考虑Md对联体结构振动控制影响的研究

提出了一种新的振动控制体系--联体多结构振动控制体系.首先,联接体质量Md作为一个附加点加以考虑,建立了分析计算模型,推导了其振动方程.其次,对结构进行时程分析并运用虚拟激励法计算了联体多结构振动控制体系在随机地震动激励下动反应谱密度及方差.最后讨论了影响控制效果的因素及控制器参数的优化.研究结果表明:联体多结构振动控制体系对结构地震响应可进行有效控制.     

Outcomes Assessment and the Faculty Culture: Conflict or Congruence?

The greatest challenge to developing an effective outcomes assessment system is the institutional culture of the faculty. This paper describes some characteristics of many engineering faculty cultures which create challenges and opportunities for those developing new outcomes assessment systems. Specific issues which the assessment team will face, and some approaches by which they can deal with the circumstances created by the faculty culture, are presented. By generating appropriate responses to the issues raised, the assessment team can develop specific, effective tactics for successfully developing and implementing an outcomes assessment system.     

结构半主动变阻尼控制性能评估

研究了地震激励下结构半主动变阻尼控制的有效性。作为半主动控制系统的经典范例之一,变阻尼控制系统已经在结构控制领域得到了广泛的应用,但是近来的研究显示变阻尼控制对于抑制柔性结构的地震反应是适宜的,而对于刚性结构则是不适宜的。通过谐波分析研究了地震激励下结构振动控制的问题。计算结果显示,变阻尼控制成立的条件与结构频率并无必然联系,而是取决于结构频率与外部激励频率的比值,即就是变阻尼控制的可行性与地面运动的频谱特性是相关联的。此外,也将变阻尼控制的效果与对应的被动上限阻尼控制效果进行了对比。结果显示,在大多数情况下变阻尼控制并不能进一步提高控制效果。     

应用时频分析方法辨识时变系统的模态参数

应用Gabor展开及Hilbert变换进行时变线性系统模态参数的辨识。利用非平稳信号的Gabor变换将结构响应信号表示在时频面上，并通过Gabor展开重构分离模态分量，建立每一阶模态的时变线性模型。对单模态时变线性模型应用Hilbert变换来辨识随时间变化的模态频率和阻尼。通过对刚度和阻尼慢变的两自由度系统模态参数的仿真辨识验证辨识方法的有效性。仿真结果表明：本文方法为时变线性系统的模态参数辨识提供了一条新的途径。     

Responses of viscoelastic polymer composites with temperature and time dependent constituents

This study formulates a concurrent micromechanical model for predicting effective responses of fiber reinforced polymer (FRP) composites, whose constituents exhibit thermo-viscoelastic behaviors. The studied FRP composite consists of orthotropic unidirectional fiber and isotropic matrix. The viscoelastic material properties for the fiber and matrix constituents are allowed to change with the temperature field. The composite microstructures are idealized with periodically distributed square fibers in a matrix medium. A unit-cell model, consisting of four fiber and matrix subcells, is generated to obtain effective nonlinear thermo-viscoelastic responses of the composites. A time-integration algorithm is formulated to link two different thermo-viscoelastic constitutive material models at the lowest level (homogeneous fiber and matrix constituents) to the effective material responses at the macro level, and to transfer external mechanical and thermal stimuli to the constituents. This forms a concurrent micromechanical model, which is needed as the material properties of the constituents depend on the temperature field. Consistent tangent stiffness matrices are formulated at the fiber and matrix constituents and also at the effective composite level to improve prediction accuracy. The thermo-viscoelastic responses obtained from the concurrent micromodel are verified with available experimental data. Detailed finite element (FE) models of the FRP microstructures are also generated using 3D continuum elements for several fiber volume fractions. Thermo-viscoelastic responses of the concurrent micromodel are also compared to the ones of the detailed FRP microstructures.     

未知激励下的无迹卡尔曼滤波新方法

无迹卡尔曼滤波（UKF）是一种识别非线性系统的有效方法,然而传统的UKF方法需要观测外部激励,这限制了UKF的应用范围。迄今为止,国内外对未知激励情况下的UKF方法的研究还非常少。该文在传统UKF的基础上,推导出在未知激励情况下的无迹卡尔曼滤波（UKF-UI）方法的递推公式,通过对观测误差的最小化,利用非线性方程求解,识别未知外部激励,进而识别非线性结构系统状态与结构未知参数。进一步采用融合部分观测的加速度响应及位移响应,消除识别结果的漂移问题。分别通过白噪声和未知地震作用下识别非线性迟滞模型的两个数值算例,考虑观测噪声对非线性系统进行识别,从而验证提出新方法的有效性。结果表明,该文所提出的UKF-UI方法,能够在部分观测结构系统响应的情况下,有效地识别非线性结构参数和未知激励。     

