Field verification of lateral-torsional coupling effects on rotor instabilities in centrifugal compressors

Lateral and torsional vibration data obtained on a centrifugal compressor train which had shaft instabilities and gear failures is examined. The field data verifies that the stability of centrifugal compressors can be adversely affected by coincidence of torsional natural frequencies with lateral instability frequencies. The data also indicates that excitation energy from gear boxes can reduce stability margins if energy is transmitted either laterally or torsionally to the compressors. The lateral and torsional coupling mechanisms of shaft systems is discussed. The coupling mechanisms in a large industrial compressor train are documented and the potential effect on rotor stability is demonstrated. Guidelines are set forth to eliminate these potential problems by minimizing the interaction of torsional and lateral responses and their effect on rotor stability

Educational Provision for Newly Arrived Unaccompanied Sanctuary Seekers aged 15-16

Local Authorities in England are rarely able to find a school place for newly arrived unaccompanied sanctuary seekers when the young person arrives in their locality aged 15-16. Criticisms regarding this exclusionary practice are plentiful; that said, it has been argued the dominance of debate regarding access to mainstream education for pupils aged 15-16 obfuscates critical analysis of the educational needs of this group. Focussed on a bespoke Local Authority educational offer for fewer than twenty newly arrived unaccompanied sanctuary seekers aged 15-16, this paper analyses the essence of this offer in relation to social inclusion. Analysed in relation to the category, structure and level/function of the young people’s social inclusion, this paper draws on interview and focus group data to shine a light on the efficacious elements of the offer which point to ways forward for mainstream schools

Positioning children as artists through a ceramic arts project and exhibition: children meaning making

This article describes a ceramic arts research project that provided children with opportunities for meaning making using bone china clay, a medium with strong cultural and historical links to the city where the research took place. The children were positioned as artists and their work was curated and presented for exhibition by an international ceramic artist, affording equal status to their work as that of adults. Findings identified that children made meaning based on lived experiences, popular culture, unique family and cultural heritage, and school identities. We also acknowledge that adult attitudes and school schedules can both enable and limit children’s creativity. We further assert that the professional exhibition validated children’s processes, competence, cultural funds of knowledge and agency.The exhibition produced as a result of this research project was funded by the Vice Chancellors Ideas Forum from the University of Derby

Children as experiencers: increasing engagement, participation and inclusion for young children in the museum

This research aimed to evaluate young children’s engagement, participation and inclusion within a city museum by utilising observations and semi structured interviews with children and families. Both groups requested more interactive exhibits, sensory experiences, making and doing activities and role play opportunities. In this article, we argue for increased visibility of children’s ‘intangible heritage’(Brookshaw, 2016) and opportunities for responding which make links with children’s lives contemporarily. We further argue that museums should view children as experiencers rather than learners

Case Histories Of Specialized Turbomachinery Problems

PaperPg. 33-50.Vibration problems in turbomachinery occur due to many factors. Some of the problems could have been prevented if more detailed design analyses were performed. Other times the problems occur due to design extrapolations which are pushing the state of the art. The case histories of excessive vibrations and failures that will be discussed in this presentation are examples of those where additional design analyses would not necessarily have predicted or anticipated the problem that occurred because the analytical models are not sufficient to take into account all the variables

Remodeling of Wall Mechanics and the Myogenic Mechanism of Rat Intramural Coronary Arterioles in Response to a Short-Term Daily Exercise Program: Role of Endothelial Factors

