The Study of Arc Rate,Friction, and Wear Performance of C/C Composites in Pantograph–Catenary System

A series of tests on arc rate, friction coefficient, and wear rate of electrical current collectors sliding against overhead contact wires under different conditions was carried out on a high-speed friction and wear testing machine with a pin-on-disc configuration. The worn surface morphology and composition were examined using a scanning electron microscope and energy dispersion spectrum analyzer, respectively. The effects of current, velocity, and load on the arc rate, friction coefficient, and wear rate of C/C composites/QCr0.5 couples were investigated, and the influence mechanism of test parameters on C/C composites was explained. It is concluded that the wear rate increases with an increase in current and velocity and has a decreasing trend with the increase in load. The friction coefficient increases with an increase in velocity and load. The arc rate of C/C composites/QCr0.5 couples increases with an increase in current and velocity. Under the condition of the same current and velocity, when the load is 70 N, the arc rate is the lowest.     

Friction,Wear, and Evaporation Rates of Various Materials in Vacuum to 10−7 mm Hg

Evaporation data on soft metals, lubricating inorganic compounds, and various reference materials are reported for temperatures from 75 to 1000 F in vacuum as low as 10^?7 mm Hg. Observations on modes of vacuum degradation (e.g., evaporation or dissociation) and methods of experimentation are related. Friction and wear data are presented for several unlubricated metals (e.g., type 440-C steel) and metals coated with inorganic (e.g., MoS₂, CaF₂) as well as with soft metal films in vacuum at ambient pressures between 10^?6 and 10^?7 mm Hg.     

Analysis of Ancient Pottery from Tel Al‐Baharia Site in Damascus,Syria

Abstract

The radioisotope x‐ray fluorescence (XRF) method has been utilized in the analysis of forty archaeological pottery fragment samples from the Tel Al‐Baharia site, Damascus City, Syria. The samples were irradiated by a ¹⁰⁹Cd radioisotope source (～9 × 10⁸ Bq) for 1000 sec. Eighteen chemical elements (K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Ga, As, Br, Rb, Sr, Y, Zr, Nb, and Pb) were determined. These elemental concentrations have been processed using two multivariate statistical methods. The purpose of the analysis was to characterize, by means of element contents, the pre‐historical pottery raw material sources from the Tel Al‐Baharia archaeological site. The results obtained by factor score confirm that the pottery samples classified by cluster analysis (CA) are correctly classified. In this study, most of the samples could be divided into four categories. The results provided persuasive evidence that Tel Al‐Baharia pottery used at least four different clay sources. Moreover, by means of a systematic local clay analysis, it will be clear whether these sources are local or not.     

Optimization of thrust force, torque, and tool wear in drilling of coir fiber-reinforced composites using Nelder–Mead and genetic algorithm methods

Machining of composite materials is an important and current topic in modern researches on manufacturing processes. Determination of optimal cutting parameters is one of the most important elements in the machinability study of composites. Optimization has significant practical importance particularly for operating the machineries. In order to increase the accuracy of drill holes, the tool must be in good condition always as much as possible. To achieve good condition of tool, the optimization of machining parameters like drill bit diameter, spindle speed, and feed rate are mandatory. The objective of this paper is to study the effect of these process parameters on thrust force, torque, and tool wear in drilling of coir fiber-reinforced composites. The optimal settings of the parameters were determined through experiments planned, conducted, and analyzed using the Box–Behnken design, Nelder–Mead, and genetic algorithm methods. This paper also aimed to increase the cutting condition of tool, i.e., minimization of tool wear by applying the optimized input parameters using Nelder–Mead and genetic algorithm techniques.     

