A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication problems

A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication (EHL) problems is presented. First, by introducing a special matrix splitting iteration method into the traditional compound direct iterative method, the full matrices for the linear systems of equations are transformed into sparse banded ones with any half-bandwidth; then, an extended Thomas method which can solve banded linear systems with any half-bandwidth is derived to accelerate the computing speed. Through the above two steps, the computational complexity of each iteration is reduced approximately from O(N ³/3) to O(β ² _N), where _N is the total number of nodes, and β is the half-bandwidth. Two kinds of numerical results of transient EHL line contact problems under sinusoidal excitation or pure normal approach process are obtained. The results demonstrate that the new algorithm increases computing speed several times more than the traditional compound direct iterative method with the same numerical precision. Also the results show that the new algorithm can get the best computing speed and robustness when the ratio, half-bandwidth to total number of nodes, is about 7.5%–10.0% in moderate load cases.     

Electrochemical determination of hydrogen peroxide using a novel prussian blue–polythiophene–graphene oxide membrane-modified glassy carbon electrode

A polythiophene–graphene oxide compound membrane and Prussian blue were deposited sequentially on the surface of a glassy carbon electrode by cyclic voltammetry. Due to its excellent electrocatalysis and its analogy with peroxidase enzymes, Prussian blue has been widely used in amperometric biosensors. The polythiophene–graphene oxide compound membrane exhibited good electroconductibility and a large specific surface area. The fabricated Prussian blue/polythiophene/graphene oxide/glassy carbon electrode was characterized by transmission electron microscopy, scanning electron microscopy, and cyclic voltammetry. Under the optimal experimental conditions, the detection of hydrogen peroxide was studied by its amperometric current–time curve. Due to the presence of polythiophene–graphene oxide compound membrane and Prussian blue, the hydrogen peroxide sensor shows a linear calibration range of 1.0?×?10^?6–1.0?×?10^?4?mol?L^?1, detection limits of 3.2?×?10^?7?mol?L^?1 at a signal-to-noise ratio of 3, and recoveries from 95.0 to 105.0%. The results show that the modified glassy carbon electrode has potential practical application for the determination of hydrogen peroxide based on its sensitivity and long-term stability.     

Quantification of the Ti oxidation state in BaTi1−xNbxO3 compounds

The Ti oxidation state of a series mixed-valence BaTi_1−xNb_xO₃ compound (where x=0.002, 0.004, 0.02, 0.10, 0.20 and 0.50) is investigated using high resolution electron energy loss spectroscopy (EELS). The energy loss near edge structure (ELNES) of the Ti-L_2,3 and O-K edges was recorded with high energy resolution. The fraction of Ti⁴⁺ and Ti³⁺ components is determined in each compound by linear profile fitting with Ti⁴⁺ and Ti³⁺ standard spectra obtained from reference compounds within the series. The fitting results indicate an increase in the fraction of the Ti³⁺ component as the Nb content increases. A deviation from the expected Ti³⁺ valence fraction based on the charge balance across the series was detected and discussed. By considering all detailed features on the spectra obtained with high energy resolution, this linear fitting method can be used to determine the oxidation state of transition metal oxides, especially for the early transition metals where conventional methods based on the L_2,3 edge ratio have shown to fail. The potential of this method to provide insight to mixed valence systems, vacancies and properties of oxides is discussed.     

Prediction of zonal and total discharges in smooth straight prismatic compound channels using regression modeling

Experimental results are presented concerning the zonal and total discharge distribution and characteristics in a compound channel cross-section comprising one rectangular main channel and two symmetrical floodplains. The discharges in the main channel, floodplains, and total compound channel are found to be highly correlated to several dimensionless parameters defined using the compound channel cross-section geometry. Multi-variable regression analysis was utilized for developing predictive models that can estimate the main channel, floodplains and total discharges as a function of four different dimensionless parameters. The developed models to predict the zonal and total discharges in compound channels are found to be highly significant according to several major statistics including the model standard error, coefficient of determination (R²), and F-statistic. The developed multi-variable regression-based models are also tested for validity using available experimental data. Several statistical tests applicable to the analysis of residuals have indicated the effectiveness of the developed predictive models.     

Evidence of dislocation dissociation in nearly stoichiometric tantalum carbide using the weak-beam technique

The dissociation of dislocations in nearly stoichiometric tantalum carbide has been revealed by the weak-beam technique; this is in agreement with the assumptions of a model of dislocation glide which had been derived for this compound. An order of magnitude of the partial spacing for the screw and the edge dislocation is 2·7 and 5.2 nm respectively, which leads to a stacking-fault energy of about 170 mJ m^?2 (erg cm^?2).     

