• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1170-1171
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• 2008

Microsources supply high quality power from 1kW to a matter of MW with higher reliability and energy efficiency than the existing large power facilities. In this paper, we designed dynamic modeling of Microturbine and Fuel cell being worthy as a small distributed energy source. Using EMTP we designed the dynamic modeling and confirmed characteristics of steady-state and dynamic analysis. In this paper, we designed dynamic modeling of Microturbine and Fuel cell being worthy as a small distributed energy source and analyzed dynamic characteristics corresponding to load variation.

• International Journal of Air-Conditioning and Refrigeration
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• v.15 no.4
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• pp.147-155
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• 2007

Mobile air conditioning systems work under widely changing operating conditions. To understand the system behavior under such dynamic conditions, a test facility that can impose transient loads as well as conducting dynamic measurements is needed. To test mobile air conditioning systems including their dynamic performance under various drive cycle patterns without using full scale vehicles in a wind tunnel, a new test facility, called "dynamic simulator," is described. It can replicate real vehicle operating conditions by interacting with the system being tested based on the measured system performance and subsequently adjusting the air properties returning to the test system based on the results of a numerical cabin model. A new dynamic simulator has been designed, constructed, and verified for performing dynamic tests. It was successful in controlling the temperature and relative humidity of the air returning to the test unit within ${\pm}0.7^{\circ}C$ and ${\pm}4%$ of their respective intended values. The verification test under the New European Driving Cycle demonstrated that detailed transient behavior of the mobile air conditioning system could be measured by using this dynamic simulator.

• Geomechanics and Engineering
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• v.29 no.4
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• pp.451-461
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• 2022

The roadways surrounded by rock and coal will lose their stability or even collapse under rock burst. Rock burst mainly involves an evolution of dynamic loading which behaves quite differently from static or quasi-static loading. To compare the dynamic response of coal and rocks with different static strengths, three different rocks and bituminous coal were selected for testing at three different dynamic loadings. It's found that the dynamic compression strength of rocks and bituminous coal is much greater than the static compression strength. The dynamic compression strength and dynamic increase factor of the rocks both increase linearly with the increase of the strain rate, while those of the bituminous coal are irregular due to the characteristics of multi-fracture and heterogeneity. Moreover, the absorbed energy of the rocks and bituminous coal both increase linearly with an increase in the strain rate. And the ratio of absorbed energy to the total energy of bituminous coal is greater than that of rocks. With the increase of dynamic loading, the failure degree of the sample increases, with the increase of the static compressive strength, the damage degree also increases. The static compassion strength of the bituminous coal is lower than that of rocks, so the number of small-scale fragments was the largest after bituminous coal rupture.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1777-1788
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• 2017

This paper presents the design and dynamic analysis of a stand-alone microgrid with high penetration of renewable energy. The optimal sizing of various components in the microgrid is obtained considering two objectives: minimization of levelized cost of energy (LCOE) and maximization of renewable energy penetration. Integrating high renewable energy in stand-alone microgrid requires special considerations to assure stable dynamic performance, we therefore develop voltage and frequency control method by coordinating Battery Energy Storage System (BESS) and diesel generators. This approach was applied to the design and development of Gasa Island microgrid in South Korea. The microgrid consists of photovoltaic panels, wind turbines, lithium-ion batteries and diesel generators. The dynamic performance of the microgrid during different load and weather variations is verified by simulation studies. Results from the real microgrid were then presented and discussed. Our approach to the design and control of microgrid will offer some lessons in future microgrid design.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.707-714
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• 2016

We present a piezoelectric energy harvester with stopper-engaged dynamic magnifier which is capable of significantly increasing the operating bandwidth and the energy (power) harvested from a broad range of low frequency vibrations (<30 Hz). It uses a mass-loaded polymer beam (primary spring-mass system) that works as a dynamic magnifier for another mass-loaded piezoelectric beam (secondary spring-mass system) clamped on primary mass, constituting a two-degree-of-freedom (2-DOF) system. Use of polymer (polycarbonate) as the primary beam allows the harvester not only to respond to low frequency vibrations but also generates high impulsive force while the primary mass engages the base stopper. Upon excitation, the dynamic magnifier causes mechanical impact on the base stopper and transfers a secondary shock (in the form of impulsive force) to the energy harvesting element resulting in an increased strain in it and triggers nonlinear frequency up-conversion mechanism. Therefore, it generates almost four times larger average power and exhibits over 250% wider half-power bandwidth than those of its conventional 2-DOF counterpart (without stopper). Experimental results indicate that the proposed device is highly applicable to vibration energy harvesting in automobiles.

