Crystal planes and reciprocal space in Clifford geometric algebra

This paper discusses the geometry of kD crystal cells given by (k+ 1) points in a projective space ?^{n+ 1}. We show how the concepts of barycentric and fractional (crystallographic) coordinates, reciprocal vectors and dual representation are related (and geometrically interpreted) in the projective geometric algebra Cl(?^{n+ 1}) (see (Die Ausdehnungslehre von 1844 und die Geom. Anal. Teubner: Leipzig, 1894)) and in the conformal algebra Cl(?^{n+ 1, 1}). The crystallographic notions of d‐spacing, phase angle, structure factors, conditions for Bragg reflections, and the interfacial angles of crystal planes are obtained in the same context. Copyright © 2011 John Wiley & Sons, Ltd.     

激光主动干涉条纹间距识别光学目标口径

利用物理光学相关知识及Collins衍射积分公式和硬边光阑的复高斯函数分解法,推导得到目标处干涉图样条纹间距与光学目标反射光时间分布关系的解析表达式.从原理分析、仿真计算和实验研究等方面研究了干涉场的条纹间距、光学目标口径参数和反射光时间分布包络的峰峰数、峰峰间距和峰峰比之间定量关系.结果表明,当条纹间距的大小约为目标的口径尺寸时,反射光时间分布包络的峰峰数由单峰向多峰过渡,峰峰间距和峰峰比曲线会出现极大值,根据这一变化规律可以估测出光学目标的口径参数,其估测精度受条纹间距可调节范围的影响.     

2μm波段双波长间隔可调谐光纤激光器

提出并实验研究了一种2μm波段全光纤间隔可调双波长光纤激光器.该激光器采用传统的环形腔设计,以最大输出功率33dBm的1 565nm光纤激光器为泵浦源,4m单模掺铥光纤为增益介质,腔内为嵌入多模干涉滤波器的Sagnac环的复合滤波结构.该复合滤波器可实现间隔可调谐,高边模抑制比的双波长激光信号输出.通过泵浦功率的控制和对复合滤波器中偏振控制器的调节,实现双波长3nm到80nm间隔可调的激光输出,边模抑制比为60dB,线宽为0.2nm,功率稳定度为±1.5dB/h,双峰能量差小于4dB.     

Wave chaos in quantum systems with point interaction

We study perturbations of the quantized version ₀ of integrable Hamiltonian systems by point interactions. We relate the eigenvalues of to the zeros of a certain meromorphic function . Assuming the eigenvalues of ₀ are Poisson distributed, we get detailed information on the joint distribution of the zeros of and give bounds on the probability density for the spacings of eigenvalues of . Our results confirm the wave chaos phenomenon, as different from the quantum chaos phenomenon predicted by random matrix theory.SFB 237 Essen-Bochum-Düsseldorf     

Influence of wire spacing and plate spacing on electrostatic precipitation of nanoparticles: An approach involving electrostatic shielding and diffusion charging

Electrostatic precipitation is a process widely used as gas cleaning device, to removal particles from gas flows. However, in a conventional and well-sized precipitator, the collection efficiency decreases for ultrafine particles, making it difficult to employ this equipment for controlling nanoparticle pollution. This paper investigates the influence of plate spacing (4 and 6.5 cm) and wire spacing (4, 6, and 12 cm) on the electric current and nanoparticle collection efficiency, considering the effect of diffusion charging and electrostatic shielding. Two laboratory-scale dry wire-plate electrostatic precipitators with different plate spacings were tested for the collection of nanoparticles (6.15–241.4 nm) at three air velocities (1.9, 2.9, and 3.9 cm/s). The results demonstrated the effectiveness of the equipment in removing nanoparticles (99.9%) under the highest electric fields. Higher values of the wire spacing led to increases in the current and the collection efficiency. This was associated with reduced electrostatic shielding, which is more evident in smaller ducts with a higher density of field lines. It is expected that the findings should improve knowledge on electrostatic precipitation of nanoparticles, enabling optimization of collection efficiency by considering the effects of geometric parameters.     

