• Transactions on Electrical and Electronic Materials
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• v.17 no.6
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• pp.335-340
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• 2016

The vibrational energy is prevalent in the natural environment, which is studied by energy researchers as a new energy resource in recent years. Vibration generation utilizes electromagnetic induction technology, piezoelectric technology and certain characteristics of smart materials to convert mechanical energy into electrical energy. In this paper, a new method of using MSMA (magnetic shape memory alloy) to generate electricity is proposed and the principle of generating electricity is demonstrated. Martensitic variants and magnetic domain characteristics of MSMA are analyzed. Combining with Gibbs free energy function thermal theory, the mathematics model of MSMA vibration generator is established. The basic structure of MSMA vibration generator is designed and simulation is done to analyze that the effects of generator output voltage when the input amplitude and frequency of vibration stress change. The simulation experiments verify the feasibility of using MSMA to make the micro vibration generators and the correctness of the mathematical model, which lays a good foundation for the further research and application of MSMA vibration generator.

• Transactions on Electrical and Electronic Materials
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• v.15 no.6
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• pp.297-304
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• 2014

Due to the nonlinearity and complexity of the three-phase photovoltaic inverter, we propose an intelligent control based on fuzzy logic and the classical proportional-integral-derivative. The feedback linearization method is applied to cancel the nonlinearities, and transform the dynamic system into a simple and linear subsystem. The system is transformed from abc frame to dq0 synchronous frame, to simplify the state feedback linearization law, and make the close-loop dynamics in the equivalent linear model. The controls improve the dynamic response, efficiency and stability of the three-phase photovoltaic grid system, under variable temperature, solar intensity, and load. The intelligent control of the nonlinear characteristic of the photovoltaic automatically varies the coefficients $K_p$, $K_i$, and $K_d$ under variable temperature and irradiation, and eliminates the oscillation. The simulation results show the advantages of the proposed intelligent control in terms of the correctness, stability, and maintenance of its response, which from many aspects is better than that of the PID controller.

• Industrial Engineering and Management Systems
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• v.14 no.1
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• pp.88-93
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• 2015

In this paper, we identify the characteristics of modeling and simulation (M&S) for military and defense and propose the method of verification, validation, and accreditation (VV&A) using the identified characteristics. M&S has been widely used for many different applications in military and defense, including training, analysis, and acquisition. Various methods and processes of VV&A have been proposed by researchers and M&S practitioners to guarantee the correctness of M&S. The notion of applying formal credibility assessment in VV&A originated in software engineering reliability testing and the systems engineering development process. However, the VV&A techniques and processes proposed for M&S by the research community have not addressed the characteristics and issues specific to military and defense. We first identify the characteristics and issues of military/defense M&S and then propose techniques and methods for VV&A that are specific for military/defense M&S. Possible approaches for the development of VV&A are also proposed.

• Journal of the Korea Society for Simulation
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• v.16 no.1
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• pp.59-68
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• 2007

IT (Intrusion Tolerant) technology is for guaranteeing the availability of service for certain amount time against the attacks which couldn't be prevented by the currently deployed information security countermeasures. IT (Intrusion Tolerant) technology mainly makes use of the replication of service and system fur enhancing availability, and voting scheme and GMP (Croup Management Protocol) are used for the correctness of service. This paper presents a scheme to analyze dependability of IT (Intrusion Tolerant) technology through probabilistic and simulation method. Using suggested analysis scheme, we can analyze the robustness and make a sensible trade-offs in of IT (Intrusion Tolerant) technology.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11a
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• pp.535-538
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• 2002

InfiniBand is a switched-fabric architecture for next generation I/O systems and data centers. The InfiniBand Architecture (IBA) promises to replace bus-based architectures, such as PCI, with a switched-based fabric whose benefits include higher performance, higher RAS (reliability, availability, scalability), and the ability to create modular networks of servers and shared I/O devices. The switched-fabric InfiniBand consists of InfiniBand subnets with channel adapters, switches, and routers. In order to fully grasp the operational characteristics of InfiniBand architecture (IBA) and use them in ongoing design specification, simulation of subnet management of IBA is inevitable. In this paper, thus, we implement an IBA simulator and test some practical sample networks using it. The simulator shows the flow of operation by which the correctness and effectiveness of the system can be verified.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.64-75
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• 2007

