On-machine wire electrical discharge dressing (WEDD) of metal-bonded grinding wheels

Traditional multivariate control charts such as Hotelling’s χ ² and T ² control charts are designed to monitor vectors of variable quality characteristics. However, in certain situations, data are expressed in linguistic terms and, under these circumstances, variable or attribute multivariate control charts are not suitable choices for monitoring purposes. Fuzzy multivariate control charts such as fuzzy Hotelling’s T ² could be considered as efficient tools to overcome the problems of linguistic observations. The purpose of this paper is to develop a fuzzy multivariate exponentially weighted moving average (F-MEWMA) control chart. In this paper, multivariate statistical quality control and fuzzy set theory are combined to develop the proposed method. Fuzzy sets and fuzzy logic are powerful mathematical tools for modeling uncertain systems in industry, nature, and humanity. Through a numerical example, the performance of the proposed control chart was compared to the fuzzy Hotelling’s T ² control chart. Results indicate uniformly superior performance of the F-MEWMA control chart over Hotelling’s T ² control chart.     

光谱范围从365至12000nm的高精度光电自动折射仪

介绍了由作者研制的光谱范围从365至12000nm的高精度光电自动折射仪的测量原理、主要误差源和仪器组成。用该仪器对包括红外材料锗在内的多种样品进行了测量,在小于2600nm和大于2600nm的波长范围内分别获得了优于±3×10^-6和±5×10^-5的折射率测量精度。     

多角度下蜡染布料的多光谱成像研究

在400~720 nm波段范围,采用基于液晶可调谐滤波器(LCTF)和CMOS相机组合的多光谱成像系统对蜡染的布料进行每隔5 nm成像。讨论了多光谱成像的基本原理和多角度下彩色图像的实现过程,并且通过计算光谱反射率展示了光谱合成颜色的基本方法。对再现后的橘色、绿色、白色、蓝色、黄色、黑色六种颜色色块进行多角度下明度值、彩度值的分析。实验结果表明,六种颜色的明度值均呈现正态分布,并且通过计算六种颜色色块的色品坐标值a~*、b~*和彩度c_(ab)~*的均方差,得出在一定的范围内,六种颜色的色品坐标a~*、b~*近似不随角度变化,其中蓝色和黑色随角度的变化更小,近似于一条直线。     

High-performance 320 × 256 long-wavelength infrared photodetector arrays based on CdHgTe layers grown by molecular beam epitaxy

This paper gives the parameters of 320 × 256 element long-wavelength infrared photodetectors fabricated by a new improved technology based on heteroepitaxial mercury-cadmium-tellur structures. In these photodetectors, the variation of the photodiode bias voltage over the area of the array is minimized; inefficient photodiode regions related to both hybridization and spike-shaped growth defects of epitaxial films are eliminated; the current-voltage characteristics of the diodes in the resulting photodetectors are homogeneous and are limited by the diffusion current component up to ?400 mV. The dark current is 0.25–0.45 nA, and R ₀ A = (0.6–3) · 10² Ω · cm². The voltage sensitivity, the threshold irradiance, and the average NETD at the maximum sensitivity are 11.8 · 10⁸ V/W, 3.7 · 10^?8 W/cm², and 26.8 mK, respectively. The percentage of defective elements is 1.5%.     

On the theory of optimal, constant thickness fibre-reinforced plates—II

The investigation of optimal fibre reinforcement layouts begun earlier¹ is continued and extended to another important combination of support conditions. It is also shown that all the deflected shapes for the slabs discussed in the previous paper are everywhere both displacement and slope continuous, and hence are global optima.     

Mobility analysis of planar four-bar mechanisms through the parallel coordinate system

This paper presents a new method for the mobility analysis of planar mechanisms. The method utilizes a geometrical representation known as “parallel coordinates.” It is a transformation that maps the Euclidean space R^N to N parallel coordinates in the projective plane. Points in R² are transformed to line segments in the parallel coordinate plane, and circles in R² are transformed to hyperbolae. Also, in this investigation, special techniques required for mobility analysis are developed. First, the intersection of circles is performed graphically through the parallel coordinate system. The parallel coordinate plane is then appended to relate this intersection data to the angular coordinates of the various members of the linkage. The ranges of these angular coordinates are the results of the mobility analysis.     