小间距隧道爆破开挖动力效应数值模拟研究

从爆破施工的特点入手,对小间距隧道在采用典型双侧导坑法时的爆破施工动力效应进行了数值模拟研究,给出了爆破施工在已有洞室周边产生的动力效应的一般规律,指出在爆破（后开挖洞室）开挖影响区以内,合理确定已有洞室二次衬砌施作时间的重要性,并给出了爆破施工对已有洞室稳定性影响较大的关键开挖位置。研究表明,爆破动载荷对小间距隧道围岩稳定性的影响主要表现为爆炸应力波造成围岩临空面的反射拉伸破坏,破坏较严重的是已有洞室的迎爆墙、拱脚、拱顶等部位。所得结论对小间距隧道爆破施工有一定的参考价值。     

基于土拱效应的抗滑桩与护壁桩的桩间距分析

抗滑桩与护壁桩分别在滑坡治理和基坑支护中发挥着巨大的作用 ,其实施正是利用了土中的成拱效应 ,然而传统桩的设计虽考虑土拱效应的存在 ,但桩间距确定理论与方法并未建立起来。本文首先基于土体的极限平衡条件对滑坡推力作用下的土体中的成拱作用进行研究 ,得出了抗滑桩的最大桩间距公式 ,并以某一具体工程为例 ,对该最大桩间距的物理意义和可用性进行了讨论。在此基础上 ,给出了在考虑土拱效应的情况下合理桩间距的确定方法 ,并以此为据 ,对边坡加固设计提出一些建议.     

Simulation of crack spacing using a reinforced concrete model with an internal length parameter

Summary A gradient-enhanced smeared crack model and bond-slip interface elements are utilized in finite element simulations of reinforced concrete. The crack model is rooted in an enhanced plasticity theory. It uses the Rankine failure surface dependent on an equivalent inelastic strain measure as well as on its Laplacian. As a result, finitely sized fracture process zones and realistic crack spacings are obtained. A reinforced concrete bar in uniaxial tension is analyzed to demonstrate the regularizing influence of the internal length parameter in the model and to evaluate the influence of the model parameters on the energy dissipation in multiple cracks. A comparison of numerical simulations with experimental results for a beam without shear reinforcement in four-point bending concludes the analysis. Received 4 November 1997; accepted for publication 23 April 1998     

Symptomatology of adductor spasmodic dysphonia: A physiologic model

Vocal symptomatology of adductor spasmodic dysphonia (SD) is reviewed critically from historical, epidemiologic, and clinical perspectives. A model of symptomatology of this disorder based on a large patient population, and clinical and physiologic observations is advanced. The model incorporates crucial symptomatic and asymptomatic phonatory and nonphonatory physiologic parameters of laryngeal behavior in these patients. These parameters include vocal fold contact area, vocal fold collision force, glottic compression, and subglottic air pressure. Inappropriate efferent discharges from brain-stem basal ganglia are hypothesized as causing overadduction of the vocal folds in phonation, generating the basic and fundamental vocal symptom of adductor SD—strained, strangled, overpressured voice quality. Cortical loops are implicated as accountable for compensatory vocal behavior, not as the primary site of the disorder. Symptom occurrence, variability, magnitude, effects, and failure of treatment approaches, as well as recurrence of symptoms after ablative or invasive procedures, are explained by this model. The model also predicts that symptomatology of adductor spasmodic dysphonia is unique to this disorder and that symptoms are phonotopically organized. The minimal diagnostic battery based on the model is presented, and it is shown how this battery aids in the differential diagnosis of adductor SD and other phonatory disorders that closely mimic the vocal symptoms of adductor spasmodic dysphonia, including tremor.     

脉冲电流冲击力对电极间距的影响

利用时变场理论和瞬态动力学方程建立了电极及其支撑结构的瞬态耦合模型,分析了瞬态电磁场各参数的分布特点,并求解了电极及其支撑结构的动态响应状态参数。计算结果表明:玻璃钢支撑结构对于脉冲电流形成的冲击力载荷具有很好的缓冲作用;低弹性模量支撑材料在脉冲上升沿和峰值阶段均会产生波动性形变,但该波动性形变对电极间距不会造成太大的影响。