• Title/Summary/Keyword: Research performance-based class

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Design and Construction of a Bottoming Organic Rankine Cycle System for an Natural Gas Engine (가스엔진용 유기랭킨사이클의 설계 및 제작)

  • Lee, Minseog;Baek, Seungdong;Sung, Taehong;Kim, Hyun Dong;Chae, Jung Min;Cho, Young Ah;Kim, Hyoungtae;Kim, Kyung Chun
    • Journal of the Korean Institute of Gas
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    • v.20 no.6
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    • pp.65-72
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    • 2016
  • ORC system was designed and constructed for utilizing the heat of the exhaust gas and coolant released from the gas engine which was modified to use natural gas as a fuel. In this paper the components of the ORC system were designed and manufactured based on measured data of the gas engine. The components are composed of two plate heat exchanger, the 5kW-class expander and multi stage centrifugal pump. The thermodynamic performance of the ORC system was analyzed by using the electric heater. Also, the developed ORC system was implemented to modified natural gas engine. Two gas engines were used to supply heat to the ORC system. As a result of test bench, when the heat source temperature is $110^{\circ}C$ expander shaft power, the pressure ratio and cycle efficiency is 5.22kW, 7.41, 9.09%. As a result of field test, when the heat source temperature is $86^{\circ}C$ expander shaft power, the pressure ratio and cycle efficiency is 2kW, 3.75, 6.45%.

An Exploratory Study on the Industry Training Activation for College's Professor -Based on Collaborative Action Research- (전문대학 교수의 산업체 연수 활성화를 위한 탐색적 연구 -협력적 실행연구를 중심으로-)

  • Namgung, Seon-Hye;Kim, Hyun-Jung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.11
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    • pp.361-367
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    • 2019
  • This exploratory study investigated the real time adaptability of industry training for college professors. For this study, the researcher whose college's professor in the department of early childhood education used collaborative action research. This research was conducted in a class of five year old children of a daycare center in D city. The researcher and the homeroom teacher interacted with each other through 4 steps during the researcher's training period. The first step was group formation between the researcher and the teacher. The second step was problem identification. The third step was a review of the literature. The forth step was problem-solving. The researcher and teacher finally developed a rhythm movement program that was based on fundamental motor performance of young children. Through this collaborative effort, the researcher and teacher had the opportunity to improve their professionalism. Especially, the researcher improved her understanding and knowledge of teaching young kids. The result of this study is meaningful in that it provided basic data to improve training of college professors.

Optimal Design Method of 1-Port Surge Protective Device Based on Zinc Oxide Varistor (선화아연바리스터 기반의 1-포트 서지보호장치의 최적 설계 기법)

  • Jeong, Tae-Hoon;Kim, Young-Sung;Park, Geun-Bo;Lee, Seung-IL
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.4
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    • pp.93-102
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    • 2018
  • This paper reports a Surge Protective Device (SPD) that is used to protect an automatic metering interface (AMI) power supplies of communication equipment on a low-voltage distribution system from a lightning current. The surge protective device (SPD) can be classified as one-port SPDs and two-port SPDs with decoupling elements depending on the connection type. The protection of internal systems against the lightning current may require a systematic approach consisting of coordinated SPDs. To deal with this, the definition of a lightning protection zone (LPZ) was studied and interpreted through a theoretical review. Because the lightning current resulting from a lightning surge is considerably high, there is limited protection from one SPD; therefore, coordinated cascaded MOV-based SPDs are installed to solve this problem. Regarding the power grid mentioned in this paper, a class II SPD for the low-voltage distribution system installed on the border of LPZ1 and LPZ2, which establish a protection coordination with the Arrester (LA, SA) that corresponds to the LPZO installed on the MOF stage connected to one system were designed to protect various communication (control) equipment, including the automatic meter reading system inside the branch-type electric supply panel of a building, not the incoming side of one system. In addition, performance-related tests were done by a comparison with the existing method through testing, and the optimal design was achieved for the 1-port SPD that uses a series connection and can bleed load current without any decoupling element.

Estimation of Fish Species Diversity of Small and Medium Rivers of Korea with Fish Species-Habitat Relationship Models od GAP (GAP기법을 이용한 종소하천의 어류종다양성 예측기법 연구)

  • 박종화;홍성학
    • Spatial Information Research
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    • v.6 no.1
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    • pp.91-102
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    • 1998
  • The objectives of this research were to develop fish-habitat relationship models which can be used to estimate fish species riclmess of small and medium rivers in Korea, and test the accuracy of the models. The models are based on the Aquatic GAP Analysis model in the New York Cooperative Fish & Wildlife Research Unit (19%), and they employ three habitat factors; river size, physical habitat, and water quality of each river segment. Model 1 and model II are based on the water quality standard for life support of EP A and the water quality class of Korea, respectively. Test sites for this study include one urban stream and three less spoiled tributaries of the Han River. The results of this research can be summarized as follows. First, the number of habitat types identified by model I and model II are nine and 14, respectively. Second, the average accuracy of the three distribution maps of rare or endangered fish species are 80.6% (model 1) and 81.2% (model II). Third, the accuracy of fish species richness are 94% (model 1) and 95% (model II), and the water quality is the most important factor affecting fish species richness. Fourth, the accuracy of fish species list are 50.5% (model 1) and 68.7% (model II), but the accuracy of less spoiled stream segments and that of polluted stream segments are 67.1% and 86.5%, respectively. Finally, it can be concluded that the overall performance of model II is better than that of model I at our test sites.

