Routing Protocol for Heterogeneous Hierarchical Wireless Multimedia Sensor Networks

Recently, wireless multimedia sensor networks (WMSNs) have emerged as one of the most important technologies, driven by the development of powerful multimedia device such as CMOS. WMSNs require several factors such as resource constraints, specific QoS, high bandwidth and so on. In this paper, we propose a hierarchical heterogeneous network model based routing protocol for WMSNs. In our proposal, proposed network model is classified into monitoring class, delivery class and aggregation class. Also we define two kinds of the routing path in order to ensure bandwidth and QoS. In simulation results, we illustrate the performance of our proposal.     

Analysis of the effects of main design parameters variation on the vibration characteristics of a vehicle sub-frame

In the design process of an automobile part, several analysis methods are usually used to evaluate the performance of the part. However, most automobile design engineers do not directly use CAE (computer aided engineering) tools since specific skills are required to obtain practical results. Moreover, CAE requires a huge amount of computation time and cost. To resolve these problems, a new design approach, termed first order analysis (FOA), has been proposed. In this paper, the FOA technique is employed to design a vehicle sub-frame. An equivalent model of the vehicle subframe which only consists of beam elements is proposed and the modal properties obtained with the model are compared to those obtained with a full scale finite element model. The effects of some parameter variations on the modal characteristics of the vehicle sub-frame are investigated by employing the FOA equivalent model. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Hong Hee Yoo graduated from the Department of Mechanical Design and Production Engineering at Seoul National University in 1980 and received his Master’s degree from the same department in 1982. He received his Ph.D. degree in 1989 from the Department of Mechanical Engineering and Applied Mechanics at the University of Michigan at Ann Arbor, U.S.A. He is currently working as a professor in the School of Mechanical Engineering in Hanyang University, Seoul, Korea.     

Mixed norm regularized recursive total least squares for group sparse system identification

A mixed l_p,0‐regularized recursive total least squares (RTLS) algorithm is considered for group sparse system identification. Regularized recursive least squares (RLS) has been successfully applied to group sparse system identification; however, the estimation performance in regularized RLS‐based algorithms deteriorates when both input and output are contaminated by noise (the error‐in‐variables problem). We propose an l_p,0‐RTLS algorithm to handle group sparse system identification with errors‐in‐variables. The proposed algorithm is an RLS‐like solution that utilizes l_p,0‐regularization. The proposed algorithm provides excellent performance as well as reduces the required complexity by effective inversion matrix handling. Simulations demonstrate the superiority of the proposed l_p,0‐regularized RTLS for a group sparse system identification setting. Copyright © 2015 John Wiley & Sons, Ltd.     

New method for low temperature fabrication of Ni–Al alloy powder for molten carbonate fuel cell applications

Lump-free Ni-5 wt% Al alloy powder was successfully prepared using an AlCl₃ activator at 400 °C under vacuum. The AlCl₃ activator served as the catalyst, lowering the fabrication temperature by 1000 °C compared with the temperature required for the conventional process. The Ni–Al alloy was formed by the following steps: the formation of NiAl by the reaction of the Ni surface with AlCl₂ or AlCl produced by the reaction between Al and AlCl₃, the formation of Ni₃Al by Al diffusion and reaction, and the formation of a Ni–Al solid solution by Al diffusion into the Ni matrix until the solubility limitation was reached. Although lowering the alloying temperature lengthens the reaction time, the time could be reduced by controlling the amount of AlCl₃. A single cell test and a creep test were also conducted using a green sheet of as-prepared Ni–Al alloy powder as an anode of a molten carbonate fuel cell (MCFC).     

Effects of bimetallic catalyst composition and growth parameters on the growth density and diameter of carbon nanotubes

Multi-wall carbon nanotubes (MWNTs) were synthesized by catalytic decomposition of acetylene over Fe, Ni and Fe-Ni bimetallic catalysts supported on alumina under various controlled conditions. The growth density and diameter of CNTs were markedly dependent on the activation time of catalysts in H₂ atmosphere, reaction time, reaction temperature, flow rate of acetylene, and catalyst composition. Bimetallic catalysts were apt to produce narrower diameter of CNTs than single metal catalysts. For the growth of CNTs at 600 ‡C under 10/100 seem flow of C₂H₂/H₂ mixture, the narrowest diameter about 20 nm was observed at the reaction time of 1 h for 20Fe : 20Ni : 60Al₂O₃ catalyst, but at that of 1.5 h for 10Fe : 30Ni : 60Al₂O₃ catalyst. It was considered that the diameter and density of CNTs decreased with the increase of the growth time mainly due to hydrogen etching. The growth of CNTs followed the tip growth mode.     

Fracture Mechanics of Solder Bumps During Ball Shear Testing: Effect of Bump Size

This paper examines the mechanics of ball shear testing with the objective of understanding the mechanism by which the maximum shear force and the rate of crack growth is dependent on the solder bump size. For this, Pb-Sn solder bumps with diameters between 460 μm and 760 μm are soldered to 400 μm-diameter Cu pads and subjected to ball shear testing. In spite of the constant interface area, the bump size significantly impacts the measured shear fracture force and the crack growth rate. Both the fracture force and the crack growth rate increase with bump size, and in the case of the fracture force, the increase is almost linear. Our analysis finds that the linear increase in the fracture force is a result of the bump deformation force, which increases with bump size. A simple model that accounts for the deformation force component is developed and used to extract the true interface fracture force. The estimated true interface fracture force is found to vary little with bump size, tightly converging to the 40 MPa to 48 MPa range. On the other hand, the dependence of crack growth rate on bump size is found to result from the higher degree of rotational moment associated with larger bumps.     

A Genetic‐Based Iterative Quantile Regression Algorithm for Analyzing Fatigue Curves

Accurate prediction of fatigue failure times of materials such as fracture and plastic deformation at various stress ranges has a strong bearing on practical fatigue design of materials. In this study, we propose a novel genetic‐based iterative quantile regression (GA‐IQR) algorithm for analyzing fatigue curves that represent a nonlinear relationship between a given stress amplitude and fatigue life. We reduce the problem to a linear framework and develop the iterative algorithm for determining the model coefficients including unknown fatigue limits. The procedure keeps updating the estimates in a direction to reduce its resulting error. Also, our approach benefits from the population‐based stochastic search of the genetic algorithms so that the algorithm becomes less sensitive to its initialization. Compared with conventional approaches, the proposed GA‐IQR requires fewer assumptions to develop fatigue model, capable of exploring the data structure in a relatively flexible manner. All procedures and calculations are quite straightforward, such that the proposed quantile regression model has a high potential value in a wide range of applications for exploring nonlinear relationships with lifetime data. Computational results for real data sets found in the literature present good evidences to support the argument. Copyright © 2012 John Wiley & Sons, Ltd.