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1

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

2

Gas Centrifuges and Nuclear Proliferation  

SciTech Connect

Gas centrifuges have been an ideal enrichment method for a wide variety of countries. Many countries have built gas centrifuges to make enriched uranium for peaceful nuclear purposes. Other countries have secretly sought centrifuges to make highly enriched uranium for nuclear weapons. In more recent times, several countries have secretly sought or built gas centrifuges in regions of tension. The main countries that have been of interest in the last two decades have been Pakistan, Iraq, Iran, and North Korea. Currently, most attention is focused on Iran, Pakistan, and North Korea. These states did not have the indigenous abilities to make gas centrifuges, focusing instead on illicit and questionable foreign procurement. The presentation covered the following main sections: Spread of centrifuges through illicit procurement; Role of export controls in stopping proliferation; Increasing the transparency of gas centrifuge programs in non-nuclear weapon states; and, Verified dismantlement of gas centrifuge programs. Gas centrifuges are important providers of low enriched uranium for civil nuclear power reactors. They also pose special nuclear proliferation risks. We all have special responsibilities to prevent the spread of gas centrifuges into regions of tension and to mitigate the consequences of their spread into the Middle East, South Asia, and North Asia.

Albright, David

2004-09-15

3

Gas centrifuge with driving motor  

Microsoft Academic Search

1. A centrifuge for separating gaseous constituents of different masses comprising a vertical tubular rotor, means for introducing a gas mixture of different masses into said rotor and means for removing at least one of the gas components from the rotor, a first bearing means supporting said rotor at one end for rotational movement, a support, a damping bearing mounted

Dancy; William H

1976-01-01

4

Gas centrifuge with driving motor  

Microsoft Academic Search

A centrifuge for separating gaseous constituents of different masses consists of: a vertical tubular rotor; means for introducing a gas mixture of different masses into the rotor and means for removing at least one of the gas components from the rotor; a first bearing means supporing the rotor at one end; a support; a damping bearing mounted on the support;

Dancy; W. H. Jr

1976-01-01

5

Gas-centrifuge unit and centrifugal process for isotope separation  

Microsoft Academic Search

An invention involving a process and apparatus for isotope-separation applications such as uranium-isotope enrichment is disclosed which employs cascades of gas centrifuges. A preferred apparatus relates to an isotope-enrichment unit which includes a first group of cascades of gas centrifuges and an auxiliary cascade. Each cascade has an input, a light-fraction output, and a heavy-fraction output for separating a gaseous-mixture

1979-01-01

6

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

7

The American Gas Centrifuge Past, Present, and Future  

SciTech Connect

The art of gas centrifugation was born in 1935 at the University of Virginia when Dr. Jesse Beams demonstrated experimentally the separation of chlorine isotopes using an ultra-high speed centrifuge. Dr. Beam’s experiment initiated work that created a rich history of scientific and engineering accomplishment in the United States in the art of isotope separation and even large scale biological separation by centrifugation. The early history of the gas centrifuge development was captured in a lecture and documented by Dr. Jesse Beams in 1975. Much of Dr. Beams lecture material is used in this paper up to the year 1960. Following work by Dr. Gernot Zippe at the University of Virginia between 1958 and 1960, the US government embarked on a centrifuge development program that ultimately led to the start of construction of the Gas Centrifuge Enrichment Plant in Piketon Ohio in the late 1970’s. The government program was abandoned in 1985 after investing in the construction of two of six planned process buildings, a complete supply chain for process and centrifuge parts, and the successful manufacture and brief operation of an initial complement of production machines that would have met 15 percent of the planned capacity of the constructed process buildings. A declining market for enriched uranium, a glut of uranium enrichment capacity worldwide, and the promise of a new laser based separation process factored in the decision to stop the government program. By the late 1990’s it had become evident that gas centrifugation held the best promise to produce enriched uranium at low cost. In1999, the United States Enrichment Corporation undertook an initiative to revive the best of the American centrifuge technology that had been abandoned fourteen years earlier. This is an exciting story and one that when complete will enable the United States to maintain its domestic supply and to be highly competitive in the world market for this important energy commodity. (auth)

Waters, Dean

2004-09-15

8

Flow Induced Vibrations in Gas Tube Assembly of Centrifuge  

Microsoft Academic Search

A centrifuge essentially consists of a rotor rotating at very high speed. Gas tube assembly, located at the center of the rotor, is used to introduce feed gas into the rotor and remove product and waste streams from it. The gas tube assembly is thus a static component, the product and waste scoops of which are lying in the high

M. ALAM; M. A. ATTA; J. A. MIRZA; A. Q. KHAN

1986-01-01

9

Centrifugation  

NSDL National Science Digital Library

The North Carolina Community College System BioNetwork's interactive eLearning tools (IETs) are reusable chunks of training that can be deployed in a variety of courses or training programs. IETs are designed to enhance, not replace hands-on training. Learners are able to enter a hands-on lab experience better prepared and more confident. This particular IET delves into centrifugation, operating a centrifuge, and hazards and safety. After completing a guided centrifuge practice, students take a quiz to assess their learning.

2011-11-30

10

Numerical simulation of the countercurrent flow in a gas centrifuge  

SciTech Connect

A finite difference method is presented for the numerical simulation of the axisymmetric countercurrent flows in gas centrifuge. A time-marching technique is used to relax an arbitrary initial condition to the desired steady-state solution. All boundary layers may be resolved, and nonlinear effects may be included. Numerical examples are presented. It is concluded that this technique is capable of accurately predicting the performance of a wide variety of machines under all operating conditions of interest.

Cloutman, L.D.; Gentry, R.A.

1981-01-01

11

Systems approach used in the Gas Centrifuge Enrichment Plant  

SciTech Connect

A requirement exists for effective and efficient transfer of technical knowledge from the design engineering team to the production work force. Performance-Based Training (PBT) is a systematic approach to the design, development, and implementation of technical training. This approach has been successfully used by the US Armed Forces, industry, and other organizations. The advantages of the PBT approach are: cost-effectiveness (lowest life-cycle training cost), learning effectiveness, reduced implementation time, and ease of administration. The PBT process comprises five distinctive and rigorous phases: Analysis of Job Performance, Design of Instructional Strategy, Development of Training Materials and Instructional Media, Validation of Materials and Media, and Implementation of the Instructional Program. Examples from the Gas Centrifuge Enrichment Plant (GCEP) are used to illustrate the application of PBT.

Rooks, W.A. Jr.

1982-01-01

12

Characteristics of the Gas Centrifuge for Uranium Enrichment and Their Relevance for Nuclear Weapon Proliferation  

Microsoft Academic Search

This article presents an analytical model, originally developed in the 1980s, for the gas centrifuge and uses this methodology to determine the main design and operational characteristics of several hypothetical centrifuge designs. A series of simulations for a typical first-generation machine is used to assess the relevance of important breakout scenarios, including batch recycling and cascade interconnection, using either natural

ALEXANDER GLASER

2008-01-01

13

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

14

Centrifugal compression of soft particle packings: theory and experiment.  

PubMed

An exact method is developed for computing the height of an elastic medium subjected to centrifugal compression, for arbitrary constitutive relation between stress and strain. Example solutions are obtained for power-law media and for cases where the stress diverges at a critical strain--for example as required by packings composed of deformable but incompressible particles. Experimental data are presented for the centrifugal compression of thermo-responsive N-isopropylacrylamide (NIPA) microgel beads in water. For small radial acceleration, the results are consistent with Hertzian elasticity, and are analyzed in terms of the Young elastic modulus of the bead material. For large radial acceleration, the sample compression asymptotes to a value corresponding to a space-filling particle volume fraction of unity. Therefore we conclude that the gel beads are incompressible, and deform without deswelling. In addition, we find that the Young elastic modulus of the particulate gel material scales with cross-link density raised to the power 3.3±0.8, somewhat larger than the Flory expectation. PMID:21230273

Nordstrom, K N; Verneuil, E; Ellenbroek, W G; Lubensky, T C; Gollub, J P; Durian, D J

2010-10-01

15

Aerodynamically induced radial forces in a centrifugal gas compressor: Part 2 -- Computational investigation  

Microsoft Academic Search

Radial loads and direction of a centrifugal gas compressor containing a high specific speed mixed flow impeller and a single tongue volute were determined both experimentally and computationally at both design and off-design conditions. The experimental methodology was developed in conjunction with a traditional ASME PTC-10 closed-loop test to determine radial load and direction. The experimental study is detailed in

M. B. Flathers; G. E. Bache?

1999-01-01

16

Design and closed loop testing of high-pressure centrifugal gas compressors  

Microsoft Academic Search

Citing the causes of subsynchronous vibration in high-pressure centrifugal gas compressors, Solar Turbines International recommends two rotor systems designed to control this type of vibration: One system employs tuned, oil-film damper bearings, while the other features a stiffened rotor geometry. High-pressure closed-loop testing of the stability thresholds of the two designs led to numerous insights into the strong influence of

A. F. Criqui; P. G. Wendt

1980-01-01

17

Design and prototyping of micro centrifugal compressor for ultra micro gas turbine  

Microsoft Academic Search

In order to establish the design methodology of an ultra micro centrifugal compressor, which is the most important component\\u000a of an ultra micro gas turbine unit, a 10 times size of the final target compressor (impeller outer diameter 40 mm, corrected\\u000a rotational speed 220,000 r\\/min) was designed. The problems to be solved for downsizing were examined and a 2-dimensional impeller

Shimpei Mizuki; Toshiyuki Hirano; Yoshiyuki Koizumi; Gaku Minorikawa; Hoshio Tsujita; Mitsuo Iwahara; Ronglei Gu; Yutaka Ohta; Eisuke Outa

2005-01-01

18

A High Reliability Gas-driven Helium Cryogenic Centrifugal Compressor  

E-print Network

A helium cryogenic compressor was developed and tested in real conditions in 1996. The achieved objective was to compress 0.018 kg/s Helium at 4 K @ 1000 Pa (10 mbar) up to 3000 Pa (30 mbar). This project was an opportunity to develop and test an interesting new concept in view of future needs. The main features of this new specific technology are described. Particular attention is paid to the gas bearing supported rotor and to the pneumatic driver. Trade off between existing technologies and the present work are presented with special stress on the bearing system and the driver. The advantages are discussed, essentially focused on life time and high reliability without maintenance as well as non pollution characteristic. Practical operational modes are also described together with the experimental performances of the compressor. The article concludes with a brief outlook of future work.

Bonneton, M; Gistau-Baguer, Guy M; Turcat, F; Viennot, P

1998-01-01

19

Centrifugal mixing in gas and liquid fuelled lean swirl stabilized primary zones  

SciTech Connect

A flat bladed axial swirler of 0.7 swirl number has been investigated in a 76 mm diameter combustor with all the combustion air passing through the swirler. Both liquid and gaseous fuels were used with eight injection points on the combustor wall just downstream of the swirler. This wall injection was aimed at the exploitation of centrifugal mixing forces acting on the burnt gas pockets at the wall to send them towards the centre and to displace higher density unburnt gas pockets to the wall and so promote mixing. For both kerosene and propane fuels there was a significant improvement in the combustion efficiency and NO/sub x/ emissions compared with central fuel injection. For kerosene the NO/sub x/ emissions were lower than for propane and very close to those for premixed fuel and air. However, for gas oil there was little improvement in performance with wall injection compared with central. This was attributed to the slower vaporisation rate with gas oil coupled with the centrifugal action on the liquid droplets with central injection.

Ahmad, N.T.; Andrews, G.E.; Kowkabi, M.; Sharif, S.F.

1985-01-01

20

Design and prototyping of micro centrifugal compressor for ultra micro gas turbine  

NASA Astrophysics Data System (ADS)

In order to establish the design methodology of an ultra micro centrifugal compressor, which is the most important component of an ultra micro gas turbine unit, a 10 times size of the final target compressor (impeller outer diameter 40 mm, corrected rotational speed 220,000 r/min) was designed. The problems to be solved for downsizing were examined and a 2-dimensional impeller was chosen as the first model due to its productivity. The conventional 1D prediction method and CFD were used. The prototyped compressor was tested by using cold air at the reduced speed of 110,000 r/min. Following to the 10 times model, a 5 times size of the final target model having fully 3-dimensional shape (impeller outer diameter 20mm, corrected rotational speed 500,000 r/min) was designed and tested by using hot gas at the reduced speed of 250,000 r/min.

Mizuki, Shimpei; Hirano, Toshiyuki; Koizumi, Yoshiyuki; Minorikawa, Gaku; Tsujita, Hoshio; Iwahara, Mitsuo; Gu, Ronglei; Ohta, Yutaka; Outa, Eisuke

2005-12-01

21

Residual moisture reduction in coarse coal centrifuges. 4. Theory, process engineering and costs  

Microsoft Academic Search

Air purging is a new way of reducing the moisture content of coarse coal (i.e. within the 50–0.5 mm size range) products from vibrating basket centrifuges. The process, which involves injecting a turbulent stream of high velocity air through the coal bed as it traverses the centrifuge basket, has recently been shown to work at commercial scale. This paper describes

R. Benito; D. Condie; B. Johnston; S. Nicol; C. Veal

2002-01-01

22

A Finite-Difference Numerical Method for Onsager's Pancake Approximation for Fluid Flow in a Gas Centrifuge  

SciTech Connect

Gas centrifuges exhibit very complex flows. Within the centrifuge there is a rarefied region, a transition region, and a region with an extreme density gradient. The flow moves at hypersonic speeds and shock waves are present. However, the flow is subsonic in the axisymmetric plane. The analysis may be simplified by treating the flow as a perturbation of wheel flow. Wheel flow implies that the fluid is moving as a solid body. With the very large pressure gradient, the majority of the fluid is located very close to the rotor wall and moves at an azimuthal velocity proportional to its distance from the rotor wall; there is no slipping in the azimuthal plane. The fluid can be modeled as incompressible and subsonic in the axisymmetric plane. By treating the centrifuge as long, end effects can be appropriately modeled without performing a detailed boundary layer analysis. Onsager's pancake approximation is used to construct a simulation to model fluid flow in a gas centrifuge. The governing 6th order partial differential equation is broken down into an equivalent coupled system of three equations and then solved numerically. In addition to a discussion on the baseline solution, known problems and future work possibilities are presented.

de Stadler, M; Chand, K

2007-11-12

23

Aerodynamically induced radial forces in a centrifugal gas compressor: Part 2 -- Computational investigation  

SciTech Connect

Radial loads and direction of a centrifugal gas compressor containing a high specific speed mixed flow impeller and a single tongue volute were determined both experimentally and computationally at both design and off-design conditions. The experimental methodology was developed in conjunction with a traditional ASME PTC-10 closed-loop test to determine radial load and direction. The experimental study is detailed in Part 1 of this paper (Moore and Flathers, 1998). The computational method employs a commercially available, fully three-dimensional viscous code to analyze the impeller and the volute interaction. An uncoupled scheme was initially used where the impeller and volute were analyzed as separate models using a common vaneless diffuser geometry. The two calculations were then repeated until the boundary conditions at a chosen location in the common vaneless diffuser were nearly the same. Subsequently, a coupled scheme was used where the entire stage geometry was analyzed in one calculation, thus eliminating the need for manual iteration of the two independent calculations. In addition to radial load and direction information, this computational procedure also provided aerodynamic stage performance. The effect of impeller front face and rear face cavities was also quantified. The paper will discuss computational procedures, including grid generation and boundary conditions, as well as comparisons of the various computational schemes to experiment. The results of this study will show the limitations and benefits of Computational Fluid Dynamics (CFD) for determination of radial load, direction, and aerodynamic stage performance.

Flathers, M.B.; Bache, G.E.

1999-10-01

24

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

25

Vacuum Technology: Kinetic Theory of Gas  

NSDL National Science Digital Library

This is a PDF version of lecture slides that discuss the kinetic theory of gases. Slide topics include vacuum basics, kinetic pressure of an ideal gas, pressure and molecular velocity, basic equations from kinetic theory, gas laws, and gas transport phenomena. Numerous charts and mathematical formulas are presented. Keywords: Boltzman's constant, collision frequency, molecular velocity, Boyle's law, Charles' law, Dalton's law

Rack, Philip D.

2012-12-14

26

Splitter-bladed centrifugal compressor impeller designed for automotive gas turbine application. [at the Lewis Research Center  

NASA Technical Reports Server (NTRS)

Mechanical design and fabrication of two splitter-bladed centrifugal compressor impellers were completed for rig testing at NASA Lewis Research Center. These impellers were designed for automotive gas turbine application. The mechanical design was based on NASA specifications for blade-shape and flowpath configurations. The contractor made engineering drawings and performed calculations for mass and center-of-gravity, for stress and vibration analyses, and for shaft critical speed analysis. One impeller was machined to print; the other had a blade height and exit radius of 2.54 mm larger than print dimensions.

Pampreen, R. C.

1977-01-01

27

Reciprocity theory of gas surface interactions  

Microsoft Academic Search

Since the Direct Simulation Monte Carlo (DSMC) method has established itself as a standard technique for numerically computing rarefied gas flows, it follows that to develop the theory of rarefied gas dynamics a framework for its fundamental microscopic processes needs to be formulated, i.e., intermolecular collisions and gas surface interactions, which lead to rigorous statistical models that can be utilized

Adolf A. Agbormbai

1989-01-01

28

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

29

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

30

Centrifugal bubble O{sub 2} ({sup 1{Delta}}) gas generator with a total pressure of 100 Torr  

SciTech Connect

A centrifugal bubbling singlet-oxygen gas generator is developed in which chlorine with helium are injected into the rotating layer of the alkali solution of hydrogen peroxide through cylindrical nozzles directed at an angle of 30{sup 0} to the bubbler surface. The concentrations of water vapour and O{sub 2} ({sup 1{Delta}}) and the gas temperature were determined by using the multichannel recording of the emission bands of oxygen at 634, 703, 762 and 1268 nm. For the chlorine and helium flow rates of 60 and 90 mmol s{sup -1}, respectively, the specific chlorine load of 3.2 mmol cm{sup -2}, a total pressure of 100 Torr in the working region of the gas generator and the oxygen partial pressure of 36 Torr, the chlorine utilisation was 90% and the content of O{sub 2} ({sup 1{Delta}}) was {approx}60%. For the ratio of the flow rates of chlorine and the alkali solution of hydrogen peroxide equal to 1 mol L{sup -1}, the water vapour content was {approx}25%. The chemical efficiency of the oxygen-iodine laser with this gas generator achieved 23% for the specific power of 12.7 W cm per 1 cm{sup 3} s{sup -1} per pass of the solution through the gas generator. (laser applications and other topics in quantum electronics)

Zagidulin, M V; Nikolaev, V D; Svistun, M I; Khvatov, N A [Samara Branch of the P. N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2008-08-31

31

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

32

The production characteristics of a solution gas-drive reservoir as measured on a centrifugal model  

E-print Network

. recoveries were obtained vhen the fluid was produced through a central weAl than when production was through a well in the extreme end of the reservoir. Lower viscosity gave substantially higher recoveries~ but larger amounts of gas in solution had.... recoveries were obtained vhen the fluid was produced through a central weAl than when production was through a well in the extreme end of the reservoir. Lower viscosity gave substantially higher recoveries~ but larger amounts of gas in solution had...

Goodwin, Robert Jennings

2012-06-07

33

Centrifugal Compressor Aeroelastic Analysis Code  

NASA Technical Reports Server (NTRS)

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 unsteadiness, etc., leading to rotating stall and surge. Considerable interest exists in small gas turbine engine manufacturers to understand and eventually eliminate the problems related to centrifugal compressors. The geometric complexity of centrifugal compressor blades and the twisting of the blade passages makes the linear methods inapplicable. Advanced computational fluid dynamics (CFD) methods are needed for accurate unsteady aerodynamic and aeroelastic analysis of centrifugal compressors. Most of the current day industrial turbomachines and small aircraft engines are designed with a centrifugal compressor. With such a large customer base and NASA Glenn Research Center being, the lead center for turbomachines, it is important that adequate emphasis be placed on this area as well. Currently, this activity is not supported under any project at NASA Glenn.

Keith, Theo G., Jr.; Srivastava, Rakesh

2002-01-01

34

Theories and Conflict: The Origins of Natural Gas. Instructional Materials.  

ERIC Educational Resources Information Center

This unit explores a recent and controversial theory of the origin of much of the Earth's natural gas and oil. The materials provided will give students the opportunity to: (1) gain an understanding of science and what is involved in the acceptance or rejection of theories; (2) learn about fossil fuels, especially natural gas; (3) learn the…

Anderson, Susan

35

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

36

SELF-CONSISTENT MEAN FIELD THEORY IN WEAKLY IONIZED GAS  

E-print Network

of the dynamo in 3D and tur- bulent diffusion in 2D in weakly ionized gas. We find that in 3D, the backreac to the fully ionized gas. Furthermore, we show that in 2D, the turbulent diffusion is suppressed by backSELF-CONSISTENT MEAN FIELD THEORY IN WEAKLY IONIZED GAS Nicolas Leprovost Groupe Instabilit´e et

Paris-Sud XI, Université de

37

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

38

Constraints complicate centrifugal compressor depressurization  

SciTech Connect

Blowdown of a centrifugal compressor is complicated by process constraints that might require slowing the depressurization rate and by mechanical constraints for which a faster rate might be preferred. The paper describes design constraints such as gas leaks; thrust-bearing overload; system constraints; flare extinguishing; heat levels; and pressure drop.

Key, B. (Hoover and Keith Inc., Houston, TX (United States)); Colbert, F.L. (Paragon Engineering Services Inc., Houston, TX (United States))

1993-05-10

39

Observations on Centrifugation: Application to Centrifuge Development  

Microsoft Academic Search

This report outlines the background to the development of an automated, serial, discrete centrifuge, reporting on the criteria considered essential in such an instrument. We established the criteria by examining the detailed logistics of centrifuge operation in a hospital laboratory. The mean sample load per run, using six centrifuges, was 13.6 samples, and the user-selectable cycle time ranged from 00:01:10

Thomas Roberts; Mathew Smith; Barry Roberts

40

Gas of wormholes in Euclidean quantum field theory  

E-print Network

We model the spacetime foam picture by a gas of wormholes in Euclidean field theory. It is shown that at large distances the presence of such a gas leads merely to a renormalization of mass and charge values. We also demonstrate that there exist a class of specific distributions of point-like wormholes which essentially change the ultraviolet behavior of Green functions and lead to finite quantum field theories.

Savelova, E P

2012-01-01

41

Theory of nonadiabatic gas-surface reactions  

Microsoft Academic Search

A theoretical description of near-resonant charge-exchange processes occurring in gas--surface collisions is presented. The diatomics in molecules method is used for the electronic description of a surface consisting of five atoms. The gas--surface interaction potentials and couplings are obtained with the polyatomics in molecules approach. Trajectories for the ''nuclear'' variables and transition probabilities are calculated with the common eikonal formalism.

J. A. Olson; B. J. Garrison

1985-01-01

42

Theory of nonadiabatic gas–surface reactions  

Microsoft Academic Search

A theoretical description of near-resonant charge-exchange processes occurring in gas–surface collisions is presented. The diatomics in molecules method is used for the electronic description of a surface consisting of five atoms. The gas–surface interaction potentials and couplings are obtained with the polyatomics in molecules approach. Trajectories for the ‘‘nuclear’’ variables and transition probabilities are calculated with the common eikonal formalism.

J. A. Olson; B. J. Garrison

1985-01-01

43

Gas-Mixture Cryocoolers Optimization: Theory & Experiment  

Microsoft Academic Search

The use gas mixture cryocoolers can be widely applied in spacecraft under 300-20K. The advantages of such mixtures are three-fold: (1) High reliability, (2) low noise level, and (3) application over the temperature range. Until recently the range we are addressing has been validated only theoretically. The results are based on calculations of gas-mixture properties and counter-flow heat exchangers. We

V. T. Arkhipov; V. F. Getmanets; Yu. I. Gorpinko; O. V. Yevdokimova; V. V. Yakuba; M. P. Lobko; H. Stears

1999-01-01

44

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.

45

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

46

The theory of transonic vortical gas flows  

Microsoft Academic Search

For cases of plane and axisymmetric transonic vortical gas flows, the approximate equations for the stream function are constructed directly on the physical plane in the vicinity of the sonic-line point at which the entropy is extremal. Certain particular solutions are found which are generalizations of the familiar integrals of transonic gasdynamics without vortices.

V. B. Gorskii

1969-01-01

47

Theory of the classical electron gas  

NASA Technical Reports Server (NTRS)

In a previous paper Cohen and Murphy (1969) used the Meeron resummation (1958) of the Mayer diagrams (1950) to calculate the pair correlation for the classical electron gas in thermal equilibrium. They found that successive terms in the expression for the pair correlation were more and more singular for small interparticle spacing, actually dominating the Debye-Hueckel result for sufficiently small distances. This led to apparent divergence in the higher order contributions to the internal energy. The present paper shows that the apparent anomalies in the Cohen-Murphy results can be removed without further resummation by a more careful treatment of the region of small interparticle spacing. It is shown that there is really no anomalous behavior at short range in any order and all integrals in the expression for the internal energy converge.

Guernsey, R. L.

1978-01-01

48

COLLISIONLESS ELECTRON HEATING IN RF GAS DISCHARGES: I. QUASILINEAR THEORY  

E-print Network

out to be a collisionless one rather than the conventional Joule heating dominant for higher pressuresCOLLISIONLESS ELECTRON HEATING IN RF GAS DISCHARGES: I. QUASILINEAR THEORY Yu.M. Aliev1 , I an interest in mechanisms of electron heating and power deposition in the plasma main- tained by radio

Kaganovich, Igor

49

Centrifuges Biological Safety  

E-print Network

, that lead to accidents involving centrifuges. Hazardous materials can include biologicals and chemicals in the event of an accident inside the centrifuge. · When loading ­ When working with potentially infectious, 4) disassemble and place other affected parts in disinfectant in BSC, 5) recover samples in BSC, 6

Pawlowski, Wojtek

50

Centrifuges for waste waters  

SciTech Connect

This article describes scroll sedimentation centrifuges for water treatment plants of different aeration capacities. The dewatering of various sediments of waste waters in OGSh-type centrifuges occurs as a result of sufficiently high centrifugal acceleration (due to a high separation factor), increased sedimentation area (increased overall dimension of the rotor), improved hydrodynamic conditions of suspension separation, and the use of chemicals (flocculants) during centrifugation. The described OGSh-501K-10 and OGSh-1001K-01 centrifuges have cocurrent flows and are operable with a flocculant. The design of the receiving chamber of the scroll provides for shockless entry of the suspension with a flocculant into the working zone of the rotor. The receiving chamber and the scroll flights are surfaced with a hard alloy, which significantly increases their service life.

Dzhincharadze, E.K.; Galienko, G.D.; Shalaev, V.A.; Yaroslavtsev, R.A.

1984-07-01

51

Theory of multicolor lattice gas - A cellular automaton Poisson solver  

NASA Technical Reports Server (NTRS)

The present class of models for cellular automata involving a quiescent hydrodynamic lattice gas with multiple-valued passive labels termed 'colors', the lattice collisions change individual particle colors while preserving net color. The rigorous proofs of the multicolor lattice gases' essential features are rendered more tractable by an equivalent subparticle representation in which the color is represented by underlying two-state 'spins'. Schemes for the introduction of Dirichlet and Neumann boundary conditions are described, and two illustrative numerical test cases are used to verify the theory. The lattice gas model is equivalent to a Poisson equation solution.

Chen, H.; Matthaeus, W. H.; Klein, L. W.

1990-01-01

52

Self-Consistent Mean Field Theory in Weakly Ionized Gas  

Microsoft Academic Search

We present a self-consistent mean field theory of the dynamo in 3D and turbulent diffusion in 2D in weakly ionized gas. We find that in 3D, the backreaction does not alter the beta effect while it suppresses the alpha effect when the strength of a mean magnetic field exceeds the critical value Bc ˜&surd;nu_in taun \\/R_m. Here, nu_in, tau_n, and

Nicolas Leprovost; Eun-Jin Kim

2003-01-01

53

Advances in electron kinetics and theory of gas discharges  

NASA Astrophysics Data System (ADS)

"Electrons, like people, are fertile and infertile: high-energy electrons are fertile and able to reproduce."—Lev Tsendin Modern 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.

2013-10-01

54

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...

55

Shale Gas Production Theory and Case Analysis We researched the process of oil recovery and shale gas  

E-print Network

Shale Gas Production Theory and Case Analysis (Siemens) We researched the process of oil recovery and shale gas recovery and compare the difference between conventional and unconventional gas reservoir and recovery technologies. Then we did theoretical analysis on the shale gas production. According

Ge, Zigang

56

Dry seal applications in centrifugal compressors  

Microsoft Academic Search

Most centrifugal compressors in refineries and petrochemical plants use shaft end seals which are either controlled leakage labyrinths (nontoxic\\/nonhazardous fluids only) or some type of fluid film seals using a liquid, primarily oil, as a barrier fluid. This article discusses the emerging technology of so-called dry seals. These seals use gas as the sealing fluid medium, and control the leakage

Fischbach

1989-01-01

57

Instanton effects in ABJM theory from Fermi gas approach  

NASA Astrophysics Data System (ADS)

We study the instanton effects of the ABJM partition function using the Fermi gas formalism. We compute the exact values of the partition function at the Chern-Simons levels k = 1 , 2 , 3 , 4 , 6 up to N = 44 , 20 , 18 , 16 , 14 respectively, and extract non-perturbative corrections from these exact results. Fitting the resulting non-perturbative corrections by their expected forms from the Fermi gas, we determine unknown parameters in them. After separating the oscillating behavior of the grand potential, which originates in the periodicity of the grand partition function, and the worldsheet instanton contribution, which is computed from the topological string theory, we succeed in proposing an analytical expression for the leading D2-instanton correction. Just as the perturbative result, the instanton corrections to the partition function are expressed in terms of the Airy function.

Hatsuda, Yasuyuki; Moriyama, Sanefumi; Okuyama, Kazumi

2013-01-01

58

Bifurcated equilibria in centrifugally confined plasma  

SciTech Connect

A bifurcation theory and associated computational model are developed to account for abrupt transitions observed recently on the Maryland Centrifugal eXperiment (MCX) [R. F. Ellis et al. Phys. Plasmas 8, 2057 (2001)], a supersonically rotating magnetized plasma that relies on centrifugal forces to prevent thermal expansion of plasma along the magnetic field. The observed transitions are from a well-confined, high-rotation state (HR-mode) to a lower-rotation, lesser-confined state (O-mode). A two-dimensional time-dependent magnetohydrodynamics code is used to simulate the dynamical equilibrium states of the MCX configuration. In addition to the expected viscous drag on the core plasma rotation, a momentum loss term is added that models the friction of plasma on the enhanced level of neutrals expected in the vicinity of the insulators at the throats of the magnetic mirror geometry. At small values of the external rotation drive, the plasma is not well-centrifugally confined and hence experiences the drag from near the insulators. Beyond a critical value of the external drive, the system makes an abrupt transition to a well-centrifugally confined state in which the plasma has pulled away from the end insulator plates; more effective centrifugal confinement lowers the plasma mass near the insulators allowing runaway increases in the rotation speed. The well-confined steady state is reached when the external drive is balanced by only the viscosity of the core plasma. A clear hysteresis phenomenon is shown.

Shamim, I.; Teodorescu, C.; Guzdar, P. N.; Hassam, A. B.; Clary, R.; Ellis, R.; Lunsford, R. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States)

2008-12-15

59

Hot Gas in Galaxy Clusters: Theory and Simulations  

E-print Network

We review the theory of the formation of galaxy clusters and discuss their role as cosmological probes. We begin with the standard cosmological framework where we discuss the origin of the CDM matter power spectrum and the growth of density fluctuations in the linear regime. We then summarize the spherical top-hat model for the nonlinear growth of fluctuations from which scaling relations and halo statistics are derived. Numerical methods for simulating gas in galaxy clusters are then overviewed with an emphasis on multiscale hydrodynamic simulations of cluster ensembles. Results of hydrodynamic AMR simulations are described which compare cluster internal and statistical properties as a function of their assumed baryonic processes. Finally, we compare various methods of measuring cluster masses using X-ray and the thermal Sunyaev-Zeldovich effect (SZE). We find that SZE offers great promise for precision measurements in raw samples of high-z clusters.

Michael L. Norman

2005-11-15

60

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

61

Modelling and simulation of heavy gas dispersion on the basis of modifications in plume path theory  

Microsoft Academic Search

An analytical model for heavy gas dispersion based on the modifications in plume path theory has been developed. The model takes into account the variations in temperature, density, and specific heat during the movement of heavy gas plume.The model has been tested for three hazardous gases — chlorine, natural gas and liquefied petroleum gas. The results have been compared with

Faisal I Khan; S. A Abbasi

2000-01-01

62

Design of centrifugal impeller blades  

NASA Technical Reports Server (NTRS)

This paper restricts itself to radial impellers with cylindrical blades since, as Prasil has shown, the flow about an arbitrarily curved surface of revolution may be reduced to this normal form we have chosen by a relatively simple conformal transformation. This method starts from the simple hypotheses of the older centrifugal impeller theory by first assuming an impeller with an infinite number of blades. How the flow is then modified is then investigated. For the computation of flow for a finite number of blades, the approximation method as developed by Munk, Prandtl and Birnbaum, or Glauert is found suitable. The essential idea of this method is to replace the wing by a vortex sheet and compute the flow as the field of these vortices. The shape of the blades is then obtained from the condition that the flow must be along the surface of the blade.

Betz, A; Flugge-Lotz, I

1939-01-01

63

Subsychronous vibration of multistage centrifugal compressors forced by rotating stall  

NASA Technical Reports Server (NTRS)

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 amplitude with the discharge flow coefficient, demonstrating the excitation to be aerodynamic. Adding two impellers allowed an increase in the diffuser flow angle (with respect to tangential) to meet the diffuser stability criteria based on factory and field tests correlated using the theory of Senoo (for rotating stall in a vaneless diffuser). This modification eliminated all significant subsynchronous vibrations in field service, thus confirming the correctness of the solution. Other possible sources of aerodynamically induced vibrations were considered, but the judgment that those are unlikely has been confirmed by subsequent experience with other similar compressors.

Fulton, J. W.

1987-01-01

64

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

65

The Human Centrifuge  

Microsoft Academic Search

Life on Earth has developed at unit gravity, 9.81 m\\/s2, which was a major factor especially when vertebrates emerged from water onto land in the late Devonian, some 375 million\\u000a years ago. But how would nature have evolved on a larger planet? We are able to address this question simply in experiments\\u000a using centrifuges. Based on these studies we have gained

Jack J. W. A. van Loon

2009-01-01

66

The human centrifuge  

Microsoft Academic Search

Life on Earth has developed at unit gravity, 9.81 m\\/s2, which was a major factor especially when vertebrates emerged from water onto land in the late Devonian, some 375 million years ago. But how would nature have evolved on a larger planet? We are able to address this question simply in experiments using centrifuges. Based on these studies we have

Loon van J. J. W. A

2009-01-01

67

LMR (liquid metal reactor) centrifugal pump coastdowns  

SciTech Connect

A centrifugal pump model which describes the interrelationships of the pump discharge flowrate, pump speed, shaft torque and dynamic head has been implemented based upon existing models. Specifically, the pump model is based upon the dimensionless-homologous pump theory of Wylie and Streeter. Given data from a representative pump, homologous theory allows one to predict the transient characteristics of similarly sized pumps. This homologous pump model has been implemented into both the one-dimensional SASSYS-1 systems analysis code and the three-dimensional COMMIX-1A code. Comparisons have been made both against other pump models (CRBR) and actual pump coastdown data (EBR-II and FFTF). Agreement with this homologous pump model has been excellent. Additionally, these comparisons indicate the validity of applying the medium size pump data of Wylie and Streeter to a range of typical LMR centrifugal pumps.

