Swarm robotic network using Lévy flight in target detection problem

One approach in swarm robotics is homogeneous system which is embedded with sensing, computing, mobile and communication components. In this study, a target detection problem, which is one of navigation problems, was employed. Once a robot detects a target, robots immediately communicate with a base station via intermediate relay robots due to the multi-hop transmission of wireless communication. Therefore, this control task is completed with connectivity of the network. In a target detection problem, we must improve the performance of exploration as well as connectivity of the network. This study investigates the performances of the two types of random walk algorithm in navigation while loosely ensuring connectivity of the robotic network based on our previous study.     

Characterization of Flemion® membranes for PEFC

Perfluorinated ion exchange membranes were studied to clarify the characteristics of membranes required for polymer electrolyte fuel cells (PEFC). The influence of membrane thickness on gas permeability and the influence of incorporation of cations on water content and ac specific resistance of Flemion® and Nafion®117 were estimated. Gas permeation rates of the membranes decreased in inverse proportion to the increase of the membrane thickness and gas permeability coefficients were nearly constant and independent of the thickness. Hydrogen permeation rates of Flemion®S at 70°C were converted to 2.1 mA/cm² as current density. Water content changed by only 5% in the region of the ion exchange ratio from 0% to 100% and was independent on the kinds of incorporated cations in the region of the ion exchange ratio under 40% except for K⁺. Ac specific resistance increased markedly when the ion exchange ratio exceeded 50%. In the case that the ion exchange ratio was under 30%, ac specific resistance increased with decrease of the numbers of protons having no relation with the kinds of cations. Area resistance of Flemion® was smaller because it has higher ion exchange capacity and thinner thickness than Nafion®117.     

Polycrystalline silicon thin-film transistors fabricated by defect reduction methods

Fabrication of n-channel polycrystalline silicon thin-film transistors (poly-Si TFTs) at a low temperature is reported. 13.56 MHz-oxygen plasma at a 100 W, 130 Pa at 250/spl deg/C for 5 min, and heat treatment at 260/spl deg/C with 1.3/spl times/10/sup 6/-Pa-H/sub 2/O vapor for 3 h were applied to reduction of the density of defect states in 25-nm-thick silicon films crystallized by irradiation of a 30 ns-pulsed XeCl excimer laser. Defect reduction was numerically analyzed. Those treatments resulted in a high carrier mobility of 830 cm/sup 2//Vs and a low threshold voltage of 1.5 V at a laser crystallization energy density of 285 mJ/cm/sup 2/.     

Technologies for electron beam direct writing

Development time of semiconductor devices which have a large volume of pattern data and fine feature size can be remarkably reduced by a high speed on-line system and an erase electron beam direct writing technology.Pattern data which is performed by a CAD system is converted by a VAX/780 and transmitted to an electron beam exposure system (EBES) through a communication controller at the speed of 1 Mbit/sec.Overlay accuracy less than 0.2 μm is obtained by scanning the alignment marks located at the periphery of a silicon wafer. The marks are fabricated by etching the silicon substrate to 2 μm depth.Radiation effects induced by electron beam irradiation is examined by Monte Carlo simulation.In production of ECL (emitter coupled logic) gate arrays using electron beam direct writing technology, the surface of the silicon nitride (SiN) interlevel insulation layer is coated with a thin conductive layer of TiW in order to avoid the charging phenomenon and the radiation damage caused by electron beam irradiation.     

A study of cumulative sum control charts

The cumulative sum (CUSUM) control chart is known as a sensitive control chart to a slight change of the process quality characteristics. This control chart is designed based on a series of cumulative sum of the statistic derived from data. For normally distributed characteristics, it should be needed to monitor both changes of the mean and variance simultaneously. However, it is difficult to design the CUSUM or joint control chart using the statistics of and s or R jointly. By the way, Kanagawa et.al . have proposed the ( )control chart which enables the user to monitor both changes of the mean and variance simultaneously based on one statistic for normally distributed characteristics. When the CUSUM control chart is considered based on the ( ) control chart, it is possible to design and use the CUSUM control chart more easily than the joint CUSUM and either R or s control charts. Hence, we consider a CUSUM ( ) control chart in order to improve the performance for a slight change of the process quality characteristics in this article. In addition, the economical operation of the CUSUM ( ) control chart is also considered.     

