Study of pass band resonance characteristics of aperture type FSS

In this paper, the resonance characteristics of aperture type frequency selective surface (FSS) is presented. A systematic investigation is carried out to design the compact FSS. The optimized structure consists of rectangular Archimedean spiral with inter-digital capacitance. Resonance characteristics is verified in both single-layer as well as the double-layer approach by embedding FSS on one side of the dielectric substrate. The performances of the dual-layer are observed by varying air-gap between two FSS layers. The structure offers satisfactory resonance (transmission and reflection) characteristics at optimum air-gap of 7 mm between two layers with the 3 dB cutoff region over a frequency range (3.66–4.66 GHz). Finally, an array of 31 × 31 FSS elements of two layers is fabricated for experimental characterization. A close agreement between simulated and measured results is observed.     

轮式装载机行驶中仰俯振动的分析及处理

轮式装载机因真轴距铰短,在行驶中易产生仰俯振动,故将影响其行驶平顺性和行驶速度的提高。本文对轮式装载机在行驶中的俯仰振动问题进行分析,得出控制其俯仰振动的有关参数,为设计时采取必要的技术措施提供理论依据。     

带式输送机托辊间距的合理确定

根据输送带垂直限制条件、避免输送带共振条件、托辊轴的刚度限制条件以及托辊轴承的寿命限制条件,给出了正常直线段托辊间距的确定方法,对托辊间距进行了分级。根据受力情况,给出了过渡段托辊间距、凸凹曲线段托辊间距和受料缓冲段托辊间距的确定方法,并附有应用实例。     

大跨预应力混凝土空心板的振颤及防范

由于高强钢铰线预应力混凝土空心板厚度减少 ,刚度降低 ,自振频率降低 ,在室内各种振动荷载作用下虽然强度和挠度满足要求 ,但有时使用者会感到不舒适。基于加拿大国家建筑法规提出了当单块预应力混凝土空心板的基频不满足限值时应采用装配整体式方案。为保证装配整体式预应力楼盖共同工作 ,应浇筑混凝土现浇层 ,用正交异性板理论分析楼板基频。通过分析得知加设现浇层可增加楼盖的基频和刚度 ,避免振颤     

Automated classification of brain tumours from short echo time in vivo MRS data using Gaussian Decomposition and Bayesian Neural Networks

Neuro-oncologists must ultimately rely on their acquired knowledge and accumulated experience to undertake the sensitive task of brain tumour diagnosis. This task strongly depends on indirect, non-invasive measurements, which are the source of valuable data in the form of signals and images. Expert radiologists should benefit from their use as part of an at least partially automated computer-based medical decision support system. This paper focuses on Magnetic Resonance Spectroscopy signal analysis and illustrates a method that combines Gaussian Decomposition, dimensionality reduction by Moving Window with Variance Analysis and classification using adaptively regularized Artificial Neural Networks. The method yields encouraging results in the task of binary classification of human brain tumours, even for tumour types that have seldom been analyzed from this viewpoint.     

Design,development and testing twin pulse tube cryocooler

The design and development of Twin Pulse Tube Cryocooler (TPTC) is presented. Both the coolers are driven by a single Linear Moving Magnet Synchronous Motor (LMMSM) with piston heads at both ends of the mover shaft. Magnetostatic analysis for flux line distribution was carried-out during design and development of LMMSM based pressure wave generator. Based on the performance of PWG, design of TPTC was carried out using Sage and Computational Fluid Dynamics (CFD) analysis. Detailed design, fabrication and testing of LMMSM, TPTC and their integration tests are presented in this paper.     

Improvement on application of Dancoff factor and resonance interference table

An improvement for application of Dancoff factor is developed. It combines Stamm'ler's two-term method for resonance integral calculation with neutron current method for Dancoff factor calculation. Stamm'ler's formulation, which is originally derived for the infinite lattice geometry, can be easily revised to contain the Dancoff factor explicitly, while the neutron current method can easily calculate the Dancoff factor for general irregular assembly geometry. For the resonance interference effects the resonance interference factor table is built in pairs of nuclides, only for the interference between 238 U and other resonance nuclides, spanning over a range of background cross-section and number density ratio of the pairing nuclides. A series of verification calculations have been carried out for problems of infinite lattice and single assembly geometry, with two or multiple resonance absorbers. For these verification calculations, our improvement on Dancoff factor application and resonance interference give good results.     

Resonance self-shielding calculation using subgroup method and ABC algorithm

In this study, we propose a new method to optimize subgroup parameters for resonance self-shielding calculation. Our approach integrates the merits of both the subgroup method and ABC optimization technique to effectively evaluate self-shielded resonance cross-sections. The ABC algorithm is used to obtain subgroup level in a way that guarantees reproduction of shielded effective cross sections in the subgroup formulation. The temperature dependency of the cross-section is included in both subgroup level and subgroup weight. We used the conjugate gradient method based on the normal equations (CGNR) to evaluate the subgroup weights. An iteration technique is also used to consider the resonance interference. The proposed method is verified by analyzing Rowlands benchmark problems and Mosteller benchmark problems and comparing the obtained results with corresponding Monte Carlo solutions. The multiplication factor results show small errors and also good agreement.     

A study on the aromaticity and kinetic stability of fullerene C38 isomers and their molecular ions

The aromaticity of the fullerene C₃₈ isomers and their molecular ions is examined by the topological resonance energy (TRE) method. The aromaticity order obtained by the TRE method is compared with relative energies found in DFT calculation results reported in literature. It is found that all C₃₈ isomers exhibit antiaromaticity when in the neutral state. However, they are highly aromatic in the hexaanionic states. The minimum bond resonance energy (min BRE) method is utilized to estimate the kinetically stability of the C₃₈ isomers and their molecular ions. According to the min BRE method, C₃₈ isomers are only have kinetic stability in penta- and hexavalent molecular anionic states.