Dunn, F.E.; Malloy, D.J.

1987-01-01

68

Design and prototyping of micro centrifugal compressor  

Microsoft Academic Search

In order to establish the design methodology of ultra micro centrifugal compressor, which is the most important component\\u000a of ultra micro gas turbine unit, a 10 times of the final target size model was designed, prototyped and tested. The problems\\u000a to be solved for downsizing were examined and 2-dimensional impeller was chosen as the first model due to its productivity.

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

2003-01-01

69

Incremental adaptation to yaw head turns during 30 RPM centrifugation  

Microsoft Academic Search

A 3-day incremental protocol was conducted with the aim of adapting human subjects to make head movements comfortably during\\u000a 30 RPM centrifugation. With motion sickness as a potentially limiting factor, the protocol was designed using a quantitative\\u000a motion sickness model based upon the neural mismatch sensory conflict theory. Centrifuge velocity was incremented from 14\\u000a RPM on day 1, to 23

Paul Z. Elias; Thomas Jarchow; Laurence R. Young

2008-01-01

70

CENTRIFUGAL MEMBRANE FILTRATION  

SciTech Connect

The overall project consists of several integrated research phases related to the applicability, continued development, demonstration, and commercialization of the SpinTek centrifugal membrane filtration process. Work performed during this reporting period consisted of Phase 2 evaluation of the SpinTek centrifugal membrane filtration technology and Phase 3, Technology Partnering. During Phase 1 testing conducted at the EERC using the SpinTek ST-IIL unit operating on a surrogate tank waste, a solids cake developed on the membrane surface. The solids cake was observed where linear membrane velocities were less than 17.5 ft/s and reduced the unobstructed membrane surface area up to 25%, reducing overall filtration performance. The primary goal of the Phase 2 research effort was to enhance filtration performance through the development and testing of alternative turbulence promoter designs. The turbulence promoters were designed to generate a shear force across the entire membrane surface sufficient to maintain a self-cleaning membrane capability and improve filtration efficiency and long-term performance. Specific Phase 2 research activities included the following: System modifications to accommodate an 11-in.-diameter, two-disk rotating membrane assembly; Development and fabrication of alternative turbulence promoter designs; Testing and evaluation of the existing and alternative turbulence promoters under selected operating conditions using a statistically designed test matrix; and Data reduction and analysis; The objective of Phase 3 research was to demonstrate the effectiveness of SpinTek's centrifugal membrane filtration as a pretreatment to remove suspended solids from a liquid waste upstream of 3M's WWL cartridge technology for the selective removal of technetium (Tc).

Daniel J. Stepan; Bradley G. Stevens; Melanie D. Hetland

1999-10-01

71

The magnetic centrifugal mass filter  

SciTech Connect

Mass filters using rotating plasmas have been considered for separating nuclear waste and spent nuclear fuel. We propose a new mass filter that utilizes centrifugal and magnetic confinement of ions in a way similar to the asymmetric centrifugal trap. This magnetic centrifugal mass filter is shown to be more proliferation resistant than present technology. This filter is collisional and produces well confined output streams, among other advantages.

Fetterman, Abraham J.; Fisch, Nathaniel J. [Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08540 (United States)

2011-09-15

72

The Magnetic Centrifugal Mass Filter  

SciTech Connect

Mass filters using rotating plasmas have been considered for separating nuclear waste and spent nuclear fuel. We propose a new mass filter that utilizes centrifugal and magnetic confinement of ions in a way similar to the asymmetric centrifugal trap. This magnetic centrifugal mass filter is shown to be more proliferation resistant than present technology. This filter is collisional and produces well confined output streams, among other advantages. __________________________________________________

Abraham J. Fetterman and Nathaniel J. Fisch

2011-08-04

73

Centrifuges Replacement Study Proposal  

E-print Network

, for requirements. 3 2.2 Details of assemblies and sections. 3 2.3 Design calculations and manufacturer's weld procedures. 3 2.4 All drawings required in the as purchase requisition 3 2.5 2.6 III. RECORD DATA AFTER APPROVAL 1.0 Within (90... for Drawings of centrifuges shall conform to the following: 1. Computer Aided Design Drawings (CADD), generated with Microstation J, are required. In addition three sets of drawings shall be submitted for review / comment, approval, and as-built. 2. A...

Iqbal, Muhammad

2005-12-16

74

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

E-print Network

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 due to absorption on both solid and liquid surfaces, we predict three possible gas states at the liquid-solid interface, i.e. complete wetting, partial wetting and pseudopartial wetting. These possible gas states correspond respectively to a gas pancake (or film) surrounded by a wet solid, a gas bubble with a finite contact angle, and a gas bubble(s) coexisting with a gas pancake. Typical thickness of the gas pancakes is at the nanoscale within the force range of the long-range interaction, whereas the radius of the gas bubbles can be large. The state of gas bubble(s) coexisting with a gas film is predicted theoretically for the first time. Our theoretical results can contribute to the development of a unified picture of gas nucleation at the liquid-solid interface.

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

2006-08-04

75

Effect of inner ring centrifugal displacement on the dynamic characteristics of high-speed angular contact ball bearing  

Microsoft Academic Search

According to the elastic theory the calculating formulas of inner ring centrifugal displacement are inferred, in consideration of inner ring centrifugal displacement the basic equations of angular contact ball bearing are set up, effect of inner ring centrifugal displacement on the dynamic characteristics of high-speed angular contact ball bearings are studied. The results from taking 7012C bearing as an example

Wang Bao-min; Mei Xue-song; Hu Chi-bing; Wu Zai-xin

2010-01-01

76

NASA low speed centrifugal compressor  

NASA Technical Reports Server (NTRS)

The flow characteristics of a low speed centrifugal compressor were examined at NASA Lewis Research Center to improve understanding of the flow in centrifugal compressors, to provide models of various flow phenomena, and to acquire benchmark data for three dimensional viscous flow code validation. The paper describes the objectives, test facilities' instrumentation, and experiment preliminary comparisons.

Hathaway, Michael D.

1990-01-01

77

Locking Centrifuge Rotor Cover Assembly  

Microsoft Academic Search

A centrifuge rotor cover assembly for use with a centrifuge having a rotor and a housing enclosing the rotor and including a lid movable between a closed position overlying the rotor and an open position providing access to the rotor. The cover assembly includes a rotor cover removably coupled to the lid. Means are provided for engaging the rotor cover

Benjamin Linder; Don Lee; Amy Battles; David M. Otten

2000-01-01

78

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

79

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

80

[Galileo and centrifugal force].  

PubMed

This work intends to focus on Galileo's study of what is now called "centrifugal force," within the framework of the Second Day of his Dialogo written in 1632, rather than on the previously published commentaries on the topic. Galileo proposes three geometrical demonstrations in order to prove that gravity will always overcome centrifugalforce, and that the potential rotation of the Earth, whatever its speed, cannot in any case project objects beyond it. Each of these demonstrations must consequently contain an error and it has seemed to us that the first one had not been understood up until now. Our analysis offers an opportunity to return to Galileo's geometrical representation of dynamical questions; actually, we get an insight into the sophistication of Galileo's practices more than into his mistakes. Our second point, concerning the historiography of the problem, shows an evolution from anachronic critics to more contextual considerations, in the course of the second half of the twentieth century. PMID:25029818

Vilain, Christiane

81

Diffusion-reaction theory for conductance response in metal oxide gas sensing thin films  

Microsoft Academic Search

A diffusion-reaction model is capable of proof by comparing theory and experiment. A relation of response time varying with film thickness and gas concentration is given. The method to study certain problems of surface and interface chemical physics by means of measuring macroscopic gas sensing conductance is proposed.

Honglong Lu; Wencai Ma; Jianhua Gao; Jianming Li

2000-01-01

82

Centrifuge modeling of shallow foundation on soft soil  

SciTech Connect

A series of centrifuge model tests was performed to study the behavior of shallow foundations on soft normally consolidated clay. The model tests included testing of foundation models with one-dimensional, plane strain, and axially symmetric geometries. The nonlinear consolidation properties of the soil were determined using specially developed laboratory testing techniques. The centrifuge test data were then compared with conventional and finite strain theories for consolidation assessment, as well as a limit analysis solution for foundation stability considerations. It is found that centrifuge testing coupled with careful laboratory testing provides a useful tool to validate analytical procedures. It has demonstrated that the finite strain theory and the limit analysis solution are valid procedures for the determination of consolidation settlement and foundation penetration of shallow foundations on soft soil, respectively.

Leung, P.K.; Ku, H.Y.; Pane, V.; Schiffman, R.L.

1984-05-01

83

The Energetics of Centrifugal Instability  

NASA Astrophysics Data System (ADS)

A recent study has argued that the California Undercurrent, and poleward eastern boundary currents in general, generate mixing events through centrifugal instability. The purpose of this study is to examine the energetics of centrifugal instability in order to develop a framework in which to estimate its regional and global impacts. We argue that centrifugal instability is roughly twice as efficient at mixing as is Kelvin-Helmholtz instability, and that roughly 1/3 of the initially energy in the current is lost to either local mixing or the generation of unbalanced flows. The latter, according to traditional thought, probably leads to non-local mixing. Thus centrifugal instability is an effective process by which energy is lost from the balanced flow and spent in mixing neighboring water masses. Its regional and global impacts are discussed.

Jiao, Yang; Dewar, William

2014-05-01

84

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

85

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

86

Density wave theory. [interstellar gas dynamics and galactic shock waves  

NASA Technical Reports Server (NTRS)

The prospect that density waves and galactic shock waves are present on the large scale in disk shaped galaxies has received support in recent years from both theoretical and observational studies. Large-scale galactic shock waves in the interstellar gas are suggested to play an important governing role in star formation, molecule formation, and the degree of development of spiral structure. Through the dynamics of the interstellar gas and the galactic shock-wave phenomenon, a new insight into the physical basis underlying the morphological classification system of galaxies is suggested.

Roberts, W. W., Jr.

1977-01-01

87

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. PMID:24608004

Lazik, Detlef

2014-01-01

88

Theory of vortical helical ideal gas flows in laval nozzles  

Microsoft Academic Search

An asymptotic solution is found for the direct problem of the motion of an arbitrarily vortical helical ideal gas flow in a nozzle. The solution is constructed in the form of double series in powers of parameters characterizing the curvature of the nozzle wall at the critical section and the intensity of stream vorticity. The solution obtained is compared with

Yu. A. Gostintsev; O. A. Uspenskii

1978-01-01

89

Fluid forces on rotating centrifugal impeller with whirling motion  

NASA Technical Reports Server (NTRS)

Fluid forces on a centrifugal impeller, whose rotating axis whirls with a constant speed, were calculated by using unsteady potential theory. Calculations were performed for various values of whirl speed, number of impeller blades and angle of blades. Specific examples as well as significant results are given.

Shoji, H.; Ohashi, H.

1980-01-01

90

Experimental characterization of high speed centrifugal compressor aerodynamic forcing functions  

Microsoft Academic Search

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

Kirk Gallier

2005-01-01

91

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

92

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

93

The Lifshitz-Kosevich-Shoenberg theory of relativistic electronic gas in neutron stars  

NASA Astrophysics Data System (ADS)

Similar to the de Haas-van Alphen magnetic oscillatory in some normal metals when the Landau quantization is predominant, the magnetic oscillation can also occur in highly degenerate and relativistic electron gas in neutron stars. At large Landau quantum number (Landau quantum number r?2), we generalize the Lifshitz-Kosevich-Shoenberg theory in non-relativistic electron gas to relativistic gas. At small Landau quantum number ( r<2), we expand the grand potential into Fourier series and get similar harmonic oscillatory formula of magnetization. These results indicate that magnetic phase transition similar as Condon transition observed in metals can appear in neutron stars when the differential susceptibility exceeds 1/4 ?.

Wang, Zhaojun; Lü, Guoliang; Zhu, Chunhua

2014-10-01

94

Parents of two-phase flow and theory of "gas-lift"  

NASA Astrophysics Data System (ADS)

This paper gives a brief overview of types of two-phase flow. Subsequently, it deals with their mutual division and problems with accuracy boundaries among particular types. It also shows the case of water flow through a pipe with external heating and the gradual origination of all kinds of flow. We have met it in solution of safety condition of various stages in pressurized and boiling water reactors. In the MSR there is a problem in the solution of gas-lift using helium as a gas and its secondary usage for clearing of the fuel mixture from gaseous fission products. Theory of gas-lift is described.

Zitek, Pavel; Valenta, Vaclav

2014-03-01

95

Impact of Airway Gas Exchange on the Multiple Inert Gas Elimination Technique: Theory  

PubMed Central

The multiple inert gas elimination technique (MIGET) provides a method for estimating alveolar gas exchange efficiency. Six soluble inert gases are infused into a peripheral vein. Measurements of these gases in breath, arterial blood, and venous blood are interpreted using a mathematical model of alveolar gas exchange (MIGET model) that neglects airway gas exchange. A mathematical model describing airway and alveolar gas exchange predicts that two of these gases, ether and acetone, exchange primarily within the airways. To determine the effect of airway gas exchange on the MIGET, we selected two additional gases, toluene and m-dichlorobenzene, that have the same blood solubility as ether and acetone and minimize airway gas exchange via their low water solubility. The airway-alveolar gas exchange model simulated the exchange of toluene, m-dichlorobenzene, and the six MIGET gases under multiple conditions of alveolar ventilation-to-perfusion, V?A/Q?, heterogeneity. We increased the importance of airway gas exchange by changing bronchial blood flow, Q?br. From these simulations, we calculated the excretion and retention of the eight inert gases and divided the results into two groups: 1) the standard MIGET gases which included acetone and ether and 2) the modified MIGET gases which included toluene and m-dichlorobenzene. The MIGET mathematical model predicted distributions of ventilation and perfusion for each grouping of gases and multiple perturbations of V?A/Q? and Q?br. Using the modified MIGET gases, MIGET predicted a smaller dead space fraction, greater mean V?A, greater log(SDVA), and more closely matched the imposed V?A distribution than that using the standard MIGET gases. Perfusion distributions were relatively unaffected. PMID:20336837

Anderson, Joseph C.; Hlastala, Michael P.

2011-01-01

96

Rare gas scattering from molten metals examined with classical scattering theory  

E-print Network

Rare gas scattering from molten metals examined with classical scattering theory Andre´ Muis and J coefficient for atoms scattering from a surface are compared with recent experiments for the scattering to the backscattered intensity, double collision events make a significant but smaller contribution, and scattering

Manson, Joseph R.

97

Post-evaluation of Power Plant Flue Gas Desulfurization Project Based on Theory of Value Management  

Microsoft Academic Search

With the rapid development of the Thermal Power Plant Flue Gas Desulfurization (FGD) industry, Desulfurization Project has a wide developing prospect in the present market. However, the levels of Desulfurization enterprises mix and owners are unfamiliar with the desulfurization project, which increase the investment and cannot reach the expected desulfurization effect. Applying the theory of value management in post-evaluation of

Yun-na Wu; Ying-ying Huang; Zhi-jun Huang

2009-01-01

98

Substituent effects on intermolecular .hydrogen bonding from a lattice gas theory for lower critical solution points  

E-print Network

Substituent effects on intermolecular .hydrogen bonding from a lattice gas theory for lower transitions in binary mixtures with hydrogen bonding, introduced and studied by Walker, Vause, and Goldstein of the intermolecular hydrogen bonding. The parametric trends are found to agree with those expected from consideration

Goldstein, Raymond E.

99

Quasilinear theory of collisionless electron heating in radio frequency gas discharges  

E-print Network

to be a collisionless one rather than the conven- tional Joule heating dominant for higher pressures. The problemQuasilinear theory of collisionless electron heating in radio frequency gas discharges Yu. M. Aliev heating of rf discharges is treated for characteristic scale lengths of the heating field much shorter

Kaganovich, Igor

100

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

101

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

102

Preliminary design of centrifugal compressors  

SciTech Connect

Preliminary design calculations are analyzed for a centrifugal compressor, after choosing as the type of the turbomachine from the curves given by Balje (1981). In impeller calculations, the effect of slip factor on exit conditions, the inducer geometry and the effect of choked flow on relative Mach number are investigated. In discharge calculation vaned diffusers are compared with vaneless diffusers.

Kocak, S. [Selcuk Univ., Konya (Turkey). Dept. of Mechanical Engineering

1996-11-01

103

Life Sciences Centrifuge Facility assessment  

NASA Technical Reports Server (NTRS)

This report provides an assessment of the status of the Centrifuge Facility being developed by ARC for flight on the International Space Station Alpha. The assessment includes technical status, schedules, budgets, project management, performance of facility relative to science requirements, and identifies risks and issues that need to be considered in future development activities.

Benson, Robert H.

1994-01-01

104

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

105

75 FR 70300 - USEC, Inc.; American Centrifuge Lead Cascade Facility; American Centrifuge Plant; Notice of...  

Federal Register 2010, 2011, 2012, 2013

...SNM-2011, for the American Centrifuge Lead Cascade Facility and the American Centrifuge Plant...Licensee), for its American Centrifuge Lead Cascade Facility (LCF) and American Centrifuge...interest in the proceeding; 4. The possible effect of any decision or order that may be...

2010-11-17

106

The function of gas vesicles in halophilic archaea and bacteria: theories and experimental evidence.  

PubMed

A few extremely halophilic Archaea (Halobacterium salinarum, Haloquadratum walsbyi, Haloferax mediterranei, Halorubrum vacuolatum, Halogeometricum borinquense, Haloplanus spp.) possess gas vesicles that bestow buoyancy on the cells. Gas vesicles are also produced by the anaerobic endospore-forming halophilic Bacteria Sporohalobacter lortetii and Orenia sivashensis. We have extensive information on the properties of gas vesicles in Hbt. salinarum and Hfx. mediterranei and the regulation of their formation. Different functions were suggested for gas vesicle synthesis: buoying cells towards oxygen-rich surface layers in hypersaline water bodies to prevent oxygen limitation, reaching higher light intensities for the light-driven proton pump bacteriorhodopsin, positioning the cells optimally for light absorption, light shielding, reducing the cytoplasmic volume leading to a higher surface-area-to-volume ratio (for the Archaea) and dispersal of endospores (for the anaerobic spore-forming Bacteria). Except for Hqr. walsbyi which abounds in saltern crystallizer brines, gas-vacuolate halophiles are not among the dominant life forms in hypersaline environments. There only has been little research on gas vesicles in natural communities of halophilic microorganisms, and the few existing studies failed to provide clear evidence for their possible function. This paper summarizes the current status of the different theories why gas vesicles may provide a selective advantage to some halophilic microorganisms. PMID:25371329

Oren, Aharon

2012-01-01

107

Finite-temperature theory of the trapped two-dimensional Bose gas  

SciTech Connect

We present a Hartree-Fock-Bogoliubov (HFB) theoretical treatment of the two-dimensional trapped Bose gas and indicate how semiclassical approximations to this and other formalisms have lead to confusion. We numerically obtain results for the quantum-mechanical HFB theory within the Popov approximation and show that the presence of the trap stabilizes the condensate against long wavelength fluctuations. These results are used to show where phase fluctuations lead to the formation of a quasicondensate.

Gies, Christopher; Hutchinson, D.A.W. [Department of Physics, University of Otago, P.O. Box 56, Dunedin (New Zealand); Zyl, Brandon P. van [Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1 (Canada); Morgan, S.A. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

2004-02-01

108

Quasiparticle theory of the electron gas: A direct-interaction approach  

Microsoft Academic Search

Landau's Fermi-liquid theory, generalized to include quasiparticle scattering with finite momentum transfer, is applied to the degenerate electron gas in a homogeneous positive background. The quasiparticle-scattering amplitude (QSA) is calculated within the framework of the direct-interaction model by an approximate, frequency-independent solution of the Bethe-Salpeter integral equation for charged systems. Vertex corrections are taken into account. Using as input an

S. Küchenhoff; S. Schiller

1991-01-01

109

Preliminary study of a centrifugal-flow singlet oxygen generator  

SciTech Connect

By using the concept of a high-pressure, gravity-independent singlet oxygen generator (SOG) proposed by Emanuel and based on the principle that a rotating fluid is capable of producing an enormous centrifugal force, a novel-type centrifugal-flow singlet oxygen generator (CFSOG) was designed and constructed. In this device, O{sub 2}({sup 1}{delta}) was generated in the reaction of gaseous Cl{sub 2} with a rotating basic hydrogen peroxide (BHP) liquid flow and then was removed from the BHP liquid phase by the centrifugal force. Meanwhile, the microdroplets formed during the Cl{sub 2}+BHP reaction were removed from the O{sub 2}({sup 1}{delta}) gas flow by the centrifugal force produced by the high-speed flow along an arc-shaped channel. Preliminary investigations showed that, because the specific reactive surface area of this SOG was noticeably larger than that of the jet-SOG normally used in current chemical oxygen-iodine lasers (COILs), the O{sub 2}({sup 1}{delta}) yield of {approx}60%, the O{sub 2}({sup 1}{delta}) partial pressure as high as 31 Torr, and chlorine utilisation higher than 96% were realised. Moreover, steady operation was obtained. (laser components)

Shi, W; Deng, L; Yang, H; Sha, G; Zhang, C [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences (China)

2008-02-28

110

Twinning of amphibian embryos by centrifugation  

NASA Technical Reports Server (NTRS)

In the frog Xenopus laevis, the dorsal structures of the embryonic body axis normally derive from the side of the egg opposite the side of sperm entry. However, if the uncleaved egg is inclined at lg or centrifuged in an inclined position, this topographic relationship is overridden: the egg makes its dorsal axial structures according to its orientation in the gravitational/centrifugal field, irrespective of the position of sperm entry. Certain conditions of centrifugation cause eggs to develop into conjoined twins with two sets of axial structures. A detailed analysis of twinning provided some insight into experimental axis orientation. First, as with single-axis embryos, both axes in twins are oriented according to the direction of centrifugation. One axis forms at the centripetal side of the egg and the other forms at the centrifugal side, even when the side of sperm entry is normal to the centrifugal force vector. Second, if eggs are centrifuged to give twins, but are inclined at lg to prevent post-centrifugation endoplasmic redistributions, only single-axis embryos develop. Thus, a second redistribution is required for high-frequency secondary axis formation. This can be accomplished by lg (as in the single centrifugations) or by a second centrifugation directed along the egg's animal-vegetal axis.

Black, S. D.

1984-01-01

111

Prototyping of ultra micro centrifugal compressor-influence of meridional configuration  

Microsoft Academic Search

In order to investigate the design method for a micro centrifugal compressor, which is the most important component of an\\u000a ultra micro gas turbine, two types of centrifugal impeller with 2-dimensional blade were designed, manufactured and tested.\\u000a These impellers have different shapes of hub on the meridional plane with each other. Moreover, these types of impeller were\\u000a made for the

Toshiyuki Hirano; Tadataka Muto; Hoshio Tsujita

2011-01-01

112

Testing of pyrochemical centrifugal contactors  

SciTech Connect

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- organic systems operation near room temperature. In tests to demonstrate the performance of the pyrocontactor, cadmium and LICl- KCl eutectic salt were the immiscible solvent phases, and rare earths were the distributing solutes. The tests showed that the pyrocontactor mixed and separated the phases well, with stage efficiencies approaching 99% at rotor speeds near 2700 rpm. The contactor ran smoothly and reliably over the entire range of speeds that was tested.

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

1996-08-01

113

Centrifugal and torque responsive clutch  

SciTech Connect

A coupling mechanism is described including a fluid coupling device with input and output elements, and a centrifugal type lock-up clutch for releasably engaging the input and output elements, characterized in that the lock-up clutch, this mechanism comprises: a cylindrical inner surface formed on the input element; a drive plate provided with friction elements displaceable in a radially outward direction for engagement with the cylindrical inner surface; the friction elements having: a friction shoe; a pair of cam weights; resilient load; a driven plate; a damper of resilient material and a biasing means.

Sakakibara, S.; Tsuzuki, S.

1987-04-28

114

Settling velocities of particulate systems: 14. Unified model of sedimentation, centrifugation  

E-print Network

Settling velocities of particulate systems: 14. Unified model of sedimentation, centrifugation August 2002; accepted 30 June 2003 Abstract This paper presents a unified theory of solid, which illustrate the theory. D 2003 Elsevier B.V. All rights reserved. Keywords: sedimentation

Bürger, Raimund

115

Theory versus experiment for the rotordynamic coefficients of labyrinth gas seals. II - A comparison to experiment  

NASA Technical Reports Server (NTRS)

An experimental test facility is used to measure the leakage and rotordynamic coefficients of teeth-on-rotor and teeth-on-stator labyrinth gas seals. The test results are presented along with the theoretically predicted values for the two seal configurations at three different radial clearances and shaft speeds to 16,000 cpm. The test results show that the theory accurately predicts the cross-coupled stiffness for both seal configurations and shows improvement in the prediction of the direct damping for the teeth-on-rotor seal. The theory fails to predict a decrease in the direct damping coefficient for an increase in the radial clearance for the teeth-on-stator seal.

Childs, D. W.; Scharrer, J. K.

1987-01-01

116

Ginzburg-Landau theory of a trapped Fermi gas with a BEC-BCS crossover  

SciTech Connect

The Ginzburg-Landau theory of a trapped Fermi gas with a BEC-BCS crossover is derived by the path-integral method. In addition to the standard Ginzburg-Landau equation, a second equation describing the total atom density is obtained. These two coupled equations are necessary to describe both homogeneous and inhomogeneous systems. The Ginzburg-Landau theory is valid near the transition temperature T{sub c} on both sides of the crossover. In the weakly interacting BEC region, it is also accurate at zero temperature where the Ginzburg-Landau equation can be mapped onto the Gross-Pitaevskii (GP) equation. The applicability of GP equation at finite temperature is discussed. On the BEC side, the fluctuation of the order parameter is studied and the renormalization to the molecule coupling constant is obtained.

Huang Kun; Yu Zengqiang; Yin Lan [School of Physics, Peking University, Beijing 100871 (China)

2009-05-15

117

Density-functional theory of the trapped two-dimensional Fermi gas in the unitary regime  

SciTech Connect

A recent paper by T. Papenbrock [Phys. Rev. A 72, 041602(R) (2005)] suggests that a determination of the universal factor {xi}{sub 3D} for a harmonically trapped, unpolarized dilute Fermi gas in the unitary regime may be obtained within the framework of a simple density-functional theory (DFT). One of the key results of that work is an estimate for the universal factor {xi}{sub 3D}{approx_equal}0.54, which is within 20% of the generally accepted quantum Monte Carlo simulation value of {xi}{sub 3D}=0.44{+-}0.01. Motivated by this result, this report investigates the determination of the universal factor {xi}{sub 2D} for a two-dimensional trapped Fermi gas, and suggests that the simple DFT approach of Papenbrock provides an exact result of {xi}{sub 2D}=1 in two dimensions.

Zyl, Brandon P. van; Need, Melodie [Department of Physics, St. Francis Xavier University, Antigonish, Nova Scotia, B2G 2W5 (Canada); Hutchinson, D. A. W. [Jack Dodd Centre for Photonics and Ultra-Cold Atoms, Department of Physics, University of Otago, Dunedin (New Zealand); Laboratoire Kastler Brossel, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris Cedex 05 (France)

2007-08-15

118

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

119

Meteor Crater: Energy of formation - Implications of centrifuge scaling  

NASA Technical Reports Server (NTRS)

Recent work on explosive cratering has demonstrated the utility of performing subscale experiments on a geotechnic centrifuge to develop scaling rules for very large energy events. The present investigation is concerned with an extension of this technique to impact cratering. Experiments have been performed using a projectile gun mounted directly on the centrifuge rotor to launch projectiles into a suitable soil container undergoing centripetal accelerations in excess of 500 G. The pump tube of a two-stage light-gas gun was used to attain impact velocities of approximately 2 km/sec. The results of the experiments indicate that the energy of formation of any large impact crater depends upon the impact velocity. This dependence, shown for the case of Meteor Crater, is consistent with analogous results for the specific energy dependence of explosives and is expected to persist to impact velocities in excess of 25 km/sec.

Schmidt, R. M.

1980-01-01

120

The Initial Design of a Centrifugal Compressor  

Microsoft Academic Search

Centrifugal compressors are used in many different applications in a wide variety of industries. Although there are a number of centrifugal compressor variants a particular type has been chosen upon which to concentrate. This is a single-state machine without inlet guide vanes and with a shroudless backswept impeller, a vaned diffuser and a volute collector. The focus of this article

E. SWAIN

1992-01-01

121

The Development of a Centrifugal Compressor Impeller  

Microsoft Academic Search

An impeller is one of the key components of industrial centrifugal compressors and turbochargers. Aerodynamic and structure designs of the impeller are critical to the success of the whole compressor stages. The requirements for efficiency and operating range of industrial centrifugal compressors and turbochargers have been increased dramatically compared with the situation in the past. The efficiency of a newly

C. Xu; R. S. Amano

2009-01-01

122

Submarine landslide flows simulation through centrifuge modelling  

E-print Network

of the mini-drum centrifuge (after Barker, 1998) ...... 95 Figure 3.9: Water supply and channel dr ainage of the mini-drum centrifuge (after Barker, 1998... ................................................................ 29   2.6.3   Flow behaviour ...................................................................................... 30   v 2.6.4   Governing equations and analyt ical solutions through mass and momentum conservations...

Gue, Chang Shin

2012-05-08

123

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

124

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

125

Sound generation in centrifugal compressors  

NASA Astrophysics Data System (ADS)

An experimental study is described to explore the dominant sound generation mechanisms of the spectral components governing the overall noise level of centrifugal compressors. At the design speed with supersonic flow conditions in the rotor blade channels, blade tone noise and buzz-saw noise are the main contributors. On the inlet, rotor-alone noise is the main source while rotor-stator interaction noise dominates on the outlet side in case of vaned outlet diffusers. Over a large range of rotor speeds with subsonic flow conditions, radial compressor noise is dominated by tip clearance noise which is produced by the secondary flow through the gap between rotor blade tips and the casing wall which in turn gives rise to the rotating instability phenomena observed earlier in axial-flow machines.

Raitor, Till; Neise, Wolfgang

2008-07-01

126

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

127

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

128

Centrifugal membrane filtration -- Task 9  

SciTech Connect

The Energy and Environmental Research Center (EERC) has teamed with SpinTek Membrane Systems, Inc., the developer of a centrifugal membrane filtration technology, to demonstrate applications for the SpinTek technology within the US Department of Energy (DOE) Environmental management (EM) Program. The technology uses supported microporous membranes rotating at high rpm, under pressure, to separate suspended and colloidal solids from liquid streams, yielding a solids-free permeate stream and a highly concentrated solids stream. This is a crosscutting technology that falls under the Efficient Separations and Processing Crosscutting Program, with potential application to tank wastes, contaminated groundwater, landfill leachate, and secondary liquid waste streams from other remediation processes, including decontamination and decommissioning systems. Membrane-screening tests were performed with the SpinTek STC-X4 static test cell filtration unit, using five ceramic membranes with different pore size and composition. Based on permeate flux, a 0.25-{micro}m TiO{sub 2}/Al{sub 2}O{sub 3} membrane was selected for detailed performance evaluation using the SpinTek ST-IIL centrifugal membrane filtration unit with a surrogate tank waste solution. An extended test run of 100 hr performed on a surrogate tank waste solution showed some deterioration in filtration performance, based on flux, apparently due to the buildup of solids near the inner portion of the membrane where relative membrane velocities were low. Continued testing of the system will focus on modifications to the shear pattern across the entire membrane surface to affect improved long-term performance.

NONE

1996-08-01

129

Premixed and diffusion flames in a centrifuge  

SciTech Connect

Combustion experiments conducted in a centrifuge are rare, and the authors present results obtained during different tests campaigns. For premixed flames or for diffusion flames, two cases are distinguished--in one, small flames are steady, and in the other, tall flames may be sensitive to a natural instability created by buoyancy in burned gases. The results show that for premixed stationary flames, the flame shape is almost insensitive to buoyancy, except for a very light modification of the streamlines in burned and fresh gases due to the hydrodynamic effects. The physicochemistry of the flame front is not modified in the range of gravity levels studied (between 1g{sub 0} and 10 g{sub 0}). On the other hand, the morphology of stationary diffusion flames is strongly changed. Both flame height and surface area are reduced as gravity increases. A correlation with a theoretical model gives good agreement. Both diffusion and premixed flames oscillate vertically, at low frequency (of the order of about 10 Hz), if the flame height is sufficiently tall. This mechanism is created in the burned gas layer surrounding the flame, where buoyancy exerts an influence. The results show that the frequency increases with gravity intensity. The last part of the paper is devoted to the evaluation of the flow deflection in the burnt gases under the action of Coriolis force.

Durox, D.; Yuan, T.; Baillot, F. [Laboratoire d`Aerothermique du CNRS, Meudon (France)] [Laboratoire d`Aerothermique du CNRS, Meudon (France); Most, J.M. [Universite de Poitiers, Mignaloux-Beauvoir (France)] [Universite de Poitiers, Mignaloux-Beauvoir (France)

1995-09-01

130

Centrifuge workers study. Phase II, completion report  

SciTech Connect

Phase II of the Centrifuge Workers Study was a follow-up to the Phase I efforts. The Phase I results had indicated a higher risk than expected among centrifuge workers for developing bladder cancer when compared with the risk in the general population for developing this same type of cancer. However, no specific agent could be identified as the causative agent for these bladder cancers. As the Phase II Report states, Phase I had been limited to workers who had the greatest potential for exposure to substances used in the centrifuge process. Phase II was designed to expand the survey to evaluate the health of all employees who had ever worked in Centrifuge Program Departments 1330-1339 but who had not been interviewed in Phase I. Employees in analytical laboratories and maintenance departments who provided support services for the Centrifuge Program were also included in Phase II. In December 1989, the Oak Ridge Associated Universities (ORAU), now known as Oak Ridge Institute for Science and Education (ORISE), was contracted to conduct a follow-up study (Phase II). Phase H of the Centrifuge Workers Study expanded the survey to include all former centrifuge workers who were not included in Phase I. ORISE was chosen because they had performed the Phase I tasks and summarized the corresponding survey data therefrom.

Wooten, H.D.

1994-09-01

131

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

132

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

133

Second order fluid dynamics for the unitary Fermi gas from kinetic theory  

E-print Network

We compute second order transport coefficients of the dilute Fermi gas at unitarity. The calculation is based on kinetic theory and the Boltzmann equation at second order in the Knudsen expansion. The second order transport coefficients describe the shear stress relaxation time, non-linear terms in the strain-stress relation, and non-linear couplings between vorticity and strain. An exact calculation in the dilute limit gives $\\tau_R=\\eta/P$, where $\\tau_R$ is the shear stress relaxation time, $\\eta$ is the shear viscosity, and $P$ is pressure. This relation is identical to the result obtained using the Bhatnagar-Gross-Krook (BGK) approximation to the collision term, but other transport coefficients are sensitive to the exact collision integral.

Thomas Schaefer

2014-04-28

134

Second order fluid dynamics for the unitary Fermi gas from kinetic theory  

E-print Network

We compute second order transport coefficients of the dilute Fermi gas at unitarity. The calculation is based on kinetic theory and the Boltzmann equation at second order in the Knudsen expansion. The second order transport coefficients describe the shear stress relaxation time, non-linear terms in the strain-stress relation, and non-linear couplings between vorticity and strain. An exact calculation in the dilute limit gives $\\tau_R=\\eta/P$, where $\\tau_R$ is the shear stress relaxation time, $\\eta$ is the shear viscosity, and $P$ is pressure. This relation is identical to the result obtained using the Bhatnagar-Gross-Krook (BGK) approximation to the collision term, but other transport coefficients are sensitive to the exact collision integral.

