Robust high order discontinuous Galerkin schemes for two-dimensional gaseous detonations

One of the main challenges in computational simulations of gas detonation propagation is that negative density or negative pressure may emerge during the time evolution, which will cause blow-ups. Therefore, schemes with provable positivity-preserving of density and pressure are desired. First order and second order positivity-preserving schemes were well studied, e.g., [6], [10]. For high order discontinuous Galerkin (DG) method, even though the characteristicwise TVB limiter in [1], [2] can kill oscillations, it is not sufficient to maintain the positivity. A simple solution for arbitrarily high order positivity-preserving schemes solving Euler equations was proposed recently in [22]. In this paper, we first discuss an extension of the technique in [22], [23], [24] to design arbitrarily high order positivity-preserving DG schemes for reactive Euler equations. We then present a simpler and more robust implementation of the positivity-preserving limiter than the one in [22]. Numerical tests, including very demanding examples in gaseous detonations, indicate that the third order DG scheme with the new positivity-preserving limiter produces satisfying results even without the TVB limiter.     

Dependence of reaction pressure on deposition and properties of boron-doped freestanding diamond films

In this paper, we investigate the reaction pressure-dependent growth and properties of boron-doped freestanding diamond films, synthesized by hot filament chemical vapor deposition (HFCVD) at different boron-doping levels. With the decrease in pressure, the growth feature of the films varies from mixed [1 1 1] and [1 1 0] to dominated [1 1 1] texture. The low reaction pressure, as well as high boron-doping level, results in the increase (decrease) of carrier concentration (resistivity). The high concentration of atomic hydrogen in the ambient and preferable [1 1 1] growth, due to the low reaction pressure, is available for the enhancement of boron doping. The estimated residual stress increases with increase in the introducing boron level.     

5-乙酰(苯甲酰)基-4-芳基-3,4-二氢嘧啶-2(1H)-酮的质谱裂解规律

利用飞行时间质谱仪的高分辨本领和离子阱串联质谱技术研究了5乙酰(苯甲酰)基4芳基3,4二氢嘧啶2(1H)酮(1-5)的电子轰击质谱的裂解规律.将所有质谱离子的精确质量数据经OpenLynx软件导出其分子离子和碎片离子的元素组成.根据质谱裂解规律,主要质谱离子得到了归属,并经离子阱串联质谱技术加以证实.化合物1-3的质谱出现了丰度很强的分子离子峰,其中1和3的分子离子为基峰,证明此类化合物的结构相当稳定.但4和5的分子离子峰却很弱(相对丰度在4%以下),这是由于嘧啶环4位上的苯环分别含有强吸电子基团-NO2(在苯环的间位才有此效应)和-Cl(苯环的2和4位均含有氯)所致.化合物1-5的主要裂解包括:分子离子失去芳基形成丰度很高的阳离子(M-Ar)+;分子离子失去羰基形成中等强度的阳离子(M-RCO)+;分子离子失去氢原子所产生的(M-H)+峰,以及消除中性分子NH=C=X的嘧啶环破裂裂解.此外,所有化合物在低质量区都发现明显的苯基阳离子Ph+(m/z77).并且还提出个别化合物的几个额外裂解过程为:化合物4(分子中苯环的3位上含有硝基)出现的基峰(M-OH)+;化合物5(分子中苯环的2和4位上都含有氯原子)出现了的基峰(M-Cl)+;化合物3和5分别出现了m/z238(16%)和m/z241(29%)的特征离子峰,它们由相应的离子消除中性分子四员内酰胺生成查耳酮离子,该离子具有共轭大Π键而稳定存在.     

氩原子共振增强多光子电离谱--奇对称性里德堡态

利用脉冲放电产生氩原子亚稳态4s2[3/2]°2和4s′2[1/2]°0,在610～670nm波长范围内,利用共振增强多光子电离和飞行时间质谱技术得到氩原子(2+1)REMPI谱.光谱分析表明所有谱线来源于氩原子4s2[3/2]2和4s′2[1/2]°0两个亚稳态向16个奇对称性里德堡态双光子跃迁,并标识所有谱线.同时首次在实验上观察到一个长序列的3p54s′2[1/2]°0→3p5nd2[1/2]°1(n=8～31)双光子跃迁.在实验技术上,提供了一种研究惰性气体原予以及其它原子高里德堡态和自电离态的新方法.     

Construction of very high order residual distribution schemes for steady inviscid flow problems on hybrid unstructured meshes

In this paper we consider the very high order approximation of solutions of the Euler equations. We present a systematic generalization of the residual distribution method of [1] to very high order of accuracy, by extending the preliminary work discussed in [2] to systems and hybrid meshes. We present extensive numerical validation for the third and fourth order cases with Lagrange finite elements. In particular, we demonstrate that we both have a non-oscillatory behavior, even for very strong shocks and complex flow patterns, and the expected accuracy on smooth problems.     

