• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제15권12호
• /
• pp.4600-4616
• /
• 2021

In cognitive radio networks where unlicensed secondary users opportunistically access to licensed spectrum unused by licensed primary users, spectrum sensing is one of the key issues in order to effectively use the frequency resource. For enhancing the sensing performance in energy detection-based spectrum sensing, spatial diversity based on multiple antennas is utilized. However, the sensing performance can be degraded when antennas are spatially correlated, resulting in inducing the harmful interference to primary users. To overcome this problem, in this paper, an advanced energy detector is proposed. In the proposed sensing method, a weight matrix based on the eigenvalues of the spatial channels without any prior information on the primary signals is defined and utilized. In numerical simulations, it is shown that the proposed detector outperforms the conventional detector with regard to false-alarm and detection probabilities when antenna are spatially correlated.

• 한국태양에너지학회 논문집
• /
• 제34권6호
• /
• pp.93-102
• /
• 2014

The aim of this study is to analyze the influence of various factors on energy consumption of apartment buildings. Energy consumption data of the Green Together, integrated building energy management system maintained by the government were used, and end-use and primary energy consumption data of 2012 were analyzed for 181 apartment complexes completed between 2004 and 2011 in Seoul. Energy consumption by use, source and heating type were analyzed. Then, energy consumption trends were analyzed and suggested according to energy efficiency ratings, number of households, areas for exclusive use, number of floors, core types, building types, orientations and completion years.

• IEIE Transactions on Smart Processing and Computing
• /
• 제2권6호
• /
• pp.357-366
• /
• 2013

Spectrum sensing, as a fundamental functionality of Cognitive Radio (CR), enables Secondary Users (SUs) to monitor the spectrum and detect spectrum holes that could be used. Recently, the security issues of Cognitive Radio Networks (CRNs) have attracted increasing research attention. As one of the attacks against CRNs, a Primary User Emulation (PUE) attack compromises the spectrum sensing of CR, where an attacker monopolizes the spectrum holes by impersonating the Primary User (PU) to prevent SUs from accessing the idle frequency bands. Energy detection is often used to sense the spectrum in CRNs, but the presence of PUE attack has not been considered. This study examined the effect of PUE attack on the performance of energy detection-based spectrum sensing technique. In the proposed protocol, the stationary helper nodes (HNs) are deployed in multiple stages and distributed over the coverage area of the PUs to deliver spectrum status information to the next stage of HNs and to SUs. On the other hand, the first stage of HNs is also responsible for inferring the existence of the PU based on the energy detection technique. In addition, this system provides the detection threshold under the constraints imposed on the probabilities of a miss detection and false alarm.

• Journal of Electrical Engineering and Technology
• /
• 제11권3호
• /
• pp.707-714
• /
• 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.

• 자원ㆍ환경경제연구
• /
• 제23권2호
• /
• pp.305-330
• /
• 2014

그 동안 에너지 소비 변화요인을 규명하기 위한 많은 연구가 이루어져 왔다. 그런데 상당수의 연구에서 최종 에너지를 기준으로 분해분석을 수행, 에너지 소비나 이산화탄소 배출량을 집약도, 구조, 생산 효과로 나누어 분석하였다. 그러나 최종 에너지를 기준으로 할 경우 많은 전환 손실이 발생하는 전력 부문으로 인하여 정확한 소비량 변화 요인의 규명이 어려울 수 있다. 이에 본 연구에서는 전력 소비 위주로 변화하고 있는 우리나라의 에너지 소비 구조를 보다 명확하게 반영하여 에너지 소비 변화 요인을 살펴보고자 1차 에너지 소비를 기준으로 지수분해 분석을 수행하였다. 분석 방법론으로는 Refined Laspeyres 모형과 LMDI 모형을 사용하였다. 분석 결과, 1차 에너지 소비량을 기준으로 분해분석 한 결과와 최종 에너지를 기준으로 분해분석 결과의 차이가 점차 커지는 경향을 확인하였다. 최종 에너지를 기준으로 분석 한 결과 1981년 대비 2011년 집약도 효과는 0.607배 감소, 구조 효과는 0.227배 증가 한 것으로 나타난 반면, 1차 에너지를 기준으로 분해분석 한 결과를 보면 집약도 효과가 0.236배 감소하고, 구조 효과가 0.434배 증가하는 것으로 분석되었다. 따라서 향후 분해분석 연구 수행에 있어서는 반드시 1차 에너지를 기준으로 분석을 수행해야 할 것이다.