Schaefer, Thomas

2014-01-01

135

A discrete theory for ion-molecule cluster formation in the gas phase  

NASA Astrophysics Data System (ADS)

A theory was developed to treat the formation of ion-molecule clusters in the gas phase as a discrete process and it includes ion-dipole and dipole-dipole interactions as a basis for depicting the electrostatic force between the central ion and the clustering molecules. All the energy of the interactions is summed over the total number of clustering molecules around a central ion. The total free energy of cluster formation is comprised of the electrostatic energy of the cluster formation, the free energy of vaporization of the condensing molecules, and the work done in changing the surface area through condensation of additional molecules about each ion cluster. A minimum in the total free energy with respect to the number of neutral molecules corresponds to the most stable ion-molecule cluster. Comparison between the theoretical predictions and experimental observations for both stable and radioactive ion clusters showed good agreement.

Gong, S. L.; Jervis, R. E.

1995-10-01

136

Second-order fluid dynamics for the unitary Fermi gas from kinetic theory  

NASA Astrophysics Data System (ADS)

We compute second-order transport coefficients of the dilute Fermi gas at unitarity. The calculation is based on kinetic theory and the Boltzmann equation at second order in the Knudsen expansion. The second-order transport coefficients describe the shear stress relaxation time, nonlinear terms in the strain-stress relation, and nonlinear couplings between vorticity and strain. An exact calculation in the dilute limit gives ?R=? /P , where ?R is the shear stress relaxation time, ? is the shear viscosity, and P is pressure. This relation is identical to the result obtained using the Bhatnagar-Gross-Krook approximation to the collision term, but other transport coefficients are sensitive to the exact collision integral.

Schäfer, Thomas

2014-10-01

137

New concepts in energy recovery: using improved centrifugal compressor technology  

SciTech Connect

The proven process recovery system discussed in this paper is applicable to many large hot gas or liquid streams. Applications for this technology exist in the chemical, paper and food industries. In general, the cost of steam produced by the process recovery system is much less than boiler produced steam, especially in oil-fired boiler applications. With the ever-changing energy picture this process recovery system offers a cost effective energy conservation alternative. The centrifugal compressor technology is directly applicable to a variety of related services where vapor recompression of other gases is economically attractive.

Snyder, C.R.

1983-11-01

138

Plasma Limiter Studies at the Maryland Centrifugal Experiment  

NASA Astrophysics Data System (ADS)

An annular limiter experiment is being designed and constructed at the Maryland Centrifugal Experiment (MCX). This experiment has been motivated by the improved performance of the Gas Dynamic Trap using a biased limiter to induce vortex flows [A. A. Ivanov, et al. paper IAEA-CN-94/EX/P5-12 at Conference ``Fusion Energy-2002'']. The limiter may be biased with respect to the MCX vacuum vessel to attempt control over the radial electric field at the plasma edge. Measurements of the radial electric field in the edge region are planned using a Langmuir probe. Early results on the limiter's effects on MCX's performance will be reported.

Reid, R. R.; Young, W. C.; Romero-Talamas, C. A.; Taylor, G.; Ellis, R. F.; Hassam, A. B.

2010-11-01

139

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

140

Improved return passages for multistage centrifugal compressors  

E-print Network

This thesis presents a design concept for return passages in multistage centrifugal compressors. Flow in a baseline return passage is analyzed to identify loss sources that have substantial potential for reduction. For the ...

Glass, Benjamin W., S.M. Massachusetts Institute of Technology

2010-01-01

141

A methodology for centrifugal compressor stability prediction  

E-print Network

The stable operation of centrifugal compressors is limited by well-known phenomena, rotating stall and surge. Although the manifestation of the full scale instabilities is similar to the ones observed in axial machines, ...

Benneke, Björn

2009-01-01

142

Application of Centrifugal Elutriation for aqueous suspension  

E-print Network

Centrifugal Elutriation, a counter-flow separation method commonly used in the medical field to fractionate cells, was applied in the dynamic sorption and desorption studies for pentachlorophenol (PCP) associated with biotic (Chlorella pyrenoidosa...

Ayers, Jeffrey Thomas

2012-06-07

143

21 CFR 864.5350 - Microsedimentation centrifuge.  

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Automated and Semi-Automated Hematology Devices § 864.5350 Microsedimentation centrifuge. (a)...

2014-04-01

144

21 CFR 864.5350 - Microsedimentation centrifuge.  

Code of Federal Regulations, 2012 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Automated and Semi-Automated Hematology Devices § 864.5350 Microsedimentation centrifuge. (a)...

2012-04-01

145

21 CFR 864.5350 - Microsedimentation centrifuge.  

Code of Federal Regulations, 2013 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Automated and Semi-Automated Hematology Devices § 864.5350 Microsedimentation centrifuge. (a)...

2013-04-01

146

Kinetic theory for a mobile impurity in a degenerate Tonks-Girardeau gas  

NASA Astrophysics Data System (ADS)

A kinetic theory describing the motion of an impurity particle in a degenerate Tonks-Girardeau gas is presented. The theory is based on the one-dimensional Boltzmann equation. An iterative procedure for solving this equation is proposed, leading to the exact solution in a number of special cases and to an approximate solution with the explicitly specified precision in a general case. Previously we reported that the impurity reaches a nonthermal steady state, characterized by an impurity momentum p? depending on its initial momentum p0 [E. Burovski, V. Cheianov, O. Gamayun, and O. Lychkovskiy, Phys. Rev. A 89, 041601(R) (2014), 10.1103/PhysRevA.89.041601]. In the present paper the detailed derivation of p?(p0) is provided. We also study the motion of an impurity under the action of a constant force F. It is demonstrated that if the impurity is heavier than the host particles, mi>mh, damped oscillations of the impurity momentum develop, while in the opposite case, mi

Gamayun, O.; Lychkovskiy, O.; Cheianov, V.

2014-09-01

147

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

148

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

149

Isolation of symbiotic dinoflagellates by centrifugal elutriation  

SciTech Connect

Centrifugal elutriation, a method combining centripetal liquid flow with centrifugal force, has been used to isolate symbiotic dinoflagellates from a cnidarian host. The elutriated cells were shown to be viable by photosynthetic incorporation of /sup 14/CO/sub 2/ and low release of photosynthetic products into the incubation medium. The level of contamination by clinging debris was low and by host solids was negligible.

Bird, A.E.; Quinn, R.J.

1986-01-01

150

Radial oscillation of a gas bubble in a fluid as a problem in canonical perturbation theory  

NASA Astrophysics Data System (ADS)

The oscillation of a gas bubble is in a fluid is of interest in many areas of physics and technology. Lord Rayleigh treated the pressure developed in the collapse of cavitation bubbles and developed an expression for the collapse period. Minnaert developed a harmonic oscillator approximation to bubble oscillation in his study of the sound produced by running water. Oscillating bubbles are important to oceanographers studying the sound spectrum produced by water waves, geophysicists employing air guns as acoustic probes, mechanical engineers concerned with erosion of turbine blades, and military engineers concerned with the acoustic signatures developed by the propeller screws of ships and submarines. For the oceanographer, Minnaert's approximation is useful, for the latter two examples, Lord Rayleigh's analysis is appropriate. On the one hand, a bubble can be treated as a harmonic oscillator in the small amplitude regime, whereas even in the relatively moderate pressure regime characteristic of air guns the oscillation is strongly nonlinear and amplitude dependent. Is it possible to develop an analytic approximation that affords insight into the behavior of a bubble beyond the harmonic approximation of Minnaert? In this spirit, the free radial oscillation of a gas bubble in a fluid is treated as a problem in canonical perturbation theory. Several orders of the expansion are determined in order to explore the dependence of the oscillation frequency with bubble amplitude. The expansion to second order is inverted to express the time dependence of the oscillation.

Stephens, James

2005-11-01

151

Magnetocentrifugal separation of particulates: Theory and principles of operation  

Microsoft Academic Search

The theory and principles of operation of the new magnetocentrifugal separation are formulated. Magnetic and centrifugal g numbers for monodisperse and polydisperse particulates are defined. It is shown that the magnitude of electromagnetic and centrifugal forces can be matched in the full scale of centrifugal fields available to date. Magnetocentrifugal separation can be applied to separation of particulates down to

Yoram Zimmels

1986-01-01

152

Design and experimental study of high-speed low-flow-rate centrifugal compressors  

SciTech Connect

This paper describes a design and experimental effort to develop small centrifugal compressors for aircraft air cycle cooling systems and small vapor compression refrigeration systems (20--100 tons). Efficiency improvements at 25% are desired over current designs. Although centrifugal compressors possess excellent performance at high flow rates, low-flow-rate compressors do not have acceptable performance when designed using current approaches. The new compressors must be designed to operate at a high rotating speed to retain efficiency. The emergence of the magnetic bearing provides the possibility of developing such compressors that run at speeds several times higher than current dominating speeds. Several low-flow-rate centrifugal compressors, featured with three-dimensional blades, have been designed, manufactured and tested in this study. An experimental investigation of compressor flow characteristics and efficiency has been conducted to explore a theory for mini-centrifugal compressors. The effects of the overall impeller configuration, number of blades, and the rotational speed on compressor flow curve and efficiency have been studied. Efficiencies as high as 84% were obtained. The experimental results indicate that the current theory can still be used as a guide, but further development for the design of mini-centrifugal compressors is required.

Gui, F.; Reinarts, T.R.; Scaringe, R.P. [Mainstream Engineering Corp., Rockledge, FL (United States); Gottschlich, J.M. [Air Force Wright Lab., Wright Patterson AFB, OH (United States)

1995-12-31

153

Experiment and Theory for the Thickness Effect of Nano Metal Oxide Gas Sensing Thin Film The Thickness Effect and Mesoscopic Theory of Conductance Activity Energy  

Microsoft Academic Search

The characteristics of conductance activity energy of SnO2 thin film varies with film thickness l and grain size r0 are given by experiment results. The cross-section current formula of porous materials and the conductance formula of gas sensing thin film with adsorbed oxygen negative ion are given. The mesoscopic theory of nano-thin film conductance activity energy was proposed, and using

Xing Jianping; Yuan Qinghua; Li Donghua; Lu Honglang; Qiu Nanwan

2006-01-01

154

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

155

The 'Jack Stone' or 'Mercedes Benz' sign--anew theory to explain the presence of gas within fissures in gallstones.  

PubMed

Gas within clefts of fissures in gallstones is not a very common finding, but when it occurs is, characteristic and indicates the presence of one or more calculi. It closely resembles the appearance of a 'Jack Stone' but has previously been termed the 'Mercedes Benz' sign. Only a few cases have previously been recognised in the U.K. Most reported cases have been associated with biliary colic or cholecystitis. Various theories have been put forward to explain the presence of gas, but the author believes that the gas is released from solution by negative pressure within cholesterol stones undergoing internal fissuring due to their crystalline structure, i.e. the gas is released from solution from the small amount of fluid trapped in the calculus, in the same way that gas may be 'pulled' out of solution in a joint, a degenerate intervertebral disc or the fibro-cartilage of the symphysis pubis. PMID:872516

Wright, F W

1977-07-01

156

Nonlinear Effects in Optical Pumping of Atoms by a High-Intensity Multimode Gas Laser. General Theory  

Microsoft Academic Search

The optical pumping of atoms by a multimode gas laser, in the presence of a magnetic field, is studied theoretically. The atoms are described by their density matrix, which is expanded on an irreducible tensorial set. The atomic relaxation is assumed to be isotropic. In order to avoid the usual perturbation theory, we use the so-called \\

Martial Ducloy

1973-01-01

157

Mechanisms of flow through compressible porous beds in sedimentation, centrifugation, deliquoring, and ceramic processing  

SciTech Connect

The major topics covered in the investigation include: centrifugation; cake filtration; sedimentation and thickening; capillary suction operations; ceramics, slip casting; optimization studies; and wastewater. The research program was aimed at the specific areas of solid/liquid separation including sedimentation, thickening, cake filtration, centrifugation, expression, washing, deep-bed filtration, screening, and membrane separation. Unification of the theoretical approaches to the various solid/liquid separation operations was the principle objective of the research. Exploring new aspects of basic separation mechanisms, verification of theory with experiment, development of laboratory procedures for obtaining data for design, optimizing operational methods, and transferring the results to industry were part of the program.

NONE

1996-01-25

158

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

159

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

160

Radial oscillation of a gas bubble in a fluid as a problem in canonical perturbation theory  

NASA Astrophysics Data System (ADS)

The oscillation of a gas bubble is in a fluid is of interest in many areas of physics and technology. Lord Rayleigh treated the pressure developed in the collapse of cavitation bubbles and developed an expression for the collapse period. Minnaert developed a harmonic oscillator approximation to bubble oscillation in his study of the sound produced by running water. Besides recent interest in bubble oscillation in connection to sonoluminescence, an understanding of oscillating bubbles is of important to oceanographers studying the sound spectrum produced by water waves, geophysicists employing air guns as acoustic probes, mechanical engineers concerned with erosion of turbine blades, and military engineers concerned with the acoustic signatures developed by the propeller screws of ships and submarines. For the oceanographer, Minnaert's approximation is useful, for the latter two examples, Lord Rayleigh's analysis is appropriate. For the case of the airgun, a period of twice Rayleigh's period for the ``total collapse'' of the cavitation bubble is often cited as a good approximation for the period of an air bubble ejected from an air gun port, typically at ˜2000 psi), however for the geophysical example, numerical integration is employed from the outset to determine the dynamics of the bubble and the emitted acoustic energy. On the one hand, a bubble can be treated as a harmonic oscillator in the small amplitude regime, whereas even in the relatively moderate pressure regime characteristic of air guns the oscillation is strongly nonlinear and amplitude dependent. Is it possible to develop an analytic approximation that affords insight into the behavior of a bubble beyond the harmonic approximation of Minnaert? In this spirit, the free radial oscillation of a gas bubble in a fluid is treated as a problem in canonical perturbation theory. Several orders of the expansion are determined in order to explore the dependence of the oscillation frequency with bubble amplitude. The expansion to second order is inverted to express the time dependence of the oscillation.

Stephens, James

2006-11-01

161

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

162

Spray generator of singlet oxygen with a centrifugal separation of liquid  

NASA Astrophysics Data System (ADS)

A new spray-type generator of singlet oxygen, O2(1?), with a following centrifugal separation of depleted liquid was studied. This generator was developed to fulfill following requirements suitable for an advanced Chemical Oxygen- Iodine Laser (COIL): (i) a high-pressure operation, (ii) a single pass of reaction liquid, (iii) an efficient disengagement of gas/liquid mixture, and (iv) a scalability for airborne and mobile application. The generator design takes advantage of very high g/l interfacial surface area of a fine spray produced by a two-phase nozzle and a very fast liquid separation by applying a high centrifugal force.

Špalek, Otomar; Jirásek, Vít; Censký, Miroslav; Kodymová, Jarmila; Picková, Irena

2008-10-01

163

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

SciTech Connect

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 is responsible for all unusual critical phenomena of the BEC phase transition in the ideal gas. The main result is an analytical solution to the problem of critical phenomena. It is derived by, first, calculating analytically the universal probability distribution of the noncondensate occupation, or a Landau function, and then using it for the analytical calculation of the universal functions for the particular physical quantities via the exact formulas which express the constraint-cutoff mechanism. We find asymptotics of that analytical solution as well as its simple analytical approximations which describe the universal structure of the critical region in terms of the parabolic cylinder or confluent hypergeometric functions. The obtained results for the order parameter, all higher-order moments of BEC fluctuations, and thermodynamic quantities perfectly match the known asymptotics outside the critical region for both low and high temperature limits. We suggest two- and three-level trap models of BEC and find their exact solutions in terms of the cutoff negative binomial distribution (which tends to the cutoff gamma distribution in the continuous limit) and the confluent hypergeometric distribution, respectively. Also, we present an exactly solvable cutoff Gaussian model of BEC in a degenerate interacting gas. All these exact solutions confirm the universality and constraint-cutoff origin of the strongly non-Gaussian BEC statistics. We introduce a regular refinement scheme for the condensate statistics approximations on the basis of the infrared universality of higher-order cumulants and the method of superposition and show how to model BEC statistics in the actual traps. In particular, we find that the three-level trap model with matching the first four or five cumulants is enough to yield remarkably accurate results for all interesting quantities in the whole critical region. We derive an exact multinomial expansion for the noncondensate occupation probability distribution and find its high-temperature asymptotics (Poisson distribution) and corrections to it. Finally, we demonstrate that the critical exponents and a few known terms of the Taylor expansion of the universal functions, which were calculated previously from fitting the finite-size simulations within the phenomenological renormalization-group theory, can be easily obtained from the presented full analytical solutions for the mesoscopic BEC as certain approximations in the close vicinity of the critical point.

Kocharovsky, Vitaly V. [Department of Physics, Texas A and M University, College Station, Texas 77843-4242 (United States); Institute of Applied Physics, Russian Academy of Science, RU-603950 Nizhny Novgorod (Russian Federation); Kocharovsky, Vladimir V. [Institute of Applied Physics, Russian Academy of Science, RU-603950 Nizhny Novgorod (Russian Federation)

2010-03-15

164

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

165

26. RW Meyer Sugar Mill: 18761889. Centrifugals, 1879, 1881. Manufacturer, ...  

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

26. RW Meyer Sugar Mill: 1876-1889. Centrifugals, 1879, 1881. Manufacturer, unknown. Supplied by Honolulu Ironworks, Honolulu, Hawaii, 1879, 1881. View: Historical view, 1934, from T. T. Waterman collection, Hawaiian Sugar Planters' Association. Once the molasses was separated from the sugar crystals it flowed through the spouts in the base of the centrifugals. The centrifugals' pulleys can be seen underneath the centrifugal. The centrifugal on the right has been reinforced with seven metal bands. The handles for the clutch mechanism are located above the centrifugal. - R. W. Meyer Sugar Mill, State Route 47, Kualapuu, Maui County, HI

166

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

167

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

168

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

169

Simulation of Fluid Flow in Centrifugal Tricanter  

NASA Astrophysics Data System (ADS)

An ANSYS simulation of the multiphase complex fluid flow motion in a centrifugal device (tricanter) is presented in the paper. This centrifugal device is designed for one step efficient solution for contaminated river water processing with oil and oil products. The proposed tricanter is one of the main objectives of the project named "Common strategy to prevent the Danube's pollution technological risks with oil and oil products CLEANDANUBE" financed by European Commission within the frame of Romania-Bulgaria Trans-Border Cooperation Program 2007 - 2013 (grant MIS-ETC code 653). Results for liquid phases (water and oil products) and for solid particles motion are presented graphically and are commented.

Puscasu, Cristian; Grigorescu, Mihaela; Axene, Ghita; Voicu, Raluca; Stefanescu, Mariana; Teleaba, Victoria; Zheleva, Ivanka

2013-06-01

170

Transport Phenomena in Zonal Centrifuge Rotors  

PubMed Central

An analysis is presented for the evaluation of velocity components and shear-stress distributions of fluid in zonal centrifuge rotors during acceleration. Analytical expressions for the distribution of tangential and radial velocity components and the tangential shear-stress and the radial shear-stress distributions of fluid are obtained for the transient case. Characteristics of each distribution for a typical density gradient liquid in a zonal centrifuge rotor are computed from the relations derived, and are presented as figures. An unusual phenomenon—the tangential velocity of the gradient exceeding the velocity of the rotor during a particular period of acceleration—is demonstrated. PMID:5678322

Hsu, H. W.

1968-01-01

171

Centrifuge modeling of coal tailing embankments  

SciTech Connect

Centrifuge model studies were conducted on eight homogeneous dams with 1.75:1 slopes using coal tailings (waste coal, shale, fine sand, silt, and clay) to obtain experience on the behavior of this low-strength material in a laboratory setting and, further, to examine the accuracy of predictions of embankment failure by the simplified Bishop limit equilibrium method. The failure of four of the model embankments simulated typical features of slope failures observed in the field. Centrifuge modeling verified that the simplified Bishop method using standard measurements of soil strength properly indexed the dam safety but did not accurately locate the embankment failure surface. 20 refs.

Rechard, R.P.; Sutherland, H.J.; Heckes, A.A.

1986-03-01

172

Wave-Driven Rotation In Centrifugal Mirrors  

SciTech Connect

Centrifugal mirrors use supersonic rotation to provide axial confinement and enhanced stability. Usually the rotation is produced using electrodes, but these electrodes have limited the rotation to the Alfven critical ionization velocity, which is too slow to be useful for fusion. Instead, the rotation could be produced using radio frequency waves. A fixed azimuthal ripple is a simple and efficient wave that could produce rotation by harnessing alpha particle energy. This is an extension of the alpha channeling effect. The alpha particle power and efficiency in a simulated devices is sufficient to produce rotation without external energy input. By eliminating the need for electrodes, this opens new opportunities for centrifugal traps.

Abraham J. Fetterman and Nathaniel J. Fisch

2011-03-28

173

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

NASA Astrophysics Data System (ADS)

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 formation of both terrestrial and giant planets has improved significantly due to new computing techniques and the continued exponential increase in computing power. In this dissertation I expand on existing theories of terrestrial planet formation to include systems similar to those currently being detected around nearby stars, and I develop new observational techniques to probe the chemistry of gas-rich circumstellar disks where such planetary systems may be forming. One of the most significant characteristics of observed extrasolar planetary systems is the presence of giant planets located much closer to their parent star than was thought to be possible. The presence of "Hot Jupiters", Jovian-mass planets with very short orbital periods detected around nearby main sequence stars, has been proposed to be primarily due to the inward migration of planets formed in orbits initially much further from the parent star. Close-in giant planets are thought to have formed in the cold outer regions of planetary systems and migrated inward, passing through the orbital parameter space occupied by the terrestrial planets in our own Solar System; the migration of these planets would have profound effects on the evolution of inner terrestrial planets in these systems. I first explore this scenario with numerical simulations showing that a significant fraction of terrestrial planets could survive the migration process; damping forces could then eventually re-circularize the orbits at distances relatively close to their original positions. Calculations suggest that the final orbits of a significant fraction of the remaining planets would be located in the Habitable Zone, suggesting that planetary systems with close-in giant planets are viable targets for searches for Earth-like habitable planets around other stars. I then present more realistic dynamical simulations of the effects of a migrating giant planet on a disk of protoplanetary material embedded in a gaseous disk, and the subsequent post-scattering evolution of the planetary system. I numerically investigate the dynamics of several types of post-migration planetary systems over 200 million years: a model with a single migrating giant planet, a model with one migrating and one nonmigrating giant planet, and a model excluding the effects of the gas disk. Material that is shepherded in front of the migrating giant planet by moving mean motion resonances accretes into "hot Earths", but survival of these bodies is strongly dependent on dynamical damping. Furthermore, a significant amount of material scattered outward by the giant planet survives in highly excited orbits; the orbits of these scattered bodies are then damped by gas drag and dynamical friction over the remaining accretion time. In all simulations Earth-mass planets accrete on approximately 100 Myr timescales, often with orbits in the Habitable Zone. These planets range in mass and water content, with both quantities increasing with the presence of a gas disk and decreasing with the presence of an outer giant planet. I use scaling arguments and previous results to derive a simple recipe that constrains which giant planet systems are able to form and harbor Earth-like planets in the Habitable Zone, demonstrating that roughly one third of the known planetary systems are potentially habitable. Finally, I present results from a search for new molecular tracers of warm gas in circumstellar disks using the NIRSPEC instrument on the Keck II telescope. I have detected emission from multiple ro-vibrational transitions in the v = 1--0 band of hydroxyl (OH) located in the inner circumstellar regions of two Herbig Ae stars, AB Aurigae and MWC 7

Mandell, Avram M.

174

Drift theory of a dense gas interacting with walls in the presence of velocity selective excitation  

NASA Astrophysics Data System (ADS)

The drift of a dense gas in a cuvette, which is larger than the mean free path, is considered. Drift arises from the difference in the velocity of excited and unexcited particles in the gas. The drift velocity of the gas is calculated, together with the decrease in the concentration of the resonance component. It is shown that the mean free path of the gas becomes much smaller than the vessel when the dense transition is made from a rarefied gas to a dense gas. The feasibility of an experiment to observe the drift phenomenon is assessed.

Vaksman, M. A.; Gainer, A. V.

1985-07-01

175

Aerodynamic performance of centrifugal compressors  

SciTech Connect

Saving money with an efficient pipeline system design depends on accurately predicting compressor performance and ensuring that it meets the manufacturer's guaranteed levels. When shop testing with the actual gas is impractical, an aerodynamic test can ascertain compressor efficiency, but the accuracy and consistency of data acquisition in such tests is critical. Low test-pressure levels necessitate accounting for the effects of Reynolds number and heat transfer. Moreover, the compressor user and manufacturer must agree on the magnitude of the corrections to be applied to the test data.

Sayyed, S.

1981-12-01

176

Development of a body force model for centrifugal compressors  

E-print Network

This project is focused on modeling the internal ow in centrifugal compressors for the purpose of assessing the onset of rotating stall and surge. The current methods to determine centrifugal compressor stability limits ...

Kottapalli, Anjaney Pramod

2013-01-01

177

A parametric study of vestibular stimulation during centrifugation  

E-print Network

Artificial Gravity (AG) provided by short-radius centrifugation is a promising countermeasure to the health problems associated with long duration human spaceflight. Head-turns performed during centrifugation, however, ...

Pouly, Jeremie M

2006-01-01

178

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

179

Quasiclassical Theory of Shubnikov-de Haas Effect in 2D Electron Gas  

NASA Astrophysics Data System (ADS)

A new approach to the theory of magneto-transport in 2D gas is developed. We make use of Keldysh technique and introduce a modified Green's function which is translationally invariant and gauge invariant. The modification simplifies the calculation of diagrams and allows us to obtain a new helpful addition theorem for the electron wave functions in magnetic field. The modified Green's function is very convenient to follow the transition between quantum magnetic transport and transport in zero magnetic field. For the calculation of conductivity we use the self-consistent Born approximation (SCBA). We carefully check its validity and figure out the physical meaning of the corresponding conditions. All specific calculations are made for the case when the separation between Landau levels, ??, is much smaller than the Fermi energy, without limiting the magnitude of ?? relative to the width of the levels (induced by scattering), ?. For the first time the case of a long-range scattering potential is carefully studied. We study magneto-oscillation effects with the help of an evolution equation for the Green's function. In this equation two relaxation times, the single particle relaxation time and the transport relaxation time, naturally come about. Analytical results for the conductivity tensor are obtained for both the Shubnikov-de Haas effect, when ?? ? ?, and the quantum Hall regime, ?? ? ?. In the latter the temperature dependence of the conductivity depends on the relation between the temperature, ??, and ?. Although SCBA does not describe localization, it, however, allows one to separate the Shubnikov-de Haas effect from the quantum Hall effect.

Laikhtman, B.; Altshuler, E. L.

1994-06-01

180

Nonsynchronous forced vibration in centrifugal compressors  

Microsoft Academic Search

Flow instabilities in centrifugal compressors produce low-frequency turbulence and pulsations, resulting in nonsynchronous rotor vibrations, vibrations of the case and attached piping, speed modulations, and reduced compressor performance. High-frequency pulsations in rotating equipment typically occur at multiples of running speed such as blade, diffuser, and nozzle passing frequencies and can excite blade natural frequencies and radial shell wall resonances. The

D. R. Smith; J. C. Wachel

2009-01-01

181

Differential white cell count by centrifugal microfluidics.  

SciTech Connect

We present a method for counting white blood cells that is uniquely compatible with centrifugation based microfluidics. Blood is deposited on top of one or more layers of density media within a microfluidic disk. Spinning the disk causes the cell populations within whole blood to settle through the media, reaching an equilibrium based on the density of each cell type. Separation and fluorescence measurement of cell types stained with a DNA dye is demonstrated using this technique. The integrated signal from bands of fluorescent microspheres is shown to be proportional to their initial concentration in suspension. Among the current generation of medical diagnostics are devices based on the principle of centrifuging a CD sized disk functionalized with microfluidics. These portable 'lab on a disk' devices are capable of conducting multiple assays directly from a blood sample, embodied by platforms developed by Gyros, Samsung, and Abaxis. [1,2] However, no centrifugal platform to date includes a differential white blood cell count, which is an important metric complimentary to diagnostic assays. Measuring the differential white blood cell count (the relative fraction of granulocytes, lymphocytes, and monocytes) is a standard medical diagnostic technique useful for identifying sepsis, leukemia, AIDS, radiation exposure, and a host of other conditions that affect the immune system. Several methods exist for measuring the relative white blood cell count including flow cytometry, electrical impedance, and visual identification from a stained drop of blood under a microscope. However, none of these methods is easily incorporated into a centrifugal microfluidic diagnostic platform.

Sommer, Gregory Jon; Tentori, Augusto M.; Schaff, Ulrich Y.

2010-07-01

182

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...

183

Electrodiffusional flow diagnostics in a centrifugal pump  

Microsoft Academic Search

This paper presents electrodiffusional measurements of the wall shear rate at the impeller surface of a radial centrifugal pump. Twelve probes of different radii and at different positions along one blade were used in a pump with an open six bladed impeller. By means of throttling and speed control the operating point of the pump was adjusted and the influence

M. Lutz; V. Denk; K. Wichterle; V. Sobolik

1998-01-01

184

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...

185

World Centrifugal Sugar Situation and Outlook.  

National Technical Information Service (NTIS)

World centrifugal sugar production for 1983/84 is estimated at 94.7 million metric tons (raw value), down 6% from the near-record production of the previous season but virtually unchanged from the Nov 1983 estimate. The decline reflects adverse growing co...

1984-01-01

186

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

187

Flow Pattern Characterization for a Centrifugal Impeller  

NASA Astrophysics Data System (ADS)

This paper proposes a model for characterizing the flow pattern of a centrifugal impeller attending to the severity of the reverse flow. The model assumes 1) a definition of an escaping particle as the one that flows in every operational point from the trailing edge towards the leading edge of the impeller blades, and 2) a characterization of flow where an operational point is said to have a theoretical flow pattern if it is not possible to establish a fully-reversed escaping particle on it. Therefore, the first part of the article is focused on defining an escaping particle for a centrifugal compressor. The model locates over the map of a centrifugal impeller the line that splits the map in two regions: the region on the right hand side, where a theoretical flow pattern can exist, and the region on the left, where a theoretical flow pattern cannot exist. Therefore, the locus of this line marks a frontier where the expected performance of the impeller cannot be sustained as high as expected. The second part of the article uses a high-performance commercial centrifugal impeller wheel for contrasting the model. A qualitative characterization of the surge line, conclusions and discussions are presented.

Benavides, Efrén M.

2014-08-01

188

Theory versus experiment for the rotordynamic coefficients of annular gas seals. Part 2: Constant clearance and convergent-tapered geometry  

NASA Technical Reports Server (NTRS)

The leakage and rotordynamic coefficients of constant-clearance and convergent-tapered annular gas seals were measured in an experimental test facility. The results are presented along with the theoretically predicted values. Of particular interest is the prediction that optimally tapered seals have significantly larger direct siffness than straight seals. The experimental results verify this prediction. Generally the theory does quite well, but fails to predict the large increase in direct stiffness when the fluid is pre-rotated.

Nelson, C. C.; Childs, D. W.; Nicks, C.; Elrod, D.

1985-01-01

189

Theory versus experiment for the rotordynamic coefficients of annular gas seals. II - Constant-clearance and convergent-tapered geometry  

NASA Technical Reports Server (NTRS)

The leakage and rotordynamic coefficients of constant-clearance and convergent-tapered annular gas seals were measured in an experimental test facility. The results are presented along with the theoretically predicted values. Of particular interest is the prediction that optimally tapered seals have significantly larger direct stiffness than straight seals. The experimental results verify this prediction. Generally the theory does quite well, but fails to predict the large increase in direct stiffness when the fluid is pre-rotated.

Nelson, C. C.; Childs, D. W.; Nicks, C.; Elrod, D.

1985-01-01

190

Application of convolution theory for solving non-linear flow problems: gas flow systems  

E-print Network

Decline Rate Integral and Integral-Derivative Versus Dimensionless Decline Time Using Semi-Empirical Real Gas Solution for Constant Pressure Production Case . . ill X tv LIST OF TABLES TABLE 3. 1 Gas and Reservoir Parameters, and the Ranges Studied... Decline Rate Integral and Integral-Derivative Versus Dimensionless Decline Time Using Semi-Empirical Real Gas Solution for Constant Pressure Production Case . . ill X tv LIST OF TABLES TABLE 3. 1 Gas and Reservoir Parameters, and the Ranges Studied...

Mireles, Thomas Joseph

2012-06-07

191

Hydraulic design, numerical simulation and BVF diagnosis of high efficiency centrifugal pump  

NASA Astrophysics Data System (ADS)

Under the Two-dimensional Flow Theory and the Velocity Coefficient Theory, a centrifugal-pump impeller has been designed, based on the parameters of IS150-125-250 centrifugal pump. And self-compiled programs have been used to complete the hydraulic design of the whole flow passage of centrifugal pump. The space bending and twisting characteristics of the design blade are more obvious. Then, numerical simulation is applied to the inner flow field of the two pumps using RANS (Reynolds Averaged N-S) Equation with a standard k-? two-equation turbulence model. The compare of the numerical simulation data of two centrifugal pumps, getting from 13 working points including design condition, shows that, the design pump has higher head and efficiency in the range of lower flow rate. Based on the numerical results of the inner flow of the design pump and model pump, the boundary vorticity flux (BVF) diagnostics has been used to analyze the BVF distribution of suction surface and pressure surface of two pumps. The result shows that, the BVF distribution of the design pump is more uniform and smooth, with smaller peak value.

Zhang, Y. X.; Chen, L.; Zhou, X.; Jiangand, C. W.; Su, M.

2012-11-01

192

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

193

Drive torque actuation in active surge control of centrifugal compressors  

E-print Network

Drive torque actuation in active surge control of centrifugal compressors Jan Tommy Gravdahl , Olav to active surge control is presented for a centrifugal compressor driven by an electrical motor. The main compressor driven by an electrical motor. 1 Background Surge is an unstable operation mode of centrifugal

Gravdahl, Jan Tommy

194

Modeling for surge control of centrifugal compresssors: comparison with experiment  

E-print Network

con- trol design, of a centrifugal compression system is vali- dated. Compressor surge is an unwanted to centrifugal compressors. Since compressors are vari- able speed machines, and surge is commonly encoun- teredModeling for surge control of centrifugal compresssors: comparison with experiment Jan Tommy

Gravdahl, Jan Tommy

195

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

196

Interaction of liquid movement and steam condensation during steam centrifugation  

Microsoft Academic Search

Steam centrifugation is a mechanical thermal process that decreases the pore liquid in the porous medium by the help of centrifugal pressure and the pressure of injected steam. The steam is used in centrifuges to overcome the capillary forces, which retain the liquid in the lower area of the porous system. Both external forces affect the pore liquid in a

Urs A. Peuker

2005-01-01

197

COMPARISON OF FATIGUE BEHAVIOR FOR CENTRIFUGALLY CAST AND  

E-print Network

COMPARISON OF FATIGUE BEHAVIOR FOR CENTRIFUGALLY CAST AND KEEL BLOCK CAST STEEL J.J. Gradman1 , R The objective of this research was to determine if location through the wall thickness of centrifugal castings affects fatigue properties and to compare fatigue and monotonic tensile properties of centrifugal castings

Beckermann, Christoph

198

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  

NASA Astrophysics Data System (ADS)

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.

Edison, John R.; Monson, Peter A.

2014-07-01

199

Development of a high-specific-speed centrifugal compressor  

SciTech Connect

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 in the open literature. Stage and component test performance characteristics are presented together with traverse results at the impeller exit. Traverse test results were compared with recent CFD computational predictions for an exploratory analytical calibration of a very high-specific-speed impeller geometry. The tested subscale (0.583) compressor essentially satisfied design performance expectations with an overall stage efficiency of 74% including, excessive exit casing losses. It was estimated that stage efficiency could be increased to 81% with exit casing losses halved.

