• KIPS Transactions on Computer and Communication Systems
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• v.13 no.1
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• pp.21-30
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• 2024

As the self-driving car market continues to grow, the need for charging infrastructure is growing. However, in the case of a wireless charging system, stability issues are being raised because it requires a large amount of power compared with conventional wired charging. SAE J2954 is a standard for building autonomous vehicle wireless charging infrastructure, and the standard defines a communication method between a vehicle and a power transmission system. SAE J2954 recommends using physical media such as Wi-Fi, Bluetooth, and UWB as a wireless charging communication method for autonomous vehicles to enable communication between the vehicle and the charging pad. In particular, UWB is a suitable solution for indoor and outdoor charging environments because it exhibits robust communication capabilities in indoor environments and is not sensitive to interference. In this standard, the process for building a wireless power transmission system is divided into several stages from the start to the completion of charging. In this study, UWB technology is used as a means of fine alignment, a process in the wireless power transmission system. To determine the applicability to an actual autonomous vehicle wireless power transmission system, experiments were conducted based on distance, and the distance information was collected from UWB. To improve the accuracy of the distance data obtained from UWB, we propose a Single Model and Multi Model that apply machine learning and deep learning techniques to the collected data through a three-step preprocessing process.

• Journal of the Korean Institute of Gas
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• v.18 no.5
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• pp.40-46
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• 2014

The hydrogen embrittlement degree of 5 type high strength DP steel charged with hydrogen by electrochemical method was evaluated by small punch test(SP test). After SP test, SP absorbed energy was remarkably decreased from 363 kgf-mm to 209 kgf-mm with increasing hydrogen charging time from 5hr to 50hr at DP5 specimen under the $200mA/cm^2$ current density condition. It was investigated that the decrease of hydrogen charging amount and SP absorbed energy according to the increase of current density and hydrogen charging time had a linear relationship. And it also investigated that the change of bulb height appeared by the SP test was decreased from 1.79mm to 1.59mm with the hydrogen charging conditions. It was supposed that it could be used as indicator of the evaluation of hydrogen embrittlement because of the similar trend of the formal results of SP absorbed energy. From the SEM observation of fracture area by crack in bulb, the morphology of fracture surface according to increasement of the hydrogen charging amount was varied with the cleavage mode.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.1
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• pp.1-6
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• 2017

Recent researches on radio frequency energy harvesting networks(RF-EHNs) with limited energy resource like battery have been focusing on the development of a new scheme that can effectively extend the whole lifetime of a network to semipermanent. In order for considerable increase both in the amount of energy obtained from radio frequency energy harvesting and its charging effectiveness, it is very important to design a network that supports energy harvesting and data transfer simultaneously with the full consideration of various characteristics affecting the performance of a RF-EHN. In this paper, we proposes an interference-based charging aware routing protocol(ICARP) that utilizes interference information and charging time to maximize the amount of energy harvesting and to minimize the end-to-end delay from a source to the given destination node. To accomplish the research objectives, this paper gives a design of ICARP adopting new network metrics such as interference information and charging time to minimize end-to-end delay in energy harvesting wireless networks. The proposed method enables a RF-EHN to reduce the number of packet losses and retransmissions significantly for better energy consumption. Finally, simulation results show that the network performance in the aspects of packet transmission rate and end-to-end delay has enhanced with the comparison of existing routing protocols.

• Journal of the Korean Institute of Gas
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• v.18 no.1
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• pp.61-67
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• 2014

Small punch(SP) tests were performed on high strength Dual Phase(DP) steels in order to evaluate the behavior of hydrogen embrittlement. For this purpose, three different kinds of DP steel specimens were charged with hydrogen by electochemical hydrogen charging experiment. After charging with hydrogen, the amount of charged hydrogen was measured. The measurement results showed that amounts of charged hydrogen were largely dependent on the martensite volume fraction of DP steel. The hydrogen charging time of 25 hrs with current densities of 150 and $200mA/cm^2$ was investigated as saturation condition with hydrogen. The analysis results on the SP energy and height of SP bulbs after SP tests showed that those were decreased as the amount of charged hydrogen increased. Fractographs of SP bulbs were observed a brittle fracture mixed with quasi-cleavage fractures, layered structures and clear facets.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.903-908
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• 2001

Residual gas acts as a diluent which results in reducing the in-cylinder temperature as well as the flame speed, significantly affecting fuel economy, NOx emissions and combustion stability. Therefore it is important to determine the residual gas fraction as a function of the engine operating parameters accurately. However, the determination of the residual gas fraction is very sophisticated due to the unsteady state of induction and exhaust process. There has been little work toward the development of a generally applicable model for quantitative predictions of residual gas fraction. In this paper, a simple model for calculating the residual gas fraction in SI engines was formulated. The effects of engine operating parameters on the residual gas were also investigated. The amount of fresh air was evaluated through AFR and fuel consumption. After this, from the intake temperature and pressure, the amount of total cylinder-charging gas was estimated. The residual fraction was derived by comparing the total charging and fresh air. This results coincide with measured value very well.

