• Title/Summary/Keyword: HHI

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Flashover Voltage of 800kV Class Composite Hollow Insulator for $SF_6$ Gas Insulated Switchgear (GIS) (800kV $SF_6$ 가스절연 개폐장치용 (GIS) 복합절연애자 (Composite Hollow Insulator)의 표면오손시 내전압특성)

  • Lee, C.R.;Yoon, J.H.;Choi, B.H.;Yoon, C.Y.;Ko, K.S.;Ban, S.G.;Huh, J.C.
    • Proceedings of the KIEE Conference
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    • 2002.07c
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    • pp.1449-1451
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    • 2002
  • A developed 800kV class composite hollow insulator for $SF_6$ Gas Insulated Switchgear (GIS) was tested as to insulation with their surfaces contaminated. The wet power frequency withstand voltage of the silicone rubber housing was about 135kV at an equivalent salt deposite density of $5kg/m^2$, to sufficiently satisfy the required performance. According to IEC 60507, the salt fog withstand voltage was measured at 565kV, and the highest measured leakage current was below 0.2mA. Therefore, it was clarified that the composite hollow insulator has sufficient insulation performance even when it is contaminated on the surface.

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Vibration Reduction of Forklift Truck Using Optimization of Engine Mount Layout (마운트 배치 최적화를 통한 지게차 엔진 진동 저감)

  • Kim, Younghyun;Kim, Kyutae;Lee, Wontae
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.2
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    • pp.102-107
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    • 2014
  • The engine excitation forces are considered as major vibration source for the forklift truck, especially in small class. Even though the current engine mounting system designs are acceptable for vibration isolation, the performance of the engine mounting system is still required for the tendency of light weight, higher power and driver's higher vibration requirement. In this paper vibration reduction technique of forklift engine which is supported on rubber mounts is presented. Based on the dynamic model of resilient engine mounting system, design evaluation program is established. The design optimization technique and evaluation method of system properties are discussed. Effects of optimal design are validated through comparison with test results.

The Determinant of Investment in Research and Development Analyze - on its Market Structure and Financial Factor - (기업의 연구개발투자 결정요인분석 -시장구조 및 재무적 요인을 중심으로-)

  • Hwang, Eun-Jeong
    • Management & Information Systems Review
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    • v.21
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    • pp.239-269
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    • 2007
  • The purpose of this thesis is to analyze empirically the relationship between market structure, measured by Herfindahl-Hershmann Index(HHI), and financial factors, and innovation in Korean industry panel datasets for 2000-2006. Results show that debt ratio and scale of the firm has a consistent positive effect on the investment in research and development. As more scale of the firm is getting bigger, the investment in R&D decrease. Also, as more debt ratio of firm rise, the investment for innovation increase. Concentration ratio, the HHI and the classification factor of High-tech industry and Low-tech industry has a consistent positive effect on the innovation. Factors affecting the investment in research and development include market structure and characteristics of industry as well as the internal affairs of the firm.

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Performance Analysis of a Dolphin-tail Rudder

  • Min K. S.;Chung K. N.;Kim Y. L
    • 한국전산유체공학회:학술대회논문집
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    • 2003.10a
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    • pp.137-139
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    • 2003
  • As a part of numerical and experimental research works for the prediction and improvement of ship's maneuvering performance, a study on the performance analysis of two different rudders has been carried out. While the planform shape and the aspect ratio of the rudders have been fixed, section shape has been changed. Conventional type of HMRI NP section and special type of dolphin-tail section have been employed. Performances of the rudders have been investigated by using CFD and compared with experimental data obtained in a wind tunnel. A commercial CFD program has been used to solve the RANS equations. Two-equation k-ro model has been applied to close the governing equations. Block-structured grids are used in the numerical calculation. Based upon the calculation results, the rudder with dolphin-tail section has shown a possibility of significantly improving rudder performance if utilized as the section of ship rudders.

