聚乙烯醇凝胶堵漏剂的室内研究

为解决地质钻孔钻井液漏失的问题,研制了一种新型堵漏剂——聚乙烯醇凝胶堵漏剂,该堵漏剂由聚乙烯醇、硼砂、二丁酯、羧甲基纤维素钠等化学交联反应而成。根据地质钻探钻孔堵漏材料性能的要求,对该堵漏剂进行了成胶时间、成胶黏度、溶胀性、抗稀释性、抗矿化物污染、堵漏等实验。结果表明:(1)当聚乙烯醇为3%、硼砂为0.8%、二丁酯为0.3%、羧甲基纤维素钠为0.3%、交联温度为35℃、p H值为10时,制备的聚乙烯醇凝胶堵漏剂性能为最好,成胶黏度达358 600 m Pa·s,成胶时间为18min;(2)成胶时间在0.1~1.0 h范围内可调,对不同大小通道适宜性好;(3)单独的凝胶堵漏剂最大承压能力达到6.0 MPa,加入1%木屑后最大承压能力提高到7.0 MPa,具有很好的堵漏效果。结论认为,所研制的聚乙烯醇凝胶堵漏剂具有较强的溶胀度、抗稀释、抗矿化物污染和堵漏能力,并且制备方便、价格低廉,可应用于裂缝、溶洞、孔隙及含有动水的复杂漏失地层。     

Optical gain of strained wurtzite GaN quantum-well lasers

A theory for the electronic band structure and the free-carrier optical gain of wurtzite-strained quantum-well lasers is presented. We take into account the strain-induced band-edge shifts and the realistic band structures of the GaN wurtzite crystals. The effective-mass Hamiltonian, the basis functions, the valence band structures, the interband momentum matrix elements, and the optical gain are presented with analytical expressions and numerical results for GaN-AlGaN strained quantum-well lasers. This theoretical model provides a foundation for investigating the electronic and optical properties of wurtzite-strained quantum-well lasers.     

Access algorithm for packetized wireless transmission in thepresence of cochannel interference

Packetized access has some potential advantages over conventional circuit-switched-based access methods because several signal sources can share the same radio channel using statistical multiplexing. We consider radio resource assignment algorithms for packetized access based on the packet-reservation multiple-access (PRMA) protocol in the presence of cochannel interference. The statistical multiplexing gain of packet access is limited by frequency reuse, especially when the reuse factor is low or duality requirement is high. We propose a fuzzy logic-based adaptive medium-access control (MAC) algorithm to improve packet-access efficiency. Computer simulations based on the example of packetized voice have confirmed that the proposed packet-access protocol can support a higher number of active users per radio port than that supported by random slot assignment     

Redshifting and broadening of quantum-well infrared photodetector'sresponse via impurity-free vacancy disordering

The partial intermixing of the well and barrier materials offers unique opportunities to shift locally the bandgap of quantum-well (QW) structures. We have demonstrated redshifting and broadening of the wavelength responses of bound-to-continuum GaAs and InP based quantum-well infrared photodetectors (QWIP's) after growth via impurity-free vacancy disordering (IFVD). A comprehensive set of experiments is conducted on QWIP's fabricated from both as-grown and multiple-quantum-well (MQW) structures. Compared to the as-grown detector, the peak spectral responses of the disordered detectors were shifted to longer wavelengths. The peak absolute response of the disordered GaAs based QWIP is lower by almost a factor of four. However, the responsivity characteristics of the disordered InP based QWIP show no major degradation. In general, with the spectral broadening taken into account, the overall performance of the disordered QWIP's has not dropped significantly. Thus, the postgrowth control of the QW composition profiles by impurity-free vacancy disordering offers unique opportunities to fine tune various aspects of a photodetector's response. Theoretical calculations of the absorption coefficient spectrum are in excellent agreement with the experimental data     

Magnetic contributions to the thermodynamic functions of pure Ni,Co, and Fe

An empirical mathematical equation is proposed for the magnetic contribution to the specific heat of pure metals. The corresponding functions for enthalpy, entropy, and Gibbs energy are of simple form. Two parameters used for each element are the critical temperature,T _c, and the total magnetic entropy. The parameters have been determined from a careful separation of magnetic and nonmagnetic contributions to the specific heat. Debye temperatures for Ni, Co, and Fe have been determined considering data to much higher temperatures than other studies. The magnetic specific heats extracted from experimental data agree very well with the proposed equation over the entire temperature range and for all three elements. Comparisons with different mathematical functions found in the literature give agreement only for the case of iron. The total magnetic entropy given by a classical relation is found to be high, and a quantitative correction is given. Various magnetic standard states are discussed. The lattice stabilities of bcc- and fcc-iron are calculated assuming that the difference of the nonmagnetic specific heats is linear from 500 K to 1810 K. A simple equation is obtained in which the anomalous temperature dependence is explained by the independently determined magnetic contribution. The calculated values agree very well with Orr and Chipman’s assessment. The stability of bcc iron at low temperatures is quantitatively rationalized.     

