• 제목/요약/키워드: Lagging

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Transonic Wing Flutter Analysis Using a Parallel Euler Solver (병렬화된 오일러 코드를 이용한 3차원 날개의 천음속 플러터 해석)

  • Kwon, Hyuk-Jun;Park, Soo-Hyung;Kim, Kyung-Seok;Kim, Jong-Yun;Lee, In;Kwon, Jang-Hyuk
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.10
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    • pp.10-16
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    • 2005
  • In this paper, a three-dimensional Euler aeroelastic analysis program is developed with a second-order staggered algorithm to reduce the lagging errors between the fluid and structural solvers. In the unsteady aerodynamic analysis, a dual-time stepping method based on the diagonalized-ADI algorithm is adopted to improve the time accuracy and a parallelized multi-grid method is used to save the computing time. The aeroelastic analyses of AGARD 445.6 wing model have been performed to verify the Euler aeroelastic analysis code. The analysis results are compared with the experimental data and other computational results. The results show comparatively good correlation when they are compared with other references.

An Energy Consumption Prediction Model for Smart Factory Using Data Mining Algorithms (데이터 마이닝 기반 스마트 공장 에너지 소모 예측 모델)

  • Sathishkumar, VE;Lee, Myeongbae;Lim, Jonghyun;Kim, Yubin;Shin, Changsun;Park, Jangwoo;Cho, Yongyun
    • KIPS Transactions on Software and Data Engineering
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    • v.9 no.5
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    • pp.153-160
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    • 2020
  • Energy Consumption Predictions for Industries has a prominent role to play in the energy management and control system as dynamic and seasonal changes are occurring in energy demand and supply. This paper introduces and explores the steel industry's predictive models of energy consumption. The data used includes lagging and leading reactive power lagging and leading current variable, emission of carbon dioxide (tCO2) and load type. Four statistical models are trained and tested in the test set: (a) Linear Regression (LR), (b) Radial Kernel Support Vector Machine (SVM RBF), (c) Gradient Boosting Machine (GBM), and (d) Random Forest (RF). Root Mean Squared Error (RMSE), Mean Absolute Error (MAE) and Mean Absolute Percentage Error (MAPE) are used for calculating regression model predictive performance. When using all the predictors, the best model RF can provide RMSE value 7.33 in the test set.

Development of Integrated System of Time-Driven Activity-Based Costing(TDABC) Using Balanced Scorecard(BSC) and Economic Value Added(EVA) (BSC와 EVA를 이용한 TDABC 통합시스템의 개발)

  • Choi, Sungwoon
    • Journal of the Korea Safety Management & Science
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    • v.16 no.3
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    • pp.451-469
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    • 2014
  • The purpose of this study is to implement and develop the integrated Economic Value Added (EVA) and Time-Driven Activity-Based Costing (TDABC) model to seek both improvement of Net Operating Profit Less Adjusted Tax (NOPLAT) and reduction of Capital Charge (CC). Net Operating Profit Less Adjusted Tax (NOPLAT) can be maximized by reducing the indirect cost of an unused resource capacity increased by Cost Capacity Ratio (CCR) of TDABC. On the other hand, Capital Charge (CC) can be minimized by improving the efficiency of Invested Capital (IC) considered by Weighted Average Cost of Capital (WACC) of EVA. In addition, the integrated system of TDABC using Balance Scorecard (BSC) and EVA is developed by linking between the lagging indicators and the three leading indicators. The three leading indicators include customer, internal process and growth and learning perspectives whereas the lagging indicator includes NOPLAT and CC in terms of financial perspective. When the Critical Success Factor (CSF) of BSC is cascading as a cause and an effect relationship, time driver of TDABC and capital driver of EVA can be used efficiently as Key Performance Indicator (KPI) of BSC. For a better understanding of the proposed EVA/TDABC model and BSC/EVA/TDABC model, numerical examples are derived from this paper. From the proposed model, the time driver of TDABC and the capital driver of EVA are known to lessen indirect cost from comprehensive income statement when increasing the efficiency of operating IC from the statement of financial position with unified KPI cascading of aligned BSC CSFs.

Analysis of Voltage Drop Characteristics of Transformer-based 3-phase Voltage Disturbance Generator (변압기 기반 3상 전압변동발생기의 전압강하 특성해석)

  • Han, Heung-Soo;Lee, Young-Ho;Song, Woong-Hyub;Nho, Eui-Cheol;Kim, In-Dong;Kim, Heung-Geun;Chun, Tae-Won
    • The Transactions of the Korean Institute of Power Electronics
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    • v.15 no.5
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    • pp.411-416
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    • 2010
  • A voltage drop characteristics of a transformer-based voltage disturbance generator with series transformers is analysed. It is well known that a voltage disturbance generator with series transformer is cost-effective and reliable compared with other types. The voltage drop depends on the %Z of the transformer, power rating, and output power factor. A wrong design of the transformer results in a severe voltage drop, which can not guarantee the proper performance of the generator. The voltage drop is analysed under the condition of 10kVA output power rating and 4% of %Z with the variation of power factor. It is found through simulations and experiments that the drop increases as the power factor decreases in lagging mode, and the drop is 4% of the rated voltage in case of 0.85 lagging power factor.

