Application of wavelet transform to 3D shape measurement

A new method for analyzing the phase distributions of deformed grating images on the surface of three-dimensional (3D) object to obtain its shape information has been presented. In the conventional technique, Fourier transform profilometry (FTP), there is an intrinsic problem of extracting the fundamental frequency component if the deformation of the grating pattern is either considerable or complicated, which will definitely bring bad influence to the analysis' accuracy. That means FTP is not appropriate to deal with the complex surfaces of 3D objects. The approach that we here introduce to solve this problem is to utilize Gabor wavelet transform (GWT), a tool excelling for its multiresolution in time-frequency domain, to analyze the phase distributions.     

Application of phase-diverse phase retrieval to wavefront sensing in non-connected complicated pupil optics

Baseline algorithm,as a tool in wavefront sensing(WFS),incorporates the phase-diverse phase retrieval (PDPR)method with hybrid-unwrapping approach to ensure a unique pupil phase estimate with high WFS accuracy even in the case of high dynamic range aberration,as long as the pupil shape is of a convex set. However,for a complicated pupil,such as that in obstructed pupil optics,the said unwrapping approach would fail owing to the fake values at points located in obstructed areas of the pupil.Thus a modified unwrapping approach that can minimize the negative effects of the obstructed areas is proposed.Simula- tions have shown the validity of this unwrapping approach when it is embedded in Baseline algorithm.     

Application of μ SR to radiation damage in metals

Proton-irradiated Al, Cu and Ni foils have been investigated by the SR technique. No trapping of ⁺ has been observed in the temperature range investigated (<300 K). In Ni a temperature-independent increase of the depolarisation rate by a factor of three is found for the irradiated target. This change is attributed to field inhomogeneities produced by defects.     

Application of the probability theory in predicting 3D focusing behaviors of compound X-ray refractive lenses

X-rays promise a high resolving power due to the veryshort wavelength. Therefore, people have been trying todevelop X-ray optical devices for focusing X-ray beam toa small spot to perform X-ray analysis techniques. In1996, Snigirev et al.[1] proposed and demonstrated thatX-ray refractive focusing could be accomplished with acompound X-ray refractive lens (CRL). And then manypublications on the further researches appeared[2-8]. Thetheoretical results on the focusing performances in the fo-c…     

Hydrothermal synthesis of WO3·H2O with different nanostructures from 0D to 3D and their gas sensing properties

In this paper, WO₃·H₂O with different nanostructures from 0D to 3D were successfully synthesized via a simple yet cost-effective hydrothermal method with the assistance of surfactants. The structures and morphologies of products were investigated by XRD and SEM. Besides, we systematically explained the evolution process and formation mechanisms of different WO₃·H₂O morphologies. It is noted that both the kinds and amounts of surfactants strongly affect the formation of WO₃·H₂O crystals, as reflected in the tailoring of WO₃·H₂O morphologies. Furthermore, the gas sensing performance of the as-prepared samples towards methanol was also investigated. 3D flower-like hierarchical architecture displayed outstanding response to target gas among the four samples. We hoped our results could be of great benefit to further investigations of synthesizing different dimensional WO₃·H₂O nanostructures and their gas sensing applications.     

Application of the D’Alembert principle to the mobile gravimetry problem

A brief substantiation of a physically and mathematically correct model of a gravitoinertial system is presented, and the results of a computational experiment that illustrate the efficiency of the model are reported.     

Application of subband adaptive filtering techniques to ultrasonic detection in multilayers

The ultrasonic testing for the defects of complete disbond in multi-layered structure with lower acoustic impedance beneath a high acoustic impedance overburden is one of the difficult problems in ultrasonic nondestructive testing field.A model of a multi-layered steel-rubber composite plate is depicted.Because the acoustic impedance of the steel differs far from that of the couplant water and the rubber,the energy of the signal refleccted from the deonded rubber layers is very weak.More over,the flaw echoes are masked by the strong echoes reverberated in the steel plate.It‘s nearly impossible to identify the debonding echoes directly.The subband adaptive filtering method is discussed in the paper,where the subband decomposition is performed by mutual wavelet packets decomposition on the criterion of maximizing the cross-correlation between the signals.The simulations on both synthetic and real signals are presented.The echoes from the delaminated flaw at the depth of 5mm in the rubber from the calculated signal,and echoes from the flaw at the depth of 3mm from the real signal are extracted successfully.     

Raman spectra of shortite Na2Ca2(CO3)3 compressed up to 8 GPa

A rare mineral shortite, Na₂Ca₂(CO₃)₃, occurs among groundmass minerals in unaltered kimberlites, which suggests its participation in the evolution of kimberlite system. This work presents a high pressure Raman spectroscopic study of natural shortite (Udachnaya east kimberlites) compressed in KBr up to 8?GPa in a diamond anvil cell. At ambient pressure the spectrum contains two strong bands related to symmetric C-O stretching vibrations, four in-plane bending modes, and several low-frequency modes of lattice vibrations. Upon the pressure increase up to 8?GPa, almost all the bands exhibit positive shift with the rate of 1–4?cm^?1/GPa for the lattice modes and 3.6 and 3.9?cm^?1/GPa for the C-O stretching modes. The shifts of Raman modes are rather regular, which implies the absence of reconstructive phase transitions within the studied pressure range, similarly to the behavior of nyerereite, a related carbonate mineral. However, minor anomalies in the ν/P and FWHM/P dependences, observed at about 2?GPa, suggest some rearrangement and disordering of carbonate groups. The obtained data can be used for the estimation of residual pressure in shortite-bearing inclusions in deep-seated minerals.     

