The foundation of the ultrasonic non-destructive determination of stresses in near-the-surface layers of solids is presented. The method is based on the regularities of Rayleigh wave propagation in solids with initial...The foundation of the ultrasonic non-destructive determination of stresses in near-the-surface layers of solids is presented. The method is based on the regularities of Rayleigh wave propagation in solids with initial （residual） stresses. A description of the above mentioned method and examples of stress determination are presented. Examples are considered as applied to the residual stresses arising at electric welding and the operating stresses arising at loading.展开更多
Indium selenide （InSe） thin films have been prepared by e-beam technique onto glass substrate at a pressure of-8 × 10^-5 Pa. The deposition rate of the InSe thin films is -8.30 nms^-1. InSe samples grown at roo...Indium selenide （InSe） thin films have been prepared by e-beam technique onto glass substrate at a pressure of-8 × 10^-5 Pa. The deposition rate of the InSe thin films is -8.30 nms^-1. InSe samples grown at room temperature have been termed as virgin, whereas the films at which the transition in electrical conductivity is shown to exhibit at a temperature of 415 to 455 K have been termed as phase-transited samples. X-ray diffraction （XRD） study reveals that lnSe thin films are amorphous in nature before phase-transition while they are polycrystalline after phase-transition. Scanning electron microscopy （SEM） has been used to study the surface morphology of InSe thin films. Before phase-transition grains are absent in the films and surfaces are almost smooth and uniform. Film surfaces are seen to exhibit a number of grains after phase-transition and they are rough in surfaces. The elemental composition of the lnSe thin films has been estimated by EDAX method. The effects of temperature on the electrical properties of InSe thin films have been studied in details. Temperature dependence of electrical conductivity shows a semiconducting behavior with activation energy. Thickness dependence of conductivity is well in conformity with the Fuchs-Sondheimer theory. Thermopower study indicates that the InSe film is an n-type semiconductor. The optical study of InSe thin films is carried out in the wavelength range 360 to 1100 nm at room temperature. The study of absorption coefficient of InSe thin films shows a direct type transition with a band gap of=1.65 eV which is well agreed with the reported values. Integrated values of luminous and solar transmittance as well as of reflectance have been calculated. Appreciable order of transmittance and reflectance suggest that this material is a potential candidate for the application in selective surface devices.展开更多
Dielectric resonators are key components in many microwave and millimetre wave circuits and applications, including high-Q filters and frequency-determining elements for precision frequency synthesis. Multilayered and...Dielectric resonators are key components in many microwave and millimetre wave circuits and applications, including high-Q filters and frequency-determining elements for precision frequency synthesis. Multilayered and bulk low-loss single crystal and polycrystalline dielectric structures have become very important for designing these devices. Proper design requires careful electromagnetic characterisation of low-loss material properties. This includes exact simulation with precision numerical software and precise measurements of resonant modes. For example, we have developed the Whispering Gallery mode technique, which has now become the standard for characterizing low-loss structures. This paper will review some of the common characterisation techniques used in the microwave to millimetre wave frequency regime.展开更多
A normal ultrasonic transducer of 5 MHz is modified using different delay lines and wedges design （made from Perspex）. Such modification is for ameliorate the capability of the transducer to detect sub-surface flaws...A normal ultrasonic transducer of 5 MHz is modified using different delay lines and wedges design （made from Perspex）. Such modification is for ameliorate the capability of the transducer to detect sub-surface flaws. Some prepared Aluminum pieces were subjected to different crosshead speed （200 and 350 ram/rain）. The ultrasonic pulse echo method was used at room temperature. The measurements have been done before and after each tensile stress. Flaws were found at different distances from the specimen＇s surface. Results showed that such delay lines and wedges were suitable to detect sub-surface flaws that were initiated under the effect of stress. In addition, a crosshead speed increment caused more sub-surface flaws formation.展开更多
Different mechanisms of laser radiation influence on the chemical transport inside a biotissue are investigated. The average size of speckles existing inside a biotissue and the radiation intensity in them are estimat...Different mechanisms of laser radiation influence on the chemical transport inside a biotissue are investigated. The average size of speckles existing inside a biotissue and the radiation intensity in them are estimated experimentally. Gradient forces and forces caused by the thermal expansion acting on the micro-volume inside a tissue as result of an irregular light field are calculated at different average light intensities including therapeutic. Using theoretical simulation taking into account nonequilibrium light absorption in structural elements of biotissue it has been obtained that the coherent light influences on the chemical transport more strongly in comparison with the incoherent one.展开更多
Interface and surface physics is an important sub-discipline within condensed matter physics in recent decades. Novel concepts like oxide-electronic device are prompted, and their performance and lifetime are highly d...Interface and surface physics is an important sub-discipline within condensed matter physics in recent decades. Novel concepts like oxide-electronic device are prompted, and their performance and lifetime are highly dependent on the flatness and abruptness of the layer surfaces and interfaces. Reflection high-energy electron diffraction （RHEED）, which is extremely sensitive to surface morphology, has proven to be a versatile technique for the growth study of oxide thin films. A differential pumping unit enables an implementation of RHEED to pulsed laser deposition （PLD） systems, ensuring an in situ monitoring of the film growth process in a conventional PLD working oxygen pressure up to 30 Pa. By optimizing the deposition conditions and analyzing the RHEED intensity oscillations, layer-by-layer growth mode can be attained. Thus atomic control of the film surface and unit-cell control of the film thickness become reality. This may lead to an advanced miniaturization in the oxide electronics, and more importantly the discovery of a range of emergent physical properties at the interfaces. Herein we will briefly introduce the principle of high-pressure RHEED and summarize our main results relevant to the effort toward this objective, including the growth and characterization of twinned Laz/3Caj/3MnO3 thin films and ReTiO〉6/2 （Re = La, Nd; ~5 = 0 - 1） AnBnO3n＋2 structures, on YSZ-buffered ＇Silicon on Insulator＇ and LaA103 substrates, respectively, as well as the study of the initial structure and growth dynamics of YBazCu307-6 thin films on SrTiO3 substrate. Presently we have realized in situ monitoring and growth mode control during oxide thin film deposition process.展开更多
文摘The foundation of the ultrasonic non-destructive determination of stresses in near-the-surface layers of solids is presented. The method is based on the regularities of Rayleigh wave propagation in solids with initial （residual） stresses. A description of the above mentioned method and examples of stress determination are presented. Examples are considered as applied to the residual stresses arising at electric welding and the operating stresses arising at loading.
