某体育馆张弦钢结构屋盖设计的若干问题分析

某体育馆根据各区域的功能不同分别采用弦支穹顶和张弦梁结构。对弦支穹顶和张弦梁结构分别进行结构选型和结构布置分析,两部分独立进行受力性能分析。通过对弦支穹顶和张弦梁的受力性能分析,并与设计的初始状态比较,说明该结构方案受力合理。同时分析了温度作用对构件应力、结构变形和支座推力的影响,并采用相应的措施减小温度作用对结构的影响。     

拱形张弦拱结构模型试验研究

本文介绍了三组不同矢(垂)跨比拱形张弦拱结构模型的静力与动力特性试验研究情况。模型静力试验包括全跨均布荷载、半跨活荷载、预应力张拉过程模拟以及极限承载力试验;模型动力特性试验测试了结构的自振频率与振型,其中质量块按拱下吊挂配重与拱上附着配重两种方式。试验结果与理论公式及有限元分析进行了比对,证明了理论公式的正确性和可靠性。静力试验得出了拱形张弦拱结构的线性特性、支座水平位移与跨中竖向挠度大小相当、预应力对支座水平位移的控制作用,动力特性试验给出结构的基本振型为反对称双半波、质量块的设置方式对自振频率与振型有较大差异等结论。本文研究成果对该新型结构的工程应用有较好的参考意义。     

Assessing the width of Gaussian density of states in organic semiconductors

The Density of States (DOS) is an ingredient of critical importance for the accurate physical understanding of the optoelectronic properties of organic semiconductors. The disordered nature of this class of materials, though, renders the task of determining the DOS far from trivial. Its extraction from experimental measurements is often performed by driving the semiconductor out of thermal equilibrium and therefore requires making assumptions on the charge transport properties of the material under examination. This entanglement of DOS and charge transport models is unfavorable since transport mechanisms in organic semiconductors are themselves still subject of debate. To avoid this, we propose an alternative approach which is based on populating and probing the DOS by means of capacitive coupling in Metal Insulator Semiconductors (MIS) structures while keeping the semiconductor in thermal equilibrium. Assuming a Gaussian shape, we extract the DOS width by numerical fitting of experimental Capacitance–Voltage curves, exploiting the fact that the DOS width affects the spatial distribution of accumulated charge carriers which in turn concurs to define the MIS capacitance. The proposed approach is successfully tested on two benchmark semiconducting polymers, one of n-type and one of p-type and it is validated by verifying the robustness of the extraction procedure with respect to varying the insulator electrical permittivity. Finally, as an example of the usefulness and effectiveness of our approach, we study the static characteristics of thin film transistors based on the aforementioned polymers in the framework of the Extended Gaussian Disorder transport model. Thanks to the extracted DOS widths, the functional dependence of current on the gate voltage is nicely predicted and physical insight on transistor operation is achieved.     

A superposition method of reflected wave for moving string vibration with nonclassical boundary

A reflected wave superposition method is proposed for an axially traveling string with classical and nonclassical boundaries, based on the reflection of the propagating wave on both sides of the string, combining its initial conditions and the continuity conditions in order to obtain the expressions for the reflected wave. The reflection process, in three phases, is deduced and a determinate expression for the transverse vibration is obtained. The correctness and superiority of the proposed method is verified by comparison with the Newmark-β method for an axially moving string with a fixed and a spring-dashpot boundary.     

改进的Fast-CNN模型在绝缘子特征检测中的研究

针对目前电网巡检系统中采用红外成像检测绝缘子串特征的效果受环境影响，提出联合显著区域和Fast-CNN网络（改进后的卷积神经网络）用于绝缘子特征检测研究。显著区域检测首先采用超像素描述各区域位置的整体信息；然后基于各超像素的特征协方差信息计算各超像素的显著度得到大致显著区域；再通过区域模块化和局部复杂度对比提取显著特征，同时将2种方法提取的显著特征分别输入改进后的Fast-CNN网络进行显著区域检测，同时引入动态自适应池化模型和余弦窗处理中间层，最后通过多次迭代训练得到绝缘子特征，避免CNN模型耗时的全图搜索。将本文算法在红外图像库中进行测试，本文算法的F-Measure以及平均误差MAE均优于当前流行算法。     

