Vol.23,

Copper ion is the essential microelement to many organisms. In this paper, the local structure of Cu²⁺ in CuBr₂ aqueous solutions with different concentrations are investigated by using X-ray absorption fine structure (XAFS) technique. XANES (X-ray Absorption Near Edge Structure) spectra indicate that charge transfer from Br^- to Cu²⁺ decreases with the solution concentration, which lead to a shift of the absorption edge. The shoulder appearing at the rising edge proves to be characteristic of a tetragonal distortion. The Fourier transform magnitudes of EXAFS (Extended X-ray absorption fine structure) data of Cu species suggest that more Cu-Br bonds may exist in high concentrations. A fivefold coordination configuration like a pyramid is used as the fitting parameters. From the analysis of the coordination numbers, the proportion of Cu-O and Cu-Br is 4:1 in the saturated solution. The Br atom is on the equatorial plane of the model. The fitting results agree well with the experiment data.

347

High brightness electron beam is one of the main goals of the research and development effort in RF photo-injectors. Compared with the normally used magnetic chicane, an alternative scheme, commonly known as 'velocity bunching', has been proposed as a tool to compress electron beam pulses in modern high brightness photo-injector sources. This paper presents numerical optimization systematically and the first attempt to demonstrate the velocity bunching scheme on SDUV-FEL linac experimentally. The relationship between the degree of bunching and the off-crest phase of the accelerating structure is explored experimentally. Velocity bunching operating mode illustrates flexible performances with an intrinsic machine jitter, which agrees well with the theoretical prediction.

349

Graphene nanoribbons (GNRs) have been synthesized by unzipping oxidized multiwalled carbon nanotubes. The thickness of the GNRs synthesized is ranged from mono-layer to four layers. The morphology of prepared GNRs is strongly dependent on structure and defects of the MWCNTs. The synchrotron radiation X-ray diffractions show the d₍₀₀₂) spacing of the GNRs decreases with the increase of the annealing temperature. This may be caused by the removing of water molecules and oxygen-containing functional groups in the GNRs.

325

A method and system for automatically and simultaneously measuring the light output of multiple scintillators, or each scintillating unit of an array, were developed. Using a large area flat panel PSPMT H8500, the light output and energy resolution were obtained automatically by comparing with reference scintillators or array using an Energy Table, Look-up Table and energy spectrum data. The aim of developing an efficient performance evaluation of scintillators was achieved. Using the method, a scintillator performance testing system was set up and six LYSO crystals and a 3×3 LYSO array were measured. The results showed that the light output and energy resolution were accurately measured automatically. The deviation of repeat measurements for the same sample was not more than 2%, and the nonlinear deviation of the system was not more than 3%. The system is suitable for measuring the performance of crystals, especially where the mass measurement of crystals and arrays is required.

292

With the development on high-speed integrated circuit, fast high resolution sampling ADC and digital signal processors are replacing analog shaping amplifier circuit. This paper firstly presents the numerical analysis and simulation on R-C shaping circuit model and C-R shaping circuit model. Mathematic models are established based on 1^st order digital differential method and Kirchhoff Current Law in time domain, and a simulation and error evaluation experiment on an ideal digital signal are carried out with Excel VBA. A digital shaping test for a semiconductor X-ray detector in real time is also presented. Then a numerical analysis for Sallen-Key (S-K) low-pass filter circuit model is implemented based on the analysis of digital R-C and digital C-R shaping methods. By applying the 2^nd order non-homogeneous differential equation, the authors implement a digital Gaussian filter model for a standard exponential-decaying signal and a nuclear pulse signal. Finally, computer simulations and experimental tests are carried out and the results show the possibility of the digital pulse processing algorithms.

