Correction of stiffness and mass matrices utilizing simulated measured modal data

Measured and analytical data are unlikely to be equal due to measured noise, model inadequacies and structural damage, etc. It is necessary to update the physical parameters of analytical models for proper simulation and design studies. Starting from simulated measured modal data such as natural frequencies and their corresponding mode shapes, this study presents the equations to update the physical parameters of stiffness and mass matrices simultaneously for analytical modelling by minimizing a cost function in the satisfaction of the dynamic constraints of orthogonality requirement and eigenvalue function. The proposed equations are straightforwardly derived by Moore–Penrose inverse matrix without using any multipliers. The cost function is expressed by the sum of the quadratic forms of both the difference between analytical and updated mass, and stiffness matrices. The results are compared with the updated mass matrix to consider the orthogonality requirement only and the updated stiffness matrix to consider the eigenvalue function only, respectively. Also, they are compared with Wei’s method which updates the mass and stiffness matrices simultaneously. The validity of the proposed method is illustrated in an application to correct the mass and stiffness matrices due to section loss of some members in a simple truss structure.     

Diagnosing departures from stability in a multidimensional multivariate system

This paper deals with a system containing n m-variable elements measured at p points of time. The data matrices for each point of time are represented by the biplot technique. Each biplot provides a map of the system which can be used to determine visually the relations between the elements and variables. The biplots are then compared by superimposing them to obtain an ‘aggregate’ graph. Differences between the biplots indicate departure from stability of the system. An example drawn from the Israeli banking system is provided.     

Determination of material functions through second sound measurements in a hyperbolic heat conduction theory

In a previous paper [1], numerical solutions to initial-boundary value problems for a semi-empirical model of heat conduction were compared with available experimental results.

In the present paper, we modify the model by introducing more realistic approximations of constitutive functions, based on measured heat conductivities and second sound speeds for NaF at low temperatures (10…20° K). We achieve good accordance between measured second sound pulses and numerical solutions in the temperature range covered by experiments, and reasonable behaviour even beyond this interval. Especially, a passage to the diffusive regime of the classical Fourier law is possible.     

Effect of mineral fillers on properties of composite matrix material

The influence of mineral fillers on thermomechanical properties of matrix material of composites is investigated. Different methods to determine elastic properties and thermal expansion coefficients of composite materials have been considered and compared. Injection moulded polyester samples containing varying concentrations of talc filler are tested and properties such as Young 's modulus, thermal expansion coefficients, and volumetric shrinkage during cure are measured. Results obtained by theoretical models and from experiments are compared and discussed.To be presented at the Ninth International Conference on the Mechanics of Composite Materials (Riga, October 1995).Published in Mekhanika Kompozitnykh Materialov, Vol. 31, No. 4, pp. 435–445, July–August, 1995.     

Maximal growth rate at the Rosensweig instability: theory,experiment, and numerics

We investigate the growth of a pattern of liquid crests emerging in a layer of magnetic liquid when subjected to a magnetic field oriented normally to the fluid surface. After a step like increase of the magnetic field, the temporal evolution of the pattern amplitude is measured by means of a Hall-sensor array. The extracted growth rate is compared with predictions from linear stability analysis by taking into account the nonlinear magnetization curve M (H). The remaining discrepancy can be resolved by numerical calculations via the finite element method. By starting with a finite surface perturbation it can reproduce the temporal evolution of the pattern amplitude and the growth rate. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The near ultraviolet emission spectrum of tetralin (tetrahydronaphthalene)

An emission spectrum of tetralin (tetrahydronaphthalene) in the near ultraviolet excited by a transformer discharge through flowing vapour has been studied and about twenty-nine bands in emission have been photographed and measured on suitable instruments. Vibrational analysis of the bands in terms of the fundamental frequencies of the molecule is proposed and is compared with those obtained in the corresponding absorption spectrum of tetrahydronaphthalene studied by the author.² The results afford further confirmation of the correctness of the analysis and particularly the assignment of the (0,0) band proposed in the absorption spectrum of the molecule.     

Experimental investigation and approximation of the temperature-dependent stiffness of short-fiber reinforced polymers

In order to predict the effective material properties of a short-fiber reinforced polymer (SFRP), homogenization of elastic properties with the self-consistent (SC) scheme and the interaction direct derivative (IDD) method is performed by means of µCT data describing the microstructure of the composite material. Using dynamic mechanical analysis (DMA), the material properties of both, polypropylene and fiber reinforced polypropylene are investigated by tensile tests under thermal load. The measured storage modulus of the matrix material is used as input parameter for the homogenization scheme. The effective properties of SFRP are compared to experimental results from DMA. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Three-dimensional effects of an air curtain used to restrict cold room infiltration

