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991.
Consolidation of machined magnesium alloy chips by hot extrusion utilizing superplastic flow 总被引:4,自引:0,他引:4
Hiroyuki Watanabe Koji Moriwaki Toshiji Mukai Koichi Ishikawa Masahide Kohzu Kenji Higashi 《Journal of Materials Science》2001,36(20):5007-5011
An examination of consolidation conditions by hot extrusion of AZ31 magnesium alloy machined chips was conducted to enhance the bonding of individual chips, in order to improve the mechanical properties. Hot extrusions were carried out in the superplastic and non-superplastic region. Microstructural observations revealed that grain refinement was attained by extruding machined chips, and the grain sizes of the chip-extruded materials were smaller than 5 m. The interfaces of individual chips of extruded materials were not identified when the chips were extruded in the superplastic region. The ultimate tensile strength was about 300 MPa and elongation-to-failure was about 10% for chip-extruded materials that were extruded in the superplastic region. These materials were comparable with the as-received alloy with respect to the room temperature strength, although the ductility was reduced to half. It was confirmed that chip consolidation utilizing superplastic flow is useful to enhance the bonding of individual grains. 相似文献
992.
A novel method was proposed to generate high-density microwave-excited plasma along metal surfaces. In our previous work, 2.45 GHz microwaves were confirmed to propagate as surface waves along the interface between overdense (>1011 cm–3) plasma and a graphite rod biased at a negative voltage against a grounded chamber. The generated plasma showed columnar structure surrounding the rod surface, and thus it was called metal-antenna surface wave-excited plasma (MASWP) column. In this work, the effect of gas pressure on the spatial distribution of MASWP column was investigated. It was confirmed that the length of MASWP column became longer along a graphite rod (25 cm in length and 1 cm in diameter) with increasing gas pressure. In particular, at an Ar gas pressure of 33 Pa, we obtained a long plasma column covering the entire surface of the rod with a negative voltage of −150 V and an input microwave power of 100 W. The same tendency, or the extension of MASWP column with increasing gas pressure was also confirmed by using a copper rod and a stainless-steel rod instead of the graphite rod. This indicates that the extension of MASWP column with increasing gas pressure occurs independently of antenna materials. 相似文献
993.
The corrosion fatigue crack propagation life of Christmas-tree type rotor groove with three hooks is studied. Each corner of the hook can be a candidate for crack initiation site therefore the condition where cracks initiate and propagate simultaneously at several hook corners must be considered. When a blade is inserted in the rotor groove, narrow gap is introduced unavoidably between the rotor groove and the blade root. The effect of this narrow gap on the crack behavior must also be considered. A procedure was presented to assess the crack initiation and propagation behavior under such a condition. Using the procedure, crack initiation and propagation behavior was evaluated for several gap conditions. It was revealed that the gap condition had little effect on the relation between crack depth at the third hook corner and life consumption ratio (ratio of loading cycle to final failure life). A corrosion fatigue test was performed using a rotor groove model specimen, and the results were compared with the evaluation results. 相似文献
994.
In this article, we develop a distributed robotic system that can provide various services in a real environment using ad-hoc
networked active radio frequency identifications (RFIDs). These services are derived from a large amount of data acquired
from sensors connected to active RFIDs. The primary advantage of this method is that it facilitates the construction of a
real-environment monitoring system. Furthermore, a human's status and position can easily be identified by fitting active
RFIDs to subjects. However, a security system is required for a radio ad-hoc network and a cooperation system between active
RFIDs. In our research, we developed a multirobot cooperating system as a multiagent system and applied it to an active RFID,
which has limited resources. We also developed a security system for active RFID communication that can be executed using
limited resources. We then integrated the multiagent system and security system. We also constructed a robotic environment
that can provide various services using active RFIDs and then evaluated it.
This work was presented in part at the 10th International Symposium on Artificial Life and Robotics, Oita, Japan, February
4–6, 2005 相似文献
995.
To investigate how robots behave as social entities, we analyze the interaction of humans and “Muu,” an embodied artificial
entity. Specifically, our purpose is to find the salient patterns of behavior that distinguish the robot from humans in the
course of an interaction. Through exploratory observations, we identify such salient patterns as the manner of repetitions
and the address mismatch. We discuss how the social display of such patterns as “marked” features plays a very important role
in mutual interaction.
This work was presented in part at the 10th International Symposium on Artificial Life and Robotics, Oita, Japan, February
4–6, 2005 相似文献
996.