Observations of Stick-Slip Friction in Velcro®

Friction, and in particular stick-slip friction, occurs on every length scale, from the movement of atomic force microscope tips at the nanoscale to the movement of tectonic plates of the Earth’s crust. Even with this ubiquity, there still appears to be outstanding fundamental questions, especially on the way that frictional motion varies generally with the mechanical parameters of a system. In this study, the frictional dynamics of the hook-and-loop system of Velcro^® in shear is explored by varying the typical parameters of driving velocity, applied load, and apparent contact area. It is demonstrated that in Velcro^® both the maximum static frictional force and the average kinetic frictional force vary linearly with apparent contact area (hook number), and moreover, in the kinetic regime, stick-slip dynamics are evident. Surprisingly, the average kinetic friction force is independent of velocity over nearly two-and-a-half orders of magnitude (~2 × 10^?4 to ~6 × 10^?2 m/s). The frictional force varies as a power law on the applied load with an exponent of 0.28 and 0.24 for the maximum static and kinetic frictional forces, respectively. Furthermore, the evolution of stick-slip friction to more smooth sliding, as controlled by contact area, is demonstrated by both a decrease in the spread of the kinetic friction and the spread of the fluctuations of the average kinetic friction when normalized to the average kinetic friction; these decreases follow power-law behaviors with respect to the increasing contact area with exponents of approximately ?0.3 and ?0.8, respectively. Lastly, we note that the coefficients of friction μ _s and μ _k are not constant with applied load but rather decrease monotonically with power-law behavior with an exponent of nearly ?0.8. Phenomenologically, this system exhibits interesting physics whereby in some instances it follows classical Amontons–Coulomb (AC) behavior and in others lies in stark contrast and hopefully will assist in the understanding of the friction behavior in dry surfaces.     

Beijing University of Chemical Technology Succeed in Technology of Tri-screw Extruder

The plastic machinery and Engineering Institute of Beijing University of Chemical Technology has successfully developed the world＇s first industrial full initiative meshed tri-screw extruder which is triangle arranged. The actual application of the industrial model shows that the tri-screw extruder is reliance for operating with low energy consumption and it shows a strong technological and economic advantages in the stronger mixing. The advantages is that：     

Summation of pulses in γ-ray spectra

It is shown that peaks formed in -ray spectra by summing the pulses due to cascades can be used to determine both the activity of the radiation source and the efficiency of detecting the rays. Possible sources of errors in determining these quantities were investigated. This method may be used to measure the cross sections of nuclear reactions, to analyze the background radiation when searching for rare decays, and in other applications.Translated from Pribory i Tekhnika Eksperimenta, No. 1, 2005, pp. 58–61.Original Russian Text Copyright ¢ 2004 by Gromov, Fominykh, Chumin, Samatov.     

Three-point method of differential correction of coordinates and pseudo-range in GPS

本文提出了对坐标和伪距进行差分修正的内插值法。它使用三个参考点的系统提高了所生成的修正的质量和稳定性。实验证明,与标准差分校正法相比,内插值法在修正质量和稳定性方面具有优越性。     

Generation of the second harmonic of laser radiation in powders of pure and doped potassium nitrate in the temperature interval of 25–160 °C

The temperature dependence of the intensity of generation of the second harmonic of laser radiation with λ = 1.064 µm in various powders of extra-pure potassium nitrate is studied. The powders are obtained from crystals grown in a KNO₃-Ba(NO₃)₂—H₂O water-salt system. It is demonstrated that the centrosymmetric phase is crystallized from pure solutions. If Ba(NO₃)₂ is added to the solution, non-centrosymmetric phases of KNO₃ or 2KNO₃ · Ba(NO₃)₂ double salt are formed. As the crystals are cooled down from the temperature of 160 °C, the samples display a ferroelectric phase transition and a hysteresis relaxation dependence of the nonlinear optical response due to the method of sample preparation.     

