Results 1 - 10 of 1748
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[en] Since its invention in 1930, Zernike phase contrast has been a pillar in optical microscopy and more recently in x-ray microscopy, in particular for low-absorption-contrast biological specimens. We experimentally demonstrate that hard-x-ray Zernike microscopy now reaches a lateral resolution below 30 nm while strongly enhancing the contrast, thus opening many new research opportunities in biomedicine and materials science.
[en] Analysis of the circuits for exciting the active medium of a copper vapour laser (CVL) has shown that the main factors limiting the mean output power of the CVL are the cathode emissive power of an electron tube and the permissible current rise rate in a thyratron switch. The laser operation reliability and the thyratron service life are determined by the reverse voltage across the thyratron anode. The service life of a TGI1-1000/25 thyratron in a CVL corresponds to its certified value, if the reverse voltage at the thyratron anode is within 3 kV. (lasers)
[en] An experimental investigation was made of a self-contained supersonic cw chemical HF laser with a 40 cm x11 cm three-jet nozzle array and the nozzle-nozzle-nozzle configuration. Such a nozzle array made it possible to form an active medium ∼12 cm long and of high optical quality. The use of a wide-aperture stable optical cavity resulted in generation of a laser beam of square (11 cmx11 cm) cross section. A specific output energy of ∼80 J g-1 was reached. (lasers and amplifiers)
[en] The article discusses calibration methods of dynamic forces measuring instruments. The relevance of work is dictated by need to valid definition of the dynamic forces transducers metrological characteristics taking into account their intended application. The aim of this work is choice justification of calibration method, which provides the definition dynamic forces transducers metrological characteristics under simulation operating conditions for determining suitability for using in accordance with its purpose. The following tasks are solved: the mathematical model and the main measurements equation of calibration dynamic forces transducers by load weight, the main budget uncertainty components of calibration are defined. The new method of dynamic forces transducers calibration with use the reference converter “force-deformation” based on the calibrated elastic element and measurement of his deformation by a laser interferometer is offered. The mathematical model and the main measurements equation of the offered method is constructed. It is shown that use of calibration method based on measurements by the laser interferometer of calibrated elastic element deformations allows to exclude or to considerably reduce the uncertainty budget components inherent to method of load weight. (paper)
[en] Alarm management in the process industries has been an increasing area of activity since the first publications of EEMUA 191 in 1999 and ISA18.2 in 2008. Most major oil and chemical companies have adopted some or all of the metrics for alarm management presented in these documents. However, simply targeting for these metrics might not be the best course of action for a company. Many of the metrics involve assumptions or logic not explicitly stated in the guidelines, assumptions that might not be valid for a given console or plant. In other cases, metrics are the result of implied, rather than explicit, relationships between alarm guidelines. Again, the implied connection might not be true under certain circumstances. Understanding these unstated underpinnings of alarm management can facilitate the implementation of a useful and efficient alarm management program. This paper explores some of the key unstated assumptions in alarm management and how changes in those assumptions can alter both the interpretation of alarm metrics as well as what metrics are utilized. (authors)
[en] The world's fourth industrial revolution has finally opened after the term Industry 4.0 was proposed by Germany at the Hannover Industrial Fair in 2011, which combined industrial production with an unmanned plant to perform automated production. With the rise of Internet of Things (IoT), cloud computing, and wearing computerized devices has brought more convenience to mankind with the immediate accessibility of the Internet and technology. For example, the development of mobile devices and network technology has inspired the rapid development of wearable devices on mobile devices. Thus, to enhance the current prospects of Taiwan's unmanned machinery factory's monitoring and maintenance capabilities, this paper studies the use of Google glass Machine Tools Monitoring system, GMTM system, to be implemented in Taiwan's machinery factories. GMTM system, via the Internet, monitors sensor tools to collect tool work data to be transferred to cloud computing for analysis, processing and show the actual working conditions of each machine tool. Furthermore, the proposed system uses the monitoring data in the database to inform the factory supervisors the working status of each machine to determine whether there is a need for machine tool maintenance. This system combines real-time monitoring of material with the presentation of Google Glass wearable devices and iBeacon interior space positioning technology. GMTM system can improve the quality of machine tool production and productivity as well as enhance Taiwan's industrial competitiveness. (authors)
[en] The accurate measurement of an angular or linear position is not an easy task. In this paper, the authors present a general overview of some existing sensors using permanent magnet. They also present a new one they developed, the originality of which stands in its response which is linear in a large displacement range, and also insensitive to external parameters like temperature. (orig.)