Rodgers, C.

1997-07-01

200

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

201

Partition Functions of Superconformal Chern-Simons Theories from Fermi Gas Approach  

E-print Network

We study the partition function of three-dimensional ${\\mathcal N}=4$ superconformal Chern-Simons theories of the circular quiver type, which is a natural generalization of the ABJM theory, the worldvolume theory of M2-branes. In the ABJM case, it was known that the perturbative part of the partition function is summed up to the Airy function $e^{A}C^{-1/3}\\mathrm{Ai}[C^{-1/3}(N-B)]$ with coefficients $C$, $B$ and $A$ and for the non-perturbative part the divergences coming from the coefficients of worldsheet instantons and membrane instantons cancel among themselves. We find that many of the interesting properties in the ABJM theory are extended to the general superconformal Chern-Simons theories. Especially, we find an explicit expression of $B$ for general ${\\mathcal N}=4$ theories, a conjectural formula of $A$ for a special class, and cancellation in the non-perturbative coefficients for the next-to-simplest theory aside from the ABJM theory.

Moriyama, Sanefumi

2014-01-01

202

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

203

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

204

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. PMID:21522503

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

2011-01-01

205

Wave-driven Countercurrent Plasma Centrifuge  

SciTech Connect

A method for driving rotation and a countercurrent flow in a fully ionized plasma centrifuge is described. The rotation is produced by radiofrequency waves near the cyclotron resonance. The wave energy is transferred into potential energy in a manner similar to the ? channeling effect. The countercurrent flow may also be driven by radiofrequency waves. By driving both the rotation and the flow pattern using waves instead of electrodes, physical and engineering issues may be avoided.

A.J. Fetterman and N.J. Fisch

2009-03-20

206

Centrifugal space-charge forces in SLC  

SciTech Connect

A preliminary estimate is made of the effect of the centrifugal space charge forces on SLC assuming that the space-charge effect is a highly nonlinear force whose important term is the second derivative at the beam center. A scaling law is used to get the horizontal chromaticity for the arcs of SLC, and the space-charge effect on the beam is calculated on that basis. (LEW)

Sands, M.

1986-04-14

207

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

208

Effects of scaling on centrifugal blood pumps.  

PubMed

Experimental studies on the effects of scaling on the performance of centrifugal blood pumps were conducted in a closed-loop test rig. For the prototype, eight different impellers of the same outer diameter of 25 mm were tested at 1,500, 2,000, and 2,500 revolutions per minute (rpm) using blood analog as fluid medium. This corresponds to Reynolds numbers (Re) of 25,900, 34,500, and 43,200, respectively. The results indicated that the nondimensional pump characteristic is a function of Re. This is understandable since the typical operating Re for centrifugal blood pumps is less than 100,000. Thus, the effects of scaling cannot be ignored for centrifugal blood pumps. Experiments on a 5x scaled-up model have also indicated that the scaled-up model is more efficient than the prototype model. Our results showed that in the range of Re tested, the nondimensional head versus flow curve is a function of Re to the power of approximately 0.25. It is observed that the nondimensional head versus flow is a function of diameter ratio to the power of 0.2. PMID:12406160

Wong, Yew Wah; Chan, Weng Kong; Yu, S C M; Chua, Leok Poh

2002-11-01

209

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

210

Stable isotope enrichment using a plasma centrifuge  

NASA Astrophysics Data System (ADS)

A primary goal of the Department of Energy's Isotope Development and Production for Research and Applications Program (Isotope Program) within the Office of Nuclear Physics (NP) is to produce isotopes that are in short supply in the U.S. and of which there exists no or insufficient domestic commercial production capability. A vacuum arc plasma centrifuge is a rigid rotor column of metal plasma in which centrifugal forces re-distribute ions radially according to their mass/charge ratio. Early work demonstrated rotation at 2 million rpm and separation of various stable isotopes. The spinning plasma column had a Gaussian flux profile, peaked on the rigid rotor axis. This work adopts a more efficient approach, with the plasma created as a hollow column, wherein the flux is concentrated at larger radii where the centrifugal action is highest. By tailoring the vacuum arc discharge geometry, the rotation rate can also be increased to ˜10 million rpm. Data from Cu, Al and other metal plasmas will be presented and discussed in light of enriched stable isotopes needed for research and medicine.

Krishnan, Mahadevan; Bures, Brian; Madden, Robert

2012-10-01

211

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

212

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

213

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

214

Effect of fluid forces on rotor stability of centrifugal compressors and pumps  

NASA Technical Reports Server (NTRS)

A simple two dimensional model for calculating the rotordynamic effects of the impeller force in centrifugal compressors and pumps is presented. It is based on potential flow theory with singularities. Equivalent stiffness and damping coefficients are calculated for a machine with a vaneless volute formed as a logarithmic spiral. It is shown that for certain operating conditions, the impeller force has a destablizing effect on the rotor.

Colding-Jorgensen, J.

1980-01-01

215

A renormalized Gross Pitaevskii theory and vortices in a strongly interacting Bose gas  

Microsoft Academic Search

We consider a strongly interacting Bose-Einstein condensate in a spherical harmonic trap. The system is treated by applying a slave-boson representation for hardcore bosons. A renormalized Gross-Pitaevskii theory is derived for the condensate wavefunction that describes the dilute regime (like the conventional Gross-Pitaevskii theory) as well as the dense regime. We calculate the condensate density of a rotating condensate for

Ch Moseley; K. Ziegler

2007-01-01

216

Hydraulic design and performance analysis of low specific speed centrifugal pump  

NASA Astrophysics Data System (ADS)

Since low specific speed centrifugal pump with long narrow flow divergent channels has positive slope of head-capacity characteristic curve, low flow rate instability and high flow rate power overload, special events about its hydraulic design are still under study. This paper demonstrates a method for hydraulic design of low specific speed centrifugal pump complex impeller (with splitter blades) which is based on 2D flow theory. In this method, obtain the basic geometry parameters by empirical correlation, adjust impeller profile according to given flow cross section area distribution and wrapping angles distribution, relate the position of splitter blades to slip factor. Based on this method, low specific speed centrifugal pump impellers have been designed using the same design parameters (Head, Capacity, Rotation Speed, etc) with different factors. And 3D turbulent flow fields in design pumps have been solved by using RANS equations with RNG k-epsilon turbulence model. The investigation to the effects of different splitter blades on velocity distributions and pressure distributions along the flow channels and hydraulic performance of centrifugal pumps are presented. The result shows that properly placed splitter blades by choosing suitable design factors will improve the flow in the pump and enhance the hydraulic performance of it.

Zhou, X.; Zhang, Y. X.; Ji, Z. L.; Chen, L.

2012-11-01

217

Spray generator of singlet oxygen with a centrifugal separation of liquid  

Microsoft Academic Search

A new spray-type generator of singlet oxygen, O2(1Delta), with a following centrifugal separation of depleted liquid was studied. This generator was developed to fulfill following requirements suitable for an advanced Chemical Oxygen- Iodine Laser (COIL): (i) a high-pressure operation, (ii) a single pass of reaction liquid, (iii) an efficient disengagement of gas\\/liquid mixture, and (iv) a scalability for airborne and

Otomar Spalek; Vít Jirásek; Miroslav Censký; Jarmila Kodymová; Irena Picková

2008-01-01

218

Average charge states of heavy and superheavy ions passing through a rarified gas: Theory and experiment  

NASA Astrophysics Data System (ADS)

The average charge states q¯ of heavy and superheavy ions (atomic numbers Z=80-114) passing through He gas are studied experimentally and theoretically. Experimental data were measured at the gas-filled recoil separator, i.e., the TransActinide Separator and Chemistry Apparatus (TASCA) at GSI Darmstadt, for ion energies of a few hundred keV/u at gas pressures of 0.2 to 2.0 mbar. An attempt is made to describe experimental q¯ values by means of atomic calculations of the binding energies and electron-loss and electron-capture cross sections. The influence of the gas-density effect is included in the calculations. The calculated q¯ reproduce the experimental values for elements with Z=80-114 within 20%. A comparison with different semiempirical models is presented as well, including a local fit of high accuracy, which is often used in superheavy-element experiments to estimate the average charge states of heavy ions, e.g., at the gas-filled recoil separator TASCA. The q¯ values for elements with Z=115, 117, 119, and 120 at He-gas pressure of 0.8 mbar are predicted.

Khuyagbaatar, J.; Shevelko, V. P.; Borschevsky, A.; Düllmann, Ch. E.; Tolstikhina, I. Yu.; Yakushev, A.

2013-10-01

219

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

220

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

221

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

222

Flowfield analysis of a backswept centrifugal impeller  

NASA Astrophysics Data System (ADS)

A time-dependent, three-dimensional Navier-Stokes algorithm has been applied to analyze the complex flowfield within a backswept centrifugal impeller. Issues studied include parametric analyses into the effect of secondary flow structures, due to tip leakage flow, on the development of the flowfield within the impeller passage, and off-design, or part load, analyses at conditions below (60 and 80 percent) the reference volumetric flow rate. Excellent agreement with available experimental data verifies the numerical rig as a viable technique, and suggests its ability to assist in the design process of impeller geometries.

Mounts, Jon S.; Dorney, Daniel J.; Brasz, Joost J.

1991-06-01

223

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

224

Thermal Creep of a Rarefied Gas on the Basis of Non-linear Korteweg-Theory  

NASA Astrophysics Data System (ADS)

The study of thermal transpiration, more commonly called thermal creep, is accomplished by use of Korteweg's theory of capillarity. Incorporation of this theory into the balance laws of continuum mechanics allows resolution of boundary value problems via solutions to systems of ordinary differential equations. The problem was originally considered by Maxwell in his classic 1879 paper Muc(axwell) (Phil Trans Roy Soc (London) 170:231-256, 1879). In that paper Maxwell derived what is now called the Burnett higher order contribution to the Cauchy stress, but was not able to solve his newly derived system of partial differential equations. In this paper the authors note that a more appropriate higher order contribution to the Cauchy stress follows from Korteweg's 1901 theory Kuc(orteweg) (Arch Neerl Sci Exactes Nat Ser II 6:1-24, 1901). The appropriateness of Korteweg's theory is based on the exact summation of the Chapman-Enskog expansion given by Gorban and Karlin. The resulting balance laws are solved exactly, qualitatively, and numerically and the results are qualitatively similar to the numerical and exact results given by Aoki et al., Loyalka et al., and Struchtrup et al.

Kim, Yong-Jung; Lee, Min-Gi; Slemrod, Marshall

2014-08-01

225

Incremental adaptation to yaw head movements during 30 RPM centrifugation  

E-print Network

Artificial Gravity (AG) provided by short-radius centrifugation is a promising countermeasure against the harmful physiological effects of prolonged weightlessness. However, the vestibular stimulus associated with making ...

Elias, Paul Z. (Paul Ziad)

2006-01-01

226

[Design and optimization of a centrifugal pump for CPCR].  

PubMed

Requirements for an optimal centrifugal pump, the vital component in the equipment for cardiopulmonary cerebral resuscitation(CPCR), have been presented. The performance of the Sarns centrifugal pump (Sarns, Inc./3M, Ann arbor, MI, U.S.A) was tested. The preliminarily optimized model for CPCR was designed according to the requirements of CPCR and to the comparison and analysis of several clinically available centrifugal pumps. The preliminary tests using the centrifugal pump made in our laboratory(Type CPCR-I) have confirmed the design and the optimization. PMID:12557770

Pei, J; Tan, X; Chen, K; Li, X

2000-06-01

227

Exercise protocols during short-radius centrifugation for artificial gravity  

E-print Network

Long-duration spaceflight results in severe physiological deconditioning, threatening the success of interplanetary travel. Exercise combined with artificial gravity provided by centrifugation may be the comprehensive ...

Edmonds, Jessica Leigh

2008-01-01

228

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

229

Thermal creep of a rarefied gas on the basis of non-linear Korteweg-theory  

E-print Network

gas where the motion is induced by a temperature gradient on the boundary of the flow domain. The theoretical treatment of problem of such a temperature gradient driven flow dates back to the clas- sical introduced a linear second gradient of temperature to the Cauchy stress tensor thus realizing

Kim, Yong Jung

230

Natural gas injection at 9200 psig  

Microsoft Academic Search

The 9200-psig discharge pressure of 2 reinjection compressors installed on the Ekofisk Phillips Norway Group gas separation plant in the North Sea represents a new record high for centrifugal compressors. The 2 reinjection compressors are part of the 6 specially designed multistage centrifugal compressors totaling 110,000 hp installed in the 2nd half of 1973 on offshore platforms to recover condensate

1973-01-01

231

Centrifugation of coal-derived liquids  

SciTech Connect

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 rates, viscosities, and dam heights were varied. Viscosity ..mu.., effluent liquid rate Q/sub e/, and Ambler's geometric parameter ..sigma.. were graphically correlated with attained separations. The separation was relatively insensitive to the variables, as a 50-fold increase in Q/sub e//..sigma.. corresponded to a decrease in ash removal only from 84% to 60% and to a decrease in organic solids removal only from 77% to 22%. Organic solids removal was poorer and more erratic than ash removal because of the lesser density differences and greater size variability of the organics. Ancillary studies demonstrated that coal liquefaction products may behave as a Bingham Plastic fluid, and that this results in an absolute limit on the attainable solids separation. Additional studies showed that little difference in density may exist between the organic solids and liquids, and that effects of aging may threaten the validity of viscosity measurements.

Weintraub, Murray; Weiss, Milton L.; Akhtar, Sayeed

1980-06-01

232

Experimental Investigation of Centrifugal Compressor Stabilization Techniques  

NASA Technical Reports Server (NTRS)

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 stabilizing effect of steadily flowing air-streams injected into the vaneless region of a vane-island diffuser through the shroud surface is described. Parametric variations of injection angle, injection flow rate, number of injectors, injector spacing, and injection versus bleed were investigated for a range of impeller speeds and tip clearances. Both the compressor discharge and an external source were used for the injection air supply. The stabilizing effect of flow obstructions created by tubes that were inserted into the diffuser vaneless space through the shroud was also investigated. Tube immersion into the vaneless space was varied in the flow obstruction experiments. Results from testing done at impeller design speed and tip clearance are presented. Surge margin improved by 1.7 points using injection air that was supplied from within the compressor. Externally supplied injection air was used to return the compressor to stable operation after being throttled into surge. The tubes, which were capped to prevent mass flux, provided 9.3 points of additional surge margin over the baseline surge margin of 11.7 points.

Skoch, Gary J.

2003-01-01

233

Centrifugally Stimulated Exospheric Ion Escape at Mercury  

NASA Technical Reports Server (NTRS)

We investigate the transport of ions in the low-altitude magnetosphere magnetosphere of Mercury. We show that, because of small spatial scales, the centrifugal effect due to curvature of the E B drift paths can lead to significant particle energization in the parallel direction. We demonstrate that because of this effect, ions with initial speed smaller than the escape speed such as those produced via thermal desorption can overcome gravity and escape into the magnetosphere. The escape route of this low-energy exosphere originating material is largely controlled by the magnetospheric convection rate. This escape route spreads over a narrower range of altitudes when the convection rate increases. Bulk transport of low-energy planetary material thus occurs within a limited region of space once moderate magnetospheric convection is established. These results suggest that, via release of material otherwise gravitationally trapped, the E B related centrifugal acceleration is an important mechanism for the net supply of plasma to the magnetosphere of Mercury.

Delcourt, Dominique; Seki, K.; Terada, N.; Moore, Thomas E.

2012-01-01

234

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.

235

Dynamic mean field theory for lattice gas models of fluid mixtures confined in mesoporous materials.  

PubMed

We present the extension of dynamic mean field theory (DMFT) for fluids in porous materials (Monson, P. A. J. Chem. Phys. 2008, 128, 084701) to the case of mixtures. The theory can be used to describe the relaxation processes in the approach to equilibrium or metastable equilibrium states for fluids in pores after a change in the bulk pressure or composition. It is especially useful for studying systems where there are capillary condensation or evaporation transitions. Nucleation processes associated with these transitions are emergent features of the theory and can be visualized via the time dependence of the density distribution and composition distribution in the system. For mixtures an important component of the dynamics is relaxation of the composition distribution in the system, especially in the neighborhood of vapor-liquid interfaces. We consider two different types of mixtures, modeling hydrocarbon adsorption in carbon-like slit pores. We first present results on bulk phase equilibria of the mixtures and then the equilibrium (stable/metastable) behavior of these mixtures in a finite slit pore and an inkbottle pore. We then use DMFT to describe the evolution of the density and composition in the pore in the approach to equilibrium after changing the state of the bulk fluid via composition or pressure changes. PMID:24102541

Edison, J R; Monson, P A

2013-11-12

236

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

237

A covariant Fokker-Planck equation for a simple gas from relativistic kinetic theory  

SciTech Connect

A manifestly covariant Fokker-Planck differential equation is derived for the case of a relativistic simple gas by taking a small momentum transfer approximation within the collision integral of the relativistic Boltzmann equation. We follow closely previous work, with the main difference that we keep manifest covariance at every stage of the analysis. In addition, we use the covariant Juettner distribution function to find a relativistic generalization of the Einstein's fluctuation-dissipation relation.

Chacon-Acosta, Guillermo; Dagdug, Leonardo; Morales-Tecotl, Hugo A. [Departamento de Fisica, Universidad Autonoma Metropolitana-Iztapalapa, Mexico D. F. 09340 (Mexico)

2010-12-14

238

Path-Integral Theory of an Electron Gas in a Random Potential  

Microsoft Academic Search

An ideal gas of non-degenerate electrons of mass m in a Gaussian random potential is investigated. The potential is characterized by two parameters: eta whose square is the variance of the potential energy) and L (correlation length). Relevance to the case of a polycrystalline non-degenerate semiconductor is suggested. The autocorrelation function of the potential is taken Gaussian, W(r' - r'

V. Bezak

1970-01-01

239

Erosion in radial inflow turbines. Volume 2: Balance of centrifugal and radial drag forces on erosive particles  

NASA Technical Reports Server (NTRS)

The particle motion in two-dimensional free and forced inward flowing vortices is considered. A particle in such a flow field experiences a balance between the aerodynamic drag forces that tend to drive erosive particles toward the axis, and centrifugal forces that prevent these particles from traveling toward the axis. Results predict that certain sizes of particles will achieve a stable orbit about the turbine axis in the inward flowing free vortex. In this condition, the radial drag force is equal to the centrifugal force. The sizes of particles that will achieve a stable orbit is shown to be related to the gas flow velocity diagram at a particular radius. A second analysis yields a description of particle sizes that will experience a centrifugal force that is greater than the radial component of the aerodynamic drag force for a more general type of particle motion.

Clevenger, W. B., Jr.; Tabakoff, W.

1974-01-01

240

Theory to boil-off gas cooled shields for cryogenic storage vessels  

NASA Astrophysics Data System (ADS)

An intermediate refrigeration with boil-off gas cooled shields using the boil-off gas stream is an alternative method to the conventional intermediate refrigeration with a cryogenic liquid. By using an analytical calculation method relations are derived, which enable complete predictions about the effectiveness of an intermediate refrigeration with boil-off gas cooled shields as a function of the number of shields for the different stored cryogenic liquids. For this theoretical derivation however, the restrictive assumption must be made that the thermal conductivity of the used insulation material has a constant value between the considered temperature boundaries. For purposes of a more exact calculation a numerical method is therefore suggested, which takes into consideration that the thermal conductivity is temperature-dependent. For a liquid hydrogen storage vessel with a perlite-vacuum insulation e.g., the effectiveness of one shield and its equilibrium temperature are given as a function of the position of the shield in the insulation space.

Hofmann, A.

2004-03-01

241

Power transmission mechanism equipped with fluid and centrifugal clutch  

SciTech Connect

This patent describes a power transmission mechanism equipped with a fluid coupling, an input shaft thereof interconnected to a power source being interconnected through the fluid coupling to an output shaft, and the output shaft being interconnected to a forward-rearward changeover mechanism including a speed changer. It is characterized in that the fluid coupling includes a shell, an impeller in the shell and a centrifugal clutch means in the shell for engaging the impeller and for driving the impeller when the shell is rotated by the input shaft at a speed above idle speed and for disengaging the impeller and the driving of the impeller when the shell is rotated by the input shaft at the idle speed. A turbine is included in the shell for standing idle in the shell when the centrifugal clutch means is disengaged and for drive by the impeller when the centrifugal clutch means is engaged and for driving the output shaft. The centrifugal clutch means comprises a support member fixed to the shell, a centrifugal shoe mounted on the support member for radial movement outwardly of the support member by centrifugal force and radial movement inwardly toward the support member. It also comprises spring means for moving the shoe inwardly toward the support member when the shell is rotated at idle speed, a cylindrical casing fixed to the impeller radially outward from the shoe and having an engaging surface for engagement by the centrifugal shoe when the shell is rotated at a speed above idle speed and the centrifugal shoe is moved radially outward by centrifugal force. The forward-rearward changeover mechanism, including the speed changer, is driven by the turbine when the centrifugal clutch means is engaged with the engaging surface and standing idle when the centrifugal clutch means is disengaged from the engaging surface and the turbine is standing idle.

Tamura, K.; Takeshita, S.; Fukunaga, T.

1986-12-30

242

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

243

AN AERODYNAMIC-THERMODYNAMIC STUDY OF CENTRIFUGAL COMPRESSORS  

Microsoft Academic Search

A procedure is presented for the aerodynamic and thermodynamic design of ; centrifugal compressors. Design equations are derived from basic laws of ; thermodynamics and fluid flow where possible. The experimental data and much of ; the mathematical treatment comes from the extensive literature on centrifugal ; compressors. An attempt has been made to assemble the bits of information which

1962-01-01

244

Meteor Crater: Energy of formation - Implications of centrifuge scaling  

Microsoft Academic Search

Recent work on explosive cratering has demonstrated the utility of performing subscale experiments on a geotechnic centrifuge to develop scaling rules for very large energy events. The present investigation is concerned with an extension of this technique to impact cratering. Experiments have been performed using a projectile gun mounted directly on the centrifuge rotor to launch projectiles into a suitable

R. M. Schmidt

1980-01-01

245

Separation of Nanoparticles in Aqueous Multiphase Systems through Centrifugation  

E-print Network

of the particles (e.g., Au = 19.3 g/cm3 and media = 1.0-1.4 g/cm3 for aqueous solutions of sucrose). ViscositySeparation of Nanoparticles in Aqueous Multiphase Systems through Centrifugation Ozge Akbulut of aqueous multiphase systems (MuPSs) as media for rate-zonal centrifugation to separate nanoparticles

Liu, David R.

246

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

247

CONVECTION DRIVEN BY CENTRIFUGAL BUOYANCY IN NEMATICS (*) C. R. CARRIGAN  

E-print Network

L-145 CONVECTION DRIVEN BY CENTRIFUGAL BUOYANCY IN NEMATICS (*) C. R. CARRIGAN Department director n. When n is horizontal, the results confirm data on gravitational buoyancy. An original first of centrifugal buoyancy is equivalent to that of gravitational buoyancy in the corresponding Rayleigh Benard

Paris-Sud XI, Université de

248

Experimental investigation of the phenomenon of centrifuging of liquids  

Microsoft Academic Search

The phenomenon of centrifuging of liquids inside a horizontal tubular device rotated about its axis of symmetry has been experimentally investigated. Extensive experiments were conducted using a transparent apparatus which enabled visualization and photographic recording of the centrifuging phenomenon. Several interesting and useful qualitative observations not reported hitherto have been recorded. The effects of liquid volume ( upsilo l ),

S. Ramesh Babu

1993-01-01

249

Molecular Theory of Mass Transfer Kinetics and Dynamics at Gas/Water Interface  

SciTech Connect

The mass transfer mechanism across gas/water interface is studied with molecu- lar dynamics (MD) simulation. The MD results provide a robust and qualitatively consistent picture to previous studies about microscopic aspects of mass transfer, including interface structure, free energy profiles for the uptake, scattering dynamics and energy relaxation of impinging molecules. These MD results are quantitatively compared with experimental uptake measurements, and we found that apparent inconsistency between MD and experiment could be partly resolved by precise de- composition of the observed kinetics into elemental steps. Remaining issues and future perspectives toward constructing a comprehensive mutli-scale description of interfacial mass transfer are summarized.

Morita, Akihiro; Garrett, Bruce C.

2008-07-01

250

A complete theory for the magnetism of an ideal gas of electrons  

NASA Astrophysics Data System (ADS)

We have explored Pauli paramagnetism, Landau diamagnetism, and de Haas-van Alphen effect in a single framework, and unified these three effects for all temperatures as well as for all strengths of magnetic field. Our result goes beyond Pauli-Landau result on the magnetism of the 3-D ideal gas of electrons, and is able to describe crossover of the de Haas-van Alphen oscillation to the saturation of magnetization. We also have obtained a novel asymptotic series expansion for the low temperature properties of the system.

Biswas, Shyamal; Sen, Swati; Jana, Debnarayan

2013-05-01

251

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

252

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

253

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

254

Monte-Carlo analysis of rarefied-gas diffusion including variance reduction using the theory of Markov random walks  

NASA Technical Reports Server (NTRS)

Molecular diffusion through a rarefied gas is analyzed by using the theory of Markov random walks. The Markov walk is simulated on the computer by using random numbers to find the new states from the appropriate transition probabilities. As the sample molecule during its random walk passes a scoring position, which is a location at which the macroscopic diffusing flow variables such as molecular flux and molecular density are desired, an appropriate payoff is scored. The payoff is a function of the sample molecule velocity. For example, in obtaining the molecular flux across a scoring position, the random walk payoff is the net number of times the scoring position has been crossed in the positive direction. Similarly, when the molecular density is required, the payoff is the sum of the inverse velocity of the sample molecule passing the scoring position. The macroscopic diffusing flow variables are then found from the expected payoff of the random walks.

Perlmutter, M.

1973-01-01

255

Centrifugal Settling of Flocculated Suspensions: A Sensitivity Analysis of Parametric Model Functions  

E-print Network

Centrifugal Settling of Flocculated Suspensions: A Sensitivity Analysis of Parametric Model Administracio´n, Universidad de La Frontera, Temuco, Chile The centrifugal settling of a flocculated suspension Centrifugation; Flocculated suspension; Numerical simulation; Parameter identification; Sedimentation

Bürger, Raimund

256

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

257

The development of the International Space Station centrifuge.  

PubMed

Gravitational biology research facility "Centrifuge" is currently under development for the International Space Station. Research in the Complex Organism Biology, indispensable to the progress in Health Science, is only possible in the Centrifuge aboard the station. So, on-orbit 1 G controls for various specimens including small mammals, fish, and higher plants will be rigorously done in the Centrifuge. This facility is also capable of providing "reduced gravity" likely on the Moon or on Mars. Thus, it will play a key role in creating knowledge of space fundamental biology. As part of the offset of NASA's Shuttle launch services for the Japanese Experiment Module, JAXA is developing the Centrifuge Rotor (CR), the Life Sciences Glovebox (LSG) and the Centrifuge Accommodation Module (CAM). Critical Design Review (CDR) of LSG was conducted on July 2004, while the system CDRs of the CAM and CR are scheduled for December 2004 and August 2005, respectively. Their launch schedules are under review. PMID:15858334

Nakano, Tamotsu

2004-11-01

258

Quantitative Centrifugation To Extract Benthic Protozoa from Freshwater Sediments  

PubMed Central

Two methods for extracting protists from freshwater sediment are described: (i) an adapted isopycnic centrifugation technique for sandy and gyttja-like sediments and (ii) a rate zonal centrifugation technique for sediments rich in particulate organic material (litter-like sediments). The recoveries of protists during isopycnic centrifugation in media of several densities were compared. No significant losses in sodium diatrizoate and Percoll were recorded. After known amounts of nanoflagellates were added to azoic sediments, the protists were extracted and counted. For sandy sediments, we found 100% recovery, and for the gyttja-like sediments we found a maximum recovery of 94%. The recovery of protozoa extracted from litter-like sediments, characteristic of littoral systems, depends on a given centrifugal force, on time, and on the dimensions of the flagellates. A recovery model which takes into account cell dimensions and centrifugation characteristics gives the minimum expected recovery. PMID:16349148

Starink, Mathieu; Bar-Gilissen, Marie-Jose; Bak, Rolf P. M.; Cappenberg, Thomas E.

1994-01-01

259

A modeling study of a centrifugal compressor  

SciTech Connect

A centrifugal compressor, which is part of a chlorofluorocarbon R-114 chiller installation, was investigated, operating with a new refrigerant, hydrofluorocarbon R-236ea, a proposed alternative to R-114. A large set of R-236ea operating data, as well as a limited amount of R-114 data, were available for this study. A relatively simple analytical compressor model was developed to describe compressor performance. The model was built upon a thorough literature search, experimental data, and some compressor design parameters. Two original empirical relations were developed, providing a new approach to the compressor modeling. The model was developed in a format that would permit it to be easily incorporated into a complete chiller simulation. The model was found to improve somewhat on the quantitative and physical aspects of a compressor model of the same format found in the literature. It was found that the compressor model is specific to the particular refrigerant.

Popovic, P.; Shapiro, H.N. [Iowa State Univ., Ames, IA (United States). Dept. of Mechanical Engineering

1998-12-31

260

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

261

Centrifuge Safety A laboratory centrifuge can be an important tool in the university lab. It can also be a dangerous  

E-print Network

, plastic adapters, or stainless steel tubes. Centrifuge Hazards Fatigue #12;Even when manufacturers of titanium alloy, other centrifuge components may be made from aluminum due to design considerations. When titanium-alloy or comparable rotors for areas where corrosive solutions, like KBr, will be used regularly

de Lijser, Peter

262

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

263

Pipeline gas pressure reduction with refrigeration generation  

Microsoft Academic Search

The high pressure of pipeline gas is reduced to the low pressure of a distribution system with simultaneous generation of refrigeration by passing the gas through two successive centrifugal compressors driven by two turbo-expanders in which the compressed gas is expanded to successively lower pressures. Refrigeration is recovered from the gas as it leaves each turbo-expander. Methanol is injected into

S. J. Markbreiter; H. P. Schorr

1985-01-01

264

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

265

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

266

Theory and practice of a variable dome splitter for gas chromatography-olfactometry.  

PubMed

For olfactometric measurements in combination with gas chromatography a device is needed to split the GC effluent between the detector and the sniffing port. Fixed split ratios are obtained by simple flow splitters with appropriate restrictions towards the two outlets. Variable split ratios are possible with additional control flows. One such device is a dome splitter with one input flow (the GC effluent), two output flows (to the two outlets) and two control inputs. Preliminary experiments revealed deviations from the expected split ratios of such a device. The dimensioning of the flow restrictors at only one working point was not sufficient to obtain the expected split ratios over the whole temperature range of a GC run. Therefore a physical model of the flow system has been developed, taking into account the temperature dependence of the restrictors and the internal pressure in the dome. This included the solution of the flow (respectively the mass) balance under the condition of a compressible, isothermal and laminar flow regime. The measurements are in good agreement with theoretical calculations. The model can therefore be used to optimise the dimensions of the restrictions and to calculate the effective split ratio at a given temperature during the GC run. PMID:23489489

Boeker, Peter; Haas, Torsten; Schulze Lammers, Peter

2013-04-19

267

Study of Some Parameters of Modified Chaplygin Gas in Galileon Gravity Theory from Observational Perspective  

E-print Network

We have assumed the FRW model of the universe in Galileon gravity, which is filled with dark matter and Modified Chaplygin gas (MCG) type dark energy. We present the Hubble parameter in terms of some unknown parameters and observational parameters with the redshift $z$. Some cosmological parameters are reconstructed and plots are generated to study the nature of the model and its viability. It is seen that the model is perfectly consistent with the present cosmic acceleration. From \\textit{observed Hubble data (OHD) set or Stern data set} of 12 points, we have obtained the bounds of the arbitrary parameters ($A,B$) & ($A,C$) by minimizing the $\\chi^{2}$ test. Next due to joint analysis of \\textit{Stern+BAO} and \\textit{Stern+BAO+CMB} observations, we have also obtained the best fit values and the bounds of the parameters ($A,B$) & ($A,C$) by fixing some other parameters. The best-fit values and bounds of the parameters are obtained with 66%, 90% and 99% confidence levels for \\textit{Stern, Stern+BAO a...

Ranjit, Chayan; Debnath, Ujjal

2014-01-01

268

Tropic responses of Phycomyces sporangiophores to gravitational and centrifugal stimuli.  

PubMed

A low-speed centrifuge was used to study the tropic responses of Phycomyces sporangiophores in darkness to the stimulus of combined gravitational and centrifugal forces. If this stimulus is constant the response is a relatively slow tropic reaction, which persists for up to 12 hours. The response is accelerated by increasing the magnitude of the gravitational-centrifugal force. A wholly different tropic response, the transient response, is elicited by an abrupt change in the gravitational-centrifugal stimulus. The transient response has a duration of only about 6 min. but is characterized by a high bending speed (about 5 degrees /min.). An analysis of the distribution of the transient response along the growing zone shows that the active phase of the response has a distribution similar to that of the light sensitivity for the light-growth and phototropic responses. Experiments in which sporangiophores are centrifuged in an inert dense fluid indicate that the sensory mechanism of the transient response is closely related to the physical deformation of the growing zone caused by the action of the gravitational-centrifugal force on the sporangiophore as a whole. However, the response to a steady gravitational-centrifugal force is most likely not connected with this deformation, but is probably triggered by the shifting of regions or particles of differing density relative to one another inside the cell. PMID:13721903

DENNISON, D S

1961-09-01

269

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

270

Study of Some Parameters of Modified Chaplygin Gas in Galileon Gravity Theory from Observational Perspective  

E-print Network

We have assumed the FRW model of the universe in Galileon gravity, which is filled with dark matter and Modified Chaplygin gas (MCG) type dark energy. We present the Hubble parameter in terms of some unknown parameters and observational parameters with the redshift $z$. Some cosmological parameters are reconstructed and plots are generated to study the nature of the model and its viability. It is seen that the model is perfectly consistent with the present cosmic acceleration. From \\textit{observed Hubble data (OHD) set or Stern data set} of 12 points, we have obtained the bounds of the arbitrary parameters ($A,B$) & ($A,C$) by minimizing the $\\chi^{2}$ test. Next due to joint analysis of \\textit{Stern+BAO} and \\textit{Stern+BAO+CMB} observations, we have also obtained the best fit values and the bounds of the parameters ($A,B$) & ($A,C$) by fixing some other parameters. The best-fit values and bounds of the parameters are obtained with 66%, 90% and 99% confidence levels for \\textit{Stern, Stern+BAO and Stern+BAO+CMB} joint analysis. Next we have also taken type Ia supernovae data set (union 2 data set with 557 data points). The distance modulus $\\mu(z)$ against redshift $z$ for our theoretical MCG model in Galileon gravity have been tested for the best fit values of the parameters and the observed \\textit{SNe Ia union 2 data} sample and from this, we have concluded that our model is in agreement with the union 2 sample data.

Chayan Ranjit; Prabir Rudra; Ujjal Debnath

2014-06-10

271

Research on 3-D discharge flow in a centrifugal impeller  

NASA Astrophysics Data System (ADS)

A method for calculating 3D discharge flow in a centrifugal impeller is developed by means of solving the incompressible steady time-averaged N-S equations, the continuity equation, and the k-epsilon turbulence model equation. This method is accomplished with calculation grids generated by an algebraic transformation, and thus it can be easily applied to the design analysis of centrifugal impellers. The discharge flow of a three-dimensional shrouded centrifugal compressor impeller was measured for assessing the validity of the present calculation procedure. The comparison between the experimental data and the calculation results shows that the present method can predict the mean velocities.