• Journal of the Korea Society of Computer and Information
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• v.24 no.5
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• pp.1-9
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• 2019

In this paper, we propose the algorithms which determine 1) the efficient anchor-node visiting route of mobile sink in terms of energy supply and 2) the efficient energy amount to be charged to each anchor node, by using the information of each anchor node and the mobile sink. Wireless sensor networks (WSNs) using mobile sinks can be deployed in more challenging environments such as those that are isolated or dangerous, and can also achieve a balanced energy consumption among sensors which leads to prolong the network lifetime. Most mobile sinks visit only some anchor nodes which store the data collected by the nearby sensor nodes because of their limited energy. The problem of these schemes is that the lifetime of the anchor nodes can be shorten due to the increased energy consumption, which rapidly reduces the overall lifetime of WSN. This study utilizes a mobile sink capable of wireless power transmission to solve this problem, so a mobile sink can gather data from anchor nodes while charging energy to them. Through the performance verification, it is confirmed that the number of blackout nodes and the amount of collected data are greatly improved regardless of the size of the network.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.723-729
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• 2016

This study compared fin-tube and parallel-flow heat pipes for their sensible heat exchange rate, heat recovery amount, and air-side pressure drop. Tests were done with different refrigerant charging rates of 40-60% vol. and air flow rates of 300-1,400. The sensible heat exchange rate was highest for both types of heat pipes at a working fluid charge of 40% vol. and low flow rate. For the parallel-flow heat pipe, the 60% vol. charge is too high and results in a low sensible heat exchange rate. The reason is that the thicker liquid film of the tube wall deteriorates the heat transfer effect. Hence, the optimal charging rate is 40 to 50% vol. The evaporator heat pipe has a larger air-side pressure drop than the condenser section heat pipe. The reason is considered to be condensation water arising from the evaporator surface. Compared to the fin-tube heat pipe, the parallel-flow heat pipe showed better performance with a working fluid charging rate of 48%, volume of 41%, and an air-side pressure drop about 37%.

• Journal of Korean Society of societal Security
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• v.3 no.2
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• pp.57-64
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• 2010

In this study, the behavior and safety of an existing tunnel and its facilities are investigated when a new tunnel adjacent to the existing tunnel is blasted. The design of the new tunnel puts priority on stability of the tunnel itself over the safety of the facilities which are installed within the existing tunnel such as jet fans. And thus, a detailed consideration on securing the safety of the existing facilities has been insufficient. An analysis on the types of traffic accidents in the last ten years shows that most incidents were due to the driver's improper response in emergency situations and unexpected obstacles. In consideration of this analysis, the safety of the facilities in the existing tunnel was secured by minimizing the charging amount for each hangfire and changing the excavation method of evacuation communication shelters to the large center hole cut blasting method to reduce blasting vibration. For a more quantitative analysis, measurement devices were installed inside the existing tunnel, at houses adjacent to the new tunnel, near jet fans in the existing tunnel. This enabled real time measurement of displacements of the existing tunnel, adjacent houses, and jet fans without interrupting traffic flow. Therefore, the improvements of charging amount for each hangfire, the blasting method, and the measurement method are suggested in this paper to secure the safety of the facilities in the existing tunnel when a new tunnel, located on a large city and adjacent to an existing tunnel, is designed.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.6
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• pp.626-632
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• 2015

The International Maritime Organization (IMO) has adopted several regulations for the prevention of air pollution from ships. In addition, there is a requirement for shipping liners to reduce greenhouse gas emissions. Accordingly, we need to take measurements to ensure that the steps taken are both efficient and environmentally friendly. It has been determined that the application of the Miller cycle in diesel engines has the effect of both reducing the amount of NOx and improving thermal efficiency. However, this method requires a considerably larger charge air pressure. Therefore, we consider a two-stage turbo-charging system, which not only results in a high charging pressure, but also improves the part load performance with an exhaust-gas bypass system or the application of the Miller cycle. Because of complications associated with the two-stage turbo-charging system, it is complex and difficult to realize a design that optimizes matching between diesel engine and turbo-chargers. Accordingly, it is necessary to perform a quantitative analysis to determine the effects and optimal conditions of these different systems in the early stage of system design. In this paper, we develop a simulation program to model these systems, and we verify that the results of this program are reliable. Further, we discuss methods that can be employed to improve its efficiency.

• Imaging Science in Dentistry
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• v.42 no.1
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• pp.1-4
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• 2012

Purpose : Hand-held dental x-ray system is a self contained x-ray machine designed to perform intraoral radiography with one or two hands. The issue about its usage as general dental radiography is still in dispute. The aim of the present study was to assess the relationship between the amount of battery charge and the tube voltage in different handheld dental x-ray systems. Materials and Methods : Seven hand-held dental x-ray units were used for the study. Tube voltage was measured with Unfors ThinX RAD (Unfors Instruments AB, Billdal, Sweden) for 3 consecutive exposures at the different amount of battery charge of each unit. The average and the deviation percentage of measured kV from indicated kV of each unit were calculated. Results : Tube voltage of only 1 unit was 70 kV (indicated by manufacturer) and those of the others were 60 kV. Tube voltage deviation percentage from the indicated kV at the fully charged battery was from 2.5% to -5.5% and from -0.8% to -10.0% at the lowest charged battery. Conclusion : Tube voltages of all units decreased as the residual amount of the battery charge decreased. It is suggested that the performance test for hand-held x-ray system should be performed for the minimum residual charged battery as well as the full charged one. Persistent battery charging is suggested to maintain the proper tube voltage of the hand-held portable x-ray system.