75 research outputs found
Reply to the letter to the editor 'Can ovarian suppression with gonadotropin releasing hormone analogs (GnRHa) preserve fertility in cancer patients?' by Rodriguez-Wallberg et al.
No full textModeling the lifetime reduction due to the superposition of TMF and HCF loadings in cast iron alloys
No full textAbstractThe superposition of small amplitude, high frequency loading cycles (HCF) to slow, large amplitude loading cycles (TMF) can significantly reduce the fatigue life. In this work, the combined TMF+HCF loading has been experimentally investigated for a cast iron alloy. In particular, the influence of the HCF frequency of the HCF amplitude and of the location of the superposed HCF cycles has been assessed. It was observed that the HCF frequency has a limited impact on the TMF fatigue life. On the other side, the HCF-strain amplitude has a highly non-linear influence on the TMF fatigue life. A simple estimate for the fatigue life reduction due to the superposed HCF cycles has been derived from fracture mechanics considerations. It is assumed that the number of propagation cycles up to failure can be neglected after a threshold for the HCF loading has been reached. The model contains only two adjustable parameters and can be combined with any TMF life prediction model. The model predictions are compared with the test results for a large range of TMF+HCF loading conditions
Generalization of the Weibull probabilistic compatible model to assess fatigue data into three domains: LCF, HCF and VHCF
No full textIn this work, three classes of fatigue models are reviewed according to the fatigue regimes commonly considered in the current components design. Particular attention is devoted to the so-called Class III fatigue models, covering the three fatigue regimes, namely, LCF, HCF and VHCF. The applicability and limitations of the proposed analytical sigmoidal solutions are discussed from the viewpoint of practical design. The compatible Weibull S-N model by Castillo and Canteli is revisited and improved by considering a new reference parameter GP = E·σM ·(dε/dσ)|M as the driving force alternative to the conventional stress range. In this way, the requirement, σM ≤ σu, according to the real experimental conditions, is fulfilled and the parametric limit number of cycles, N0, recovers its meaning. The probabilistic definition of the model on the HCF and VHCF regimes is maintained and extended to the LCF regime. The strain gradients may be calculated from the monotonic or cyclic stress–strain curve of the material although a direct derivation from the hysteresis loop is recommended. Some Class III fatigue models from the literature and another one improved by the authors are applied to the assessment of one experimental campaign under different stress ratios conditions and the results compared accordingly. Finally, the new probabilistic GP-N field is evaluated. The results confirm the practical confluence of the stress- and the strain-based approaches into a single and advantageous unified methodology.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Steel & Composite Structure
Capacitance Tip Timing Techniques in Gas Turbines
No full textThe vibration of turbomachinery blades is an important phenomenon to understand, observe and predict
and is the reason for developing a tip timing measurement system. Vibration leads to High Cycle Fatigue
(HCF), which limits blade durability and life. HCF can result in blade failure, having expensive
consequences for the engine involved. The traditional method for monitoring blade vibration under test
conditions is to use blade mounted strain gauges. However, strain gauges are costly and time consuming
to install. They have a limited operating life as they are subjected to the harsh on-engine conditions. Only
a limited number of blades can be monitored with strain gauges as the number that can be used is limited
by the number of channels in the slip ring or telemetry. They can also interfere with the assembly
aerodynamics. Consequently non-intrusive alternative techniques such as tip timing are sought.
Capacitance probe based clearance measurement systems see widespread use in turbomachinery
applications to establish rotor blade tip clearance. This thesis reports investigations into an alternative
and additional use in aero-engine rotor blade tip timing measurement for these commercially available
systems. Tip clearance is of great importance in the gas turbine industry; this is clear from the fact that
gas turbine efficiency has an inverse relationship with tip clearance. Large tip clearance leads to large
leakage flows, hence low efficiency, thus the common use of the capacitance probe clearance
measurement technique in monitoring turbomachinery.
Optical systems have been successfully used to measure rotor blade tip timing on test rigs with several
optical probes mounted equally spaced around the turbomachine casing. However, there are practical
problems associated with mounting such monitoring systems on in-service jet engines. Optical probes
require high maintenance to keep the lenses clean, probably incorporating a purge air system to keep the
lenses from fouling. Such impracticalities and added weight make it unlikely that an optical probe based
tip timing system will be fitted on an in-service engine in the foreseeable future.
