• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.563-566
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• 2006

An investigation has been carried for the thermal characteristics of the seasonal storage installation in Cheju. It features the solar collector area of $340m^2$ and the storage capacity of $600m^3$. Four different types of solar collector systems are compared for their performance of collecting solar energy throughout the year. Of these, two are made of tubular shaped vacuum collectors and the others are flat plate collectors. Results indicate that each system could play an important role in exploiting solar energy depending on the temperature range in its operation. Especially, the vacuum collectors outperformed the others when the inlet temperatures of the collector loop were raised beyond $40m^2$. This became more conspicuous as the return temperatures from the storage tank rose reflecting the seasonal variation. Due to the large heat capacity of the storage tank, temperature changes were rather small compared to those in the collecting loop regardless of seasonal fluctuations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.748-753
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• 2000

Nowadays, many studies and researches in data storage have been carried out and storage capacity is increased. But the limitation of storage capacity is happened for several problems. One of them is spot & pit size in optical and magnetic data storage and another is the resolution of actuators. The problems in spot & pit size is covered by new data storage methods- for example, NFR{Near-Field Recoding) system. But the resolution limit of an actuator doesn't follow up the development of spot & pit size. Because of them, we should improve a resolution of an actuator. Especially, in this paper an actuator is studied and designed for NFR(in using SIL(Solid Immersion Lens) system. It is a dual stage actuator, which consists of a Fine actuator and a Coarse actuator, and should desire 100nm accuracy. But, our actuator system only includes tracking mechanism execpt focusing mechanism which is controlled by slider mechanism used in HDD. Its actuating force generation method is VCM(Voice Coil Motor). The Fine actuator is composed of 4-leaf springs and a bobbin wrapped by coil. The Coarse actuator has Coils and 3-Roller bearings.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.3
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• pp.169-177
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• 2014

Operation and control system has been installed and tested to use energy storage system(ESS) for frequency regulation at 4MW class of ESS demonstration facility installed at Jeju island, Korea in 2013. Simulation tests were performed by programing language C# for power system of Jeju island to develop control algorithm. Site simulation tests were performed in control system itself without connecting power system and energy storage system. Control algorithm was coded, modified and tested to load to controller and communication system and human-machine interface were developed and tested in the process of simulation tests. After similar results to that of simulation tests by programing language were obtained, power system and energy storage system demonstration facility were connected to control system by communication system. Energy storage system for frequency regulation was tested for actual frequency and simulation frequency. The site tests showed the similar results to that of simulation tests and the control systems is possible to be operated for frequency regulation. Faster response of energy storage system for frequency regulation, less costs and less capacity of energy storage systems which cover for frequency regulation of power plants. It is expected that more studies for time-reduction and time-delay elements can make less capacity of energy storage system cover more role of frequency regulation of power plants.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.60-66
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• 2014

A control oriented model of the Lean $NO_x$ trap (LNT) was developed to determine the timing of $NO_x$ regeneration. The LNT model consists of $NO_x$ storage and reduction model. Once $NO_x$ is stored ($NO_x$ storage model), at the right timing $NO_x$ should be released and then reduced ($NO_x$ reduction model) with reductants on the catalyst active sites, called regeneration. The $NO_x$ storage model simulates the degree of stored $NO_x$ in the LNT. It is structured by an instantaneous $NO_x$ storage efficiency and the $NO_x$ storage capacity model. The $NO_x$ storge capacity model was modeled to have a Gaussian distribution with a function of exhaust gas temperature. $NO_x$ release and reduction reactions for the $NO_x$ reduction model were modeled as Arrhenius equations. The parameter identification was optimally performed by the data of the bench flow reactor test results at space velocity 50,000/hr, 80,000/hr, and temperature of $250-500^{\circ}C$. The LNT model state, storage fraction indicates the degree of stored $NO_x$ in the LNT and thus, the timing of the regeneration can be determined based on it. For practical purpose, this model will be verified more completely by engine test data which simulate the NEDC transient mode.

• Journal of Electrical Engineering and Technology
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• v.5 no.2
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• pp.228-238
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• 2010

There is an increasing interest in research to help overcome the energy crisis that has been focused on energy storage applications in various parts of power systems. Energy storage systems are good at enhancing the reliability or improving the efficiency of a power system by creating a time gap between the generation and the consumption of power. As a contribution to the various applications of storage devices, this paper describes a novel algorithm that determines the power and storage capacity of selected energy storage devices in order to improve upon railroad system efficiency. The algorithm is also demonstrated by means of simulation studies for the Korean railroad lines now in service. A part of this novel algorithm includes the DC railroad powerflow algorithm that considers the mobility of railroad vehicles, which is necessary because the electric railroad system has a distinct distribution system where the location and power of vehicles are not fixed values. In order to derive a more accurate powerflow result, this algorithm has been designed to consider the rail voltage as well as the feeder voltage for calculating the vehicle voltage. By applying the resultant control scheme, the charging or discharging within a specific voltage boundary, energy savings and a substation voltage stabilization using storage devices are achieved at the same time.