PURPOSE: Exercise elicits early adaptation of coronary vessels enabling the coronary circulation to respond adequately to higher flow demands. We hypothesized that short-term daily exercise induces biomechanical and functional remodeling of the coronary resistance arteries related to pressure. METHODS: Male rats were subjected to a progressively increasing 4-week treadmill exercise program (over 60 min/day, 1 mph in the final step). In vitro pressure-diameter measurements were performed on coronary segments (119 +/- 5 mum in diameter at 50 mm Hg) with microarteriography. The magnitude of the myogenic response and contribution of endogenous nitric oxide and prostanoid production to the wall mechanics and pressure-diameter relationship were assessed. RESULTS: Arterioles isolated from exercised ani mals - compared to the sedentary group - had thicker walls, increased distensibility, and a decreased elastic modulus as a result of reduced wall stress in the low pressure range. The arterioles of exercised rats exhibited a more powerful myogenic response and less endogenous vasoconstrictor prostanoid modulation at higher pressures, while vasodilator nitric oxide modulation of diameter was augmented at low pressures (\u3c 60 mm Hg). CONCLUSIONS: A short-term daily exercise program induces remodeling of rat intramural coronary arterioles, likely resulting in a greater range of coronary autoregulatory function (constrictor and dilator reserves) and more effective protection against great changes in intraluminal pressure, contributing thereby to the optimization of coronary blood flow during exercise

Analysis Of Torsional Vibrations In Rotating Machinery.

Tutorialpg. 127-15

Transient Analyses Of Synchronous Motor Trains

LecturePg. 111-117.This paper discusses the philosophy of optimum location of torsional critical speeds which will be excited by the transient startup, as well as methods of adjusting the resonant frequencies. Pulsating torque, average torque, and acceleration rate during startup are considered in choosing the best frequency range for the resonances. Both steady-state and transient torsional excitation are discussed along with the applicable stress criterion. A method to determine the allowable number of startups is presented involving cumulative fatigue considerations which apply to the transient torsional stresses. The severity of backlash in gears and geared couplings is discussed and methods for calculating the response of the system to instantaneous negative torque are presented. The proper choice of couplings can change mode shapes, reduce backlash severity, and add damping which can reduce the detrimental effects to the torsional system. The proper specifications of couplings and gears in the design stage and the proper definition of service conditions greatly aid the gear and coupling manufacturers and can result in a system which will operate reliably, even under backlash conditions

Spreading depolarization remarkably exacerbates ischemia-induced tissue acidosis in the young and aged rat brain

Spreading depolarizations (SDs) occur spontaneously in the cerebral cortex of subarachnoid hemorrhage, stroke or traumatic brain injury patients. Accumulating evidence prove that SDs exacerbate focal ischemic injury by converting zones of the viable but non-functional ischemic penumbra to the core region beyond rescue. Yet the SD-related mechanisms to mediate neurodegeneration remain poorly understood. Here we show in the cerebral cortex of isoflurane-anesthetized, young and old laboratory rats, that SDs propagating under ischemic penumbra-like conditions decrease intra and- extracellular tissue pH transiently to levels, which have been recognized to cause tissue damage. Further, tissue pH after the passage of each spontaneous SD event remains acidic for over 10 minutes. Finally, the recovery from SD-related tissue acidosis is hampered further by age. We propose that accumulating acid load is an effective mechanism for SD to cause delayed cell death in the ischemic nervous tissue, particularly in the aged brain

Contribution of prostanoid signaling to the evolution of spreading depolarization and the associated cerebral blood flow response.

The significance of prostanoid signaling in neurovascular coupling during somatosensory stimulation is increasingly more appreciated, yet its involvement in mediating the cerebral blood flow (CBF) response to spreading depolarization (SD) has remained inconclusive. Selective cyclooxygenase (COX) enzyme inhibitors (NS-398, SC-560) or an antagonist (L161,982) of the EP4 type prostaglandin E2 receptor were applied topically to a cranial window over the parietal cortex of isoflurane-anesthetized Sprague-Dawley rats (n = 60). Global forebrain ischemia was induced by occlusion of both common carotid arteries in half of the animals. SDs were triggered by the topical application of 1M KCl. SD occurrence was confirmed by the acquisition of DC potential, and CBF variations were recorded by laser-Doppler flowmetry. EP4 receptor antagonism significantly decreased peak hyperemia and augmented post-SD oligemia in the intact but not in the ischemic cortex. COX-1 inhibition and EP4 receptor blockade markedly delayed repolarization after SD in the ischemic but not in the intact brain. COX-2 inhibition achieved no significant effect on any of the end points taken. The data suggest, that activation of EP4 receptors initiates vasodilation in response to SD in the intact brain, and - together with COX-1 derived prostanoids - shortens SD duration in the acute phase of ischemia