This paper presents an effective scheme for clustering a huge data set using a PC cluster system, in which each PC is equipped
with a commodity programmable graphics processing unit (GPU). The proposed scheme is devised to achieve three-level hierarchical
parallel processing of massive data clustering. The divide-and-conquer approach to parallel data clustering is employed to
perform the coarse-grain parallel processing by multiple PCs with a message passing mechanism. By taking advantage of the
GPU’s parallel processing capability, moreover, the proposed scheme can exploit two types of the fine-grain data parallelism
at the different levels in the nearest neighbor search, which is the most computationally-intensive part of the data-clustering
process. The performance of our scheme is discussed in comparison with that of the implementation entirely running on CPU.
Experimental results clearly show that the proposed hierarchial parallel processing can remarkably accelerate the data clustering
task. Especially, GPU co-processing is quite effective to improve the computational efficiency of parallel data clustering
on a PC cluster. Although data-transfer from GPU to CPU is generally costly, acceleration by GPU co-processing is significant
to save the total execution time of data-clustering. 相似文献
997.
Hironori Katagiri Kotoe Saitoh Tsukasa Washio Hiroyuki Shinohara Tomomi Kurumadani Shinsuke Miyajima 《Solar Energy Materials & Solar Cells》2001,65(1-4)
Cu2ZnSnS4 (hereafter CZTS) thin films were successfully formed by vapor-phase sulfurization of precursors on a soda lime glass substrate (hereafter SLG) and a Mo-coated one (hereafter Mo-SLG). From the optical properties, we estimate the band-gap energy of this thin film as 1.45–1.6 eV which is quite close to the optimum value for a solar cell. By using this thin film as an absorber layer, we could fabricate a new type of thin film solar cell, which was composed of Al/ZnO:Al/CdS/CZTS/Mo-SLG. The best conversion efficiency achieved in our study was 2.62% and the highest open-circuit voltage was 735 mV. These device results are the best reported so far for CZTS. 相似文献
998.
Giuseppe Pezzotti Hiroyuki Ichimaru Luca Paolo Ferroni Kiyoshi Hirao Orfeo Sbaizero 《Journal of the American Ceramic Society》2001,84(8):1785-1790
The microscopic bridging stress distribution developed behind the crack tip of a highly anisotropic silicon nitride has been measured along the crack profile using Raman microprobe spectroscopy with a micrometer spatial resolution. The near-tip rising R -curve behavior and the crack-opening displacement (COD) profile of the material were also determined and discussed in comparison with the Raman microstress data. A comparison with the fracture behavior of a previously investigated silicon nitride material with a three-dimensional random microstructure is also proposed. According to this set of micro/macroscopic fracture characterizations, a self-consistent view of toughening behavior in silicon nitride ceramics is obtained, and the role on toughness of anisotropically oriented acicular grains clarified. In agreement with previous studies, it is confirmed that crack-face bridging is the most effective mechanism for toughening silicon nitride ceramics. 相似文献
999.
Qiu-Wang Wang Gang Wang Min Zeng Hiroyuki Ozoe 《International Journal of Heat and Mass Transfer》2008,51(7-8):1675-1682
Infinite horizontal fluid layer is considered between the top and bottom walls. Either top or bottom wall temperature is sinusoidally oscillated in terms of the constant average temperature in an opposing horizontal wall. This is the system with no temperature difference between the top and bottom walls in time-averaged sense, as studied by Kalabin et al. for a square channel. The fluid is Newtonian and Boussinesq approximation is made. The fluid layer of height 1 versus the horizontal width 1 or 4 is adopted and numerical computations are carried out for Pr = 1. The time-averaged Nusselt numbers computed both at top and bottom walls give the upward time-averaged heat flux without depending on the temperature oscillation either at the upper or lower walls. This is because the time-dependent convection plumes occur at the almost largest temperature of the bottom wall in comparison to the top wall. The time-averaged heat flux is always positive, i.e., upward, even if the time-averaged temperature difference is zero between the top and bottom walls. 相似文献
1000.
Masaki Nakano Hiroyuki Takeda Fumitoshi Yamashita Hirotoshi Fukunaga 《IEEJ Transactions on Electrical and Electronic Engineering》2007,2(4):450-452
After a postannealing process, the magnetic properties of pulsed laser deposition (PLD)‐made Nd–Fe–B film magnets prepared at the deposition rate of 20–90 µm/h showed constant values, and the average values of Hc, Br and (BH)max were 1050 kA/m, 0.6 T, and 60 kJ/m3, respectively. The obtained results were comparable to those previously reported. In conclusion, it was found that a maximum deposition rate of 90 µm/h could be achieved without deterioration of magnetic and mechanical properties. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献