Queueing Delay Analysis for the Joint Scheduling Exploiting Multiuser Diversity over a Fading Channel

In this paper, we consider a joint packet scheduling algorithm for wireless networks and investigate its characteristics. The joint scheduling algorithm is a combination of the Knopp and Humblet (KH) scheduling, which fully exploits multiuser diversity, and the probabilistic weighted round-robin (WRR) scheduling, which does not use multiuser diversity at all. Under the assumption that the wireless channel process for each user is described by the Nakagami-m model, we develop a formula to estimate the tail distribution of the packet delay for an arbitrary user under the joint scheduling. Numerical results exhibit that under the joint scheduling, the ratio of the number of slots assigned for the WRR scheduling to that for the KH scheduling dominates the characteristics of the delay performance.

Technologies for Energy Saving in Industrial Field

This paper summarizes practical and developed techniques and technologies for energy saving in the industrial field. Newly developed high‐efficiency electrical equipment or combined technologies, which are about ‘power electronics’, ‘microcomputers’ and ‘motion control’ in addition to the progress of sensing devices and monitoring systems, bring both energy saving and high productivity in the factory. The technology trend of new factory facilities is concerned about changing power sources from pneumatic (compressed air) or hydraulic power (oil system) to electrical direct‐driven servomotor systems, which have the technical characteristics of fine‐grained and regenerative control. These technologies are able to reduce and recover idling (standby) power consumption during the holding period at the production stage in the factory. The items in this paper were published as Technical Report No. 988 in January 11, 2004 by IEEJ, and that report is reviewed and updated in this paper. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Biological strain/stress sensing power in plants and modelling mechanisms

This paper describes a cell based mechanosensing power and adapting modelling mechanisms found in plants. Biological structures consist of mechanical load carriers, which are strongly optimised in terms of mechanical strength and minimum mass. It is shown that bamboo structures are designed to have uniform stresses at all positions, applying various sizes of bamboo fibre at the optimal locations. As a significant biological design system, a biological sensing power for detecting the strain/stress induced by external loads can be accepted. The mechanosensing system can be regarded as that in which live cells detect the external mechanical strain/stress as biological electric signals generated by the motions of various ions throughout and/or into the channels of the cell membrane. The modelling mechanism is a cell based mechanosensor that depends on the kind of plant. Three types for detecting the mechanical strain/stress (tension sensitive, compression sensitive, and tension and compression sensitive types) are investigated. Changes in electrical signals at the local portion of a plant body due to the mechanical deformation of cell membranes, affect the modelling of a plant's tissue to fit external mechanical environments.     

Viewing-zone enlargement method for sampled hologram that uses high-order diffraction

We demonstrate a method of enlarging the viewing zone for holography that has holograms with a pixel structure. First, aliasing generated by the sampling of a hologram by pixel is described. Next the high-order diffracted beams reproduced from the hologram that contains aliasing are explained. Finally, we show that the viewing zone can be enlarged by combining these high-order reconstructed beams from the hologram with aliasing.     

Mechanochemical Synthesis of Ammonium Hexafluorogallate

Mechanochemical reaction between ammonium fluoride (NH₄F) and gallium fluoride trihydrate (GaF₃·3H₂O) at a ratio of 3:1 is conducted by grinding the mixture at room temperature using a planetrary ball mill. A single phase of ammonium hexafluorogallate ((NH₄)₃GaF₆) is obtained as a product of the reaction. Other alkali hexafluorogallates (K₃GaF₆, Na₃GaF₆, and Li₃GaF₆) also can be synthesized by grinding constituent components (AF and GaF₃·3H₂O) under proper grinding conditions. A reaction mechanism related to the dissolution of alkali fluorides in water is suggested.     

