WorldWideScience

Sample records for prepackaged buoyancy system

  1. Modeling the Buoyancy System of a Wave Energy Power Plant

    DEFF Research Database (Denmark)

    Pedersen, Tom S.; Nielsen, Kirsten M.

    2009-01-01

    A nonlinear dynamic model of the buoyancy system in a wave energy power plant is presented. The plant ("Wave Dragon") is a floating device using the potential energy in overtopping waves to produce power. A water reservoir is placed on top of the WD, and hydro turbines lead the water to the sea...

  2. Modeling the Buoyancy System of a Wave Energy Power Plant

    DEFF Research Database (Denmark)

    Pedersen, Tom S.; Nielsen, Kirsten M.

    2009-01-01

    A nonlinear dynamic model of the buoyancy system in a wave energy power plant is presented. The plant ("Wave Dragon") is a floating device using the potential energy in overtopping waves to produce power. A water reservoir is placed on top of the WD, and hydro turbines lead the water to the sea...

  3. Design and Analysis of Typical Buoyancy Tank Riser Tensioner Systems

    Institute of Scientific and Technical Information of China (English)

    Zhuang Kang; Lusheng Jia; Liping Sun; Wenzhou Liang

    2012-01-01

    The method for design and analysis of a buoyancy tank riser tensioner system (BTRTS) was put forward in this paper,taking the free standing hybrid riser's top buoyancy tank as an example.The design procedure was discussed and was also illustrated in a flowchart,after a short description of the global arrangement,structure configuration,and the function of different types of buoyancy tanks (BT).The objective of this paper is to describe a way of developing a BT with minimal hydro force,maximal net lift,and no redundancy of comparunents.The method of determining the main dimensions of the BT,namely the length and the outer diameter,was outlined.A series of investigations was conducted for a West Africa FSHR BT design,and the effect of the ratio of the length to the outer diameter (L/D) on the hydrodynamics and the weight of the BT was discussed.The methodology of designing the internal structure of the BT was presented.The effects of the number of compartments and the dimension of the inner stem on the BT weight and strength were compared.The relationship between inner structure and the number one index of the BT as well as the riser's top tension factor (TTF) were illustrated for normal operating conditions and conditions with one or more compartments (or inner stem) damaged.A design instance was given in this paper,when L/D is 4-6,the BT weight and the drag force are compromised.When the BT is divided into 10 compartments,the riser TTF will reach the maximum value,and the ratio of the stem OD to shell OD is about 0.3.A global strength analysis method of the BT and the main load case matrix was also included in the paper,together with the local strength analysis of the buoyancy tank's pad-eye assembly.

  4. Maximum acceptable inherent buoyancy limit for aircrew/passenger helicopter immersion suit systems.

    Science.gov (United States)

    Brooks, C J

    1988-12-01

    Helicopter crew and passengers flying over cold water wear immersion suits to provide hypothermic protection in case of ditching in cold water. The suits and linings have trapped air in the material to provide the necessary insulation and are thus very buoyant. By paradox, this buoyancy may be too much for a survivor to overcome in escaping from the cabin of a rapidly sinking inverted helicopter. The Canadian General Standard Board requested that research be conducted to investigate what should be the maximum inherent buoyancy in an immersion suit that would not inhibit escape, yet would provide adequate thermal insulation. This experiment reports on 12 subjects who safely escaped with 146N (33 lbf) of added buoyancy from a helicopter underwater escape trainer. It discusses the logic for and recommendation that the inherent buoyancy in a helicopter crew/passenger immersion suit system should not exceed this figure.

  5. Fluid mechanics of ventilation system generated by buoyancy and momentum sources and experiments research

    Institute of Scientific and Technical Information of China (English)

    WANG Xin; HUANG Chen; FU Yu-ying; CAO Wei-wu

    2010-01-01

    This paper presents fluid mechanics of ventilation system formed by the momentum source and the buoyancy source,which investigates inter-action between the plume and the non-isothermal air jet since buoyancy source is produced by the plume and momentum source is generated by the air jet,respectively.The interaction is discussed by a mathematical model,an idealized situation of the plume rising from a point heat source of buoyancy alone-in particular the initial momentum flux at the source is zero.Furthermore,the paper discusses the effects of the parameters such as strength of source,air-flow volume and air-flow velocity used in the mathematical-physical model.Considering the effect of the plume generated by the indoor heat source,one expression of trajectory of the non-isothermal air jet produced by jet diffuser is deduced.And field-experiment has also been carried out to illustrate the effect on flowing-action of the air jet and validate the theoretical work.It can be concluded that the heat sources do have effect on the flowing-action of the air jet,and the effect mainly depends on the interaction produced by the plume and the air jet.The results show that the thermal buoyant effect of plumes on the air jet should be taken into account if the indoor heat sources are large enough.Numerical simulation is conducted and coincides with the experimental results as well.

  6. A transient thermal model of a neutral buoyancy cryogenic fluid delivery system

    Science.gov (United States)

    Bue, Grant C.; Conger, Bruce S.

    A thermal-performance model is presently used to evaluate a preliminary Neutral Buoyancy Cryogenic fluid-delivery system for underwater EVA training. Attention is given to the modeling of positional transients generated from the moving of internal components, including the control of cycling artifacts, as well as to the convection and boiling characteristics of the cryofluid, 250-psi N2/O2 gas, and water contained in the tank. Two piston designs are considered according to performance criteria; temperature and heat-transfer rate profiles are presented.

  7. Parametric Studies on Buoyancy Induced Flow through Circular Pipes in Solar water heating system

    Directory of Open Access Journals (Sweden)

    Dr. S. V. Prayagi

    2011-01-01

    Full Text Available Solar energy is the primary source of energy for our planet. The average solar energy reaching the earth in the tropical zone is about 1kWh/m2 giving approximately 5 to 10 kWh/m2 per day. Increased utilization of solar energy in India would result in all around benefits, both in term of cleaner environment and monetary gain.The energy from the sun can be used for various purposes such as water heating, water distillation, refrigeration, drying, power generation etc. The present work deals with solar water heating system in particular. Performance of the solar collectors can be determined using the famous Hottel-Whillier-Bliss equation [1]. The analysis is simple for the forced convection situation, where the flow rate is artificially maintained constant to a desired value and the heat transfer coefficient can easily be predicted using the information available in the literature. However the natural convection situation it is very difficult to analyze as appropriate correlations for predicting the values of induced mass flow rate due to thermosiphon effect and the associated heat transfer coefficient are not available. The aim of the present investigation, therefore, is to establish correlations for heat transfer and flow characteristics for the buoyancy induced flow through inclined tubes in case of solar water heating system in particular. Considering the complexity of the problem, experimental approach is preferred. In order to produce required data, experiments were performed using inclined tubes of various lengths, diameters, inclinations, and different heat inputs.