Cohesive fracture modeling of crack growth in thick-section composites

This paper presents a combined method for modeling the mode-I and II crack growth behavior in thick-section fiber reinforced polymeric composites having a nonlinear material response. The experimental part of this study includes crack growth tests of a thick composite material system manufactured using the pultrusion process. It consists of alternating layers of E-glass unidirectional roving and continuous filament mats in a polymeric matrix. Integrated micromechanical and cohesive finite element (FE) models are used to simulate the crack growth response in eccentrically loaded single-edge-notch, (tension), ESE(T) and notched butterfly specimens. Micromechanical constitutive models for the mat and the roving layers are used to generate the effective nonlinear material behavior from the in situ fiber and matrix responses. The validity of the numerical modeling approach before the onset of crack growth is investigated using an infrared thermal method. Cohesive FE models are calibrated and used to simulate the complete crack growth behavior for different crack configurations. The proposed integrated framework of multi-scale material models with cohesive fracture models is shown to be an effective method for predicting the structural and material responses including failure load and crack growth in thick-section fiber reinforced polymeric composites.     

计算结构非线性地震峰值响应的等价线性化模型

多自由度体系的等价线性化方法是预测结构的非线性地震峰值响应的有效方法。单自由度等价线性化模型是该方法的基础。该文在前人研究的基础上,从定性和定量的两个方面综合分析了结构周期、延性系数以及恢复力模型等因素对单自由度等价线性化模型的影响,并通过对大量地震动记录下动力弹塑性分析结果的拟合回归,提出了能够综合反映各方面参数影响的单自由度等价线性化模型。与现有代表性的等价线性化模型相比,该文模型所反映的参数最为全面,预测峰值位移的平均相对误差最小,且略偏于保守。     

Clay Nanoparticles Elicit Long‐Term Immune Responses by Forming Biodegradable Depots for Sustained Antigen Stimulation

Nanomaterials have been widely tested as new generation vaccine adjuvants, but few evoke efficient immunoreactions. Clay nanoparticles, for example, layered double hydroxide (LDH) and hectorite (HEC) nanoparticles, have shown their potent adjuvanticity in generating effective and durable immune responses. However, the mechanism by which clay nanoadjuvants stimulate the immune system is not well understood. Here, it is demonstrated that LDH and HEC–antigen complexes form loose agglomerates in culture medium/serum. They also form nodules with loose structures in tissue after subcutaneous injection, where they act as a depot for up to 35 d. More importantly, clay nanoparticles actively and continuously recruit immune cells into the depot for up to one month, and stimulate stronger immune responses than FDA‐approved adjuvants, Alum and QuilA. Sustained antigen release is also observed in clay nanoparticle depots, with 50–60% antigen released after 35 d. In contrast, Alum–antigen complexes show minimal antigen release from the depot. Importantly, LDH and HEC are more effective than QuilA and Alum in promoting memory T‐cell proliferation. These findings suggest that both clay nanoadjuvants can serve as active vaccine platforms for sustained and potent immune responses.     

Reliability in individual monitoring service

As a laboratory certified to ISO 9001:2008 and accredited to ISO/IEC 17025, the Secondary Standard Dosimetry Laboratory (SSDL)-Nuclear Malaysia has incorporated an overall comprehensive system for technical and quality management in promoting a reliable individual monitoring service (IMS). Faster identification and resolution of issues regarding dosemeter preparation and issuing of reports, personnel enhancement, improved customer satisfaction and overall efficiency of laboratory activities are all results of the implementation of an effective quality system. Review of these measures and responses to observed trends provide continuous improvement of the system. By having these mechanisms, reliability of the IMS can be assured in the promotion of safe behaviour at all levels of the workforce utilising ionising radiation facilities. Upgradation of in the reporting program through a web-based e-SSDL marks a major improvement in Nuclear Malaysia's IMS reliability on the whole. The system is a vital step in providing a user friendly and effective occupational exposure evaluation program in the country. It provides a higher level of confidence in the results generated for occupational dose monitoring of the IMS, thus, enhances the status of the radiation protection framework of the country.     

