Pulsations In Liquid Pumps And Piping Systems

PaperPg. 55-62.The existence of high intensity, low frequency pulsation problems in centrifugal compressor and pump piping systems has now been well documented throughout industry. Strong pulsations have been observed at frequencies ranging from two to several hundred Hz which typically are not harmonically related to (and do not vary with) pump rotor speed. Investigation has revealed that in most cases, the problem is not caused simply by pump or compressor characteristics, but instead is the result of dynamic interaction of the passive response of the piping, the head curve characteristics of the pump, dynamic flow damping, and location of the pump in the piping geometry. Since pulsation problems are usually vibration fatigue problems of the piping or machine internals, problems can often be mitigated by effective vibration control. A more fundamental and often more economical approach, however, lies in controlling the pulsation levels and frequencies, either by controlling the generation sources or pulsation response of the piping. Unfortunately, these two phenomena cannot be effectively separated, and the problem must be solved with a more comprehensive system dynamic analysis. It has been shown, for example, that relative low level vortex formation at piping discontinuities can be amplified by the pump or compressor, but such amplification must be at one of the responsive acoustic length resonant modes of the piping system, and then only if the pump or compressor is situated at or near a velocity maximum in the standing wave field. Additionally, however, the compressor itself may influence the acoustic response (distributed impedance) of the piping as well as serve as an amplifying element. Flow or pressure drop is also an important factor in sustaining such pulsations as it affects modal damping. Techniques have now been developed whereby many of the phenomena associated with low frequency pulsations in centrifugal pump and compressor systems can be effectively simulated either for design or problem solving. The paper will briefly describe the phenomena associated with low frequency pump pulsations and will illustrate use of the technology in several case histories

Extending the International Space Station Life and Operability

The International Space Station (ISS) is in an operational configuration with final assembly complete. To fully utilize ISS and extend the operational life, it became necessary to upgrade and extend the onboard systems with the Obsolescence Driven Avionics Redesign (ODAR) project. ODAR enabled a joint project between the Johnson Space Center (JSC) and Marshall Space Flight Center (MSFC) focused on upgrading the onboard payload and Ku-Band systems, expanding the voice and video capabilities, and including more modern protocols allowing unprecedented access for payload investigators to their on-orbit payloads. The MSFC Huntsville Operations Support Center (HOSC) was tasked with developing a high-rate enhanced Functionally Distributed Processor (eFDP) to handle 300Mbps Return Link data, double the legacy rate, and incorporate a Line Outage Recorder (LOR). The eFDP also provides a 25Mbps uplink transmission rate with a Space Link Extension (SLE) interface. HOSC also updated the Payload Data Services System (PDSS) to incorporate the latest Consultative Committee for Space Data Systems (CCSDS) protocols, most notably the use of the Internet Protocol (IP) Encapsulation, in addition to the legacy capabilities. The Central Command Processor was also updated to interact with the new onboard and ground capabilities of Mission Control Center -- Houston (MCC-H) for the uplink functionality. The architecture, implementation, and lessons learned, including integration and incorporation of Commercial Off The Shelf (COTS) hardware and software into the operational mission of the ISS, is described herein. The applicability of this new technology provides new benefits to ISS payload users and ensures better utilization of the ISS by the science communit

A review of elliptical and disc galaxy structure, and modern scaling laws

A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their models to describe the radial distribution of stars in `nebulae'. This article reviews the progress since then, providing both an historical perspective and a contemporary review of the stellar structure of bulges, discs and elliptical galaxies. The quantification of galaxy nuclei, such as central mass deficits and excess nuclear light, plus the structure of dark matter halos and cD galaxy envelopes, are discussed. Issues pertaining to spiral galaxies including dust, bulge-to-disc ratios, bulgeless galaxies, bars and the identification of pseudobulges are also reviewed. An array of modern scaling relations involving sizes, luminosities, surface brightnesses and stellar concentrations are presented, many of which are shown to be curved. These 'redshift zero' relations not only quantify the behavior and nature of galaxies in the Universe today, but are the modern benchmark for evolutionary studies of galaxies, whether based on observations, N-body-simulations or semi-analytical modelling. For example, it is shown that some of the recently discovered compact elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies.Comment: Condensed version (due to Contract) of an invited review article to appear in "Planets, Stars and Stellar Systems"(www.springer.com/astronomy/book/978-90-481-8818-5). 500+ references incl. many somewhat forgotten, pioneer papers. Original submission to Springer: 07-June-201

Nearby early-type galaxies with ionized gas. IV. Origin and powering mechanism of the ionized gas

