VIBRATION ANALYSIS OF A BEAM WITH EMBEDDED SHAPE MEMORY ALLOY WIRES

In this study, analytical relations for evaluating the exact solution of natural fre- quency and mode shape of beams with embedded shape memory alloy （SMA） wires are presented. Beams are modeled according to Euler-Bernoulli, Timoshenko and third order beam （Reddy） the- ories. A relation is obtained for determining the effect of axial load generated by the recovery action of pre-strained SMA wires. By defining some dimensionless quantities~ the effect of different me- chanical properties on the frequencies and mode shapes of the system are carefully examined. The effect of axial load generated by SMA wires with buckling load and frequency jump is accurately studied.     

不同铺层厚度复合材料的低速冲击特性与损伤模式研究

复合材料凭借其轻质、高强的特性逐渐在工程材料界占据重要地位,对于复合材料的冲击损伤的研究也一直吸引着诸多研究学者的关注．为表征不同铺层厚度复合材料层合板的抗冲击性能,利用自由落体冲击设备,进行了复合材料层合板的冲击实验研究．给出了不同冲击能量下的损伤模式,并利用位移、速度、接触力以及能量的时间变化曲线,深入分析了侵入和穿透两种损伤模式的特点．研究发现,随着铺层厚度的增加,复合材料在冲击过程中吸收的能量也随之增加．引入能量平衡法,基于体系的能量守恒定律,利用Newton-Raphson数值方法求解了侵入损伤模式下的接触力大小,通过实验结果给定挠度求解了对应的速率变化情况,并将理论结果与实验结果进行比较．     

常压下固态KNO2热力学性质的密度泛函理论研究

采用密度泛函理论结合准谐德拜模型研究常压下300~725 K间KNO₂立方结构的热力学性质,重点分析常压下定压热容、定容热容、熵、德拜温度、体膨胀系数、平衡体积和体弹模量随温度的变化.结果显示,常压下计算的定压热容随温度的变化与实验数据符合较好,而计算的熵与实验数据相差较大.计算得到KNO₂的平均体膨胀系数约为1.837 8×10^-5K^-1,常温下(300 K)KNO₂的德拜温度约为667.13K.     

漂浮基柔性关节空间机器人自适应滑模运动控制及振动主动抑制

讨论了关节柔性且系统参数不确定的漂浮基空间机器人系统的动力学建模过程、运动轨迹跟踪控制算法设计及系统柔性振动的主动抑制问题。利用系统动量、动量矩守恒关系和拉格朗日法对系统动力学进行分析,并建立系统动力学方程。基于奇异摄动法将系统分解为表示系统刚性运动部分的慢变子系统和表示系统柔性运动部分的快变子系统。针对慢变子系统提出了一种自适应滑模控制算法。该控制算法是由基于滑模面的等效控制项、自适应控制项和PID反馈控制项组成。因此,它集合了滑模控制、自适应算法和PID技术的优点,且弥补了三种算法各自的缺点。该控制算法能够有效地补偿系统的转动误差和不确定参数,提高控制系统的精度。针对快变子系统,提出基于速度差值的反馈控制算法来抑制柔性关节引起的系统柔性振动,保证系统的稳定性。最后,通过仿真实验证明了提出的混合控制算法的有效性。     

Photodissociation Spectra of OCS+ via B2∑+←X2∏ Transitions

In the wavelength range of 231-275 nm, we have studied the mass-resolved dissociation spectra of OCS⁺ via B²∑⁺←X²∏_3/2(000) and B²∑⁺←X²∏_1/2(000, 001) transitions by preparing OCS⁺ ions in the well-defined spin-orbit states. The spectroscopic constants ofυ1(CS stretch)=828.9 (810.4) cm^-1, υ2(bend)=491.3 cm^-1 and υ3(CO stretch)=1887.2 cm^-1 for OCS⁺(B²∑⁺) are deduced. The observed dependence of the υ2(bend) mode excitation of B²∑⁺ on the spin-orbit splitting of X²∏(Ω=1/2, 3/2) in the B²∑⁺←X²∏ transition can be attributed to the K coupling between the (000)²∏_1/2 and (010)²∑⁺_1/2 vibronic levels of X²∏ state, which makes the B²∑⁺(010)←X²∏_1/2(000) transition possible.     

发展PBL模式改革药学专业的分析化学课堂教学

PBL教学是以问题为基础的教学模式,将PBL教学模式应用到分析化学课堂教学中,有助于提高学生发现问题、分析问题和在实践中解决问题的能力。对发展PBL模式用于药学专业的分析化学课堂教学进行了探讨,提出了可以在教学及考核阶段从教学内容和课堂教学方式上应用PBL模式,结合多媒体、网络、CAI等现代化的教学手段,促进分析化学课堂教学的改革,培养具备创新能力的药学专业大学生。     

新疆高师院校中学化学实验课程内容建构与实验模式研究

通过对新疆高师院校中学化学实验内容需求现状进行调查分析,并依据分析结果,构建出适合新疆高师院校的中学化学实验课程体系,提出了适应新疆高师院校的中学化学实验模式,以满足新疆高师院校化学专业师范生成长的实际需要.     

应用型地方院校仪器分析实训教学的探索与实践——以导数紫外分光光度法实训为例

主要探讨将仪器实训教学引入到地方院校应用化学等相关专业的教学体系。尝试“任务领引型”实训模式,将所要学习的知识和实践技能蕴藏在一个或几个具体的任务中,让学生通过循序渐进完成一系列任务,提高学生的综合应用能力。通过教学实践获得较好效果。     

Piezoelectric transducer parameter selection for exciting a single mode from multiple modes of Lamb waves

Excitation and propagation of Lamb waves by using rectangular and circular piezoelectric transducers surface-bonded to an isotropic plate are investigated in this work. Analytical stain wave solutions are derived for the two transducer shapes, giving the responses of these transducers in Lamb wave fields. The analytical study is supported by a numerical simulation using the finite element method. Symmetric and antisymmetric components in the wave propagation responses are inspected in detail with respect to test parameters such as the transducer geometry, the length and the excitation frequency. By placing only one piezoelectric transducer on the top or the bottom surface of the plate and weakening the strength of one mode while enhancing the strength of the other modes to find the centre frequency, with which the peak wave amplitude ratio between the S0 and A0 modes is maximum, a single mode excitation from the multiple modes of the Lamb waves can be achieved approximately. Experimental data are presented to show the validity of the analyses. The results are used to optimize the Lamb wave detection system.     

Propagation of high-power partially coherent fibre laser beams in a real environment

The propagation performance of high-power partially coherent fibre laser beams in a real environment is investigated and the theoretical model of a high-power fibre laser propagating in a real environment is established. The influence of a collimating system and thermal blooming is considered together with atmospheric turbulence and mechanical jitter. The laser energy concentration of partially coherent beams in the far field is calculated and analysed based on the theoretical model. It is shown that the propagation performance of partially coherent beams depends on the collimating system, atmospheric turbulence, mechanical jitter and thermal blooming. The propagation performance of partially coherent beams and fully coherent beams is studied and the results show that partially coherent beams are less sensitive to the influence of thermal blooming, which results in that the energy degeneration for partially coherent beams is only 50% of that for fully coherent beams. Both partially coherent beams and fully coherent beams become less sensitive to thermal blooming when the average structural constant of the refraction index fluctuations increases to 1.7 × 10^-14 m^-2/3. The investigation presents a reference for applications of a high-power fibre laser system.