• 한국기술혁신학회:학술대회논문집
• /
• 한국기술혁신학회 1999년도 춘계학술대회
• /
• pp.395-408
• /
• 1999

From the dependence the primary energy of about 97% on imported energy from abroad in Korea, 1997, and the pressure by international address to the Global Climate Change and environmental problem, we should do our best efforts to develop and diffuse of energy technologies. Also, the developed countries such USA, EU, Japan, and so on, are promoting and accelerating the development of energy technologies. From those point of views, we thought that Korea now in the time to provide the new and updated strategies to develop the energy technologies more actively for enhancing national capability, The Korea Institute of Energy Research(KIER), the complex research institution for energies except nuclear energy sponsored by government, prepared the mid and long term strategies and primary research projects, must be worked in and with the KIER, for the areas related to the energy conservation and efficiency increase, the energy environment, the alternative energy, and the diffusion of developed energy technologies.

• KIEAE Journal
• /
• 제14권4호
• /
• pp.47-52
• /
• 2014

The problem of energy consumption is more serious in university buildings than primary, middle and high school buildings. Because university buildings have generally heating and cooling systems, and various incidental facilities. In university, the library is one of the building that many people use and the most energy is spent. So, investigation on energy saving is very important and urgent. This study aims finally to present the guideline for low-energy design of University library by aiding a designer to select best solution in the side of energy-saving. In this paper, composition of space, utilization schedule and performance of construction materials are grasped, some primary factors that effect to energy saving are analyzed by energy simulation. The result of this study is as follows; First, the subject library has more cooling load than heating load because of cooling load generated during middle season. Second, green roofs is the most effective to heating load saving, but not to cooling energy. Third, outdoor air cooling is the most effective to cooling energy saving among the investigated strategies included in this study.

• Corrosion Science and Technology
• /
• 제21권6호
• /
• pp.466-475
• /
• 2022

Surface oxides and intergranular (IG) oxidation phenomena in Alloy 600 depending on hydrogen concentration were characterized to obtain clear insight into the primary water stress corrosion cracking (PWSCC) behavior upon exposure to pressurized water reactor primary water. When hydrogen concentration was between 5 and 30 cm³ H₂/kg H₂O, NiFe₂O₄ and NiO type oxides were found on the surface. NiO type oxides were found inside the oxidized grain boundary when hydrogen concentration was 5 cm³ H₂/kg H₂O. However, only NiFe₂O₄ spinel on the surface and Ni enrichment were observed when hydrogen concentration was 30 cm³ H₂/kg H₂O. These results indicate that the oxidation/reduction reaction of Ni in Alloy 600 depending on hydrogen concentration can considerably affect surface oxidation behavior. It appears that the formation of NiO type oxides in a Ni oxidation state and Ni enrichment in a Ni reduction (or metallic) state are common in primary water. It is believed that the above different oxidation/reduction reactions of Ni in Alloy 600 depending on hydrogen concentration can also significantly affect the resistance to PWSCC of Alloy 600.

• Journal of Communications and Networks
• /
• 제17권3호
• /
• pp.265-266
• /
• 2015

In a recent paper [1], the authors investigated the maximum stable throughput region of a network composed of a rechargeable primary user and a secondary user plugged to a reliable power supply. The authors studied the cases of an infinite and a finite energy queue at the primary transmitter. However, the results of the finite case are incorrect. We show that under the proposed energy queue model (a decoupled M/D/1 queueing system with Bernoulli arrivals and the consumption of one energy packet per time slot), the energy queue capacity does not affect the stability region of the network.

• 천문학회보
• /
• 제36권1호
• /
• pp.70.2-70.2
• /
• 2011

Ultra-high energy cosmic rays(UHECRs) refer cosmic rays with energy above 1018eV. UHECR experiments have employed air shower simulations to quantify the properties of cosmic rays. Using COSMOS and CORSIKA, we have produced a library of over 15000 thinned extensive air shower(EAS) simulations with the primary energies ranging from 1018.5eV to 1020eV and the zenith angle of primary cosmic ray particles from 0 to 45 for proton and iron primaries. We have compared the results from CORSIKA and COSMOS. The comparison has shown perceptible differences in the ground distributions, longitudinal distributions, Calorimetric energy, and Xmax distributions. We have also measured the detector response evaluated using GEANT4 simulations. Here, we discuss S(800), i.e. the signal at a distance of 800 m from the shower core, as the primary energy estimator and present the lateral distribution function(LDF) with S(800).