• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.5
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• pp.396-403
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• 2016

Usually, large-sized buses and trucks have a very high load. In addition, frequent braking during downhill or long-distance driving, causes the conventional method using the brake friction to have a problem in safety because of brake fade and brake burst phenomenon. Auxiliary brakes dividing the braking load is essential. Hence, environment-friendly auxiliary brakes, such as contactless brake rather than the engine auxiliary brake system are needed. A study aimed at improving the energy efficiency by recharging electric energy with changing mechanical to electrical energy that occurs when braking is actively in progress. In this paper, the voltage control method is utilized to recover the electric energy generated in the electromagnetic retarder instead of the eddy current. To regenerate the braking energy into the electrical energy, the resonant L-C circuit is configured in the retarder. The voltage generated in the retarder is simply modeled as a transformer. However, retarder voltage control in this paper is simulated by modeling the induction generator because this induction generator modeling is more practical than transformer modeling. The changes in the voltage of the resonance circuit, which depends on the switch pulse duration of the control device, were analyzed. A PI controller algorithm to control this voltage is proposed. The feasibility of modeling retarder and voltage controller are shown by using MATLAB Simulink in this paper.

• Journal of Energy Engineering
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• v.29 no.3
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• pp.86-90
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• 2020

This paper examines a blockchain network-based transaction system using location proofing in power direct transactions between networked energy clouds, energy communities, and prosumer machines participating in smart cities. It utilizes location-based blockchain network technology, which enables long-distance travel with recharging by power purchases during autonomous movements, autonomous electric vehicles that can purchase and sell electricity, and solar street lights that can be produced and sold in fixed form. In addition, it is possible to provide optimum power transaction matching and settlement reliability between machines without human intervention in power transactions between electric chargers. It also introduces a business-to-object business model between autonomous machines that exist in multiple and different spaces and through energy clouds that are expected to be scattered with various transaction prices, policies, and incentives.

• Journal of Acupuncture Research
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• v.28 no.2
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• pp.49-55
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• 2011

Objectives : This study was to develop programmable and rechargeable electronic moxibustion device as an interdisciplinary research focusing on traditional Korean medicine. Methods : This device deployed several advances on safety and conveniences with the advantage of programmable heat stimulation, heating material and recharging method. The gradient of heat stimulation was programmed with the reference of previous studies and own measurements. The heat curve reached its efficacious stimulus temperature after three minutes, and maintained until 13 minutes with $42^{\circ}C$. We also incorporated feedback from field hospital experiences with the help of hospital staffs. Results : This device can prevent damages from skin burn and fire accidents, and control the smoke, smell and residue of moxa itself. Conclusions : This study will contribute for the development and improvement of efficacious and safe treatment methods for the traditional Korean medicine.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.1
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• pp.31-36
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• 2011

Ubiquitous network and wireless sensor networks is being applied in various fields. Located at target areas, node of wireless sensor network uses batteries as a power source. Batteries have a limited energy in sensor network applications. Also, before use, the battery must be charged and It is difficult to replace the battery. Therefore, energy harvesting technology is being researched and being developed for long life of sensor node. Especially, sola energy is being extensively researched. because that can have great amounts of energy than other environmental energy in a short time. In this study, we tested battery charging and recharging, operation of sensor node using Solar Cell. Also, monitoring data gathering and voltage Analysis showed energy harvesting time of Sola Cell battery for sensor node and operation of sensor node.

• Journal of Ocean Engineering and Technology
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• v.21 no.3 s.76
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• pp.33-39
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• 2007

The more deeply the researches make progress in ocean researches including the seabed resource investigation or the oceanic ecosystem investigation, the more important the role of UUV gets. In case of study on the deep sea, there are difficulties in telecommunications between AUV and ships, and in data communication and recharging. Therefore, docking is required. In AUV docking system, the AUV should identify the position of docking device and make contact with a certain point of docking device. MOERI (Maritime & Ocean Engineering Research Institute), KORDI has conducted the docking testing on AUV ISIMI in KORDI ocean engineering water tank. As AUV ISIMI approachs the docking device, there is some cases of showing an unstable attitude, because the lights which is on Image Frame are disappeared. So we propose the docking algorithm that is fixing the rudder and stem, if the lights on image frame are reaching the specific area in the Image Frame. Also we propose the new docking device, which has a variety of position and light number. In this paper, we intend to solve the some cases of showing an unstable attitude that were found in the testing, which, first, will be identified the validity via simulation.

