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1

THE THEORY OF URANIUM ENRICHMENT BY THE GAS CENTRIFUGE  

SciTech Connect

Onsager's analysis of the hydrodynamics of fluid circulation in the boundary layer on the rotor wall of a gas centrifuge is reviewed. The description of the flow in the boundary layers on the top and bottom end caps due to Carrier and Maslen is summarized. The method developed by Wood and Morton of coupling the flow models in the rotor wall and end cap boundary layers to complete the hydrodynamic analysis of the centrifuge is presented. Mechanical and thermal methods of driving the internal gas circulation are described. The isotope enrichment which results from the superposition of the elementary separation effect due to the centrifugal field in the gas and its internal circulation is analyzed by the Onsager-Cohen theory. The performance function representing the optimized separative power of a centrifuge as a function of throughput and cut is calculated for several simplified internal flow models. The use of asymmetric ideal cascades to exploit the distinctive features of centrifuge performance functions is illustrated.

Olander, Donald R.

1981-03-01

2

THE THEORY OF URANIUM ENRICHMENT BY THE GAS CENTRIFUGE  

Microsoft Academic Search

Onsager's analysis of the hydrodynamics of fluid circulation in the boundary layer on the rotor wall of a gas centrifuge is reviewed. The description of the flow in the boundary layers on the top and bottom end caps due to Carrier and Maslen is summarized. The method developed by Wood and Morton of coupling the flow models in the rotor

D OLANDER; Donald R

1981-01-01

3

Valve for gas centrifuges  

DOEpatents

The invention is pneumatically operated valve assembly for simulatenously (1) closing gas-transfer lines connected to a gas centrifuge or the like and (2) establishing a recycle path between two on the lines so closed. The value assembly is especially designed to be compact, fast-acting, reliable, and comparatively inexpensive. It provides large reductions in capital costs for gas-centrifuge cascades.

Hahs, C.A.; Rurbage, C.H.

1982-03-17

4

Valve for gas centrifuges  

DOEpatents

The invention is a pneumatically operated valve assembly for simultaneously (1) closing gas-transfer lines connected to a gas centrifuge or the like and (2) establishing a recycle path between two of the lines so closed. The valve assembly is especially designed to be compact, fast-acting, reliable, and comparatively inexpensive. It provides large reductions in capital costs for gas-centrifuge cascades.

Hahs, Charles A. (Oak Ridge, TN); Burbage, Charles H. (Oak Ridge, TN)

1984-01-01

5

Laser and gas centrifuge enrichment  

NASA Astrophysics Data System (ADS)

Principles of uranium isotope enrichment using various laser and gas centrifuge techniques are briefly discussed. Examples on production of high enriched uranium are given. Concerns regarding the possibility of using low end technologies to produce weapons grade uranium are explained. Based on current assessments commercial enrichment services are able to cover the global needs of enriched uranium in the foreseeable future.

Heinonen, Olli

2014-05-01

6

Centrifuge for separating helium from natural gas  

Microsoft Academic Search

Ultra Centrifuge Nederland N.V.'s improved centrifuge for separating helium from natural gas comprises a hollow cylindrical rotor, designated as a separating drum, within a stationary housing. Natural gas liquids that condense under pressure in the separating drum pass through openings in the drum into the space between the drum and housing. In this space, a series of openings, or throttling

F. H. Theyse; F. E. T. Kelling

1980-01-01

7

Separation of gas mixtures by centrifugation  

NASA Technical Reports Server (NTRS)

Magnetohydrodynamic (MHD) centrifuge utilizing electric currents and magnetic fields produces a magnetic force which develops supersonic rotational velocities in gas mixtures. Device is superior to ordinary centrifuges because rotation of gas mixture is produced by MHD force rather than mechanical means.

Park, C.; Love, W. L.

1972-01-01

8

Separation of Uranium Isotopes by Gas Centrifugation.  

National Technical Information Service (NTIS)

The uranium isotope enrichment is studied by means of the countercurrent gas centrifuge driven by thermal convection. A description is given of (a) the transfer and purification of the uranium hexafluoride used as process gas in the present investigation;...

I. Jordan

1980-01-01

9

Theory of centrifugally driven magnetospheric diffusion  

NASA Technical Reports Server (NTRS)

A general model of centrifugally driven diffusion is formulated that incorporates the effects of the pressure gradient of a radiation belt ion population and includes a realistic precipitation loss rate of the radiation belt ions that takes on a spatially peaked form, leading to a spatially varying ionospheric conductivity. The model is applied specifically to Jupiter. Model solutions for the flux tube content of the radiation belt ion population are found to compare favorably with reported Voyager 1 observations of ions in the energy range 0.2-30 MeV. Solution profiles for the flux-tube content of the cool Iogenic ion population typically favor a gradient near L = 7.5 of between one-half and one-third of the value originally reported by Bagenal and Sullivan (1981) and Siscoe et al. (1981). The model solutions are characterized by unexpectedly low values of the precipitation parameter.

Summers, Danny; Thorne, Richard M.; Mei, YI

1988-01-01

10

Centrifuge for separating helium from natural gas  

Microsoft Academic Search

A centrifuge is claimed for the separation of gaseous mixtures with a rotor inside a housing, comprising a hollow, cylindrical or nearly cylindrical rotorpart also called a separating drum, in which drum a gaseous component may condense as a liquid. This liquid is admitted thereafter through openings in the drum to the space between drum and housing. In this space

F. E. Kelling; F. H. Theyse

1980-01-01

11

Review of the gas centrifuge until 1962. Part I: Principles of separation physics  

SciTech Connect

There are two sets of principles involved in the development of the gas centrifuge, the internal separation physics and the external means of spinning a rotor at very high speeds. Only the first aspect is discussed in this part of the review. First, the industrial requirement for the separation of the uranium isotopes is defined so that the separation history can be put in a modern perspective. The history of separation physics itself is then traced back to the theory of centrifugal force by Huygens and the equivalence of this force to that of gravity. The barometric equation giving the variation of atmospheric pressure with height and the law of partial pressures can then be adapted to the centrifuge to give the steady-state theory of separation. This work was completed in the last century but was not confirmed in its application to isotope separation until 1936. The detailed separation physics for non-steady-state conditions required for a production centrifuge was developed during the American wartime Manhattan Project. During this work the theory giving the maximum output of a centrifuge was developed by Dirac, and soon afterwards Cohen and Kaplan showed that the best method of operation for a production centrifuge is in a countercurrent mode of operation. This method gives a large separation factor at relatively small flow rates through the rotor. The theory of how to set up an internal countercurrent was given by Martin during an equivalent wartime German project, and refinements to the theory, showing how the countercurrent persists along a centrifuge rotor, was given by Dirac and Steenbeck, the latter during a postwar Russian project. This theory was extended by Parker, Ging, and Mayo of the University of Virginia, whose work was completed by 1962, the limit of this review.

Whitley, S.

1984-01-01

12

Defining the needs for gas centrifuge enrichment plants advanced safeguards  

Microsoft Academic Search

Current safeguards approaches used by the International Atomic Energy Agency (IAEA) at gas centrifuge enrichment plants (GCEPs) need enhancement in order to verify declared low-enriched (LEU) production, detect undeclared LEU production and detect highly enriched uranium (HEU) production with adequate detection probability using nondestructive assay (NDA) techniques. At present inspectors use attended systems, systems needing the presence of an inspector

Brian David Boyer; Heather H Erpenbeck; Karen A Miller; Martyn T Swinhoe; Kiril Ianakiev; Johnna B Marlowe

2010-01-01

13

Parallel centrifugal gas compressors can be controlled more effectively  

SciTech Connect

Energy efficiency of parallel, centrifugal gas compressors can be improved by controlling the compressors to unload simultaneously to their surge limits. Simultaneous unloading to the surge limits can also allow more precise pressure control, provide better compressor protection, and allow simpler automated control systems. Specific power consumption is also offered as an improved definition of energy efficiency. Because polytropic efficiency, the most common efficiency measure, defines only the energy efficiency to compress a gas between the inlet port and the discharge port of a compressor, it does not account for the efficiency of gas delivery to the user. Specific power consumption includes energy costs that must be paid for but which are not accounted for by polytropic efficiency. This first of two articles discusses the concept of simultaneous loading and unloading of centrifugal compressors and compares the method with other control strategies. The concept of specific power consumption is also defined. The conclusion describes an algorithm for simultaneous loading and unloading to the surge limit. The efficiency and reliability of centrifugal compressors can be severely limited by the control system. Less-than-effective controls, rather than mechanical design, is often the cause of lost efficiency, shutdowns, and damage.

Staroselsky, N.; Ladin, L.

1986-11-03

14

Centrifugal Compressor Design Criteria - A Comparison of Theory and Experiment.  

National Technical Information Service (NTIS)

The objective of this program was to define the utility of the Detroit Diesel Allison Centrifugal Compressor Performance (CCP) analysis. This objective was accomplished by comparing the preexisting analysis of the performance of a new high-pressure-ratio ...

S. Baghdadi B. A. Hopkins W. F. Osborn

1974-01-01

15

Defining the needs for gas centrifuge enrichment plants advanced safeguards  

SciTech Connect

Current safeguards approaches used by the International Atomic Energy Agency (IAEA) at gas centrifuge enrichment plants (GCEPs) need enhancement in order to verify declared low-enriched (LEU) production, detect undeclared LEU production and detect highly enriched uranium (HEU) production with adequate detection probability using nondestructive assay (NDA) techniques. At present inspectors use attended systems, systems needing the presence of an inspector for operation, during inspections to verify the mass and {sup 235}U enrichment of declared UF{sub 6} containers used in the process of enrichment at GCEPs. In verifying declared LEU production, the inspectors also take samples for off-site destructive assay (DA) which provide accurate data, with 0.1% to 0.5% measurement uncertainty, on the enrichment of the UF{sub 6} feed, tails, and product. However, taking samples of UF{sub 6} for off-site analysis is a much more labor and resource intensive exercise for the operator and inspector. Furthermore, the operator must ship the samples off-site to the IAEA laboratory which delays the timeliness of results and interruptions to the continuity of knowledge (CofK) of the samples during their storage and transit. This paper contains an analysis of possible improvements in unattended and attended NDA systems such as process monitoring and possible on-site analysis of DA samples that could reduce the uncertainty of the inspector's measurements and provide more effective and efficient IAEA GCEPs safeguards. We also introduce examples advanced safeguards systems that could be assembled for unattended operation.

Boyer, Brian David [Los Alamos National Laboratory; Erpenbeck, Heather H [Los Alamos National Laboratory; Miller, Karen A [Los Alamos National Laboratory; Swinhoe, Martyn T [Los Alamos National Laboratory; Ianakiev, Kiril [Los Alamos National Laboratory; Marlowe, Johnna B [Los Alamos National Laboratory

2010-01-01

16

Application of energy gradient theory in flow instability in a centrifugal pump  

NASA Astrophysics Data System (ADS)

The flow instability in a centrifugal pump is studied using the energy gradient theory. Since the Re is high, the base flow is assumed to be turbulent. The distribution of the energy gradient function K at various flow rates is obtained from numerical simulations. According to the energy gradient method, the area with larger value of K is the place to cause instability and to be of high turbulence intensity. The results show that instability is easier to be excited in the area of impeller outlet and volute tongue. In order to improve the stability of centrifugal pumps working under low flow rate condition, carefulness must be taken in these two key areas.

Dou, H. S.; Jiang, W.

2013-12-01

17

An accurate theory of Mercury's rotation and centrifugal librations  

Microsoft Academic Search

The internal structure of Mercury is the most puzzling among the terrestrial planets. MESSENGER and the upcoming Bepi-Colombo space missions as well as ground-based radar measurements will play an important role in furthering our understanding of the structure, formation, and evolution of Mercury. A complete theory of the coupled spin-orbit motion of Mercury within the Solar System is an essential

N. Rambaux; T. van Hoolst; V. Dehant; E. Bois

2005-01-01

18

An accurate theory of Mercury's rotation and centrifugal librations  

NASA Astrophysics Data System (ADS)

The internal structure of Mercury is the most puzzling among the terrestrial planets. MESSENGER and the upcoming Bepi-Colombo space missions as well as ground-based radar measurements will play an important role in furthering our understanding of the structure, formation, and evolution of Mercury. A complete theory of the coupled spin-orbit motion of Mercury within the Solar System is an essential complement to observational data and will improve significantly our knowledge of the planet. Here, core-mantle interactions are studied in a realistic model of the orbital and rotational motions of Mercury. We use the SONYR model of the Solar System including Mercury's spin-orbit motion (SONYR is the acronym of Spin-Orbit N-bodY Relativistic model) and investigate the dynamical behavior of the rotational motion of Mercury considered as a solid body including either a solid core or a liquid core. The liquid core and the solid mantle are assumed to be coupled through an inertial torque on the ellipsoidal core-mantle boundary. We determine Mercury's rotation for a large set of interior structure models of Mercury in order to identify and to clarify the impact of core motions on the librations.

Rambaux, N.; van Hoolst, T.; Dehant, V.; Bois, E.

2005-12-01

19

InBorn Radio Frequency Identification Devices for Safeguards Use at Gas-Centrifuge Enrichment Plants  

Microsoft Academic Search

Global expansion of nuclear power has made the need for improved safeguards measures at Gas Centrifuge Enrichment Plants (GCEPs) imperative. One technology under consideration for safeguards applications is Radio Frequency Identification Devices (RFIDs). RFIDs have the potential to increase IAEA inspector\\

R. Ward; M. Rosenthal

2009-01-01

20

Review of the gas centrifuge until 1962. Part II: Principles of high-speed rotation  

NASA Astrophysics Data System (ADS)

The principles of the separation physics of the gas centrifuge were described in Part I of this review. In this second section the principles involved in spinning the rotors of these centrifuges are described. Three types of rotor can be identified, depending on the ratio of length to diameter. If the rotor is very short, length-diameter ratio less than one, it is gyroscopically stable and easy to spin. If the length-diameter ratio is in the region of 4 or 5, the rotor behaves as a rigid body and is relatively easy to accelerate to speed; however, it has a tendency at full speed to exhibit gyroscopic precessions. Finally, if the length-diameter ratio is very large, the rotor becomes easy to stabilize gyroscopically, but it is difficult to get it to speed because long rotors are very flexible and have resonant frequencies of flexure lower than the operating speed. The problems of these three types of centrifuge (the rotor dynamics, the bearings used to support the rotor, and the stress analysis of the rotating components) were investigated in the last century as part of classical mechanics because of the emergence of steam turbines during the latter part of the industrial revolution. These early principles are briefly reviewed, with particular reference to the work of De Laval, who invented the principle of self-balancing, Reynolds and Evershed, who developed hydrodynamic and magnetic bearing, respectively, and Chree, who did the most extensive early work on the stress analysis of tubes and discs. The work is described as it applies to the centrifuges developed in America and Germany during the war and in the Soviet Union after the war. The work of Beams in America is described in most detail, since he and his colleagues developed all three types of centrifuge during the Manhattan Project. The other work described is that of Groth and Beyerle, who developed subcritical machines in Germany during the war, and of Steenbeck and Zippe, who helped to develop both subcritical and supercritical centrifuges in the Soviet Union after the war. Little of this latter work has been published, but Zippe redeveloped the subcritical machine at the University of Virginia. The description of this machine concludes the present review.

Whitley, Stanley

1984-01-01

21

Aerodynamically induced radial forces in a centrifugal gas compressor. Part 1: Experimental measurement  

SciTech Connect

Net radial loading arising from asymmetric pressure fields in the volutes of centrifugal pumps during off-design operation is well known and has been studied extensively. In order to achieve a marked improvement in overall efficiency in centrifugal gas compressors, vaneless volute diffusers are matched to specific impellers to yield improved performance over a wide application envelope. As observed in centrifugal pumps, nonuniform pressure distributions that develop during operation above and below the design flow create static radial loads on the rotor. In order to characterize these radial forces, a novel experimental measurement and post-processing technique is employed that yields both the magnitude and direction of the load by measuring the shaft centerline locus in the tilt-pad bearings. The method is applicable to any turbomachinery operating on fluid film radial bearings equipped with proximity probes. The forces are found to be a maximum near surge and increase with higher pressures and speeds. The results are nondimensionalized, allowing the radial loading for different operating conditions to be predicted.

Moore, J.J.; Flathers, M.B. [Solar Turbines Inc., San Diego, CA (United States)

1998-04-01

22

Centrifugal reciprocating compressor  

NASA Technical Reports Server (NTRS)

Efficient compressor uses centrifugal force to compress gas. System incorporates two coupled dc motors, each driving separate centrifugal reciprocating-compressor assembly. Motors are synchronized to accelerate and decelerate alternately.

High, W. H.

1980-01-01

23

RADIO FREQUENCY IDENTIFICATION DEVICES: EFFECTIVENESS IN IMPROVING SAFEGUARDS AT GAS-CENTRIFUGE URANIUM-ENRICHMENT PLANTS.  

SciTech Connect

Recent advances in radio frequency identification devices (RFIDs) have engendered a growing interest among international safeguards experts. Potentially, RFIDs could reduce inspection work, viz. the number of inspections, number of samples, and duration of the visits, and thus improve the efficiency and effectiveness of international safeguards. This study systematically examined the applications of RFIDs for IAEA safeguards at large gas-centrifuge enrichment plants (GCEPs). These analyses are expected to help identify the requirements and desirable properties for RFIDs, to provide insights into which vulnerabilities matter most, and help formulate the required assurance tests. This work, specifically assesses the application of RFIDs for the ''Option 4'' safeguards approach, proposed by Bruce Moran, U. S. Nuclear Regulatory Commission (NRC), for large gas-centrifuge uranium-enrichment plants. The features of ''Option 4'' safeguards include placing RFIDs on all feed, product and tails (F/P/T) cylinders, along with WID readers in all FP/T stations and accountability scales. Other features of Moran's ''Option 4'' are Mailbox declarations, monitoring of load-cell-based weighing systems at the F/P/T stations and accountability scales, and continuous enrichment monitors. Relevant diversion paths were explored to evaluate how RFIDs improve the efficiency and effectiveness of safeguards. Additionally, the analysis addresses the use of RFIDs in conjunction with video monitoring and neutron detectors in a perimeter-monitoring approach to show that RFIDs can help to detect unidentified cylinders.

JOE,J.

2007-07-08

24

Realities of verifying the absence of highly enriched uranium (HEU) in gas centrifuge enrichment plants  

SciTech Connect

Over a two and one-half year period beginning in 1981, representatives of six countries (United States, United Kingdom, Federal Republic of Germany, Australia, The Netherlands, and Japan) and the inspectorate organizations of the International Atomic Energy Agency and EURATOM developed and agreed to a technically sound approach for verifying the absence of highly enriched uranium (HEU) in gas centrifuge enrichment plants. This effort, known as the Hexapartite Safeguards Project (HSP), led to the first international concensus on techniques and requirements for effective verification of the absence of weapons-grade nuclear materials production. Since that agreement, research and development has continued on the radiation detection technology-based technique that technically confirms the HSP goal is achievable. However, the realities of achieving the HSP goal of effective technical verification have not yet been fully attained. Issues such as design and operating conditions unique to each gas centrifuge plant, concern about the potential for sensitive technology disclosures, and on-site support requirements have hindered full implementation and operator support of the HSP agreement. In future arms control treaties that may limit or monitor fissile material production, the negotiators must recognize and account for the realities and practicalities in verifying the absence of HEU production. This paper will describe the experiences and realities of trying to achieve the goal of developing and implementing an effective approach for verifying the absence of HEU production. 3 figs.

Swindle, D.W.

1990-03-01

25

Centrifugal spray singlet oxygen generator for a COIL with nitrogen as a buffer gas  

NASA Astrophysics Data System (ADS)

A scalable high pressure centrifugal spray generator of singlet oxygen for chemical oxygen-iodine laser (COIL) was developed. This generator uses nitrogen as chlorine diluting gas. Different spray nozzles were tested which could be assembled together and so enable a high chlorine flow rates for a high-power COIL. The designed generator can produce singlet oxygen, O2(1?g), with reasonable chlorine utilization and O2(1?g) yield even at very high generator pressures, which cannot be attained by other O2(1?g) generators. This high-pressure operation is beneficial for a pressure recovery system of the laser. Another advantage of this generator is a very high BHP utilization. The problem of heating of exit gas was solved by introducing additional nitrogen between the separator rotor and stator.

Å palek, Otomar; Jirásek, Vít.; ?enský, Miroslav; Kodymová, Jarmila

2012-01-01

26

Approach to IAEA material-balance verification at the Portsmouth Gas Centrifuge Enrichment Plant  

SciTech Connect

This paper describes a potential approach by which the International Atomic Energy Agency (IAEA) might verify the nuclear-material balance at the Portsmouth Gas Centrifuge Enrichment Plant (GCEP). The strategy makes use of the attributes and variables measurement verification approach, whereby the IAEA would perform independent measurements on a randomly selected subset of the items comprising the U-235 flows and inventories at the plant. In addition, the MUF-D statistic is used as the test statistic for the detection of diversion. The paper includes descriptions of the potential verification activities, as well as calculations of: (1) attributes and variables sample sizes for the various strata, (2) standard deviations of the relevant test statistics, and (3) the detection sensitivity which the IAEA might achieve by this verification strategy at GCEP.

Gordon, D.M.; Sanborn, J.B.; Younkin, J.M.; DeVito, V.J.

1983-01-01

27

Microstructural characterization of rapidly solidified Type 304 stainless steel. [Powders produced by vacuum gas and centrifugal atomization  

Microsoft Academic Search

The microstructures of rapidly solidified Type 304 stainless steel powders produced by vacuum gas (VGA) and centrifugal (CA) atomization have been examined. The solidification morphology and phase distribution have been characterized using optical and scanning electron microscopy, and the relative amounts of ferrite and austenite have been quantified using x-ray diffraction. It has been found that most CA powder particles

R. N. Wright; J. E. Flinn; G. E. Korth

1985-01-01

28

In-Born Radio Frequency Identification Devices for Safeguards Use at Gas-Centrifuge Enrichment Plants  

SciTech Connect

Global expansion of nuclear power has made the need for improved safeguards measures at Gas Centrifuge Enrichment Plants (GCEPs) imperative. One technology under consideration for safeguards applications is Radio Frequency Identification Devices (RFIDs). RFIDs have the potential to increase IAEA inspector"s efficiency and effectiveness either by reducing the number of inspection visits necessary or by reducing inspection effort at those visits. This study assesses the use of RFIDs as an integral component of the "Option 4" safeguards approach developed by Bruce Moran, U.S. Nuclear Regulatory Commission (NRC), for a model GCEP [1]. A previous analysis of RFIDs was conducted by Jae Jo, Brookhaven National Laboratory (BNL), which evaluated the effectiveness of an RFID tag applied by the facility operator [2]. This paper presents a similar evaluation carried out in the framework of Jo’s paper, but it is predicated on the assumption that the RFID tag is applied by the manufacturer at the birth of the cylinder, rather than by the operator. Relevant diversion scenarios are examined to determine if RFIDs increase the effectiveness and/ or efficiency of safeguards in these scenarios. Conclusions on the benefits offered to inspectors by using in-born RFID tagging are presented.

Ward,R.; Rosenthal,M.

2009-07-12

29

Analysis of the effectiveness of gas centrifuge enrichment plants advanced safeguards  

SciTech Connect

Current safeguards approaches used by the International Atomic Energy Agency (IAEA) at gas centrifuge enrichment plants (GCEPs) need enhancement in order to verify declared low-enriched uranium (LEU) production, detect undeclared LEU production and detect highly enriched uranium (HEU) production with adequate detection probability using non destructive assay (NDA) techniques. At present inspectors use attended systems, systems needing the presence of an inspector for operation, during inspections to verify the mass and 235U enrichment of declared UF6 containers used in the process of enrichment at GCEPs. This paper contains an analysis of possible improvements in unattended and attended NDA systems including process monitoring and possible on-site destructive assay (DA) of samples that could reduce the uncertainty of the inspector's measurements. These improvements could reduce the difference between the operator's and inspector's measurements providing more effective and efficient IAEA GCEPs safeguards. We also explore how a few advanced safeguards systems could be assembled for unattended operation. The analysis will focus on how unannounced inspections (UIs), and the concept of information-driven inspections (IDS) can affect probability of detection of the diversion of nuclear materials when coupled to new GCEPs safeguards regimes augmented with unattended systems.

Boyer, Brian David [Los Alamos National Laboratory; Erpenbeck, Heather H [Los Alamos National Laboratory; Miller, Karen A [Los Alamos National Laboratory; Swinjoe, Martyn T [Los Alamos National Laboratory; Ianakiev, Kiril D [Los Alamos National Laboratory; Marlow, Johnna B [Los Alamos National Laboratory

2010-01-01

30

A Monte Carlo Analysis of Gas Centrifuge Enrichment Plant Process Load Cell Data  

SciTech Connect

As uranium enrichment plants increase in number, capacity, and types of separative technology deployed (e.g., gas centrifuge, laser, etc.), more automated safeguards measures are needed to enable the IAEA to maintain safeguards effectiveness in a fiscally constrained environment. Monitoring load cell data can significantly increase the IAEA s ability to efficiently achieve the fundamental safeguards objective of confirming operations as declared (i.e., no undeclared activities), but care must be taken to fully protect the operator s proprietary and classified information related to operations. Staff at ORNL, LANL, JRC/ISPRA, and University of Glasgow are investigating monitoring the process load cells at feed and withdrawal (F/W) stations to improve international safeguards at enrichment plants. A key question that must be resolved is what is the necessary frequency of recording data from the process F/W stations? Several studies have analyzed data collected at a fixed frequency. This paper contributes to load cell process monitoring research by presenting an analysis of Monte Carlo simulations to determine the expected errors caused by low frequency sampling and its impact on material balance calculations.

Garner, James R [ORNL; Whitaker, J Michael [ORNL

2013-01-01

31

Recent ORNL (Oak Ridge National Laboratory) Experience in Site Performance Prediction: The Gas Centrifuge Enrichment Plant and the Oak Ridge Central Waste Disposal Facility.  

National Technical Information Service (NTIS)

The suitability of the Portsmouth Gas Centrifuge Enrichment Plant Landfill and the Oak Ridge, Tennessee, Central Waste Disposal Facility for disposal of low-level radioactive waste was evaluated using pathways analyses. For these evaluations, a conservati...

F. G. Pin

1985-01-01

32

Brane Gas Cosmology, M-Theory and Little String Theory.  

National Technical Information Service (NTIS)

We generalize the Brane Gas Cosmological Scenario to M-theory degrees of freedom, namely M5 and M2 branes. Without brane intersections, the Brandenberger Vafa(BV) arguments applied to M-theory degrees of freedom generically predict a large 6 dimensional s...

S. H. S. Alexander

2003-01-01

33

Centrifugal Lyophobic Separator.  

National Technical Information Service (NTIS)

A centrifugal separator is described using a lyophobic filter for removing liquid particles from a mixed stream of gas and liquid under various negative or positive external acceleration conditions as well as zero g or weightless conditions. Rotating the ...

F. W. Booth R. A. Bruce

1974-01-01

34

Theory of finite disturbances in a centrifugal compression system with a vaneless radial diffuser  

NASA Technical Reports Server (NTRS)

A previous small perturbation analysis of circumferential waves in circumferential compression systems, assuming inviscid flow, is shown to be consistent with observations that narrow diffusers are more stable than wide ones, when boundary layer displacement effect is included. The Moore-Greitzer analysis for finite strength transients containing both surge and rotating stall in axial machines is adapted for a centrifugal compression system. Under certain assumptions, and except for a new second order swirl, the diffuser velocity field, including resonant singularities, can be carried over from the previous inviscid linear analysis. Nonlinear transient equations are derived and applied in a simple example to show that throttling through a resonant value of flow coefficient must occur in a sudden surge-like drop, accompanied by a transient rotating wave. This inner solution is superseded by an outer surge response on a longer time scale. Surge may occur purely as result of circumferential wave resonance. Numerical results are shown for various parametric choices relating to throttle schedule and the characteristic slope. A number of circumferential modes considered simultaneously is briefly discussed.

Moore, F. K.

1990-01-01

35

RESEARCH AND DEVELOPMENT OF AN INTEGRAL SEPARATOR FOR A CENTRIFUGAL GAS PROCESSING FACILITY  

SciTech Connect

A COMPACT GAS PROCESSING DEVICE WAS INVESTIGATED TO INCREASE GAS PRODUCTION FROM REMOTE, PREVIOUSLY UN-ECONOMIC RESOURCES. THE UNIT WAS TESTED ON AIR AND WATER AND WITH NATURAL GAS AND LIQUID. RESULTS ARE REPORTED WITH RECOMMENDATIONS FOR FUTURE WORK.

LANCE HAYS

2007-02-27

36

Corrosion evaluation of cooling-water treatments for gas centrifuge facilities  

SciTech Connect

The corrosion resistance of six different types of weighted metal coupons was evaluated at 29/sup 0/C (84/sup 0/F) in flowing water containing nitrite-borate-silicate corrosion inhibitors. The question for evaluation was whether it would be more advantageous: (1) to drain the treated cooling water from the centrifuge machine and to expose them to moisture-laden air over an assumed shop downtime and repair perid of 1 month; or (2) to let the treated cooling water remain stagnant in the machines during this downtime. The moisture-laden-air exposure was more detrimental.

Schmidt, C. R.; Meredith, P. F.

1980-11-24

37

Centrifugal compressors  

Microsoft Academic Search

Design of centrifugal compressors and performance prediction methods are presented. Impeller work equation, impeller velocity triangles, impeller sweepback, overall pressure rise characteristics, surges, and design analysis are treated.

R. L. Elder; C. P. Forster

1987-01-01

38

Centrifugal compressors  

NASA Astrophysics Data System (ADS)

Design of centrifugal compressors and performance prediction methods are presented. Impeller work equation, impeller velocity triangles, impeller sweepback, overall pressure rise characteristics, surges, and design analysis are treated.

Elder, R. L.; Forster, C. P.

39

Approach to IAEA verification of the nuclear-material balance at the Portsmouth Gas Centrifuge Enrichment Plant (GCEP)  

SciTech Connect

This paper describes a potential approach by which the International Atomic Energy Agency (IAEA) might verify the nuclear-material balance at the Portsmouth Gas Centrifuge Enrichment Plant (GCEP), should that plant be placed under IAEA safeguards. The strategy makes use of the attributes and variables measurement verification approach, whereby the IAEA would perform independent measurements on a randomly selected subset of the items comprising the U-235 flows and inventories at the plant. In addition, the MUF-D statistic is used as the test statistics for the detection of diversion. The paper includes descriptions of the potential verification activities, as well as calculations of (a) attributes and variables sample sizes for the various strata, (b) standard deviations of the relevant test statistics, and (c) the sensitivity for detection of diversion which the IAEA might achieve by this verification strategy at GCEP.

Gordon, D.M.; Sanborn, J.B.; Younkin, J.M.; DeVito, V.J.

1982-01-01

40

Centrifugal adsorption system  

NASA Technical Reports Server (NTRS)

A gas-liquid separator uses a helical passageway to impart a spiral motion to a fluid passing therethrough. The centrifugal force generated by the spiraling motion urges the liquid component of the fluid radially outward which forces the gas component radially inward. The gas component is then separated through a gas-permeable, liquid-impervious membrane and discharged through a central passageway. A filter material captures target substances contained in the fluid.

Gonda, Steve R. (Inventor); Tsao, Yow-Min D. (Inventor); Lee, Wenshan (Inventor)

2006-01-01

41

Defining the needs for non-destructive assay of UF6 feed, product, and tails at gas centrifuge enrichment plants and possible next steps  

Microsoft Academic Search

Current safeguards approaches used by the IAEA at gas centrifuge enrichment plants (GCEPs) need enhancement in order to detect undeclared LEU production with adequate detection probability using non destructive assay (NDA) techniques. At present inspectors use attended systems, systems needing the presence of an inspector for operation, during inspections to verify the mass and ²³U enrichment of UF bulk material

Brian D Boyer; Martyn T Swinhoe; Bruce W Moran; Alain Lebrun

2009-01-01

42

Centrifuge Apparatus.  

National Technical Information Service (NTIS)

A method and apparatus for operating a continuous flow blood separation centrifuge are provided. The hematocrit of the entrant whole blood is continuously maintained at an optimum constant value by the addition of plasma to the entrant blood. The hematocr...

W. K. Sartory J. W. Eveleigh

1976-01-01

43

Centrifugal Compressor Aeroelastic Analysis Code  

Microsoft Academic Search

Centrifugal compressors are very widely used in the turbomachine industry where low mass flow rates are required. Gas turbine engines for tanks, rotorcraft and small jets rely extensively on centrifugal compressors for rugged and compact design. These compressors experience problems related with unsteadiness of flowfields, such as stall flutter, separation at the trailing edge over diffuser guide vanes, tip vortex

Theo G. Keith Jr.; Rakesh Srivastava

2002-01-01

44

Theory of a multistage light gas gun  

Microsoft Academic Search

The theory of multistage kinetic energy transfer is applied to the acceleration of a light projectile in a light gas gun (LGG). It is argued that a better overall gun efficiency can be obtained if the kinetic energy 1\\/2M1V12 of the first piston is not directly transferred to the light projectile but proceeds via an intermediate stage transfer mediated by

J. G. Linhart; F. Cattani

2007-01-01

45

Centrifugal Scaling of Isothermal Gas-Liquid Flows in Horizontal Tubes.  

National Technical Information Service (NTIS)

To test the similarity criteria of two-phase gas-liquid flows, arising from the governing equations and boundary conditions, the flow of air and a water-glycerine mixture in a 50 mm diameter horizontal tube is compared with a two-phase flow of helium and ...

J. J. M. Geraets

1986-01-01

46

Gas gun consolidation of centrifugally atomized-type 304 SS powders  

Microsoft Academic Search

The consolidation of RSP Type 304 SS powders is being addressed using shock wave techniques. Controlled tests are underway using a gas gun for the powder consolidation. Pertinent test parameters include peak pressure, shock duration, and particle size distribution. The latter involves two near mono-sized fractions of 30 {plus minus} 10μm and 75 {plus minus} 10μm, in addition to the

J. E. Flinn; Y Gupta; P Bellamy; L. H. Schoenlein

2008-01-01

47

Centrifugal scaling of isothermal gas-liquid flows in horizontal tubes  

NASA Astrophysics Data System (ADS)

To test the similarity criteria of two-phase gas-liquid flows, arising from the governing equations and boundary conditions, the flow of air and a water-glycerine mixture in a 50 mm diameter horizontal tube is compared with a two-phase flow of helium and water in a 5 mm diameter tube rotating around a parallel vertical axis (the effective gravity is 113 g0). Results emphasize that in general only dimensionless correlations provide meaningful predictions. The homogeneous Dukler case 1 (1964b) correlation, which contains no two-phase information, provides the best fit (the standard deviation is 21%) with the measured pressure drops. For predicting flow pattern the most promising approach is that of Taitel and Dukler (1976). Examples of scaling down large diameter, high pressure pipelines are presented. With a scale factor of 1/30 equality of the Froude number, the gas-liquid density ratio, and either the Reynolds number or the Weber number can be realized. Compressibility and gas viscosity are not properly scaled.

Geraets, Jacques Joseph Marie

1986-05-01

48

Approach to IAEA material-balance verification with intermittent inspection at the Portsmouth Gas Centrifuge Enrichment Plant  

SciTech Connect

This paper describes a potential approach by which the International Atomic Energy Agency (IAEA) might verify the nuclear-material balance at the Portsmouth Gas Centrifuge Enrichment Plant (GCEP) for the circumstance in which the IAEA inspections occur on an intermittent basis. The verification approach is a variation of the standard IAEA attributes/variables measurement-verification method. This alternative approach is useful and applicable at the Portsmouth GCEP, which will ship all its product and tails UF/sub 6/ to United States facilities not eligible for IAEA safeguards. The paper reviews some of the relevant results of the Hexapartite Safeguards Project (HSP), describes the standard IAEA material-balance-verification approach for bulk-handling facilities, and provides the procedures to be followed in handling and processing UF/sub 6/ cylinders at the Portsmouth GCEP. The paper then discusses the assumptions made in the approach, and derives a formula for the probability with which the IAEA could detect the diversion of a significant quantity of uranium (75 kg of U-235 in depleted, normal, and low-enriched uranium) if this method were applied. The paper also provides numerical examples of IAEA detection probability should the operator divert uranium from the feed, product, or tails streams for the Portsmouth GCEP with a capacity of 1100 tonnes of separative work per year.

Gordon, D.M.; Sanborn, J.B.

1984-05-18

49

Centrifugal main fuel pump  

SciTech Connect

For a gas turbine power plant having a fuel supply and a fuel metering valve and variable geometry for the power plant including servo actuating mechanisms for the fuel metering valve and variable geometry, a fuel pumping system, is described to supply pressurized fuel for the servo actuating mechanisms and for the engine working fluid medium. The pumping system includes a centrifugal pump solely supplying the fuel to the fuel metering valve to be delivered to the power plant for its working fluid medium, a positive displacement pump in parallel with the centrifugal pump and solely to supply pressurized fuel to the servo actuating mechanisms for the fuel metering valve and for the variable geometry, and a boost pump means disposed in serial relationship with the positive displacement pump and the centrifugal pump for augmenting the pressure supplied by the positive displacement pump and the centrifugal pump during predetermined operating conditions of the power plant. The combined boost pump and centrifugal pump capability is sufficient to satisfy the vapor to liquid ratio requirements of the power during its entire operating envelope.

Cole, E.F.

1986-08-26

50

Centrifugal gas-phase transition magnetophoresis (GTM)--a generic method for automation of magnetic bead based assays on the centrifugal microfluidic platform and application to DNA purification.  

PubMed

Transportation of magnetic beads between different reagents plays a crucial role in many biological assays e.g. for purification of biomolecules or cells where the beads act as a mobile solid support. Therefore, usually a complex set-up either for fluidic processing or for manipulation of magnetic beads is required. To circumvent these drawbacks, we present a facile and automated method for the transportation of magnetic beads between multiple microfluidic chambers on a centrifugal microfluidic cartridge "LabDisk". The method excels by requiring only one stack of stationary permanent magnets, a specific microfluidic layout without actively controlled valves and a predefined frequency protocol for rotation of the LabDisk. Magnetic beads were transported through three fluidically separated chambers with a yield of 82.6% ± 3.6%. Bead based DNA purification from a dilution series of a Listeria innocua lysate and from a lambda phage DNA standard was demonstrated where the three chambers were used for binding, washing and elution of DNA. Recovery of L. innocua DNA was up to 68% ± 24% and for lambda phage DNA 43% ± 10% compared to manual reference purification in test tubes. Complete purification was conducted automatically within 12.5 min. Since all reagents can be preloaded onto the LabDisk prior to purification, no further hands-on steps are required during processing. Due to its modular and generic character, the presented method could also be adapted to other magnetic bead based assays e.g. to immunoassays or protein affinity purification, solely requiring the adjustment of number and volumes of the fluidic chambers. PMID:23142800

Strohmeier, Oliver; Emperle, Alexander; Roth, Günter; Mark, Daniel; Zengerle, Roland; von Stetten, Felix

2013-01-01

51

Centrifugal Compressors  

SciTech Connect

The article discusses small high speed centrifugal compressors. This topic was covered in a previous ASHRAE Journal column (2003). This article reviews another configuration which has become an established product. The operation, energy savings and market potential of this offering are addressed as well.

Hastbacka, Mildred; Dieckmann, John; Bouza, Antonio

2013-02-06

52

Centrifugal Challenge  

NSDL National Science Digital Library

In this activity, can you place a marble into a cup without touching anything but a wine glass? Pose this challenge to friends or family and discover the importance of centrifugal forces. This activity guide includes a step-by-step instructional video.

Center, Saint L.

2013-01-17

53

Application of Condition-Based Monitoring Techniques for Remote Monitoring of a Simulated Gas Centrifuge Enrichment Plant  

SciTech Connect

This paper presents research into the adaptation of monitoring techniques from maintainability and reliability (M&R) engineering for remote unattended monitoring of gas centrifuge enrichment plants (GCEPs) for international safeguards. Two categories of techniques are discussed: the sequential probability ratio test (SPRT) for diagnostic monitoring, and sequential Monte Carlo (SMC or, more commonly, particle filtering ) for prognostic monitoring. Development and testing of the application of condition-based monitoring (CBM) techniques was performed on the Oak Ridge Mock Feed and Withdrawal (F&W) facility as a proof of principle. CBM techniques have been extensively developed for M&R assessment of physical processes, such as manufacturing and power plants. These techniques are normally used to locate and diagnose the effects of mechanical degradation of equipment to aid in planning of maintenance and repair cycles. In a safeguards environment, however, the goal is not to identify mechanical deterioration, but to detect and diagnose (and potentially predict) attempts to circumvent normal, declared facility operations, such as through protracted diversion of enriched material. The CBM techniques are first explained from the traditional perspective of maintenance and reliability engineering. The adaptation of CBM techniques to inspector monitoring is then discussed, focusing on the unique challenges of decision-based effects rather than equipment degradation effects. These techniques are then applied to the Oak Ridge Mock F&W facility a water-based physical simulation of a material feed and withdrawal process used at enrichment plants that is used to develop and test online monitoring techniques for fully information-driven safeguards of GCEPs. Advantages and limitations of the CBM approach to online monitoring are discussed, as well as the potential challenges of adapting CBM concepts to safeguards applications.

Hooper, David A [ORNL; Henkel, James J [ORNL; Whitaker, Michael [ORNL

2012-01-01

54

Centrifugal compressors handle high pressures  

Microsoft Academic Search

Applications for high-pressure centrifugal compressors include reinjection of gas associated with oil production or residue gas from NGL recovery into the producing formation. This application serves several purposes. It maintains oil-field pressure to obtain higher production rates and maintains gas-field pressures to maximize liquids recovery. Gas reinjection also conserves gas resources by eliminating flaring until the gas can be produced.

1979-01-01

55

Continuous-Flow Centrifugal Separator  

NASA Technical Reports Server (NTRS)

Apparatus combines principles of centrifugal and cyclone separators to control movement of solid or liquid particles suspended in flowing gas. Spinning disk contains radial channels, width varys as function of distance from center. Gas flows from outer ring around disk toward center. Particles in gas collected at periphery, center or both.

Waldron, Robert D.

1988-01-01

56

Gas bearings. [fluid lubrication theory of sliding contact surfaces  

NASA Technical Reports Server (NTRS)

The present work deals with the fundamentals of gas lubrication theory, which forms the foundation of all analytical design tools for gas bearings. Most of the hard lessons learned in the past are outlined with reference to dry contact, debris ingestion, sliding speed, and chemical stability of lubricant. The mathematical theory of gas lubrication is described for scaling rules in thin-film viscous flow, momentum conservation, mass conservation, energy conservation, isothermal gas bearing theory, coupling effects, and global bearing characteristics. Particular attention is given to the governing differential equations for common bearing configurations. Also discussed are representative solutions of self-acting gas bearings, externally pressurized bearings, and time-dependent effects.

Pan, C. H. T.

1980-01-01

57

Calculo dos parametros de separacao de uma centrifuga a contracorrente com variacao axial do fluxo interno. (Calculation of the separate parameters of a countercurrent centrifuge with an axially varying internal flow).  

National Technical Information Service (NTIS)

A review of the isotope separation theory for the countercurrent gas centrifuge is presented. The diffusion-convection equation is solved according to the ONSAGER-COHEN solution for the constant internal flow and adapted to an axially varying countercurre...

S. C. P. Migliavacca

1991-01-01

58

Centrifugal pyrocontactor  

DOEpatents

A method for mixing and separating immiscible liquid salts and liquid metals in a centrifugal contractor. The method includes introducing the liquids into an annular mixing zone and intensely mixing the liquids using vertical vanes attached to a rotor cooperating with vertical baffles, a horizontal baffle, and bottom vanes attached to the contactor housing. The liquids enter the contactor in the range of 700-800 degrees Celsius. The liquids are separated in the rotor into a dense phase and a light phase which are discharged from the contactor.

Chow, Lorac S. (Willowbrook, IL); Leonard, Ralph A. (River Forest, IL)

1993-01-01

59

Centrifugal pyrocontactor  

DOEpatents

A method is described for mixing and separating immiscible liquid salts and liquid metals in a centrifugal contractor. The method includes introducing the liquids into an annular mixing zone and intensely mixing the liquids using vertical vanes attached to a rotor cooperating with vertical baffles, a horizontal baffle, and bottom vanes attached to the contactor housing. The liquids enter the contactor in the range of 700-800 degrees Celsius. The liquids are separated in the rotor into a dense phase and a light phase which are discharged from the contactor. 6 figures.

Chow, L.S.; Leonard, R.A.

1993-10-19

60

Centrifugal pump fuel system  

SciTech Connect

A centrifugal pump fuel system for an engine driven fuel pump for an aircraft gas turbine engine is described comprising: a centrifugal pump having at constant speed rising head/flow characteristic at low flows; a plumbing system receiving flow from the pump, and having at least one control valve located down stream of and defining a discrete volume of the plumbing system; a plumbing resonant frequency defined by the discrete volume, the geometry of the plumbing system, and the bulk modulus of the fuel; a pressure difference regulating valve located adjacent to the discharge of the pump, up stream of the vast majority of the discrete volume; and the frequency response of the regulating valve being significantly less than the frequency response of the plumbing system such that the response of the regulating valve is attenuated at the resonant frequency of the plumbing system.

McGlone, M.E.; Larkins, L.J.; Johnson, R.O.; Moeller, K.A.

1993-06-22

61

Monitoring the enrichment of the UF/sub 6/ in the pipework of a gas centrifuge enrichment plant  

SciTech Connect

Research in the UK and the US has resulted in the development of a nondestructive assay instrument which can confirm the presence of low enriched uranium, on a rapid Go, No-Go basis, in cascade header pipework in the centrifuge enrichment plant at Capenhurst. The instrument is based on gamma-ray spectrometry and x-ray fluorescence analysis. It allows pipes, 120mm outer diameter, to be inspected in a total measurement time of approximately 30 minutes. This paper describes the techniques developed and includes the results obtained during a demonstration to, and preliminary in-plant measurements by, members of the IAEA and EURATOM Inspectorates at Capenhurst.

Packer, T.W.; Close, D.A.; Pratt, J.C.

1987-01-01

62

Theory of relativistic ideal gas for quasi and ordinary particles  

NASA Astrophysics Data System (ADS)

A theory of relativistic ideal gas (RIG), fluxons and electrons is presented. A distribution function of velocities (FRS) and the equation of state of the RIG are found, together with the distribution function of the observed frequencies.

Jumaev, Mustaqim

63

Theory of fluctuations in non-equilibrium Fermi gas  

Microsoft Academic Search

We present the equations for the equal-time two-particle correlation functions in degenerate electron gas. In association with the Onsager-type equation for the time-displaced correlation function, the equations constitute the basis of the theory of fluctuations in non-equilibrium degenerate electron gas. Thanks to the prevalence of the small-angle inter-electron scattering, the theory takes a rather simple form.

R. Katilius; S. V. Gantsevich; V. D. Kagan; M. I. Muradov

2009-01-01

64

Theory of an Optically Pumped Gas Laser.  

