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71.
Atomic Insights into Phase Evolution in Ternary Transition‐Metal Dichalcogenides Nanostructures 下载免费PDF全文
Phase engineering through chemical modification can significantly alter the properties of transition‐metal dichalcogenides, and allow the design of many novel electronic, photonic, and optoelectronics devices. The atomic‐scale mechanism underlying such phase engineering is still intensively investigated but elusive. Here, advanced electron microscopy, combined with density functional theory calculations, is used to understand the phase evolution (hexagonal 2H→monoclinic T′→orthorhombic Td) in chemical vapor deposition grown Mo1− x W x Te2 nanostructures. Atomic‐resolution imaging and electron diffraction indicate that Mo1− x W x Te2 nanostructures have two phases: the pure monoclinic phase in low W‐concentrated (0 < x ≤ 10 at.%) samples, and the dual phase of the monoclinic and orthorhombic in high W‐concentrated (10 < x < 90 at.%) samples. Such phase coexistence exists with coherent interfaces, mediated by a newly uncovered orthorhombic phase Td′. Td′, preserves the centrosymmetry of T′ and provides the possible phase transition path for T′→Td with low energy state. This work enriches the atomic‐scale understanding of phase evolution and coexistence in multinary compounds, and paves the way for device applications of new transition‐metal dichalcogenides phases and heterostructures. 相似文献
72.
Mean shift(均值漂移)算法核函数窗口的带宽目前仍没有一个统一的确定标准.对整体图像根据Canny算子提取的边缘方向信息分成3类子图,一类是规则边缘子图,由规则边缘像素组成;第2类为非规则边缘子图,由边界方向变化剧烈的边缘像素组成;第3类是非边缘子图,由区域内部平坦区域和噪声区域组成.规则边缘子图和非边缘子图采用大窗口使区域内部更为平滑,并使噪声区域达到更高的抗噪性能,非规则边缘子图用小窗口可保持更高的边界精度.实验采用金属断口图像进行分割,结果表明,针对不同子图采用不同核函数带宽的方法使分割后的金属断口图像边界更准确,抗噪性能也更强. 相似文献
73.
Jan Kapa?a 《Calphad》2011,35(2):219-223
The thermodynamic properties of ABr-PrBr3(A=Li-Cs) systems were assessed by the CALPHAD method. The liquid phase in the systems was described by the non-stoichiometric associate model. The entropies of mixing in the liquid were evaluated from experimental liquidus and enthalpy of mixing data. For the pseudobinary compounds A3PrBr6,APr2Br7, and A2PrBr5 (A=K,Rb) and Cs3PrBr6 and CsPr2Br7, the dependences of Gibbs energies of formation on temperature were calculated. The anomalies of sequences of thermodynamic properties in RbBr-PrBr3 were observed and discussed. The nature of the liquid phase and precision of calculations of the Rb2PrBr5(s) compound were discussed. 相似文献
74.
Binary oxides of manganese and vanadium have been synthesized by solid state sintering, in which the mass ratio of the individual components Mn2O3 and VO2 have been varied from 90:10 to 5:95. The bulk ceramic samples were characterized by X-ray diffraction and scanning electron microscopy with energy dispersive X-ray analysis. The initial compositions either rich in Mn2O3 or in equi-proportion by mass with VO2 yield β-Mn2V2O7 or a new crystalline form of Mn2V2O7, with unit cell parameters: a = 7.73091 Å, b = 6.640788 Å, c = 6.70779 Å α = γ = 90° and β = 98.7086° which is designated as γ-Mn2V2O7. The compositions, richer in VO2 produce MnV2O6 co-existing with V2O5 the proportion of which increases with increase in VO2. The surface microanalysis shows a spherical-granular morphology in Mn2V2O7 structure and plate/rod-like structures co-existing with granular morphology in case of MnV2O6 together with V2O5. The electrical parameters of the negative temperature coefficient thermistors were determined. Depending on the constituent oxide composition, the NTC thermistors showed room temperature resistivity in the range of 6.52 × 102 to 6.1 × 106 Ω-cm. The thermistor constant and activation energy are in the range of 0.12–0.458 eV and 1393–4801 K, respectively. 相似文献
75.