High-speed contouring control with NURBS-based C2 PH spline curves

This paper presents a C² Pythagorean hodograph (PH) spline curve constructed by the non-uniform rational B-spline (NURBS) curve for high-speed contouring control. With the knot vector, weights, and control points given, the C² PH spline curve is defined to be a “good” interpolant for Hermit data obtained from a NURBS curve of degree 3 specified by the same control polygon, weights, and the knot vector. To this end, the first- and second-order derivatives are evaluated at the nodal points on the NURBS curve. These boundary conditions are imposed on the PH segments of degree 9 to preserve continuity between the connecting segments. The S-curve motion planning architecture with variable feed rate for a planar NURBS-based C² PH spline curve is also developed in this paper. In particular, C¹ cubic feed acceleration/deceleration is imposed on the first and last PH segments. Several NURBS-based C² PH spline curve-following tasks were conducted to verify the effectiveness of the proposed interpolation algorithm. Experimental results show that the proposed interpolator is not only feasible for machining the complicated parametric curves represented in the NURBS-based C² PH spline form but also yields satisfactory contouring performance under variable feed rate control.     

Digital Synthesizers of Frequency-Modulated Signals

The method of digital synthesis is based on the straightforward calculation of the output signal phase used to increase the operation rate and to extend the functional capabilities of digital frequency synthesizers. In this paper, schematic diagrams are presented for devices operating in the frequency range from 10^–2to 2.5 × 10⁶Hz. The minimum frequency step is 0.0025 Hz, and the frequency tuning rate is 1–10 000 kHz/s.     

Lattice Boltzmann simulation of turbulent natural convection in a square cavity using Cu/water nanofluid

In this paper, lattice Boltzmann simulation of turbulent natural convection with large-eddy simulations (LES) in a square cavity which is filled by water/copper nanofluid has been investigated. The present results are validated by experimental data at Ra = 1.58×10⁹. This study is conducted for high Rayleigh numbers (Ra = 10⁷–10⁹) and volume fractions of nanoparticles (0 ≤ Φ ≤ 0.06). In this research, the effects of nanoparticles are displayed on streamlines and isotherms counters, local and average Nusselt numbers. The average Nusselt number is enhanced by the augmentation of nanoparticle volume fraction in the base fluid while the manner has an erratic trend toward different Rayleigh numbers.     

Non-linear oil film response model for the dynamically misaligned sterntube bearing

This paper presents a non-linear oil film response model which has been developed from a model for the aligned full circumferential groove bearing, described earlier by Jakeman¹. The model is specifically intended to represent the dynamically misaligned sterntube bearing, for the purpose of conducting lateral vibration analysies of marine propeller shafting. Some predicted data are presented for the oil film response to lateral and angular motion of the journal axis, upon which the non-linear model is based. A comparison of lateral vibration predictions using the non-linear and linear oil film models, and measurements by Hyakutake et al², will be given in a separate paper.     

1.0μm掺钕介质全固化调Q脉冲激光技术

以量子阱激光二极管(LD)为泵浦源、三价钕离子(Nd³⁺)晶体为增益介质、发射波长在1.0μm附近的全固体脉冲激光器团结构紧凑、性能可靠,而能够在许多方面得到广泛的应用.本文介绍了近年来这种全固化调Q激光技术的发展与运用,主要有主动(电光、声光)调Q激光器、被动调Q激光器等.实验表明,将Cr⁴⁺:YAG为代表的掺四价铬离子晶体作为被动调Q元件,能够实现这一波段内高重复率和高峰值功率的脉冲运转,为全固化低成本、中小功率/能量输出的脉冲激光器指出了一条具有实际意义的道路.     

Anterograde tracing in the brain using autoradiography and HRP-histochemistry. A comparison at the ultrastructural level

The present paper decribes the use of ³H-leucine and WGA-HRP as anterograde tracers in the brain at the ultrastructural level. In addition the different aspects of the two tracing techniques are compared, including the analysis of the results, the reliability and relative efficiency.     

LASEM — a novel combined device for laser modification in SEM

An intense localized heat source inside a microscope could be useful in the improvement of electron microscopic in-situ investigations. For this reason a JEOL scanning electron microscope was combined with a pulsed Nd-glass laser which allowed power densities up to about 10⁹ W/cm² on the specimen under Q-switch conditions. The mechanical and electrical adaptations necessary for the SEM-to-laser coupling, as well as some tests of the method involving the new equipment are discussed in detail in this paper. Various applications to materials are reviewed, including melting processes, thermal cracking and surface hardening of tungsten carbide alloys and other hard materials.     