Xi, Guang; Wang, Shangjin

1993-01-01

272

Increased mitogenic response in lymphocytes from chronically centrifuged mice  

NASA Technical Reports Server (NTRS)

The effects upon the mitogenic response of splenic lymphocytes when exposing mice to prolonged hypergravity conditions (3.5 G for 1 year) were studied. Cultures of splenic lymphocytes isolated from both centrifuged and control (1 G) animals were stimulated with Concanavalin A and the response measured using both morphological and biochemical means. Lymphocytes obtained from centrifuged mice exhibited much higher activation rates (as measured by the incorporation of H-3 thymidine) and larger cell aggregates consisting of more lymphoblasts and mitotic figures than those observed in non centrifuged control animals. Isolated splenic lymphocytes thus appear to have been conditioned by hypergravity state.

Mueller, Otfried; Hunzinger, E.; Cogoli, Augusto; Bechler, B.; Lee, J.; Moore, J.; Duke, J.

1990-01-01

273

27. RW Meyer Sugar Mill: 18761889. Centrifugals, 1879, 1881. Manufacturer, ...  

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

27. RW Meyer Sugar Mill: 1876-1889. Centrifugals, 1879, 1881. Manufacturer, Unknown. Supplied by Honolulu Ironworks, Honolulu Hawaii, 1879, 1881. View: Historical view, 1934, from T.T. Waterman collection, Hawaiian Sugar Planters' Association. With the inner basket of the centrifugal revolving at 1200 rpm molasses flew outward from the granulated sugar, through the holes in the brass lining, and into the stationary outer basket. The molasses drained through the spout at the right and into molasses storage pits below the floor. The centrifugals were underdriven with a belt connected to the pulley beneath the basket. - R. W. Meyer Sugar Mill, State Route 47, Kualapuu, Maui County, HI

274

Efficiency calculation and the vortex characteristics research of centrifugal pump  

NASA Astrophysics Data System (ADS)

Efficiency is an important performance indicator of the centrifugal pump, this paper establish three-dimensional model of one high head centrifugal pump in domestic with CFD software, though changing the operating conditions, statistics the calculation efficiency and energy loss under different operating conditions, compare the impact to efficiency and head calculation with steady and unsteady calculation methods, and research the affect when runner in different locations in the centrifugal pump, given and analysis the reasons of the flow field and pressure distribution of runner in different steps.

Ge, X. F.; Gao, Z. X.; Zheng, Y.; Shen, M. H.

2012-11-01

275

Numerical simulation for a centrifugal heart pump  

NASA Astrophysics Data System (ADS)

The primary focus of this work is to investigate unsteady flow simulations for an incompressible fluid. Computational codes are developed and applied for the purpose of analyzing the flow in a centrifugal heart pump, the Innovative Ventricular Assist System (IVAS) pump, which was developed by the Cleveland Clinic Foundation as a part of the National Institute of Health's artificial heart program. In order to simulate the complex flow in the IVAS pump, three capabilities must be incorporated into the simulation codes. The first capability is that the code must be able to simulate the flow through an IVAS pump for Reynolds numbers 30,000~80,000 with numerical stability. The Reynolds numbers in this range are considered to be high in incompressible flow and to have difficulty in simulating a flow with numerical stability. The second capability is that the codes must solve 2-1/2 dimensional Navier-Stokes equations. The 2-1/2 dimensional Navier- Stokes equations are written in such a way that the effect of the variable thickness is included in two- dimensions. The 2-1/2 dimensional analysis enables the simulation of the flow, including the various thickness effects, at nearly the computational speed of two- dimensional analysis. The third capability is that the code must simulate the flow for the entire centrifugal pump, which includes an inlet, rotating blades, a volute, and a diffuser. To perform this intensive calculation, parallel computing is used because of its high computing speed and its ability to accommodate the large computational domain by task partitioning. An intensive parametric study using a single-processor computer is performed with a view to identifying certain problematic aspects of the design methodology. According to the present analysis, the effects of a Reynolds number based on the blade radius and its velocity are not significant for typical pump operation conditions. The flow characteristics, however, change with the Reynolds numbers when they are low. In general, the pressure rise across the pump impeller increases as the radius of the blade arc increases and as the number of blades increases. The findings of this study qualitatively agree with the Euler turbine equation with respect to the effects of the leading edge (inflow) angle and the trailing edge (outflow) angle.

Yano, Keiji

276

Recovery of materials from waste printed circuit boards by vacuum pyrolysis and vacuum centrifugal separation.  

PubMed

In this research, a two-step process consisting of vacuum pyrolysis and vacuum centrifugal separation was employed to treat waste printed circuit boards (WPCBs). Firstly, WPCBs were pyrolysed under vacuum condition at 600 °C for 30 min in a lab-scale reactor. Then, the obtained pyrolysis residue was heated under vacuum until the solder was melted, and then the molten solder was separated from the pyrolysis residue by the centrifugal force. The results of vacuum pyrolysis showed that the type-A of WPCBs (the base plates of which was made from cellulose paper reinforced phenolic resin) pyrolysed to form an average of 67.97 wt.% residue, 27.73 wt.% oil, and 4.30 wt.% gas; and pyrolysis of the type-B of WPCBs (the base plates of which was made from glass fiber reinforced epoxy resin) led to an average mass balance of 72.20 wt.% residue, 21.45 wt.% oil, and 6.35 wt.% gas. The results of vacuum centrifugal separation showed that the separation of solder was complete when the pyrolysis residue was heated at 400 °C, and the rotating drum was rotated at 1200 rpm for 10 min. The pyrolysis oil and gas can be used as fuel or chemical feedstock after treatment. The pyrolysis residue after solder separation contained various metals, glass fibers and other inorganic materials, which could be recycled for further processing. The recovered solder can be reused directly and it can also be a good resource of lead and tin for refining. PMID:20655190

Zhou, Yihui; Wu, Wenbiao; Qiu, Keqiang

2010-11-01

277

A finite element model of the turbulent flow field in a centrifugal impeller  

E-print Network

-called "actuator-disk" theory (Church, 1944) in the turbomachinery community, which is a rather primitive flow analysis tool. Moore and Moore (1981) analyzed the three-dimensional flow field inside a centrifugal impeller using a partially parabolized flow... momentum leads to a spiral-like flow path downstream from the impeller, a constant-angle spiral emitting from the trailing edge was taken to represent the wake centerline. As a result, the wake center became a natural extension of the vane mean camber...

Hlavaty, Steven Todd

2012-06-07

278

Deconfinement in super Yang-Mills theory on via dual-Coulomb gas and "affine" XY-model  

NASA Astrophysics Data System (ADS)

We study finite-temperature SU(2) super Yang-Mills theory, compactified on a spatial circle of size L with supersymmetric boundary conditions. In the semi-classical small- L regime, a deconfinement transition occurs at T c ? 1 /L. The transition is due to a competition between non-perturbative topological "molecules" — magnetic and neutral bion-instantons — and electrically charged W -bosons and superpartners. Compared to deconfinement in non-supersymmetric QCD(adj) [1], the novelty is the relevance of the light modulus scalar field. It mediates interactions between neutral bions (and W -bosons), serves as an order parameter for the center symmetry associated with the non-thermal circle, and explicitly breaks the electric-magnetic (Kramers-Wannier) duality enjoyed by non-supersymmetric QCD(adj) near T c . We show that deconfinement can be studied using an effective two-dimensional gas of electric and magnetic charges with (dual) Coulomb and Aharonov-Bohm interactions, or, equivalently, via an XY-spin model with a symmetry-breaking perturbation, where each system couples to the scalar field. To study the realization of the discrete R-symmetry and the thermal and non-thermal center symmetries, we perform Monte Carlo simulations of both systems. The dual-Coulomb gas simulations are a novel way to analyze deconfinement and provide a new venue to study the phase structure of a class of two-dimensional condensed matter models that can be mapped into dual-Coulomb gases. Our results indicate a continuous deconfinement transition, with remaining unbroken at the transition. Thus, the SYM transition appears similar to the one in SU(2) QCD(adj) [1] and is also likely to be characterized by continuously varying critical exponents.

Anber, Mohamed M.; Collier, Scott; Poppitz, Erich; Strimas-Mackey, Seth; Teeple, Brett

2013-11-01

279

The Maryland Centrifugal Experiment : status and plans  

NASA Astrophysics Data System (ADS)

The Maryland Centrifugal Experiment (MCX) studies supersonic rotation of plasma produced by the application of a steady state electric field perpendicular to a linear confining magnetic field. MCX has achieved high density (ne > 10^20 m-3 ) fully ionized plasmas rotating supersonically with azimuthal velocities v? in the range of 100 - 250 km/sec with ion temperatures typically 30 eV and sonic Mach numbers (v?/vti) in the range of 1 to 3 and Alfvèn Mach numbers (v?/vA ) of somewhat less than unity. Plasmas remain stationary for milliseconds, much longer than MHD instability timescales. MCX has implemented extensive new diagnostics including a multi-chord ion Doppler spectrometer, arrays of magnetic probes, an H? emission array of detectors, and a two color interferometer. Results will be reported on velocity profiles and related MHD activity. A higher voltage (20 kV) discharge capacitor bank is being tested and results on velocity limits will also be reported. The major upgrade plans include increasing the midplane magnetic field to 1 T and installing extensive surface conditioning. Work supported by USDOE.

Teodorescu, Catalin

2005-10-01

280

Centrifuge impact cratering experiments: Scaling laws for non-porous targets  

NASA Technical Reports Server (NTRS)

This research is a continuation of an ongoing program whose objective is to perform experiments and to develop scaling relationships for large body impacts onto planetary surfaces. The development of the centrifuge technique has been pioneered by the present investigator and is used to provide experimental data for actual target materials of interest. With both powder and gas guns mounted on a rotor arm, it is possible to match various dimensionless similarity parameters, which have been shown to govern the behavior of large scale impacts. Current work is directed toward the determination of scaling estimates for nonporous targets. The results are presented in summary form.

Schmidt, Robert M.

1987-01-01

281

Cross plane transfer of vestibular adaptation to human centrifugation  

E-print Network

Human short-radius centrifugation (SRC) is being investigated as a volume-efficient means of delivering intermittent doses of "artificial gravity" to counter the deleterious effects of long exposures to weightlessness. ...

Garrick-Bethell, Ian, 1980-

2004-01-01

282

Squat exercise biomechanics during short-radius centrifugation  

E-print Network

Artificial gravity (AG) created by short-radius centrifugation is a promising countermeasure to the physiological de-conditioning that results from long-duration spaceflight. However, as on Earth, gravity alone does not ...

Duda, Kevin R., 1979-

2007-01-01

283

Return channel loss reduction in multi-stage centrifugal compressors  

E-print Network

This thesis presents concepts for improving the performance of return channels in multi-stage centrifugal compressors. Geometries have been developed to reduce both separation and viscous losses. A number of different ...

Aubry, Anne-Raphaëlle

2012-01-01

284

Characterization of unsteady flow processes in a centrifugal compressor stage  

E-print Network

Numerical experiments have been implemented to characterize the unsteady loading on the rotating impeller blades in a modem centrifugal compressor. These consist of unsteady Reynolds-averaged Navier Stokes simulations of ...

Gould, Kenneth A. (Kenneth Arthur)

2006-01-01

285

25. RW Meyer Sugar Mill: 18761889. Centrifugals, 1879, 1881. Manufacturer, ...  

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

25. RW Meyer Sugar Mill: 1876-1889. Centrifugals, 1879, 1881. Manufacturer, Unknown. Supplied by Honolulu Iron Works, Honolulu, Hawaii, 1879, 1881. View: After sugar was granulated and cooled it had to be dried and drained, completely separating the sugar crystals from the molasses. Revolving at 1200 rpm the inner basket drove the molasses outward into the stationary outer basket leaving dried sugar behind. The steam engine counter-shaft at the left was belt driven and belts running from the counter-shaft pulleys to the centrifugals' base-pulleys provided the necessary power. Part of the clutch system which moved the belt from a moving to a stationary pulley, thus turning the centrifugals on and off, is seen in Between the counter-shaft and the centrifugals. - R. W. Meyer Sugar Mill, State Route 47, Kualapuu, Maui County, HI

286

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

287

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

288

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

289

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

290

16. View northwest of Arctic Chamber Worthington centrifugal compressor and ...  

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

16. View northwest of Arctic 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

291

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

292

Algal Harvesting for Biodiesel Production: Comparing Centrifugation and Electrocoagulation  

E-print Network

Electrocoagulation was compared to centrifugation at pilot scale for harvesting Nannochloris oculata and Nannochloropsis salina for biodiesel production. The pilot scale testing is a proof of concept and no optimization was conducted. Testing used...

Kovalcik, Derek John

2013-08-09

293

Isolation and retrieval of circulating tumor cells using centrifugal forces  

E-print Network

Presence and frequency of rare circulating tumor cells (CTCs) in bloodstreams of cancer patients are pivotal to early cancer detection and treatment monitoring. Here, we use a spiral microchannel with inherent centrifugal ...

Hou, Han Wei

294

Multi-parameter control for centrifugal compressor performance optimization  

E-print Network

The potential performance benefit of actuating inlet guide vane (IGV) angle, variable diffuser vane (VDV) angle and impeller speed to implement a multi-parameter control on a centrifugal compressor system is assessed. The ...

Mannai, Sébastien (Sébastien Karim)

2014-01-01

295

2. View of centrifugal pump house sitting at edge of ...  

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

2. View of centrifugal pump house sitting at edge of drainage canal, looking E. - Laurel Valley Sugar Plantation, Drainage Plant, 2 Miles South of Thibodaux on State Route 308, Thibodaux, Lafourche Parish, LA

296

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...

297

Forced response predictions in modern centrifugal compressor design  

E-print Network

A computational interrogation of the time-averaged and time-unsteady flow fields of two centrifugal compressors of nearly identical design (the enhanced, which encountered aeromechanical difficulty, and production, which ...

Smythe, Caitlin J. (Caitlin Jeanne)

2005-01-01

298

Centrifugal compressor return channel shape optimization using adjoint method  

E-print Network

This thesis describes the construction of an automated gradient-based optimization process using the adjoint method and its application to centrifugal compressor return channel loss reduction. A proper objective function ...

Guo, Wei, S.M. Massachusetts Institute of Technology

2013-01-01

299

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

300

Fractionation of suspended aqueous materials using centrifugal elutriation  

E-print Network

of solids and particulate material. Centrifugal Elutriation, a common technique in the medical field to kactionate cells, was applied to the fracdonation of a series of suspended aqueous materiah into discrete mnges based on size snd density. Pericles were... of solids and particulate material. Centrifugal Elutriation, a common technique in the medical field to kactionate cells, was applied to the fracdonation of a series of suspended aqueous materiah into discrete mnges based on size snd density. Pericles were...

Ginn, Jon Stephen

2012-06-07

301

Experimental investigation of the phenomenon of centrifuging of liquids  

Microsoft Academic Search

The phenomenon of centrifuging of liquids inside a horizontal tubular device rotated about its axis of symmetry has been experimentally\\u000a investigated. Extensive experiments were conducted using a transparent apparatus which enabled visualization and photographic\\u000a recording of the centrifuging phenomenon. Several interesting and useful qualitative observations not reported hitherto have\\u000a been recorded. The effects of liquid volume (?\\u000a \\u000a l\\u000a ), density(?),

S. Ramesh Babu

1993-01-01

302

COMPARISON OF FATIGUE BEHAVIOR FOR CENTRIFUGALLY CAST AND KEEL BLOCK CAST STEEL  

Microsoft Academic Search

The objective of this research was to determine if location through the wall thickness of centrifugal castings affects fatigue properties and to compare fatigue and monotonic tensile properties of centrifugal castings to statically cast keel block castings. Specimens were machined from centrifugal and keel block AISI 8630 steel castings. Centrifugal casting specimens were taken from three different locations (outer, middle

J. J. Gradman; R. I. Stephens; R. A. Hardin; C. Beckermann

303

Exploring the discrepancies between experiment, theory, and simulation for the homogeneous gas-to-liquid nucleation of 1-pentanol  

NASA Astrophysics Data System (ADS)

Using an efficient Monte Carlo approach known as Aggregation-Volume-bias Monte Carlo with self-adaptive Umbrella Sampling and Histogram Reweighting (AVUS-HR), we obtained the nucleation free energy profile of 1-pentanol at various temperatures from 220 to 360 K. From these profiles, differences between the free energy barrier heights obtained from our simulations and those predicted by the classical nucleation theory (CNT) were calculated. Our results strongly support that the logarithm of the nucleation rate ratio between simulation (or experiment) and CNT increases almost linearly with the inverse temperature. Among the various factors that contribute to the discrepancy between simulation and CNT nucleation rates, the nonzero surface free energy of the monomer included in the CNT makes the largest contribution. On the molecular level, the simulations indicate that a gas-phase cluster of 1-pentanol molecules is relatively compact and can contain multiple hydrogen bonded aggregates of various sizes and that this aggregate size distribution depends strongly on temperature and also on the overall size of the cluster system.

Nellas, Ricky B.; Keasler, Samuel J.; Siepmann, J. Ilja; Chen, Bin

2010-04-01

304

A numerical theory of lattice gas and lattice Boltzmann methods in the computation of solutions to nonlinear advective-diffusive systems  

SciTech Connect

A numerical theory for the massively parallel lattice gas and lattice Boltzmann methods for computing solutions to nonlinear advective-diffusive systems is introduced. The convergence theory is based on consistency and stability arguments that are supported by the discrete Chapman-Enskog expansion (for consistency) and conditions of monotonicity (in establishing stability). The theory is applied to four lattice methods: Two of the methods are for some two-dimensional nonlinear diffusion equations. One of the methods is for the one-dimensional lattice method for the one-dimensional viscous Burgers equation. And one of the methods is for a two-dimensional nonlinear advection-diffusion equation. Convergence is formally proven in the L{sub 1}-norm for the first three methods, revealing that they are second-order, conservative, conditionally monotone finite difference methods. Computational results which support the theory for lattice methods are presented. In addition, a domain decomposition strategy using mesh refinement techniques is presented for lattice gas and lattice Boltzmann methods. The strategy allows concentration of computational resources on regions of high activity. Computational evidence is reported for the strategy applied to the lattice gas method for the one-dimensional viscous Burgers equation. 72 refs., 19 figs., 28 tabs.

Elton, A.B.H.

1990-09-24

305

Experiment and Theory for the Thickness Effect of Nano Metal Oxide Gas Sensing Thin Film Dynamic Thickness Effect and Theory of Diffusion Reaction  

Microsoft Academic Search

The rule of characteristic time varies with film thickness, gas concentration is given by experiment results. The diffusion reaction model of conductance response for porous gas sensing thin film is proposed; with solution and non-dimensional analyze the reaction diffusion equation, the rule of character time can be yielded. Using the method of combination of theoretical and experimental, the surface adsorption

Wang Yan; Sun Jingjing; Xing Jianping; Hong Debin; Qiu Nanwan

2006-01-01

306

Theory and economics of by-generation of electricity at city gate stations using a gas expander turbine  

Microsoft Academic Search

The transmission pressure of pipeline gas entering a city-gate station offers an untapped energy source that gas-distribution companies can easily use to produce low-cost electricity. The high-pressure inlet gas can be heated, then isentropically expanded through a turbine that powers a generator and simultaneously reduces the gas pressure and temperature. The gas turboexpander behaves like a pinwheel in the line

Bockert

1980-01-01

307

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

308

Parametric limitations on discharge performance in the Maryland centrifugal experiment  

NASA Astrophysics Data System (ADS)

Inherent in any experiment is a set of bounding limitations. In the Maryland Centrifugal eXperiment (MCX) these limitations are manifest as restrictions upon discharge performance as defined by program goals. We therefore examine the multidimensional parameter space in which MCX operates so as to ascertain the performance boundaries along each of the variable axes. In as much as is possible, the variables are expressly decoupled in order to determine their unique effect upon discharge performance. This study has led to the following conclusions. First, the nascent cause of transitions within the MCX discharge from a higher voltage mode (H-mode) into a lower voltage mode (O-mode) appears to be consistent with the formation of a secondary breakdown within the vacuum vessel. These transitions have been shown to be mitigated by auspicious choice of insulator position and geometry. Second, the effect of variations to the radial extent of the discharge has been studied and a set of parametric dependencies determined. These show the MCX discharge to be diffusive in nature, and highly dependant upon radial extent. Thus leading to the conclusion that a minor increase to the midplane vessel extent should result in substantial performance enhancement. Finally, a global limitation to the MCX discharge has been discovered. It is manifest as an abrupt maximum attainable voltage across the plasma. This has been interpreted as a velocity limitation due to the direct relationship between plasma voltage and rotation velocity (v? = Vp/aB). An examination of a discharge struck in a background helium environment, as opposed to the standard hydrogen backfill, has shown that this limit is consistent with Alfven's theory of a critical ionization velocity (v? = 2eFi/mi ). While this limitation has been observed on the historic predecessors to MCX, there have also been cases where supercritical velocities have been achieved. Suggestions for facilitating access to this regime as well as projections for an enhanced iteration of the MCX device are listed.

Lunsford, Robert

309

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

310

Theory and economics of by-generation of electricity at city gate stations using a gas expander turbine  

SciTech Connect

The transmission pressure of pipeline gas entering a city-gate station offers an untapped energy source that gas-distribution companies can easily use to produce low-cost electricity. The high-pressure inlet gas can be heated, then isentropically expanded through a turbine that powers a generator and simultaneously reduces the gas pressure and temperature. The gas turboexpander behaves like a pinwheel in the line as the gas flow creates the rotary motion that drives the generator. The pressure and temperature differential that occurs across the inlet and outlet of the device can be held constant, functioning similarly to a standard regulator. The gas exiting the turbine is thus available at entry conditions for the gas-distribution system, while the electricity can be either used onsite or (in the case of a combination utility) fed into the network for electrical baseloading.

Bockert, B.J.

1980-01-01

311

Variational stabilization of the ionic charge densities in the electron-gas theory of crystals: Applications to MgO and CaO  

Microsoft Academic Search

The electron-gas theory of crystals is extended to include the effects of many-body forces that arise from both electrostatic and overlap interactions. These effects are incorporated through a self-consistent spherical relaxation of the ionic charge distributions such that the crystal binding energy is minimized. This variational model is used to compute the elastic constants and equations of state of MgO

George H. Wolf; Mark S. T. Bukowinski

1988-01-01

312

A fuzzy controlled three-phase centrifuge for waste separation  

SciTech Connect

The three-phase centrifuge technology discussed in this paper was developed by Neal Miller, president of Centech, Inc. The three-phase centrifuge is an excellent device for cleaning up oil field and refinery wastes which are typically composed of hydrocarbons, water, and solids. The technology is unique. It turns the waste into salable oil, reusable water, and landfill-able solids. No secondary waste is produced. The problem is that only the inventor can set up and run the equipment well enough to provide an optimal cleanup. Demand for this device has far exceeded a one man operation. There is now a need for several centrifuges to be operated at different locations at the same time. This has produced a demand for an intelligent control system, one that could replace a highly skilled operator, or at least supplement the skills of a less experienced operator. The control problem is ideally suited to fuzzy logic, since the centrifuge is a highly complicated machine operated entirely by the skill and experience of the operator. A fuzzy control system was designed for and used with the centrifuge.

Parkinson, W.J.; Smith, R.E. [Los Alamos National Lab., NM (United States); Miller, N. [Centech, Inc., Casper, WY (United States)

1998-02-01

313

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

314

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

315

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

316

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

317

A centrifuge CO{sub 2} pellet cleaning system  

SciTech Connect

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 CO{sub 2} or argon are accelerated in a high-speed rotor. The accelerated pellet stream is used to clean or etch surfaces. The advantage of this system is that the spent pellets and debris resulting from the cleaning process can be filtered leaving only the debris for disposal. This paper discusses the centrifuge CO{sub 2} pellet cleaning system, the physics model of the pellet impacting the surface, the centrifuge apparatus, and some initial cleaning and etching tests.

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

1994-10-01

318

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

319

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

320

Experiment Study of the Internal Flow in Centrifugal Pump  

NASA Astrophysics Data System (ADS)

To study the phenomena of two-phase flow with salt-out in centrifugal pump, it is important to investigate the real flow in the pump with clear water. Based on the Reynolds-averaged N-S equations and standard ?-? two-equation turbulent model, the 3D turbulent flow was simulated through the full flow passage by the fluid dynamics software FLUENT.PIV was also applied to measure the flow inside the modified centrifugal pump. Relative velocity distributions in the impeller were obtained. Combined with the results from numerical simulation and experiment, preliminary analysis of inner flow field in the centrifugal pump was presented. The experiment results also show that standard ?-? turbulent model used in simulation coincides with the inner flow of the pump basically.

Liu, D.; Wang, C. L.

2011-09-01

321

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.

Post, Richard F. (Walnut Creek, CA)

1994-01-01

322

Recycle dynamics during centrifugal compressor ESD, start-up and surge control  

SciTech Connect

Recycle systems are important components in the operation of centrifugal compressor stations. They are essential during a start-up operation, for surge protection and for emergency shutdown (ESD). These operations are inherently dynamic where interactions between equipment, control and gas flow occur in a complex manner with the associated risk of compressor surge. Of particular importance are the effects or recycle system capacity, the recycle valve characteristics, check valve dynamic behavior, piping geometry and capacitance around the compressor unit, and the performance characteristics of the centrifugal compressor itself. This paper presents numerical results of the effects of some of these parameters on surge control, ESD and unit startup. These parameters are: (1) The effects of damping the surge control flow signal in an attempt to suppress the signal noise, on the integrity of the surge control system; (2) The effects of recycle valve characteristics, stroke time and valve capacity on ESD; (3) The effects of recycle line size on ESD; and (4) The effects of the recycle valve closing time (or rate) on the startup operation, with the intent of shortening this time to minimum for environmental reasons. Results were obtained from the solution of the pertinent dynamic equations describing the gas and equipment dynamics which has been verified against field and laboratory measurements. The samples presented in this paper were applied to a 24 MW natural gas compressor station on the NOVA Gas Transmission system, and to a scale-down laboratory model. Influence of other parameters from this investigation were published elsewhere and are cited in the reference section.

Botros, K.K.; Jones, B.J. [Novacor Research and Technology Corp., Calgary, Alberta (Canada); Richards, D.J. [NOVA Gas Transmission Ltd., Calgary, Alberta (Canada)

1996-12-31

323

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 ...

324

Penetration in spot GTA welds during centrifugation  

Microsoft Academic Search

Convective flow during arc welding processes mainly depends on electromagnetic force, Marangoni force, and buoyancy force.\\u000a The Marangoni flow (caused by surface tension gradient,d?\\/dT)and the buoyancy driven flow are the major factors in controlling weld penetration in austenitic stainless steels, such as\\u000a types 304 and 316. Alloys 304 and 316 were subjected to a 7 s spot gas-tungsten arc (SGTA)

D. K. Aidun; S. A. Martin

1998-01-01

325

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

326

Apparatus and method for centrifugation and robotic manipulation of samples  

NASA Technical Reports Server (NTRS)

A device for centrifugation and robotic manipulation of specimen samples, including incubating eggs, and uses thereof are provided. The device may advantageously be used for the incubation of avian, reptilian or any type of vertebrate eggs. The apparatus comprises a mechanism for holding samples individually, rotating them individually, rotating them on a centrifuge collectively, injecting them individually with a fixative or other chemical reagent, and maintaining them at controlled temperature, relative humidity and atmospheric composition. The device is applicable to experiments involving entities other than eggs, such as invertebrate specimens, plants, microorganisms and molecular systems.

Vellinger, John C. (Inventor); Ormsby, Rachel A. (Inventor); Kennedy, David J. (Inventor); Thomas, Nathan A. (Inventor); Shulthise, Leo A. (Inventor); Kurk, Michael A. (Inventor); Metz, George W. (Inventor)

2007-01-01

327

24. RW Meyer Sugar Mill: 18761889. Centrifugal inner basket, 1879. ...  

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

24. RW Meyer Sugar Mill: 1876-1889. Centrifugal inner basket, 1879. Manufacturer, unknown. Supplied by Honolulu Iron Works, Honolulu, Hawaii, 1879. View: After sugar was granulated and cooled it was dried and drained, completely separating the sugar crystals from the molasses, in the centrifugal. Revolving at 1200 rpm the sugar charge was forced outward with the molasses flying through the holes in the brass lining. Dried sugar was left behind in the inner basket and was dug out by hand. - R. W. Meyer Sugar Mill, State Route 47, Kualapuu, Maui County, HI

328

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

329

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

330

An investigation of real gas effects in supercritical CO? compressors  

E-print Network

This thesis presents a comprehensive assessment of real gas effects on the performance and matching of centrifugal compressors operating with CO2 at supercritical conditions. The analytical framework combines first principles ...

Baltadjiev, Nikola D. (Nikola Dimitrov)

2012-01-01

331

Experiment and Theory for the Thickness Effect of Nano Metal Oxide Gas Sensing Thin Film Optimum Size of Crystal Grains and Theory of Mesoscopic Effect  

Microsoft Academic Search

For pt. I see ibid., p.Z001463-8, (2006). The existence of the optimum film thickness and optimum grain size of nano metal oxide gas sensing thin films is given by experiment results. The existence of the optimum grain size is examined theoretically to be a new mesoscopic effect, resulting from the failure of Fermi statistic law of the adsorbed negative oxygen

Lu Honglang; Sun Jingjing; Xing Jianping; Liu Wenli; Qiu Nanwan

2006-01-01

332

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

333

Scales modified for use on board the human centrifuge in the MIT Man Vehicle Lab  

E-print Network

The MIT Man Vehicle Lab (MVL) is currently performing research on the effects of rotational artificial gravity on humans through the use of a short-radius centrifuge. The MVL centrifuge allows subjects to spin in the supine ...

Samuelson, Heather Marie

2006-01-01

334

Effect of Density Gradient Centrifugation on Quality and Recovery Rate of Equine Sperm  

E-print Network

gradient volume (height) on stallion sperm quality and recovery rate in sperm pellets following centrifugation. In all three experiments, equine semen was initially centrifuged to increase sperm concentration. In Experiment 1, one-mL aliquots were layered...

Edmond, Ann J.

2010-07-14

335

Numerical simulation of the impeller tip clearance effect on centrifugal compressor performance.  

E-print Network

??This thesis presents the numerical simulation of flow in centrifugal compressors. A three-dimensional Navier-Stokes solver was employed to simulate flow through two centrifugal compressors. The… (more)

Hoenninger, Corbett Reed

2012-01-01

336

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

337

Quasi-steady centrifuge method for unsaturated hydraulic properties  

NASA Astrophysics Data System (ADS)

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.

Caputo, Maria C.; Nimmo, John R.

2005-11-01

338

Design and CFD analysis of centrifugal compressor for a microgasturbine  

Microsoft Academic Search

Purpose – This paper aims to show how a good compressor can be designed and modeled with CFD steady models and to explain reasons for discrepancies between experiment (1D design) and 3D CFD analysis. Design\\/methodology\\/approach – A model with only one impeller channel was used to compare 1D design data, which were obtained from centrifugal compressor design code, written and

Reza Aghaei tog; A. Mesgharpoor Tousi; M. Soltani

2007-01-01

339

INTELLIGENT PERFORMANCE CFD OPTIMISATION OF A CENTRIFUGAL IMPELLER  

Microsoft Academic Search

A typical centrifugal impeller characterised by a low flow coefficient and cylindrical blades is optimised by means of an intelligent automatic search program. The procedure consists of a Feasible Sequential Quadratic Programming (FSQP) algorithm (6) coupled to a Lazy Learning (LL) interpolator (1) to speed-up the process. The program is able to handle geometrical constraints to reduce the computational effort

Simone Pazzi; Francesco Martelli; Vittorio Michelassi; Marco Giachi; Frank Van den Berghen; Hugues Bersini

340

DEMONSTRATION BULLETIN: THE PLASMA CENTRIFUGAL FURNACE RETECH, INC.  

EPA Science Inventory

The plasma centrifugal furnace is a thermal technology which uses the heat generated from a plasma torch to decontaminate metal and organic contaminated waste. This is accomplished by melting metal-bearing solids and, in the process, thermally destroying organic contaminants. The...

341

Flow measurements in a centrifugal diffusor test device  

Microsoft Academic Search

This work sought to verify concepts used in the design of a large scale, low speed, radial cascade wind tunnel which was to be used to investigate flow phenomena in and the performance of vaned radial diffusors. A major contributor to centrifugal compressor efficiency is the performance of the vaned diffusor which closely follows the impeller of the compressor. The

T. Vitting

1985-01-01

342

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

343

Centrifuge models simulating magma emplacement during oblique rifting  

Microsoft Academic Search

A series of centrifuge analogue experiments have been performed to model the mechanics of continental oblique extension (in the range of 0° to 60°) in the presence of underplated magma at the base of the continental crust. The experiments reproduced the main characteristics of oblique rifting, such as (1) en-echelon arrangement of structures, (2) mean fault trends oblique to the

Giacomo Corti; Marco Bonini; Fabrizio Innocenti; Piero Manetti; Genene Mulugeta

2001-01-01

344

[Examination of the sample centrifugation time for emergency coagulation test].  

PubMed

The rapidity of coagulation testing is important for use as appropriate substitution therapy in patients with, or at risk of critical bleeding requiring massive transfusion. Whereas the ordinary method of coagulation testing is known to be slow, in a critically haemorrhaging patient, a rapid turnaround time of coagulation testing becomes indispensable. To find out if coagulation test results will be affected by a shortened centrifugation time, we measured PT (prothrombin time), APTT (activated partial thromboplastin time), FIB (fibrinogen) and PLT (platelet) in plasma, using different centrifugation times (10 min, 5 min, 3 min), and analyzed the measurements. We found that, whereas centrifugation time significantly affected the PLT count in plasma (10 min; 5.17 +/- 3.71 x 10(3)/microl, 5min; 28. +/- 26.9 x 10(3)/microl, 3min; 63.7 x 10(3)/microl), PT(10min; 14.6 +/- 5.76 sec, 5min; 14.7 +/- 5.84 sec, 3min; 14.9 +/- 6.40 sec), APTT (10min; 36.4 +/- 15.9 sec, 5min; 36.8 +/- 16.5 sec, 3min; 34.7 +/- 11.4 sec) and FIB(10min; 361 +/- 134 mg/dl, 5min; 356 +/- 132 mg/dl, 3min; 356 +/- 125 mg/dl) were not affected. These data suggest that shortening centrifugation time will have no significant effect on the value of PT, APTT and FIB, in an emergency situation. PMID:23383570

Watanabe, Yumi; Kawahara, Yoshie; Hanada, Daisuke; Nozawa, Keisuke; Tomoda, Yutaka; Kino, Shuichi

2012-11-01

345

Prediction of performance of centrifugal pumps during starts under pressure  

NASA Technical Reports Server (NTRS)

Method which calculates start-up characteristics of centrifugal pumps reveals a capacity to predict pressure drop characteristics of pumps with vaned diffusers. Calculations are based on pump geometry, design-point flow, speed, and pressure rise, and the pump characteristic within range of approximately ten percent of the design-point flow.

Rostafinski, W.

1969-01-01

346

Centrifugal casting of TiAl exhaust valves  

Microsoft Academic Search

The mould filling process and solidification of TiAl exhaust valves by centrifugal investment casting have been simulated. Two types of runner and gating systems are designed and analysed. In the preliminary design, a “tree-type” set up system is used and a significant amount of porosity is found in many valves of the simulation result. The fluid field simulations indicate that

P. X. Fu; X. H. Kang; Y. C. Ma; K. Liu; D. Z. Li; Y. Y. Li

2008-01-01

347

Effect of chronic centrifugation on body composition in the rat.  