Aims. A significant fraction of early-type galaxies (ETGs) exhibit emission lines in their optical spectra. We attempt to identify the producing the emission mechanism and the ionized gas in ETGs, and its connection with the host galaxy evolution. Methods. We analyzed intermediate-resolution optical spectra of 65 ETGs, mostly located in low density environments and exhibiting spectros-copic diagnostic lines of ISM from which we had previously derived stellar population properties. To extract the emission lines from the galaxy spectra, we developed a new fitting procedure that accurately subtracts the underlying stellar continuum, and accounts for the uncertainties caused by the age-metallicity degeneracy. Results. Optical emission lines are detected in 89% of the sample. The incidence and strength of emission correlate with neither the E/S0 classification, nor the fast/slow rotator classification. By means of the classical [OIII]/H\u3b2 versus [NII]/H\u3b1 diagnostic diagram, the nuclear galaxy activity is classified such that 72% of the galaxies with emission are LINERs, 9% are Seyferts, 12% are composite/transition objects, and 7% are non-classified. Seyferts have young luminostiy-weighted ages ( 725 Gyr), and appear, on average, significantly younger than LINERs and composites. Excluding the Seyferts from our sample, we find that the spread in the ([OIII], H\u3b1, or [NII]) emission strength increases with the galaxy central velocity dispersion . Furthermore, the [NII]/H\u3b1 ratio tends to increase with . The [NII]/H\u3b1 ratio decreases with increasing galactocentric distance, indicative of either a decrease in the nebular metallicity, or a progressive \u201csoftening\u201d of the ionizing spectrum. The average nebular oxygen abundance is slightly less than solar, and a comparison with the results obtained in Paper III from Lick indices shows that it is 480.2 dex lower than that of stars. Conclusions. The nuclear (r &lt; re/16) emission can be attributed to photoionization by PAGB stars alone only for 4822% of the LINER/composite sample. On the other hand, we cannot exclude an important role of PAGB star photoionization at larger radii. For the major fraction of the sample, the nuclear emission is consistent with excitation caused by either a low-accretion rate AGN or fast shocks (200\u2013500 km\u2009s-1) in a relatively gas poor environment ( cm-3), or both. The derived [SII]6717/6731 ratios are consistent with the low gas densities required by the shock models. The derived nebular metallicities are indicative of either an external origin of the gas, or an overestimate of the oxygen yields by SN models

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Surge Model: Predicting Damping and Excitation Frequencies of Complex Pumping Systems

ABSTRACT Frequency domain analysis is presented to define susceptibility of complex pumping systems to surge oscillations. In the analysis, piping spans are considered as distributed elements, compressors or pumps, orifices, valves, and junctions as lumped acoustic four pole elements. The piping elements are connected into one network through the use of appropriate matching boundary conditions. The analysis is most readily applicable to single stage units, typical of gas transmission stations. The surge model is based on predicting damping (logarithmic decrement values) and mode shapes for pressure and flow pulsations of the interactive dynamic system at its various natural acoustic frequencies. The system design is optimized by assuring that all operating points are sufficiently removed from surge, i.e., logarithmic decrements are above certain specified value. The effects of mean flow on acoustic wave propagation, pipe friction, viscothermal dissipation, and pressure losses at various piping locations (junctions, valves, orifices) are accounted for in the model. Results of the computational modeling of a complex centrifugal compressor system is presented. The analytical model is also verified by comparing the analytical results with experimental data

A TECHNOLOGY ASSESSMENT AND FEASIBILITY EVALUATION OF NATURAL GAS ENERGY FLOW MEASUREMENT ALTERNATIVES

Deregulation and open access in the natural gas pipeline industry has changed the gas business environment towards greater reliance on local energy flow rate measurement. What was once a large, stable, and well-defined source of natural gas is now a composite from many small suppliers with greatly varying gas compositions. Unfortunately, the traditional approach to energy flow measurement [using a gas chromatograph (GC) for composition assay in conjunction with a flow meter] is only cost effective for large capacity supplies (typically greater than 1 to 30 million scfd). A less costly approach will encourage more widespread use of energy measurement technology. In turn, the US will benefit from tighter gas inventory control, more efficient pipeline and industrial plant operations, and ultimately lower costs to the consumer. An assessment of the state and direction of technology for natural gas energy flow rate measurement is presented. The alternative technologies were ranked according to their potential to dramatically reduce capital and operating and maintenance (O and M) costs, while improving reliability and accuracy. The top-ranked technologies take an unconventional inference approach to the energy measurement problem. Because of that approach, they will not satisfy the fundamental need for composition assay, but have great potential to reduce industry reliance on the GC. Technological feasibility of the inference approach was demonstrated through the successful development of data correlations that relate energy measurement properties (molecular weight, mass-based heating value, standard density, molar ideal gross heating value, standard volumetric heating value, density, and volume-based heating value) to three inferential properties: standard sound speed, carbon dioxide concentration, and nitrogen concentration (temperature and pressure are also required for the last two). The key advantage of this approach is that inexpensive on-line sensors may be used to measure the inferential variables, which can then be applied (through the data correlations) to convert existing flow meters (ultrasonic, orifice, turbine, rotary, Coriolis, diaphragm, etc.) for on-line energy measurement. The practical issues for field development were evaluated using two transducers extracted from a $100 ultrasonic domestic gas meter, and a$400 infrared sensor

Supermassive black holes in the Sbc spiral galaxies NGC 3310, NGC 43-3 and NGC 4258

Original article can be found at:http://www.aanda.org/--Copyright The European Southern Observatory DOI : 10.1051/0004-6361:20066784Peer reviewe

Cardiovascular Efficacy and Safety of Bococizumab in High-Risk Patients

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