  8. Performance enhancement of a Lorentz force velocimeter using a buoyancy-compensated magnet system

    Science.gov (United States)

    Ebert, R.; Leineweber, J.; Resagk, C.

    2015-07-01

    Lorentz force velocimetry (LFV) is a highly feasible method for measuring flow rate in a pipe or a duct. This method has been established for liquid metal flows but also for electrolytes such as saltwater. A decrease in electrical conductivity of the medium causes a decrease of the Lorentz force which needs to be resolved, affecting the accuracy of the measurement. We use an electrical force compensation (EFC) balance for the determination of the tiny force signals in a test channel filled with electrolyte solution. It is used in a 90°-rotated orientation with a magnet system hanging vertically on its load bar. The thin coupling elements of its parallel guiding system limit the mass of the magnets to 1 kg. To overcome this restriction, which limits the magnetic flux density and hence the Lorentz forces, a weight force compensation mechanism is developed. Therefore, different methods such as air bearing are conceivable, but for the elimination of additional horizontal force components which would disturb the force signal, only compensation by lift force provided by buoyancy is reasonable. We present a swimming body setup that will allow larger magnet systems than before, because a large amount of the weight force will be compensated by this lift force. Thus the implementation of this concept has to be made with respect to hydrodynamical and mechanical stability. This is necessary to avoid overturning of the swimming body setup and to prevent inelastic deformation. Additionally, the issue will be presented and discussed whether thermal convection around the lifting body diminishes the signal-to-noise ratio (SNR) significantly or not.

  9. Neutral Buoyancy Laboratory (NBL)

    Data.gov (United States)

    Federal Laboratory Consortium — The Neutral Buoyancy Laboratory (NBL) is an astronaut training facility and neutral buoyancy pool operated by NASA and located at the Sonny Carter Training Facility,...

  10. Wave Dragon Buoyancy Regulation Study

    DEFF Research Database (Denmark)

    Jakobsen, Jens; Kofoed, Jens Peter

    Wave Dragon is a wave energy converter, which was deployed offshore at Nissum Bredning in Denmark in 2003. The experience gained from operating Wave Dragon during 2003 and 2004 has shown that the buoyancy regulation system can be improved in a number of ways. This study describes the current situ...... situation, and proposes a number of activities in order to improve the buoyancy regulation system. This work was performed under EU ENERGIE contract no. ENK5-CT-2002-00603, and is a contribution to WP 2.3/2.4 and D40/D41....

  11. Wave Dragon Buoyancy Regulation Study

    DEFF Research Database (Denmark)

    Jakobsen, Jens; Kofoed, Jens Peter

    Wave Dragon is a wave energy converter, which was deployed offshore at Nissum Bredning in Denmark in 2003. The experience gained from operating Wave Dragon during 2003 and 2004 has shown that the buoyancy regulation system can be improved in a number of ways. This study describes the current...

  12. Zero-power autonomous buoyancy system controlled by microbial gas production

    Science.gov (United States)

    Wu, Peter K.; Fitzgerald, Lisa A.; Biffinger, Justin C.; Spargo, Barry J.; Houston, Brian H.; Bucaro, Joseph A.; Ringeisen, Bradley R.

    2011-05-01

    A zero-power ballast control system that could be used to float and submerge a device solely using a gas source was built and tested. This system could be used to convey sensors, data loggers, and communication devices necessary for water quality monitoring and other applications by periodically maneuvering up and down a water column. Operational parameters for the system such as duration of the submerged and buoyant states can be varied according to its design. The gas source can be of any origin, e.g., compressed air, underwater gas vent, gas produced by microbes, etc. The zero-power ballast system was initially tested using a gas pump and further tested using gas produced by Clostridium acetobutylicum. Using microbial gas production as the only source of gas and no electrical power during operation, the system successfully floated and submerged periodically with a period of 30 min for at least 24 h. Together with microbial fuel cells, this system opens up possibilities for underwater monitoring systems that could function indefinitely.

  13. Use of pre-packaged chloroquine for the home management of presumed malaria in Malagasy children

    Directory of Open Access Journals (Sweden)

    Malvy Denis

    2006-09-01

    Full Text Available Abstract Objective The main objective of this study was to assess the quality of home malaria management with pre-packaged chloroquine in two areas in the Moramanga district of Madagascar. The knowledge, attitude and practices of care providers in terms of home treatment options were evaluated and compared. The availability of treatment options by studying retailers and community-based service providers was also investigated. Methods A cross-sectional investigation in two communities, in the hamlets and villages located close to carers, retailers, community-based service providers and primary health centres was carried out. Results Carers in the two districts were equally well aware of the use of pre-packaged chloroquine. Their first response to the onset of fever was to treat children with this antimalarial drug at home. The dose administered and treatment compliance were entirely satisfactory (100% with pre-packaged chloroquine and rarely satisfactory (1.6% to 4.5% with non pre-packaged chloroquine. In cases of treatment failure, the carers took patients to health centres. Chloroquine was supplied principally by private pharmacies and travelling salesmen selling unpackaged chloroquine tablets. Non pre-packaged chloroquine was the most common drug used at health centres. The frequency of positive rapid malaria tests (P = 0.01 was significantly higher in children treated with non pre-packaged chloroquine (38% than in children treated with pre-packaged chloroquine (1.3%. Conclusion Home malaria management should be improved in Madagascar. Efforts should focus on communication, the training of community-based service providers, access to pre-packaged drugs and the gradual withdrawal of pre-packaged chloroquine and its replacement by pre-packaged artemisinin-based combination therapies.