GDP dissociation inhibitor prevents intrinsic and GTPase activating protein-stimulated GTP hydrolysis by the Rac GTP-binding protein

The majority of the GTP-binding proteins of the Ras superfamily hydrolyze GTP to GDP very slowly. A notable exception to this are the Rac proteins, which have intrinsic GTPase rates at least 50-fold those of Ras or Rho. A protein (or proteins) capable of inhibiting this GTPase activity exists in human neutrophil cytosol. Since Rac appears to exist normally in neutrophils as a cytosolic protein complexed to (Rho)GDI, we examined the ability of (Rho)GDI to inhibit GTP hydrolysis by Rac. (Rho)GDI produced a concentration-dependent inhibition of GTP hydrolysis by Rac1 that paralleled its ability to inhibit GDP dissociation from the Rac protein. Maximal inhibition occurred at or near equimolar concentrations of the GDI and the Rac substrate. The ability of two molecules exhibiting GTPase activating protein (GAP) activity toward Rac to stimulate GTP hydrolysis was also inhibited by the presence of (Rho)GDI. The inhibitory effect of the GDI could be overcome by increasing the GAP concentration to levels equal to that of the GDI. (Rho)GDI weakly, but consistently, inhibited GTP gamma S (guanosine 5'-3-O-(thio)triphosphate) dissociation from Rac1, confirming an interaction of (Rho)GDI with the GTP-bound form of the protein. These data describe an additional activity of (Rho)GDI and suggest a mechanism by which Rac might be maintained in an active form in vivo in the presence of regulatory GAPs.     

The extraction of platinum from Pt(II) chloride solution by a quaternary ammonium compound

The fundamental aspects of the extraction and stripping of platinum (II) from its chloride solution by Aliquat 336 diluted with toluene have been studied. The extraction and stripping was at 99.5 and 97.6% equilibrium within 30 s and 20 min respectively. The percentage extraction increased slightly with decreasing hydrochloric acid concentration. In 0.1 mol dm^?3 hydrochloric acid, 1.0 volume percent Aliquat 336 in toluene could load 9.8 mmol dm^?3 of platinum (II). The percentage stripping of platinum (II) from Pt(II)-load organic solvent increased with increasing sodium bisulphite concentration. The enthalpy changes of extraction and of stripping were 12.8 and 114.9 kJ mol^?1 respectively. Both of the reactions were endothermic.     

Soft-output equalization and TCM for wireless personalcommunication systems

This paper investigates the use of a maximum a posteriori probability (MAP) algorithm to realize soft-output equalization in a concatenated equalization and trellis-coded modulation (TCM) decoding-based wireless communication system. Specifically, we first begin with a general MAP algorithm and then focus on studying Bahl's (1974) MAP and Lee's (1974) MAP algorithms. We then propose a modified version of Lee's MAP algorithm which is much simpler than the original, in terms of complexity, and is more practical. In particular, a very simple channel estimation method which employs orthogonal training sequences is proposed. In order to improve the system performance, equal-gain combining and selection diversity are also considered. Finally, we compare the performance of the MAP algorithm-based equalization with our previously proposed equalization scheme, which combines decision feedback equalization and TCM     

Identification of heat load loops and downstream paths in heat exchanger networks

To achieve the optimal trade-off between economies and operability, simplifications of heat exchanger networks (HENs) are required. To do so, identifications of heat load loops and downstream paths are necessary. This paper proposes new methods for identifications of independent and dependent loops as well as downstream paths in HENs, respectively. Stream table and node adjacency matrix are defined in this paper to represent the structures of HENs. Based on graph theory, identification of loops in HENs is decomposed into three procedures: (a) finding a maximal tree, (b) identifying a maximal set of independent loops and (c) searching all loops. Locating the downstream paths in HENs is accomplished by finding directed trees which are generated by modifying the procedure for finding a maximal tree. A complex network with a splitting stream is used for detailed illustrations of the procedures.     

规格说明语言ChiSL

ＣｈｉＳＬ是一种作用式可执行的功能规格说明语言，它是以数据抽象为核心的将代数规格说明和面向模型的规格说明两种技术有机地结合起来的模块化语言，具有良好的数据性质和可读性，能比较方便地书写大型规格说明?由于该语言是可执行的，因此ＣｈｉＳＬ规格说明可作为所要开发的软件系统的一个原型在该语言的支撑系统上执行。本文后面介绍了使用ＣｈｉＳＬ语言及其支撑系统开发软件原型的一些应用实例。