Papers by Keyword: Fluence

Abstract: There is a solution of the problem of stress-strain state determining in a concrete thick-walled tube, when the temperature field and the neutron fluence at the inner face are set. The mutual action of the specified factors is identified in this axisymmetric problem, as well as influence of inhomogeneity of shell materials, which is due to radiation and heat impact. The problem reduces to a differential equation with variable coefficients. The allowance for the mutual action of the specified factors and the variable Young’s module lets to arrive to a more accurate solution.

Abstract: The purpose of this study was to analyze treatment effect for skin aging according to changes of fluence and pulse duration of 1064nm Nd:YAG laser. For this purpose, we designed skin model composed of epidermis, dermis, and fat, and each layer had similar thickness of facial skin. Environmental temperature was set to 26°C, and the initial temperature of each skin layer was designated as human body temperature (36.5°C). The fluence of the treatment laser was divided into 8, 9 and 10J/cm², and the pulse duration was classified to 0.35, 0.50, 0.70 and 1.00ms, respectively. Based on experimental results, we found that the skin temperature increased along with penetration depth as increase in fluence. In addition, the treatment condition with fluence of 8J/cm² and pulse duration of 0.7ms, as well as fluence of 9J/cm² and pulse duration of 0.5ms, transmitted the heat into the dermis most effectively without any skin damage.

Abstract: Laser beam welding (LBW) show clear advantages compared with other techniques, as the low heat input, the high localization ability, the high welding speed, the high flexibility, the high weld quality and the high production rate. However, its applicability to aluminium alloys is limited, as they generally have high reflectivity, high thermal conductivity and low viscosity. In the present study, the laser weldability of four aluminium alloys (2024, 5083, 6082 and 7075) under conduction regime is analysed. High penetration butt welds could be obtained with a High Power Diode Laser (HPDL) under conduction regime. The properties of the weld beads such as the microstructure and microhardness were analysed. A linear function between the input laser fluence and the volume of melted material was obtained for the four alloys.

Abstract: Laser Shot Peening without protective Coating (LPPC) was performed on SS304 austenitic stainless steel using a 300 mJ, 10 ns pulse, 1064 nm wavelength Nd:YAG laser with three different pulse densities. A thin layer of water was used as a confinement layer. The peened specimen was characterised with XRD, AFM and a Profilometer. The stress evaluated at the surface of the laser peened sample shows a maximum compressive stress of 1.6 GPa. The surface roughness and depth profile of microhardness before and after LPPC were investigated.The LPPC region indicate substantial improvement in microhardness and compressive residual stress, with marginal increase of surface roughness.

Abstract: The effect of irradiation with protons, electrons, neutrons, x-ray radiation and gamma-ray photons as well as with different ions on properties of starting SiC material and devices based on it was studied. The rectifying properties of the diode structures, which degraded as a result of irradiation with high energy particles, were recovered at higher operation temperatures. The transistor structure SiC-based detectors were realized with the signal amplification by a factor of tens under irradiation. The energy resolution of 0.34 %, commensurable with Si-detectors, has been achieved for SiC detectors and is correct for all classes of short range ions. The maximum signal amplitude corresponds, in SiC, to a mean electron-hole pair creation energy of 7.7 eV.

Abstract: Nano-imprinting Lithography (NIL) has been considered as the most promising technique for nano-scaled fabrication and patterning. Recently, a new approach known as Laser-Assisted Direct Imprinting(LADI) has been proposed and demonstrated as an even more efficient way for direct nanofabrication and nanopatterning. In this study, we focused on silicon materials and utilized a single KrF excimer laser pulse (248 nm wavelength and 30 ns pulse duration) as the heating source. Molds of micro-scaled size have been prepared using conventional photolithography techniques. A working platform based on an Excimer Laser Micro-Machining system is constructed for LADI process. The influence of laser fluence and the imprinted pressure on the resulting structures was verifying by varying the laser fluence (1.0 ~ 1.2 J/cm2) and the imprinted load (3 ~ 9kg). The results have shown that the morphology and the imprinted depth were directly related to the laser fluence and the imprinted pressure. Quantitative data are obtained and will be addressed.