• International Journal of Air-Conditioning and Refrigeration
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• 제10권2호
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• pp.88-96
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• 2002

The present study was conducted to estimate the effect on fouling reduction in tubes of the condenser. It shows in detail how to calculate the fouling factor from the experimental results of refrigeration systems with or without the automatic cleaning system using sponge balls and to predict the variation of the factor with time. It also represents how to calculate the temperature and pressure decrease of the refrigerant vapor in the condenser and the load decrease of the compressor in the refrigeration system by fouling reduction.

• 설비공학논문집
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• 제13권6호
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• pp.482-489
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• 2001

The present study was conducted to estimate the effect on fouling reduction in tubes of the condenser. It shows in detail how to calculate the fouling factor from the experimental results of refrigeration systems with or without the automatic cleaning system using sponge balls and to predict the variation of the factor with time. It also represents how to calculate the temperature and pressure decrease of the refrigerant vapor in the condenser and the load decrease of the compressor in the refrigeration system by fouling reduction.

• 전력전자학회논문지
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• 제5권4호
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• pp.403-408
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• 2000

본 논문애서는 비선형부하에서 발생하는 고조파 문제와 역률 저하 문제의 해결을 위한 능동필터를 제연하었다. 인버터와 수동필터로 구성된 능동전력필터 비선형부하에 병렬로 위치하고 전압제어방식으로 동작된다. 제안된 전압제어방식은 기존의 전류제어행 방식에 비해 입럭전압 변동에 강인한 특성을 갖는다. 능통전력필터의 작용으로 부하에 필요한 유효전력은 상용전원에서 공급되며 능동진력필터는 무효전력을 공급하에 입력 역률을 개선하­였다. 또한 부하전압을 정현적으로 유지함ㅇ 따라서 부하전압, 입럭전류 고조파 성분이 저감되있다. 본 논문에서 전압제어용 제어기의 구조를 딘순화하여 전체 시스템의 안정성을 높였다. 다수의 시뮬레이션과 실제 실험을 통하여 제안된 제안된 방식의 타당성을 검증하였다.

• 전기학회논문지
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• 제66권7호
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• pp.1039-1046
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• 2017

Campus microgrid is designed and built by considering not only power generation but also power consumption management as connected microgrid type because the main goal of the campus microgrid is to save power consumption costs. There are many functions to achieve the goal and they are mainly to use generation-based functions such as islanding operation for peak management and for emergency events. In power distribution operation, Conservation Voltage Reduction (CVR) is applied in order to reduce power consumption. The CVR is defined as a function for load consumption reduction by voltage reduction in order to reduce peak demands and energy consumption. However, application of CVR to microgrid is difficult because the microgrid cannot control a tap of transformer in a substation and the microgrid normally is not designed with phase modifying equipment like a step-voltage-regulator which can control voltage in power distribution system operation. In addition, an impact of the CVR is depended on load characteristics such as a normal load, a rated power, and synchronous motors. Therefore, this paper proposes an application of CVR using linear voltage control based AVR in campus microgrid with power consumption reduction considering characteristics of load and component in the microgrid. The proposed system can be applied to each buildings by a configuration of power distribution cables; and the application results and CVR factor are presented in this paper.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.329-337
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• 2016

With the increasing deployment of distributed generators in the distribution system, a very large search space is required when dynamic programming (DP) is applied for the optimized dispatch schedules of voltage and reactive power controllers such as on-load tap changers, distributed generators, and shunt capacitors. This study proposes a new optimal voltage and reactive power scheduling method based on dynamic programming with a heuristic searching space reduction approach to reduce the computational burden. This algorithm is designed to determine optimum dispatch schedules based on power system day-ahead scheduling, with new control objectives that consider the reduction of active power losses and maintain the receiving power factor. In this work, to reduce the computational burden, an advanced voltage sensitivity index (AVSI) is adopted to reduce the number of load-flow calculations by estimating bus voltages. Moreover, the accumulated switching operation number up to the current stage is applied prior to the load-flow calculation module. The computational burden can be greatly reduced by using dynamic programming. Case studies were conducted using the IEEE 30-bus test systems and the simulation results indicate that the proposed method is more effective in terms of saving electric charges and improving the voltage profile than loss minimization.

