• 제목/요약/키워드: Average energy ratio

검색결과 718건 처리시간 0.023초

Preparation of Chitosan-coated Magnetite Nanoparticles by Sonochemical Method for MRI Contrast Agent

  • Cho, Jun-Hee;Ko, Sang-Gil;Ahn, Yang-Kyu;Choi, Eun-Jung
    • Journal of Magnetics
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    • 제14권3호
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    • pp.124-128
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    • 2009
  • Magnetic nanoparticles were synthesized by using the sonochemical method with oleic acid as a surfactant. The average size of the magnetite nanoparticles was controlled by varying the ratio R=[$H_2O$]/[surfactant] in the range of 2 to 9 nm. To prepare chitosan-coated magnetite nanoparticles, chitosan solution was added to a magnetite colloid suspension under ultrasonication at room temperature for 20 min. The chitosan-coated magnetite nanoparticles were characterized by several techniques. Atomic force microscopy (AFM) was used to image the chitosan-coated nanoparticles. Magnetic hysteresis measurement was performed by using a superconducting quantum interference device (SQUID) magnetometer to investigate the magnetic properties of the magnetite nanoparticles and the chitosan-coated magnetite nanoparticles. The SQUID measurements revealed the superparamagnetism of both nanoparticles. The T1- and T2-weighted MR images of these chitosan-coated magnetite colloidal suspensions were obtained with a 4.7 T magnetic resonance imaging (MRI) system. The chitosancoated magnetite colloidal suspensions exhibited enhanced MRI contrasts in vitro.

Performance Analysis of WHR-ORC Using Hydrocarbon Mixtures for 20kW Gross Power at Low Temperature

  • Kwakye-Boateng, Patricia;Yoon, Jung-In;Son, Chang-Hyo;Hui, Kueh Lee;Kim, Hyeon-Uk
    • 동력기계공학회지
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    • 제18권6호
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    • pp.140-145
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    • 2014
  • Exploitation of renewable energies is on the increase to mitigate the reliance on fossil fuels and other natural gases with rocketing prices currently due to the depletion of their reserves not to mention their diverse consequences on the environment. Divergently, there are lots of industries "throwing" heat at higher temperatures as by products into the environment. This waste heat can be recovered through organic Rankine systems and converted to electrical energy with a waste heat recovery organic Rankine cycle system (WHR-ORC). This study uses the annual average condenser effluent from Namhae power plant as heat source and surface seawater as cooling source to analyze a waste heat recovery organic Rankine cycle using the Aspen HYSYS simulation software package. Hydrocarbon mixtures are employed as working fluid and varied in a ratio of 9:1. Results indicate that Pentane/Isobutane (90/10) mixture is the favorable working fluid for optimizing the waste heat recovery organic Rankine cycle at the set simulation conditions.

End-to-end Reliable Message Transmission Considering Load Balancing in Wireless Networks

  • Tran, Anh Tai;Kim, Myung Kyun
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • 제8권9호
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    • pp.3094-3109
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    • 2014
  • This paper proposes a load balanced reliable routing protocol called LBR (Load Balanced Reliable routing) in wireless networks. The LBR protocol transmits messages through a reliable path considering the balancing of the traffic load. Recently, the authors have proposed a multipath-based reliable routing protocol called MRFR, which is an appealing protocol for fault tolerant reliable data transmission. However, However, MRFR has no concern with the problem of load balancing, which results in increasing congestion and consuming high energy at some network nodes. As a result, the problem affects negatively the performance of the network. Taking account of load balancing as a route selection criteria can avoid routing through the congested nodes and allows to find better routes. In this paper, we extend MRFR by considering load balancing in the route discovery process of reliable communication. The simulation results showed that the proposed protocol outperforms AODV in terms of end-to-end delay, packet delivery radio, and average jitter. Compared to MRFR, the LBR protocol has the same packet delivery ratio, and obtains a better efficiency of load balancing.

Clay의 Aminopropyltriethoxysilane 그라프트에 영향을 미치는 인자 (Factors Affecting the Grafting of Aminopropyltriethoxysilane in Swelling Clay Materials)

  • ;이경엽;류승훈
    • Elastomers and Composites
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    • 제41권4호
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    • pp.238-244
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    • 2006
  • Monmorillonite 클레이를 물을 분산제로 이용하여 3-aminopropyltriethoxy 실란 기능화를 실시하였다. 실란의 그라프트 여부는 FT-IR을 이용하여 정성분석하였다. 실란의 농도가 증가함에 따라 흡착/삽입 비가 감소함을 알 수 있었다. X-ray를 이용하여 평균 d-간격을 측정한 결과 초기에는 실란농도가 증가하다 다소 감소하였다. 기능화 공정온도의 영향을 살펴본 결과 온도가 증가함에 따라 화학적인 그라프트가 증가함을 알 수 있었다.

