• Journal of Energy Engineering
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• v.29 no.2
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• pp.23-29
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• 2020

In this study, the last 10 years of news data on fine dust was collected and 80 topics are selected through LDA analysis. As a result, weather-related information made up the main words for the topic, and we can see that fine dust becomes a big issue below 10 degrees Celsius. The frequency of exposure to the media and the maximum concentration of fine dust are correlated with positive. Topics related to fine dust reduction measures and the government's comprehensive measures over the past decade, topics related to products such as air purifiers related to fine dust, topics related to policies protecting vulnerable people from fine dust, and topics on fine dust reduction through R&D were found to be major topics. Measures against fine dust as a social issue can be seen to be closely related to the government's policy.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.1900-1911
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• 2015

In this paper, we introduce backscatter communication for power-limited sensors to enable long-range transmission in wireless sensor networks, and envision a way to avoid doubly near-far problem in wireless-powered communication network (WPCN) with this technology. In backscatter based WPCN, users harvest energy from both the signal broadcasted by the hybrid access point and the carrier signal transmitted by the carrier emitter in the downlink, and then transmit their own information in a passive way via the reflection of the carrier signal using frequency-shift keying modulation in the uplink. We characterize the energy-free condition and the signal-to-noise ratio (SNR) outage zone in backscatter based WPCN. Further, we propose backscatter based harvest-then-transmit protocol to maximize the sum-throughput of the backscatter based WPCN by optimally allocating time for energy harvesting and information transmission. Numerical results demonstrate that the backscatter based WPCN increases significantly the transmission range and diminishes greatly the SNR outage zone.

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.137-148
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• 2012

In this paper, we proposed the location-aware coordinate routing algorithm for improving the performance of routing algorithm by using ZigBee in Smart Grid environment. A distributed address allocation scheme used an existing algorithm that has wasted in address space. The x, y and z coordinate axes from divided address space of 16 bit to solve this problems. However, coordinate routing does not take account of wireless link condition. If wiress link condition is not considered, when the routing table is updated, the nodes with bad link conditions are updated in the routing table and can be chosen as the next hop. This brings out the retransmissions because of received packet's errors. Also, because of these retransmissions, additional power is consumed. In this paper, we propose the location-aware coordinate routing algorithm considering wiress link condition, where reliable data transmission is made and the consumed enegy is minimize. and we compared and connected region and transition region of ZigBee location based routing in the aspect of average number of multi hops, subordinate packet delivery ratio, delay time, and energy consumption of proposed algorithm. It turned out that there were improvements in performances of each items.

• Journal of Energy Engineering
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• v.28 no.3
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• pp.55-64
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• 2019

This study identified key patents on U.S. underground water technology through patent network analysis. As a result, there were many technologies that used the technology to remove heavy metals to prevent contamination of groundwater. While patents between groundwater technology patents were in charge of intermediaries, the connectivity between groundwater technologies is not high. The patented technologies related to groundwater were largely distinguishable by pumping, monitoring, and decontamination. Monitoring includes techniques that enable identification of physical and biological properties, such as the type of contaminants, as well as geographic characteristics for analysis of groundwater flow, flow or water quality. Pollution purification technology refers to the process of physiochemical and biological purification for soil and groundwater. U.S. technology cases showed that the U.S. had high technology in water treatment area. And patent protection were also needed to cope with water shortages caused by climate change.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.6
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• pp.163-171
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• 2021

In this paper, the energy transaction system was optimized by applying a resource allocation algorithm and deep reinforcement learning in the distributed power system. The power demand and supply environment were predicted by deep reinforcement learning. We propose a system that pursues common interests in power trading and increases the efficiency of long-term power transactions in the paradigm shift from conventional centralized to distributed power systems in the power trading system. For a realistic energy simulation model and environment, we construct the energy market by learning weather and monthly patterns adding Gaussian noise. In simulation results, we confirm that the proposed power trading systems are cooperative with each other, seek common interests, and increase profits in the prolonged energy transaction.

