FINITE ELEMENT METHODS FOR STRUCTURAL ACOUSTICS ON MISMATCHED MESHES

2009 ◽  
Vol 17 (03) ◽  
pp. 247-275 ◽  
Author(s):  
TIMOTHY WALSH ◽  
GARTH REESE ◽  
CLARK DOHRMANN ◽  
JERRY ROUSE
Keyword(s):  
Acoustic Analysis ◽  
Linear Constraint ◽  
Linear Constraints ◽  
Structural Acoustics ◽  
Weak Formulation ◽  
Simple Method ◽  
Constraint Equations ◽  
Static Condensation ◽  
A New Technique ◽  
Acoustic Interfaces

In this paper, a new technique is presented for structural acoustic analysis in the case of nonconforming acoustic–solid interface meshes. We first describe a simple method for coupling nonconforming acoustic–acoustic meshes, and then show that a similar approach, together with the coupling operators from conforming analysis, can also be applied to nonconforming structural acoustics. In the case of acoustic–acoustic interfaces, the continuity of acoustic pressure is enforced with a set of linear constraint equations. For structural acoustic interfaces, the same set of linear constraints is used, in conjunction with the weak formulation and the coupling operators that are commonly used in conforming structural acoustics. The constraint equations are subsequently eliminated using a static condensation procedure. We show that our method is equally applicable to time domain, frequency domain, and coupled eigenvalue analysis for structural acoustics. Numerical examples in both the time and frequency domains are presented to verify the methods.

scholarly journals A new technique for the efficient use of Macro-Mistnets

Koedoe ◽  
1985 ◽  
Vol 28 (1) ◽  
Author(s):  
I.L. Rautenbach
Keyword(s):  
New Technique ◽  
Simple Method ◽  
A New Technique

A cheap and simple method of adapting yacht masts to allow quick and efficient stringing and versatile manipulation of a 6,0 x 30,0 metre macro-mistnet, is described.

A New Algorithm for Calculating the Degrees of Freedom of Complex Mechanisms

2011 ◽  
Vol 346 ◽  
pp. 324-331
Author(s):  
Wei Jiang ◽  
Xin Luo ◽  
Wen Chuan Jia ◽  
Yuan Tai Hu ◽  
Hong Ping Hu
Keyword(s):  
Degrees Of Freedom ◽  
Linear Equations ◽  
Linear Constraint ◽  
Coefficient Matrix ◽  
Constraint Matrix ◽  
Constraint Equations ◽  
Complex Mechanisms ◽  
Traditional Approaches ◽  
Homogeneous Linear

A new algorithm is presented to calculate the degrees of freedom (DOFs) of spatial complex mechanisms by using the coefficient matrix of the linear constraint equations. A joint constraint matrix is firstly put forward for each kind of joint to formulate linear constraint equations in terms of spatial fine displacements of joint acting point with respect to joint frame. Two kinds of transformation are then proposed to rewrite all the constraint equations in terms of a set of fine displacements of all bodies and it leads to a set of homogeneous linear equations. The rank of the resulting coefficient matrix stands for the number of effective constraints and therefore the DOFs of the mechanism can be easily figured out. The proposed method can be widely used to solve the problem of DOFs for many spatial complex mechanisms, which may not be correctly solved with traditional approaches. Besides, the proposed method is very easy for implementation.

scholarly journals Statistical properties of cloud lifecycles in cloud-resolving models

2009 ◽  
Vol 9 (6) ◽  
pp. 2195-2205 ◽  
Author(s):  
R. S. Plant
Keyword(s):  
Statistical Properties ◽  
New Technique ◽  
Average Lifetime ◽  
Cumulus Clouds ◽  
Simple Method ◽  
Model Simulations ◽  
Cloud Resolving Model ◽  
Time Histories ◽  
A New Technique

Abstract. A new technique is described for the analysis of cloud-resolving model simulations, which allows one to investigate the statistics of the lifecycles of cumulus clouds. Clouds are tracked from timestep to timestep within the model run. This allows for a very simple method of tracking, but one which is both comprehensive and robust. An approach for handling cloud splits and mergers is described which allows clouds with simple and complicated time histories to be compared within a single framework. This is found to be important for the analysis of an idealized simulation of radiative-convective equilibrium, in which the moist, buoyant updrafts (i.e., the convective cores) were tracked. Around half of all such cores were subject to splits and mergers during their lifecycles. For cores without any such events, the average lifetime is 30 min, but events can lengthen the typical lifetime considerably.

The DOMAIN family of propagation operations for intervals on simultaneous linear equations

1995 ◽  
Vol 9 (3) ◽  
pp. 197-210 ◽  
Author(s):  
R. Chen ◽  
A.C. Ward
Keyword(s):  
Linear Equations ◽  
Constraint Equation ◽  
Linear Constraint ◽  
The Other ◽  
Interval Matrix ◽  
Domain Family ◽  
Output Vector ◽  
Constraint Equations ◽  
Simultaneous Linear Equations ◽  
Mathematical Operations

AbstractThis paper defines, develops algorithms for, and illustrates the utility in design of a class of mathematical operations. These accept as inputs a system of linear constraint equations, Ax = b, an interval matrix of values for the coefficients, A, and an interval vector of values for either x or b. They return a set of values for the “domain” of the other vector, in the sense that all combinations of the output vector values set and values for A, when inserted into the constraint equation, correspond to values for the input vector that lie within the input interval. These operations have been mostly overlooked by the interval matrix arithmetic community, but are mathematically interesting and useful in the design, for example, of structures.

