• Title/Summary/Keyword: Propagation efficiency

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Packet Size Optimization for Improving the Energy Efficiency in Body Sensor Networks

  • Domingo, Mari Carmen
    • ETRI Journal
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    • v.33 no.3
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    • pp.299-309
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    • 2011
  • Energy consumption is a key issue in body sensor networks (BSNs) since energy-constrained sensors monitor the vital signs of human beings in healthcare applications. In this paper, packet size optimization for BSNs has been analyzed to improve the efficiency of energy consumption. Existing studies on packet size optimization in wireless sensor networks cannot be applied to BSNs because the different operational characteristics of nodes and the channel effects of in-body and on-body propagation cannot be captured. In this paper, automatic repeat request (ARQ), forward error correction (FEC) block codes, and FEC convolutional codes have been analyzed regarding their energy efficiency. The hop-length extension technique has been applied to improve this metric with FEC block codes. The theoretical analysis and the numerical evaluations reveal that exploiting FEC schemes improves the energy efficiency, increases the optimal payload packet size, and extends the hop length for all scenarios for in-body and on-body propagation.

Experimental Study on the Characteristics of Brown Gas (브라운가스의 특성에 대한 실험적 연구)

  • Kim Chang-Hee;Oh Kyu-Hyung;Kang Kyung-Soo;Park Chu-Sik;Bae Ki-Kwang;Kim Jong-Won
    • Proceedings of the Korea Society for Energy Engineering kosee Conference
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    • 2006.05a
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    • pp.262-262
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    • 2006
  • The characteristics of Brown gas was experimentally studied in view of efficiency and flame propagation. For this study, the Brown gas stack with 7 cells was manufactured following the Brown gas related patents and reports. All measuring equipments were re-tested and calibrated by Korea Laboratory Accreditation Scheme (KOLAS) certified laboratories. Since the amount of produced gas is most crucial in determining the efficiency, we adopted two gas collecting methods such as bottle trap method and wet gas meter method. The energy efficiency of our own fabricated stack was measured to be 75%, which is comparable to general alkaline water electrolysis efficiency. In order to analyze the flame propagation characteristics of Brown gas, we measured the flame propagation pressure, velocity, and shape by using strain type pressure sensor, optical sensor, and high speed camera in conjunction with Schliren system, respectively. From the experimental results, it was found that the flame propagation behavior of Brown gas was almost the same as that of hydrogen and oxygen mixture gas in 2:1 molar ratio. Moreover, from the high speed camera analysis, we concluded that Brown gas flame exhibits explosion behavior as does mixture gas ($H_{2}:O_{2}=2:1$).

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PREDICTION OF CODED SIGNAL PROPAGATION IN FADING CHANNEL

  • Swun, Z.G.;Yang, J.J.
    • Proceedings of the Acoustical Society of Korea Conference
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    • 1994.06a
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    • pp.1088-1091
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    • 1994
  • This paper presents a method to predict in statistics the coded signal propagation in fading channel with the help of the ray theory. This method features its high speed and efficiency. The predictions of received signal envelope and pulse width can be give out quickly.

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Towards A Better Understanding of Space Debris Environment

  • Hanada, Toshiya
    • International Journal of Aerospace System Engineering
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    • v.3 no.1
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    • pp.5-9
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    • 2016
  • This paper briefly introduces efforts into space debris modeling towards a better understanding of space debris environment. Space debris modeling mainly consists of debris generation and orbit propagation. Debris generation can characterize and predict physical properties of fragments originating from explosions or collisions. Orbit propagation can characterize, track, and predict the behavior of individual or groups of space objects. Therefore, space debris modeling can build evolutionary models as essential tools to predict the stability of the future space debris populations. Space debris modeling is also useful and effective to improve the efficiency of measurements to be aware of the present environment.

Fundamental study on combustion characteristics of methanol fuel in a constant volume chamber (정적연소기를 사용한 메탄올의 연소특성에 관한 연구)

  • 이태원;이중순;정성식;하종률
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.2
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    • pp.389-396
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    • 1994
  • It is very important to clarify the ignition and flame propagation processes of methanol fuel in the Spark-ignition engine. High speed Schlieren photography and pressure trace analyses were used to study on combustion characteristics of methanol fuel in a constant volume chamber. Methanol-air mixtures equivalence rations from lean limit to 1.4 were ignited at initial pressure (0.1, 0.3, 0.5 MPa), temperature (313 343, 373 K) and ignition energy (40, 180 mJ). As the result of this study, we verified the characteristics such as ignition delay, effective thermal efficiency, flame propagation velocity, lean limit, ignitability and combustion duration. Obatained results are as follows. (1) The time to 10% reach of maximum pressure was 40-50% of the total combustion duration for this experimental condition hardly affected by equivalence ratio. (2) The Effective thermal efficiency, as calculated from maximum pressure was the highest when the mixture was slightly lean $({\phi} 0.8-0.9)$ and maximum pressure was the highest when the mixiture was slightly rich $({\phi} 1.2-1.2).$

