• 한국자동차공학회논문집
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• 제10권3호
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• pp.192-200
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• 2002

Semi-active suspension systems are greatly expected to be in the mainstream of future controlled suspensions for passenger cars. In this study, a continuous variable damper for a passenger car suspension is developed, which is controlled actively and exhibits high performance with light weight, low cost, and low energy consumption. To get fast response of the damper, reverse damping mechanism is adapted, and to get small pressure change rate after blow-off, a pilot controlled proportional valve is designed and analyzed. The reverse continuous variable damper is designed as a HS-SH damper that offers good body control with reduced transferred input force from tire, compared with any other type of suspension system. The damper structure is designed, so that rebound and compression damping force can be tuned independently, of which variable valve is placed externally. The rate of pressure change with respect to the flow rate after blow-off becomes smooth when the fixed orifice size increases, which means that the blow-off slope is controllable using the fixed orifice size. The damping force variance is wide and continuous, and is controlled by the spool opening, of which scheme is usually adapted in proportional valves. The reverse continuous variable damper developed in this study is expected to be utilized in the semi-active suspension systems in passenger cars after its performance and simplicity of the design is confirmed through real car test.

• KIEE International Transactions on Power Engineering
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• 제3A권1호
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• pp.17-26
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• 2003

In this paper, the comparative steady-state operating performance analysis algorithms of the stand-alone single-phase self-excited induction generator (SEIG) is presented on the basis of the two nodal admittance approaches using the per-unit frequency in addition to a new state variable de-fined by the per-unit slip frequency. The main significant features of the proposed operating circuit analysis with the per-unit slip frequency as a state variable are that the fast effective solution could be achieved with the simple mathematical computation effort. The operating performance results in the simulation of the single-phase SEIG evaluated by using the per-unit slip frequency state variable are compared with those obtained by using the per-unit frequency state variable. The comparative operating performance results provide the close agreements between two steady-state analysis performance algorithms based on the electro-mechanical equivalent circuit of the single-phase SEIG. In addition to these, the single-phase static VAR compensator; SVC composed of the thyristor controlled reactor; TCR in parallel with the fixed excitation capacitor; FC and the thyristor switched capacitor; TSC is ap-plied to regulate the generated terminal voltage of the single-phase SEIG loaded by a variable inductive passive load. The fixed gain PI controller is employed to adjust the equivalent variable excitation capacitor capacitance of the single-phase SVC.

• International Journal of Automotive Technology
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• 제3권1호
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• pp.27-32
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• 2002

Semi-active suspension systems are greatly expected to be in the mainstream of future controlled suspensions fur passenger cars. In this study, a continuous variable damper for a passenger car suspension is developed. It is controlled actively and exhibits high performance with light weight, low cost, and low energy consumption. To get fast response of the damper, reverse damping mechanism is adapted, and to get small pressure change rate after blow-off, a pilot controlled proportional valve is designed and analyzed. The reverse continuous variable damper is designed as a HS-SH damper which offers good body control with reduced transferred input force from tire, compared with any other type of suspension system. The damper structure is designed, so that rebound and compression damping force can be tuned independently, of which variable valve is placed externally. The rate of pressure change with respect to the flow rate after blow-offbecomes smooth when the fixed orifice size increases. Damping forces are measured with the change of the solenoid current at the different piston velocities to confirm the maximum hysteresis of 20N, linearity, and variance of damping farce. The damping farce variance is wide and continuous, and is controlled by the spoof opening, of which scheme is usually adapted in proportional valves. The reverse continuous variable damper developed in this study is expected to be utilized in the semi-active suspension systems in passenger cars after its performance and simplicity of the design is confirmed through real car test.

