一种微带谐振式含水量测量传感器设计

设计了一种用于土壤含水量测量的微带谐振环式传感器。利用仿真软件对所设计传感器进行了仿真分析,并完成了谐振环的制作及实验测量。仿真与测量结果表明,这种谐振环式含水量传感器可用于测量土壤含水量,相较传统的电容传感方法、时域反射仪传感方法等,其在测量准确性上具有优势,且体积小巧,易于安装使用。     

基于多模态双向导向注意的视觉问答

针对视觉问答(VQA)任务中现存深度协同注意模型只考虑问题引导图像的单向注意方式,导致多模态学习交互性不足的问题,提出一种多模态双向导向注意力网络.该网络由多模态特征提取模块、双向导向注意力模块、特征融合模块以及分类器组成.将提取出的图像和问题特征分别经过层层注意后输出加权的注意特征;经过特征线性融合后送入softma...     

NCS中的信息安全求解策略

网络控制是计算机、通信与控制技术结合发展的必然产物，具有开放性特征的网络控制系统面临着控制信息安全问题。针对网络控制系统的典型体系结构和信息安全需求，提出了基于分层思想和资源匹配的网络控制系统信息安全求解策略。     

水平导向钻技术在某排水管道施工中的应用

该文分析了水平导向钻施工的技术特点。并根据该技术在广州地区的实际应用，说明在该技术在广州地区进行排水管网施工的可行性。     

Performance evaluation of CSMA/ID MAC protocol for IP over WDM ring networks

In this paper, a packet pre‐classification media access control protocol based on a carrier sense multiple access with idle detection (CSMA/ID) scheme is investigated for supporting IP packets over all‐optical WDM ring networks. The purpose of the protocol is to increase throughput and to decrease the packet transmission delay of IP packets over optical networks in a metropolitan area network. This protocol avoids both packet collision and packet fragmentation. In order to improve the utilization of the network, the packets transmitted from a local area network are first pre‐classified into various class queues of an access point (AP) according to their length. After checking the available space based on the wavelength received by the receivers of the AP, the packets in the queues are transmitted. An analytical model is developed to evaluate the performance of the protocol, with simulation results showing good network efficiency. The proposed network has short‐term variations that introduce unfairness conditions. This problem could be overcome by assigning a quota on individual queues to allow all queues fair access. Copyright © 2008 John Wiley & Sons, Ltd.     

TDFA/Raman hybrid amplifiers covering the entire S-band pumped by a single laser

Hybrid amplifier configurations are reported cascading one Raman and one or two Tm/sup 3+/-doped fiber stages, using a single pump at 1426 nm, allowing seamless amplification of the entire S-band (1460-1530 nm). Different configurations were studied, with gain over the entire band width and peak gain up to 24 dB. Noise figure as low as 7 dB was achieved.     

脂肪酶催化反应的研究进展

综述了脂肪酶催化特性及近年对反应体系中水、介质、载体等对脂肪酶催化活性影响的研究成果。     

双羟基脲与HNO2的反应动力学及对Pu(Ⅲ)的稳定作用

研究了HClO4和HNO3体系中双羟基脲(DHU)与HNO2的反应动力学.结果表明,HClO4和HNO3体系下DHU与HNO2的反应动力学速率方程式均为-dc(HNO2)/dt=k·c(HNO2 )1·c(DHU )0·c(H+)-0.15,反应对DHU均呈零级.在HClO4体系下,θ=15 ℃, I=0.5 mol/kg时,反应速率常数k1=(2.37±0.04) mol0.15/(L0.15·min);在HNO3体系下,θ=10 ℃, I=0.5 mol/kg时,反应速率常数k2= (1.29±0.06) mol0.15/(L0.15·min)(n=8).同时考察了反应温度对反应速率的影响,结果表明,随着温度的升高, 反应速率均明显加快, HClO4和HNO3体系对应的反应活化能分别为68.2 kJ/mol和76.8 kJ/mol.在HClO4和HNO3体系中,随着离子强度的增加,氧化还原反应的表观速率常数k'均下降.过量的DHU在HNO3溶液中可以很好的稳定Pu(Ⅲ)48 h而不被氧化.     

Effects of Chopped Carbon Fiber on the Forming,Structure, and Mechanical Properties of CCF/SiC Composites Fabricated by Selective Laser Sintering and Reactive Melt Infiltration

Silicon carbide (SiC) composites are fabricated by selective laser sintering (SLS) combined with reactive melt infiltration (RMI) using SiC powder mixed with various contents (0–32 vol%) of chopped carbon fiber (CCF) as reinforcement phase and carbon source. The introduction of an appropriate amount of CCF can reduce the shrinkage and step effect caused by slicing, improving the forming quality of the CCF/SiC preforms after pyrolysis. Meanwhile, as a carbon resource, CCF can react with molten silicon to form the β-SiC, improving the mechanical properties of CCF/SiC composites. The result shows that the CCF/SiC powder shows excellent fluidity, and the angle of repose of the CCF/SiC powder is 32–40° when the proportion of CCF is less than 24 vol%. CCF/SiC preforms shrinkage is lower than 1.74% and 1.94% along the nonadditive and additive manufacturing directions, respectively. Compared without CCF, the bending strength and fracture toughness of the CCF/SiC composites with 8 vol% CCF improve from 137.9 MPa and 2.69 MPa m^1/2 to 177.1 MPa and 3.10 MPa m^1/2, respectively. This study is believed to provide a new strategy for additive manufacturing of high-performance CCF/SiC composites with high CCF content by SLS.     

分数阶导数系统非平稳随机振动灵敏度分析的时域显式方法EI北大核心CSCD

分数阶导数模型是描述黏弹性材料本构关系的理想模型。进行了分数阶导数线性系统非平稳随机振动的灵敏度分析。建立分数阶导数系统动力响应的时域显式表达式;采用灵敏度分析的直接求导法或伴随变量法,推导系统动力响应灵敏度的时域显式表达式;提出分数阶导数系统响应统计矩灵敏度高效计算的时域显式方法。所提出的基于直接求导法和伴随变量法的时域显式方法,分别适用于少设计变量和多设计变量两种情况下的响应统计矩灵敏度分析。以非平稳地震激励下设置分数阶导数黏弹性阻尼器的层剪切结构为数值算例,验证了所提方法的计算精度和计算效率。