MR动态增强联合扩散加权成像技术在乳腺疾病诊断中的价值

目的探讨乳腺MR动态增强扫描联合扩散加权成像技术在乳腺疾病影像诊断中的价值。方法对48例女性乳腺患者进行MRI检查,先进行双侧乳腺常规MRI平扫,再进行双侧乳腺扩散加权平面回波（EPI）序列扫描,最后行乳腺动态增强扫描。通过后处理,得到病灶处表观弥散系数（ADC）值及时间-信号强度曲线。结果根据时间-信号强度曲线特点及ADC值,结合常规MRI形态学特点进行良、恶性病变诊断。MRI诊断为恶性肿瘤19例,良性病变29例。手术或活检病理结果证实MRI诊断为恶性肿瘤的19例患者中,18例为恶性肿瘤,另外1例为良性肿瘤（旺炽性腺瘤）;MRI诊断为良性病变的29例患者,手术或病理活检均证实为良性病变。MRI区分乳腺良、恶性病变的准确率为97.9%（47/48）,与手术或病理活检准确率（100%）比较差异无统计学意义（字2=0.044,P=0.834）。结论动态增强扫描联合扩散加权成像技术,可提高乳腺疾病影像诊断准确率。     

Correlation between flow characteristics and interfacial friction behaviour of a Zr-based metallic glass during micro-extrusion

The interfacial friction behaviour of Zr₃₅Ti₃₀Be_26.75Cu_8.25 metallic glass during micro-extrusion was investigated at various strain rates and temperatures in the supercooled liquid region. A friction mechanism map that distributes adhesion regime, furrow regime and mechanical engagement regime was constructed. These regimes respectively correspond to Newtonian flow, non-Newtonian flow and inhomogeneous flow by comparing with the typical deformation map. The correlation between flow characteristics and interfacial friction behaviour is well analysed by combining the viscosity theory with the finite-element simulations.     

Band gap tunable and improved microstructure characteristics of Cu2ZnSn(S1−x,Sex)4 thin films by annealing under atmosphere containing S and Se

Cu₂ZnSn(S_xS_1?x)₄ (CZTSSe) thin films were prepared by annealing a stacked precursor prepared on Mo coated glass substrates by the sputtering technique. The stacked precursor thin films were prepared from Cu, SnS₂, and ZnS targets at room temperature with stacking orders of Cu/SnS₂/ZnS. The stacked precursor thin films were annealed using a tubular two zone furnace system under a mixed N₂ (95%) + H₂S (5%) + Se vaporization atmosphere at 580 °C for 2 h. The effects of different Se vaporization temperature from 250 °C to 500 °C on the structural, morphological, chemical, and optical properties of the CZTSSe thin films were investigated. X-ray diffraction patterns, Raman spectroscopy, and X-ray photoelectron spectroscopy results showed that the annealed thin films had a single kesterite crystal structure without a secondary phase. The 2θ angle position for the peaks from the (112) plane in the annealed thin films decreased with increasing Se vaporization temperature. Energy dispersive X-ray results showed that the presence of Se in annealed thin films increased from 0 at% to 42.7 at% with increasing Se vaporization temperatures. UV–VIS spectroscopy results showed that the absorption coefficient of all the annealed thin films was over 10⁴ cm^?1 and that the optical band gap energy decreased from 1.5 eV to 1.05 eV with increasing Se vaporization temperature.     

Thermodynamic properties of 3C-SiC

In the present paper, we report on the results of various thermodynamic properties of 3C-SiC at high pressure and temperature using first principles calculations. We use the plane-wave pseudopotential density functional theory as im- plemented in Quantum ESPRESSO code for calculating various cohesive properties in ambient condition. Further, ionic motion at a finite temperature is taken into account using the quasiharmonic Debye model. The calculated thermody- namic properties, phonon dispersion curves, and phonon densities of states at different temperatures and structural phase transitions at high pressures are found to be in good agreement with experimental and other theoretical results.     

A novel non-uniformity evaluation metric of infrared imaging system

Non-uniformity (NU) evaluation metric of infrared thermal imaging system is important for evaluating the thermal imager and also can help to improve existing NU correction methods. However, in existing evaluation metrics, there are still some problems, such as not objective enough and not comprehensive enough. This paper brings forward a novel NU evaluation metric, in which we adopt the average derivative of the response of thermal imager with the temperature of test blackbody as a new parameter. A metric-temperature curve which shows the change trend of the NU with the temperature of test blackbody was achieved to enhance the performance of NU evaluation metric. Both the subjective images and objective data indicate that the new method raised in this work is much more objective and comprehensive. Our work is expected to become a general NU evaluation metric in the future.     