文摘Indium selenide （InSe） thin films have been prepared by e-beam technique onto glass substrate at a pressure of-8 × 10^-5 Pa. The deposition rate of the InSe thin films is -8.30 nms^-1. InSe samples grown at room temperature have been termed as virgin, whereas the films at which the transition in electrical conductivity is shown to exhibit at a temperature of 415 to 455 K have been termed as phase-transited samples. X-ray diffraction （XRD） study reveals that lnSe thin films are amorphous in nature before phase-transition while they are polycrystalline after phase-transition. Scanning electron microscopy （SEM） has been used to study the surface morphology of InSe thin films. Before phase-transition grains are absent in the films and surfaces are almost smooth and uniform. Film surfaces are seen to exhibit a number of grains after phase-transition and they are rough in surfaces. The elemental composition of the lnSe thin films has been estimated by EDAX method. The effects of temperature on the electrical properties of InSe thin films have been studied in details. Temperature dependence of electrical conductivity shows a semiconducting behavior with activation energy. Thickness dependence of conductivity is well in conformity with the Fuchs-Sondheimer theory. Thermopower study indicates that the InSe film is an n-type semiconductor. The optical study of InSe thin films is carried out in the wavelength range 360 to 1100 nm at room temperature. The study of absorption coefficient of InSe thin films shows a direct type transition with a band gap of=1.65 eV which is well agreed with the reported values. Integrated values of luminous and solar transmittance as well as of reflectance have been calculated. Appreciable order of transmittance and reflectance suggest that this material is a potential candidate for the application in selective surface devices.
文摘Dielectric resonators are key components in many microwave and millimetre wave circuits and applications, including high-Q filters and frequency-determining elements for precision frequency synthesis. Multilayered and bulk low-loss single crystal and polycrystalline dielectric structures have become very important for designing these devices. Proper design requires careful electromagnetic characterisation of low-loss material properties. This includes exact simulation with precision numerical software and precise measurements of resonant modes. For example, we have developed the Whispering Gallery mode technique, which has now become the standard for characterizing low-loss structures. This paper will review some of the common characterisation techniques used in the microwave to millimetre wave frequency regime.
文摘A normal ultrasonic transducer of 5 MHz is modified using different delay lines and wedges design （made from Perspex）. Such modification is for ameliorate the capability of the transducer to detect sub-surface flaws. Some prepared Aluminum pieces were subjected to different crosshead speed （200 and 350 ram/rain）. The ultrasonic pulse echo method was used at room temperature. The measurements have been done before and after each tensile stress. Flaws were found at different distances from the specimen＇s surface. Results showed that such delay lines and wedges were suitable to detect sub-surface flaws that were initiated under the effect of stress. In addition, a crosshead speed increment caused more sub-surface flaws formation.
文摘Different mechanisms of laser radiation influence on the chemical transport inside a biotissue are investigated. The average size of speckles existing inside a biotissue and the radiation intensity in them are estimated experimentally. Gradient forces and forces caused by the thermal expansion acting on the micro-volume inside a tissue as result of an irregular light field are calculated at different average light intensities including therapeutic. Using theoretical simulation taking into account nonequilibrium light absorption in structural elements of biotissue it has been obtained that the coherent light influences on the chemical transport more strongly in comparison with the incoherent one.
基金supported by the National Natural Science Foundation of China(Grant Nos.10974229 and 11174342)
文摘Interface and surface physics is an important sub-discipline within condensed matter physics in recent decades. Novel concepts like oxide-electronic device are prompted, and their performance and lifetime are highly dependent on the flatness and abruptness of the layer surfaces and interfaces. Reflection high-energy electron diffraction （RHEED）, which is extremely sensitive to surface morphology, has proven to be a versatile technique for the growth study of oxide thin films. A differential pumping unit enables an implementation of RHEED to pulsed laser deposition （PLD） systems, ensuring an in situ monitoring of the film growth process in a conventional PLD working oxygen pressure up to 30 Pa. By optimizing the deposition conditions and analyzing the RHEED intensity oscillations, layer-by-layer growth mode can be attained. Thus atomic control of the film surface and unit-cell control of the film thickness become reality. This may lead to an advanced miniaturization in the oxide electronics, and more importantly the discovery of a range of emergent physical properties at the interfaces. Herein we will briefly introduce the principle of high-pressure RHEED and summarize our main results relevant to the effort toward this objective, including the growth and characterization of twinned Laz/3Caj/3MnO3 thin films and ReTiO〉6/2 （Re = La, Nd; ~5 = 0 - 1） AnBnO3n＋2 structures, on YSZ-buffered ＇Silicon on Insulator＇ and LaA103 substrates, respectively, as well as the study of the initial structure and growth dynamics of YBazCu307-6 thin films on SrTiO3 substrate. Presently we have realized in situ monitoring and growth mode control during oxide thin film deposition process.