National Technical Information Service (NTIS)

A theoretical description of the steady-state operation of an optically-pumped gas laser is presented. The three-level gas is described by a suitably modified form of the Boltzmann equation. This formulation is intermediate between the rate equation and s...

J. J. Healy T. F. Morse

1972-01-01

65

Centrifugal Adsorption Cartridge System  

NASA Technical Reports Server (NTRS)

The centrifugal adsorption cartridge system (CACS) is an apparatus that recovers one or more bioproduct(s) from a dilute aqueous solution or suspension flowing from a bioreactor. The CACS can be used both on Earth in unit gravity and in space in low gravity. The CACS can be connected downstream from the bioreactor; alternatively, it can be connected into a flow loop that includes the bioreactor so that the liquid can be recycled. A centrifugal adsorption cartridge in the CACS (see figure) includes two concentric cylinders with a spiral ramp between them. The volume between the inner and outer cylinders, and between the turns of the spiral ramp is packed with an adsorbent material. The inner cylinder is a sieve tube covered with a gas-permeable, hydrophobic membrane. During operation, the liquid effluent from the bioreactor is introduced at one end of the spiral ramp, which then constrains the liquid to flow along the spiral path through the adsorbent material. The spiral ramp also makes the flow more nearly uniform than it would otherwise be, and it minimizes any channeling other than that of the spiral flow itself. The adsorbent material is formulated to selectively capture the bioproduct(s) of interest. The bioproduct(s) can then be stored in bound form in the cartridge or else eluted from the cartridge. The centrifugal effect of the spiral flow is utilized to remove gas bubbles from the liquid. The centrifugal effect forces the bubbles radially inward, toward and through the membrane of the inner cylinder. The gas-permeable, hydrophobic membrane allows the bubbles to enter the inner cylinder while keeping the liquid out. The bubbles that thus enter the cylinder are vented to the atmosphere. The spacing between the ramps determines rate of flow along the spiral, and thereby affects the air-bubble-removal efficiency. The spacing between the ramps also determines the length of the fluid path through the cartridge adsorbent, and thus affects the bioproduct-capture efficiency of the cartridge. Depending on the application, several cartridges could be connected in a serial or parallel flow arrangement. A parallel arrangement can be used to increase product-capturing and flow capacities while maintaining a low pressure drop. A serial arrangement can be used to obtain high product-capturing capacity; alternatively, series-connected cartridges can be packed with different adsorbents to capture different bioproducts simultaneously.

Gonda, Steve R.; Tsao, Yow-Min D.; Lee, Wenshan

2004-01-01

66

Theory for a gas composition sensor based on acoustic properties  

NASA Technical Reports Server (NTRS)

Sound travelling through a gas propagates at different speeds and its intensity attenuates to different degrees depending upon the composition of the gas. Theoretically, a real-time gaseous composition sensor could be based on measuring the sound speed and the acoustic attenuation. To this end, the speed of sound was modelled using standard relations, and the acoustic attenuation was modelled using the theory for vibrational relaxation of gas molecules. The concept for a gas composition sensor is demonstrated theoretically for nitrogen-methane-water and hydrogen-oxygen-water mixtures. For a three-component gas mixture, the measured sound speed and acoustic attenuation each define separate lines in the composition plane of two of the gases. The intersection of the two lines defines the gas composition. It should also be possible to use the concept for mixtures of more than three components, if the nature of the gas composition is known to some extent.

Phillips, Scott; Dain, Yefim; Lueptow, Richard M.

2003-01-01

67

Centrifuging a Sample  

NSDL National Science Digital Library

The demonstration on this page shows a technique that should not be used by undergraduate chemistry laboratory. This video shows what happens to sample in a centrifuge while the centrifuge is on, and the result of stopping the centrifuge improperly. A narrative is included in this video: The centrifuging process allows the solvent to completely settle out. The jarring caused by hand braking destroys the distinct separation between supernatant and solid.

68

Development of turbine driven centrifugal compressors for non-condensible gas removal at geothermal power plants. Final report  

SciTech Connect

Initial field tests have been completed for a Non-Condensible Gas (NCG) turbocompressor for geothermal power plants. It provides alternate technology to steam-jet ejectors and liquid-ring vacuum pumps that are currently used for NCG removal. It incorporates a number of innovative design features to enhance reliability, reduce steam consumption and reduce O&M costs. During initial field tests, the turbocompressor has been on-line for more than 4500 hours as a third stage compressor at The Geysers Unit 11 Power Plant. Test data indicates its overall efficiency is about 25% higher than a liquid-ring vacuum pump, and 250% higher than a steam-jet ejector when operating with compressor inlet pressures of 12.2 in-Hga and flow rates over 20,000 lbm/hr.

NONE

1997-12-16

69

Lecture 2: Bogoliubov theory of a dilute Bose gas  

Microsoft Academic Search

Second quantization for bosons is reviewed. Bose-Einstein condensation for non-interacting bosons is interpreted as an example of spontaneous symmetry breaking. The spectrum of a dilute Bose gas with hardcore repulsion is calculated within Bogoliubov mean-field theory. It is shown that a Goldstone mode, an acoustic phonon, emerges in association with spontaneous symmetry breaking. Landau criterion for superfluidity is presented.

Christopher Mudry

70

Advances in electron kinetics and theory of gas discharges  

SciTech Connect

“Electrons, like people, are fertile and infertile: high-energy electrons are fertile and able to reproduce.”—Lev TsendinModern physics of gas discharges increasingly uses physical kinetics for analysis of non-equilibrium plasmas. The description of underlying physics at the kinetic level appears to be important for plasma applications in modern technologies. In this paper, we attempt to grasp the legacy of Professor Lev Tsendin, who advocated the use of the kinetic approach for understanding fundamental problems of gas discharges. We outline the fundamentals of electron kinetics in low-temperature plasmas, describe elements of the modern kinetic theory of gas discharges, and show examples of the theoretical approach to gas discharge problems used by Lev Tsendin. Important connections between electron kinetics in gas discharges and semiconductors are also discussed. Using several examples, we illustrate how Tsendin's ideas and methods are currently being developed for the implementation of next generation computational tools for adaptive kinetic-fluid simulations of gas discharges used in modern technologies.

Kolobov, Vladimir I. [CFD Research Corporation, Huntsville, Alabama 35805 (United States) [CFD Research Corporation, Huntsville, Alabama 35805 (United States); The University of Alabama in Huntsville, Huntsville, Alabama 35899 (United States)

2013-10-15

71

USE OF MAILBOX APPROACH, VIDEO SURVEILLANCE, AND SHORT-NOTICE RANDOM INSPECTIONS TO ENHANCE DETECTION OF UNDECLARED LEU PRODUCTION AT GAS CENTRIFUGE ENRICHMENT PLANTS.  

SciTech Connect

Current safeguards approaches used by the IAEA at gas centrifuge enrichment plants (GCEPs) need enhancement in order to detect undeclared LEU production with adequate detection probability. ''Mailbox'' declarations have been used in the last two decades to verify receipts, production, and shipments at some bulk-handling facilities (e.g., fuel-fabrication plants). The operator declares the status of his plant to the IAEA on a daily basis using a secure ''Mailbox'' system such as a secure tamper-resistant computer. The operator agrees to hold receipts and shipments for a specified period of time, along with a specified number of annual inspections, to enable inspector access to a statistically large enough population of UF{sub 6} cylinders and fuel assemblies to achieve the desired detection probability. The inspectors can access the ''Mailbox'' during randomly timed inspections and then verify the operator's declarations for that day. Previously, this type of inspection regime was considered mainly for verifying the material balance at fuel-fabrication, enrichment, and conversion plants. Brookhaven National Laboratory has expanded the ''Mailbox'' concept with short-notice random inspections (SNRIs), coupled with enhanced video surveillance, to include declaration and verification of UF{sub 6} cylinder operational data to detect activities associated with undeclared LEU production at GCEPs. Since the ''Mailbox'' declarations would also include data relevant to material-balance verification, these randomized inspections would replace the scheduled monthly interim inspections for material-balance purposes; in addition, the inspectors could simultaneously perform the required number of Limited-Frequency Unannounced Access (LFUA) inspections used for HEU detection. This approach would provide improved detection capabilities for a wider range of diversion activities with not much more inspection effort than at present.

BOYER, B.D.; GORDON, D.M.; JO, J.

2006-07-16

72

AFCESA Geotechnical Centrifuge.  

National Technical Information Service (NTIS)

The objective of this project was to compile a user's manual for the Air Force Civil Engineering Support Agency geotechnical centrifuge. In the process it was also necessary to upgrade the centrifuge to a state-of-the-art geotechnical research facility. T...

M. R. Purcell C. R. Hollopeter

1993-01-01

73

A parametric starting study of an axial-centrifugal gas turbine engine using a one-dimensional dynamic engine model and comparisons to experimental results. Part 2: Simulation calibration and trade-off study  

SciTech Connect

A generic one-dimensional gas turbine engine model, developed at the Arnold Engineering Development Center, has been configured to represent the gas generator of a General Electric axial-centrifugal gas turbine engine in the six-kg/sec airflow class. The model was calibrated against experimental test results for a variety of initial conditions to insure that the model accurately represented the engine over the range of test conditions of interest. These conditions included both assisted (with a starter motor) and unassisted (altitude windmill) starts. The model was then exercised to study a variety of engine configuration modifications designed to improve its starting characteristics and thus quantify potential starting improvements for the next generation of gas turbine engines. This paper presents the model calibration results and the results of the trade-off study. A companion paper discusses the model development and describes the test facilities used to obtain the calibration data.

Owen, A.K.; Daugherty, A. [Army Vehicle Propulsion Directorate, Cleveland, OH (United States); Garrard, D. [Sverdrup Technology, Inc./AEDC Group, Arnold AFB, TN (United States); Reynolds, H.C.; Wright, R.D. [General Electric Corp., Lynn, MA (United States)

1999-07-01

74

Defining the needs for non-destructive assay of UF6 feed, product, and tails at gas centrifuge enrichment plants and possible next steps  

SciTech Connect

Current safeguards approaches used by the IAEA at gas centrifuge enrichment plants (GCEPs) need enhancement in order to detect undeclared LEU production with adequate detection probability using non destructive assay (NDA) techniques. At present inspectors use attended systems, systems needing the presence of an inspector for operation, during inspections to verify the mass and {sup 235}U enrichment of UF{sub 6} bulk material used in the process of enrichment at GCEPS. The inspectors also take destructive assay (DA) samples for analysis off-site which provide accurate, on the order of 0.1 % to 0.5% uncertainty, data on the enrichment of the UF{sub 6} feed, tails, and product. However, DA sample taking is a much more labor intensive and resource intensive exercise for the operator and inspector. Furthermore, the operator must ship the samples off-site to the IAEA laboratory which delays the timeliness of the results and contains the possibility of the loss of the continuity of knowledge of the samples during the storage and transit of the material. Use of the IAEA's inspection sampling algorithm shows that while total sample size is fixed by the total population of potential samples and its intrinsic qualities, the split of the samples into NDA or DA samples is determined by the uncertainties in the NDA measurements. Therefore, the larger the uncertainties in the NDA methods, more of the sample taken must be DA samples. Since the DA sampling is arduous and costly, improvements in NDA methods would reduce the number of DA samples needed. Furthermore, if methods of on-site analysis of the samples could be developed that have uncertainties in the 1-2% range, a lot of the problems inherent in DA sampling could be removed. The use of an unattended system that could give an overview of the entire process giving complementary data on the enrichment process as well as accurate measures of enrichment and weights of the UF{sub 6} feed, tails, and product would be a major step in enhancing the ability of NDA beyond present attended systems. The possibility of monitoring the feed, tails, and product header pipes in such a way as to gain safeguards relevant flow and enrichment information without compromising the intellectual property of the operator including proprietary equipment and operational parameters would be a huge step forward. This paper contains an analysis of possible improvements in unattended and attended NDA systems including such process monitoring and possible on-site analysis of DA samples that could reduce the uncertainty of the inspector measurements reducing the difference between the operator's and inspector's measurements providing more effective and efficient IAEA GeEPs safeguards.

Boyer, Brian D [Los Alamos National Laboratory; Swinhoe, Martyn T [Los Alamos National Laboratory; Moran, Bruce W [IAEA; Lebrun, Alain [IAEA

2009-01-01

75

Centrifugal-Reciprocating Compressor.  

National Technical Information Service (NTIS)

A centrifugal compressor is presented which includes at least a pair of cylinders arranged in coaxial alignment and supported for angular displacement about a common axis of rotation normally bisecting a common longitudinal axis of symmetry for the cylind...

W. H. Higa

1979-01-01

76

Aircraft Centrifugal Pump Units.  

National Technical Information Service (NTIS)

A general description of the experience of Soviet and foreign industry with respect to calculation, designing, experimental studies, and operation of aircraft centrifugal pump units is given. The contemporary level of designs and prospects of their develo...

L. S. Arinushkin R. B. Abramovich E. A. Glozman A. Y. Polinovskii L. B. Leshchiner

1969-01-01

77

DESIGN INFORMATION REPORT: CENTRIFUGES  

EPA Science Inventory

In the 1960s, manufacturers began to design centrifuges specifically for wastewater sludge applications. In addition, sludge thickening and dewatering processes were improved with the introduction of polyelectrolytes for chemical sludge conditioning. The report contains a brief d...

78

A variational principle for the plasma centrifuge  

Microsoft Academic Search

A variational principle is derived which describes the stationary state of the plasma column in a plasma centrifuge. Starting with the fluid equations in a rotating frame the theory is developed using the method of irreversible thermodynamics. This formulation easily leads to an expression for the density distribution of the l-species at sedimentation equilibrium, taking into account the effect of

G. O. Ludwig

1986-01-01

79

Flank millable blade design for centrifugal compressors  

Microsoft Academic Search

A novel design approach for the centrifugal compressor blade is proposed in this paper. It is set up based on the offset theory and line geometry. The designed blade surface is represented as a tool path, which consists of two guide curves. It can be manufactured by flank milling method with a cylindrical cutter. The drive surface is a ruled

Yayun Zhou; J. Schulze; S. Schaffler

2009-01-01

80

Gas Bubbles and Gas Pancakes at Liquid\\/Solid Interface: A Continuum Theory Incorporated with Molecular Interactions  

Microsoft Academic Search

The states of gas accumulated at the liquid-solid interface are analyzed based on the continuum theory where the Hamaker constant is used to describe the long-range interaction at the microscopic scale. The Hamaker constant is always negative, whereas the gas spreading coefficient can be either sign. Despite the complexity of gas, including that the density profile may not be uniform

Zhaoxia Li; Xuehua Zhang; Lijuan Zhang; Xiaocheng Zeng; Jun Hu; Haiping Fang

2006-01-01

81

Subsychronous Vibration of Multistage Centrifugal Compressors Forced by Rotating Stall.  

National Technical Information Service (NTIS)

A multistage centrifugal compressor, in natural gas re-injection service on an offshore petroleum production platform, experienced subsynchronous vibrations which caused excessive bearing wear. Field performance testing correlated the subsynchronous ampli...

J. W. Fulton

1987-01-01

82

Unsteady Flow Phenomena in Discrete Passage Diffusers for Centrifugal Compressors.  

National Technical Information Service (NTIS)

Research is described on the fluid dynamic behavior of high performance diffusers for centrifugal compressors, with particular application to small gas turbine engine applications. Using a unique swirl generator, experiments have been carried out to defin...

V. Filipenco J. M. Johnston E. M. Greitzer

1994-01-01

83

Lattice-gas model in kinetic theory of gas-solid interface processes  

NASA Astrophysics Data System (ADS)

The improvement of the experimental methods for investigating surface processes changes the existing ideas about the role of the different factors of the gas-solid system and the mechanisms of the processes. The recent studies have confirmed the conception of surface processes as the ones taking place in the condensed phases. At the same time, the surface processes generally are described by fairly rough models based on the law of mass action, which is true of the ideal systems. The contradiction is eliminated to a certain degree when a lattice-gas model which takes into account the proper volume of the adspecies and adspecies interaction is used. On this basis it is easy to consider the effect of the local environment on the activation barrier of an elementary process. This enables one to apply it extensively to be the atomic-molecular processes associated with a change in the spatial arrangement of the adspecies and their chemical conversion. The review describes the development of the kinetic theory of the surface processes at the gas-solid interface using on the lattice-gas model and its modern modifications. Applications of the theory to the adsorption-desorption processes and the catalytic reactions are considered. The reaction rates in the condensed phases and the role of the correlation effects of the interacting adspecies and the distribution of the system's components are described. The lattice-gas model helps us explain the empirical principles of the adsorption processes; a variable order of desorption rate; the splitting of the thermodesorption spectra on the homogeneous surfaces; an increase in the sticking coefficient with coverage at its small values; phase transitions in the adlayers and their effect on the adsorption-desorption rate and the diffusion coefficients; a great mutual effect of the adspecies of the different kinds on the rate of the elementary processes; the dependence of the course of a process on the conditions in which the initial surface coverages are formed; multiplicity of the steady states of the reaction systems and the isothermal oscillation conditions of the reaction mode; etc. At present the theory of surface processes enables one to take into account a wide range of the real properties of the gas-solid system: the lateral interaction between the adspecies and their phase transitions, surface inhomogeneity, a limited mobility of the adspecies and the solid body surface atoms, the rearrangement of the subsurface solid region and so on. The joint influence of the factors mentioned above are also taken into account. Theoretical results are compared with the numerical calculations by the Monte Carlo methods.

Tovbin, Yu. K.

84

Protein Purification by Continuous Centrifugation.  

National Technical Information Service (NTIS)

The project assessed the potential of continuous centrifugation for the separation and purification of medical proteins from liquor harvested from large-scale cell-culture bioreactors. Continuous means that the harvest liquor is fed into the centrifuge co...

H. G. Wood

1988-01-01

85

Centrifugally enhanced paper microfluidics  

Microsoft Academic Search

Fluid flow in paper is currently limited by capillary forces. Here we show how capillary flow control can be improved by integrating paper sectors in lab-on-a-disc platforms. To this end we combine the rotationally controlled centrifugal force with the capillary action to enable basic liquid handling steps such as blood separation, liquid recirculation, liquid routing and valving. The integration of

Neus Godino; Eamon Comaskey; Robert Gorkin; Jens Ducree

2012-01-01

86

Central centrifugal cicatricial alopecia  

PubMed Central

Central centrifugal cicatricial alopecia is a common cause of progressive permanent apical alopecia. This unique form of alopecia includes entities previously know as “hot comb alopecia,” “follicular degeneration syndrome,” “pseudopelade” in African Americans and “central elliptical pseudopelade” in Caucasians. The etiology appears to be multifactorial and the condition occurs in all races.

Blattner, Collin; Polley, Dennis C.; Ferritto, Frank; Elston, Dirk M.

2013-01-01

87

Ekman boundary conditions for numerical models of centrifuge flows  

NASA Astrophysics Data System (ADS)

The boundary layers which form on the ends of a gas centrifuge have received a great deal of analytical attention in predicting flows within gas centrifuges. Three basic approaches were taken in estimating the heat transfer and drag at the solid gas interfaces at the ends of a centrifuge. First, the details of the flow may be estimated numerically using finite difference techniques and a very fine grid in the vicinity of the ends. The cost in computer time and memory charges is great and the extensive detail is difficult to utilize effectively. Second, the boundary layers may simply be ignored. With this approach, the size of the finite difference mesh is controlled by other considerations which allow economically attractive simulation of centrifuge flows for many situations. The third effort is to model the boundary layers analytically and couple those models to solutions for the interior flow. Previous efforts to model the the boundary layers are reviewed.

Park, J. E.; Drake, J. B.

1984-04-01

88

Centrifuge-based fluidic platforms  

Microsoft Academic Search

In this paper, centrifuge-based microfluidic platforms are reviewed and compared with other popular microfluidic propulsion methods. The underlying physical principles of centrifugal pumping in microfluidic systems are presented and the various centrifuge fluidic functions such as valving, decanting, calibration, mixing, metering, heating, sample splitting, and separation are introduced. Those fluidic functions have been combined with analytical measurement techniques such as

JIM V. ZOVAL; MARC J. MADOU

2004-01-01

89

Application of Ideal Gas Theory to the Gaseous Expansion from an Electric Spark  

Microsoft Academic Search

The gaseous expansion from an electric spark is described in this paper in terms of ideal gas theory. The assumption is made that a quantity of energy is injected into a small gas volume in an infinitesimally short time and that the initial volume of gas then expands until it reaches the pre-spark pressure at an elevated temperature. Experimental results

R. B. Edmonson; H. L. Olsen; E. L. Gayhart

1954-01-01

90

Coral reef formation theory may apply to oil, gas exploration  

SciTech Connect

This paper reports a coral reef formation theory that has implications for hydrocarbon exploration. The theory states that many coral reefs and carbonate buildups from at and are dependent upon nutrient rich fluids seeping through the seabed.

Not Available

1990-12-10

91

A parametric starting study of an axial-centrifugal gas turbine engine using a one-dimensional dynamic engine model and comparisons to experimental results. Part 1: Model development and facility description  

SciTech Connect

A generic one-dimensional gas turbine engine model, developed at the Arnold Engineering Development Center, has been configured to represent the gas generator of a General Electric axial-centrifugal gas turbine engine in the six kg/sec airflow class. The model was calibrated against experimental test results for a variety of initial conditions to insure that the model accurately represented the engine over the range of test conditions of interest. These conditions included both assisted (with a starter motor) and unassisted (altitude windmill) starts. The model was then exercised to study a variety of engine configuration modifications designed to improve its starting characteristics, and, thus, quantify potential starting improvements for the next generation of gas turbine engines. This paper discusses the model development and describes the test facilities used to obtain the calibration data. The test matrix for the ground level testing is also presented. A companion paper presents the model calibration result and the results of the trade-off study.

Owen, A.K.; Daugherty, A. [Army Vehicle Propulsion Directorate, Cleveland, OH (United States); Garrard, D. [Sverdrup Technology, Inc./AEDC Group, Arnold AFB, TN (United States); Reynolds, H.C.; Wright, R.D. [General Electric Corp. Lynn, MA (United States)

1999-07-01

92

Centrifugal unbalance detection system  

DOEpatents

A system consisting of an accelerometer sensor attached to a centrifuge enclosure for sensing vibrations and outputting a signal in the form of a sine wave with an amplitude and frequency that is passed through a pre-amp to convert it to a voltage signal, a low pass filter for removing extraneous noise, an A/D converter and a processor and algorithm for operating on the signal, whereby the algorithm interprets the amplitude and frequency associated with the signal and once an amplitude threshold has been exceeded the algorithm begins to count cycles during a predetermined time period and if a given number of complete cycles exceeds the frequency threshold during the predetermined time period, the system shuts down the centrifuge.

Cordaro, Joseph V. (Martinez, GA); Reeves, George (Graniteville, SC); Mets, Michael (Aiken, SC)

2002-01-01

93

Thermodynamic theory of the shock wave structure in a rarefied polyatomic gas: beyond the Bethe-Teller theory.  

PubMed

The structure of a shock wave in a rarefied polyatomic gas is studied on the basis of the theory of extended thermodynamics. Three types of the shock wave structure observed in experiments, that is, the nearly symmetric shock wave structure (type A, small Mach number), the asymmetric structure (type B, moderate Mach number), and the structure composed of thin and thick layers (type C, large Mach number), are explained by the theory in a unified way. The theoretical prediction of the profile of the mass density agrees well with the experimental data. The well-known Bethe-Teller theory of the shock wave structure in a polyatomic gas is reexamined in the light of the present theory. PMID:24580338

Taniguchi, Shigeru; Arima, Takashi; Ruggeri, Tommaso; Sugiyama, Masaru

2014-01-01

94

Viscosity Prediction of Natural Gas Using the Friction Theory  

Microsoft Academic Search

Based on the concepts of the friction theory (f-theory) for viscosity modeling, a procedure is introduced for predicting the viscosity of hydrocarbon mixtures rich in one component, which is the case for natural gases. In this procedure, the mixture friction coefficients are estimated with mixing rules based on the values of the pure component friction coefficients. Since natural gases contain

C. K. Zéberg-Mikkelsen; S. E. Quiñones-Cisneros; E. H. Stenby

2002-01-01

95

Galactic evolution. I - Single-zone models. [encompassing stellar evolution and gas-star dynamic theories  

NASA Technical Reports Server (NTRS)

The two basic approaches of physical theory required to calculate the evolution of a galactic system are considered, taking into account stellar evolution theory and the dynamics of a gas-star system. Attention is given to intrinsic (stellar) physics, extrinsic (dynamical) physics, and computations concerning the fractionation of an initial mass of gas into stars. The characteristics of a 'standard' model and its variants are discussed along with the results obtained with the aid of these models.

Thuan, T. X.; Hart, M. H.; Ostriker, J. P.

1975-01-01

96

National geotechnical centrifuge  

NASA Technical Reports Server (NTRS)

A high G-ton centrifuge, able to take a 2700 kg (6000 lb) payload up to 300 G, is described. The stability of dams and embankments, the bearing capacity of soil foundations, and the dynamic behavior of foundations due to vibration of machinery are examples of applications. A power rating of 6,000 kW (9,000 hp) was established for the motor. An acceptable maximum speed of 70 rpm was determined. A speed increase with a ratio of 1:3 is discussed. The isolated tension straps, the anti-spreader bar and the flexwall bucket, and safety precautions are also discussed.

Hallam, J. A.; Kunz, N.; Vallotton, W. C.

1982-01-01

97

Centrifuge impact cratering experiment 5  

NASA Technical Reports Server (NTRS)

Transient crates motions, cratering flow fields, crates dynamics, determining impact conditions from total crater welt, centrifuge quarter-space cratering, and impact cratering mechanics research is documented.

1984-01-01

98

Performance analysis of mini centrifugal pump with splitter blades  

NASA Astrophysics Data System (ADS)

Design method for a mini centrifugal pump is not established because the internal flow condition for these small-sized fluid machines is not clarified and conventional theory is not suitable for small-sized pumps. Then, a semi-open impeller for the mini centrifugal pump with 55mm impeller diameter is adopted in this research to take simplicity and maintenance into consideration. Splitter blades are adopted in this research to improve the performance and internal flow condition of mini centrifugal pump having large blade outlet angle. The performance tests are conducted with these rotors in order to investigate the effect of the splitter blades on the performance and internal flow condition of the mini centrifugal pump. A three dimensional steady numerical flow analysis is conducted to analyze rotor, volute efficiency and loss caused by a vortex. It is clarified from the experimental results that the performance of the mini centrifugal pump is improved by the effect of the splitter blades. Flow condition at outlet of the rotor becomes uniform and back flow regions are suppressed in the case with the splitter blades. Further, the volute efficiency increases and the vortex loss decreases. In the present paper, the performance of the mini centrifugal pump is shown and the flow condition is clarified with the results of the experiment and the numerical flow analysis. Furthermore, the performance analyses of the mini centrifugal pumps with and without the splitter blades are conducted.

Shigemitsu, T.; Fukutomi, J.; Wada, T.; Shinohara, H.

2013-12-01

99

Design and Performance Analysis of Centrifugal Pump  

Microsoft Academic Search

This paper deals with the design and performance analysis of centrifugal pump. In this paper, centrifugal pump is analyzed by using a single-stage end suction centrifugal pump. Two main components of a centrifugal pump are the impeller and the casing. The impeller is a rotating component and the casing is a stationary component. In centrifugal pump, water enters axially through

Khin Cho Thin; Mya Mya Khaing; Khin Maung Aye

2008-01-01

100

Centrifugal precipitation chromatography  

PubMed Central

Centrifugal precipitation chromatography separates analytes according their solubility in ammonium sulfate (AS) solution and other precipitants. The separation column is made from a pair of long spiral channels partitioned with a semipermeable membrane. In a typical separation, concentrated ammonium sulfate is eluted through one channel while water is eluted through the other channel in the opposite direction. The countercurrent process forms an exponential AS concentration gradient through the water channel. Consequently, protein samples injected into the water channel is subjected to a steadily increasing AS concentration and at the critical AS concentration they are precipitated and deposited in the channel bed by the centrifugal force. Then the chromatographic separation is started by gradually reducing the AS concentration in the AS channel which lowers the AS gradient concentration in the water channel. This results in dissolution of deposited proteins which are again precipitated at an advanced critical point as they move through the channel. Consequently, proteins repeat precipitation and dissolution through a long channel and finally eluted out from the column in the order of their solubility in the AS solution. The present method has been successfully applied to a number of analytes including human serum proteins, recombinant ketosteroid isomerase, carotenoid cleavage enzymes, plasmid DNA, polysaccharide, polymerized pigments, PEG-protein conjugates, etc. The method is capable to single out the target species of proteins by affinity ligand or immunoaffinity separation.

Ito, Yoichiro; Lin, Qi

2009-01-01

101

Air gas dynamic spraying of powder mixtures: Theory and application  

Microsoft Academic Search

The radial injection gas dynamic spray (RIGDS) technology of powder coatings deposition was considered for this work. A coating\\u000a was created by injecting powders with variable compositions into a supersonic air jet and depositing powder on the substrate.\\u000a This study describes the preliminary analysis of an air gas dynamic spray method realized by a portable RIGDS apparatus with\\u000a a radial

R. Gr. Maev; V. Leshchynsky

2006-01-01

102

Application of the vacancy solution theory to describe the enthalpic effects accompanying mixed-gas adsorption.  

PubMed

The possibility of utilizing vacancy solution theory (VST) to study the enthalpic effects accompanying mixed-gas adsorption equilibria is presented. Besides heterogeneity, the interaction effects by using the regular adsorbed solution, Flory-Huggins, and Wilson models of nonideality in the adsorbed phase are taken into account. To predict adsorption phase diagrams and calorimetric effects in the mixed-gas adsorption system, only a knowledge of the single-gas adsorption isotherms and accompanying calorimetric effects is required. The possibility of simplification of the obtained theoretical expressions is shown. The obtained agreement between theory and experiment is very satisfactory. PMID:17073489

Nieszporek, K

2006-11-01

103

Modelling of multistage centrifugal compressor  

Microsoft Academic Search

Surge is an unstable operating mode of the centrifugal compressor that occurs at mass flows below the surge line, and it results in considerable loss of performance and efficiency of the compression system. Modelling of the centrifugal compressor is the basis of getting the surge line and carrying out anti-surge control. Based on fluid mechanics, mass and energy conservation principles,

Dapeng Niu; Aiping Shi; Yuqing Chang; Fuli Wang

2011-01-01

104

Unshrouded Centrifugal Turbopump Impeller  

NASA Technical Reports Server (NTRS)

The ratio of rocket engine thrust to weight is a limiting constraint in placing more payload into orbit at a low cost. A key component of an engine's overall weight is the turbopump weight, Reducing the turbopump weight can result in significant engine weight reduction and hence, increased delivered payload. There are two main types of pumps: centrifugal and axial pumps. These types of pumps can be further sub-divided into those with shrouds and those without shrouds (unshrouded pumps). Centrifugal pumps can achieve the same pump discharge pressure as an axial pump and it requires fewer pump stages and lower pump weight than an axial pump. Also, with unshrouded centrifugal pumps (impeller), the number of stages and weight can be further reduced. However. there are several issues with regard to using an unshrouded impeller: 1) there is a pump performance penalty due to the front open face recirculation flow; 2) there is a potential pump axial thrust problem from the unbalanced front open face and the back shroud face; and, 3) since test data is very linu'ted for this configuration, there is uncertainty in the magnitude and phase of the rotordynamics forces due to the front impeller passage. The purpose of the paper is to discuss the design of an unshrouded impeller and to examine the design's hydrodynamic performance, axial thrust, and rotordynamics performance. The design methodology will also be discussed. This work will help provide some guidelines for unshrouded impeller design. In particular, the paper will discuss the design of three unshrouded impellers - one with 5 full and 5 partial blades (5+5). one with 6+6 blades and one with 8+8 blades. One of these designs will be selected for actual fabrication and flow test. Computational fluid dynamics (CFD) is used to help design and optimize the unshrouded impeller. The relative pump performance penalty is assessed by comparing the CFD results of the unshrouded impeller with the equivalent shrouded impeller for a particular design. Limited unshrouded - versus - shrouded impeller data from the J-2 pump is used to anchor the CFD. Since no detailed impeller blade force data is available, axial thrust and rotordynamic force predictions are based on the CFD model. For the axial thrust, the impeller front flow passage axial force is integrated from the CFD results and compared to the equivalent shrouded impeller axial force. For the rotordynamics forces, the fluid reaction forces are computed from unsteady flow CFD results using a moving boundary method; the rotor- shaft is moved at several whirl-to-speed frequency ratios to extract the rotordynamics coefficients.

Prueger, George; Williams, Morgan; Chen, Wei; Paris, John; Stewart, Eric; Williams, Robert

1999-01-01

105

Rat growth during chronic centrifugation  

NASA Technical Reports Server (NTRS)

Female weanling rats were chronically centrifuged at 4.15 G with controls at terrestrial gravity. Samples were sacrificed for body composition studies at 0, 28, 63, 105 and 308 days of centrifugation. The centrifuged group approached a significantly lower mature body mass than the controls (251 and 318g) but the rate of approach was the same in both groups. Retirement to 1G on the 60th day resulted in complete recovery. Among individual components muscle, bone, skin, CNS, heart, kidneys, body water and body fat were changed in the centrifuged group. However, an analysis of the growth of individual components relative to growth of the total fat-free compartment revealed that only skin (which increased in mass) was responding to centrifugation per se.

Pitts, G. C.; Oyama, J.

1978-01-01

106

Membrane-Based Characterization of a Gas Component -- A Transient Sensor Theory  

PubMed Central

Based on a multi-gas solution-diffusion problem for a dense symmetrical membrane this paper presents a transient theory of a planar, membrane-based sensor cell for measuring gas from both initial conditions: dynamic and thermodynamic equilibrium. Using this theory, the ranges for which previously developed, simpler approaches are valid will be discussed; these approaches are of vital interest for membrane-based gas sensor applications. Finally, a new theoretical approach is introduced to identify varying gas components by arranging sensor cell pairs resulting in a concentration independent gas-specific critical time. Literature data for the N2, O2, Ar, CH4, CO2, H2 and C4H10 diffusion coefficients and solubilities for a polydimethylsiloxane membrane were used to simulate gas specific sensor responses. The results demonstrate the influence of (i) the operational mode; (ii) sensor geometry and (iii) gas matrices (air, Ar) on that critical time. Based on the developed theory the case-specific suitable membrane materials can be determined and both operation and design options for these sensors can be optimized for individual applications. The results of mixing experiments for different gases (O2, CO2) in a gas matrix of air confirmed the theoretical predictions.

Lazik, Detlef

2014-01-01

107

Theory of gas bubble nucleation in supersaturated solution of vacancies, interstitials and gas atoms  

Microsoft Academic Search

A general form of the kinetic coefficients of the Fokker–Planck equation describing gas bubble nucleation in supersaturated solution of vacancies, interstitials and gas atoms is obtained. No assumptions concerning the detailed balance are used to describe the absorption and desorption of point defects and gas atoms at the bubble surface. This allows us to investigate limits of the usual formalisms

A. E. Volkov; A. I. Ryazanov

1999-01-01

108

Reaction-diffusion lattice gas: Theory and computer results  

Microsoft Academic Search

We report on the study of nonequilibrium ordering in the reaction-diffusion lattice gas. It is a kinetic model that relaxes towards steady states under the simultaneous competition of a thermally activated creation-annihilation (-reaction)- process at temperature T, and a diffusion process driven by a heat bath at temperature T'!=T. The phase diagram as one varies T and T', the system

J. J. Alonso; J. Marro; J. M. González-Miranda

1993-01-01

109

Centrifuge (ChemPages Lab)  

NSDL National Science Digital Library

Centrifuge: this is a resource in the collection "ChemPages Laboratory Resources". The centrifuge is used to separate a solid from a solution quickly. A centrifuge is used for small-scale separations; typically the volume is less than 5 mL. Larger volumes of mixtures can be separated by filtration. The ChemPages Laboratory Resources are a set of web pages that include text, images, video, and self check questions. The topics included are those that are commonly encountered in the first-year chemistry laboratory. They have been put together for use as both a pre-laboratory preparation tool and an in-laboratory reference source.

110

Study on the methods of determining main geometric parameters of centrifugal fan impeller  

Microsoft Academic Search

Because of the complexity of internal flow characteristics of centrifugal fan, a set of wholly mature design methods of impeller theory do not exist at the present time. The paper tries to investigate and analyze the internal relations between a large number of existing aerodynamic sketches and performance parameters of centrifugal fans by means of statistical method and finds regularity.

Yan Gui; Pingyuan Xi

2010-01-01

111

Centrifugation. Sludge Treatment and Disposal Course #166. Instructor's Guide [and] Student Workbook.  

ERIC Educational Resources Information Center

An introductory description of the use of centrifuges in the process of volume reduction is provided in this lesson. Three basic centrifuges, their theory of operation, quality of cake and centrate, and operational control testing are discussed. The lesson includes an instructor's guide and student workbook. The instructor's guide contains a…

Best, Richard A.

112

Analysis of filament-wound cylindrical shells under combined centrifugal, pressure and axial loading  

Microsoft Academic Search

An analytical procedure is developed to assess the stresses and deformations of filament-wound structures under loading conditions particular to centrifuge rotors and to assess the effects of wind angle variation through the centrifuge wall. This procedure is based on classical laminated plate theory and models both plane stress and plane strain states of a cylindrical shell comprising a number of

G. W. Vickers

1997-01-01

113

Design and prototyping of micro centrifugal compressor  

NASA Astrophysics Data System (ADS)

In order to establish the design methodology of ultra micro centrifugal compressor, which is the most important component of ultra micro gas turbine unit, a 10 times of the final target size model was designed, prototyped and tested. The problems to be solved for downsizing were examined and 2-dimensional impeller was chosen as the first model due to its productivity. The conventional 1D prediction method, CFD and the inverse design were attempted. The prototyped compressor was driven by using a turbocharger and the performance characteristics were measured.

Mizuki, Shimpei; Minorikawa, Gaku; Hirano, Toshiyuki; Asaga, Yuichiro; Yamaguchi, Naoki; Ohta, Yutaka; Outa, Eisuke

2003-02-01

114

Testing of pyrochemical centrifugal contactors.  

National Technical Information Service (NTIS)

A centrifugal contactor that performs oxidation and reduction exchange reactions between molten metals and salts at 500 degrees Centigrade has been tested successfully at Argonne National Laboratory (ANL). The design is based on contactors for aqueous- or...

L. S. Chow E. L. Carls J. K. Basco T. R. Johnson

1996-01-01

115

Centrifuge Enrichment: Benefits and Risks.  

National Technical Information Service (NTIS)

The President decided to use the new centrifuge technology instead of the proven diffusion technology for the uranium enrichment plant to be built at Portsmouth, Ohio. This report addresses the appropriateness of (1) substituting the new technology and (2...

1978-01-01

116

Density functional theory study on water–gas-shift reaction over molybdenum disulfide  

Microsoft Academic Search

Density functional theory calculations have been carried out to investigate the adsorption of reaction intermediates appearing during water–gas-shift reaction at the sulfur covered MoS2 (100) surfaces, Mo-termination with 37.5% S coverage and S-termination with 50% S coverage using periodic slabs. The pathway for water–gas-shift reaction on both terminations has been carefully studied where the most favorable reaction path precedes the

Xue-Rong Shi; Sheng-Guang Wang; Jia Hu; Hui Wang; Yan-Yan Chen; Zhangfeng Qin; Jianguo Wang

2009-01-01

117

Theory of Electron Collision Experiments at Intermediate and High Gas Densities  

Microsoft Academic Search

By means of a two-stream approximation, an analytical solution is obtained to the equation of transfer governing the steady-state concentration of mono-energetic electrons within a slab of gas bounded by two infinite planes, one of which emits a constant current density normal to its surface. The theory places no restriction on the gas pressure and includes the effects of inelastic

P. J. Chantry; A. V. Phelps; G. J. Schulz

1966-01-01

118

Theory of gas sensors: response of an electrochemical sensor to multi-component gas mixtures  

Microsoft Academic Search

A first-principles model of the operation of an electrochemical metal oxide gas sensor had been previously used to analyze the response when the sensor was exposed to a simple gas mixture (e.g. O2\\/CO\\/CO2). Here, the model is extended to study the sensor response to a complex gas mixture containing two reducing gases e.g. O2\\/CO\\/CO2\\/H2\\/H2O. In a first version, it is

A. D. Brailsford; M. Yussouff; E. M. Logothetis

1996-01-01

119

Improving centrifugal pump efficiency by impeller trimming  

Microsoft Academic Search

Centrifugal pumps as inevitable part of any desalination plant are significant consumers of energy. Due to high capacities of desalination plants, efficient operation of all their components, including centrifugal pumps is very important. It is often found that centrifugal pumps do not operate in their optimal points for various reasons. One of the methods to improve efficiency of centrifugal pump

Mario Šavar; Hrvoje Kozmar; Igor Sutlovi?

2009-01-01

120

Microwave assisted centrifuge and related methods  

DOEpatents

Centrifuge samples may be exposed to microwave energy to heat the samples during centrifugation and to promote separation of the different components or constituents of the samples using a centrifuge device configured for generating microwave energy and directing the microwave energy at a sample located in the centrifuge.

Meikrantz, David H. (Idaho Falls, ID) [Idaho Falls, ID

2010-08-17

121

Centrifugal dryers keep pace with the market  

SciTech Connect

New plant design and upgrades create a shift in dewatering strategies. The article describes recent developments. Three major manufacturers supply centrifugal dryers - TEMA, Centrifugal & Mechanical Industries (CMI) and Ludowici. CMI introduced a line of vertical centrifugal dryers. TEMA improved the techniques by developing a horizontal vibratory centrifuge (HVC) which simplified maintenance. 3 figs., 1 photo.

Fiscor, S.

2008-03-15

122

Variable-Speed Instrumented Centrifuges  

NASA Technical Reports Server (NTRS)

Report describes conceptual pair of centrifuges, speed of which varied to produce range of artificial gravities in zero-gravity environment. Image and data recording and controlled temperature and gravity provided for 12 experiments. Microprocessor-controlled centrifuges include video cameras to record stop-motion images of experiments. Potential applications include studies of effect of gravity on growth and on production of hormones in corn seedlings, experiments with magnetic flotation to separate cells, and electrophoresis to separate large fragments of deoxyribonucleic acid.

Chapman, David K.; Brown, Allan H.

1991-01-01

123

Centrifugation during the Manhattan Project  

Microsoft Academic Search

Manhattan Engineer District documents from 1942 to early 1944 reveal that consideration of centrifugation as a means of enriching\\u000a uranium-235 during World War II was more extensive than is commonly appreciated. A full-scale prototype centrifuge was fabricated\\u000a and tested at near-production speeds; enrichments at close to levels expected theoretically was demonstrated with pilot-plant\\u000a units; and plans for production plants were

B. Cameron Reed

2009-01-01

124

Theory of heterogeneous decay of a gas-supersaturated solution on passive gas bubbles  

Microsoft Academic Search

It is shown that there can be barrierless heterogeneous nucleation of bubbles of a mixture of active and passive gases on bubbles of a passive gas in a solution supersaturated with active gas. The threshold solution supersaturation above which barrierless heterogeneous nucleation commences is found. All the thermodynamic data on heterogeneous formation of nucleating centers needed to describe the kinetics

F. M. Kuni; A. A. Melikhov

1993-01-01

125

Hyperbolically shaped centrifugal compressor  

NASA Astrophysics Data System (ADS)

Starting from the classical centrifugal compressor, cone shaped in meridional cross section, two modifications are considered on the basis of results from 2D and 3D flow models. The first modification is the change of the meridional cross section to hyperbolically shaped channel. The second modification, proposed on the basis of 2D axisymmetric solution, concerns the shape of blading. On the strength of this solution the blades are formed as 3D shaped blades, coinciding with the recent tendency in 3D designs. Two aims were considered for the change of meridional compressor shape. The first was to remove the separation zone which appears as the flow turns from axial to radial direction. The second aim is to uniformize the flow at exit of impeller. These two goals were considered within the frame of 2D axisymmetric model. Replacing the cone shaped compressor by a hyperbolically shaped one, the separation at the corner was removed. The disc and shroud shape of the compressor was chosen in the way which satisfies the condition of most uniform flow at the compressor exit. The uniformity of exit flow from the rotor can be considered as the factor which influences the performance of the diffuser following the rotor. In the 2D model a family of stream surfaces of S 1 type is given in order to find S 2 surfaces which may be identified with the midblade surfaces of compressor blading. A computation of 3D type has been performed in order to establish the relations between 2D and 3D models in the calculation of flow parameters. In the presented example the 2D model appears as the inverse model which leads to 3D shape of blading whereas the 3D model has been used for the direct solution. In the presented example the confrontation of two models, 2D and 3D, leads to a better understanding of the application of these models to the design procedure.

Puzyrewski, Romuald; Flaszy?ski, Pawel

2003-08-01

126

Bubble Eliminator Based on Centrifugal Flow  

NASA Technical Reports Server (NTRS)

The fluid bubble eliminator (FBE) is a device that removes gas bubbles from a flowing liquid. The FBE contains no moving parts and does not require any power input beyond that needed to pump the liquid. In the FBE, the buoyant force for separating the gas from the liquid is provided by a radial pressure gradient associated with a centrifugal flow of the liquid and any entrained bubbles. A device based on a similar principle is described in Centrifugal Adsorption Cartridge System (MSC- 22863), which appears on page 48 of this issue. The FBE was originally intended for use in filtering bubbles out of a liquid flowing relatively slowly in a bioreactor system in microgravity. Versions that operate in normal Earth gravitation at greater flow speeds may also be feasible. The FBE (see figure) is constructed as a cartridge that includes two concentric cylinders with flanges at the ends. The outer cylinder is an impermeable housing; the inner cylinder comprises a gas-permeable, liquid-impermeable membrane covering a perforated inner tube. Multiple spiral disks that collectively constitute a spiral ramp are mounted in the space between the inner and outer cylinders. The liquid enters the FBE through an end flange, flows in the annular space between the cylinders, and leaves through the opposite end flange. The spiral disks channel the liquid into a spiral flow, the circumferential component of which gives rise to the desired centrifugal effect. The resulting radial pressure gradient forces the bubbles radially inward; that is, toward the inner cylinder. At the inner cylinder, the gas-permeable, liquid-impermeable membrane allows the bubbles to enter the perforated inner tube while keeping the liquid in the space between the inner and outer cylinders. The gas thus collected can be vented via an endflange connection to the inner tube. The centripetal acceleration (and thus the radial pressure gradient) is approximately proportional to the square of the flow speed and approximately inversely proportional to an effective radius of the annular space. For a given FBE geometry, one could increase the maximum rate at which gas could be removed by increasing the rate of flow to obtain more centripetal acceleration. In experiments and calculations oriented toward the original microgravitational application, centripetal accelerations between 0.001 and 0.012 g [where g normal Earth gravitation (.9.8 m/s2)] were considered. For operation in normal Earth gravitation, it would likely be necessary to choose the FBE geometry and the rate of flow to obtain centripetal acceleration comparable to or greater than g.

Gonda, Steve R.; Tsao, Yow-Min D.; Lee, Wenshan

2004-01-01

127

On the Characteristics of Centrifugal-Reciprocating Machines.  