Assessment of dynamical properties in EDM process—detecting signature of latent change to deleterious process in advance

Time series data of gap state were often used as feedback signal in EDM control systems. An effective way to quantify gap state in machining was developed in this paper. Based on a time series of gap states recording a machining process, the entire process was partitioned into three parts, transient process, efficient machining process, and deleterious process. It is expected that efficient machining process should be maintained long enough in consideration of machining efficiency and avoiding workpiece surface damage. In this case, a signature of structural change from efficient machining process to deleterious process has to be detected or detected in advance. It has been found that linear analysis methods failed the task. In this paper, a nonlinear analysis method, cross-prediction error, was employed to track this structural change in efficient machining process in two tests. In the first test, the efficient machining process was roughly split into 30 segments. By using the cross-prediction-error method in this test, the non-stationarity, a signature of structural change from stationary process in efficient machining process to non-stationary process, was successfully revealed in the last segment of the process. In another test, efficient machining process was even more finely split into 70 segments, and by using the cross-prediction-error method again it is found that the detected non-stationarity in the process was in the last segment but one. The second test not only proves the effectiveness of the method, but also brings forward the detected non-stationarity more than 10s. The detected non-stationarity in advance, thus, is supposed to be used for avoiding the occurrence of abnormal deleterious process and maintaining a persisted efficient machining process.     

The Effectiveness of the ZDDP Tribofilms in Lubrication of Sol–Gel Titania in Technical Dry Friction Conditions

The objective of this study was the investigation of the tribological properties of the sol–gel derived titania modified by physically deposited zinc dialkyldithiophosphate (ZDDP) films. Titania coatings were prepared on silicon wafers Si(100) using sol–gel dip-coating method. Amorphous, anatase, and rutile titania were obtained in the post-preparation annealing process conducted at 100, 500, and 1000 °C, respectively. Deposition of ZDDP having butyl- (C4) or dodecyl- (C12) alkyl chain was performed by means of dip-coating (DC), self-assembly (SA), and Langmuir–Blodgett (LB) methods. The effectiveness of the modification was monitored by the wetting contact angle measurement. An increase of the surface hydrophobicity was observed upon modification. The surface topography, imaged with the use of Atomic Force Microscopy (AFM), revealed the presence of island-like agglomerates having different size of ZDDP films deposited using DC and SA method. Smooth and compact C12ZDDP films were observed when LB deposition was applied. The tribological performance of the ZDDP films on titania coatings was tested with the use of microtribometer operating in the normal loads range of 30–100 mN in the technical dry friction conditions. It was found that ZDDP tribofilms effectively decrease the coefficient of friction and effectively reduce the wear of titania coatings.     

The Influence of Speed,Grease Type,and Temperature on Radial Contaminant Particle Migration in a Double Restriction Seal

Microparticle image velocimetry (μPIV) is used to measure the grease velocity profile in small seal-like geometries and the radial migration of contaminant particles is predicted. In the first part, the influence of shaft speed, grease type, and temperatures on the flow of lubricating greases in a narrow double restriction sealing pocket is evaluated. Such geometries can be found in, for example, labyrinth-type seals. In a wide pocket the velocity profile is one-dimensional and the Herschel-Bulkley model is used. In a narrow pocket, it is shown by the experimental results that the side walls have a significant influence on the grease flow, implying that the grease velocity profile is two-dimensional. In this area, a single empirical grease parameter for the rheology is sufficient to describe the velocity profile.

In the second part, the radial migration of contaminant particles through the grease is evaluated. Centrifugal forces acting on a solid spherical particle are calculated from the grease velocity profile. Consequently, particles migrate to a larger radius and finally settle when the grease viscosity becomes large due to the low shear rate. This behavior is important for the sealing function of the grease in the pocket and relubrication.     