基于位串内容感知的数据分块算法

针对基于内容的可变长度的分块CDC算法中数字签名计算需要耗费大量CPU开销的问题,提出了一种基于位串内容感知的数据块分块算法。算法利用每一次失败匹配尝试所带来的位特征信息,最大限度地排除不能匹配的位置,从而获得最大的跳跃长度,减少中间计算和比较的开销。实验结果表明,本算法减小了数据分块过程中数字签名计算的开销,降低了确定块边界时的CPU资源消耗,从而优化了数据分块的时间性能。     

Performance tests of a new non-invasive sensor unit and ultrasound electronics

Industrial applications involving pulsed ultrasound instrumentation require complete non-invasive setups due to high temperatures, pressures and possible abrasive fluids. Recently, new pulser-receiver electronics and a new sensor unit were developed by Flow-Viz. The complete sensor unit setup enables non-invasive Doppler measurements through high grade stainless steel. In this work a non-invasive sensor unit developed for one inch pipes (22.5 mm ID) and two inch pipes (48.4 mm ID) were evaluated. Performance tests were conducted using a Doppler string phantom setup and the Doppler velocity results were compared to the moving string target velocities. Eight different positions along the pipe internal diameter (22.5 mm) were investigated and at each position six speeds (0.1–0.6 m/s) were tested. Error differences ranged from 0.18 to 7.8% for the tested velocity range. The average accuracy of Doppler measurements for the 22.5 mm sensor unit decreased slightly from 1.3 to 2.3% across the ultrasound beam axis. Eleven positions were tested along the diameter of the 48.4 mm pipe (eight positions covered the pipe radius) and five speeds were tested (0.2–0.6 m/s). The average accuracy of Doppler measurements for the 48.4 mm sensor unit was between 2.4 and 5.9%, with the lowest accuracy at the point furthest away from the sensor unit. Error differences varied between 0.07 and 11.85% for the tested velocity range, where mostly overestimated velocities were recorded. This systematic error explains the higher average error difference percentage when comparing the 48.4 mm (2.4–5.9%) and 22.5 mm (1.3–2.3%) sensor unit performance. The overall performance of the combined Flow-Viz system (electronics, software, sensor) was excellent as similar or higher errors were typically reported in the medical field. This study has for the first time validated non-invasive Doppler measurements through high grade stainless steel pipes by using an advanced string phantom setup.     

Unconventional pairing in doped band insulators on a honeycomb lattice: the role of the disconnected Fermi surface and a possible application to superconducting β-MNCl (M=Hf,Zr)

Abstract

We investigate the possibility of realizing unconventional superconductivity in doped band insulators on the square and honeycomb lattices. The latter lattice is found to be a good candidate due to the disconnectivity of the Fermi surface. We propose applying the theory to the superconductivity in doped layered nitride β-MNCl (M= Hf, Zr). Finally, we compare two groups of superconductors with disconnected Fermi surface, β-MNCl and the iron pnictides, which have high critical temperature T_c, despite some faults against superconductivity are present.     

Gate-tuned Josephson effect on the surface of a topological insulator

In the study, we investigate the Josephson supercurrent of a superconductor/normal metal/superconductor junction on the surface of a topological insulator, where a gate electrode is attached to the normal metal. It is shown that the Josephson supercurrent not only can be tuned largely by the temperature but also is related to the potential and the length of the weak-link region. Especially, the asymmetry excess critical supercurrent, oscillatory character, and plateau-like structure have been revealed. We except those phenomena that can be observed in the recent experiment.     

Crosslinked polymer-mixture gate insulator for high-performance organic thin-film transistors

In this paper, we report on the fabrication of a crosslinked polymer-mixture gate insulator for high-performance organic thin-film transistors (TFTs). We used cyanoethylated pullulan (CEP) as a crosslinkable high-k polymer matrix and poly(ethylene-alt-maleic anhydride) (PEMA) as a polymeric crosslinking agent. Because PEMA has a high number of functional groups reactive to the hydroxyl groups of CEP, the use of PEMA is effective for minimizing the amount of remaining hydroxyl groups strongly related to the large current hysteresis and high off current of the organic TFTs. To investigate the potential of the CEP-PEMA mixture as a gate insulator, we fabricated 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C₈-BTBT) TFTs. The C₈-BTBT TFT with the 60 nm-thick CEP-PEMA gate insulator showed excellent TFT performance with a field-effect mobility of 1.4 cm²/V s and an on/off ratio of 2.4 × 10⁶.