Force measurement in cutting metals at 100–700 m/sec

Kuznetsov [1] in 1947 proposed a new method of obtaining very high cutting speeds by firing past the tool. This method has been used in an apparatus for measuring the tangential component of the cutting force and for extracting swarf in undamaged form [2]. Recently there have been several papers [3–5] describing high-speed cutting tests by this method. Research on cutting is of interest also in relation to the behavior of materials at high speeds. Here we describe a method of measuring cutting forces, and results are given on the forces acting on the tool in free cutting of aluminum at 100–700 m/sec with various tool angles.     

超分子荧光探针用于环境水样中百草枯的测定

基于七元瓜环可使中性红的荧光增强从而设计荧光探针,当在荧光探针中加入百草枯后荧光强度又逐渐降低,利用此种超分子配合物的荧光“开-关”效应,从而建立了一种新颖的检测百草枯的荧光方法。当百草枯浓度在(1~8)×10-6 mol·L-1范围内,百草枯浓度与探针的荧光强度具有良好的线性关系,且检出限为1.4×10-8 mol·L-1,加标回收率为104%~108%,可在河水样品中检测百草枯的含量。     

Quantum Kalman filtering and the Heisenberg limit in atomic magnetometry

The shot-noise detection limit in current high-precision magnetometry [Nature (London) 422, 596 (2003)] is a manifestation of quantum fluctuations that scale as 1/sqrt[N] in an ensemble of N atoms. Here, we develop a procedure that combines continuous measurement and quantum Kalman filtering [Rep. Math. Phys. 43, 405 (1999)]] to surpass this conventional limit by exploiting conditional spin squeezing to achieve 1/N field sensitivity. Our analysis demonstrates the importance of optimal estimation for high bandwidth precision magnetometry at the Heisenberg limit and also identifies an approximate estimator based on linear regression.     

气相外延ZnSe单晶薄膜的蓝色电致发光

本文在300℃—700℃温度范围内,在GaAs衬底上气相外延生长了ZnSe单晶薄膜。讨论了衬底温度对外延层电学性质及光学特性的影响。ZnSe外延层经Zn气氛热处理后,发光特性大为改善。用处理后的ZnSe外延膜做成MIS发光二极管,首次得到了室温下气相外延ZnSe单晶薄膜的蓝色电致发光。     

高阶有限单元边界积分方法

本文在文献[1]的基础上,将高阶元引入边界积分方程方法,对导热问题的求解作了详细说明,给出了几个算例。并在精度上与线性元做了比较。     

Deformation of single crystal sample using D-DIA apparatus coupled with synchrotron X-rays: In situ stress and strain measurements at high pressure and temperature

We present a technique for high pressure and high temperature deformation experiment on single crystals, using the Deformation-DIA apparatus at the X17B2 beamline of the NSLS. While deformation experiments on polycrystalline samples using D-DIA in conjunction with synchrotrons have been previously reported, this technical paper focuses on single crystal application of the technique. Our single crystals are specifically oriented such that only [1 0 0] slip or [0 0 1] slip in (0 1 0) plane is allowed. Constant applied stress (sigma <300 MPa) and specimen strain rates were monitored using in situ time-resolved X-ray diffraction and radiography imaging, respectively. Rheological properties of each activated slip system in the crystals can be revealed using this technique. In this paper, we describe the principle of sample preparation (e.g. [1 1 0]_c and [0 1 1]_c orientations) to activate specific slip systems (i.e. [1 0 0](0 1 0) and [0 0 1](0 1 0), respectively), stress measurement and procedures of the deformation experiments.     

Design and properties of binary axilens

A novel optical element, axilens, proposed by Davidson et al., for achieving extended focal length is introduced. We propose a method to design the binary axilens which has high diffraction efficiency. Using computer numerical simulation, we designed 4 axilenses each has different parameters. In this paper we present our results and make comparison with that in ref. [1]. The properties of binary axilens such as the focal depth, the lateral resolution and the intensity distribution along axis is discussed.     

Observation of a new rotational band in 104Nb nucleus

The high spin states in neutron-rich 104Nb have been investigated from study of prompt γ-rays in spontaneous fission of 252Cf with the Gammasphere detector array. A new rotational band has been identified for the first time. This band is proposed as a semi-decoupled band based on the configuration π5/2-[303](⊕)v1/2-[541].     

New approaches for growth control of GaN-based HEMT structures

This paper reports on new approaches for growth control of GaN-based heterostructures for high frequency and high power application. First in situ methods are presented and their further development discussed [1]. The development leads to a greatly improved observation of growth parameter influences in the MOVPE of GaN. A new growth process is introduced which enhances growth reproducibility [2]. This new growth process is then optimized with respect to the envisaged application. To this end process modeling will be employed. The application envisaged is the Al_xGa_1-xN/GaN high electron mobility transistor (HEMT). At last device results will be presented. All in all it will be shown how fundamental research can drive technology and how basic knowledge can be employed for process development with respect to device applications. PACS 68.35.Ct; 68.55.Ac; 78.66.Fd; 81.15.Kk     

MILLIMETER WAVES DETECTOR BASED ON JOSEPHSON’s JUNCTIONS WITH OPTIMAL SUBSTRATE

The detectors based on superconductors are used for the registration of signals in the millimeter range [1]. Specially, the quantum radio receptor is widely used due to its very high sensibility. The structure of such receptor consists usually of a periodic Josephson’s Junctions (JJs) lattice and its very high sensibility may be obtained with the synchronization of the JJs using resonators of superficial electromagnetic wave [2]. These resonators realize automatically the synchronization of several hundreds of JJs, including the electro dynamical especial line like lattice [2]. The purposes of this article are: the analysis of the quality factor of the periodic JJs lattice, the optimal choice of the substrate for this system and the construction of the millimeter waves detector based on these elements.     

