高压高线性度锯齿波电路的设计与实现

本文论述了高线性度锯齿波的产生以及把锯齿波不失真地放大到足够幅度的方法。在输出电压为２５０Ｖ的情况下，非线性误差在１０Ｈｚ时小于５×１０＾－４，１００Ｈｚ时小于１．０×１０＾－３，１００Ｈｚ时小于２．７×１０＾－３。     

高压高线性度锯齿波电路的设计与实现

本文论述了高线性度锯齿波的产生以及把锯齿波不失真地放大到足够幅度的方法。在输出电压为２５０Ｖ的情况下，非线性误差在１０Ｈｚ时小于５×１０－４，１００Ｈｚ时小于１．０×１０－３，１００Ｈｚ时小于２．７×１０－３。     

冷阴极电离真空规中离子能量的分析

利用１２７°电子能且分析器，测量了冷规内部在低压潘宁放电时的离子能量分布。在压强为２．５× １０－４托、冷规阳极电压为１．６千伏时，得到冷规的轴上电位仅３００伏，离子能量峰值的位置为３５７ 电子伏，半宽度为２２电子伏。在３．０× １０－４托时观察到了放电模式的变化。     

关于日本辐射温度计的一些情况（续）

关于日本辐射温度计的一些情况（续）朱其俊（中国测试技术研究院，成都６１００６１）如果温升率在－１／１０到１／５０范围内，即如表３中中温区和高温区比较黑体炉允许的范围，那么，当λＴ０之积从０．５×１０－３变到１０×１０－３·ｋ时，有效温度与Ｔ０之比有异...     

压漏孔校准装置性能测试

正压漏孔校准装置可采用定容法和定量气体动态比较法进行正压漏孔的校准。定容法的校准范围是１００～５ × １０~（－３） Ｐａ· Ｌ／ｓ,不确定度小于９．１０％;定量气体动态比较法的校准范围是１×１０~（－２）～５×１０~（－５）Ｐａ·Ｌ／ｓ,不确定度小于１４．２０％。     

铜在夹封中的出气

本文描述了对铜管在夹封中出气的研究工作。所释气体约为９９．５％的ＣＯ２和０．５％的Ｏ２。气体量随着铜的型号、尺寸以及夹封前对铜管的处理的不同而不同。气体量可以在这样的范围内变化：对于未经清洗和烘烤过的、外径０．２５０时、内径０．１８２时的无氧铜管，是１×１０－６ｃｍ３（ＳＴＰ） ；对于先经化学清洗，后在真空系统中烘烤过的同样的铜管，则有 ３ ×１０－９ｃｍ３（ＳＴＰ）。冷拉管子表现出相同的初始出气量，但甚至在清洗之后仍释气 ３ × １０－８ｃｍ（ＳＴＰ）。（译者注：应是 ３ × １０－８ｃｍ３（ＳＴＰ）之误。）经过细致的处理之后，外径０．１２５时 ×内径０．０８０时的无氧铜管在夹封中释出的ＣＯ２－Ｏ２混合气体少于 ３ × １０－１０ ｃｍ３ （ＳＴＰ）。     

聚苯硫醚合成反应的动力学研究

以脱水硫化钠和对二氯苯为单体，在六甲基磷酰三胺溶剂中常压下研究了聚苯硫醚合成的反应动力学。结果表明，该聚合反应符合二级反应动力学规律，在１８２、１９２、２０２和２１２℃条件下的聚合反应速率常数分别为１．７５×１０~（－４）、３．０２×１０~（－４）、５．５６×１０~（－４）和１．３１×１０~（－３）ｋｇ／ｍｏｌ·ｓ，反应的活化能为１２３ｋＪ／ｍｏｌ。     

改进型分离规

本文描述了一种用于超高真空测量的改进型分离规的设计和特性。栅网的开端结构可防止直接打到离子收集极的ｘ射线，除了那些各电极上反射的少数间接的ｘ射线以外。在相当于残余气体１毫安电子流时，灵敏度系数约为８．３×１０－２Ｐａ－１（１１托－１）。可实现的压强测量范围在 １×１０－６到９×１０－１０Ｐａ（１× １０－８到 ７× １０－ １２托）。业已证实，这种规管的ｘ射线极限低于裸体 Ｂ－Ａ规。文章还叙述了通过把帽电极装在栅网顶部的简化方法，可用于高真空压强测量的改进型规管设计。     