  14. Fun with Buoyancy.

    Science.gov (United States)

    Cuicchi, Paul M.; Winter, Joshua B.; Hamil, Burnette

    2003-01-01

    Presents an activity to teach buoyancy. The lab determines what mass of sand can be added to the open end of hollow plastic containers of various shapes so that objects just float at the surface, without sinking, with their entire volume submerged. Discusses Archimedes' principle and aligns with current national science education standards.…

  15. A buoyancy-propelled airship

    Science.gov (United States)

    Purandare, Ravi Yeshwant

    2007-12-01

    The concept of buoyancy propulsion (BP) is investigated for a lighter-than-air platform in the upper-stratosphere. This alternative to conventional thrust propulsion (TP) requires a cyclical change in net buoyancy (buoyancy minus weight). Methods have proved efficient in water. 'Underwater Gliders' undertake long missions covering vast distances using little power. High altitude, long endurance craft can perform many functions provided by satellites at potentially much lower cost. Such functions include meteorological monitoring, surveillance, and communications. The proposed craft is a super-pressure, helium-filled, aerodynamic airship. It would use a blower to fill an inner bladder with ambient air thus increasing its weight.

  16. Prepackaged central line kits reduce procedural mistakes during central line insertion: a randomized controlled prospective trial.

    Science.gov (United States)

    Fenik, Yelena; Celebi, Nora; Wagner, Robert; Nikendei, Christoph; Lund, Frederike; Zipfel, Stephan; Riessen, Reimer; Weyrich, Peter

    2013-04-30

    Central line catheter insertion is a complex procedure with a high cognitive load for novices. Providing a prepackaged all-inclusive kit is a simple measure that may reduce the cognitive load. We assessed whether the use of prepackaged all-inclusive central line insertion kits reduces procedural mistakes during central line catheter insertion by novices. Thirty final year medical students and recently qualified physicians were randomized into two equal groups. One group used a prepackaged all-inclusive kit and the other used a standard kit containing only the central vein catheter and all other separately packaged components provided in a materials cart. The procedure was videotaped and analyzed by two blinded raters using a checklist. Both groups performed central line catheter insertion on a manikin, assisted by nursing students. The prepackaged kit group outperformed the standard kit group in four of the five quality indicators: procedure duration (26:26 ± 3:50 min vs. 31:27 ± 5:57 min, p = .01); major technical mistakes (3.1 ± 1.4 vs. 4.8 ± 2.6, p = .03); minor technical mistakes (5.2 ± 1.7 vs. 8.0 ± 3.2, p = .01); and correct steps (83 ± 5% vs. 75 ± 11%, p = .02). The difference for breaches of aseptic technique (1.2 ± 0.8 vs. 3.0 ± 3.6, p = .06) was not statistically significant. Prepackaged all-inclusive kits for novices improved the procedure quality and saved staff time resources in a controlled simulation environment. Future studies are needed to address whether central line kits also improve patient safety in hospital settings.

  17. Biologically inspired highly efficient buoyancy engine

    Science.gov (United States)

    Akle, Barbar; Habchi, Wassim; Abdelnour, Rita; Blottman, John, III; Leo, Donald

    2012-04-01

    Undersea distributed networked sensor systems require a miniaturization of platforms and a means of both spatial and temporal persistence. One aspect of this system is the necessity to modulate sensor depth for optimal positioning and station-keeping. Current approaches involve pneumatic bladders or electrolysis; both require mechanical subsystems and consume significant power. These are not suitable for the miniaturization of sensor platforms. Presented in this study is a novel biologically inspired method that relies on ionic motion and osmotic pressures to displace a volume of water from the ocean into and out of the proposed buoyancy engine. At a constant device volume, the displaced water will alter buoyancy leading to either sinking or floating. The engine is composed of an enclosure sided on the ocean's end by a Nafion ionomer and by a flexible membrane separating the water from a gas enclosure. Two electrodes are placed one inside the enclosure and the other attached to the engine on the outside. The semi-permeable membrane Nafion allows water motion in and out of the enclosure while blocking anions from being transferred. The two electrodes generate local concentration changes of ions upon the application of an electrical field; these changes lead to osmotic pressures and hence the transfer of water through the semi-permeable membrane. Some aquatic organisms such as pelagic crustacean perform this buoyancy control using an exchange of ions through their tissue to modulate its density relative to the ambient sea water. In this paper, the authors provide an experimental proof of concept of this buoyancy engine. The efficiency of changing the engine's buoyancy is calculated and optimized as a function of electrode surface area. For example electrodes made of a 3mm diameter Ag/AgCl proved to transfer approximately 4mm3 of water consuming 4 Joules of electrical energy. The speed of displacement is optimized as a function of the surface area of the Nafion

  18. Buoyancy in tropical cyclones and other rapidly rotating atmospheric vortices

    Science.gov (United States)

    Smith, Roger K.; Montgomery, Michael T.; Zhu, Hongyan

    2005-07-01

    Motivated primarily by its application to understanding tropical-cyclone intensification and maintenance, we re-examine the concept of buoyancy in rapidly rotating vortices, distinguishing between the buoyancy of the symmetric balanced vortex or system buoyancy, and the local buoyancy associated with cloud dynamics. The conventional definition of buoyancy is contrasted with a generalized form applicable to a vortex, which has a radial as well as a vertical component. If, for the special case of axisymmetric motions, the balanced density and pressure distribution of a rapidly rotating vortex are used as the reference state, the buoyancy field then characterizes the unbalanced density perturbations, i.e. the local buoyancy. We show how to determine such a reference state without approximation. The generation of the toroidal circulation of a vortex, which is necessary for vortex amplification, is characterized in the vorticity equation by the baroclinicity vector. This vector depends, inter-alia, on the horizontal (or radial) gradient of buoyancy evaluated along isobaric surfaces. We show that for a tropical-cyclone-scale vortex, the buoyancy so calculated is significantly different from that calculated at constant height or on surfaces of constant σ ( σ = ( p - p*)/( ps - p*), where p is the actual pressure, p* some reference pressure and ps is the surface pressure). Since many tropical-cyclone models are formulated using σ-coordinates, we examine the calculation of buoyancy on σ-surfaces and derive an expression for the baroclinicity vector in σ-coordinates. The baroclinic forcing term in the azimuthal vorticity equation for an axisymmetric vortex is shown to be approximately equal to the azimuthal component of the curl of the generalized buoyancy. A scale analysis indicates that the vertical gradient of the radial component of generalized buoyancy makes a comparatively small contribution to the generation of toroidal vorticity in a tropical cyclone, but may be

  19. A comparative risk assessment for Listeria monocytogenes in prepackaged versus retail-sliced deli meat.

    Science.gov (United States)

    Endrikat, Sarah; Gallagher, Daniel; Pouillot, Régis; Hicks Quesenberry, Heather; Labarre, David; Schroeder, Carl M; Kause, Janell

