大展弦比机翼的非线性气动弹性缩比优化

针对几何非线性效应明显的大展弦比机翼,使用两种传统线性缩比方法(刚度和质量耦合下直接进行模态匹配与解耦刚度和质量后进行模态响应匹配的方法)与非线性的缩比方法对某大展弦比机翼进行了仿真计算与比较分析,得出传统的线性缩比方法得到的缩比模型与设计目标相差较大,非线性缩比方法误差较小,即非线性缩比方法更加适用于存在明显几何非线性效应的大展弦比机翼的结论。     

基于PI-QPR控制的双向变流器并网研究

针对双向变流器在并网馈能过程中采用比例积分控制存在稳定性误差和系统扰动等问题,在传统的PI双闭环控制策略的基础上,设计了一种新型的双闭环复合控制方法,即在两相静止坐标系下将准比例谐振控制应用于电流内环控制,电压外环采用PI的控制策略;通过MATLAB/Simulink仿真,结果表明:采用该复合控制策略可以实现无静差控制,降低了双向变流器并网电流的谐波含量,系统具备良好的动态性能和鲁棒性能。     

装配式混凝土框架顶层端节点抗震性能试验

进行了5个配置500 MPa级纵筋框架顶层端节点试件的低周反复加载试验,研究了采用两种新型构造的装配整体式混凝土框架顶层端节点的破坏形态、滞回曲线、骨架曲线和位移延性等抗震性能及承载力,并提出了柱端无上伸节点的斜截面受弯承载力计算方法.结果表明:装配式试件均发生了梁端受弯破坏,且集中在梁端结合面较小范围内,但梁水平叠合面未见开裂;装配式试件的滞回曲线相对现浇试件更为饱满,其位移延性和耗能能力均优于现浇试件;装配式试件的位移延性系数为2.54～3.66,极限位移角为1/29～1/26,且柱端无上伸试件的延性略优于柱端上伸试件;装配式试件的极限承载力比现浇试件平均约低10%,但其极限承载力计算值与试验值之比平均为0.62～0.71,仍具有较高的安全储备.     

Q690高性能焊接钢管轴压临界承载力实验研究

为研究国家电网输电塔中Q690高性能钢焊接圆管的临界承载力,取长细比45和60,且考虑径厚比为31.25、37.50和43.75的三种截面,以厚度为8mm的国产Q690高性能钢板设计制作了18根焊接圆管足尺试件并进行轴向受压试验。由试验结果分析表明:试件与普钢圆管发生相同的弹性整体失稳破坏,破坏瞬时突然;而相对普通钢材,Q690高性能钢材料弹性段相对较长,管材环向约束增强,试件失稳相对滞后,临界承载力相应提高。与中国和美国相关行业规范公式计算值对比分析发现:所有规范计算值均不同程度小于试验实测结果,且长细比越大,差异越明显。上述结果进一步验证了将河南省电力勘测设计院"Q690钢管杆塔设计试验研究技术报告"得出的轴压稳定系数取值的相关规范设计公式应用于指导工程设计的可行性。     

带式输送机从动轴的疲劳分析

通过Pro／E软件的参数化建模思想对带式输送机从动轴进行实体建模,添加约束和载荷后对其进行工作载荷作用下的有限元分析,找出最大应力应变作用点,在静力分析的基础上对其进行疲劳分析,确定轴的安全系数。研究结果为传动轴的结构设计提供理论依据,为轴的优化提供前提条件,在许用应力范围内最大限度地减小了应力集中。     

Dependence of effective screening length in granular columns on bead and silo sizes and their ratio

Apparent mass measurements at the bottom of silos have been carried out. An important parameter in the Janssen model known as the effective screening length has been investigated for different bead and silo diameters as well as of their ratios. It is found that the effective screening length augments with the grain diameter d in addition to the granular column size. It is also revealed that λ exhibits stronger correlation with the bead diameter than that of the silo. This phenomenon is attributed to the reduced-shielding of the vertical stresses to the horizontal ones.     

Effects of transverse trapping on the ground state of a cigar-shaped two-component Bose-Einstein condensate

We derive the coupled nonpolynomial nonlinear Schro¨dinger equations for a two-component Bose-Einstein condensate in a quasi-one-dimension geometry and investigate the effects of a tightly transverse trapping on the ground state and the miscibility-immiscibility threshold. We find that the density profile of the matter wavepacket is remarkably dependent on the transverse width and the effective one-dimension nonlinear coupling strengths in miscible and immiscible regimes.     

航空光谱相机反射镜部件的有限元分析

反射镜是光谱相机的关键元件,为保证在复杂环境下的成像质量,有必要对其进行研究分析以验证结构设计的可靠性。针对反射镜在工作中的面形变化及结构的动力学性能,应用有限元分析软件MSC.Nastran对反射镜部件进行了静力分析及随机振动分析。计算结果表明,装配时压紧力对反射镜面形变化影响明显,可根据计算结果指导装调;随机振动分析结果表明,反射镜部件结构设计可靠,符合结构破坏的3σ原则,能够满足成像对反射镜位置精度和面形精度的要求。     

静态热老化对锂-钙基润滑脂微观结构和流变性的影响

采用静态热老化模拟润滑脂在轴承中的热老化过程,通过红外光谱特征波峰面积变化、扫描电镜和差热分析表征热老化后润滑脂微观结构,并采用流变测试仪考察热老化过程中润滑脂流变性能的变化.结果发现：随着老化时间延长,基础油分子碳链发生断裂,稠化剂浓度下降,产生含羰基类氧化产物,该类物质浓度逐渐增强;老化后的润滑脂晶体结构遭到严重破坏,皂纤维网状结构逐渐瓦解,润滑脂结构稳定性变差,剪切过后,结构恢复速率变慢;超过热老化288 h润滑脂热稳定临界点后,润滑脂老化反应加剧,易从润滑部位流失,润滑失效.     

Properties of hydrogen molecular ion with static screened coulomb and exponential cosine screened coulomb potentials

We have investigated the properties of hydrogen molecular ion (H) interacting with screened Coulomb potentials. Two types of potentials have been considered, namely, static screened Coulomb potential and exponential cosine‐screened Coulomb potential. Simulating the localized motion of the nuclei by using high powers of the internuclear coordinate in the generalized Hylleraas‐type wave function we have been able to obtain reasonably accurate binding energies for 1¹S(J = 0, ν = 0) and 2¹S(J = 0, ν = 1) states for various values of the screening parameter within the frame work of Ritz variational method. Borromean bindings are found to exist in the ion for a wide range of the screening parameter. Furthermore, expectation values for various operators and cusp condition have been calculated. Results for the unscreened case are in nice agreement with some of the accurate results available in the literature. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010