• Journal of Power Electronics
• /
• v.12 no.3
• /
• pp.410-417
• /
• 2012

In this paper, a direct current control method based on a one-cycle controller (DCOCC) for double frequency buck converters (DF buck) is proposed. This control method can make the average current through the high frequency and low frequency inductors of a DF buck converter equal. This is similar to the average current control method. However, the design of the loop compensator is much easier when compared with the average current control. Since the average current though the high frequency and low frequency inductors is equivalent, the current stress of the high frequency switches and the switch losses are minimized. Therefore, the efficiency of the DF buck converter is improved. Firstly, the operation principle of DCOCC is described, then the small signal models of a one cycle controller and a DF buck converter are presented based on the state space average method. Eventually, a system block diagram of the DCOCC controlled DF buck is established and the compensator is designed. Finally, simulation and experiment results are given to verify the correction of the theory analysis.

• Fire Science and Engineering
• /
• v.23 no.2
• /
• pp.1-5
• /
• 2009

We studies wish to investigated establishment form of cabinet board, and confirm possibility of electrical disaster prevention through reappearance experiment of odor detection system. Established breaker consists of MCCB, RCD order in cabinet board for house, but industry is used together with. When imposed shock using shaker to terminal block that contact becomes in appropriate, flame was made sure. According to result that experiment attaching odor capsule in terminal block, capsule commissioned exactly by occurred heat. According to establishment position of sensor, difference of inspection time was about 10 seconds. Estimate odor inspection system by thing which electrical device accident prevention is available. When there is abnormal generated heat in connection of electric wire, accident prevention estimates that is possible by giving an alarm state of overheat to administrator.

• Macromolecular Research
• /
• v.17 no.2
• /
• pp.104-109
• /
• 2009

Solid-state facilitated, olefin transport membranes were prepared by complexation of poly(styrene-b-iso-prene-b-styrene) (SIS) block copolymer and silver salt. Facilitated olefin transport was not observed up to a silver mole fraction of 0.14, representing a threshold concentration, above which transport increased almost linearly with increasing silver salt concentration. This was because firstly the silver ions were selectively coordinated with the C=C bonds of PI blocks up to a silver mole fraction of 0.20, and secondly the coordinative interaction of the silver ions with the aliphatic C=C bond was stronger than that with the aromatic C=C bond, as confirmed by FT-Raman spectroscopy. Small angle X-ray scattering (SAXS) analysis showed that the cylindrical morphology of the neat SIS block copolymer was changed to a disordered structure at low silver concentrations ($0.01{\sim}0.02$). However, at intermediate silver concentrations ($0.15{\sim}0.20$), disordered-ordered structural changes occurred and finally returned to a disordered structure again at higher silver concentrations (>0.33). These results demonstrated that the facilitated olefin transport of SIS/silver salt complex membrancs was significantly affected by their coordinative interactions and nano-structural morphology.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.4
• /
• pp.1241-1250
• /
• 1996

The characteristics of fatigue cumulative damage and fatigue life of 8-harness satin woven CFRP composites with a circular hole under constant amplitude and 2-level block loading are estimated by Stochastic Makov chain model. It is found in this study that the fatigue damage accumulation behavior is very random and the fatigue damage is accumulated as two regions under constant amplitude fatigue loading. In constant amplitude fatigue loading the predicted mean number of cycles to a specified damage state by Markov chain model shows a good agreement with the test result. The predicted distribution of the fatigue cumulative damage by Markov chain model is similar to the test result. The fatigue life predictions under 2-level block loading by Markov chain model revised are good fitted to the test result more than by 2-parameter Weibull distribution function using percent failure rule.

• Proceedings of the KIEE Conference
• /
• 1998.11b
• /
• pp.410-412
• /
• 1998

Some resent papers deals with the solution of LTI singular systems described in state-space via orthogonal functions. There are some complexity to derive the solution because all the previous works[2]-[5] used orthogonal function's integral operation. Therefore, in this paper, some new results are introduced by using a differential operation of orthogonal function to solve the LTI singular systems.

• Proceedings of the KIEE Conference
• /
• 1993.07a
• /
• pp.54-56
• /
• 1993

A systematic procedure for determining the elements of system state matrix is suggested. The interrelation of submatrices of the system matrix is investigated. Each element or each block can be represented in algebraic form. These results can be applied in the eigenvalue sensitivity analysis with respect to the changes in controller parameters.