    2010-04-01

    Deli meat was ranked as the highest-risk ready-to-eat food vehicle of Listeria monocytogenes within the 2003 U.S. Food and Drug Administration and U.S. Department of Agriculture, Food Safety and Inspection Service risk assessment. The comparative risk of L. monocytogenes in retail-sliced versus prepackaged deli meats was evaluated with a modified version of this model. Other research has found that retail-sliced deli meats have both higher prevalence and levels of L. monocytogenes than have product sliced and packaged at the manufacturer level. The updated risk assessment model considered slicing location as well as the use of growth inhibitors. The per annum comparative risk ratio for the number of deaths from retail-sliced versus prepackaged deli meats was found to be 4.89, and the per-serving comparative risk ratio was 4.27. There was a significant interaction between the use of growth inhibitors and slicing location. Almost 70% of the estimated deaths occurred from retail-sliced product that did not possess a growth inhibitor. A sensitivity analysis, assessing the effect of the model's consumer storage time and shelf life assumptions, found that even if retail-sliced deli meats were stored for a quarter of the time prepackaged deli meats were stored, retail-sliced product is 1.7 times more likely to result in death from listeriosis. Sensitivity analysis also showed that the shelf life assumption had little effect on the comparative risk ratio.

  20. Statistical Change Detection for Diagnosis of Buoyancy Element Defects on Moored Floating Vessels

    DEFF Research Database (Denmark)

    Blanke, Mogens; Fang, Shaoji; Galeazzi, Roberto;

    2012-01-01

    Floating platforms with mooring systems are used extensively in off-shore operations. Part of the mooring systems are underwater buoyancy elements that are attached to the mooring lines. Loss or damage of a buoyancy element is invisible but changes the characteristics of the mooring system...

  1. Buoyancy instability of homologous implosions

    CERN Document Server

    Johnson, Bryan M

    2015-01-01

    I consider the hydrodynamic stability of imploding gases as a model for inertial confinement fusion capsules, sonoluminescent bubbles and the gravitational collapse of astrophysical gases. For oblate modes under a homologous flow, a monatomic gas is governed by the Schwarzschild criterion for buoyant stability. Under buoyantly unstable conditions, fluctuations experience power-law growth in time, with a growth rate that depends upon mean flow gradients and is independent of mode number. If the flow accelerates throughout the implosion, oblate modes amplify by a factor (2C)^(|N0| ti)$, where C is the convergence ratio of the implosion, N0 is the initial buoyancy frequency and ti is the implosion time scale. If, instead, the implosion consists of a coasting phase followed by stagnation, oblate modes amplify by a factor exp(pi |N0| ts), where N0 is the buoyancy frequency at stagnation and ts is the stagnation time scale. Even under stable conditions, vorticity fluctuations grow due to the conservation of angular...

  2. Characteristics of Buoyancy Driven Natural Ventilation through Horizontal Openings

    DEFF Research Database (Denmark)

    Li, Zhigang

    and smoke. Air flow through vertical openings has been widely investigated but little is known about the flow in the horizontal openings, especially when they are driven by buoyancy. A literature survey shows that the brine-water system and the scale model are normally used forthe research work of air flow...... through horizontal openings. Two cases of full-scale measurements of buoyancy driven natural ventilation through horizontal openings are performed: one horizontal opening and one horizontal opening combined with one vertical opening. For the case of one horizontal opening, the measurements are made...

  3. Use of Whole Genome Sequencing and Patient Interviews To Link a Case of Sporadic Listeriosis to Consumption of Prepackaged Lettuce.

    Science.gov (United States)

    Jackson, K A; Stroika, S; Katz, L S; Beal, J; Brandt, E; Nadon, C; Reimer, A; Major, B; Conrad, A; Tarr, C; Jackson, B R; Mody, R K

    2016-05-01

    We report on a case of listeriosis in a patient who probably consumed a prepackaged romaine lettuce-containing product recalled for Listeria monocytogenes contamination. Although definitive epidemiological information demonstrating exposure to the specific recalled product was lacking, the patient reported consumption of a prepackaged romaine lettuce-containing product of either the recalled brand or a different brand. A multinational investigation found that patient and food isolates from the recalled product were indistinguishable by pulsed-field gel electrophoresis and were highly related by whole genome sequencing, differing by four alleles by whole genome multilocus sequence typing and by five high-quality single nucleotide polymorphisms, suggesting a common source. To our knowledge, this is the first time prepackaged lettuce has been identified as a likely source for listeriosis. This investigation highlights the power of whole genome sequencing, as well as the continued need for timely and thorough epidemiological exposure data to identify sources of foodborne infections.

  4. Total and Free Sugar Content of Canadian Prepackaged Foods and Beverages

    Directory of Open Access Journals (Sweden)

    Jodi T. Bernstein

    2016-09-01

    Full Text Available A number of recommendations for policy and program interventions to limit excess free sugar consumption have emerged, however there are a lack of data describing the amounts and types of sugar in foods. This study presents an assessment of sugar in Canadian prepackaged foods including: (a the first systematic calculation of free sugar contents; (b a comprehensive assessment of total sugar and free sugar levels; and (c sweetener and free sugar ingredient use, using the University of Toronto’s Food Label Information Program (FLIP database 2013 (n = 15,342. Food groups with the highest proportion of foods containing free sugar ingredients also had the highest median total sugar and free sugar contents (per 100 g/mL: desserts (94%, 15 g, and 12 g, sugars and sweets (91%, 50 g, and 50 g, and bakery products (83%, 16 g, and 14 g, proportion with free sugar ingredients, median total sugar and free sugar content in Canadian foods, respectively. Free sugar accounted for 64% of total sugar content. Eight of 17 food groups had ≥75% of the total sugar derived from free sugar. Free sugar contributed 20% of calories overall in prepackaged foods and beverages, with the highest at 70% in beverages. These data can be used to inform interventions aimed at limiting free sugar consumption.

  5. EVA Development and Verification Testing at NASA's Neutral Buoyancy Laboratory

    Science.gov (United States)

    Jairala, Juniper C.; Durkin, Robert; Marak, Ralph J.; Sipila, Stepahnie A.; Ney, Zane A.; Parazynski, Scott E.; Thomason, Arthur H.