In this thesis the scope for a dual use sensor to measure both turbomachinery tip clearance and tip timing
is investigated. Since it is impractical to measure blade tip clearance with an optical probe, then the
obvious choice for such a sensor is a capacitance probe. Therefore, a commercially available FM
capacitance probe based blade tip clearance measurement system is used in a series of tip timing practical
investigations. The equipment and instrumentation designed, assembled and produced to facilitate this
investigation is documented. These include the development of an optical once per revolution sensor and
the design of an independent vibration measurement system based on blade mounted strain gauges.
Through an extensive body of experimental work the practicalities in this alternate use of the tip
clearance measurement equipment have been assessed. System responses pertaining to tip timing
measurement have been investigated, characterised and quantified. The accuracy by which tip timing can
be measured using the system has been reported through the findings of an experimental programme
carried out on a full-sized, low-speed compressor.
Specifically, dual capacitance probe tip timing derived vibration amplitudes have been compared to
those derived from blade mounted strain gauge signals. Sources of error have been identified and
quantified. Amplitudes were found to agree within the calculated error bands. Instantaneous resonant
blade vibrations measured through single capacitance probe tip timing have been correlated with strain
gauge derived vibration levels. This has also been done as the rotor traverses blade resonant speed. In
this case the vibration phase change across resonance expected from theory was successfully detected
through tip timing. Also, the accuracy by which blade time of arrival can be determined by using
capacitance probe tip timing has been assessed using a precision OPR sensor and a non-vibrating
compressor rotor blade. The characteristics of a DC capacitance probe based clearance measurement
system's response to movement in 3D space in proximity to a blade tip have been mapped. Detection of
small vibrations have also been investigated in a series of static impulse tests
Debated role of ovarian protection with gonadotropin-releasing hormone agonists during chemotherapy for preservation of ovarian function and fertility in women with cancer
No full textSCOPUS: le.jinfo:eu-repo/semantics/publishe
Public hospital costs and quality in the Dominican Republic
No full textMeasuring costs in public hospitals in developing countries is hampered by the lack of an appropriate costing system, or of any systematic cost accounting. Invoices for goods and services, prices for inputs, and patient records are generally absent. As a result, cost measures have historically been based on budget figures - the only available financial data. But budget allocations bear little relationship to the resources actually required to provide services to hospital patients. The patient-based methodology described by the authors circumvents this problem by measuring actual hospital resources allocated to patients. Their study was conducted in a single Dominican hospital during a one week period in April 1989. Their approach documents and gives prices for goods, services, and personnel time provided by the hospital to emergency patients, inpatients, and outpatients. They used the following to measure quality and efficiency: (a) the qualifications and relative costs of medical manpower delivering services; (b) the extent and nature of shortages; (c) comparisons of physician orders and actual services provided; and (d) (for selected diagnoses) the specifics of clinical practices in the hospital, compared with accepted clinical norms for the Dominican Republic. They found that average and total costs of services understate the true costs - because of shortages, inappropriate and underused personnel, and nonfunctioning equipment. Quality of care measures suggest low quality and poor efficiency. Norms of medical practice were not followed in more than 80 percent of the cases examined. Rates of completion for diagnostic tests were below 50 percent for outpatient services and between 60 and 70 percent for inpatient and emergency services. The study registered significant monthly savings of 824 for nonavailability of drugs. Policy recommendations of the authors center on the need to reform the organization and delivery of health care as well as physician payment practices - and to giving more authority to hospital administrators. To make Dominican hospitals more efficient, there must be greater authority and accountability for hospital directors and better incentives for improving medical and management performance. Quality assurance needs great improvement if the Dominican system is to ensure a basic standard of care.Health Monitoring&Evaluation,Health Systems Development&Reform,Business Environment,Business in Development,Health Economics&Finance