Adaptive Cooperative Spectrum Sensing Based on SNR Estimation in Cognitive Radio Networks

  • Ni, Shuiping;Chang, Huigang;Xu, Yuping
    • Journal of Information Processing Systems
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    • 제15권3호
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    • pp.604-615
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    • 2019
  • Single-user spectrum sensing is susceptible to multipath effects, shadow effects, hidden terminals and other unfavorable factors, leading to misjudgment of perceived results. In order to increase the detection accuracy and reduce spectrum sensing cost, we propose an adaptive cooperative sensing strategy based on an estimated signal-to-noise ratio (SNR). Which can adaptive select different sensing strategy during the local sensing phase. When the estimated SNR is higher than the selection threshold, adaptive double threshold energy detector (ED) is implemented, otherwise cyclostationary feature detector is performed. Due to the fact that only a better sensing strategy is implemented in a period, the detection accuracy is improved under the condition of low SNR with low complexity. The local sensing node transmits the perceived results through the control channel to the fusion center (FC), and uses voting rule to make the hard decision. Thus the transmission bandwidth is effectively saved. Simulation results show that the proposed scheme can effectively improve the system detection probability, shorten the average sensing time, and has better robustness without largely increasing the costs of sensing system.

High-Temperature Deformation Behavior of MnS in 1215MS Steel

  • Huang, Fei-Ya;Su, Yen-Hao Frank;Kuo, Jui-Chao
    • Metals and materials international
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    • 제24권6호
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    • pp.1333-1345
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    • 2018
  • The effect of manganese sulfide (MnS) inclusions on the machinability of free-cutting steel is based on their morphology, size and distribution. Furthermore, the plasticity of MnS is high during the hot working caused different characterization of MnS. In this study, the deformation behavior of MnS in 1215MS steel after a thermomechanical process was investigated at 1323 K. The microstructures of MnS inclusions were characterized by optical microscopy, scanning electron microscopy, energy-dispersive spectrometry, and electron backscattering diffraction (EBSD). As the thickness reduction of the inclusions increased from 10 to 70%, their average aspect ratio increased from 1.20 to 2.39. In addition, the deformability of MnS inclusions was lower than that of the matrix. The possible slip systems of A, B, C, and D plane traces were (${\bar{1}}0{\bar{1}}$)[${\bar{1}}01$], ($10{\bar{1}}$)[101], (011)[$01{\bar{1}}$], and (110)[$1{\bar{1}}0$]. Furthermore, the EBSD measurements suggested that slip planes in MnS inclusions occur on {110} planes.

Comparison of Topology Based-Routing Protocols in Wireless Network

  • Sharma, Vikas;Ganpati, Anita
    • Journal of Multimedia Information System
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    • 제6권2호
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    • pp.61-66
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    • 2019
  • VANET (Vehicular Ad-hoc Network) is a mobile Ad-hoc Network which deals with the moving vehicles. VANET supports Intelligent Transport Systems (ITS) which is related to different modes of transport and traffic management techniques. VANETs enabled users to be informed and make them safer. VANET uses IEEE 802.11p standard wireless access protocol for communication. An important and necessary issue of VANET is to design routing protocols. In a network, communication takes place by the use of the routing protocols. There are mainly two types of communications used such as Vehicle to Vehicle (V2V) and Vehicle to Infrastructure (V2I) in VANET. Vehicles can send and receive messages among them and also to and from infrastructure used. In this paper, AODV, DSR and DSDV are compared by analysing the results of simulation on various metrics such as average throughput, instant throughput, packet delivery ratio and residual energy. Findings indicates utilization of AODV and DSR is more applicable for these metrics as compared to DSDV. A network simulator (NS2) is used for simulation.

Investigation on alkalinity of pore solution and microstructure of hardened cement-slag pastes in purified water

  • Hu, Ya-Ru;Zuo, Xiao-Bao;Li, Xiang-Nan;Jiang, Dong-Qi
    • Advances in concrete construction
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    • 제12권6호
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    • pp.507-515
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    • 2021
  • To evaluate the influence of slag on the alkalinity of pore solution and microstructure of concrete, this paper performs a leaching experiment on hardened cement-slag pastes (HCSP) slice specimens with different slag content in purified water. The pH value of pore solution, average porosity, morphology, phase composition and Ca/Si of HCSP specimens in the leaching process are measured by solid-liquid extraction, saturated-dried weighing, scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) and X-ray diffraction (XRD). Results shows that the addition of slag can mitigate an increase in porosity and a decrease in Ca/Si of HCSP in the leaching process. Besides, an appropriate slag content can improve the microstructure so as to obtain the optimum leaching resistance of HCSP, which can guarantee the suitable alkalinity of pore solution to prevent a premature corrosion of reinforced bar. The optimum slag content is 40% in HCSP with a water-binder ratio of 0.45, and an excessive slag causes a significant decrease in the alkalinity of pore solution, resulting in a loss of protection on reinforced bar in HCSP.

