On Node Lifetime Problem for Energy-Constrained Wireless Sensor Networks

A fundamental problem in wireless sensor networks is to maximize network lifetime under given energy constraints. In this paper, we study the network lifetime problem by considering not only maximizing the time until the first node fails, but also maximizing the lifetimes for all the nodes in the network, which we define as the Lexicographic Max-Min (LMM) node lifetime problem. The main contributions of this paper are two-fold. First, we develop a polynomial-time algorithm to derive the LMM-optimal node lifetime vector, which effectively circumvents the computational complexity problem associated with an existing state-of-the-art approach, which is exponential. The main ideas in our approach include: (1) a link-based problem formulation, which significantly reduces the problem size in comparison with a flow-based formulation, and (2) an intelligent exploitation of parametric analysis technique, which in most cases determines the minimum set of nodes that use up their energy at each stage using very simple computations. Second, we present a simple (also polynomial-time) algorithm to calculate the flow routing schedule such that the LMM-optimal node lifetime vector can be achieved. Our results in this paper advance the state-of-the-art algorithmic design for network-wide node lifetime problem and facilitate future studies of the network lifetime problem in energy-constrained wireless sensor networks. Y. Thomas Hou obtained his B.E. degree from the City College of New York in 1991, the M.S. degree from Columbia University in 1993, and the Ph.D. degree from Polytechnic University, Brooklyn, New York, in 1998, all in Electrical Engineering. From 1997 to 2002, Dr. Hou was a research scientist and project leader at Fujitsu Laboratories of America, IP Networking Research Department, Sunnyvale, California(Silicon Valley). Since Fall 2002, he has been an Assistant Professor at Virginia Tech, the Bradley Department of Electrical and Computer Engineering, Blacksburg, Virginia. Dr. Hou's research interests are in the algorithmic design and optimization for network systems. His current research focuses on wireless sensor networks and multimedia over wireless ad hoc networks. In recent years, he has worked on scalable architectures, protocols, and implementations for differentiated services Internet; service overlay networking; multimedia streaming over the Internet; and network bandwidth allocation policies and distributed flow control algorithms. He has published extensively in the above areas and is a co-recipient of the 2002 IEEE International Conference on Network Protocols (ICNP) Best Paper Award and the 2001 IEEE Transactions on Circuits and Systems for Video Technology (CSVT) Best Paper Award. He is a member of ACM and a senior member of IEEE. Yi Shi received his B.S. degree from University of Science and Technology of China, Hefei, China, in 1998, a M.S. degree from Institute of Software, Chinese Academy of Science, Beijing, China, in 2001, and a second M.S. degree from Virginia Tech, Blacksburg, VA, in 2003, all in computer science. He is currently working toward his Ph.D. degree in electrical and computer engineering at Virginia Tech. While in undergraduate, he was a recipient of Meritorious Award in International Mathematical Contest in Modeling and 1997 and 1998, respectively. Yi's current research focuses on algorithms and optimization for wireless sensor networks and wireless ad hoc networks. His work has appeared in highly selective international conferences (e.g., ACM MobiCom and MobiHoc). Hanif D. Sherali is the W. Thomas Rice Endowed Chaired Professor of Engineering in the Industrial and Systems Engineering Department at Virginia Polytechnic Institute and State University. His area of research interest is in discrete and continuous optimization, with applications to location, transportation, and engineering design problems. He has published about 200 papers in Operations Research journals, has co-authored four books in this area, and serves on the editorial board of eight journals. He is a member of the National Academy of Engineering.     

Carriers-mediated ferromagnetic enhancement in Al-doped ZnMnO dilute magnetic semiconductors

Nano-crystalline Zn_{0.95 – x}Mn_0.05Al_xO (x = 0, 0.05, 0.10) dilute magnetic semiconductors (DMS) were synthesized by sol–gel derived auto-combustion. X-ray diffraction (XRD) analysis shows that the samples have pure wurtzite structure typical of ZnO without the formation of secondary phases or impurity. Crystallite sizes were approximated by Scherrer formula while surface morphology and grain sizes were measured by field emission scanning electron microscopy. Incorporation of Mn and Al into the ZnO structure was confirmed by energy-dispersive X-ray analysis. Temperature dependent electrical resistivity measurements showed a decreasing trend with the doping of Al in ZnMnO, which is attributable to the enhancement of free carriers. Vibrating sample magnetometer studies confirmed the presence of ferromagnetic behavior at room temperature. The results indicate that Al doping results in significant variation in the concentration of free carriers and correspondingly the carrier-mediated magnetization and room temperature ferromagnetic behavior, showing promise for practical applications. We attribute the enhanced saturation magnetization and electrical conductivity to the exchange interaction mediated by free electrons.     

Mathematical Modeling of Lake Tap Flows

A lake tap is the submerged piercing of a tunnel at the intake to connect the reservoir to the tunnel system. It is referred to as a dry lake tap if the tunnel is dry before the blasting of the last rock plug at the tunnel entrance. Transient state conditions in the tunnel following a dry lake tap are modeled using the lumped and distributed-system approaches. Fourth-order Runge-Kutta method and the method of characteristics are used in the lumped-system model and distributed-system models, respectively. The results computed by the lumped and distributed-system approaches agree with one another. Pressures computed by using distributed-system and lumped-system models are compared with the experimental results available in literature for rapid filling of a pipeline with closed end. The rate of dissipation of pressure oscillations in the measured air pressure during prototype lake tap at Crater Lake Snettisham project in Alaska, and in the experiments reported in the literature is higher than that computed by the mathematical models using steady state friction and constant wave velocity.     

