Electromagnetic radiation emitted during friction process

A series of studies of electromagnetic radiation (EMR) emitted during fracture of materials, enabled us to obtain a relationship between the width of a fracture and the wavelength of the emitted EMR. Applying this relation to friction we could check one of its suggested mechanisms, namely the Bowden-Tabor model, which states that during a friction process, asperities on the two contacting surfaces are welded together (at a microscopic level) and fractured. A uniaxial tension machine was used, whereby two half cylinders of chalk (CaCO3) bound together, were moved one against the other, generating friction. Calculations based on EMR observations showed that the average width of the fractured asperities was 26.3 m, while mechanical profilograph measurements of the average width of the total number of long asperilies before and after the experiment, yielded values of 15.6 and 18.4 m, respectively, implying that 25% of long asperities were fractured during a single friction process.     

Detection of crack nucleation in sheet metalforming by monitoring infrared radiation

In the present work a method is described for the early detection of large plastic strains localisation and subsequent crack nucleation in sheet metalforming. The method is based on the monitoring of the infrared radiation emitted from the material during stretching. It is concluded that the point of the final crack nucleation can be located in the very early stages of stretching, when overall mean strains are insignificant (less than 20% of the yielding strain of the material).     

Ultraviolet radiation emitted by compact fluorescent lamps

To meet the objective of energy efficiency, increasing emphasis on use of energy saver compact fluorescent lamps (CFLs), makes it necessary to analyze the effect of radiation especially ultraviolet (UV) radiation on human health. Various types of CFLs in terms of various shapes, sizes and electrical powers are studied for UV content present in their radiation. Various parameters such as UV irradiance, ratio of UV irradiance to electrical power (η) and ratio of UV power to luminous flux (k), for eighteen types of CFLs are studied to dictate their performance. As expected, both the UV output power and the luminous flux are reduced in the case of double envelope CFLs in comparison to single envelope CFLs, however, the k value is reduced more effectively. For all types of CFLs under study, k₁ for UVA remains less than 104 μW/lm, which is a safe limit for UVA. However, the study demonstrates that the use of CFLs might be detrimental to human health if these are used at shorter distance, e.g., in table lamps.     

Detection of heat inleaks in cryogenic enclosures by infrared thermal imaging

Localized heat inleaks in cryogenic enclosures can be detected by the ‘cool spots’ they produce on the ambient temperature surface of the vessel outer walls. Infrared thermography, a simple technique permitting detailed thermal mapping of surfaces, has been successfully used for locating such ‘cool spots’ on cryogenic vessels and transfer lines.     

Far infrared radiation generated during femtosecond laser excitation of a semiconductor surface in magnetic field

The effect of a magnetic field on the generation of electromagnetic radiation pulses in the terahertz frequency range from a semiconductor surface excited by an ultrashort laser pulse is considered within the framework of a hydrodynamic model. The appearance of a photocurrent component in the Hall direction leads to elliptic polarization of the microwave radiation and to a severalfold increase in the generation efficiency. This is consistent with the results of Monte Carlo modeling of a self-consistent field and photogenerated carrier dynamics.     

Conversion of infrared radiation into visible in ZBLAN glass with three-component doping by rare-earth elements

Experimental results are presented that lead to the conclusion that new laser systems and elements of fiber-optic communication lines can in principle be made on the basis of the material studied here, which have new spectroscopic characteristics. The effect studied in this paper is the following: an increase in the luminescence efficiency with frequency upconversion for three-element doping; this is a novel finding and has no analog. Pis’ma Zh. Tekh. Fiz. 23, 51–57 (January 26, 1997)     

Energy flow lines for the radiation emitted by a dipole

An oscillating electric dipole emits radiation, and the flow of energy in the electromagnetic field is represented by the field lines of the Poynting vector. In the most general state of oscillation the dipole moment vector traces out an ellipse. We have evaluated analytically the field lines of the Poynting vector for the emitted light, and it appears that each field line lies on a cone, which has its axis perpendicular to the plane of the ellipse. The field lines exhibit a vortex structure near the location of the dipole, and they approach a straight line in the far field. It is shown that due to the spiraling of the field lines near the source, the asymptotic limit of a field line is displaced as compared to a ray which would come directly out of the source. Both the spatial extent of the vortex in the near field and the magnitude of the displacement of the image in the far field are of nanoscale dimension.     