The aim of this study was to compare the measured effectiveness of an air curtain device at different jet velocities against a three-dimensional (3-D) computational fluid dynamics (CFD) model. The air curtain device was not as wide as the entrance and had a geometry that encouraged 3-D flow. By carefully setting up the air curtain an effectiveness of 0.71 was achieved compared to the initial value of only 0.31 as set by the air curtain device installer. The 3-D CFD model predicted the infiltration through the entrance with no air curtain to an accuracy of within 20–32%. The predicted effectiveness, E, of the air curtain at different jet velocities was 0.10–0.15 lower than measured. The shape of the effectiveness curve against jet velocity was well predicted. CFD has shown that the flow from this air curtain cannot be considered as 2-D. The central part of the jet is deflected away from the cold store by the Coanda effect caused by the air curtain device’s fan body. The edges of the jet are deflected into the cold store by the stack pressures and turn into the void caused by the deflected central jet.     

Measurement of excitation spectra for highly ionized sulphur

The excitation spectra in the wavelength range of 19—40 nm for highly ionized sulphur ions were measured by using the beam-foil method at the Heavy lon Research Facility in Lanzhou. In this experiment, more than 30 spectral lines were observed, which belonged to the transitions of the excitation energy levels for highly ionized SX—SXV ions, and 5 new lines were determined. The experimental results were compared with those from other experiments and theoretical calculations.     

Dynamic response analysis of the two stators hybrid transducer type piezoelectric ultrasonic motor using finite element simulation

This paper presents the finite element simulation with an aim to analyse the dynamic response of the two stators hybrid transducer type piezoelectric ultrasonic motor. The three dimensional–model which includes the effects of piezoelectric coupling are formulated. The dynamic behaviours of a motor stator are calculated and later compared to the experimental results measured from the prototype of this motor. The impedance characteristic of the complete stator is validated using HP4294A precision impedance analyzer. In addition to the electrical measurements, the mechanical displacement and the mechanical velocity of the stator are measured directly using a single point laser Doppler vibrometer. This is to verify that finite element modelling is an appropriate approach to analyse the dynamic behaviour of this piezoelectric ultrasonic motor. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spectroscopic method of measuring the stresses at stress raisers in polymers

A method of measuring the mechanical stresses near stress raisers from the frequency shift of the IR absorption bands is proposed. The stresses at the edge of an ellipse as determined by IR spectroscopy, from the birefringence, and by theoretical calculation are compared. It is shown that the results coincide. The stress near the tip of a crack has been measured by the IR spectroscopy technique. It is shown that these stresses may be ten or more times greater than the external tensile stress.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 167–170, January–February, 1970.     

梯形复式断面均匀流水力计算

对由主槽、斜边坡以及边滩三部分组成的梯形复式断面渠道均匀流的水力计算进行了研究,采用表观切应力表示各子断面间的横向动量交换,结合各部分力的平衡关系式,推导出了主槽、斜边坡和边滩平均流速的计算公式．采用UK-FCF的实验数据对公式进行了验证,滩槽相对水深为0.057~0.4的7组工况计算值与实测值的比较表明,不考虑表观切应力的计算值与实测值的一致性都较差．比较而言,斜边坡部分平均流速在水深较小时计算值大于实测值,在水深较大时计算值小于或接近实测值,表观切应力对边滩部分平均流速的影响不明显,而主槽部分若不考虑表观切应力的影响,则计算值与实测值差别较大．运用三段式模型与刘沛清等提出的两段式模型分别进行了有边坡梯形断面复式渠道的水力计算,结果表明对于有边坡段的梯形断面渠道（河道）,三段式模型更加有效．最后,将计算的表观切应力与实测表观切应力进行了比较,两者的一致性表明采用的动量输运系数是合适的．     

Operational competitiveness analysis on software development

The focus of this study is the application of a non-parametric model called operational competitiveness rating analysis (OCRA), to obtain ratings that gauge the relative operational performance of the application software development teams of a large bank in Hong Kong. The computed ratings would be the basis of important management decisions relating to the connection between personnel performance and benefits. This application of OCRA requires the values of resources consumed and outputs generated. Cost figures were used to measure the teams' resource consumption. The value of the teams' software output was measured by function point analysis. The performance ratings obtained by OCRA are compared with data envelopment analysis (DEA) ratings and ratio scores. Comments are offered on the implementation of the proposed approach.     

