Investigating the parameters of electron beams in the presence of ion compensation of the charge using the “hole chamber” method

The parameters of electron beams produced by a hollow-anode gas-discharge electron gun based on a glow discharge and operated in an ion focusing mode at medium and low vacuum have been investigated. The “hole chamber” method is proposed. Using a device based on this method, it is possible to measure the electron beam parameters with a high efficiency under conditions of ion focusing when testing the performance of the gas-discharge electron gun in technological processes.     

Facility for investigating the propagation of sound in the surface layer of the earth’s atmosphere

The facility is intended for investigating the propagation of sound waves in the surface layer of the Earths atmosphere. It permits the directional radiation, and recording, of high-level audio-frequency sound. The maximum sound level (referred to a distance of 1 m) is as high as 151 dB; the antenna beamwidth is 6° to 16°, depending on the frequency; the side-lobe level does not exceed –20 dB; and the lengths of the investigated propagation paths, with various underlying surfaces, are up to 3 km.__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 130–132.Original Russian Text Copyright © 2005 by Krasnenko, Kudryavtsev, Mananko.     

Measurement of the Background Level in the Spectra of Internal-Conversion Electrons Using the МАС-1 Microscope Complex

A method for measuring the spectral lines in an -50 photoemulsion plate with a varying background level is described. The -ray spectrograph of the Joint Institute for Nuclear Research's Laboratory of Nuclear Problems, was used to record the spectra. The plate was exposed to internal-conversion electrons produced by the decay of erbium isotopes (erbium fraction). The spectral measurements were performed using the -1 microscope complex. The distribution of the background level over the plate surface was measured. Using the L-structure of the -ray line of ¹⁶¹Ho with an energy of 175.5 keV as an example, it was shown that the accuracy of the intensity measurements was 10% or better. The accuracy in measuring the background level governed the accuracy in identifying the multipolarity of nuclear transitions. A precision TV system for data readout based on a 768 × 576 pixel CCD matrix provided a measurement accuracy of 0.5 m for both coordinates.     

The influence of a change in the electron trajectory in the vacuum-diode anode–cathode gap on the impedance

The analysis of the influence of the electron-trajectory curvature in the anode–cathode gap of a vacuum diode on its impedance during generation of high-current electron beams is performed, and the applicability of the one-dimensional Child–Langmuir formula for the electron-current calculation is evaluated. The results of an experimental study of a flat diode with explosive-emission graphite, copper, and carbon- fabric cathodes and also with a multipointed cathode are presented. These investigations were performed on the TEU-500 accelerator (350–500 kV, 60 ns). A strip diode with a graphite cathode was also studied in the mode of magnetic self-insulation of electrons. The experiments were performed on the TEMP-4М accelerators (150–200 kV, 400–600 ns). The investigation results showed that the satisfactory coincidence of the experimental values of the total current with those calculated from the one-dimensional Child–Langmuir formula (for the working area of the cathode) is observed in diodes not only in the absence of a change in the electron trajectory in the anode–cathode gap but also upon a deflection of the trajectory from the normal to the cathode surface by an angle of <90°. An increase in the electron current owing to a decrease in the anode–cathode gap and an increase in the emission area of the cathode during the cathode-plasma production and also at the expense of the presence of microirregularities on the cathode is properly described by the onedimensional Child-Langmuir formula, if the above factors are taken into account.     

A Model for the Assessment of Wheel–Rail Contact in the Presence of Solid Contaminants

An analytical model for the assessment of a contact in the presence of a solid contaminant is presented, mainly aimed at studying the damage to railway wheels and rails operating in third-body-contaminated environments. The model, developed under 2D plane strain idealization, includes multiple evenly spaced rigid cylindrical contaminant bodies entrapped between two elastic cylinders. It allows a very fast calculation of the pressure distribution on the surfaces in contact and it can be used for evaluating the stress field in the subsurface region, at both the small scale of the contact between the main body and the contaminant body and the full scale of the contact between the two main bodies. The model was validated by comparison with finite element (FE) analyses, showing its accuracy. Some examples of application showed the model’s ability to predict the limit of the influence of the solid contaminant bodies and the depth where cyclic plasticity phenomena occur in wheel–rail contacts.     

