A study on the applications of the acoustic design sensitivity analysis of vibrating bodies

The determination of the sensitivity of the acoustical characteristics of vibrating systems with respect to the variation of the design parameters predicting these characteristics is a necessary and important step of the acoustic design and optimization process. Acoustic design sensitivity analysis includes the computation and evaluation of the sensitivity information required for this procedure. In this study, a boundary element code performing the sensitivity analysis of the acoustic pressure by using the matrix sensitivities with respect to different design variables has been developed. The effect of the precision of boundary element discretization on the acoustic pressure sensitivity is examined via this code. The formulation is applied to a multi-source system and the dimension sensitivity analysis of near field pressures of two-dilating-spherical source is performed. The last application is devoted to a real sound source: a washing machine sitting on the floor. Sensitivity of the field pressures to the machine’s dimensions (size), surface velocity and frequency is examined on the bases of the boundary element model of the machine and half-space condition. The impacts of these variables are compared; and a limiting speed for the machine responding both the acoustical and operational requirements is determined.     

On existence and asymptotic stability of solutions of a nonlinear integral equation

We prove an existence theorem for a nonlinear integral equation being a Volterra counterpart of an integral equation arising in the traffic theory. The method used in the proof allows us to obtain additional characterization in terms of asymptotic stability of solutions of an equation in question.     

A new VOF‐based numerical scheme for the simulation of fluid flow with free surface. Part II: application to the cavity filling and sloshing problems

Finite element analysis of fluid flow with moving free surface has been performed in 2‐D and 3‐D. The new VOF‐based numerical algorithm that has been proposed by the present authors (Int. J. Numer. Meth. Fluids, submitted) was applied to several 2‐D and 3‐D free surface flow problems. The proposed free surface tracking scheme is based on two numerical tools; the orientation vector to represent the free surface orientation in each cell and the baby‐cell to determine the fluid volume flux at each cell boundary. The proposed numerical algorithm has been applied to 2‐D and 3‐D cavity filling and sloshing problems in order to demonstrate the versatility and effectiveness of the scheme. The proposed numerical algorithm resolved successfully the free surfaces interacting with each other. The simulated results demonstrated applicability of the proposed numerical algorithm to the practical problems of large free surface motion. It has been also demonstrated that the proposed free surface tracking scheme can be easily implemented in any irregular non‐uniform grid systems and can be extended to 3‐D free surface flow problems without additional efforts. Copyright © 2003 John Wiley & Sons, Ltd.     

The binding of manganese(II) and zinc(II) to the synthetic oligonucleotide d(C-G-C-G-A-A-T-T-C-G-C-G)2. A 1H NMR study

The interaction of the synthetic oligonucleotide d(C-G-C-G-A-A-T-T-C-G-C-G)2 with two different transition-metal ions has been investigated in aqueous solution by means of 1H NMR spectroscopy. The effects on the DNA due to the presence of manganese(II) or zinc(II) have been monitored by observing the paramagnetic broadening and diamagnetic shifts of the non-exchangeable proton resonance lines, respectively. The 1H NMR spectra acquired during the course of the manganese(II) titration show very distinct broadening effects on certain DNA resonance lines. Primarily, the H8 resonance of G4 is affected, but also the H5 and H6 resonances of C3 are clearly affected by the metal. The results imply that the binding of manganese(II) to DNA is sequence specific. The 1H spectra obtained during the zinc(II) titration reveal diamagnetic shift effects which largely conform with the paramagnetic broadening effects due to the presence of manganese(II), although this picture is somewhat more complex. The H8 resonance of G4 displays a clearly visible high-field shift, while for the other guanosine H8 protons this effect is absent. The H1' and H2' protons of C3 show an effect of similar strength, although in the opposite direction, while H5 and H6 of C3 are only slightly affected. Local differences in the structure of the DNA and the basicities of potential binding sites on different base steps in the sequence might account for the observed sequence selectivity.     

trans-Bis(azido-κN)bis(pyridine-2-carboxamide-κ2N1,O2)nickel(II)

In the title compound, [Ni(N₃)₂(C₆H₆N₂O)₂], the Ni^II atom lies on an inversion centre. The distorted octahedral nickel(II) coordination environment contains two planar trans-related N,O-chelating picolinamide ligands in one plane and two monodentate azide ligands perpendicular to this plane. Molecules are linked into a three-dimensional framework by N—H...N hydrogen bonds.     

Multiparameter Polynomial Adaptive Stabilizers

In 1983 Morse proved, for unknown scalar one-dimensional linearsystems, the nonexistence of rational or polynomial universalstabilizers (UAS). In 1983, Nussbaum gave an example of an analyticUAS. In our paper, it is shown that there exist time-invariantpolynomial UAS's with multidimensional gain adaptation. Thedesign procedure is developed for linear, minimum-phase systemsof relative degree one. Convergence of the closed-loop systemis proved. Some numerical simulations are provided.     

Cyclic trihydroxamic acid derivatives

In the crystal structures of two cyclic trihydroxamic acid derivatives containing the same substructure unit, viz. 1,3,5‐trihydroxy‐1,3,5‐triazinane‐2,4,6‐trione dihydrate, C₃H₃N₃O₆·2H₂O, (I), and 1,3,5‐benz­yloxy‐1,3,5‐triazinane‐2,4,6‐trione, C₂₄H₂₁N₃O₆, (II), there is no significant difference in the geometric parameters. In (I), there are 11 hydrogen bonds of the O—H⋯O type inter­connecting the mol­ecules in a three‐dimensional network, while in (II) there are only two weak C—H⋯O hydrogen bonds. The results of IR spectroscopic analysis are in good agreement with the crystallographic study.     

Experimental verification of drop/impact simulation for a cellular phone

Conducting drop tests to investigate impact behavior and identify failure mechanisms of small-size electronic products is generally expensive and time-consuming. Nevertheless, strict drop/impact performance criteria for hand-held electronic products such as cellular phones play a decisive role in the design because they must withstand unexpected shocks. The design of product durability on impact has heavily relied on the designer's intuition and experience. In this study, a reliable drop/impact simulation for a cellular phone is carried out using the explicit code LS-DYNA. Subsequently globallocal experimental verification is accomplished by means of high-speed photography and impact response measurement. Using this methodology, we predict potential damage locations in a cellular phone and compare them with real statistical data. It is envisaged that development of a reliable methodology of drop/impact simulation will provide us with a powerful and efficient vehicle for improvement of the design quality and reduction of the product development cycle.