工业铯钟速率变化主要因素的探讨

上海天文台（ＳＯ）原子时实验室的４台工业铯钟１９８３～１９９０年连续工作了４或７年，它们的速率的长期变化与钟房的环境参数和性能参数的变化有关。本文根据有关数据，用不同的方法进行了分析，得到了一些明晰的结果。１）钟的速率变化受湿度的季节性变化影响：在相对湿度变化１％时，Ｃｓ２（１２６７）和Ｃｓ４（１４５７４）的速率变化分别为１．８９５ｕｓ／ｄ（２．２×１０－１４）和０．６１８ｎｓ／ｄ（７．１×１０－１５）。ＳＯ的原子钟房的相对湿度的年变化为２０％～８５％，引起这两台钟的速率年变化分别为１．４３×１０－１２和４．６５×１０－１４２）钟的速率变化受钟的离子泵电流参数的线性变化（从钟束管寿命的中期开始）影响：在离子泵电流参数变化１μＡ时，Ｃｓ３（１６１８０）和Ｃｓｌ（１２９９７）的速率变化分别为０．４３９ｎｓ／ａ（５．０８×１０－１５）和０．５５２ｎｓ／ａ（６．３９×１０－１５）。这两台钟的离子系电流参数的年变化分别为１６．４７μＡ／ａ和６．５３μＡ／ａ，引起的频率漂移率分别为１．６７×１０－１３／ａ（０．０３９５ｎｓ／ｄ２）和８．３×１０１４／ａ（０．０１９７ｎｓ／ｄ２）     

快离子导体Na1＋xZr2—yV0.8ySixP3—xO12系统的制备与电性能研究

Ｎａｓｉｃｏｎ型快离子导体Ｎａ１＋ｘＺｒ２－ｙＭ０．８ｙＳｉｘＰ３－ｘＯ１２系统采用高温固相合成，春合成温度在１３７３Ｋ左右完成，该的合成温度在ｘ不变的情况下，随着ｙ的增大而降低，大多烽合成物为单斜晶系；空间群为Ｃ３／ｃ。当ｙ不变，ｘ增大地基地率的变化是先增大，后减小。最佳导一的起始组成为ｘ＝１．５、ｙ＝０．１，其电导率在室温时为３．２０×１０＾－４Ｓ／ｃｍ，在６７３Ｋ时为６．８８×１０＾－２Ｓ／     

Increased time-constant dual-input integrators

Two active-RC integrators are proposed. They provide ideal integration function realization with dual-input capability, the use of a grounded capacitor, and an increase in time-constant ( tau /sub 0/) over its nominal value ( tau ), which is made possible by a single resistor-controlled multiplier. Sensitivity characteristics of the proposed networks are considered. The integrators have been built in the laboratory with mu A 741 amplifiers and using tau =0.4 mu F*10 k Omega and n=1-10. With square-wave testing under continuous tuning, the expected triangular wave generation was observed at the output (V/sub 0/). The variation of the slope lambda =V/sub 0//t of the rising and falling edges of the output triangular wave for different settings of n has been measured; the results are shown. The differential integration function for each network has been tested by feeding two square-wave inputs of the same magnitude (3.6 V), but different periods; the integrator responses are given.<>     

Optimization of sawtooth surface-relief gratings: effects of substrate refractive index and polarization

The effect of the refractive index of the substrate together with the incident polarization on the optimization of sawtooth surface-relief gratings (SRGs) is investigated. The global optimum diffraction efficiencies of the -1st forward-diffracted order of sawtooth SRGs are 63.3% occurring at n2=1.47 for TE polarization and 73.8% occurring at n2=2.88 for TM polarization. Incident TE polarization has higher optimum diffraction efficiency than TM polarization for all n2<1.85. In contrast, TM polarization has higher optimum diffraction efficiency than TE polarization for all n2>1.85. A polymer (n2=1.5) optimum sawtooth SRG exhibits 62.6% efficiency for TE polarization. A silicon (n2=3.475) optimum sawtooth SRG exhibits 68.6% efficiency for TM polarization. These sawtooth SRGs are compared to right-angle-face trapezoidal SRGs. It is found that the optimum profiles of right-angle-face trapezoidal SRGs have only very slightly increased efficiencies over sawtooth SRGs (0.04% for TE and 0.55% for TM).     