Measurement of the Specific α-Activity in Environmental Objects

We describe a new technique for nuclear-radiation spectrometry and identification by the pulse's shape in CsI(Tl) scintillators. The specific -activity of soil samples taken from the Adit 139 and the Southeast Trace of the Semipalatinsk Test Range was determined by the method of -particle identification in a CsI(Tl) crystal at a 1-MeV detection threshold. The results were compared to the data obtained using radiochemical separation.     

Digital manufacturing—the development direction of the manufacturing technology in the 21st century

After introducing the concepts of digital manufacturing technology, the discipline framework of digital manufacturing is presented in the paper by discussing its basic concept, theory foundation, key technology and scientific problems in detail. As the core of the advanced manufacturing technology, digital manufacturing is gradually becoming the main manufacturing technology of the twenty-first century. Firstly, the main features of digital manufacturing are indicated and its key supporting technologies are investigated by grouping them into four levels related to product development, numerical control, production management, and enterprise collaboration, respectively. Moreover, the existing problems in the research on the multi-discipline theory foundation of digital manufacturing such as manufacturing informatics, computational manufacturing, and manufacturing intelligence, are also indicated. Then, the core scientific problems of digital manufacturing are discussed in depth, which focuses on digitization of manufacturing information, modeling of manufacturing constraints, high-speed and high-precision numerical control theory, and Internet-based collaboration and integration. Lastly, the development trends and application perspectives of digital manufacturing are concluded.     

An Automated Setup for Investigating the Temperature Dependence of the Permittivity Spectra of Polar Liquids in the Range of 0.1–1.25 GHz

An automated setup for measurements of the temperature dependences of permittivity spectra is described. It uses an irregular microstrip resonator and allows measurements to be performed at a junction of methods using lumped elements and electrodynamic systems with distributed parameters. Measurements can be carried out without expensive thermostabilization devices in the temperature range of 200–350 K with a step of 1 K. The temperature dependences of the permittivity of polar liquids—water, methanol, and ethanol, whose dielectric relaxation regions lie within the frequency range of 0.1–1.25 GHz—are presented. Comparing the measured values of the permittivity to the Debye curve calculated from the reference data shows agreement within the limits of 3% for and 1% for . The random error of measurements was 2–3% for and 5–7% for .     

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).     

The rôle of particle properties in the erosion of brittle materials

The erosion of a range of brittle materials (soda-lime glass, borosilicate glass, fused silica, boron carbide, partially stabilized zirconia, alumina and silicon carbide) with number of different erodent particle types (silicon, silica, alumina and silicon carbide) has been examined. The mechanisms of erosion depend upon the ratio of particle to target hardness. As this ratio falls towards unity, less damaging mechanisms of erosion dominate. Indentation-induced fracture models for erosion of brittle materials are not valid when this mechanism ceases to operate. The erosion rates decrease rapidly, and the velocity exponents of erosion rate increase, as the ratio of particle to target hardness decreases towards unity. The consequences of this in accelerated erosion testing are addressed.     

Experimental Depiction of the Hypothesis of Flake-Like Wear Debris Generation in Rolling Contact Fatigue of the Rail–Wheel Contact Interface

Flake-like particles represent a common type of wear debris generated during the rolling contact fatigue wear test using a twin-disc test rig. It is argued that these flake-like particles are generated during the delamination process due to plastic shear strain accumulation at the wearing surfaces. This hypothesis has been developed in the last decades to explain the particle generation mechanism, yet it has not been proven conclusively. This research provides strong experimental evidence of the creation processes of wear debris propagation, aggregation, transfer, and compaction, therefore confirming the existing hypothesis and enhancing the understanding of wear mechanisms in the rolling contact interface.     

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.     

On the thermal aspect of fretting wear—temperature measurement in the subsurface layer

In fretting wear, the kinetics of the oxide film formation as well as the microstructure and the mechanical properties of the subsurface layer depend significantly on the temperature field produced in the fretted zone. Information reported in the open literature indicates contradicting values for the temperature produced at the interface. In the present study, an experimental method for direct measurement of the temperature profile in the subsurface layer has, therefore, been developed and verified. This method overcomes the limitations and the uncertainties inherent in methods of measurement used before. An error analysis indicated that the temperature gradient can be measured within ± 2.5%. The extent of the temperature measurement zone has been estimated by the theory of thermal constriction resistance and found to be in good agreement with some available experimental data.     

