巫山县乡村地区公路网通达性空间格局研究

以巫山县为研究区域,运用GIS技术,以乡镇和行政村为节点单元,采用公路网密度、乡镇间直达性指数、乡镇内直达性指数、居民点道路临近性、乡镇间节点可达性指数、乡镇内节点可达性指数、干线衔接距离、地形位指数8项指标,引入熵权-TOPSIS模型,综合分析和评价巫山县乡村地区公路网通达性及其空间分布格局。研究表明,各项指标对巫山县乡村公路网的影响程度由高到低为：公路网密度＞地形位指数＞干线衔接距离＞居民点临近性＞乡镇内直达性指数＞乡镇间节点可达性指数＞乡镇内节点可达性指数＞乡镇间直达性指数;除中心城区外,各乡镇贴近度为0.170 0＞0.831 9,区域差异明显,其中铜鼓最高,当阳最低;整体上,巫山县乡村公路通达性以中等、较好等级为主,通达性空间格局总体以铜鼓、建平、三溪为核往外围扩散,与交通干线骨架吻合度较高,呈现“三核、一环、一域”的空间格局。研究成果对巫山县山区乡村公路网建设和优化有一定的指导作用,在一定程度上完善了乡村地区公路网通达性分析和评价方法。     

Synthesis of starfish-like Cu2O nanocrystals through ��-irradiation and their application in lithium-ion batteries

In this study, single-crystalline starfish-like cuprous oxide (Cu₂O) nanocrystals with the backbones lengths in the range of 660 nm~16 ??m are successfully prepared through ??-irradiation, the cetyltrimethylammonium bromide (CTAB) is used as a capping material or soft colloidal templates. Without the addition of CTAB in the reaction system, irregular Cu₂O nanoclusters were obtained and their diameter is about 200 nm~1 ??m. Controlling the concentration ratio of CTAB to the copper ions, starfish-like morphology of Cu₂O can be obtained in high yield. Their structures are characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. The possible growth mechanism of the starfish structure is discussed in the text. For potential application in lithium-ion batteries, an electrode made of the starfish-like Cu₂O shows excellent electrochemical cycling performance and high-rate capability. Compared with the Cu₂O nanoclusters, the starfish-like Cu₂O exhibits an improved electrochemical cycling stability. The capacity of the starfish-like Cu₂O can maintain 340 and 215 mAh g^?1 after 50 cycles at the rate of 0.1 C and 5 C, respectively. The reversible capacity holds 60% as the discharge?Ccharge rate even increases by 50 times.     

Microstructure and wear resistance of laser clad cobalt-based alloy multi-layer coatings

Multi-layer Co-based alloy (HMSP 2537) were deposited on Ni-based superalloy plate with a TJ-TL-T5000 type CO₂ laser. Sections of such coatings were examined to reveal their microstructure and phase composition using optical microscope, scanning electron microscope (SEM), and X-ray diffractometer (XRD). The hardness and wear resistance of the coatings were tested. The results showed that the prime phase (γ-Co dendrite) and other phases, such as CrNi, Co₇W₆, and Cr₂₃C₆ existed in the coatings. Dendrite or cellular microstructures were observed perpendicular to the interface, and coarsening microstructures were obtained as more layers deposited. Dendrite paralleling to laser scan speed was also found near the top surface of the last layer. Fine microstructures of γ-Co dendrite and lamellar eutectic in inter-dendritic regions strengthened the coatings. Microhardness and wear resistance of the coatings were much higher than that of substrate but slightly decreased with layers increased.     

两种测试高温超导薄膜微波表面电阻方法的讨论

介绍两种工作在12GHz附近的高温超导薄膜微波表面电阻Rs测试系统,并分析各自的特点.同时简介电子科技大学在提高Rs测试精度上所作的一些改进.     

Surface-enhanced Raman scattering of 4-mercaptobenzoic acid and hemoglobin adsorbed on self-assembled Ag monolayer films with different shapes

Polyvinylpyrrolidone (PVP)-protected silver nanostructures of various shapes, including nanocubes, nanospheres, and hybrid shapes with nanospheres and nanorods, on the surface of glass or Si substrates (PVP-Ag films) are prepared by using electrostatic self-assembly. With 4-mercaptobenzoic acid (4-MBA) as a probe molecule, it is demonstrated that the PVP-protected silver nanocubes films (PVP-Ag NCs) have better surface-enhanced Raman scattering (SERS) activity with an order of magnitude larger enhancement factors (EF) than the PVP-protected silver nanospheres films and the PVP-protected silver hybrid shapes films, which is confirmed by our numerical simulations. The EF of 4-MBA on the PVP-Ag NCs film are up to ~5.38 × 10⁶, and the detection limit is at least down to ~10^?8 M. The uniformity and reproducibility of the SERS signals on PVP-Ag NCs film are tested by point-to-point and batch-to-batch measurements. Meanwhile, the PVP-Ag films are also shown to be an excellent SERS substrate with good biocompatibility for hemoglobin detection. It is shown that the PVP-Ag NCs films can be used as excellent SERS substrate with good activity, uniformity, reproducibility, and biocompatibility and are promising for a myriad of chemical and biochemical sensing applications.     

