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41.
This Letter reports on the acceleration of the rate of formation of the boron–oxygen defect in p‐type Czochralski silicon with illumination intensities in excess of 2.1 × 1017 photons/cm2/s. It is observed that increased light intensities greatly enhance the rate of defect formation, without increasing the saturation concentration of the defect. These results suggest a dependence of the defect formation rate upon the total majority carrier concentration. Finally, a method using temperatures up to 475 K and an illumination intensity of 1.68 × 1019 photons/cm2/s is shown to result in near‐complete defect formation within seconds. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
42.
Hugh Rieley Daniel J. Colby Darren P. McMurray Stuart M. Reeman 《Surface science》1997,390(1-3):243-249
The effects of physisorption and two-dimensional ordering on the photochemistry of N2O4 were investigated. Ordered monolayers were prepared by adsorption of NO2 at 100 K on a water-ice surface. Irradiation with a continuous light source in the wavelength region 300–400 nm or with pulsed laser radiation at 355 nm resulted in exclusive desorption of NO2. This desorption was induced by electronic absorption directly in the adsorbate via a transition corresponding to the (
)1B2u←(
)1Ag transition in N2O4, as in the gas phase. However, the subsequent dynamics in the excited state were markedly different from the gas-phase counterpart. Time-of-flight mass spectrometry of NO2 photodesorbed at 355 nm revealed a most probable fragment translational energy of ca. 17 meV; and the angular distribution of the nascent NO2 was peaked sharply in a direction around 10° from the normal. It is apparent that, despite the weak interaction with the substrate, significant energy transfer occurs in the ordered physisorbed monolayer to yield nascent NO2 with very low translational energy and a constrained angle of escape which is consistent with a high degree of adsorbate order and alignment. 相似文献
43.
In modern magnetic resonance imaging (MRI), patients are exposed to strong, nonuniform static magnetic fields outside the central imaging region, in which the movement of the body may be able to induce electric currents in tissues which could be possibly harmful. This paper presents theoretical investigations into the spatial distribution of induced electric fields and currents in the patient when moving into the MRI scanner and also for head motion at various positions in the magnet. The numerical calculations are based on an efficient, quasi-static, finite-difference scheme and an anatomically realistic, full-body, male model. 3D field profiles from an actively shielded 4T magnet system are used and the body model projected through the field profile with a range of velocities. The simulation shows that it possible to induce electric fields/currents near the level of physiological significance under some circumstances and provides insight into the spatial characteristics of the induced fields. The results are extrapolated to very high field strengths and tabulated data shows the expected induced currents and fields with both movement velocity and field strength. 相似文献
44.
Sensitizer-free holmium-doped silica and fluoride mid-infrared fiber lasers are pumped using a high-power diode laser operating at 1148 nm. A maximum output power of 162 mW at 2.86 microm was produced at a slope efficiency of 24% using Ho(3+), Pr(3+)-doped fluoride fiber. Using Ho(3+)-doped silica fiber, a maximum output power of 55 mW at 2.1 microm was generated at a slope efficiency of 27%, a value limited by the presence of pump excited state absorption. 相似文献
45.
Stuart A Givens GD Walker LJ Elangovan S 《The Journal of the Acoustical Society of America》2006,119(4):1946-1949
The purpose of this study was to examine temporal resolution in normal-hearing preschool children. Word recognition was evaluated in quiet and in spectrally identical continuous and interrupted noise at signal-to-noise ratios (S/Ns) of 10, 0, and -10 dB. Sixteen children 4 to 5 years of age and eight adults participated. Performance decreased with decreasing S/N. At poorer S/Ns, participants demonstrated superior performance or a release from masking in the interrupted noise. Adults performed better than children, yet the release from masking was equivalent. Collectively these findings are consistent with the notion that preschool children suffer from poorer processing efficiency rather than temporal resolution per se. 相似文献
46.
一种新的自动调焦方法—离轴探测法 总被引:2,自引:0,他引:2
本文提出了的种新的自动调焦方法——离轴探测法,此法没用任何附加元件,结构简单、装调容易、线性度好、灵敏度高、调焦范围大、实用性强;介绍了此法的原理、理论计算结果及实验结果;给出了应用实例. 相似文献
47.
Stuart D Breedon RE Kim GN Ko W Lander RL Maeshima K Malchow RL Smith JR Imlay R Kirk P Lim J McNeil RR Metcalf W Myung SS Cheng CP Gu P Li J Li YK Ye MH Zhu YC Abashian A Gotow K Hu KP Low EH Mattson ME Piilonen L Sterner KL Lusin S Rosenfeld C Wang AT Wilson S Frautschi M Kagan H Kass R Trahern CG Abe K Fujii Y Higashi Y Kim SK Kurihara Y Maki A Nozaki T Omori T Sagawa H Sakai Y Sugimoto Y Takaiwa Y Terada S Walker R Kajino F Perticone D Poling R Thomas T Ishi Y Miyano K Miyata H Sasaki T 《Physical review letters》1990,64(9):983-986
48.
Eno S Auchincloss P Blanis D Bodek A Budd H Fry CA Harada H Ho YH Kim YK Kumita T Mori T Olsen SL Shaw NM Sill A Thorndike EH Ueno K Zheng HW Imlay R Kirk P Lim J McNeil RR Metcalf W Myung SS Cheng CP Gu P Li J Li YK Mao ZP Xu YT Zhu YC Abashian A Gotow K Hu KP Low EH Mattson ME Piilonen L Sterner KL Lusin S Rosenfeld C Wang AT Wilson S Frautschi M Kagan H Kass R Trahern CG Breedon RE Kim GN Ko W Lander RL Maeshima K Malchow RL Smith JR Stuart D Williams MC Abe K Fujii Y Higashi Y Kim SK 《Physical review letters》1989,63(18):1910-1913
49.
The potential role of ultrasound in differentiating solid and cystic swellings of the true vocal fold 总被引:3,自引:0,他引:3
John S. Rubin Stuart Lee John McGuinness Ian Hore David Hill Leslie Berger 《Journal of voice》2004,18(2):231-235
This study was designed to investigate the potential role of ultrasound in the diagnosis of cysts of the true vocal fold. Materials and Methods: Grayscale ultrasound of the larynx was carried out in 29 patients with a swelling of the true vocal fold and dysphonia. The findings were then compared with those at subsequent microlaryngoscopy, in the majority of cases. Results and Conclusions: Whereas preoperative laryngeal ultrasound correctly predicted the surgical findings of a cystic lesion in only 5 of 11 cases, it correctly identified that no cyst was present in 15 of 16 instances when this had been queried. This study suggests that ultrasound may have some role in investigation of unilateral vocal fold pathology, but that further fine-tuning of the technique may be necessary. 相似文献
50.
John D. Harvey Stuart G. Murdoch Stephane Coen Rainer Leonhardt David Mechin Gordon K. L. Wong 《Optical and Quantum Electronics》2007,39(12-13):1103-1114
Optical parametric amplification is an important nonlinear process in photonic crystal fibres driven by the small effective area and the special dispersion characteristics of these fibres. Aside from its role in supercontinuum generation, parametric amplification can lead to efficient wavelength conversion, limited primarily by the uniformity of the diameter of currently available fibres. The related Bragg scattering process can be used for both wavelength conversion and optical switching, again limited by the physical characteristics of the fibres used. 相似文献