Virtual test facilities for building acoustic predictions using FEM

The most important characteristic in building acoustics is the transmission loss which describes the insulation performance of a separating component. This quantity is defined by the ratio of inclined sound power to transmitted power. The transmission loss is usually measured in costly experimental set-ups of either real size facilities or down scaled test models. In order to reduce the effort and to gain further insight into the complex behavior of wave propagation in coupled structure-fluid systems, virtual test facilities using numerical methods (FEM) are established. An appropriate determination of the reverberation time is essential for obtaining good quality simulations. The results of the simulated transmission loss are presented and compared with common analytical prediction methods based on the transfer matrix method. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the formation of vortex rings: Rolling-up and production of circulation

The temporal development of the rolling-up process of vortex rings produced in water at a circular nozzle is investigated by flow visualization. The results are compared with similarity laws for the rolling-up of vortex sheets in plane flow. The unsteady flow field in the nozzle-exit plane is measured by laser anemometry. The vorticity distribution in the boundary layers at the inner and outer nozzle wall and the vorticity flux through the exit plane are derived from the measurements. The flow conditions measured at the nozzle are used to explain the production of the ring-vortex circulation (measured three nozzle-diameters downstream) in relation to the generation conditions.

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Zusammenfassung Durch Strömungs-Sichtbarmachung wird für Ringwirbel, die an einer kreisförmigen Rohrmündung in Wasser erzeugt werden, der zeitliche Verlauf des Aufrollvorgangs untersucht und mit Ähnlichkeitsgesetzen für die Aufrollung von ebenen Wirbelschichten verglichen. Aus Messungen des instationären Strömungsfeldes im Mündungsquerschnitt mit einem Laser-Anemometer wird die Wirbelstärke-Verteilung in den Grenzschichten an der inneren und äußeren Rohrwand sowie der Wirbelfluß durch den Mündungsquerschnitt bestimmt. Dadurch wird die Entstehung der Zirkulation, die im fertig ausgebildeten Ringwirbel drei Rohrdurchmesser stromabwärts gemessen wird, in Abhängigkeit von den Erzeugungsbedingungen verständlich.

     

Identification of Viscoelastic Properties and Damaging Effects of Highly Extensible Polyurea

The present work aims particular at the experimental identification of the viscoelastic properties of polyurea as well as on the onset of the damage. For the viscoelastic part, several relaxation experiments are performed. From the measured data a general viscoelastic model is derived where we use two different approaches. At first we identify a general Maxwell model (combining spring and damping elements for finite deformations) to use a prony series with N elements, which requires the identification of 2N + 1 parameters. At second, a model of generalized fractional elements [3] is employed. Both approaches are studied in detail and are compared to data from literature; furthermore a comparison concerning the effort is presented. Damaging effects of Polyurea are investigated using tensile tests with and without cyclic loading. In particular we focus on the the onset of damage by cavitation. To this end the recovered specimens were analyzed using a laser microscope; the surfaces of the ruptured areas are compared in terms of quantity and size of voids. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Tunneldiode-Transistorschaltungen für die Pulstechnik

Summary Based on a novel tunneldiode-transistor configuration a pulse former and a full adder circuit are being derived. The pulse former shapes waveforms of repetition rates of up to 700 MHz into pulses of standardized amplitude and the full adder exhibits a carry signal delay of 1 nsec. Both a.c. and d.c. behaviour is analysed and compared to measured results.     

Optimal np control chart with curtailment

This article presents an algorithm for the optimization design of the np control chart with curtailment. The objective is to maximize the effectiveness of the np chart, while holding the false alarm rate at a specified level and maintaining its simplicity for understanding and operation to a large degree. The optimization algorithm can be applied to a 100% inspection as well as a general random sampling inspection. The effectiveness of the chart is measured by the out-of-control average time to signal (ATS) under the steady-state mode. This mode allows a shift in fraction nonconforming, p, to occur at any time during the inspection of a sample and, therefore, provides more realistic results than the zero-state mode. According to several performance studies and an illustrative example that are conducted in this research, the optimal np chart with curtailment may reduce the out-of-control ATS by nearly half, on average, compared to the conventional np charts.     

Morphological studies of tin oxide gel

X-ray and electron diffraction patterns of tin oxide gel, with the gel samples heated to 400, 600, 800 and 1000° C, and tin oxide precipitate have been taken. Sharp diffraction rings prove, beyond doubt, the crystallic nature of all these samples. Electron transmission photographs of the samples have been taken, and from the photographs, the pore diameter and crystallite length have been measured. The pore diameters obtained thus have been compared with the values obtained by applying the relationshipd=4V/S whereV is the pore volume andS the surface area. The values are in quite good agreement. Thehkl planes of the sample have been calculated based upon the tetragonal equation.     

A comparison of asymptotic covariance matrices of three consistent estimators in the Poisson regression model with measurement errors

We consider a Poisson model, where the mean depends on certain covariates in a log-linear way with unknown regression parameters. Some or all of the covariates are measured with errors. The covariates as well as the measurement errors are both jointly normally distributed, and the error covariance matrix is supposed to be known. Three consistent estimators of the parameters—the corrected score, a structural, and the quasi-score estimators—are compared to each other with regard to their relative (asymptotic) efficiencies. The paper extends an earlier result for a scalar covariate.