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A Study on the Analysis of Export Structure in Jeollabuk-do for the Activation of Saemangeum New Port (새만금신항 활성화를 위한 전라북도 수출구조 분석에 관한 연구)

  • Min-Ju Song
    • Korea Trade Review
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    • v.47 no.4
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    • pp.293-309
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    • 2022
  • The purpose of this paper is to analyze the import and export volume of Jeollabuk-do to establish a plan to activiation Saemangeum New Port. To this end, this study utilized the HHI(Herfindahl-Hirschman Index), LQ(Location Quotient) analysis using the annual data set from the Korea Trade Statistics Promotion Institution between 2015 to 2020. As a result, it has been confirmed that the degree of export volume concentration (HHI (Herfindahl-Hirschman Index)) in Jeollabuk-do has been increasing over the past 5 years. According to results of LQ(Location Quotient) analysis, Brazil had the highest index in the case of exporting countries, and Meat, edible meat offal (HS 2) had the highest index in the case of export items. This paper is meaningful in analyzing the export structure using import and export volumes and proposing a plan to improve the competitiveness of Saemangeum New Port.

A Study on Competitiveness Improvement of Chittagong Container Port

  • Haque Md Jubair;Woo-Chul Ahn
    • Asia-Pacific Journal of Business
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    • v.14 no.1
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    • pp.439-451
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    • 2023
  • Purpose - Market structure is crucial to identify as it defines the market states for new and existing container ports to perform within a given region. the study aims to compare the major ports in the Bay of Bengal in the context of Chittagong Port. Design/methodology/approach - For this study, the past 9 years of container volume data have been collected and analyzed through the HHI index, BCG matrix and shift effect analysis. Based on the analysis, this study has found that the Chittagong Port is in an oligopoly competitive market structure. Findings - The findings have shown that port in low market share and low growth in very recent years with the moderately concentrated ports HHI index. The shift effect analysis shows that the container volumes shifted from one port to another in the 2019 and 2020 periods. This study is the pioneer study in the Bay of Bengal region to identify the market structure, analyze market share and growth, and analyze the market concentration. Research implications or Originality - Future recommendations for the port authority is to take advantage of geolocation; attract international; tax exemption, faster clearance process, reduced waiting charges; increasing storage and technological machinery; promoting maritime logistics education; promoting Chittagong tourism; collaboration with other countries. Also, this study can be used as basic data for the establishment of a new supply chain between Korea and Southwest Asia for the Korean government and companies.

The Effect of Meta-Features of Multiclass Datasets on the Performance of Classification Algorithms (다중 클래스 데이터셋의 메타특징이 판별 알고리즘의 성능에 미치는 영향 연구)

  • Kim, Jeonghun;Kim, Min Yong;Kwon, Ohbyung
    • Journal of Intelligence and Information Systems
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    • v.26 no.1
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    • pp.23-45
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    • 2020
  • Big data is creating in a wide variety of fields such as medical care, manufacturing, logistics, sales site, SNS, and the dataset characteristics are also diverse. In order to secure the competitiveness of companies, it is necessary to improve decision-making capacity using a classification algorithm. However, most of them do not have sufficient knowledge on what kind of classification algorithm is appropriate for a specific problem area. In other words, determining which classification algorithm is appropriate depending on the characteristics of the dataset was has been a task that required expertise and effort. This is because the relationship between the characteristics of datasets (called meta-features) and the performance of classification algorithms has not been fully understood. Moreover, there has been little research on meta-features reflecting the characteristics of multi-class. Therefore, the purpose of this study is to empirically analyze whether meta-features of multi-class datasets have a significant effect on the performance of classification algorithms. In this study, meta-features of multi-class datasets were identified into two factors, (the data structure and the data complexity,) and seven representative meta-features were selected. Among those, we included the Herfindahl-Hirschman Index (HHI), originally a market concentration measurement index, in the meta-features to replace IR(Imbalanced Ratio). Also, we developed a new index called Reverse ReLU Silhouette Score into the meta-feature set. Among the UCI Machine Learning Repository data, six representative datasets (Balance Scale, PageBlocks, Car Evaluation, User Knowledge-Modeling, Wine Quality(red), Contraceptive Method Choice) were selected. The class of each dataset was classified by using the classification algorithms (KNN, Logistic Regression, Nave Bayes, Random Forest, and SVM) selected in the study. For each dataset, we applied 10-fold cross validation method. 10% to 100% oversampling method is applied for each fold and meta-features of the dataset is measured. The meta-features selected are HHI, Number of Classes, Number of Features, Entropy, Reverse ReLU Silhouette Score, Nonlinearity of Linear Classifier, Hub Score. F1-score was selected as the dependent variable. As a result, the results of this study showed that the six meta-features including Reverse ReLU Silhouette Score and HHI proposed in this study have a significant effect on the classification performance. (1) The meta-features HHI proposed in this study was significant in the classification performance. (2) The number of variables has a significant effect on the classification performance, unlike the number of classes, but it has a positive effect. (3) The number of classes has a negative effect on the performance of classification. (4) Entropy has a significant effect on the performance of classification. (5) The Reverse ReLU Silhouette Score also significantly affects the classification performance at a significant level of 0.01. (6) The nonlinearity of linear classifiers has a significant negative effect on classification performance. In addition, the results of the analysis by the classification algorithms were also consistent. In the regression analysis by classification algorithm, Naïve Bayes algorithm does not have a significant effect on the number of variables unlike other classification algorithms. This study has two theoretical contributions: (1) two new meta-features (HHI, Reverse ReLU Silhouette score) was proved to be significant. (2) The effects of data characteristics on the performance of classification were investigated using meta-features. The practical contribution points (1) can be utilized in the development of classification algorithm recommendation system according to the characteristics of datasets. (2) Many data scientists are often testing by adjusting the parameters of the algorithm to find the optimal algorithm for the situation because the characteristics of the data are different. In this process, excessive waste of resources occurs due to hardware, cost, time, and manpower. This study is expected to be useful for machine learning, data mining researchers, practitioners, and machine learning-based system developers. The composition of this study consists of introduction, related research, research model, experiment, conclusion and discussion.