Recent Developments and Mid‐ and Long‐Term CO2 Mitigation Projects in Ironmaking

CO₂ mitigation and the stable supply of raw materials are two major issues for the steel industry. The Japanese steel industry has promoted short term developments and investments to comply with the Japan Iron and Steel Federation's voluntary action plan in parallel with developing plans for drastic CO₂ mitigation programs toward the post Kyoto protocol period. This paper describes short‐term measures in the ironmaking field such as natural gas injection technology to the sintering bed and burden distribution control with coke mixed charging. For mid and long term CO₂ mitigation, the joint project, ‘Preparatory research work for the blast furnace based innovative ironmaking technologies’ was actively promoted by the New Energy and industrial Technology Development Organization (NEDO) from FY2006 to FY2008. Based on the enhancement of carbon ‐ CO₂ reaction by close positioning of carbon and iron oxide/metallic iron, the production process and reaction mechanism in a blast furnace were studied for two innovative composites with iron oxide, metallic iron and carbon. For development at a pilot plant scale, a new project, ‘Development of innovative ironmaking process using low cost iron ore and coal’ started in FY2009. Key technologies of the project are the production process and evaluation in a blast furnace of a hybrid composite of metallic iron and carbon, so called ‘Ferro‐coke’. This paper describes key technologies and recent developments of the project.     

Melting and precision casting of Ti-6Al-4V alloy by use of electron beam furnace

For melting and casting of Ti-6Al-4V alloy by use of an electron beam furnace, key technologies have been developed: measurement and control of temperature, amount, and chemical composition of molten pool. Temperature in the molten pool was measurred by applying three devices; a thermocouple, a two color pyrometer and the rate of vaporization from the molten pool. Temperature measured by an optical pyrometer without influence of plasma by shifting the wave lengths of the light for the optical pyrometry from those of plasma evolved above the molten pool was in a good accordance with that estimated from the vaporization rate. By combining temperatures measured by three methods, the temperature gradient in the molten pool was estimated to be a level of 100 K/cm. In order to derive an empirical equation for the depth of molten pool of various metals, the depth of the molten pool was determined for Ti, Ti-6Al-4V alloy, solar grade Si, low carbon steel, and stainless steel by chemical etching of vertical cross section of an ingot melted and solidified in a skull crucible. Chemical compositions of Ti-6Al-4V alloy melt before casting was adjusted by adding an aluminum block into the pool before pouring, which compensated vaporization loss of Al from the pool surface under high vacuum. Since, a key to settle Al content in the specified range is the yield and distribution of Al in every castparts, influences of operating variables on the yield have been studied by paying attention to rapid temperature change observed immediately after addition of aluminum. Formerly Graduate School of Iron and Steel Technology Pohang University of Science and Technology San 31 Hyoja-dong, Nam-gu, Pohang 790-784, Korea     

Chromium etching characteristics using a planar type plasma reactor

The dry etching characteristics of Cr film in the CCl₄/O₂ mixed gas plasma have been investigated with a variety of etching parameters in the planar type reactor with the 13.56 MHz rf power. Moreover the dry etching resistance of EB resists and variation of the feature size on a 12.5 and 15 cm Cr-Mask are described. The etch rate of Cr film depends strongly on the etchant gas composition ratio, the electrode separation and the electrode surface materials. In the cathode coupling mode with a gas pressure of 0.2 Torr, a gas flow rate of CCl₄/O₂ of 0.5, electrode separation of 80 mm and rf power density of 0.38 W/cm², the following results are obtained: (1) The etch rate of Cr film is about 30 nm/min, Paper presented partially at 23rd Annual Electronic Materials Conference, University of California, Santa Barbara, California, June 24, 1981.