• Steel and Composite Structures
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• 제11권2호
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• pp.149-168
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• 2011

This paper presents a computational study of column loss scenarios for typical multi-story steel buildings with perimeter moment frames and composite steel-concrete floors. Two prototype buildings (three-story and ten-story) were represented using three-dimensional nonlinear finite element models and explicit dynamic analysis was used to simulate instantaneous loss of a first-story column. Twelve individual column loss scenarios were investigated in the three-story building and four in the ten-story building. This study provides insight into: three-dimensional load redistribution patterns; demands on the steel deck, concrete slab, connections and members; and the impact of framing configuration, building height and column loss location. In the dynamic simulations, demands were least severe for perimeter columns within a moment frame, but the structures also exhibited significant load redistribution for interior column loss scenarios that had no moment connectivity. Composite action was observed to be an important load redistribution mechanism following column loss and the concrete slab and steel deck were subjected to high localized stresses as a result of the composite action. In general, the steel buildings that were evaluated in this study demonstrated appreciable robustness.

• 한국전자파학회논문지
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• 제27권1호
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• pp.42-49
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• 2016

본 논문에서는 지연 선로의 경로차를 이용하여 4~6 GHz의 연속파 신호를 감지하여 125 MHz의 해상도로 순시 주파수를 측정하는 순시 주파수 측정용 수신기를 설계 및 제작하였다. 수신기는 4 비트 지연 선로 구조를 가졌으며, 전력 분배기, 지연 선로, 전력 합성기, 전력 검파기, 비교기 등으로 구성되었다. 각각의 비트에 배정된 지연 선로의 주파수에 따른 경로 손실 차이를 보상하고, 전력 검파 특성의 주파수 의존성을 보정하기 위해 오프셋 전압 보상을 비교기에 적용하여 측정의 정확성을 향상시켰다.

• Journal of Power Electronics
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• 제8권4호
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• pp.345-353
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• 2008

In this paper, a novel loss minimization of an induction generator in wind energy generation systems is presented. The proposed algorithm is based on the flux level reduction, for which the generator d-axis current reference is estimated using support vector regression (SVR). Wind speed is employed as an input of the SVR and the samples of the generator d-axis current reference are used as output to train the SVR algorithm off-line. Data samples for wind speed and d-axis current are collected for the training process, which plots a relation of input and output. The predicted off-line function and the instantaneous wind speed are then used to determine the d-axis current reference. It is shown that the effect of loss minimization is more significant at low wind speed and the loss reduction is about to 40% at 4[m/s] wind speed. The validity of the proposed scheme has been verified by experimental results.

• Journal of Communications and Networks
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• 제5권3호
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• pp.275-281
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• 2003

Random Early Detection (RED) [1] is an active queue management scheme which has been deployed extensively to reduce packet loss during congestion. Although RED can improve loss rates, its performance depends severely on the tuning of its operating parameters. The idea of adaptively varying RED parameters to suit the network conditions has been investigated in [2], where the maximum packet dropping probability $max_p$ has been varied. This paper focuses on adaptively varying the queue weight $\omega_q$ in conjunction with $max_p$ to improve the performance. We propose two algorithms viz., $\omega_q$-thresh and $\omega_q$-ewma to adaptively vary $\omega_q$. The performance is measured in terms of the packet loss percentage, link utilization and stability of the instantaneous queue length. We demonstrate that varying $\omega_q$ and $max_p$ together results in an overall improvement in loss percentage and queue stability, while maintaining the same link utilization. We also show that $max_p$ has a greater influence on loss percentage and queue stability as compared to $\omega_q$, and that varying $\omega_q$ has a positive influence on link utilization.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.5-8
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• 1988

A digital simulation method for Hysteresis motor using Preisach model is proposed. From this, the instantaneous torque, hysteresis loss of rotor can be calculated, considering slot and winding distribution and current harmonics.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.15-17
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• 1995

Hysteresis motor is a synchronous machine which has simple structure and self-start characteristic but also has serious difficulties in numerical analysis. In this study, a finite element analysis for hysteresis motor considering the hysteresis characteristics is presented. The hysteresis model is the magnetization-dependent Preisach model which explains hysteresis phenomena very well. From this, we estimate the instantaneous torque, average torque and hysteresis loss of the rotor, considering slot and winding distribution.

• Korea-Australia Rheology Journal
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• 제13권3호
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• pp.109-123
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• 2001

A stress jump, defined as the instantaneous gain or loss of stress on startup or cessation of a deformation, has been predicted by various models and has relatively recently been experimentally observed. In 1993, Liang and Mackay measured shear stress jump data of xanthan gum solutions, and in 1996, Orr and Sridhar reported extensional stress jump data of Boger fluids. Shear stress jumps of suspensions and liquid crystal polymers have also been observed. In this contribution, experimental work as well as a variety of theoretical models, which are able to predict a stress jump, are reviewed.

• 대한산업공학회지
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• 제11권1호
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• pp.33-39
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• 1985

A stochastic model for an inventory system in which depletion of stock takes place due to random demand as well as random loss of items is studied under the assumption that the intervals between successive unit demands, as well as those between successive unit losses are independently and identically distributed random variables having negative exponential distribution with respective parameters. We have derived the steady state probability distribution of the stock level assuming instantaneous delivery of order under (s, S) inventory policy. Also we have derived total expected cost expression and the necessary conditions to be satisfied for an optimal solution.

• Journal of Communications and Networks
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• 제11권2호
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• pp.157-165
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• 2009

In this paper, we investigate a dynamic spectrum sharing problem for the centralized uplink cognitive radio networks using orthogonal frequency division multiple access. We formulate a large-scale joint rate and power allocation as an optimization problem under quality of service constraint for secondary users and interference constraint for primary users. We also suggest admission control to nd a feasible solution to the optimization problem. To implement the resource allocation on a large-scale, we introduce a notion of using the conservative factors $\alpha$ and $\beta$ depending on the outage and violation probabilities. Since estimating instantaneous channel gains is costly and requires high complexity, the proposed algorithm pursues a practical and implementation-friendly resource allocation. Simulation results demonstrate that the large-scale joint rate and power allocation incurs a slight loss in system throughput over the instantaneous one, but it achieves lower complexity with less sensitivity to variations in shadowing statistics.

• 전력전자학회논문지
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• 제4권1호
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• pp.57-65
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• 1999

본 논문은 충방전 제어기를 사용한 독립형 태양광 발전시스템을 다루고 있다. 독립형 태양광 발전시스템의 주전원은 일반적으로 태양전지와 배터리이다. 그러므로 독립형 태양광 발전시스템은 배터리와 태양전지와의 결선에 따라서 다양한 형태로 구분할 수 있다. 그중 주로 사용되는 결선은 태양전지와 배터리를 직접 연결하는 것으로 단순하고 간결한 구조를 갖는 이점이 있다. 그러나 그러한 시스템은 배터리와 솔라셀 사이의 전압불균형으로 인한 손실을 갖는다. 그러므로 태양전지를 최대전력점으로 운전할 수 있는 충방전 제어기를 갖는 독립형 태양광 발전시스템을 제안하여 순시치제어기로 설계하였다. 시스템의 동작특성을 실험실의 초기 시작품으로 검증되었다.