National Technical Information Service (NTIS)

A method of compressing helium gas for cryogenic coolers is presented which uses centrifugal force to reduce the forces on the connecting rod and crankshaft in the usual reciprocating compressor. This is achieved by rotating the piston-cylinder assembly a...

W. H. Higa

1980-01-01

128

Process and Apparatus for Separating Isotopes by Centrifugation.  

National Technical Information Service (NTIS)

The invention concerns a process for separating isotopes by centrifugation, in which the isotopes are introduced into the electrode gap of a magnetron diode in the form of an ion gas, and are separated by the effect of the electromagnetic magnetron field....

H. Gehm

1987-01-01

129

Developments in centrifugal compressor surge control: A technology assessment  

Microsoft Academic Search

There are a number of surge control schemes in current use for centrifugal compressors employed in natural gas transmission systems. Basically, these schemes consist of a set of detection devices that either anticipate surge or detect it at its inception, and a set of control devices that act to prevent surge from occurring. A patent search was conducted in an

K. K. Botros; J. F. Henderson

1994-01-01

130

Theory of gas hydrates: effect of the approximation of rigid water lattice.  

PubMed

One of the assumptions of the van der Waals and Platteeuw theory for gas hydrates is that the host water lattice is rigid and not distorted by the presence of guest molecules. In this work, we study the effect of this approximation on the triple-point lines of the gas hydrates. We calculate the triple-point lines of methane and ethane hydrates via Monte Carlo molecular simulations and compare the simulation results with the predictions of van der Waals and Platteeuw theory. Our study shows that even if the exact intermolecular potential between the guest molecules and water is known, the dissociation temperatures predicted by the theory are significantly higher. This has serious implications to the modeling of gas hydrate thermodynamics, and in spite of the several impressive efforts made toward obtaining an accurate description of intermolecular interactions in gas hydrates, the theory will suffer from the problem of robustness if the issue of movement of water molecules is not adequately addressed. PMID:21728316

Pimpalgaonkar, Hrushikesh; Veesam, Shivanand K; Punnathanam, Sudeep N

2011-08-25

131

Biot-Gassmann theory for velocities of gas hydrate-bearing sediments  

USGS Publications Warehouse

Elevated elastic velocities are a distinct physical property of gas hydrate-bearing sediments. A number of velocity models and equations (e.g., pore-filling model, cementation model, effective medium theories, weighted equations, and time-average equations) have been used to describe this effect. In particular, the weighted equation and effective medium theory predict reasonably well the elastic properties of unconsolidated gas hydrate-bearing sediments. A weakness of the weighted equation is its use of the empirical relationship of the time-average equation as one element of the equation. One drawback of the effective medium theory is its prediction of unreasonably higher shear-wave velocity at high porosities, so that the predicted velocity ratio does not agree well with the observed velocity ratio. To overcome these weaknesses, a method is proposed, based on Biot-Gassmann theories and assuming the formation velocity ratio (shear to compressional velocity) of an unconsolidated sediment is related to the velocity ratio of the matrix material of the formation and its porosity. Using the Biot coefficient calculated from either the weighted equation or from the effective medium theory, the proposed method accurately predicts the elastic properties of unconsolidated sediments with or without gas hydrate concentration. This method was applied to the observed velocities at the Mallik 2L-39 well, Mackenzie Delta, Canada.

Lee, M. W.

2002-01-01

132

Comparison between theory and experiment for universal thermodynamics of a homogeneous, strongly correlated Fermi gas  

NASA Astrophysics Data System (ADS)

We compare the theoretical predictions for universal thermodynamics of a homogeneous, strongly correlated Fermi gas with the latest experimental measurements reported by the ENS group [S. Nascimbène , Nature (London)NATUAS0028-083610.1038/nature08814 463, 1057 (2010)] and the Tokyo group [M. Horikoshi , ScienceSCIEAS0036-807510.1126/science.1183012 327, 442 (2010)]. The theoretical results are obtained using two diagrammatic theories, together with a virial expansion theory combined with a Páde approximation. We find good agreement between theory and experiment. In particular, the virial expansion, using a Páde approximation up to third order, describes the experimental results extremely well down to the superfluid transition temperature, Tc~0.16TF, where TF is the Fermi temperature. The comparison in this work complements our previous comparative study on the universal thermodynamics of a strongly correlated but trapped Fermi gas. The comparison also raises interesting issues about the unitary entropy and the applicability of the Páde approximation.

Hu, Hui; Liu, Xia-Ji; Drummond, Peter D.

2011-06-01

133

Comparison between theory and experiment for universal thermodynamics of a homogeneous, strongly correlated Fermi gas  

SciTech Connect

We compare the theoretical predictions for universal thermodynamics of a homogeneous, strongly correlated Fermi gas with the latest experimental measurements reported by the ENS group [S. Nascimbene et al., Nature (London) 463, 1057 (2010)] and the Tokyo group [M. Horikoshi et al., Science 327, 442 (2010)]. The theoretical results are obtained using two diagrammatic theories, together with a virial expansion theory combined with a Pade approximation. We find good agreement between theory and experiment. In particular, the virial expansion, using a Pade approximation up to third order, describes the experimental results extremely well down to the superfluid transition temperature, T{sub c{approx}}0.16T{sub F}, where T{sub F} is the Fermi temperature. The comparison in this work complements our previous comparative study on the universal thermodynamics of a strongly correlated but trapped Fermi gas. The comparison also raises interesting issues about the unitary entropy and the applicability of the Pade approximation.

Hu Hui; Liu Xiaji; Drummond, Peter D. [ARC Centre of Excellence for Quantum-Atom Optics, Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122, Victoria (Australia)

2011-06-15

134

On the characteristics of centrifugal-reciprocating machines. [cryogenic coolers  

NASA Technical Reports Server (NTRS)

A method of compressing helium gas for cryogenic coolers is presented which uses centrifugal force to reduce the forces on the connecting rod and crankshaft in the usual reciprocating compressor. This is achieved by rotating the piston-cylinder assembly at a speed sufficient for the centrifugal force on the piston to overcome the compressional force due to the working fluid. The rotating assembly is dynamically braked in order to recharge the working space with fluid. The intake stroke consists of decelerating the rotating piston-cylinder assembly and the exhaust stroke consists of accelerating the assembly.

Higa, W. H.

1980-01-01

135

Investigation of surge behavior in a micro centrifugal compressor  

NASA Astrophysics Data System (ADS)

This paper reports the experimental and theoretical study of the surge occurred in prototyping an ultra micro centrifugal compressor. As the first step, the 10 times size model of an ultra micro centrifugal compressor having the 40 mm outer diameter was designed and manufactured. The detailed experimental investigations for the transient behavior of surge with several different values of B parameter were carried out. The experimental results during the surge were compared with those obtained by the non-linear lumped parameter theory in order to validate the effectiveness of the theoretical surge model for the micro centrifugal compressor. As a result, the quite different behavior of the surge appeared for the different values of B both in the experiment and in the analysis.

Mizuki, Shimpei; Asaga, Yuichiro; Ono, Yushi; Tsujita, Hoshio

2006-06-01

136

Miniature Centrifugal Compressor  

NASA Technical Reports Server (NTRS)

Miniature turbocompressor designed for reliability and long life. Cryogenic system includes compressor, turboexpander, and heat exchanger provides 5 W of refrigeration at 70 K from 150 W input power. Design speed of machine 510,000 rpm. Compressor has gas-lubricated journal bearings and magnetic thrust bearing. When compressor runs no bearing contact and no wear.

Sixsmith, Herbert

1989-01-01

137

Structural Materials Evaluation for Oxygen Centrifugal Compressors. Final Report, Project 3528, Report XXXVI.  

National Technical Information Service (NTIS)

Several of the processes for producing high Btu gas from coal require large volumes of high pressure oxygen. Large centrifugal compressors can supply the volumes needed, and the basic engineering technologies for design, stress analysis, rotor balancing, ...

1978-01-01

138

Centrifugation and the Manhattan Project  

NASA Astrophysics Data System (ADS)

A study of U. S. Army Manhattan Engineer District documents reveals that consideration of centrifugation as a means of uranium enrichment during World War II was considerably more extensive than is commonly appreciated. By the time the centrifuge project was abandoned in early 1944 a full-scale prototype unit had been fabricated and tested at near-production speeds, enrichments of close to theoretically-expected levels had been demonstrated with pilot-plant units, and plans for production plants had been developed. This paper will review the history of this little-known aspect of the Project and examine the circumstances of how it came to be discontinued.

Reed, Cameron

2009-05-01

139

Centrifugation and the Manhattan Project  

NASA Astrophysics Data System (ADS)

A study of U. S. Army Manhattan Engineer District documents reveals that consideration of centrifugation as a means of uranium enrichment during World War II was considerably more extensive than is commonly appreciated. By the time the centrifuge project was abandoned in early 1944 a full-scale prototype unit had been fabricated and tested at near-production speeds, enrichments of close to theoretically-expected levels had been demonstrated with pilot-plant units, and plans for production plants had been developed. This paper will review the history of this little-known aspect of the Project and examine the circumstances of how it came to be discontinued.

Reed, Cameron

2009-04-01

140

Generalized anti-centrifugal potential  

NASA Astrophysics Data System (ADS)

We generalize the quantum anti-centrifugal potential in the two-dimensional Euclidean plane to two-dimensional surfaces embedded in three-dimensional Euclidean space. We consider the sphere with two caps removed in some detail. We show that quantum particles in this space are “pushed” towards either of the cap boundaries. We also consider the two-dimensional Euclidean plane with an elliptic area removed and compute the quantum anti-centrifugal potential on the elliptic boundary. It is argued that a sufficiently thin electrically conducting nano-wire shaped as an ellipse will exhibit an inhomogeneous charge distribution due to this quantum potential.

Dandoloff, Rossen; Jensen, Bjørn; Saxena, Avadh

2014-01-01

141

Kinetic Theory of a Spin-1 Bose Condensed Gas at Finite Temperatures  

NASA Astrophysics Data System (ADS)

We derive a kinetic theory of a spin-1 Bose condensed gas at finite temperatures. The theory consists of coupled equations for the condensate and noncondensate. The condensate dynamics is described by a generalized Gross-Pitaevskii (GP) equation including the spin degree of freedom. The condensate and noncondensate atoms interact with each other through the mean field and collisions. From the coupled equations, we determine the condition for static equilibrium of the spin-1 system. We also use the static thermal cloud approximation to derive a generalized GP equation including a dissipative term due to the coupling to a thermal cloud.

Endo, Yuki; Nikuni, Tetsuro

2011-05-01

142

Theory of Bose-Einstein condensation in a microwave-driven interacting magnon gas.  

PubMed

Room temperature Bose-Einstein condensation (BEC) of magnons in YIG films under microwave driving has been recently reported. We present a theory for the interacting magnon gas driven out of equilibrium that provides rigorous support for the formation of the BEC. The theory relies on the cooperative mechanisms created by the nonlinear magnetic interactions and explains the spontaneous generation of quantum coherence and magnetic dynamic order when the microwave driving power exceeds a critical value. The results fit very well the experimental data for the intensity and the decay rate of Brillouin light scattering and for the microwave emission from the BEC as a function of driving power. PMID:21386417

Rezende, Sergio M

2010-04-28

143

Structure and dynamics of noble gas-halogen and noble gas ionic clusters: When theory meets experiment  

NASA Astrophysics Data System (ADS)

As part of this special issue in honor of Gerardo Delgado Barrio, we have reviewed the interplay between experimental and theoretical work on halogen and interhalogen diatomic molecule bonded to one or more noble gas atoms and also ionic clusters consisting of noble gas atoms. Although the Madrid group has worked on many theoretical issues, they have made particularly important contributions to these two topics. Delgado Barrio has often chosen topics for study for which close interactions between theorists and experimentalists are especially useful. During the historical span of the group, we have progressed from approximate models whose goal was to capture the essence of a process even if the details were impossible to reproduce, to an era in which theory is an equal partner with experiment, and, in fact, often provides a detailed understanding beyond that obtained from a careful analysis of state-of-the-art data.

Beswick, J. A.; Halberstadt, N.; Janda, K. C.

2012-05-01

144

Induced velocities of grains embedded in a turbulent gas. [test particle theory application to protostellar clouds  

NASA Technical Reports Server (NTRS)

A theory is presented for the dynamics of dust particles in an incompressible turbulent fluid. Grain-gas coupling occurs through friction forces that are proportional to the mean grain velocity relative to the gas. This test particle theory is applied to the case of Kolmogoroff spectrum in a protostellar cloud. The mean turbulence induced grain velocity and the mean turbulent relative velocity of two grains are calculated. Whereas the former should determine the dust scale height, grain-grain collisions are influenced by the latter. For a reasonable strength of turbulence, the mean induced relative velocity of two particles turns out to be at least as large as the corresponding terminal velocity difference during gravitational settling.

Voelk, H. J.; Morfill, G.; Roeser, S.; Jones, F. C.

1978-01-01

145

Physical Simulation of Subsidence by Centrifuge Techniques.  

National Technical Information Service (NTIS)

The subsidence of linearly elastic strata above shallow mine drifts is studied by using centrifuge simulation techniques and finite-element calculational techniques. The centrifuge simulations, conducted on a 6 ft radius machine, examined six configuratio...

H. F. Sutherland R. A. Schmidt K. W. Schuler S. E. Benzley

1979-01-01

146

High Stability Design for New Centrifugal Compressor.  

National Technical Information Service (NTIS)

It is essential that high-performance centrifugal compressors be free of subsynchronous vibrations. A new high-performance centrifugal compressor has been developed by applying the latest rotordynamics knowledge and design techniques: (1) To improve the s...

H. Kanki K. Katayama S. Morii Y. Mouri S. Umemura

1989-01-01

147

Liquid centrifugation for nuclear waste partitioning.  

National Technical Information Service (NTIS)

The performance of liquid centrifugation for nuclear waste partitioning is examined for the Accelerator Transmutation of Waste Program currently under study at the Los Alamos National Laboratory. Centrifugation might have application for the separation of...

C. D. Bowman

1992-01-01

148

Experimental Investigation of Centrifugal Compressor Stabilization Techniques.  

National Technical Information Service (NTIS)

Results from a series of experiments to investigate techniques for extending the stable flow range of a centrifugal compressor are reported. The research was conducted in a high-speed centrifugal compressor at the NASA Glenn Research Center. The stabilizi...

G. J. Skoch

2003-01-01

149

Life Sciences Centrifuge Facility review  

NASA Technical Reports Server (NTRS)

The Centrifuge Facility Project at ARC was reviewed by a code U team to determine appropriateness adequacy for the ISSA. This report represents the findings of one consultant to this team and concentrates on scientific and technical risks. This report supports continuation of the project to the next phase of development.

Young, Laurence R.

1994-01-01

150

Centrifugal pumps for rocket engines  

NASA Technical Reports Server (NTRS)

The use of centrifugal pumps for rocket engines is described in terms of general requirements of operational and planned systems. Hydrodynamic and mechanical design considerations and techniques and test procedures are summarized. Some of the pump development experiences, in terms of both problems and solutions, are highlighted.

Campbell, W. E.; Farquhar, J.

1974-01-01

151

Vortex flows from centrifugal fan  

Microsoft Academic Search

A comprehensive work has been accomplished for the observation of flow details from a centrifugal fan inside an indoor unit of air conditioners. The present study is finding optimum flow paths in the system that supplies temperature-controlled air into the space human being. Fig. 1 shows the outlet grill of the system (left) and the flow details by PIV system

Jae Won KIM

152

Quantum scattering theory of rotational relaxation and spectral line shapes in H2He gas mixtures  

Microsoft Academic Search

A systematic study is presented of the rotational relaxation and spectral line shape properties of dilute gas mixtures of H2 in He, in an effort to determine the radial and angular dependence of the H2&sngbnd;He intermolecular potential. The quantum mechanical theory of relaxation in gases is reviewed, and we express the results in terms of a matrix of cross sections

Richard Shafer; Roy G. Gordon

1973-01-01

153

Classical Theory of Collision-Induced Absorption in Rare-Gas Mixtures  

Microsoft Academic Search

Collision-induced far-infrared absorption has been observed experimentally in several rare-gas mixtures. A theoretical calculation of these spectra is carried out using classical radiation theory to determine the emission spectrum and converting to absorption via Kirchhoff's law. Using a simple empirical form to describe the variation of the collision-induced dipole moment with internuclear separation, and assuming straight-line collision paths, an analytic

Howard B. Levine; George Birnbaum

1967-01-01

154

Theory of light and atom scattering in the Bose-Einstein condensate of a dilute gas  

SciTech Connect

A semiclassical theory of superradiant light scattering from a Bose-Einstein condensate of a dilute gas is developed without recourse to the mean field approximation. The dynamics and spectrum of superradiant field, as well as the kinetics of formation of coherent atomic states with various translational momenta are calculated. The results are qualitatively consistent with experimental data for atoms scattered in the backward direction relative to that of the exciting laser beam propagation.

Avetisyan, Ya. A. [Russian Academy of Sciences, Institute of Problems of Fine Mechanics and Control (Russian Federation); Trifonov, E. D. [Herzen State Pedagogical University (Russian Federation)], E-mail: thphys@herzen.spb.ru

2006-11-15

155

Theory of metal\\/rare-gas clusters: aspects of open-shell atomic dopants  

Microsoft Academic Search

Studies are reported of the structures and vibronic spectra of metal\\/rare-gas clusters and their ions employing new theoretical methods devised recently for these purposes. Particular attention is addressed to open-shell atomic dopants (B, Al,...), in which cases the theory must include anisotropic (M-Rg) and spin-orbit interactions in the ground states, the avoided crossings of nearly degenerate electronically excited potential energy

J. A. Boatz; R. J. Hinde; J. A. Sheehy; P. W. Langhoff

2003-01-01

156

Modeling gas displacement kinetics in coal with Maxwell-Stefan diffusion theory  

SciTech Connect

The kinetics of binary gas counter-diffusion and Darcy flow in a large coal sample were modeled, and the results compared with data from experimental laboratory investigations. The study aimed for a better understanding of the CO{sub 2}-sequestration enhanced coalbed methane (ECBM) recovery process. The transport model used was based on the bidisperse diffusion mechanism and Maxwell-Stefan (MS) diffusion theory. This provides an alternative approach to simulate multicomponent gas diffusion and flow in bulk coals. A series of high-stress core flush tests were performed on a large coal sample sourced from a Bowen Basin coal mine in Queensland, Australia to investigate the kinetics of one gas displacing another. These experimental results were used to derive gas diffusivities, and to examine the predictive capability of the diffusion model. The simulations show good agreements with the displacement experiments revealing that MS diffusion theory is superior for describing diffusion of mixed gases in coals compared with the constant Fick diffusivity model. The optimized effective micropore and macropore diffusivities are comparable with experimental measurements achieved by other researchers.

Wei, X.R.; Wang, G.X.; Massarotto, P.; Rudolph, V.; Golding, S.D. [University of Queensland, Brisbane, Qld. (Australia). Division of Chemical Engineering

2007-12-15

157

Centrifugal separator devices, systems and related methods  

DOEpatents

Centrifugal separator devices, systems and related methods are described. More particularly, fluid transfer connections for a centrifugal separator system having support assemblies with a movable member coupled to a connection tube and coupled to a fixed member, such that the movable member is constrained to movement along a fixed path relative to the fixed member are described. Also, centrifugal separator systems including such fluid transfer connections are described. Additionally, methods of installing, removing and/or replacing centrifugal separators from centrifugal separator systems are described.

Meikrantz, David H. (Idaho Falls, ID); Law, Jack D. (Pocatello, ID); Garn, Troy G. (Idaho Falls, ID); Todd, Terry A. (Aberdeen, ID); Macaluso, Lawrence L. (Carson City, NV)

2012-03-20

158

Development of a high-specific-speed centrifugal compressor  

Microsoft Academic Search

This paper describes the development of a subscale single-stage centrifugal compressor with a dimensionless specific speed (Ns) of 1.8, originally designed for full-size application as a high volume flow, low pressure ratio, gas booster compressor. The specific stage is noteworthy in that it provides a benchmark representing the performance potential of very high-specific-speed compressors, of which limited information is found

1997-01-01

159

Performance of high pressure COIL with centrifugal bubble singlet oxygen generator  

NASA Astrophysics Data System (ADS)

A centrifugal bubbling SOG is a perspective source of oxygen at high pressure with high depletion of the BHP in the single burn dawn. The theoretical estimations show that at high centrifugal acceleration gas-liquid contact specific surface 30cm -1, frequency of the surface renewal can less than 10 -3s and bubble rise velocity up to 500 cm/s be realized in the bubble SOG. The results of the measurements of O II(1?) yield, chlorine utilization and water fraction at the exit of the centrifugal bubble SOG are presented. A high O II(1?) yield and chlorine utilization higher than 90% have been obtained at chlorine gas loading up to 6 mmole/s per 1 cm2 of the bubbler surface. The ejector COIL powered by centrifugal bubbling SOG demonstrated ~25% of chemical efficiency with specific power 6 kW per 1 litre/s of the BHP volumetric rate.

Zagidullin, Marsel V.; Nikolaev, Valery D.; Khvatov, Nikolay A.; Svistun, Michael I.

2007-05-01

160

Kinetic theories of dynamics and persistent caging in a one-dimensional lattice gas  

PubMed Central

The one-dimensional, single-occupancy lattice gas exhibits highly cooperative particle motion and provides an interesting challenge for theoretical methods designed to describe caging in liquids. We employ this model in an effort to gain insight into caging phenomena in more realistic models of liquids, using a diagrammatic kinetic theory of density fluctuations to develop a series of approximations to the kinetic equations for the van Hove self-correlation function. The approximations are formulated in terms of the irreducible memory function, and we assess their efficacy by comparing their solutions with computer simulation results and the well-known subdiffusive behavior of a tagged particle at long times. The first approximation, a mode coupling theory, factorizes the 4-point propagators that contribute to the irreducible memory function into products of independent single-particle propagators. This approximation fails to capture the subdiffusive behavior of a tagged particle at long times. Analysis of the mode coupling approximation in terms of the diagrammatic kinetic theory leads to the development of two additional approximations that can be viewed as diagrammatic extensions or modifications of mode coupling theory. The first, denoted MC1, captures the long-time subdiffusive behavior of a tagged particle. The second, denoted MC2, captures the subdiffusive behavior of a tagged particle and also yields the correct amplitude of its mean square displacement at long times. Numerical and asymptotic solutions of the approximate kinetic equations share many qualitative and quantitative features with simulation results at all timescales.

Abel, Steven M.; Steve Tse, Ying-Lung; Andersenb, Hans C.

2009-01-01

161

Gas-Kinetic Theory Based Flux Splitting Method for Ideal Magnetohydrodynamics  

NASA Technical Reports Server (NTRS)

A gas-kinetic solver is developed for the ideal magnetohydrodynamics (MHD) equations. The new scheme is based on the direct splitting of the flux function of the MHD equations with the inclusion of "particle" collisions in the transport process. Consequently, the artificial dissipation in the new scheme is much reduced in comparison with the MHD Flux Vector Splitting Scheme. At the same time, the new scheme is compared with the well-developed Roe-type MHD solver. It is concluded that the kinetic MHD scheme is more robust and efficient than the Roe- type method, and the accuracy is competitive. In this paper the general principle of splitting the macroscopic flux function based on the gas-kinetic theory is presented. The flux construction strategy may shed some light on the possible modification of AUSM- and CUSP-type schemes for the compressible Euler equations, as well as to the development of new schemes for a non-strictly hyperbolic system.

Xu, Kun

1998-01-01

162

Time-dependent density functional theory molecular dynamics simulation of doubly charged uracil in gas phase  

NASA Astrophysics Data System (ADS)

We use time-dependent density functional theory and Born-Oppenheimer molecular dynamics methods to investigate the fragmentation of doubly ionized uracil in gas phase. Different initial electronic excited states of the dication are obtained by removing electrons from different inner-shell orbitals of the neutral species. We show that shape-equivalent orbitals lead to very different fragmentation patterns revealing the importance of the intramolecular chemical environment. The results are in good agreement with ionion coincidence measurements of uracil collision with 100 keV protons.

López-Tarifa, Pablo; Hervé du Penhoat, Marie-Anne; Vuilleumier, Rodophe; Gaigeot, Marie-Pierre; Rothlisberger, Ursula; Tavernelli, Ivano; Le Padellec, Arnaud; Champeaux, Jean-Philippe; Alcamí, Manuel; Moretto-Capelle, Patrick; Martín, Fernando; Politis, Marie-Françoise

2014-02-01

163

Gas production in the Barnett Shale obeys a simple scaling theory.  

PubMed

Natural gas from tight shale formations will provide the United States with a major source of energy over the next several decades. Estimates of gas production from these formations have mainly relied on formulas designed for wells with a different geometry. We consider the simplest model of gas production consistent with the basic physics and geometry of the extraction process. In principle, solutions of the model depend upon many parameters, but in practice and within a given gas field, all but two can be fixed at typical values, leading to a nonlinear diffusion problem we solve exactly with a scaling curve. The scaling curve production rate declines as 1 over the square root of time early on, and it later declines exponentially. This simple model provides a surprisingly accurate description of gas extraction from 8,294 wells in the United States' oldest shale play, the Barnett Shale. There is good agreement with the scaling theory for 2,057 horizontal wells in which production started to decline exponentially in less than 10 y. The remaining 6,237 horizontal wells in our analysis are too young for us to predict when exponential decline will set in, but the model can nevertheless be used to establish lower and upper bounds on well lifetime. Finally, we obtain upper and lower bounds on the gas that will be produced by the wells in our sample, individually and in total. The estimated ultimate recovery from our sample of 8,294 wells is between 10 and 20 trillion standard cubic feet. PMID:24248376

Patzek, Tad W; Male, Frank; Marder, Michael

2013-12-01

164

Gas production in the Barnett Shale obeys a simple scaling theory  

PubMed Central

Natural gas from tight shale formations will provide the United States with a major source of energy over the next several decades. Estimates of gas production from these formations have mainly relied on formulas designed for wells with a different geometry. We consider the simplest model of gas production consistent with the basic physics and geometry of the extraction process. In principle, solutions of the model depend upon many parameters, but in practice and within a given gas field, all but two can be fixed at typical values, leading to a nonlinear diffusion problem we solve exactly with a scaling curve. The scaling curve production rate declines as 1 over the square root of time early on, and it later declines exponentially. This simple model provides a surprisingly accurate description of gas extraction from 8,294 wells in the United States’ oldest shale play, the Barnett Shale. There is good agreement with the scaling theory for 2,057 horizontal wells in which production started to decline exponentially in less than 10 y. The remaining 6,237 horizontal wells in our analysis are too young for us to predict when exponential decline will set in, but the model can nevertheless be used to establish lower and upper bounds on well lifetime. Finally, we obtain upper and lower bounds on the gas that will be produced by the wells in our sample, individually and in total. The estimated ultimate recovery from our sample of 8,294 wells is between 10 and 20 trillion standard cubic feet.

Patzek, Tad W.; Male, Frank; Marder, Michael

2013-01-01

165

FORCE2: A multidimensional flow program for gas solids flow theory guide  

SciTech Connect

This report describes the theory and structure of the FORCE2 flow program. The manual describes the governing model equations, solution procedure and their implementation in the computer program. FORCE2 is an extension of an existing B&V multidimensional, two-phase flow program. FORCE2 was developed for application to fluid beds by flow implementing a gas-solids modeling technology derived, in part, during a joint government -- industry research program, ``Erosion of FBC Heat Transfer Tubes,`` coordinated by Argonne National Laboratory. The development of FORCE2 was sponsored by ASEA-Babcock, an industry participant in this program. This manual is the principal documentation for the program theory and organization. Program usage and post-processing of code predictions with the FORCE2 post-processor are described in a companion report, FORCE2 -- A Multidimensional Flow Program for Fluid Beds, User`s Guide. This manual is segmented into sections to facilitate its usage. In section 2.0, the mass and momentum conservation principles, the basis for the code, are presented. In section 3.0, the constitutive relations used in modeling gas-solids hydrodynamics are given. The finite-difference model equations are derived in section 4.0 and the solution procedures described in sections 5.0 and 6.0. Finally, the implementation of the model equations and solution procedure in FORCE2 is described in section 7.0.

Burge, S.W.

1991-05-01

166

Centrifugal separators and related devices and methods  

DOEpatents

Centrifugal separators and related methods and devices are described. More particularly, centrifugal separators comprising a first fluid supply fitting configured to deliver fluid into a longitudinal fluid passage of a rotor shaft and a second fluid supply fitting sized and configured to sealingly couple with the first fluid supply fitting are described. Also, centrifugal separator systems comprising a manifold having a drain fitting and a cleaning fluid supply fitting are described, wherein the manifold is coupled to a movable member of a support assembly. Additionally, methods of cleaning centrifugal separators are described.

Meikrantz, David H. (Idaho Falls, ID); Law, Jack D. (Pocatello, ID); Garn, Troy G. (Idaho Falls, ID); Macaluso, Lawrence L. (Carson City, NV); Todd, Terry A. (Aberdeen, ID)

2012-03-06

167

Theories  

NSDL National Science Digital Library

This activity will help the students understand that science theories change in the face of new evidence, but those changes can be slow in coming. Students will observe how scientific theories change over time, Be introduced to the sophistication of the geocentric model and the time it took to change the theory underpinning the heliocentric model, Compare the heliocentric model to the geocentric model.

2010-01-01

168

Tautochronic centrifugal pendulum vibration absorbers. General design and analysis  

NASA Astrophysics Data System (ADS)

Since the 1930s, centrifugal pendulum vibration absorbers have been used in rotating and reciprocating machinery for the attenuation of torsional vibrations. A large variety of absorber types were suggested and the design was done by linearization theory until the introduction of the tautochronic bifilar pendulum absorbers. Since then, the performance and dynamic stability of this specific absorber type have been considered in analytical and numerical investigations. Different perturbations, e.g. nonlinear mistuning, were considered in order to optimize the system performance, but the characteristic bifilar design remained unchanged. In this paper, a general approach for the design of tautochronic pendulum vibration absorbers is proposed. As a result, it is possible to deal with a large variety of non-bifilar centrifugal vibration absorber designs which provide application-related optimal performance and resolve some of the existing design limitations.

Mayet, J.; Ulbrich, H.

2014-02-01

169

Solid deuterium centrifuge pellet injector  

SciTech Connect

Pellet injectors are needed to fuel long pulse tokamak plasmas and other magnetic confinement devices. For this purpose, an apparatus has been developed that forms 1.3-mm-diam pellets of frozen deuterium at a rate of 40 pellets per second and accelerates them to a speed of 1 km/s. Pellets are formed by extruding a billet of solidified deuterium through a 1.3-mm-diam nozzle at a speed of 5 cm/s. The extruding deuterium is chopped with a razor knife, forming 1.3-mm right circular cylinders of solid deuterium. The pellets are accelerated by synchronously injecting them into a high speed rotating arbor containing a guide track, which carries them from a point near the center of rotation to the periphery. The pellets leave the wheel after 150/sup 0/ of rotation at double the tip speed. The centrifuge is formed in the shape of a centrifugal catenary and is constructed of high strength Kevlar/epoxy composite. This arbor has been spin-tested to a tip speed of 1 km/s.

Foster, C.A.

1983-04-01

170

Solid deuterium centrifuge pellet injector  

SciTech Connect

Pellet injectors are needed to fuel long pulse tokamak plasmas and other magnetic confinement devices. For this purpose, an apparatus has been developed that forms 1.3-mm-diam pellets of frozen deuterium at a rate of 40 pellets per second and accelerates them to a speed of 1 km/s. Pellets are formed by extruding a billet of solidified deuterium through a 1.3-mm-diam nozzle at a speed of 5 cm/s. The extruding deuterium is chopped with a razor knife, forming 1.3-mm right circular cylinders of solid deuterium. The pellets are accelerated by synchronously injecting them into a high speed rotating arbor containing a guide track, which carries them from a point near the center of rotation to the periphery. The pellets leave the wheel after 150/sup 0/ of rotation at double the tip speed. The centrifuge is formed in the shape of a centrifugal catenary and is constructed of high strength KEVLAR/epoxy composite. This arbon has been spin-tested to a tip speed of 1 km/s.

Foster, C.A.

1982-01-01

171

Extended Chaplygin gas as a unified fluid of dark components in varying gravitational constant theory  

NASA Astrophysics Data System (ADS)

Varying gravitational constant G(t) (VG) cosmology is studied in this paper, where the modified Friedmann equation and the modified energy conservation equation are given with respect to the constant-G theory. Considering the extended Chaplygin gas (ECG) as background fluid (or thinking that ECG fluid is induced by the variation of G), the unified model of dark matter and dark energy is obtained in VG theory. The parameter spaces are investigated in the VG-ECG model by using the recent cosmic data. Constraint results show ? =-G/.HG =-0.003-0.020-0.055+0.021+0.034 for the VG-GCG unified model and ?=-0.027-0.032-0.066+0.032+0.059 for the VG-MCG unified model. Equivalently, they correspond to the limits on the current variation of Newton's gravitational constant at 95.4% confidence level |G/.G|today?4.1×10-12 yr-1 and |G/.G|today?6.6×10-12 yr-1. And for z ?3.5, bounds on the variation of G.G in the VG-ECG unified model are in accordance with the experiment explorations of varying G. In addition, in VG theory the used observational data point still cannot distinguish the VG-GCG and VG-MCG unified model from the most popular ?CDM cosmology. Furthermore, to see the effects of varying G and physical properties for VG-ECG fluid, we discuss the evolutionary behaviors of cosmological quantities in VG theory, such as G.G, G..G and equation of state w, etc. For ? <0 a quintom scenario crossing over w=-1 can be realized in the VG-GCG model.

Lu, Jianbo; Xu, Lixin; Tan, Hongyan; Gao, Shanshan

2014-03-01

172

Optimum design for LRE centrifugal pumps  

Microsoft Academic Search

We set up a mathematical model to predict low specific speed liquid rocket engine (LRE) centrifugal pump unit performance. Using the model in question, performance predictions were carried out for 10 types of LRE centrifugal pumps. Relative errors between experimental values and predicted values associated with efficiency and lift were all within 4%. Using the model in question, design optimization

Zuchao Zhu; Guoqian Zhang; Jiren Sun

1995-01-01

173

Influence of Centrifugation on Agglutination of Salmonella.  

National Technical Information Service (NTIS)

The findings of a number of earlier authors on the influence of centrifugation on the agglutination of microbes were confirmed and extended with observations on the influence of temperature, time and centrifugal force. It was shown that the H-agglutinatio...

V. Wagner M. Zdenka

1965-01-01

174

Centrifugation of Coal-Derived Liquids.  

National Technical Information Service (NTIS)

The application of the continuous solid bowl centrifuge to the removal of solids from coal liquefaction products was investigated. The centrifuge removed from 23 to 88% of the input ash from 8 to 73% of the input organic benzene insolubles while flow rate...

Weintraub. M M. L. Weiss S. Akhtar

1980-01-01

175

Different analysis methods for centrifugal fan noise  

Microsoft Academic Search

This work tackles the difficulties that appear with measuring- and analysis techniques for industrial centrifugal fans. In the made study we've tried to achieve data of a centrifugal fan in order to find a characterising fingerprint of the fan itself. Simply looking to the spectral information seems not to offer a detailed view of the underlying phenomenons. This due to

G. Pispolab Touhafi; F. Asdrubali

176

Simplified quality assurance of floor model centrifuges.  

PubMed

Present methods for calibration of the rotor speed of large floor model centrifuges used for blood component preparation can be cumbersome and/or dangerous. This report describes a safe and inexpensive method of modifying a centrifuge lid so that calibration of the machine with a photoelectric tachometer is a simple and safe procedure. PMID:867475

Tregellas, W M; Bourland, D L

1977-01-01

177

Centrifugally driven diffusion of Iogenic plasma  

Microsoft Academic Search

The plasma distribution around Io as measured by Voyager 1 displays an asymmetric discontinuity at Io's orbit that has been suggested to be the signature of centrifugally driven interchange diffusion fed by plasma derived from Io. This hypothesis is explored further and found to be valid. The particular form for the diffusion coefficient appropriate to centrifugally driven turbulence is derived.

G. L. Siscoe; Danny Summers

1981-01-01

178

Centrifugal enhancement of retroviral mediated gene transfer  

Microsoft Academic Search

Centrifugation has been used for many years to enhance infection of cultured cells with a variety of different types of viruses, but it has only recently been demonstrated to be effective for retroviruses (Ho et al. (1993) J. Leukocyte Biol. 53, 208–212; Kotani et al. (1994) Hum. Gene Ther. 5, 19–28). Centrifugation was investigated as a means of increasing the

Alfred B. Bahnsonz; James T. Dunigan; Bora E. Baysal; Trina Mohney; R. Wayne Atchison; Maya T. Nimgaonkar; Edward D. Ball; John A. Barranger

1995-01-01

179

A method of centrifugal compressor performance prediction  

Microsoft Academic Search

Predictions of compressor performance are often wanted for tentative designs where the detailed geometry of blade shapes and flow passages is not completely specified. A method of performance prediction for centrifugal compressors has been developed which requires knowledge of only overall dimensions and blade angles. This method can be applied to any centrifugal compressor with radial outflow (i.e. with no

M. V. Herbert

1979-01-01

180

Gas Clouds in Whirlpool Galaxy Yield Important Clues Supporting Theory on Spiral Arms  

NASA Astrophysics Data System (ADS)

Astronomers studying gas clouds in the famous Whirlpool Galaxy have found important clues supporting a theory that seeks to explain how the spectacular spiral arms of galaxies can persist for billions of years. The astronomers applied techniques used to study similar gas clouds in our own Milky Way to those in the spiral arms of a neighbor galaxy for the first time, and their results bolster a theory first proposed in 1964. M51 The spiral galaxy M51: Left, as seen with the Hubble Space Telescope; Right, radio image showing location of Carbon Monoxide gas. CREDIT: STScI, OVRO, IRAM (Click on image for larger version) Image Files Optical and Radio (CO) Views (above image) HST Optical Image with CO Contours Overlaid Radio/Optical Composite Image of M51 VLA/Effelsberg Radio Image of M51, With Panel Showing Magnetic Field Lines The Whirlpool Galaxy, about 31 million light-years distant, is a beautiful spiral in the constellation Canes Venatici. Also known as M51, it is seen nearly face-on from Earth and is familiar to amateur astronomers and has been featured in countless posters, books and magazine articles. "This galaxy made a great target for our study of spiral arms and how star formation works along them," said Eva Schinnerer, of the National Radio Astronomy Observatory in Socorro, NM. "It was ideal for us because it's one of the closest face-on spirals in the sky," she added. Schinnerer worked with Axel Weiss of the Institute for Millimeter Radio Astronomy (IRAM) in Spain, Susanne Aalto of the Onsala Space Observatory in Sweden, and Nick Scoville of Caltech. The astronomers presented their findings to the American Astronomical Society's meeting in Denver, Colorado. The scientists analyzed radio emission from Carbon Monoxide (CO) molecules in giant gas clouds along M51's spiral arms. Using telescopes at Caltech's Owens Valley Radio Observatory and the 30-meter radio telescope of IRAM, they were able to determine the temperatures and amounts of turbulence within the clouds. Their results provide strong support for a theory that "density waves" explain how spiral arms can persist in a galaxy without winding themselves so tightly that, in effect, they disappear. The density-wave theory, proposed by Frank Shu and C.C. Lin in 1964, says that a galaxy's spiral pattern is a wave of higher density, or compression, that revolves around the galaxy at a speed different from that of the galaxy's gas and stars. Schinnerer and her colleagues studied a region in one of M51's spiral arms that presumably has just overtaken and passed through the density wave. Their data indicate that gas on the trailing edge of the spiral arm, which has most recently passed through the density wave, is both warmer and more turbulent than gas in the forward edge of the arm, which would have passed through the density wave longer ago. "This is what we would expect from the density-wave theory," Schinnerer said. "The gas that passed through the density wave earlier has had time to cool and lose the turbulence caused by the passage," she added. "Our results show, for the first time, how the density wave operates on a cloud-cloud scale, and how it promotes and prevents star formation in spiral arms," Aalto said. The next step, the scientists say, is to look at other spiral galaxies to see if a similar pattern is present. That will have to wait, Schinnerer said, because the radio emission from CO molecules that provides the information on temperature and turbulence is very faint. "When the Atacama Large Millimeter Array (ALMA) comes on line, it will have the ability to extend this type of study to other galaxies. We look forward to using ALMA to test the density-wave model more thoroughly," Schinnerer said. ALMA is a millimeter-wave observatory that will use 64, 12-meter-diameter dish antennas on the Atacama Desert of northern Chile. Now under construction, ALMA will provide astronomers with an unprecedented capability to study the Universe at millimeter wavelengths. The Whirlpool Galaxy was

2004-06-01

181

Kinetic theory analysis of rarefied gas flow through finite length slots  

NASA Technical Reports Server (NTRS)

A kinetic-theory analysis is made of the flow of a rarefied monatomic gas through a two-dimensional slot connecting two reservoirs. Numerical solutions are obtained by the moment and discrete-ordinate methods. The former method portrays the transition-regime characteristics well but has limitations in the free-molecule regime. The latter method gives accurate results in the free-molecule and slip regimes and bolsters confidence in the accuracy of the transition-regime results. The numerical solution for the mass flux through the slot agrees well with an approximate analytical solution of the moment equations for length-to-width ratios from 6 to 0.5, pressure ratios from 0.8 to 0.1, and Knudsen numbers from 5 to 0.5.

Raghuraman, P.; Willis, D. R.

1977-01-01

182

Gas-phase reactions of pd with acetone: A theoretical investigation using density functional theory  

NASA Astrophysics Data System (ADS)

The gas-phase reaction of palladium atom with acetone is investigated using density functional theory. Geometries and energies of the reactants, intermediates, and products involved are calculated. Both ground and excited state potential energy surfaces are investigated in detail. The present results show that the title reaction start with the formation of an ?2-CH3COCH3-metal complex, followed by C-O, C-H, and C-C activation. These reactions can lead to four different products (PdO + C3H6, PdCH2COCH3 + H, PdCH2 + CH3CHO, and PdCOCH2 + CH4). The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.

Dai, Guo-Liang; Wang, Chuan-Feng

2012-12-01

183

Rotor for centrifugal fast analyzers  

DOEpatents

The invention is an improved photometric analyzer of the rotary cuvette type, the analyzer incorporating a multicuvette rotor of novel design. The rotor (a) is leaktight, (b) permits operation in the 90.degree. and 180.degree. excitation modes, (c) is compatible with extensively used Centrifugal Fast Analyzers, and (d) can be used thousands of times. The rotor includes an assembly comprising a top plate, a bottom plate, and a central plate, the rim of the central plate being formed with circumferentially spaced indentations. A UV-transmitting ring is sealably affixed to the indented rim to define with the indentations an array of cuvettes. The ring serves both as a sealing means and an end window for the cuvettes.

Lee, Norman E. (Knoxville, TN)

1985-01-01

184

Centrifuges in gravitational physiology research  

NASA Technical Reports Server (NTRS)

Data from space flight and ground based experiments have clearly demonstrated the importance of Earth gravity for normal physiological function in man and animals. Gravitational Physiology is concerned with the role and influence of gravity on physiological systems. Research in this field examines how we perceive and respond to gravity and the mechanisms underlying these responses. Inherent in our search for answers to these questions is the ability to alter gravity, which is not physically possible without leaving Earth. However, useful experimental paradigms have been to modify the perceived force of gravity by changing either the orientation of subjects to the gravity vector (i.e., postural changes) or by applying inertial forces to augment the magnitude of the gravity vector. The later technique has commonly been used by applying centripetal force via centrifugation.

Ballard, Rodney W.; Davies, Phil; Fuller, Charles A.

1993-01-01

185

Rotor for centrifugal fast analyzers  

DOEpatents

The invention is an improved photometric analyzer of the rotary cuvette type, the analyzer incorporating a multicuvette rotor of novel design. The rotor (a) is leaktight, (b) permits operation in the 90/sup 0/ and 180/sup 0/ excitation modes, (c) is compatible with extensively used Centrifugal Fast Analyzers, and (d) can be used thousands of times. The rotor includes an assembly comprising a top plate, a bottom plate, and a central plate, the rim of the central plate being formed with circumferentially spaced indentations. A uv-transmitting ring is sealably affixed to the indented rim to define with the indentations an array of cuvettes. The ring serves both as a sealing means and an end window for the cuvettes.

Lee, N.E.

1984-01-01

186

Lattice model theory of the equation of state covering the gas, liquid, and solid phases  

NASA Technical Reports Server (NTRS)

The three stable states of matter and the corresponding phase transitions were obtained with a single model. Patterned after Lennard-Jones and Devonshires's theory, a simple cubic lattice model containing two fcc sublattices (alpha and beta) is adopted. The interatomic potential is taken to be the Lennard-Jones (6-12) potential. Employing the cluster variation method, the Weiss and the pair approximations on the lattice gas failed to give the correct phase diagrams. Hybrid approximations were devised to describe the lattice term in the free energy. A lattice vibration term corresponding to a free volume correction is included semi-phenomenologically. The combinations of the lattice part and the free volume part yield the three states and the proper phase diagrams. To determine the coexistence regions, the equalities of the pressure and Gibbs free energy per molecule of the coexisting phases were utilized. The ordered branch of the free energy gives rise to the solid phase while the disordered branch yields the gas and liquid phases. It is observed that the triple point and the critical point quantities, the phase diagrams and the coexistence regions plotted are in good agreement with the experimental values and graphs for argon.

Bonavito, N. L.; Tanaka, T.; Chan, E. M.; Horiguchi, T.; Foreman, J. C.

1975-01-01

187

Boundary-driven nonequilibrium gas flow in a grooved channel via kinetic theory  

NASA Astrophysics Data System (ADS)

The nonequilibrium flow of a gas in a two-dimensional grooved channel, due to the motion of the wall of the channel, is investigated based on kinetic theory. The presence of the rectangular grooves that are placed periodically on the stationary wall results in a two-dimensional flow pattern. The problem is modeled by the linearized Bhatnagar-Gross-Krook (BGK) and S-model kinetic equations, which are solved for the corresponding perturbed distribution functions by the discrete velocity method. Maxwell diffuse type reflecting boundary conditions are used to model the gas-surface interaction, while periodic boundary conditions are imposed at the inlet and outlet of the channel. The computed macroscopic quantities of practical interest include velocity profiles, contours of pressure, density, and temperature, as well as the flow rate and the heat flux through the channel and the drag coefficient along the moving boundary. The results are valid in the whole range of the Knudsen number, from the free molecular regime through the transition and slip regimes up to the hydrodynamic limit, for various values of the depth and the width of the groove and the periodic length of the channel. A comparison between the BGK and S-model results is performed. Several interesting flow patterns and characteristics are examined in terms of the geometrical parameters of the flow configuration, including an unexpected behavior of the velocity profile across the channel at large Knudsen numbers.

Naris, Steryios; Valougeorgis, Dimitris

2007-06-01

188

Plasma instability of a vacuum arc centrifuge.  

