SiCw/AZ91镁基复合材料的时效行为研究

本文采用显微硬度计、绝热型比热测定仪和SEM对AZ91镁合金以及SiCw/AZ91镁基复合材料进行了时效显微硬度测定、连续升温比热测定以及时效组织观察.并分析了时效温度、时效时间对析出组织的影响.结果表明:经时效处理,上述两种材料的显微硬度均有提高;复合材料的比热曲线类似镁合金的比热曲线;复合材料的时效组织只在200℃到225℃温度区间的时效过程中出现,其形貌类似于连续析出组织.      

Speculative Computation and Action Execution in Multi-Agent Systems

In some multi-agent systems, when an agent cannot retrieve information from another agent, the agent makes an assumption and tentatively performs the computation. When the agent comes across a mistake in the preliminary assumption, the computation is modified. This kind of speculative computation is effective when the assumption is correct. However, once the agent executes an action, it is impossible to modify the computation in these systems. This paper shows how to integrate speculative computation and action execution through logic programming.     

Verification of the analysis method for extracting the spatial continuity of the vegetation distribution on a regional scale

Vegetation plays a key role in not only improving urban environments, but also conserving ecosystems. The spatial continuity of vegetation distributions can be expected to make green corridors for landscape management, wind paths against heat island phenomena. In this paper, we develop a spatial analysis method of vegetation distributions using remotely sensed data on a regional scale. The method consists of a spatial autocorrelation analysis, an overlay analysis, and a hydrological analysis with the Normalized Difference Vegetation Index (NDVI) adopted as the proxy of vegetation abundance. Application of the method leads to the extraction of the lines between the core areas and sparse areas of vegetation. The purpose of this study is to verify our method through applying a vegetation map digitized from aerial photographs. The map contained three vegetation types of land cover: grasslands, agricultural fields, and tree-covered areas. We use remotely sensed data collected at four different time periods at the regional scale, along with information on the seasonal fluctuations of the vegetation. As a result, the exclusion of seasonal land-cover changes, as in the reaping of agricultural fields, in the process of applying the proposed method produces an effect. The analysis reveals steady areas unaffected by the seasonal fluctuation of vegetation along the lines extracted by applying the proposed method.     

On-line monitoring of boring tools for control of boring operations

In order to carry out precision and quality control of boring operations, on-line monitoring of boring tools is essential. Fourteen features were extracted by processing cutting force signals using virtual instrumentation. A Sequential Forward Search (SFS) algorithm was employed to select the best combination of features. Backpropagation neural networks (BPNs) and adaptive neuro-fuzzy inference systems (ANFIS) were used for on-line classification and measurement of tool wear. The input vectors consist of selected features. For the on-line classification, the outputs are boring tool conditions, which are either usable or worn out. For the on-line measurement, the outputs are estimated value of the tool wear. Using BPN, five features were needed for the on-line classification of boring tools. They are the average longitudinal force, average value of the ratio between the tangential and radial forces, skewness of the longitudinal force, skewness of the tangential force, and kurtosis of the longitudinal force. Three features, the average longitudinal force, average of the ratio between the tangential and radial forces, and kurtosis of the longitudinal force, were needed for on-line measurement of tool wear. Using ANFIS, three features were needed for the on-line classification of boring tools. They are the average longitudinal force, average of the ratio between the tangential and radial forces, and kurtosis of the longitudinal force. Only one feature, kurtosis of the longitudinal force, was needed for the on-line measurement of tool wear using ANFIS. Both 5×20×1 BPN and 3×5 ANFIS can achieve a 100% success rate for the on-line classification of boring tool conditions. Using a 3×20×1 BPN for neural computing, the minimum flank wear estimation error is 0.29% while the minimum flank wear estimation error is 2.04% using a 1×5 ANFIS.     

