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21.
Thermal behaviors of a few kinds of poly(fluoroalkyl methacrylate-co-methyl methacrylate) prepared by γ-ray copolymerization were investigated by using thermogravimetric measurements together with the intermittent analysis of the gaseous products. The thermal degradation of copolymers composed of one of fluoroalkyl methacrylates of the following structures: CH2?C(CH3)COOCH2(CF2CF2)nH, where n = 1,2, and 3, and methyl methacrylate proceeded according to the depolymerization mechanism reproducing the pristine component comonomers exclusively, but their thermograms in inert atmosphere showed the feature of a two-step reaction. In air, however, thermograms of copolymers did not show such a stepwise decrease in weight with the elevating temperature, and temperatures at which depolymerization was introduced shifted to a much higher region. The overall aspects of depolymerization of copolymers seemed to be much similar to that of fluoroalkyl methacrylate homopolymer previously reported, and the retardation of depolymerization by air was considered to be due mainly to the stabilization of once-formed polymer radicals by oxygen. 相似文献
22.
Yoshiyuki Sakamoto Tomoyoshi Motohiro Shinichi Matsunaga Kohei Okumura Tomoyuki Kayama Kiyoshi Yamazaki Toshiyuki Tanaka Yoshimi Kizaki Naoki Takahashi Hirofumi Shinjoh 《Catalysis Today》2007,121(3-4):217-225
The release and reduction of NOx in a NOx storage-reduction (NSR) catalyst were studied with a transient reaction analysis in the millisecond range, which was made possible by the combination of pulsed injection of gases and time resolved time-of-flight mass spectrometry. After an O2 pulse and a subsequent NO pulse were injected into a pellet of the Pt/Ba/Al2O3 catalyst, the time profiles of several gas products, NO, N2, NH3 and H2O, were obtained as a result of the release and reduction of NOx caused by H2 injection. Comparing the time profiles in another analysis, which were obtained using a model catalyst consisting of a flat 5 nmPt/Ba(NO3)2/cordierite plate, the release and reduction of NOx on Pt/Ba/Al2O3 catalyst that stored NOx took the following two steps; in the first step NO molecules were released from Ba and in the second step the released NO was reduced into N2 by H2 pulse injection. When this H2 pulse was injected in a large amount, NO was reduced to NH3 instead of N2.
A only small amount of H2O was detected because of the strong affinity for alumina support. We can analyze the NOx regeneration process to separate two steps of the NOx release and reduction by a detailed analysis of the time profiles using a two-step reaction model. From the result of the analysis, it is found that the rate constant for NOx release increased as temperature increase. 相似文献
23.
Yu-ichi Yoshizawa Kiyoshi Hirao Shuzo Kanzaki 《Journal of the American Ceramic Society》2004,87(11):2147-2149
The mechanical properties of a textured alumina made by high-temperature deformation of normal-purity sintered alumina have been investigated. The textured alumina shows very high bending strength and extremely high fracture toughness. Fracture toughness of more than 10 MPa·m1/2 was measured by the single-edge precracked beam method, and even using the single-edge V-notched beam method, toughness of over 8 MPa·m1/2 was obtained. This high fracture toughness was attributed to a large number of aligned small platelike grains of the textured structure enhancing the grain bridging effect. 相似文献
24.
Kiyoshi Itatani Ryuji Tsukamoto Anne C. A. Delsing Hubertus T. Hintzen Isao Okada 《Journal of the American Ceramic Society》2002,85(7):1894-1896
Aluminum nitride (AlN)–silicon carbide (SiC) nanocomposite powders were prepared by the nitridation of aluminum-silicon carbide (Al4 SiC4 ) with the specific surface area of 15.5 m2 ·g−1 . The powders nitrided at and above 1400°C for 3 h contained the 2H-phases which consisted of AlN-rich and SiC-rich phases. The formation of homogeneous solid solution proceeded with increasing nitridation temperature from 1400° up to 1500°C. The specific surface area of the AlN–SiC powder nitrided at 1500°C for 3 h was 19.5 m2 ·g−1 , whereas the primary particle size (assuming spherical particles) was estimated to be ∼100 nm. 相似文献
25.
Ping Shen Hidetoshi Fujii Taihei Matsumoto Kiyoshi Nogi 《Journal of the American Ceramic Society》2005,88(4):912-917
Wetting phenomena and the effect of alumina surface orientation on the wettability in Si/α-Al2 O3 system were studied by an improved sessile drop method using , , C(0001) faces of single crystals and polycrystals at 1723 K in a reducing Ar–3% H2 atmosphere. The contact angles show a vibration behavior for all the single crystals but to a less extent for the polycrystals. The extent of the vibration correlates not only with the reaction intensity but also with the stability of the Si droplet on the alumina surfaces. The interfacial reaction leads to the formation of a series of reaction rings, which is more serious at the single crystal surfaces. More importantly, the wettability is dependent on the alumina surface orientation, with the intrinsic contact angles being about 98±2°, 101±1°, 69±1°, and 98±2°, respectively, for the , , C(0001) and polycrystal α-Al2 O3 substrates. The much smaller contact angle for molten Si on the C(0001) surface is explained by the favorable reduction in the Si/α-Al2 O3 interfacial free energy by the terminated and enriched aluminum atoms at the reconstructed surface. The importance of the aluminum presence at the Si/α-Al2 O3 interface to the wettability of this system was further demonstrated by a substantial improvement in the wettability of the α-Al2 O3 substrates by Si–Al alloys. 相似文献
26.
