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With the characteristics of wide range of sources of raw materials, environmental protection and cost-effective, Basalt Fiber, which is used as a kind of reinforced material of concrete, has received the attention of civil engineering. This paper summarizes the research status of Basalt Fiber Reinforced Concrete in China and abroad, and put forward proposals for the research of Basalt Fiber Reinforced Concrete.

Quantum dots (QDs) or semiconductor nanocrystals have been receiving great interest in the last few years. In this paper, L-cysteine-coated CdSe/CdS core-shell QDs (λem = 585 nm) have been prepared, which have excellent water-solubility. The full width at half maximum (FWHM) of the photoluminescence of these nanocrystals is very narrow (about 30 nm), and the quantum yield (QY) is 15% relative to Rhodamine 6G in ethanol (QY = 95%). With excess free L-cysteine in the solution, the fluorescence intensity of L-cysteine-coated CdSe/CdS QDs showed improved stability. It was found that the fluorescence of L-cysteine-capped CdSe/CdS QDs could be quenched only by copper (II) ions and was insensitive to other physiologically important cations, such as Ca2+, Mg2+, Zn2+, Al3+, Fe3+, Mn2+ and Ni2+ etc. Based on this finding, the quantitative analysis of Cu2+ with L-cysteine-capped CdSe/CdS QDs has been established. The linear range was from 1.0 × 10− 8 to 2.0 × 10− 7 mol L− 1 and the limit of detection (LOD) was 3.0 × 10− 9 mol L− 1 (S/N = 3). The proposed method has first been applied to the determination of Cu2+ in vegetable samples with recoveries of 99.6–105.8%.

Scattering of an elastic wave by a cylindrical shell embedded in poroelastic medium is investigated theoretically with the assumption that the shell material is also a porous elastic medium. The porous medium is modellized via Biot's theory and the scattering by cylindrical shell is expressed by the definition of scattering matrix. The normal mode expansion technique is employed for analysing the scattering field, and the asymptotic solutions of displacements, stresses and pore pressure are derived. Two limiting cases-scattering by a poroelastic cylinder in Biot medium and a elastic cylindrical shell in elastic medium are obtained from the general solutions. The dispersion curves of displacement amplitude at the interface of shell and medium is compared with the case of elastic shell. The scattering amplitude associated with the fast, slow and transverse waves are identified by numerical simulation. Furthermore, the influence of the poroelastic property of shell material on scattering amplitude is analysed. Copyright © 2005 John Wiley & Sons, Ltd.

A rapid evaluation method, temperature ramp method, for GaAs MESFETs ohmic contacts is proposed, and an automatic evaluation system has been developed. By use of this method and system, activation energy for ohmic contacts degradation can be obtained using less time and a small number of samples than traditional method, and the results are in agreement with those obtained by traditional methods. In accordance with some drawbacks of traditional AuGeNi/Au ohmic contacts, a new ohmic contacts system with TiN diffusion barrier layer is proposed. Experiment results show that the reliability of ohmic contacts with TiN is greatly superior to that of traditional AuGeNi/Au ohmic contacts.

The effect of base dopant out-diffusion and undoped (i-) SiGe or Si layers at both sides of the base on the characteristics have been studied by device simulator ISE-TCAD. It has been found that small amounts of base dopant out-diffusion from heavily doped bases will degrade DC and frequency characteristics. The insertion of an i-SiGe layer at both sides of the base can improve collector current, current gain /spl beta/ and cut-off frequency f/sub T/, the insertion of an i-Si layer between emitter and base and an i-SiGe layer between the base and collector can also improve /spl beta/ and f/sub T/. These simulation results promise more freedom in the design of HBTs.

