A New Type of Stretched Solutions Excited by Initially Stretched Vortex Filaments for the Local Induction Equation

We solve the initial value problem of the stretched vortex filament with the local induction equation and obtain a new type of stretched solution analytically, a solution that was suggested numerically. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 144, No. 2, pp. 354–363, August, 2005.     

细旦聚丙烯卷绕丝的结晶结构与其后拉伸性能的关系

应用电子计算机对一系列细旦聚丙烯卷绕丝样品的大角Ｘ射线衍射图进行分峰处理，发现用常规熔融纺丝制得的聚丙烯卷绕丝的Ｘ射线衍射曲线可以分解成六个峰：一个非晶峰，对应于α晶型的三个典型峰（２θ值分别为１４．０°，１６．８°，１８．５°），对应于次晶的典型的二个峰（２０＝１５．２°，２１．４°）。对样品中所含次晶和α晶相对含量与其后拉伸性能相互关系的研究结果表明：卷绕丝次晶对α晶的相对含量越高，后拉伸性能越好。这将有助于选择合适的纺丝工艺条件，制备具有优良物理机械性能的细旦聚丙烯长丝。     

详解EVO-18型扫描电镜钨灯丝的更换及其日常维护

以EVO-18型扫描电子显微镜为例,阐述了钨灯丝扫描电镜灯丝更换的详细注意事项及灯丝日常维护保养的具体办法.     

Tuned Transport Path of Perovskite MAPbI3-based Memristor Structure

In this study, the features of resistive random access memory (RRAM) employing a straightforward Cr/MAPbI₃/FTO three-layer structure have been examined and clarified. The device displays various resistance switching (RS) behavior at various sweep voltages between 0.5 and 5 V. The RS effect has a conversion in the direction of the SET and RESET processes during sweeping for a number of cycles at a specific voltage. The directional change of the RS processes corresponds to the dominant transition between the generation/recombination of iodide ion and vacancy in the MAPbI₃ perovskite layer and the electrochemical metallization of the Cr electrode under the influence of an electric field, which results in the conductive filament (CF) formation/rupture. At each stage, these processes are controlled by specific charge conduction mechanisms, including Ohmic conduction, space-charge-limited conduction (SCLC), and variable-range hopping (VRH). By identifying the biased voltage and the quantity of voltage sweep cycles, one can take a new approach to control or modulate the pathways for effective charge transport. This new approach is made possible by an understanding of the RS characteristics and the corresponding mechanisms causing the variation of RS behavior in the structure.     

Consistent hybrid finite volume/element formulations: model and complex viscoelastic flows

The accuracy and consistency of a new cell‐vertex hybrid finite element/volume scheme are investigated for viscoelastic flows. Finite element (FE) discretization is employed for the momentum and continuity equation, with finite volume (FV) applied to the constitutive law for stress. Here, the interest is to explore the consequences of utilizing conventional cell‐vertex methodology for an Oldroyd‐B model and to demonstrate resulting drawbacks in the presence of complex source terms on structured and unstructured grids. Alternative strategies worthy of consideration are presented. It is demonstrated how high‐order accuracy may be achieved in steady state by respecting consistency in the formulation. Both FE and FV spatial discretizations are embedded in the scheme, with FV triangular sub‐cells referenced within parent triangular finite elements. Both model and complex flow problems are selected to quantify and assess accuracy, appealing to analysis and experimental validation. The test problem is that of steady sink flow, a pure extensional flow, which reflects some of the numerical difficulties involved in solving more generalized viscoelastic flows, where both source and flux terms may contribute equally to stress propagation. In addition, a complex transient filament‐stretching flow is chosen to compute the evolution of stress fields within liquid bridges. Shortcomings of the various stress upwinding schemes are discussed in this context, whilst dealing with such free‐surface type problems. Here, stress fluctuation distribution alone is advocated, and a Lax‐scheme is found to deliver accuracy and stability to the computational results, comparing well with the literature. Copyright © 2004 John Wiley & Sons, Ltd.     

连续碳纳米管线及其应用

如何将碳纳米管组装成宏观尺度的结构对于碳纳米管的宏观应用来说具有重要意义．自从碳纳米管被发现以来，在合成大面积碳纳米管阵列方面已经取得很多的进展，并有望应用于场发射平板显示器．然而，在如何将碳纳米管顺排起来连成连续的长线方面则鲜有进展．这里介绍的是作者最近的新发现：当从一种作者称之为“超顺排”碳纳米管阵列中拔出一束碳纳米管时，碳纳米管以可自组织成一条连续的长线．在这个过程中，“超顺排”碳纳米管阵列起的作用如同一个蚕茧，阵列中的碳纳米管则由范德瓦耳斯力首尾相连形成连续的纯碳纳米管线．这种碳纳米管线平行排列起来构成的偏振片可以工作在紫外波段．这种碳纳米管线还可以用作白炽灯的灯丝，仅需很小的功率就可以发出白炽光．不仅如此，这种碳纳米管线经过高温处理后，强度和导电性都得到明显增强，这将使碳纳米管线在宏观领域内得到更多的应用．     

Measurement of CO,HCN, and NO productions in atmospheric reaction induced by femtosecond laser filament

It is proved that the chemical reaction induced by femtosecond laser filament in the atmosphere produces CO, HCN, and NO, and the production CO and HCN are observed for the first time. The concentrations of the products are measured by mid-infrared tunable laser absorption spectroscopy. In the reduced pressure air, the decomposition of CO₂ is enhanced by vibration excitation induced by laser filament, resulting in the enhanced production of CO and HCN. At the same time, the CO and HCN generated from the atmosphere suffer rotation excitation induced by laser filament, enhancing their absorption spectra. It is found that NO, CO, and HCN accumulate to 134 ppm, 80 ppm, and 1.6 ppm in sealed air after sufficient reaction time. The atmospheric chemical reaction induced by laser filament opens the way to changing the air composition while maintaining environmental benefits.     

Growth of diamond thin film on tool materials from a gas phase

Abstract

In the present paper, diamond films have been synthesized on tungsten carbide, sintered diamond and high pressure diamond by hot filament chemical vapour deposition method from the mixture gas of methane and hydrogen, and growth features of diamond were studied.     

Efficient generation of third harmonic radiation in air filaments: A revisit

In this paper we revisit the third harmonic generation from a femtosecond laser filament in air and its significant enhancement (~ 100 times) with a intercepting pump pulse, which has been reported very recently. The enhanced third harmonic is studied as a function of the pulse polarization, time delay between the pump and signal pulses, laser pulse energy, etc. We provide an explanation for the enhancement of third harmonic based on a quenching of interference effects present near filamentation threshold. Simulations based on a two-color propagation code reproduce well the experimental observations and confirm our interpretation.