重组家蚕核多角体病毒（rBmNPV）的复制及所载HuIFN－α基因的表达

报道了重组家蚕核多角体病毒（ＢｏｍｂｙｘｍｏｒｉｎｕｃｌｅａｒＰｏｌｙｈｅｄｒｏｓｉｓＶｉｒｕｓＢｍＮＰＶ）在家蚕细胞ＢｍＮ中复制的细胞病理学变化，除了不形成多角体以外，与野生型病毒相同．研究了病毒感染复数、细胞接种密度和细胞生长阶段对重组病毒复制和α－干扰素（ＩＦＮ－α）表达量的影响．在一定低感染复数时，α－干扰素的产量较高．对于重组病毒的复制，最适的细胞接种密度为３．６～７．０×１０５细胞／瓶．在细胞指数生长前期（４８～６０ｈ）接种重组病毒，对于获得较高的重组病毒复制效价和α－干扰素的产量都是有利的．

Homogenization on microstructure and mechanical properties of 2A50 aluminum alloy prepared by liquid forging

The homogenization on microstructure and mechanical properties of 2A50 aluminum alloy prepared by liquid forging was investigated.Wheel hubs were produced using direct and compound loading.The results show that the microstructure and mechanical properties are inhomogeneous in direct forged samples.The microstructure of the wall is coarser than that of the base,and the mechanical properties are lower and some defects are detected at the wheel corner.Using compound loading,the microstructure and mechanical properties of the wall are improved evidently.With increasing feeding amount,the microstructure and mechanical properties become more homogeneous.The defects disappear when the feeding amount is 4 mm.The forged wheel hubs could obtain fine and homogeneous microstructure with grain size of 20-30 μm,tensile strength of 355 MPa and elongation of 10% when the feeding amount is 10 mm.The microstructure and mechanical properties of liquid forged workpieces could be controlled and homogenized using compound loading.

EXPERIMENTAL RESEARCH AND NONLINEAR FINITE ELEMENT ANALYSIS ON NEW TYPE JOINT BETWEEN COLUMN AND STEEL BEAM OF CONCRETE-FILLED RECTANGULAR STEEL TUBULAR

Experimental results of new type joints between the column and the. steel beam of concrete-filled rectangular steel tubular （CFRT） under reversed cyclic loads are presented. The earthquake resistant capacity of the joint is influenced by infilled concrete, stiffener length and relative dimensions of column and beam. It is found that the hysteresis curves obtained in the experiment are full and the joints have a good energy dissipation capacity. The nonlinear finite element models are also used to analyze the hysteresis behavior of the joints under reversed cyclic loads using ANSYS 8.0. The influences of the stiffener length and the infilled concrete are analyzed. Analytical results show that the stiffener length and the infilled concrete are critical for the joints. Furthermore, the skeleton curves of the finite element models are in good agreement with those of experiments.

Effect of electrical current on tribological property of Cu matrix composite reinforced by carbon nanotubes

Cu matrix composite reinforced with 10%（volume fraction） carbon nanotubes（CNTs/Cu） and pure Cu bulk were prepared by powder metallurgy techniques under the same consolidation processing condition.The effect of electrical current on tribological property of the materials was investigated by using a pin-on-disk friction and wear tester.The results show that the friction coefficient and wear rate of CNTs/Cu composite as well as those of pure Cu bulk increase with increasing the electrical current without exception,and the effect of electrical current is more obvious on tribological property of pure Cu bulk than on that of CNTs/Cu composite;the dominant wear mechanisms are arc erosion wear and plastic flow deformation,respectively;CNTs can improve tribological property of Cu matrix composites with electrical current.

Study on Mutagenic Effect of Space Flight in Two-line Sterile Rice

Seeds of two-line sterile rice cultivars Zhu 1S and Lu 18S were carried into space by ＂Shijian 8＂ breeding recoverable satellite, then planted in ground. Mutagenic effects from space induction were compared with those from y-irradiation and complex processing of space induction and y-irradiation. The results showed that agronomic effect was stimulated in Mo progenies of the two-line sterile rice varieties treated by space flight, and their radiosensitivities to the irradiation of space flight performed non-sensitive. The order of mutation frequency was determined to be SP ＋ γ 〉 γ 〉 SP in M2 generation. And a series of mutated elites（individuals） were screened. Physiological indices of mutants screened like the activity of protective enzymes were measured to explore the physiological and biochemical basis of biological effect in space environment to two-line sterile rice. The results of this study show that space mutation breeding is an effective novel mean for breeding.