scholarly journals A new technique to prevent curling of guide wire in urinary bladder during J stent insertion with flexible cystoscope

2016 ◽  
Vol 10 (1-2) ◽  
pp. 34 ◽  
Author(s):  
Nasir Mahmood ◽  
Tahir Pasha
Keyword(s):  
Urinary Bladder ◽  
Local Anaesthetic ◽  
Ureteral Obstruction ◽  
Guide Wire ◽  
New Technique ◽  
Stent Insertion ◽  
Common Procedure ◽  
Simple Method ◽  
Flexible Cystoscope ◽  
A New Technique

Insertion of J stent is a very common procedure performed by urologists. This procedure is often performed to relieve ureteral obstruction due to stones, tumours, ureteral kink, or stricture on urgent basis. An increasing number of urologists are using a flexible cystoscope and local anaesthetic for J stent insertion. Occasionally, the guide wire curls in the bladder, making it impossible to insert the J stent. Here, we describe a simple method to overcome this problem using modified ureteral dilator, which is usually available in the cystoscopy suite.

scholarly journals Statistical properties of cloud lifecycles in cloud-resolving models

2008 ◽  
Vol 8 (6) ◽  
pp. 20537-20564 ◽  
Author(s):  
R. S. Plant
Keyword(s):  
Statistical Properties ◽  
New Technique ◽  
Average Lifetime ◽  
Cumulus Clouds ◽  
Simple Method ◽  
Model Simulations ◽  
Cloud Resolving Model ◽  
Time Histories ◽  
A New Technique

Abstract. A new technique is described for the analysis of cloud-resolving model simulations, which allows one to investigate the statistics of the lifecycles of cumulus clouds. Clouds are tracked from timestep-to-timestep within the model run. This allows for a very simple method of tracking, but one which is both comprehensive and robust. An approach for handling cloud splits and mergers is described which allows clouds with simple and complicated time histories to be compared within a single framework. This is found to be important for the analysis of an idealized simulation of radiative-convective equilibrium, in which the moist, buoyant, updrafts (i.e., the convective cores) were tracked. Around half of all such cores were subject to splits and mergers during their lifecycles. For cores without any such events, the average lifetime is 30 min, but events can lengthen the typical lifetime considerably.

scholarly journals Constraint Equations for a Planar Parallel Platform

2021 ◽  
Author(s):  
◽  
Amani Ahmed Otaif
Keyword(s):  
Gröbner Basis ◽  
Linear Constraints ◽  
Grobner Basis ◽  
Real Solutions ◽  
Constraint Equations ◽  
Kinematic Mapping ◽  
Univariate Polynomials ◽  
Forward Kinematic Problem ◽  
Bézout’S Theorem ◽  
Forward Kinematic

<p>The aim of this thesis is to apply the Grünwald–Blaschke kinematic mapping to standard types of parallel general planar three-legged platforms in order to obtain the univariate polynomials which provide the solution of the forward kinematic problem. We rely on the method of Gröbner basis to reach these univariate polynomials. The Gröbner basis is determined from the constraint equations of the three legs of the platforms. The degrees of these polynomials are examined geometrically based on Bezout’s Theorem. The principle conclusion is that the univariate polynomials for the symmetric platforms under circular constraints are of degree six, which describe the maximum number of real solutions. The univariate polynomials for the symmetric platforms under linear constraints are of degree two, that describe the maximum number of real solutions.</p>

THE CORRECTIVE GRADIENT PROJECTION METHOD AND RELATED ALGORITHMS APPLIED TO SEISMIC ARRAY PROCESSING

Geophysics ◽  
1976 ◽  
Vol 41 (5) ◽  
pp. 970-984 ◽  
Author(s):  
Anthony F. Gangi ◽  
Bok S. Byun
Keyword(s):  
Adaptive Algorithm ◽  
Array Processing ◽  
Nonlinear Function ◽  
Linear Constraint ◽  
Gradient Projection ◽  
Constraint Equations ◽  
Multiple Parameters ◽  
Sensor Array Processing ◽  
Noise Statistics ◽  
General Iterative Method

A general iterative method is described for the problem of optimizing a nonlinear function of multiple parameters subject to a system of linear constraint equations. This scheme, derived by Frost (1972), is called the “corrective gradient projection (CGP)” method. It is obtained by modifying Rosen’s (1960) “gradient projection (GP)” method to correct for any deviation of the parameters from the constraint equations. The CGP method can be applied to the problem of multichannel tapped‐delay‐line (TDL) sensor array processing as used in the fields of seismic, radar and acoustic communications. A variety of algorithms associated with signal processing problems—such as those developed by Frost (1972), Rosen (1960), Booker and Ong (1971), Widrow et al. (1967), and Griffiths (1969)—can be derived from or related to the CGP method. They are obtained by making some basic assumptions and statistical approximations. Comparative simulation experiments have been made using a digital computer to examine the performance of some of the algorithms for real seismic data. The algorithms examined are the constrained (unbiased) adaptive algorithm of Frost (1972), the unconstrained adaptive algorithm of Widrow et al. (1967) and the constrained (unbiased) optimum processor (Claerbout, 1968; Frost, 1972). The adaptive algorithms are capable of discriminating against noise signals in real time. The Frost algorithm strictly maintains a specified constrained frequency response for the array, while the Widrow algorithm alters the equivalent array response during the adaptations. For the Frost algorithm, the adaptive processor approaches the optimum one as the number of adaptations increases because it progressively learns the noise statistics.

Sign in / Sign up

Export Citation Format

Share Document