Thermoluminescence glow curve deconvolution of LiF:Mg,Cu,Si with more realistic kinetic models

Thermoluminescence (TL) glow curves of LiF:Mg,Cu,Si were deconvoluted with the introduction of enhanced physical model which envisages that both electrons and holes, produced by ionization radiation and trapped at the respective traps, can be thermally released into the conduction and the valence band, respectively and the holes may also radiatively recombine with electrons at the electron recombination centers. The model is more generalized than the ordinary trap interaction model which only permits the traffic of electrons through the conduction band. An effective numerical analysis method was developed to calculate the glow curve to be compatible with the measured curves. The validity of the numerical method was verified through artificially generated TL glow curves for a wide range of trap parameters. In order to identify TL kinetics of LiF:Mg,Cu,Si with higher accuracy, its glow curves were deconvoluted for two more generalized models, namely, the Schön–Klasens model and the Chen–Pagonis–Lawless model as well as the ordinary trap interactive model. The parameters in the more generalized multi-trap multi-recombination center (MTMR) model were found to be consistent with the quasi-static approximation(QSA) method.     

Effects of inclined impermeable bed on the turbulent characteristics of the flow using particle image velocimetry

In this study, the turbulent characteristics of the flow in an open channel with horizontal and inclined impermeable beds were studied experimentally using two-dimensional particle image velocimetry (PIV). The experiments were conducted in a channel of 6.5 m in length, 7.5 cm in width and 25 cm in height. The slope of the channel was S = 0 for the horizontal impermeable bed and for S = ?0.002, S = ?0.004 and S = ?0.006 for the inclined impermeable bed. Hydraulic characteristics such as distributions of velocities, turbulent intensities and Reynolds stress are investigated at a fine resolution using the PIV. Velocity is measured above the horizontal and inclined impermeable bed for the same different heights (h = 5, 7, 9, 11 and 13 cm) and for the same different discharges (Q = 0.735, 0.845 and 0.970 lt/s). Results show that the channel slope influences significantly near the impermeable bed but not near the free surface the variation of turbulent characteristics of the flow and also the alteration of the channel slope from ?0.002 to ?0.006 doesn't influence the variation of turbulent characteristics of the flow, which are the longitudinal turbulent intensity u′U_*, the vertical turbulent intensity v′/U_* and the turbulent kinetic energy. The channel slope doesn't influence the Reynolds stress.     

On the noise limit of stress and temperature measurements with micro‐Raman spectroscopy

We report for the first time on the thorough experimental and theoretical assessment of the noise limit of mechanical stress and temperature measurements with micro‐Raman spectroscopy. A comprehensive study has been performed in which, for different incident laser light intensities and acquisition times, 1000 Raman spectra of mono‐crystalline silicon were acquired per setting. Curve fitting was employed to obtain the peak positions of all the spectra, from which the standard deviations of the measured peak positions were obtained versus the total accumulated amount of laser light incident on the sample during one measurement. It has been found that the noise in the obtained peak position decreases as 1/sqrt(n) over more than three decades of the incident amount of laser light. At very low light conditions, the noise decreases as 1/n. By comparing the experimental results obtained to recent theoretical work, we show that the acquisition is limited by photon shot noise over most of the range and is limited by electronic detector noise at very low light conditions only. Pixelation errors do not play a role. It is concluded that the low electronic noise of typical Raman spectroscope detectors is overkill for the investigation of mechanical stress and temperature in silicon and other materials with comparable peaks, as it has absolutely no influence on the noise level of such an experiment. Maximum Raman signal intensity on the detector and high quantum efficiency detection are more important. Copyright © 2013 John Wiley & Sons, Ltd.     

Continuous Wavelet Transform to Improve Resolution of Overlapped Peaks Based on Curve Fitting

An improved curve fitting for the resolution of the overlapped peaks was proposed. The main work is to use the continuous wavelet transform (CWT) to sharpen peaks and get reasonable initial estimates for the parameters of each peak. As a result, the fitted condition was improved and accurate results could be acquired. To verify the suggested method, separation of several kinds of overlapping peaks simulated by computer and the experimental voltammogram have been performed and are discussed.