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The commonly used phase processing techniques include coherence method, zero-crossing comparison method and FFT method. Due to the influence of noise, amplitude modulation and frequency modulation, these phase processing methods are easy to cause errors, thus affecting the measurement accuracy. In this paper, a phase processor based on all-phase fast Fourier transform is developed. The principle of the phase processing algorithm is analyzed, and the implementation process of the algorithm on FPGA is described. The effectiveness of the method is tested under different conditions. The experimental results show that the standard deviation of phase processing is 0.387° when the signal is sampled simultaneously under 90% AM modulation. When asynchronous sampling and 50% FM, the phase processing error is 0.371°. This phase processer has been used to the terahertz interferometer of the HL-2M device, the phase change of the output signal of the interferometer can be accurately processed when the plasma density changes dramatically, and the loss of phase processing information can be effectively avoided in the plasma diagnosis process. Based on the technical research proposed in this paper, a more accurate phase processing reference scheme is provided for plasma diagnosis of interferometer.

The effects of Mn-doping on CaCu 3 Ti 4 O 12 (CCTO), i.e. the electrical properties of CaCu 3 Ti (4− x ) Mn x O 12 were studied in order to get a deep insight into the origin of the colossal dielectric constant of CCTO. It was found that 1 mol% substitution of Mn for Ti decreases the dielectric constant largely to a factor of 1/100, supporting the point of view that the native defects are responsible for the dielectric response of CCTO.

(1− x )PZT5/ x NiFe 2 O 4 ( x = 0, 0.2, 0.3, 0.4, 0.5 and 1, abb. PZT/NFO) ceramic particle composites were fabricated of commercial PZT5 powder and self-fabricated NiFe 2 O 4 by solid-state sintering at 1150 °C for 2 h. The formation of cubic spinel structure of ferrite phase and cubic perovskite structure of ferroelectric phase in the composites were confirmed by X-ray diffraction studies besides slight peaks of pyrochlore phase. The formation of pyrochlore phase could be restrained by increasing magnetic content and the ferroelectric behaviors of the composite were properly promoted at x = 0.2. On the other hand, remanant polarization ( P r ) of PZT/NFO composites monotonously increased according to the adding content of PZT5 except for x = 0.2. Vice verse, ferromagnetic properties would be dominant with increasing NiFe 2 O 4 phase. The direct magnetic field ( H dc ) and ac electric field ( E ac ) were applied to the composites simultaneously for magnetocapacitance behaviors measurement. As a result, the self-modulation of dielectric and impedance were found for PZT/NFO composites. More interestingly, the magnetocapacitance of the composite probably was not related to the magnetoresistance as reported a lot but to the piezomagnetoeffects as expected. The PZT/NFO ceramic particle composites should be prospectively applied in multistate memories and else fields.

Influence of bismuth substitution on calcium site in CaCu3Ti4O12 has been investigated. Compositions of Ca1-3/2xBixCu3Ti4O12 (x = 0, 0.05, 0.10, 0.15 and 0.20) were fabricated by solid-state sintering method. Crystal structure is remained cubic. X-ray diffraction indicates the presence of secondary phase of CuO in CCTO ceramics. Bismuth doping restrains the formation of CuO phase apparently. The grain size of CaCu3Ti4O12 ceramics was greatly decreased by Bi3+ doping, resulting from the ability of bismuth to inhibit the grain growth. The dielectric and electric properties of CCTO ceramics were found to be influenced by bismuth doping. The fitting results of the complex impedance spectra showed an increase of the resistance of grain and grain boundary by bismuth substitution. Ca0.70Bi0.20Cu3Ti4O12 showed the highest dielectric constant in the low frequency range. A modest composition such as Ca0.85Bi0.10Cu3Ti4O12 expressed the optimized dielectric properties of higher dielectric constant (1.3 × 104) and lower dielectric loss (0.06) than pure CCTO. The low and high temperature dielectric loss spectra demonstrate the interfacial polarization of the initial and secondary oxygen ionization, relating with the grain and grain boundary (the electrode contact for Ca0.70Bi0.20Cu3Ti4O12) respectively.

Ca 1−3 x /2 Bi x Cu 3 Ti 4 O 12 ( x = 0.0–0.3) ceramics were prepared by the conventional solid-state reaction method. X-ray powder diffraction analysis confirmed the formation of cubic CCTO phase except for subtle peaks of CuO. SEM micrographs suggested that the morphologies of doped CCTO ceramics had been sheet-like for high Bi-doping amount, and the dominant grain size decreasing could be seen for the small content of Bi-doping CCTO. Dielectric properties of pure and doped CCTO were investigated in a broad temperature range of 20–420 K. The results showed that bismuth doping could decrease the dielectric loss but suppress the dielectric temperature stability at the same time. Bi doped CCTO ceramics presented different relaxation properties. As to pure CCTO and BCCTO ( x = 0.3) only one MW relaxation (Relaxation I) could be found, which moves to higher frequency with temperature increasing. However, two relaxation processes (Relaxation I and II) appear for BCCTO ( x = 0.1–0.2). By means of complex impedance spectra analysis and Arrhenius fitting, we successfully separated the different conductive segments and explained the mechanisms of the two relaxation processes. Relaxation I appeared at low temperature could be attributed to the V O doping energies inside CCTO grains which did not showed significant changing of activation energy after bismuth doping. For Relaxation II at higher temperature than Relaxation I, with activation energy obviously depending on the Bi-ion concentration, may be related with the V O point defects at the grain boundaries.

