311,664 research outputs found
Design and fabrication of prototype system for early warning of impending bearing failure
A test program was conducted with the objective of developing a method and equipment for on-line monitoring of installed ball bearings to detect deterioration or impending failure of the bearings. The program was directed at the spin-axis bearings of a control moment gyro. The bearings were tested at speeds of 6000 and 8000 rpm, thrust loads from 50 to 1000 pounds, with a wide range of lubrication conditions, with and without a simulated fatigue spall implanted in the inner race ball track. It was concluded that a bearing monitor system based on detection and analysis of modulations of a fault indicating bearing resonance frequency can provide a low threshold of sensitivity
Frontiers of parasitology research in the People's Republic of China : infection, diagnosis, protection and surveillance
ABSTRACT: Control and eventual elimination of human parasitic diseases in the People's Republic of China (P.R. China) requires novel approaches, particularly in the areas of diagnostics, mathematical modelling, monitoring, evaluation, surveillance and public health response. A comprehensive effort, involving the collaboration of 188 scientists (<85% from P.R. China) from 48 different institutions and universities (80% from P.R. China), covers this collection of 29 articles published in Parasites & Vectors. The research mainly stems from a research project entitled 'Surveillance and diagnostic tools for major parasitic diseases in P.R. China' (grant no. 2008ZX10004-011) and highlights the frontiers of research in parasitology. The majority of articles in this thematic series deals with the most important parasitic diseases in P.R. China, emphasizing Schistosoma japonicum, Plasmodium vivax and Clonorchis sinensis plus some parasites of emerging importance such as Angiostrongylus cantonensis. Significant achievements have been made through the collaborative research programme in the following three fields: (i) development of control strategies for the national control programme; (ii) updating the surveillance data of parasitic infections both in human and animals; and (iii) improvement of existing, and development of novel, diagnostic tools to detect parasitic infections. The progress is considerable and warrants broad validation efforts. Combined with the development of improved tools for diagnosis and surveillance, integrated and multi-pronged control strategies now pave the way for elimination of parasitic diseases in P.R. China. Experiences and lessons learned can stimulate control and elimination efforts of parasitic diseases in other parts of the world
Systematic study of the symmetry energy coefficient in finite nuclei
The symmetry energy coefficients in finite nuclei have been studied
systematically with a covariant density functional theory (DFT) and compared
with the values calculated using several available mass tables. Due to the
contamination of shell effect, the nuclear symmetry energy coefficients
extracted from the binding energies have large fluctuations around the nuclei
with double magic numbers. The size of this contamination is shown to be
smaller for the nuclei with larger isospin value. After subtracting the shell
effect with the Strutinsky method, the obtained nuclear symmetry energy
coefficients with different isospin values are shown to decrease smoothly with
the mass number and are subsequently fitted to the relation . The resultant volume and
surface coefficients from axially deformed covariant DFT calculations are
and MeV respectively. The ratio is in good
agreement with the value derived from the previous calculations with the
non-relativistic Skyrme energy functionals. The coefficients and
corresponding to several available mass tables are also extracted. It is shown
that there is a strong linear correlation between the volume and surface
coefficients and the ratios are in between for all
the cases.Comment: 16 pages, 6 figure
Microdosimetry of diagnostic X-rays: applications of the variance-covariance method.
Microdosimetric measurements in beams of diagnostic X rays (between 30 and 125 kV) have been performed. In these pulsed radiation fields, microdosimetric measurements are possible only by application of the variance-covariance technique. The dose mean lineal energy, yD, is determined for various simulated diameters, at different depths in the absorber, and at different points within the pulse intervals. From the measured temporal dependences one can also obtain values of yD for different X-ray pulse generators. The results demonstrate the potential of the variance-covariance method for a diversity of microdosimetric measurements in radiation protection and in the quality control of radiation beams
Criteria of applicability for autoradiography of tritium
Autoradiography is an effective tool for the imaging of radionuclide distributions in various samples. In sophisticated applications with special preparation and development of sample-emulsion combinations and subsequent grain counts it can be highly quantitative, but it requires carefully controlled conditions and a variety of counter-checks, for example through scintillation spectroscopy. Less refined applications use X-ray films as detectors, and their seeming simplicity tends to invite artefacts and misinterpretations. Particular care needs to be taken, if one deals, or presumes to deal, with the low-energy ß-emitter tritium. Because of the short electron ranges the film must be in intimate contact with the sample, which tends to produce chemographic artefacts; without added spectroscopic measurements it is impossible to discriminate the spurious signals from a blackening of the film due to tritium. Recent statements concerning autoradiographic tritium measurements in tree samples have created considerable public concern and have demonstrated the pitfalls of uncritical use. This paper presents order-of-magnitude criteria for the detection threshold in the autoradiography of tritium; they can serve as an exclusion principle for some of the more extravagant misinterpretations.
Dedication to Prof. Wolfgang Jacobi on the occasion of his 65th birthda
The STAR MAPS-based PiXeL detector
The PiXeL detector (PXL) for the Heavy Flavor Tracker (HFT) of the STAR
experiment at RHIC is the first application of the state-of-the-art thin
Monolithic Active Pixel Sensors (MAPS) technology in a collider environment.
Custom built pixel sensors, their readout electronics and the detector
mechanical structure are described in detail. Selected detector design aspects
and production steps are presented. The detector operations during the three
years of data taking (2014-2016) and the overall performance exceeding the
design specifications are discussed in the conclusive sections of this paper
Charge Modulations in the Superconducting State of the Cuprates
Motivated by the recent scanning tunneling microscopy (STM) and neutron
scattering experiments, we investigate various charge density wave orders
coexisting with superconductivity in the cuprate superconductors. The explicit
expressions of the local density of states and its Fourier component at the
ordering wavevector for the weak charge modulations are derived. It is shown
that the STM experiments in cannot be explained by
a site- or bond-centered charge modulation alone, but agree well with the
presence of the dimerization hopping and transverse pairing modulations. We
also calculate the spectral function for the charged stripes, which is measured
by the ARPES experiments.Comment: 3 pages with 4 figures. To be published in PR
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