[en] Complete test of publication follows. The use of the XUV/X-ray radiation emitted in the interaction of femtosecond laser beam with the matter calls for optical instrumentation with unique characteristics. The peculiarities of this class of source are very challenging: in the case of harmonics generation the emission is discrete although tunable in the EUV, XUV and soft X-ray spectral region, highly collimated, of extremely short duration, presently in the attosecond regime, and the source is of very small spatial dimensions. A time compensated monochromator for the selection and utilisation of the harmonics is here presented. Its design prevents the negative effect of time broadening induced by selecting a single harmonic order with a conventional dispersing type of instrument. Time-delay compensated monochromators requires the use of at least two gratings in subtractive and compensated dispersion, in order to impose the two requirements: 1) for all the rays transmitted by the instrument and having the same wavelength, the differences in the optical-path lengths that are caused by the first grating have to be compensated by the second grating; 2) two rays with different wavelengths within the spectrum of the pulse to be selected have to follow a path with the same optical length and have to be focused on the same point. Both these conditions are satisfied by a scheme with two equal concave gratings mounted with opposite diffraction orders. A new configuration for a time-delay compensated monochromator based on the conical diffraction has been recently theoretically analyzed. It envisage the use of two blazed gratings in the conical diffraction mounting, in which the light approaches the grating in a plane parallel to the direction of the grooves. It consists of a generation chamber, where the ultra-short Ti:Sapphire laser interacts with the gas jet generating the HHs, and of a monochromator divided in two equal sections, each of them with two toroidal mirrors and a plane blazed grating. The first mirror of each section acts as a collimator, the second one acts as a condenser. The first section creates a spectrally dispersed image of the source on an intermediate plane, where a slit carries out the spectral selection of the HHs. Only a selected portion of the spectrum, i.e. a single harmonic or a set of few harmonics, is propagating through the slit toward the second section that compensates for the temporal delay introduced by the first grating and gives an image of the source on the output plane. The wavelength scanning is performed by rotating the gratings around an axis lying at the centre of the grating surface and parallel to the grooves. The optical setup and the XUV experimental characterization of the instrument will be detailed in the paper.
[en] Field emitter arrays with a low turn-on voltage have been fabricated by using the selective growth of carbon nanotubes (CNTs) in a microwave plasma-enhanced chemical vapor deposition (MPCVD) system. CNTs with multi-walled structure were grown on a patterned Ni catalyst layer by a gas mixture of methane and hydrogen at a low temperature of 500 .deg. C. In order to avoid gate-emitter short, the gate electrodes were placed underneath the cathode electrodes, this being called an under-gate-type triode structure. Electron emission from CNT emitters was easily modulated by changing the gate voltage. The turn-on voltage was as low as 38 V, and the anode current of 14 μA was extracted at a gate voltage of 55 V, which corresponds to an emission current density of 275 mA/cm2. The excellent emission properties suggest that the arrays have potential for application in field-emission displays and vacuum microelectronics.
[en] The problem of the operational stability of a KrF laser with an average output power of at least 600 W was investigated. An experimental study was made of the dependences of the rms deviation σ of the output energy on the charging voltage, on the pulse repetition rate, and on the operating time. The value of σ varied from 1.2% to 6.0%, depending on the experimental conditions. For an average power of ∼ 600 W, the deviation σ did not exceed 3.2%. (lasers and amplifiers)