复眼位标器的标定与探测

介绍了一种新型大视场、高灵敏度的复眼位标器,用于探测低空飞行目标并快速获取目标物体的运动参数。叙述了复眼模型的结构和制作方法,并利用Zemax对子眼成像通道光线追迹考察其成像特性。介绍了复眼标定与探测方法。采用基于LM算法的神经网络训练,建立各个通道精确的物像对应关系。为了检验神经网络标定算法的效果,采用传统的基于二次多项式拟合的算法进行校正对比。仿真结果表明,神经网络算法可以提供更好的精度,从像点可以准确地预测主光线的方向角(10-3～10-4rad),而且具有易于集成,方便快捷的特点。此外,进行了目标定位检测的仿真实验,计算了若干目标点的坐标,结果表明各个坐标相对误差均在3%以内,对于牺牲空间横向分辨率来提升视场角的复眼光学系统,该结果符合目标探测的要求。     

纳米半导体复合薄膜的非线性光学性质及其在激光器中的应用

采用射频磁控溅射技术制备了Ge掺二氧化硅（Ge-SiO₂）和Ge,Al共掺二氧化硅（Ge/Al-SiO₂）两种复合薄膜,并进行了热退火处理形成了纳米Ge镶嵌结构。通过紫外-可见吸收谱测量,确定了两种薄膜中纳米Ge的光学带隙,并采用皮秒激光Z-扫描技术研究了薄膜的非线性光学性质。测试结果显示,在1 064 nm激发下得到的Ge-SiO₂和Ge/Al-SiO₂薄膜的非线性吸收系数分别为-1.23×10^-7 m/V和4.35×10^-8 m/W,前者为饱和吸收,而后者为双光子吸收。把两种薄膜作为可饱和吸收体均可实现1.06 μm激光的被动调Q和被动锁模运转。与Ge-SiO₂薄膜比较,采用Ge/Al-SiO2薄膜可以获得较窄的调Q脉冲和锁模脉冲。最后,理论分析和实验比较了两种薄膜实现被动调Q和锁模的机理。     

Analysis of boron-10 in soft tissue by dynamic secondary ion mass spectrometry

We report here a preliminary study in which dynamic secondary ion mass spectrometry (SIMS) has provided images of boron‐10 (¹⁰B) in biological tissue as used in research into boron neutron capture therapy. Cultured tumour cells incubated in media containing known concentrations of a ¹⁰B‐containing compound, p‐boronophenylalanine (BPA), and intracranial tumour tissue from animals previously injected with BPA were analysed by an in‐house constructed SIMS. Investigations were conducted in positive secondary ion detection mode using a 25‐keV, 5‐nA gallium primary ion source. For calibration purposes, tissue standards were also analysed and their boron‐to‐carbon signal ratios correlated to bulk boron concentrations measured by inductively coupled plasma atomic emission spectroscopy (ICP‐AES). Ion maps of ¹⁰B, ¹²C, ²³Na and ³⁹K showing gross tissue and cell features were acquired. SIMS and ICP‐AES standard measurements were in good agreement. Tissue regions with high or low ¹⁰B concentrations were identified along with ¹⁰B hotspots in normal brain areas. Cultured cells revealed the intracellular localization of ¹⁰B. SIMS is capable of producing images showing the distribution of ¹⁰B at p.p.m. levels in cells and in normal and tumour‐bearing brain tissue.     

A Modified Method for Measuring the Spin Relaxation in Nuclear Quadrupole Resonance

A simple and rather efficient method for measuring the spin–spin relaxation time T ₂ in nuclear quadrupole resonance (NQR) is proposed. The method uses the phase cycling (or alternation) technique and is rather efficient in measuring short T ₂ times. Results on the use of this method for detecting NQR signals on nuclei of nitrogen ¹⁴N in a (CH₂)₆H₄ polycrystal are presented. The application of modified pulse sequences enables rather accurate measurements of the T ₂ time for this compound.     

