design feedbacks from these kinds of the experiments are adapted to the system to enhance its performance. However, it usually takes much time and costs a lot due to the repetition of the tests. In this research, a process to calculate temperature of the clutch system was developed to determine whether the design can be passed the anti-fade test and hill start test in the design phase. The process incorporates many CAE techniques such as heat transfer analysis using 1D dynamic simulation method, system dynamics, CFD and parametric optimization. CFD is utilized to analyze 3-dimensional heat transfer of the clutch system and fluid dynamics of air in the clutch housing. The process was applied for the clutch systems in several vehicle models. The results was compared with those of the experiment. The applicability of the developed process was verified by comparing the predicted results with experimental results.

• 한국정보기술학회논문지
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• 제17권6호
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• pp.9-16
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• 2019

최근 제조 공정을 개선하려는 기업들은 스마트 팩토리를 도입, 이에 따른 도약이 특별히 눈에 띈다. 이는 최소한의 수동 제어를 통해 완벽하게 생산시설의 프로세스를 수행하는 스마트 팩토리의 영역을 최대화하고 추론의 오차를 최소화 하는 것이 최종 목적이다. 본 연구는 무인 생산, 관리, 포장, 배송 관리를 위한 프로젝트의 일부로써 무인생산의 자동화 설비의 철근 추적을 통해 롤러의 자동 교정을 수행하기 위해 철근 추적 시작점 검출에 대한 연구이며, 시작지점부터 끝점까지의 위치를 정확히 추적해야 하는 요구사항을 만족해야 한다. 추적성능을 높이기 위해서는 시작점 설정이 주요한데 기존의 시간 기반 검출방법을 통해서는 조도, 분진 등 환경에 따라 추적오류의 발생 확률이 높다. 본 논문에서는 환경에 따른 오차를 줄이기 위해 고속 IR카메라의 평균 밝기 변화를 이용한 시작점 검출 방법을 제안하며, 제안 사항을 통해 15%이상의 성능 향상을 확인하였다.

• 대한의용생체공학회:의공학회지
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• 제43권6호
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• pp.424-433
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• 2022

As the proportion of non-contact telemedicine increases and the number of electrocardiogram (ECG) data measured using portable ECG monitors increases, the demand for automatic algorithms that can precisely analyze vast amounts of ECG is increasing. Since the P, QRS, and T waves of the ECG have different shapes depending on the location of electrodes or individual characteristics and often have similar frequency components or amplitudes, it is difficult to distinguish P, QRS and T waves and measure each parameter. In order to measure the widths, intervals and areas of P, QRS, and T waves, a new algorithm that recognizes the start and end points of each wave and automatically measures the time differences and amplitudes between each point is required. In this study, the start and end points of the P, QRS, and T waves were measured using six Deep Neural Networks (DNN) that recognize the start and end points of each wave. Then, by synthesizing the results of all DNNs, 12 parameters for ECG characteristics for each heartbeat were obtained. In the ECG waveform of 10 subjects provided by Physionet, 12 parameters were measured for each of 660 heartbeats, and the 12 parameters measured for each heartbeat well represented the characteristics of the ECG, so it was possible to distinguish them from other subjects' parameters. When the ECG data of 10 subjects were combined into one file and analyzed with the suggested algorithm, 10 types of ECG waveform were observed, and two types of ECG waveform were simultaneously observed in 5 subjects, however, it was not observed that one person had more than two types.

• 공업화학
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• 제34권5호
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• pp.541-547
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• 2023

The effect of temperature and influent alkalinity/ammonia (K/A) ratio on the start-up of the partial nitrification (PN) process for an activated sludge-based domestic wastewater treatment was studied. Two different sequence batch reactors (SBR) were operated at 26 ℃ and 32 ℃. The relationship between temperature and the concentration of free ammonia (FA) and free acid nitrite (FNA) was investigated. A stable PN process was achieved in the 32 ℃ reactor when the influent ammonium concentration was lower than 150 mg-N/L. In contrast, the PN process in the 26 ℃ reactor had a higher nitrite accumulation rate (NAR) and ammonium removal efficiency (ARE) when the influent ammonia concentration was increased to more than 150 mg-N/L. Then three different ranges of the K/A ratio were applied to an SBR reactor. In the K/A range of 2.48~1.65, the SBR reactor achieved the highest NAR ratio (75.78%). This ratio helps to achieve the appropriate level of alkalinity to maintain a stable pH and provide a sufficient amount of inorganic carbon source for the activity of microorganisms. At the same time, FA and FNA values also reached the threshold to inhibit nitrite-oxidizing bacteria (NOB) without a significant effect on ammonia-oxidizing bacteria (AOB). Results showed that the control of temperature and K/A ratio during the start-up period may be important in establishing a stable and steady PN process for the treatment of domestic wastewater.