Service discovery protocols is software components to find specific services or resources on network. The SLP defined by IETF protocol is a framework for automatic service discovery on IP based networks. Automatic service discovery is an important component on ubiquitous computing environment. This paper proposes a service discovery architecture named as SLPA(Service Location Protocol based on AMAAM). AMAAM(Mobility Agent Advertisement Mechanism) is an aggregation-based Mobile IP implementation in MANET. In SLPA, the role of the directory agent is assigned to the mobility agent in AMAAM. The mobility agent periodically beacons an advertisement message which contains both the advertisement of the directory agent in SLP and the advertisement of the mobility agent in Mobile IP. For evaluating the functional correctness of SLPA and the overhead of maintaining a service directory of SLPA. We simulate SLPA using ns-2 and analyze the overhead of control overheads for the aggregation. Through the simulation experiments we show the functional correctness of the proposed architecture and analyze the performance results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3B
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• pp.152-158
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• 2008

Recently, DDoS (Distributed Denial of Service) attack has emerged as one of the major threats and it's main characteristic is to send flood of data packets toward a specific victim. Thus, several attack detection schemes which monitor the destination IP address of packets have been suggested. The existing Bloom Filter based attack detection scheme is simple and can support real-time monitoring. However, since this scheme monitors the separate fields of destination IP address independently, wrong detection is comparatively high. In this paper, in order to solve this drawback, an efficient Bloom Filter based destination address monitoring scheme is proposed, which monitors not only separate fields but also relationship among separate fields. In the results of simulation, the proposed monitoring scheme outperforms the existing Bloom Filter based detection scheme. Also, to improve the correctness of detection, multi-layerd structure is proposed and the correctness of result is improved according to the number of layers and extra tables.

• Advances in aircraft and spacecraft science
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• v.3 no.4
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• pp.471-502
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• 2016

This paper presents the dynamic instability analysis of un-damped elastically supported piezoelectric functionally graded (FG) beams subjected to in-plane static and dynamic periodic thermomechanical loadings with uncertain system properties. The elastic foundation model is assumed as one parameter Pasternak foundation with Winkler cubic nonlinearity. The piezoelectric FG beam is subjected to non-uniform temperature distribution with temperature dependent material properties. The Young's modulus and Poison's ratio of ceramic, metal and piezoelectric, density of respective ceramic and metal, volume fraction exponent and foundation parameters are taken as uncertain system properties. The basic nonlinear formulation of the beam is based on higher order shear deformation theory (HSDT) with von-Karman strain kinematics. The governing deterministic static and dynamic random instability equation and regions is solved by Bolotin's approach with Newmark's time integration method combined with first order perturbation technique (FOPT). Typical numerical results in terms of the mean and standard deviation of dynamic instability analysis are presented to examine the effect of slenderness ratios, volume fraction exponents, foundation parameters, amplitude ratios, temperature increments and position of piezoelectric layers by changing the random system properties. The correctness of the present stochastic model is examined by comparing the results with direct Monte Caro simulation (MCS).

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.1
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• pp.120-126
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• 2013

The main aim of this paper is to expound high-efficiency operation of Switched Reluctance Generator (SRG) based on the current waveform. For this purpose, theoretical analysis of the copper loss and iron loss of the system is done first. Then, necessary simulation is done to find the variation trend of the copper loss and iron loss with the variation of the current waveform at the same output power. Finally, the best current waveform which can make the system operate with high efficiency is obtained by considering the influence of these two kinds of loss. In order to verity the simulation results, the experimental platform of DC motor-SRG is built and the modified angle position control (APC) method which can specify the current shape optionally is presented. By comparing the system efficiency at the three kinds of typical current waveform, the correctness and feasibility of the theory is verified. The proposed method is simple, reliable, and easy to achieve.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.843-846
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• 2004

Cavity tone is generated due to the feedback between flow and acoustic wave. It is recognized that the period is determined by the time required for the flow convection in one direction, the time required for the acoustic propagation in the other direction and the time for phase shift depending on the flows and mode. Most of the phenomena have been investigated by experiments and a simple but fundamental theory. But the cause of the phase shift and the correctness of the theory have not been clearly explained so far. In this paper, the phenomena are calculated numerically to obtain detail information of flow and acoustic wave to explain the mechanism including the phase. High order high resolution scheme of optimized high order compact is used to resolve the small acoustic quantities and large flow quantities at the same time. The data are reduced using cross correlation function in space and time and cross spectral density function which has phase information. Abrupt change in pressure near corner in cavity is observed and is relate to phase variation. The time required for the feedback between the flow and acoustic wave is calculated after the numerical simulation f3r various modes. The periods based on the time calculated using the above method and direct observation from the acoustic waves generated and propagated in the numerical simulation are compared. It is found that no phase shift is required if we examine the time required carefully. Rossiter's formula for the cavity tone used for quick estimation needs to be modified far some modes.