Sound transmission in multilayered structures – Introducing finite structural connections in the transfer matrix method

The transfer matrix technique is an efficient tool for calculating sound transmission through multilayered structures. Recent developments, as to the calculation of the sound reduction index, have given better fit to measurement data, e.g. due to the simulation of finite size samples by the spatial windowing technique. In practice, however, finite size structural connections (points or lines) normally do exist between leaves in wall constructions and these are not “natural” elements in the transfer matrix method. The paper describes a simple method to account for the effect of point- and line-connections in double-leaf constructions in a transfer matrix setup. To cover the frequency range above the critical frequency of the constituent plates, some new developments as to the forced radiation from plates were needed. Predicted results compare favorably with measurement results for a number of different cases, also including a heavy wall.     

Synthesis, structural and optical properties of a novel bilayered organic-inorganic perovskite C5Pb2I5

Single crystals of [C₅H₁₁NH₃]Pb₂I₅, abbreviated C₅Pb₂I₅, have been prepared. This compound is a new member of the family of the bilayered organic-inorganic lead-iodide based perovskites. Its crystal structure has been determined by X-ray diffraction. The inorganic sub-lattice consists of periodic bilayers of iodoplumbate octahedra. Each PbI₆ octahedra exhibits both edge- and corner-sharing with adjacent octahedra. The vibrational properties of this compound have been studied by Raman scattering spectroscopy. Optical absorption, photoluminescence and diffuse reflectance measurements have been performed. The room-temperature bandgap and free exciton absorption bands are observed at 2.46 and 2.23 eV, respectively. The exciton binding energy is 230 meV which is the largest value ever reported till date for the bilayered PbI based perovskites. Calculations assuming Wannier-type quasi-two-dimensional excitons and taking into account the image potential of the exciton charges showed that nearly 64% of the exciton binding energy is due to the dielectric confinement effect.     

An analysis of optimal structural features in the peacock tail feather

This paper presents an analysis of the optimal structural features in the peacock tail feather. Peacock tail feathers are highly optimized in three respects. The feathers are highly efficient structures that can support their own weight in a deployed position. The feathers are also optimized for producing thin-film colours with a high degree of lustre. The feathers also have a structure which produces intricate patterns with a high degree of aesthetic merit. There are structural features that allow simultaneous optimization in the different areas of performance. In particular, the thin-film sandwich structure is ideal for producing optimal structural performance and optimal optical performance.     

PLS Path modelling: computation of latent variables with the estimation mode B

PLS Path modelling has several interesting advantages compared to other existing approaches traditionally used for structural modelling. However, the lack of convergence properties of the existing iterative procedures for the computation of the latent variables, has always been considered as a major drawback. The convergence is stated only in practice. The present paper shows that when the estimation mode B is chosen for all blocks, the iterative procedure for the computation of latent variables proposed by Wold (in Encyclopaedia of statistical sciences, vol 6. Wiley, New York, pp. 581–591, 1985) is monotonically convergent.     

Finite element analysis and modeling of structure with bolted joints

In this work, in order to investigate a modeling technique of the structure with bolted joints, four kinds of finite element models are introduced; a solid bolt model, a coupled bolt model, a spider bolt model, and a no-bolt model. All the proposed models take into account pretension effect and contact behavior between flanges to be joined. Among these models, the solid bolt model, which is modeled by using 3D solid elements and surface-to-surface contact elements between head/nut and the flange interfaces, provides the best accurate responses compared with the experimental results. In addition, the coupled bolt model, which couples degree of freedom between the head/nut and the flange, shows the best effectiveness and usefulness in view of computational time and memory usage. Finally, the bolt model proposed in this study is adopted for a structural analysis of a large marine diesel engine consisting of several parts which are connected by long stay bolts.     

Structure profile of complex networks by a model of precipitation

The organizational structure of a network is investigated with a simulated precipitation model which does not make use of prior knowledge about the community structure of the network. The result is presented as a structure profile through which various definitions of communities can be applied for specific applications. The simulated precipitation model performs the grouping of nodes so that nodes belonging to the same “community” automatically aggregate, thereby revealing regions of the adjacency matrix with denser interconnections. The process is analogous to massive particles precipitating towards the lower potential layer. Without loss of the infrastructure information, a community structure profile of a network can be obtained as the ground state of the Hamiltonian. The method is also applicable to directed and weighted networks.     

Structural design and analysis for a sensor-integrated ball bearing

The structural design issues associated with the development of a sensor-integrated ball bearing were investigated. A finite element model was established to analyze the structural integrity of a ball bearing whose outer ring was modified to accommodate a miniaturized load sensor module. The sensor module was designed to monitor dynamic load variations within the bearing, which is an important indicator of a bearings safe operation. This structural integration of “intelligence” is significant in that it bring's automated, on-line, self-diagnosis capability to a dynamic system for which reliable, safe operation is of critical importance. A design tool was developed to evaluate the effect of outer ring modification on the dynamic load-carrying capability of the bearing. The tool also provided quantitative guidelines for the design of load and other types of sensor modules that will be structurally embedded into the outer ring of a conventional bearing for industrial applications.     

A Flexible Model for Generalized Linear Regression with Measurement Error

This paper focuses on the question of specification of measurement error distribution and the distribution of true predictors in generalized linear models when the predictors are subject to measurement errors. The standard measurement error model typically assumes that the measurement error distribution and the distribution of covariates unobservable in the main study are normal. To make the model flexible enough we, instead, assume that the measurement error distribution is multivariate t and the distribution of true covariates is a finite mixture of normal densities. Likelihood–based method is developed to estimate the regression parameters. However, direct maximization of the marginal likelihood is numerically difficult. Thus as an alternative to it we apply the EM algorithm. This makes the computation of likelihood estimates feasible. The performance of the proposed model is investigated by simulation study.     

A new component mode synthesis method: Quasi-static mode compensation

A new component mode synthesis method is presented in this paper that combines the computational efficiency of the well-known constraint mode approach with the dynamic compensation accuracy obtained by higher-order expansion methods. Instead of employing static constraint modes, quasi-static modes are used to capture inertial effects of the truncated modes. The method is ideally suited for mid-band frequency analysis in which both high-frequency and low-frequency modes may be omitted. A tuning parameter, designated as the centering frequency, controls the dynamic range of the quasi-static modes. Numerical examples are provided which demonstrate the improved accuracy of the proposed method.     

地下坑道开挖前方结构面超前探测

本文在分析总结现有地球物理勘探方法的基础上, 提出了一种适合地下工程开挖前方结构面探测的新的方法--TVSP法, 同时对该方法进行了必要的分析。