• Geophysics and Geophysical Exploration
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• v.22 no.2
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• pp.56-61
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• 2019

In this paper, we studied efficient modeling strategies when we simulate the 3D time-domain acoustic wave propagation using a cell-based finite difference method which can handle the variations of both P-wave velocity and density. The standard finite difference method assigns physical properties such as velocities of elastic waves and density to grid points; on the other hand, the cell-based finite difference method assigns physical properties to cells between grid points. The cell-based finite difference method uses average physical properties of adjacent cells to calculate the finite difference equation centered at a grid point. This feature increases the computational cost of the cell-based finite difference method compared to the standard finite different method. In this study, we used additional memory to mitigate the computational overburden and thus reduced the calculation time by more than 30 %. Furthermore, we were able to enhance the performance of the modeling on several media with limited density variations by using the cell-based and standard finite difference methods together.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8A
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• pp.1223-1230
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• 2000

In this paper, we proposed a handoff decision method based on signal-to-interference ratio(SIR) of the pilot channel in order to perform a handoff more effectively and to complement disadvantages - deterioration quality of a call, decreasing capacity of the system, and wasting power of the mobile station - which is caused when handoff is performed by the classical method that execute a handoff based on received signal strength. Moreover, when we change that the minimum threshold, the cell loading which is defined active traffic channels to total traffic channels ratio, and the fraction of the transmit power from base station allocated to the pilot channel on the forward link of a DS-CDMA system, we analyzed mean numbers of handoff depending on hysteresis level during the mobile station moving from one base station to another base station.

• Korea Petroleum Association Journal
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• s.292
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• pp.32-35
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• 2014

한국로버트보쉬 디젤사업부가 지난 2008년부터 실시해 온 승용차 이용 실태 및 디젤 소비자 인식 조사는 2014년에 4회째 조사되었다. 디젤 엔진의 '친환경성'에 대한 인식 변화는 크지 않으나, '연비 효율성'에 대한 인식이 강화되면서 디젤에 대한 긍정적 인식 및 태도의 변화가 크게 나타난 것으로 판단된다. 이전 조사 결과의 특징 중의 하나는 '디젤' 자체에 대한 소비자의 긍정적 태도 개선 정도가 크게 나타났으며, 특히 '구입 의향이 증가'하는 등 실질적 소비 태도로 연결될 수 있는 index의 개선은 의미 있는 변화로 보여 고무적인 현상이다. 아울러, 재미 있는 결과는 '클린디젤 용어에 대한 인지도, 클린디젤 자동차 호감도, 클린 디젤 자동차 구입의향'에 대한 결과다. 이 항목들에 대해 '08년 11월부터 '12년 1월까지 증가하는 경향을 보였으나, '14년 2월 조사에서 다시 감소하는 경향이 나타난 것인데 이는 '디젤'이란 용어에 대한 긍정적인 인식이 크게 증가하여, 클린디젤이란 용어 자체의 의미가 무색해진 것으로 클린디젤이란 용어보다는 디젤 그 자체로 깨끗하고 친환경적인 연료로 인식된다고 할 수 있겠다. 2014년 조사는 2008년 이래 4회 차 조사로 한국갤럽조사연구소를 통해 진행 되었으며, 지난 2월 14일부터 3월 15일까지 전국 6대 도시(서울, 인천, 부산, 대구, 대전, 광주)에 거주하고 있는 만 20세 이상, 59세 이하의 남녀 자가 운전자 1,007명을 대상으로 지역별/성별/연령별 할당 추출법(Purposive Quota Sampling)과 개별면접 조사 방법(Face-to-Face Interview)으로 진행되었고, 95% 의 신뢰수준에 +/- 3% 오차범위를 가지고 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2B
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• pp.269-278
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• 2010

In the clustering protocol, lifetime of the cluster members radically decrease because frequency interference between clusters make every cluster member consume a lot of energy to maintain or increase its transmission rate. In this paper, we analyze the frequency interference among the clusters with the game theory which deals with resource bargaining problems between players, and present a rational power allocation strategy. Both the cases that each cluster tries to selfishly occupy and cooperatively share the resource are analyzed in terms of non-cooperative and cooperative games. In simulation, we compare the cooperative game with non-cooperative game in terms of the node lifetime.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.2
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• pp.213-221
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• 2012

In this paper, a dynamic power management system is proposed to reduce energy consumption for multiple clients in cloud computing environments. The proposed system monitors both keyboard and mouse input from the user, available memory, and CPU usage in the virtual machine. If the system detects no keyboard and mouse input for a certain amount of time and both available memory and CPU usage reach predefined threshold value, the manager in the virtual machine orders the client to shutdown the client machine, which results in significant power save. The developed system is applied to the real university computer lab and the performance of the system is evaluated.