    2012-01-01

    As an early step in the preparation for future Extravehicular Activities (EVAs), astronauts perform neutral buoyancy testing to develop and verify EVA hardware and operations. Neutral buoyancy demonstrations at NASA Johnson Space Center's Sonny Carter Training Facility to date have primarily evaluated assembly and maintenance tasks associated with several elements of the International Space Station (ISS). With the retirement of the Shuttle, completion of ISS assembly, and introduction of commercial players for human transportation to space, evaluations at the Neutral Buoyancy Laboratory (NBL) will take on a new focus. Test objectives are selected for their criticality, lack of previous testing, or design changes that justify retesting. Assembly tasks investigated are performed using procedures developed by the flight hardware providers and the Mission Operations Directorate (MOD). Orbital Replacement Unit (ORU) maintenance tasks are performed using a more systematic set of procedures, EVA Concept of Operations for the International Space Station (JSC-33408), also developed by the MOD. This paper describes the requirements and process for performing a neutral buoyancy test, including typical hardware and support equipment requirements, personnel and administrative resource requirements, examples of ISS systems and operations that are evaluated, and typical operational objectives that are evaluated.

  6. Dietary exposure of secondary school students in Hong Kong to benzoic acid in prepackaged non-alcoholic beverages.

    Science.gov (United States)

    Ma, Ka Ming; Chan, Cheok Man; Chung, Stephen Wai Cheung; Ho, Yuk Yin; Xiao, Ying

    2009-01-01

    This study evaluated the dietary exposure of secondary school students in Hong Kong to benzoic acid from pre-packaged non-alcoholic beverages. Exposure was estimated using local food consumption data of secondary school students obtained by a semi-quantitative food frequency questionnaire in 2000 and the benzoic acid level detected in pre-packaged beverages, including soft drink (both diet/light and regular types), fruit juice, soy milk, Chinese tea and coffee/tea) available locally in late 2006. The estimated dietary exposure to benzoic acid from pre-packaged beverages of average and high consumers (95(th) percentile) was 0.31 and 0.97 mg kg(-1) bw day(-1), respectively. These exposures accounted for 6.1 and 19.3% of the acceptable daily intake (ADI: 0-5 mg kg(-1) bw) of benzoic acid for average and high consumers, respectively. As in other countries, soft drinks contributed most to dietary exposure to benzoic acid from pre-packaged beverages in Hong Kong.

  7. Buoyancy-driven Magnetohydrodynamic Waves

    Science.gov (United States)

    Hague, A.; Erdélyi, R.

    2016-09-01

    Turbulent motions close to the visible solar surface may generate low-frequency internal gravity waves (IGWs) that propagate through the lower solar atmosphere. Magnetic activity is ubiquitous throughout the solar atmosphere, so it is expected that the behavior of IGWs is to be affected. In this article we investigate the role of an equilibrium magnetic field on propagating and standing buoyancy oscillations in a gravitationally stratified medium. We assume that this background magnetic field is parallel to the direction of gravitational stratification. It is known that when the equilibrium magnetic field is weak and the background is isothermal, the frequencies of standing IGWs are sensitive to the presence of magnetism. Here, we generalize this result to the case of a slowly varying temperature. To do this, we make use of the Boussinesq approximation. A comparison between the hydrodynamic and magnetohydrodynamic cases allows us to deduce the effects due to a magnetic field. It is shown that the frequency of IGWs may depart significantly from the Brunt-Väisälä frequency, even for a weak magnetic field. The mathematical techniques applied here give a clearer picture of the wave mode identification, which has previously been misinterpreted. An observational test is urged to validate the theoretical findings.

  8. Making of Nutrition LabeIing of Prepackaged Condiments%预包装调味品营养标签的制作

    Institute of Scientific and Technical Information of China (English)

    冯吉; 杨明月; 庞源

    2015-01-01

    总结调味品营养标签的制作经验,探讨调味品营养标签制作中的几个问题,对制作调味品营养标签有所借鉴。%How to make nutrition labeling of prepackaged condiments is introduced and discussed;the problems in making process of nutrition labeling of prepackaged condiments are described,which provide references for the making of nutrition labeling of prepackaged condiments;making.

  9. Neutral Buoyancy Simulator - SADE NBS Test

    Science.gov (United States)

    1983-01-01

    One of the main components of the Hubble Space Telescope (HST) is the Solar Array Drive Electronics (SADE) system. This system interfaces with the Support System Module (SSM) for exchange of operational commands and telemetry data. SADE operates and controls the Solar Array Drive Mechanisms (SADM) for the orientation of the Solar Array Drive (SAD). It also monitors the position of the arrays and the temperature of the SADM. During the first HST servicing mission, the astronauts replaced the SADE component because of some malfunctions. This turned out to be a very challenging extravehicular activity (EVA). Two transistors and two diodes had been thermally stressed with the conformal coating discolored and charred. Soldered cornections became molten and reflowed between the two diodes. The failed transistors gave no indication of defective construction. All repairs were made and the HST was redeposited into orbit. Prior to undertaking this challenging mission, the orbiter's crew trained at Marshall Space Flight Center's (MSFC) Neutral Buoyancy Simulator (NBS) to prepare themselves for working in a low gravity environment. They also practiced replacing HST parts and exercised maneuverability and equipment handling. Pictured is an astronaut practicing climbing a space platform that was necessary in making repairs on the HST.

  10. Buoyancy package for self-contained acoustic doppler current profiler mooring

    Digital Repository Service at National Institute of Oceanography (India)

    Venkatesan, R.; Krishnakumar, V.

    A buoyancy package for self-contained Acoustic Doppler Current Profiler(SC-ADCP 1200 RD instruments USA) was designed and fabricated indigenously, for subsurface mooring in coastal waters. The system design is discussed. The design to keep SC...

  11. Completeness of nutrient declarations and the average nutritional composition of pre-packaged foods in Beijing, China.

    Science.gov (United States)

    Huang, Liping; Neal, Bruce; Dunford, Elizabeth; Ma, Guansheng; Wu, Jason H Y; Crino, Michelle; Trevena, Helen

    2016-12-01

    Increasing consumption of pre-packaged foods is likely an important driver of diet-related diseases in China. From January 2013 it became mandatory to provide a standardised nutrient declaration on pre-packaged foods in China. We collected data on pre-packaged foods from large chain supermarkets in Beijing in 2013, examined the completeness of the nutrient declaration of core required nutrients and summarised the average nutritional composition of 14 different major food groups. We also illustrated the potential use of the data by comparing sodium levels. Photos of 14,279 pre-packaged foods were collected from 16 chain supermarkets in Beijing. Data for 11,489 products were included in the evaluation of nutrient declarations and data for 10,048 in the summary analysis of average nutritional composition. Compliant nutrient declarations were displayed by 87% of products with 88% of foods displaying data for each of energy, protein, total fat, carbohydrate and sodium. Nutrients not required by the Chinese regulation were infrequently reported: saturated fat (12%), trans fat (17%) and sugars (11%). Mean sodium levels were higher in Chinese products compared to UK products for 8 of 11 major food categories, often markedly so (e.g. 1417 mg/100 g vs. 304 mg/100 g for convenience foods). There has been substantial uptake of the recently introduced Chinese nutrition labelling regulation which should help consumers to choose healthier foods. As the comparison against corresponding data about sodium from the United Kingdom shows, the nutrient data can also be used to identify broader opportunities for improvement of the food supply.