Traction and wear of an elastomer in combined rolling and sliding

Under combined rolling and sliding materials can experience millions of cycles as well as complex loading and slip conditions, which can dramatically affect their friction and wear behaviour. It was shown that for a carbon black‐filled natural rubber compound in combined rolling and sliding contact with a smooth alumina coated disk, the traction coefficient, as a function of slip percent, was dependent upon the normal load and independent of rolling velocity. The wear rate of this material pair was found to be independent of slip percentage as well as rolling velocity but dependent upon sliding distance. The wear rate was found to be approximately the same for all tested cases (K ~ 1 × 10⁻⁴ mm³·Nm⁻¹). The worn profiles of the ball specimens showed that this wear occurred preferentially on the left side (inner radius) of the contacting area. Copyright © 2015 John Wiley & Sons, Ltd.     

Physical properties and cutting performance of silicon nitride ceramic

Silicon nitride, a nitrogen compound of highly covalent bond character, has low density, high hardness, low thermal expansion and high thermal conductivity and excellent oxidation and corrosion resistance. Therefore it is considered to be a promising material for high temperature engineering components.However, it has very poor sinterability compared with the conventional oxide ceramics owing to its low self-diffusivity. By investigating starting materials, sintering additives and processing, a hot-pressed silicon nitride ceramic having grains enveloped by crystalline boundary phases can be produced.The silicon-nitride-based ceramic has high strength, high Weibull modulus, fracture toughness and thermal conductivity, and low thermal expansion compared with existing cutting tool ceramics such as Al₂O₃ + TiC, and it is expected to have superior thermal shock resistance.This new ceramic cutting tool shows superior performance in cutting cast irons at high speeds (10–16.75 m s^?1 (600–1000 m min^?1)) and rates (about 1.0 mm rev^?1), where conventional tools cannot be used.     

Tribological behaviours of Cu nanoparticles recovered from electroplating effluent as lubricant additive

Nowadays, many efforts have been made to minimise the pollution risks of copper electroplating effluent, such as chemical methods, physical methods, etc. Among them, chemical reduction has been used in this paper for its simplicity and potential for industrial production, and the recovered Cu nanoparticles (CuNPs) were innovatively used as a lubricant additive to prolong the lifetime of lubrication equipment and enhance energy conservation via emission reduction. In this paper, the relationships of the remaining Cu²⁺ concentration ([Cu²⁺]) with NaBH₄/CuSO₄ mole ratio, reaction time and reaction temperature were discussed separately. Then, L₉(3³) orthogonal experiment was carried out to determine optimal reaction conditions. Finally, the tribological behaviours [e.g. friction coefficients (FCs) and wear scar diameter (WSD)] of base oil samples with and without addition of the recovered CuNPs were investigated. Results indicate that the optimal reaction conditions were as follows: NaBH₄/CuSO₄ (4∶6) react at 30°C for 25 min, under which [Cu²⁺] was minimised to 0·2 mg L^?1 with a mean particle size of 33 nm. The FC and WSD of oil with 0·3 wt-%CuNPs were decreased by 33·4 and 19% respectively compared with the base oil. This compound oil was much more suitable for moderate load and high load than for low load. This paper provides a new idea on dealing with the copper electroplating effluent.     

A GREEN METHOD FOR THE DETERMINATION OF CHROMIUM(VI) AND IRON(III) IN WATER BY SEQUENTIAL INJECTION ANALYSIS AND SPECTROPHOTOMETRIC DETECTION

In this article, an organic-reagent-free method was described for the determination of Cr(VI) and Fe(III) by double-system double-wavelength sequential injection technique with a single sample injection. In this approach, the determination of Cr(VI) was based on the detection of a blue unstable intermediate compound resulting from the reaction of Cr(VI) with hydrogen peroxide, and the determination of Fe(III) was based on the color reaction of Fe(III) with thiocyanate in acidic medium. Sequential injection analysis (SIA) parameters, including spacer solution volume, aspiration order, aspiration volumes, flow rate, acid medium, solution acidity, and reagent concentrations, were optimized. The linear range for the determination was 3.0–60.0 μg mL^?1 for Cr(VI) and 1.0–40.0 μg mL^?1 for Fe(III), respectively. The limit of detection (LOD) was 0.6 μg mL^?1 for Cr(VI) and 0.2 μg mL^?1 for Fe(III), and the limit of quantitation (LOQ) was 2.0 μg mL^?1 for Cr(VI) and 0.67 μg mL^?1 for Fe(III). The total volume of the reagent consumed in each determination was only 0.11 mL. The proposed method was applied to the simultaneous determination of Cr(VI) and Fe(III) in electroplating wastewater and environmental waters. The results were in good agreement with those obtained by atomic absorption spectrometry. The recoveries were in the range of 97.5–101.1%.     

