Bounds for the greatest characteristic root of an irreducible nonnegative matrix

AbstractA new lower bound for the Perron root for irreducible, non-negative matrices is obtained which is, in particular, a better bound than the Frobenius bound [w = max(akk)] if all the main diagonal elements are zero

Space station structures and dynamics test program

The design, construction, and operation of a low-Earth orbit space station poses challenges for development and implementation of technology. One specific challenge is the development of a dynamics test program for defining the space station design requirements, and identifying and characterizing phenomena affecting the space station's design and development. The test proposal, as outlined, is a comprehensive structural dynamics program to be launched in support of the space station (SS). Development of a parametric data base and verification of the mathematical models and analytical analysis tools necessary for engineering support of the station's design, construction, and operation provide the impetus for the dynamics test program. The four test phases planned are discussed: testing of SS applicable structural concepts; testing of SS prototypes; testing of actual SS structural hardware; and on-orbit testing of SS construction

Brain neurons as quantum computers: {\it in vivo} support of background physics

The question: whether quantum coherent states can sustain decoherence, heating and dissipation over time scales comparable to the dynamical timescales of the brain neurons, is actively discussed in the last years. Positive answer on this question is crucial, in particular, for consideration of brain neurons as quantum computers. This discussion was mainly based on theoretical arguments. In present paper nonlinear statistical properties of the Ventral Tegmental Area (VTA) of genetically depressive limbic brain are studied {\it in vivo} on the Flinders Sensitive Line of rats (FSL). VTA plays a key role in generation of pleasure and in development of psychological drug addiction. We found that the FSL VTA (dopaminergic) neuron signals exhibit multifractal properties for interspike frequencies on the scales where healthy VTA dopaminergic neurons exhibit bursting activity. For high moments the observed multifractal (generalized dimensions) spectrum coincides with the generalized dimensions spectrum calculated for a spectral measure of a {\it quantum} system (so-called kicked Harper model, actively used as a model of quantum chaos). This observation can be considered as a first experimental ({\it in vivo}) indication in the favour of the quantum (at least partially) nature of the brain neurons activity

Tip timing techniques for turbomachinery HCF condition monitoring

High Cycle Fatigue (HCF) has been established as the major common failure mode in the US Air Force large fleet of aero-engines. Corrective measures for this failure mode in themselves deliver additional technical, managerial and cost pressures. Two responses are in place to address this problem; risk mitigation through accelerated engine development fixes and technology transition through targeted and focussed R&D studies. It is the latter that is of interests and is discussed in this paper. Aero-engine blade vibrations of sufficient amplitude cause High Cycle Fatigue, which reduces blade life. In order to observe this vibration a non-intrusive monitoring system is sought. The vibration can be detected by measuring blade tip timing since in the presence of vibration the blade timing will differ slightly from the passing time calculated from rotor speed. Work done to investigate the suitability of a commercially available capacitance probe tip clearance measurement system for application as a non-intrusive turbomachinery blade tip timing measurement device is reported. Capacitance probe results are correlated with simultaneously measure strain gauge results and the performance of the capacitance system in measuring blade vibration is analysed. The growing interest in blade high cycle fatigue within the aerospace industry, and an approach to monitoring their condition are discussed as an extension to the above study. The suggested approach is based upon the tip-timing method, using non-contact optical probes located around the engine’s casing. Two current tip-timing techniques are suggested for the purpose. The techniques are summarised, the experimental validation of both methods outlined, and the approach taken to investigate the potential use as a condition monitoring tool described. The paper is concluded with a discussion of the future use of tiptiming as a condition monitoring tool

Syntactic development in the oral and written language of profoundly deaf adolescents

This paper reviews a study to investigate oral and written syntactic development of profoundly deaf adolescents

The Measurement of Turbomachinery Blade Vibration Through Tip Timing With Capacitance Tip Clearance Probes

ABSTRACT Turbomachinery blade vibrations can cause High Cycle Fatigue, which reduces blade life. In order to observe this vibration a non-intrusive monitoring system is sought. The vibration can be detected by measuring blade tip timing since in the presence of vibration the blade timing will differ slightly from the passing time calculated from rotor speed. Much research and development has gone into investigating the ability of optical probes to achieve this. However, this paper looks at the potential for a dual use capacitance probe sensor to measure both tip timing and tip clearance. This paper provides new insights into the ability of a commercially available capacitance probe tip clearance measurement system for application as a non-intrusive turbomachinery blade tip timing measurement device. This is done by correlating capacitance probe tip timing results with simultaneously measured blade-mounted strain gauge vibration results and precise rotational speeds. Thus the characterisation of the performance of the capacitance probe system when measuring blade vibration on a full-sized lowspeed research compressor is analysed and reported

Experimental testing of tip-timing methods used for blade vibration measurement in the aero-engine

An important component within the jet engine in terms of vibration and high cycle fatigue (HCF) is the blade. This is the component where continuously higher demands on weight and loading are being made. As a consequence of this, there has been a growing interest in developing both numerical methods and instrument technology for blade HCF measurement. This growing interest has also been attributed to changing attitude within the military and aerospace industry, which has tended towards driving down costs and lengthening the engine's life span. Many development technologies have been reported. One of which, is the development of a non-intrusive system for measuring blade vibratory stress. Research in non-intrusive techniques for the measurement of blade vibration has been ongoing since the early 1970' s. The aim of which, has been to replace the conventional method, using strain gauges and slip rings, with an improved system based upon non-intrusive type instrumentation such as optical or capacitance probes. One such approach is known as tip-timing. Tip-timing is a technique used to measure blade vibration using non-contact probes located around the engine casing. Many tip-timing techniques have been developed over the years, but there still remain significant problems associated with the approach. Such problems include sensitivity to noise and the high number of probes required. The development of two tip-timing methods known as the Autoregressive (AR) method and the Two Parameter Plot (2PP) method has recently been published in the open literature. This thesis describes the work done to experimentally test these two techniques. During the course of this work, an experimental optical tip-timing test facility was built. This included purpose-built optical tip-timing instrumentation, a tip-timing data acquisition system, and a post processing system incorporated into the Cranfield University low speed compressor facility. Experimental testing of the Autoregressive method and the Two Parameter Plot method was carried out using a controlled test environment, representative of a real engine. An analysis of the two methods was conducted using data from a comprehensive range of frequencies and RPM speeds. The results were then compared with previously published numerical results and the two algorithms were evaluated in terms of replacing the conventional strain gauge method. Testing of the AR method presented some interesting findings, with acceptable results produced at low rotational RPM speeds. However, as the rotational speed was increased, the accuracy of the results deteriorated. This type of result had not be highlighted in previous work. The 2PP method performed relatively well when using data sampled from the smaller 16 Engine Order (EO) response. However, this was not repeated when using the larger 72EO data. Additionally, this type of result had not been shown in previously published work. Overall, it was concluded that the issues associated with the frequency measurements should be remedied and a technique for measuring Multiple-Degree-of-Freedom responses should be explored before tip-timing techniques can be considered as a replacement to the strain gauge approach.EThOS - Electronic Theses Online ServiceGBUnited Kingdo