Quality‐of‐service guarantees architecture with weighted fair shaping

Weighted Fair Queuing (WFQ), conducted for each flow at ATM nodes, is effective for ensuring fairness among differently behaving flows, and for preventing incremental delay as cells are transmitted through multiple nodes. Implemented thus in accordance with rates assigned to flows and actual cell transmission conditions, WFQ is known as “shaping”. This paper proposes a new installable algorithm that dynamically adapts WFQ to each of multiple flows. The Quality‐of‐Service (QoS) guaranteed by this algorithm is also explained. This revised version was published online in June 2006 with corrections to the Cover Date.     

A Hybrid Centralized Routing Protocol for 802.11s WMNs

Wireless mesh networks (WMNs) are being widely accepted as a critical wireless access solution for various applications. Due to minimal mobility in mesh nodes, a backbone topology can be effectively maintained in WMN using a proactive routing protocol. In IEEE 802.11s standard, a tree-based routing (TBR) protocol is adopted as a viable proactive routing protocol for a WMN with user traffic flowing to/from a wired network through a root (i.e., a mesh portal). However, the performance of the TBR protocol degrades rapidly as the user traffic becomes dominated by intra-mesh traffic. The reason is that the routing path through the root even for intra-mesh traffic unnecessarily overloads the root. Furthermore, the TBR performance becomes more severe when the network size of WMN is large, which could lead to the huge amount of intra-mesh traffic towards the root. To overcome these problems, we propose a new routing mechanism, root driven routing (RDR) protocol, for the root to quickly determine the best-metric route for any source-destination pair of intra-mesh traffic. For inter-mesh traffic, the original TBR protocol is employed. Thus, the hybrid centralized routing protocol that combines TBR and RDR and is adaptive to all traffic scenarios. Our simulation results reveal that the proposed RDR protocol outperforms the TBR protocol with much lower average end-to-end delay and much higher packet delivery ratio for intra-mesh traffic. The simulation results also provide some insight into the right tradeoff between the TBR protocol and the RDR protocol to achieve the best performance of the hybrid centralized routing protocol for WMNs.     

Wireless Power Transmission via Sheet Medium Using Automatic Phase Adjustments of Multiple Inputs

Wireless power transmission via a sheet medium is a novel physical form of communication that utilizes a surface as a medium to provide both data and power transmission services. To efficiently transmit a relatively large amount of electric power (several watts), we have developed a wireless power transmission system via sheet medium that concentrates electric power on a specific spot by using phase control of multiple inputs. However, to find the optimal phases of the multiple inputs that let the microwave energy converge on a specific spot in the sheet medium, prior knowledge of the device's position and a preliminary experiment measuring the output power are needed. In the field of wireless communication, it is known that the retrodirective array scheme can efficiently transmit power in a self‐phasing manner, which uses pilot signals sent by client devices. In this paper, we apply the retrodirective array scheme to our wireless power transmission system via a sheet medium, and propose a power transmission scheme using the phase‐adjusted power transmission inputs. To confirm the effectiveness of the proposed scheme, we evaluate its performance by computer simulation and real‐world measurement. Both results show that the proposed scheme can achieve retrodirectivity over wireless power transmission via a sheet medium.     

Direct dark matter search program with bolometers at the University of Tokyo

Bolometers are being developed at the University of Tokyo aiming at a search for galactic dark matter. We have succeeded in constructing a small-sized bolometer with 2.8 gram of lithium fluoride crystal with an rms energy resolution of 3.8 ke V for 60-ke V rays. Both lithium and fluorine are expected to be suitable for the detection of possible particle dark matter with a spin-dependent interaction like supersymmetric neutralinos. Fabrication of Neutron Transmutation Doped (NTD) germanium is also in progress to make a number of thermistors with uniform sensitivities to be used for multi-module bolometers. When the development of a full-sized detector with a total mass of order one kilogram is completed, we plan to install it in the Kamioka underground laboratory.     

Development of high-resolution field emission scanning electron microscopy with multifunctions for chargeless observation of nonconducting surface

We have developed a fully digital field emission scanning electron microscope (FE-SEM) with multifunctions to compensate the charging up of nonconducting surfaces. High-voltage observation, minimum electron dose, variable scanning speed, averaging, integration, tuning of surface potential, and cyclotron movements of secondary electrons have been achieved. This FE-SEM was successfully applied to observe resist, diatomaceous earth, aluminum oxide, and zeolite surfaces. The accelerating voltage is changeable in a range from 0.5 to 30 kV, and the probe current on the sample can be varied from 2×10^-9 to l×10^-13A to supply optimum electron dose. By using a snorkel- type, strongly excited objective lens (OL) immersing the samples in the magnetic field, the secondary electrons are extracted from the sample. For guiding electrons into the built-in lens-type secondary electron detector (SED), newly developed accelerating and retarding electrodes are installed in the OL to tune the surface potential. Furthermore, this FE-SEM can select 10 scan speeds, and the averaging and integration of secondary electron image signals are possible under every selected scan speed.     

Beam-foil interaction of highly ionized chlorine ions in the high energy region

Distributions of charge states and multiple scattering widths of angular distributions have been simultaneously measured using a two dimensional-position sensitive detector for 150 MeV ³⁷Cl¹⁰⁺ ions emerging from carbon foils with thickness of 2.5–180 $\text{μg}\text{cm}{}^2$. For thinner foils, the scattering angle dependence of mean charge states verifies the evidence for the so-called single violent and/or plural collisions