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In this study, the rubber natural pumice concrete was taken as the research object, and the orthogonal test method was employed to design the experiment, the rubber particles were added to the concrete as precast pores to test the actual porosity, compressive strength and splitting tensile strength of the natural pumice concrete under different precast porosities. According to the change rule, the actual porosity, compressive strength and split tensile strength distribution were respectively fitted. The results show that there is a good correlation between the actual porosity of natural pumice concrete and the precast porosity, and then the empirical formula of rubber particle content and concrete strength is established, which provides a certain theoretical reference for the research on the porosity of natural pumice concrete.

GaN interlayers deposited with pulsed NH 3 flow were inserted into the In ai6 Ga 0.8 4N active layer to suppress phase separation. The then fabricated metal-semiconductor-metal visible- light photodiode exhibit the significantly decreased dark current and sharpened response cutoff.

Two-terminal GaN/Al 0.1 Ga 0.9 N based avalanche phototransistors have been fabricated and characterized. The devices exhibit peak responsivity at 335 nm and optical gain of 3.6 ×104 at 53.5 V, providing feasibility in realizing high-sensitive visible-blind detection.

The plane wave expansion method (PWM) was employed to study the relation between the photonic band gap (PBG) of 2D triangular lattice photonic crystal (PC) and the shapes of rods and dielectric constant. It is shown that the PBG of PC with quadrangular rods is the widest one, compared with the other case with cross section shapes of triangular, circular and hexagon under the same filling ratio, and a peak value appears when the side length ratio of lx/ly is equal to 1.21 approximately to any filling ratio. In the aspect of the effects of dielectric constant, the PBG width does not increase monotonically with the increase permittivity ɛ2 of the background material to certain permittivity ɛ1 of the quadrangular rods, but has a peak value instead. However, the larger the permittivity ɛ1 is, the narrower the band width is and the lower the central frequency is, and the dispersion Δɛ = ɛ2 − ɛ1 is larger also.

Carbon disulfide (CS 2 ) is used as indirect sulfur source to synthesize spherical semiconductor lead sulfide (PbS) quantum dots (QDs) in a Quaternary W/O microemulsion by γ-ray irradiation at room temperature under ambient pressure. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible (UV–Vis) spectrum are used to characterize the obtained product. A possible reaction process is discussed.

Low-temperature photoluminescence studies have been performed on Si-doped and Be-doped self-organized InAs/GaAs quantum dot (QD) samples to investigate the effect of doping. When Si or Be is doped into the sample, a remarkable decrease in line-width is observed. We relate this phenomenon to a model that takes the Si or Be atoms as the nucleation centers for the formation of QDs. When Si or Be is doped, more small uniform quantum dots are formed. The result will be of significance for the application of self-organized InAs quantum dots in semiconductor devices.

Si-doped Ga0.7Al0.3As grown by molecular beam epitaxy (MBE) and undoped Ga0.47Al0.53As grown by chemical beam epitaxy (CBE) have been investigated using a new deep level characterization method-transient photo-resistivity spectroscopy, which we recently developed. This method measures directly the capture process of deep centers. In GaAlAs, apparent capture barrier energy EB = 0.25 eV of DX center was determined and intrinsic capture barrier energy Eσ = 0.16 eV was directly measured. In GaInAs, a defect with capture barrier energy EB = 0.28 eV was observed. The result proved that DX centers capture electron only from band L, belonging to small lattice relaxation model. The theoretical deduction of transient photo-resistivity spectroscopy was improved.

We report on abnormal lasing spectra of InAs/GaAs quantum dot lasers, where a single-mode peak exists with optical intensity several times larger than that of other modes. The maximum side mode suppression ratio of the single-mode peak is measured to be 10.11 dB at 29°C with injection current of 413 mA. It is found that the emergence of this abnormal lasing spectrum happens in a certain range of operation temperature and current. The sharp increase in optical intensity of the single-mode peak is closely related to the disappearance of optical lasing modes located at the higher energy side of the enhanced mode.