• 산경연구논집
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• 제10권10호
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• pp.67-79
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• 2019

Purpose - The purpose of this study was to explore the model that supports the recipient country by using the ODA (Official Development Assistance) project and at the same time fits the global start-up/employment support of donor country with CSV business model. Specifically, we wanted to examine the feasibility of the project based on the existing ODA projects. Research design, data, and methodology - As the methodology, case studies and interview were conducted as well as literature studies. The case analysis is based on a press release of the entire KOICA's ODA project, which has been implemented for one year, based on 2017. After consideration, the actual results and future feasibility were analyzed. The interviews were conducted on senior Korean officials and Indian officials involved in Vietnam's ODA project. Results - As a result, some of the project cases applied and analyzed according to the model of this study were judged to be highly potential. Based on the results of this analysis, as the model derived from this study pursues, the global business model is developed under the CSV (Creating Shared Value) strategy through ODA projects to support recipient countries and global start-up/employment support of donor country. The possibility of simultaneously pursuing this model based on CSV business model was also confirmed. Conclusions - In the past, free aid agencies like KOICA focused solely on supporting recipient countries, but in terms of sustainability, they could discover the potential of supporting the global start-up/employment of the donor country using CSV business model in ODA project. In this study, we tried to find the theoretical background and potential possibilities in some ODA projects based on CSV business model. As a result of the analysis of KOICA ODA projects in 2017 and interviews, some ODA projects could be used to improve the economic development of the recipient country as well as the global start-up/employment of the donor country. Therefore, it is necessary for the ministries of the government to promote ODA projects to understand the framework that achieves these two objectives simultaneously and to promote ODA projects based on various strategic considerations.

• 디지털융복합연구
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• 제17권6호
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• pp.201-209
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• 2019

최근 정부 및 공공, 민간 분야의 다양한 창업경진대회를 통해 대다수의 예비 창업자 및 초기 창업자들의 비즈니스 모델이 발전되고 사업화 가능성이 제고되는 있는 반면에 일부 우수 참가자들의 사업 아이디어가 소멸되는 문제를 개선해야 할 필요가 제기되고 있다. 이에 본 연구는 국내 주요 창업경진대회 운영자와 주요 참가자 등을 대상으로 한 실태조사 결과를 기반으로 다양한 창업경진대회의 현황을 분석하고 정책적이고 실무적인 개선방안 등을 제시하고자 한다. 주요 연구 결과 첫째, 경진대회 운영에서는 이벤트 성격의 탈피, 대회 진행시 창업기업의 비즈니스 모델 공개 지양, 투입 시간을 고려한 수상금액 책정, 형식적 절차의 축소, 운영자들의 권위적인 태도 지양, 서류양식의 간소화, 발표자료 활용방식 개선, 경진대회의 목적과 모집대상의 정확한 명시 등이 요구된다. 둘째 전문성을 갖춘 심사위원 및 멘토진의 보완이 필요하겠다. 분야별로 전문성을 갖춘 심사위원 멘토 구성, 심사위원 구성 시 지역별 배분, 창업경험 보유 심사위원 위촉, 심사위원에 대한 사후 평가시스템 도입이 필요하겠다. 셋째, 제조업 등에 치중될 것이 아니라 산업분야별로 특성화된 경진대회 운영이 필요하다고 하겠다. 향후 연구에서는 운영주체들을 대상으로 심층 인터뷰 및 실증적인 연구가 보완될 필요가 있을 것이다.

• The Journal of the Acoustical Society of Korea
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• 제17권2E호
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• pp.38-46
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• 1998

In this paper, we propose a remote speech input device, a new method of user-friendly speech input in spontaneous speech recognition system. We focus the user friendliness on hands-free and microphone independence in speech recognition applications. Our method adopts two algorithms, the automatic speech detection and the microphone array delay-and-sum beamforming (DSBF)-based speech enhancement. The automatic speech detection algorithm is composed of two stages; the detection of speech and nonspeech using the pitch information for the detected speech portion candidate. The DSBF algorithm adopts the time domain cross-correlation method as its time delay estimation. In the performance evaluation, the speech detection algorithm shows within-200 ms start point accuracy of 93%, 99% under 15dB, 20dB, and 25dB signal-to-noise ratio (SNR) environments, respectively and those for the end point are 72%, 89%, and 93% for the corresponding environments, respectively. The classification of speech and nonspeech for the start point detected region of input signal is performed by the pitch information-base method. The percentages of correct classification for speech and nonspeech input are 99% and 90%, respectively. The eight microphone array-based speech enhancement using the DSBF algorithm shows the maximum SNR gaing of 6dB over a single microphone and the error reductin of more than 15% in the spontaneous speech recognition domain.

• World Technopolis Review
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• 제4권2호
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• pp.87-103
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• 2015

This paper aims to explore how firms develop and grow in regional clusters based in a developing country. The argument is that start-ups / small and large firms are able to grow by developing linkages or networks for resources within clusters - and this tenet is based on studies of firms that are based from such clusters as Silicon Valley in the US, Cambridge in UK and other clusters from which have evolved over long periods of time. Most of the time we hear narratives from the developed world where there are brownfield cluster development efforts. In developing countries governments are making efforts to develop clusters from scratch - which in this paper we term as greenfield cluster versus a brownfield development, which is where the cluster is developed based on existing and new organisations in a region. In this paper, we believe the context of clusters can be important in determining the way firms develop linkages for their growth - and we look at two contexts in Malaysia ie. A greenfield cluster and a brownfield cluster. The paper presents findings from case studies of firms in a greenfield cluster (Cyberjaya) and a brown field cluster (Penang) in Malaysia. The cases reveal fairly different approaches to development of linkages or networks, which we hope will provides insights to cluster development officials and policy makers and implications to researchers for developing studies of clusters and innovation systems.