Application of fuzzy logic for autonomous bay parking of automobiles

In this paper, we investigate the control problem of autonomous bay parking system. We choose a referenced parking lot and define a suitable parking spot based on some measurements at various places. A kinetic model is set up for the convenience of analysis and simulation. The pose of the car during the parking procedure can be determined by the initial pose, the backward speed, and the steering angle of the wheel. Then, both a fuzzy speed controller and a fuzzy steering controller are designed for the bay parking. Finally, simulation results show the effectiveness of our designed controllers.     

Effect of Silicone Nano,Nano/Micro and Nano/Macro‐Emulsion Softeners on Color Yield and Physical Characteristics of Dyed Cotton Fabric

The study of silicone nano‐emulsions and softeners to alter physical properties of undyed cotton fabric has recently gained a substantial interest. However, systematic investigation of silicon nano‐emulsion softeners on dyed cotton fabric has not so far been conducted. This paper deals with the application of silicone nano‐, micro‐, and macro‐emulsion softeners, and combinations of nano/micro and nano/macro, on dyed cotton fabric. We report the effect of silicon nano/micro‐ and nano/macro‐emulsion softeners on color yield and physical characteristics of dyed cotton fabric. All bleached fabrics were dyed with CI Reactive Black 5 and then treated with known concentrations of silicone softeners by the pad‐dry method. The silicone nano‐emulsion was combined with micro‐ and macro‐emulsion softeners using blending ratios of nano/micro (1:1) and nano/macro (1:1). Treated fabrics were compared in terms of physical properties such as fabric handling, wrinkle recovery angle, bending length, abrasion resistance and tensile strength. The color changes were evaluated by color yield (K/S) values and total color difference (ΔE_cmc). The results revealed that the silicon nano‐emulsion had better physical properties than micro‐, macro‐ and combination nano/micro‐ and nano/macro‐emulsion softeners. Among all treated samples, nano‐emulsion softeners showed better ΔE_cmc values. Scanning electron microscopy analysis suggests that the fiber morphology of treated fabrics was very smooth and uniform.     

Magnetization Process of the Spin-1/2 Two-Leg Ladder Compound (C5H12N)2 CuBr4: The Jordan-Wigner Approach

We have studied the magnetization process in the spin S = 1/2 antiferromagnetic two-leg ladder compound (C₅H₁₂N)₂ CuBr₄ by using the analytical fermionization technique. The magnetization and the susceptibility are calculated as functions of the temperature and the external magnetic field. The magnetization of the system shows various behaviors in different regions of the magnetic field. The field-dependence of the susceptibility is almost symmetric about the average of quantum critical fields in the low-temperature region leading to a complete agreement with the experimental results.     

Effect of Particle Size on Direct Compaction of Urea Fertilizer

The effect of particle size on compaction properties and characteristics of urea tablets manufactured from available urea granules (TG tablets) and ground urea powders (TP tablets) was investigated. The compaction properties, namely, plastic work, elastic work, friction work, and maximum ejection pressure were analyzed from the force-displacement profile of the compaction process. Five applied pressures ranging between 37.67 MPa and 188.35 MPa were used to compact the materials using a universal testing machine. Characteristics of the tablets tested were mechanical strength and the release of ammonium ion through dissolution test. The results demonstrated that TG tablets underwent high plastic work and elastic work but low friction work compared to the TP tablets. TG tablets released lower amount of ammonium ion compared to the TP tablets at almost all applied pressures, except at 75.34 MPa. This study provides a valuable data for evaluating the behavior of urea in the form of granules and powders during the compaction process as well as the suitability in choosing the form of raw material for the production of urea tablets.     

An enhanced distributed power control algorithm for mobile femtocells under limited dynamic range and its convergence

This paper presents a distributed power control algorithm for wireless backhaul links of mobile femtocells by using the pilot’s information. Taking into account the limited dynamic range of transmitted powers, the SINR balancing of mobile (vehicular) femto base stations in their home macro base station and the load balancing among the macrocells are achieved by the proposed approach at the cost of exchanging some limited information among both macro and vehicular femto base stations. The algorithm is very beneficial especially in a high load heterogeneous network. Monte Carlo simulation results denote that the mobile femtocells can be uniformly assigned to the macrocells and the SINR balancing is achievable via the proposed scheme.

     

Effect of vanadium and tin additives on structural and magnetic properties of Bi-YIG nano-particles

In this research work, substituted tin and vanadium garnets Y_2.5Bi_0.5Fe_2?2xSn_xFe_3?xV_x O₁₂ (0?≤?x?≤?0.2) were prepared by mechanochemical processing following with 10 h milling and post-annealing at different temperatures. Physical properties of samples were studied by X-ray diffraction analysis (XRD), Far-infrared spectroscopy (Far-IR), and field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and vibrating sample magnetometer (VSM). XRD patterns of prepared garnets show that the samples are all single phase with garnet structure at 900 °C. Further, the average crystallite size was calculated by Debye–Scherrer, and Williamson–Hall methods. We also studied the magnetic properties of prepared samples by using a vibrating sample magnetometer (VSM). Experiments showed that the maximum value of vanadium that can be entered in the garnet structure is 0.2.