To develop insulating materials with a high thermally conductive anisotropy, planarly aligned mesogenic epoxy (ME) resin film was fabricated by uniaxial coating on a hydrophobic polyethylene terephthalate substrate. Grazing incidence small-angle X-ray scattering (GISAXS) and transmission SAXS measurements exhibited that the films spontaneously formed uniaxially aligned monodomain-like smectic structures by curing on the hydrophobic substrate. Then, an in- and out-of-plane thermal conductivity of 10 and 0.048 W m−1 K−1 and outstanding thermal conductivity anisotropy of 208 have been confirmed, respectively. The ME resin films with high thermal conductivity can be applied as insulating materials for multiple-layer electrical and electronic devices. 相似文献
27.
Kiyoshi Kusabiraki Noriaki Kuroda Isao Motohira Takayuki Ooka 《Oxidation of Metals》1997,48(3-4):289-302
The oxidation behavior of pure titanium has been investigated in the temperature range of 1000 K to 1300 K in CO2 or Ar-10%CO2. Optical microscopy, electron probe microanalyses, and X-ray measurements on the oxide scales formed during oxidation indicate that their structures are nearly independent of temperature and the corrosion atmosphere. The scales consisted of two layers, an external one and an internal one, having a rutile (TiO2) structure. The parabolic rate law was confirmed for growth of the external scale and the permeation depth of oxygen in titanium with apparent activation energies of 266 and 226 kJ/mol, respectively. The rate-determining diffusion species in the oxidation processes are discussed. 相似文献
28.
Amorphous Al50Ta60 alloy powders have been synthesized by mechanical alloying (MA) from elemental powders of aluminium and tantalum, and mechanical disordering (MD) from crystalline intermetallic compound powders of AlTa respectively using the rod milling technique. The mechanically alloyed and the mechanically disordered alloy powders were characterized by X-ray diffraction, scanning electron microscopy, electron probe microanalysis, transmission electron microscopy, differential thermal analysis, differential scanning calorimetry and chemical analysis. The results have shown that the crystal-to amorphous transformation in the MD process occurs through one stage, while the crystallineto-amorphous formation in the MA process occurs through three stages. At the early and intermediate stages of the MA time, heating the alloy powders to 700 K leads to the formation of an amorphous phase by a solid-state amorphizing reaction. At the final stage of the MA time, the amorphous phase is crystallized through a single sharp exothermic peak. Contrary to this, amorphous alloy powders produced by MD are crystallized through two broad exothermic peaks. 相似文献
29.
Kiyohiko Hattori Eri Homma Toshinori Kagawa Masayuki Otani Naoki Tatebe Yasunori Owada Lin Shan Katsuhiro Temma Kiyoshi Hamaguchi 《Artificial Life and Robotics》2016,21(4):451-459
Recently, many extensive studies have been conducted on robot control via self-positioning estimation techniques. In the simultaneous localization and mapping (SLAM) method, which is one approach to self-positioning estimation, robots generally use both autonomous position information from internal sensors and observed information on external landmarks. SLAM can yield higher accuracy positioning estimations depending on the number of landmarks; however, this technique involves a degree of uncertainty and has a high computational cost, because it utilizes image processing to detect and recognize landmarks. To overcome this problem, we propose a state-of-the-art method called a generalized measuring-worm (GMW) algorithm for map creation and position estimation, which uses multiple cooperating robots that serve as moving landmarks for each other. This approach allows problems of uncertainty and computational cost to be overcome, because a robot must find only a simple two-dimensional marker rather than feature-point landmarks. In the GMW method, the robots are given a two-dimensional marker of known shape and size and use a front-positioned camera to determine the marker distance and direction. The robots use this information to estimate each other’s positions and to calibrate their movement. To evaluate the proposed method experimentally, we fabricated two real robots and observed their behavior in an indoor environment. The experimental results revealed that the distance measurement and control error could be reduced to less than 3 %. 相似文献
30.
Hiroyuki Sato Hernán Aguirre Kiyoshi Tanaka 《Annals of Mathematics and Artificial Intelligence》2013,68(4):197-224
In this work, we analyze variable space diversity of Pareto optimal solutions (POS) and study the effectiveness of crossover and mutation operators in evolutionary many-objective optimization. First we examine the diversity of variables in the true POS on many-objective 0/1 knapsack problems with up to 20 items (bits), showing that variables in POS become noticeably diverse as we increase the number of objectives. We also verify the effectiveness of conventional two-point and uniform crossovers, Local Recombination that selects mating parents based on proximity in objective space, and two-point and uniform crossover operators which Controls the maximum number of Crossed Genes (CCG). We use NSGA-II, SPEA2, IBEA ??+? and MSOPS, which adopt different selection methods, and many-objective 0/1 knapsack problems with $n=\{100,250,500,750,\mbox{1,000}\}$ items (bits) and m?=?{2,4,6,8,10} objectives to verify the search performance of each crossover operator. Simulation results reveal that Local Recombination and CCG operators significantly improve search performance especially for NSGA-II and MSOPS, which have high diversity of genes in the population. Also, results show that CCG operators achieve higher search performance than Local Recombination for m?≥?4 objectives and that their effectiveness becomes larger as the number of objectives m increases. In addition, the contribution of CCG and mutation operators for the solutions search is analyzed and discussed. 相似文献