Testing interconnections to static RAMs

A method for testing the interconnections of ordinary static RAMs with a processor that has a boundary-scan register and an IEEE 1149.1 test-access port is described. The method uses an enhanced boundary-scan-register design that manipulates the test-access-port controller states to meet the static RAM's timing constraints. The implementation is more economical than a boundary-scan register that strictly conforms to IEEE 1149.1. Test operation is more efficient, requiring a third of the number of scan operations. A test-pattern set and a method for detecting and diagnosing the interconnection faults on RAMs are also described. The test-pattern set can be enhanced as necessary to increase coverage and diagnosing ability and to handle any RAM configuration. The implementation of the proposed boundary-scan register is independent of the test algorithm used. It is believed that the methodology is extendable to RAMs that use an access protocol different from the one described, for example dynamic RAMs and synchronous RAMs     

The influence of annealing on the conductivity of magnesium films

Polycrystalline magnesium films were deposited under ultrahigh vacuum by thermal evaporation onto a cooled silica substrate. During the growth process of a film a number of lattice defects are incorporated. It was found that the defect density decreases with increasing thickness. An annealing study of the electrical resistance and defect density in magnesium films was made. The results were interpreted on the basis of Vand's theory. The function F₀ expressing the law of distribution of the decay energies exhibited a maximum. For thick films there was no appreciable variation in the activation energy with thickness. In this case the evaluated activation energy E was found to be about 0.35 eV. For very thin films this energy decreases with increasing thickness.     

Investigations of high-performance GaAs solar cells grown on Ge-Si/sub 1-x/Ge/sub x/-Si substrates

High-performance p/sup +//n GaAs solar cells were grown and processed on compositionally graded Ge-Si/sub 1-x/Ge/sub x/-Si (SiGe) substrates. Total area efficiencies of 18.1% under the AM1.5-G spectrum were measured for 0.0444 cm/sup 2/ solar cells. This high efficiency is attributed to the very high open-circuit voltages (980 mV (AM0) and 973 mV (AM1.5-G)) that were achieved by the reduction in threading dislocation density enabled by the SiGe buffers, and thus reduced carrier recombination losses. This is the highest independently confirmed efficiency and open-circuit voltage for a GaAs solar cell grown on a Si-based substrate to date. Larger area solar cells were also studied in order to examine the impact of device area on GaAs-on-SiGe solar cell performance; we found that an increase in device area from 0.36 to 4.0 cm/sup 2/ did not degrade the measured performance characteristics for cells processed on identical substrates. Moreover, the device performance uniformity for large area heteroepitaxial cells is consistent with that of homoepitaxial cells; thus, device growth and processing on SiGe substrates did not introduce added performance variations. These results demonstrate that using SiGe interlayers to produce "virtual" Ge substrates may provide a robust method for scaleable integration of high performance III-V photovoltaics devices with large area Si wafers.     

Conduction band states of transition metal (TM) high-k gate dielectrics as determined from X-ray absorption spectra

This paper uses X-ray absorption spectroscopy to study the electronic structure of the high-k gate dielectrics including TM and RE oxides. The results are applicable to TM and rare earth (RE) silicate and aluminate alloys, as well as complex oxides comprised of mixed TM/TM and TM/RE oxides. These studies identify the nature of the lowest conduction band d^* states, which define the optical band gap, E_g, and the conduction band offset energy with respect to crystalline Si, E_B. E_g and E_B scale with the atomic properties of the TM and RE atoms providing important insights for identification high-k dielectrics that meet performance targets for advanced CMOS devices.     

Strain-induced corrosion cracking of low-alloy steels in LWR systems — case histories and identification of conditions leading to susceptibility

The term “strain-induced corrosion cracking” (SICC) is introduced to describe crack formation involving dynamic straining, but in the absence of obvious, cyclic loading. Its origins in slow-strain-rate testing and in corrosion failures in boiler systems are described and the links with “classical” stress corrosion cracking and low-cycle corrosion fatigue are identified. Four areas, in which SICC of low-alloy steels in LWR systems has occurred, are described in detail and the typical features are used, together with literature data from laboratory testing, to identify conditions leading to susceptibility. Indications are given of remedial measures and of areas in which further work is necessary.     

Effect of the magnetic-flux variations on SQUID stability

The oscillation dynamics of a nonhysteretic, one-contact superconducting quantum interferometer under low-frequency modulation of an external magnetic flux has been studied. It is shown that even in the case of adiabatic, equilibrium, and nonhysteretic operation modes of a superconducting ring enclosed by a weak link, there can appear chaotic oscillations. The conditions of chaos arising have been considered analytically and numerically; mechanisms and destruction scenarios of periodic oscillations have been studied. The stochastic instability could impose limitations on the increase in sensitivity of nonhysteretic SQUIDs, which was earlier predicted to be high enough.     

On certain classes of exact solutions of Einstein equations for rotating fields in conventional and nonconventional form

Using the symmetry reduction approach we have herein examined, under continuous groups of transformations, the invariance of Einstein exterior equations for stationary axisymmetric and rotating case, in conventional and nonconventional forms, that is a coupled system of nonlinear partial differential equations of second order. More specifically, the said technique yields the invariant transformation that reduces the given system of partial differential equations to a system of nonlinear ordinary differential equations (nlodes) which, in the case of conventional form, is reduced to a single nlode of second order. The first integral of the resulting nlode has been obtained via invariant-variational principle and Noether’s theorem and involves an integration constant. Depending upon the choice of the arbitrary constant two different forms of the exact solutions are indicated. The generalized forms of Weyl and Schwarzschild solutions for the case of no spin have also been deduced as particular cases. Investigation of nonconventional form of Einstein exterior equations has not only led to the recovery of solutions obtained through conventional form but it also yields physically important asymptotically flat solutions. In a particular case, a single third order nlode has been derived which evidently opens up the possibility of finding many further interesting solutions of the exterior field equations.     

Generalized Nakagami-m phase crossing rate

This paper provides simple, exact, new closed-form expressions for the generalized phase crossing rate of Nakagami-m fading channels. Sample numerical results obtained by simulation are presented that validate the formulations developed here. A special case of this formulation is the Rayleigh case, whose result agrees with that obtained elsewhere in the literature. In passing, several new closed-form results concerning the statistics of the envelope, its in-phase and quadrature components, phase, and their time derivatives are obtained.     

Exciton-polariton transition induced by elastic exciton-exciton collisions in ultrahigh quality AIGaAs alloys

The stationary and time-resolved polariton radiation in ultrahigh quality AIGaAs layers have been studied. It has been found that elastic exciton-exciton collisions lead to the appearance of a low-energy line of polariton radiation. We show that the rate of exciton-to-polariton transitions caused by elastic exciton-exciton collisions is determined not only by the density of the excitonic gas, but also by its temperature; this is in accordance with existing theoretical predictions. The text was submitted by the authors in English.     

不同施钾水平对玉米干物质及产量的影响

生物产量是提高经济产量的基础,而施肥是调控生物产量及其组分动态转化的重要手段。本研究通过不同施钾水平对玉米干物质积累动态变化的影响分析,确定出钾肥合理用量,为玉米高产高效栽培提供理论依据。