A Consistent Description of Scaling Law for Flux Pinning in ${hbox{Nb}}_{3}{hbox{Sn}}$ Strands Based on the Kramer Model (Corrected)*

There are a lot of experimental reports on the scaling of flux pinning in the form of F = F_mb^1/2(1 - b)², with b = B/B_c2.The temperature dependence of F_m is approximately proportional to B'.2 , whereas the strain dependence of Fm is reported to be proportional to the upper critical field Bc2. In this work, we re-analyze our previous data with the Kramer model including the pin-breaking dynamic pinning force (F_p) for a low field region. It is shown that the extrapolated upper critical field B_c2*, strongly depend on the ratio between the mean of the parameter K_p for F_p (p>) and the parameter K, for the flux line lattice shearing pinning force F_s. It is found that the strain dependence of F_m at 4.2 K is approximately proportional to (B_c2*)^1.5. We further compare the data with the prediction of our recent scaling theory based on Eliashberg theory of strongly coupled superconductors. It is shown that the strain dependence of F_m at 4.2 K is proportional to BC₂ ^5/2 kappa^-2, consistent with the temperature dependence of Fm. Moreover, this model agrees reasonably well even with the data in a high compressive strain region (<-0.8%).     

QoS‐aware routing and power control algorithm for multimedia service over multi‐hop mobile ad hoc network

This paper presents a QoS (quality of service) aware routing and power control algorithm consuming low transmission power for multimedia service over mobile ad hoc network. Generally, multimedia services need stringent QoS over the network. However, it is not easy to guarantee the QoS over mobile ad hoc network since its network resources are very limited and time‐varying. Furthermore, only a limited amount of power is available at mobile nodes, which makes the problem more challenging. We propose an effective routing and power control algorithm for multimedia services that satisfies end‐to‐end delay constraint with low transmission power consumption. The proposed algorithm supports the required bandwidth by controlling each link channel quality over route in a tolerable range. In addition, a simple but effective route maintenance mechanism is implemented to avoid link failures that may significantly degrade streaming video quality. Finally, performance comparison with existing algorithms is presented in respect to traditional routing performance metrics, and an achievable video quality comparison is provided to demonstrate the superiority of the proposed algorithm for multimedia services over mobile ad hoc network. Copyright © 2010 John Wiley & Sons, Ltd.     

Enhancement of the Performance of a Reflective SOA-Based Hybrid WDM/TDM PON System With a Remotely Pumped Erbium-Doped Fiber Amplifier

A passive optical network (PON) architecture based on a hybrid wavelength-division multiplexing (WDM) and time-division multiplexing (TDM) PON system with a remotely pumped erbium-doped fiber amplifier (EDFA) is presented as an excellent candidate for use in a next-generation optical access network. The remotely pumped EDFA operates as a bidirectional amplifier and provides a 15-dB gain to both upstream signals and seed light sources, so the sensitivity of upstream transmission is greatly improved. An upstream transmission of 1.25 Gb/s with a low seed channel power of -14 dBm is made feasible over a total reach of 25 km for 32-WDM channels and 16-TDM splits by the use of the remotely pumped EDFA. This scheme has advantages that it uses a single transmission fiber for both down-and up-stream signals and that it reduces the Rayleigh scattering contribution.     

ZnO-Based Low-Voltage Inverter With Quantum-Well-Structured Nanohybrid Dielectric

We report on the fabrication of 2-V-operating ZnO-based inverter with two n-channel thin-film transistors (TFTs) on 22-nm-thin organic/inorganic nanohybrid dielectric, which contains AlO_x/TiO_x/AlO_x in triple-layer structure. The inverter shows a high voltage gain of ~20 under the supply voltage (V_DD) of 2 V but with a marginal transition voltage of 0.1 V (operation range of 0-2 V). To control the transition voltage to a more adequate value, an 8-V gate pulse was applied on driving ZnO-TFT so that some of the channel electrons would be tunneled through the AlO_x-based barrier and trapped in the TiO_x-based layer. Our inverter then displayed an optimum transition voltage of 0.75 V.     

Call admission control strategy for system throughput maximization considering both call- and packet-level QoSs

This letter presents a call admission control (CAC) strategy for system throughput maximization in wireless uplink systems. This strategy considers not only the call-level quality of service (QoS) (i.e., blocking probability) but also the packet-level QoS (i.e., outage probability). Using the statistical co-channel interference (CCI) model and state diagram, the outage probability and the blocking probability are investigated as a function of the relative traffic load. We formulate the CAC strategy problem based on relative traffic load, and suggest a solution. The numerical results show that maximum system throughput can be achieved by controlling the relative traffic load. In addition, we illustrate the region where system throughput is constrained by call- and packet-level QoSs. This examination shows that the call and packet-level QoSs must be considered together to achieve maximum system throughput.     

