G. Rosenhouse

Determination of fruit and vegetable properties by ultrasonic excitation

ABSTRACT Problems involved in non-desctructive quality determination of fresh food products through sonic and ultrasonic excitation were discussed. An experimental setup for basic measurements of acoustic properties of fruits and vegetables was described. Preliminary tests were made with tissue specimens of some fruit and vegetables; the velocity of wave propagation, the attenuation rate, and the reflection properties of these products were calculated. The results demonstrate the feasibility of low frequency ultrasonic testing of agricultural products.

ACOUSTICAL, MECHANICAL, AND QUALITY PARAMETERS OF WINTER-GROWN MELON TISSUE

ABSTRACT Acoustical, mechanical, and quality parameters of ripe winter-grown melons were tested in sample fruit sectors from different depths, and the relationships among them were analyzed. The modulus of elasticity and the tangent modulus of the sample tissues decreased ckastically with the sample depth; the acoustical attenuation of a transmitted pulse, as well as the quality characteristics tested in this study, strongly increased with the depth of the fruit sample. This strong dependence on depth (R = 0.842) indicates the potential for using the attenuation coefficient for the identification of internal fruit quality. Wave propagation velocity was found to be a poor predictor for internal properties of ripe winter grown melons.

Measurements and Theory of Normal Tracheal Breath Sounds

We studied the mechanisms by which turbulent flow induces tracheal wall vibrations detected as tracheal breath sounds (TRBSs). The effects of flow rate at transitional Reynolds numbers (1300–10,000) and gas density on spectral patterns of TRBSs in eight normal subjects were measured. TRBSs were recorded with a contact sensor during air and heliox breathing at four flow rates (1.0, 1.5, 2.0, and 2.5 l/s). We found that normalized TRBSs were proportional to flow to the 1.89 power during inspiration and to the 1.59 power during expiration irrespective of gas density. The amplitude of TRBSs with heliox was lower than with air by a factor of 0.33 ± 0.12 and 0.44 ± 0.16 during inspiration and expiration, respectively. The spectral resonance frequencies were higher during heliox than air breathing by a factor of 1.75 ± 0.2—approximately the square root of the reciprocal of the air/heliox wave propagation speed ratio. In conclusion, the flow-induced pressure fluctuations inside the trachea, which cause tracheal wall vibrations, were detected as TRBSs consist of two components: (1) a dominant local turbulent eddy component whose amplitude is proportional to the gas density and nonlinearly related to the flow; and (2) a propagating acoustic component with resonances whose frequencies correspond to the length of the upper airway and to the free-field sound speed. Therefore, TRBSs consist primarily of direct turbulent eddy pressure fluctuations that are perceived as sound during auscultation.

Noise absorption by woven fabrics

Abstract The paper describes an investigation of the relationship between the noise absorption coefficients of a cover made of woven fabric and its intrinsic parameters. The parameters considered were: fibre content, yarn count, cover factor, the air gap behind the fabric, the frequency of the impinging sound wave, and the influence of washing on the sound absorption capacity of the woven fabric. The results show a potential of obtaining NRC ranging between 0·09 and 0·22, which may be useful when coating rigid surfaces. The absorption coefficient is much higher at higher frequencies, say, 4000 Hz.

Rectangular hybrid shell element for analysing folded plate structures

Abstract A new rectangular hybrid stress element for analysing folded plate structures is presented. The new four-node element, which is based on the classical hybrid stress method, is called the hybrid coupling element and is generated by a combination of a hybrid plane stress element and a hybrid plate bending element. An invariant equilibrated stress field in each element and an inter-element compatible boundary displacement field are assumed independently in this model. Two additional degrees of freedom at the two nodes which lie along the line of intersection of two planes enable the displacement compatibility. They correspond to the rotation about the local z -axis of the element and are called ‘drilling’ degrees of freedom. The new hybrid finite element system has been used for an investigation of the response of a variety of elastic mountings and has yielded reliable results compared with classical methods. Finally, the advantages of such mountings in engineering design are emphasized.

Noise-insulating blankets made of textile

Abstract The insulation of noise by folded panel partitions made of several layers of nonwoven fiberwebs and a layer of woven fabric was examined. The resulting transmission loss of the composite structure was an oscillatory function of the opening angle between the individual panels and an increasing function of the number of fiberweb layers that comprise the partition. For most frequencies, the angle which yields the highest transmission loss was about 70°. The effect of the woven fabric on the transmission loss was most significant at small opening angles—about 10°—where values up to 20 dB were observed.

Ultrasonic evaluation of some ripening parameters of autumn and winter-grown Galia melons

Abstract Autumn-grown (without internal breakdown) and winter-grown (with internal breakdown) melons were evaluated for firmness, dry weight (DW) and total soluble solids (TSS) content in sample fruit sectors from different depths within the fruit. Acoustical and quality parameters of the samples were tested, and the relationships between them analyzed. In the fruit of both seasons, the DW and TSS showed increasing gradients toward the center of the fruit, although winter-grown fruits had much higher values of the two parameters. The acoustical attenuation of transmitted pulse in ripe wintergrown melons, as well as the DW and TSS characteristics, increased drastically with the depth of the fruit sample. The dependence on depth (R = 0.842) indicates the potential for using the attenuation coefficient to predict internal fruit quality.

Mixed-hybrid finite strip method for folded plate structures

Abstract The present work proposed a new mixed-hybrid finite strip formulation for stress analysis of long folded plates combined with rectangular simply supported panels. The formulations evolved coupled in-plane and flexural stresses, while the model for the plate bending followed the Mindlin plate. A comparison with other numerical methods and an exact solution highlight the advantages of the proposed method.

THE BOUNDARY STRIP METHOD IN ELASTOSTATICS AND POTENTIAL EQUATIONS

The present paper develops the idea of the boundary strip method, and presents its fundamentals, merits, applications and also some closed-form or non-element solutions based on it. The present approach combines the Boundary Integral Equation Method (BIEM) and the finite strip method, taking the advantages of both. The finite strip method is installed into the BIEM by expanding the unknown parameters of problems in terms of trigonometric series. This combination creates a new powerful numerical method with three advantages over other numerical methods, namely, a shorter computation time, a better accuracy and a reduction of one and a half dimensions in mesh generation. Applications in two-dimensional potential and field problems demonstrate the efficiency and the accuracy of the proposed method. Finally, closed-form presentations for Laplace equation and elastostatics are given, along circular segments.

A new boundary spectral strip method for non-periodical geometrical entities based on analytical integrations

Abstract A method based on expanding the boundary integral equation into a trigonometric series or a high-order polynom is proposed, depending on the domain geometry. It is a non-element method which yields solutions to elastostatic and potential problems, using a small computer memory, yet obtaining more precise results as compared with other common numerical methods. When the geometry of the problem contains circles and straight lines, all the integrations required for solution of the boundary integral are solved analytically. Some elastostatic problems are solved here, and compared with the boundary element method (BEM), which shows some remarkable advantages of the boundary strip method over the BEM.