Current Status of Extreme Ultraviolet Lithography in Japan

ASET, Association of Super- advanced Electronics Technologies, has been taking the initiative in developing EUV lithography technology in Japan for the past three years. The aspherical mirror metrology using a visible light point diffraction interferometer (PDI), the wave-front measurement using an at - wavelength PDI, and an at-wavelength reflectometry for multilayers, various imaging simulations, multilayer coatings for the mask, the development of absorber materials for mask patterning, the mask substrate cleaning technique, and various photoresist processes have been developed. The visible light PDI employs a 0.5 -μm pinhole as an aperture to generate an ideal spherical wave-front and can measure a 0.3 - N A mirror maximum. The at - wavelength PDI can measure the wave-front error of the projection optics. The at- wavelength reflectometer can measure the reflectivity of multilayers and the round - robin test is taking place among ASET, the ALS in Lawrence Berkeley, and BESSY in Germany.The mask cleaning technique employs a supersonic hydro- cleaning technique. We have confirmed that the single layer resists can be used for EUV lithography.     

Interference of selective higher-order modes in optical fibers

1IntroductionIn recent years,multimode interference(MMI)effectsin integrated optics have attracted enormous research atten-tion and MMI-based devices with various functionalities,in-cluding directional couplers,powersplitters,sensors,modu-lators,bistable lasers,and optical switches,have been dem-onstrated[1-4].The obvious advantages of the MMI-based de-vices are their compact size,large fabrication tolerance,andlow-cost.MMI is becoming a promising technique in opticalcommutations,optical s…     

Application of RLS adaptive filtering in signal de-noising

针对信号中混有噪声的问题,介绍了一种基于RLS算法的自适应信号消噪系统,并阐述了自适应滤波的原理以及RLS算法的步骤与流程。通过实例仿真,得到了基于RLS算法的自适应消噪系统仿真图。经过对比分析可知,RLS自适应滤波能较好地消除噪声,获得有用信号,从而验证了该方法的有效性和系统的合理性。     

Analysis of Thermal Stability of High-Performance Rolling–Sliding Contacts in Mixed Lubrication

Thermal instability has been considered by pioneer researchers to be one of the most promising lines for a fundamental investigation into the failure mechanisms of rolling–sliding contacts. This article uses a recently developed mixed lubrication model that integrates interrelated topographical, mechanical, thermal, and tribochemical aspects to study the thermal instability of high-performance rolling–sliding contacts. The effects of various system parameters on the relation between the system bulk temperature and the heat generation in the contact are analyzed. The parameters include surface roughness; contact component size; surface and lubricant mechanical, thermal, and tribochemical properties; and operating conditions. Key results and their implications to system design and operation considerations are summarized in the Conclusion section of the article in relation to enhancing the thermal stability of the contact, particularly under adverse lubrication conditions.     

Design of PLC control system of RTG spreader in Qingdao Port Container Terminal

在青岛前湾集装箱码头有限责任公司运行的轮胎吊吊具电控系统采用的是逻辑电路板的控制方式,该系统存在备件昂贵,故障率高的缺陷。本文应用可编程控制器设计了一套新型的集中控制系统替代了原控制系统,主要完成了控制系统方案设计、硬件选型和可编程控制器程序开发等,并实现了可编程控制器控制系统的现场应用,实践表明,新系统具有工作效率高,运行成本低,维护方便等特点。     

Kinetics of formation of boundary lubricating film in zone of facing–tool contact under metal cutting

Tribological processes that occur in the zone of the facing–tool contact can be satisfactorily described using a three-zone model in which zones of adhesion, seizure, and friction are distinguished. An expression that relates the coefficient of friction under cutting to the distribution of the zones of friction over the surface of contact has been obtained, causes for the origination of the zone of adhesion have been analyzed, and the shear strength of boundary films has been estimated. A model that describes the kinetics of the formation of a boundary lubricating film in the zone of friction with account for the dimensions and the shape of surfactant molecules, as well as the concentration of surfactants, has been developed. The results of the calculations have shown good agreement with the experimental data.     

Study of the Wheel–Rail System of Open-Pit Locomotives in Traction Mode

As a result of theoretical and experimental surveys, it is established that the value of the limiting gradient of industrial railways affects the temperature change in the contact area of the wheel–rail system of the locomotives and is characterized by the temperature coefficient of the gradient (k_gradient).