• 한국정보통신학회논문지
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• 제14권7호
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• pp.1589-1596
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• 2010

본 논문에서는 CBP(coded block pattern) 및 colocated-MB(macro block)의 부호화 정보를 이용하여 인터모드 결정에 소요되는 계산량을 감소시키는 방법을 제안한다. 제안한 방법은 MB를 CBP 특성에 따라 best-CBP와 normal-CBP 로 나눈다. Best-CBP에서는 SKIP 모드 및 M-Type 모드일 확률이 통계적으로 96.3%이므로 인터모드 결정 과정에서 $8{\times}8$ 모드 계산을 제거한다. Normal-CBP에서는 SKIP 모드 및 M-Type 모드 결정에 colocated-MB의 부호화 정보와 MVcost(motion vector cost)를 이용하여 비트율-왜곡 치에 소요되는 계산량을 선택적으로 제거한다. 실험 결과, 제안한 방법은 전체 부호화 시간이 평균적으로 58.44% 감소되었으며, 움직임이 적은 영상에서 계산량 감소 효과가 우수함을 알 수 있었다.

• 대한기계학회논문집A
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• 제31권1호
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• pp.26-35
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• 2007

The vehicle of urban transit is a complex system that consists of various electric, electronic, and mechanical equipments, and the maintenance cost of this complex and large-scale system generally occupies sixty percent of the LCC (Life Cycle Cost). For reasonable establishing of maintenance strategies, safety security and cost limitation must be considered at the same time. The concept of system reliability has been introduced and optimized as the key of reasonable maintenance strategies. For optimization, three preceding studies were accomplished; standardizing a maintenance classification, constructing RBD (Reliability Block Diagram) of VVVF (Variable Voltage Variable Frequency) urban transit, and developing a web based reliability evaluation system. Historical maintenance data in terms of reliability index can be derived from the web based reliability evaluation system. In this paper, we propose applying inverse problem analysis method and hybrid neuro-genetic algorithm to system reliability optimization for using historical maintenance data in database of web based system. Feed-forward multi-layer neural networks trained by back propagation are used to find out the relationship between several component reliability (input) and system reliability (output) of structural system. The inverse problem can be formulated by using neural network. One of the neural network training algorithms, the back propagation algorithm, can attain stable and quick convergence during training process. Genetic algorithm is used to find the minimum square error.

• The Journal of Asian Finance, Economics and Business
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• 제7권7호
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• pp.349-360
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• 2020

The study aims to empirically examine the determinants of bank margins from Pakistan, an emerging South Asian economy. To elucidate the importance of the Pakistani banking sector, secondary data has been used, which was extracted from the annual accounts of twenty-four Pakistani scheduled commercial banks (20 conventional, four full-fledged Islamic) over a sample period of 2006 to 2017. The factors identified in the dealership model and the subsequent empirical developments in the dealership model categorized as bank-specific, diversification, regulatory, and industry concentration are analyzed by applying the most-common linear dynamic panel-data estimator, the Generalized Method of Moments (GMM) estimator, developed by Arellano and Bond (1991). The findings reveal that, among the bank-specific variables, funding cost, credit risk, managerial efficiency, market share, and operating cost are significant predictors of bank margins. For diversification variables employed in the study, both variables including net non-interest income and asset diversity are as well significant predictors of bank margins. It is also found that the market concentration variable proxied by the Herfindahl-Hirschman Index (HHI) is significantly predicting bank margins. Subsequently, one of the regulatory variables, the opportunity cost of holding reserves, and one bank-specific variable, the degree of risk aversion, are insignificant in the model.

• 대한교통학회지
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• 제28권2호
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• pp.33-43
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• 2010

본 연구에서는 1995~2007년까지의 도시가계조사 원시자료를 이용하여 국내의 가구 교통비 지출구조를 분석함과 동시에 교통비 지출에 영향을 미치는 요인들을 회귀모형을 통해 분석하고, 교통비 지출에 의한 소득분배 효과를 분석하였다. 특히 본 연구에서는 교통비 지출구조 및 소득효과 분석에 있어 경제학적 방법론의 적용과 탄력성 분석을 통해 다양한 정책적 시사점을 도출하고 있다는 점에서 의의를 지닌다. 분석결과, 가구 교통비 지출 부담은 고소득층보다 저소득층에서 상대적으로 더 크고, 공공교통비보다는 개인교통비의 증가가 도시 근로자들의 교통비 지출액 증가에 크게 영향을 미치고 있다. 또한 경제 사회 및 통행특성 등 가구 특성을 반영하는 다양한 요인들이 공공교통비, 개인교통비, 대중교통비용, 자가용 승용차 비용 등 4개의 개별 교통비 지출에 미치는 영향은 서로 다른 것으로 분석되었다. 마지막으로 교통비 지출은 소득 양극화를 가중시키고 있으며, 특히 공공교통비보다는 개인교통비 지출에 의한 부정적 영향이 상대적으로 큼을 알 수 있다.

