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排序方式: 共有763条查询结果,搜索用时 31 毫秒
31.
You Zhou Tatsuki Ohji Hideki Hyuga Yu‐ichi Yoshizawa Norimitsu Murayama Kiyoshi Hirao 《International Journal of Applied Ceramic Technology》2014,11(5):872-882
Silicon nitride ceramics were prepared from a high‐purity silicon powder doped with 2 mol% Y2O3 and 5 mol% MgO as sintering additives via a route of sintering of reaction‐bonded silicon nitride (SRBSN). The materials sintered at 1900°C for 3, 6, 12, and 24 h had thermal conductivities of 109, 125, 146, and 154 W/m/K, and four‐point bending strengths of 786, 676, 608, and 505 MPa, respectively. The fracture toughness values, determined by the single‐edge‐precracked‐beam (SEPB) method, were 8.4, 8.6, 9.7, and 10.7 MPa m1/2 for the materials sintered for 3, 6, 12, and 24 h, respectively, which were similar to the results measured by the chevron‐notched‐beam (CNB) test method. The materials sintered for longer times (12 and 24 h) showed stronger R‐curve behaviors over longer range of crack extension, in comparison with the materials sintered for shorter times (3 and 6 h). 相似文献
32.
T. Hirao S. Onoda M. Oikawa T. Satoh T. Kamiya T. Ohshima 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(12-13):2216-2218
Single Event Effects (SEEs) triggered by energetic heavy ions traversing a sensitive parts of electric devices have been studied using high-energy heavy ion microbeams connected with Transient Ion Beam Induced Current (TIBIC) measuring system at the Japan Atomic Energy Agency (JAEA) Takasaki Ion Accelerators for Advanced Radiation Applications (TIARA) facility. In the TIBIC system, SEE for semiconductor device, that is fast charge collection, has been observed in timescales of the order of picoseconds. In this paper, we show successful demonstration of the performance of the system, in which clear images of TIBIC map have been observed for Si pin photodiodes irradiated by 260 MeV 20Ne7+ and also by 520 MeV 40Ar14+ microbeams. 相似文献
33.
You Zhou Yu-ichi Yoshizawa Kiyoshi Hirao Zoltán Lenčéš Pavol Šajgalík 《Journal of the European Ceramic Society》2011,31(1-2):151-157
LaSi3N5:Eu2+ phosphor powders were prepared by a highly efficient combustion synthesis method. It was found that the compositions of the raw powder mixtures had great influences on the phase compositions and particle morphologies of the synthesized powders. By selecting appropriate starting compositions and combustion parameters, single phase LaSi3N5:Eu2+ phosphors could be synthesized. When excited by a UV light, the LaSi3N5:Eu2+ phosphors emitted green light. The wavelength and intensity of the emission spectra were affected by the amount of Eu2+ dopant. With increasing amount of Eu2+ dopant, concentration quenching could occur and emission spectra shifted to longer wavelengths. 相似文献
34.
Huan-Bang Li Takashi Takahashi Masahiro Toyoda Yasuyuki Mori Ryuji Kohno 《Wireless Personal Communications》2009,51(4):697-709
Wireless Body Area Network (WBAN) is expected to play an important role in supporting medical and healthcare services with
increased convenience and comfort. One main advantage of WBAN is that it enables automatic biosignal collection in real time
which is essential in medical treatment and healthcare vigilance. To harmonize with the strong demands from both medical and
healthcare societies, and information and communications technology industries, IEEE 802 Standard Committee set up a task
group of TG15.6 to develop an IEEE wireless standard on WBAN. In this paper, we first review the main activities of TG15.6
with the updated status. Then, we present a prototype WBAN system that is implemented by using ultra-wideband technology.
Multi-hop mechanism is adopted to guarantee reliable connection. Finally, we describe an experimental system that uses the
developed WBAN system by combining with satellite communication in supporting remote medical treatment and healthcare. In
case of less of medical resources such as in emergency, in rural or isolated areas, such a system is important in sending
the corresponding biosignal to a remote hospital in real time to help patient management. The relative delay of WBAN data
delivery via satellite is measured which is dependent on the satellite link capacity. 相似文献
35.