In situ measurement of silicon oxidation kinetics by monitoring spectrally emitted radiation

When a highly polished silicon wafer is thermally oxidized, its spectral emittance fluctuates systematically, as the protective silica film grows thicker. If the spectral intensity of the emitted radiation at a wavelength where silica is transparent is monitored, the film thickness can be obtained.     

Investigation of the parameters of laser radiation emitted by a single-frequency high-power gas laser

Studies to determine whether it is possible to obtain a stable single-frequency mode of generation in large He–Ne lasers were undertaken. Selection of the frequencies in the particular lasers was performed by means of a Fabry–Perot interferometer situated at a low angle to the axis of the cavity resonator. It is shown that a laser that has been converted to function in a single-frequency mode of emission assures a coherence length of at least 10 m even when subjected to technical vibratory and acoustic effects. Translated from Izmeritel’naya Tekhnika, No. 3, pp. 24–26, March, 2009.     

Magnetization reversal simulation of diamond-shaped NiFe nanofilm elements

We have studied magnetization reversal behaviors of diamond-shaped NiFe nanofilm elements with different length-to-width ratios (LWRs) between long and short diagonals by micromagnetic simulation. The results show that the reversal process of the diamond-shaped element strongly depends on the LWR. If the LWR is smaller than 2, the reversal starts at the element edge, but it starts from the center of the element with larger LWR. With a bias field and when the LWR is larger than 2, all the elements experience a similar reversal process, which is simple and unique. In addition, the switching field becomes stable and nearly constant. These results suggest that the diamond-shaped NiFe nanofilm element can be potentially used in magnetic random access memory.     

Modelling of radiation damping in fluids by finite elements

A very efficient technique is presented to model the effects of radiation damping in the computation of added mass for the dynamic analysis of submerged structures. The structure is assumed to be surrounded by an infinite, incompressible and inviscid fluid field and the effect of the free surface is neglected. The technique is implemented in the finite element analysis of two-dimensional problems, assuming pressure to be the nodal unknown. The implementation procedure is quite simple and the symmetrical and banded form of the matrix of coefficients remains unchanged. With the use of the proposed radiation condition, the fluid field may be truncated at a relatively very short distance from the solid—fluid interface. This results in great computational advantages. Furthermore, a guideline is suggested for the selection of the geometry and the location of the truncation boundary to enhance the computational efficiency. The effectiveness and efficiency of the technique is demonstrated by analysing several cases for different geometries of the solid—fluid interface and the truncation boundary.     

Scattering matrix of infrared radiation by ice finite circular cylinders

Scattering matrix characteristics of polydisperse, randomly oriented, small ice crystals modeled by finite circular cylinders with various ratios of the length to diameter (L/D) ratio are calculated by use of the exact T-matrix approach, with emphasis on the thermal infrared spectral region that extends from the atmospheric short-wave IR window to the far-IR wavelengths to as large as 30 microm. The observed ice crystal size distribution and the well-known power-law distribution are considered. The results of the extensive calculations show that the characteristics of scattering matrix elements of small ice circular cylinders depend strongly on wavelengths and refractive indices, particle size distributions, and the L/D ratios. The applicability of the power-law distribution and particle shapes for light scattering calculations for small ice crystals is discussed. The effects of the effective variance of size distribution on light scattering characteristics are addressed. It seems from the behavior of scattering matrix elements of small ice crystals that the combination of 25 and 3.979 microm has some advantages and potential applications for remote sensing of cirrus and other ice clouds.     

