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991.
In image reconstruction for X-ray computed tomography, images reconstructed by filtered backprojection (FBP) include systematic errors because the FBP method does not take into account some of the properties of the actual imaging system such as the divergence of X-ray beam. One solution to this problem is to use algebraic reconstruction methods, such as generalized analytic reconstruction from discrete samples and natural pixel decomposition. However, in the process of reconstruction using these methods, it is necessary to solve the linear algebraic equations which have a large coefficient matrix. In this paper, we propose a method to accelerate the iteration solving these equations by preconditioning the coefficient matrix using a polynomial function. The results of the computer simulations show the effectiveness of the proposed method. 相似文献
992.
Formation of Anatase Nanocrystals in Sol-Gel Derived TiO2-SiO2 Thin Films with Hot Water Treatment 总被引:8,自引:0,他引:8
Yoshinori Kotani Atsunori Matsuda Masahiro Tatsumisago Tsutomu Minami Taku Umezawa Toshihiro Kogure 《Journal of Sol-Gel Science and Technology》2000,19(1-3):585-588
We have successfully prepared transparent and porous anatase nanocrystals-dispersed films by treating the sol-gel derived TiO2-SiO2 films containing poly(ethylene glycol), PEG, with hot water. This process was done at temperatures lower than 100°C under atmospheric pressure, and thus anatase nanocrystals-dispersed films can be formed on various kinds of substrates including organic polymers with poor heat resistance. The changes in structure and composition of the TiO2-SiO2 gel films with hot water treatment were related to the formation process of anatase nanocrystals in the TiO2-SiO2 gel films with hot water treatment. The formation of anatase nanocrystals was found to proceed to hydrolysis of Si–O–Ti bonds and dissolution of SiO2 component. In addition, porous film structure formed by leaching of PEG with hot water treatment led to homogenous dispersion of anatase nonocrystals in the films. 相似文献
993.
Matsuda Atsunori Matsuno Yoshihiro Tatsumisago Masahiro Minami Tsutomu 《Journal of Sol-Gel Science and Technology》2001,20(2):129-134
Porous silica films were obtained by a heat treatment of poly(ethyleneglycol)-containing gels for micro-patterning. Changes in porosity and the amount of adsorbed water with the heat treatment temperature in the silica films were evaluated from the refractive index of the films. The apparent refractive index of the silica films in an ambient atmosphere was much higher than the intrinsic refractive index of the film due to the large amount of adsorbed water in the films. The amount of adsorbed water in the films decreased with an increase in the heat treatment temperature and became almost zero after a heat treatment at 850°C. The decrease in the amount of adsorbed water in the films was caused by the decrease in silanol groups, which acted as the sites for water adsorption in the films. The drastic decreases in thickness and in porosity of the films at temperatures from 850 to 950°C occurred after the disappearance of silanol groups in the films. The densification of the films due to collapse of the pores at high temperatures should have resulted from the viscous flow of silica network. 相似文献
994.
Masahiro Sekiya Takeshi Noro You Osanai Toshikatsu Koga 《Theoretical chemistry accounts》2001,106(4):297-300
Contracted Gaussian-type function sets are proposed for polarization functions of the atoms Ga–Kr and In–Xe. We also report
polarization functions for Ca and Sr. A segmented contraction scheme is used for its compactness and computational efficiency.
The contraction coefficients and orbital exponents are fully optimized to minimize the deviation from accurate atomic natural
orbitals. The present polarization functions yield more than 99% of atomic correlation energies predicted by accurate natural
orbitals of the same size.
Received: 23 February 2001 / Accepted: 19 April 2001 / Published online: 13 June 2001 相似文献
995.
In the tight-binding random Hamiltonian on Z
d
, we consider the charge transport induced by an electric potential which varies sufficiently slowly in time, and prove that it is almost surely equal to zero at high disorder. In order to compute the charge transport, we adopt the adiabatic approximation and prove a weak form of adiabatic theorem while there is no spectral gap at the Fermi energy. 相似文献
996.
Opto-Electronic Block-Cipher Based on Iteration of the 2-D Toggle Cellular Automata: Algorithm 总被引:2,自引:0,他引:2
Maria Madjarova Mitsugu Kakuta Takashi Obi Masahiro Yamaguchi Nagaaki Ohyama 《Optical Review》1999,6(2):110-117
Parallel architectures and algorithms may offer a solution to the system bottleneck arising from the need to encrypt a very large amount of data without compromising security. In this respect the use of cellular automata with their parallel, simple, regular and modular structure is very promising. We extend the blockcipher algorithm, based on the iterations of so called “toggle” cellular automata rules to two dimensions.The advantages are higher complexity of the crypt-analytical attacks and substantial increase in the speed of the algorithm. Due to its massive parallelism and interconnectivity, the algorithm is very suitable for opto-electronic implementation. 相似文献
997.
Masahiro Mitsuyama Reiko Ishii Koichi Kondo 《Journal of polymer science. Part A, Polymer chemistry》2000,38(18):3419-3427
A variety of long alkyl acetylenic compounds was synthesized and polymerized by using Rh(I) catalysts. Particularly, the monomer having a terminal hydroxyl group was converted into the high molecular weight of polymer in good conversion, which was soluble in THF, DMSO, and DMF. The high stereoregularity (cis) in the main chain was confirmed by 1H‐NMR in DMSO‐d6 and the rod‐like structure by wide‐angle X‐ray diffraction. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3419–3427, 2000 相似文献
998.
999.
1000.
Amane Mochizuki Michie Sakamoto Masahiro Yoshioka Takahiro Fukuoka Kazumasa Takeshi Mitsuru Ueda 《Journal of polymer science. Part A, Polymer chemistry》2000,38(2):329-336
A novel photosensitive polymer based on end‐capped polycarbodiimide (E‐PCD) and the photoamine generator N‐{[(4,5‐dimethoxy‐2‐nitrobenzyl)oxy]carbonyl}‐2,6‐dimethylpiperidine (1) was developed. The E‐PCD was prepared by polycondensation of tolylene‐2,4‐diisocyanate in the presence of 3‐methy‐1‐phenyl‐2‐phospholene‐1‐oxide as a catalyst. The reaction of carbodiimide and secondary amine was studied. The nucleophilic addition of amine to the carbodiimide moiety proceeded smoothly and provided a guanidine base that acted as a crosslinking agent. A lithographic evaluation of the system of E‐PCD and 1 revealed that the dissolution rate of the exposed area after the postexposure bake decreased drastically, although no obvious change of the dissolution rate in the unexposed area was observed. The E‐PCD containing 10 wt % 1 functioned as a negative working photosensitive polymer when it was exposed to 365‐nm UV light, postbaked at 120 °C for 5 min, and developed with toluene at 25 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 329–336, 2000 相似文献