MULTIPHOTON SPECTROSCOPY OF SINGLET CARBENES: HCF AND DCF
No full textAuthor Institution: Chemical Kinetics and Thermodynamics Division, National Institute of Standards and TechnologyThe 2+1 resonance-enhanced multiphoton ionization (REMPI) spectrum of fluorocarbene has been observed. Singlet HCF is generated by sequential reactions of atomic fluorine in either methane or methyl fluoride. Both (bend) and (C-F stretch) are active in the Rydberg transition, as expected from ab initio calculations. Observed rotational structure is also in accord with the calculations. Preliminary constants for the upper state are as follow:[FIGURE] In addition, the adiabatic ionization potential has been calculated to be 10.04 eV
A Novel Method for Uniaxial HCF Testing of Austenitic Stainless Steels
No full textAbstractFatigue endurance testing of nuclear plant materials is typically carried out using uniaxial specimens tested under strain control using a triangular waveform and a defined strain rate. This leads to long test durations and high testing costs when testing in the High Cycle Fatigue (HCF) regime, meaning few results for fatigue lives above 106 cycles are available. A novel test method is proposed here, in which the traditional strain-controlled test method is used until 105 cycles have elapsed, before testing is switched to load control at a higher frequency. Testing of a Type 304LN austenitic stainless steel in room temperature air was performed at an R ratio of -1, strain rate of 0.4%/s and strain amplitude of 0.18%. The results show no statistically significant difference between the HCF lives gained from the traditional and new test methods. The proposed new fatigue endurance test method is considered to be validated for use in the testing of nuclear grades of unstabilised austenitic stainless steel in air at room temperature
Croton sanctae-crucis Moore 1895
No full text30. Croton sanctae-crucis Moore (1895: 455). Type: — BRAZIL. “Santa Cruz”, s.d., S. Moore 567 (holotype BM 000947402!; isotypes E 00164718!, P 00634706!, K 000254426!, R 000100773!, NY 00262949!). (Fig. 15, E–I) This shrub can be recognized by its leaves with basilaminar nectary glands, and delicate inflorescences with sessile staminate and pistillate flowers. As observed by Caruzo (2006), the analyzed collections presented only unisexual basal cymules, differing from the description of Moore (1895). Croton sanctae-crucis shows similarities with C. polygonoides, but they can be differentiated by vegetative and reproductive characteristics (see comments under C. polygonoides). The species belongs to section Adenophylli. Based on morphology, this species likely belongs to subsect. Pungentes. Distribution and habitat:— Caruzo et al. (2020) reported the species for the Brazilian midwest (DF, GO, MS) and southeastern region (SP). We extend the distribution range with the first record for Paraná (PR) state. Croton sanctae-crucis grows in ‘cerrado’ vegetation, between 510 and 525 m elevation. (Fig. 16). Phenology:— Flowering and fruiting from October and November. Representative specimens:— PARANÁ: Tuneiras do Oeste, Cerrado alterado, 27 November 2012, M. G . Caxambu & F. F. Sanches 4492 (HCF); acesso pela BR-487, 23°54’39.18”S, 52°45’17.15”W, 524 m, 19 October 2016, A. P. N . Pereira, F. S. Petrongari & O. L. M . Silva 35 (SP).Published as part of Pereira, Amanda Da Paixão Noronha, Riina, Ricarda & Caruzo, Maria Beatriz Rossi, 2022, Croton (Euphorbiaceae) of the Brazilian state of Paraná: an annotated checklist, species distribution, and identification key, pp. 231-274 in Phytotaxa 570 (3) on page 257, DOI: 10.11646/phytotaxa.570.3.1, http://zenodo.org/record/726027
ROTATIONAL PERTURBATION AND ZEEMAN EFFECT IN THE TRANSITION OF HCF
No full textA. J. Merer and D. N. Travis, J. Mol. Spectrosc. 44, 1541 (1966).Author Institution: Institute for Molecular ScienceMerer and Travis reported that the vibronic transition of HCF was remarkably In view of the importance of carbene derivatives in various fields, we investigated this HCF band by cw dye laser spectroscopy with the Doppler-limited resolution. Furthermore, we studied the perturbed lines of the band under the magnetic field up to 2.3 T. HCF was produced by the reaction of microwave discharged with . The subbands of and were assigned using ground state combination differences. Every subband was found to be perturbed to some decree. The perturbations observed in this band were very irregular except the low J transitions with . The perturbations for the levels were well explained by an electronic Coriolis interaction with a highly excited vibrational level in the electronic ground state, The irregularly perturbed lines often showed considerably large magnetic activity. Therefore the origin of some of these perturbations has been believed to be the lowest triplet state
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