The advantages of InGaN based light-emitting diodes with InGaN/GaN multilayer barriers are studied. It is found that the structure with InGaN/GaN multilayer barriers shows improved light output power, lower current leakage, and less efficiency droop over its conventional InGaN/GaN counterparts. Based on the numerical simulation and analysis, these improvements on the electrical and the optical characteristics are mainly attributed to the alleviation of the electrostatic field in the quantum wells (QWs) when the InGaN/GaN multilayer barriers are used.

The structure of water molecules encapsulated in single-walled carbon nanotubes (SWCNTs) was studied using a self-consistent charge density functional tight binding method with dispersion correction. The most interesting and important feature observed is the diameter shrinkage of SWCNTs when water chains are confined inside them. The diameter shrinking of SWCNTs may be due to the van der Waals and H-π interaction between water chains and SWCNTs. The binding energy decreases with the increase of the nanotube radius. But when the radius is increased to 6.78 ?, the binding energy is a little increased, and the water chain has changed as a "book-like" structure, which suggests that the weak hydrogen bonding in the isolated water chains is larger than the interaction between water chains and the SWCNTs.

The electromagnetic characteristics of the model with an electric line source radiating in the direction parallel to a lossy metamaterial covered infinitely long dielectric circular cylinder have been investigated. Firstly, the electromagnetic model is presented and the exact solution is derived. Secondly, this exact solution is employed in numerical calculations. The patterns of the near field under different electromagnetic parameters are obtained. The characteristics of the far field properties are also studied through the directivity and the normalized radiation resistance. Due to the effect of the negative refraction and the loss of the lossy metamaterial, in comparing the lossless metamaterial layer and the lossy conventional material layer, very different electromagnetic characteristics on the near and the far field of the lossy metamaterial covered dielectric cylinder are revealed.

The crystallization of Ti3Al amorphous alloy during tensile deformation was studied with molecular dynamics. The simulation results show that the crystallization of amorphous alloy is induced by the local plastic deformation. The microstructure evolution was analyzed in the tension process. It is found that the nucleation and growth are induced by the shear localization and the final crystal phase has fcc structure. It is also found that the crystallization process is accompanied by strengthening of the material. The nanocrystal grains embedded in the amorphous phase can enhance the rigidity of the sample.

The electromagnetic characteristics of the model for an electric line source radiating parallel to a lossless metamaterial covered infinitely long conductor circular cylinder is investigated. First, the electromagnetic model is presented and exact solution is derived. Second, the exact solution is employed in numerical calculations. The figures of the near field under different geometric and electromagnetic parameters are obtained; the characteristics of the far field properties are also studied through the directivity and normalized radiation resistance. Because of the negative refraction of the metamaterial, the distinct “focus”, which could not be seen in the conventional material, could be obtained in the material layer from the near field pattern. The presented electromagnetic model is compared with the former approach and its validity is proven.

Molecular dynamics simulations of surface melting process at different strain values were performed for metal Cu(110). The variation of the structure and energy in the system and the movement of the interface position between solid and liquid during surface melting were observed. The interaction between atoms in the system adopts the embedded atom potential proposed by Mishin. Cu(110) surface pr emelts below thermal melting point and the thickness of quasi-liquid film grows with temperature increasing. Beyond the thermal melting point, the velocity of t he interface between solid and liquid is linearly proportional to temperature, t he melting point is extrapolated to be 1380K which accords with the experimental data of 1358K. Strain lowers the melting point and accelerates the premelting p rocess. The thickness of quasi-liquid grows with increasing strain at the same t emperature. The increase of solid free energy induced by strain is the main fact or that decreases surface thermal stability, the direction of strain relative to the surface stress also effects the premelting process.

A 2-D isotropic left-handed metamaterial (LHM) in C band with broad bandwidth and low loss is designed. The size of its unit cell is much smaller and configuration of its unit cell is symmetrical compared with previous LHM. The double negative (DNG) feature and the negative index of refraction (NIR) feature are verified by numerical simulation to prove the existence of the LHM. The numerical results show that the DNG and NIR phenomenon appear simultaneously as predicted.