  12. 14 CFR 29.755 - Hull buoyancy.

    Science.gov (United States)

    2010-01-01

    ... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Floats and Hulls § 29.755 Hull buoyancy. Water-based and amphibian rotorcraft. The hull and auxiliary floats, if used, must have enough... stability great enough to minimize the probability of capsizing the rotorcraft for the worst combination...

  13. Exploring Titan with Autonomous, Buoyancy Driven Gliders

    Science.gov (United States)

    Morrow, M. T.; Woolsey, C. A.; Hagerman, G. M.

    Buoyancy driven underwater gliders are highly efficient winged underwater vehicles which locomote by modifying their internal shape. The concept, which is already well-proven in Earth's oceans, is also an appealing technology for remote terrain exploration and environmental sampling on worlds with dense atmospheres. Because of their high efficiency and their gentle, vertical take-off and landing capability, buoyancy driven gliders might perform long duration, global mapping tasks as well as light-duty, local sampling tasks. Moreover, a sufficiently strong gradient in the planetary boundary layer may enable the vehicles to perform dynamic soaring, achieving even greater locomotive efficiency. Shape Change Actuated, Low Altitude Robotic Soarers (SCALARS) are an appealing alternative to more conventional vehicle technology for exploring planets with dense atmospheres. SCALARS are buoyancy driven atmospheric gliders with a twin-hulled, inboard wing configuration. The inboard wing generates lift, which propels the vehicle forward. Symmetric changes in mass distribution induce gravitational pitch moments that provide longitudinal control. Asymmetric changes in mass distribution induce twist in the inboard wing that provides directional control. The vehicle is actuated solely by internal shape change; there are no external seals and no exposed moving parts, save for the inflatable buoyancy ballonets. Preliminary sizing analysis and dynamic modeling indicate the viability of using SCALARS to map the surface of Titan and to investigate features of interest.

  14. Buoyancy Driven Natural Ventilation through Horizontal Openings

    DEFF Research Database (Denmark)

    Heiselberg, Per

    2009-01-01

    An experimental study of the phenomenon of buoyancy driven natural ventilation through single-sided horizontal openings was performed in a full-scale laboratory test rig. The measurements were made for opening ratios L/D ranging from 0.027 to 4.455, where L and D are the length of the opening...

  15. 14 CFR 27.751 - Main float buoyancy.

    Science.gov (United States)

    2010-01-01

    ... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Floats and Hulls § 27.751 Main float buoyancy. (a) For main floats, the buoyancy necessary to support the maximum weight of the rotorcraft in...

  16. 14 CFR 29.751 - Main float buoyancy.

    Science.gov (United States)

    2010-01-01

    ... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Floats and Hulls § 29.751 Main float buoyancy. (a) For main floats, the buoyancy necessary to support the maximum weight of the rotorcraft...

  17. 46 CFR 197.342 - Buoyancy-changing devices.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Buoyancy-changing devices. 197.342 Section 197.342... STANDARDS GENERAL PROVISIONS Commercial Diving Operations Equipment § 197.342 Buoyancy-changing devices. (a) A dry suit or other buoyancy-changing device not directly connected to the exhaust valve of...

  18. The Island Wind-Buoyancy Paradox

    Science.gov (United States)

    de Boer, A. M.; Nof, D.

    2003-04-01

    In recent years, a variety of studies have suggested that the meridional overturning circulation is at least partially controlled by the Southern Ocean winds. However, the overturning requires transformation of water masses, a process driven by buoyancy fluxes. This seems paradoxical as the wind and buoyancy fluxes are generally thought to be independent. The paradox is resolved qualitatively, using salinity and temperature mixed dynamical-box models, and quantitatively, employing a numerical model. The salinity and temperature box models suggest that stronger southern winds will tend to weaken the vertical and horizontal salinity stratification so that it is easier for the conversion of deep to surface water (and vice versa) to take place. The (process-orientated) reduced-gravity numerical model is adapted to include a thermodynamic parameterization for the surface heat and freshwater fluxes. In response to stronger southern winds, the thermocline thickens in the north, releasing more heat to the atmosphere and, thereby, converting more surface to deep water.

  19. Influence of Buoyancy Control Performance on Power Production by the Wave Dragon Nissum Bredning Prototype

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter; Tedd, James; Friis-Madsen, E.

    2007-01-01

    This paper reports on the real sea performance of the buoyancy control system of Wave Dragon, a floating wave energy converter using the overtopping principle. The device operates with the full independent control system which has been tested during three years of operation. The impact of the buo......This paper reports on the real sea performance of the buoyancy control system of Wave Dragon, a floating wave energy converter using the overtopping principle. The device operates with the full independent control system which has been tested during three years of operation. The impact...

  20. Energy spectrum of buoyancy-driven turbulence.

    Science.gov (United States)

    Kumar, Abhishek; Chatterjee, Anando G; Verma, Mahendra K

    2014-08-01

    Using high-resolution direct numerical simulation and arguments based on the kinetic energy flux Π(u), we demonstrate that, for stably stratified flows, the kinetic energy spectrum E(u)(k)∼k(-11/5), the potential energy spectrum E(θ)(k)∼k(-7/5), and Π(u)(k)∼k(-4/5) are consistent with the Bolgiano-Obukhov scaling. This scaling arises due to the conversion of kinetic energy to the potential energy by buoyancy. For weaker buoyancy, this conversion is weak, hence E(u)(k) follows Kolmogorov's spectrum with a constant energy flux. For Rayleigh-Bénard convection, we show that the energy supply rate by buoyancy is positive, which leads to an increasing Π(u)(k) with k, thus ruling out Bolgiano-Obukhov scaling for the convective turbulence. Our numerical results show that convective turbulence for unit Prandt number exhibits a constant Π(u)(k) and E(u)(k)∼k(-5/3) for a narrow band of wave numbers.

