如何加强信号路径的性能

为传感器提供缓冲 若传感器无法驱动模拟/数字转换器的电容负载,可以利用运算放大器为其提供缓冲.由于许多应用系统都规定只可采用一个电源供应,因此所选运算放大器的工作电压必须与模拟/数字转换器的电压相同,这一点非常重要.虽然共用供电电压有助于精简系统设计,节省成本,但运算放大器因为受供电电压的掣肘,以致其输入输出能力无法得到充分发挥.以ADC121S101为例,由于芯片的参考电压（VREF）也同时是供电电压,因此选用设有轨到轨输出（RRO）功能的运算放大器如LMP2011较为理想.     

Rheumatoid arthritis treated with chlorambucil: a five-year follow-up

Tympanotomy and a transvestibular approach to the fundus of the internal auditory meatus is described. The surgical technique is modified from that proposed by Alvarez de Cozar and Antoli-Candela in 1970. The surgical anatomy of the operative sites is detailed. The surgical procedure is found indicated in patients in whom preservation of hearing is not considered and vestibular neurectomy required. The described technique provides a simple but efficient and safe alternative to the translabyrinthine approach to the internal auditory meatus for division of the vestibular and cochlear nerves.     

Duration illusion and auditory grouping in infancy.

Extended previous research on perceptual grouping in infancy (Thorpe, Trehub, Morrongiello, & Bull, 1988). Infants' detection of temporal increments to silent intervals between groups of tones was compared with their detection of comparable silent increments within groups of tones. Ss were presented with standard 6-tone sequences, with the first 3 tones differing from the last 3 in harmonic structure, frequency, or intensity, and contrasting sequences with increments of 80 or 100 ms to the silent interval between the 3rd and 4th tone (XXX OOO, between groups) or between the 4th and 5th tone (XXXO OO, within group). Infants discriminated temporally altered sequences from the standard only when the increments occurred within a group. The authors conclude that perceptual grouping processes are operative in infancy and that infants perceive the silent increments between groups of sounds as longer than identical intervals within a group, as do adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Radiation-Induced Changes in the Photoluminescence Spectra of Cadmium Sulfide

Radiation-induced changes in the photoluminescence spectra of cadmium sulfide have been measured over a wavelength range from 4800 to 5400 ?. Gamma-ray induced changes in the 4.2°K photoluminescence spectra show a reduction in intensity of bound exciton transitions I1 and I5 and edge emission in contrast to an enhancement of a spectral line at 4867.2 ? (which we designate as IR). These changes were measured for irradiation temperatures of 300°, 78°, and 4.2°K. The 78°K photoluminescence shows that exciton emission is more sensitive to radiation-induced changes than is edge emission. Thermal annealing takes place below room temperature, particularly in the 140° to 260°K region. The sensitivity of the luminescence intensity to radiation exposure only at cryogenic temperature anid the thermal annealing of the radiation-induced changes are attributed to the mobility of defects at and below room temperature. Studies of polarized luminescence and the temperature dependence of the luminescence show that IR is like the I2; exciton lines. Optical quenching at 4.2°K indicates that the defect responsible for IR is sensitive to its charge state. The results of electron exposures at various energies at approximately 90°K show that IR is associated with a sulfur defect, possibly SI     

The Fe-rich corner of the metastable C-Cr-Fe liquidus surface

The liquidus surface of the C-Cr-Fe system has been experimentally determined in the Fe-rich region —C ≤6 wt pct, Cr ≤40 wt pct —using a sensitive differential thermal analysis technique, along with optical and scanning electron microscopy and X-ray diffraction. Previous liquidus surfaces for this system have differed on the extent of the (Cr,Fe)₂₃C₆ liquidus field, with one version reporting its existence at ∼20 wt pet Cr, and others finding that it did not occur at Cr levels of less than ∼60 wt pct. The present investigation provides evidence in favor of the second contention, with the (Cr,Fe)₂₃C₆ field not being detected at Cr ≤40 wt pct. Changes are proposed to the accepted liquidus surface in respect of the compositions of the invariant reactions—L + αδFe ⇌γFe + (Cr,Fe)₇C₃ andL + (Cr,Fe)₇C₃ ⇌γFe + (Fe,Cr)₃C —and of the monovariant eutectic valley—L⇌ γFe + (Cr,Fe)₇C₃.     

Improving inter-destination synchronization in hierarchical reliable multicast

In hierarchical reliable multicast schemes, the number of repair proxies and their locations influence inter-destination synchronization. The inter-destination synchronization in multicast environments means the adjustment of the output timing among destinations over the Internet. Improving the inter-destination synchronization is beneficial to collaborative applications such as multi-conference system and multi-playing online game. In this paper, we propose a scheme to find the optimal locations of repair proxies that can improve inter-destination synchronization maximally in heterogeneous network environments. The simulation results show that if repair proxies are placed by the proposed scheme, delivery delay fairness of inter-destination can be improved by 0.05 maximally. In addition, we perform t-Test on the simulation results in order to verify that our optimal placement improves synchronization.     

Development of a Position Sensitive Neutron Detector with High Efficiency and Energy Resolution for Use at High-Flux Beam Sources

We are developing a high-efficiency neutron detector with 1 cm position resolution and coarse energy resolution for use at high-flux neutron source facilities currently proposed or under construction. The detector concept integrates a segmented ³He ionization chamber with the position sensitive, charged particle collection methods of a MicroMegas detector. Neutron absorption on the helium produces protons and tritons that ionize the fill gas. The charge is amplified in the field region around a wire mesh and subsequently detected in current mode by wire strips mounted on a substrate. One module consisting of a high-voltage plate, a field-shaping high-voltage plate, a grid and wire strips defines a detection region. For 100 % efficiency, detector modules are consecutively placed along the beam axis. Analysis over several regions with alternating wire strip orientation provides a two-dimensional beam profile. By using ³He, a 1/v absorption gas, each axial region captures neutrons of a different energy range, providing an energy-sensitive detection scheme especially useful at continuous beam sources.