背景响应、共振响应定义及其相关性分析方法

以模态加速度法为基础,推导了脉动风响应中背景响应和共振响应的严密数学定义;在此基础上,根据随机振动理论,推导了频域内的背景响应、共振响应,以及两者间相关性的分析方法;指出脉动风响应谱包括背景响应谱、共振响应谱和两者问的耦合谱三部分.并给出了背景响应和共振响应的精确组合方法.将该方法用于一单层球面网壳,结果表明:对于该结构,背景响应和共振响应的相关系数在[-0.3,-0.1]之间,若忽略该相关性时,将高估该结构的实际响应,比例在3%～10%范围内.     

大跨度屋盖结构脉动风振响应的振型能量参与系数

采用振型叠加方法计算大跨度屋盖结构的脉动风振响应时,计算结果的精度取决于振型的选取。在总结总背景响应、振型背景响应、振型共振响应的基础上,提出了背景响应和共振响应的振型能量参与系数的计算方法。按照振型能量参与系数的降序排列振型,分别计算背景响应和共振响应的累积振型能量参与系数。背景响应位移计算值的精度可通过背景响应振型参与系数及其累积参与系数来控制。共振响应累积振型能量参与系数则反映了参与计算的振型的共振响应总能量与背景响应总能量之比。     

大跨屋盖结构风致背景响应和共振响应实用组合方法

以随机振动理论为基础,推导了大跨屋盖结构风致背景响应及其模态耦合项、共振响应及其模态耦合项以及背景响应和共振响应耦合项的计算公式,提出了考虑耦合效应的脉动风总响应组合方法;在此基础上,引入耦合效应修正系数,并根据结构动力特性与风荷载特性对提出的脉动风总响应组合公式进行了简化分析,得到了相应的实用组合公式,据此可以实现大跨屋盖结构考虑耦合效应的风致背景响应和共振响应实用高效组合。最后,通过国家体育场屋盖主结构风致背景响应和共振响应组合计算对所提方法的有效性进行了验证。     

高层建筑风致动态响应中的背景响应

本文研究了高层建筑风致动态响应中的背景响应。首先推导了结构风致动态背景响应的计算公式,然后在此基础上指出了传统的计算高层建筑风致动态响应方法的实质和适用条件,并给出了本文方法与传统方法对比的算例。研究表表,当背景响应占结构的整个动态响应的比例较大时,用传统方法计算高层建筑的背景响应将产生不能忽视的误差。     

聚合物凝胶光子晶体及其对物理环境的响应

文中简要介绍了物理响应性光子晶体的国内外研究动态。重点介绍以下几种物理响应性光子晶体:温度响应性光子晶体,溶剂响应性光子晶体,电场响应性光子晶体,磁场响应性光子晶体,机械力响应性光子晶体等。     

基于控制释放的光响应性聚合物微纳米粒子的研究进展

对现阶段倍受关注的光响应性高分子微纳米粒子在控制释放方面的研究进展进行了综述。分别介绍了具有光响应性的微球、多孔材料以及基于光响应性的多重响应材料的研究现状,并对光响应性凝胶未来的研究方向进行了展望。     

基于主成分分析的多响应稳健性优化方法研究

将主成分分析法与双响应曲面法相结合,提出了一种同时优化响应均值和标准差的多响应优化方法.通过主成分分析,将多个响应的位置和散布特性值转化为主成分综合得分,并以二者的加权和作为优化指标,克服了传统的多响应优化方法只考虑响应均值的不足,将响应的标准差也纳入优化范畴,实现优化的稳健性.实例表明,该方法充分考虑了响应标准差对优化结果的影响,优化结果得到一定改善.     

智能型聚合物材料的研究进展

智能型聚合物材料是目前药剂学研究的热点。综述了温度响应型、pH响应型、磁响应型、光响应型和多重刺激响应型智能聚合物材料的研究进展,介绍了各种智能型聚合物材料的主要性质及其在药物释放系统中的应用,展望了各种智能材料的发展和应用前景。     

高层建筑风致响应的简化分析方法

简化高层建筑风致响应的计算对实际工程和规范应用均具重要意义。对高层建筑风致响应的简化计算方法进行了研究。定义了背景响应修正因子,并根据试验结果和对典型建筑风致响应的分析,给出了典型高层建筑的背景响应修正因子的建议取值。在对共振响应计算进行简化研究时,引入等效风谱技术,并给出了等效相干系数的新的表达式。提出的方法可以大大简化高层建筑风致响应的计算,并具有很高的精度。     

光响应形状记忆聚合物的研究进展

光响应形状记忆聚合物是一类刺激响应智能材料，它可以根据光照变化做出相应的形状改变。相比于传统的热响应形状记忆聚合物，光响应形状记忆聚合物具有远程控制、非接触式操作、局部驱动等优点。通过综述光响应形状记忆聚合物的研究进展，介绍光响应形状记忆聚合物的定义、机理、研究现状，以及光响应形状记忆聚合物在自修复材料、柔性电子器件和传感驱动领域的应用前景。总结了光响应形状记忆聚合物的优点，提出所面临的问题并进行了展望。     

Limitation of the achievable signal-to-noise ratio in optical coherence tomography due to mismatch of the balanced receiver

Owing to the limited spectral response of the fiber directional coupler used in a balanced optical coherence tomography configuration, the spectra are different in the two outputs. This affects unfavorably operation of the balanced photodetector unit. Excess photon noise makes a larger contribution than a directional coupler with a flat spectral response. A theoretical model is developed that shows that an optimum set of parameters may be defined to maximize the achievable signal-to-noise ratio. The model leads to a redefinition of the effective noise bandwidth, which takes into account the nonflat response of the directional coupler used. The model also predicts a limitation on the signal-to-noise ratio even when the stray reflectances in the interferometer are brought to zero.     

