The Solutions for Adjustment and Reconstruction of Water-Drive Surface Systems in the Old Areas of Daqing Oilfield

Introduction 　　Owing to long-time running, more facilities including stations, pipelines, vessels have become corrosive and aged ,some process has grown old, it has exert more burden for the maintenance and repair.Simultaneously, the fluid production rate, oil production rate and water injection rate has changed greatly so that the inflicts and problems from the established surface systems will become more obvious. Energy cost of production and running has increasing continuously. Capacity has been unbalance in systems and areas. 　　……     

Discussion of "Hybrid-secondary-uncluttered induction (HSU-I)machine" [and closure]

J. Perahia comments on the paper by J. S. Hsu (see ibid., vol.16, p.192-7, 2001) and expands on the case of a two stator three phase squirrel cage induction machine where one stator housing is stationary and other stator housing is mounted on a worm gear assembly. The original author replies to the comments     

Changes in Lake Ontario Total Phosphorus Concentrations 1976–1978

An apparent decrease in total phosphorus concentrations of approximately 4.l μgP/L has been reported recently for the spring values of 1977 and 1978 in Lake Ontario. Investigation of the loading reduction for this period independent of sedimentation factors can account for only 10% of the change. The results indicate that changes in the sedimentation rate of total phosphorus during this period offer an explanation for the majority of the change in concentration.     

Dynamical considerations of network properties

Elasticity is discussed as an aspect of viscoelasticity, which is described by the tube model. The effects of both crosslinks and entanglements contribute to this model and a discussion of how these effects can be quantified is given. At high enough concentration, entanglements ensure the existence of elastic effects even without crosslinks, and a theory is presented on how this dynamical phase change comes about.     

The effects of pressure on the isothermal fluid behavior of bituminous coals

An investigation into the effects of pressure (helium gas) on the isothermal fluid behavior includes: (1) the effect of pressure on the rate of melting and coking as evidenced by the rate constants k(melt) and k(coke); (2) the effect of pressure on the energies of activation of melting and coking; (3) the effects of pressure on the characteristic times; (4) the effects of pressure on the maximum isothermal fluidity. Results from the effects of pressure on k(melt) revealed that it was generally the high total sulfur, low nitrogen, low reactives/mineral matter ratio, medium rank coals which show the greatest increase in k(melt), whereas the highest rank coals show the least decrease in k(coke). The energies of activation of melting and coking were not significantly affected by pressure. The investigation also reveals increases or decreases in the respective times of softening, maximum fluidity, resolidification and total time of fluid behavior under isothermal pressurized conditions. There appears the possibility that these shifts may be rank dependent. Additionally, the lower rank coals show the largest relative increase in their fluidities when subjected to pressure. Empirical relationships were derived in order to quantitatively predict the maximum isothermal fluidity for most (fluid) coals at a given pressure.     

Performance engineering and topological design of metro WDM opticalnetworks using computer simulation

This paper demonstrates the use of computer simulation for topological design and performance engineering of transparent wavelength-division multiplexing metropolitan-area networks. Engineering of these networks involves the study of various transport-layer impairments such as amplifier noise, component ripple, chirp/dispersion, optical crosstalk, waveform distortion due to filter concatenation, fiber nonlinearities, and polarization effects. A computer simulation methodology composed of three main simulation steps is derived and implemented. This methodology obtains performance estimations by applying efficient wavelength-domain simulations on the entire network topology, followed by time-/frequency-domain simulations on selected paths of the network and finally Q-budgeting on an identified worst case path. The above technique provides an efficient tool for topological design and network performance engineering. Accurate simulation models are presented for each of the performance impairments, and the computer simulation methodology is used for the design and engineering of a number of actual metro network architectures     

Systematic characterization of Cl2 reactive ion etchingfor improved ohmics in AlGaN/GaN HEMTs

Pre-metal-deposition reactive ion etching (RIE) was performed on an Al_0.3Ga_0.7N/AlN/GaN heterostructure in order to improve the metal-to-semiconductor contact resistance. An optimum AlGaN thickness for minimizing contact resistance was determined. An initial decrease in contact resistance with etching time was explained in terms of removal of an oxide surface layer and/or by an increase in tunnelling current with the decrease of the AlGaN thickness. The presence of a dissimilar surface layer was confirmed by an initial nonuniform etch depth rate. An increase in contact resistance for deeper etches was experienced. The increase was related to depletion of the two-dimensional (2-D) electron gas (2-DEG) under the ohmics. Etch depths were measured by atomic force microscopy (AFM). The contact resistance decreased from about 0.45 Ωmm for unetched ohmics to a minimum of 0.27 Ωmm for 70 Å etched ohmics. The initial thickness of the AlGaN layer was 250 Å. The decrease in contact resistance, without excessive complications on device processing, supports RIE etching as a viable solution to improve ohmic contact resistance in AlGaN/GaN HEMTs     

New insights in polarity-dependent oxide breakdown for ultrathin gate oxide

In this work, a quantitative analysis is applied to resolve the newly reported polarity-dependent charge-to-breakdown (Q/sub BD/) data from thick oxides of 6.8 nm down to ultrathin oxides of 1.9 nm. Three independent sets of Q/sub BD/ data, i.e., n/sup +/poly/NFET stressed under inversion and accumulation, and p/sup +/ poly/PFET under accumulation are carefully investigated. The Q/sub BD/ degradation observed for p-type anodes, either poly-Si or Si-substrate, can be nicely understood with the framework of maximum energy released by injected electrons. Thus, this work provides a universal and quantitative account for a variety of experimental observations in the time-to-breakdown (T/sub BD/) and Q/sub BD/ polarity-dependence of oxide breakdown.