预制混凝土夹芯保温墙桁架连接件抗剪性能研究

桁架连接件是连接混凝土夹芯墙板内外叶墙板的重要构件。为了研究桁架连接件的抗剪性能,对2组不同保温层厚度的4个受剪试件进行了试验研究和有限元分析。试验研究表明：剪力作用下夹芯墙桁架连接件的破坏形式为其腹杆受压屈曲后受拉腹杆断裂或受拉腹杆被拔出的锚固破坏。在试验的基础上,对夹芯墙体桁架连接件抗剪性能做了变参数数值分析,主要考虑了桁架腹杆直径、节点间距和保温层厚度等参数的变化。模拟结果表明：夹芯墙的屈服和极限承载力随着腹杆直径的增大而增加,随着节点间距的减小而增大;随着保温层厚度的减小,墙体的抗剪屈服承载力增大,而由于保温板的高压缩性,导致其极限荷载与保温层厚度的相关性不明显。     

基于解析冗余式的风机传动系统故障诊断

为了以系统有序的方法对风机的具体元件参数进行故障诊断,给出一种基于键合图模型的故障诊断方法。键合图模型是一种跨能域的元件级模型,因此能够定位到具体的故障元件。同时键合图模型能够清晰地表明各元件之间的关系,因此适用于推导解析冗余式。通过解析冗余式可以对系统进行故障检测和隔离。为了能够系统地得到尽量多的解析冗余式,提高故障的可隔离性,该方法首先建立风机的键合图模型,然后由键合图模型导出时间因果图,由时间因果图导出变量关系图,最后由变量关系图消除键合图中结点方程的未知变量得到解析冗余式。实验结果验证了采用该方法推导的解析冗余式能够用于风机参数故障的诊断。     

特型燃气喷口对补燃室掺混燃烧的影响

采用N-S方程、k-ε双方程和非预混燃烧简化PDF模型,对3种特型燃气喷口结构的固冲发动机补燃室掺混燃烧流场进行了数值研究。分析3种特型燃气喷口对补燃室中掺混燃烧的影响,并与常规型燃气喷口的仿真结果进行了对比分析。结果表明:特型燃气喷口可以有效增强补燃室中燃气与空气的掺混效果,提高燃气的完全燃烧程度,提升固冲发动机补燃室的特征速度;2#和3#特型喷口的补燃室掺混燃烧效果要比1#特型喷口更好,但是会带来更大的总压损失。     

N‐Bromosuccinimide‐Mediated Radical Cyclization of 3‐Arylallyl Azides: Synthesis of 3‐Substituted Quinolines

Visible light irradiation of N‐bromosuccinimide serves as an effective means to convert methyl 2‐(azidomethyl)‐3‐arylpropenoates and 2‐(azidomethyl)‐3‐arylacrylonitriles to the corresponding iminyl radicals via α‐hydrogen abstraction and subsequent extrusion of dinitrogen. Thus formed iminyl radicals then undergo intramolecular ortho attack on the aryl ring, affording methyl quinoline‐3‐carboxylates and quinoline‐3‐carbonitriles respectively.

     

Modeling attempt of shape memory performance of epoxy resin with experimental methods

Epoxy resin samples with low cross-linking density were prepared, and their shape recovery rate and glass transition were studied. The results showed that the shape fixity ratio was over 99 % for all of the samples. Without constraint, the final recovery ratio was approximate to 100 % for all of the samples. The temperature with rapid recovery rate for different samples changed in accordance with T _g. Under a constant temperature, the folding angle for the samples of EP80 decreased with the increase in time rapidly, at first, and then tended to level off. Curves can be fitted with the formula of $ y + A_{0} = A/(1 + \exp ((t - t_{0} )/\tau )) $ with R ² higher than 99.9 %. The fitting results demonstrated that the value of τ decreased from 15.1 to 6.39 when the temperature increased from 88 to 98 °C for EP80. The recovery rate decreased a little by extending the holding time from 10 to 60 s. By keeping the testing temperature constant, glass transition temperature (T _g) decreased with the increase in curing agents, and the value of τ reduced with the decrease in T _g. Usually, when temperature was close to T _g, segments of macromolecules were idle to move, and then, the relaxation process, τ, was lengthened and the shape recovery rate decreased accordingly. In a word, τ showed the similar change rules with that of relaxation process of polymers; therefore, the shape recovering process could be predicted with the model of relaxation time and modulus according to relaxation formulas.     