Layered δ-MnO2 as positive electrode for lithium intercalation

Layer structured δ-MnO₂ was synthesized by a microwave-assisted hydrothermal method. The morphology of the product consists of flower-like spheres that range from about 200 nm to 3 μm in diameter and are composed of sheets about 5-10 nm in thickness. When tested in the voltage range of 2 to 4.5 V vs. Li⁺/Li in coin cells, the separator is blocked, handicapping Li⁺ conductivity and leading to cell failure. When tested in the voltage range of 2 to 4 V in ethylene carbonate/dimethyl carbonate (EC/DMC), the δ-MnO₂ delivers an initial reversible capacity of 143.7 mAh g⁻¹ and can maintain 120 mAh g⁻¹ at the 60th cycle. The δ-MnO₂ electrode shows good cycling stability at different current densities and delivers a discharge capacity of about 90 mAh g⁻¹ at 1 C, indicating that it is a promising cathode material for lithium ion batteries.     

The influence of skin depth on crack measurement by the ac field technique

A general solution is given to describe the ac field around surface-breaking cracks for arbitrary values of the ratio of skin depth δ to crack depthd. This solution allows accurate interpretation of crack depth from voltage readings taken by a Crack Microgauge instrument in cases where δ andd are comparable. It is shown to agree with asymptotic formulae obtained for the cases where δ/d is very small and very large. Provided that the probe length Δ is large compared with δ, the calculations show that a very good approximation to the crack depth may be obtained, irrespective of the ratio δ/d, by using the thin-skin asymptotic formula $$d = \frac{1}{2}\Delta (V_2 - V_1 )/V_1 $$ whereV ₁ andV ₂ are probe voltages registered at positions just off and across the crack, respectively. The problem is solved for a crack of infinite aspect ratio which has no opening, but it can be applied with confidence at the centerline of cracks of fairly large aspect ratio.     

Classification of 2 × 2 non-strictly hyperbolic systems for plane waves in isotropic elastic solids

The governing equations for plane waves in generally nonlinear isotropic elastic solids are a system of 6 × 6 hyperbolic conversation laws. For the half-space Riemann problem in which the initial conditions at t = 0, x > 0 and the boundary conditions at x = 0, t > 0 are constant, the system is equivalent to 3 × 3 system in the full-space Riemann problem. It is further reduced to a 2 × 2 system due to the fact that one of the characteristic wave speeds is linearly degenerate. For hyperelastic materials for which there exists a potential W whose gradients provide the strains, the wave curves near an isolated umbilic point are represented by the potential of the form

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which contains two parameters k and m. The classification of the geometry of wave curves depends on the values of k and m and can be classified into five cases. The potential function considered here is equivalent to considered by Schaeffer and Shearer where a and b are parameters. The classification presented here seems to provide simpler algebraic expressions. It also renders more refined classification as shown in the paper.     

Heterovalent cation substitutions in the layered compound YBaCuFeO<Subscript>5 + δ</Subscript>

(Y,M)BaCuFeO_{5 + δ} (M = Ce, Ca, Na), Y(Ba,K)CuFeO_{5 + δ}, YBa(Cu,Co)FeO_{5 + δ}, YBaCu(Fe,M)O_{5 + δ} (M = Zn, Nb), (Y,Ca)BaCu(Fe,Zn)O_{5 + δ}, and (Y,Ca)(Ba,La)Cu(Fe,Zn)O_{5 + δ} solid solutions have been prepared by ceramic processing techniques and have been characterized by x-ray diffraction, IR absorption spectroscopy, and thermal expansion and electrical conductivity (σ) measurements in air at temperatures from 300 to 1100 K. It is shown that, in the range 650–700 K, the linear thermal expansion coefficient of the (Y,M)BaCuFeO_{5 + δ} phases rises from (11–12) × 10^?6 to (14–15) × 10^?6 K^?1, while that of the YBa(Cu,Co)FeO_{5 + δ} solid solution decreases from 18 × 10^?6 to 14 × 10^?6 K^?1. The conductivity data (an increase in σ upon Ca²⁺ → Y³⁺ and Zn²⁺ → Fe³⁺ substitutions and a reduction in σ upon Ce⁴⁺ → Y³⁺ and Nb⁵⁺ → Fe³⁺ substitutions) demonstrate that the transport properties of YBaCuFeO_{5 + δ} can be tuned by electron-hole doping.     