Hongbo Gang Xiaona Zhuanghui Baojian Qinghui Jianlong Qiu-Shi 《Sensors and actuators. A, Physical》2009,150(2):296-301
In this paper, we present a new process for fabricating tip-shaped polymer microstructure array coated by patterned metal layer. This new process involves three techniques including: micro-molding, patterned metal layer transfer, and electrochemical-based sacrificial layer. As we know, it is very difficult to remove the extra photoresist (PR) in the concave areas in traditional micro-fabrication technology, which hinders patterning metal layers on three-dimensional (3D) microstructures. The electrochemical-based sacrificial layer technique can effectively resolve this problem, which is verified by scanning electron microscopy (SEM) characterization. Comparative study between the 3D metal-coated polyimide microstructures fabricated with and without the electrochemical-based sacrificial layer step is also performed and SEM images proved the effect of the presented process. The applicability of the developed process is also demonstrated with the successful fabrication of a pyramid-shaped polyimide microelectrodes array for neural stimulation. 相似文献
76.
Meiling Liu Xiangnan Liu Menxin Wu Lufeng Li Lina Xiu 《Computers & Geosciences》2011,37(10):1642-1652
A generalized dynamic fuzzy neural network (GDFNN) was created to estimate heavy metal concentrations in rice by integrating spectral indices and environmental parameters. Hyperspectral data, environmental parameters, and heavy metal content were collected from field experiments with different levels of heavy metal pollution (Cu and Cd). Input variables used in the GDFNN model were derived from 10 variables acquired by gray relational analysis. The assessment models for Cd and Cu concentration employed five and six input variables, respectively. The results showed that the GDFNN for estimating Cu and Cd concentrations in rice performed well at prediction with a compact network structure using the training, validation, and testing sets (for Cu, fuzzy rules=9, R2 greater than 0.75, and RMSE less than 2.5; for Cd, fuzzy rules=9, R2 greater than 0.75, and RMSE less than 1.0). The final GDFNN model was then compared with a back-propagation (BP) neural network model, adaptive-network-based fuzzy interference systems (ANFIS), and a regression model. The accuracies of GDFNN model prediction were usually slightly better than those of the other three models. This demonstrates that the GDFNN model is more suitable for predicting heavy metal concentrations in rice. 相似文献
77.
高灵敏度金属分离器传感线圈的设计 总被引:1,自引:0,他引:1
分析了电感线圈探测金属的理论,针对传统的金属探测传感器灵敏度低,抗干扰能力差和结构复杂的缺点,根据电磁感应原理提出了一种具有高探测精度和高抗干扰能力的新型金属探测传感器,并描述了其结构和材料设计方案。最后用试验验证了设计思想和设计方案的正确性和实用性。 相似文献
78.
单一尺寸矩形毛坯排样时长板的最优分割 总被引:12,自引:2,他引:10
讨论了存在剪刃长度约束时单一尺寸矩形毛坯的优化排样问题,将板材分割成多张子板,通过优化确定子板张数、各子板长度和毛坯在各子板上的排列,使事 板材中所含毛坯数达到最大;并对Agrawal提出的单一尺寸矩形毛了优化排样方法进行扩展,构造出一种分支定界方法,用于解决长板最优分割问题,实验计算结果表明,所述算法非常有效;最后给出了例题数据的排样结果,与企业的通常做法相比较,说明了采用本方法的节材潜力。 相似文献
79.
80.
Metal matrix composites reinforced by three-dimensional (3-D) continuous network structure reinforcement (3DCNRMMC) are difficult to machine due to serious tool wear and poor surface roughness caused by the brittle and hard reinforcement which interpenetrate into ductile matrix. In order to achieve the approach of low cost of 3DCNRMMC, the machinability of it needs to be understood. The influences of three cutting parameters and volume fraction of reinforcement on cutting force were analyzed in detail. The results indicate that: (1) Due to the brittle phase(s) introduced into ductile matrix of composites, there is a large fluctuation of cutting force causing deterioration of machinability. The fluctuation ranges of cutting forces, initially increase rapidly with the increase of volume fraction of reinforcement and then decrease finally, are largest at the range of the volume fraction of 55–65%; (2) The influence of cutting parameters on cutting force is obvious. With the increases of cutting speed, cutting force decreases gradually unless cutting speed exceeds the value of 209 m/min. Cutting forces increase with increasing feed rate and depth of cut; (3) Owing to the large fluctuation of cutting force, there were some cratered surfaces caused by Si3N4 reinforcement pulling-out and flaking-off. Some brittle phase protruding from the machined surface caused the deterioration of machined surface. 相似文献