Creep rupture strength and grain-boundary sliding in austenitic 21 Cr-4Ni-9Mn steels with serrated grain boundaries

The effect of grain-boundary strengthening on the creep-rupture strength by modification of the grain-boundary configuration is studied using austenitic 21 Cr-4Ni-9Mn steel in the temperature range from 600 to 1000° C in air. Grain-boundary sliding is also examined on a steel with serrated grain boundaries during creep at 700° C. The improvement of creep-rupture strength by the strengthening of grain boundaries is observed at high temperatures above 600° C. The 1000 h rupture strength of steels with serrated grain boundaries is considerably higher than that of steels with straight grain boundaries, especially at 700 and 800° C. The strengthening by serrated grain boundaries is effective in retarding both the crack initiation and the crack propagation at 700° C, while it does not improve the life to crack initiation at 900° C. Grain-boundary sliding is considerably inhibited by the strengthening of grain boundaries at 700° C. The amount of it in steels with serrated grain boundaries is less than about one-third of that of steels with straight grain boundaries at the same creep strain. The stress dependence of grain-boundary sliding rate in the steady-state regime is also examined from the steels with these two types of grain-boundary configuration.     

An instrument for manufacturing zone-plates by using a lathe

A laser writing system is developed in order to manufacture precise and inexpensive zone-plates. The zone-plates are a key component of an interferometer that measures shape error of spherical or aspherical mirrors on an ultrapecision lathe. The laser writer is mounted on the sliding table of the lathe. A glass plate coated with photoresist is attached to a chuck of the lathe and rotated. The zone-plate grating is written on the glass plate by a focused laser beam. Zone-plate writing is sped up by reducing the necessary number of computer instructions, causing no loss in the accuracy of the zone-plate. The accuracy of the zone-plate obtained by this inexpensive method is 0.1 μm and the same as that achieved by an electron beam writer.     

Photodegradation of polymer materials containing flame-cut agents

Photodegradation of incombustible materials [polystyrene (PSt) and polypropyrene (PP) containing 2 wt% of decabromodiphenyl oxide (DBDE) or tetrabromobisphenol-A (TBA) as a flame-cut agent] were studied using Okazaki Large Spectrograph (OLS). Samples were irradiated in air at 23°C with monochromatic light of wavelengths at 260, 280, 300, 320, 340, and 360 nm, UV-visible spectra and FTIR spectra were measured to identify the chemical structural changes of the polymers. Number of chain scissions, which is a measure of the polymer degradation, was estimated from the results of GPC measurements. It was found that the photostability of PP and PSt was reduced by the addition of DBDE or TBA. Photodegradation of these polymers took place by the irradiation of the light of wavelengths lower than 320 and 360 nm for the polymers containing TBA and DBDE, respectively. The most effective irradiation wavelengths for main chain scission are found to be 260–280 and 300 nm for PP or PSt–TBA samples and PP or PSt–DBDE samples, respectively. © 1993 John Wiley & Sons, Inc.     

Syntheses and radical ring-opening polymerizations of 1,1-bis(hydroxymethyl)-2-vinylcyclopropane and 1,1-bis(methoxymethyl)-2-vinylcyclopropane

Homo- and copolymerizations of 1,5-hexadiene with ethene and styrene using halfsandwich metallocene catalyst Me₂Si(Me₄Cp)(N-tert.-butyl)TiCl₂/MAO (Cp = cyclopentadienyl, Me = methyl, MAO = methylalumoxane) were investigated. According to ¹³C-NMR spectroscopic microstructure analysis, cyclopolymerization of 1,5-hexadiene afforded randomly distributed cis- and trans-cyclopentane rings in the homo- and copolymer backbone. 1,5-hexadiene incorporation reached 52 mol-%. The ratio of vinyl side chains to cyclopentane rings was controlled by 1,5-hexadiene concentration, where low 1,5-hexadiene concentration promoted cyclopolymerization. Copolymer glass transition temperatures increased with increasing content of cyclic units in the backbone. Styrene was used successfully as termonomer in ethene/1,5-hexadiene polymerization, resulting in a semicrystalline terpolymer with cyclic and styrenic units in the polymer backbone. Received: 5 September 1996/Accepted: 11 November 1996