Deep learning of sweep signal for damage detection on the surface of concrete

  • Gao Shanga;Jun Chen
    • Computers and Concrete
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    • 제32권5호
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    • pp.475-486
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    • 2023
  • Nondestructive evaluation (NDE) is an important task of civil engineering structure monitoring and inspection, but minor damage such as small cracks in local structure is difficult to observe. If cracks continued expansion may cause partial or even overall damage to the structure. Therefore, monitoring and detecting the structure in the early stage of crack propagation is important. The crack detection technology based on machine vision has been widely studied, but there are still some problems such as bad recognition effect for small cracks. In this paper, we proposed a deep learning method based on sweep signals to evaluate concrete surface crack with a width less than 1 mm. Two convolutional neural networks (CNNs) are used to analyze the one-dimensional (1D) frequency sweep signal and the two-dimensional (2D) time-frequency image, respectively, and the probability value of average damage (ADPV) is proposed to evaluate the minor damage of structural. Finally, we use the standard deviation of energy ratio change (ERVSD) and infrared thermography (IRT) to compare with ADPV to verify the effectiveness of the method proposed in this paper. The experiment results show that the method proposed in this paper can effectively predict whether the concrete surface is damaged and the severity of damage.

경기지역 일부 대학생의 지방제한 섭취 행동단계에 따른 영양소 섭취상태 비교 (Comparison of Nutrient Intakes Regarding Stages of Change in Dietary Fat Reduction for College Students in Gyeonggi-Do)

  • 정은정
    • 한국식품영양과학회지
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    • 제33권8호
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    • pp.1327-1336
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    • 2004
  • 경기지역 일부 대학생의 지방제한식에 대한 행동단계 분포는 연구대상자의 19.3%가 자각이전, 13.8%는 자각, 31.1%는 준비, 28.7%는 실시, 7.1%는 유지단계로, 성인보다 실시 및 유지 단계 비율이 낮아 대학생의 지방질을 선호하는 식생활을 엿볼 수 있었다. 행동변화 단계별로 BMI, 자신의 건강평가, 음주, 흡연 등은 차이가 없었으나 성별에 의한 차이는 뚜렷하여 남학생은 자각이전 및 자각단계가, 여학생은 준비, 실행 및 유지단계의 비율이 많았다. 식행동 단계의 주요 예측인자인 자아효능감은 자각이전에서 유지단계로 갈수록 증가하였다. 열량, 지방질, 포화지방산, linoleic acid($\omega$6), 콜레스테롤 섭취량은 남여 모두 자각이전과 준비단계에서 많고, 실행과 유지단계에서 적었다. 섭취열량중 지방질의 비율은 자각이전과 준비단계에는 권장수준인 20%를 크게 상회하였으나, 실행과 유지단계에서는 권장수준을 섭취하는 양호한 식습관을 갖고 있었다. 섭취 지방산의 P/S 비율은 모두 권장비율에 속하였으며, $\omega$6/$\omega$3 비율은 여학생은 권장범위에 속하였으나(자각이전단계 예외), 남학생은 모든 단계에서 권장범위 이상으로, 지방질의 질적 영양문제가 지적되었다. 행동단계별 영양소 섭취량의 차이는 여학생에게서 더 뚜렷하였으며 , 남학생은 실행단계보다 유지단계에서 열량, 포화지방산, 콜레스테롤 섭취량, $\omega$6/$\omega$3 비율 등이 오히려 증가하는 경향을 보여, 행동변화 모형 에 의한 대상자의 구분은 여학생에서 더 유용한 도구였다. 남학생의 열량, 지방질, 단백질 섭취량은 저녁식사에서만 행동단계별로 차이를 보였으나, 여학생은 저녁을 포함한 다른 끼니에서도 차이를 보여, 남학생보다 단계별 식행동의 차이가 뚜렷하였다. 이상의 결과에서와 같이 아주 간단한 과정을 통해 식행동 단계를 구분지어 주는 행동변화단계 모형은 대상자의 특성과 지방질 영양의 문제점을 파악할 수 있게 되어 각 개인별 맞춤 영양교육의 한 도구가 되어질 수 있음을 알 수 있었다. 따라서 본 행동변화단계 모형에서 자각이전, 자각, 준비 단계로 분류된 대상자들에게는 양적, 질적으로 모두 양호한 지방질의 섭취 패턴을 보이는 실행과 유지 단계가 되도록, 자아효능감 등을 증가시키는 영양교육이 이루어져야 할 것이다. 또한 남학생의 경우 여학생보다 지방제한식을 실시하는 비율이 적었으며, 행동변화 단계에 따라 영양소 섭취량의 차이도 뚜렷하지 않아, 이들을 위한 영양교육의 필요성이 지적되었다. 따라서 이들에게 구체적인 내용의 영양교육을 실시하기 위해, 열량과 지방질, 포화지방, 콜레스테롤 섭취량의 주요 급원식품에 대한 후속 연구가 이루어져야 할 것으로 생각된다.