The superstructure toward open bioinformatics grid

The grid design strongly depends on not only a network infrastructure but also a superstructure, that is, a social structure of virtual organizations where people trust each other, share resources and work together. Open Bioinformatics Grid (OBIGrid) is a grid aimed at building a cooperative bioinformatics environment for computer sicentists and biologists. In October 2003, OBIGrid consisted of 293 nodes with 492 CPUs provided by 27 sites at universities, laboratories and other enterprises, connected by a virtual private network over the Internet. So many organizations have participated because OBIGrid has been conscious of constructing a superstructure on a grid as well as a grid infrastructure. For the benefit of OBIGrid participants, we have developed a series of life science application services: an open bioinformatics environment (OBIEnv), a scalable genome database (OBISgd), a genome annotation system (OBITco), a biochemical network simulator (OBIYagns), and to name a few. Akihiko Konagaya, Dr.Eng.: He is Project Director of Bioinformatics Group, RIKEN Genomic Sciences Center. He received his B.S. and M.S. from Tokyo Institute of Technology in 1978 and 1980 in Informatics Science, and joined NEC Corporation in 1980, Japan Advanced Institute of Science and Technology in 1997, RIKEN GSC in 2003. His research covers wide area from computer architectures to bioinformatics. He has been much involved into the Open Bioinformatics Grid project since 2002. Fumikazu Konishi, Dr.Eng.: He is researcher at Bioinformatics Group, RIKEN Genomic Sciences Center since 2000. He received his M.S. (1996) and Ph.D. (2001) from Tokyo Metropolitan Institute of Technology. He served as an assistant in Department of Production and Information Systems Engineering, Tokyo Metropolitan Institute of Technology since 2000. He also works in Structurome Research Group, RIKEN Harima Institute from 2001. His research interests include concurrent engineering, bioinformatics and the Grid. He has deeply affected to the design of OBIGrid. Mariko Hatakeyama, Ph.D.: She recieved her Ph.D. degree from Tokyo University of Agriculture and Technology. She is Research Scientist at Bioinformactis Group, RIKEN Genomic Sciences Center. Her research topics are: microbiology, enzymology and signal transduction of mammalian cells. She is now working on computational simulation of signal transduction systems and on thermophilic bacteria project. Kenji Satou, Ph.D.: He is Associate Professor of School of Knowledge Science at Japan Advanced Institute of Science and Technology. He received B.S., M.E. and Ph.D. degrees from Kyushu University, in 1987, 1989 and 1995 respectively. For each degree, he majored in computer engineering. His research interests have progressed from deductive database application through data mining to Grid computing and natural language processing. His current field of research is bioinformatics. He prefers set-oriented manner of thinking, and usually wonders how he can construct an intelligent-looking system based on large amount of heterogeneous data and computer resources.     

LASER AND ELECTRON BEAM PROCESSING OF AMORPHOUS SURFACE ALLOYS ON CONVENTIONAL CRYSTALLINE METALS

During last fifteen years various superior surface characteristics including extremely high corrosion resistance and unique electrocatalytic activity have been found for novel melt-spun ribbon-shaped amorphous alloys. Preparation of those amorphous alloys as surface alloys covering bulk conventional crystalline metals has been eagerly awaited for the purpose of utilizing their superior surface characteristics. This is a review of efforts devoted to developing methods for processing amorphous surface alloys by instantaneous melting of a very restricted volume of the surface by irradiation with a CO₂ laser or electron beam and subsequent self quenching by the cold bulk substrates. Processing of a wide area by these high energy density beams requires heating the previously amorphized phase, which is easily crystallized by heating. Consequently, high energy density beam processing is most difficult among various methods for preparation of thermodynamically metastable amorphous alloys. Nevertheless, various amorphous surface alloys have been successfully prepared. The materials consisting of the amorphous surface alloys and bulk crystalline metals are quite suitable for corrosion resistant materials and electrodes for electrolysis of aqueous solutions. A comparison of CO₂ laser and electron beam processing showed the superiority of the latter to the former because of a significantly shorter processing time.     