基于频域辨识的振动台控制参数整定方法研究

地震模拟振动台控制参数是决定系统性能的主要因素之一,采用简谐信号扫频作为辨识输入激励振动台系统,由实际输入输出信号通过最小二乘频域拟合辨识得到系统传递函数,通过辨识模型的控制参数理论计算得到振动台的三参量理论控制参数,经微调得到实际系统参数。仿真计算表明:所提出算法可以得到较理想的控制参数,该方法可应用于振动台三参量控制参数整定。     

Design of dual-diameter nanoholes for efficient solar-light harvesting

A dual-diameter nanohole (DNH) photovoltaic system is proposed, where a top (bottom) layer with large (small) nanoholes is used to improve the absorption for the short-wavelength (long-wavelength) solar incidence, leading to a broadband light absorption enhancement. Through three-dimensional finite-element simulation, the core device parameters, including the lattice constant, nanohole diameters, and nanohole depths, are engineered in order to realize the best light-matter coupling between nanostructured silicon and solar spectrum. The designed bare DNH system exhibits an outstanding absorption capability with a photocurrent density (under perfect internal quantum process) predicted to be 27.93 mA/cm², which is 17.39%, 26.17%, and over 100% higher than the best single-nanohole (SNH) system, SNH system with an identical Si volume, and equivalent planar configuration, respectively. Considering the fabrication feasibility, a modified DNH system with an anti-reflection coating and back silver reflector is examined by simulating both optical absorption and carrier transport in a coupled way in frequency and three-dimensional spatial domains, achieving a light-conversion efficiency of 13.72%.

PACS

85.60.-q; Optoelectronic device; 84.60.Jt; Photovoltaic conversion     

Quantum dot cascade laser

We demonstrated an unambiguous quantum dot cascade laser based on InGaAs/GaAs/InAs/InAlAs heterostructure by making use of self-assembled quantum dots in the Stranski-Krastanow growth mode and two-step strain compensation active region design. The prototype generates stimulated emission at λ ~ 6.15 μm and a broad electroluminescence band with full width at half maximum over 3 μm. The characteristic temperature for the threshold current density within the temperature range of 82 to 162 K is up to 400 K. Moreover, our materials show the strong perpendicular mid-infrared response at about 1,900 cm^-1. These results are very promising for extending the present laser concept to terahertz quantum cascade laser, which would lead to room temperature operation.

PACS

42.55.Px; 78.55.Cr; 78.67.Hc     

用主成分回归法同时测定Zn~(2+)、Cd~(2+)、Pb~(2+)和Cu~(2+)的研究

使用聚类分析对不同缓冲体系下Zn2+、Cd2+、Pb2+、Cu2+的吸光度光谱数据分析,通过数量化的方法确定pH值=6.0的最佳缓冲体系。通过单因素实验分析确定缓冲溶液用量为5.0ml、显色剂用量为3.0ml、环糊精用量为2.0ml及最佳显色时间10min。绘制Zn2+、Cd2+、Pb2+、Cu2+的标准曲线,结果表明其具有良好的线性范围和线性加和性。应用主成分回归法计算含有干扰离子的待测水样中Zn2+、Cd2+、Pb2+、Cu2+的浓度,并计算出平均回收率为109.64%、92.77%、98.18%、102.28%,相对标准偏差为11.48%、11.12%、6.34%、4.72%。