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941.
A buck DC-DC switching regulator with high efficiency is implemented by automatically altering the modulation mode according to load current,and it can operate with an input range of 4.5 to 30 V.At light load current,the converter operates in skip mode.The converter enters PWM mode operation with increasing load current.It reduces the switching loss at light load and standby state,which results in prolonging battery lifetime and stand-by time.Meanwhile, externally adjustable soft-start minimizes the inru... 相似文献
942.
A 10-bit 30-MS/s pipelined analog-to-digital converter(ADC) is presented.For the sake of lower power and area,the pipelined stages are scaled in current and area,and op amps are shared between the successive stages. The ADC is realized in the 0.13-μm 1-poly 8-copper mixed signal CMOS process operating at 1.2-V supply voltage. Design approaches are discussed to overcome the challenges associated with this choice of process and supply voltage, such as limited dynamic range,poor analog characteristic device... 相似文献
943.
Boryssenko A. O. Liao J. Zeng J. Deng S. Joyner V. M. Huang Z. R. 《Microwave Theory and Techniques》2010,58(2):403-410
944.
Through an investigation of oxygen precipitation and extended defects in Czochralski silicon (CZ-Si) specimens subjected to
different isothermal anneals, by scanning infrared microscopy and preferential etching combined with optical microscopy, the
correlation between the sizes of oxygen precipitates and the generation of extended defects is revealed. It is found that
extended defects are generated when oxygen precipitates grow. Afterward, the sizes of extended defects increase, while those
of oxygen precipitates do not change significantly. For the onset of the generation of extended defects, we define the maximum
size of oxygen precipitates as a critical size for the generation of extended defects. Moreover, it is revealed that this
critical size decreases for higher annealing temperatures or more oxidizing ambients. 相似文献
945.
This paper reports on a theoretical analysis of spin‐Hamiltonian parameters and local lattice structure for Pd(I) center in γ‐irradiated Pd(II)(acac)2. Through the crystal‐ and ligand‐field theory, the microscopic spin‐Hamiltonian parameters and local molecular structure for Pd(I) center in the γ‐irradiated Pd(II)(acac)2 system have been studied by using the high‐order perturbation formulas and Newman's superposition model. Based on these calculations, it was found that the distance of the metal‐ligand bonds in the square planar complex for Pd(I) center in the γ‐irradiated Pd(II)(acac)2 system increases by 0.1Å. To understand the detailed physical and chemical properties of the [Pd(I)(acac)2]2– complex, the contributions of the spin‐orbit coupling of ligand to spin‐Hamiltonian parameters for Pd(I) ion are considered. The theoretical results are in reasonable agreement with the experimental values. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
946.
采用沉淀法与异相共沸蒸馏技术相结合制备了ZnO纳米粉体,并利用X射线粉末衍射、扫描电镜、透射电镜和液氮吸-脱附等技术对制备的样品进行了分析与表征.考察了Pt的负载量、煅烧温度以及牺牲试剂的种类和浓度对制备的纳米ZnO的光催化产氢效率的影响.结果表明:与其他温度下煅烧获得的产物相比,400 oC煅烧产物表现出最佳的光催化产氢效率,且以甲醇为牺牲试剂时纳米ZnO悬浮体系的光催化产氢效率远高于以三乙醇胺为牺牲试剂时的产氢效率.其原因在于光催化过程中甲醇氧化也对体系的产氢有贡献.此外,探讨了基于实验结果对含甲醇的 相似文献
947.
We present a laser architecture to obtain continuous-wave blue radiation at 488 nm. A 808 nm diode-pumped the Nd:YVO4 crystal emitting at 914 nm. A part of the pump power was then absorbed by the Nd:YVO4 crystal. The remaining was used to pump the Nd:YLiF4 (Nd:YLF) crystal emitting at 1047 nm. Intracavity sum-frequency mixing at 914 and 1047 nm was then realized in a BiB3O6 (BiBO) crystal to reach the blue radiation. We obtained a continuous-wave output power of 339 mW at 488 nm with a pump laser diode emitting 18.3 W at 808 nm. 相似文献
948.
The factors affecting performance of fractured wells are analyzed in this work. The static and dynamic geologic data of fractured
well and fracturing treatment parameters obtained from 51 fractured wells in sand reservoirs of Zhongyuan oilfield are analyzed
by applying the grey correlation method. Ten parameters are screened, including penetrability, porosity, net thickness, oil
saturation, water cut, average daily production, and injection rate, amount cementing front spacer, amount sand-carrying agent
and amount sand. With the novel Radial Basis Function neural network model based on immune principles, 13 parameters of 42
wells out of 51 are used as the input samples and the stimulation ratios as the output samples. The nonlinear interrelationship
between the input samples and output samples are investigated, and a productivity prediction model of optimizing fracture
design is established. The data of the rest 7 wells are used to test the model. The results show that the relative errors
are all less than 7%, which proves that the novel Radial Basis Function neural network model based on immune principles has
less calculation, high precision and good generalization ability. 相似文献
949.
Bilateral cochlear implant (BiCI) users gain an advantage in noisy situations from a second implant, but their bilateral performance falls short of normal hearing listeners. Channel interactions due to overlapping electrical fields between electrodes can impair speech perception, but its role in limiting binaural hearing performance has not been well characterized. To address the issue, binaural masking level differences (BMLD) for a 125 Hz tone in narrowband noise were measured using a pair of pitch-matched electrodes while simultaneously presenting the same masking noise to adjacent electrodes, representing a more realistic stimulation condition compared to prior studies that used only a single electrode pair. For five subjects, BMLDs averaged 8.9 ± 1.0 dB (mean ± s.e.) in single electrode pairs but dropped to 2.1 ± 0.4 dB when presenting noise on adjacent masking electrodes, demonstrating a negative impact of the additional maskers. Removing the masking noise from only the pitch-matched electrode pair not only lowered thresholds but also resulted in smaller BMLDs. The degree of channel interaction estimated from auditory nerve evoked potentials in three subjects was significantly and negatively correlated with BMLD. The data suggest that if the amount of channel interactions can be reduced, BiCI users may experience some performance improvements related to binaural hearing. 相似文献
950.
Yang TY Balakrishnan J Volmer F Avsar A Jaiswal M Samm J Ali SR Pachoud A Zeng M Popinciuc M Güntherodt G Beschoten B Özyilmaz B 《Physical review letters》2011,107(4):047206
We report on the first systematic study of spin transport in bilayer graphene (BLG) as a function of mobility, minimum conductivity, charge density, and temperature. The spin-relaxation time τ(s) scales inversely with the mobility μ of BLG samples both at room temperature (RT) and at low temperature (LT). This indicates the importance of D'yakonov-Perel' spin scattering in BLG. Spin-relaxation times of up to 2 ns at RT are observed in samples with the lowest mobility. These times are an order of magnitude longer than any values previously reported for single-layer graphene (SLG). We discuss the role of intrinsic and extrinsic factors that could lead to the dominance of D'yakonov-Perel' spin scattering in BLG. In comparison to SLG, significant changes in the carrier density dependence of τ(s) are observed as a function of temperature. 相似文献