Determination of the elastic properties of a barrier film on aluminium by Brillouin spectroscopy

The surface wave dispersion for a barrier oxide film on aluminium has been determined from surface Brillouin scattering measurements carried out on films of thicknesses of 0.2, 0.35 and 0.45 μm. The measured velocities of the generalised Rayleigh mode, the pseudo interfacial mode and of several Lamb modes conform to simulations performed for stiffening layers [1]. The longitudinal velocity and the shear velocity of the layer have been calculated from the experimental dispersion curve.     

Vertical MOS-gated pin-diodes: MOS-gated tunneling transistors in Si(100) and Si(111)

Tunneling devices are an interesting alternative to conventional MOS-devices due to their high speed switching capabilities. Recently, it was shown that tunneling transistors based on vertical MOS-gated pin-diodes can be fabricated. The pin-diodes themselves were grown by means of UHV-MBE on highly n⁺-doped Si(100)-substrates with a 100 nm thick intrinsic channel region. The top contact was formed by the deposition of a highly-doped B δ-layer with a peak doping amount of approximately 10²¹ cm⁻³ for the necessary abrupt pn-junction and 300-nm p⁺-contact region. At a low supply voltage of −0.2 V, a current gain of three orders of magnitude with saturation behavior is achieved [1]. In the present contribution, we have shown the influence of the amount of B in the δ-layer and of the abruptness of the drain-channel-junction on the transistor behavior. For that, we have discussed the characteristics of MOS-gated pin-diodes on Si(111) with ultra-sharp B δ's with a peak doping amount between 10²⁰ and 10²¹ cm⁻³ and a peak width <3 nm, in comparison with MOS-gated pin-diodes on Si(100) presented in Hansch et al. [1]. In order to obtain these highly doped ultra-sharp B δ-layers, a phase-transition from an electrically inactive Si(111)- -R30° B surface phase into an electrically active one was induced by rapid thermal annealing.     

High-sensitivity bolometers from self-oriented single-walled carbon nanotube composites

In this work, films of horizontally aligned single-walled carbon nanotubes were thermally and electrically characterized in order to determine the bolometric performance. An average thermal time constant of τ = 420 μs along with a temperature coefficient of resistance of TCR = -2.94% K(-1) were obtained. The maximum voltage responsivity and detectivity obtained were R(V) =230 V/W and D* = 1.22 × 10(8) cm Hz(1/2)/W, respectively. These values are higher than the maximum voltage responsivity (150 V/W) and maximum temperature coefficient of resistance (1.0% K(-1)) previously reported for carbon nanotube films at room temperature. The maximum detectivity was obtained at a frequency of operation of 1.25 kHz.     

Tunning pore filling of anodic alumina templates by accurate control of the bottom barrier layer thickness

The role of the alumina barrier layer thickness (δ(b)) on the growth of Ni nanowires (NWs) in porous anodic alumina (PAA) has been revealed. By varying the final anodization voltage to form dendrites at the bottom of the nanoporous structure, we are able to optimize δ(b) (in the 2-16 nm range), allowing us to obtain a Ni pore filling percentage (f(p)) of almost 100% for δ(b) = 10 nm. However, deviations from this optimal δ(b)-value led to a strong decrease of f(p). Moreover, an increase of the electrodeposition efficiency (EE) and NW homogeneity was also verified for δ(b) up to 10 nm. Such increase in nominal δ(b) leads to a consistent growth rate in all pores and consequently a complete and uniform nanopore filling. On the other hand, the decrease in electrodeposition efficiency visible for δ(b) > 10 nm is related with hydrogen evolution and dielectric breakdown of the insulator layer due to the required high deposition voltages. Non-uniform NW growth is then visible, with the consequent decrease in f(p). The control of the pore filling and length homogeneity of the fabricated 1D metallic nanostructures, combined with the ability to adjust the pore dimensions of PAA, can bring novel approaches for the fabrication of nano-objects and thus exciting new applications.