Tracking and Coordination of Multiple Agents Using Sensor Networks: System Design, Algorithms and Experiments

This paper considers the problem of pursuit evasion games (PEGs), where the objective of a group of pursuers is to chase and capture a group of evaders in minimum time with the aid of a sensor network. The main challenge in developing a real-time control system using sensor networks is the inconsistency in sensor measurements due to packet loss, communication delay, and false detections. We address this challenge by developing a real-time hierarchical control system, named LochNess, which decouples the estimation of evader states from the control of pursuers via multiple layers of data fusion. The multiple layers of data fusion convert noisy, inconsistent, and bursty sensor measurements into a consistent set of fused measurements. Three novel algorithms are developed for LochNess: multisensor fusion, hierarchical multitarget tracking, and multiagent coordination algorithms. The multisensor fusion algorithm converts correlated sensor measurements into position estimates, the hierarchical multitarget tracking algorithm based on Markov chain Monte Carlo data association (MCMCDA) tracks an unknown number of targets, and the multiagent coordination algorithm coordinates pursuers to chase and capture evaders using robust minimum-time control. The control system LochNess is evaluated in simulation and successfully demonstrated using a large-scale outdoor sensor network deployment     

A Low‐Cost Method to Evaluate Absorber Reflectivity Using an Antenna with a Small Radiating Aperture and Frequency‐Domain Instrument

We propose a way to measure the absorber reflectivity at a low cost. Only one simple antenna with a small radiating aperture and a frequency‐domain instrument are utilized. The previously used equation for calculating the reflectivity of an absorber is inaccurate, and, therefore, a new equation is derived based on multiple reflection analysis and three test models. Notably, the reflection coefficient of the antenna is included in the derived equation. The accuracy of the proposed method is proven through simulation and measurements. It can be easily applied to a product examination by absorber manufacturers and customers owing to its advantages of simplicity, cost effectiveness, and non‐cutting examination.     

Novel service protocol for supporting remote and mobile users in wireless sensor networks with multiple static sinks

A wireless sensor network typically consists of users, a sink, and a number of sensor nodes. The users may be remotely connected to a wireless sensor network and via legacy networks such as Internet or Satellite the remote users obtain data collected by the sink that is statically located at a border of the wireless sensor network. However, in practical sensor network applications, there might be two types of users: the traditional remote users and mobile users such as firefighters and soldiers. The mobile users may move around sensor fields and they communicate with the static sink only via the wireless sensor networks in order to obtain data like location information of victims in disaster areas. For supporting the mobile users, existing studies consider temporary structures. However, the temporary structures are constructed per each mobile user or each source nodes so that it causes large energy consumption of sensor nodes. Moreover, since some of them establish the source-based structure, sinks in them cannot gather collective information like mean temperature and object detection. In this paper, to effectively support both the remote users and the mobile users, we propose a novel service protocol relying on the typical wireless sensor network. In the protocol, multiple static sinks connect with legacy networks and divide a sensor field into the number of the multiple sinks. Through sharing queries and data via the legacy networks, the multiple static sinks provide high throughput through distributed data gathering and low latency through short-hops data delivery. Multiple static sinks deliver the aggregated data to the remote users via the legacy networks. In case of the mobile users, when a mobile user moves around, it receives the aggregated data from the nearest static sink. Simulation results show that the proposed protocol is more efficient in terms of energy consumption, data delivery ratio, and delay than the existing protocols.     

Simple Synthesis of Hollow Tin Dioxide Microspheres and Their Application to Lithium‐Ion Battery Anodes

Hollow tin dioxide (SnO₂) microspheres were synthesized by the simple heat treatment of a mixture composed of tin(IV ) tetrachloride pentahydrate (SnCl₄·5H₂O) and resorcinol–formaldehyde gel (RF gel). Because hollow structures were formed during the heat treatment, the pre‐formation of template and the adsorption of target precursor on template are unnecessary in the current method, leading to simplified synthetic procedures and facilitating mass production. Field‐emission scanning electron microscopy (FE‐SEM) images showed 1.7–2.5 μm sized hollow spherical particles. Transmission electron microscopy (TEM) images showed that the produced spherical particles are composed of a hollow inner cavity and thin outer shell. When the hollow SnO₂ microspheres were used as a lithium‐battery anode, they exhibited extraordinarily high discharge capacities and coulombic efficiency. The reported synthetic procedure is straightforward and inexpensive, and consequently can be readily adopted to produce large quantities of hollow SnO₂ microspheres. This straightforward approach can be extended for the synthesis of other hollow microspheres including those obtained from ZrO₂ and ZrO₂/CeO₂ solid solutions.     

Evaluation of motor characteristics for hybrid electric vehicles using the hardware-in-the-loop concept

If the concept of Hardware-in-the-Loop (HIL) is applied to component testing, characteristic of component of hybrid electric vehicle in real vehicle environment can be evaluated without actually installing that component in real vehicle. In this paper, when commercially available test motor is adopted as a drivetrain of hybrid vehicle, we need to figure out which drive train configuration would be best for specific purpose. The characteristic of the motor when it is installed in the vehicle at different drive train and driving mode can be simulated and actual characteristic can be measured. Also both results can be compared. For the hardware characteristic measurement, test facility which consists of vehicle simulator and dynamometer is required. In this case, vehicle controller in the vehicle simulator is used as a vehicle controller and dynamometer is used to simulate vehicle dynamics. Two drive train types, 4-motor series, and 2-motor parallel type are proposed. Vehicle speed tracks driving cycle speed command well in both simulation and HIL implementation.