• Journal of the Korean Society for Railway
• /
• v.7 no.4
• /
• pp.319-325
• /
• 2004

In this study, analysis and design programs of bending of RC beams strengthened with fiber sheets are developed by using Visual Basic Language. The program consists two groups, ultimate strength method and nonlinear flexural analysis method. Ultimate strength method regards concrete compressive stress as a rectangular stress block and do not consider tensile stress of concrete and load-deflection curves. On the other hand, nonlinear flexural analysis considers tensile stress of concrete, load-deflection curves, state of stress distribution and failure strain of strengthening material. Also, the analysis method used in this study regards nonlinear flexural stress as compressive stress of concrete. This program can be a good tool for determining the bending strength of strengthened RC beams and estimating the amount of fiber sheets for practical use.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.13 no.4
• /
• pp.1961-1974
• /
• 2019

In this letter, a harmonic-mean-based dual-antenna selection scheme at relay node is proposed in two-way relaying networks (TWRNs). With well-designed distributed orthogonal concatenated Alamouti space-time block code (STBC), a dual-antenna selection problem based on the instantaneous achievable sum-rate criterion is formulated. We propose a low-complexity selection algorithm based on the harmonic-mean criterion with linearly complexity $O(N_R)$ rather than the directly exhaustive search with complexity $O(N^2_R)$. From the analysis of network outage performance, we show that the asymptotic diversity gain function of the proposed scheme achieves as $1/{\rho}{^{N_R-1}}$, which demonstrates one degree loss of diversity order compared with the full diversity. This slight performance gap is mainly caused by sacrificing some dual-antenna selection freedom to reduce the algorithm complexity. In addition, our proposed scheme can obtain an extra coding gain because of the combination of the well-designed orthogonal concatenated Alamouti STBC and the corresponding dual-antenna selection algorithm. Compared with the common-used selection algorithms in the state of the art, the proposed scheme can achieve the best performance, which is validated by numerical simulations.

• Journal of Advanced Research in Ocean Engineering
• /
• v.1 no.3
• /
• pp.148-156
• /
• 2015

Deck plates of ships or offshore structures would make out-of-plane distortion for their thin thickness. These distortions are usually straightened by thermal straightening such as flame heating method. After thermal straightening, the blocks are lifted and moved by cranes to assemble it at dry-dock stage. After this lifting process, out-of-plane deformation again happens frequently. And then, they continuously cause quality and accuracy problems in the final dry-dock process. So, it takes more time for repair and correction working. According to preceding research, the lifting process by cranes would offset the effect on thermal straightening. The target of this study is to develop a methodology analyzing the remaining efficiency of thermal straightening after block lifting. The development was based on the assumption of yield state at straightening region. Therefore the remaining efficiency was obtained by different stiffness slope while lifting & relieving. The efficiency formula was designed using inherent strain, and we made a table of zero-efficiency by cooling speed and class rule's steels. As a result, if the stress orthogonal to straightened line is calculated during lifting analysis by FEA, the efficiency can be obtained linearly to the values in the table. Finally, even optimized carling position can be designed by considering the regional data from series project and welding region on deck.

• Journal of the Korea Safety Management & Science
• /
• v.13 no.3
• /
• pp.45-53
• /
• 2011

The research proposes seven elimination rules of redundant gates and blocks in Fault Tree Analysis (FTA) and Reliability Block Diagram (RBD). The computational complexity of cut sets and path sets is NP-hard. In order to reduce the complexity of Minimal Cut Set (MCS) and Minimal Path Set (MPS), the paper classifies generation algorithms. Moreover, the study develops six implementation steps which reflect structural importance (SI) and reliability importance (RI) from Reliability Centered Maintenance (RCM) that a priority of using the functional logic among components is to reduce (improve) the system unavailability (or availability). The proposed steps include efficient generation of state structure function by Rare Event Enumeration (REA). Effective use of importance measures, such as SI and ill measures, is presented based on the number and the size of MCS and MPS which is generated from the reference[5] of this paper. In addition, numerical examples are presented for practitioners to obtain the comprehensive understanding of six steps that is proposed in this research.