An improved method for predicting discharge of homogeneous compound channels based on energy concept

Accurate estimation of flow discharge in a compound river channel is increasingly important in river management and hydro-environment design. In this paper, a new model is developed to improve the prediction of flow based on Energy Concept Method (ECM) and Weighted Divided Channel Method (WDCM) along with the apparent shear stress at the interface between main channel and floodplain. The new model is compared with a wide range of our experimental data and the data available in the literature. The 27 datasets used include homogenous symmetric channels (22 datasets) and asymmetric channels (5 datasets) with various aspect ratios [channel total width (B) at bankfull / main channel bottom (b) =1.5–15.8], and bed slopes (S_o = 4.3 × 10⁻⁴–1.3 × 10⁻²). It was found that the new model has significantly improved the accuracy of flow prediction compared with the traditional Divided Channel Method (DCM), and has also considerably better results than the ECM and WDCM methods against all the datasets, particularly for relatively low flow depths of floodplain where the flow discharges are most difficult to predict correctly. The new model predicts the total discharge well for both symmetric and asymmetric channels, within an averaged relative error of about 5%.     

High-resolution imaging of organic pharmaceutical crystals by transmission electron microscopy and scanning moiré fringes

Formulation processing of organic crystalline compounds can have a significant effect on drug properties, such as dissolution rate or tablet strength/hardness. Transmission electron microscopy (TEM) has the potential to resolve the atomic lattice of these crystalline compounds and, for example, identify the defect density on a particular crystal face, provided that the sensitivity of these crystals to irradiation by high-energy electrons can be overcome. Here, we acquire high-resolution (HR) lattice images of the compound furosemide using two different methods: low-dose HRTEM and bright-field (BF) scanning TEM (STEM) scanning moiré fringes (SMFs). Before acquiring HRTEM images of furosemide, a model system of crocidolite (asbestos) was used to determine the electron flux/fluence limits of low-dose HR imaging for our scintillator-based, complementary metal-oxide semiconductor (CMOS) electron camera by testing a variety of electron flux and total electron fluence regimes. An electron flux of 10 e⁻/(Ų s) and total fluence of 10 e⁻/Ų was shown to provide sufficient contrast and signal-to-noise ratio to resolve 0.30 nm lattice spacings in crocidolite at 300 kV. These parameters were then used to image furosemide which has a critical electron fluence for damage of ≥10 e⁻/Ų at 300 kV. The resulting HRTEM image of a furosemide crystal shows only a small portion of the total crystal exhibiting lattice fringes, likely due to irradiation damage during acquisition close to the compound's critical fluence. BF-STEM SMF images of furosemide were acquired at a lower electron fluence (1.8 e⁻/Ų), while still indirectly resolving HR details of the (001) lattice. Several different SMFs were observed with minor variations in the size and angle, suggesting strain due to defects within the crystal. Overall BF-STEM SMFs appear to be more useful than BF-STEM or HRTEM (with a CMOS camera) for imaging the crystal lattice of very beam-sensitive materials since a lower electron fluence is required to reveal the lattice. BF-STEM SMFs may thus prove useful in improving the understanding of crystallization pathways in organic compounds, degradation in pharmaceutical formulations and the effect of defects on the dissolution rate of different crystal faces. Further work is, however, required to quantitatively determine properties such as the defect density or the amount of relative strain from a BF-STEM SMF image.     

用于热机械微纳加工的掺Al多晶硅加热器

针对热机械式微纳米结构的加工,提出了一种以掺Al多晶硅为材料,集成于微悬臂梁上的加热器.采用Al诱导退火晶化(AIC)方法,在750 K对Al/a-Si∶H复合薄膜低温晶化18 h,制备出掺Al多晶硅.通过低温退火,使复合薄膜的拉曼特征峰由478 cm-1移至520 cm-1,完成由非晶硅向多晶硅的转变;由四探针仪测得...     