A directional dose equivalent monitor for neutrons

A directional dose equivalent monitor is introduced which consists of a 30 cm diameter spherical phantom hosting a superheated drop detector embedded at a depth of 10 mm. The device relies on the similarity between the fluence response of neutron superheated drop detectors based on halocarbon-12 and the quality-factor-weighted kerma factor. This implies that these detectors can be used for in-phantom dosimetry and provide a direct reading of dose equivalent at depth. The directional dose equivalent monitor was characterised experimentally with fast neutron calibrations and numerically with Monte Carlo simulations. The fluence response was determined at angles of 0, 45, 90, 135 and 180 degrees for thermal to 20 MeV neutrons. The response of the device is closely proportional to the fluence-to-directional dose equivalent conversion coefficient, h'phi (10; alpha, E). Therefore, our monitor is suitable for a direct measurement of neutron directional dose equivalent, H'(10), regardless of angle and energy distribution of the neutron fluence.     

Photorefractive Correction of the Coupling Ratio of an Integrated Optical Directional X-Coupler on a Lithium Niobate Substrate

Technical Physics Letters - The possibility of correcting the power coupling ratio of an integrated optical directional X-coupler upon excitation of a local photorefractive response in the...     

超指向性扬声器的系统设计与测试

超指向性扬声器是一种利用声波在空气中传播的非线性由不可听超声产生可听声的参量阵装置,这种声源相比相同大小的传统扬声器,可以产生非常强的指向性、像聚光灯光束一样的宽带可听声束.文章介绍了超指向性扬声器的基本原理,给出了一个基于模拟电路的系统实现方案,并着重介绍了基于所完成的工程样机所做的频率响应、总谐波失真和指向性测试及相关实验分析,还讨论了进一步工作的发展方向.     

一种声场空间特性测量系统的性能研究

室内声学测量中,在声源重复发射声信号的同时,将单个无指向性传声器缓慢而匀速地转动,其测量结果等效于以转盘转轴为中心的圆形传声器阵列,相应的测量系统简称为RRS。通过消声室测量,着重分析此测量系统在方向脉冲响应测量中的性能及主要影响因素：结果表明,在满足传声器旋转半径大于1／4信号波长的条件下,系统可具有令人满意的方向分辨能力。     

Energy and directional response for the Harshaw dosemeter holders 8814 and 8891, and its effect on the appropriate radiation qualities for absolute calibration

The personal dosimetry laboratory at the Norwegian radiation protection authority utilises a two-element dosemeter card for measuring Hp(10) and Hp(0.07), in a Harshaw dosemeter holder type 8814. Energy and directional responses for photons and betas for this holder have been assessed, as well as for the new Harshaw holder type 8891. The energy response characteristics for the 12-1250 keV photon energy range, in terms of TL output per unit Hp(10) and Hp(0.07) have been evaluated. The maximum over-response to under-response ratio for the Hp(10) element was found to be 1.46 for the new type 8891 holder, as compared to 1.55 for the older type 8814. The new holder also displays a more favourable directional response for this element. For the Hp(0.07) element, no significant differences with regard to energy or directional responses were found. Selecting radiation energy for absolute calibration of the Hp(10) and Hp(0.07) elements are discussed.     

飞行员在空间定向动态任务中的加工优势

目的:探讨飞行员在空间定向动态任务中的加工优势。方法:采用空间定向动态任务修订版对飞行员组和对照组进行比较研究。结果:飞行员在对运动客体的方向控制上好于对照组,完成任务操作时反应潜伏时间更长,在操作过程中反应频率更少。结论:飞行员在空间定向动态任务上的高定向能力表现为更好利用了整体的动态的权衡策略。     

转换器型方向规性能研究

本文介绍了球锥形转换器型方向规的工作原理、结构及性能参数,具有结构简单、方向性高、反应速度快、转换效果好等特点,并通过实验对其性能参数进行了测试,其方向性角为15°,动力学时间常数为5 ms,转换器平衡度系数为98.3％.     

An adaptive directional importance sampling method for structural reliability

In this paper, an adaptive directional importance sampling (ADIS) method is presented. The algorithm is based on a directional simulation scheme in which the most important directions are sampled exact and the others by means of a response surface approach. These most important directions are determined by a β-sphere enclosing the most important part(s) of the limit state. The β-sphere and response surface are constantly updated during sampling with information that becomes available from the exact evaluations making the scheme adaptive.Various widely used test problems, representing a broad range of complex limit states that can occur in practice, of which several that pose potential problems to stochastic methods in general, demonstrate the high efficiency, accuracy and robustness of the method. As such, the ADIS method is of particular interest in applications with a low probability of failure and medium number (up to about 40) of stochastic variables, for instance in aircraft and nuclear industry.     

Traveling waves in 2D hexagonal granular crystal lattices

This study describes the dynamic response of a two-dimensional hexagonal packing of uncompressed stainless steel spheres excited by localized impulsive loadings. The dynamics of the system are modeled using the Hertzian normal contact law. After the initial impact strikes the system, a characteristic wave structure emerges and continuously decays as it propagates through the lattice. Using an extension of the binary collision approximation for one-dimensional chains, we predict its decay rate, which compares well with numerical simulations and experimental data. While the hexagonal lattice does not support constant speed traveling waves, we provide scaling relations that characterize the directional power law decay of the wave velocity for various angles of impact. Lastly, we discuss the effects of weak disorder on the directional amplitude decay rates.