Plane wave analysis of acoustic wedges using the boundary-condition-transfer algorithm

The present work delineates the applicability of the boundary-condition-transfer algorithm for analyzing the performance of the acoustic wedge. The theoretical model, based on the plane wave acoustical coupling between two interacting ducts of variable cross-sectional area, outlines the simplicity as well as the usefulness of the current approach. The proposed model assumes bulk reaction and hence a wave propagation in the wedge material. An asymptotic solution using the Peano-Baker series of matrix calculus is derived with the aid of an inherently stable boundary condition transfer (BCT) algorithm. The proposed method is validated extensively against the available literature in order to establish the utility of this elemental approach over its much more complex and time consuming counterparts like FEM and BEM.     

An algorithm for the analysis of multiplicity measurements

An algorithm to extract the multiplicity and the higher moments of a multiplicity distribution from the measured counting rates of multiple coincidences is described. In the statistical averaging process a direct transformation to the central moments is performed which results in a well converging procedure to obtain the moments. Important aspects of error analysis and of numerics are outlined. The generality of the formalism allows applications beyond nuclear physics. Guidelines for optimizing an experimental set-up are given.     

An investigation on the acoustic characteristics of microperforated muffler

I.lntroductionTheac0usticperformanccofmicropcrforatedmumerhasbeengreatlynoticedinre-ccntyears.Especially,itshighsi1encingva1ueandbroadsi1encingfrequencyrangeenableittobeusedwidelyinmanyyiclds,suchasvehicleexhaustsystem,ventilator.Butitisdifficulttodesignagoodsilcnccrbecauseoritscomp1exacousticperformanccwithinPerforatedtubes.Thegoverningwaveequationofmicroperforatedmufflerisnotlinearduetothenonuniformmassflowofgasaswc11asthetcmpcraturegradientalongthePerforatedducts.Inordertoutilizethegoodsi…     

An automated algorithm for stability analysis of hybrid dynamical systems

There are many hybrid dynamical systems encountered in nature and in engineering, that have a large number of subsystems and a large number of switching conditions for transitions between subsystems. Bifurcation analysis of such systems poses a problem, because the detection of periodic orbits and the computation of their Floquet multipliers become difficult in such systems. In this paper we propose an algorithm to solve this problem. It is based on the computation of the fundamental solution matrix over a complete period–where the orbit may contain transitions through a large number of subsystems. The fundamental solution matrix is composed of the exponential matrices for evolution through the subsystems (considered linear time invariant in this paper) and the saltation matrices for the transitions through switching conditions. This matrix is then used to compose a Newton-Raphson search algorithm to converge on the periodic orbit. The algorithm–which has no restriction of the complexity of the system–locates the periodic orbit (stable or unstable), and at the same time computes its Floquet multipliers. The program is written in a sufficiently general way, so that it can be applied to any hybrid dynamical system.     

An algorithm for unified analysis on the thermoluminescence glow curve

An algorithm was developed to integrally handle excitation by radiation, relaxation and luminescence by thermal or optical stimulation in thermoluminescence (TL) and optically stimulated luminescence (OSL) processes. This algorithm reflects the mutual interaction between traps through a conduction band. Electrons and holes are created by radiation in the beginning, and these electrons move to the trap through the conduction band. These holes move to the recombination center through a valence band. The ratio of the electrons allocated to each trap differs with the recombination probability and these values also relevant to the process of luminescence. Accordingly, the glow curve can be interpreted by taking the rate of electron–hole pairs created by ionizing radiation as a unique initial condition. This method differs from the conventional method of interpreting the measured glow curve with the initial electron concentration allocated to each trap at the end of irradiation. A program using the Visual Studio's C# subsystem was made to realize such a developed algorithm. To verify this algorithm it was applied to LiF:Mg,Cu,Si. The TL glow curve was deconvoluted with a model of five traps, one deep trap and one recombination center (RC).     

Generalized analysis of a muffler with any number of interacting ducts

The muffler elements that use perforated elements for acoustic attenuation are common in practice. In typical commercial mufflers perforated elements are used involving two, three, four or more interacting ducts. Analysis of such configurations involves writing down the basic governing equations of mass continuity, momentum balance, etc., and then elimination of velocity variables to obtain the coupled ordinary differential equations in terms of acoustic pressure variables. Mathematical modelling and the consequent analytical derivation of the transmission loss for these multi-duct acoustical elements become increasingly tedious, as just not the number of ducts, but also their relative arrangement along with the boundary conditions dictate the analysis considerably. In the present paper, authors have proposed a generalization and thus an algebraic algorithm to directly produce the system matrix, eliminating the tedium of writing the basic governing equations and elimination of velocity variables. Also, a convenient approach for applying the boundary conditions is outlined here.     