Hiroshi Kominami Masaaki Kohno Yukino Matsunaga Yoshiya Kera 《Journal of the American Ceramic Society》2001,84(5):1178-1180
Silica-modified titanium oxide (S-TiO2 ) powders that have an anatase structure were synthesized via the thermal decomposition of mixtures of titanium(IV) isopropoxide (TIP) and tetramethyl orthosilicate (TMOS) in toluene at 300°C. These S-TiO2 materials had high rutile-transformation temperatures and maintained large surface areas at elevated temperatures (550°–1000°C). For example, the product that was prepared from a 9:1 TIP:TMOS mixture transformed to rutile at ∼1100°C and possessed a surface area of 160 m2 /g, even after calcination at 800°C for 1 h. 相似文献
36.
37.
Proposes a method for designing spread sequences for a spread spectrum (SS) communication and ranging system. The proposed sequence is composed by concatenated equivalently odd and even (EOE) inner-sequences and an M outer sequence. We have previously proposed EOE sequences that have equivalently good properties of both even and odd correlation, what are important features for acquisition and demodulation in SS communications. Usually, simple concatenation of pseudonoise-sequences results in sequences with bad autocorrelation properties. Unlike the latter, concatenation of EOE inner sequences result in sequences with good correlation properties, exhibiting low sidelobe peaks, what is useful for achieving stable acquisition. The proposed sequences have long period. Therefore, the single concatenated EOE sequence is suitable for a spread spectrum system with both communication and ranging functions 相似文献
38.
Chun Li Naoe Isshiki Hiromu Saito Kazufumi Kohno Akinori Toyota 《Polymer Bulletin》2009,63(6):779-788
We investigated the formation of inclusion complexes (ICs) between cyclodextrins (CDs) with different cavity size and polyolefin
(PO) with different side chains by using Fourier transform infrared (FTIR) spectroscopy, wide-angle X-ray diffraction (WAXD)
and differential scanning calorimetry. The analysis of FTIR spectra revealed that the resultants were complexes of CD and
PO, and the analysis of WAXD revealed that the molecules of CD had a channel structure due to the formation of ICs. We found
that IC could not be obtained when the cavity size of CD was small for PO molecules to thread and it was too large for cross-sectional
area of PO molecules. Thus, it was found that PO1 with few side chains could form IC with α-CD, and PO2 with ethyl side chain
could form IC with β-CD and γ-CD, while the PO3 with 2-methyl-propyl side chain could form IC with γ-CD. These results suggest
that the cross-sectional areas of polymer and the cavity size of CDs play critical roles in the formation of ICs. It is only
possible to form ICs when the polymer chains can tread into cavities of CDs, and the space between the polymer and CD is suitable
to provide enough intermolecular interaction to keep the structure of IC stable. 相似文献
39.
Processing and Thermal Conductivity of Sintered Reaction-Bonded Silicon Nitride. I: Effect of Si Powder Characteristics 总被引:2,自引:0,他引:2
Xinwen Zhu You Zhou Kiyoshi Hirao Zoltán Lené 《Journal of the American Ceramic Society》2006,89(11):3331-3339
This paper will present sintered reaction-bonded silicon nitride (SRBSN) material with a high thermal conductivity of 121 W·(m·K)−1 , which has been successfully prepared from a coarse Si powder with lower levels of oxygen and aluminum impurities, using a mixture of Y2 O3 and MgSiN2 as sintering additives, by nitriding at 1400°C for 8 h and subsequent post-sintering at 1900°C for 12 h at a nitrogen pressure of 1 MPa N2 . This thermal conductivity value is higher than that of the materials prepared from high-purity α-Si3 N4 powder (UBE SN-E10) with the same additive composition under the same sintering conditions. In order to study the effects of Si powder characteristics on the processing, microstructure, and thermal conductivity of SRBSN, the other type of fine powder with higher native oxygen and metallic impurity (typically Al and Fe) contents was also used. The effects of Si particle size, native oxygen, and metallic impurities on the nitriding process, post-sintering process, and thermal conductivity of the resultant SRBSN materials were discussed in detail. This work demonstrates that the improvement in thermal conductivity of SRBSN could be achieved by using higher purity coarse Si powder with lower levels of oxygen and aluminum impurities. In addition, this work also shows that the nitriding temperature has no significant effect on the microstructure and thermal conductivity of SRBSN during post-sintering, although it does affect the characteristics of RBSN formed during nitridation. 相似文献
40.