In this paper, the carrier freeze-out in strained p-Si/sub 1-x/Ge/sub x/ layers grown on [001] substrates is studied analytically. It is found that as the Ge fraction increases, the valence effective density of states (N/sub V/)/sub SiGe//(N/sub V/)Si normalized by that in Si decreases. Furthermore, as the temperature becomes lower, the decrease in (N/sub V/)/sub SiGe//(N/sub V/)Si becomes more rapid. It is also show that as the Ge fraction increases, although it has little effect on the ionized doping concentration at room temperature, the ionized doping concentration increases at low temperatures compared with that in Si. This implies that carrier freeze-out is mitigated at low temperatures, which can have a beneficial effect on the operation of Si/sub -x/Ge/sub x/-based devices at low temperatures.

Effect of high gate current density and temperature stress on performance of GaAs MESFETs with TiAl and TiPtAu Gate is presented. Experimental results show that (1). The TiAl gate Schottky diode characteristics (gate series resistance R/sub g/, ideality factor n, barrier height /spl Phi//sub b/) degrades rapidly whereas the device parameters such as maximum drain saturation current I/sub dss/, open channel resistance R/sub g/, below the gate, pinch-off-voltage V/sub p0/ etc., remain fairly unchanged; (2) for TiPtAu gate MESFET, for suitable annealing, the Schottky diode characteristics (ideality factor n, barrier height /spl Phi//sub b/) remains stable whereas the device parameters such as maximum drain saturation current I/sub dss/, open channel resistance below the gate R/sub g/, pinch-off-voltage V/sub p0/, the transconductance g/sub m/ etc. degrade rapidly; (3) the increase in gate series resistance R/sub g/ is a the main factor that leads to increase in ideality factor n of TiAl and TiPtAu gate Schottky diodes. The parameter degradation of the two types of MESFETS is different.

The size-dependent elastic property of rectangular nanobeams (nanowires or nanoplates) induced by the surface elasticity effect is investigated by using a developed modified core-shell model. The effect of surface elasticity on the elastic modulus of nanobeams can be characterized by two surface related parameters, i.e., inhomogeneous degree constant and surface layer thickness. The analytical results show that the elastic modulus of the rectangular nanobeam exhibits a distinct size effect when its characteristic size reduces below 100 nm. It is also found that the theoretical results calculated by a modified core-shell model have more obvious advantages than those by other models (core-shell model and core-surface model) by comparing them with relevant experimental measurements and computational results, especially when the dimensions of nanostructures reduce to a few tens of nanometers.

Using nonequilibrium Green's function method, the thermal transport properties of zigzag graphene nanoribbons (ZGNR) embedding a finite (semi-infinite or infinite) long linear defect are investigated in this paper. The results show that defect type and defect length have significant influence on the thermal conductance of ZGNR. When the embedded linear defects have the same lengths, thermal conductance of ZGNR embedding t5t7 defect is lower than that of ZGNR embedding Stone-Wales defect. As for the ZGNR embedding finite and the same type defects, their thermal conductance reduce with the increase of the defect length. However, as the linear defect is long enough, the thermal conductance is insensitive to the change of length. By comparing the ZGNRs embedding finite, semi-infinite and infinite long defects, we find that the thermal conductance of ZGNR embedding an infinite long defect is higher than that of ZGNR embedding a semi-infinite defect, while the thermal conductance of the latter is higher than that of ZGNR embedding a finite long defect. This is due to the fact that different structures possess different numbers of scattering interfaces in the phonon transmission direction. The more the scattering interfaces, the lower the thermal conductance is. These thermal transport phenomena are explained by analyzing transmission coefficient and local density of states. These results indicate that linear defects can tune thermal transport property of ZGNR efficiently.

We theoretically demonstrate the possibility of realizing the valley and subband-selective electronic transport properties if line defects are embedded in an armchair carbon nanotube. The physical mechanism for such an interesting transport property is clearly due to the appearance of the special subband spanning two valleys without dispersion, caused by the presence of the line defect. In contrast to a perfect zigzag-edged graphene nanoribbon, which was previously suggested to be a nanodevice prototype to manipulate the valley and subband degrees of freedom, our structure, the line defect embedded carbon nanotube, is less demanding for the current nanotechnique. Therefore, our theoretical investigation provides an alternative and feasible structure to design carbon-based nanoelectronic devices.