Non-Gaussian water diffusion kurtosis imaging of prostate cancer

Purpose

To evaluate the non-Gaussian water diffusion properties of prostate cancer (PCa) and determine the diagnostic performance of diffusion kurtosis (DK) imaging for distinguishing PCa from benign tissues within the peripheral zone (PZ), and assessing tumor lesions with different Gleason scores.

Materials and Methods

Nineteen patients who underwent diffusion weighted (DW) magnetic resonance imaging using multiple b-values and were pathologically confirmed with PCa were enrolled in this study. Apparent diffusion coefficient (ADC) was derived using a monoexponential model, while diffusion coefficient (D) and kurtosis (K) were determined using a DK model. Differences between the ADC, D and K values of benign PZ and PCa, as well as those of tumor lesions with Gleason scores of 6, 7 and ≥ 8 were assessed. Correlations between parameters D and K in PCa were analyzed using Pearson’s correlation coefficient. ADC, D and K values were correlated with Gleason scores of 6, 7 and ≥ 8, respectively.

Results

ADC and D values were significantly (p < 0.001) lower in PCa (0.79 ± 0.14 μm²/ms and 1.56 ± 0.23 μm²/ms, respectively) compared to benign PZ (1.23 ± 0.19 μm²/ms and 2.54 ± 0.24 μm²/ms, respectively). K values were significantly (p < 0.001) greater in PCa (0.96 ± 0.20) compared to benign PZ (0.59 ± 0.08). D and K showed fewer overlapping values between benign PZ and PCa compared to ADC. There was a strong negative correlation between D and K values in PCa (Pearson correlation coefficient r = − 0.729; p < 0.001). ADC and K values differed significantly in tumor lesions with Gleason scores of 6, 7 and ≥ 8 (p < 0.001 and p = 0.001, respectively), although no significant difference was detected for D values (p = 0.325). Significant correlations were found between the ADC value and Gleason score (r = − 0.828; p < 0.001), as well as the K value and Gleason score (r = 0.729; p < 0.001).

Conclusion

DK model may add value in PCa detection and diagnosis. K potentially offers a new metric for assessment of PCa.     

Improved l1-SPIRiT using 3D walsh transform-based sparsity basis

l1-SPIRiT is a fast magnetic resonance imaging (MRI) method which combines parallel imaging (PI) with compressed sensing (CS) by performing a joint l1-norm and l2-norm optimization procedure. The original l1-SPIRiT method uses two-dimensional (2D) Wavelet transform to exploit the intra-coil data redundancies and a joint sparsity model to exploit the inter-coil data redundancies. In this work, we propose to stack all the coil images into a three-dimensional (3D) matrix, and then a novel 3D Walsh transform-based sparsity basis is applied to simultaneously reduce the intra-coil and inter-coil data redundancies. Both the 2D Wavelet transform-based and the proposed 3D Walsh transform-based sparsity bases were investigated in the l1-SPIRiT method. The experimental results show that the proposed 3D Walsh transform-based l1-SPIRiT method outperformed the original l1-SPIRiT in terms of image quality and computational efficiency.     

Search for exclusive multibody non- decays at the resonance

Using data collected at the psi(3770) resonance with the CLEO-c detector at the Cornell e+e- storage ring, we present searches for 25 charmless decay modes of the psi(3770), mostly multibody final states. No evidence for charmless decays is found.     

Influence of potential function asymmetries on the performance of nonlinear energy harvesters under white noise

To improve the broadband transduction capabilities of vibratory energy harvesters (VEHs) under random and non-stationary excitations, many researchers have resorted to purposefully introducing nonlinearities into the restoring force of the harvester. While performing this task, it is often very challenging to maintain a perfectly symmetric restoring force which yields a VEH with an asymmetric potential energy function. This paper investigates the influence of potential function asymmetries on the performance of nonlinear VEHs under white noise inputs. To that end, a quadratic nonlinearity is introduced into the restoring force and its influence on the mean output power of the harvester for mono- and bi-stable quartic potentials is investigated. It is shown that, for VEHs with a mono-stable quartic potential function, the mean output power increases with the degree of potential function asymmetry. On the other hand, for energy harvesters with a bi-stable quartic potential function, asymmetries in the restoring force appear to worsen performance especially for low to moderate noise intensities. When the noise intensity becomes sufficiently large, the influence of the potential function?s asymmetry on the mean power diminishes. Results also reveal that a VEH with a symmetric bi-stable quartic potential function produces higher mean power levels than the one with the most asymmetric mono-stable potential. As such, it is concluded that a VEH with a symmetric bi-stable potential is most desirable to improve performance under white noise.