PubMed

Ever since conception of the vacuum arc centrifuge in 1980, periodic fluctuations in the ion saturation current and floating potential have been observed in Langmuir probe measurements in the rotation region of a vacuum arc centrifuge. In this work we develop a linearized theoretical model to describe a range of instabilities in the vacuum arc centrifuge plasma column, and then test the validity of the description through comparison with experiment. We conclude that the observed instability is a "universal" instability, driven by the density gradient, in a plasma with finite conductivity. PMID:12006025

Hole, M J; Dallaqua, R S; Simpson, S W; Del Bosco, E

2002-04-01

189

Centrifugal pneumatic disintegration of melts  

Microsoft Academic Search

UDC 621.762.224 In the manufacture of metal powders extensive use is made of the pneumatic method [1] of atomizing melts with compressed gas streams. However, even at considerable specific rates of flow (--0.5--1 NTP m 3 per 1 kg of product) and high pressures (-1.5--2 MPa) of the gas (often an expensive inert gas which is in short supply) it

Sh. M. Sheikhaliev; O. A. Ivanov; S. A. Areshkin

1990-01-01

190

Evaluation of non-centrifuged dried plasma spots versus centrifuged and non-centrifuged plasma for determination of HIV-1 viral load.  

PubMed

Accurate viral load measurement in plasma specimens is subject to the transport conditions applied since the stability of HIV-1 RNA can be at risk. Also, except during the primary infection, HIV is unlikely to be free in circulation because most patients produce specific antibodies in the weeks following primary infection. This study evaluated non centrifuged dried plasma spots versus centrifuged and non centrifuged plasma in the determination of HIV-1 viral load. A total of 40 patients infected with HIV were bled and three groups of samples were prepared from each patient. The first group was centrifuged at 1500×g for 20min, the second was not centrifuged but left to sediment by gravity for up to 3h, and the third was for dried plasma spots prepared from the same non centrifuged plasma. HIV RNA quantitation in plasma and dried plasma spots was evaluated by the Pearson correlation and a T-test. The three groups yielded average viral loads of 58,249; 83,355 and 116,963 copies/ml for centrifuged, non centrifuged and dried plasma spot samples respectively. The correlation for centrifuged versus non centrifuged was R(2)=0.78, that of centrifuged and dried plasma spots was R(2)=0.72 and finally R(2)=0.81 between non centrifuged and dried plasma spot samples. A significant difference in viral load results of centrifuged and DPS samples prepared from non centrifuged plasma was observed. PMID:23422513

Mwebaza, S; Batamwita, R; Karamagi, Y; Mugasa, C; Namwanje, C; Mujuzi, G; Nanteza, A

2013-04-01

191

Two-Stage Centrifugal Fan  

NASA Technical Reports Server (NTRS)

Fan designs are often constrained by envelope, rotational speed, weight, and power. Aerodynamic performance and motor electrical performance are heavily influenced by rotational speed. The fan used in this work is at a practical limit for rotational speed due to motor performance characteristics, and there is no more space available in the packaging for a larger fan. The pressure rise requirements keep growing. The way to ordinarily accommodate a higher DP is to spin faster or grow the fan rotor diameter. The invention is to put two radially oriented stages on a single disk. Flow enters the first stage from the center; energy is imparted to the flow in the first stage blades, the flow is redirected some amount opposite to the direction of rotation in the fixed stators, and more energy is imparted to the flow in the second- stage blades. Without increasing either rotational speed or disk diameter, it is believed that as much as 50 percent more DP can be achieved with this design than with an ordinary, single-stage centrifugal design. This invention is useful primarily for fans having relatively low flow rates with relatively high pressure rise requirements.

Converse, David

2011-01-01

192

Gas-phase uranyl, neptunyl, and plutonyl: hydration and oxidation studied by experiment and theory.  

PubMed

The following monopositive actinyl ions were produced by electrospray ionization of aqueous solutions of An(VI)O(2)(ClO(4))(2) (An = U, Np, Pu): U(V)O(2)(+), Np(V)O(2)(+), Pu(V)O(2)(+), U(VI)O(2)(OH)(+), and Pu(VI)O(2)(OH)(+); abundances of the actinyl ions reflect the relative stabilities of the An(VI) and An(V) oxidation states. Gas-phase reactions with water in an ion trap revealed that water addition terminates at AnO(2)(+)·(H(2)O)(4) (An = U, Np, Pu) and AnO(2)(OH)(+)·(H(2)O)(3) (An = U, Pu), each with four equatorial ligands. These terminal hydrates evidently correspond to the maximum inner-sphere water coordination in the gas phase, as substantiated by density functional theory (DFT) computations of the hydrate structures and energetics. Measured hydration rates for the AnO(2)(OH)(+) were substantially faster than for the AnO(2)(+), reflecting additional vibrational degrees of freedom in the hydroxide ions for stabilization of hot adducts. Dioxygen addition resulted in UO(2)(+)(O(2))(H(2)O)(n) (n = 2, 3), whereas O(2) addition was not observed for NpO(2)(+) or PuO(2)(+) hydrates. DFT suggests that two-electron three-centered bonds form between UO(2)(+) and O(2), but not between NpO(2)(+) and O(2). As formation of the UO(2)(+)-O(2) bonds formally corresponds to the oxidation of U(V) to U(VI), the absence of this bonding with NpO(2)(+) can be considered a manifestation of the lower relative stability of Np(VI). PMID:22656318

Rios, Daniel; Michelini, Maria C; Lucena, Ana F; Marçalo, Joaquim; Bray, Travis H; Gibson, John K

2012-06-18

193

Scalar susceptibilities and four-quark condensates in the meson gas within chiral perturbation theory  

NASA Astrophysics Data System (ADS)

We analyze the properties of four-quark condensates and scalar susceptibilities in the meson gas, within finite temperature chiral perturbation theory (ChPT). The breaking of the factorization hypothesis does not allow for a finite four-quark condensate and its use as an order parameter, except in the chiral limit. This is rigorously obtained within ChPT and is therefore a model-independent result. Factorization only holds formally in the large Nc limit and breaks up at finite temperature even in the chiral limit. Nevertheless, the factorization breaking terms are precisely those needed to yield a finite scalar susceptibility, deeply connected to chiral symmetry restoration. Actually, we provide the full result for the SU(3) quark condensate to next-to-next-to- leading order in ChPT, thus extending previous results to include kaon and eta interactions. This allows us to check the effect of those corrections compared to previous approaches and the uncertainties due to low-energy constants. We provide a detailed analysis of scalar susceptibilities in the SU(3) meson gas, including a comparison between the pure ChPT approach and the virial expansion, where the unitarization of pion scattering is crucial to achieve a more reliable prediction. Through the analysis of the interactions within this approach, we have found that the role of the ? resonance is largely canceled with the scalar isospin two-channel interaction, leaving the ?(770) as the main contribution. Special attention is paid to the evolution towards chiral restoration, as well as to the comparison with recent lattice analysis.

Gómez Nicola, A.; Peláez, J. R.; de Elvira, J. Ruiz

2013-01-01

194

The optimum design on LRE centrifugal pumps  

Microsoft Academic Search

A mathematical model for performance prediction of low-specific-speed (LRE) centrifugal pumps is presented. The predicted performance is shown to be in agreement with experimental results within three to four percent.

Zuchao Zhu; Guoqian Zhang; Jiren Sun

1992-01-01

195

Environmental Applications of the Centrifugal Fast Analyzer.  

National Technical Information Service (NTIS)

The centrifugal fast analyzer (GeMSAEC Fast Analyzer) was applied to the analysis of pollutants in air and water. Since data acquisition and processing are computer controlled, considerable effort went into devising appropriate software. A modified versio...

G. Goldstein J. E. Strain J. L. Bowling

1975-01-01

196

Processing of Centrifuged Solids from Liquefied Coal.  

National Technical Information Service (NTIS)

The centrifuged residues from coal liquefaction processes present two problems which the Pittsburgh ETC has found to be controllable by thermal processing of the material: the residues contain significant amounts of carbon and oil that should be recovered...

M. Weintraub S. Akhtar P. M. Yavorsky R. J. Belt

1978-01-01

197

Closed Continuous-Flow Centrifuge Rotor.  

National Technical Information Service (NTIS)

A blood separation centrifuge rotor is described having a generally parabolic core disposed concentrically and spaced apart within a housing having a similarly shaped cavity. Blood is introduced through a central inlet and into a central passageway enlarg...

J. P. Breillatt C. J. Remenyik W. K. Sartory L. H. Thacker W. Z. Penland

1976-01-01

198

Unsteady Flow Phenomena in Centrifugal Turbomachinery.  

National Technical Information Service (NTIS)

The research is an experimental investigation of system dynamics, unsteady effects, and detailed flow instabilities in a centrifugal compressor. The surge line, which marks the onset of instability and hence limits the minimum stable operating regime, is ...

D. A. Fink

1986-01-01

199

Study of a continuous plasma centrifuge  

Microsoft Academic Search

Results of experiments on a partially ionised argon plasma centrifuge are presented and interpreted. Centrifuge operation is quasi-continuous with a driving current pulse lasting for several seconds. An optical cross-correlation technique has been used to study plasma non-uniformities. Two distinct types of non-uniformity have been identified: (i) slow-moving contra-rotating spokes associated with cathode arc spots, and (ii) rapidly moving co-rotating

S. W. Simpson; P. J. Seebacher; H. K. Messerle

1987-01-01

200

Combination Of Investment And Centrifugal Casting  

NASA Technical Reports Server (NTRS)

Modifications, including incorporation of centrifugal casting, made in investment-casting process reducing scrap rate. Used to make first- and second-stage high-pressure-fuel-turbopump nozzles, containing vanes with thin trailing edges and other thin sections. Investment mold spun for short time while being filled, and stopped before solidification occurs. Centrifugal force drives molten metal into thin trailing edges, ensuring they are filled. With improved filling, preheat and pour temperatures reduced and solidification hastened so less hot tearing.

Creeger, Gordon A.

1994-01-01

201

Renal Response to Chronic Centrifugation in Rats  

NASA Technical Reports Server (NTRS)

Previously reported effects of chronic centrifugation on renal function in mammals are contradictory. The present study was conducted as an effort to provide a comprehensive analysis of renal response to chronic centrifugation (12 days at +2 Gz). Sixteen male Sprague-Dawley rats (210-230 g) were used: eight centrifuged (EC) and eight off centrifuge controls (OCC). During centrifugation EC had lower body weight and food consumption. EC showed a decrease (72%) in water intake for the first two days (T1 and T2) followed by significant increases from T4-T6. EC urine output increased two-fold over the first four days, returning to baseline by T9. EC urea excretion was elevated on T3 through T5. Creatinine, Na(+), K(+), and osmolar excretion were lower than OCC over the last four days of the study. Assuming constant plasma osmolarity and creatinine levels, EC free water clearance (C(sub H2O)) was elevated significantly on T4 when the peak urine output was exhibited. EC also had a greater C(sub H2O) over the last four days, associated with a significantly lower osmolar clearance and GFR. The initial diuresis exhibited during centrifugation can be attributed to a reduced water resorption and increased urea excretion. This diuresis was mediated independent of changes in GFR over the first eight days. However, differences in excretion seen after eight days of centrifugation are probably GFR mediated which would imply animals established a new homeostatic setpoint by that time. Centrifugation elicites an acute alteration in fluid homeostasis followed by adaptation within a week.

Ortiz, Rudy M.; Wang, T. J.; Corbin, B. J.; Wade, C. E.; Hargens, Alan R. (Technical Monitor)

1996-01-01

202

Hydration of gas-phase ytterbium ion complexes studied by experiment and theory  

SciTech Connect

Hydration of ytterbium (III) halide/hydroxide ions produced by electrospray ionization was studied in a quadrupole ion trap mass spectrometer and by density functional theory (DFT). Gas-phase YbX{sub 2}{sup +} and YbX(OH){sup +} (X = OH, Cl, Br, or I) were found to coordinate from one to four water molecules, depending on the ion residence time in the trap. From the time dependence of the hydration steps, relative reaction rates were obtained. It was determined that the second hydration was faster than both the first and third hydrations, and the fourth hydration was the slowest; this ordering reflects a combination of insufficient degrees of freedom for cooling the hot monohydrate ion and decreasing binding energies with increasing hydration number. Hydration energetics and hydrate structures were computed using two approaches of DFT. The relativistic scalar ZORA approach was used with the PBE functional and all-electron TZ2P basis sets; the B3LYP functional was used with the Stuttgart relativistic small-core ANO/ECP basis sets. The parallel experimental and computational results illuminate fundamental aspects of hydration of f-element ion complexes. The experimental observations - kinetics and extent of hydration - are discussed in relationship to the computed structures and energetics of the hydrates. The absence of pentahydrates is in accord with the DFT results, which indicate that the lowest energy structures have the fifth water molecule in the second shell.

Rutkowski, Philip X; Michelini, Maria C.; Bray, Travis H.; Russo, Nino; Marcalo, Joaquim; Gibson, John K.

2011-02-11

203

Liquid/Gas Vortex Separator  

NASA Technical Reports Server (NTRS)

Liquid/gas separator vents gas from tank of liquid that contains gas randomly distributed in bubbles. Centrifugal force separates liquid and gas, forcing liquid out of vortex tube through venturi tube. Gas vented through exhaust port. When liquid detected in vent tube, exhaust port closed, and liquid/gas mixture in vent tube drawn back into tank through venturi.

Morris, B. G.

1986-01-01

204

Importance of centrifugal effects for the internal kink mode stability in toroidally rotating tokamak plasmas  

SciTech Connect

Analytical theory and two different magnetohydrodynamical stability codes are used in a study of the effects of toroidal plasma rotation on the stability of the ideal, internal kink mode in tokamaks. The focus of the paper is on the role that the centrifugal effects on the plasma equilibrium play for the stability of this mode, and results from one code where centrifugal effects are self-consistently included (CASTOR-FLOW) [E. Strumberger et al., Nucl. Fusion 45, 1156 (2005)] are compared with the results from another code where such effects are not taken into account (MISHKA-F) [I. T. Chapman et al., Phys. Plasmas 13, 062511 (2006)]. It is found that, even at rather modest flow speeds, the centrifugal effects are very important for the stability of the internal kink mode. While the results from the two codes can be quite similar for certain profiles in the plasma, completely opposite results are obtained for other profiles. A very good agreement between analytical theory and the numerical results are, both for inconsistent and consistent equilibria, found for plasmas with large aspect ratio. From the analytical theory, the distinctly different stability properties of equilibria with and without centrifugal effects included can be traced to the stabilizing effect of the geodesic acoustic mode (GAM) induced by the plasma rotation. This GAM exists solely as a consequence of the nonuniform plasma density and pressure created by the centrifugal force on the flux surfaces, and a stabilizing coupling of the internal kink instability to this mode cannot therefore take place if the centrifugal effects are not included in the equilibrium. In addition to the GAM stabilization, the effects of the radial profiles of the plasma density and rotation velocity are also found to be significant, and the importance of these effects increases with decreasing aspect ratio.

Wahlberg, C. [Department of Physics and Astronomy, EURATOM/VR Fusion Association, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden); Chapman, I. T. [EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Graves, J. P. [Centre de Recherches en Physique des Plasmas, Association EURATOM-Confederation Suisse, EPFL, 1015 Lausanne (Switzerland)

2009-11-15

205

Experimental investigation of the process of powder manufacture by centrifugal atomization  

Microsoft Academic Search

A plant has been constructed, and a method developed, for the production of nickel alloy powders by centrifugal atomization of molten metal. A high-quality powder produced by this method was virtually free from gas pores in its <630-µm fraction and contained not more than 0.008 wt. % of oxygen.

A. G. Tsipunov; Yu. F. Ternovoi; S. B. Kuratchenko; O. M. Kuimova

1983-01-01

206

Pressure and Field Strength Considerations on the Plasma Centrifuge for Isotope Separation.  

National Technical Information Service (NTIS)

The plasma centrifuge is shown to give an isotope separation ratio alpha approximately equal to the gamma power of the rotationally induced pressure ratio, where gamma is isotope mass difference divided by mean particle mass. This assumes an ideal gas mod...

D. L. Lessor

1976-01-01

207

Characterization of a centrifugal pump impeller under two-phase flow conditions  

Microsoft Academic Search

Multiphase pumping is an area of primary interest, particularly for the petroleum industry, where fair amount of gas can be found in oil wells production. This study presents the results of numerical simulations carried out in a centrifugal pump impeller of an Electrical Submersible Pump (Ns=2063) conveying an air–water mixture. The results include the impeller head and the relative flow

Jose Caridad; Miguel Asuaje; Frank Kenyery; Andrés Tremante; Orlando Aguillón

2008-01-01

208

An investigation of particle dynamics within a centrifugal accelerator type erosion tester  

Microsoft Academic Search

Particle impact erosion is usually tested experimentally using one of two major types of erosion testing device; the gas-blast tester and the centrifugal accelerator type tester. The influence of the choice of the tester on the erosion results obtained has been recognised, together with the need for a better understanding of particle dynamics within the testers to allow correct interpretation

T Deng; M. S. A Bradley; M. S Bingley

2001-01-01

209

Centrifugal Separation and Equilibration Dynamics in an Electron-Antiproton Plasma  

SciTech Connect

Charges in cold, multiple-species, non-neutral plasmas separate radially by mass, forming centrifugally separated states. Here, we report the first detailed measurements of such states in an electron-antiproton plasma, and the first observations of the separation dynamics in any centrifugally separated system. While the observed equilibrium states are expected and in agreement with theory, the equilibration time is approximately constant over a wide range of parameters, a surprising and as yet unexplained result. Electron-antiproton plasmas play a crucial role in antihydrogen trapping experiments.

Andresen, G. B.; Bowe, P. D.; Hangst, J. S. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Ashkezari, M. D.; Hayden, M. E. [Department of Physics, Simon Fraser University, Burnaby BC, V5A 1S6 (Canada); Baquero-Ruiz, M.; Chapman, S.; Fajans, J.; Povilus, A.; So, C. [Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300 (United States); Bertsche, W.; Butler, E.; Charlton, M.; Deller, A.; Eriksson, S.; Humphries, A. J.; Madsen, N.; Werf, D. P. van der [Department of Physics, Swansea University, Swansea SA2 8PP (United Kingdom); Cesar, C. L. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-972 (Brazil); Friesen, T. [Department of Physics and Astronomy, University of Calgary, Calgary AB, T2N 1N4 (Canada)

2011-04-08

210

Supersonic COIL driven by centrifugal bubbling SOG with efficient depletion of chemicals in single pass  

NASA Astrophysics Data System (ADS)

An efficient and compact centrifugal bubbling SOG was employed as energy source in supersonic COIL. A centrifugal bubbling SOG generated gas at 100 torr of total pressure providing 90% of chlorine utilization and 60% of O2(1?) yield with efficient depletion of BHP chemicals in single pass through SOG. A 1 kW class ejector COIL powered by this SOG demonstrated a specific power of 12.5 W per 1cm3/s of BHP volumetric rate at chemical efficiency 22.7%.

Zagidullin, Marsel V.; Nikolaev, Valery D.; Khvatov, Nikolay A.; Svistun, Michael I.

2008-10-01

211

Properties of the electron gas in a magnetic field and their implications for Thomas-Fermi type theories of matter  

NASA Astrophysics Data System (ADS)

We discuss the energy density of the homogeneous three-dimensional electron gas in a magnetic field in the Hartree-Fock approximation and demonstrate that it exhibits a series of first-order phase transitions when new Landau levels begin to be populated. We investigate consequences of this behavior for Thomas-Fermi type theories of matter in magnetic fields, and show that within this approximation it leads to singular features in electron density profiles.

Fushiki, I.; Gudmundsson, E. H.; Pethick, C. J.; Yngvason, J.

1991-01-01

212

Theory of Monte Carlo simulations of the magnetic circular dichroism spectra of alkali metal\\/rare gas systems  

Microsoft Academic Search

The history of magnetic circular dichroism (MCD) spectroscopy in the study of alkali metal\\/rare gas (M\\/Rg) cryogenic systems is reviewed in the context of developing a better understanding of alkali metal\\/hydrogen systems of current interest to the U.S. Air Force as enhanced-performance cryogenic rocket propellants. A new theory for simulating the MCD spectra of M\\/Rg systems is presented together with

John W. Kenney; Jerry A. Boatz; Heidi A. Terrill Vosbein

2005-01-01

213

Similarity theory for the physical simulation of natural gas hydrate reservoir development  

Microsoft Academic Search

In order to apply physical simulation results to natural gas hydrate reservoir parameters to provide a theoretical framework for the design of a development plan, an analytical equation method was used to obtain the similarity criteria of natural gas hydrate reservoir development by physical simulation, based on a mathematical model of natural gas hydrate development. Given the approach of numerical

Yaping LIU; Yueming CHEN; Yuhu BAI; Shuxia LI

2010-01-01

214

Adsorption of SF6 decomposed gas on anatase (101) and (001) surfaces with oxygen defect: A density functional theory study  

NASA Astrophysics Data System (ADS)

The detection of partial discharge by analyzing the components of SF6 gas in gas-insulated switchgears is important to the diagnosis and assessment of the operational state of power equipment. A gas sensor based on anatase TiO2 is used to detect decomposed gases in SF6. In this paper, first-principle density functional theory calculations are adopted to analyze the adsorption of SO2, SOF2, and SO2F2, the primary decomposition by-products of SF6 under partial discharge, on anatase (101) and (001) surfaces. Simulation results show that the perfect anatase (001) surface has a stronger interaction with the three gases than that of anatase (101), and both surfaces are more sensitive and selective to SO2 than to SOF2 and SO2F2. The selection of a defect surface to SO2, SOF2, and SO2F2 differs from that of a perfect surface. This theoretical result is corroborated by the sensing experiment using a TiO2 nanotube array (TNTA) gas sensor. The calculated values are analyzed to explain the results of the Pt-doped TNTA gas sensor sensing experiment. The results imply that the deposited Pt nanoparticles on the surface increase the active sites of the surface and the gas molecules may decompose upon adsorption on the active sites.

Zhang, Xiaoxing; Chen, Qinchuan; Tang, Ju; Hu, Weihua; Zhang, Jinbin

2014-04-01

215

Adsorption of SF6 decomposed gas on anatase (101) and (001) surfaces with oxygen defect: A density functional theory study.  

PubMed

The detection of partial discharge by analyzing the components of SF6 gas in gas-insulated switchgears is important to the diagnosis and assessment of the operational state of power equipment. A gas sensor based on anatase TiO2 is used to detect decomposed gases in SF6. In this paper, first-principle density functional theory calculations are adopted to analyze the adsorption of SO2, SOF2, and SO2F2, the primary decomposition by-products of SF6 under partial discharge, on anatase (101) and (001) surfaces. Simulation results show that the perfect anatase (001) surface has a stronger interaction with the three gases than that of anatase (101), and both surfaces are more sensitive and selective to SO2 than to SOF2 and SO2F2. The selection of a defect surface to SO2, SOF2, and SO2F2 differs from that of a perfect surface. This theoretical result is corroborated by the sensing experiment using a TiO2 nanotube array (TNTA) gas sensor. The calculated values are analyzed to explain the results of the Pt-doped TNTA gas sensor sensing experiment. The results imply that the deposited Pt nanoparticles on the surface increase the active sites of the surface and the gas molecules may decompose upon adsorption on the active sites. PMID:24755845

Zhang, Xiaoxing; Chen, Qinchuan; Tang, Ju; Hu, Weihua; Zhang, Jinbin

2014-01-01

216

Centrifugal compressor design for electrically assisted boost  

NASA Astrophysics Data System (ADS)

Electrically assisted boost is a prominent method to solve the issues of transient lag in turbocharger and remains an optimized operation condition for a compressor due to decoupling from turbine. Usually a centrifugal compressor for gasoline engine boosting is operated at high rotational speed which is beyond the ability of an electric motor in market. In this paper a centrifugal compressor with rotational speed as 120k RPM and pressure ratio as 2.0 is specially developed for electrically assisted boost. A centrifugal compressor including the impeller, vaneless diffuser and the volute is designed by meanline method followed by 3D detailed design. Then CFD method is employed to predict as well as analyse the performance of the design compressor. The results show that the pressure ratio and efficiency at design point is 2.07 and 78% specifically.

Y Yang, M.; Martinez-Botas, R. F.; Zhuge, W. L.; Qureshi, U.; Richards, B.

2013-12-01

217

Effects of chronic centrifugation on mice  

NASA Technical Reports Server (NTRS)

Previous studies have shown that exposure to excess gravity in vitro alters the developmental sequence in embryonic mouse limbs and palates (Duke, Janer and Campbell, 1984; Duke, 1983). The effects of excess gravity on in vivo mammalian development was investigated using a small animal centrifuge. Four-week old female mice exposed to excess gravities of 1.8-3.5 G for eight weeks weighed significantly less than controls. Mice were mated after five weeks of adaptation to excess G, and sacrificed either at gestational day 12 or 18. There were fewer pregnancies in the centrifuged group (4/36) than in controls (9/31), and crown rump lengths (CRL) of embryos developing in the centrifuge were less than CRLs of 1-G embryos. These results show that although immersed in amniotic fluid, embryos are responsive to Delta-G.

Janer, L.; Duke, J.

1984-01-01

218

Prototyping of ultra micro centrifugal compressor-influence of meridional configuration  

NASA Astrophysics Data System (ADS)

In order to investigate the design method for a micro centrifugal compressor, which is the most important component of an ultra micro gas turbine, two types of centrifugal impeller with 2-dimensional blade were designed, manufactured and tested. These impellers have different shapes of hub on the meridional plane with each other. Moreover, these types of impeller were made for the 5 times and the 6 times size of the final target centrifugal impeller with the outer diameter of 4mm in order to assess the similitude for the impellers. The comparison among the performance characteristics of the impellers revealed the influence of the meridional configuration on the performance and the similitude of the compressors.

Hirano, Toshiyuki; Muto, Tadataka; Tsujita, Hoshio

2011-08-01

219

Dynamic mean field theory for lattice gas models of fluids confined in porous materials: Higher order theory based on the Bethe-Peierls and path probability method approximations.  

PubMed

Recently we have developed a dynamic mean field theory (DMFT) for lattice gas models of fluids in porous materials [P. A. Monson, J. Chem. Phys. 128(8), 084701 (2008)]. The theory can be used to describe the relaxation processes in the approach to equilibrium or metastable states for fluids in pores and is especially useful for studying system exhibiting adsorption/desorption hysteresis. In this paper we discuss the extension of the theory to higher order by means of the path probability method (PPM) of Kikuchi and co-workers. We show that this leads to a treatment of the dynamics that is consistent with thermodynamics coming from the Bethe-Peierls or Quasi-Chemical approximation for the equilibrium or metastable equilibrium states of the lattice model. We compare the results from the PPM with those from DMFT and from dynamic Monte Carlo simulations. We find that the predictions from PPM are qualitatively similar to those from DMFT but give somewhat improved quantitative accuracy, in part due to the superior treatment of the underlying thermodynamics. This comes at the cost of greater computational expense associated with the larger number of equations that must be solved. PMID:25028037

Edison, John R; Monson, Peter A

2014-07-14

220

Effects of Centrifuge Diameter and Operation on Rodent Adaptation to Chronic Centrifugation  

NASA Technical Reports Server (NTRS)

This study examined the responses of rats to centrifugation in a constant acceleration field (1.5 G). Centrifuge diameter (1.8m, 2.5m or 6.0m) and schedule of operation (Daily or weekly stop) varied between groups. Body mass, food consumption, water consumption and neurovestibular function were measured weekly. Body temperature and activity were continuously monitored using telemetry. A subset of subjects were videotaped (50 minutes per day) to allow for movement analysis. Exposure to a hyperdynamic field of this magnitude did cause the expected depression in the physiological variables monitored. Recovery was accomplished within a relatively rapid time frame; all variables returned to precentrifugation levels. In general, the magnitudes of the changes and the rate of recovery were similar at different centrifuge diameters and stopping frequency. There were cases, however, in which the magnitude of the response and/or the rate of recovery to a new steady-state were altered as a result of centrifuge diameter. In summary, these results indicate that stopping frequency has little, if any, effect on adaptation to chronic centrifugation. However, the angular velocity (omega), and therefore centrifuge diameter is an important consideration in the adaptation of an organism to chronic centrifugation.

Fuller, Charles A.

1997-01-01

221

Effects of Centrifuge Diameter and Operation on Rodent Adaptation to Chronic Centrifugation  

NASA Technical Reports Server (NTRS)

This study examined the responses of rats to centrifugation in a constant acceleration field (1.5 G). Centrifuge diameter (1.8m, 2.5m or 6.0m) and schedule of operation (Daily or weekly stop) varied between groups. Body mass, food consumption, water consumption and neurovestibular function were measured weekly. Body temperature and activity were continuously monitored using telemetry. A subset of subjects were videotaped (50 minutes per day) to allow for movement analysis. Exposure to a hyperdynamic field of this magnitude did cause the expected depression in the physiological variables monitored. Recovery was accomplished within a relatively rapid time frame; all variables returned to precentrifugation levels. In general, the magnitudes of the changes and the rate of recovery were similar at different centrifuge diameters and stopping frequency. There were cases, however, in which the magnitude of the response and/or the rate of recovery to a new steady-state were altered as a result of centrifuge diameter. In summary, these results indicate that stopping frequency has little, if any, effect on adaptation to chronic centrifugation. However, the angular velocity (omega), and therefore centrifuge diameter is an important consideration in the adaptation of an organism to chronic centrifugation.

Fuller, Charles A.

1992-01-01

222

System analysis of plasma centrifuges and sputtering  

NASA Technical Reports Server (NTRS)

System analyses of cylindrical plasma centrifuges are presented, for which the velocity field and electromagnetic fields are calculated. The effects of different electrode geometrics, induced magnetic fields, Hall-effect, and secondary flows are discussed. It is shown that speeds of 10000 m/sec can be achieved in plasma centrifuges, and that an efficient separation of U238 and U235 in uranium plasmas is feasible. The external boundary-value problem for the deposition of sputtering products is reduced to a Fredholm integral equation, which is solved analytically by means of the method of successive approximations.

Hong, S. H.

1978-01-01

223

Bacterial Cell Surface Damage Due to Centrifugal Compaction  

PubMed Central

Centrifugal damage has been known to alter bacterial cell surface properties and interior structures, including DNA. Very few studies exist on bacterial damage caused by centrifugation because of the difficulty in relating centrifugation speed and container geometry to the damage caused. Here, we provide a simple, versatile method of analysis for describing the compaction of bacteria during centrifugation based on a proposed centrifugation coefficient, C. Values of C can be related to different bacterial cell surface properties. Changing the geometry of the centrifugation container or centrifugation speeds changed the value of C significantly. Initial deposition rates of Staphylococcus aureus ATCC 12600 to a glass surface decayed exponentially from 4,217 to 1,478 cm?2 s?1 with increasing C, while the proportion of staphylococci with a zeta potential of around ?15 mV decreased from 97 to 58%. These surface-sensitive parameters were used independently to derive a critical centrifugation coefficient (0.040), above which centrifugation was considered to impact the outcome of surface-sensitive experiments due to cell surface damage. The critical centrifugation coefficient could successfully predict staphylococcal cell surface damage, i.e., a significant change in initial deposition rate or zeta potential distribution, in 84% of all cases included here, whereas the centrifugation speed could predict damage in only 58% of all cases. Moreover, controlling the centrifugation coefficient within narrow limits over a series of experiments yielded 43% smaller standard deviations in initial staphylococcal deposition rates than with centrifugation at fixed speeds for replicate experiments.

Peterson, Brandon W.; van der Mei, Henny C.; Busscher, Henk J.

2012-01-01

224

Investigations of acidity and nucleophilicity of diphenyldithiophosphinate ligands using theory and gas-phase dissociation reactions  

SciTech Connect

Diphenyldithiophosphinate (DTP) ligands modified with electron-withdrawing trifluoromethyl (TFM) substitutents are of high interest because they have demonstrated potential for exceptional separation of Am3+ from lanthanide3+ cations. Specifically, the bis(ortho-TFM) (L1-) and (ortho-TFM)(meta-TFM) (L2-) derivatives have shown excellent separation selectivity, while the bis(meta-TFM) (L3)- and unmodified DTP (Lu-) did not. Factors responsible for selective coordination have been investigated using density functional theory (DFT) calculations in concert with competitive dissociation reactions in the gas phase. To evaluate the role of (DTP+H) acidity, density functional calculations were used to predict pKa values, which followed the trend of L3 < L2 < L1 < Lu. The order of the TFM-modified (DTP+H) acids was opposite of what would be expected based on the e--withdrawing effects of the TFM group, suggesting that secondary factors are influencing the pKa and nucleophilicity. The relative nucleophilicities of the DTP anions were evaluated by forming metal-mixed ligand complexes in a trapped ion mass spectrometer, and then fragmenting them using competitive collision induced dissociation. Relative to Na+, the unmodified Lu- anion was the strongest nucleophile. Comparing the TFM derivatives, the bis(ortho-TFM) derivative L1- was found to be the strongest nucleophile, while the bis(meta-TFM) L3- was the weakest, a trend consistent with the pKa calculations. DFT modeling of the Na+ complexes suggested that the elevated cation affinity of the L1- and L2- anions was due to donation of electron density from fluorine atoms to the metal center, which was occurring in rotational conformers where the TFM moiety was proximate to the Na+-dithiophosphinate group. Competitive dissociation experiments were performed with the dithiophosphinate anions complexed with europium nitrate species; ionic dissociation of these complexes always produced the TFM-modified dithiophosphinate anions, showing again that the unmodified Lu- was the strongest nucleophile. The Eu(III) nitrate complexes also underwent redox elimination of radical ligands; the tendency of the ligands to undergo oxidation and be eliminated as neutral radicals followed the same trend as the nucleophilicities for Na+, viz. Lu- > L1- > L2- > L3-.

Christopher M. Leavitt; Garold L. Gresham; Michael T. Benson; Jean-Jaques Gaumet; Dean Peterman; John Klaehn; Megan Moser; Frederic Aubriet; Michael J. Van Stipdonk; Gary S. Groenewold

2008-04-01

225

A Very Approximate Theory for Gas Transport in a Polymer Foam  

SciTech Connect

The author is involved with a project that requires calculation of the flow of gas through thin sheets of a flexible polymer foam. Essentially, the foam is a collection of interconnected spherical holes in the polymer matrix. When the material is made, its porosity is in the range of 60-70%. Initially, the sheets are roughly a millimeter thick. In the application, the sheets are compressed between solid surfaces so that their thickness is reduced to approximately 50-75% of the original (thereby reducing the porosity to as low as 20%). The project requires calculating gas transport in the longitudinal direction (in other words, parallel to the thin section of the sheets and perpendicular to the direction of compression). The transport calculations must be done in three different flow regimes. First, with gas pressures high enough so that the gas in the pores is in the continuum regime and thus the transport is governed by the usual equations for flow of a compressible gas in a porous medium. Second, with gas pressures low enough so that the flow is in the free molecular region. In the third regime, the foam is filled with a carrier gas (with pressure high enough to be in continuum) and the flow of interest is that of a small amount of an additional gas. In this third regime, the driving force is diffusion of the trace gas in the carrier.

Kirkpatrick, J.R.

1999-12-01

226

Bureau of Mines Geotechnical Centrifuge Research: A Review.  

National Technical Information Service (NTIS)

The U.S. Bureau of Mines has, primarily through its contract program, used large-scale centrifuges to determine design criteria for tailings embankments. The centrifuge runs were made at two installations, the University of Cambridge, Cambridge, England a...

P. C. McWilliams

1989-01-01

227

Vacuum chamber-free centrifuge with magnetic bearings  

NASA Astrophysics Data System (ADS)

Centrifuges are devices that separate particles of different densities and sizes through the application of a centrifugal force. If a centrifuge could be operated under atmospheric conditions, all vacuum-related components such as the vacuum chamber, vacuum pump, diffusion pump, and sealing could be removed from a conventional centrifuge system. The design and manufacturing procedure for centrifuges could then be greatly simplified to facilitate the production of lightweight centrifuge systems of smaller volume. Furthermore, the maintenance costs incurred owing to wear and tear due to conventional ball bearings would be eliminated. In this study, we describe a novel vacuum chamber-free centrifuge supported by magnetic bearings. We demonstrate the feasibility of the vacuum chamber-free centrifuge by presenting experimental results that verify its high-speed support capability and motoring power capacity.

Park, Cheol Hoon; Kim, Soohyun; Kim, Kyung-Soo

2013-09-01

228

Vacuum chamber-free centrifuge with magnetic bearings.  

PubMed

Centrifuges are devices that separate particles of different densities and sizes through the application of a centrifugal force. If a centrifuge could be operated under atmospheric conditions, all vacuum-related components such as the vacuum chamber, vacuum pump, diffusion pump, and sealing could be removed from a conventional centrifuge system. The design and manufacturing procedure for centrifuges could then be greatly simplified to facilitate the production of lightweight centrifuge systems of smaller volume. Furthermore, the maintenance costs incurred owing to wear and tear due to conventional ball bearings would be eliminated. In this study, we describe a novel vacuum chamber-free centrifuge supported by magnetic bearings. We demonstrate the feasibility of the vacuum chamber-free centrifuge by presenting experimental results that verify its high-speed support capability and motoring power capacity. PMID:24089865

Park, Cheol Hoon; Kim, Soohyun; Kim, Kyung-Soo

2013-09-01

229

Centrifuge Modeling of Torsionally Loaded Pile Groups  

Microsoft Academic Search

This paper reports a series of centrifuge model tests on torsionally loaded 1 2, 2 2, and 3 3 pile groups in sand. The objectives of the paper are to investigate: 1 the response of the pile groups subjected to torsion; 2 the way in which the applied torque is transferred in the pile groups; 3 the internal forces mobilized

L. G. Kong; L. M. Zhang

2007-01-01

230

Specific speed and efficiency of centrifugal impellers  

Microsoft Academic Search

Analysis of the test performance of centrifugal impellers showing a satisfactory correlation of impeller polytropic efficiency vs specific speed based on average impeller density is presented. The use of polytropic efficiency and speed reduces the impeller flow path to an equivalent incompressible frictional path; examination of test impeller efficiency levels and of internal losses indicates that the majority of the

C. Rodgers

1979-01-01

231

Parameterized Design of Centrifugal Fan's Impeller  

Microsoft Academic Search

On the base of the study on the selecting method and regularity of a large number of existing high performance centrifugal fans' main parameters, the corresponding relations between specific speed and specific diameter, as well as between specific speed and exit width of blade, were found. Base on the statistical datas,a new method, which determines the main geometric parameters of

Gui Yan; Pan Dilin; Zhang Lixiang

2010-01-01

232

Research centrifuge accommodations on Space Station Freedom  

NASA Technical Reports Server (NTRS)

Life sciences research using plants and animals on the Space Station Freedom requires the ability to maintain live subjects in a safe and low stress environment for long durations at microgravity and at one g. The need for a centrifuge to achieve these accelerations is evident. Programmatic, technical, and cost considerations currently favor a 2.5 meter diameter centrifuge located either in the end cone of a Space Station Freedom node or in a separate module. A centrifuge facility could support a mix of rodent, plant, and small primate habitats. An automated cage extractor could be used to remove modular habitats in pairs without stopping the main rotor, minimizing the disruption to experiment protocols. The accommodation of such a centrifuge facility on the Space Station represents a significant demand on the crew time, power, data, volume, and logistics capability. It will contribute to a better understanding of the effects of space flight on humans, an understanding of plant growth in space for the eventual production of food, and an understanding of the role of gravity in biological processes.

Arno, Roger D.; Horkachuk, Michael J.

1990-01-01

233

APPLICATION ANALYSIS REPORT: RETECH PLASMA CENTRIFUGAL FURNACE  

EPA Science Inventory

This document is an evaluation of the performance of the Retech, Inc. Plasma Centrifugal Furnace (PCF) and its applicability as a treatment for soils contaminated with organic and/or inorganic compounds. Both the technical and economic aspectsof the technology were examined. A...

234

APPLICATIONS ANALYSIS REPORT: RETECH PLASMA CENTRIFUGAL FURNACE  

EPA Science Inventory

This document is an evaluation of the performance of the Retech Inc. Plasma Centrifugal Furnace (PCF) and its applicability as a treatment technique for soils contaminated with organic and/or inorganic compounds. oth the technical and economic aspects of the technology were exami...

235

Fatigue failure of a centrifugal compressor  

Microsoft Academic Search

A single stage centrifugal type compressor failed during operation and a blade detached. Failure analysis was carried out to delineate the cause of the failure.Investigation shows that multiple fatigue cracks were generated during service from forging defects in the root area of the blade. When they grew to a critical size under (high cycle fatigue) HCF, the blade detached from

N. Ejaz; I. Salam; A. Tauqir

2007-01-01

236

Centrifugal Pump Experiment for Chemical Engineering Undergraduates  

ERIC Educational Resources Information Center

The purpose of this paper is to describe a Centrifugal Pump Experiment that provided an experiential learning experience to chemical engineering undergraduates at the University of Missouri in the spring of 2010 in the Unit Operations Laboratory course. Lab equipment was used by senior students with computer-based data and control technology. In…

Vanderslice, Nicholas; Oberto, Richard; Marrero, Thomas R.

2012-01-01

237

Acoustic similarity law for centrifugal fans  

Microsoft Academic Search

Acoustic similarity laws for fans were experimentally verified. Three, dimensionally similar centrifugal fans of 140, 280 and 560 mm impeller diameter were used. The fans were connected to anechoically terminated discharge ducts. It is shown that the influence of the Reynolds number on the radiated sound pressure is negligible within 140,000 or = Reynolds number or = 2,200,000 which is

W. Neise; B. Barsikow

1980-01-01

238

Acoustic similarity laws for centrifugal fans  

Microsoft Academic Search

Acoustic similarity laws for fans were experimentally verified. Three, dimensionally similar centrifugal fans of 140, 280 and 560 mm impeller diameter were used. The fans were connected to anechoically terminated discharge ducts. It is shown that the influence of the Reynolds number on the radiated sound pressure is negligible within 140,000 or = Reynolds number or = 2,200,000 which is

W. Neise; B. Barsikow

1982-01-01

239

Noise reduction methods in centrifugal fans  

Microsoft Academic Search

A noise control procedure for centrifugal fans is described which reduces both the harmonic and the random noise components. This procedure entails the use of an acoustically soft fan-casing volute and anechoically terminated ducts at the fan inlet and outlet. Experimental measurements show that increasing the cutoff clearance reduces the noise level of higher harmonics of the blade passage frequency,

R. Agnon; T. Gikadi; M. Bartenwerfer; W. Neise

1976-01-01

240

A note on centrifugal particle size analysis  

Microsoft Academic Search

In some centrifugal sedimentation methods of particle size analysis, integral equations arise that must be solved to obtain the particle size distribution. Heretofore, approximate solutions have been used. Exact solutions in useful form are here provided for the suspension sampling and sediment weight methods.

H J Kamack

1972-01-01

241

Family assessment: Centripetal and centrifugal family systems  

Microsoft Academic Search

A consideration of interactional style is useful to both researchers and clinicians interested in family assessment. This paper offers data and process evaluation scales designed to determine family interactional style, conceptualized as a continuum ranging from centripetal (CP) to centrifugal (CF), and containing at the midpoint a mixed area in which facets of both the CP and the CF styles

Martha Kelsey-smith; W. Robert Beavers M. D

1981-01-01

242

Centrifugal Length Separation of Carbon Nanotubes  

SciTech Connect

Separation of single-wall carbon nanotubes (SWCNTs) by length via centrifugation in a high density medium, and the characterization of both the separated fractions and the centrifugation process are presented. Significant quantities of the separated SWCNTs ranging in average length from < 50 nm to ?2 ?m were produced, with the distribution width being coupled to the rate of the separation. Less rapid separation is shown to produce narrower distributions; these length fractions, produced using sodium deoxycholate dispersed SWCNTs, were characterized by UV-visible-nearinfrared absorption and fluorescence spectroscopy, dynamic light scattering, Raman scattering, and atomic force microscopy. Several parameters of the separation were additionally explored: SWCNT concentration, added salt concentration, liquid density, rotor speed, surfactant concentration, and the processing temperature. The centrifugation technique is shown to support 10 mg per day scale processing and is applicable to all of the major SWCNT production methods. The cost per unit of the centrifugation-based separation is also demonstrated to be significantly less than size exclusion chromatography-based separations.

Fagan, Jeffrey A.; Becker, Matthew L.; Chun, Jaehun; Nie, Pingting; Bauer, Barry J.; Simpson, Jeffrey R.; Hight-Walker, Angela; Hobbie, Erik K.

2008-12-16

243

Centrifugal compressor surge and speed control  

Microsoft Academic Search

Previous work on stabilization of compressor surge is extended to include control of the angular velocity of the compressor. A low-order centrifugal compressor model is presented, where the states are mass flow, pressure rise, and rotational speed of the spool. Energy transfer considerations are used to develop a compressor characteristic. In order to stabilize equilibria to the left of the

Jan Tommy Gravdahl; Olav Egeland

1999-01-01

244

Dynamic centrifugal compressor model for system simulation  

Microsoft Academic Search

A dynamic model of a centrifugal compressor capable of system simulation in the virtual test bed (VTB) computational environment is presented. The model is based on first principles, i.e. the dynamic performance including the losses is determined from the compressor geometry and not from the experimentally determined characteristic performance curves. In this study, the compressor losses, such as incidence and

Wei Jiang; Jamil Khan; Roger A. Dougal

2006-01-01

245

Nonlinear Sensitive Control of Centrifugal Compressor  

Microsoft Academic Search

In this work, we treat the problems related to chemical and petrochemical plants of a certain complex process taking the centrifugal compressor as an example, a system being very complex by its physical structure as well as its behaviour (surge phenomenon). We propose to study the application possibilities of the recent control approaches to the compressor behaviour, and consequently evaluate

F. Laaouad; M. Bouguerra; A. Hafaifa; A. Iratni

2007-01-01

246

Positive feedback stabilization of centrifugal compressor surge  

Microsoft Academic Search

Abstract Stable operation of axial and centrifugal compressors is limited towards low mass 1ows due to the occurrence of surge. The stable operating region can be enlarged by active control. In this study, we use a control valve which is fully closed in the desired operating point and only opens to stabilize the system around this point. As a result,

Frank Willems; W. P. M. H. Heemels; Bram de Jager; Anton A. Stoorvogel

2002-01-01

247

Mechanisms of Sensorimotor Adaptation to Centrifugation  

NASA Technical Reports Server (NTRS)

We postulate that centripetal acceleration induced by centrifugation can be used as an inflight sensorimotor countermeasure to retain and/or promote appropriate crewmember responses to sustained changes in gravito-inertial force conditions. Active voluntary motion is required to promote vestibular system conditioning, and both visual and graviceptor sensory feedback are critical for evaluating internal representations of spatial orientation. The goal of our investigation is to use centrifugation to develop an analog to the conflicting visual/gravito-inertial force environment experienced during space flight, and to use voluntary head movements during centrifugation to study mechanisms of adaptation to altered gravity environments. We address the following two hypotheses: (1) Discordant canal-otolith feedback during head movements in a hypergravity tilted environment will cause a reorganization of the spatial processing required for multisensory integration and motor control, resulting in decreased postural stability upon return to normal gravity environment. (2) Adaptation to this "gravito-inertial tilt distortion" will result in a negative after-effect, and readaptation will be expressed by return of postural stability to baseline conditions. During the third year of our grant we concentrated on examining changes in balance control following 90-180 min of centrifugation at 1.4 9. We also began a control study in which we exposed subjects to 90 min of sustained roll tilt in a static (non-rotating) chair. This allowed us to examine adaptation to roll tilt without the hypergravity induced by centrifugation. To these ends, we addressed the question: Is gravity an internal calibration reference for postural control? The remainder of this report is limited to presenting preliminary findings from this study.