Micromirrors and microlenses fabricated on polymer materials by means of infrared radiation

A simple method for fabricating micromirrors and microlenses on polymer substrates is presented. Microelements with diameters of approximately several hundred micrometers and f numbers ranging from 3 to 11 have been produced.     

Performance and application of far infrared rays emitted from rare earth mineral composite materials

Rare earth mineral composite materials were prepared using tourmaline and cerous nitrate as raw materials. Through characterization by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, dynamic contact angle meter and tensiometer, and Fourier transform infrared spectroscopy, it was found that the composite materials had a better far infrared emitting performance than tourmaline, which depended on many factors such as material composition, microstructure, and surface free energy. Based on the results of the flue gas analyzer and the water boiling test, it was found that the rare earth mineral composite materials could accelerate the combustion of liquefied petroleum gas and diesel oil. The results showed that the addition of Ce led to the improvement of far infrared emitting performance of tourmaline due to the decrease of cell volume caused by the oxidation of more Fe2+ ions and the increase of surface free energy. The application of rare earth mineral composite materials to diesel oil led to a decrease in surface tension and flash point, and the fuel saving ratio could reach 4.5%. When applied to liquefied petroleum gas, the composite materials led to the enhanced combustion, improved fuel consumption by 6.8%, and decreased concentration of CO and O2 in exhaust gases by 59.7% and 16.2%, respectively; but the temperature inside the flue increased by 10.3%.     

Scattering of visible and near infrared radiation by NaCl ice and glacier ice

Measurements are presented for the phase functions of glacier ice, columnar NaCl ice, and grease ice. Results for glacier ice show a shoulder at 80° characteristic of scattering from vapor bubbles. The NaCl ice types show similar forward scattering but significantly stronger backscattering. The scattering is predominantly due to the brine inclusions, and in the visible region the phase functions are independent of wavelength. For columnar NaCl ice samples, the phase functions depend on sample orientation as well as deflection angle; however, this effect can be ignored for many applications. Orientation-averaged values are presented for general use, and the empirical results are fitted to bimodal Henyey-Greenstein functions.     

A superconducting transducer of infrared radiation

A discussion is given of the principles of constructing an infrared transducer permitting the spatial resolution to be increased by using the whole IR-sensitive area of the receiving film, and the information signal to be picked off by two busbars, regardless of the number of signal-forming elementary receiving areas on the photosensitive surface, also permitting the elementary receivers to be interrogated in any required manner, and to form a superconducting channel of the configuration excluding the interrogation of defective elementary receivers.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 48–50, June, 1993.     

Assessment of radiofrequency/microwave radiation emitted by the antennas of rooftop-mounted mobile phone base stations

Radiofrequency (RF) and microwave (MW) radiation exposures from the antennas of rooftop-mounted mobile telephone base stations have become a serious issue in recent years due to the rapidly evolving technologies in wireless telecommunication systems. In Malaysia, thousands of mobile telephone base stations have been erected all over the country, most of which are mounted on the rooftops. In view of public concerns, measurements of the RF/MW levels emitted by the base stations were carried out in this study. The values were compared with the exposure limits set by several organisations and countries. Measurements were performed at 200 sites around 47 mobile phone base stations. It was found that the RF/MW radiation from these base stations were well below the maximum exposure limits set by various agencies.     

Quenching of technical superconductors by heat and magnetic field pulses

The transition of a superconductor into the normal conducting state can be caused by external or internal disturbances. The initiation of normal conduction by external disturbances was investigated for technical superconductors by means of thermal and magnetic pulses applied locally to the superconductor. The dependence on transport current and matrix material respectively of the minimum energy and the minimum magnetic field to initiate normal conduction were determined. The conclusion was that the heat conducting along the superconductor has the most effective influence in stabilizing against thermal disturbances. The transition to normal conduction by magnetic field pulses could be explained by eddy current heating in the matrix. A 50 μm single core conductor was insensitive to the highest applied magnetic field pulses up to 0.3 T amplitude and a field rise of 75 Ts^?1 and consequently did behave according to the adiabatic stability criteria.