NASA Technical Reports Server (NTRS)

Two groups of adult female rats were chronically centrifuged for 60 days (2.76 G, 4.15 G, controls at 1.00 G). Live weights of centrifugal rats decreased about 20 g (6%) per Delta 1 G above control. This weight loss comprised reductions in both body fat and fat-free body weight (FFBW) as determined by body-composition studies on eight rats per group killed at the end of centrifugation. Of nine components constituting the FFBW, only skeletal muscle, liver, and heart changed significantly in weight. Chemical composition showed reductions (compared with controls) in the fat fraction of most components and increases in the water fraction of liver and gut. Identical measurements were made on the remaining eight rats per group killed 43 days after return to 1 G. Neither centrifuged group had reached the control body-weight level at this time. No statistically significant effect of previous G level was found in any of the body-composition parameters. The possible involvment of physiological regulation was considered.

Pitts, G. C.; Bull, L. S.; Oyama, J.

1972-01-01

348

Effects of fluid leakage on performance of a centrifugal compressor  

Microsoft Academic Search

Fluid loss caused by leaks through the impeller tip clearance was investigated for a centrifugal compressor. Operating conditions, Reynolds number, and clearance were varied independently during the experiment. It was found that the average compressor performance would be reduced by about 4 percent when the relative clearance was increased from 0.0125 to 0.125 and the resulting leakage loss was dependent

T. Mashimo; I. Watanabe; I. Ariga

1979-01-01

349

Fluid dynamic interaction between water hammer and centrifugal pumps  

Microsoft Academic Search

Centrifugal pumps generate in piping systems noticeable pressure pulsations. In this paper the dynamic interaction between water hammer and pressure pulsations is presented. The experimental investigations were performed at a piping system with nominal diameter DN 100 (respectively NPS 4) and 75m total length, built at the Institute for Process Technology and Machinery. Different measurements at this testing facility show

A. Ismaier; E. Schlücker

2009-01-01

350

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

351

Experimental use of a compact centrifugal pump and membrane oxygenator as a cardiopulmonary support system.  

PubMed

Compactness and high performance are the most important requirements for a cardiopulmonary support system. The Nikkiso (HPM-15) centrifugal pump is the smallest (priming volume; 25 ml, impeller diameter; 50 mm) in clinically available centrifugal pumps. The Kuraray Menox (AL-2000) membrane oxygenator, made of double-layer polyolefin hollow fiber, has a minimum priming volume (80 ml) and a low pressure loss (65 mm Hg at 2.0 L/min of blood flow) compared with other oxygenators. The aim of this study was to evaluate the performance of the most compact cardiopulmonary support system (total priming volume: 125 ml) in animal experiments. The cardiopulmonary bypass was constructed in a canine model with the Nikkiso pump and Menox oxygenator in comparison with a conventional cardiopulmonary support system. The partial cardiopulmonary bypass was performed for 4 h to evaluate the gas exchange ability, blood trauma, serum leakage, hemodynamics, and blood coagulative parameters. The postoperative plasma free hemoglobin level of the compact cardiopulmonary system was 29.5 +/- 10.21 mg/dl (mean +/- SD), which was lower than that of the conventional cardiopulmonary system, 48.75 +/- 27.39 mg/dl (mean +/- SD). This compact cardiopulmonary system provided the advantage in terms of reduction of the priming volume and less blood damage. These results suggested the possibility of miniaturization for the cardiopulmonary bypass support system in open-heart surgery in the near future. PMID:11119082

Suenaga, E; Naito, K; Cao, Z L; Suda, H; Ueno, T; Natsuaki, M; Itoh, T

2000-11-01

352

Screen bowl centrifuge: a high-efficiency particle size separator  

SciTech Connect

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 coarse and fine particles achievable by a screen bowl centrifuge has not been systematically studied in the past. The present investigation was aimed at conducting a parametric study using a statistically designed experimental program to better understand and optimize the size classification performance of a screen bowl centrifuge. A continuously operating screen bowl centrifuge having a bowl diameter of 0.5 m was used for this study at the Illinois Coal Development Park. Three key operating parameters, i.e., feed flow rate, feed solid content and pool depth, were varied to conduct a total of 17 experiments using a three-level factorial test matrix. Some of the best size separation performances achieved in this study may be described as having an imperfection value of 0.13 at an effective separation size (d(50c)) of 38 mu m and an imperfection value of 0.27 at an effective separation size (d(50c)) of 2.8 mu m. Due to an effective separation of ultrafine high ash materials, the ash content of the screen bowl feed was reduced from 22.3% to a minimum of 8.84% with a combustible recovery of 84.1% and an ash rejection of 71.6%. A higher combustible recovery of 92.1% was achieved at a product ash content of 12.5% with a d(50c) of 2.8 mu m and imperfection of 0.27.

Mohanty, M.K.; Zhang, B.; Khanna, N.; Palit, A.; Dube, B. [South Illinois University, Carbondale, IL (United States). Dept. for Mining & Mineral Resources Engineering

2008-05-15

353

21 CFR 864.9285 - Automated cell-washing centrifuge for immuno-hematology.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Automated cell-washing centrifuge for immuno-hematology...Blood Products § 864.9285 Automated cell-washing centrifuge for immuno-hematology. (a) Identification. An automated cell-washing centrifuge for...

2010-04-01

354

Evaluation of a vertical continuous centrifuge for clarification of HTGR dissolver slurries  

SciTech Connect

A series of statistically designed centrifuge performance tests was conducted to evaluate the solid-liquid separation efficiency of a vertical continuous centrifuge. Test results show that 100% of the particles greater than 4 microns in diameter were removed from simulated HTGR fuel reprocessing dissolver solutions. Centrifugal force and liquid density are the principal variables affecting separation efficiency.

Olguin, L.J.

1980-03-01

355

How to Use CEPA Z-41 High Speed Centrifuge Prepared by Sung-Hye H. Grieco  

E-print Network

How to Use CEPA Z-41 High Speed Centrifuge Prepared by Sung-Hye H. Grieco Single Cell Fermenter. Picture taken by Sung-Hye #12;How to use CEPA Z-41 High Speed Centrifuge prepared by Sung-Hye Fermenter High Speed Centrifuge prepared by Sung-Hye Fermenter Suite in Centre for Blood Research in UBC Updated

Strynadka, Natalie

356

Harmonic generation of noble-gas atoms in the Near-IR regime using ab-initio time-dependent R-matrix theory  

E-print Network

We demonstrate the capability of ab-initio time-dependent R-matrix theory to obtain accurate harmonic generation spectra of noble-gas atoms at Near-IR wavelengths between 1200 and 1800 nm and peak intensities up to 1.8 X 10(14) W/cm(2) . To accommodate the excursion length of the ejected electron, we use an angular-momentum expansion up to Lmax = 279. The harmonic spectra show evidence of atomic structure through the presence of a Cooper minimum in harmonic generation for Kr, and of multielectron interaction through the giant resonance for Xe. The theoretical spectra agree well with those obtained experimentally.

Hassouneh, O; van der Hart, H W

2014-01-01

357

76 FR 50767 - In the Matter of USEC Inc., American Centrifuge Lead Cascade Facility, and American Centrifuge...  

Federal Register 2010, 2011, 2012, 2013

...Lead Cascade Facility (Lead Cascade) and American Centrifuge Plant...nuclear material at the Lead Cascade at the Portsmouth Gaseous Diffusion...USEC's licenses for the Lead Cascade and the ACP from USEC to ACO...remains in full force and effect. For further details...

2011-08-16

358

Theory for the effects of free gas in subsea formations on tidal pore pressure variations and seafloor displacements  

NASA Astrophysics Data System (ADS)

Loading of the seafloor by regional-scale pressure variations, such as those imposed by ocean tides, is supported by both the rock matrix and interstitial fluid. The nature of the partitioning of the support between the two depends primarily on the compressibility of the fluid and the compressibility and fluid-transport properties of the rock matrix. In this paper, we examine theoretically the influence of free gas on pore fluid compressibility, on the nature of time-dependent load partitioning, and on the consequent vertical rock deformation and seafloor displacement. An example is the gas trapped below deep-sea gas hydrate. We have derived an expression for the steady state compressibility of pore fluid considering the influence of gas solubility in water. The effect of gas solubility is seen to be important at low, such as tidal, loading frequencies and thus must be included when observations of tidally induced pore fluid pressure variations or seafloor displacements are used to constrain gas content. For very low gas concentrations ng (much less than 0.1%), the steady state fluid compressibility can be enhanced by gas solution/dissolution over the loading cycle by several factors at high ambient pressure and more than an order of magnitude at low ambient pressures (< 5 MPa). At ng > 2%, the fluid compressibility increases sensitively with ng and greatly affects the tidal response of the pore fluid pressure regardless of the solubility. Thus, with careful experimental design, tidally induced pore pressure variations may be used to detect very small amounts of free gas and constrain the quantity if ng > 2%. This method is complementary to using acoustic velocity to constrain the quantity of free gas, which works well in the ng = 0.2-2% range. We have also given an expression for the vertical deformation of subsea formations and hence of the seafloor displacement under tidal loading. The presence of free gas enhances tidally induced seafloor displacement, but the maximum effect is limited by the compressibility of the matrix frame. Given relatively low frame compressibility, tidally induced seafloor displacement is small, of the order of 1 mm, which is presently difficult to detect at tidal frequencies.

Wang, Kelin; Davis, Earl E.; van der Kamp, Garth

1998-06-01

359

Ab initio and density functional theory study of keto-enol equilibria of deltic acid in gas and aqueous solution phase: a bimolecular proton transfer mechanism.  

PubMed

Keto-enol tautomerism in deltic acid (2,3-dihydroxycycloprop-2-en-1-one) has been studied using ab initio methods and the B3LYP functional of density functional theory, as well as complete basis set (CBS-QB3 and CBS-APNO) and G4 methods. Relative and absolute energies were calculated with each of the methods, whereas computations of geometries and harmonic frequencies for dihydroxycyclopropenone and hydroxycyclopropanedione were computed in the gas phase but were limited to HF, MP2, and the B3LYP functional, in combination with the 6-31++G(3df,3pd) basis set. Using the MP2/6-31++G(3df,3pd) gas phase optimized structure, each species was then optimized fully in aqueous solution by using the polarizable continuum model (PCM) self-consistent reaction field approach, in which HF, MP2, and B3LYP levels of theory were utilized, with the same 6-31++G(3df,3pd) basis set. In both gas and aqueous solution phases, the keto form is higher in energy for all of the model chemistries considered. From the B3LYP/6-31++G(3df,3pd) Gibbs free energy, the keto-enol tautomeric equilibrium constant for 2,3-dihydroxycycloprop-2-en-1-one/3-hydroxy-1,2-cyclopropanedione is computed to be K(T)(gas) = 2.768 × 10(-12) and K(T)(aq) = 5.469 × 10(-14). It is concluded that the enol form is overwhelmingly predominant in both environments. PMID:22954314

Tadi?, Jovan M; Xu, Lai

2012-10-01

360

[Magnetic field numerical calculation and analysis for magnetic coupling of centrifugal blood pump for extracorporeal circulation].  

PubMed

This paper mainly studies the driving system of centrifugal blood pump for extracorporeal circulation, with the core being disc magnetic coupling. Structure parameters of disc magnetic coupling are related to the ability of transferring magnetic torque. Therefore, it is necessary to carry out disc magnetic coupling permanent magnet pole number (n), air gap length (L(g)), permanent magnet thickness (L(m)), permanent magnet body inside diameter (R(i)) and outside diameter (R(o)), etc. thoroughly. This paper adopts the three-dimensional static magnetic field edge element method of Ansys for numerical calculation, and analyses the relations of magnetic coupling each parameter to transmission magnetic torque. It provides a good theory basis and calculation method for further optimization of the disc magnetic coupling. PMID:24645605

Hu, Zhaoyan; Lu, Lijun; Zhang, Tianyi; Chen, Zhenglong; Zhang, Tao

2013-12-01

361

Centrifugal correction to hyperfine structure constants in the ground state of lead monofluoride  

NASA Astrophysics Data System (ADS)

The sensitivity of the PbF molecule to the electron electric dipole moment has motivated detailed microwave spectroscopy. Previous theoretical approaches cannot fully explain the spectra. In turn, the explanation from “first principles” is very important both for molecular theory and for confirmation of the correctness of the interpretation of experimental data obtained with high precision. All of these issues are decisively addressed here. We have determined centrifugal correction parameters for hyperfine structure constants, both on lead and fluorine nuclei, of the X2?1/2 state of lead monofluoride. These parameters were obtained by fitting experimentally observed pure rotational transitions and from ab initio calculations. We show that taking this correction into account is required to reproduce the experimental transition energies obtained by R. J. Mawhorter [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.84.022508 84, 022508 (2011)].

Petrov, A. N.; Skripnikov, L. V.; Titov, A. V.; Mawhorter, R. J.

2013-07-01

362

Technology evaluation report of Retech, Inc., Plasma Centrifugal Furnace, volume 1  

NASA Astrophysics Data System (ADS)

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 generated from a plasma arc to melt and vitrify solid feed material. The feed soil was a mixture of Silver Bow Creek soil and 10 percent by weight No. 2 diesel oil, spiked to provide 28,000 ppm zinc oxide and 1000 ppm hexichlorobenzene in the soil/oil mixture. Pre-treatment soil and scrubber liquor/makeup sampling was performed to characterize the material inputs to the process. Following treatment, the vitrified soil, scrubber liquor, and stack gas were sampled to determine the technology's suitability for use in destroying and immobilizing contaminants in the test soil. The results from the test were used to draw conclusions on the technology. The conclusions derived from the test results are presented.

1992-07-01

363

Production of Biodiesel at Kinetic Limit Achieved in a Centrifugal Reactor/Separator  

SciTech Connect

The kinetics of the transesterification of soybean oil has been investigated in a centrifugal reactor at temperatures from 45 to 80 C and pressures up to 2.6 bar using gas chromatography flame ionization detection (GC-FID) and infrared (IR) spectroscopy. The yields of product methyl esters were quantified using IR, proton Nuclear Magnetic Resonance (H1NMR), and viscosity measurements and were found to achieve 90% of the yield in 2 min; however, to meet ASTM specifications with one pass through the reactor, a 15 min residence time was needed. Performance was improved by sequential reactions, allowing separation of by-product glycerine and injection of additional small aliquots of methanol. The kinetics was modeled using a three-step mechanism of reversible reactions, which was used to predict performance at commercial scale. The mechanism correctly predicted the exponential decline in reaction rate as the concentration of the products allowed significant reverse reactions to occur.

McFarlane, Joanna [ORNL; Tsouris, Costas [ORNL; Birdwell Jr, Joseph F [ORNL; Lee, Denise L [ORNL; Jennings, Hal L [ORNL; Pahmer Boitrago, Amy M [ORNL; Terpstra, Sarah M [ORNL

2010-01-01

364

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

365

Selection of gas sensing materials using the Hard Soft Acid Base theory; application to Surface Acoustic Wave CO2 detection  

Microsoft Academic Search

The Hard Soft Acid Base (HSAB) theory is introduced as a new tool to select or design sensitive materials for carbon dioxide detection with SAW-BAW (Surface Acoustic Waves - Bulk Acoustic Waves) devices. According to HSAB, CO2 is hard acid, thus small organic or inorganic molecules, or polymers which can act as hard bases could be suitable candidates as sensing

B. Serban; A. K. Sarin Kumar; C. Cobianu; O. Buiu; S. Costea; C. Bostan; N. Varachiu

2010-01-01

366

Turbulent Chemically Reacting Flows According to a Kinetic Theory. Ph.D. Thesis; [statistical analysis/gas flow  

NASA Technical Reports Server (NTRS)

A review of various methods of calculating turbulent chemically reacting flow such as the Green Function, Navier-Stokes equation, and others is presented. Nonequilibrium degrees of freedom were employed to study the mixing behavior of a multiscale turbulence field. Classical and modern theories are discussed.

Hong, Z. C.

1975-01-01

367

Pressure, centrifugal, and electrically assisted dewatering of coal  

SciTech Connect

CSIRO and its collaborators have developed a major R and D project on dewatering of coal. This involves sub-projects on (1) the fundamentals of coal-water associations; (2) reducing the variability of product moisture levels from small coal centrifuges; (3) process mechanisms and optimization for fine coal dewatering; (4) pilot scale testing, engineering development and innovation. Results from each of these sub-projects are presented, and the pilot facility incorporating a vacuum filter, belt press, membrane press, hyperbaric filters and centrifuges, is discussed. The vacuum filter and membrane press can be configured for electric-field assisted dewatering, which provides substantial enhancements in the rate and degree of dewatering for fine coal, coal tailings, and other suspensions.

Bainbridge, N.W.; Johnston, B.K.; Lockhart, N.C. [CSIRO, North Ryde, New South Wales (Australia). Div. of Coal and Energy Technology

1995-10-01

368

Computational prediction of hemolysis in a centrifugal ventricular assist device.  

PubMed

This paper describes the use of computational fluid dynamics (CFD) to predict numerically the hemolysis in centrifugal pumps. A numerical hydrodynamical model, based on the full Navier-Stokes equation, was used to obtain the flow in a vaneless centrifugal pump (of corotating disks type). After proper postprocessing, critical zones in the channel were identified by means of two-dimensional color-coded maps of %Hb release. Simulation of different conditions revealed that flow behavior at the entrance region of the channel is the main cause of blood trauma in such devices. A useful feature resulting from the CFD simulation is the visualization of critical flow zones that are impossible to determine experimentally with in vitro hemolysis tests. PMID:7779017

Pinotti, M; Rosa, E S

1995-03-01

369

Experiment of a centrifugal pump during changing speed operation  

NASA Astrophysics Data System (ADS)

In this paper, a method of changing rotational speed of impeller periodically as the pulsatile working condition is developed to realize pulse outputs both of flow discharge and of head for a centrifugal pump through experiment. The performance of the centrifugal pump under pulsatile working operation condition is measured which indicates this model pump could produce desired pulse flow under such condition. Flow patterns at four testing points under pulsatile conditions are obtained by means of the particle image velocimetry (PIV) technology both with laser induced fluorescence (LIF) particles and refractive index matched (RIM) fluid. Results of PIV measurement show the distributions of velocity, streamlines, and the principal Reynolds normal stress (PRNS). Under the design flow rate condition, the relative velocity in the blade channel distributes smoothly and decreases from inlet to exit. And at the impeller exit, the relative velocity is lower close to suction side than that near pressure side of blade in most of blade channels.

Yuan, H. J.; Shao, J.; Wu, Y. L.; Liu, S. H.

2012-11-01

370

Numerical Simulation of Centrifugal Pump with Double-Suction Impeller  

NASA Astrophysics Data System (ADS)

Numerical simulation is carried out to investigate 3-D complex flow and performance characteristics of double-suction centrifugal pump by using a CFX code. Double-section centrifugal pump consisted of six blades impeller and shroud ring. Rotating speed of closed type impeller is 3000 rpm. Finite-volume method with structured mesh and k-? Shear Stress Transport turbulence model was used to guaranty more accurate prediction of turbulent flow in the pump impeller. Total head, power and overall efficiency were calculated according to the variation of flow rate to obtain performance characteristics of two types of pump. From the results, impeller having smooth curve along the shroud line obtained good performance. Complicated internal flow phenomena through impellers such as flow separation, pressure loss, flow unsteadiness and performance are investigated and discussed.

An, Young-Joon; Shin, Byeong Rog

2010-06-01

371

Probing biomechanical properties with a centrifugal force quartz crystal microbalance  

NASA Astrophysics Data System (ADS)

Application of force on biomolecules has been instrumental in understanding biofunctional behaviour from single molecules to complex collections of cells. Current approaches, for example, those based on atomic force microscopy or magnetic or optical tweezers, are powerful but limited in their applicability as integrated biosensors. Here we describe a new force-based biosensing technique based on the quartz crystal microbalance. By applying centrifugal forces to a sample, we show it is possible to repeatedly and non-destructively interrogate its mechanical properties in situ and in real time. We employ this platform for the studies of micron-sized particles, viscoelastic monolayers of DNA and particles tethered to the quartz crystal microbalance surface by DNA. Our results indicate that, for certain types of samples on quartz crystal balances, application of centrifugal force both enhances sensitivity and reveals additional mechanical and viscoelastic properties.

Webster, Aaron; Vollmer, Frank; Sato, Yuki

2014-10-01

372

Centrifugal buoyancy as a mechanism for neutron star glitches  

E-print Network

The frequent glitches (sudden increases of the apparent angular velocity) observed in certain pulsars are generally believed to be attributable to discontinuous angular momentum transfer to the outer neutron star crust from a differentially rotating superfluid layer, but the precise mechanism is not quite elucidated. Most explanations invoke vortex pinning as the essential mechanism responsible for the build up of strain in the crust that is relaxed, either by fracture of the solid structure or by discontinous unpinning, during the glitch. It is shown here that there is another mechanism that could give rise to strain, and subsequent fracture, of the solid crust, even if vortex pinning is ineffective: this is the effective force arising from the deficit of centrifugal buoyancy that will be present whenever there is differential rotation. This centrifugal buoyancy deficit force will be comparable in order of magnitude, but opposite in direction, to the force that would arise from vortex pinning if it were effective.

Brandon Carter; David Langlois; David M. Sedrakian

2000-04-10

373

Reverse-Tangent Injection in a Centrifugal Compressor  

NASA Technical Reports Server (NTRS)

Injection of working fluid into a centrifugal compressor in the reverse tangent direction has been invented as a way of preventing flow instabilities (stall and surge) or restoring stability when stall or surge has already commenced. The invention applies, in particular, to a centrifugal compressor, the diffuser of which contains vanes that divide the flow into channels oriented partly radially and partly tangentially. In reverse-tangent injection, a stream or jet of the working fluid (the fluid that is compressed) is injected into the vaneless annular region between the blades of the impeller and the vanes of the diffuser. As used here, "reverse" signifies that the injected flow opposes (and thereby reduces) the tangential component of the velocity of the impeller discharge. At the same time, the injected jet acts to increase the radial component of the velocity of the impeller discharge.

Skoch, Gary J.

2007-01-01

374

Centrifugal sedimentation of virus particles for electron microscopic counting.  

PubMed

Centrifuge cells with conical chambers were provided by using special inserts for the stainless-steel tubes that fit the Spinco SW-39 rotor. Particulate material, centrifuged in these cells, was collected on carbon-coated glass discs. These discs were exposed to OsO(4) vapor, dehydrated in graded alcohols, air-dried, and metal-shadowed. The metal-shadowed carbon film was floated from the glass, mounted on a grid, and examined. A knowledge of cell geometry and microscope magnification allowed correlation of the number of particles observed to a volume of the original suspension. A precision of +/-6% at the 95% confidence level was attained when counting approximately 100 particles per 10,000 x field. Applications and advantages of the method are discussed. PMID:5419912

Mathews, J; Buthala, D A

1970-05-01

375

Production of centrifugal fields greater than 100 million times gravity.  

PubMed

A high-speed rotation instrument to produce centrifugal fields greater than 100 million times gravity has been constructed. Small, solid, spherical high-carbon chromium steel rotors are suspended magnetically in high vacuum and spun by a rotating magnetic field. It is found that the spinning rotor explodes when the calculated average value of stress in the meridian plane reaches about 1.2 times the tensile strength of the material. The maximum speed of rotation so far achieved for more than a few days without bursting was obtained with a rotor of 1.50 mm diameter. The speed of 2.11 x 10(5) rev/s corresponded to a centrifugal field of 1.34 x 10(8) times gravity. Our instrument will find application in the study of nuclear atomic phenomena. PMID:18699609

Katano, R; Shimizu, S

1979-07-01

376

Probing biomechanical properties with a centrifugal force quartz crystal microbalance.  

PubMed

Application of force on biomolecules has been instrumental in understanding biofunctional behaviour from single molecules to complex collections of cells. Current approaches, for example, those based on atomic force microscopy or magnetic or optical tweezers, are powerful but limited in their applicability as integrated biosensors. Here we describe a new force-based biosensing technique based on the quartz crystal microbalance. By applying centrifugal forces to a sample, we show it is possible to repeatedly and non-destructively interrogate its mechanical properties in situ and in real time. We employ this platform for the studies of micron-sized particles, viscoelastic monolayers of DNA and particles tethered to the quartz crystal microbalance surface by DNA. Our results indicate that, for certain types of samples on quartz crystal balances, application of centrifugal force both enhances sensitivity and reveals additional mechanical and viscoelastic properties. PMID:25331000

Webster, Aaron; Vollmer, Frank; Sato, Yuki

2014-01-01

377

Molecular Theory and Computer Simulation Studies of Natural and Synthetic Gas Mixtures. Final Report, July 1, 1991-December 31, 1993.  

National Technical Information Service (NTIS)

FTIR and FT Raman spectroscopic measurements have been shown to provide an important new technique for the study of the formation, kinetics and inhibition of gas hydrates. Important advantages of these methods are (1) being non-invasive, they enable in-si...

K. E. Gubbins

1993-01-01

378

A theory of neutral gas emissions from a plasma contactor and its effect on electrodynamic tether performance  

NASA Astrophysics Data System (ADS)

An existing anisotropic anodic plasma contactor model is extended to include neutral gas emissions. Within the framework of the contactor model, the inclusion of external ionization leads to an integrodifferential equation. By choosing the ratio of the contactor radius to the neutral gas-electron ionization mean free path at the contactor exit as a suitable expansion parameter, an analytical expression for the current-voltage characteristic can be found. The performance of this contactor model is examined via a dynamic simulation model developed for electrodynamic tethers. Detailed models of the geomagnetic field and the ionosphere are used to create a realistic environment. The highly nonlinear contactor voltagle-current characteristic is incorporated into a circuit equation, which includes radiation impedance, and is solved along the tether's orbit. Results show that it is more effective to fully ionize the contactor gas internally, than to partially ionize it externally, and that based on the specific power for the tether system, the optimum gas to use is argon. In addition, the effect of the radiation impedance on tether system performance is examined.

Roy, R. I. S.; Hastings, D. E.

1991-06-01

379

A theory of neutral gas emissions from a plasma contactor and its effect on electrodynamic tether performance  

NASA Technical Reports Server (NTRS)

An existing anisotropic anodic plasma contactor model is extended to include neutral gas emissions. Within the framework of the contactor model, the inclusion of external ionization leads to an integrodifferential equation. By choosing the ratio of the contactor radius to the neutral gas-electron ionization mean free path at the contactor exit as a suitable expansion parameter, an analytical expression for the current-voltage characteristic can be found. The performance of this contactor model is examined via a dynamic simulation model developed for electrodynamic tethers. Detailed models of the geomagnetic field and the ionosphere are used to create a realistic environment. The highly nonlinear contactor voltagle-current characteristic is incorporated into a circuit equation, which includes radiation impedance, and is solved along the tether's orbit. Results show that it is more effective to fully ionize the contactor gas internally, than to partially ionize it externally, and that based on the specific power for the tether system, the optimum gas to use is argon. In addition, the effect of the radiation impedance on tether system performance is examined.

Roy, R. I. S.; Hastings, D. E.

1991-01-01

380

Numerical simulation of impeller-volute interaction in centrifugal compressors  

Microsoft Academic Search

A numerical procedure to predict the impeller-volute interaction in a single-stage centrifugal compressor is presented. The method couples a three-dimensional unsteady flow calculation in the impeller with a three-dimensional time-averaged flow calculation in the volute through an iterative updating of the boundary conditions on the interface of both calculation domains. The method has been used to calculate the flow in

K. Hillewaert; R. A. Van den Braembussche

1999-01-01

381

Series design of compressors for two-stage centrifugal chiller  

Microsoft Academic Search

A preliminary series design of compressors for a two-stage centrifugal chiller is suggested. Six groups of hydrodynamically\\u000a similar compressors, ranging from 233RT to 1,200RT, are introduced. Flow rates, impeller diameters, and wheel speeds for each\\u000a group are determined from hydrodynamic similarity to share impellers of adjacent groups. It is expected that these compressors\\u000a can have the same performance and efficiency

Jinhee Jeong; Hyeonkoo Lee

2003-01-01

382

Analysis and optimization of aerodynamic noise in a centrifugal compressor  

Microsoft Academic Search

The numerical methods for the performance analysis and the noise prediction of the centrifugal compressor impeller are developed, which are coupled with the optimization design methodology consisting of response surface method, statistical approach, and genetic algorithm. Navier–Stokes equations with the two-equation (k–?) turbulence model are applied to calculate impeller aerodynamic characteristics, and Ffowcs Williams–Hawkings formulation and boundary element method are

Hyosung Sun; Hyungki Shin; Soogab Lee

2006-01-01

383

The ERCOFTAC centrifugal pump OpenFOAM case-study  

Microsoft Academic Search

This work investigates the rotor-stator interaction features of OpenFOAM-1.5-dev, such as frozen rotor and sliding grid. The case studied is the ERCOFTAC Test Case U3: Centrifugal Pump with a Vaned Diffuser, a testcase from the ERCOFTAC Turbomachinery Special Interest Group. The case was presented by Combès at the ERCOFTAC Seminar and Workshop on Turbomachinery Flow Prediction VII, in Aussois, 1999.

Olivier PETIT; Maryse PAGE; Martin BEAUDOIN; Håkan NILSSON

384

Losses in pendular suspensions due to centrifugal coupling  

Microsoft Academic Search

We present an analysis of the centrifugal coupling of a simple pendulum to a dissipative support. We show that such a coupling\\u000a leads to an amplitude dependent quality factor. For amplitudes which could be present in laser interferometer gravitational\\u000a wave detector suspensions, this mechanism could limit the quality factor of the test mass suspension significantly to 1010 and should be

Sangita N Pitre; S V Dhurandhar; D G Blair; Ju Li

1994-01-01

385

At 1050 Gallery, Block 12, two centrifugal pumps, Buffalo Pumps, ...  

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

At 1050 Gallery, Block 12, two centrifugal pumps, Buffalo Pumps, Buffalo, NY, driven by Allis Chalmers motors (size 3 HSO, head 230, 120 cpm, 1750, rpm, Impulse dia. 15) installed in the 1960s and used for water-cooling system for 230-kv cable; the cables have been removed and the pumps are not currently used. - Columbia Basin Project, Grand Coulee Dam & Franklin D. Roosevelt Lake, Across Columbia River, Southeast of Town of Grand Coulee, Grand Coulee, Grant County, WA

386

Isothermal Polymerase Amplification in a Centrifugal Microfluidic Foil Cartridge  

Microsoft Academic Search

Recombinase polymerase amplification (RPA) is a new isothermal DNA amplification method that runs at 37°C, amplifies single copies in less than 15 minutes, and allows real-time fluorescence detection. For the first time we automated this method by microfluidic integration into a centrifugal lab-on-a-chip system, comprising unit operations for reconstitution of reagents, mixing with the sample, and aliquoting to test cavities.

S. Lutz; P. Weber; M. Focke; B. Faltin; G. Roth; O. Piepenburg; N. Armes; D. Mark; R. Zengerle; F. von Stetten

2009-01-01

387

Estimation of capillary pressure functions from centrifuge data  

E-print Network

ESTIMATION OF CAPILLARY PRESSURE FUNCTIONS FROM CENTRIFUGE DATA A Thesis by WILLIAM PBOIIY DULANEY, IR. Submitted to the Graduate College of Texas A8 M University in partial fulfillment, of the requirement for the degree of MASTER OF SCIENCF.... May 1986 Major Subject: Chemical I' ngineering ESTIMATION OF CAPILLARY PRESSURE FUNCTIONS FROM CENTRIFUGL" DATA A Thesis WH. LIAM PROBY DULANEY JR. Approved as to style and content by: Wgc ~~ A. T. Wat, son (Cha. irman of Commitl, ee) G. B...

Dulaney, William Proby

2012-06-07

388

Body Weight Gain during Altered Gravity: Spaceflight, Centrifugation and Transitions  

NASA Technical Reports Server (NTRS)

Gravity is a force that influences all living systems, and is often disregarded in the study of environment on growth and development. To assess the effect of gravity exposure on growth, immature rats (130-200 g) were evaluated during chronic altered gravity exposure and during transition between gravity fields. The effects of 14 days of spaceflight on body weight gain were evaluated (n=12) and compared to controls. Spaceflight did not affect weight gain. In 6 rats, the transition from spaceflight to 1 G showed a significant (p less than 0.05) post flight weight loss over 48 hr of 13 g compared to controls. Over subsequent days this loss was compensated for with no difference noted after 5 days. Exposure to hypergravity, 2 G for 16 days, was evaluated in groups of n=6 (Control; On Center Control (OCC); Centrifuged). With centrifugation or OCC there was a reduction in body weight within 24 hr. The OCC regained control weights within 13 days. The weight difference, 26 +/- 1 g, persisted with 2 G with no subsequent difference in weight gain over days 3-16 compared to controls; 3.7 +/- 0.1 versus 3.9 +/- 0.1 g/day respectively. Transition from centrifugation to 1 G resulted in a weight increase within 48 hours. Over 16 days the rate of gain was increased 3.1 +/- 0.1 g/day for centrifuge compared to 2.1 +/- 0.1 g/day for controls between Day 3 to 16. However, differences from control were still noted on Day 16. Transition from one gravity field to another causes acute changes in body weight. Transition to microgravity or 1 G, following the acute changes, results in adjustments to attain a normal weight. In hypergravity the acute reduction in body weight persist, but weight gain is normal. Transitioning from hypergravity to 1G results in an increased weight gain to compensate for the persistent reduction during exposure.

Wade, Charles E.; Harper, J. S.; Daunton, N. G.; Corcoran, M. L.; Morey-Holton, E.; Hargens, Alan R. (Technical Monitor)

1995-01-01

389

Use of partially shrouded impeller in a small centrifugal compressor  

Microsoft Academic Search

Numerical analysis is conducted for the 3-dimensional impeller and vaneless diffuser of a small centrifugal compressor. The\\u000a influence of impeller tip clearance on the flow field of the impeller is investigated. Detailed investigation on the leaking\\u000a flow across the tip clearance of the impeller shows that the leaking flow rate is higher near the exit of the impeller than\\u000a that

Jin Tang; Teemu Turunen-Saaresti; Jaakko Larjola

2008-01-01

390

Flow measurements in a centrifugal diffusor test device  

NASA Astrophysics Data System (ADS)

This work sought to verify concepts used in the design of a large scale, low speed, radial cascade wind tunnel which was to be used to investigate flow phenomena in and the performance of vaned radial diffusors. A major contributor to centrifugal compressor efficiency is the performance of the vaned diffusor which closely follows the impeller of the compressor. The purpose of this diffusor is to efficiently convert most of the kinetic energy of the transonic flow entering the vane into pressure. The need for an experimental facility which could simulate adequately, at low cost and in a controlled way, the environment of the centrifugal compressor motivated the development of the Centrifugal Diffusor Test Device (CDTD). It was expected that the generation of a three dimensional flow would provide improved empirical data on annular cascade performance. This measurement program surveyed the axial and circumferential uniformity of the flow at the inlet of a transonic wedge-type blading mounted in the device. Evaluation of the results showed the flow uniformity to be unsatisfactory. Leakage and other small perturbations in the flow field in the swirl generator are believed to be amplified by the basic flow configuration of the device.

Vitting, T.

1985-06-01

391

Massively Parallel Single-Molecule Manipulation Using Centrifugal Force  

NASA Astrophysics Data System (ADS)

Precise manipulation of single molecules has led to remarkable insights in physics, chemistry, biology, and medicine. However, two issues that have impeded the widespread adoption of these techniques are equipment cost and the laborious nature of making measurements one molecule at a time. To meet these challenges, we have developed an approach that enables massively parallel single- molecule force measurements using centrifugal force [1]. This approach is realized in the centrifuge force microscope, an instrument in which objects in an orbiting sample are subjected to a calibration-free, macroscopically uniform force- field while their micro-to-nanoscopic motions are observed. We demonstrate high- throughput single-molecule force spectroscopy with this technique by performing thousands of rupture experiments in parallel, characterizing force-dependent unbinding kinetics of an antibody-antigen pair in minutes rather than days. Currently, we are taking steps to integrate high-resolution detection, fluorescence, temperature control and a greater dynamic range in force. With significant benefits in efficiency, cost, simplicity, and versatility, single-molecule centrifugation has the potential to expand single-molecule experimentation to a wider range of researchers and experimental systems.[4pt] [1] K. Halvorsen, W.P. Wong, Biophysical Journal - Letters 98 (11), (2010).