高速曳引式电梯振动主动控制技术研究

运用运动弹性动力学方法建立高速曳引式电梯机械系统的动力学模型，进行其动态特性分析及振动控制研究。利用模糊自适应主动振动控制的方法，使模糊控制规则在控制过程中自动调整、完善，从而达到最佳的控制效果。应用MATLAB语言编程仿真表明，所设计的模糊自适应控制系统的振动控制效果优于传统的机械被动隔振，而且对振动环境的自适应能力强，控制器响应快，超调量小，有很强的鲁棒性，因而使电梯的乘坐舒适性得到很大的改善。     

Nanoparticulate Delivery of Cancer Cell Membrane Elicits Multiantigenic Antitumor Immunity

Anticancer vaccines train the body's own immune system to recognize and eliminate malignant cells based on differential antigen expression. While conceptually attractive, clinical efficacy is lacking given several key challenges stemming from the similarities between cancerous and healthy tissue. Ideally, an effective vaccine formulation would deliver multiple tumor antigens in a fashion that potently stimulates endogenous immune responses against those antigens. Here, it is reported on the fabrication of a biomimetic, nanoparticulate anticancer vaccine that is capable of delivering autologously derived tumor antigen material together with a highly immunostimulatory adjuvant. The two major components, tumor antigens and adjuvant, are presented concurrently in a fashion that maximizes their ability to promote effective antigen presentation and activation of downstream immune processes. Ultimately, it is demonstrated that the formulation can elicit potent antitumor immune responses in vivo. When combined with additional immunotherapies such as checkpoint blockades, the nanovaccine demonstrates substantial therapeutic effect. Overall, the work represents the rational application of nanotechnology for immunoengineering and can provide a blueprint for the future development of personalized, autologous anticancer vaccines with broad applicability.     

Light‐Triggered In Situ Gelation to Enable Robust Photodynamic‐Immunotherapy by Repeated Stimulations

Photodynamic therapy (PDT) has shown the potential of triggering systemic antitumor immune responses. However, while the oxygen‐deficient hypoxic tumor microenvironment is a factor that limits the PDT efficacy, the immune responses after conventional PDT usually are not strong enough to eliminate metastatic tumors. Herein, a light‐triggered in situ gelation system containing photosensitizer‐modified catalase together with poly(ethylene glycol) double acrylate (PEGDA) as the polymeric matrix is designed. Immune adjuvant nanoparticles are further introduced into this system to trigger robust antitumor immune responses after PDT. Following local injection of the mixed precursor solution into tumors and the subsequent light exposure, polymerization of PEGDA can be initiated to induce in situ gelation. Such hybrid hydrogel with long‐term tumor retention of various agents and the ability to enable persistent tumor hypoxia relief can enable multiple rounds of PDT, which results in significantly enhanced immune responses by multiround stimulation. Further combination of such gel‐based multiround PDT with anticytotoxic T‐lymphocyte antigen‐4 checkpoint blockade offers not only the abscopal effect to inhibit growth of distant tumors but also effective long‐term immune memory protection from rechallenged tumors. Therefore, such a light‐triggered in situ gelation system by a single‐dose injection can enable greatly enhanced photoimmunotherapy by means of repeated stimulations.     

Analytical model for mesh stiffness calculation of spur gear pair with non-uniformly distributed tooth root crack

Gear tooth crack is likely to happen when a gear transmission train is working under excessive and/or long-term dynamic loads. Its appearance will reduce the effective tooth thickness for load carrying, and thus cause a reduction in mesh stiffness and influence the dynamic responses of the gear transmission system, which enables the possibility for gear fault detection from variations of the dynamic features. Accurate mesh stiffness calculation is required for improving the prediction accuracy of the dynamic features with respect to the tooth crack fault. In this paper, an analytical mesh stiffness calculation model for non-uniformly distributed tooth root crack along tooth width is proposed based on previous studies. It enables a good prediction on the mesh stiffness for a spur gear pair with both incipient and larger tooth cracks. This method is verified by comparisons with other analytical models and finite element model (FEM) in previous papers. Finally, a dynamic model of a gear transmission train is developed to simulate the dynamic responses when cracks with different dimensions are seeded in a gear tooth, which could reveal the effect of the tooth root crack on the dynamic responses of the gear transmission system. The results indicate that both the mesh stiffness and the dynamic response results show that the proposed analytical model is an alternative method for mesh stiffness calculation of cracked spur gear pairs with a good accuracy for both small and large cracks.     