VLSI Implementation of a Single-Chip DVB-C Demodulator

A single-chip DVB-C quadrature amplitude modulation（QAM） demodulator is proposed,which integrates a 3.3V 10bit 40MSPS analog-to-digital converter and a forward error correction decoder. The demodulator chip can support 4-256 QAM with variable bit rate up to 80Mbps. It features a wide carrier offset acquisition range,optimal demodulation algorithm,and small circuit area. The chip is implemented in SMIC 0.25μm 1P5M mixed-signal CMOS technology with a die size of 3.5mm×3. 5mm. The maximum power consumption is 447mW.

A New Lifetime Prediction Model for pMOSFETs Under V_g=V_d/2 Mode with 2.5nm Oxide

Gate current for pMOSFETs is composed of direct tunneling current,channel hot hole,electron injection current,and highly energetic hot holes by secondary impact ionization.The device degradation under V g=V d/2 is mainly caused by the injection of hot electrons by primary impact ionization and hot holes by secondary impact ionization,and the device lifetime is assumed to be inversely proportional to the hot holes,which is able to surmount Si-SiO 2 barrier and be injected into the gate oxide.A new lifetime prediction model is proposed on the basis and validated to agree well with the experiment.

Photocatalytic activity and kinetics for acid yellow degradation over surface composites of TiO_2-coated activated carbon under different photocatalytic conditions

TiO2-coated activated carbon surface （TAs） composites were prepared by a sol-gel method with supercritical pretreatment. The photocatalytic degradation of acid yellow （AY） was investigated under UV radiation to estimate activity of catalysts and determine the kinetics. And the effects of parameters including the initial concentration of AY, light intensity and TiO2 content in catalysts were examined. The results indicate that TAs has a higher efficiency in decomposition of AY than P25, pure TiO2 particles as well as the mixture of TiO2 powder and active carbon. The photocatalytic degradation rate is found to follow the pseudo-first order kinetics with respect to the AY concentration. The new kinetic model fairly resembles the classic Langmuir-Hinshelwood equation, and the rate constant is proportional to the square root of the light intensity in a wide range. However, its absorption performance depends on the surface areas of catalysts. The model fits quite well with the experimental data and elucidates phenomena about the effects of the TiO2 content in TAs on the degradation rate.

Performance analysis of complex wavelet packet based multicarrier CDMA system over Nakagami-m fading channels

On the basis of analyzing the principle of multicarrier code division multiple access (MC-CDMA), an optimized complex wavelet packet based MC-CDMA system (CWP-MC-CDMA) is proposed. The system performances with equal gain combining (EGC) technique and maximum ratio combining (MRC) technique in Nakagami-m fading channels are investigated, respectively; and the corresponding bit error rate (BER) expression is derived. The system can overcome the decrease of spectrum efficiency of discrete Fourier transform (DFT) based conventional MC-CDMA (DFT-MC-CDMA) due to inserting a cyclic prefix (CP). Theoretical analysis and simulation results show that the CWP-MC-CDMA system outperforms DFT-MC-CDMA as well as the real wavelet packet based MC-CDMA (RWP-MC-CDMA) system, and has superior ability to combat multi-path fading and multi-access interference (MAI). Moreover, the BER performance of the proposed system is also superior to that of the conventional MC-CDMA with CP.

Ultimate flexural strength of normal section of FRP-confined RC circular columns

Numerical analysis is carried out to study the sectional properties of the fiber-reinforced polymer（FRP）-confined reinforced concrete（RC）circular columns. The axial load ratio, the FRP confinement ratio and the longitudinal reinforcement characteristic value are the three main parameters that can influence the neutral axis depth when concrete compression strain reaches an ultimate value. The formula for computing the central angle θ, corresponding to the compression zone, is established according to the data regression of the numerical analysis results. The numerical analysis results demonstrate that the concrete stress enhancement from transverse confinement and strain hardening of the longitudinal reinforcement can cause a much greater flexural strength than that defined by the design code. Based on the analytical studies and the test results of 36 large scale columns, the formula to calculate the flexural strength when columns fail under seismic loading is proposed, and the calculated results agree well with the test results. Finally, parametric studies are conducted on a typical column with different axial load ratios, longitudinal reinforcement characteristic value and FRP confinement ratios. Analysis of the results shows that the calculated flexural strength can be increased by 50% compared to that of unconfined columns defined by the code.