• 한국산업정보학회논문지
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• 제14권4호
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• pp.205-212
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• 2009

현재 지능형교통시스템(Intelligent Transport Systems, ITS)은 교통시설에 대한 다양한 정보와 자료를 수집하여 가공할 수 있는 첨단교통시스템으로서 사회적 관심이 커지고 있으며, 고속국도 뿐 아니라 일반국도에도 ITS 인프라 구축이 활발히 진행되고 있다. 하지만 ITS 설치에 대한 명확한 효과 분석이 어려워 이에 대한 계량화된 방법론이 필요한 실정이다. 이에 본 연구에서는 익산지방국토관리청에서 관할하고 있는 국도 ITS 사업의 효과분석을 위해 경제성분석을 실시하였다. 분석기간을 10년, 할인률을 5.5%로 가정하였으며 효과척도로는 통행시간 절감, $CO_2$ 배출 절감, 연료 절감, 도로전광표지(Variable Message Sign, VMS) 정보의 가치를 선정하여 각 항목에 대한 계량화 방안을 마련하였다. 경제성 분석 결과 익산지방국토관리청의 ITS 구축사업은 편익/비용 비율이 1.20, 내부 수익률이 12.4%, 순 현재 가치가 14.8억원으로 나타나 ITS 구축이 경제성이 있는 것으로 나타났다.

• 방사성폐기물학회지
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• 제18권2_spc호
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• pp.247-260
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• 2020

본 논문에서는 고리 1호기 해체 비용 추정을 위해 외국 원자력발전소 해체 비용 데이터를 현가화한 후 원자력발전소 해체 비용 추정 회귀 분석모델을 개발하였다. 이 모델 개발에 사용된 데이터는 해체 또는 진행 중인 BWR 13기, PWR 16기의 해체 비용 데이터이다. 회귀 분석모델 도출을 위해, 해체 비용을 종속변수로 정하고, 해체 원전의 운전 특성을 반영할 수 있게 고안된 Contamination factor와 해체 기간을 독립변수로 선정하였다. 빅데이터 분석 도구인 R language의 통계패키지를 이용하여 회귀 분석모델을 도출하였다. 이 회귀 분석 모델을 적용하여 고리 1호기 해체 비용을 예측한 결과, 미화 663.40~928.32백만 달러, 한화 약 7,828.12억~1조 954.18억 원이 소요될 것으로 예측되었다.

• Industrial Engineering and Management Systems
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• 제8권3호
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• pp.194-200
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• 2009

This study provides a heuristic algorithm to solve the locating problem of repair service centers (RSCs). To enhance the customer service level with more satisfaction and quicker responsiveness, the locating problem of RSCs has become one of the important issues in reverse supply chain management. This problem is formulated as a zero-one mixed integer programming in which an exiting distributor will be considered to be an un-capacitated repair service center for the objective of cost-minimizing. Since logistical costs are highly interrelated with the multinational location of distributors and RSCs, the fixed cost for setting a repair service center, variable cost, transportation cost, and exchange rates are considered in this study. Recognizing the selection of un-capacitated RSCs' locations is a combinatorial optimization problem and is a zero-one mixed integer programming with NP-hard complexity, we provide a heuristic algorithm named as incremental cost matrix procedure (ICMP) to simplify the solving procedure. By using the concise and structural cost matrix, ICMP can efficiently screen the potential location with cost advantage and effectively decide which distributor should be a RSC. Results obtained from the numerical experiments conducted in small scale problem have shown the fact that ICMP is an effective and efficient heuristic algorithm for solving the RSCs locating problem. In the future, using the extended ICMP to solve problems with larger industrial scale or problems with congestion effects caused by the variation of customer demand and the restriction of the RSC capacity is worth a further investigation.