Methods of quantitative matrix analysis of Zircaloy-2

The zirconium-based alloy Zircaloy-2 contains small amounts of iron, chromium and nickel dissolved in the matrix. Several attempts to measure these amounts have been made in the past, but the results are conflicting and inconclusive. The advent of wide angle, laser pulsed atom probe tomography motivates a new attempt to analyze the matrix. Large datasets are now easily obtained using laser pulsing but quantification is not straightforward due to rather complex mass spectra. Zircaloy-2 contains about 1 wt% tin, 0.1 wt% oxygen and trace amounts of Si, C and Al. Severe overlaps make quantification of any Fe⁺, Cr⁺ and Ni⁺ ions impossible. Quantification of Fe, Cr and Ni therefore requires that they appear as doubly charged ions only, and consequently the field must be kept high enough. In addition, adsorbed CO⁺ may appear at the main peak of Fe²⁺. In the paper a method is reported, which gives what we believe an accurate quantitative analysis of at least iron and chromium in the matrix.     

A review of principles and methods applied to the optimum calculation and design of externally-pressurized bearings: Part 2: Moderate/high-speed bearings

This paper in the second of two parts¹, and is a review of the characteristic aspects of optimizing hybrid bearings and the possibilities of applying mathematical programming methods. The most important physical implications of the high relative speed between the two bearing surfaces are briefly presented: non-laminar flow, thermal effects, film rupture. The flow graph representations of lubricant flow in the bearing are also given. Finally, elements are provided for the application of nonlinear programming in the externally-pressurized bearing (epb) optimization. The conclusions show the nonlinear programming processes to be superior and recommendable. The final section of the paper deals with the solving methodology based on the epb optimizing nonlinear programming.     

高功率移相器的电子束封焊技术

研究了高功率移相器盒体与盖板的电子束封焊工艺技术。通过接头的结构设计解决了一次启盖返修问题;通过专用夹具的设计有效地控制了温升,经点温计测量最大温升不大于60℃;采用一条焊缝两次焊接工艺保证了焊缝的熔深要求,改善了焊缝质量,经氦质谱检漏仪测试,气密性优于1．013X10^-3Pa．cm^3／s的氦漏气率。该移相器已成功地应用于某雷达天馈系统。     

Determination of (S)-(+)-Ibuprofen Using Enantioselective,Potentiometric Membrane Electrodes Based on Macrocyclic Antibiotics

Abstract

The enantioselective, potentiomeric membrane electrode based on vancomycin and teicoplanin modified with acetonitrile were proposed for the assay of (S)-(+)-ibuprofen. The linear concentration ranges for the proposed enantioselective membrane electrodes were 10^?2 to 10^?4 and 10^?2 to 10^?6 mol/Lfor electrodes based on vancomycin and acetonitrile modified teicoplanin, respectively, with slopes of 58.5 and 57.0 mV/decade of concentration, respectively. The proposed electrodes could be employed reliably for the assay of (S)-(+)-ibuprofen raw material and in its pharmaceutical formulations, Myprodol capsules and Nurofen tablets. The surfaces of the electrodes are stable and easily renewable by polishing on alumina paper.     

The shear properties of molecular films

This paper describes a preliminary study of the shear properties of calcium stearate monolayers and multilayers trapped between curved mica surfaces. The thickness and area of the sheared film can be measured during the shearing process itself. It is found that the shear strength of monolayers over contact pressures covering the range 0.1 to 1 kg mm² is of order 0.3 to 0.4 kg mm^?2. Monolayers are relatively viable. Multilayers are churned up by the shearing process.     

Environmental effects on wear and friction of toughened zirconia ceramics

The friction and wear of toughened zirconia ceramics in self-mated sliding contacts in various liquid environments were investigated and compared with those observed in air. Tests were performed in distilled water, pure ethyl alcohol and synthetic silicone oil. A pin-on-plate tribometer with reciprocating sliding motion was used to carry out the experiments. It was found that the friction and wear characteristics of the tested pairs were significantly influenced by environment. The lubricated coefficients of friction in the range of 0.1–0.4 were found and wear was generally low. All three environments reduced wear of zirconia ceramics from about 10⁻¹⁴ m³ N⁻¹ m⁻¹ in dry sliding down to about 10⁻¹⁶ m³ N⁻¹ m⁻¹ at the tested temperature and load-speed conditions. The wear scars were examined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) and the effects of the environment on wear morphology are presented in this paper.     

NMR and DSC studies of base oils

The effect of the composition of a base oil matrix on additive response is an indication of its behaviour in a dynamic system. In this paper, a novel method involving quantitative ¹H and ¹³C NMR to explain the molecular chemistry of base oil is used. Oxidative degradation of base oils (pure as well as additivated) has been studied using DSC. The results are explained in terms of molecular composition of the different base stocks to get a clear understanding of additive response in a matrix of different hydrocarbon oils.