An evidence for a possible stable dibaryon

A search for stableH-dibaryon ofI=0,Y=0,J ^P =0⁺ was undertaken in negative pion-, neutron-,¹²C-nucleus- and proton-propane interactions at 4.0, 7.0, 50.4 and 10 GeV/c, respectively, using 55 cm and 2 m propane bubble chambers. This technique permite one to examine the whole range of possibleH-mass value. In the range ofM _H >2M _Λ=2231.2 MeV/c² an enhancement ofM _ΛΛ=(2365.3±9.6) MeV/c², Γ _ΛΛ =(47.2±15.1) MeV/c² with production cross section σ=(24.2±7.0) μb per carbon nucleus was found. The mass rangeM _Σ?p<M _H <2M _Λ was explored via the search for a weak decay modeH→Σ^?+p. AV ⁰-particle was found pointing to a two-prong interaction and satisfying the kinematics of the above two-body decay mode with a high confidence level. The possibility of imitation of the observed event by background processes was investigated for a series of two-step strong reactions and weak decays. We succeeded to show the significance of theH-production hypothesis on a deuteron-mass nuclear fluctuon via thepd→HpK ⁺ K ⁰ reaction. The mass of the event treated as aH→Σ^?+p weak decay appeared to be (2173.94±1.32) MeV/c², its life-time being 0.668·10^?10 s. Both are in agreement with predictions of the MIT Bag Model for the so-calledH-dihyperon. The formally determined production cross section of theH in proton-propane interactions at 10 GeV/c is estimated to be 40 nb. Perhaps, this event can be considered as a first evidence for a six-quark bound state-H-dihyperon. An independent way for the search for theH-particle, based on a specific conversion processHN→YYN, peculiar to its intranuclear strong interactions was proposed and tried. For this purpose all events with two Λ-hyperons and identified protons were tested for the hypothesesH _p →ΛΛp at three fixed masses:M _H =1880.00, 2173.94 MeV/c² and the ΛΛ invariant mass for the event in question. The kinematics of this reaction fits successfully only one event and only atM _H =2173.94 MeV/c². It seems worthy of note that the final state ΛΛ invariant massM _ΛΛ=2344 MeV/c² is rather close to the observed peak at 2365 MeV/c². It is shown that the intranuclear conversion processes Ξ^? p→ΛΛ and Ξ⁰ n→ΛΛ fail to imitate the observed event. The ΛΛp invariant mass of this event equal to 3363 MeV/c² is out of a 3568 MeV/c² peak region of the ΛΛp invariant mass spectrum observed earlier. TheH conversion cross section exceeds the production one. Thus, we consider this event as providing a new evidence for the stableH-dibaryon ofM _H =(2173.94±1.32) MeV/c².     

A critical survey of basic theories used in muffler design and analysis

The acoustic equations are derived for the general case of sound wave propagation in circular ducts. The exact and approximate methods for solution are reviewed, analyzed and compared for the purpose of ICE muffler design. Different types of mufflers are also presented; their attenuation properties are estimated according to different theoretical approaches.     

穿孔管消声器声学长度修正的理论公式

推导出穿孔管消声器声学长度修正以及共振频率的理论公式。证明了在均匀分布情况下,多小孔向膨胀腔声辐射与单个小孔向膨胀腔声辐射的声学长度修正系数是一致的。对于小孔向主管道的声辐射,根据理论公式研究了穿孔率、周向均布数以及亥姆赫兹数对声学长度修正的影响,有限元计算得出在直径比小于0.4的情况下声学长度修正系数理论公式与仿真计算结果吻合良好。并利用理论公式的性质以及仿真结果获得了实用的拟合公式,提升了穿孔管消声器在高频时共振频率的计算精度。     

An algorithm for the efficient acoustic analysis of silencers of any general geometry

Transfer matrix analysis provides a very efficient means to analyse the linear plane-wave acoustic performance of silencer systems in the frequency domain. However, the nature of the algorithm for combination and reduction of the matrices is different for different combinations of elements. This paper describes an efficient algorithm for acoustic analysis of any general silencer system. The basic format of the algorithm is the identification of sub-systems of two-port acoustic elements. Computational time is also reduced by recording the order in which all of the elements are analysed and the sub-systems are reduced. Examples of the analysis of several complex silencer systems are presented. The gain in efficiency over a general global matrix approach is exceptional.     

An algorithm for finding Bell-type inequalities

This paper deals with the calculation of all the necessary and sufficient conditions for the classical characterization of the probabilities of some events. It shows how a scarcely known method devised by Boole is particularly useful to the solution of this problem. Based on this method, a general and simple algorithm is found that enables the deduction of the inequalities that, like Bell inequalities, express the conditions for classical characterization. The results of the application of the algorithm to some open problems are reported.This work follows the graduation thesis work of the author under the supervision of Professor Enrico G. BNeltrametti at the University of Genoa, Italy.     

An unconditionally stable rotational velocity-correction scheme for incompressible flows

We present an unconditionally stable splitting scheme for incompressible Navier–Stokes equations based on the rotational velocity-correction formulation. The main advantages of the scheme are: (i) it allows the use of time step sizes considerably larger than the widely-used semi-implicit type schemes: the time step size is only constrained by accuracy; (ii) it does not require the velocity and pressure approximation spaces to satisfy the usual inf–sup condition: in particular, the equal-order finite element/spectral element approximation spaces can be used; (iii) it only requires solving a pressure Poisson equation and a linear convection–diffusion equation at each time step. Numerical tests indicate that the computational cost of the new scheme for each time step, under identical time step sizes, is even less expensive than the semi-implicit scheme with low element orders. Therefore, the total computational cost of the new scheme can be significantly less than the usual semi-implicit scheme.     

Phase-crossing algorithm for white-light fringes analysis

The phase-crossing algorithm is proposed for white-light interferometry, which uses the multi-color phase information of spectrally decomposed interferograms recorded simultaneously with color-sensitive image sensors. The location of zero optical path difference is identified as the singular point at which the phase becomes color invariant, and is determined accurately with a sub-sampling-interval resolution from the crossing point of the multi-color phase distributions obtained by the Fourier transform method. An experimental result is presented that demonstrates the performance of the phase-crossing algorithm.