China——the market with the biggest potential in the 21st century

The year 2001 was not an optimistic one for the worldeconomy.The United States and Japan,which were describedas the power engine of the world economy,suffered from adecline in economic growth,which led to the slow-down ofthe global economic development.Against this background,the Chinese economy,however,maintained sustainable and     

Calibrating the Prototype Calorimeter for the GAMMA-400 γ-Ray Telescope on the Positron Beam at the Pakhra Accelerator

Instruments and Experimental Techniques - A prototype of the electromagnetic calorimeter for the GAMMA-400 γ-ray telescope has been calibrated at the Pakhra S-25R electron synchrotron of the...     

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.     

Meanwhile,towards the end of the decade …

The 1930s saw the practical developments that led from the invention of the electron microscope to the construction of commercial models and experimental prototypes in several countries. This work was complemented by vigorous activity on the part of the theoreticians, many of whose results had repercussions at much later dates. We draw attention to a few of these and take the opportunity of demonstrating that the trajectory and eikonal methods of calculating asymptotic aberration coefficients do indeed lead to the same answer.     

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.     

On the analogy between the bias flow aperture theory and the Coriolis flowmeter “bubble theory”

Two different physical phenomena, described by the bias flow aperture theory and the Coriolis flowmeter “bubble theory”, are compared. The bubble theory is simplified and analogies with the bias flow aperture theory are appraised.     

New Method to Measure the Fill Level of the Ball Mill Ⅱ-Analysis of the Vibration Signals

The exact measurement of the fill level is the key and basic problem for automatic control and optimized operation of the coal pulverizing system. Because the ball mill pulverizing system is non-linearity, long time delay and time-varying, the reliable and effective method for measuring the fill level was lacked at present. In order to reduce the influence by various factors on measuring the fill level and improve the measuring accuracy of the fill level, a novel characteristic variable is proposed. A set o...     

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.     

Greeting the New Century

The Chinese Journal of Mechanical Engineering-English Edition(CJME-ED) enjoys a good reputation in the field of the world mechanical engineering industry. This reputation is based on adherence to regular standards in the publication of papers with high quality.……     

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...     

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.     

Modernization of the Duoplasmatron of the И-2 Linear Accelerator

A modified ion source of the duoplasmatron type used in the -2 linear accelerator for generating a proton beam is described. Improving the designs of the electrodes, the magnetic circuit, the gas-supply channel, and the electromagnetic valve has made it possible to considerably increase the service life of the source (up to 10⁷ pulses), to reduce the consumption of hydrogen (up to 10 cm³/h at a pulse repetition rate of 1 Hz), and to increase the stability and reliability of the source operation in the regime of everyday service of the linear accelerator in applied research as an injector of the ITEP U-10 proton synchrotron.     

An HCN Interferometer for Measuring the Electron Density Distribution in the Plasma of the Л-2M Stellarator

A diagnostic setup for determining the electron density profile in the plasma of the -2M stellarator is described. An interferometer based on an HCN laser (337 m) with a mirror in a vacuum chamber and built according to the Michelson scheme is the main element of the setup. To translate the phase shift to a frequency range convenient for recording, a system with a mechanical frequency shifter based on the Doppler effect is used. InSb photoresistors cooled with liquid helium are used as radiation detectors. Seven mirrors are arranged in the vacuum chamber. Any of these can be included in the optical system of the interferometer by rotating an external mirror; scanning along seven chords is thus accomplished. The results are recorded in digital form. The subsequent data processing makes it possible to determine the parameters of the spatial density distribution functions belonging to an a priori selected family.     

Measuring the asymmetry of the longitudinal charge distribution in an electron bunch on the ВЭПП-4М collider

A method for measuring the asymmetry of the longitudinal charge distribution in an electron bunch of the ВЭПП-4М collider by an electron beam probe is proposed. The operating principle of the electron beam probe and the measuring technique are described. Interaction between the testing beam and an asymmetric relativistic bunch is simulated, and the asymmetry of the electron bunch on the ВЭПП-4 collider is measured. The main components of the error in measuring the asymmetry are determined.     

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.     

The Development Mechanism and the Technical Characteristics of the Modern Cutting Technology

Introduction Since 1980s cuttingtechnology has developedrapidly inthe developed countries .Uptothe end of 20 centuryor the beginningof 21 centurythe cuttingtechnology has en- teredthe development phase of modern cuttingtechnology featuringthe highcuttingspeed and high performance ma- chining.Looking back to the history of cutting technolo- gy,one century has passedsincethe metal cutting became one of the machiningtechnologiesfromthe very beginning of 20 century. Since then,cutting technology h…