• Food Engineering Progress
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• v.15 no.4
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• pp.311-317
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• 2011

Rice bread premix was prepared from rice flour and vital wheat gluten, and the changes in the premix properties were studied during storage at 5, 25 and $35^{\circ}C$ for 4 months. Optimum level of 14-17% vital gluten could be added to the rice bread premix. The pH, sedimentation value, and Pelshenke value of the rice bread premix decreased with increasing storage period, whereas water retention capacity (WRC) and alkaline water retention capacity (AWRC) increased with increasing storage temperature. Mixograph peak time increased with increasing storage temperature. Rapid Visco Analyser (RVA) peak viscosity and setback values increased with increasing storage temperature and period. Decreased loaf volume was observed at the rice bread prepared from the premix during storage, especially at higher temperatures. Crumb hardness of the rice bread prepared from the premix increased during 4-month storage period.

• Journal of Korea Water Resources Association
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• v.36 no.3 s.134
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• pp.385-398
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• 2003

The concept of the effective storage ratio has been suggested to determine the size of detention pond by the previous researchers. The 11 pump - pond facilities in Dongdu-chun city were selected to analyze the critical duration for design rainfall and the storage ratio for each rainfall duration in this study It has been then found that the criteria of the maximum storage ratio is not reasonable for determining the size of detention pond because the difference of storage ratio with respect to each rainfall duration is too small. Moreover, since the size of pond compared with the pump capacity is not always big enough, the pump should be frequently operated, which may result in pump failure. Thus, the pond should be sufficiently sized to prevent the possibility of the pump failure due to frequent operation. According to the analyses for changing pump capacity, it has been found that if the function of the pond compared with the pump is concentrated, determining the size of pond based on the storage ratio is operationally feasible for even small basin. Thus, an improved procedure based on the storage ratio for determining the size of detention pond in small basin has been suggested. The results by the proposed procedure considering pump switching frequency may lead to reasonable pump operation. A simple linear programming model has been also adopted to figure out the relationship between pump capacity and pond size. It has been shown that the determination lot the size of detention pond based on conventional hydrologic flood routing in pond is feasible for only urban districts not rural areas.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.4
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• pp.350-357
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• 2002

Optimal control algorithms for the full storage ice cooling system were developed by using a dynamic simulation program. Control algorithms for the storage charging mode were developed for the chiller outlet temperature setpoint control and the chiller capacity control. Control algorithms for the storage discharging mode were developed for the proper mode selection, the storage-only mode control, and the storage-priority chiller-shared mode control. Two different cases of the expected outdoor air temperature profile and the expected cooling load profile were used to analyze the effectiveness of these algorithms. Simulation results show the energy savings and the satisfactory controls of the ice storage system. Therefore, control algorithms developed for this study may effectively be used for the improved control of the ice storage cooling system.

• Journal of the Korean Solar Energy Society
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• v.24 no.1
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• pp.7-12
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• 2004

Mixtures type PCM, $H_2O$-NaOH that has relatively large capacity of the latent heat and long duration of phase change temperature was developed and experimentally analyzed for the low temperature storage of the food and medical products. The results could be summarized as follows; 1. Borax as nucleating agent and acrylic polymer as thickening agent were added to $H_2O$ to prevent the supercooling and phase separation. 2. Phase change (solid$\leftrightarrows$liquid) duration of $H_2O$ added with NaOH was prolonged longer 50% than that of pure $H_2O$. 3. Phase change temperature of the latent heat material, $H_2O$-NaOH was $1.5\sim2^{\circ}C$ the maximum latent Heat was 279 kJ/kg at the NaOH addition of 1.3 wt.%. 4. The specific heat of $H_2O$-NaOH at the solid and liquid state was increased in proportion to the wt.% of NaOH, when NaOH of $1.15\sim1.60$ wt.% was added to $H_2O$, the specific heat of the solid state was increased from 3.19 kJ/kg to 5.84 kJ/kg and that of liquid state from 7.8 kJ/kg to 10.28 kJ/kg. 5. When NaOH of $1.15\sim1.60$ wt.% was added to $H_2O$, the total heat storage capacity composed of sensible and latent heat was $313\sim331.3$ kJ/kg and the maximum heat storage capacity was occurred at NaOH addition of 1.30 wt. %.

• Journal of Korea Soil Environment Society
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• v.2 no.2
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• pp.35-51
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• 1997

To clarify the effect of forest environmental changes (forest type difference and clearcut) on water storage capacity in soil and stream flow, watershed had been investigated in Pyungchang, Kangwon-Do during 1983∼1993. Hydrological datas such as runoff, monthly ratio of runoff to precipitation, runoff-duration, monthly runoff(by plenty, ordinary, low and scanty duration), total runoff, direct runoff by runoff components, bulk density, porosity, coarse pore, fine pore, permeability and effective water storage were obtained from Backokpo and Yimokjong watersheds. The monthly ratio of runoff to precipitation, runoff and runoff-duration were higher in Yimokiong than in Backokpo due to forest type difference. On compararing pre-treatment with trement period in two experimental watersheds, pre-treatment period was lower than treatment period. Physical properties of soil such as bulk density, porosity, permeability, and effective water storage capacity conditions were better during the pre-trement period than treatment period in the two experiment plots.