  1. Energy spectrum of buoyancy-driven turbulence

    KAUST Repository

    Kumar, Abhishek

    2014-08-25

    Using high-resolution direct numerical simulation and arguments based on the kinetic energy flux Πu, we demonstrate that, for stably stratified flows, the kinetic energy spectrum Eu(k)∼k-11/5, the potential energy spectrum Eθ(k)∼k-7/5, and Πu(k)∼k-4/5 are consistent with the Bolgiano-Obukhov scaling. This scaling arises due to the conversion of kinetic energy to the potential energy by buoyancy. For weaker buoyancy, this conversion is weak, hence Eu(k) follows Kolmogorov\\'s spectrum with a constant energy flux. For Rayleigh-Bénard convection, we show that the energy supply rate by buoyancy is positive, which leads to an increasing Πu(k) with k, thus ruling out Bolgiano-Obukhov scaling for the convective turbulence. Our numerical results show that convective turbulence for unit Prandt number exhibits a constant Πu(k) and Eu(k)∼k-5/3 for a narrow band of wave numbers. © 2014 American Physical Society.

  2. On the coupling between buoyancy forces and electroconvective instability near ion-selective surfaces

    CERN Document Server

    Karatay, Elif; Mani, Ali

    2016-01-01

    Recent investigations have revealed that ion transport from aqueous electrolytes to ion-selective surfaces is subject to electroconvective instability that stems from coupling of hydrodynamics with electrostatic forces. Electroconvection is shown to enhance ion mixing and the net rate of transport. However, systems subject to electroconvection inherently involve fluid density variation set by salinity gradient in the bulk fluid. In this study we thoroughly examine the interplay of gravitational convection and chaotic electroconvection. Our results reveal that buoyant forces can significantly influence the transport rates, otherwise set by electroconvection, when the Rayleigh number $Ra$ of the system exceeds a value $Ra \\sim 1000$. We show that buoyancy forces can significantly alter the flow patterns in these systems. When the buoyancy acts in the stabilizing direction, it limits the extent of penetration of electroconvection, but without eliminating it. When the buoyancy destabilizes the flow, it alters the...

  3. A continuous and prognostic convection scheme based on buoyancy, PCMT

    Science.gov (United States)

    Guérémy, Jean-François; Piriou, Jean-Marcel

    2016-04-01

    A new and consistent convection scheme (PCMT: Prognostic Condensates Microphysics and Transport), providing a continuous and prognostic treatment of this atmospheric process, is described. The main concept ensuring the consistency of the whole system is the buoyancy, key element of any vertical motion. The buoyancy constitutes the forcing term of the convective vertical velocity, which is then used to define the triggering condition, the mass flux, and the rates of entrainment-detrainment. The buoyancy is also used in its vertically integrated form (CAPE) to determine the closure condition. The continuous treatment of convection, from dry thermals to deep precipitating convection, is achieved with the help of a continuous formulation of the entrainment-detrainment rates (depending on the convective vertical velocity) and of the CAPE relaxation time (depending on the convective over-turning time). The convective tendencies are directly expressed in terms of condensation and transport. Finally, the convective vertical velocity and condensates are fully prognostic, the latter being treated using the same microphysics scheme as for the resolved condensates but considering the convective environment. A Single Column Model (SCM) validation of this scheme is shown, allowing detailed comparisons with observed and explicitly simulated data. Four cases covering the convective spectrum are considered: over ocean, sensitivity to environmental moisture (S. Derbyshire) non precipitating shallow convection to deep precipitating convection, trade wind shallow convection (BOMEX) and strato-cumulus (FIRE), together with an entire continental diurnal cycle of convection (ARM). The emphasis is put on the characteristics of the scheme which enable a continuous treatment of convection. Then, a 3D LAM validation is presented considering an AMMA case with both observations and a CRM simulation using the same initial and lateral conditions as for the parameterized one. Finally, global

  4. Titan Montgolfiere Buoyancy Modulation System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Titan is ideally suited for balloon exploration due to its low gravity and dense atmosphere. Current NASA mission architectures baseline Montgolfiere balloon...

  5. Buoyancy Driven Mixing with Continuous Volumetric Energy Deposition

    Science.gov (United States)

    Wachtor, Adam J.; Jebrail, Farzaneh F.; Dennisen, Nicholas A.; Andrews, Malcolm J.; Gore, Robert A.

    2014-11-01

    An experiment involving a miscible fluid pair is presented which transitioned from a Rayleigh-Taylor (RT) stable to RT unstable configuration through continuous volumetric energy deposition (VED) by microwave radiation. Initially a light, low microwave absorbing fluid rested above a heavier, more absorbing fluid. The alignment of the density gradient with gravity made the system stable, and the Atwood number (At) for the initial setup was approximately -0.12. Exposing the fluid pair to microwave radiation preferentially heated the bottom fluid, and caused its density to drop due to thermal expansion. As heating of the bottom fluid continued, the At varied from negative to positive, and after the system passed through the neutral stability point, At = 0, buoyancy driven mixing ensued. Continuous VED caused the At to continue increasing and further drive the mixing process. Successful VED mixing required careful design of the fluid pair used in the experiment. Therefore, fluid selection is discussed, along with challenges and limitations of data collection using the experimental microwave facility. Experimental and model predictions of the neutral stability point, and onset of buoyancy driven mixing, are compared, and differences with classical, constant At RT driven turbulence are discussed.

  6. An empirical determination of consumers’ reaction to nutritional labeling of pre-packaged food products in Lagos, Nigeria

    Directory of Open Access Journals (Sweden)

    Ben. E.A. Oghojafor

    2012-09-01

    Full Text Available The incidence of diet induced diseases such as cancer, high blood pressure, stroke, cardiovascular/heart disease, diabetes, obesity, osteoporosis and malnutrition are rampant in our world today and therefore topical. The practice of nutritional labeling is being advocated as a panacea for this malaise and hence a sizeable number of researches are being undertaken in this direction. Large chunk of these studies are concentrated in the advanced countries. Unfortunately, there is dearth of such studies in developing countries including Nigeria. Consequently, this study sought to empirically determine consumers’ reaction to nutritional labeling of pre-packaged food products in Nigeria. The study was purely descriptive and data collected aptly analyzed through the instrumentality of pertinent statistical tools. Findings show that consumers read, comprehend, trust the authenticity and are significantly aware of nutritional labeling and are able to relate the effects of nutrition information to their health. Not surprising therefore, consumers consciously search for nutrition information, which significantly influence their purchase decisions of these kinds of products. These results hold some implications for both policy-makers and pre-packaged food marketers. Further research should be in areas of quantity and position of disclosure of nutrition information and use of symbols in nutritional labeling in Nigeria.