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Effect of Systems Thinking Based STEAM Education Program on Climate Change Topics (시스템 사고에 기반한 STEAM 교육 프로그램이 기후변화 학습에 미치는 효과)

  • Cho, Kyu-Dohng;Kim, Hyoungbum
    • The Journal of the Korea Contents Association
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    • v.17 no.7
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    • pp.113-123
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    • 2017
  • This research is designed to review the systems thinking and STEAM theory while ascertaining the effects of the classroom application of the STEAM programs based on systems thinking appropriate for studying climate change. The systems thinking based STEAM program has been developed by researchers and experts, who had participated in expert meetings in a continued manner. The program was applied to science classes over the course of eight weeks. Therefore, the application effects of the systems thinking based STEAM program were analyzed in students' systems thinking, STEAM semantics survey, and students' academic achievement. The findings are as follows. First, the test group has shown a statistically meaningful difference in the systems thinking analysis compared to the control group in the four subcategories of 'Systems Analysis', 'Personal Mastery', 'Shared Vision' and 'Team Learning' except for 'Mental Model'. Second, in the pre- and post-knowledge tests, the independent sample t-test results in the areas of science, technology, engineering, art and mathematics show statistically meaningful differences compared to the control group. Third, in the academic performance test regarding climate change, the test group displayed higher achievement than the control group. In conclusion, the system-based STEAM program is considered appropriate to enhance amalgamative thinking skills based on systems thinking. In addition, the program is expected to improve creative thinking and problem-solving abilities by offering new ideas based on climate change science.

Anomaly Detection for User Action with Generative Adversarial Networks (적대적 생성 모델을 활용한 사용자 행위 이상 탐지 방법)

  • Choi, Nam woong;Kim, Wooju
    • Journal of Intelligence and Information Systems
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    • v.25 no.3
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    • pp.43-62
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    • 2019
  • At one time, the anomaly detection sector dominated the method of determining whether there was an abnormality based on the statistics derived from specific data. This methodology was possible because the dimension of the data was simple in the past, so the classical statistical method could work effectively. However, as the characteristics of data have changed complexly in the era of big data, it has become more difficult to accurately analyze and predict the data that occurs throughout the industry in the conventional way. Therefore, SVM and Decision Tree based supervised learning algorithms were used. However, there is peculiarity that supervised learning based model can only accurately predict the test data, when the number of classes is equal to the number of normal classes and most of the data generated in the industry has unbalanced data class. Therefore, the predicted results are not always valid when supervised learning model is applied. In order to overcome these drawbacks, many studies now use the unsupervised learning-based model that is not influenced by class distribution, such as autoencoder or generative adversarial networks. In this paper, we propose a method to detect anomalies using generative adversarial networks. AnoGAN, introduced in the study of Thomas et al (2017), is a classification model that performs abnormal detection of medical images. It was composed of a Convolution Neural Net and was used in the field of detection. On the other hand, sequencing data abnormality detection using generative adversarial network is a lack of research papers compared to image data. Of course, in Li et al (2018), a study by Li et al (LSTM), a type of recurrent neural network, has proposed a model to classify the abnormities of numerical sequence data, but it has not been used for categorical sequence data, as well as feature matching method applied by salans et al.(2016). So it suggests that there are a number of studies to be tried on in the ideal classification of sequence data through a generative adversarial Network. In order to learn the sequence data, the structure of the generative adversarial networks is composed of LSTM, and the 2 stacked-LSTM of the generator is composed of 32-dim hidden unit layers and 64-dim hidden unit layers. The LSTM of the discriminator consists of 64-dim hidden unit layer were used. In the process of deriving abnormal scores from existing paper of Anomaly Detection for Sequence data, entropy values of probability of actual data are used in the process of deriving abnormal scores. but in this paper, as mentioned earlier, abnormal scores have been derived by using feature matching techniques. In addition, the process of optimizing latent variables was designed with LSTM to improve model performance. The modified form of generative adversarial model was more accurate in all experiments than the autoencoder in terms of precision and was approximately 7% higher in accuracy. In terms of Robustness, Generative adversarial networks also performed better than autoencoder. Because generative adversarial networks can learn data distribution from real categorical sequence data, Unaffected by a single normal data. But autoencoder is not. Result of Robustness test showed that he accuracy of the autocoder was 92%, the accuracy of the hostile neural network was 96%, and in terms of sensitivity, the autocoder was 40% and the hostile neural network was 51%. In this paper, experiments have also been conducted to show how much performance changes due to differences in the optimization structure of potential variables. As a result, the level of 1% was improved in terms of sensitivity. These results suggest that it presented a new perspective on optimizing latent variable that were relatively insignificant.