Distortion-product otoacoustic emissions in kanamycin-treated guinea pig cochlea

Measurement of distortion-product otoacoustic emissions (DPOAE) is widely accepted as one of the most valuable tools for evaluating the frequency of specific cochlear pathology. Previous studies have revealed that distortion-product levels in the ear canal are definitely correlated with degree of damage in the cochlea. However, there seem to be no clear data of help in predicting the distribution and grade of damage in the cochlea quantitatively on the basis of the results of this non-invasive test. The present study is designed to assess correlations between degree of outer hair cell (OHC) damage by a potent ototoxic antibiotic, kanamycin, and DPOAE levels at the characteristic frequency at the site. Guinea pigs were used after daily intramuscular administration of kanamycin for 7 or 10 days. DPOAE levels were measured using a system (CUBDIS: Etymotic Research) with 78 frequency combinations of iso-intensity primaries from 0.5kHz to 16kHz of f2. The frequency ratio (f2/f1) was set at 1.2. Distortion-product level plots versus f2 (DP-grams) were constructed. The integrity of the OHC system was evaluated histologically by the succinic dehydrogenase (SDH) method under a light microscope. Cochleograms were constructed by calculating percentages of intact OHCs along the basilar membrane in 1-mm blocks. The DP-grams and the histopathological cochleograms showed essentially identical patterns in the kanamycin-damaged guinea pig cochlea. The results suggest that: 1) The generation of DPOAE requires functioning OHCs. 2) DPOAE measurement provides information allowing prediction of OHC damage distribution in the cochlea without histological investigations. 3) Careful setting of primary levels and other parameters is necessary to reliably predict the pathology. 4) Attempts to detect of minimal OHC damage could fail. 5) DPOAE seem very useful for monitoring cochlear function in clinically.     

SiC coating as hydrogen permeation reduction and oxidation resistance for nuclear fuel cladding

Silicon carbide (SiC) coating is one of the countermeasures for the prevention of oxidation and hydrogen embrittlement of fuel claddings because SiC has high resistance of oxidation and hydrogen permeation. Hydrogen permeation and oxidation experiments for the cladding materials with SiC coatings were conducted in unirradiated conditions. The sputtering method was employed to make SiC coatings. In the hydrogen permeation experiment, 316 type of stainless steel (SS316) was used as a base material of the coating. SS316 with SiC coatings showed hydrogen permeation reduction by one order of magnitude. In the oxidation experiments, Zircaloy 4 (Zry-4) and SS316 were used as base materials of the coatings. The weight gain of the Zry-4 specimens with a SiC coating decreased by about one-fifth compared to the uncoated ones at 750 °C and 1200°C. This phenomenon was observed for SS316 at 750 °C as well. The peel-off of the coating was observed in several experiments, and it is considered that the peel-off was caused by the difference of the thermal expansions between coatings and base materials. Thicker coatings showed better oxidation resistance, but thinner coatings showed more tolerance of peel-off.     

Effects of deletion in the flexible loop of the protease inhibitor SSI (Streptomyces subtilisin inhibitor) on interactions with proteases

The Streptomyces subtilisin inhibitor (SSI) is a proteinaceousprotease inhibitor which inhibits serine proteases by forminga stable Michaelis complex. The flexible loop region (Thr64–Val69)is a very flexible region in an SSI molecule and its importancein interactions with proteases has been suggested, since conformationalchange of this loop was found to occur for the smooth bindingof SSI with various proteases. In this study, mutated SSIs lackingone or two residues in this region were generated and the effectsof deletions on the interaction with proteases were investigated.Deletion was introduced into mutated SSI(Lys73) and SSI(Gly70Lys73)both known to be trypsin inhibitors, to examine the effectsof deletion on interactions with subtilisin BPN' or trypsin.The deletion of one residue (Gly66) caused increased inhibitoryactivity toward trypsin, indicating the protruding flexibleloop hinders binding with trypsin. Reduction of such hindranceby one-residue shortening in this loop is shown to be effectivefor the interaction of SSI(Lys73) with trypsin. In contrast,one-residue shortening had virtually no effect on inhibitiontoward subtilisin BPN'. Differences in the subsite structuresof these proteases may have been the reason for this contrast.The deletion of two residues (Thr64 and Gly66) in this regionconverted SSI into a temporary inhibitor. Structural analysisof the degradation intermediate showed that the peptide bondat the reactive site of doubly deleted SSI was cleaved by subtilisinBPN' after its binding with protease. Thus, the irreversibilityof the cleaved peptide bond at the reactive site of mutatedSSI in the complex with protease may possibly be the cause forits temporary inhibition. Irregular conformation around thereactive site caused by the deletion of two residues in theflexible loop would convert SSI into a temporary inhibitor.Thus, moderate flexibility in the flexible loop region may possiblybe a structural requirement for SSI to function.