373

Optical and electrical properties of composites, prepared by filling of high density polyethylene (HDPE) with two kinds of multi-walled carbon nanotubes (MWNTs) differing in diameters, were explored by terahertz time-domain spectroscopy (THz-TDS) in the frequency range from 0.2 to 1.6 THz. It is found that composite with larger-diameter MWNTs possesses larger absorption coefficient and conductivity at the same concentration. The real part of the ac conductivity of the composites follows a power law dependence on frequency. And the power index is around 0.75 regardless of the MWNT concentration and diameter. The experimental data were analyzed with Cole-Cole equation under the assumption that the conductive clusters dispersed in the polymer matrix behave like dipoles and contribute mainly to the dielectric loss. It is found that both of the composites have similar values of relaxation time and distribution parameter. With increase of the MWNTs concentration, the relaxation time increases and tends to saturate at 0.7 ps after passing through the percolation threshold.

302

Copper nano-particles were prepared by 100 kGy room temperature γ-ray irradiation of CuSO₄ aqueous solution added with surfactant and inactive agent. Effects of the surfactants and pH value on particle size and morphology of the Cu powder, and the storage stability, were investigated. Structure, morphology, particle size and melting point of the copper nano-particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), laser particle size analyzer and differential scanning calorimetry (DSC), respectively. The results show that the Cu nano-particles prepared with PCM as surfactant and N, N-bis-hydroxyethyl dodecyl amide as inactive agent, in pH=4.0–6.5 of the aqueous solution, can be stored in air for 140 days.

332

In this paper, eleven consecutive hepatocellular carcinoma (HCC) patients with an embolus in the hepatic vein (HV), inferior vena cava (IVC)and right atrium (RA) were studied with ¹⁸F-FDG PET/CT and contrast enhanced CT. When correlated with final diagnosis, ¹⁸F-FDG PET/CT and contrast enhanced CT was positive in 11 patients (100%), 7 patients (63.6%), respectively. The accuracy of PET/CT and contrast-enhanced CT were 100%, 63.6%. Three cases with secondary blood thrombi in the distant IVC, which were confirmed by PET/CT, cannot be identified by contrast enhanced CT. The average survival was 3 months (range, 1-12mo). The 12 months survival rate was 9.1%. Our results suggest that highly metabolic tumor thrombus in the HV, IVC and RA may be depicted on ¹⁸F-FDG PET/CT in HCC patients. It may discriminate between malignant and secondary benign blood thrombi.

317

In humid environment, a particles can be picked up from the substrate by the capillary force, such as in the colloidal probe of atomic force microscopy technique. In this paper, a model of the capillary bridge between spherical particles is used to study effect of the friction force in nanoparticles manipulation. Based on the Young-Laplace equation, Newtonian equation and adopted the constant volume boundary condition to calculate the particle motion, the friction force effects on nanoparticles manipulation are analyzed. The results show that the friction force has little effect on the particle motion, and the particle velocity decreases slightly in presence of the friction force. The friction force is opposed to the motion of the nanoparticle. As the tip velocity increases, there is a critical velocity beyond that the particle cannot be picked up from the substrate, and the critical velocity decreases in presence of the friction force. These provide a better understanding of the nanoparticle mechanical properties in humid environment.

424

The study of thermal characteristics during startup is one of the most important aspects for safety analysis of supercritical water-cooled reactor (SCWR). According to the given sliding pressure mode of SCWR, thermal analysis on temperature-raising phase and power-raising phase of startup are carried out. Considering the radial heterogeneity of power distribution, thermal characteristics for different assemblies during startup are also put forward. The results show that, during temperature-raising phase with core power increased only, the temperature of moderator, coolant and fuel cladding in inner assemblies are increased with little amplitude. During power-raising phase with core power and feed-water flow rate increased, the coolant temperature keeps unchanged, but the moderator temperature is decreased. With a greater variation of power, fuel cladding temperature shows a greater increase. Furthermore, considering the uneven distribution of radial power, thermo-hydraulic characteristics with uneven cladding temperature distribution shows a certain horizontal heterogeneity for different fuel assemblies, which becomes serious as flow rate and power increase. By adjusting flow rate distribution in different fuel assemblies or changing power setting during startup, the cladding temperature difference could be effectively reduced, which provides a certain reference for startup optimization of SCWR.

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