• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권5호
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• pp.1682-1701
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• 2015

In this paper, we propose an intergraded unified imperfect CSI model and investigate the joined effects of feedback delay and channel estimation errors (CEE) for two-hop relaying systems with transmit beamforming and relay selection. We derived closed-form expressions for important performance measures including the exact analysis and lower bounds of outage probability as well as error performance. The ergodic capacity is also included with closed-form results. Furthermore, diversity and coding gains based on the asymptotic analysis at high SNRs are also presented, which are simple and concise and provide new analytical insights into the corresponding power allocation scheme. The analysis indicates that delay effect results in the coding gain loss and the diversity order loss, while CEE will merely cause the coding gain loss. Numerical results verify the theoretical analysis and illustrate the system is more sensitive to transmit beamforming delay compared with relay selection delay and also verify the superiority of optimum power allocation. We further investigate the outage loss due to the CEE and feedback delays, which indicates that the effect of the CEE is more influential at low-to-medium SNR, and then it will hand over the dominate role to the feedback delay.

• Communications for Statistical Applications and Methods
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• 제20권4호
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• pp.311-319
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• 2013

Cooray and Ananda (2005) proposed a composite lognormal-Pareto model to analyze loss payment data in the actuarial and insurance industries. Their model is based on a lognormal density up to an unknown threshold value and a two-parameter Pareto density. In this paper, we implement the minimum density power divergence estimation for the composite lognormal-Pareto density. We compare the performances of the minimum density power divergence estimator (MDPDE) and the maximum likelihood estimator (MLE) by simulations and an example. The minimum density power divergence estimator performs reasonably well against various violations in the distribution. The minimum density power divergence estimator better fits small observations and better resists against extraordinary large observations than the maximum likelihood estimator.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1345-1351
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• 2013

Variable iron loss as function of current phase angle of Interior Permanent Magnet Synchronous Motor(IPMSM) was calculated through Curve Fitting Method(CFM). Also, a magnetic flux density distribution of iron core according to current phase angle was analyzed, and an iron loss calculation was performed including harmonic distortion. The experiment was performed by production of non-magnetizing model for the separation of mechanical loss, and the iron loss was calculated by the measurement of input using power analyzer and output power using dynamometer. Some error was generated between experimental results and calculation value, but an iron loss diminution according to current phase angle followed a same pattern. So, errors were generated by measurement, vibration, noise, harmonic distortion loss, etc.

• 한국초전도ㆍ저온공학회논문지
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• 제12권3호
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• pp.16-20
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• 2010

For large scale power applications of HTS conductor, it is getting more important to have a stacked HTS coated conductor with low loss and large current capacity. But it was not easy to measure some electric properties. Stabilizer free YBCO CC for striated/ stacked conductors is easily burned out during the measurement of the critical current density because it has no stabilizer and it is difficult to set-up the current lead and voltage taps because it has many pieces of YBCO CC in a conductor. Instead of direct measuring the critical current of a stacked HTS coated conductor, indirect estimation from measuring a magnetization loss of HTS coated conductor could be useful for practical estimation of the critical current. The magnetization loss of a superconductor is supposed to be affected by a full penetrating magnetic field, and it tends to show an inflection point at the full penetrating magnetic field when we generate the graph of magnetization loss vs. external magnetic field. The full penetrating magnetic field depends on the shape of the conductor and its critical current density, so we can estimate the effective critical current density from measuring the magnetization loss. In this paper, to prove the effectiveness of this indirect estimation of the critical current, we prepared several different kinds of YBCO CC(coated conductor) including a stacked conductor short samples and measured the magnetization losses and the critical currents of each sample by using linked pick up coils and direct voltage measurement with transport current respectively.

• Nuclear Engineering and Technology
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• 제46권1호
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• pp.39-46
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• 2014

A total loss of all heat sinks is considered a severe accident with a low probability of occurrence. Following a total loss of all heat sinks, the degasser/condenser relief valves (DCRV) become the sole means available for the depressurization of the primary heat transport system. If a nuclear power plant has a total loss of heat sinks accident, high-temperature steam and differential pressure between the primary heat transport system (PHTS) and the steam generator (SG) secondary side can cause a SG tube creep rupture. To protect the PHTS during a total loss of all heat sinks accident, a sufficient depressurization capability of the degasser/condenser relief valve and the SG tube integrity is very important. Therefore, an accurate estimation of the discharge through these valves is necessary to assess the impact of the PHTS overprotection and the SG tube integrity of the primary circuit. This paper describes the analysis of DCRV discharge capacity and the SG tube integrity under a total loss of all heat sink using the CATHENA code. It was found that the DCRV's discharge capacity is enough to protect the overpressure in the PHTS, and the SG tube integrity is maintained in a total loss of all heat accident.

