Domain,dielectric and optical studies in antiferroelectric (Pb,La) (Zr,Sn, Ti)O3 single crystals

Antiferroelectric (Pb, La) (Zr, Sn, Ti)O₃ (PLZST) single crystals have been successfully grown by flux method using PbO–PbF₂–B₂O₃ as the flux. The obtained crystals are pale yellow in color and translucent. Domain structures, dielectric constants and optical transmission measurements have been performed on the 〈001〉-oriented PLZST single crystals. Two types of domains, namely, 90° and 180° domains, are observed. The extinction of 90° domains at P/A: 0° reveals a tetragonal structure in the crystal. The sequence of phase transitions from antiferroelectric to ferroelectric and then paraelectric has been established with increasing temperature. According to the modified Curie–Weiss relationship, the PLZST crystal is in an intermediate state between normal and relaxor antiferroelectrics. The broad optical transparent region (from 0.4 to 7.0 μm) and high optical transmittance (up to 65%) indicate that PLZST crystals are promising for optical uses.     

Experimental Study on Soft X-ray Contact Microscopy for Biological Specimens

Using Hefei Synchrotron radiation as X-ray source and photoresist PMMA as recording medium, soft X-ray contact microscopic imaging experiment on hydrated leaf epidermal cells of a kind of dicotyledon is performed and its latent image is read out by a light microscope. Several main factors degrading the resolution of the image are discussed in detail.     

Study on optical electron polarimeter and measurement of the relative Stokes parameters of weak light

In this paper, we present the research on an optical electron polarimeter, which is used to determine the polarization of an incident electron beam by measuring the relative Stokes parameters of the fluorescence emitted from the He gas following the impact excitation with the electron beam. The fundamental theory of the optical electron polarimeter is discussed with the 3³P→2³S transition of He. The structure and performance of the instrument are described, which are different in some aspects from previous works. The arrangement of the experiment for measuring the relative Stokes parameters of linearly polarized weak light is also investigated, which actually involves the same processes as the polarization measurement with the incident electron beam. The results obtained are in agreement with the theoretical prediction.     

Absorption properties of a driven Doppler—broadened ladder system with hyperfine structure

We have studied the absorption spectrum of a Doppler-broadened ladder system,where the highest level is coupled into two middle hyperfine sublevels by a strong coherent field.We find that,when the system is considered as homogeneous,either two or three spectral components are observed,depending on the detuning of the coherent field.but when the velocity distribution of atoms is considered,we can always observe one electromagnetically induced transparency (EIT) window with high dispersion.So the atomic hyperfine structure cannot be an impediment for obtaining EIT.     

Atomic force microscopy investigation of growth process of organic TCNQ aggregates on SiO2 and mica substrates

<正>Deposition patterns of tetracyanoquinodimethane(TCNQ) molecules on different surfaces are investigated by atomic force microscopy.A homemade physical vapour deposition system allows the better control of molecule deposition. Taking advantage of this system,we investigate TCNQ thin film growth on both SiO_2 and mica surfaces.It is found that dense island patterns form at a high deposition rate,and a unique seahorse-like pattern forms at a low deposition rate.Growth patterns on different substrates suggest that the fractal pattern formation is dominated by molecule-molecule interaction.Finally,a phenomenal "two-branch" model is proposed to simulate the growth process of the seahorse pattern.     

Molecular-Dynamics Simulations of Droplets on a Solid Surface

By using a semi-empirical Lennard-Jones embedded-atom-method potential, we study the influence of many-body forces and atomic size mismatch on the wetting behavior of nano droplets on a solid surface. With molecular dynamics simulations, we find that the contact angle decreases with increasing many-body forces. The increase of atomic size mismatch between solid and liquid results in the decrease of contact angles. Our calculation also shows that the interface structure is strongly affected by the interaction between liquid and solid as well as the atomic size mismatch. For weak solid-liquid interaction, the interface layer of the droplet nearest to the solid exhibits a typical simple liquid structure regardless of the size mismatch. For strong solid-liquid interaction, evident ordering in the interface layer is observed for well matched cases.     

基于586-Driver的无人机飞控计算机智能检测系统研制

传统飞控计算机检测方法以人工操作为主,存在一定的主观性且效率低下的缺点。采用信号门限检测技术,设计了飞控计算机一键式全功能检测方案。以586-Driver板卡为核心,设计了智能检测系统,实现了在全程无人干预情况下对飞控计算机按预设时序逻辑的自动检测。通过系统测试表明：满足某型飞控计算机的检测需求,提高了飞控计算机检测效率,具有实际工程应用价值。     

Deterministic secure quantum communication using four-particle genuine entangled state and entanglement swapping

A deterministic secure quantum communication scheme using entanglement swapping is proposed. The sender prepares four-particle genuine entangled states and sends two particles in each state to the receiver and remains the rest particles. If the quantum channel is secure, they begin to communicate. After their four-particle projective measurements, the receiver can obtain the secret information according to his measurement outcomes and classical information from the sender. Using entanglement swapping, there are no particles carrying secret information to be transmitted.     

Improved biological performance of low modulus Ti-24Nb-4Zr-7.9Sn implants due to surface modification by anodic oxidation

Dental implants are usually made from commercially pure titanium or titanium alloys. The purpose of this study was to evaluate the influence of surface treatment to low modulus Ti-24Nb-4Zr-7.9Sn (TNZS) on cell and bone responses. The TNZS alloy samples were modified using anodic oxidation (AD). Surface oxide properties were characterized by using various surface analytic techniques, involving scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS), X-ray diffractometry (XRD) and surface profilometer. During the AD treatment, porous titanium oxide layer was formed and Ca ions were incorporated into the oxide layer. The viability and morphology of osteoblasts on Ca-incorporated TNZS were studied. The bone responses of Ca-incorporated TNZS were evaluated by pull-out tests and morphological analysis after implantation in rabbit tibiae. The non-treated Ti and TNZS samples were used as the control. Significant increases in cell viability and pull-out forces (p < 0.05) were observed for Ca-incorporated TNZS implants compared with those for the control groups. Porous structures supplied positive guidance cues for osteoblasts to attach. The enhanced cell and bone responses to Ca-incorporated TNZS implants could be explained by the surface chemistry and microtopography.     

The effect of metastable states of the impurities on quantized acoustoelectric current

We report a detailed experimental study of the fluctuations of acoustoelectric (AE) current induced by surface acoustic waves in a shallow-etched quantum point contact defined in a GaAs/Al_xGa_1?xAs heterostructure at 1.7 K. We observe that current fluctuations between two AE current plateaus are more obvious than those at the plateaus. Switching the metastable states of the impurities is considered as the physical origin of the current fluctuations.