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981.
A new symbolic technique for the realization of simulators for nonlinear analog circuits is presented. The generated simulators work with input/output in numerical form, but they are very efficient due to the use of the symbolic approach. For nonlinear components a PWL (PieceWise Linearization) method is used. The proposed approach permits to obtain libraries of simulators which can be very useful in many application fields. In particular we present a possible application to an expert system devoted to nonlinear circuit fault diagnosis. The program package, realized for this application, is described from both algorithmic and functional points of view. Some simple examples are presented in order to illustrate the main features of the program.1. We are supposing that all the nonlinear elements are represented by a characteristic of the kindI =G(V) 相似文献
982.
In order to study the possible relationship between gene amplification and DNA repair we analyzed the amplification of the CAD gene in four mutants hypersensitive to UV light (CHO43RO, CHO7PV, UV5 and UV61) isolated in vitro from Chinese hamster cell lines (CHO-K1 and AA8). These mutants are characterized by different defects in the nucleotide excision repair mechanism and represent complementation groups 1, 9, 2, and 6 respectively. To evaluate the amplification ability of each cell line we measured the rate of appearance of PALA resistant clones with the Luria and Delbrück fluctuation test. Resistance to PALA is mainly due to amplification of the CAD gene. In the mutants CHO43RO, UV5 and CHO7PV we reproducibly found an amplification rate lower than in the parental cell lines (2-5 times), while in UV61 the amplification rate was about 4 times higher. This result indicates that each mutant is characterized by a specific amplification ability and that the unefficient removal of UV induced DNA damage can be associated with either a higher or a lower amplification rate. However, the analysis of randomly isolated CHO-K1 clones with normal UV sensitivity has shown variability in their amplification ability, making it difficult to relate the specific amplification ability of the mutants to the DNA repair defect and suggesting clonal heterogeneity of the parental population. 相似文献
983.
Eynard C. Lenti M. Lombardo A. Marengo O. Palazzo S. 《Selected Areas in Communications, IEEE Journal on》1995,13(5):893-907
The anticipated emergence of third-generation mobile systems, referred to as universal mobile telecommunication systems (UMTS), raises the problem of reconsidering the design of the databases destined to contain the user information. In particular, it is expected that the key concepts of the new database architectures will be high distribution and fast updating of information. So far, the problem of determining the most appropriate distributed database (DDB) architectures for third-generation mobile systems has not been widely dealt with in literature. This paper presents a methodology for evaluating hierarchical DDB architectures by means of an analytical model of the data querying operation. This methodology allows for structural alternatives, differing on account of the number of levels and branches in the hierarchy, to be evaluated in terms of query loads and mean response times, according to a given user mobility characterization and a given search protocol operation. By way of illustration, the paper discusses a case study, concerning a query operation arising from a location updating procedure and applied to a hierarchical tree-like DDB in which some structural alternatives are considered 相似文献
984.
Daniel C. Mattis 《Journal of Superconductivity and Novel Magnetism》1995,8(4):479-481
We study a 3-band model of CuO2 with “bare bones” interactions: hopping from copper ions to nearest-neighbor oxygenst pd only, a two-body interaction on the copper ionsU dd only, and an overlap copper-oxygen parameter λpd. In the limitt pd ∝U dd 1/2→∞, t*=t pd 2/2U dd is the unit of energy with 8λpd 2 as the only parameter of significance. If the two-body interaction is invariant under particle-hole interchange, the low-lying states (energy O(t*)) can be described by conserved particles and can all be classified. They are quite distinct from the high-lying states (energies O(U dd)). The dynamics of the conserved fermion-like elementary particles are well described by a modifiedt-J model with extended hopping and nearest-neighbor superexchange attraction. This is a scenario known to be favorable to high-temperature superconductivity, but it must be noted that both the hopping range and the exchange are functions of 8λpd 2. Moreover, if the Hamiltonian isnot invariant under particle-hole interchange the dynamics becomes much more complex and possibly more inimical to high-temperature superconductivity. This may provide an explanation for the deleterious effect on superconductivity of very small concentrations of certain impurities. 相似文献
985.
C. T. Ho 《Journal of Materials Science》1996,31(21):5781-5786
Nickel and copper were deposited over brominated, surface treated, and pristine P-100 carbon fibres using cementation and electroplating techniques. The fibres were brominated by bromine vapour for 48 h and then desorbed at 200 °C in air for 12 h. The anodic oxidation treatment of the fibres involved electrochemical etching in a dilute sodium hydroxide electrolyte for 3 min. Electroplated coated fibres showed better tensile properties than cementation coated fibres. In addition, nickel coating exhibited better bonding with the carbon fibres compared to copper coating. The effect of bromination and surface treatment was improved adhesion between coating and fibres. Nickel- and copper-coated fibres, which were brominated, anodically oxidized, and pristine, reinforced tin-lead alloy composites were fabricated by squeeze casting. The composites containing coated treated carbon fibres had higher tensile and shear strength than the ones containing coated pristine carbon fibres. Moreover, the composite with coated brominated carbon fibres had better tensile strength and shear strength than the surface treatment. The results also showed the composites containing nickel-coated fibres had higher tensile and shear strength than the ones containing copper-coated fibres. 相似文献
986.
The material properties of new sulphonated phenolic resin (SP) reinforced cement mortars have been investigated. SP was found to promote the dispersion of cement particles and to interact with Ca(OH)2. As a result, the resulting mortars exhibit better workability, more compact structure and higher compressive strength than plain mortars. The mortar with 1 wt% SP present after 28 days curing exhibits a compressive strength of 66MPa, which is about 18% higher than that of plain mortar. 相似文献
987.
Diederich C.J. Burdette E.C. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1996,43(6):1011-1022
This study presents the initial evaluation of an applicator designed for transurethral ultrasound thermotherapy (TUST) of prostate tissue in the treatment of benign prostatic hyperplasia (BPH) and cancer. A tubular multitransducer applicator, consisting of four piezoceramic tubes (2.5 mm diameter, 6 mm long, 6.8 MHz) under separate power control, was designed to fit within a semiflexible water-cooled temperature-regulated delivery catheter to be placed within the prostatic urethra during therapy. Sonication patterns were tailored to produce power depositions which avoid nontargeted tissues, such as the rectum. Computer simulations have demonstrated that 1.4-2.0 cm radial therapeutic zones (temperatures ⩾50-55°C, thermal doses >300 EM43) with concurrent sparing of the urethral mucosa can be produced within prostate tissue having blood perfusion as high as 10 kg m-3 s-1 within 15-30 min. Acoustic distributions and power output measurements of a prototype applicator have demonstrated acoustic power levels approaching 10 W per each sectored transducer segment are attainable, with beam profiles collimated within the transducer length and with desired circumferential distributions. In vivo thermal dosimetry characterizations of these transurethral applicators have indicated that therapeutic temperatures between 50 and 90°C are attainable, controllable in the longitudinal and circumferential directions, and have effective radial heating. These results clearly indicate that transurethral ultrasound applicators have potential to provide improved spatial localization and control of the heating distribution over existing transurethral thermal therapy techniques for both hyperthermia and thermal coagulative therapy of the prostate 相似文献
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