Paloski, W. H.; Wood, S. J.; Kaufman, G. D.

1999-01-01

248

Measurement of ground shock in explosive centrifuge model tests  

Microsoft Academic Search

Los Alamos National Laboratory has begun a project to simulate the formation and collapse of underground cavities produced by nuclear explosions using chemical explosions at much smaller scale on a large geotechnical centrifuge. Use of a centrifuge for this project presents instrumentation challenges which are not encountered in tests at similar scale off of the centrifuge. Electromagnetic velocity measuring methods

E. S. Gaffney; K. H. Wohletz; R. G. McQueen

1985-01-01

249

Numerical Research on Performance Prediction for Centrifugal Pumps  

Microsoft Academic Search

Performance prediction for centrifugal pumps is now mainly based on numerical calculation and most of the studies merely focus on one model. Therefore, the research results are not representative. To make an improvement of numerical calculation method and performance prediction for centrifugal pumps, performance of six centrifugal pump models at design flow rate and off design flow rates, whose specific

TAN Minggao; YUAN Shouqi; LIU Houlin; WANG Yong; WANG Kai

250

Development and application of centrifugal contactors in China  

SciTech Connect

Compared with mixer-settlers and extraction columns, centrifugal contactors have some advantages. Since the late 1970's, a series of centrifugal contactors with rotor diameters of 10 to 550 mm have been developed and applied in some industrial fields in China. In this paper, both new improvements and applications of centrifugal contactors in China are reviewed. (authors)

Cao, Pijia; Duan, Wuhua [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 102201 (China)

2008-07-01

251

Lattice Model Theory of the Equation of State Covering the Gas, Liquid, and Solid Phases.  

National Technical Information Service (NTIS)

The three stable states of matter and the corresponding phase transitions were obtained with a single model. Patterned after Lennard-Jones and Devonshires's theory, a simple cubic lattice model containing two fcc sublattices (alpha and beta) is adopted. T...

N. L. Bonavito T. Tanaka E. M. Chan T. Horiguchi J. C. Foreman

1975-01-01

252

Radiatively Driven Acoustic Waves in a Gas in a Cylindrical Tube - Theory and Experiment at Resonance.  

National Technical Information Service (NTIS)

Analysis and measurements have been made for the acoustic pressure generated by the absorption of radiation in an infrared-active gas. This is a relatively simple and fundamental problem with coupling between radiative transfer and acoustic motion, and on...

D. L. Compton

1969-01-01

253

The effects of circumstellar gas on terrestrial planet formation: Theory and observation  

Microsoft Academic Search

Our understanding of the evolution of circumstellar material from dust and gas to fully-formed planets has taken dramatic steps forward in the last decade, driven by rapid improvements in our ability to study gas- and dust-rich disks around young stars and the discovery of more than 200 extra-solar planetary systems around other stars. In addition, our ability to model the

Avram M. Mandell

2007-01-01

254

Unsteady flow phenomena in industrial centrifugal compressor stage  

NASA Technical Reports Server (NTRS)

The results of an experimental investigation on a typical centrifugal compressor stage running on an atmospheric pressure test rig are shown. Unsteady flow was invariably observed at low flow well before surge. In order to determine the influence of the statoric components, the same impeller was repeatedly tested with the same vaneless diffuser, but varying return channel geometry. Experimental results show the strong effect exerted by the return channel, both on onset and on the behavior of unsteady flow. Observed phenomena have been found to confirm well the observed dynamic behavior of full load tested machines when gas density is high enough to cause appreciable mechanical vibrations. Therefore, testing of single stages at atmospheric pressure may provide a fairly accurate prediction of this kind of aerodynamic excitation.

Bonciani, L.; Terrinoni, L.; Tesei, A.

1982-01-01

255

Distribution of fluids in the body of the centrifuged rat  

NASA Technical Reports Server (NTRS)

The effects of exposure to an elevated g-level throughout the period of rapid growth is investigated in a comparison of a group of female Sprague-Dawley rats centrifuged as adults with other groups centrifuged for prolonged intervals starting shortly after weaning. The fluid-solid composition of total body, heart, liver, gut, skin, and muscle for both study groups is compared with that of a control group. None of the changes as a result of centrifugation were truly persistent. The only increases in mass associated with centrifugation and the only responses to centrifugation per se were observed in the skin values.

Pitts, G. C.

1983-01-01

256

The Effects of Neutral Gas Release on Vehicle Charging: Experiment and Theory  

NASA Astrophysics Data System (ADS)

This paper describes an experimental and theoretical research effort related to the mitigation of spacecraft charging by Neutral Gas Release (NGR). The Space Power Experiments Aboard Rockets programs (SPEAR I and III) [Mandel et al., 1998; Berg et al., 1995] and other earlier efforts have demonstrated that NGR is an effective method of controlling discharges in space. The laboratory experimentswere conducted in the large volume Space Physics Simulation Chamber (SPSC) at the Naval Research Laboratory (NRL). A realistic near-earth space environment can be simulated in this device for whichminimumscalingneeds to be performedtorelate the data to space plasma regimes. This environment is similar to that encountered by LEO spacecraft, e.g., the Space Station, Shuttle, and high inclination satellites. The experimental arrangement consists of an aluminum cylinder which can be biased to high negative voltage (0.4 kVgas release valve designed for millisec release times, a pressure-regulated neutral gas reservoir, and variable Mach number nozzles. After the cylinder is charged to high voltage, the neutral gas is released, inducing a breakdown of the gas in the strong electric field about the cylinder. Collection of ions from the newly created dense plasma, along with secondary electron emission from the cylinder surface, provide the return current necessary for grounding the body. The theoretical treatment assumes a simple Townsend discharge along with the fundamental assumption of exponential electron growth in an avalanche fashion as one proceeds from the cathode toward the anode during neutral gas breakdown in the presence of high potentials. In addition the nozzle release of neutral gas is modeled and a simple linear spatial dependence of the applied potential is assumed. This basic model produces quite good results when compared to the experiment.

Walker, D. N.; Amatucci, W. E.; Bowles, J. H.; Fernsler, R. F.; Siefring, C. L.; Antoniades, J. A.; Keskinen, M. J.

1998-11-01

257

Novel Kinetic Theory of the Classical Isotropic Oscillator Gas, the Flexible Shell Model  

NASA Astrophysics Data System (ADS)

Ever since Chapman and Enskog first used the hard sphere model to evaluate the collision integral in the Boltzmann equation, more sophisticated models for molecular encounters have been sought. Rotation of molecules in kinetic theory has been pursued with a number of models, such as the spherocylinder or loaded sphere, to account for that aspect. As these efforts continued, more workers started to incorporate quantum mechanics methods in pursuit of solutions to the Boltzmann equation. Progress there with both rotational and vibrational features of molecules has been attained. Until now though, there has been no classical vibration model for molecules in kinetic theory. Far from standard kinetic theory, here a simple classical mechanics isotropic oscillator is combined, through a flexible shell, with the hard sphere model in a full Chapman Enskog procedure. The intent here has been to introduce the model, so items like translational-vibrational coupling have not been included. Still, the results compliment literature.

Schruben, Dale

2013-12-01

258

Spaceborne centrifugal relays for spacecraft propulsion  

NASA Technical Reports Server (NTRS)

Acceleration using centrifugal relays is a recently discovered method for the acceleration of spaceborne payloads to high velocity at high thrust. Centrifugal relays are moving rotors which progressively accelerate reaction mass to higher velocities. One important engineering problem consists of accurately tracking the position of the projectiles and rotors and guiding each projectile exactly onto the appropriate guide tracks on each rotor. The topics of this research are the system kinematics and dynamics and the computerized guidance system which will allow the projectile to approach each rotor with exact timing with respect to the rotor rotation period and with very small errors in lateral positions. Kinematics studies include analysis of rotor and projectile positions versus time and projectile/rotor interactions. Guidance studies include a detailed description of the tracking mechanism (interrupt of optical beams) and the aiming mechanism (electromagnetic focusing) including the design of electromagnetic deflection coils and the switching circuitry.

Ouzidane, Malika

1991-01-01

259

Colloidal crystallization by a centrifugation method  

NASA Astrophysics Data System (ADS)

Colloidal crystals of high particle concentration were smoothly and continuously fabricated by simple centrifugation of a dispersion of polystyrene particles in water. The larger the applied centrifugal acceleration ? at the bottom of the growing crystals (i.e., the interior wall of the container), the higher the growth rates are. The average grain sizes in the crystals increased with decrease in ?, and below a critical value of ?, we obtained relatively large columnar-shaped grains. The average volume fraction of the obtained colloidal crystals ?ave. increased with an increase in the dispersion's KCl concentration CKCl: at ?=82 G, ?ave.=0.57 and 0.61 at CKCl=2×10 -3 and 8×10 -3 mol kg -1 water, respectively. The grain size also increased with an increase in CKCl. The maximum grain size in this study was greater than 0.3 mm in width and 8 mm in length.

Suzuki, Yoshihisa; Sawada, Tsutomu; Tamura, Katsuhiro

2011-03-01

260

Electrochemical velocimetry on centrifugal microfluidic platforms.  

PubMed

Expanding upon recent applications of interfacing electricity with centrifugal microfluidic platforms, we introduce electrochemical velocimetry to monitor flow in real-time on rotating fluidic devices. Monitoring flow by electrochemical techniques requires a simple, compact setup of miniaturized electrodes that are embedded within a microfluidic channel and are connected to a peripherally-located potentiostat. On-disc flow rates, determined by electrochemical velocimetry, agreed well with theoretically expected values and with optical measurements. As an application of the presented techniques, the dynamic process of droplet formation and release was recorded, yielding critical information about droplet frequency and volume. Overall, the techniques presented in this work advance the field of centrifugal microfluidics by offering a powerful tool, previously unavailable, to monitor flow in real-time on rotating microfluidic systems. PMID:23787459

Abi-Samra, Kameel; Kim, Tae-Hyeong; Park, Dong-Kyu; Kim, Nahui; Kim, Jintae; Kim, Hanshin; Cho, Yoon-Kyoung; Madou, Marc

2013-08-21

261

Acceleration mechanism in vacuum arc centrifuges  

NASA Astrophysics Data System (ADS)

The azimuthal component of the 0022-3727/29/4/015/img1 force, which establishes rotation in vacuum arc centrifuges, is investigated. It is found that the design of the anode grid is one important factor influencing rotation. A range of tungsten-wire grids have been studied experimentally in a vacuum centrifuge operating with a magnesium cathode, and angular velocities have been determined by cross correlation of voltage probe signals. It has been verified that angular velocity increases when grids with higher effective electrical resistivity are used, as predicted theoretically. Grid heating during the 14 ms operating pulse increases resistivity and should also increase angular velocity; this effect has been observed experimentally and agrees with predictions.

Simpson, S. W.; Dallaqua, R. S.; DelBosco, E.

1996-04-01

262

High stability design for new centrifugal compressor  

NASA Technical Reports Server (NTRS)

It is essential that high-performance centrifugal compressors be free of subsynchronous vibrations. A new high-performance centrifugal compressor has been developed by applying the latest rotordynamics knowledge and design techniques: (1) To improve the system damping, a specially designed oil film seal was developed. This seal attained a damping ratio three times that of the conventional design. The oil film seal contains a special damper ring in the seal cartridge. (2) To reduce the destabilizing effect of the labyrinth seal, a special swirl canceler (anti-swirl nozzle) was applied to the balance piston seal. (3) To confirm the system damping margin, the dynamic simulation rotor model test and the full load test applied the vibration exciting test in actual load conditions.

Kanki, H.; Katayama, K.; Morii, S.; Mouri, Y.; Umemura, S.; Ozawa, U.; Oda, T.

1989-01-01

263

Vibration analysis of large centrifugal pump rotors  

NASA Astrophysics Data System (ADS)

Through the critical speed of centrifugal pumps, internal flow field and the force of the impeller, we analyze centrifugal pump vibration. Using finite element analysis software ANSYS to calculate the natural frequency of the rotor system and the critical speed; with the help of the Fluent software to simulate pump internal flow field, we conclude that speed increase will not cause intense vibration of the fluid in the pump. Using unsteady numerical simulation we discovered that in an impeller suffering transient radial force cyclical change periodically, as well as the frequency size determined by the product of the impeller speed and number of blades, resonance phenomena should make impeller to transient radial force frequency. If wanting to avoid pump resonance when it is running away, the transient radial force frequency should avoid the frequency range which can cause resonance.

Y Zhao, W.; Ge, J. G.; Ma, D.; Li, C. M.; Bao, S. B.

2013-12-01

264

Supernatant decanting on a centrifugal platform  

PubMed Central

This study presents a novel approach to decant supernatant on a centrifugal platform. By manipulating the centrifugally induced pressure and the elastic deformation of the plastic lids in the decanting chamber, fixed amounts of the supernatant can be decanted into the detection chamber at lower rotational speeds. The experimental results showed that decanted volume is affected by the volume of deformation and the operating parameters. Factors that influence the decanting ratio are also discussed. This approach has the advantages of simple design and low manufacturing cost; further, it has no need of surface modification. It has been applied to on-disk separation of plasma from whole blood, and the results showed good stability and repeatability.

Shih, Chih-Hsin; Lu, Chien-Hsing; Yuan, Wei-Li; Chiang, Wei-Ling; Lin, Chia-Hui

2011-01-01

265

Optimum design for LRE centrifugal pumps  

NASA Astrophysics Data System (ADS)

We set up a mathematical model to predict low specific speed liquid rocket engine (LRE) centrifugal pump unit performance. Using the model in question, performance predictions were carried out for 10 types of LRE centrifugal pumps. Relative errors between experimental values and predicted values associated with efficiency and lift were all within 4%. Using the model in question, design optimization with efficiency as the target function was carried out on AM-7H and O pumps as well as AM-1R pumps and AM-50 pumps. Results clearly show that, with a presupposition of surety systems possessing high vapor corrosion characteristics, the efficiencies of these four types of pumps can be respectively raised 6.5%, 5.22%, 5.2%, and 4.41%.

Zhu, Zuchao; Zhang, Guoqian; Sun, Jiren

1995-05-01

266

Centrifugally driven diffusion of Iogenic plasma  

NASA Technical Reports Server (NTRS)

The plasma distribution around Io as measured by Voyager 1 displays an asymmetric discontinuity at Io's orbit that has been suggested to be the signature of centrifugally driven interchange diffusion fed by plasma derived from Io. This hypothesis is explored further and found to be valid. The particular form for the diffusion coefficient appropriate to centrifugally driven turbulence is derived. The nonlinear character of this kind of diffusion is thereby made explicit. Solutions to the nonlinear, time-independent and linearized, time-dependent diffusion equations are given. These display a markedly conservative behavior. The nonlinear, steady state solutions are identical in form to the solutions of the previously studied equation of linear, atmospherically driven diffusion. The linearized, time-dependent solutions exhibit a negative feed-back quality that buffers the response of the density to changes in the source strength. Estimates of the source strength, the diffusion coefficient, and the signal propagation speed are also given.

Siscoe, G. L.; Summers, D.

1981-01-01

267

Behavior of capillary valves in centrifugal microfluidic devices prepared by three-dimensional printing  

Microsoft Academic Search

This paper details the behavior of capillary valves in centrifugal microfluidic devices prepared by three-dimensional (3D),\\u000a or solid-object, printing. Microfluidic structures containing valve channels with different widths, heights, and radial distances\\u000a from the center of rotation were studied and compared with extant capillary valve theories. Due to the printing process, the\\u000a produced valve channels possessed a ridged or “scalloped” pattern.

Jessica L. Moore; Austin McCuiston; Isaac Mittendorf; Rudy Ottway; R. Daniel Johnson

2011-01-01

268

Spreading of thin rotating films: Competition of thermal Marangoni, centrifugal, and gravitational forcing  

NASA Astrophysics Data System (ADS)

We experimentally probe the quasi static spreading of a sessile drop on a substrate under the influence of competing gravitational, thermo capillary (Marangoni) and centrifugal forcing. We use silicone oil on a prewetted silicon wafer, and we employ an interferometric technique to study the evolution of the film height profile. We discuss our results in the context of recent theory developed by Bostwick et al.

Dijksman, Joshua; Mukhopadhyay, Shomeek; Behringer, Robert

2011-11-01

269

Potential flow through centrifugal pumps and turbines  

NASA Technical Reports Server (NTRS)

The methods of conformal transformation up to the present have been applied to the potential flows in the rotation of solid bodies only to a limited extent. This report deals with aspects of centrifugal pumps and turbines such as: the complex potential for rotation, potential for the flow due to the blade rotation, velocities at the blade tip, comparison with "infinite number of blades," and a variable number of blades.

Sorensen, E

1941-01-01

270

CENTRIFUGAL VIBRATION TEST OF RC PILE FOUNDATION  

NASA Astrophysics Data System (ADS)

It is necessary that nonlinear responses of structures are clarified by soil-structure interaction analysis for the purpose of evaluating the seismic performances of underground structure or foundation structure. In this research, centrifuge shake table tests of reinforced concrete pile foundation installed in the liquefied ground were conducted. Then, finite element analyses for the tests were conducted to confirm an applicability of the analytical method by comparing the experimental results and analytical results.

Higuchi, Shunichi; Tsutsumiuchi, Takahiro; Otsuka, Rinna; Ito, Koji; Ejiri, Joji

271

A centrifuge COâ pellet cleaning system  

Microsoft Academic Search

Centrifuge-based cryogenic pellet accelerator technology, originally developed at Oak Ridge National Laboratory (ORNL) for the purpose of refueling fusion reactors with high-speed pellets of frozen deuterium\\/tritium,is now being developed as a method of cleaning without the use of conventional solvents. In these applications large quantities of pellets made of frozen COâ or argon are accelerated in a high-speed rotor. The

C. A. Foster; P. W. Fisher; W. D. Nelson; D. E. Schechter

1993-01-01

272

A centrifuge COâ pellet cleaning system  

Microsoft Academic Search

Centrifuge-based cryogenic pellet accelerator technology, originally developed at Oak Ridge National Laboratory (ORNL) for the purpose of refueling fusion reactors with high-speed pellets of frozen deuterium\\/tritium, is now being developed as a method of cleaning without the use of conventional solvents. In these applications large quantities of pellets made of frozen COâ or argon are accelerated in a high-speed rotor.

C. A. Foster; P. W. Fisher; W. D. Nelson; D. E. Schechter

1994-01-01

273

Centrifugal shot blasting. Innovative technology summary report  

SciTech Connect

At the US Department of Energy (DOE) Fernald Environmental Management Project (FEMP), the Facilities Closure and Demolition Projects Integrated Remedial Design/Remedial Action (RD/RA) work plan calls for the removal of one inch (1 in) depth of concrete surface in areas where contamination with technetium-99 has been identified. This report describes a comparative demonstration between two concrete removal technologies: an innovative system using Centrifugal Shot Blasting (CSB) and a modified baseline technology called a rotary drum planer.

Not Available

1999-07-01

274

Operating and maintenance guidelines for screenbowl centrifuges  

SciTech Connect

Plant dewatering circuits equipped with screenbowl centrifuges need to be well designed, properly operated, and adequately maintained to maximize the dewatering performance. The most important 'feed variables' are particle size, dry solids feed rate and slurry flow rate. The most important 'machine variables' include pool depth, rotational speed and gearbox ratio. The article discusses the effect of these parameters and offers some maintenance guidelines. The article was adapted from a paper presented at CoalPrep 2008. 6 refs., 2 figs., 2 tabs.

Jahnig, W.S.R.; Bratton, R.; Luttrell, G. [Decanter Machine, Johnson City, TN (United States)

2009-01-15

275

Theory versus experiment for the rotordynamic coefficients of annular gas seals. I - Test facility and apparatus  

NASA Technical Reports Server (NTRS)

A facility and apparatus are described for determining the rotordynamic coefficients and leakage characteristics of annular gas seals. The coefficients and leakage characteristics of annular gas seals. The apparatus has a current top speed of 8000 cpm with a nominal seal diameter of 15.24 cmn (6 in.). The air supply unit yields a seal pressure ratio of approximately 7. An external shaker is used to excite the test rotor. The capability to independently calculate all rotordynamic coefficients at a given operating condition with one excitation frequency are discussed.

Childs, D. W.; Nelson, C. E.; Nicks, C.; Scharrer, J.; Elrod, D.

1985-01-01

276

EM Task 9 - Centrifugal Membrane Filtration  

SciTech Connect

This project is designed to establish the utility of a novel centrifugal membrane filtration technology for the remediation of liquid mixed waste streams at US Department of Energy (DOE) facilities in support of the DOE Environmental Management (EM) program. The Energy and Environmental Research Center (EERC) has teamed with SpinTek Membrane Systems, Inc., a small business and owner of the novel centrifugal membrane filtration technology, to establish the applicability of the technology to DOE site remediation and the commercial viability of the technology for liquid mixed waste stream remediation. The technology is a uniquely configured process that makes use of ultrafiltration and centrifugal force to separate suspended and dissolved solids from liquid waste streams, producing a filtered water stream and a low-volume contaminated concentrate stream. This technology has the potential for effective and efficient waste volume minimization, the treatment of liquid tank wastes, the remediation of contaminated groundwater plumes, and the treatment of secondary liquid waste streams from other remediation processes, as well as the liquid waste stream generated during decontamination and decommissioning activities.

Stevens, B.G.; Stepan, D.J.; Hetland, M.D.

1998-11-01

277

The Application of Centrifuges 'Reduced Gravity' Research.  

NASA Astrophysics Data System (ADS)

It is shown that life has emerged on Earth somewhere in the early Archaean (3800-2500 million years ago). Since then life has evolved from single cell into to multicellular complex organism under unit gravity conditions. Little is known about how life would have been evolved under different gravity conditions. In light of the current quests for Earth-like planets by astronomers; what life forms could be expected on planets with different gravity fields? Also the human endeavors in spaceflight (microgravity) and exploration programs (Moon, Mars) it is interesting and might be even vital to know and understand how gravity acts upon the human body in long duration space flights. Hyper-gravity, any acceleration acceding 9.81 ms-2, can relatively easily be generated on Earth using centrifuges. Long duration hypo-gravity (¡9.81 ms-2) is more cumbersome. For real microgravity we need free falling satellites such as ISS. For simulation on ground one can use clinostats, random positioning machines or levitating magnets. But could centrifuges also be applied to study a reduced gravity environment? What I would explore in this paper are the possibilities how centrifuges could be applied to study the effects of a 'reduced gravity environment' in, especially, life sciences studies.

van Loon, Jack J. W. A.

278

Compact, Automated Centrifugal Slide-Staining System  

NASA Technical Reports Server (NTRS)

The Directional Acceleration Vector-Driven Displacement of Fluids (DAVD-DOF) system, under development at the time of reporting the information for this article, would be a relatively compact, automated, centrifugally actuated system for staining blood smears and other microbiological samples on glass microscope slides in either a microgravitational or a normal Earth gravitational environment. The DAVD-DOF concept is a successor to the centrifuge-operated slide stainer (COSS) concept, which was reported in Slide-Staining System for Microgravity or Gravity (MSC-22949), NASA Tech Briefs, Vol. 25, No. 1 (January, 2001), page 64. The COSS includes reservoirs and a staining chamber that contains a microscope slide to which a biological sample is affixed. The staining chamber is sequentially filled with and drained of staining and related liquids from the reservoirs by use of a weighted plunger to force liquid from one reservoir to another at a constant level of hypergravity maintained in a standard swing-bucket centrifuge. In the DAVD-DOF system, a staining chamber containing a sample would also be sequentially filled and emptied, but with important differences. Instead of a simple microscope slide, one would use a special microscope slide on which would be fabricated a network of very small reservoirs and narrow channels connected to a staining chamber (see figure). Unlike in the COSS, displacement of liquid would be effected by use of the weight of the liquid itself, rather than the weight of a plunger.

Feeback, Daniel L.; Clarke, Mark S. F.

2004-01-01

279

Research opportunities with the Centrifuge Facility  

NASA Technical Reports Server (NTRS)

The Centrifuge Facility on Space Station Freedom will consist of a 2.5-meter diameter Centrifuge accommodating two concentric rings of habitats and providing variable g-forces between 0.01 g and 2.0 g; modular habitats providing housing and lifesupport for rats, mice, and plants; a habitat holding system providing power, water, airflow and other utilities to several modular habitats; and a life sciences glovebox, an isolated work volume accommodating simultaneous operations by at least two scientists and providing lighting, airflow, video and data access, and other experiment support functions. The centrifuge facility will enable long-duration animal and plant microgravity research not previously possible in the NASA flight research program. It will offer unprecedented opportunities for use of on-board 1-g control populations and statistically significant numbers of specimens. On orbit 1-g controls will allow separation of the effects of microgravity from other environmental factors. Its selectable-g and simultaneous multiple-g capabilities will enable studies of gravitational thresholds, the use of artificial gravity as a countermeasure to the effects of microgravity, and ready simulation of Lunar and Martian gravities.

Funk, Glenn A.

1992-01-01

280

Theory, Theory  

NSDL National Science Digital Library

This lesson includes a theory-evaluation activity. A set of five scenarios (theories for how diverse life came into existence on Earth) is divided evenly throughout the class, so each student is asked to evaluate one theory. Students then come together in groups of five, so that all theories are represented in each group, where they are compared and evaluated. Each group reports to the entire class for further discussion and clarifications.

Kimmel, Michael

2007-12-12

281

A UNIFIED THEORY OF NON-IDEAL GAS LATTICE BOLTZMANN MODELS  

Microsoft Academic Search

A non-ideal gas lattice Boltzmann model is directly derived, in an a priori fashion, from the Enskog equation for dense gases. The model is rigorously obtained by a systematic procedure to discretize the Enskog equation (in the presence of an external force) in both phase space and time. The lattice Boltzmann model derived here is thermodynamically consistent and is free

LI-SHI LUO

282

High speed active gas\\/odor sensing system using adaptive control theory  

Microsoft Academic Search

An active gas\\/odor sensing system using an internal blender was previously proposed to measure the mixture composition of an aroma. In the system, the mixture composition of the blender outlet was repeatedly adjusted using an optimization algorithm to match the sensor array output pattern of blended vapor to that of a test vapor. The system is highly flexible and can

T. Nakamoto; N. Okazaki; T. Mornzumi

1997-01-01

283

Analysis and theory of gas transport in microporous sol-gel derived ceramic membranes  

Microsoft Academic Search

Sol-gel modification of mesoporous alumina membranes is a very successful technique to improve gas separation performance. Due to the formed microporous top layer, the membranes show activated transport and molecular sieve-like separation factors. This paper concentrates on the mechanism of activated transport (also often referred to as micropore diffusion or molecular sieving). Based on a theoretical analysis, results from permeation

R. S. A. de Lange; K. Keizer; A. J. Burggraaf

1995-01-01

284

Axial inlet conversion to a centrifugal compressor with magnetic bearings  

SciTech Connect

NOVA's Alberta Gas Transmission Division transports natural gas via pipeline throughout the province of Alberta, Canada, exporting it to eastern Canada, US, and British Columbia. There is a continuing effort to operate the facilities and pipeline at the highest possible efficiency. One area being addressed to improve efficiency is compression of the gas. By improving compressor efficiency, fuel consumption and hence operating costs can be reduced. One method of improving compressor efficiency is by converting the compressor to an axial inlet configuration, a conversion that has been carried out more frequently in the past years. Concurrently, conventional hydrodynamic bearings have been replaced with magnetic bearings on many centrifugal compressors. This paper discusses the design and installation for converting a radial overhung unit to an axial inlet configuration, having both magnetic bearings and a thrust reducer. The thrust reducer is required to reduce axial compressor shaft loads, to a level that allows the practical installation of magnetic bearings within the space limitations of the compressor (Bear and Gibson, 1992).

Novecosky, T. (NOVA Corp., Edmonton, Alberta (Canada))

1994-01-01

285

Temperature controlled centrifugation improves sperm retrieval.  

PubMed

Sperm retrieval techniques form an integral part of the assisted reproductive programme. The success of sperm separation is measured by the number of motile sperm retrieved from a given semen sample. The study aimed to evaluate the effect of temperature during sperm preparation events on the number and percentage motile sperm retrieved following a double wash swim-up procedure. Thirty semen samples were obtained from 10 normozoospermic donors. After collection samples were divided into two aliquots, one aliquot was placed in an incubator at 34 °C, while the second aliquot was left at room temperature (25 °C). Sperm motility assessments were recorded with a computer assisted sperm analyser. Motile sperm fractions were retrieved from the semen samples following a double wash swim-up technique. Two tubes were prepared for each experiment. Tubes were placed in two different centrifuges: (i) SpermFuge (Shivani Industries, India) with temperature centrifuge control (34 °C) and (ii) Sigma with no temperature control facilities. Both centrifuges were set at 484 g for 5 min. Following the second wash, sperm pellets were layered with culture medium, and sperm was allowed to swim up. Supernatants were removed and analysed for sperm concentration and motility values. Percentage motile sperm was transformed to ARCSIN values and results of the two centrifugation methods at 34 °C and room temperature were compared with Mann-Whitney test for independent samples. The mean sperm concentration retrieved at 34 °C was 43.8 ± 50 (SpermFuge) and 32.7 ± 21 (Sigma) (P < 0.05), compared to retrieved concentration at room temperature namely, 30.9 ± 33 (SpermFuge) and 30.6 ± 17 (Sigma) (P ? 0.05). The mean percentage motile sperm at 34 °C was 64.0 ± 19 (SpermFuge) and 44.2 ± 24 (Sigma) (P = 0.02), while at room temperature the percentage motile sperm was 54.7 ± 17 (SpermFuge) compared to 46.5 ± 14 (Sigma) (P ? 0.05). Centrifuge temperature and incubation temperature significantly influenced the percentage retrieved motile sperm. The use of temperature-controlled sperm preparation might have clinical value for men with poor sperm motility values. PMID:21561464

Franken, D R; van Wyk, R; Stoumann, C; Avari, K

2011-06-01

286

Theory of dark resonances for alkali-metal vapors in a buffer-gas cell  

SciTech Connect

We develop an analytical theory of dark resonances that accounts for the full atomic-level structure, as well as all field-induced effects such as coherence preparation, optical pumping, ac Stark shifts, and power broadening. The analysis uses a model based on relaxation constants, which assumes the total collisional depolarization of the excited state. A good qualitative agreement with the experiments for Cs in Ne is obtained.

Taichenachev, A.V.; Yudin, V.I. [Novosibirsk State University, Pirogova 2, Novosibirsk 630090 (Russian Federation); Institute of Laser Physics SD RAS, Novosibirsk 630090 (Russian Federation); Time and Frequency Division, NIST Boulder, 325 South Broadway, Boulder, Colorado 80305 (United States); Wynands, R.; Staehler, M. [Institut fuer Angewandte Physik, Universitaet Bonn, Wegelerstrasse 8, D-53115 Bonn (Germany); Kitching, J.; Hollberg, L. [Time and Frequency Division, NIST Boulder, 325 South Broadway, Boulder, Colorado 80305 (United States)

2003-03-01

287

Theory for radiatively driven harmonic acoustic waves in a confined gas.  

NASA Technical Reports Server (NTRS)

A detailed theoretical study is made of radiatively driven acoustic waves inside a closed cylindrical tube. The formulation accounts for all the essential phenomena for a gas in vibrational equilibrium - namely, gas motion, longitudinal and radial viscous dissipation, longitudinal and radial heat conduction, and radiative transfer with spectral detail included. An approximate expression is derived for the pressure response. This solution is applicable to arbitrary spectral distribution of the radiative absorption coefficient, under conditions attainable in the laboratory. The solution includes both tuned and untuned acoustic conditions as well as the spectrophone limit - that is, the condition where the length of the tube is much smaller than the length of the acoustic wave. The influence of spectral detail on the pressure response is illustrated.

Chapman, G. T.; Compton, D. L.; Vincenti, W. G.

1973-01-01

288

Rayleigh-Taylor Instability within Sediment Layers Due to Gas Retention: Preliminary Theory and Experiments  

SciTech Connect

In Hanford underground waste storage tanks, a typical waste configuration is settled beds of waste particles beneath liquid layers. The settled beds are typically composed of layers, and these layers can have different physical and chemical properties. One postulated configuration within the settled bed is a less-dense layer beneath a more-dense layer. The different densities can be a result of different gas retention in the layers or different degrees of settling and compaction in the layers. This configuration can experience a Rayleigh-Taylor (RT) instability where the less dense lower layer rises into the upper layer. Previous studies of gas retention and release have not considered potential buoyant motion within a settle bed of solids. The purpose of this report is to provide a review of RT instabilities, discuss predictions of RT behavior for sediment layers, and summarize preliminary experimental observations of RT instabilities in simulant experiments.

Gauglitz, Phillip A.; Wells, Beric E.; Buchmiller, William C.; Rassat, Scot D.

2013-03-21

289

Many-body theory of excitation dynamics in an ultracold Rydberg gas  

SciTech Connect

We develop a theoretical approach for the dynamics of Rydberg excitations in ultracold gases,with a realistically large number of atoms. We rely on the reduction of the single-atom Bloch equations to rate equations, which is possible under various experimentally relevant conditions. Here, we explicitly refer to a two-step excitation scheme. We discuss the conditions under which our approach is valid by comparing the results with the solution of the exact quantum master equation for two interacting atoms. Concerning the emergence of an excitation blockade in a Rydberg gas, our results are in qualitative agreement with experiment. Possible sources of quantitative discrepancy are carefully examined. Based on the two-step excitation scheme, we predict the occurrence of an antiblockade effect and propose possible ways to detect this excitation enhancement experimentally in an optical lattice, as well as in the gas phase.

Ates, C.; Pattard, T.; Rost, J. M. [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, D-01187 Dresden (Germany); Pohl, T. [ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS14, Cambridge, Massachusetts 02138 (United States)

2007-07-15

290

Analytical theory of mesoscopic Bose-Einstein condensation in an ideal gas  

Microsoft Academic Search

We find the universal structure and scaling of the Bose-Einstein condensation (BEC) statistics and thermodynamics (Gibbs free energy, average energy, heat capacity) for a mesoscopic canonical-ensemble ideal gas in a trap with an arbitrary number of atoms, any volume, and any temperature, including the whole critical region. We identify a universal constraint-cutoff mechanism that makes BEC fluctuations strongly non-Gaussian and

Vitaly V. Kocharovsky; Vladimir V. Kocharovsky

2010-01-01

291

Theory of contacts in a two-dimensional electron gas at high magnetic fields  

Microsoft Academic Search

General properties of a contact in a two-dimensional electron gas (2D EG), where more than one Landau level is occupied at high magnetic fields, and is quantitatively analyzed on the basis of a Landauer-Büttiker formalism. When acting as a current source (drain), a contact generally populates different Landau levels to different degrees. When acting as a voltage probe, a contact

S. Komiyama; H. Hirai

1989-01-01

292

Single gas permeation of thin zeolite (MFI) membranes: theory and analysis of experimental observations  

Microsoft Academic Search

Theoretical expressions for single gas permeation are analysed and evaluated with selected literature and some new experimental data on Silicalite\\/ZSM-5 membranes. The phenomenological sorption–diffusion (PSD) description (and its equivalent Maxwell–Stefan equation) covers both the microscopic models based on configurational diffusion (CD) with ?=1.0 and on surface diffusion (SD) with ??1.24. The ratio ? of the pore diameter over the (kinetic)

A. J. Burggraaf

1999-01-01

293

Photoabsorption to Stark Rydberg States of Heavy Noble Gas Atoms: Testing Limits of Closed Orbit Theory  

Microsoft Academic Search

The selective dramatic effects of a dc electric field on the photoabsorption spectrum of Rydberg states and the associated recurrence strengths and closed orbits are studied in heavy noble gas atoms. Using collinear atom-laser beam spectroscopy, complex scaled-energy photoabsorption spectra are mapped experimentally in high resolution for pi and sigma transitions from the ns[3\\/2] and ns[1\\/2] metastable states, formed by

Heric Flores-Rueda; Matthew L. Keeler; David Wright; Thomas J. Morgan

2003-01-01

294

Theory of Critical Temperature Adiabatic Change for Ideal Gas Bose-Einstein Condensation in Optical Lattices  

Microsoft Academic Search

We present a scheme of analytical calculations determining the critical temperature and the number of condensed atoms of ideal gas Bose-Einstein condensation in external potentials with 1D, 2D or 3D periodicity. In particular we show that the width of the lowest energy band appears as the main parameter determining the critical temperature of condensation. Is obtained a very simple, proportional

G. A. Muradyan; A. Zh. Muradyan

2006-01-01

295

Theory of Critical Temperature Adiabatic Change for Ideal Gas Bose-Einstein Condensation in Optical Lattices  

Microsoft Academic Search

We present a scheme of analytical calculations determining the critical\\u000atemperature and the number of condensed atoms of ideal gas Bose-Einstein\\u000acondensation in external potentials with 1D, 2D or 3D periodicity. In\\u000aparticular we show that the width of the lowest energy band appears as the main\\u000aparameter determining the critical temperature of condensation. Is obtained a\\u000avery simple, proportional

G. A. Muradyan; A. Zh

2006-01-01

296

Problems of combustion, explosion, and gas detonation in the theory of nonisothermal chain processes  

NASA Astrophysics Data System (ADS)

Results of the studies show that the occurrence of chain avalanches is a necessary condition of gasphase processes of combustion not only at pressures tens of times lower than atmospheric pressure, as was thought earlier, but at almost any higher pressures in any temperature regime. It is concluded that considering the specifics of nonisothermal chain processes over a broad range of pressures allows us to explain and adequately describe observed features of combustion, explosion, and detonation (including some that were unexplained earlier). New laws important in theory and practice are predicted and revealed.

Azatyan, V. V.

2014-05-01

297

Extension of compressible ideal-gas rapid distortion theory to general mean velocity gradients  

NASA Astrophysics Data System (ADS)

The homogeneity condition in compressible flows requires that mean velocity gradient and mean thermodynamic variables must be spatially invariant. This has restricted the use of rapid distortion theory (RDT) for compressible flows to a small set of mean-velocity gradients. By introducing an appropriate body force, we show that the homogeneity condition can be satisfied for a large class of compressible turbulence. We proceed to derive RDT spectral covariance equations of all relevant moments and recover the limiting behavior at vanishing and infinite (pressure-release) Mach numbers for homogeneous shear, plain-strain, axisymmetric expansion, and contraction cases.

Yu, Huidan; Girimaji, Sharath S.

2007-04-01

298

Gas cleaning apparatus  

Microsoft Academic Search

A description is given of an apparatus and method for removing very finely divided alkali fumes and other particulate material from a coal-gasifier make-gas comprising the introduction of char granules into the constricted passage of a venturi-shaped gas duct to adsorb the very fine particulate from the make-gas flowing therethrough, and centrifugally separating the fume-laden char granules from the make-gas.

R. H. Boll; W. C. Lapple

1980-01-01

299

Gas cleaning apparatus  

SciTech Connect

A description is given of an apparatus and method for removing very finely divided alkali fumes and other particulate material from a coal-gasifier make-gas comprising the introduction of char granules into the constricted passage of a venturi-shaped gas duct to adsorb the very fine particulate from the make-gas flowing therethrough, and centrifugally separating the fume-laden char granules from the make-gas.

Boll, R.H.; Lapple, W.C.

1980-03-04

300

Density Functional Theory and Reaction Kinetics Studies of the Water–Gas Shift Reaction on Pt–Re Catalysts  

SciTech Connect

Periodic, self-consistent density functional theory calculations (DFT-GGA-PW91) on Pt(111) and Pt3Re(111) surfaces, reaction kinetics measurements, and microkinetic modeling are employed to study the mechanism of the water–gas shift (WGS) reaction over Pt and Pt–Re catalysts. The values of the reaction rates and reaction orders predicted by the model are in agreement with the ones experimentally determined; the calculated apparent activation energies are matched to within 6% of the experimental values. The primary reaction pathway is predicted to take place through adsorbed carboxyl (COOH) species, whereas formate (HCOO) is predicted to be a spectator species. We conclude that the clean Pt(111) is a good representation of the active site for the WGS reaction on Pt catalysts, whereas the active sites on the Pt–Re alloy catalyst likely contain partially oxidized metal ensembles.

Carrasquillo-Flores, Ronald; Gallo, Jean Marcel R.; Hahn, Konstanze; Dumesic, James A.; Mavrikakis, Manos

2013-12-01

301

Vortex-antivortex pair in a Bose-Einstein condensate. Type-II quantum lattice gas as a nonlinear ?4 theory of a complex field  

NASA Astrophysics Data System (ADS)

Presented is a type-II quantum algorithm for superfluid dynamics, used to numerically predict solutions of the GP equation for a complex scalar field (spinless bosons) in ?4 theory. The GP equation is a long wavelength effective field theory of a microscopic quantum lattice gas with nonlinear state reduction. The quantum lattice gas algorithm for modeling the dynamics of the one-body BEC state in 3+1 dimensions is presented. To demonstrate the method's strength as a computational physics tool, a difficult situation of filamentary singularities is simulated, the dynamics of solitary vortex-antivortex pairs, which are a basic building block of morphologies of quantum turbulence.

Yepez, J.; Vahala, G.; Vahala, L.

2009-04-01

302

Probability theory for 3-layer remote sensing in ideal gas law environment.  

PubMed

We extend the probability model for 3-layer radiative transfer [Opt. Express 20, 10004 (2012)] to ideal gas conditions where a correlation exists between transmission and temperature of each of the 3 layers. The effect on the probability density function for the at-sensor radiances is surprisingly small, and thus the added complexity of addressing the correlation can be avoided. The small overall effect is due to (a) small perturbations by the correlation on variance population parameters and (b) cancellation of perturbation terms that appear with opposite signs in the model moment expressions. PMID:24105525

Ben-David, Avishai; Davidson, Charles E

2013-08-26

303

A Unified Theory of Non-Ideal Gas Lattice Boltzmann Models  

NASA Technical Reports Server (NTRS)

A non-ideal gas lattice Boltzmann model is directly derived, in an a priori fashion, from the Enskog equation for dense gases. The model is rigorously obtained by a systematic procedure to discretize the Enskog equation (in the presence of an external force) in both phase space and time. The lattice Boltzmann model derived here is thermodynamically consistent and is free of the defects which exist in previous lattice Boltzmann models for non-ideal gases. The existing lattice Boltzmann models for non-ideal gases are analyzed and compared with the model derived here.

Luo, Li-Shi

1998-01-01

304

Kinetic theory analysis of rarefied gas flow through finite length slots  

NASA Technical Reports Server (NTRS)

An analytic study is made of the flow a rarefied monatomic gas through a two dimensional slot. The parameters of the problem are the ratios of downstream to upstream pressures, the Knudsen number at the high pressure end (based on slot half width) and the length to slot half width ratio. A moment method of solution is used by assuming a discontinuous distribution function consisting of four Maxwellians split equally in angular space. Numerical solutions are obtained for the resulting equations. The characteristics of the transition regime are portrayed. The solutions in the free molecule limit are systematically lower than the results obtained in that limit by more accurate numerical methods.

Raghuraman, P.

1972-01-01

305

Effects of Prolonged Centrifugation on Orthostasis  

NASA Technical Reports Server (NTRS)

A feasibility study conducted on the Ames 20-G Human Centrifuge examined how well humans can maintain orthostatic tolerance during and after prolonged exposures to hypergravity. Three adult males lived for periods of 22 hours in the centrifuge while it was at rest (1.00 G), and while it rotated at 9.38 RPM to provide 1.25 G-total at the mean radius of 7.62 m. Two participants also experienced 22-hour habitation sessions at 11.46 RPM, which provided 1.50 G-total. Both before and after each habitation session, the participants were given gradual onset rate (GOR) acceleration profiles at 0.067 G/sec to determine their Gz tolerance. In addition, cardiovascular responses were compared while subjects were supine, siting, and standing at various times during the habitation (stand test), and cardiovascular responsiveness was determined using a lower body negative pressure tilt table (LBNPTT) at the beginning of the experiment and after each session. Post-Pre changes in G tolerance were -0.33 (mean) +/- 0.11 (std. error) Gz for habitation at 1.00 G, -0.02 +/- 0.12 Gz for habitation at 1.25 G, and +0.41 +/- 0.13 Gz for habitation at 1.50 G. Performance on the stand test generally improved with duration of habitation in hypergravity. Our results suggest that habitation in a confined chamber at 1.00 G reduces G tolerance and leads to lowered LBNPTT tolerance. Exposure to increased G in the centrifuge leads to enhanced performance on the stand test, and to increased GOR acceleration tolerance, but only when fluid balance is maintained; when motion sickness and negative fluid balance were observed, G tolerance was reduced. The data indicate that enhanced G tolerance can result from prolonged exposure to hypergravity, but that these changes are complex and depend on multiple underlying physiological processes.

Cohen, Malcolm M..; Hargens, A. R.; Yates, B. J.; Bowley, Susan M. (Technical Monitor)

2000-01-01

306

Laminar flow effects in the coil planet centrifuge  

NASA Technical Reports Server (NTRS)

The coil planet centrifuge designed by Ito employs flow of a single liquid phase, through a rotating coiled tube in a centrifugal force field, to provide a separation of particles based on sedimentation rates. Mathematical solutions are derived for the linear differential equations governing particle behavior in the coil planet centrifuge device. These solutions are then applied as the basis of a model for optimizing particle separations.

Herrmann, F. T.

1984-01-01

307

Development of the screen bowl centrifuge for dewatering coal fines  

SciTech Connect

Dewatering fine clean coal fractions, -595 MUm (-28 mesh), represents one of the most difficult and costly separations in typical plant circuits. The screen bowl centrifuge offers an economical alternative to filtration/thermal drier combinations. The performance of screen bowl centrifuges has been continuously modified and improved to dewater not only coarse coals, but also ultrafine material. Tests comparisons with alternative methods show the screen bowl centrifuge to be most cost-effective and efficient when all factors are considered.

Policow, N.D.; Orphanos, J.S.

1983-04-01

308

High-G centrifuge test results: Fine coal dewatering  

Microsoft Academic Search

This paper presents the results of 18 high-G centrifuge tests performed at the Electric Power Research Institute's Coal Cleaning Test Facility in January 1985. These tests, using -28 mesh (0.6mm) froth flotation product, show that the high-G, solid-bowl centrifuge can produce clean-coal moistures of less than 12 percent at solids recovery rates exceeding 98 percent. The high-G centrifuge achieved these

C. D. Harrison; J. R. Cavalet

1985-01-01

309

Optimizing centrifugation of coagulation samples in laboratory automation.  