A Study on the Optimal Shape of Arc Chute for Molded Case Circuit Breakers (배선용 차단기 Arc Chute의 최적형상에 관한 연구)

  • Kim, J.S.;Lee, C.R.;Song, T.H.;Choi, M.J.;Kim, D.J.;Lee, G.H.
    • Proceedings of the KIEE Conference
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    • 2002.07b
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    • pp.926-928
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    • 2002
  • Much progress has been made during the past two decades in numerical analysis of electromagnetic forces in molded case circuit breakers (MCCB) for increasing arc voltage due to the change of the configuration of arc chute and fixed conductor. A review on this topic is given. which mainly covers the past research activities associated with that of our company.

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Short Circuit Test of Power Transformer for Evaluation of Numerical Analysis (전산해석 검증을 위한 전력용 변압기의 단락강도 측정)

  • Oh, Y.H.;Song, K.D.;Sun, C.H.;Kim, S.C.;Woo, C.H.
    • Proceedings of the KIEE Conference
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    • 2002.07b
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    • pp.793-795
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    • 2002
  • This study shows method of measuring mechanical stresses during short circuit test, to evaluate numerical analysis of short circuit force. As test model, 400kVA transformers are used, to acquire short circuit force acceleration sensors used. Weak region of winding is found through short circuit test, and verification data of numerical calculation is obtained.

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On the Negative Drift Force Acting on a Freely Floating Surface-Piercing Cylinder (2차원 부유체에 작용하는 음의 수평방향 표류력에 대한 고찰)

  • Hong, Do-Chun
    • Journal of Ocean Engineering and Technology
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    • v.10 no.3
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    • pp.74-82
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    • 1996
  • 수면상에 떠있는 2차원 물체에 작용하는 시간평균 표류력 및 표류모오멘트를 비점성 선형 포텐셜 이론을 사용하여 계산하는 방법에 대하여 검토하였다. 부유체 접수면상의 압력을 직접적분하여 구한 수평방향 표류력이 특정주파수 부근에서 음의 값을 보이고 있다. 이는 무한원방에서의 에너지 보전방법에 의한 표류력이 항상 양의 값을 취한다는 기존 이론과 상이하다. 본 논문에서, 이러한 차이가 부유체의 횡요 및 상하동요에 기인한 복원력의 성분과 횡요와의 연성효과에 의하여 발생하였음을 규명하였다. 이는 횡요가 있는 경우, 표류력을 산출하는 기존의 무한원방 방법에 결함이 있음을 보이고 있다. 이에 반하여 기존의 접수면압력 직접적방법은 부유체에 작용하는 시간평균 표류력 및 표류모오멘트를 모든 주파수에 대하여 정확하게 산출한다고 결론지울 수 있다.

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