FINITE ELEMENT MODELING OF MODERATELY THICK COMPOSITE PLATE WITH PIEZOELECTRIC SENSORS AND ACTUATORS

A rectangular finite element for laminated plate with bonded and/or embedded piezoelectric sensors and actuators is developed based on the variational principle and the first order shear deformation theory. The element has four-node, 20-degrees-of-freedom with one potential degree of freedom for each piezoelectric layer to represent the piezoelectric behavior. The higher order derivation of deflection is obtained by using the normal rotation expressions to take the effects of transverse shear deformation into considerations. The finite element can accurately simulate the deformation of both thin and moderately thick plates. A Fortran program is written and a number of benchmark tests are exercised to verify its effectiveness. Results are compared well with the existing data. The unbalanced composite with piezoelectric layers is then analyzed by using the model. Results show that the changes of the ratio between the thickness of positive angle layers and the negative angle layers have an effect on the deformation of the structure under the same electric loading.

Performance of STBC-MC-CDMA system based on complex wavelet packet and turbo coding

On the basis of analyzing the principle of the space-time coding technique and the multi-carrier code division multiple access （MC-CDMA） technique, adopting the turbo codes as channel coding and the optimized complex wavelet packet as multi-carrier modulation, a novel space-time block coded the MC-CDMA system based on complex wavelet packet and turbo coding is proposed, and the system bit error rate （BER） performance in the Rayleigh fading channel is investigated. The system can make full use of space-time block codes＇ transmit diversity and turbo codes＇ good ability against fading channel to improve the BER performance significantly, and it can also avoid the decrease of spectrum efficiency of conventional MC-CDMA due to inserting cyclic prefix （CP） by utilizing superior characteristics of the optimized complex wavelet packet. Simulation results show that the proposed space-time block coded MC-CDMA system based on the complex wavelet packet performs better than the conventional space-time block coded MC-CDMA （STBC-MC-CDMA） system, and slightly outperforms the STBC-MC-CDMA with CP. Moreover, the application of the space-time block coding technique concatenated with turbo codes strengthens the system ability to combat various interferences in fading channel further.

PIEZOSPECTROSCOPIC STUDY OF RESIDUAL STRESSES AROUND INDENTATIONS IN SiC/Al_O_3 NANOCOMPOSITE

A new experimental measurement of residual stresses around Vickers′ indentations on the surface of the SiC/Al 2O 3 nanocomposites is proposed with the aid of a Raman microprobe. Results s how that the shifts of R lines in the fluorescence spectra va ry with the distance from the centre of indentation. The magnitude of load appli ed on the surface of the materials through the indenter influences the shifts of R lines to great extent. The luminescence of R lines of the materials before indenting is used to determine the residual stresses around the indentation in the materials, assuming that the stress tensor is transversely isotropic. Final ly, the term of hydrostatic stress is adopted to explain and compare different residual stresses around indentations with the increase of the indenting load an d the distance from the centre of indentations. <

A Novel TDD Multicarrier System Using Pre-Equalizer in Downlink

In this paper, a time division duplex (TDD) multicarrier system based on Nyquist filter bank is proposed for wireless broadband communications. In this system a novel two tap pre equalizer is adopted to effectively suppress the inter symbol interference (ISI). Studies show that the system has almost the same frequency spectrum efficiency as the orthogonal frequency division multiplexing (OFDM) system. Simulation results show that the proposed system outperforms the conventional OFDM system with one tap ...

Load-bearing characteristics of square footing on geogrid-reinforced sand subjected to repeated loading

A series of dynamic model tests that were performed on a geogrid-reinforced square footing are presented.The dynamic(sinusoidal)loading was applied using a mechanical testing and simulation(MTS)electro-hydraulic servo loading system.In all the tests,the amplitude of loading was±160 kPa;the frequency of loading was 2 Hz.To better ascertain the effect of reinforcement,an unreinforced square footing was first tested.This was followed by a series of tests,each with a single layer of reinforcement.The reinforcement was placed at depths of 0.3B,0.6B and 0.9B,where B is the width of footing.The optimal depth of reinforcement was found to be 0.6B.The effect of adopting this value versus the other two depths was quantified.The single layer of geogrid had an effective reinforcement depth of 1.7B below the footing base.The increase of the depth between the topmost geogrid layer and the bottom of the footing(within the range of 0.9B)did not change the failure mode of the foundation.

