五元联系数在高职院校学生综合素质评价中的应用

学生综合素质评价是高校素质教育测量的重要侧面,其综合素质的概念、评价指标内容的确定、权重的分配及评价方法选定直接影响着学生评价的客观性和公正性,采用"三选"法概括评价指标,用矩阵法确定各指标的权重,利用五元联系数建立数学模型试行评价,最后算例表明了它的有效性和实用性.     

Four‐Wave Mixing in a Nonlinear Fabry–Perot Interferometer

A theoretical model of fourdk54e/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">wave mixing in a Fabry–Perot interferometer with resonant nonlinearity has been developed. The conditions for the realization of the effect of interferometer transmission symmetry breaking and the specific features of the formation of spacedk54e/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">time structures of light fields have been analyzed. The laws of hysteresis of the lateral laser beam profiles have been established.     

In-vivo validation of fast spectral velocity estimation techniques

Spectrograms in medical ultrasound are usually estimated with Welch’s method (WM). WM is dependent on an observation window (OW) of up to 256 emissions per estimate to achieve sufficient spectral resolution and contrast. Two adaptive filterbank methods have been suggested to reduce the OW: Blood spectral Power Capon (BPC) and the Blood Amplitude and Phase EStimation method (BAPES). Ten volunteers were scanned over the carotid artery. From each data set, 28 spectrograms were produced by combining four approaches (WM with a Hanning window (W.HAN), WM with a boxcar window (W.BOX), BPC and BAPES) and seven OWs (128, 64, 32, 16, 8, 4, 2). The full-width-at-half-maximum (FWHM) and the ratio between main and side-lobe levels were calculated at end-diastole for each spectrogram. Furthermore, all 280 spectrograms were randomized and presented to nine radiologists for visual evaluation: useful/not useful. BAPES and BPC compared to WM had better resolution (lower FWHM) for all OW < 128 while only BAPES compared to WM had improved contrast (higher ratio). According to the scores given by the radiologists, BAPES, BPC and W.HAN performed equally well (p > 0.05) at OW 128 and 64, while W.BOX scored less (p < 0.05). At OW 32, BAPES and BPC performed better than WM (p < 0.0001) and BAPES was significantly superior to BPC at OW 16 (p = 0.0002) and 8 (p < 0.0001). BPC at OW 32 performed as well as BPC at OW 128 (p = 0.29) and BAPES at OW 16 as BAPES at OW 128 (p = 0.55). WM at OW 16 and 8 failed as all four methods at OW 4 and 2. The intra-observer variability tested for three radiologist showed on average good agreement (90%, κ = 0.79) and inter-observer variability showed moderate agreement (78%, κ = 0.56). The results indicated that BPC and BAPES had better resolution and BAPES better contrast than WM, and that OW can be reduced to 32 using BPC and 16 using BAPES without reducing the usefulness of the spectrogram. This could potentially increase the temporal resolution of the spectrogram or the frame-rate of the interleaved B-mode images.     

Sustained multi-kHz flamefront and 3-component velocity-field measurements for the study of turbulent flames

We describe an approach of imaging the dynamic interaction of the flamefront and flowfield. Here, a diode-pumped Nd:YLF laser operating at 5 kHz is used to pump a dye laser, which is then frequency doubled to 283 nm to probe flamefront OH, while a dual cavity diode-pumped Nd:YAG system produces pulse-pairs for particle image velocimetry (PIV). CMOS digital cameras are used to detect both planar laser-induced fluorescence (PLIF) and particle scattering (in a stereo arrangement) such that a 5 kHz measurement frequency is attained. This diagnostic is demonstrated in lifted-jet and swirl-stabilized flames, wherein the dynamics of the flame stabilization processes are seen. Nonperiodic effects such as local ignition and/or extinction, lift-off and flashback events, and their histories can be captured by this technique. As such, this system has the potential to significantly extend our understanding of nonstationary combustion processes relevant to industrial and technical applications. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

Thermoactivated transport of molecules H<Subscript>2</Subscript> in narrow single-wall carbon nanotubes

By use both of the plane wave DFT and the empirical exp-6 Lennard-Jones potential methods we calculate the inner potential in narrow single-wall carbon nanotubes (SWCNT) (6, 0), (7, 0) and (3, 3) which affects the hydrogen molecules. The inner potential forms a goffered potential surface and can be approximated as V(z,r,φ)≈V₀sin (2πz/a)+V(r). We show that in these SWCNTs transport of molecules is given mainly by thermoactivated hoppings between minima of the periodic potential along the tube axis. The rate hoppings is substantially depends on temperature because of thermal fluctuations of tube wall.     

First principles study of barium chalcogenides

In this study, ab initio calculation results of the vibrational properties and elastic parameters as well as characteristic Debye temperature and Poisson's ratios of two barium chalcogenides, BaSe and BaS, which crystallize in NaCl-type structure, were presented. Calculations were based on plane wave basis sets together with ultrasoft pseudopotentials in the framework of density functional theory (DFT) with generalized gradient approximation. Phonon dispersion spectra were obtained using the first principles linear response approach of the density functional perturbation theory (DFPT). The detailed total energy calculations were performed in order to obtain elastic constants using distortions on cubic phase. The calculated structural, elastic, and thermal parameters of BaSe and BaS systems agree well with the available experimental data and theoretical calculations.