Performance optimization of a transcritical CO2 refrigeration system using a controlled ejector

An on-line optimal quasi cascade controller for an ejector with variable nozzle throat area is proposed to improve the operating performance of the transcritical CO₂ ejector refrigeration system. The optimal gas cooler pressure is tracked in real time by the controller including a tracker and a predictor. Using the system dynamic model, the dynamic responses of the system performance and ejector efficiency under variable nozzle throat area are first analyzed. Then the parameters of the tracker and predictor are determined by simulation respectively which exhibits a good dynamic characteristic with an acceptable settling time. Besides, the controller presents a good robustness under variable compressor speeds and mass flow rate of cooling water. Furthermore, the system performance is actually increased to the maximal value by the controller even at the variable operating conditions. Finally, the optimal controller is verified by experiments to be an effective way to improve the system performance automatically.     

斜齿行星传动多体动力学建模与分析

建立了斜齿行星传动的多体动力学模型,对其进行了动态特性仿真,获知了该类系统的自由振动特性、稳态动力响应以及部分设计参数对系统动态特性的影响规律。根据系统特征值的重根数、中心构件的振型坐标及各行星轮间振型坐标的比例,将斜齿行星轮系的自由振动归结为3类典型振动模式,即：轴向平移—扭转振动模式、径向平移—扭摆振动模式和行星轮振动模式,并进一步给出了各类模式的特点。当不考虑构件自身柔性时,基于多体动力学模型的自由振动特性与前人的集中参数模型的仿真结果完全一致,表明了本文所建模型的正确性。斜齿行星轮系的稳态动力学响应表明,内、外啮合力在一个啮合周期内围绕静态均值作较大幅度的波动,而啮频激励是引起该类系统振动的主要原因。参数影响分析表明,构件支承刚度和行星轮周向安装误差对系统动态特性的影响明显,浮动太阳轮、严控行星轮周向安装误差可有效抑制系统的振动。     

Effects of CNT waviness on the effective elastic responses of CNT-reinforced polymer composites

In this study, the effects of fiber waviness on the effective elastic responses of CNT–polymer composites are investigated based on the framework of micromechanics and homogenization. By taking advantage of an ad hoc Eshelby tensor, the load-transfer capability of wavy carbon nanotube (CNT) embedded in the polymer matrix is accounted for. Further, the effective elastic responses of composites are simulated by using the multi-phase Mori–Tanaka method to study the influence of randomly oriented wavy CNT. It is demonstrated that the proposed micromechanics-based closed form solution is effective to tackle the underlying problem. The present predictions and the comparisons with the available experimental data indicate that the CNT waviness leads to the degradation of effective responses of composites. Finally, in addition to the effect of CNT waviness, the significance of CNT interface is briefly discussed based on the experimental observations.     

多源激励下浮筏隔振系统导纳功率流研究

建立了浮筏隔振系统的振子力学统计分析模型，使用导纳功率流的方法研究了隔振系统的振动响应和振动功率流特性，并通过数值方法分析了筏体和隔振器参数变化对传递到基础结构功率流的影响。分析结果表明：增大基础厚度、减小系统中耦合元件的耦合刚度和增大筏体质量可以有效控制系统的传递功率流。     

由有限元-Wavelet-Galerkin法识别桥面移动载荷

基于欧拉梁模型，将有限元法与Wavelet—Galerkin法相结合应用于车桥系统移动载荷识别中，建立了一种动载荷识别的新方法。该方法的优点在于利用小波识别的方法将原来复杂的微分方程（组）分解成小波空间里互相独立的线性方程（组），简化了计算，同时也消除现有方法如力平衡法Ⅱ、有限元法等由位移（应变）信号得到速度、加速度信号过程中的拟合求导的误差。文中讨论了测点排布，采样频率等因素对识别精度的影响，数值仿真表明该方法能正确而方便地进行车桥系统的移动载荷识别。     

色噪声激励Rayleigh-Duffing振子瞬态响应及最优有界控制

该文研究了受色噪声激励的Rayleigh-Duffing振子瞬态响应及其最优有界控制问题。在弱扰动假设下应用标准随机平均法得到了原系统振幅过程的部分平均It#x000f4;随机微分方程。应用Bellman动态规划原理,结合控制力有界条件,得到了最优有界控制率。完成所有平均过程得到了系统振幅过程的完全平均It#x000f4;随机微分方程和相应的Fokker-Planck-Kolmogorov方程。基于退化线性系统得到一组正交基空间,在此基空间内进行Galerkin变分近似求解Fokker-Planck-Kolmogorov方程得到了受控系统的瞬态响应。采用Monte-Carlo模拟验证了所有理论结果的有效性。计算表明:1)所提方法求解受最优有界控制率作用的随机非线性系统瞬态响应有效;2)最优有界控制率成功降低了系统瞬态响应;3)该方法的求解效率高于Monte-Carlo数值模拟方法。