Seismic Behavior of Specially Shaped Column Joints with X-Shaped Reinforcement

To investigate the seismic behavior of specially shaped column joints with X-shaped reinforcement,two groups of specimens with or without X-shaped reinforcement in joint core region were tested under constant axial compression load and low reversed cyclic loading,which imitated low to moderate earthquake force.The seismic behavior of specially shaped column joints with X-shaped reinforcement in terms of bearing capacity,displacement,ductility,hysteretic curve,stiffness degradation and energy dissipation was studied and compared to that without Xshaped reinforcement in joint core region.With the damage estimation model,the accumulated damage was analyzed.The shearing capacity formula of specially shaped column joints reinforced by X-shaped reinforcement was proposed with a simple form.The test results show that X-shaped reinforcement is an effective measure for improving the seismic behavior of specially shaped column joints including deformation behavior,ductility and hysteretic characteristic.All specimens were damaged with gradual stiffness degeneration.In addition,X-shaped reinforcement in the joint core region is an effective way to lighten the degree of cumulated damage.The good seismic performance obtained from the specially shaped column joint with X-shaped reinforcement can be used in engineering applications.The test value is higher than the calculated value,which indicates that the formula is safe for the design of specially shaped column joints.

Axisymmetrical Nonlinear Bending and Buckling of a Circular Plate Under Large Load

With the terms of the exact series solution taken as trial functions, the method of point collocation was used to calculate the large deflection of a circular plate. The axisymmetrical bending formulae were developed for the calculation of a circular plate subjected to polynomial distributed loads, a concentrated load at the center, uniform radial forces and moments along the edge or their combinations. The support may be elastic. The buckling load was calculated. Under action of uniformly distributed load, central load or their compound load, solutions were compared with those obtained by other methods. Buckling beyond critical thrust was compared with that calculated by the power series method. The method presented in this paper has advantages of wide convergent range, high precision and short computing time. Moreover, the computing time is nearly independent of the complexity of the loads.

Post-fire cyclic behavior of reinforced concrete shear walls

The effects of fire exposure,reinforcement ratio and the presence of axial load under fire on the seismic behavior of reinforced concrete(RC) shear walls were investigated.Five RC shear walls were tested under low cyclic loading.Prior to the cyclic test,three specimens were exposed to fire and two of them were also subjected to a constant axial load.Test results indicate that the ultimate load of the specimen with lower reinforcement ratio is reduced by 15.8%after exposure to elevated temperatures.While the reductions in the energy dissipation and initial stiffness are 59.2%and 51.8%,respectively,which are much higher than those in the ultimate load.However,this deterioration can be slowed down by properly increasing reinforcement due to the strength and stiffness recovery of steel bars after cooling.In addition,the combined action of elevated temperatures and axial load results in more energy dissipation than the action of fire exposure alone.

Biaxial mechanical behavior of closed-cell aluminum foam under combined shear-compression loading

Combined shear-compression tests and simulations were performed on a closed-cell aluminum foam over a wide range of loading angles in order to probe their yield behaviors under biaxial loading conditions.Combined shear-compression tests were carried out by using a pair of cylindrical bars with beveled ends.The yield surfaces were experimentally measured and compared with various theoretical yield surface models.The cellular structures of closed-cell aluminum foams were modeled as tetrakaidecahedrons and their biaxial crushing behaviors were simulated by the finite element method.The results show that,yield initiates from the stress-concentrated corners in the specimens under combined shear-compression loading and the stress distribution is no longer uniform at the specimen/bar interfaces.In the range of cell sizes studied,the larger the foam cell size is,the higher the yield stress is.Aluminum foam density is found to be the dominant factor on its mechanical properties compared with the cell size and is much more significant in engineering practice.

Experimental study on the seismic performance of staggered slab-column joints

The low-cycle loading test of two staggered slab-column-boundary beam joints was carried out to study their seismic performance.The crack development,load-displacement relationship,displacement ductility,and energy dissipation performance of the staggered slab-column joints(SSCJ)were studied.Experimental results reveal that both specimens present short-column brittle shear failure.Furthermore,an obvious hysteretic curve pinching phenomenon occurred.Thus,it can be concluded that the seismic performance of the joints is insufficient.These results suggest that the anchorage of the longitudinal reinforcement of the slab in the joint’s core area should be improved,and attention should be paid to the short-column stirrup configuration of the SSCJ.These results can provide a research basis for the design of such joints in future applications.