Electrical resistivity of fluid methane multiply shock compressed to 147 GPa

Shock wave experiments were carried out to measure the electrical resistivity of fluid methane. The pressure range of 89–147?GPa and the temperature range from 1800 to 2600?K were achieved with a two-stage light-gas gun. We obtained a minimum electrical resistivity value of 4.5?×?10^?2?Ω?cm at pressure and temperature of 147?GPa and 2600?K, which is two orders of magnitude higher than that of hydrogen under similar conditions. The data are interpreted in terms of a continuous transition from insulator to semiconductor state. One possibility reason is chemical decomposition of methane in the shock compression process. Along density and temperature increase with Hugoniot pressure, dissociation of fluid methane increases continuously to form a H₂-rich fluid.     

Application of soluble salt-assisted route to synthesis of β-Ga2O3 nanopowders

In the past β-Ga₂O₃ nanopowders were usually prepared from gallium-based compounds via wet chemical processes. However, those wet chemical routes would lead not only to high cost, but also to the inevitable contamination of the targeted products from unexpected doping. In this work, the soluble salt-assisted route has been applied to prepare β-Ga₂O₃ nanopowders with a yield of 96.5 % through the direct oxidation of Ga–Na₂SO₄ mixture at 600 °C followed by water washing. Systematical characterizations including SEM, TEM, XRD, Raman, IR, XPS, BET, UV–Vis diffuse reflectance and PL spectrum were conducted. The as-prepared nanopowders were composed of mesoporous nanoparticles and nanosheets with monoclinic Ga₂O₃, and had a broad UV and blue emissions band from 350  to 550 nm. Furthermore their optical band gap was 4.68 eV, exhibiting a red shift of 0.22 eV in comparison with pure bulk matrix. The interesting results indicated a wide range of soluble salt-assisted route for promising industrial production of β-Ga₂O₃ nanopowders.     

Application of complementary coding signal to seismic profiling

A pulse-compression system composed of a complementarycoding CC signal generator and a corresponding processor has been devel-oped.The working principle of using this system in seismic profiling atsea is described,and the effect of wave modulation on CC signal pro-cessing is examined in detail.Computer simulations have confirmed theeffectiveness of applying this new approach to practical seismic profiling.     

Application of movable collimators to the BEPCⅡ

BEPCⅡ is a double ring e＋ecollider with high beam currents and luminosity,so the high beamrelated backgrounds may disturb the detector.In order to have a good quality of data taking,backgrounds should be kept at a level as low as possible.A series of collimators are designed and installed in both the e＋ and erings.Two of the collimators are horizontally movable,each for one ring,about 8 m upstream from the interaction point.Experiments have been done to identify the e-ectiveness of the movable collimators with different apertures and beam currents.The results show that the movable collimators are very effective and can reduce as much as about 50% of beam-related backgrounds.     

Application of Time-Dependent Density-Functional Theory to C6

We employ a real-space pseudopotential method to determine the ground state structure of the carbon cluster C6 via simulated annealing and the corresponding optical absorption spectra from the adiabatic time-dependent density-functional theory (TDDFT) and the local density approximation (TDLDA).It is found that the ground state structure of the carbon cluster C6 belongs to a monocyclic D3h structure and the calculated spectra exhibit a variety of features that can be used for comparison against future experimental investigations.     

Application of movable collimators to the BEPC Ⅱ

BEPC Ⅱ is a double ring e+e-collider with high beam currents and luminosity,so the high beamrelated backgrounds may disturb the detector.In order to have a good quality of data taking,backgrounds should be kept at a level as low as possible.A series of collimators are designed and installed in both the e+and e-rings.Two of the collimators are horizontally movable,each for one ring,about 8 m upstream from the interaction point.Experiments have been done to identify the effectiveness of the movable collimators with different apertures and beam currents.The results show that the movable collimators are very effective and can reduce as much as about 50% of beam-related backgrounds.     

Application of CPLD in CSR Control System

CPLD is the complex programmable logic device. The logic function of CPLD can be changed by different; program. The applications of CPLD have not only simplified the circuit‘s design and reduced its costs, but also enhanced the reliability and secrecy of the system. Here we introduce an example of the CPLD‘s implementation in the CSR control system.     

Application of two-mode fiber in voltage sensor

A new mode patter's demodulation technique is put forward. Researches of experiment and theory show that the coupling efficiency of two kinds of different fibers depends on the relative offset between the two fibers when the core diameter of the information pick-up fiber is a little smaller than the major semi-axes of the elliptical-core two-mode fiber. Especially, when the relative offsetδ≈1, fusing splice coupling efficiency reaches peak value. Furthermore, based on the new demodulation scheme, the sine voltage signal applied on the piezoelectric lead zirconate titanate (PZT) is obtained and the detection precision of the system is within±0.2% when the voltage changes between 0.1 and 20 V.     

Application of time reversal in underwater communication

Time reversal is applied to the underwater spreading spectrum coding communication. On the base of analyzing the focusing characteristics of the time reversal in underwater waveguide, the time reversal is studied to overcome the wave distortion of the encoded signal caused by the multi-path effect. The experiment research for underwater coding communication is carried out in a lab water tank and the corresponding theoretical analysis is also conducted by Binary Phase Shift Keying (BPSK) encoding and Barker code with 7 chips for the spreading spectrum signal. The results show that the time reversal can improve the focusing gain and increase the ratio of the principal to the second lobe of the coding signal, and can decrease the bit error rate and increase the communication distance.