强流相对论性电子束与高Z等离子体靶相互作用磁场效应的研究

本文应用简化的Fokker-plancu方程^[1],加上限流扩散和Marshak边界条件,与流体力学程序耦合,研究相对论电子束与高Z等离子体靶相互作用的磁场效应。     

（CTAB）_9[Sb_1W_9O_（33）]的制备及其光谱分析

利用溶胶-凝胶法合成了K9[Sb1W9O33],用十六烷基三甲基溴化铵（CTAB）对K9[Sb1W9O33]改性,得到了（CTAB）9[Sb1W9O33],以过氧化氢氧化环己醇制取环己酮为探针反应,考察了n（Sb）∶n（W）对催化剂催化活性的影响,评价结果表明：催化剂金属原子配比n（Sb）∶n（W）=1∶9,催化活性最高,在该条件下,环己酮的选择性达到了最大值99.2%。通过XRD、FT IR的检测,揭示了（CTAB）9[Sb1W9O33]的微观结构和内在规律性,[Sb1W9O33]9-与CTAB＋之间存在协同效应,实验结果为工业装置的技术改造提供了较好的实验依据。     

3D DDD modelling of dislocation–precipitate interaction in a nickel-based single crystal superalloy under cyclic deformation

Strain-controlled cyclic deformation of a nickel-based single crystal superalloy has been modelled using three-dimensional (3D) discrete dislocation dynamics (DDD) for both [0?0?1] and [1?1?1] orientations. The work focused on the interaction between dislocations and precipitates during cyclic plastic deformation at elevated temperature, which has not been well studied yet. A representative volume element with cubic γ′-precipitates was chosen to represent the material, with enforced periodical boundary conditions. In particular, cutting of superdislocations into precipitates was simulated by a back-force method. The global cyclic stress–strain responses were captured well by the DDD model when compared to experimental data, particularly the effects of crystallographic orientation. Dislocation evolution showed that considerably high density of dislocations was produced for [1?1?1] orientation when compared to [0?0?1] orientation. Cutting of dislocations into the precipitates had a significant effect on the plastic deformation, leading to material softening. Contour plots of in-plane shear strain proved the development of heterogeneous strain field, resulting in the formation of shear-band embryos.     

Raman Scattering of Synthetic Polymers‐A Review

Abstract

Four years after Raman discovered the Raman effect, the first spectrum of a high polymer, i.e., polystyrene, was observed by Signer and Weiler 111, so the field of Raman spectroscopy of polymers is not a new field. However, it was not until twenty years later that the second Raman spectrum of a polymer, that of poly(methy1 methacrylate), was observed [2]. The reasons for this lack of activity rest on the fact that the sample had to be clear, transparent, and nonfluorescing to obtain a Raman spectrum. Most polymers do not fall in any of these categories. Workers like Nielsen [3,4] (PE and PTFE), Tobin [5,6] (PE, PP, PTFE), Brown [7] (PE), and Tadokoro [8,9] (POM, PEG) obtained spectra with Toronto arc spectrometers out only after an enormous amount of diligent effort. However, these workers were successful in drawing attention to the potential of Raman spectroscopy as a tool for the characterization of polymers. Nielsen's review [lo] presented substantial motivation for work in this area, but the experimental difficulties tended to discourage everyone. With the advent of laser excitation and the high quality of the first reported [ll] laser Raman spectrum of a polymer, a revival of work and interest in this field ensued and many workers are now active in the field, as reflected by the increasing number of papers in Raman spectroscopy of polymers. One review of laserexcited Raman spectroscopy of polymers has already beenwritten [12].     

Lattice Boltzmann simulation of a binary fluid with different phase viscosities and its application to fingering in two dimensions

A thermodynamically consistent lattice Boltzmann scheme for simulating the flow of a binary fluid is extended to allow the fluid components to have different viscosities. The approach is tested for the shear and Poiseuille flow of layered immiscible fluids and for the dispersion relation and the damping of a capillary wave. We then consider the fingering that results when a fluid is displaced by a less viscous fluid in a two-dimensional channel. The finger widths obtained match the results of Reinelt and Saffman [#!Reinelt85!#], but differ somewhat from those of Halpern and Gaver [#!Halpern94!#] for capillary numbers above 2. A limiting finger width close to 1/2 is obtained for high capillary numbers and high viscosity ratios. Received 25 May 1999 and Received in final form 19 November 1999