PubMed

Abstract Background: High acceleration centrifugation conditions are used in laboratory automation systems to reduce the turnaround time (TAT) of clinical chemistry samples, but not of coagulation samples. This often requires separate sample flows. The CLSI guideline and manufacturers recommendations for coagulation assays aim at reducing platelet counts. For measurement of prothrombin time (PT) and activated partial thromboplastin time (APTT) platelet counts (Plt) below 200×109/L are recommended. Other coagulation assays may require even lower platelet counts, e.g., less than 10×109/L. Unifying centrifugation conditions can facilitate the integration of coagulation samples in the overall workflow of a laboratory automation system. Methods: We evaluated centrifugation conditions of coagulation samples by using high acceleration centrifugation conditions (5 min; 3280×g) in a single and two consecutive runs. Results of coagulation assays [PT, APTT, coagulation factor VIII (F. VIII) and protein S] and platelet counts were compared after the first and second centrifugation. Results: Platelet counts below 200×109/L were obtained in all samples after the first centrifugation and less than 10×109/L was obtained in 73% of the samples after a second centrifugation. Passing-Bablok regression analyses showed an equal performance of PT, APTT and F. VIII after first and second centrifugation whereas protein S measurements require a second centrifugation. Conclusions: Coagulation samples can be integrated into the workflow of a laboratory automation system using high acceleration centrifugation. A single centrifugation was sufficient for PT, APTT and F. VIII whereas two successive centrifugations appear to be sufficient for protein S activity. PMID:24695042

Suchsland, Juliane; Friedrich, Nele; Grotevendt, Anne; Kallner, Anders; Lüdemann, Jan; Nauck, Matthias; Petersmann, Astrid

2014-08-01

310

Rotational spectroscopy with an optical centrifuge.  

PubMed

We demonstrate a new spectroscopic method for studying electronic transitions in molecules with extremely broad range of angular momentum. We employ an optical centrifuge to create narrow rotational wave packets in the ground electronic state of (16)O2. Using the technique of resonance-enhanced multi-photon ionization, we record the spectrum of multiple ro-vibrational transitions between X(3)?g(-) and C(3)?g electronic manifolds of oxygen. Direct control of rotational excitation, extending to rotational quantum numbers as high as N ? 120, enables us to interpret the complex structure of rotational spectra of C(3)?g beyond thermally accessible levels. PMID:24448425

Korobenko, Aleksey; Milner, Alexander A; Hepburn, John W; Milner, Valery

2014-03-01

311

Anion-exchange displacement centrifugal partition chromatography.  

PubMed

Ion-exchange displacement chromatography has been adapted to centrifugal partition chromatography. The use of an ionic liquid, benzalkonium chloride, as a strong anion-exchanger has proven to be efficient for the preparative separation of phenolic acid regioisomers. Multigram quantities of a mixture of three hydroxycinnamic acid isomers were separated using iodide as a displacer. The displacement process was characterized by a trapezoidal profile of analyte concentration in the eluate with narrow transition zones. By taking advantage of the partition rules involved in support-free liquid-liquid chromatography, a numerical separation model is proposed as a tool for preliminary process validation and further optimization. PMID:15516108

Maciuk, Alexandre; Renault, Jean-Hugues; Margraff, Rodolphe; Trébuchet, Philippe; Zèches-Hanrot, Monique; Nuzillard, Jean-Marc

2004-11-01

312

Equilibrium and stability of centrifugally confined plasmas  

NASA Astrophysics Data System (ADS)

Rapidly rotating mirror plasmas where the parallel component of the centrifugal force helps support pressure gradients along open field lines is an old idea that has been recently revived in the MCT experiment of Maryland and the magneto-Bernoulli experiment of FRC. Building upon the already considerable amount of work done on such configurations, we are continuing our equilibrium and stability calculations. We have already demonstrated the existence of equilibria with almost completely "detached" plasmas under certain approximations. We are examining the accessibility of these equilibria under more general equations of state and studying their stability against interchange and velocity-shear driven instabilities.

Gott, A. B.; Aydemir, A. Y.

2003-10-01

313

Centrifugal cytology of nipple aspirate cells.  

PubMed

Two improvements in the methodology for obtaining and preparing nipple aspirates from nonlactating women are reported. The first is the development and use of a new breast pump with a controllable vacuum and cups of various sizes. The second is the use of centrifugal cytology to prepare the dispersions. Twenty-one of 24 breasts of patients in the age range 30 to 49 years produced cellular dispersions which contained foam cells; of them, 13 contained ductal cells. A comparison of glutaraldehyde and ethanol fixation indicated that the cells appeared substantially the same. PMID:6931468

Leif, R C; Bobbitt, D; Railey, C; Guarino, V; DerHagopian, R; Ng, A B; Silverman, M

1980-01-01

314

Characterization of centrifugally-loaded flame migration for ultra-compact combustors  

NASA Astrophysics Data System (ADS)

The Air Force Research Laboratory (AFRL) has designed a centrifugally-loaded Ultra-Compact Combustor (UCC) showing viable merit for reducing gas turbine combustor length by as much as 66%. The overarching goal of this research was to characterize the migration of centrifugally-loaded flames in a sectional model of the UCC to enable scaling of the design from 15 cm to the 50--75 cm diameter of most engines. Two-line Planar Laser-Induced Fluorescence thermometry (PLIF) of OH, time-resolved Particle Image Velocimetry (PIV), and high-speed video data were collected. Using a sectional UCC model, the flame migration angle was determined to be a function of the UCC/core velocity ratio (VR) while both the VR and the centrifugal or "g-load" affected the migration quantity. Higher g-loads and lower VRs yielding higher migration but lower VRs had lower core flow temperatures due to higher core air mass flow. A comparison of the straight and curved UCC sections showed the centrifugal load increased the flame migration but increased unsteadiness. The flame migration into the core was estimated using pressure and temperature measurements upstream, and PIV measurements downstream of the core flow interface with constant density and velocity profile assumptions. The flame migration quantity was used to estimate the core flow temperature which was in relatively good agreement with the measured PLIF values. The migration quantity scaled relatively linearly with the UCC tangential velocity, which corresponds to the g-load value, with the slope determined by the VR. A simple analytical model resulted for the dependence of the migration quantity on the tangential velocity and VR. The quantitative relationships determined in this research provided a detailed description of the migration of centrifugally-loaded flames in a sectional UCC.

LeBay, Kenneth D.

315

Autobalancing and FDIR for a space-based centrifuge prototype  

NASA Technical Reports Server (NTRS)

This report summarizes centrifuge-related work performed at the Smart Systems Research Laboratory at NASA Ames Research Center's Computational Sciences Division from 1995 through 2003. The goal is to develop an automated system that will sense an imbalance (both static and dynamic3) in a centrifuge and issue control commands to drive counterweights to eliminate the effects of the imbalance. This autobalancing development began when the ISS centrifuge design was not yet finalized, and was designed to work with the SSRL Centrifuge laboratory prototype, constructed in 1993-1995. Significant differences between that prototype and the current International Space Station (ISS) Centrifuge design are that: the spin axis for the SSRL Centrifuge prototype can translate freely in x and y, but not wobble, whereas the ISS centrifuge spin axis has 3 translational and two rotational degrees of freedom, supported by a vibration 34. The imbalance sensors are strained gauges both in the rotor and the stator, measuring the imbalance forces, whereas the ISS centrifuge uses eddy current displacement sensors to measure the displacements resulting from imbalance. High fidelity autobalancing and FDIR systems (for both counterweights and strain gauges) are developed and tested in MATLAB simulation, for the SSRL Centrifuge configuration. Hardware implementation of the autobalancing technology was begun in 1996, but was terminated due to lack of funding. The project lay dormant until 2001-2002 when the FDIR capability was added.

Wilson, Edward; Mah, Robert W.

2005-01-01

316

Effects of centrifugation on gonadal and adrenocortical steroids in rats  

NASA Technical Reports Server (NTRS)

Many endocrine systems are sensitive to external changes in the environment. Both the pituitary adrenal and pituitary gonadal systems are affected by stress including centrifugation stress. The effect of centrifugation on the pituitary gonadal and pituitary adrenocortical systems was examined by measuring the gonadal and adrenal steroids in the plasma and brain following different duration and intensity of centrifugation stress in rats. Two studies were completed and the results are presented. The second study was carried out to describe the developmental changes of brain, plasma and testicular testosterone and dihydrotestosterone in Sprague Dawley rats so that the effect of centrifugation stress on the pituitary gonadal syatem could be better evaluated in future studies.

Kakihana, R.; Butte, J. C.

1980-01-01

317

Application of Momentum Transfer Theory for Ion and Electron Transport in Pure Gases and in Gas Mixtures  

SciTech Connect

In this paper we have presented two applications of Momentum Transfer Theory (MTT), which were both aimed at obtaining reliable data for modeling of non-equilibrium plasma. Transport properties of ion swarms in presence of Resonant Charge Transfer (RCT) collisions are studied using Momentum Transfer Theory (MTT). Using the developed MTT we tested a previously available anisotropic set of cross-sections for Ar++Ar collisions bay making the comparisons with the available data for the transverse diffusion coefficient. We also developed an anisotropic set of Ne++Ne integral cross-sections based on the available data for mobility, longitudinal and transverse diffusion. Anisotropic sets of cross-sections are needed for Monte Carlo simulations of ion transport and plasma models. Application of Blanc's Law for drift velocities of electrons and ions in gas mixtures at arbitrary reduced electric field strengths E/n0 was studied theoretically and by numerical examples. Corrections for Blanc's Law that include effects of inelastic collisions were derived. In addition we have derived the common mean energy procedure that was proposed by Chiflikian in a general case both for ions and electrons. Both corrected common E/n0 and common mean energy procedures provide excellent results even for electrons at moderate E/n0 where application of Blanc's Law was regarded as impossible. In mixtures of two gases that have negative differential conductivity (NDC) even when neither of the two pure gases show NDC the Blanc's Law procedure was able to give excellent predictions.

Jovanovic, J.V. [Institute of Physics, P.O.Box 68, 11080 Zemun, Belgrade (Serbia and Montenegro); Faculty of Mechanical Engineering, 11000 Belgrade (Serbia and Montenegro); Vrhovac, S. B. [Institute of Physics, P.O.Box 68, 11080 Zemun, Belgrade (Serbia and Montenegro)

2004-12-01

318

Metal/gas MHD conversion  

SciTech Connect

Operation features, theory, performance, and possible spatial applications of metal/gas MHD electrical generators are described. The working principle comprises an MHD channel, surrounded by a magnet, filled with a molten, highly conductive metal into which gas is pumped. The heat of the metal expands the gas, forcing a flow through the magnetic field crossing the channel, thus creating an electrical current conducted by the metal. The gas and metal are separated by a centrifugal device and both are redirected into the channel, forming thereby a double closed circuit when the heat of the molten metal is returned to the flow. Necessary characteristics for the gas such as a fairly low vaporization temperature and nonmiscibility with the metal, are outlined, and a space system using Li-Cs or Z-K as the heat carrier kept molten by a parabolic dish system is sketched. Equations governing the fluid mechanics, thermodynamics, and the electrical generation are defined. The construction of a prototype MHD generator using a tin-water flow operating at 250 C, a temperature suitable for coupling to solar heat sources, is outlined, noting expected efficiencies of 20-30 percent.

Thibault, J.P.; Joussellin, F.

1982-01-01

319

Some theories of dissolved gas release from Tank 241-SY-101  

SciTech Connect

This report explains the ammonia release data to an order of magnitude agreement by the combination of three mechanisms of release: (1) bubble transport, (2) permeation/diffusion through the upper layers of the waste, and (3) diffusion/evaporation from freshly exposed liquid surfaces. Bounded by these mechanisms, there is low danger of extremely high ammonia concentrations in the off gas. This condition would occur through some (unlikely) continuous replenishing of fresh liquid on the surface. This would not occur unless there were continuous energetic rollovers, which seem very unlikely given historical evidence, or by energetic mixing of the waste with more power than provided by the current mixing pump. Nitrous oxide is of low solubility in the waste and behaves similarly to hydrogen.

Allemann, R.T.

1994-09-01

320

Spectroscopy in finite density lattice field theory: An exploratory study in the relativistic Bose gas  

NASA Astrophysics Data System (ADS)

We analyze 2-point functions in the relativistic Bose gas on the lattice, i.e., a charged scalar ?4 field with chemical potential ?. Using a generalized worm algorithm we perform a Monte Carlo simulation in a dual representation in terms of fluxes where the complex action problem is overcome. We explore various aspects of lattice spectroscopy at finite density and zero temperature, such as the asymmetry of forward and backward propagation in time and the transition into the condensed phase. It is shown that after a suitable subtraction the exponents for forward and backward propagation are independent of ? and agree with the mass obtained from the propagator at ?=0. This holds for ?

Gattringer, Christof; Kloiber, Thomas

2013-03-01

321

Spherical spin-glass-Coulomb-gas duality: solution beyond mean-field theory.  

PubMed

We present an alternate solution of a Gaussian spin-glass model with infinite ranged interactions and a global spherical constraint at zero magnetic field. The replicated spin-glass Hamiltonian is mapped onto a Coulomb gas of logarithmically interacting particles confined by a logarithmic single particle potential. The precise free energy is obtained by analyzing the Painlevé ?{IV}[n] function in the n?0 limit. The large-N thermodynamics exactly recovers that of Kosterlitz, Thouless, and Jones [Phys. Rev. Lett. 36, 1217 (1976)10.1103/PhysRevLett.36.1217]. It is hoped that the approach here can be extended to apply to systems beyond the spherical model, particularly those in which destabilizing terms lead to replica symmetry breaking. PMID:20867882

Akhanjee, Shimul; Rudnick, Joseph

2010-07-23

322

Structural optimization including centrifugal and Coriolis effects  

NASA Astrophysics Data System (ADS)

Investigated are the effects of centrifugal and Coriolis forces on the mode shapes and frequencies of a rotating system. The rotational effects have a profound influence on the eigenfrequencies; this is important in optimal structural redesign where the frequencies must be adjusted. The structural matrices for the rotating system were obtained by examining the expression for the total system energy. This provides a differential stiffness matrix that models centrifugal force and provides velocity-dependent Coriolis matrix. By using a high-level programming language (Direct Matrix Abstraction Programming) a modal analysis solution sequence was modified to account for rotational effects in free vibration. Finite element models were then created for a typical compressor blade in a modern jet engine and for a cantilever beam rotating about the vertical axis. The optimal redesign was done by deriving complex nonlinear inverse perturbation equations for the problem involving both magnitude and phase components. The perturbation problem is solved by using nonlinear mathematical programming. Optimal redesign uses an underdetermined system, i.e., the feasible design must not be unique. This allows the application of an objective function, such as minimum structural weight or minimum change from the baseline design. Constraints, such as those on frequency, are applied. Optimal structural changes are obtained that meet the frequency goals to within three percent.

Gans, Howard D.

323

Numerical analysis of flow in ultra micro centrifugal compressor -influence of meridional configuration  

NASA Astrophysics Data System (ADS)

A single stage ultra micro centrifugal compressor constituting ultra micro gas turbine is required to operate at high rotational speed in order to achieve the pressure ratio which establishes the gas turbine cycle. As a consequence, the aerodynamic losses can be increased by the interaction of a shock wave with the boundary layer on the blade surface. Moreover, the centrifugal force which exceeds the allowable stress of the impeller material can act on the root of blades. On the other hand, the restrictions of processing technology for the downsizing of impeller not only relatively enlarge the size of tip clearance but also make it difficult to shape the impeller with the three-dimensional blade. Therefore, it is important to establish the design technology for the impeller with the two-dimensional blade which possesses the sufficient aerodynamic performance and enough strength to bear the centrifugal force caused by the high rotational speed. In this study, the flow in two types of impeller with the two-dimensional blade which have different meridional configuration was analyzed numerically. The computed results clarified the influence of the meridional configuration on the loss generations in the impeller passage.

Kaneko, Masanao; Tsujita, Hoshio; Hirano, Toshiyuki

2013-04-01

324

Characterization of nanoporous materials by gas adsorption and density-functional theory  

NASA Astrophysics Data System (ADS)

Nanoporous materials with pores ranging from several molecular diameters to ca. 10 nm currently find numerous applications in modern separation and catalytic technologies. Adsorption is one of the most informative experimental techniques for structural characterization of nanoporous materials. Practical problems of characterization and prediction of adsorption properties of active carbons, zeolites, pillared clays, mesoporous molecular sieves, carbon nanotubes, and many other traditional and newly synthesized adsorbents gave rise to a number of theoretical models capable of constructing adsorption isotherms in model pores. Modern methods of statistical thermodynamics such as Monte Carlo (MC) simulations, molecular dynamics (MD) and density functional theory (DFT) provide molecular level understanding of adsorption in pores, and can be used for characterization of nanoporous materials and predicting their adsorption properties. The main focus of the present work is experimental and theoretical studies of adsorption in nanoporous materials. A nonlocal density functional theory (NLDFT) model has been developed for predicting adsorption/desorption isotherms in nanopores of different geometries over a wide range of pore sizes (0.3-100 nm), and for calculating pore size distributions from the experimental adsorption isotherms based on given intermolecular fluid-fluid and fluid-solid potentials. The NLDFT model has been applied to studies of N2 and Ar adsorption and hysteresis phenomena in mesoporous molecular sieves of MCM-41-type, N 2 and CO2 adsorption on activated carbons. An important issue of comparison of the theoretical and experimental excess adsorption isotherms have been studied in details. A method of ``virtual helium calibration'' has been introduced, which makes the theoretical and experimental isotherms entirely consistent. The method is applicable to any molecular model of adsorption. Several new methods for calculating pore size distributions from experimental adsorption isotherms have been developed. Using regularization techniques NLDFT- based methods make possible the calculation of pore size distributions of (1)mesoporous molecular sieves of M41S type from low temperature N2 and Ar isotherms, (2)microporous carbons from low temperature N2, Ar isotherms, and from CO2 isotherms at ambient temperature. Theoretical results have been validated by extensive comparisons with the experimental data, and results of Monte Carlo simulations. Pore size distributions of mesoporous molecular sieves calculated from the NLDFT method are consistent with other independent methods for characterization of pore structure, such as X-ray diffraction and Transmission Electron Microscopy. The NLDFT method is a rigorous approach which is recommended for characterization of nanoporous materials.

Ravikovitch, Peter I.

325

Chemical oxygen-iodine laser with a centrifugal spray generator of singlet oxygen  

NASA Astrophysics Data System (ADS)

A chemical oxygen-iodine laser driven by the centrifugal spray generator of singlet oxygen was developed and experimentally studied. Modeling and experimental studies showed that the designed generator can produce singlet oxygen, O2(1?g), with a high efficiency (chlorine utilization 0.68 - 0.87 and O2(1?g) yield 0.35 - 0.7) even at very high generator pressures (25 - 70 kPa), which cannot be attained by other O2(1?g) generators. This high-pressure operation should be beneficial for a pressure recovery system of the laser. Another specific feature of the generator is a very high BHP utilization (0.24-0.6). The developed separator can effectively remove even small droplets (> 1 ?m) from gas at the generator exit. Preliminary experiments on the COIL driven the centrifugal spray generator provided the small signal gain up to 0.5 % cm-1.

Špalek, Otomar; Jirásek, Vít; ?enský, Miroslav; Kodymová, Jarmila

2010-09-01

326

The Formation of Molecular Gas in the Perseus Molecular Cloud: Observations Meet Theory  

NASA Astrophysics Data System (ADS)

The formation of molecular hydrogen (H2) is a critical step in the conversion of interstellar gas into stars, yet the physical processes involved still remain unclear. We present two studies of H2 in the Perseus molecular cloud on sub-pc scales. In the first study, we derive the atomic hydrogen (HI) and H2 surface density images and compare the observed H2-to-HI ratio of several dark and star-forming regions to the analytic model by Krumholz et al. (2009; KMT09). To derive the H2 surface density image, we use the dust column density measured by far-infrared data from IRAS in combination with the HI data from the GALFA-HI survey. We find a uniform HI surface density of 6-8 solar mass/pc2 for both dark and star-forming regions, in agreement with KMT09's prediction for the existence of the minimum HI surface density to shield H2 against photodissociation. In addition, we find that H2 linearly increases with the total gas surface density. Both results are consistent with KMT09's steady state model for equilibrium H2 formation and suggest that turbulence may play a secondary role in H2 formation. In the second study, we investigate how the X-factor (the ratio of the H2 column density to the CO integrated intensity) varies with environmental conditions. We find X-factor ~ 3 x 10^19 cm^-2 K^-1 km^-1 s in Perseus, with a factor of ~3 variation across the cloud. In addition, X-factor has the lowest value at Av ~ 2 mag and gradually increases up to 10 mag. The photodissociation region model by Wolfire et al. (2010) reproduces the observed X-factor versus Av profile reasonably well, while the MHD simulations by Shetty et al. (2011) predict the minimum X-factor at Av ~ 8 mag, suggesting that turbulence allows UV photons to penetrate much deeper into the cloud due to a less effective shielding. However, both models have difficulties producing the observed CO integrated intensity in the lowest column density regions in Perseus.

Lee, Min-Young

2013-01-01

327

Numerical solution of the inverse problem of the theory of the Laval nozzle as applied to two-dimensional nonequilibrium flows of a perfect gas  

Microsoft Academic Search

Introduction. The article describes the method of calculation and presents the results of a numerical solution of the inverse problem of Laval nozzle theory as applied to a two-dimensional stationary flow of a perfect gas with chemical reactions; the equilibrium, nonequi[ibrium, and frozen flows in the subsonic, transonic, and supersonic ranges. The numerical solution of the inverse problem is carried

V. F. Kolmogorov

1974-01-01

328

The NATA code: Theory and analysis, volume 1. [user manuals (computer programming) - gas dynamics, wind tunnels  

NASA Technical Reports Server (NTRS)

A computer program for calculating quasi-one-dimensional gas flow in axisymmetric and two-dimensional nozzles and rectangular channels is presented. Flow is assumed to start from a state of thermochemical equilibrium at a high temperature in an upstream reservoir. The program provides solutions based on frozen chemistry, chemical equilibrium, and nonequilibrium flow with finite reaction rates. Electronic nonequilibrium effects can be included using a two-temperature model. An approximate laminar boundary layer calculation is given for the shear and heat flux on the nozzle wall. Boundary layer displacement effects on the inviscid flow are considered also. Chemical equilibrium and transport property calculations are provided by subroutines. The code contains precoded thermochemical, chemical kinetic, and transport cross section data for high-temperature air, CO2-N2-Ar mixtures, helium, and argon. It provides calculations of the stagnation conditions on axisymmetric or two-dimensional models, and of the conditions on the flat surface of a blunt wedge. The primary purpose of the code is to describe the flow conditions and test conditions in electric arc heated wind tunnels.

Bade, W. L.; Yos, J. M.

1975-01-01

329

Gas-phase kinetics of hydroxyl radical reactions with alkenes: experiment and theory.  

PubMed

Reactions of the hydroxyl radical with propene and 1-butene are studied experimentally in the gas phase in a continuous supersonic flow reactor over the range 50?T/K?224. OH radicals are produced by pulsed laser photolysis of H(2)O(2) at 266 nm in the supersonic flow and followed by laser-induced fluorescence in the (1, 0) A(2)?(+)?X(2)?(3/2) band at about 282 nm. These reactions are found to exhibit negative temperature dependences over the entire temperature range investigated, varying between (3.1-19.2) and (4.2-28.6)×10(-11) cm(3) molecule(-1) s(-1) for the reactions of OH with propene and 1-butene, respectively. Quantum chemical calculations of the potential energy surfaces are used as the basis for energy- and rotationally resolved Rice-Ramsperger-Kassel-Marcus calculations to determine the rate constants over a range of temperatures and pressures. The negative temperature dependences of the rate constants are explained by competition between complex redissociation and passage to the adducts by using a model with two transition states. The results are compared and contrasted with earlier studies and discussed in terms of their potential relevance to the atmosphere of Saturn. PMID:20839269

Daranlot, Julien; Bergeat, Astrid; Caralp, Françoise; Caubet, Philippe; Costes, Michel; Forst, Wendell; Loison, Jean-Christophe; Hickson, Kevin M

2010-12-17

330

Fitting Cosmological Data to the Function q( z) from GR Theory: Modified Chaplygin Gas  

NASA Astrophysics Data System (ADS)

In the Friedmann cosmology, the deceleration of the expansion q plays a fundamental role. We derive the deceleration as a function of redshift q( z) in two scenarios: ?CDM model and modified Chaplygin gas (MCG) model. The function for the MCG model is then fitted to the cosmological data in order to obtain the cosmological parameters that minimize ? 2. We use the Fisher matrix to construct the covariance matrix of our parameters and reconstruct the q( z) function. We use Supernovae Ia, WMAP5, and BAO measurements to obtain the observational constraints. We determined the present acceleration as q 0 = - 0.65 ±0.19 for the MCG model using the Union2 dataset of SNeIa, BAO, and CMB and q 0 = - 0.67 ±0.17 for the Constitution dataset, BAO and CMB. The transition redshift from deceleration to acceleration was found to be around 0.80 for both datasets. We have also determined the dark energy parameter for the MCG model: ? X0 = 0.81 ±0.03 for the Union2 dataset and ? X0 = 0.83 ±0.03 using the Constitution dataset.

Velasquez-Toribio, Alan M.; Bedran, Maria Luiza

2011-05-01

331

Development of the screen bowl centrifuge for dewatering coal fines  

Microsoft Academic Search

Dewatering fine clean coal fractions, -595 MUm (-28 mesh), represents one of the most difficult and costly separations in typical plant circuits. The screen bowl centrifuge offers an economical alternative to filtration\\/thermal drier combinations. The performance of screen bowl centrifuges has been continuously modified and improved to dewater not only coarse coals, but also ultrafine material. Tests comparisons with alternative

N. D. Policow; J. S. Orphanos

1983-01-01

332

Screen bowl centrifuge: a high-efficiency particle size separator  

Microsoft Academic Search

Over the years, screen bowl centrifuges have been widely used for dewatering fine coal in coal preparation plants in the United States and elsewhere. It is generally recognized in the engineering and scientific communities that screen bowl centrifuges provide some degree of particle size separation while dewatering fine coal in a common application. However, the extent of differential partitioning of

M. K. Mohanty; B. Zhang; N. Khanna; A. Palit; B. Dube

2008-01-01

333

Ballistic to centrifuging flow of granular materials in rotating tumblers  

Microsoft Academic Search

The critical rotation speed for centrifuging of granular materials in horizontal rotating tumblers, determined by the Froude number, was studied experimentally and computationally as a function of the particle diameter, tumbler fill fraction, interstitial fluid, and tumbler length. Particle size does not affect the critical speed for centrifugation provided that the fill fraction is below 50%. The actual critical speed

Richard M. Lueptow; Gabriel Juarez; Pengfei Chen; Julio M. Ottino

2009-01-01

334

Centrifugal Barrel Finishing Of Turbine-Blade "Fir Trees"  

NASA Technical Reports Server (NTRS)

Modified centrifugal barrel-finishing machine imparts desired residual compressive stresses to "fir trees" of turbine blades. Centrifugal forces generate compressive stresses, which are transmitted to turbine blades through abrasive slurries in which suspended. Eliminates need for shot peening, rounding of edges and burrs caused by shot peening and, consequently, need for mass finishing operations to remove burrs. Improves surface finish of "fir trees".

Mandel, Johnny L.

1990-01-01

335

Separation of metals in wastewater sludge by centrifugal classification  

Microsoft Academic Search

Municipal wastewater sludges frequently contain undesirably high concentrations of heavy metals and\\/or organic pollutants that interfere with beneficial use of sludge on farmland and with some disposal practices such as ocean disposal. Centrifugal classification is a low-cost procedure that has been demonstrated in the study to concentrate contaminants into the centrate stream, thus reducing the contaminants in the centrifuge cake

Carol Ann Fronk; Joseph B. Farrell; William Strachan

1985-01-01

336

Coil planet centrifugation as a means for small particle separation  

NASA Technical Reports Server (NTRS)

The coil planet centrifuge uses a centrifugal force field to provide separation of particles based on differences in sedimentation rates by flow through a rotating coiled tube. Three main separations are considered: (1) single phase fresh sheep and human erythrocytes, (2) single phase fixed heep and human erythrocytes, and (3) electrophoretically enhanced single phase fresh sheep and human erythrocytes.

Herrmann, F. T.

1983-01-01

337

Solvent-free cleaning using a centrifugal cryogenic pellet accelerator  

Microsoft Academic Search

An advanced centrifuge that accelerates frozen COâ pellets to high speeds for surface cleaning and paint removal is being developed at the Oak Ridge National Laboratory. The centrifuge-based accelerator was designed, fabricated, and tested under a program sponsored by the Warner Robins Air Logistics Center, Robins Air Force Base, Georgia. In comparison to the more conventional compressed air ``sandblast`` pellet

J. R. Haines; P. W. Fisher; C. A. Foster

1995-01-01

338

Synaptic Connections of the Centrifugal Fibers in the Pigeon Retina  

Microsoft Academic Search

The centrifugal fibers in the pigeon retina end in the inner nuclear layer and form two kinds of terminals, convergent and divergent. In the inner nuclear layer the fibers synapse with amacrine and displaced ganglion cells. Because of their great number and their even distribution these fibers appear to constitute a system for the localized centrifugal control of the retinal

H. R. Maturana; S. Frenk

1965-01-01

339

Development of a Low Flow Coefficient Single Stage Centrifugal Compressor  

Microsoft Academic Search

A low flow coefficient unshrouded centrifugal compressor would give up clearance in relation to the span of the blades, because centrifugal compressors produce a sufficiently large pressure rise in fewer stages. This problem is more acute for a low flow high-pressure ratio impeller. The large tip clearance would cause flow separations, and as a result it would drop both the

C. Xu; R. S. Amano

2009-01-01

340

Theory of femtosecond coherent anti-Stokes Raman scattering spectroscopy of gas-phase transitions  

NASA Astrophysics Data System (ADS)

A theoretical analysis of coherent anti-Stokes Raman scattering (CARS) spectroscopy of gas-phase resonances using femtosecond lasers is performed. The time-dependent density matrix equations for the femtosecond CARS process are formulated and manipulated into a form suitable for solution by direct numerical integration (DNI). The temporal shapes of the pump, Stokes, and probe laser pulses are specified as an input to the DNI calculations. It is assumed that the laser pulse shapes are 70 fs Gaussians and that the pulses are Fourier-transform limited. A single excited electronic level is defined as an effective intermediate level in the Raman process, and transition strengths are adjusted to match the experimental Raman polarizability. The excitation of the Raman coherence is investigated for different Q-branch rotational transitions in the fundamental 2330 cm-1 band of diatomic nitrogen, assuming that the pump and Stokes pulses are temporally overlapped. The excitation process is shown to be virtually identical for transitions ranging from Q(2) to Q(20). The excitation of the Raman coherences is also very efficient; for laser irradiances of 5×1017 W/m2, corresponding approximately to a 100 ?J, 70 fs pulse focused to 50 ?m, approximately 10% of the population of the ground Raman level is pumped to the excited Raman level during the impulsive pump-Stokes excitation, and the magnitude of the induced Raman coherence reaches 40% of its maximum possible value. The theoretical results are compared with the results of experiments where the femtosecond CARS signal is recorded as a function of probe delay with respect to the impulsive pump-Stokes excitation.

Lucht, Robert P.; Kinnius, Paul J.; Roy, Sukesh; Gord, James R.

2007-07-01

341

77 FR 65360 - Grant of Authority for Subzone Status (Centrifugal and Submersible Pumps); Auburn, NY  

Federal Register 2010, 2011, 2012, 2013

...for Subzone Status (Centrifugal and Submersible Pumps); Auburn, NY Pursuant to its...special-purpose subzone at the centrifugal and submersible pump manufacturing and warehousing facilities...the manufacturing of centrifugal and submersible pumps and related controllers at...

2012-10-26

342

Centrifugal regulator for control of deployment rates of deployable elements  

NASA Technical Reports Server (NTRS)

The requirements, design, and performance of a centrifugal regulator aimed at limiting deployment rates of deployable elements are discussed. The overall mechanism is comprised of four distinct functional parts in a machined housing: (1) the centrifugal brake device, which checks the payout of a deployment cable; (2) the reducing gear, which produces the spin rate necesary for the braking device; (3) the payout device, which allows the unwinding of the cable; and (4) the locking device, which prevents untimely unwinding. The centrifugal regulator is set into operation by a threshold tension of the cable which unlocks the mechanism and allows unwinding. The pulley of the windout device drives the centrifugal brake with the help of the reducing gear. The centrifugal force pushes aside weights that produce friction of the studs in a cylindrical housing. The mechanism behaved well at qualification temperature and vibrations.

Vermalle, J. C.

1980-01-01

343

Improved blood culture technique based on centrifugation: clinical evaluation.  

PubMed Central

A total of 3,335 blood samples from 1,180 patients suspected of having bacteremia were analyzed concurrently by two methods: (i) supplemented peptone broth with sodium polyanethanol sulfonate and a CO2 atmosphere; and (ii) lysis centrifugation at 3,000 X g for 30 min onto a high-density, hydrophobic cushion. The centrifugation technique recovered 80% of the positive cultures as compared with 67% for the broth method. The centrifugation technique showed an apparent increase in the isolation of staphylococcus aureus, Pseudomonas, and yeasts. In almost every instance, the time required for detection of a positive culture was shortest for the centrifugation method. Contamination rates for both systems were comparable (1.4%). Quantitation, offered only by the centrifugation method, proved useful on several occasions in discriminating between an opportunistic infection versus a skin contaminant and in judging efficacy of antimicrobial therapy. Images

Dorn, G L; Land, G A; Wilson, G E

1979-01-01

344

Rotordynamic forces on centrifugal pump impellers  

NASA Technical Reports Server (NTRS)

The asymmetric flow around an impeller in a volute exerts a force upon the impeller. To study the rotordynamic force on an impeller which is vibrating around its machine axis of rotation, the impeller, mounted on a dynamometer, is made to whirl in a circular orbit within the volute. The measured force is expressed as the sum of a steady radial force and an unsteady force due to the eccentric motion of the impeller. These forces were measured in separate tests on a centrifugal pump with radically increased shroud clearance, a two-dimensional impeller, and an impeller with an inducer, the impeller of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine). In each case, a destabilizing force was observed over a region of positive whirl.

Franz, R.; Arndt, N.; Caughey, T. K.; Brennen, C. E.; Acosta, A. J.

1987-01-01

345

Recent advances in centrifugal contactors design  

SciTech Connect

Advances in thedesign of the Argonne centrifugal contactor for solvent extaction are being realized as these contactors are built, tested, and used to implement the TRUEX process for the cleanup of nuclear waste liquids. These advances include (1) using off-the-shelf, face-mounted motors, (2) modifying the contractor so that relatively volatile solvents can be used, (3) adding a high-level liquid detector that can be used to alert the plant operator of process upsets, (4) providing secondary feed ports, (5) optimizing support frame design, (6) maintaining a linear design with external interstage lines so the stages can be allocated as needed for extraction, scrub, strip, and solvent cleanup operations, and (7) developing features that facilitate contractor operation in remote facilities. 11 refs., 8 figs.

Leonard, R.A.

1987-10-01

346

Rotordynamic forces on centrifugal pump impellers  

NASA Astrophysics Data System (ADS)

The asymmetric flow around an impeller in a volute exerts a force upon the impeller. To study the rotordynamic force on an impeller which is vibrating around its machine axis of rotation, the impeller, mounted on a dynamometer, is made to whirl in a circular orbit within the volute. The measured force is expressed as the sum of a steady radial force and an unsteady force due to the eccentric motion of the impeller. These forces were measured in separate tests on a centrifugal pump with radically increased shroud clearance, a two-dimensional impeller, and an impeller with an inducer, the impeller of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine). In each case, a destabilizing force was observed over a region of positive whirl.

Franz, R.; Arndt, N.; Caughey, T. K.; Brennen, C. E.; Acosta, A. J.

347

Acoustic similarity laws for centrifugal fans  

NASA Astrophysics Data System (ADS)

Acoustic similarity laws for fans were experimentally verified. Three, dimensionally similar centrifugal fans of 140, 280 and 560 mm impeller diameter were used. The fans were connected to anechoically terminated discharge ducts. It is shown that the influence of the Reynolds number on the radiated sound pressure is negligible within 140,000 or = Reynolds number or = 2,200,000 which is the range covered by the measurements. This result is in agreement with earlier studies in which the Reynolds number was varied from 14,000 to 450,000. Experimental results support the conclusion that fan noise data which is taken on model fans can be extrapolated to other dimensionally similar fans of different size for arbitrary fan speeds and working fluids, provided that the operating condition and the measurement position are the same.

Neise, W.; Barsikow, B.

1982-02-01

348

Acoustic similarity law for centrifugal fans  

NASA Astrophysics Data System (ADS)

Acoustic similarity laws for fans were experimentally verified. Three, dimensionally similar centrifugal fans of 140, 280 and 560 mm impeller diameter were used. The fans were connected to anechoically terminated discharge ducts. It is shown that the influence of the Reynolds number on the radiated sound pressure is negligible within 140,000 or = Reynolds number or = 2,200,000 which is the range covered by the measurements. This result is in agreement with earlier studies in which the Reynolds number was varied from 14,000 to 450,000. Experimental results support the conclusion that fan noise data which is taken on model fans can be extrapolated to other dimensionally similar fans of different size for arbitrary fan speeds and working fluids, provided that the operating condition and the measurement position are the same.

Neise, W.; Barsikow, B.

1980-08-01

349

Algorithm for Controlling a Centrifugal Compressor  

NASA Technical Reports Server (NTRS)

An algorithm has been developed for controlling a centrifugal compressor that serves as the prime mover in a heatpump system. Experimental studies have shown that the operating conditions for maximum compressor efficiency are close to the boundary beyond which surge occurs. Compressor surge is a destructive condition in which there are instantaneous reversals of flow associated with a high outlet-to-inlet pressure differential. For a given cooling load, the algorithm sets the compressor speed at the lowest possible value while adjusting the inlet guide vane angle and diffuser vane angle to maximize efficiency, subject to an overriding requirement to prevent surge. The onset of surge is detected via the onset of oscillations of the electric current supplied to the compressor motor, associated with surge-induced oscillations of the torque exerted by and on the compressor rotor. The algorithm can be implemented in any of several computer languages.

Benedict, Scott M.

2004-01-01

350

Multiphase flow modeling in centrifugal partition chromatography.  

PubMed

The separation efficiency in Centrifugal Partition Chromatography (CPC) depends on selection of a suitable biphasic solvent system (distribution ratio, selectivity factor, sample solubility) and is influenced by hydrodynamics in the chambers. Especially the stationary phase retention, the interfacial area for mass transfer and the flow pattern (backmixing) are important parameters. Their relationship with physical properties, operating parameters and chamber geometry is not completely understood and predictions are hardly possible. Experimental flow visualization is expensive and two-dimensional only. Therefore we simulated the flow pattern using a volume-of-fluid (VOF) method, which was implemented in OpenFOAM®. For the three-dimensional simulation of a rotating FCPC®-chamber, gravitational centrifugal and Coriolis forces were added to the conservation equation. For experimental validation the flow pattern of different solvent systems was visualized with an optical measurement system. The amount of mobile phase in a chamber was calculated from gray scale values of videos recorded by an image processing routine in ImageJ®. To visualize the flow of the stationary phase polyethylene particles were used to perform a qualitative particle image velocimetry (PIV) analysis. We found a good agreement between flow patterns and velocity profiles of experiments and simulations. By using the model we found that increasing the chamber depth leads to higher specific interfacial area. Additionally a circular flow in the stationary phase was identified that lowers the interfacial area because it pushes the jet of mobile phase to the chamber wall. The Coriolis force alone gives the impulse for this behavior. As a result the model is easier to handle than experiments and allows 3D prediction of hydrodynamics in the chamber. Additionally it can be used for optimizing geometry and operating parameters for given physical properties of solvent systems. PMID:21324465

Adelmann, S; Schwienheer, C; Schembecker, G

2011-09-01

351

•¿? EFFECTS OF CENTRIFUGAL FORCE ON FERTILIZED EGGS OF ARBACIA PUNCTULATA AS OBSERVED WITH THE CENTRIFUGE-MICROSCOPE  

Microsoft Academic Search

By means of the centrifuge-microscope of Harvey and Loomis (1930), it is possible to observe continuously the effects of centrifugal force on eggs at various stages of development, while they are being rotated. A striking difference in behavior of the fertilized and un fertilized eggs of Arbacia is immediately apparent when studied in this wayâ€\\

ETHEL BROWNE HARVEY

352

A straight path centrifugal blood pump concept in the Capiox centrifugal pump.  

PubMed

This article describes comparative studies of a newly developed "straight path" centrifugal pump (Capiox centrifugal pump) targeted for open-heart surgery and circulatory support. A unique straight path design of the rotor was very effective in reducing the pump's rotational speed and prime volume. This pump was evaluated for hydraulics, hemolysis, depriming characteristics, cavitation, and heat generation. Two commercially available centrifugal pumps, the Biomedicus cone-type pump and the Sarns 3M impeller-type pump, were used as controls. The new pump required the lowest pump speed to produce the same flow rates under the same pressure loads and demonstrated the lowest hemolysis and the lowest temperature rise with the outlet clamped. The air volume required to deprime the new pump was one-third to one-half that for the other pumps, and no sign of cavitation was observed even if a small amount of air was introduced to the pump inlet under a negative pressure of 200 mm Hg. PMID:8338432

Kijima, T; Oshiyama, H; Horiuchi, K; Nogawa, A; Hamasaki, H; Amano, N; Nojiri, C; Fukasawa, H; Akutsu, T

1993-07-01

353

Computational analysis of stall and separation control in centrifugal compressors  

NASA Astrophysics Data System (ADS)

A numerical technique for simulating unsteady viscous fluid flow in turbomachinery components has been developed. In this technique, the three-dimensional form of the Reynolds averaged Navier-Stokes equations is solved in a time-accurate manner. The flow solver is used to study fluid dynamic phenomena that lead to instabilities in centrifugal compressors. The results indicate that large flow incidence angles, at reduced flow rates, can cause boundary layer separation near the blade leading edge. This mechanism is identified as the primary factor in the stall inception process. High-pressure jets upstream of the compressor face are studied as a means of controlling compressor instabilities. Steady jets are found to alter the leading edge flow pattern and effectively suppress compressor instabilities. Yawed jets are more effective than parallel jets and an optimum yaw angle exists for each compression system. Numerical simulations utilizing pulsed jets have also been done. Pulsed jets are found to yield additional performance enhancements and lead to a reduction in external air requirements for operating the jets. Jets pulsed at higher frequencies perform better than low-frequency jets. These findings suggest that air injection is a viable means of alleviating compressor instabilities and could impact gas turbine technology. Results concerning the optimization of practical air injection systems and implications for future research are discussed. The flow solver developed in this work, along with the postprocessing tools developed to interpret the results, provide a rational framework for analyzing and controlling current and next generation compression systems.

Stein, Alexander

2000-10-01

354

Unsteady flow phenomena in discrete passage diffusers for centrifugal compressors  

NASA Astrophysics Data System (ADS)

Research is described on the fluid dynamic behavior of high performance diffusers for centrifugal compressors, with particular application to small gas turbine engine applications. Using a unique swirl generator, experiments have been carried out to define the performance and stall onset behavior of a modern discrete passage diffuser as a function of inlet conditions. Two diffusers were examined, one with 30 passages and one with 38 passages. Inlet blockage and axial asymmetry were varied over Mach numbers up to unity and over a range of inlet swirl angles. Diffuser pressure recovery and operating range were calculated using traverse measurements made upstream of the diffuser. It was found that the performance of the diffuser under different inlet conditions could be expressed to a high degree of accuracy as a single curve of nondimensional static pressure recovery coefficient, based on availability averaged inlet stagnation pressure, and momentum-averaged inlet flow angle. Unsteady pressure measurements showed that the diffuser entered rotating stall at reduced flow rates. No long wavelength stall precursor was determined from the measurements.

Filipenco, V.; Johnston, J. M.; Greitzer, E. M.

1994-05-01

355

Developments in a centrifugal compressor surge control -- a technology assessment  

SciTech Connect

There are a number of surge control schemes in current use for centrifugal compressors employed in natural gas transmission systems. Basically, these schemes consist of a set of detection devices that either anticipate surge or detect it at its inception, and a set of control devices that act to prevent surge from occurring. A patent search was conducted in an attempt to assess the level and direction of technology development over the last 20 years and to define the focus for future R D activities. In addition, the paper presents the current state of technology in three areas: surge control, surge detection, and surge suppression. Patent data obtained from on-line databases showed that most of the emphasis has been on surge control rather than on detection and control and that the current trend in surge control will likely continue toward incremental improvement of a basic or conventional surge control strategy. Various surge suppression techniques can be grouped in two categories: (1) those that are focused on better compressor interior design, and (2) others that attempt to suppress surge by external and operational means.

Botros, K.K.; Henderson, J.F. (NOVACOR Research Technology Corp., Calgary, Alberta (Canada))

1994-04-01

356

Developments in centrifugal compressor surge control: A technology assessment  

NASA Astrophysics Data System (ADS)

There are a number of surge control schemes in current use for centrifugal compressors employed in natural gas transmission systems. Basically, these schemes consist of a set of detection devices that either anticipate surge or detect it at its inception, and a set of control devices that act to prevent surge from occurring. A patent search was conducted in an attempt to assess the level and direction of technology development over the last 20 years and to define the focus for future R&D activities. In addition, the paper presents the current state of technology in three areas: surge control, surge detection, and surge suppression. Patent data obtained from on-line databases showed that most of the emphasis has been on surge control rather than on detection and control and that the current trend in surge control will likely continue toward incremental improvement of a basic or conventional surge control strategy. Various surge suppression techniques can be grouped in two categories: (i) those that are focused on better compressor interior design, and (ii) others that attempt to suppress surge by external and operational means.

Botros, K. K.; Henderson, J. F.

1994-04-01

357

Ligand field photofragmentation spectroscopy of [Ag(L)N]2+ complexes in the gas phase: experiment and theory.  