• Steel and Composite Structures
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• 제45권1호
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• pp.51-66
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• 2022

This paper presents the axial compression behavior of partially encased composite (PEC) columns using H-shaped structural steel. In the experimental program, a total of eight PEC columns with H-shaped steel sections of different flange and web slenderness ratios were tested to investigate the interactive mechanism between steel and concrete. The test results showed that the PEC columns could sustain the load well beyond the peak load provided that the flange slenderness ratio was not greater than five. In addition, the previous analytical model was extended to predict the axial load-strain relationships of the PEC columns with H-shaped steel sections. A good agreement between the predicted load-strain relationships and test data was observed. Using the analytical model, the effects of compressive strength of concrete (21 to 69 MPa), yield strength of steel (245 to 525 MPa), slenderness ratio of flange (4 to 10), and slenderness ratio of web (10 to 25) on the interactive mechanism (K_h = confinement factor for highly confined concrete and K_w = reduction factor for steel web) and ductility index (DI = ratio between strain at peak load and strain at proportional load) were assessed. The numerical results showed that the slenderness of steel flange and yield strength of steel significantly influenced the compression behavior of the PEC columns.

• 한국축산시설환경학회지
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• 제15권1호
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• pp.17-28
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• 2009

PEB system is more economical when compared with structures commonly used Hot rolled and welded light H-beam was introduced in the Standard Livestock Housing. This study suggested more economical technology for structural design by the reduction of live load, relief of deflection limit and reduction of importance factor. And, when applying wind Load as a result of examination with Low Rise Building Systems Manual considering open model, we can know that when the wind load is big, enclosed model is more stable than open model. In short, Suggesting more economical model and providing the method to reduce natural disaster, by the application of PEB system and the development of technology for structural design, are considered to strengthen the competitive power of farmhouse.

• 한국지진공학회논문집
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• 제9권1호통권41호
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• pp.25-32
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• 2005

지진하중을 받는 구조물은 모드참여계수에 의하여 각각의 모드에 지진하중이 분배, 전달된다. 이러한 특성 때문에 모드참여계수는 지진하중을 받는 구조물의 해석에서 매우 중요한 요소이다. 그러나 이상화된 해석 구조물의 모드참여계수는 해석적 모델링이나 시공오차 등에 의하여 실 구조물의 참여계수와 다르기 때문에 실제 거동을 예측, 반영하기에 한계가 있다. 본 연구에서는 시스템 식별기술과 $H^{\infty}$ 최적 모델 응축법을 활용하여, 구조물의 1차 모드참여계수를 산정하는 기법을 제안한다. 이 기법은 시스템 식별로부터 구현된 상태방정식을 전형의 상태방정식과 비교하는 과정에서 시스템의 가제어, 가관측 행렬의 비에 의하여 결정된다. 본 연구에서 제안한 모드참여계수산정기법은 단자유도, 다자유도 전단구조물에 대한 수치해석을 통하여 검증하였다.

• Earthquakes and Structures
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• 제8권5호
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• pp.977-994
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• 2015

In this study, earthquake loads are investigated statistically and compared with the nominal earthquake loads calculated according to the Turkish Earthquake Code, namely: "Specifications for Structures to be Built in Earthquake Areas". For this purpose, the "actual" mean load values estimated from statistical methods and the nominal load values computed according the Seismic Code are compared, with respect to some variations in the basic parameters, such as the importance factor, building height, site coefficient, seismic zone and seismic load reduction factor. In addition to the data compiled from different regions of Turkey, the published data and information in the foreign literature are also used in the determination of the earthquake load statistics. Although the dead and live loads acting on a structure are independent of the geographical location of the structure, environmental loads, such as earthquake loads are highly dependent on the location of the structure. Accordingly, for the assessment of statistical parameters associated with earthquake loads, twelve different locations which can represent the different seismic zones of Turkey as accurately as possible are chosen. As a result of the code calibration procedure considered in this study, it is observed that the load values obtained from the Turkish Seismic Code may overestimate or underestimate the actual seismic loads in some of the seismic zones.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.96-99
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• 1990

Recently, electric energy consumption pattern shows very high peak load with low load factor. This Load pattern have made electric utilities be interested in Load Management, many studies are reported. But most of these studies are concerned with Rate - Load shape relation, a few of these are concerned with generating cost reduction. In this study, the effect of Load Management is incorporated to establish optimal Generation Expansion Planning. Using avoided cost, optimal generation expansion planning is achieved to make maximum avoided cost of Electric utility. Dynamic programming technique is used to solve this algorithm.