Change Impact Analysis in Engineering Design Process (공학 설계 프로세스에서 설계 변경 영향 해석)

  • 정태형;박승현
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.1
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    • pp.151-158
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    • 2003
  • Design changes frequently occur while design activities are performed. If the impact of design changes is estimated, design efficiency can be improved. But, the types of design changes are various and they can affect other design parts. Hence, it is difficult to deal with design changes directly. The purpose of this research is to develop systematic algorithms for change propagation tracing and change impact analysis, and then to implement a change impact analysis system. We have selected a process-based design and a design environment which is composed of design parameters and constraints. The algorithm for change propagation tracing tracks the change propagation of design parameters and finds design parameters, constraints and tasks which are probably changed. In the algorithm for change impact analysis, a change impact value is calculated from the list of changeable tasks. These two algorithms have been implemented into change impact analysis system (CIAS). CIAS has been applied to the redesign of 2 stage gear drives. CIAS can improve the efficiency of design activities. If there are many alternatives for a design change at the redesign step, designers can calculate the change impact value of each alternative and perform design change activities in the direction of minimizing design change impact.

Effect of Different Budding Methods and Times on Grafting Success of Walnut

  • Nosrati, Zia;Khadivi-Khub, Abdollah
    • Horticultural Science & Technology
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    • v.32 no.6
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    • pp.788-793
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    • 2014
  • Vegetative propagation of walnut is difficult compared with that of other fruit and nut species. The present study assessed three methods of grafting (patch, shield, and chip) at various periods of walnut growth and with different timings of grafting in walnut. Early May was the best time for grafting, at which time the highest success rate was obtained by the patch method (96%), followed by chip-budding (75%), while shield-grafting showed the lowest efficiency (10%). Patch-grafting was also successful (75-80%) in early August and moderately successful in mid-June (51-55%), while the shield and chip methods had no success during these two times (0.00%). Patch-grafting was more efficient and also induced better callus formation and scion growth than the other two methods. The genotypes used did not affect grafting efficiency. The best results were obtained by patch-budding in both tested genotypes. The present findings show the potential value of patch-grafting in early May as a propagation method for walnut for establishment of guidelines for propagation.

On the enhancement of the learning efficiency of the adaptive back propagation neural network using the generating and adding the hidden layer node (은닉층 노드의 생성추가를 이용한 적응 역전파 신경회로망의 학습능률 향상에 관한 연구)

  • Kim, Eun-Won;Hong, Bong-Wha
    • Journal of the Institute of Electronics Engineers of Korea TE
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    • v.39 no.2
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    • pp.66-75
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    • 2002
  • This paper presents an adaptive back propagation algorithm that its able to enhancement for the learning efficiency with updating the learning parameter and varies the number of hidden layer node by the generated error, adaptively. This algorithm is expected to escaping from the local minimum and make the best environment for the convergence of the back propagation neural network. On the simulation tested this algorithm on three learning pattern. One was exclusive-OR learning and the another was 3-parity problem and 7${\times}$5 dot alphabetic font learning. In result that the probability of becoming trapped in local minimum was reduce. Furthermore, the neural network enhanced to learning efficient about 17.6%~64.7% for the existed back propagation. 

Adaptive Crack Propagation Analysis with the Element-free Galerkin Method (Element-free Galerkin 방법을 이용한 적응적 균열진전해석)

  • 최창근;이계희;정흥진
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2001.04a
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    • pp.84-91
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    • 2001
  • In this study, the adaptive analysis procedure of crack propagation based on the element-free Galerkin(EFG) method is presented. The adaptivity analysis in quasi-static crack propagation is achieved by adding and/or removing the node along the background integration cell that are refined or recovered according to the estimated error. These errors are obtained basically by calculating the difference between the values of the projected stresses and original EFG stresses. To evaluate the performance of proposed adaptive procedure, the crack propagation behavior is investigated for several examples. The results of these examples show the efficiency and accuracy of proposed scheme in crack propagation analysis.

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Polygonal finite element modeling of crack propagation via automatic adaptive mesh refinement

  • Shahrezaei, M.;Moslemi, H.
    • Structural Engineering and Mechanics
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    • v.75 no.6
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    • pp.685-699
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    • 2020
  • Polygonal finite element provides a great flexibility in mesh generation of crack propagation problems where the topology of the domain changes significantly. However, the control of the discretization error in such problems is a main concern. In this paper, a polygonal-FEM is presented in modeling of crack propagation problems via an automatic adaptive mesh refinement procedure. The adaptive mesh refinement is accomplished based on the Zienkiewicz-Zhu error estimator in conjunction with a weighted SPR technique. Adaptive mesh refinement is employed in some steps for reduction of the discretization error and not for tracking the crack. In the steps that no adaptive mesh refinement is required, local modifications are applied on the mesh to prevent poor polygonal element shapes. Finally, several numerical examples are analyzed to demonstrate the efficiency, accuracy and robustness of the proposed computational algorithm in crack propagation problems.