Modeling and analysis of the effects of processing parameters on the performance characteristics in the high pressure die casting process of Al–SI alloys

The high pressure die casting (HPDC) process has achieved remarkable success in the manufacture of aluminum–silicon (Al–SI) alloy components for the modern metal industry. Mathematical models are proposed for the modeling and analysis of the effects of machining parameters on the performance characteristics in the HPDC process of Al–SI alloys which are developed using the response surface methodology (RSM) to explain the influences of three processing parameters (die temperature, injection pressure and cooling time) on the performance characteristics of the mean particle size (MPS) of primary silicon and material hardness (HBN) value. The experiment plan adopts the centered central composite design (CCD). The separable influence of individual machining parameters and the interaction between these parameters are also investigated by using analysis of variance (ANOVA). With the experimental values up to a 95% confidence interval, it is fairly well for the experimental results to present the mathematical models of both the mean particle size of primary silicon and its hardness value. Two main significant factors involved in the mean particle size of primary silicon are the die temperature and the cooling time. The injection pressure and die temperature also have statistically significant effect on microstructure and hardness.     

A study on the variation of the performance and the cost of power generation in a combined heat and power plant with the change of the user facility’s return temperature

Journal of Mechanical Science and Technology - A combined heat and power (CHP) system generates electricity from thermal energy and generates heat by utilizing the remaining thermal energy. The...     

Exoemission Testing of Violations of the Stoichiometry in High-Temperature Superconducting Ceramics on the Basis of YBa2Cu3O7–δ

Samples of high-temperature superconducting (HTSC) ceramics YBa₂Cu₃O_7– thermally treated in oxidizing and reducing media are investigated by means of the exoelectron emission method. It is found that the thermostimulated exoemission (TSE) increases considerably in the maximum at 470 K after reducing thermal treatment of HTSC ceramics at temperatures of 800–860 K. Correlation dependences between the exoemission activity, the deviation from the stoichiometry in the oxygen sublattice, and the temperature of transition of YBa₂Cu₃O_7– ceramics to the superconducting state are found. These dependences indicate that the exoemission testing can be used in the design of technologies of the synthesis and treatment of HTSC materials on the basis of complex oxides.     

Analysis of the Contribution of Adhesion and Hysteresis to Shoe–Floor Lubricated Friction in the Boundary Lubrication Regime

Slip and fall accidents cause frequent occupational injuries. Despite recent evidence that boundary lubrication is relevant to slipping, few studies have examined the mechanisms that contribute to shoe?Cfloor friction in this lubrication regime. This study aims to identify the contributions of adhesion and hysteresis to friction in boundary lubrication. Three shoe materials (40 Shore A hardness polyurethane, 60 Shore A hardness rubber, and 70 Shore A hardness rubber), two floor materials (vinyl and marble), and six lubricants (water, 1.5?% detergent, 25?% glycerol?C75?% water, 50?% glycerol?C50?% water, 75?% glycerol?C25?% water, and canola oil) were tested at a single sliding speed (0.01?m?s^?1). Dry adhesion and hysteresis were quantified for each of the shoe?Cfloor combinations and lubricated adhesion was quantified for all shoe?Cfloor-fluid combinations. The contribution of adhesion and hysteresis to shoe?Cfloor-lubricant friction was affected by both the shoe and floor material due to differences in hardness and roughness. Lubricated adhesion was complex and multifactorial with contributions from the shoe, fluid, shoe?Cfloor interaction, floor-lubricant interaction, and shoe-lubricant interactions. A simple regression model including two fluid coefficients and the dry adhesion friction force was able to predict 49?% of the lubricated adhesion friction variability.     

The optimization of annealing and cold-drawing in the manufacture of the Ni�CTi shape memory alloy ultra-thin wire

In this paper, the mechanical properties of the Ni?C50.5?at.%?CTi alloy super-elastic wires manufactured by a conditioned multi-passed process of annealing and cold-drawing have been studied. The annealing temperature of 450~800°C, time of 20?min~3?h and the cold-drawing amount of 6.9%~39% were chosen. Their effects on the thermo, mechanical, and surface morphology of the Ni?CTi wires have been studied. The differential scanning calorimetry and tensile-recovery tests were adopted to obtain the phase transformation temperatures and mechanical hysteresis of the Ni?CTi SMA wires with different treatment conditions. The results show that the phase transition temperature of Ni?CTi wire can be changed by varying the annealing temperature and time; cold-drawing deformation and subsequent annealing have a great influence on the super-elasticity. The process with 39% cold-drawing amount, 600°C and 20?min annealing is shown to be effective in the manufacturing.