Design Simulation of Czerny–Turner Configuration-Based Raman Spectrometer Using Physical Optics Propagation Algorithm

We report the design simulation of the Raman spectrometer using Zemax optical system design software. The design is based on the Czerny–Turner configuration, which includes an optical system consisting of an entrance slit, two concave mirrors, reflecting type diffraction grating and an image detector. The system’s modeling approach is suggested by introducing the corresponding relationship between detector pixels and wavelength, linear CCD receiving surface length and image surface dimension. The simulations were carried out using the POP (physical optics propagation) algorithm. Spot diagram, relative illumination, irradiance plot, modulation transfer function (MTF), geometric and encircled energy were simulated for designing the Raman spectrometer. The simulation results of the Raman spectrometer using a 527 nm wavelength laser as an excitation light source are presented. The present optical system was designed in sequential mode and a Raman spectrum was observed from 530 nm to 630 nm. The analysis shows that the system’s image efficiency was quite good, predicting that it could build an efficient and cost-effective Raman spectrometer for optical diagnostics.

Small Angle X-ray Scattering Test of Hami Coal Sample Nanostructure Parameters with Gas Adsorbed Under Different Pressures

The complexity and multiscale structure of coal pores significantly influence the gas diffusion and seepage characteristics of coal. To apply small angle X-ray scattering (SAXS) to study the coal pore structure parameters within the scale of 1–100 nm in the methane adsorption process, the X-ray window was optimized and a gas adsorption chamber was designed to interface with the small angle X-ray scattering platform. The fractal dimension and porosity of Hami coal samples under different methane pressures were studied using the small angle X-ray scattering platform and adsorption chamber. The surface and nanopore fractal information of the nanopores in coal were distinguished. The variation trends of the pores and surface fractal dimension with time under the same methane pressure were compared. The results indicate that the surface dimension changes from 2.56 to 2.75, and the extremum point may indicate that the primary nanopore structure is crushed by the adsorbed gas after approximately 15 minutes. This work clarifies that the fractal dimension can characterize the changes in nanopores in the process of gas adsorption by using SAXS. According to the fractal characteristics, the adsorption of gas in coal nanopores is summarized as four steps: expansion from adsorbance, deformation, crushing and recombination. The minimum porosity is 0.95% and the extreme value point is 1.47%. This work also shows that decrease in surface energy affect the porosity changes in nano-size pores. This work is of some significance to coalbed methane permeability improvement and gas extraction.

Sound Field Properties of Non-Cavitating Marine Propellers

The sound field properties of non-cavitating marine propellers are investigated using a hybrid method, in which the FWH (Ffowcs William-Hawkings) analogy is coupled with the BEM (Boundary Element Method) approach. The investigations include both the uniform and non-uniform inflow conditions. For both conditions, the dominant sound source terms and the decay rate of the noise with regard to the distance to propeller centre are investigated. The influence of the permeable surface dimensions in the permeable FWH approach on the hydroacoustic result is also investigated. To carry out the investigations, the formulation to calculate acoustic pressure generated by the propeller wake sheet is proposed for the first time. The issues associated to coupling permeable FWH approach and BEM are also discussed, including the fictitious volume flux problem and the consideration of the ship wake field. It was found that the influence of the permeable surface dimension is little for the 1st BPF (Blade Passage Frequency), but cannot be ignored for the 3rd BPF. In the uniform inflow situation the thickness terms are found to be dominant, while in the non-uniform inflow situation the loading terms are dominant.

Underground Object Size Approximation using GPR Signal and Image Processing

This paper comprises a step wise method of approximating the size of an underground object using GPR (Ground Penetrating Radar). It involves more than just using predefined filters and techniques. Usage of Trivial method of mathematics to calculate the top surface dimensions of the buried objects is the main purpose of this paper. Problem that is faced that, only the presence of any object can be known using the GPR resource, but not exactly how to derive the size of the object using the same data. This method consists of a dual approach to the problem to make sure that the data that is being given out is accurate. The objectives of this paper are to use the GPR to calculate the top surface dimension of a buried object at a suitable depth according to the frequency. The steps that are incorporated include pre-processing of raw data, determination of ROI (Region of interest) from the pre-processed data, Application of appropriate filters for image processing and estimating surface area and depth of the concealed object. The main reason of this paper is to serve the purpose of detecting what is under the ground in a quick and simpler way using the algorithm proposed

A Novel Triangular Prism Element Based on Smoothed Finite Element Method

In this paper, a novel triangular prism element based on smoothed finite element method (SFEM) is proposed for three-dimensional static and dynamic mechanics problems. The accuracy of the proposed element is comparable to that of the hexahedral element while keeping good adaptability as the tetrahedral element on a surface dimension. In the process of constructing the proposed element, one triangular prism element is further divided into two smoothing cells. Very simple shape functions and a constant smoothing function are used in the construction of the smoothed strains and the smoothed nominal stresses. The divergence theorem is applied to convert the volume integral to the integrals of all the surrounding surfaces of a smoothing cell. Thus, no gradient of shape function and no mapping or coordinate transformation are involved in the process of creating the discretized system equations. Afterwards, several numerical examples include elastic-static and free vibration problems are provided to demonstrate the accuracy and efficiency of the proposed element. Meanwhile, an explicit scheme of the proposed element is given for dynamic large-deformation analysis of elastic-plastic materials, and the numerical results show good agreement with the experimental data.

Effect of Shoulder Surface Dimension and Geometries on FSW of AA7039

In the present study, friction stir welding of AA7039 butt plates were investigated with respect to threaded probed tools having different shoulder diameters and shoulder surface geometries. The ultimate tensile properties, micro hardness and grain size of the welds were investigated with respect to the varying tool geometries. The mechanical properties of the welded joints were observed to be influenced by the shoulder diameter and shoulder surface geometry. With the increase in the shoulder diameter, the effect of shoulder concavity on refining the weld grain size diminished. Good quality welds were produced by using tools with semi-concave shoulder surface having shoulder and probe diameters of 19 mm and 7 mm respectively. The fracture surfaces of AA7039 weld samples were dimpled and the crack front energy-dispersive X-ray spectroscopy analysis exhibited absence of segregation of Zn.