An experimental study on the pumping performance of molecular drag pumps

The pumping performance of molecular drag pumps (MDP) has been investigated experimentally. The experimented MDPs are a disk-type drag pump (DTDP), helical-type drag pump (HTDP) and compound drag pump (CDP), respectively. In the case of the DTDP, spiral channels of a rotor are cut on both upper surface and lower surface of a rotating disk, and the corresponding stator is a planar disk. In the case of the HTDP, the rotor has six rectangular grooves. The CDP consists with the DTDP, at lower part, and with the HTDP, at upper part. The experiments are performed in the outlet pressure range of 0.2–533 Pa. The inlet pressure and compression ratio are measured under the various conditions of outlet pressure and throughputs, and nitrogen is used for the test gas. At the outlet pressure of 0.2 Pa, the ultimate pressure has been reached to 1.0 × 10⁻² Pa for the HTDP, 1.3 × 10⁻⁴ Pa for the DTDP, and 3.6 × 10⁻⁵ Pa for the CDP. The maximum compression ratio of the CDP is much higher than those of the DTDP or HTDP. Consequently, the ultimate pressure of the CDP is the lowest one.     

Leucine enkephalin—A mass spectrometry standard

The present article reviews the mass spectrometric fragmentation processes and fragmentation energetics of leucine enkephalin, a commonly used peptide, which has been studied in detail and has often been used as a standard or reference compound to test novel instrumentation, new methodologies, or to tune instruments. The main purpose of the article is to facilitate its use as a reference material; therefore, all available mass spectrometry‐related information on leucine enkephalin has been critically reviewed and summarized. The fragmentation mechanism of leucine enkephalin is typical for a small peptide; but is understood far better than that of most other compounds. Because ion ratios in the MS/MS spectra indicate the degree of excitation, leucine enkephalin is often used as a thermometer molecule in electrospray or matrix‐assisted laser desorption ionization (ESI or MALDI). Other parameters described for leucine enkephalin include collisional cross‐section and energy transfer; proton affinity and gas‐phase basicity; radiative cooling rate; and vibrational frequencies. The lowest‐energy fragmentation channel of leucine enkephalin is the MH⁺ → b₄ process. All available data for this process have been re‐evaluated. It was found that, although the published E_a values were significantly different, the corresponding Gibbs free energy change showed good agreement (1.32 ± 0.07 eV) in various studies. Temperature‐ and energy‐dependent rate constants were re‐evaluated with an Arrhenius plot. The plot showed good linear correlation among all data (R² = 0.97), spanned over a 9 orders of magnitude range in the rate constants and yielded 1.14 eV activation energy and 10^11.0 sec^?1 pre‐exponential factor. Accuracy (including random and systematic errors, with a 95% confidence interval) is ±0.05 eV and 10^±0.5 sec^?1, respectively. The activation entropy at 470 K that corresponds to this reaction is ?38.1 ± 9.6 J mol^?1 K^?1. We believe that these re‐evaluated values are by far the most accurate activation parameters available at present for a protonated peptide and can be considered as “consensus” values; results on other processes might be compared to this reference value. © 2010 Wiley Periodicals, Inc., Mass Spec Rev 30:298–320, 2011     

基于空芯光纤的复合双腔光纤法珀盐度传感器

为实现高灵敏度的盐度测量,提出了一种基于空芯光纤的单模光纤–空芯光纤–单模光纤(SMF-HCF-SMF)复合双腔光纤法珀(F-P)盐度传感器。该传感器通过精密切割结合光纤熔接技术制备,结构小巧,工艺简单。通过HCF段空气腔与SMF段介质腔所对应的反射光谱干涉信号的振幅之比对盐度进行测量,可以有效剔除光源功率起伏以及其他外部干扰的影响,实现盐度的高灵敏度测量。利用该传感器进行了盐度测量实验,在0%～24%的范围内实现了高达0.101%~(-1)的盐度测量灵敏度,同时传感器表现出了良好的线性响应。     

Histochemical implications of the chemical and biological properties of SITS and some related compounds

Since commercial samples of the fluorochrome SITS (sodium 4-acetamido-4′-isothiocyanatostilbene-2,2′disulphonate) are of varied, and often of uncertain, composition, the synthesis of SITS has been repeated. The identities of SITS and certain of its precursors and derivatives have been established using modern spectroscopic methods (IR, ¹H and ¹³C NMR), as well as microanalysis. When pure SITS underwent hydrolysis at room temperature the products were amines, not the expected thioureas. This suggests that SITS, contrary to previous expectations, will not bind covalently to proteins, whether immunoglobulins or membrane constituents. Again contrary to earlier statements, pure SITS is not retrogradely transported in neuronal axons. The transported material is a red-orange impurity which arises very occasionally during the preparation of SITS. A possible structure for this red-orange compound is proposed: namely a dimeric azo or azoxy condensation product. Comparison of pure SITS with commercial samples indicated that the latter were extremely varied in composition, with SITS contents varying from high to trivial.