• Journal of Ecology and Environment
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• v.33 no.1
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• pp.47-57
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• 2010

To understand day-to-day fluctuations in soil moisture content in Seoul, I simulated daily soil moisture content from 1908 to 2009 using long-term climatic precipitation and temperature data collected at the Surface Synoptic Meteorological Station in Seoul for the last 98 years with a hydrological simulation model, BROOK. The output data set from the BROOK model allowed me to examine day-to-day fluctuations and the severity and duration of droughts in the Seoul area. Although the soil moisture content is highly dependent on the occurrence of precipitation, the pattern of changes in daily soil moisture content was clearly quite different from that of precipitation. Generally, there were several phases in the dynamics of daily soil moisture content. The period from mid-May to late June can be categorized as the initial period of decreasing soil moisture content. With the initiation of the monsoon season in late June, soil moisture content sharply increases until mid-July. From the termination of the rainy season in mid-July, daily soil moisture content decreases again. Highly stochastic events of typhoons from late June to October bring large amount of rain to the Korean peninsula, culminating in late August, and increase the soil moisture content again from late August to early September. From early September until early October, another sharp decrease in soil moisture content was observed. The period from early October to mid-May of the next year can be categorized as a recharging period when soil moisture content shows an increasing trend. It is interesting to note that no statistically significant increase in mean annual soil moisture content in Seoul, Korea was observed over the last 98 years. By simulating daily soil moisture content, I was also able to reconstruct drought phenomena to understand the severity and duration of droughts in Seoul area. During the period from 1908 to 2009, droughts in the years 1913, 1979, 1939, and 2006 were categorized as 'severe' and those in 1988 and 1982 were categorized as 'extreme'. This information provides ecologists with further potential to interpret natural phenomenon, including tree growth and the decline of tree species in Korea.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.4 s.15
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• pp.27-34
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• 2004

In this paper, in order to analyse the variation of runoff characteristics depending upon installation of the groundwater recharge facilities, the experiment basin was prepared and the ratio of infiltration and runoff volume were observed in the rainfall events. For the rainfall analysis, 4 types of rainfall events were examined during July 11${\sim}$July 17, 2004. The results show that the mean ratio of infiltration was 89.39% and the mean ratio of runoff was 10.61%. For the artificial rainfall events, which are in the range of rainfall intensities between 60mm/hr and 100mm/hr, all the rainfall volume was infiltrated through the groundwater recharging basin. However, it is necessary to be careful for the long term rainfall, the runoff can be occurred based on the groundwater table.

• Journal of Energy Engineering
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• v.19 no.2
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• pp.92-102
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• 2010

Plug-in hybrid electric vehicle(PHEV) is a hybrid electric vehicle (HEV) with more added battery capacity that can be recharged from the electric power grid. Plug-in battery electric vehicle(PBEV) is a pure electric vehicle that uses only electric motor using electricity from battery that recharged from the power grid. PHEV and PBEV requires recharging of batteries in the vehicles from electric power grid. Recently, PHEVs and PBEV are being developed around the world. It is important to understand how these electric vehicles affect power demands and carbon dioxide emissions. From vehicle customer viewpoint, running energy cost will be imporatnt factor to consider. This paper analyzes the potential impacts of PHEVs and PBEVs on electric power demand, and associated CO2 emissions in 2020 with an projection that the vehicles will be penetrated with 10% market share. Energy costs for the vehicles are also calculated and compared with the conventional combustion vehicle.

• Journal of Environmental Impact Assessment
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• v.16 no.4
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• pp.251-265
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• 2007

In this study, the influence of the construction of a large sized building on the flow and level of groundwater in a metropolitan area was investigated with simulation model MODFLOW for a selected area located in Gangseo-gu, Seoul, where a large business center was scheduled to be built. It was simulated that the groundwater level in the study area was suddenly lowered by the construction of a large building and groundwater in the surrounding area fast flowed into the study area. And even after the construction finished, the falling down of groundwater level consistently continued in some degree. The flow state of groundwater appeared to be the same in both cases where a soil cement wall is applied and where it is not during the construction. But for the case of application of a soil cement wall as the amount of groundwater flowing into the study site became reduced, it was estimated that the time for underground watershed getting far away from the site was also reduced and the influence of a building construction on the surrounding groundwater became reduced. Thus, it is deemed necessary that recharging the spilled ground water and rainfall into the construction area to lessen the abrupt change in flow and level of ground water should be considered in design of construction of a large sized building in a metropolitan area.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.6
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• pp.67-74
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• 2011

The objective of this study was to compare concentrations of nutrients such as total nitrogen (TN), nitrate nitrogen ($NO_3$-N) total phosphorous (TP), and phosphate phosphorous ($PO_4$-P) in groundwater under paddy and upland fields, and surface water recharging from a rural mixed land-use watershed. Chinese cabbage and hot pepper were cultivated on the upland field plot. The TN concentrations in upland groundwater showed double peaks (4.7, 4.3 mg/L, respectively) in April 2009 shortly after fertilizer application, indicating that TN concentrations are greatly influenced by fertilization. However, the TN concentrations in paddy groundwater were always lower than 2.0 mg/L irrespective of fertilization. Whereas the mean concentrations of TN and $NO_3$-N in upland groundwater significantly (p<0.05) higher than those in surface water, the mean concentrations of TP and $PO_4$-P in upland groundwater were significantly lower than those in surface water. On the other hand, the mean concentrations of TN, $NO_3$-N, TP and $PO_4$-P in paddy groudwater were significantly (p<0.05) lower than those in surface water. The TN concentrations in upland groundwater were generally higher than those in surface water during early April to early December due to the effect of fertilization, but vice versa in the other periods. In contrast, the TP concentrations in upland groundwater were always lower than those in surface water due to the sorption of inorganic phosphorous by soil. Moreover, the TN and TP concentrations in paddy groundwater were always lower than those in surface water, and therefore paddy groundwater may dilute nutrient concentrations in surface water when paddy groundwater and surface water mix.