• Journal of Magnetics
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• 제16권2호
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• pp.124-128
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• 2011

This study estimated experimentally the loss distribution caused by magnetic friction in magnetic parts of a superconductor flywheel energy storage system (SFES) to obtain information for the design of high efficiency SFES. Through the spin down experiment using the manufactured vertical shaft type SFES with a journal type superconductor magnetic bearing (SMB), the coefficients of friction by the SMB, the stator core of permanent magnet synchronous motor/generator (PMSM/G), and the leakage flux of the metal parts were calculated. The coefficients of friction by the stator core of PMSM/G in case of using Si-steel and an amorphous core were calculated. The energy loss by magnetic friction in the stator core of PMSM/G was much larger than that in the other parts. The level of friction loss could be reduced dramatically using an amorphous core. Energy loss by the leakage magnetic field was small. On the other hand, the energy loss could be increased under other conditions according to the type of metal nearby the leakage magnetic fields. In manufactured SFES, the rotational loss by the amorphous core was approximately 2 times the loss of the superconductor and leakage. Moreover, the rotational loss by the Si-steel core is approximately 3~3.5 times the loss of superconductor and leakage.

• 한국전자파학회논문지
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• 제25권7호
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• pp.757-766
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• 2014

본 논문은 거시적인 접근방법을 이용하여 고출력 전자기파에 대한 피해 비용을 보다 실제적으로 산출하기 위한 방법을 제시하고, 이에 대한 피해액을 계산하였다. 먼저 취약성 분석을 통하여 사회 기반 시설 중 사회적으로 가장 큰 혼란을 야기할 수 있을 것이라고 판단되는 전력망에 집중하여 연구하였으며, 이에 대해 고출력 전자기파에 의한 피해액 계산식은 GDP에 대한 총 에너지 소비를 고려하여 고출력 전자기파 피해 시 발생할 수 있는 피해 손실을 효과적으로 예측하기 위한 방법을 제시하였다. 피해액은 고출력 전자기파의 공격 형태에 따라 피해 범위를 설정하고 계산하였으며, 이러한 피해액 계산을 통하여 고출력 전자기파에 취약한 시설에 대해서는 피해액 산출 후 방호 비용과 비교하여 시설 방호 대책을 수립할 수 있는 기반을 마련할 수 있을 것이다.

• Journal of Advanced Research in Ocean Engineering
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• 제1권2호
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• pp.73-84
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• 2015

The turbine is one of the most important components in the tidal current power device which can convert current flow to rotational energy. Generally, a tidal turbine has two or three blades that are subjected to hydrodynamic loads. The blades are continuously deformed by various incoming flow velocities. Depending on the velocities, blade size, and material, the deformation rates would be different that could affect the power production rate as well as turbine performance. Surely deformed blades would decrease the performance of the turbine. However, most studies of turbine performance have been carried out without considerations on the blade deformation. The power estimation and analysis should consider the deformed blade shape for accurate output power. This paper describes a fluid-structure interaction (FSI) analysis conducted using computational fluid dynamics (CFD) and the finite element method (FEM) to estimate practical turbine performance. The loss of turbine efficiency was calculated for a deformed blade that decreased by 2.2% with maximum deformation of 216mm at the blade tip. As a result of the study, principal causes of power loss induced by blade deformation were analysed and summarised in this paper.

• International Journal of Advanced Culture Technology
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• 제3권2호
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• pp.144-148
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• 2015

The paper presents the estimation of power losses in distribution transformer of Provincial Electricity Authority (PEA) distribution system at Muang district of Suphanburi province in Thailand. Data of 416 power distribution transformers composed of transformer (kVA), load current, no load loss and full load loss which were used for calculating energy losses. It was found that the total energy loss of all transformers is approximately 1,756,380 kWh/year.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.86-88
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• 2008

The rotational loss is one of the most important problems for the practical use of the high power Flywheel Energy Storage System (FESS). This rotational loss is divided as the mechanical loss by windage and bearing and iron loss by hysteresis loop and eddy current in the part of the magnetic field. So, In this paper, a double-sided PMSM/G without the iron loss is designed by analytical method of the magnetic field and estimation of the back-EMF constant represented as the design parameter. This design model consists of the double-sided PM rotor with Halbach magnetized any and coreless 3-phase winding stator. The results show that the double-sided PMSM/G without iron loss can be applicable to the high power FESS.