Wong, Wesley; Halvorsen, Ken

2011-03-01

392

Numerical analysis and centrifuge modeling of shallow foundations  

NASA Astrophysics Data System (ADS)

The influence of non-coaxial constitutive model on predictions of dense sand behavior is investigated in this paper. The non-coaxial model with strain softening plasticity is applied into finite-element program ABAQUS, which is first used to predict the stress-strain behavior and the non-coaxial characteristic between the orientations of the principal stress and principal plastic strain rate in simple shear tests. The model is also used to predict load settlement responses and bearing capacity factors of shallow foundations. A series of centrifuge tests for shallow foundations on saturated dense sand are performed under drained conditions and the test results are compared with the corresponding numerical results. Various footing dimensions, depths of embedment, and footing shapes are considered in these tests. In view of the load settlement relationships, the stiffness of the load-displacement curves is significantly affected by the non-coaxial model compared with those predicted by the coaxial model, and a lower value of non-coaxial modulus gives a softer response. Considering the soil behavior at failure, the coaxial model predictions of bearing capacity factors are more advanced than those of centrifuge test results and the non-coaxial model results; besides, the non-coaxial model gives better predictions. The non-coaxial model predictions are closer to those of the centrifuge results when a proper non-coaxial plastic modulus is chosen.

Luo, Qiang; Luan, Mao-tian; Yang, Yun-ming; Wang, Zhong-tao; Zhao, Shou-zheng

2014-04-01

393

Assessment and mitigation of DNA loss utilizing centrifugal filtration devices.  

PubMed

Maximizing DNA recovery during its isolation can be vital in forensic casework, particularly when DNA yields are expected to be low, such as from touch samples. Many forensic laboratories utilize centrifugal filtration devices to purify and concentrate the DNA; however, DNA loss has been reported when using them. In this study, all centrifugal filtration devices tested caused substantial DNA loss, affecting low molecular weight DNA (PCR product) somewhat more than high molecular weight DNA. Strategies for mitigating DNA loss were then examined, including pre-treatment with glucose, glycogen, silicone (RainX(®)), bovine serum albumin, yeast RNA, or high molecular weight DNA. The length of pre-treatment and UV irradiation of pre-treatment reagents were also investigated. Pre-treatments with glucose and glycogen resulted in little or no improvement in DNA recovery, and most or all DNA was lost after silicone pre-treatment. Devices pre-treated with BSA produced irregular and uninterpretable quantitative PCR amplification curves for the DNA and internal PCR control. On the other hand, nucleic acid pre-treatments greatly improved recovery of all DNAs. Pre-treatment time and its UV irradiation did not influence DNA recovery. Overall, the results show that centrifugal filtration devices trap DNA, yet their proper pre-treatment can circumvent that loss, which is critical in the case of low copy forensic DNA samples. PMID:25173492

Doran, Ashley E; Foran, David R

2014-11-01

394

Subchronic centrifugal mechanical assist in an unheparinized calf model.  

PubMed

The purpose of this study was to determine whether the major centrifugal pumps currently in use in the United States (Medtronic, BioMedicus BioPump and Carmeda-coated BioPump, Sarns 3M centrifugal pump, and St. Jude Medical Lifestream) could function as left mechanical assist devices in the subchronic (72 h) unheparinized calf model. Calves were instrumented for left atrial to aorta ex vivo assist, and the pump flow was set at 3.5 +/- 0.4 L/min. Two calves (Sarns 3M and St. Jude) survived 72 h of pumping without clinical complications. The other 2 calves died at 62 and 66 h (Medtronic BioPump and Carmeda-coated BioPump, respectively); both had pelvic limb paralysis. The seal of the Sarns 3M pump head ruptured after approximately 36 h of pumping and required replacement. On postmortem examination, pump-associated thromboembolic lesions were detected in 3 of the 4 calves in one or more of the following organs: kidneys, pancreas, abomasum, duodenum, ileum, spleen, and lumbar spinal cord. The calf with the Sarns 3M pump had no discernable lesions. Because of the clinical abnormalities and postmortem lesions in the unheparinized calf model, it was suggested that anticoagulation is necessary for conducting centrifugal mechanical assist studies in calves using presently available technology. PMID:8817974

Wagner-Mann, C; Curtis, J; Mann, F A; Turk, J; Demmy, T; Turpin, T

1996-06-01

395

Experimental investigation of the phenomenon of centrifuging of liquids  

NASA Astrophysics Data System (ADS)

The phenomenon of centrifuging of liquids inside a horizontal tubular device rotated about its axis of symmetry has been experimentally investigated. Extensive experiments were conducted using a transparent apparatus which enabled visualization and photographic recording of the centrifuging phenomenon. Several interesting and useful qualitative observations not reported hitherto have been recorded. The effects of liquid volume ( ? l ), density (?), viscosity (?), surface tension ( ?), and the apparatus geometry, viz., diameter ( d) and length ( l), on the critical speed ( n) required to centrifuge 100 pct of the liquid were systematically studied using several inorganic liquids, the physical properties of which were also experimentally determined. The generated data over a wide range of variables have been shown to fit the following dimensionless correlation derived from first principles: 1 11663_2007_Article_BF02666429_TeX2GIFE1.gif n/{60}left( {? /{? g^3 }} right)^{1/4} = KP^a left\\{ {? left( {g/{? ? ^3 }} right)^{1/4} } right\\}^c ;P = {4v_l }/{? d^2 l} × 100 where K, a, and c are constants specific to a prescribed value of P.

Babu, S. Ramesh

1993-06-01

396

Effect of centrifugal forces on dimensional error of bored shapes  

NASA Astrophysics Data System (ADS)

Boring operations of deep holes with a slender boring bar are often hindered by the precision because of their low static stiffness and high deformations. Because of that, it is not possible to remove much larger depths of cuts than the nose radius of the tool, unlike the case of turning and face milling operations, and consequently, the relationship between the cutting force distribution, tool geometry, feed rate and depth of cut becomes non-linear and complex. This problem gets worse when working with a rotating boring head where apart from the cutting forces and the variation of the inclination angle because of shape boring, the bar and head are affected by de centrifugal forces. The centrifugal forces, and therefore the centrifugal deflection, will vary as a function of the rotating speed, boring bar mass distribution and variable radial position of the bar in shape boring. Taking in to account all this effects, a load and deformation model was created. This model has been experimentally validated to use as a corrector factor of the radial position of the U axis in the boring head.

Arsuaga, M.; de Lacalle, L. N. López; Lobato, R.; Urbikain, G.; Campa, F.

2012-04-01

397

Sturmian theory of three-body recombination: Application to the formation of H2 in primordial gas  

NASA Astrophysics Data System (ADS)

A Sturmian theory of three-body recombination is presented which provides a unified treatment of bound states, quasibound states, and continuum states. The Sturmian representation provides a numerical quadrature of the two-body continuum which may be used to generate a complete set of states within any desired three-body recombination pathway. Consequently, the dynamical calculation may be conveniently formulated using the simplest energy transfer mechanism, even for reactive systems which allow substantial rearrangement. The Sturmian theory generalizes the quantum kinetic theory of Snider and Lowry [J. Chem. Phys.10.1063/1.1682310 61, 2330 (1974)] to include metastable states which are formed as independent species. Steady-state rate constants are expressed in terms of a pathway-independent part plus a nonequilibrium correction which depends on tunneling lifetimes and pressure. Numerical results are presented for H2 recombination due to collisions with H and He using quantum-mechanical coupled states and infinite-order sudden approximations. These results may be used to remove some of the uncertainties that have limited astrophysical simulations of primordial star formation.

Forrey, Robert C.

2013-11-01

398

Kinetic theory of radio frequency quadrupole ion traps. I. Trapping of atomic ions in a pure atomic gas.  

PubMed

A kinetic theory based on the Boltzmann equation is developed for the trapping of atomic ions in a radio-frequency quadrupole ion trap containing enough neutral atoms that ion-neutral collisions cannot be ignored. The collisions are treated at the same level of sophistication and detail as is used to deal with the time- and space-dependent electric fields in the trap. As a result, microscopic definitions are obtained for the damping and stochastic forces that originate from such collisions. These definitions contrast with corresponding phenomenological terms added ad hoc in previous treatments to create damped Mathieu and Langevin equations, respectively. Furthermore, the theory indicates that either collisional cooling or heating of the ions is possible, depending upon details of the ion-neutral mass ratios and interaction potential. The kinetic theory is not dependent on any special assumptions about the electric field strengths, the ion-neutral interaction potentials, or the ion-neutral mass ratio. It also provides an ab initio way to describe the ion kinetic energies, temperatures, and other properties by a series of successive approximations. PMID:15267845

Viehland, Larry A; Goeringer, Douglas E

2004-05-15

399

Water Drainage from Unsaturated Soils in a Centrifuge Permeameter  

NASA Astrophysics Data System (ADS)

This study involves an analysis of water drainage from an initially saturated silt layer in a centrifuge permeameter to evaluate the hydraulic properties of the soil layer in unsaturated conditions up to the point where the water phase becomes discontinuous. These properties include the soil water retention curve (SWRC) and the hydraulic conductivity function (HCF). The hydraulic properties of unsaturated silt are used in soil-atmosphere interaction models that take into account the role of infiltration and evaporation of water from soils due to atmospheric interaction. These models are often applied in slope stability analyses, landfill cover design, aquifer recharge analyses, and agricultural engineering. The hydraulic properties are also relevant to recent research concerning geothermal heating and cooling, as they can be used to assess the insulating effects of soil around underground heat exchangers. This study employs a high-speed geotechnical centrifuge to increase the self-weight of a compacted silt specimen atop a filter plate. Under a centrifuge acceleration of N times earth's gravity, the concept of geometric similitude indicates that the water flow process in a small-scale soil layer will be similar to those in a soil layer in the field that is N times thicker. The centrifuge acceleration also results in an increase in the hydraulic gradient across the silt specimen, which causes water to flow out of the pores following Darcy's law. The drainage test was performed until the rate of liquid water flow out of the soil layer slowed to a negligible level, which corresponds to the transition point at which further water flow can only occur due to water vapor diffusion following Fick's law. The data from the drainage test in the centrifuge were used to determine the SWRC and HCF at different depths in the silt specimen, which compared well with similar properties defined using other laboratory tests. The transition point at which liquid water flow stopped (and Darcy's law is no longer valid) was at a relatively high degree of saturation of 0.8. This finding is important as many water flow analyses in the literature assume that Darcy's law is valid over a much wider range of degrees of saturation, an error that potentially may lead to overestimates of water flow in unsaturated soil layers.

Ornelas, G.; McCartney, J.; Zhang, M.

2013-12-01

400

Theory versus experiment for the rotordynamic coefficients of annular gas seals. Part 1: 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 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. K.; Elrod, D.; Hale, K.

1983-01-01

401

Influence of centrifuge brake on residual platelet count and routine coagulation tests in citrated plasma.  

PubMed

Sample centrifugation is an essential step in the coagulation laboratory, as clotting tests are typically performed on citrated platelet (PLT) poor plasma (PPP). Nevertheless, no clear indication has been provided as to whether centrifugation of specimens should be performed with the centrifuge brake set to on or off. Fifty consecutive sodium citrate anticoagulated samples were collected and divided into two aliquots. The former was centrifuged as for Clinical Laboratory Standards Institute (CLSI) guidelines with the centrifuge brake set to on, whereas the latter was centrifuged again as for CLSI guidelines, but with the brake set to off. In the PPP of all samples, a PLT count was performed, followed by the analysis of activated partial thromboplastin time (APTT), prothrombin time (PT) and fibrinogen (FBG). The PLT count after samples centrifugation was substantially reduced, either with centrifuge brake set to on or off (5?±?1 versus 3?±?1?×?10/l; P?=?0.009). The frequency of samples exceeding a PLT count less than 10?×?10/l was nearly double in samples centrifuged with the brake on than in those with the brake off (14 versus 8%; P?centrifuge brake set to on (mean bias 0.2?s; P?centrifuge brake set to on (mean bias 0.29?g/l; P?centrifugation for routine coagulation testing should be preferably performed with the centrifuge brake set to off for providing a better quality specimen. PMID:24389587

Daves, Massimo; Giacomuzzi, Katia; Tagnin, Enrico; Jani, Erika; Adcock Funk, Dorothy M; Favaloro, Emmanuel J; Lippi, Giuseppe

2014-04-01

402

Many-body dimensional perturbation theory for quantum confined systems with a focus on atomic gas Bose-Einstein condensates  

NASA Astrophysics Data System (ADS)

Systems that involve N identical, interacting particles under quantum confinement appear throughout many areas of physics, including chemical, condensed matter, and atomic physics. In this thesis, we present the methods of dimensional perturbation theory, a powerful set of tools that uses symmetry to yield simple results for studying such many-body systems. We present a detailed discussion of the dimensional continuation of the N-particle Schrodinger equation, the D ? infinity equilibrium structure, and the normal-mode oscillations of this structure. We use the Wilson FG matrix method to derive general, analytical expressions for the many-body normal-mode vibrational frequencies, and we give analytical results for three N-body quantum-confined systems: the N-electron atom, N-electron quantum dot, and N-atom inhomogeneous Bose-Einstein condensate with a repulsive hard-core potential. The focus of this thesis will be on the many-body physics of Bose-Einstein condensates (BEC). The achievement of BEC in magnetically trapped alkali-metal atoms in 1995 has generated a considerable amount of experimental and theoretical activity in recent years. In typical BEC experiments, the average distance between the bose atoms is much larger than the range of the atomic interactions, and hence, the properties of these weakly interacting condensates have been successfully described by the mean-field nonlinear Gross-Pitaevskii equation. Recently, however, no longer restricted to the atom's natural interaction parameter, experimentalists have created condensates with a "knob" (i.e., a Feshbach resonance) that allows them to adjust the interaction to whatever strength, repulsive or attractive, they wish. These strongly interacting condensates provide a new test bed for fundamental atomic and many-body physics. In this thesis we develop a theory that goes beyond the standard mean-field approximation for many-body systems. Feshbach resonances notwithstanding, most experimentally realized atomic-vapor condensates are dilute and are best described by the mean-field Gross-Pitaevskii equation. For this reason, we use dimensional scaling methods to obtain an analytical approximation to the GP equation that is more accurate and flexible than the commonly used ground-state Thomas-Fermi approximation. We also demonstrate the power of dimensional perturbation theory by providing a full solution of a model BEC Hamiltonian and a two-electron quantum dot Hamiltonian. A feature shared by these examples is the high degree of accuracy provided by the lowest orders of the perturbation theory. In our approach to the full many-body BEC Hamiltonian, we use the lowest orders of many-body dimensional perturbation theory to obtain semi-analytical ground-state energies and collective excitation frequencies. Our many-body calculations for BEC's compare well with the Gross-Pitaevskii results in the weakly-interacting regime, as they should, and are much improved over mean-field theory predictions in the strongly-interacting regime.

McKinney, Brett Allen

403

Lattice thermal conductivity: Computations and theory of the high-temperature breakdown of the phonon-gas model  

Microsoft Academic Search

We use classical molecular dynamics to evaluate the thermal conductivity kappa(T) from the heat-flux correlation for a two-dimensional Lennard-Jones triangular lattice. Our work, which follows Ladd, Moran, and Hoover [Phys. Rev. B 34, 5058 (1986)]10.1103\\/PhysRevB.34.5058, finds large deviations from the Eucken-Debye result kappa(T)=A\\/T predicted by the phonon-gas model, even though phonon quasiparticles are fairly well defined. The main source of

Tao Sun; Philip B. Allen

2010-01-01

404

On the inverse problem of blade design for centrifugal pumps and fans  

NASA Astrophysics Data System (ADS)

The inverse problem of blade design for centrifugal pumps and fans has been studied. The solution to this problem provides the geometry of rotor blades that realize specified performance characteristics, together with the corresponding flow field. Here a three-dimensional solution method is described in which the so-called meridional geometry is fixed and the distribution of the azimuthal angle at the three-dimensional blade surface is determined for blades of infinitesimal thickness. The developed formulation is based on potential-flow theory. Besides the blade impermeability condition at the pressure and suction side of the blades, an additional boundary condition at the blade surface is required in order to fix the unknown blade geometry. For this purpose the mean-swirl distribution is employed. The iterative numerical method is based on a three-dimensional finite element method approach in which the flow equations are solved on the domain determined by the latest estimate of the blade geometry, with the mean-swirl distribution boundary condition at the blade surface being enforced. The blade impermeability boundary condition is then used to find an improved estimate of the blade geometry. The robustness of the method is increased by specific techniques, such as spanwise-coupled solution of the discretized impermeability condition and the use of under-relaxation in adjusting the estimates of the blade geometry. Various examples are shown that demonstrate the effectiveness and robustness of the method in finding a solution for the blade geometry of different types of centrifugal pumps and fans. The influence of the employed mean-swirl distribution on the performance characteristics is also investigated.

Kruyt, N. P.; Westra, R. W.

2014-06-01

405

Natural frequencies of a pre-twisted blade in a centrifugal force field  

NASA Astrophysics Data System (ADS)

In this paper, starting with the thin shell theory, the governing partial differential equation of motion for the transverse deflection of a rotating pre-twisted plate is derived. Strain-displacement relationships include the effect of warping of the cross-section due to twist-bend coupling effect introduced as a result of pre-twist in the plate of non-circular (rectangular) cross-section. Then the equation of motion, thus derived, is used to formulate the free vibration of a typical turbo-machinery cantilevered airfoil blade by considering it as a plate of an equivalent rectangular cross-section subjected to a quasi-static load due to centrifugal force field. The analytical derivation considers both the stress-stiffening as well as stress-softening effects of the centrifugal forces on the spinning airfoil. The partial differential equation governing the flexural motion of the plate is transformed into a matrix-eigenvalue form using a Rayleigh-Ritz technique. The plate deformations are represented by a set of 'admissible' sinusoidal trial functions, which fully satisfy all the clamped-end constrains as well as the free-edge boundary conditions. The results of the analytical model exhibit an excellent agreement with the previously published test data both for thin and thick plate geometries and even in highly twisted configurations. The results of the eigenvalue solution are presented in a non-dimensional form for plates of varying aspect ratios and different amounts of pre-twist in the plate. The numerical results are directly applicable in determining the static and running frequencies of typical blades used in turbo-machinery.

Sinha, Sunil K.; Turner, Kevin E.

2011-05-01

406

Optimization of Power Consumption for Centrifugation Process Based on Attenuation Measurements  

NASA Astrophysics Data System (ADS)

The main objective of this research is to produce a mathematical model that allows decreasing the electrical power consumption of centrifugation process based on attenuation measurements. The centrifugation time for desired separation efficiency may be measured to determine the power consumed of laboratory centrifuge device. The power consumption is one of several parameters that affect the system reliability and productivity. Attenuation measurements of wave propagated through blood sample during centrifugation process were used indirectly to measure the power consumption of device. A mathematical model for power consumption was derived and used to modify the speed profile of centrifuge controller. The power consumption model derived based on attenuation measurements has successfully save the power consumption of centrifugation process keeping high separation efficiency. 18kW.h monthly for 100 daily time device operation had been saved using the proposed model.

Salim, M. S.; Abd Malek, M. F.; Sabri, Naseer; Omar, M. Iqbal bin; Mohamed, Latifah; Juni, K. M.

2013-04-01

407

Research on energy conversion mechanism of a screw centrifugal pump under the water  

NASA Astrophysics Data System (ADS)

In order to research screw centrifugal pump impeller power capability and energy conversion mechanism, we used Navier-Stokes equation and standard k-? equation turbulence model on the basis of the Euler equations to carry out screw centrifugal pump internal flow numerical simulation. This was explored by simulating specific design conditions; the medium is water, variation of speed and pressure of flow filed under the action of the impeller, and the screw centrifugal impeller shroud line and wheel line segment take monitoring sites. The monitoring points are between dynamic head and static head change to analyze the energy conversion capability along the impeller corners of screw centrifugal pump. The results show that the energy of fluid of the screw centrifugal pump is provided by spiral segment, the spiral segment in front of the impeller has played a multi-level role, it has significant reference value to research the energy conversion mechanism of screw centrifugal pump under solid-liquid two phase.

Quan, H.; Li, R. N.; Su, Q. M.; Han, W.; Cheng, X. R.; Shen, Z. J.

2013-12-01

408

Design considerations of volute geometry of a centrifugal blood pump.  

PubMed

This article compares two different design techniques that are conventionally used in the design of volutes for centrifugal pumps. The imbalanced forces due to the geometry of the volute need to be taken into consideration especially in centrifugal blood pumps with magnetically suspended impeller. A reduction of these forces can reduce the instability of the impeller motion as well as the power needed to counteract its influence. Volutes using the constant angular momentum (CAM) and the constant mean velocity (CMV) methods were developed and modeled numerically. The computational results on the effect of volute geometry on the performance of a centrifugal blood pump impeller for six different volutes are presented here. For volutes designed using the CAM method, model B (volute expansion angle of 3 degrees ) had the lowest radial force of 0.26 N while the pressure head generated was 12,900 Pa. For volutes designed using the CMV method, model F (1.6 m/s) had the lowest imbalanced force of 0.45 N. However, the pressure developed by this pump was also one of the lowest at 10,652 Pa. Furthermore, when the peak scalar stresses and the mean exposure time of particles for all designs were determined using Lagrangian particle tracking method, it was observed that in general, the peak scalar stresses in CAM designed volutes are lower than those designed using CMV method. The mean exposure time of particles in the pump ranged from 400 to 500 ms. The simulation results showed that the volute designed using CAM method was superior to that of a CMV volute in terms of the magnitude of the radial force and the peak scalar stresses for the same pressure head generated. Results show that the design of volutes for blood pumps should go beyond conventional empirical methods to obtain optimal results. PMID:16305649

Chan, Weng Kong; Wong, Yew Wah; Hu, Wei

2005-12-01

409

Theory versus experiment for the rotordynamic coefficients of labyrinth gas seals. I - A two control volume model  

NASA Technical Reports Server (NTRS)

The basic equations are derived for a two-control-volume model for compressible flow in a labyrinth seal. The recirculation velocity in the cavity is incorporated into the model for the first time. The flow is assumed to be completely turbulent and isoenergetic. The wall friction factors are determined using the Blasius formula. Jet flow theory is used for the calculation of the recirculation velocity in the cavity. Linearized zeroth- and first-order perturbation equations are developed for small motion about a centered position by an expansion in the eccentricity ratio. The zeroth-order pressure distribution is found by satisfying the leakage equation while the circumferential velocity distribution is determined by satisfying the momentum equations. The first-order equations are solved by a separation of variable solution. Integration of the resultant pressure distribution along and around the seal defines the reaction force developed by the seal and the corresponding dynamic coefficients.

Scharrer, J. K.

1987-01-01

410

A novel technique using the Hendrickx centrifuge for extracting winter sporangia of Synchytrium endobioticum from soil  

Microsoft Academic Search

A zonal centrifugation method, known as the Hendrickx centrifuge technique, was tested for routine detection of winter sporangia\\u000a of Synchytrium endobioticum in soil. In four experiments the ability of the Hendrickx centrifuge to extract the sporangia from soil was compared with\\u000a a method used by the Dutch Plant Protection Service, which is a modification of the recommended EPPO method. Naturally

J. G. N. Wander; W. van den Berg; P. H. J. F. van den Boogert; J. G. Lamers; G. C. M. van Leeuwen; G. Hendrickx; P. J. M. Bonants

2007-01-01

411

Morphology and integrity of surfaces finished by centrifugal force assisted abrasive flow machining  

Microsoft Academic Search

Centrifugal force assisted abrasive flow machining (CFAAFM) process has recently been tried as a hybrid machining process\\u000a with the aim towards performance improvement of assisted abrasive flow machining (AFM) process by applying centrifugal force\\u000a on the abrasive-laden media with a rotating centrifugal force generating (CFG) rod introduced in the workpiece passage. In\\u000a the CFAAFM process, the surfaces are generated by

R. S. Walia; H. S. Shan; P. Kumar

2008-01-01

412

Modelling of nitric acid and U(VI) Co-extraction in annular centrifugal contactors  

NASA Astrophysics Data System (ADS)

British Nuclear Fuels Limited (BNFL) is currently developing novel flow sheets for an advanced PUREX process using centrifugal contactors. This technology provides two major advantages. Firstly, centrifugal contactors can process high throughputs of liquid, while being an equipment of small size, compared to pulsed columns for example. Secondly, during the reprocessing of actinides with diluted tributyl phosphate (TBP) solutions, centrifugal contactors also minimize solvent hydrolysis and radiolysis because of the very short contact times involved.

Gaubert, E. T.; Jobson, M.; Birket, J. E.; Denniss, I. S.; May, I.

2000-07-01

413

Optimising the refrigeration cycle with a two-stage centrifugal compressor and a flash intercooler  

Microsoft Academic Search

The optimisation of a refrigeration process with a two-stage centrifugal compressor and flash intercooler is presented in this paper. The two-stage centrifugal compressor stages are on the same shaft and the electric motor is cooled with the refrigerant. The performance of the centrifugal compressor is evaluated based on semi-empirical specific-speed curves and the effect of the Reynolds number, surface roughness

Pekka Röyttä; Teemu Turunen-Saaresti; Juha Honkatukia

2009-01-01

414

Towards development of an incipient surge detection device for centrifugal compressors  

E-print Network

practical technique for the prevention of surge within the centrifugal compressor is presented in this thesis. The technique used was based on the state of flow within the boundary ? layer adjacent to the diffuser vanes. The device developed to monitor... OF FIGURES Page 10 12 13 14 Typical Compressor Performance Nap. Centrifugal Compressor Components. Variation of Lift Coefficient due to Changing Angle of Incidence. Inducer Blade Stall. Common Centrifugal Compressor Diffusers Diffuser Vane Stall...

Hassinger, David Alan

2012-06-07

415

Numerical simulation of impeller-volute interaction in centrifugal compressors  

SciTech Connect

A numerical procedure to predict the impeller-volute interaction in a single-stage centrifugal compressor is presented. The method couples a three-dimensional unsteady flow calculation in the impeller with a three-dimensional time-averaged flow calculation in the volute through an iterative updating of the boundary conditions on the interface of both calculation domains. The method has been used to calculate the flow in a compressor with an external volute at off-design operation. Computed circumferential variations of flow angles, total temperature, and pressure are shown and compared with measurements. The good agreement between the predictions and measurements confirms the validity of the approach.

Hillewaert, K.; Van den Braembussche, R.A. [von Karman Inst. for Fluid Dynamics, St-Genesius-Rode (Belgium)

1999-07-01

416

Effect of Centrifugal Transverse Wakefield for Microbunch in Bend  

SciTech Connect

We calculate centrifugal force for a short bunch in vacuum moving in a circular orbit and estimate the emittance growth of the beam in a bend due to this force. Many of the basic features of the coherent synchrotron radiation (CSR) of short bunches and its effect on beam dynamics in accelerators are now well established. The effect is usually described in terms of the longitudinal force, or wakefield, that causes the energy loss in the beam, and also redistributes the energy between the particles by accelerating the head and decelerating the tail of the bunch. Coherent radiation becomes most important for short bunches and high currents. More subtle features of CSR such as transition effect due to the entrance to and exit from the bend, CSR force in the undulator, and shielding due to the close metallic boundaries have been also studied. Much less is known about the transverse force in a short bunch moving on a circular orbit. The problem has been treated in several papers beginning from R. Talman's work, who pointed out that the centrifugal force of a rotating bunch can result in a noticeable tune shift of betatron oscillations. Later, an important correction to the Talman paper has been added, where it was shown that due to the energy variation in the bunch, the effect of the transverse force proportional to R{sup -1} is canceled, and the residual effect is of the order of R{sup -2}, that is much smaller than originally predicted. Recently, however, Derbenev and Shiltsev found the centrifugal force of the order of R{sup -1} that differs from Talman's result by a logarithmic factor only. Taking into account the existing controversy in the literature, in this paper, we consider the transverse force in a bunch based on simple physical arguments, starting from a dc beam. We will derive the centrifugal force for a relativistic coasting beam in vacuum, and then generalize the result for a short bunch, and estimate its effect on the emittance growth in a bend. Throughout this paper we assume ultrarelativistic beam, v = c, moving on a circular orbit of radius R.

Stupakov, G.V.; /SLAC

2006-03-22

417

Analyses of hydrodynamic radial forces on centrifugal pump impellers  

NASA Technical Reports Server (NTRS)

An experimental and theoretical study of the hydrodynamic interactions occurring between a centrifugal pump impeller and a volute is presented. The theoretical analysis provides a quasi-one-dimensional treatment of the flow in the volute, and it is extended to include the hydrodynamic force perturbations caused by the impeller whirling eccentrically in the volute. It is noted that these perturbations are often destabilizing. The theoretical models were found to accurately predict the radial forces caused by the flow through the impeller. The pressure acting on the front shroud of the impeller is shown to have a significant effect on the destabilizing hydrodyamic forces.

Adkins, D. R.; Brennen, C. E.

1988-01-01

418

Oxygen consumption measurements during continual centrifugation of mice.  

NASA Technical Reports Server (NTRS)

A simple method is described for measurement of metabolism of conscious, unrestrained animals, during chronic centrifugation or other conditions of isolation (23.75 hr/day) from the investigators in an essentially normal atmospheric environment for as long as seven days. This involves telemetry of pressure changes in a metabolic chamber. At 7 G's, increased O2 intake lasting two to seven days and a decreased excursion of the day-night difference were measured for male white mice with less effect or even an opposite effect at lower fields. Base-line measurements of metabolic rate per mouse are less affected by animal size than expected from the surface area law.

Fethke, W.; Cook, K. M.; Porter, S. M.; Wunder, C. C.

1973-01-01

419

Silver nanodisks: Size selection via centrifugation and optical properties  

NASA Astrophysics Data System (ADS)

Silver nanodisks, having two different sizes, and spherical particles are synthesized by soft chemistry. By using centrifugation, nanodisks are mainly selected. The experimental absorption spectra of these nanodisks with different sizes are compared to those simulated using the discrete dipole approximation method. For small nanodisk sizes, the nanodisk shape is neglected and the simulated spectra closest to the experiments are obtained by assuming a spheroidal particle. Conversely, for larger nanodisks, the precise geometries represented by snip and aspect ratio are needed for good agreement between experiments and simulations.

Germain, V.; Brioude, A.; Ingert, D.; Pileni, M. P.

2005-03-01

420

Centrifuge-operated specimen staining method and apparatus  

NASA Technical Reports Server (NTRS)

A method of staining preselected, mounted specimens of either biological or nonbiological material enclosed within a staining chamber where the liquid staining reagents are applied and removed from the staining chamber using hypergravity as the propelling force. In the preferred embodiment, a spacecraft-operated centrifuge and method of diagnosing biological specimens while in orbit, characterized by hermetically sealing a shell assembly. The assembly contains slide stain apparatus with computer control therefor, the operative effect of which is to overcome microgravity, for example on board an International Space Station.

Clarke, Mark S. F. (Inventor); Feeback, Daniel L. (Inventor)

1999-01-01

421

Mechanisms of the water-gas shift reaction catalyzed by ruthenium pentacarbonyl: a density functional theory study.  

PubMed

The mechanism of the water-gas shift reaction catalyzed by Ru(CO)5 is analyzed using density functional methods in solution within the conductor-like screening model. Four different mechanistic pathways have been considered. It turned out that the incorporation of solvent effects is very important for a reasonable comparison among the mechanistic alternatives. The explicit inclusion of a water solvent molecule significantly changes the barriers of those steps which involve proton transfer in the transition state. The corresponding barriers are either lowered or increased, depending on the structure of the corresponding cyclic transition states. The results show that protolysis steps become competitive due to solution effects. The formation of formic acid as an intermediate in another, alternative pathway is also found to be competitive. PMID:23600366

Schulz, Hannes; Görling, Andreas; Hieringer, Wolfgang

2013-05-01

422

Solvation theory to provide a molecular interpretation of the hydrophobic entropy loss of noble-gas hydration.  

PubMed

An equation for the chemical potential of a dilute aqueous solution of noble gases is derived in terms of energies, force and torque magnitudes, and solute and water coordination numbers, quantities which are all measured from an equilibrium molecular dynamics simulation. Also derived are equations for the Gibbs free energy, enthalpy and entropy of hydration for the Henry's law process, the Ostwald process, and a third proposed process going from an arbitrary concentration in the gas phase to the equivalent mole fraction in aqueous solution which has simpler expressions for the enthalpy and entropy changes. Good agreement with experimental hydration free energies is obtained in the TIP4P and SPC/E water models although the solute's force field appears to affect the enthalpies and entropies obtained. In contrast to other methods, the approach gives a complete breakdown of the entropy for every degree of freedom and makes possible a direct structural interpretation of the well-known entropy loss accompanying the hydrophobic hydration of small non-polar molecules under ambient conditions. The noble-gas solutes experience only a small reduction in their vibrational entropy, with larger solutes experiencing a greater loss. The vibrational and librational entropy components of water actually increase but only marginally, negating any idea of water confinement. The term that contributes the most to the hydrophobic entropy loss is found to be water's orientational term which quantifies the number of orientational minima per water molecule and how many ways the whole hydrogen-bond network can form. These findings help resolve contradictory deductions from experiments that water structure around non-polar solutes is similar to bulk water in some ways but different in others. That the entropy loss lies in water's rotational entropy contrasts with other claims that it largely lies in water's translational entropy, but this apparent discrepancy arises because of different coordinate definitions and reference frames used to define the entropy terms. PMID:21399280

Irudayam, Sheeba Jem; Henchman, Richard H

2010-07-21

423

Characterization of unsteady loading due to impeller-diffuser interaction in centrifugal compressors.  

E-print Network

??Time dependent simulations are used to characterize the unsteady impeller blade loading due to imipeller-diffuser interaction in centrifugal compressor stages. The capability of simulations are… (more)

Lusardi, Christopher (Christopher Dean)

2012-01-01

424

The percentage of spermatozoa lost during the centrifugation of brown bear (Ursus arctos) ejaculates is associated with some spermatozoa quality and seminal plasma characteristics.  

