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151.
Takafumi Kusunose Tohru Sekino Yong Ho Choa Koichi Niihara 《Journal of the American Ceramic Society》2002,85(11):2678-2688
A chemical process for fabrication of Si3 N4 /BN nanocomposite was devised to improve the mechanical properties. Si3 N4 /BN nanocomposites containing 0 to 30 vol% hexagonal BN ( h -BN) were successfully fabricated by hot-pressing α-Si3 N4 powders, on which turbostratic BN ( t -BN) with a disordered layer structure was partly coated. The t -BN coating on α-Si3 N4 particles was prepared by reducing and heating α-Si3 N4 particles covered with a mixture of boric acid and urea. TEM observations of this nanocomposite revealed that the nanosized hexagonal BN ( h -BN) particles were homogeneously dispersed within Si3 N4 grains as well as at grain boundaries. As expected from the rules of composites, Young's modulus of both micro- and nanocomposites decreased with an increase in h -BN content, while the fracture strength of the nanocomposites prepared in this work was significantly improved, compared with the conventional microcomposites. 相似文献
152.
Yong-Ho Choa Tatachika Nakayama Tohru Sekino Koichi Niihara 《Metals and Materials International》1999,5(2):135-139
Nanocrystalline iron-oxide powder was fabricated with an inert gas condensation (IGC) method combined with evaporation, and
in-situ oxidation techniques. The particle size of iron-oxide powder was controlled by varying the helium gas pressure between
0.1 and 10 Torr, with the smallest one =10 nm at 0.1 Torr. The nanostructure was characterized by TEM. Nanocrystalline iron-oxide
powder was sintered with the pulse electric current sintering (PECS) method to obtain densified γ-Fe2O3 materials, and suitably densified nano-grained γ-Fe2O3 materials (≈ 40 nm) of great hardness were obtained. The correlation between the nanostructure and magnetic properties of
nanocrystalline powder and densified γ-Fe2O3 materials was also investigated. 相似文献
153.
154.
Peer-to-Peer Networking and Applications - Current IP based tracking method include host based traceback method, using traceback module installed in all system to locate the hacker’s real... 相似文献
155.
The effects of interactions between the perforated and baffle plates, of pulse amplitude and of pulse frequency on axial dispersion in the continuous phase, on the dispersed phase holdup and on the flooding condition have been determined for a 10.2 cm 1D pulsed extraction column. The axial dispersion coefficient increased with both the pulse amplitude and the frequency, but it decreased with the decrease in baffle spacing in the unit module. Dispersed phase holdup increased with the number of perforated plates in the unit module at the lower pulsation velocities and increased with the pulse velocity. The baffle plate reduced the total throughputs, but baffle spacing did not have any significant effect on the total throughput. 相似文献
156.
A number of APT(Advanced Persistent Threat) attack malwares are being detected as of late together with attempts by the state and enterprises to leak personal information. To detect and respond to them, malwares must first be detected by security monitoring system. In particular, availability of a method to detect and predict such malwares in advance will lead to preventing security incidents. This study will propose a method of prediction based on intrusion detection event and a functional configuration to realize the method and will assess the prediction model based on intrusion detection events proposed through a test consisting of the stages of learning, prediction and evaluation. 相似文献
157.
Tae-Won Lee Yong-Ho YoonYuen-Chung Kim Byoung-Kuk LeeChung-Yuen Won 《Electric Power Systems Research》2007
This paper deals with the analysis of switched reluctance motor drives for different drive circuit topologies used in automobile. Therefore, we attempt to improve the weaknesses associated with the asymmetric bridge converter in the limited internal environment of automotive application. Two kinds of c-dump converters are tested in terms of dump capacitor voltage, speed response according to the variation of advance angle and efficiency for the radiator cooling-fan drive of an automobile. They enable more economical and efficient converter topology for automobile industries. This paper describes the performance characteristics of 12 V–250 W–3000 rpm SRM drives for automobiles. Computer simulation and experiment results are then presented to verify the performance of the two kinds of c-dump converters. 相似文献
158.
Synthesis and thermoelectric characterization of bulk-type tellurium nanowire/polymer nanocomposites
Seil Kim Young-In Lee Seung Han Ryu Tae-Yeon Hwang Yoseb Song Sungho Seo Bongyoung Yoo Jae-Hong Lim Hong-Baek Cho Nosang V. Myung Yong-Ho Choa 《Journal of Materials Science》2017,52(21):12724-12733
A simple method to fabricate three-dimensionally (3-D) aligned thermoelectric nanowires attached polymer particle was demonstrated by combination of solution casting of thermoelectric nanostructures (e.g., tellurium nanowires (Te NWs)) on the surface of thermoplastic polymer (e.g., poly(methyl methacrylate (PMMA)) microbeads followed by hot compaction of thermoplastic matrix. The percolation threshold of composite with 3-D assembled Te NWs (i.e., 3.45 vol%) significantly was lower than that of a randomly dispersed Te NWs (i.e., 5.26 vol%), which resulted in an order of magnitude greater thermoelectric figure of merit (ZT of 2.8 × 10?3) compared to randomly dispersed Te NWs in PMMA matrix (ZT of 6.4 × 10?4) at room temperature by enhancing the electrical conductivity without increasing thermal conductivity. 相似文献
159.
Sung-Hoon Choa 《Microsystem Technologies》2009,15(5):677-686
In this paper, we developed a hermetic wafer level packaging for MEMS devices. Au–Sn eutectic bonding technology in a relatively
low temperature is used to achieve hermetic sealing, and the vertical through-hole via filled with electroplated copper for
the electrical connection is also used. The MEMS package has the size of 1 mm × 1 mm × 700 μm, and a square loop Au–Sn metallization
of 70 μm in width for hermetic sealing. The robustness of the package is confirmed by several tests such as shear strength
test, reliability tests, and hermeticity test. The reliability issues of Au–Sn bonding technology, and copper through-wafer
interconnection are discussed, and design considerations to improve the reliability are also presented. By applying O2 plasma ashing and fabrication process optimization, we can achieve the void-free structure within the bonding interface.
The mechanical effects of copper through-vias are also investigated numerically and experimentally. Several factors which
could induce via hole cracking failure are investigated such as thermal expansion mismatch, via etch profile, copper diffusion
phenomenon, and cleaning process. Alternative electroplating process is suggested for preventing Cu diffusion and increasing
the adhesion performance of the electroplating process. 相似文献
160.
We report in this paper the architectural design and implementation of all-optical packet networks. Using photonic switches to route information, an all-optical network has the advantages of bit rate, wavelength, and signal format transparencies. Within the transparency distance, the network is capable of handling a widely heterogeneous mix of traffic. We will describe our research on the implementation of all-optical backbone switches. The switch components including frame synchronizers, frame delineation units, frame header over-writing units, wavelength converters, frame concentrators, and WDM buffers were constructed at 2.5 Gb/s. Their subsystem and device structure as well as preliminary performance are reported. 相似文献