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32.
33.
Afreen Azhari Takamaro Kikkawa 《International Journal of Circuit Theory and Applications》2019,47(8):1293-1301
An ultra-wideband 2- to 12-GHz transmit/receive (T/R) double-pole–eight-throw (DP8T) switching matrix is developed with a 65-nm complementary metal oxide semiconductor (CMOS) process for a radar-based breast cancer detection system. The measured average insertion losses are 5.2, 7, and 10.6 dB at 2, 6, and 12 GHz, respectively, with input and output matching bandwidths of 2 to 12 GHz and a third-order input intercept point (IIP3) of 31 dBm at 8 GHz. The power consumption is less than 1 mW for a 1.2-V power supply. To the best of the authors' knowledge, this is the first reported DP8T CMOS switching matrix to replace the conventional mechanical switch to control a portable radar antenna. 相似文献
34.
Microwave breast imaging exploits dielectric contrasts between cancerous and healthy tissues at microwave frequencies to detect breast tumors. The estimation of breast optimal effective dielectric properties has a significant influence on the image quality. Recently, a novel method based on focal quality metrics (FQMs) has been proposed to investigate the patient‐specific effective dielectric properties. Although FQMs can be used to estimate the effective permittivity, the small increment of permittivity during the imaging process may lead to large computational resource consumption. In this article, an optimized microwave breast imaging method is proposed. In this method, a hybrid image quality metric is put forward which mixes the signal‐to‐clutter ratio (SCR) and focal quality metric. In addition, the simulated annealing algorithm is incorporated to facilitate image reconstruction. Experimental results demonstrate that using the proposed method, SCR is improved by 0.2 dB and tumor location error is reduced by 3.5 mm in realistic breast phantom. 相似文献
35.
A mathematical model which describes the influence of various parameters on formaldehyde concentration in the atmosphere of a room containing wood-based boards was developed. The physical meanings and measuring methods of the parameters of the model are also discussed. Based on this model, two indices for commenting the formaldehyde emission process of wood-based boards are proposed, and inequality estimation for the formaldehyde content of wood-based boards at any moment and a time estimation which shows when the room satisfies the environment quality standard are also given. 相似文献
36.
Photoluminescence (PL) identifies spectroscopic signatures of intertube transfer of optically pumped carriers in single-walled carbon nanotube (SWNT) ensembles. Resonant photoexcitation of large band gap SWNTs produces strong PL from smaller band gap SWNTs. Magnetic alignment measurements associate the energy-transfer PL peaks with the formation of SWNT bundles, suggesting that efficient coupling results from physical contact. 相似文献
37.
Yagai S Seki T Murayama H Wakikawa Y Ikoma T Kikkawa Y Karatsu T Kitamura A Honsho Y Seki S 《Small (Weinheim an der Bergstrasse, Germany)》2010,6(23):2731-2740
Extremely long nanofibers, whose lengths reach the millimeter regime, are generated via co-aggregation of a melamine-appended perylene bisimide semiconductor and a substituted cyanurate, both of which are ditopic triple-hydrogen-bonding building blocks; they co-aggregate in an unexpected stoichiometrically mismatched 1:2 ratio. Various microscopic and X-ray diffraction studies suggest that hydrogen-bonded polymeric chains are formed along the long axis of the nanofibers by the 1:2 complexation of the two components, which further stack along the short axis of the nanofibers. The photocarrier generation mechanism in the nanofibers is investigated by time-of-flight (TOF) experiments under electric and magnetic fields, revealing the birth and efficient recombination of singlet geminate electron-hole pairs. Flash-photolysis time-resolved microwave conductivity (FP-TRMC) measurements revealed intrinsic 1D electron mobilities up to 0.6 cm(2) V(-1) s(-1) within nanofibers. 相似文献
38.
Shinichi Kikkawa Naoya Hatta Takashi Takeda 《Journal of the American Ceramic Society》2008,91(3):924-928
Spinel-type AlON, Al2.75 □0.25 O3.74 N0.26 , was obtained by ammonia nitridation of an oxide precursor prepared by peptizing a glycine gel with aluminum nitrate. To achieve crystallization, the nitrided product had to be annealed at 1500°C for 10 min in flowing nitrogen. The use of glycine instead of citric acid was important for obtaining a white product without residual carbon. A similar preparation method was used for adding small amounts of europium below 10 mol%. A strong blue emission was observed for products ranging from 0.5 to 3.0 mol% Eu doping. The product with 0.5 mol% doping had a maximum emission intensity at 400 nm for an excitation of 254 nm. The products with 1 and 3 mol% doping showed double maxima at 475 and 520 nm. These three emissions were due to the presence of divalent europium in the EuAl12 O19 magnetoplumbite-like aluminum oxynitride impurity mixed with the AlON spinel major phase. The 1 mol% Eu-doped product exhibited expanded hexagonal lattice parameters ( a =0.5591 and c =2.236 nm) compared with the values for EuAl12 O19 magnetoplumbite itself, observed in the 7.7 mol%-doped product without any strong emission. The above spectrum change was discussed in relation to the coordination around Eu2+ . 相似文献
39.
Y. Masubuchi Y. SatoA. Sawada T. MotohashiH. Kiyono S. Kikkawa 《Journal of the European Ceramic Society》2011,31(14):2459-2462
Crystallization and magnetic property of Fe2O3 nanoparticle precipitated in SiO2 matrix was investigated. Fe2O3/SiO2 nanocomposite thin film was obtained by annealing of the amorphous Fe-Si-O thin film deposited by RF-magnetron sputtering of (α-Fe2O3)1−x/(SiO2)x composite targets. The Fe2O3 crystallite size increased with decreasing SiO2 area ratio, x of the target and increasing annealing temperature. ?-Fe2O3 with the crystallite size of 20-30 nm was obtained after annealing the film deposited in SiO2 area ratio, x = 0.33-0.42 at 900 °C. Lower SiO2 area ratio (x) than 0.25 and higher annealing temperature resulted in precipitation of α-Fe2O3 with the larger crystallite size than 40 nm. In the case of SiO2 area ratio, x ≥ 0.50, the annealed film was amorphous and showed higher magnetization and smaller coercivity due to the precipitation of very small crystalline γ-Fe2O3. The ?-Fe2O3/SiO2 composite thin film showed ferromagnetic hysteresis with coercive force of 0.14 T. 相似文献
40.
Sadanobu?Sumiya Jun?Fujiwara Yasunori?Oumi Masahiro?Sadakane Tsuneji?SanoEmail author 《Journal of Porous Materials》2011,18(4):493-500
Incorporation of aluminum on the inner surfaces of mesopores was carried out under hydrothermal conditions for synthesizing
mesoporous silica using an anionic surfactant. The synthesis concept was based on ionic interactions between aluminum cations
and anionic surfactants, with the latter as templates. We easily obtained aluminum-containing microporous silica with supermicropores.
The results of pyridine adsorption and cumene cracking reactions strongly indicated that unlike the materials prepared by
the previously reported post synthesis and direct synthesis methods, the larger amount of aluminum incorporated into the materials
were effectively present on the inner surfaces of supermicropores. 相似文献