PubMed

Cryopreservation of brown bear (Ursus arctos) semen requires centrifugation to increase concentration and/or remove urine contamination. However, a percentage of the spermatozoa are lost in the process. This percentage varies considerably between males and ejaculates, and we have studied the effect of sperm quality and seminal plasma characteristics on the spermatozoa recovery rate after centrifugation. One hundred and thirty one sperm samples obtained from fifteen brown bear males by electroejaculation under general anaesthesia were used. The ejaculates were centrifuged 600 × g for 6 min. Motility was assessed by CASA, and acrosomal status (PNA-FITC) and viability (SYBR-14/propidium iodide) were determined by flow cytometry. Seminal plasma characteristics (albumin, alkaline phosphatase, calcium, cholesterol, creatine, glucose, glutamic oxaloacetic transaminase (GOT), lactate, lipase, magnesium, phosphate and total protein) were determined by a biochemical and gas analysis. Total motility (r = 0.26; P=0.005) and cell viability (r = 0.20; P = 0.033) were positively correlated with the percentage of recovered spermatozoa. Sperm recovery was correlated with the concentration of several components of seminal plasma: negatively with glucose concentration (r = -0.47; P = 0.005) and positively with the enzymes GOT (r = 0.36; P = 0.040) and lactate dehydrogenase (r = 0.36; P = 0.041). After sorting the data into classes according to sperm recovery (Low: 0-39, Medium: 40-69, High: 70-100), we observed that the samples with a lower recovery rate derived from ejaculates with lower values for TM, VAP and viability (P<0.05). Multiple regression analysis rendered two models to define the post-centrifugation spermatozoa recovery which included total motility and damaged acrosome or glucose, GOT and lactate dehydrogenase. We discuss these relationships and their implications in the electroejaculation procedure and the handling of the sample during centrifugation. PMID:23084761

Alvarez, M; Nicolas, M; Borragán, S; Lopez-Urueña, E; Anel-López, L; Martinez-Pastor, F; Tamayo-Canul, J; Anel, L; de Paz, P

2012-11-01

425

Pipeline gas pressure reduction with refrigeration generation  

SciTech Connect

The high pressure of pipeline gas is reduced to the low pressure of a distribution system with simultaneous generation of refrigeration by passing the gas through two successive centrifugal compressors driven by two turbo-expanders in which the compressed gas is expanded to successively lower pressures. Refrigeration is recovered from the gas as it leaves each turbo-expander. Methanol is injected into the pipeline gas before it is expanded to prevent ice formation. Aqueous methanol condensate separated from the expanded gas is distilled for the recovery and reuse of methanol.

Markbreiter, S. J.; Schorr, H. P.

1985-06-11

426

Centrifugal accelerator, system and method for removing unwanted layers from a surface  

DOEpatents

A cryoblasting process having a centrifugal accelerator for accelerating frozen pellets of argon or carbon dioxide toward a target area utilizes an accelerator throw wheel designed to induce, during operation, the creation of a low-friction gas bearing within internal passages of the wheel which would otherwise retard acceleration of the pellets as they move through the passages. An associated system and method for removing paint from a surface with cryoblasting techniques involves the treating, such as a preheating, of the painted surface to soften the paint prior to the impacting of frozen pellets thereagainst to increase the rate of paint removal. A system and method for producing large quantities of frozen pellets from a liquid material, such as liquid argon or carbon dioxide, for use in a cryoblasting process utilizes a chamber into which the liquid material is introduced in the form of a jet which disintegrates into droplets. A non-condensible gas, such as inert helium or air, is injected into the chamber at a controlled rate so that the droplets freeze into bodies of relatively high density.

Foster, Christopher A. (Clinton, TN); Fisher, Paul W. (Heiskell, TN)

1995-01-01

427

Changes in bull sperm kinematics after single layer centrifugation.  

PubMed

The objective of this study was to evaluate bull sperm kinematics after centrifugation through a single layer of a colloid [Single Layer Centrifugation (SLC)]. Ejaculates from 20 bulls were extended and stored at 4-6°C for 24 h during transport to the laboratory for SLC through Androcoll-B, followed by measurement of sperm kinematics in all samples. Total motility (86% and 88% for uncentrifuged and SLC samples, respectively) and progressive motility (84% for both the groups) were similar (p > 0.05). In contrast, straightness (STR) (0.65 vs 0.69), linearity (LIN) (0.32 vs 0.35) and beat cross frequency (BCF) (22.3 vs 23.6 Hz) were significantly higher in the SLC-selected samples than in the uncentrifuged samples, whereas velocity of the average path (VAP) (95 vs 90 ?m/s), curvilinear velocity (VCL) (192 vs 180 ?m/s), amplitude of lateral head deviation (ALH) (7 ?m vs 6.5 ?m) and hypermotility (49% vs 38%) were significantly decreased. The kinematics of the samples with the poorest motility was improved most by SLC. In conclusion, even though SLC had no direct effect on total and progressive motility, it appeared to have a positive influence on several other kinematic parameters that may be important for fertilization after artificial insemination. PMID:25251345

Yulnawati, Y; Abraham, Mc; Laskowski, D; Johannisson, A; Morrell, Jm

2014-12-01

428

Effect of Speed (Centrifugal Load) on Gear Crack Propagation Direction  

NASA Technical Reports Server (NTRS)

The effect of rotational speed (centrifugal force) on gear crack propagation direction was explored. Gears were analyzed using finite element analysis and linear elastic fracture mechanics. The analysis was validated with crack propagation experiments performed in a spur gear fatigue rig. The effects of speed, rim thickness, and initial crack location on gear crack propagation direction were investigated. Crack paths from the finite element method correlated well with those deduced from gear experiments. For the test gear with a backup ratio (rim thickness divided by tooth height) of nib = 0.5, cracks initiating in the tooth fillet propagated to rim fractures when run at a speed of 10,000 rpm and became tooth fractures for speeds slower than 10,000 rpm for both the experiments and anal sis. From additional analysis, speed had little effect on crack propagation direction except when initial crack locations were near the tooth/rim fracture transition point for a given backup ratio. When at that point, higher speeds tended to promote rim fracture while lower speeds (or neglecting centrifugal force) produced tooth fractures.

Lewicki, David G.

2001-01-01

429

Anatomical consideration for an implantable centrifugal biventricular assist system.  

PubMed

A miniaturized pivot bearing-supported centrifugal blood pump (Gyro PI) has been developed as a long-term biventricular assist system (BiVAS). In this study we determined the anatomical configuration of this system using a bovine model. Under general anesthesia, a left lateral thoracotomy was performed to open the chest. Two Gyro PI-601 pumps for left and right assists were placed in the preperitoneal pocket by a subcostal abdominal incision. The left pump could be placed along the dome of the diaphragm just beneath the apex of the left ventricle. The right pump could be placed next to the left pump. The inlet and outlet ports of both pumps penetrated the diaphragm. The inlet port of the left pump, with a length of 55 mm, was inserted directly into the apex of the left ventricle. A woven Dacron graft (150 mm long, 11 mm inner diameter) was placed between the outlet port of the left pump and the descending aorta. As for the right pump, a 100 mm long and 120 degree angled inflow conduit was placed between the inlet port and the right ventricular infundibulum. The outlet port of the right pump was connected to the main trunk of the pulmonary artery using a 90 mm long, 11 mm inner diameter Dacron graft. We could perform biventricular assistance to confirm the anatomical feasibility of the Gyro implantable centrifugal BiVAS. PMID:9335374

Takami, Y; Nakazawa, T; Otsuka, G; Tayama, E; Ohashi, Y; Sueoka, A; Schima, H; Schmallegger, H; Wolner, E; Nosé, Y

1997-10-01

430

Prediction of leakage flow in a shrouded centrifugal blood pump.  

PubMed

This article proposes a phenomenological model to predict the leakage flow in the clearance gap of shrouded centrifugal blood pumps. A good washout in the gap clearance between the rotating impeller surfaces and volute casing is essential to avoid thrombosis. However, excessive leakage flow will result in higher fluid shear stress that may lead to hemolysis. Computational fluid dynamics (CFD) analysis was performed to investigate the leakage flow in a miniaturized shrouded centrifugal blood pump operating at a speed of 2000 rpm. Based on an analytical model derived earlier, a phenomenological model is proposed to predict the leakage flow. The leakage flow rate is found to be proportional to h(?) , where h is the gap size and the exponent ? ranges from 2.955 to 3.15 for corresponding gap sizes of 0.2-0.5 mm. In addition, it is observed that ? is a linear function of the gap size h. The exponent ? compensates for the variation of pressure difference along the circumferential direction as well as inertia effects that are dominant for larger gap clearances. The proposed model displays good agreement with computational results. The CFD analysis also showed that for larger gap sizes, the total leakage flow rate is of the same order of magnitude as the operating flow rate, thus suggesting low volumetric efficiency. PMID:20883397

Teo, Ji-Bin; Chan, Weng-Kong; Wong, Yew-Wah

2010-09-01

431

Analysis of cavitation behaviour in a centrifugal pump  

NASA Astrophysics Data System (ADS)

Cavitation is a well-known problem in centrifugal pumps, causing serious damage and substantial head losses. However, the reason for the sudden head drop in cavitation curves is not fully understood. In this paper, the transient three-dimensional cavitating flow field in a centrifugal pump was calculated using RNG k-? turbulence model and Rayleigh Plesset cavitation model. The NPSH-H curve and the cavitation development in the whole passage were predicted. The blade loading and energy transfer are analyzed for various cavitation conditions. The results show that the existing of the cavities changes the load distribution on blades. With the decrease of NPSH the loads on blades tend to increases in the rear part but decreases in the front part. If NPSH is not so low, sometimes the overall torque may increase slightly, thus the head may also increase slightly. But if the NPSH become low and reach a threshold value, the overall torque will also decrease. At the same time, the energy dissipation in the vortices increases greatly because of the growth of the cavities. These two reasons make the head drop rapidly.

He, M.; Fu, L. P.; Zhou, L. J.; Guo, Q.; Wang, Z. W.

2012-11-01

432

Current-voltage relation of a centrifugally confined plasma  

NASA Astrophysics Data System (ADS)

Observations of Jupiter's auroral regions indicate that electrons are accelerated into Jupiter's atmosphere creating emissions. The acceleration of the electrons intimate that parallel electric fields and field-aligned currents develop along the flux tubes which connect the equatorial plane to the areas with auroral emission. The relationship between the development of parallel electric fields and the parallel currents is often assumed to be the same as that on Earth. However, the relationship is significantly different at Jupiter due to a lack of plasma at high latitudes as large centrifugal forces caused by Jupiter's fast rotation period (about 9.8 h) constrain the magnetospheric plasma to the equatorial plane. We use a 1-D spatial, 2-D velocity space Vlasov code which has been modified to include centrifugal forces to examine the current-voltage relationship that exists at Jupiter. In particular, we investigate this relationship at a distance of 5.9 Jovian radii, the orbital radius of Io, which is coupled with the auroral spot and Io wake auroral emissions.

Ray, L. C.; Su, Y.-J.; Ergun, R. E.; Delamere, P. A.; Bagenal, F.

2009-04-01

433

Sheets within diapirs - Results of a centrifuge experiment  

NASA Astrophysics Data System (ADS)

We carried out a centrifuge experiment to model the diapiric rise of a stratified PDMS layer from three perturbations through a non-Newtonian, ductile overburden. The experiment carried out at 700 g resulted in three composite diapirs fed by different PDMS layers. The three resulting diapirs represent two different stages of diapirism. One of the diapirs (diapir 1), which reached its level of neutral buoyancy and extruded at the surface of the model, was tabular in profile and copied by an internal intrusive body. The other two diapirs (diapirs 2 and 3) were still in the ascending stage when centrifuging was stopped and thus did not extrude at the surface. They displayed a typical balloon-on-string geometry, which develops at a high viscosity contrast between a highly viscous overburden and a less viscous buoyant material. The internal geometry of these last two diapirs, fed by the lower impure PDMS, however, did not copy the shape of their precursors. Instead, they had a finger-like shape. The finger geometry of the internal part of the diapirs might be the result of the higher viscosity of the impure lower PDMS intruding a less viscous clean PDMS. Compared to nature, diapir 1 represents a fully developed concentrically expanded pluton or nested diapir, while diapirs 2 and 3 resemble composite plutons which host magma batches of dyke-like geometry. Based on the results of our experiment we suggest that truly concentrically expanded plutons develop from the latter.

Dietl, C.; Koyi, Hemin

2011-01-01

434

Artificial gravity: head movements during short-radius centrifugation  

NASA Technical Reports Server (NTRS)

Short-radius centrifugation is a potential countermeasure to long-term weightlessness. Unfortunately, head movements in a rotating environment induce serious discomfort, non-compensatory vestibulo-ocular reflexes, and subjective illusions of body tilt. In two experiments we investigated the effects of pitch and yaw head movements in participants placed supine on a rotating bed with their head at the center of rotation, feet at the rim. The vast majority of participants experienced motion sickness, inappropriate vertical nystagmus and illusory tilt and roll as predicted by a semicircular canal model. However, a small but significant number of the 28 participants experienced tilt in the predicted plane but in the opposite direction. Heart rate was elevated following one-second duration head turns. Significant adaptation occurred following a series of head turns in the light. Vertical nystagmus, motion sickness and illusory tilt all decreased with adaptation. Consequences for artificial gravity produced by short-radius centrifuges as a countermeasure are discussed. Grant numbers: NCC 9-58. c 2001. Elsevier Science Ltd. All rights reserved.

Young, L. R.; Hecht, H.; Lyne, L. E.; Sienko, K. H.; Cheung, C. C.; Kavelaars, J.

2001-01-01

435

Physical modeling of tailings dams using centrifuge simulation techniques  

SciTech Connect

The development of the phreatic surface in a stable tailings dam is investigated by using centrifuge simulation techniques and analytical techniques. The centrifuge simulations, conducted on an 8 m (25 ft) radius machine, uses a modeling-of-models approach to determine the effects of scaling and model construction on the development of the phreatic surface. The analytical and numerical techniques include predictions of the effects of scaling on the development of the phreatic surface, determination of the location of the steady-state phreatic surface in a full scale prototype dam, and determination of the stability of a prototype dam in terms of the conventional factor-of-safety. While these analyses indicate that there should be no scaling effect on the steady-state phreatic surface, tests run at over 100 g scaling show a rise in the phreatic surface with increasing g load. Numerical predictions of the steady-state phreatic surface compare well with data taken below 100 g scaling.

Sutherland, H.J.; Rechard, R.P.

1982-08-01

436

Gas pile-up, gap overflow and Type 1.5 migration in circumbinary discs: general theory  

NASA Astrophysics Data System (ADS)

Many astrophysical binaries, from planets to black holes, exert strong torques on their circumbinary accretion discs, and are expected to significantly modify the disc structure. Despite the several decade long history of the subject, the joint evolution of the binary + disc system has not been modelled with self-consistent assumptions for arbitrary mass ratios and accretion rates. Here, we solve the coupled binary-disc evolution equations analytically in the strongly perturbed limit, treating the azimuthally averaged angular momentum exchange between the disc and the binary and the modifications to the density, scaleheight, and viscosity self-consistently, including viscous and tidal heating, diffusion limited cooling, radiation pressure and the orbital decay of the binary. We find a solution with a central cavity and a migration rate similar to those previously obtained for Type II migration, applicable for large masses and binary separations, and near-equal mass ratios. However, we identify a distinct new regime, applicable at smaller separations and masses, and mass ratio in the range 10-3 ? q ? 0.1. For these systems, gas piles up outside the binary's orbit, but rather than creating a cavity, it continuously overflows as in a porous dam. The disc profile is intermediate between a weakly perturbed disc (producing Type I migration) and a disc with a gap (with Type II migration). However, the migration rate of the secondary is typically slower than both Type I and Type II rates. We term this new regime 'Type 1.5' migration.

Kocsis, Bence; Haiman, Zoltán.; Loeb, Abraham

2012-12-01

437

Cardio-postural interactions and short-arm centrifugation.  

NASA Astrophysics Data System (ADS)

INTRODUCTION: We are interested in mechanisms associated with orthostatic tolerance. In previous studies we have shown that postural muscles in the calf contribute to both posture and blood pressure regulation during orthostatic stress. In this study we investigated the relationship between cardiovascular and postural muscle control before, during and after short arm human centrifuge (SAHC) up to 2.2 G. METHODS: Eleven healthy young subjects (6 m, 5 f), with no history of cardiovascular disease, falls or orthostatic hypotension, participated. All were familiarized with the SAHC with 10 minutes at 1-G at the feet. Each subject was instrumented in the supine position on the SAHC for beat-to-beat ECG and blood pressure (Portapres derived SBP). Bilateral lower leg EMG was collected from four leg postural muscles: tibialis anterior, medial gastrocnemius, lateral gastrocnemius, and medial soleus. Transdermal differential recording of signals was performed using an 8-channel EMG system, (Myosystem 1200, Noraxon Inc., Arizona, USA). Postural sway data of the body COP was computed from the force and moment data collected with a force platform (Accusway, AMTI, MA, USA). Before and after SAHC, the subject stood on a force platform with their gaze fixed on a point at eye level, closed their eyes and stood quietly for 5 min. A final stand was conducted 30 min after centrifugation with supine rest in between. During clockwise centrifugation (10-min 1g and 10-min 2.2g at the foot) the subjects’ head was hooded and in the dark. The subject’s body was restrained into the rotation arm with a parachute harness and given additional body support with a foot-plate. ECG, EMG and BP data were collected throughout and centre of pressure trajectory (COP) collected during the stand test. Subjects were requested to relax and not to voluntarily contract the leg muscles; however, they were not to suppress contractions as they occurred involuntarily or by reflex. A Continuous Wavelet Transform was applied to decompose the representative signals on a time-scale basis in a frequency region of [0.01 - 0.1] Hz. Their linear coupling was quantified through a coherence metric and the synchrony was characterised via the phase information to determine regions where pairs of signals were in phase lock and thereby inferring an interaction or coupling. From these data we investigate the percent time in each of two coupled interactions: EMG-SBP and COP-SBP. RESULTS: The time percentages from EMG-SBP was 6.2% (baseline), 8.1% (pre-stand), 7.7% (1g), 13.6% (2g), 10.8% (post-stand), and 8.2 (recovery-stand).ANOVA comparison (EMG-SBP) among baseline supine (6.2%), 1g (7.7%), and 2g (13.6%) yielded a p value of 0.04. Student-Newman-Keuls post hoc test showed that 2g is significantly higher than supine1 (p=0.04) and marginal significant difference between 1g and 2g (p=0.052). There was no effect of centrifugation on stand EMG-SBP, but COP-SBP was marginally increased in the recovery stand (pre-stand: 10.5%; post-stand 8.9%; recovery-stand 15.7%, p=0.20). CONCLUSION: These data indicated the activation of cardio-postural control system throughout stand and supine centrifugation, with elevation of the recruitment of muscle pump at 2g.

Blaber, Andrew; Goswami, Nandu; Xu, Da; Laurin, Alexendre

438

Compaction of Chromite Cumulates applying a Centrifuging Piston-Cylinder  

NASA Astrophysics Data System (ADS)

Stratiform accumulations of chromite cumulates, such as the UG2 chromitite layer in the Bushveld Complex, is a common feature in most of the large layered mafic intrusions. The time scales and mechanics of gravitationally driven crystal settling and compaction and the feasibility of these processes for the formation of such cumulate layers is investigated through a series of high temperature (1280-1300 °C) centrifuge-assisted experiments at 100-2000 g, 0.4-0.6 GPa. A mixture of natural chromite, with defined grain sizes (means of 5 ?m, 13 ?m, and 52 ?m), and a melt with a composition thought to represent the parental magma of the Bushveld Complex, was first chemically and texturally equilibrated at static conditions and then centrifuged. Centrifugation leads to a single cumulate layer formed at the gravitational bottom of the capsule. This layer was analysed for porosity, mean grain size, size distribution and also travelling distance of chromite crystals. The experimentally observed mechanical settling velocity of chromite grains in a suspension with ~ 24 vol% crystals is calculated to be about half (~ 0.53) of the Stokes settling velocity, consistent with a sedimentation exponent n of 2.35±0.3. The settling leads to a porosity of about 52 % in the chromite layer. Formation times of chromite orthocumulates with initial crystal content in the melt of 1 % and grain sizes of 2 mm are thus around 0.6 m/day. To achieve more compacted chromite piles, centrifugation times and acceleration were increased. Within each experiment the crystal content of the cumulate layer increases downward almost linearly at least in the lower 2/3 of the cumulate pile. Although porosity in the lowermost segment of the chromite layer decreases with increasing effective stress integrated over time, the absolute decrease is smaller than for experiments with olivine (from a previous study). Formation times of a ½ meter single chromite layer with 70 vol% chromite, is calculated to be around 20 years whereas this value is around 0.4 years for olivine cumulates. When considering a natural outcrop of a layered intrusion with multiple layers of about 50 meters height, adcumulate formation time decreases to a few months. With increasing the effective stress integrated over time, applied during centrifugation, crystal size distribution histograms move slightly toward larger grain sizes, but looking at mean grain sizes, a narrow range of changes can be observed. Classic crystal size distribution profiles corrected for real 3D sizes (CSDCorrectin program) of the chromite grains in different experiments illustrate a collection of parallel log-linear trends at larger grain sizes with a very slight overturn at small grain sizes. This is in close agreement with the idealized CSD plots of adcumulus growth.

Manoochehri, S.; Schmidt, M. W.

2012-12-01

439

Density functional theory and RRKM calculations of the gas-phase unimolecular rearrangements of methylfuran and pyran ions before fragmentations.  

PubMed

The potential energy profiles for the mutual conversion of the isomeric molecular ions [C5H6O]+* of 2-methylfuran, 3-methylfuran and 4H-pyran and the fragmentations that lead to [C(5)H(5)O](+) ions were obtained from calculations at the B3LYP/6-311G++(3df,3pd)//B3LYP/6-31G(d,p) level of theory. The various competing unimolecular processes were characterized by their RRKM microcanonical rate coefficients, k(E), using the sets of reactant and transition state frequencies and the kinetic barriers obtained from the density functional method. In either a high- or a low-energy regime, the pyrylium ion [C5H5O]+ is generated directly from the 4H-pyran molecular ion by a simple cleavage. In contrast, in the metastable kinetic window, the molecular ions of methylfurans irreversibly isomerize to a mixture of interconverting structures before dissociation, which includes the 2H- and 3H-pyran ions. The hydrogen atoms attached to saturated carbons of the pyran rings are very stabilizing at the position 2, but they are very labile at position 3 and can be shifted to adjacent positions. Once 4H-pyran ion has been formed, the C-H bond cleavage begins before any hydrogen shift occurs. According to our calculation, there would not be complete H scrambling preceding the dissociation of the molecular ions [C5H6O]+*. On the other hand, as the internal energy of the 2-methylfuran molecular ion increases, H* loss can become more important. These results agree with the available experimental data. PMID:19722223

Solano Espinoza, Eduardo A; Vallejo Narváez, Wilmer E

2009-10-01

440

Structures of protonated thymine and uracil and their monohydrated gas-phase ions from ultraviolet action spectroscopy and theory.  

PubMed

The strong UV chromophores thymine (Thy) and uracil (Ura) have identical heteroaromatic rings that only differ by one methyl substituent. While their photophysics has been elucidated in detail, the effect on the excited states of base protonation and single water molecules is less explored. Here we report gas-phase absorption spectra of ThyH(+) and UraH(+) and monohydrated ions and demonstrate that the substituent is not only responsible for spectral shifts but also influences the tautomer distribution, being different for bare and monohydrated ions. Spectra interpretation is aided by calculations of geometrical structures and transition energies. The lowest free-energy tautomer (denoted 178, enol-enol form) accounts for 230-280 nm (ThyH(+)) and 225-270 nm (UraH(+)) bands. ThyH(+) hardly absorbs above 300 nm, whereas a discernible band is measured for UraH(+) (275-320 nm), ascribed to the second lowest free-energy tautomer (138, enol-keto form) comprising a few percent of the UraH(+) population at room temperature. Band widths are similar to those measured of cold ions in support of very short excited-state lifetimes. Attachment of a single water increases the abundance of 138 relative to 178, 138 now clearly present for ThyH(+). 138 resembles more the tautomer present in aqueous solution than 178 does, and 138 may indeed be a relevant transition structure. The band of ThyH(+)(178) is unchanged, that of UraH(+)(178) is nearly unchanged, and that of UraH(+)(138) blue-shifts by about 10 nm. In stark contrast to protonated adenine, more than one solvating water molecule is required to re-establish the absorption of ThyH(+) and UraH(+) in aqueous solution. PMID:24874819

Pedersen, Sara Øvad; Byskov, Camilla Skinnerup; Turecek, Frantisek; Brøndsted Nielsen, Steen

2014-06-19

441

Effects of space flight, clinorotation, and centrifugation on the growth and metabolism of Escherichia coli  

NASA Astrophysics Data System (ADS)

Previous experiments have shown that space flight stimulates bacterial growth and metabolism An explanation for these results is proposed, which may eventually lead to improved terrestrial pharmaceutical production efficiency. It is hypothesized that inertial acceleration affects bacterial growth and metabolism by altering the transport phenomena in the cells' external fluid environment. It is believed that this occurs indirectly through changes in the sedimentation rate acting on the bacteria and buoyancy-driven convection acting on their excreted by-products. Experiments over a broad range of accelerations consistently supported this theory. Experiments at 1 g indicated that higher concentrations of excreted byproducts surrounding bacterial cells result in a shorter lag phase. Nineteen additional experiments simulated 0 g and 0.5 g using a clinostat, and achieved 50 g, 180 g, and 400 g using a centrifuge. These experiments showed that final cell density is inversely related to the level of acceleration. The experiments also consistently showed that acceleration affects the length of the lag phase in a non-monotonic, yet predictable, manner. Additional data indicated that E. coli metabolize glucose less efficiently at hypergravity, and more efficiently at hypogravity. A space-flight experiment was also performed. Samples on orbit had a statistically significant higher final cell density and more efficient metabolism than did ground controls. These results, which were similar to simulations of 0 g using a clinostat, support the theory that gravity only affects bacterial growth and metabolism indirectly, through changes in the bacteria's fluid environment. Evidence of buoyancy-driven convection associated with bacterial growth was also obtained by photographing a plume rising from metabolizing bacteria. These plumes were analyzed mathematically. Additional analysis, using a computer simulation, investigated the effects of diffusion and sedimentation. All of the analyses agreed with observed results and supported the proposed theory.

Brown, Robert Bayne

442

Centrifuge enrichment plants. (Latest citations from the NTIS bibliographic database). Published Search  

SciTech Connect

The bibliography contains citations concerning the design, control, monitoring, and safety of centrifuge enrichment plants. Power supplies, enrichment plant safeguards, facility design, cascade heater test loops to monitor the enrichment process, inspection strategies, and the socioeconomic effects of centrifuge enrichment plants are examined. Radioactive waste disposal problems are considered. (Contains a minimum of 171 citations and includes a subject term index and title list.)

NONE

1993-09-01

443

Centrifuge enrichment plants. (Latest citations from the NTIS bibliographic database). Published Search  

SciTech Connect

The bibliography contains citations concerning the design, control, monitoring, and safety of centrifuge enrichment plants. Power supplies, enrichment plant safeguards, facility design, cascade heater test loops to monitor the enrichment process, inspection strategies, and the socioeconomic effects of centrifuge enrichment plants are examined. Radioactive waste disposal problems are considered. (Contains a minimum of 172 citations and includes a subject term index and title list.)

Not Available

1994-03-01

444

Design and Numerical Investigation of Advanced Radial Inlet for a Centrifugal Compressor Stage  

Microsoft Academic Search

The performance of a centrifugal compressor stage can be seriously affected by inlet flow distortions due to an unsatisfactory inlet configuration and the resulting flow structure. In this study, two radial inlets were designed for a centrifugal compressor stage and investigated numerically using a commercially available 3D viscous Navier-Stokes code. The intent of the design was to minimize the total

Yunbae Kim; Jay Koch

445

An investigation of the three-dimensional flow field in a centrifugal compressor  

Microsoft Academic Search

A series of experiments was performed to provide three-dimensional flow field data in centrifugal compressor passages and to describe the characteristic flow phenomena at the point of incipient rotating stall. These experiments entailed the acquisition and analysis of one-dimensional Laser Doppler Velocimeter (LDV) data in the impeller passages of the Purdue Research Centrifugal Compressor at two compressor operating points: the

John Robert Fagan Jr.

1989-01-01

446

Centripetal/Centrifugal Family Style of Families with Aggressive and Non-Aggressive Boys.  

ERIC Educational Resources Information Center

Research on family interaction has characterized family style on centripetal and centrifugal dimensions, representing opposing natures with their own continua. Centripetal forces produce binding, or a prolonged process of separation of parent and child; centrifugal forces preciptate expelling, or hastened separation and premature autonomy. To…

Hurst, Duane F.; And Others

447

Drive actuation in active control of centrifugal compressors Jan Tommy Gravdahl and Olav Egeland  

E-print Network

Drive actuation in active control of centrifugal compressors Jan Tommy Gravdahl and Olav Egeland-1375 Billingstad NORWAY CompressorShaft Electric drive Active surge control law Shaft speed Compressor performance control Figure 1: Active surge control using drive 1 Introduction Traditionally, centrifugal

Gravdahl, Jan Tommy

448

Bond Graph Modeling of Centrifugal Compressor System Nur Uddin and Jan Tommy Gravdahl  

E-print Network

Bond Graph Modeling of Centrifugal Compressor System Nur Uddin and Jan Tommy Gravdahl Dept surge, surge avoidance system, active surge control. Abstract A novel method of modeling centrifugal damage, espe- cially to compressor blades and bearings. It is of interest to study the surge phenomena

Gravdahl, Jan Tommy

449

Respiratory Syncytial Virus Isolation by Combined Continuous Flow-Isopycnic Banding Centrifugation  

PubMed Central

A new zonal centrifuge rotor (B-IX) which combines continuous sample flow centrifugation with isopycnic banding has been used to isolate and concentrate respiratory syncytial virus from liter volumes of culture fluid. This isolation technique utilizes a sucrose density gradient to trap and isopycnically band the virus particles, and permits recovery of the particles from the rotor in an unaggregated condition. PMID:5621468

Cline, G. B.; Coates, Helen; Anderson, N. G.; Chanock, R. M.; Harris, W. W.

1967-01-01

450

Centrifugal effects of the flow of plasma round the geomagnetic hollow  

Microsoft Academic Search

A method of calculating the shape and position of the geomagnetic hollow, taking into account centrifugal effects in the flow of plasma round the hollow, is considered. Comparison is made with the results of Chapman and Kendall (1961), who investigated a cylindrical sheet problem in which centrifugal effects are also present, and with the hollow calculated by Beard (1960), who

Angela M. Downs

1965-01-01

451

Inward ``Centrifugal'' Force on a Helium-Filled Balloon: An Illustrative Experiment  

Microsoft Academic Search

A demonstration of a paradoxical ``inward centrifugal force'' in a circular motion is presented. It can be visualized by placing a helium balloon inside a car that is taking a bend. The analysis of the problem in an inertial frame allows for the right explanation of the phenomenon observed, and avoids the use of a centrifugal force directed-in this case-to

Vicente M. Aguilella; Antonio Alcaraz; Patricio Ramírez

2002-01-01

452

Centrifugal separation. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search  

SciTech Connect

The bibliography contains citations of selected patents concerning processes used for centrifugal separation of nonsimilar materials. Topics include sugars, bloodcells, gasses, coal, isotopes, and partially molten metals. Apparatus for centrifugal separation using rotors or tubular containers are also presented. (Contains a minimum of 60 citations and includes a subject term index and title list.)

NONE

1995-05-01

453

Numerical modeling and experimental validation of uniform microchamber filling in centrifugal microfluidics  

E-print Network

microfluidics Jonathan Siegrist,*a Mary Amasia,a Navdeep Singh,b Debjyoti Banerjeeb and Marc Madoua Received 1st analysis of microchamber filling in centrifugal microfluidics is presented. In the development of micro on centrifugal microfluidic platforms, numerical modeling using the Volume of Fluids method is performed

Banerjee, Debjyoti

454

Residual moisture reduction in coarse coal centrifuges using air purging. Part 3. Commercial scale trials  

Microsoft Academic Search

CSIRO\\/Novatech Consulting have been developing air purging as a new way of reducing the moisture content of coarse coal products from vibrating basket centrifuges. The process involves injecting a turbulent stream of high velocity air, via an air knife manifold, through the coal bed as it traverses the centrifuge basket. This paper describes the results obtained when the process was

D. Condie; B. Johnston; S. Nicol; M. Thomas; C. Veal

2002-01-01

455

Elimination of Adverse Leakage Flow in a Miniature Pediatric Centrifugal Blood Pump by Computational Fluid Dynamics  

E-print Network

Elimination of Adverse Leakage Flow in a Miniature Pediatric Centrifugal Blood Pump by Computational Fluid Dynamics­ Based Design Optimization JINGCHUN WU,* JAMES F. ANTAKI, WILLIAM R. WAGNER, TREVOR levitated centrifugal blood pump intended to deliver 0.3­1.5 l/min of support to neo- nates and infants

Paden, Brad

456

Experimental Investigation on a Centrifugal Compressor by means of Squealer Tips Based on exit Flow Measurements  

Microsoft Academic Search

Centrifugal compressors are suitable for low specific speed, high pressure ratio and low mass flow applications. They are used in large refrigeration units, petro-chemical plants, and power plants for small aircraft and helicopters. Performance of the centrifugal compressor is slightly lower than that of the axial type. However, a much higher pressure ratio-per stage, single piece impeller and a wider

S. Senthil; N. Krishna Mohan

457

DETERMINATION OF THE SWELL-STRESS CURVE OF AN EXPANSIVE SOIL USING CENTRIFUGE TECHNOLOGY  

E-print Network

to an increased unit weight. A method is initially proposed to define a representative effective stressDETERMINATION OF THE SWELL-STRESS CURVE OF AN EXPANSIVE SOIL USING CENTRIFUGE TECHNOLOGY to determine the relationship between swell and effective stress of a soil using centrifuge testing. Samples

Zornberg, Jorge G.

458

Density functional theory investigations on the structure and dissolution mechanisms for cellobiose and xylan in an ionic liquid: gas phase and cluster calculations.  

PubMed

Density functional theory (DFT) calculations have been carried out for cellobiose and xylan chosen as models for cellulose and hemicellulose, respectively, in gas phase, implicit and explicit solvent (water, methanol, and the ionic liquid, 1,3-dimethylimidazolium acetate) media using plane wave and atom centered basis set approaches in order to find out lowest energy conformers and configurations. Geometry, vibrational properties, and (1)H and (13)C NMR chemical shift values have been discussed under all three conditions. Calculations predict that inter- and intramolecular hydrogen bonding play an important role in the dissolution processes. In the gas phase and in implicit solvent, the anti-anti conformer of cellobiose and the anti-syn conformer of xylan are the most stable due to the formation of a large number of intramolecular hydrogen bonds. However, in the cluster calculations containing ion pairs of the ionic liquid (IL) surrounding the cellulosic units, the anti-syn conformer of cellobiose is more stable as intramolecular hydrogen bonds are substituted by intermolecular ones formed with the ions of the IL. The complexes of cellobiose (or of xylan) with the ions of the ionic liquid are stable with large negative binding energies ranging between -21 and -55 kcal mol(-1). The predicted (1)H NMR values of the lowest energy cellobiose conformers are in good agreement with the experimental value. Xylan binds stronger with the IL than cellobiose does by 20 kcal mol(-1). Furthermore, the two pentose rings in xylan are rotated by 60° to each other in contrast to their coplanarity in cellobiose, which can explain the higher solubility and the amorphous nature of hemicellulose in ionic liquids. The fewer number of hydroxyl groups in xylan (relative to cellobiose) does not affect the number of cations present in its first solvation shell while the number of anions is reduced. PMID:22171976

Payal, Rajdeep Singh; Bharath, R; Periyasamy, Ganga; Balasubramanian, S

2012-01-19

459

Rotary heat pump driven by natural gas  

Microsoft Academic Search

This paper describes the development of an efficient cycle based upon the rotation of a hybrid absorption\\/recompression arrangement. This novel refrigeneration cycle combines a mechanical compressor and absorption system, together with process intensification which exploits radial flow driven by centrifugal force. The system is driven by a gas-engine, in order to utilise the waste heat produced by the engine. The

S. B. Riffat; A. P. Warren; R. A. Webb

1995-01-01

460

A Centrifugo-Magnetically Actuated Gas Micropump  

Microsoft Academic Search

This paper describes a novel gas micropump on a centrifugal microfluidic platform. The pump is integrated on a passive and microstructured polymer disk which is sealed with an elastomer lid featuring paramagnetic inlays. The rotational motion of this hybrid disk over a stationary magnet induces a designated sequence of volume displacements of the elastic lid, leading to a net transport

S. Haeberle; N. Schmitt; R. Zengerle; J. Ducree

2006-01-01