Influence of wall vibrations on the sound of brass wind instruments

The results of an experimental and theoretical investigation of the influence of wall vibrations on the sound of brass wind instruments are presented. Measurements of the transmission function and input impedance of a trumpet, with the bell both heavily damped and freely vibrating, are shown to be consistent with a theory that assumes that the internal pressure causes an oscillation of the diameter of the pipe enclosing the air column. These effects are shown to be most significant in sections where there are flaring walls, which explains why damping these vibrations in cylindrical pipes normally produces no measurable effects

BAMBI -A transient 2D-MESFET model with general boundary conditions including Schottky and current controlled contacts

Boundary conditions using a current-dependent carrier recombination velocity distribution are developed for modelling Schottky contacts by computer-aided physical simulation. In addition, a boundary condition in the form of an abitrary linear combination of voltage and current at the contact is presented. Thus MESFET devices with simple circuits connected to device terminals can be simulated by solving additional equations. As an example the switching behaviour of a MESFET with a drain resistor is investigated

Railway-induced ground vibrations – a review of vehicle effects

This paper is a review of the effect of vehicle characteristics on ground- and track borne-vibrations from railways. It combines traditional theory with modern thinking and uses a range of numerical analysis and experimental results to provide a broad analysis of the subject area. First, the effect of different train types on vibration propagation is investigated. Then, despite not being the focus of this work, numerical approaches to vibration propagation modelling within the track and soil are briefly touched upon. Next an in-depth discussion is presented related to the evolution of numerical models, with analysis of the suitability of various modelling approaches for analysing vehicle effects. The differences between quasi-static and dynamic characteristics are also discussed with insights into defects such as wheel/rail irregularities. Additionally, as an appendix, a modest database of train types are presented along with detailed information related to their physical attributes. It is hoped that this information may provide assistance to future researchers attempting to simulate railway vehicle vibrations. It is concluded that train type and the contact conditions at the wheel/rail interface can be influential in the generation of vibration. Therefore, where possible, when using numerical approach, the vehicle should be modelled in detail. Additionally, it was found that there are a wide variety of modelling approaches capable of simulating train types effects. If non-linear behaviour needs to be included in the model, then time domain simulations are preferable, however if the system can be assumed linear then frequency domain simulations are suitable due to their reduced computational demand

Motives and comprehension in a public goods game with induced emotions

This study analyses the sensitivity of public goods contributions through the lens of psychological motives. We report the results of a public goods experiment in which subjects were induced with the motives of care and anger through autobiographical recall. Subjects' preferences, beliefs, and perceptions under each motive are compared with those of subjects experiencing a neutral autobiographical recall control condition. We find, but only for those subjects with the highest comprehension of the game, that care elicits significantly higher contributions than anger, with the control treatment in between. This positive influence of the care motive on unconditional giving is accounted for partly by preferences for giving and partly by the beliefs concerning greater contributions by others. Anger also affects attention to own and other's payoffs (using mouse tracking) and perceptions of the game's incentive structure (cooperative or competitive)

Brass instruments as a cascade of two-port networks : Transfer functions, chain parameters, and power efficiency in theory and practice

This paper investigates how two-port network theory as a means for system identification can be applied to the analysis of brass instruments. A special focus is placed on the energy conversion efficiency as this is limited by inner damping, which receives much attention by expert players and makers of brasses. Theory suggests that a reconstruction of the 2 × 2 matrix representing the network requires input impedance and transfer function for two different boundary conditions. Besides the normal case of free sound radiation, instruments are also analyzed with the bell closed by a spherical cap. For this purpose, a customized 3D-printed spherical cap was fabricated and attached to the bell. Four measured spectra and the passivity condition over-determine the set of system equations. It is shown how to take advantage of this freedom when analyzing wind instruments. Measurements and simulations of a trumpet and a trombone are presented and compared

Proceedings of the first world conference on structural control [Book Review]

The subject of structural control deals with modifying the response of structures to undesirable motions that are produced by earthquake, wind or man-made forces. In the case of wind forces, the motions are usually of small amplitude caused by moderate gusts but are objectionable to the tenants of the upper floors. Various methods of control have been employed, including introducing damping, installing moveable masses on the upper floor, etc

ON-RESISTANCE IN THE ALDMOST

Recently a new lateral power MOSFET named accumulation lateral DMOS transistor (ALDMOST) has been proposed. We have investigated the dependence of the ON-resistance of this type of device on the oxide thickness and the additional semi-insulating layer along the surface of the gate oxide above the drift region. This layer has been introduced in order to lower the high ON-resistance which is in general a disadvantage of this type of MOS transistors

Elastic Wave Propagation in an Infinite Media

For most of the complicated geometries encountered in ultrasonic nondestructive evaluation (NDE) applications, finite element (FE) solutions [1–4] of the elastic wave equation are usually limited because of the spatial discretization required for accuracy. Artificial boundaries introduced to limit the spatial dimensions of a given problem can cause unwanted reflections which corrupt the desired response. The simplest approach to this problem is to ensure that the model is large enough for the unwanted reflections to be separated from the desired signal in the time domain. But this becomes very expensive for most applications, especially for full 3-D geometries. Models for infinite media, therefore, are very important for numerical modeling in 3-D and even in many 2-D practical applications