Pure and Pr6O11-doped CaCu3Ti4O12 (CCTO) ceramics were prepared by conventional solid-state reaction method. The compositions and structures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influences of Pr-ion concentration on dielectric properties of CCTO were measured in the ranges of 60 Hz–3 MHz and 290–490 K. The third phase of Ca2CuO3 was observed from the XRD of CCTO ceramics. From SEM, the grain size was decreased obviously with high valence Pr-ion (mixing valence of Pr3+ and Pr4+) substituting Ca2+. The room temperature dielectric constant of Pr-doped CCTO ceramics, sintered at 1323 K, was an order of magnitude lower than the pure CCTO ceramics due to the grain size decreasing and Schottky potential increasing. The dielectric spectra of Pr-doped CCTO were flatter than that of pure CCTO. The loss tangent of Pr-doped CCTO ceramics was less than 0.20 in 2 × 102–105 Hz region below 440 K. The complex impedance spectra of pure and Pr-doped CCTOs were fitted by ZView. From low to high frequency, three semicircles were observed corresponding to three different conducting regions: electrode interface, grain boundary and grain. By fitting the resistors R and capacitors C, the activation energies of grain boundary and electrode contact were calculated. All doped CCTOs showed higher activation energies of grain boundary and electrode than those of pure CCTO ceramics, which were concordant with the decreasing of dielectric constant after Pr6O11 doping.

The structure and martensitic transition (MT) temperatures of Ni 44 Mn 45 Sn 10 R (R = Al, Ga, In and Sn) alloys were investigated. Valence electron concentration and cell volume are two main factors affecting the MT temperatures in Ni–Mn based Heusler alloys. Our results indicated that the MT temperatures do not vary monotonously with either of the two factors, but increase with the increasing of electron density. Combining the two factors, electron density might be a more appropriate parameter to describe the variations of MT temperatures.

We systemically studied the OH-terminated diamond (0 0 1) surfaces by first-principles calculations. A set of network structures are investigated, two of them are found to be energetically favored over a recently proposed anti-parallel configuration [S.J. Sque, R. Jones, P.B. Briddon, Phys. Rev. B 73 (2006) 085313]. The transition paths and barriers between the anti-parallel configuration and the network structures are calculated. Furthermore, using ab initio molecular dynamics, a scissor mode of pseudo-water molecules in vibrational spectra was found, which is in well agreement with available experiments.

Ca[Formula: see text]Bi[Formula: see text]Cu3Ti4O[Formula: see text] ([Formula: see text] = 0.0, 0.1, 0.2 and 0.3; BCCTO) ceramics were prepared by traditional solid-state sintering method. All samples had pure cubic perovskite-like structure. A drastic grain size reduction was observed with bismuth doping. Dielectric spectra showed two obvious relaxation steps corresponding to two series of peaks in the imaginary part of electric modulus spectra and dielectric loss spectra too. Activation energy fitting by electric modulus spectra reflected different conducting segments in BCCTO ceramics of grains and oxygen vacancies below room temperature. Normalized capacitance dependent of extra bias showed different voltage–capacitance coefficients at special frequencies that suggested multirelaxation mechanisms related with grain and oxygen vacancy. A positive capacitance curvature implies dipolar relaxations in CCTO grains. Whereas a negative curvature suggests oxygen-related relaxations at the interface.

A Gaussian wave packet confined to move on a plane perpendicular to a magnetic field remains a Gaussian wave packet in its time evolution. The average position and momentum follow the Ehrenfest equations which are identical to the classical Hamilton equations. A set of nonlinear equations decoupled from the Ehrenfest equation is derived for the parameters describing the time evolution of the density distribution and phases of a wave packet. Explicit solutions are then obtained when the "internal" angular momentum of the wave packet vanishes. In this case it is shown that the motion of the wave packet is a superposition of a translational motion, a rotation and a vibration.

Presents work on the realization of Bose-Einstein condensates (BEC) in optical and electro-magnetic traps. We have done some theoretical and experimental work on the project. We have proposed an optical funnel or a hollow beam, which are produced from a short micron-sized hollow optical fiber or a set-up of lenses. The cold atoms extracted from an magneto-optical trap experience effective Sisyphus cooling in the dark hollow beam. We calculate the potential barriers for atomic guiding in the dark hollow beam, and analyze the atomic losses during the guiding process. Inside the hollow beam atoms experience an efficient Sisyphus cooling and repumping-beam induced geometric cooling. We have estimated the total loss rate of the cold atoms, and it shows that an ultracold and dense Rb atomic sample with a 3D temperature of /spl sim/1 K can be obtained and the appearance of an optically-trapped Bose-Einstein condensation may be possible in this optical trap. We have also made a proposal of a micro-wave electro-magnetic trap, which is working at the frequency which is very far from the optical transition of the cold atoms. The trapping force comes from the interaction between the electro-magnetic induced magnetic dipole moment with the electro-magnetic field. Theoretical calculation shows that the force can be used to trap the cold atoms in the trap.