• Journal of Radiation Protection and Research
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• v.28 no.3
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• pp.239-245
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• 2003

Every nuclear power plant measured concentrations of tritium in groundwater and surface water around the plants periodically. It was not easy to predict the tritium concentration only with these measurement data in case of various release scenarios. KAERI developed a new approach to find the relationship between the tritium release rate and tritium concentration in the environment. The approach was based upon a dynamic compartment model. In this paper the dynamic compartment model was modified to predict the tritium behavior more accurately. The mechanisms considered for the transfer of tritium between the compartments were evaporation, groundwater flow, infiltration, runoff, and hydrodynamic dispersion. Time dependent source terms of the compartment model were introduced to refine the release scenarios. Also, transfer coefficients between the compartments were obtained using realistic geographical data. In order to illustrate the model various release scenarios were developed, and the change of tritium concentration in groundwater and surface water around the nuclear power plants was estimated.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.5
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• pp.949-966
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• 2013

Recently, Wireless Body Area Network (WBAN) has promise to revolutionize human daily life. The need for multiple sensors and constant monitoring lead these systems to be energy hungry and expensive with short operating lifetimes. In this paper, we offer a review of existing work of WBAN and focus on energy-aware management in it. We emphasize that nodes computation, wireless communication, topology deployment and energy scavenging are main domains for making a long-lived WBAN. We study the popular power management technique Dynamic Voltage and Frequency Scaling (DVFS) and identify the impact of slack time in Dynamic Power Management (DPM), and finally propose an enhanced dynamic power management method to schedule scaled jobs at slack time with the goal of saving energy and keeping system reliability. Theoretical and experimental evaluations exhibit the effectiveness and efficiency of the proposed method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.12
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• pp.2157-2164
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• 2010

Microgrid is generally defined as cluster of small distributed generators, energy storages and loads. Through monitoring and coordinated control, microgrid can provide various benefits such as reduction of energy cost, peak shaving and power quality improvement. In design stage of microgrid, system dynamic simulation is necessary for optimizing of sizing and siting of DER(distributed energy resources). As number of the system components increases, simulation time will be longer. This problem can restrict optimal design. So we used simplified modeling on energy sources and average switching model on power converters to reduce simulation time. The effectiveness of this method is verified by applying to prototype microgrid system, which is consist of photovoltaic, wind power, diesel engine generators, battery energy storage system and loads installed in laboratory. Simulation by Matlab/Simulink and measurements on prototype microgrid show that the proposed method can reduce simulation time not sacrificing dynamic characteristics.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.8
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• pp.1825-1842
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• 2013

Rapid growth of the IT industry has led to significant energy consumption in the last decade. Data centers swallow an enormous amount of electrical energy and have high operating costs and carbon dioxide excretions. In response to this, the dynamic consolidation of virtual machines (VMs) allows for efficient resource management and reduces power consumption through the live migration of VMs in the hosts. Moreover, each client typically has a service level agreement (SLA), this leads to stipulations in dealing with energy-performance trade-offs, as aggressive consolidation may lead to performance degradation beyond the negotiation. In this paper we propose a heuristic based resource allocation of VM selection and a VM allocation approach that aims to minimize the total energy consumption and operating costs while meeting the client-level SLA. Our experiment results demonstrate significant enhancements in cloud providers' profit and energy savings while improving the SLA at a certain level.

• ETRI Journal
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• v.43 no.3
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• pp.427-435
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• 2021

Data filtering is an essential task for improving the energy efficiency of radiofrequency identification (RFID) networks. Among various energy-efficient approaches, clustering-based data filtering is considered to be the most effective solution because data from cluster members can be filtered at cluster heads before being sent to base stations. However, this approach quickly depletes the energy of cluster heads. Furthermore, most previous studies have assumed that readers are fixed and interrogate mobile tags in a workspace. However, there are several applications in which readers are mobile and interrogate fixed tags in a specific area. This article proposes a model for dynamic clustering-based data filtering (DCDF) in mobile RFID networks, where mobile readers are re-clustered periodically and the cluster head role is rotated among the members of each cluster. Simulation results show that DCDF is effective in terms of balancing energy consumption among readers and prolonging the lifetime of the mobile RFID networks.