PubMed

Experiments have been undertaken to record photofragmentation spectra from a series of [Ag(L)N]2+ complexes in the gas phase. Spectra have been obtained for silver(II) complexed with the ligands (L): acetone, 2-pentanone, methyl-vinyl ketone, pyridine, and 4-methyl pyridine (4-picoline) with N in the range of 4-7. A second series of experiments using 1,1,1,3-fluoroacetone, acetonitrile, and CO2 as ligands failed to show any evidence of photofragmentation. Interpretation of the experimental data has come from time-dependent density functional theory (TDDFT), which very successfully accounts for trends in the spectra in terms of subtle differences in the properties of the ligands. Taking a sample of three ligands, acetone, pyridine, and acetonitrile, the calculations show all the spectral transitions to involve ligand-to-metal charge transfer, and that wavelength differences (or lack of spectra) arise from small changes in the energies of the molecular orbitals concerned. The calculations account for an absence in the spectra of any effects due to Jahn-Teller distortion, and they also reveal structural differences between complexes where the coordinating atom is either oxygen or nitrogen that have implications for the stability of silver(II) compounds. Where possible, comparisons have also been made with the physical properties of condensed phase silver(II) complexes. PMID:17705600

Guan, Jingang; Puskar, Ljiljana; Esplugas, Ricardo O; Cox, Hazel; Stace, Anthony J

2007-08-14

358

Water-gas shift reaction on oxide/Cu(111): Rational catalyst screening from density functional theory  

NASA Astrophysics Data System (ADS)

Developing improved catalysts based on a fundamental understanding of reaction mechanism has become one of the grand challenges in catalysis. A theoretical understanding and screening the metal-oxide composite catalysts for the water-gas shift (WGS) reaction is presented here. Density functional theory was employed to identify the key step for the WGS reaction on the Au, Cu-oxide catalysts, where the calculated reaction energy for water dissociation correlates well with the experimental measured WGS activity. Accordingly, the calculated reaction energy for water dissociation was used as the scaling descriptor to screen the inverse model catalysts, oxide/Cu(111), for the better WGS activity. Our calculations predict that the WGS activity increases in a sequence: Cu(111), ZnO/Cu(111) < TiO2/Cu(111), ZrO2/Cu(111) < MoO3/Cu(111). Our results imply that the high performances of Au, Cu-oxide nanocatalysts in the WGS reaction rely heavily on the direct participation of both oxide and metal sites. The degree that the oxide is reduced by Cu plays an important role in determining the WGS activity of oxide/Cu catalysts. The reducible oxide can be transformed from the fully oxidized form to the reduced form due to the interaction with Cu and, therefore, the transfer of electron density from Cu, which helps in releasing the bottleneck water dissociation and, therefore, facilitating the WGS reaction on copper.

Liu, Ping

2010-11-01

359

Water-gas Shift Reaction on oxide/Cu(111): Rational Catalyst Screening from Density Functional Theory  

SciTech Connect

Developing improved catalysts based on a fundamental understanding of reaction mechanism has become one of the grand challenges in catalysis. A theoretical understanding and screening the metal-oxide composite catalysts for the water-gas shift (WGS) reaction is presented here. Density functional theory was employed to identify the key step for the WGS reaction on the Au, Cu-oxide catalysts, where the calculated reaction energy for water dissociation correlates well with the experimental measured WGS activity. Accordingly, the calculated reaction energy for water dissociation was used as the scaling descriptor to screen the inverse model catalysts, oxide/Cu(111), for the better WGS activity. Our calculations predict that the WGS activity increases in a sequence: Cu(111), ZnO/Cu(111) < TiO{sub 2}/Cu(111), ZrO{sub 2}/Cu(111) < MoO{sub 3}/Cu(111). Our results imply that the high performances of Au, Cu-oxide nanocatalysts in the WGS reaction rely heavily on the direct participation of both oxide and metal sites. The degree that the oxide is reduced by Cu plays an important role in determining the WGS activity of oxide/Cu catalysts. The reducible oxide can be transformed from the fully oxidized form to the reduced form due to the interaction with Cu and, therefore, the transfer of electron density from Cu, which helps in releasing the bottleneck water dissociation and, therefore, facilitating the WGS reaction on copper.

Liu, P.

2010-11-28

360

Centrifugal distortion and the ring puckering vibration in the microwave spectrum of 2,3-dihydrofuran  

NASA Astrophysics Data System (ADS)

The microwave spectrum of 2,3-dihydrofuran has been reinvestigated and measurements for the ground and first five excited states of the ring puckering vibration have been extended to higher frequencies and rotational quantum numbers in order to study the vibrational dependence of the rotational and centrifugal distortion constants. The ring puckering potential function derived by Green from the far infrared spectrum does not reproduce the vibrational dependence of the rotational constants well. A slightly different potential function is derived which gives a reasonable fit both to the far infrared spectrum and the rotational constants. This changes the barrier to ring inversion from 1.00 kJ mol -1 to 1.12 kJ mol -1. The vibrational dependence of the centrifugal distortion constants is accounted for satisfactorily by the theory developed by Creswell and Mills. An attempt to reproduce the vibrational dependence of the rotational and centrifugal distortion constants using the ring puckering potential function and a simple model for this vibration has very limited success.

Cervellati, R.; Degli Esposti, A.; Lister, D. G.; Lopez, J. C.; Alonso, J. L.

1986-10-01

361

Axial and centrifugal continuous-flow rotary pumps: a translation from pump mechanics to clinical practice.  

PubMed

The recent success of continuous-flow circulatory support devices has led to the growing acceptance of these devices as a viable therapeutic option for end-stage heart failure patients who are not responsive to current pharmacologic and electrophysiologic therapies. This article defines and clarifies the major classification of these pumps as axial or centrifugal continuous-flow devices by discussing the difference in their inherent mechanics and describing how these features translate clinically to pump selection and patient management issues. Axial vs centrifugal pump and bearing design, theory of operation, hydrodynamic performance, and current vs flow relationships are discussed. A review of axial vs centrifugal physiology, pre-load and after-load sensitivity, flow pulsatility, and issues related to automatic physiologic control and suction prevention algorithms is offered. Reliability and biocompatibility of the two types of pumps are reviewed from the perspectives of mechanical wear, implant life, hemolysis, and pump deposition. Finally, a glimpse into the future of continuous-flow technologies is presented. PMID:23260699

Moazami, Nader; Fukamachi, Kiyotaka; Kobayashi, Mariko; Smedira, Nicholas G; Hoercher, Katherine J; Massiello, Alex; Lee, Sangjin; Horvath, David J; Starling, Randall C

2013-01-01

362

Effect of centrifugation on herpes simplex virus isolation.  

PubMed

The effects of high-speed centrifugation on the isolation of herpes simplex virus (HSV) were studied. Aliquots of laboratory or clinical specimens were inoculated into test tubes and flat-bottomed tubes containing HEp2 monolayers. Test tubes were incubated at 35 degrees C on roller drums (standard method), and flat-bottomed tubes were centrifuged at 15,000g at 35 degrees C for 1 hr, before being incubated at 35 degrees C without rolling (centrifuged method). Centrifugation of clinical and laboratory specimens of HSV type 1 and HSV type 2 produced significantly increased isolation rates compared with the standard method. When clinical and laboratory specimens were diluted, the centrifuged method was more sensitive at all dilutions. When 20 specimens were used for end-point titrations, the centrifuged method was 10 times more sensitive for 15 specimens and 100 times more sensitive for five specimens. There was no difference in the time taken for the appearance of cytopathic effect (CPE) between the standard and centrifuged methods. PMID:6278068

Darougar, S; Gibson, J A; Thaker, U

1981-01-01

363

Experimental characterization of high speed centrifugal compressor aerodynamic forcing functions  

NASA Astrophysics Data System (ADS)

The most common and costly unexpected post-development gas turbine engine reliability issue is blade failure due to High Cycle Fatigue (HCF). HCF in centrifugal compressors is a coupled nonlinear fluid-structure problem for which understanding of the phenomenological root causes is incomplete. The complex physics of this problem provides significant challenges for Computational Fluid Dynamics (CFD) techniques. Furthermore, the available literature fails to address the flow field associated with the diffuser potential field, a primary cause of forced impeller vibration. Because of the serious nature of HCF, the inadequacy of current design approaches to predict HCF, and the fundamental lack of benchmark experiments to advance the design practices, there exists a need to build a database of information specific to the nature of the diffuser generated forcing function as a foundation for understanding flow induced blade vibratory failure. The specific aim of this research is to address the fundamental nature of the unsteady aerodynamic interaction phenomena inherent in high-speed centrifugal compressors wherein the impeller exit flow field is dynamically modulated by the vaned diffuser potential field or shock structure. The understanding of this unsteady aerodynamic interaction is fundamental to characterizing the impeller forcing function. Unsteady static pressure measurement at several radial and circumferential locations in the vaneless space offer a depiction of pressure field radial decay, circumferential variation and temporal fluctuation. These pressure measurements are coupled with high density, full field measurement of the velocity field within the diffuser vaneless space at multiple spanwise positions. The velocity field and unsteady pressure field are shown to be intimately linked. A strong momentum gradient exiting the impeller is shown to extend well across the vaneless space and interact with the diffuser vane leading edge. The deterministic unsteady pressure field is found to be dominated by the blade-vane interaction. HCF concerns are illuminated by persistent pressure waves extending radially across the vaneless space and impacting the impeller pressure surface. Finally, the average impeller exit flow field is found to present a highly unsteady velocity field to the downstream vane row, challenging the common design assumption of a rapid mixing model for diffuser design.

Gallier, Kirk

364

Centrifugal Casting Features/Metallurgical Characterization of Aluminum Alloys  

NASA Astrophysics Data System (ADS)

This paper deals with the study of centrifugal effects on aluminium castings under high G values. Most of the studies in this domain (FGMs obtained by centrifugal casting) deal with functionally graded composites reinforced with a solid phase such as silicon particles or others. However, in this study it will be shown that unreinforced aluminium alloys may be significantly influenced by the centrifugal effect and that functionally graded castings are also obtained. It has been observed that the centrifugal effect may increase in some alloys, depending on the relative position in the castings, the rupture strength by approx. 50%, and rupture strain by about 300%, as compared to the gravity casting technique. The Young's modulus may also increase by about 20%. It has also been reported that in vertical centrifugal castings there are mainly three aspects that affect the components thus obtained, namely: fluid dynamics; vibration (inherent to the system) and centrifugal force. These features have a different effect on the castings depending on the aluminium alloy. In this paper, an analysis of the most important effects of the centrifugal casting process on metallurgical features is conducted. A solidification characterization at several points along the mould will be made in order to have an accurate idea of both the fluid dynamics inside the mould during the casting and the solidification behavior in different parts of the component. These two analyses will be related to the metallurgical properties (phase distribution; SDAS; eutectic silicon content and shape, pores density and shape) along the component and mainly along the direction of the centrifugal pressure. A comparison between castings obtained by both centrifugal casting technique and gravity casting technique is made for reference (gravity casting).

Chirita, G.; Stefanescu, I.; Soares, D.; Cruz, D.; Silva, F. S.

2008-02-01

365

Centrifugal Casting Features/Metallurgical Characterization of Aluminum Alloys  

SciTech Connect

This paper deals with the study of centrifugal effects on aluminium castings under high G values. Most of the studies in this domain (FGMs obtained by centrifugal casting) deal with functionally graded composites reinforced with a solid phase such as silicon particles or others. However, in this study it will be shown that unreinforced aluminium alloys may be significantly influenced by the centrifugal effect and that functionally graded castings are also obtained. It has been observed that the centrifugal effect may increase in some alloys, depending on the relative position in the castings, the rupture strength by approx. 50%, and rupture strain by about 300%, as compared to the gravity casting technique. The Young's modulus may also increase by about 20%. It has also been reported that in vertical centrifugal castings there are mainly three aspects that affect the components thus obtained, namely: fluid dynamics; vibration (inherent to the system); and centrifugal force. These features have a different effect on the castings depending on the aluminium alloy. In this paper, an analysis of the most important effects of the centrifugal casting process on metallurgical features is conducted. A solidification characterization at several points along the mould will be made in order to have an accurate idea of both the fluid dynamics inside the mould during the casting and the solidification behavior in different parts of the component. These two analyses will be related to the metallurgical properties (phase distribution; SDAS; eutectic silicon content and shape, pores density and shape) along the component and mainly along the direction of the centrifugal pressure. A comparison between castings obtained by both centrifugal casting technique and gravity casting technique is made for reference (gravity casting)

Chirita, G.; Soares, D.; Cruz, D.; Silva, F. S. [Mechanical Engineering Department, School of Engineering, Minho University (Portugal); Stefanescu, I. [Faculty of Mechanical Engineering, Dunarea de Jos University Galati (Romania)

2008-02-15

366

Ocular counterrolling induced by centrifugation during orbital space flight  

NASA Technical Reports Server (NTRS)

During the 1998 Neurolab mission (STS-90), four astronauts were exposed to interaural centripetal accelerations (Gy centrifugation) of 0.5 g and 1 g during rotation on a centrifuge, both on Earth and during orbital space flight. Subjects were oriented either left-ear out or right-ear out, facing or back to motion. Binocular eye movements were measured in three dimensions using a video technique. On Earth, tangential centrifugation that produces 1 g of interaural linear acceleration combines with gravity to tilt the gravitoinertial acceleration (GIA) vector 45 degrees in the roll plane relative to the head vertical, generating a summed vector of 1.4 g. Before flight, this elicited mean ocular counterrolling (OCR) of 5.7 degrees. Due to the relative absence of gravity during flight, there was no linear acceleration along the dorsoventral axis of the head. As a result, during in-flight centrifugation, gravitoinertial acceleration was strictly aligned with the centripetal acceleration along the interaural axis. There was a small but significant decrease (mean 10%) in the magnitude of OCR in space (5.1 degrees). The magnitude of OCR during postflight 1 g centrifugation was not significantly different from preflight OCR (5.9 degrees). Findings were similar for 0.5 g centrifugation, but the OCR magnitude was approximately 60% of that induced by centrifugation at 1 g. OCR during pre- and postflight static tilt was not significantly different and was always less than OCR elicited by centrifugation of Earth for an equivalent interaural linear acceleration. In contrast, there was no difference between the OCR generated by in-flight centrifugation and by static tilt on Earth at equivalent interaural linear accelerations. These data support the following conclusions: (1) OCR is generated predominantly in response to interaural linear acceleration; (2) the increased OCR during centrifugation on Earth is a response to the head dorsoventral 1 g linear acceleration component, which was absent in microgravity. The dorsoventral linear acceleration could have activated either the otoliths or body-tilt receptors that responded to the larger GIA magnitude (1.4 g), to generate the increased OCR during centrifugation on Earth. A striking finding was that magnitude of OCR was maintained throughout and after flight. This is in contrast to most previous postflight OCR studies, which have generally registered decreases in OCR. We postulate that intermittent exposure to artificial gravity, in the form of the centripetal acceleration experienced during centrifugation, acted as a countermeasure to deconditioning of this otolith-ocular orienting reflex during the 16-day mission.

Moore, S. T.; Clement, G.; Raphan, T.; Cohen, B.

2001-01-01

367

Investigation of the jet-wake flow of a highly loaded centrifugal compressor impeller  

NASA Technical Reports Server (NTRS)

Investigations, aimed at developing a better understanding of the complex flow field in high performance centrifugal compressors were performed. Newly developed measuring techniques for unsteady static and total pressures as well as flow directions, and a digital data analysis system for fluctuating signals were thoroughly tested. The loss-affected mixing process of the distorted impeller discharge flow was investigated in detail, in the absolute and relative system, at impeller tip speeds up to 380 m/s. A theoretical analysis proved good coincidence of the test results with the DEAN-SENOO theory, which was extended to compressible flows.

Eckardt, D.

1978-01-01

368

Centrifugal Consolidation Testing of Soft Soil.  

National Technical Information Service (NTIS)

The objective of this research is to provide physical modelling data which will enable the validation of existing theory and/or will provide data to permit empirical correction factors to existing theories which will model field geometries. A series of ce...

R. E. Gibson

1986-01-01

369

Gas-phase reactions of [VO2(OH)2]- and [V2O5(OH)]- with methanol: experiment and theory.  

PubMed

The gas-phase reactivity of the vanadium hydroxides [VO(2)(OH)(2)](-) and [V(2)O(5)(OH)](-) toward methanol was examined using a combination of ion-molecule reactions (IMRs) and collision-induced dissociation (CID) in a quadrupole ion trap mass spectrometer. Isotope-labeling experiments with CD(3)OH, (13)CH(3)OH, and CH(3)(18)OH were used to confirm the stoichiometry of ions and the observed sequence of reactions. The experimental data were interpreted with the aid of density functional theory calculations, carried out at the B3LYP/SDD6-311++G** level of theory. While [VO(2)(OH)(2)](-) is unreactive, [V(2)O(5)(OH)](-) undergoes a metathesis reaction to yield [V(2)O(5)(OCH(3))](-). The DFT calculations reveal that the metathesis reaction of methanol with [VO(2)(OH)(2)](-) suffers from a barrier of +0.52 eV (relative to separated reactants) but that the reaction of [V(2)O(5)(OH)](-) with methanol readily proceeds via addition/elimination reactions with both transition states being below the energy of the separated reactants. CID of [V(2)O(5)(OCH(3))](-) (m/z 213) yields three ions arising from activation of the methoxo ligand: [V(2), O(6), C, H](-) (m/z 211); [V(2), O(5), H](-) (m/z 183); and [V(2), O(4), H](-) (m/z 167). Additional experiments and DFT calculations suggest that these ions arise from losses of H(2), formaldehyde and the sequential losses of H(2) and CO(2), respectively. The use of an (18)O-labeled methoxo ligand in [V(2)O(5)((18)OCH(3))](-) (m/z 215) showed the competing losses of H(2)C(16)O and H(2)C(18)O and [H(2) and C(16)O(18)O] and [H(2) and C(16)O(2)], highlighting that (16)O/(18)O exchange between the methoxo ligand and the vanadium oxide occurs prior to the subsequent fragmentation of the ligand. DFT calculations reveal that a key step involves hydrogen atom transfer from the methoxo ligand to the oxo ligand of the same vanadium center, producing the intermediate [V(2)O(4)(OH)(OCH(2))](-) containing a ketyl radical ligand and a hydroxo ligand. This intermediate can either undergo CH(2)O loss, or the ketyl radical can couple with an oxo ligand of the adjacent vanadium center, producing [V(2)O(3)(?(2)-O(2)CH(2))](-), which is a key intermediate in the (16)O/(18)O scrambling and in the H(2) loss channel. PMID:22889366

Harris, Benjamin L; Waters, Tom; Khairallah, George N; O'Hair, Richard A J

2013-02-14

370

Relaxation dynamics in a lattice gas: A test of the mode-coupling theory of the ideal glass transition  

NASA Astrophysics Data System (ADS)

By means of computer simulations we investigate the dynamical behavior of a binary lattice-gas mixture with short-range interactions in order to provide a stringent test of mode-coupling theory (MCT). The dynamics of the particles is given by Monte Carlo-like moves that change the positions of the particles and binary collisions that change the velocities. By monitoring the self part of the van Hove correlation function we find the low-temperature dynamics to be glasslike. In accordance with MCT the imaginary part of the dynamic susceptibility ?'' shows a well-defined ? peak whose high-frequency wing follows a von Schweidler law with an exponent that is independent of temperature. The low-frequency wing of the peak follows a different power-law dependence that corresponds to a power law of the form -P+A/t? (A,P,?>0) in the self part of the intermediate scattering function Fs1(k,t). In agreement with MCT we find that the diffusion constant for one of the two types of particles, the relaxation times of Fs1(k,t), the location of the ? peak in the susceptibility, and the prefactor of the von Schweidler law all have a power-law dependence on temperature, (T-Tc)?, for T>Tc at constant density. As predicted by the theory the critical temperatures Tc for the different quantities are the same within the statistical error. However, in contradiction to MCT, the critical exponents ? vary from one quantity to another. The value of the Lamb-Mössbauer factor shows qualitatively the wave-vector dependence predicted by MCT. The self part of a second kind of correlation function exhibits the two power laws predicted by MCT for the high- and low-frequency wings of the ? relaxation. We show that in the vicinity of the minimum of the susceptibility the scaling behavior predicted by MCT holds. However, the location of this minimum at a given temperature depends on the quantity investigated, contrary to the predictions of MCT. Moreover, the value of ?'' at this minimum exhibits a power-law dependence on temperature with an exponent that is significantly larger than the one predicted by MCT. We also find that the height of the ? peak as well as the total energy per particle have a power-law dependence on temperature and that the corresponding critical temperatures are close to those obtained for the other quantities.

Kob, Walter; Andersen, Hans C.

1993-05-01

371

A parametric study for high-efficiency gas-liquid separator design  

Microsoft Academic Search

A gas liquid centrifugal separator is widely used in industry on account of its simple geometry and little maintenance. These\\u000a separators have considerable advantages over filters, scrubbers or precipitators in term of compact design, lower pressure\\u000a drop and higher capacity. A gas liquid centrifugal separator is a device that utilizes centrifugal forces and low pressure\\u000a caused by rotational motion to

S. Nagdewe; J. K. Kwoon; H. D. Kim; D. S. Kim; K. M. Kwak; Toshiaki Setoguchi

2008-01-01

372

Current topics on centrifugal plasmapheresis technologies.  

PubMed

In the field of plasmapheresis centrifugal technology has recently focused on the collection of peripheral blood stem cells (PBSCs) for both autologous and allogeneic transplantation in patients with malignancies or hematological diseases and on donor plasmapheresis. PBSC transplantation is rapidly replacing bone marrow transplantation in such patients. Various kinds of apheresis equipment were applied and described for PBSC collection. Comparison among machines is described. Allogeneic PBSCs were collected from healthy normal donors. Specific attention to the dose and administration duration of granulocyte colony-stimulating factor and a careful apheresis procedure should be made for donor safety. In platelet transfusion practice, a platelet concentrate product derived plateletpheresis from a single donor is preferable to minimize and to prevent adverse transfusion reactions. The status of platelet collection and its efficacy by various kinds of plateletpheresis equipment are discussed. The Amicus and CCS might be preferable plateletpheresis machines because of their collection efficiencies and wider indication for donors. With the limited number of donors, it is essential that plateletpheresis should be more effectively performed and managed by each regional blood center. The status of plasma and red cell collection by apheresis technologies is described also briefly. PMID:11724511

Omokawa, S

2001-08-01

373

Hybridization enhancement using microfluidic planetary centrifugal mixing.  

PubMed

DNA microarrays produce their greatest sensitivities when hybridized using concentrated samples and effective mixing; however, these goals have proved elusive to combine. If samples are diluted enough to fill larger chambers, then mixing works well using either pumping or gravity with rotation, although sensitivities will suffer. Various techniques for mixing concentrated samples in small thin chambers have been proposed; however, they often leave streaks or scars, and their reusable components require careful cleaning. Here we introduce a versatile new microfluidics platform, a two-axis centrifuge whose fluidic chambers rotate in a planetary relationship to a radial gravitational field. This paradigm readily overcomes surface and viscous forces even in chambers only 50 microm thin. Thin chambers obviate the need for sample dilution and increase sensitivities and dynamic ranges 10-fold. In comparisons against conventional mixing using the same 10 microg of starting total RNA on 22 000-probe arrays, 10 000 more usable signals rose above the noise. In other experiments, planetary mixing was able to produce comparable results while using only one-tenth the starting sample. The benefits of planetary mixing include sample conservation, shorter hybridizations, less reliance on amplification, and the ability to quantify many gene signals otherwise obscured by noise. PMID:15571357

Bynum, Magdalena A; Gordon, Gary B

2004-12-01

374

Wave Augmented Diffuser for Centrifugal Compressor  

NASA Technical Reports Server (NTRS)

A wave augmented diffuser for a centrifugal compressor surrounds the outlet of an impeller that rotates on a drive shaft having an axis of rotation. The impeller brings flow in in an axial direction and imparts kinetic energy to the flow discharging it in radial and tangential directions. The flow is discharged into a plurality of circumferentially disposed wave chambers. The wave chambers are periodically opened and closed by a rotary valve such that the flow through the diffuser is unsteady. The valve includes a plurality of valve openings that are periodically brought into and out of fluid communication with the wave chambers. When the wave chambers are closed, a reflected compression wave moves upstream towards the diffuser bringing the flow into the wave chamber to rest. This action recovers the kinetic energy from the flow and limits any boundary layer growth. The flow is then discharged in an axial direction through an opening in the valve plate when the valve plate is rotated to an open position. The diffuser thus efficiently raises the static pressure of the fluid and discharges an axially directed flow at a radius that is predominantly below the maximum radius of the diffuser.

Skoch, Gary J. (Inventor); Paxson, Daniel E. (Inventor)

2001-01-01

375

Classical nucleation theory with a radius-dependent surface tension: A two-dimensional lattice-gas automata model  

NASA Astrophysics Data System (ADS)

The constant surface tension assumption of the Classical Nucleation Theory (CNT) is known to be flawed. In order to probe beyond this limitation, we consider a microscopic, two-dimensional Lattice-Gas Automata (LGA) model of nucleation in a supersaturated system, with model input parameters Ess (solid particle-to-solid particle bonding energy), Esw (solid particle-to-water bonding energy), ? (next-to-nearest-neighbor bonding coefficient in solid phase), and Cin (initial solute concentration). The LGA method has the advantages of easy implementation, low memory requirements, and fast computation speed. Analytical results for the system's concentration and the crystal radius as functions of time are derived and the former is fit to the simulation data in order to determine the equilibrium concentration. The “Mean First-Passage Time” technique is used to obtain the nucleation rate and critical nucleus size from the simulation data. The nucleation rate and supersaturation data are evaluated using a modification to the CNT that incorporates a two-dimensional radius-dependent surface tension term. The Tolman parameter, ?, which controls the radius dependence of the surface tension, decreases (increases) as a function of the magnitude of Ess (Esw), at fixed values of ? and Esw (Ess). On the other hand, ? increases as ? increases while Ess and Esw are held constant. The constant surface tension term of the CNT, ?0, increases (decreases) with increasing magnitudes of Ess (Esw) at fixed values of Esw (Ess) and increases as ? is increased. ?0 increases linearly as a function of the change in energy during an attachment or detachment reaction, |?E|, however, with a slope less than that predicted for a crystal that is uniformly packed at maximum density. These results indicate an increase in the radius-dependent surface tension, ?, with respect to increasing magnitude of the difference between Ess and Esw.

Hickey, Joseph; L'Heureux, Ivan

2013-02-01

376

Density functional theory study of ATA, BTAH, and BTAOH as copper corrosion inhibitors: adsorption onto Cu(111) from gas phase.  

PubMed

A low-coverage gas-phase adsorption of three corrosion inhibitors-3-amino-1,2,4-triazole (ATA), benzotriazole (BTAH), and 1-hydroxybenzotriazole (BTAOH)-on perfect Cu(111) surface has been studied and characterized using density functional theory calculations. We find that the molecules in neutral form chemisorb weakly to the perfect surface in an upright geometry. The strength of the chemisorption increases in the order BTAH < BTAOH < ATA with adsorption energies of -0.40, -0.53, and -0.60 eV, respectively. The molecules bond to the surface with triazole nitrogen atoms and also through X-H···Metal hydrogen bonds (X = N or O). In addition to chemisorption, BTAH and BTAOH can also physisorb with the molecular plane being nearly parallel to the surface and the energies of the physisorption are -0.72 and -0.97 eV, respectively, hence being more exothermic than the corresponding chemisorption energies. On the other hand, the molecules in dehydrogenated form chemisorb strongly to the surface and the strength of the chemisorption increases in the order BTAO· < ATA· < BTA· with the adsorption energies of -1.65, -2.22, and -2.78 eV, respectively. This order is compatible with the trend of experimentally observed corrosion inhibition effectiveness on copper in near-neutral chloride solutions. Although the calculations are performed at the metal/vacuum interface, they provide enough insight to rationalize why in some experiments the BTAH was observed to be adsorbed with an upright geometry and in the others with parallel geometry. PMID:20731342

Kokalj, Anton; Peljhan, Sebastijan

2010-09-21

377

Miniature Gas-Circulating Machine  

NASA Technical Reports Server (NTRS)

Proposed gas-circulating machine consists essentially of centrifugal pump driven by induction motor. Noncontact bearings suppress wear and contamination. Used to circulate helium (or possibly hydrogen or another gas) in regeneration sorption-compressor refrigeration system aboard spacecraft. Also proves useful in terrestrial applications in which long life, reliability, and low contamination essential.

Swift, Walter L.; Valenzuela, Javier A.; Sixsmith, Herbert; Nutt, William E.

1993-01-01

378

Looking Southeast at Precipitation System, Steam Dryer and Centrifuge in ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Looking Southeast at Precipitation System, Steam Dryer and Centrifuge in Red Room within Recycle Recovery Building - Hematite Fuel Fabrication Facility, Recycle Recovery Building, 3300 State Road P, Festus, Jefferson County, MO

379

Astronaut Alan Shepard prepares for testing in centrifuge  

NASA Technical Reports Server (NTRS)

Astronaut Alan B. Shepard Jr., one of three NASA astronauts chosen for the Project Mercury first manned suborbital flight, prepares for testing in capsule of the U.S. Navy's centrifuge at Johnsville, Pennsylvania.

1961-01-01

380

Effects of Impeller-Diffuser Interaction on Centrifugal Compressor Performance.  

National Technical Information Service (NTIS)

This research program focuses on characterizing the effect of impeller-diffuser interactions in a centrifugal compressor stage on its performance using unsteady threedimensional Reynolds-averaged Navier-Stokes simulations. The computed results show that t...

C. S. Tan

2003-01-01

381

19. LOWER OIL ROOM DIABLO POWERHOUSE: SHARPLES OIL CENTRIFUGE AND ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

19. LOWER OIL ROOM DIABLO POWERHOUSE: SHARPLES OIL CENTRIFUGE AND OIL TANK, 1989. - Skagit Power Development, Diablo Powerhouse, On Skagit River, 6.1 miles upstream from Newhalem, Newhalem, Whatcom County, WA

382

Centrifugally-assisted combustion synthesis of functionally-graded materials  

SciTech Connect

Functionally graded materials (FGM`s) have been prepared by a variety of techniques, including combustion synthesis, and the use of a centrifugal force in this method of synthesis has been demonstrated previously. However, in the earlier work, a centrifugal force was applied to investigate the changes in the dynamics of self-propagating combustion waves or to deposit coatings on the inside surfaces of pipes. The use of a centrifugal force to investigate the formation of FGM`s has not been reported previously and is the focus of this communication. In this work, the authors have chosen thermite reactions to investigate the feasibility of FGM formation by centrifugally-assisted combustion synthesis.

Lai, W.; Munir, Z.A.; McCoy, B.J.; Risbud, S.H. [Univ. of California, Davis, CA (United States)] [Univ. of California, Davis, CA (United States)

1997-02-01

383

Ballistic to centrifuging flow of granular materials in rotating tumblers  

NASA Astrophysics Data System (ADS)

The critical rotation speed for centrifuging of granular materials in horizontal rotating tumblers, determined by the Froude number, was studied experimentally and computationally as a function of the particle diameter, tumbler fill fraction, interstitial fluid, and tumbler length. Particle size does not affect the critical speed for centrifugation provided that the fill fraction is below 50%. The actual critical speed is typically 1.4 times the theoretical speed for centrifugation. Above 50% fill, the critical speed increases with particle size. Simulations indicate that even for the centrifuging condition there is relative motion of particles due to gravity, especially near the free surface. The presence of an interstitial fluid alters the critical speed due to buoyancy.

Lueptow, Richard M.; Juarez, Gabriel; Chen, Pengfei; Ottino, Julio M.

2009-11-01

384

18. View north of Tropic Chamber Worthington centrifugal compressor and ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

18. View north of Tropic Chamber Worthington centrifugal compressor and control panel, in machine area. - Natick Research & Development Laboratories, Climatic Chambers Building, U.S. Army Natick Research, Development & Engineering Center (NRDEC), Natick, Middlesex County, MA

385

Measurement of ground shock in explosive centrifuge model tests  

SciTech Connect

Los Alamos National Laboratory has begun a project to simulate the formation and collapse of underground cavities produced by nuclear explosions using chemical explosions at much smaller scale on a large geotechnical centrifuge. Use of a centrifuge for this project presents instrumentation challenges which are not encountered in tests at similar scale off of the centrifuge. Electromagnetic velocity measuring methods which have been very successfully applied to such models at 1 g would be very difficult, if not impossible, to implement at 100 g. We are investigating the feasibility of other techniques for monitoring the ground shock in small-scale tests including accelerometers, stress gauges, dynamic strain meters and small, mutual-inductance particle velocity gauges. Initial results indicate that some of these techniques can be adapted for centrifuge applications. 17 references, 4 figures.

Gaffney, E.S.; Wohletz, K.H.; McQueen, R.G.

1985-01-01

386

A multiplexed immunoassay system based upon reciprocating centrifugal microfluidics  

NASA Astrophysics Data System (ADS)

A novel, centrifugal disk-based micro-total analysis system (?TAS) for low cost and high throughput semi-automated immunoassay processing was developed. A key innovation in the disposable immunoassay disk design is in a fluidic structure that enables very efficient micro-mixing based on a reciprocating mechanism in which centrifugal acceleration acting upon a liquid element first generates and stores pneumatic energy that is then released by a reduction of the centrifugal acceleration, resulting in a reversal of direction of flow of the liquid. Through an alternating sequence of high and low centrifugal acceleration, the system reciprocates the flow of liquid within the disk to maximize incubation/hybridization efficiency between antibodies and antigen macromolecules during the incubation/hybridization stage of the assay. The described reciprocating mechanism results in a reduction in processing time and reagent consumption by one order of magnitude.

Noroozi, Zahra; Kido, Horacio; Peytavi, Régis; Nakajima-Sasaki, Rie; Jasinskas, Algimantas; Micic, Miodrag; Felgner, Philip L.; Madou, Marc J.

2011-06-01

387

Study of Blade Clearance Effects on Centrifugal Pumps.  

National Technical Information Service (NTIS)

A program of analysis, design, fabrication, and testing has been conducted to develop and experimentally verify analytical models to predict the effects of impeller blade clearance on centrifugal pumps. The effect of tip clearance on pump efficiency, and ...

R. K. Hoshide C. E. Nielson

1972-01-01

388

Development of Aerodynamic Design System for Centrifugal Compressors,  

National Technical Information Service (NTIS)

An improvement of the aerodynamic performance of centrifugal compressors for industrial use is necessary to achieve high efficiency and low energy consumption. The compressor is usually composed of many stages with different flow coefficients and the perf...

N. Nojima B. Nagata H. Kawasaki S. Sugitani

1988-01-01

389

14. CENTRIFUGAL FREQUENCY RELAY IN WAYSIDE CABINET, NEW HAVEN YARD ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

14. CENTRIFUGAL FREQUENCY RELAY IN WAYSIDE CABINET, NEW HAVEN YARD - New York, New Haven & Hartford Railroad, Automatic Signalization System, Long Island Sound shoreline between Stamford & New Haven, Stamford, Fairfield County, CT

390

15. FRONT VIEW, DETAIL, CENTRIFUGAL FREQUENCY RELAY IN WAYSIDE CABINET, ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

15. FRONT VIEW, DETAIL, CENTRIFUGAL FREQUENCY RELAY IN WAYSIDE CABINET, NEW HAVEN YARD - New York, New Haven & Hartford Railroad, Automatic Signalization System, Long Island Sound shoreline between Stamford & New Haven, Stamford, Fairfield County, CT

391

8. FLOOR 1: TENTERING GEAR FOR SOUTH STONES, CENTRIFUGAL GOVERNOR ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

8. FLOOR 1: TENTERING GEAR FOR SOUTH STONES, CENTRIFUGAL GOVERNOR MOUNTED ON STONE SPINDLE, VERY SHORT STEELYARD - Windmill at Water Mill, Montauk Highway & Halsey Lane, Water Mill, Suffolk County, NY

392

TECHNOLOGY EVALUATION REPORT: RETECH'S PLASMA CENTRIFUGAL FURNACE - VOLUME I  

EPA Science Inventory

A demonstration of the Retech, Inc. Plasma Centrifugal Furnace (PCF) was conducted under the Superfund Innovative Technology Evaluation (SITE) Program at the Department of Energy's (DOE's) Component Development and Integration Facility in Butte, Montana. The furnace uses heat gen...

393

Noise Reduction in Centrifugal Fans: A Literature Survey.  

National Technical Information Service (NTIS)

In order to help the industrial engineer construct quieter fans, the research work done by various experimenters during the last fifteen years on noise reduction methods in centrifugal fans used in air conditioning and ventilating equipment is summarized....

W. Neise

1975-01-01

394

Centrifuge Facility for the International Space Station Alpha  

NASA Technical Reports Server (NTRS)

The Centrifuge Facility planned for the International Space Station Alpha has under-one considerable redesign over the past year, primarily because the Station is now viewed as a 10 year mission rather than a 30 year mission and because of the need to simply the design to meet budget constraints and a 2000 launch date. The basic elements of the Centrifuge Facility remain the same, i.e., a 2.5 m diameter centrifuge, a micro-g holding unit, plant and animal habitats, a glovebox and a service unit. The centrifuge will still provide the full range of artificial gravity from 0.01 a to 2 - as originally planned; however, the extractor to permit withdrawal of habitats from the centrifuge without stopping the centrifuge has been eliminated. The specimen habitats have also been simplified and are derived from other NASA programs. The Plant Research Unit being developed by the Gravitational Biology Facility will be used to house plants in the Centrifuge Facility. Although not as ambitious as the Centrifuge Facility plant habitat, it will provide much better environmental control and lighting than the current Shuttle based Plant Growth Facility. Similarly, rodents will be housed in the Advanced Animal Habitat being developed for the Shuttle program. The Centrifuge Facility and ISSA will provide the opportunity to perform repeatable, high quality science. The long duration increments available on the Station will permit multigeneration studies on both plants and animals which have not previously been possible. The Centrifuge Facility will accommodate sufficient number of specimens to permit statistically significant sampling of specimens to investigate the time course of adaptation to altered gravity environments. The centrifuge will for the first time permit investigators to use gravity itself as a tool to investigate fundamental processes, to investigate the intensity and duration of gravity to maintain normal structure and function, to separate the effects of micro-g from other 0 environmental factors and to examine artificial gravity as a potential countermeasure for the physical deconditioning observed during spaceflight.

Johnson, Catherine C.; Hargens, Alan R.

1994-01-01

395

Dual asymmetric centrifugation (DAC)—A new technique for liposome preparation  

Microsoft Academic Search

This is the first report on the use of a “dual asymmetric centrifuge (DAC)” for preparing liposomes. DAC differs from conventional centrifugation by an additional rotation of the sample around its own vertical axis: While the conventional centrifugation constantly pushes the sample material outwards, this additional rotation constantly forces the sample material towards the center of the centrifuge. This unique

Ulrich Massing; Sanja Cicko; Vittorio Ziroli

2008-01-01

396

Centrifuges and filters team up on tar sands separation  

SciTech Connect

A process is described in which synthetic crude oil is separated from oil bearing sand by a series of centrifuges. First, the sand is treated with hot water, steam and caustic for separation of the bitumen from the sand by flotation. The recovered froth is diluted with naphtha to reduce the viscosity and density, and then it is fed through a series of centrifuges for separation.

Dunens, E.; Hodel, A.E.

1984-02-01

397

Iron in Rat Milk: Distribution Between Centrifugally Separated Phases  

Microsoft Academic Search

Following centrifugation at 4 C, about one-fourth of the iron of whole rat milk separates with the whey and more than two-thirds sediments with casein. When mixtures of radioactive iron-59 labelled whey and unlabelled whole milk were incubated together and subsequently fractionated by centrifugation, nearly all of the label was recovered in the whey fraction. These results indicate that iron

T. T. Loh; I. Kaldor

1974-01-01

398

Synthesis and Analytical Centrifugation of Magnetic Model Colloids  

Microsoft Academic Search

This thesis is a study of the preparation and thermodynamic properties of magnetic colloids. First, two types of magnetic model colloids are investigated: composite colloids and single-domain nanoparticles. Thermodynamics of magnetic colloids is studied using analytical centrifugation, including a specially adapted centrifuge for measuring heavy and strongly light absorbing colloids.\\u000a\\u000aMagnetic composite colloids can be prepared from thermodynamically stable Pickering

B. Luigjes

2012-01-01

399

Ocular counterrolling induced by centrifugation during orbital space flight  

Microsoft Academic Search

.   During the 1998 Neurolab mission (STS-90), four astronauts were exposed to interaural centripetal accelerations (Gy centrifugation)\\u000a of 0.5g and 1g during rotation on a centrifuge, both on Earth and during orbital space flight. Subjects were oriented either left-ear out\\u000a or right-ear out, facing or back to motion. Binocular eye movements were measured in three dimensions using a video technique.

Steven T. Moore; Gilles Clément; Theodore Raphan; Bernard Cohen

2001-01-01

400

Attempts to produce Genetical Changes in Drosophila by Centrifugation  

Microsoft Academic Search

STUBBE1 was the first to observe an increase in the mutational frequency in Antirrhinum by subjecting chemically treated seeds and seedlings to centrifugation. Irrespective of the chemical used, he always found approximately the same increase in mutation rate over the non-centrifuged controls. Additional evidence in plant material was obtained by Kostoff2-4, who found that mechanical stress applied in the form

O. S. Reddi

1963-01-01

401

Steady-state model of centrifugal liquid chillers  

Microsoft Academic Search

A new steady-state model of vapour-compression type centrifugal liquid chillers is presented. The model has a number of advanced features and is capable of simulating both hermetic and open-drive centrifugal compressors. The model accounts for the real process phenomena such as superheating and subcooling in the heat exchangers as well as a capacity control formulation of the inlet guide vanes.

M. W. Browne; P. K. Bansal

1998-01-01

402

Methods of rotating stall and surge detection in centrifugal compressors  

Microsoft Academic Search

Systems for prevention of surging of centrifugal compressors and methods of rotating stall detection and early surge diagnosis\\u000a using statistical processing of sensor signals of various parameters, i.e., the method of calculation of the correlation function\\u000a of the signal and the method of calculation of signal dispersion, are discussed. The results of routine tests of air and high-speed\\u000a air centrifugal

Ya. Z. Guzel’baev; A. L. Khavkin; I. G. Khisameev

2006-01-01

403

Investigation of surge behavior in a micro centrifugal compressor  

Microsoft Academic Search

This paper reports the experimental and theoretical study of the surge occurred in prototyping an ultra micro centrifugal\\u000a compressor. As the first step, the 10 times size model of an ultra micro centrifugal compressor having the 40 mm outer diameter\\u000a was designed and manufactured. The detailed experimental investigations for the transient behavior of surge with several different\\u000a values of B

Shimpei Mizuki; Yuichiro Asaga; Yushi Ono; Hoshio Tsujita

2006-01-01

404

Application of pressure sensitive paint measurement to a low-solidity cascade diffuser of a transonic centrifugal compressor  

Microsoft Academic Search

A pressure sensitive paint (PSP) measurement has been known as a pressure field measurement technique based on the oxygen\\u000a quenching phenomenon of luminescence of specific luminophores. A PSP measurement was applied for pressure field measurement\\u000a in a low-solidity circular cascade diffuser of a single-stage transonic centrifugal compressor with 5 in pressure ratio for\\u000a HFC134a gas. The oxygen concentration was about

H. Hayami; M. Hojo; M. Matsumoto; S. Aramaki; K. Yamada

2002-01-01

405

Cerebral Hypoperfusion Precedes Nausea During Centrifugation  

PubMed Central

Introduction Nausea and motion sickness are important operational concerns for aviators and astronauts. Understanding the underlying mechanisms associated with motion sickness may lead to new treatments. The goal of this work was to determine if changes in cerebral blood flow precede the development of nausea in subjects susceptible to motion sickness. Methods Cerebral flow velocity in the middle cerebral artery (transcranial Doppler), BP, and end-tidal CO2 were measured while subjects were rotated on a centrifuge (250°· s–1). Following 5 min of rotation, subjects were translated 51.5 cm off-center, creating a +1 G× centripetal acceleration in the nasal-occipital plane. Results There were 10 subjects who completed the protocol without symptoms while 5 developed nausea (4 while off-center and 1 while rotating on-center). Prior to nausea, subjects had significant increases in BP (+13 ± 3 mmHg, p < 0.05) and cerebrovascular resistance (+46 ± 17%, p < 0.05) and decreases in cerebral flow velocity both in the second (–13 ± 4%) and last minute (–22 ± 5%) before symptoms (p < 0.05). In comparison, subjects resistant to motion sickness demonstrated no change in BP or cerebrovascular resistance in the last minute of off-center rotation and only a 7 ± 2% decrease in cerebral flow velocity. All subjects had significant hypocapnia (–3.8 ± 0.4 mmHg, p < 0.05); however, this hypocapnia could not fully explain the cerebral hypoperfusion associated with the development of nausea. Conculsions These data indicate that reductions in cerebral blood flow precede the development of nausea. Further work is necessary to determine what role cerebral hypoperfusion plays in motion sickness and whether cerebral hypoperfusion can be used to predict the development of nausea in susceptible individuals.

Serrador, Jorge M.; Schlegel, Todd T.; Black, F. Owen; Wood, Scott J.

2009-01-01

406

Cerebral Hypoperfusion Precedes Nausea During Centrifugation  

NASA Technical Reports Server (NTRS)

Nausea and motion sickness are important operational concerns for aviators and astronauts. Understanding underlying mechanisms associated with motion sickness may lead to new treatments. The goal of this work was to determine if cerebral blood flow changes precede the development of nausea in motion sick susceptible subjects. Cerebral flow velocity in the middle cerebral artery (transcranial Doppler), blood pressure (Finapres) and end-tidal CO2 were measured while subjects were rotated on a centrifuge (250 degrees/sec). Following 5 min of rotation, subjects were translated 0.504 m off-center, creating a +lGx centripetal acceleration in the nasal-occipital plane. Ten subjects completed the protocol without symptoms while 5 developed nausea (4 while 6ff-center and 1 while rotating on-center). Prior to nausea, subjects had significant increases in blood pressure (+13plus or minus 3 mmHg, P less than 0.05) and cerebrovascular resistance (+46 plus or minus 17%, P less than 0.05) and decreases in cerebral flow velocity both in the second (-13 plus or minus 4%) and last minute (-22 plus or minus 5%) before symptoms (P less than 0.05). In comparison, controls demonstrated no change in blood pressure or cerebrovascular resistance in the last minute of off-center rotation and only a 7 plus or minus 2% decrease in cerebral flow velocity. All subjects had significant hypocapnia (-3.8 plus or minus 0.4 mmHg, P less than 0.05), however this hypocapnia could not fully explain the cerebral hypoperfusion associated with the development of nausea. These data indicate that reductions in cerebral blood flow precede the development of nausea. Further work is necessary to determine what role cerebral hypoperfusion plays in motion sickness and whether cerebral hypoperfusion can be used to predict the development of nausea in susceptible individuals.

Serrador, Jorge M.; Schlegel, Todd T.; Black, F. Owen; Wood, Scott J.

2004-01-01

407

Flow Range of Centrifugal Compressor Being Extended  

NASA Technical Reports Server (NTRS)

General Aviation will benefit from turbine engines that are both fuel-efficient and reliable. Current engines fall short of their potential to achieve these attributes. The reason is compressor surge, which is a flow stability problem that develops when the compressor is subjected to conditions that are outside of its operating range. Compressor surge can occur when fuel flow to the engine is increased, temporarily back pressuring the compressor and pushing it past its stability limit, or when the compressor is subjected to inlet flow-field distortions that may occur during takeoff and landing. Compressor surge can result in the loss of an aircraft. As a result, engine designers include a margin of safety between the operating line of the engine and the stability limit line of the compressor. Unfortunately, the most efficient operating line for the compressor is usually closer to its stability limit line than it is to the line that provides an adequate margin of safety. A wider stable flow range will permit operation along the most efficient operating line of the compressor, improving the specific fuel consumption of the engine and reducing emissions. The NASA Glenn Research Center is working to extend the stable flow range of the compressor. Significant extension has been achieved in axial compressors by injecting air upstream of the compressor blade rows. Recently, the technique was successfully applied to a 4:1 pressure ratio centrifugal compressor by injecting streams of air into the diffuser. Both steady and controlled unsteady injection were used to inject air through the diffuser shroud surface and extend the range. Future work will evaluate the effect of air injection through the diffuser hub surface and diffuser vanes with the goal of maximizing the range extension while minimizing the amount of injected air that is required.