Preliminary Research of Regenerative Cooling Channel Design for Small Scale Bipropellant Thruster (소형 이원추진제 추력기를 위한 재생냉각 유로형상 설계에 대한 선행연구)

  • Jang, Dong-Wook;Jo, Sung-Kwon;Cho, Hwang-Rae;Bang, Jeong-Seok;Kwon, Se-Jin
    • Journal of the Korean Society of Propulsion Engineers
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    • v.16 no.2
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    • pp.1-9
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    • 2012
  • Applicability of regenerative cooling in 2,500 N-class bipropellant thruster using hydrogen peroxide and kerosene was considered for improvement of performance and application in various missions. Calculation was performed by one dimensional approach using hydrogen peroxide as a coolant. The heat flux of thruster at nozzle throat was estimated at 18 - 20 MW/$m^2$. Designed cooling channel width and height were 2.5 mm and 0.5 mm, respectively. Based on designed cooling channel configuration, flat plate model was manufactured and tested for estimation of pressure drop in cooling channel, and CFD analysis was compared with the test result. The maximum error between CFD analysis and experimental result was approximately 13% and average error was approximately 5%.

Structural Properties of High-Strength and Low-Yield-Steel Beam-Column for High-Rise Architecture Structure (건축구조용 저항복 고장력강 Beam-Column의 구조특성)

  • Kim, Jong-Sung;Meng, Ming Hua
    • Journal of Korean Society of Steel Construction
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    • v.24 no.1
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    • pp.13-21
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    • 2012
  • Recently, the development of high-strength thicker steel plate above 600MPa is becoming active due to the increase in both height and member size of architectural structure. However, such steel, which is being investigated in Korea nowadays, has possibility of limited practical application because of high design code strength and high-yield ratio. Therefore, this study performed the validation for the structural performance of beam-column with combined axial force and bending moment whether this beam-column might be attributable as an architectural purpose steel. This study was conducted from the result of monotonic loading test of beam-column, based on the material properties of low-yield, 600MPa class steel which was developed during 1988-1993 in Japan. This study might provide the fundamental database for practical research for these steel which are actively being tested in Korea.

Research on a 2.5kW 8-Phase Bi-directional Converter for Mild Hybrid Electric Vehicles (마일드 하이브리드 전기 차량용 2.5kW급 8상 양방향 컨버터에 관한 연구)

  • Lim, Jae-Woo;Kim, Hee-Jun;Choi, Jun-Sam
    • Transactions of the Korean Society of Automotive Engineers
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    • v.25 no.1
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    • pp.82-91
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    • 2017
  • This paper is a study on the bi-directional DC-DC converter, one of the key elements of 48V-12V dual systems in mild hybrid electric vehicles. Mild hybrid electric vehicles require a bi-directional DC-DC converter that can efficiently transmit power in two directions between a 48V battery and a 12V battery. To develop a bi-directional DC-DC converter with better price competitiveness, upgraded fuel economy, excellent performance and smaller size, this study designed, produced and presented a circuit that improved on the existing one. In the proposed 8-phase bi-directional DC-DC converter, the size of the passive element was reduced through the 8-phase interleaved topology, whereas downscaling had previously posed a difficulty. This study also designed and produced a 2.5kW class prototype. Based on the proposed 8-phase interleaved topology, a size of 227.5 (W) * 172 (L) * 64.35 (H) was achieved. In the boost mode operation and buck operation modes, the maximum efficiency was recorded at 94.04 % and 95.78 %, respectively.

Detection of Abnormal Heartbeat using Hierarchical Qassification in ECG (계층구조적 분류모델을 이용한 심전도에서의 비정상 비트 검출)

  • Lee, Do-Hoon;Cho, Baek-Hwan;Park, Kwan-Soo;Song, Soo-Hwa;Lee, Jong-Shill;Chee, Young-Joon;Kim, In-Young;Kim, Sun-Il
    • Journal of Biomedical Engineering Research
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    • v.29 no.6
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    • pp.466-476
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    • 2008
  • The more people use ambulatory electrocardiogram(ECG) for arrhythmia detection, the more researchers report the automatic classification algorithms. Most of the previous studies don't consider the un-balanced data distribution. Even in patients, there are much more normal beats than abnormal beats among the data from 24 hours. To solve this problem, the hierarchical classification using 21 features was adopted for arrhythmia abnormal beat detection. The features include R-R intervals and data to describe the morphology of the wave. To validate the algorithm, 44 non-pacemaker recordings from physionet were used. The hierarchical classification model with 2 stages on domain knowledge was constructed. Using our suggested method, we could improve the performance in abnormal beat classification from the conventional multi-class classification method. In conclusion, the domain knowledge based hierarchical classification is useful to the ECG beat classification with unbalanced data distribution.