Cytogenetic Studies in Hybrids from a Pair of Sibling Drosophila Species

  • Park, Yung-Hyun;Kim, Heui-Soo;Lee, Won-Ho
    • Journal of Life Science
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    • v.10 no.1
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    • pp.48-50
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    • 2000
  • The cytogenetic pattern of autosome and sex chromiosome after Giemas staining were examined in the hybrids between two sibling species, Drosophila melanogaster and D. simulans. The analysis of karyotype in the hybrid female between D. melanogaster females and D. simulans males could be easily distinguished the characteriation of eight chromosomes from bothe species, especially with regard to X chromosomes. The lagging duplication of Y chromosome was investigated in the interspecific hybrid males from the cross between female of Drosophila melanogaster(OR) and males of D. simulasn (K18). On the other hand, the X chromatids of D. simulans were loosely separated in the early stage of anaphase.

Power Factor Characteristic of DFIG (DFIG의 역률특성)

  • Kim, Chul-Ho;Lee, Woo-Suk;Kong, Jeong-Sik;Seo, Young-Taek;Oh, Chul-Soo
    • Proceedings of the KIEE Conference
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    • pp.613-615
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    • 2002
  • This paper deals with power factor of doubly fed induction generator for wind power generation in range of sub- and super-synchronous speed. To supply active and reactive power to grid. stator is connected to grid directly and rotor is connected to back-to-back PWM inverter for excitation. According to excitation level. DFIG could operate at the different mode. i.e., unity, leading, and lagging power factor.

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Finite Element Analysis of the Electromagnetic System Considering the Rotational Hysteresis Characteristics (회전 히스테리시스 특성을 고려한 전자계의 유한요소 해석)

  • 홍선기;김홍규;정현교
    • Journal of the Korean Magnetics Society
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    • v.7 no.2
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    • pp.109-116
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    • 1997
  • This paper describes an implementation of the rotational hysteresis analysis using the finite element method and a vector hysteresis model. The vector hysteresis model is extended from the magnetization-dependent Preisach model. The magnetization of each element is calculated for a given history of the rotating field. The lagging angle and the magnitude of the magnetization for an applied field are evaluated. The experimental results show that the magnetization characteristics of the magnetic materials under the rotating field can be analyzed accurately by the proposed method.

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Characteristics of Walls Supported by Prefabricated Strut (조립식 버팀보로 지지된 흙막이 구조물의 거동 특성에 관한 연구)

  • 김낙경;박종식
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.553-560
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    • 2003
  • From the analytical standpoint, it is advantageous to consider the behavior of supported walls as plane strain condition. But supported walls constitute geotechnical problems which, in strut terms, are not plane strain cases. These represent differences between the measured and the predicted due to the stiffness and spacing of supported walls and the behavior of discontinuous walls such as solider beams with lagging. This study is to investigate simulations of a system behavior along a horizontal section of walls supported by prefabricated strut. Using a beam column method, relative effects associated with prefabricated strut stiffness and spacing in a systematic behavior were investigated.

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High Efficiency Design Considerations for the Self-Driven Synchronous Rectified Phase-Shifted Full-Bridge Converters of Server Power Systems

  • Cetin, Sevilay
    • Journal of Power Electronics
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    • v.15 no.3
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    • pp.634-643
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    • 2015
  • This paper presents a high frequency design approach for improving efficiency over a wide load range in the self-driven phase-shifted full-bridge converters for server power systems. In the proposed approach, a detailed ZVS analysis of the lagging leg switches in both the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM) is presented. The optimum dead time and the determination of the appropriate operation mode are given for high efficiency according to the load conditions. Finally, the optimum operation conditions are defined to achieve a high-efficiency. A laboratory prototype operating at 80 kHz, rated 1 kW (12 V-83.3 A), is built to verify proposed theoretical analysis and evaluations. The experimental results show that the maximum efficiency is achieved as 95% and 83.5% at full load and 5% load conditions, respectively.

Research on the Urban Ecological Space Changes under Modern Passive Industrialization Case Study of Zhengzhou City in China

  • Yang, Juntao;Baek, Seungman
    • Architectural research
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    • v.23 no.2
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    • pp.29-37
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    • 2021
  • Early in the communist era, many cities in modern China experienced a special period of passive industrialization during which the construction of urban spaces laid the spatial urban foundation. During this period, the city construction was carried out rapidly under the administrative intervention of the government. The passive industrialization caused by taking economic construction as the center made the city construction deviate from the correct track and resulted in a variety of problems. Focusing on ecological space change, this paper selects Zhengzhou as an example of many similar cities in China, and analyzes the impact of passive industrialization on urban ecological spaces from the perspectives of city scale, city layout and city construction management system. The analysis results reveal that the construction of urban ecological space under the influence of passive industrialization induced a lagging characteristic, led to insufficient integrity of urban ecological space, and placed great pressure on the urban environment. Finally, the paper puts forward some methods to optimize the urban ecological space.