Skoch, Gary J.

2001-01-01

408

Effects of centrifugation before freezing on boar sperm cryosurvival.  

PubMed

Current protocols for boar sperm cryopreservation require the centrifugation of semen in order to separate sperm cells from the seminal plasma. This study evaluated the influence of different centrifugation regimes on both sperm recovery and yield (percentage of viable sperm with an intact acrosome relative to the initial sperm population) after centrifugation (experiment 1) as well as the influence of different centrifugation regimes on boar sperm cryosurvival (experiment 2). In both experiments, sperm-rich fractions from 3 boars were diluted, pooled, and cooled to 17 degrees C before centrifugation. In experiment 1, the g-forces tested were 400, 800, 1600, and 2400 x g for 3 or 5 minutes, using the standard regime (800 x g for 10 minutes) as a reference. Sperm recovery (Bürker Chamber) and yield (triple fluorescent stain of PI/R123/FITC-PNA [DNA-specific fluorochrome propidium iodide/mitochondria-specific fluorochrome rhodamine-123/acrosome-specific fluorochrome fluorescein isothiocyanate-labeled peanut (Arachis hypogaea) agglutinin]) were calculated. The highest recovery and yield (P <.05) values were achieved using 2400 x g for 5 or 3 minutes and 1600 x g for 5 minutes, which showed no differences (P >.05) from the reference in terms of sperm yield. In experiment 2, cooled semen was centrifuged using 3 different regimes: C1 (2400 x g for 3 minutes), C2 (1600 x g for 5 minutes), and C3 (800 x g for 10 minutes). Pellets were diluted in lactose-egg yolk (LEY)-glycerol-Equex STM (1 x 10(9) cells/mL) and frozen in 0.5-mL straws. After thawing, sperm quality was assessed after 30 and 150 minutes of incubation (37 degrees C). Centrifugation regimes C1 and C2 showed significantly (P <.05) higher postthaw sperm motility (assessed with a computer-assisted semen analysis system), viability (evaluated as for experiment 1), and percentage of uncapacitated sperm (assessed with a chlortetracycline assay) than did C3. In addition, C1 had the highest (P <.05) oocyte penetrating ability (assessed with the homologous in vitro penetration test performed with immature oocytes). Malondialdehyde production, assessed with the thiobarbituric acid reactive species test, was unaffected (P >.05) by the centrifugation regime used. We conclude that high g-force (2400 x g) and short centrifugation time (3 minutes) do not affect sperm recovery and yield and that, moreover, they have a positive effect on the cryosurvival of boar sperm. Therefore, we recommend the use of short-term centrifugation with a relatively high g-force (2400 x g for 3 minutes) in boar sperm cryopreservation protocol. PMID:15064317

Carvajal, Gema; Cuello, Cristina; Ruiz, Maria; Vázquez, Juan María; Martínez, Emilio Arsenio; Roca, Jordi

2004-01-01

409

Active stabilization to prevent surge in centrifugal compression systems  

NASA Technical Reports Server (NTRS)

This report documents an experimental and analytical study of the active stabilization of surge in a centrifugal engine. The aims of the research were to extend the operating range of a compressor as far as possible and to establish the theoretical framework for the active stabilization of surge from both an aerodynamic stability and a control theoretic perspective. In particular, much attention was paid to understanding the physical limitations of active stabilization and how they are influenced by control system design parameters. Previously developed linear models of actively stabilized compressors were extended to include such nonlinear phenomena as bounded actuation, bandwidth limits, and robustness criteria. This model was then used to systematically quantify the influence of sensor-actuator selection on system performance. Five different actuation schemes were considered along with four different sensors. Sensor-actuator choice was shown to have a profound effect on the performance of the stabilized compressor. The optimum choice was not unique, but rather shown to be a strong function of some of the non-dimensional parameters which characterize the compression system dynamics. Specifically, the utility of the concepts were shown to depend on the system compliance to inertia ratio ('B' parameter) and the local slope of the compressor speedline. In general, the most effective arrangements are ones in which the actuator is most closely coupled to the compressor, such as a close-coupled bleed valve inlet jet, rather than elsewhere in the flow train, such as a fuel flow modulator. The analytical model was used to explore the influence of control system bandwidth on control effectiveness. The relevant reference frequency was shown to be the compression system's Helmholtz frequency rather than the surge frequency. The analysis shows that control bandwidths of three to ten times the Helmholtz frequency are required for larger increases in the compressor flow range. This has important implications for implementation in gas turbine engines since the Helmholtz frequencies can be over 100 Hz, making actuator design extremely challenging.

Epstein, Alan H.; Greitzer, Edward M.; Simon, Jon S.; Valavani, Lena

1993-01-01

410

Classical nucleation theory with a radius-dependent surface tension: a two-dimensional lattice-gas automata model.  

PubMed

The constant surface tension assumption of the Classical Nucleation Theory (CNT) is known to be flawed. In order to probe beyond this limitation, we consider a microscopic, two-dimensional Lattice-Gas Automata (LGA) model of nucleation in a supersaturated system, with model input parameters E(ss) (solid particle-to-solid particle bonding energy), E(sw) (solid particle-to-water bonding energy), ? (next-to-nearest-neighbor bonding coefficient in solid phase), and C(in) (initial solute concentration). The LGA method has the advantages of easy implementation, low memory requirements, and fast computation speed. Analytical results for the system's concentration and the crystal radius as functions of time are derived and the former is fit to the simulation data in order to determine the equilibrium concentration. The "Mean First-Passage Time" technique is used to obtain the nucleation rate and critical nucleus size from the simulation data. The nucleation rate and supersaturation data are evaluated using a modification to the CNT that incorporates a two-dimensional radius-dependent surface tension term. The Tolman parameter, ?, which controls the radius dependence of the surface tension, decreases (increases) as a function of the magnitude of E(ss) (E(sw)), at fixed values of ? and E(sw) (E(ss)). On the other hand, ? increases as ? increases while E(ss) and E(sw) are held constant. The constant surface tension term of the CNT, ?(0), increases (decreases) with increasing magnitudes of E(ss) (E(sw)) at fixed values of E(sw) (E(ss)) and increases as ? is increased. ?(0) increases linearly as a function of the change in energy during an attachment or detachment reaction, |?E|, however, with a slope less than that predicted for a crystal that is uniformly packed at maximum density. These results indicate an increase in the radius-dependent surface tension, ?, with respect to increasing magnitude of the difference between E(ss) and E(sw). PMID:23496525

Hickey, Joseph; L'Heureux, Ivan

2013-02-01

411

MODELING AEROSOL FORMATION FROM ALPHA-PINENE + NOX IN THE PRESENCE OF NATURAL SUNLIGHT USING GAS PHASE KINETICS AND GAS-PARTICLE PARTITIONING THEORY. (R826771)  

EPA Science Inventory

A kinetic mechanism was used to link and model the gas-phase reactions and aerosol accumulation resulting from -pinene reactions in the presence of sunlight, ozone (O3), and oxides of nitrogen (NO ...

412

Estimating the amount of gas-hydrate using effective medium theory: a case study in the Blake Ridge  

Microsoft Academic Search

Estimating the amount of gas-hydrate and free-gas is difficult in deep seas even with scientific coring and downhole measurements.\\u000a Well data may be incompatible between holes of a site as well as with depth in the same hole. In this paper, we demonstrate\\u000a an approach to estimate saturation of gas-hydrate from seismic velocities at any site where data set is

Ranjana Ghosh; Kalachand Sain; Maheswar Ojha

2010-01-01

413

[The analytical setting of rotary speed of centrifuge rotor and centrifugation time in chemical, biochemical and microbiological practice].  

PubMed

The researchers happen to face with suspensions in their chemical, biochemical and microbiological practice. The suspensions are the disperse systems with solid dispersed phase and liquid dispersion medium and with dispersed phase particle size > 100 nm (10-7 m). Quite often the necessity occurs to separate solid particles from liquid. To use for this purpose the precipitation in gravitation field can make the process to progress too long. In this respect an effective mode is the precipitation in the field of centrifugal forces--the centrifugation. The rotary speed of centrifuge rotor and centrifugation time can be set analytically using regularities of general dynamics and hydrodynamics. To this effect, should be written and transformed the equation of First and Second Newton Laws for suspension particle being in the field of centrifugal forces and forces of resistance of liquid and vessel wall. The force of liquid resistance depends on particle motion condition in liquid. To determine the regimen the Archimedes and Reynolds numerical dimensionless criteria are to be applied. The article demonstrates the results of these transformations as analytical inverse ratio dependence of centrifugation time from rotary speed. The calculation of series of "rate-time" data permits to choose the optimal data pair on the assumption of centrifuge capacity and practical reasonability. The results of calculations are validated by actual experimental data hence the physical mathematical apparatus can be considered as effective one. The setting progress depends both from parameter (Reynolds criterion) and data series calculation. So, the most convenient way to apply this operation is the programming approach. The article proposes to use the program Microsoft Excel and VBA programming language for this purpose. The possibility to download the file from Internet to use it for fast solution is proposed. PMID:23097986

Zolotarev, K V

2012-08-01

414

Substrate Nanotexture and Hypergravity Through Centrifugation Enhance Initial Osteoblastogenesis  

PubMed Central

Mimicking the structural nanomolecular extracellular matrix with synthetically designed nanosized materials is a relatively new approach, which can be applied in the field of bone tissue engineering. Likewise, bone tissue-engineered constructs can be aided in their development by the use of several types of mechanical stimuli. In this study, we wanted to combine nanotextured biomaterials and centrifugation in one multifactorial system. Mesenchymal stem cells were isolated from rat bone marrow, and cultured on a nanogrooved polystyrene substrate (200-nm-wide pitch with a depth of 50?nm). Constant centrifugation of 10 g was applied to cells up to 7 days. Results showed that on a nanogrooved substrate osteoblast-like cells align parallel to the groove direction. Centrifugation of 10 g also affected cell morphology on a smooth surface. Moreover, cell alignment was significantly reduced for cells grown on nanogrooved substrates, which were subsequently subjected to centrifugation. Independently, both stimuli increased the number of cells after 7 days of culture. However, when both stimuli were combined, an additive effect on cell number was observed, followed by an enhanced effect on osteocalcin mRNA expression and matrix mineralization. In conclusion, biomaterial surface modification as well as centrifugation are effective means to enhance bone cell behavior, moreover, readily available to many tissue engineers.

Prodanov, Ljupcho; van Loon, Jack J.W.A.; te Riet, Joost; Walboomers, X. Frank

2013-01-01

415

Development of a Feeder for Uninterrupted Centrifugation Studies  

NASA Technical Reports Server (NTRS)

A specialized paste diet feeder was developed in support of a hypergravity (2G) centrifuge study. The centrifuge study was to be compared to a previously flown Russian Cosmos spaceflight so experimental parameters of the 14 day spaceflight had to be duplicated. In order to duplicate at hyper G an experiment that took place in weightlessness, all other conditions must be as identical as possible. Stopping the centrifuge to provide maintenance for the animals causes unacceptable changes in experimental research results. Thus the experimental protocol required the delivery of a designated amount of paste diet at regular intervals for a two week period without stopping the centrifuge. A centrifuge and a stationary control cage, each containing 10 laboratory rats, were fitted with feeders that were calibrated to provide 140 plus or minus 2g of paste diet every 6 hours. This paper describes development of the feeder design and results of its operation over the two week experiment. The design philosophy and details of the feeder system are provided with recommendations for future such devices.

Mulenburg, Gerald M.; Vasques, Marilyn F.; Gundo, Daniel P.; Griffith, Jon B.; Wade, Charles E. (Technical Monitor)

1994-01-01

416

Rules governing the classification of coal slurries for filtering centrifuges  

SciTech Connect

The feasibility of using filtering centrifuges for the cleaning of a coking-coal slurry is confirmed in principle, and regime operating parameters which ensure the production of a concentrate of conditioned quality are determined on the basis of results of experimental-industrial tests of a new procedure for this operation at the Neryungrinskaya Concentrating Mill. An equation is proposed for determination of solid carry-off in the centrifuge effluent, which completely satisfactorily (with a correlation coefficient of 0.7-0.8) describes the dependence of the parameter in question on the solid content in the centrifuge feed, and on its content of -0.2-mm material. It is noted that special investigations to determine the effect of the speed of the rotor and shape of the particles on the amount of solid carry-off in the centrifuge effluent are required for construction of a model describing the size reduction of solid-phase particles in the effluent during centrifuge filtration.

G.Y. Gol'berg; Y.B. Rubinshtein; S.A. Osadchii [Institute for Enrichment of Solid Fuel (IOTT), Moscow Oblast (Russian Federation)

2008-07-01

417

Centrifugation Effects on Estrous Cycling, Mating Success and Pregnancy Outcome in Rats  

NASA Technical Reports Server (NTRS)

We analyzed the effects of 2-g centrifugation on estrous cycling, mating success and pregnancy outcome in rats. Sexually mature female and male rats were assigned to either 2-g centrifuge or non-centrifuge conditions, and to non-breeding or breeding conditions. In non-breeding females, estrous cycles were analyzed by examining vaginal cytology before and for 35 days during centrifugation. Breeding females were time-mated following 7 days of adaptation to centrifugation. Following adaptation to centrifugation, estrous cycle duration over a five-cycle period was similar in centrifuged and non-centrifuged females. Identical numbers of centrifuged and non-centrifuged females conceived, however centrifuged females took four-times longer than controls to achieve conception. Births occurred at the normal gestational length. Pup birth weight and postnatal survival were p<0.05 reduced in centrifuged as compared to non-centrifuged groups. In conclusion, 2-g centrifugation had no effect on estrous cycle length or the probably of becoming pregnant but delayed conception and diminished pregnancy outcome.

Ronca, April E.; Rushing, Linda S.; Tou, Janet; Wade, Charles E.; Baer, Lisa A.

2005-01-01

418

The interaction effects between adsorbed molecules in the Statistical Rate Theory approach to the kinetics of mixed-gas adsorption  

NASA Astrophysics Data System (ADS)

Kinetics of adsorption of single gases and their binary mixture on an energetically homogeneous surface are studied theoretically using the Statistical Rate Theory (SRT) of interfacial transport. Additionally, the influence of intermolecular interactions on the rate of adsorption is modeled using the Regular Adsorbed Solution Theory. The theoretical results are classified and assigned to different types of experimental conditions under which the changes of the adsorbate concentration near the adsorbing surface are considerable or they are negligible. Predictions of the theory are verified using adsorption data measured in real systems.

Nieszporek, Krzysztof; Banach, Tomasz

2010-09-01

419

Centrifugal spray generator of singlet oxygen for a chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

A centrifugal spray generator of singlet oxygen, O2(1?g), for driving a chemical oxygen-iodine laser was developed and its operation was experimentally studied. Modeling of the liquid separation from the gas flow showed that the separator designed could remove droplets larger than 0.5 ?m from gas, which is very important for the laser operation. This result was confirmed by experiments. Experimental studies proved that O2(1?g) could be produced with a high efficiency (chlorine utilization 0.68-0.87 and O2(1?g) yield 0.35-0.7) even at very high generator pressures (25-70 kPa), which cannot be attained by other O2(1?g) generators.

Špalek, O.; Hrubý, J.; ?enský, M.; Jirásek, V.; Kodymová, J.

2010-09-01

420

Sedimentation of a two-dimensional colloidal mixture exhibiting liquid-liquid and gas-liquid phase separation: A dynamical density functional theory study  

NASA Astrophysics Data System (ADS)

We present dynamical density functional theory results for the time evolution of the density distribution of a sedimenting model two-dimensional binary mixture of colloids. The interplay between the bulk phase behaviour of the mixture, its interfacial properties at the confining walls, and the gravitational field gives rise to a rich variety of equilibrium and non-equilibrium morphologies. In the fluid state, the system exhibits both liquid-liquid and gas-liquid phase separation. As the system sediments, the phase separation significantly affects the dynamics and we explore situations where the final state is a coexistence of up to three different phases. Solving the dynamical equations in two-dimensions, we find that in certain situations the final density profiles of the two species have a symmetry that is different from that of the external potentials, which is perhaps surprising, given the statistical mechanics origin of the theory. The paper concludes with a discussion on this.

Malijevský, Alexandr; Archer, Andrew J.

2013-10-01

421

Sedimentation of a two-dimensional colloidal mixture exhibiting liquid-liquid and gas-liquid phase separation: a dynamical density functional theory study.  

PubMed

We present dynamical density functional theory results for the time evolution of the density distribution of a sedimenting model two-dimensional binary mixture of colloids. The interplay between the bulk phase behaviour of the mixture, its interfacial properties at the confining walls, and the gravitational field gives rise to a rich variety of equilibrium and non-equilibrium morphologies. In the fluid state, the system exhibits both liquid-liquid and gas-liquid phase separation. As the system sediments, the phase separation significantly affects the dynamics and we explore situations where the final state is a coexistence of up to three different phases. Solving the dynamical equations in two-dimensions, we find that in certain situations the final density profiles of the two species have a symmetry that is different from that of the external potentials, which is perhaps surprising, given the statistical mechanics origin of the theory. The paper concludes with a discussion on this. PMID:24116640

Malijevský, Alexandr; Archer, Andrew J

2013-10-14

422

Researches on fluid dynamics of centrifugal compressors  

NASA Astrophysics Data System (ADS)

Turbo-machines (e.g. compressors, blowers and pumps) obtain energy transfer from their rotating impellers to fluid flowing through them, and they are used for a wide range of purposes obtaining pressurized fluid flow. The author created theoretical models to clearly describe the complicated flow phenomena in impellers and in diffusers, based on the fluid dynamic theory. Furthermore, he succeeded in inventing a new diffuser to control a part of the complicate flow, which improved performance of compressors dramatically.

Senoo, Y.

423

Space Station Centrifuge: A Requirement for Life Science Research  

NASA Technical Reports Server (NTRS)

A centrifuge with the largest diameter that can be accommodated on Space Station Freedom is required to conduct life science research in the microgravity environment of space. (This was one of the findings of a group of life scientists convened at the University of California, Davis, by Ames Research Center.) The centrifuge will be used as a research tool to understand how gravity affects biological processes; to provide an on-orbit one-g control; and to assess the efficacy of using artificial gravity to counteract the deleterious biological effect of space flight. The rationale for the recommendation and examples of using ground-based centrifugation for animal and plant acceleration studies are presented. Included are four appendixes and an extensive bibliography of hypergravity studies.

Smith, Arthur H.; Fuller, Charles A.; Johnson, Catherine C.; Winget, Charles M.

1992-01-01

424

Solvent-free cleaning using a centrifugal cryogenic pellet accelerator  

SciTech Connect

An advanced centrifuge that accelerates frozen CO{sub 2} pellets to high speeds for surface cleaning and paint removal is being developed at the Oak Ridge National Laboratory. The centrifuge-based accelerator was designed, fabricated, and tested under a program sponsored by the Warner Robins Air Logistics Center, Robins Air Force Base, Georgia. In comparison to the more conventional compressed air ``sandblast`` pellet accelerators, the centrifugal accelerator system can achieve higher pellet speeds, has precise speed control, and is more than ten times as energy efficient. Furthermore, the use of frozen CO{sub 2} pellets instead of conventional metal, plastic, sand, or other abrasive materials that remain solid at room temperature, minimizes the waste stream. This apparatus has been used to demonstrate cleaning of various surfaces, including removal of paint, oxide coatings, metal coatings, organic coatings, and oil and grease coatings from a variety of surfaces. The design and operation of the apparatus is discussed.

Haines, J.R.; Fisher, P.W.; Foster, C.A.

1995-06-01

425

Planarization process of BPSG: capillary vs. centrifugal/gravitational forces  

NASA Astrophysics Data System (ADS)

Film planarization process, of importance in semiconductor IC manufacturing, results from mutual competition between three forces: capillary, viscous, and gravitation. In this communication we compare, using simple geometric arguments, the order of magnitudes between the capillary force and a generalized centrifugal/gravitational force acting perpendicular to the surface. For patterns of sub-micron dimension and conditions similar to BPSG reflow and photo-resist coating we found that, within instrumental accessibility, the centrifugal term is much smaller than the capillary term. We conclude that the centrifugal/gravitational forces affect global patterns, i.e., with dimension larger than 1000 micrometers , while the capillary force dominates the sub-micro leveling process.

Perng, Baw-Ching; Linliu, Kung

2000-08-01

426

Numerical Investigations of Slip Phenomena in Centrifugal Compressor Impellers  

NASA Astrophysics Data System (ADS)

This study systematically investigates the slip phenomena in the centrifugal air compressor impellers by CFD. Eight impeller blades for different specific speeds, wrap angles and exit blade angles are designed by compressor design software to analyze their flow fields. Except for the above three variables, flow rate and number of blades are the other two. Results show that the deviation angle decreases as the flow rate increases. The specific speed is not an important parameter regarding deviation angle or slip factor for general centrifugal compressor impellers. The slip onset position is closely related to the position of the peak value in the blade loading factor distribution. When no recirculation flow is present at the shroud, the variations of slip factor under various flow rates are mainly determined by difference between maximum blade angle and exit blade angle, ??max-2. The solidity should be of little importance to slip factor correlations in centrifugal compressor impellers.

Huang, Jeng-Min; Luo, Kai-Wei; Chen, Ching-Fu; Chiang, Chung-Ping; Wu, Teng-Yuan; Chen, Chun-Han

2013-03-01

427

Centrifugally activated bearing for high-speed rotating machinery  

DOEpatents

A centrifugally activated bearing is disclosed. The bearing includes an annular member that extends laterally and radially from a central axis. A rotating member that rotates about the central axis relative to the annular member is also included. The rotating member has an interior chamber that surrounds the central axis and in which the annular member is suspended. Furthermore, the interior chamber has a concave shape for retaining a lubricant therein while the rotating member is at rest and for retaining a lubricant therein while the rotating member is rotating. The concave shape is such that while the rotating member is rotating a centrifugal force causes a lubricant to be forced away from the central axis to form a cylindrical surface having an axis collinear with the central axis. This centrifugally displaced lubricant provides restoring forces to counteract lateral displacement during operation. 4 figures.

Post, R.F.

1994-02-15

428

Biohazards Assessment in Large-Scale Zonal Centrifugation  

PubMed Central

A study was conducted to determine the biohazards associated with use of the large-scale zonal centrifuge for purification of moderate risk oncogenic viruses. To safely and conveniently assess the hazard, coliphage T3 was substituted for the virus in a typical processing procedure performed in a National Cancer Institute contract laboratory. Risk of personnel exposure was found to be minimal during optimal operation but definite potential for virus release from a number of centrifuge components during mechanical malfunction was shown by assay of surface, liquid, and air samples collected during the processing. High concentration of phage was detected in the turbine air exhaust and the seal coolant system when faulty seals were employed. The simulant virus was also found on both centrifuge chamber interior and rotor surfaces. Images

Baldwin, C. L.; Lemp, J. F.; Barbeito, M. S.

1975-01-01

429

Incipient fluidization condition for a centrifugal fluidized bed  

SciTech Connect

A model has been proposed for the condition of incipient fluidization in a centrifugal fluidized bed. The model is based on the balance between the overall forces, including the centrifugal and fluid frictional forces, exerted on the fluidized particles and the overall effective weight of the particles. Equations have been derived from the model for predicting the critical fluidizing velocity and the maximum pressure differential (or pressure drop) through the centrifugal bed. A series of experiments was carried out with different solid particles, bed rotational speeds, and bed heights. The resultant data for the critical fluidizing velocity and the maximum pressure drop of the bed indicate that the proposed model is valid and the derived equations are of practical use.

Fan, L.T.; Chang, C.C.; Takahashi, T.; Tanaka, Z.; Yu, Y.S.

1985-06-01

430

Passively Shunted Piezoelectric Damping of Centrifugally-Loaded Plates  

NASA Technical Reports Server (NTRS)

Researchers at NASA Glenn Research Center have been investigating shunted piezoelectric circuits as potential damping treatments for turbomachinery rotor blades. This effort seeks to determine the effects of centrifugal loading on passively-shunted piezoelectric - damped plates. Passive shunt circuit parameters are optimized for the plate's third bending mode. Tests are performed both non-spinning and in the Dynamic Spin Facility to verify the analysis, and to determine the effectiveness of the damping under centrifugal loading. Results show that a resistive shunt circuit will reduce resonant vibration for this configuration. However, a tuned shunt circuit will be required to achieve the desired damping level. The analysis and testing address several issues with passive shunt circuit implementation in a rotating system, including piezoelectric material integrity under centrifugal loading, shunt circuit implementation, and tip mode damping.

Duffy, Kirsten P.; Provenza, Andrew J.; Trudell, Jeffrey J.; Min, James B.

2009-01-01

431

Centrifuge Techniques and Apparatus for Transport Experiments in Porous Media  

SciTech Connect

This paper describes experimental approaches and apparatus that we have developed to study solute and colloid transport in porous media using Idaho National Laboratory's 2-m radius centrifuge. The ex-perimental techniques include water flux scaling with applied acceleration at the top of the column and sub-atmospheric pressure control at the column base, automation of data collection, and remote experimental con-trol over the internet. These apparatus include a constant displacement piston pump, a custom designed liquid fraction collector based on switching valve technology, and modified moisture monitoring equipment. Suc-cessful development of these experimental techniques and equipment is illustrated through application to transport of a conservative tracer through unsaturated sand column, with centrifugal acceleration up to 40 gs. Development of such experimental equipment that can withstand high accelerations enhances the centrifuge technique to conduct highly controlled unsaturated solute/colloid transport experiments and allows in-flight liquid sample collection of the effluent.

Earl D. Mattson; Carl D. Paler; Robert W. Smith; Markus Flury

2010-06-01

432

Dynamic stress analysis of sewage centrifugal pump impeller based on two-way coupling method  

NASA Astrophysics Data System (ADS)

Current research on the operational reliability of centrifugal pumps has mainly focused on hydrodynamic instability. However, the interaction between the fluid and structure has not been sufficiently considered; this interaction can cause vibration and dynamic stress, which can affect the reliability. In this study, the dynamic stresses in a single-blade centrifugal pump impeller are analysed under different operating conditions; the two-way coupling method is used to calculate the fluid-structure interaction. Three-dimensional unsteady Reynolds-averaged Navier-Stokes equations are solved with the SST k-? turbulence model for the fluid in the whole flow passage, while transient structure dynamic analysis is used with the finite element method for the structure side. The dynamic stresses in the rotor system are computed according to the fourth strength theory. The stress results show that the highest stress is near the loose bearing and that the equivalent stress increases with the flow rate because the dynamic stresses are closely related to the pressure load. The stress distributions on the blade pressure side, suction side, leading edge, and trailing edge are each analysed for different flow rates; the highest stress distribution is found on the pressure side. On the blade pressure side, a relatively large stress is found near the trailing edge and hub side. Based on these results, a stress distribution prediction method is proposed for centrifugal pumps, which considers the interaction between the fluid and structure. The method can be used to check the dynamic stress at different flow rates when optimising the pump design to increase the pump reliability.

Pei, Ji; Yuan, Shouqi; Yuan, Jianping

2014-03-01

433

Dimethoxymethane-hydrogen chloride interaction: gas phase versus low-temperature behavior studied using matrix isolation infrared and density functional theory methods.  

PubMed

Premixing of dimethoxy methane (DMM) and hydrogen chloride (HCl) with Ar/N2 in the gas phase resulted in a nucleophilic substitution reaction and yielded products, cis-chloromethyl methyl ether (cis-CMME) and methanol. On the contrary, when DMM and HCl were separately codeposited in a low-temperature Ar matrix produced hydrogen-bonded alkoxy adduct, probably the intermediate in the gas phase nucleophilic substitution reaction. The formation of the alkoxy adduct was evidenced by the shifts in the vibrational frequencies of the DMM and HCl submolecules. The structure and energy of the alkoxy adduct were computed at the B3LYP/6-311++G** level of theory. The computations indicated only one minimum for the DMM-HCl adduct. The nucleophilic substitution reaction between DMM and HCl is prevented in the low-temperature matrix probably due to the cage effect in the matrix. PMID:23431963

Sundararajan, K; Ramanathan, N

2013-03-21

434

Development and characterization of a continuous centrifugal bioreactor  

SciTech Connect

A new continuous centrifugal bioreactor (CCBR), has been developed and characterized. A densely packed fluidized bed was maintained by balancing the drag and buoyancy forces of the incoming substrate with that of the centrifugal forces. With this approach, effluent streams were relatively free of cells and a small residence time assured the provision of adequate nutrient requirements and rapid removal of the product. This concept was tested using a nonflocculating strain of the yeast Saccharomyces cerevisiae. The focus of this research was to clarify operating regimes and assess the feasibility of cell culture in a high gravity environment. (Refs. 14).

Van Wie, B.J.; Elliott, M.L.; Lee, J.M.; Scott, C.D. (ed.)

1986-01-01

435

Review of noise reduction methods for centrifugal fans  

NASA Astrophysics Data System (ADS)

Several methods for the reduction of centrifugal fan noise are presented, the most of which are aimed at a lower blade passage frequency level. The methods are grouped into five categories: casing modifications to increase the distance between impeller and cutoff, the introduction of a phase shift of the source pressure fluctuations, impeller modifications, radial clearance between impeller eye and inlet nozzle, and acoustical measures. Resonators mounted at the cutoff of centrifugal fans appear to be a highly efficient and simple means of reducing the blade passage tone, and the method can be used for new fan construction and existing installations without affecting the aerodynamic performance of the fan.

Neise, W.

1981-11-01

436

Centrifugal inertia effects in two-phase face seal films  

NASA Technical Reports Server (NTRS)

A simplified, semianalytical model has been developed to analyze the effect of centrifugal inertia in two-phase face seals. The model is based on the assumption of isothermal flow through the seal, but at an elevated temperature, and takes into account heat transfer and boiling. Using this model, seal performance curves are obtained with water as the working fluid. It is shown that the centrifugal inertia of the fluid reduces the load-carrying capacity dramatically at high speeds and that operational instability exists under certain conditions. While an all-liquid seal may be starved at speeds higher than a 'critical' value, leakage always occurs under boiling conditions.

Basu, P.; Hughes, W. F.; Beeler, R. M.

1987-01-01

437

The use of centrifugation to study early Drosophila embryogenesis  

NASA Technical Reports Server (NTRS)

By the end of 10th nuclear cycle, the somatic nuclei of the Drosophila embryo have migrated to the periphery of the egg. Centrifugation of embryos did not result in the displacement of these nuclei, since cytoskeletal elements anchor them to the cortex. But, mild centrifugal forces displace the centrally located, nascent yolk nuclei. If this increased sensitivity to hypergravity occurs before the beginning of nuclear differentiation during cycle 8, when the nascent yolk and somatic nuclei physically separate, then it would mark the earliest functional difference between these two lineages.

Abbott, M. K.; Spooner, B. S. (Principal Investigator)

1993-01-01

438

Experimental and Theoretical Study on Circular Disk Particles Suspended in Centrifugal and Non-Centrifugal Force Environments  

SciTech Connect

Theoretical and experimental studies are performed on suspension particle motion in Centrifugal and Non-Centrifugal Force Environment, i.e., in both an axially rotating drum and a stable liquid tank. The particle velocity of circular disks is measured by PTV (Particle Tracking Velocimetry) method and is predicted by BBO (Basset-Boussinesq-Ossen) equation. It is found that (1) as time progresses, one side of the disk in the axially rotating drum is attracted toward the drum wall and its velocity is affected by the rotating speed, (2) when the particle moves in the Stokes' regime, its velocity is linearly increased with the distance from the center of the drum, (3) in contrast, the autorotation of the disk occurs in the non-centrifugal force field, and (4) the corresponding drag coefficient in the low Reynolds number region is in good agreement with the theoretical value of the sphere.

Torii, Shuichi [Department of Mechanical System Engineering, Kumamoto University (Japan); Watanabe, Yoshimi [Department of Engineering Physics, Electronics and Mechanics, Nagoya Institute of Technology (Japan); Tanaka, Satoyuki; Yano, Toshiaki; Iino, Naoko [Depertment of Mechanical Engineering, Kagoshima University (Japan)

2008-02-15

439

Prediction of dynamic and aerodynamic characteristics of the centrifugal fan with forward curved blades  

NASA Astrophysics Data System (ADS)

The main aim of this paper is determine the centrifugal fan with forward curved blades aerodynamic characteristics based on numerical modeling. Three variants of geometry were investigated. The first, basic "A" variant contains 12 blades. The geometry of second "B" variant contains 12 blades and 12 semi-blades with optimal length [1]. The third, control variant "C" contains 24 blades without semi-blades. Numerical calculations were performed by CFD Ansys. Another aim of this paper is to compare results of the numerical simulation with results of approximate numerical procedure. Applied approximate numerical procedure [2] is designated to determine characteristics of the turbulent flow in the bladed space of a centrifugal-flow fan impeller. This numerical method is an extension of the hydro-dynamical cascade theory for incompressible and inviscid fluid flow. Paper also partially compares results from the numerical simulation and results from the experimental investigation. Acoustic phenomena observed during experiment, during numerical simulation manifested as deterioration of the calculation stability, residuals oscillation and thus also as a flow field oscillation. Pressure pulsations are evaluated by using frequency analysis for each variant and working condition.

Polanský, Ji?í; Kalmár, László; Gášpár, Roman

2013-12-01

440

Zonal approach to centrifugal, elliptic and hyperbolic instabilities in Stuart vortices with external rotation  

NASA Astrophysics Data System (ADS)

The stability analysis of a street of Stuart vortices in a rotating frame is performed by integrating the Kelvin Townsend equations along the mean flow trajectories, using the geometrical optics technique (Lifschitz & Hameiri 1991) for short-wave perturbations. A parallel is drawn between the formulations of this zonal approach and that of rapid distortion theory, better known to the turbulence community. The results presented confirm those obtained by the standard stability analysis based on normal-mode decomposition: depending on the rotation parameter and the oblique mode considered, three unstable zones are identified, related to the centrifugal, elliptic and hyperbolic instabilities, as observed for Taylor Green cells (Sipp et al. 1999). Anticyclonic rotation is shown to destabilize Stuart vortices through a combination of the elliptical and centrifugal instability mechanisms, depending on the ratio of its rate to the structure core vorticity. Available stability criteria are discussed in the general case of two-dimensional rotating flows, in relation to their streamline topology and the values of the local Rossby number or vorticity.

Godeferd, Fabien S.; Cambon, Claude; Leblanc, S.

2001-12-01

441

21 CFR 862.2140 - Centrifugal chemistry analyzer for clinical use.  

Code of Federal Regulations, 2012 CFR

... 2012-04-01 false Centrifugal chemistry analyzer for clinical use. 862.2140...CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical...Instruments § 862.2140 Centrifugal chemistry analyzer for clinical use. (a)...

2012-04-01

442

Potential of centrifugal casting for the production of near net shape uranium parts.  

National Technical Information Service (NTIS)

This report was written to provide a detailed summary of a literature survey on the near net shape casting process of centrifugal casting. Centrifugal casting is one potential casting method which could satisfy the requirements of the LANL program titled ...

E. Robertson

1993-01-01

443

21 CFR 862.2140 - Centrifugal chemistry analyzer for clinical use.  

Code of Federal Regulations, 2010 CFR

... 2010-04-01 false Centrifugal chemistry analyzer for clinical use. 862.2140...CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical...Instruments § 862.2140 Centrifugal chemistry analyzer for clinical use. (a)...

2010-04-01

444

21 CFR 864.9285 - Automated cell-washing centrifuge for immuno-hematology.  

Code of Federal Regulations, 2010 CFR

...cell-washing centrifuge for immuno-hematology. 864.9285 Section 864.9285...SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Products Used...cell-washing centrifuge for immuno-hematology. (a) Identification. An...

2009-04-01

445

21 CFR 864.9285 - Automated cell-washing centrifuge for immuno-hematology.  

Code of Federal Regulations, 2010 CFR

...cell-washing centrifuge for immuno-hematology. 864.9285 Section 864.9285...SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Products Used...cell-washing centrifuge for immuno-hematology. (a) Identification. An...

2010-04-01

446

Effects of centrifugation stress on pituitary-gonadal function in male rats  

NASA Technical Reports Server (NTRS)

The effects of centrifugation for various lengths of time on circulating levels of luteinizing hormone (LH) and testosterone in male rats were investigated. In a chronic 52-day experiment, centrifugation at 4.1 G significantly reduced LH and testosterone levels for the entire period. Centrifugation at 2.3 G had less effect inasmuch as LH levels were not significantly decreased and testosterone levels were significantly reduced only during the first few days of centrifugation. In more acute experiments, centrifugation at 4.1 G for 4 h resulted in reduced testosterone levels, whereas centrifugation for 15 min did not significantly alter the hormone levels. These results indicate that centrifugation can decrease circulating LH and testosterone levels if the gravitational force is of sufficient magnitude and is maintained for a period of hours. Chronic centrifugation may also inhibit the acute excitatory response of LH to handling and ether stress.

Gray, G. D.; Smith, E. R.; Damassa, D. A.; Davidson, J. M.

1980-01-01

447

A 400-pellet feed system for the ORNL centrifuge pellet injector  

SciTech Connect

An improved and extended pellet fabrication and feed mechanism is being developed for the Oak Ridge National Laboratory (ORNL) centrifuge pellet injector that is presently installed on Tore Supra. This upgrade will extend the number of pellets available for a single-plasma discharge from 100 to 400. In addition, a new pusher and delivery system is expected to improve the performance of the device. As in the original system, deuterium ice is deposited from the gas phase on a liquid-helium-cooled rotating disk, forming a rim of solid deuterium. The rim of ice is machined to a parabolic profile from which pellets are pushed. In the new device, a stack of four ice rims are formed simultaneously, thereby increasing the capacity from 100 to 400 pellets. An improved method of ice formation has also been developed that produces clear ice. The pellet pusher and delivery system utilizes a four-axis, brushless dc servo system to precisely cut and deliver the pellets from the ice rim to the entrance of the centrifuge wheel. Pellets can be formed with sizes ranging from 2.5- to 4-mm diam at a rate of up to 8 per second. The operation of the injector is fully automated by a computer control system. The design and test results of the device are reported.

Foster, C.A.; Qualls, A.L.; Baylor, L.R.; Schechter, D.E.; Dyer, G.R.; Milora, S.L.

1993-11-01

448

Assembling gas-phase reaction mechanisms for high temperature inorganic systems based on quantum chemistry calculations and reaction rate theories  

NASA Astrophysics Data System (ADS)

Detailed chemical kinetic modeling based on computational quantum chemistry has been quite successful in making quantitative predictions about some systems, particularly the combustion of small hydrocarbons and certain areas of atmospheric chemistry. The gas phase chemistry of many processes in high-temperature inorganic systems, from materials synthesis to propulsion to waste incineration, could in principle be modeled with equal or greater success using detailed chemical kinetic modeling. This contribution provides examples from our own work of how computational quantum chemistry can be used in developing gas phase reaction mechanisms for modeling of high temperature materials processing. In the context of CVD of silicon from dichlorosilane, CVD of alumina from AlCl3/H2/CO2 mixtures, and particle nucleation from silane, this detailed chemical kinetic modeling has given us insight into gas phase reaction pathways that we would not likely have gained by other means.

Swihart, Mark T.

2005-02-01

449

Statistical analysis of metallic granules produced by centrifugal atomization  

Microsoft Academic Search

The particle size distribution of granules produced by centrifugal atomization may be analyzed statistically. For the equipment employed, the yield of fractions of different sizes may be calculated with a satisfactory degree of accuracy from the number of cylinder revolutions and the aperture diameter. Using this technique, it is possible to regulate various process parameters with the aim of achieving

P. Ramakrishnan Vinaykumar

1970-01-01

450

Inverted disk centrifugal atomization of AZ91 magnesium alloy  

Microsoft Academic Search

Magnesium AZ91 alloy powder was produced by centrifugal atomization under various conditions using an inverted disk atomizer. The particle size distribution was obtained as a function of the disk shape and rotation speed. The microstructure of particles and their shape were examined and characterized. Their cooling rates were obtained from theoretical relations and related to the secondary dendrite arm spacing.

C. Labrecque; R. Angers; R. Tremblay; D. Dubé

1997-01-01

451

Ultrasound treatment of centrifugally atomized 316 stainless steel powders  

Microsoft Academic Search

The Bureau of Mines is studying the surface characteristics of rapidly solidified powders and the potential for surface modification of fine powders prior to consolidation. The surface modification and work hardening of fine powders were accomplished by applying high-energy ultrasound to centrifugally atomized austenitic 316 stainless steel powders suspended in liquid media. Cavitation implosion changed the surface morphology, hammering the

James C. Rawers; Robert A. McCune; John S. Dunning

1991-01-01

452

A multiple disk centrifugal pump as a blood flow device  

Microsoft Academic Search

A study of a multiple-disk, shear force, valveless centrifugal pump to determine its suitability as a blood flow device is discussed. A pulsatile version of the Tesla viscous flow turbine was designed by modifying the original steady flow pump concept to produce physiological pressures and flows with the aid of controlling circuitry. Pressures and flows from this pump were compared

GERALD E. MILLER; BRADLEY D. ETTER; JEAN M. DORSI

1990-01-01

453

Experimental investigation of the transient behaviour of centrifugal fans  

Microsoft Academic Search

In the present experimental investigation of the transient behavior of three different centrifugal fans employing the same volute, the fans were excited in the low frequency range by either periodic or nonperiodic test signals. Complex impedances were then deduced from the measured time-dependent mass fluxes and inlet-discharge pressure difference. Attention is given to variations of mean operating state, steady state

Thomas Carolus

1987-01-01

454

Numerical study of a high-speed miniature centrifugal compressor  

Microsoft Academic Search

A miniature centrifugal compressor is a key component of reverse Brayton cycle cryogenic cooling system. The system is commonly used to generate a low cryogenic temperature environment for electronics to increase their efficiency, or generate, store and transport cryogenic liquids, such as liquid hydrogen and oxygen, where space limit is also an issue. Because of space limitation, the compressor is

Xiaoyi Li

2005-01-01

455

Quasi-steady centrifuge method for unsaturated hydraulic properties  

USGS Publications Warehouse

[1] We have developed the quasi-steady centrifuge (QSC) method as a variation of the steady state centrifuge method that can be implemented simply and inexpensively with greater versatility in terms of sample size and other features. It achieves these advantages by somewhat relaxing the criterion for steadiness of flow through the sample. This compromise entails an increase in measurement uncertainty but to a degree that is tolerable in most applications. We have tested this new approach with an easily constructed apparatus to establish a quasi-steady flow of water in unsaturated porous rock samples spinning in a centrifuge, obtaining measurements of unsaturated hydraulic conductivity and water retention that agree with results of other methods. The QSC method is adaptable to essentially any centrifuge suitable for hydrogeologic applications, over a wide range of sizes and operating speeds. The simplified apparatus and greater adaptability of this method expands the potential for exploring situations that are common in nature but have been the subject of few laboratory investigations. Copyright 2005 by the American Geophysical Union.

Caputo, M. C.; Nimmo, J. R.

2005-01-01

456

8. TENTERING GEAR OF EAST BURR STONES; CENTRIFUGAL GOVERNOR MOUNTED ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

8. TENTERING GEAR OF EAST BURR STONES; CENTRIFUGAL GOVERNOR MOUNTED ON STONE SPINDLE; ALSO SEEN IS THE CHUTE FROM THE TUN OF THE BURR STONES; HANGING IN THE BACKGROUND ARE THE MILL SAILS. - Hayground Windmill, Windmill Lane, East Hampton, Suffolk County, NY

457

Centrifugal acceleration of ions in the polar magnetosphere  

Microsoft Academic Search

The transport of ionospheric ions originating near the dayside cusp into the magnetotail is parametrically studied using a 3-D model of ion trajectories. It is shown that the centrifugal term in the guiding center parallel force equation dominates the parallel motion after about 4 Re geocentric distance. The dependence of the equatorial crossing distance on initial latitude, energy and convection

Kenneth R. Swinney; James L. Horwitz; D. Delcourt

1987-01-01

458

SEPARATION OF METALS IN WASTEWATER SLUDGE BY CENTRIFUGAL CLASSIFICATION  

EPA Science Inventory

Municipal wastewater sludges frequently contain undesirably high concentrations of heavy metals and/or organic pollutants which interfere with beneficial use of sludge on farmland and with some disposal practices such as ocean disposal. Centrifugal classification is a low-cost pr...

459

Conical slotted screens for centrifugal grates (a survey)  

Microsoft Academic Search

In order to improve the efficiency of the processes of dewatering and classification of coal on centrifugal grates, the VNIImetiz Institute improved the design and production technology for conical slotted screens with horizontal and vertical slots, using new methods of fabricating the rotating screen units. The screens are made only by welding of smooth cold rolled grates and support ribs

I. K. Lazarev; Yu. A. Nemudryi

1983-01-01

460

Noise Reduction in Centrifugal Fans by Use of Resonators.  

National Technical Information Service (NTIS)

The significant reduction of aerodynamically generated blade passage noise at the source by mounting a lambda/4 resonator at the cut-off lip on centrifugal fans is considered. While preserving the original cut-off lip geometry, the perforated mouth of the...

W. Neise G. H. Koopmann

1981-01-01

461

The performance of a centrifugal fan with enlarged impeller  

Microsoft Academic Search

The influence of enlarged impeller in unchanged volute on G4-73 type centrifugal fan performance is investigated in this paper. Comparisons are conducted between the fan with original impeller and two larger impellers with the increments in impeller outlet diameter of 5% and 10% respectively in the numerical and experimental investigations. The internal characteristics are obtained by the numerical simulation, which

Li Chunxi; Wang Song Ling; Jia Yakui

2011-01-01

462

Noise generation and noise propagation in centrifugal fans  

Microsoft Academic Search

Velocity oscillations at the impeller exit of centrifugal fans were investigated in order to explain the relationship between flow condition and the aerodynamic noise. Two procedures, based on linear equation systems, for the calculation of the frequency distribution of the system are discussed. It was found that the Reynolds number has no appreciable influence on the noise generation.

M. Bartenwerfer; T. Gikadi

1978-01-01

463

Prediction and control of the noise generated by centrifugal fans  

Microsoft Academic Search

A systematic analysis of research on sound generated by centrifugal fans, and a more general study based on sound generated aerodynamically (Lighthill, Curle, Doak) was made, leading to a coherent synthesis of the results of different authors and an explanation of their divergences.

R. Cubaud; P. Bonnet

1976-01-01

464

Review of noise reduction methods for centrifugal fans  

Microsoft Academic Search

Several methods for the reduction of centrifugal fan noise are presented, the most of which are aimed at a lower blade passage frequency level. The methods are grouped into five categories: casing modifications to increase the distance between impeller and cutoff, the introduction of a phase shift of the source pressure fluctuations, impeller modifications, radial clearance between impeller eye and

W. Neise

1981-01-01

465

Modeling the solidification of functionally graded materials by centrifugal casting  

Microsoft Academic Search

A numerical investigation of the solidification process during centrifugal casting of functionally graded materials (FGMs) is conducted. Focus is placed o