  7. Effects of Buoyancy on Langmuir Circulation

    Institute of Scientific and Technical Information of China (English)

    SONG Jun; SONG Jin-Bao

    2008-01-01

    Based on the Navier-Stokes equation,an equation describing the Langmuir circulation is derived by a perturbation method when the influences of Coriolis force and buoyancy force are both considered.The approach used in the analysis is similar to the works carried out by Craik and Leibovich[J.Fluid Mech.73 (1976)401],Leibovich [J.Fluid Mech.79 (1977) 715]and Huang[J.Fluid Mech.91 (1979) 191].Potential applications of the equation proposed are discussed in the area of Antarctic circumpolar current.

  8. Lagrangian chaos in three- dimensional steady buoyancy-driven flows

    Science.gov (United States)

    Contreras, Sebastian; Speetjens, Michel; Clercx, Herman

    2016-11-01

    Natural convection plays a key role in fluid dynamics owing to its ubiquitous presence in nature and industry. Buoyancy-driven flows are prototypical systems in the study of thermal instabilities and pattern formation. The differentially heated cavity problem has been widely studied for the investigation of buoyancy-induced oscillatory flow. However, far less attention has been devoted to the three-dimensional Lagrangian transport properties in such flows. This study seeks to address this by investigating Lagrangian transport in the steady flow inside a cubic cavity differentially-heated from the side. The theoretical and numerical analysis expands on previously reported similarities between the current flow and lid-driven flows. The Lagrangian dynamics are controlled by the Péclet number (Pe) and the Prandtl number (Pr). Pe controls the behaviour qualitatively in that growing Pe progressively perturbs the integable state (Pe =0), thus paving the way to chaotic dynamics. Pr plays an entirely quantitative role in that Pr1 amplifies and diminishes, respectively, the perturbative effect of non-zero Pe. S.C. acknowledges financial support from Consejo Nacional de Ciencia y Tecnología (CONACYT).

  9. Experimental Study of Wind-Opposed Buoyancy-Driven Natural Ventilation

    DEFF Research Database (Denmark)

    Andersen, A.; Bjerre, M.; Chen, Z. D.

    Natural ventilation driven by natural forces, i.e. wind and thermal buoyancy, is an environmentally friendly system for buildings and has been increasingly used around the world in recent years to mitigate the impact on the global environment due to the significant energy consumption by heating...

  10. Standard Guide for Irradiation of Pre-packaged Processed Meat and Poultry Products to Control Pathogens and Other Microorganisms

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2005-01-01

    1.1 This guide outlines procedures for the irradiation of pre-packaged refrigerated and frozen processed meat and poultry products. Note 1—The Codex Alimentarius Commission defines "meat" (including poultry and game) as "the edible part of any mammal slaughtered in an abattoir," and "poultry meat" as "the edible part of slaughtered domesticated birds, including chicken, turkeys, ducks, geese, guinea-fowls, or pigeons." (CAC/RCP 13-1976) Note 2—Current U.S. regulations limit the definition of livestock species to cattle, sheep, swine, goat, horse, mule, or other equine and poultry species to chicken, turkey, duck, goose, and guinea (2, 3). 1.2 This guide addresses all refrigerated and frozen meat and poultry products NOT covered by Guide F 1356. 1.3 This guide provides information regarding absorbed doses used for inactivation of parasites and reduction of bacterial load. Such doses are typically less than 10 kilogray (kGy).

  11. Buoyancy Driven Natural Ventilation through Horizontal Openings

    DEFF Research Database (Denmark)

    Heiselberg, Per; Li, Zhigang

    2009-01-01

    An experimental study of the phenomenon of buoyancy driven natural ventilation through single-sided horizontal openings was performed in a full-scale laboratory test rig. The measurements were made for opening ratios L/D ranging from 0.027 to 4.455, where L and D are the length of the opening...... and the diameter of the opening, respectively. The basic nature of airflow through single-sided openings, including airflow rate, air velocity, temperature difference between the rooms and the dimensions of the horizontal openings, were measured. A bi-directional airflow rate was measured using the constant...... injection tracer gas technique. Smoke visualizations showed that the airflow patterns are highly transient and unstable, and that the airflow rate oscillates with time. Correlations between the Froude (Archimedes) number Fr (Ar) and the L/D ratio are presented. In some cases the measured airflow rates fit...

  12. Buoyancy driven turbulence and distributed chaos

    CERN Document Server

    Bershadskii, A

    2016-01-01

    It is shown, using results of recent direct numerical simulations, laboratory experiments and atmospheric measurements, that buoyancy driven turbulence exhibits a broad diversity of the types of distributed chaos with its stretched exponential spectrum $\\exp(-k/k_{\\beta})^{\\beta}$. The distributed chaos with $\\beta = 1/3$ (determined by the helicity correlation integral) is the most common feature of the stably stratified turbulence (due to the strong helical waves presence). These waves mostly dominate spectral properties of the vertical component of velocity field, while the horizontal component is dominated by the diffusive processes both for the weak and strong stable stratification ($\\beta =2/3$). For the last case influence of the low boundary can overcome the wave effects and result in $\\beta =1/2$ for the vertical component of the velocity field (the spontaneous breaking of the space translational symmetry - homogeneity). For the unstably stratified turbulence in the Rayleigh-Taylor mixing zone the di...

  13. Patient views on an electronic dispensing device for prepackaged polypharmacy: a qualitative assessment in an ambulatory setting

    Directory of Open Access Journals (Sweden)

    Allemann SS

    2015-11-01

    Full Text Available Samuel S Allemann, Kurt E Hersberger, Isabelle ArnetPharmaceutical Care Research Group, Department of Pharmaceutical Sciences, University of Basel, Basel, SwitzerlandObjective: To collect opinions on medication management aids (MMAs in general and on an electronic MMA (e-MMA dispensing prepackaged polypharmacy in sealed pouches.Study setting: The setting involved community-dwelling older adults in Basel, Switzerland, in 2013.Study design: The study involved 1 a 14-day trial with the e-MMA and 2 a focus group to identify general attributes of MMAs, their applicability to the e-MMA, and possible target groups for the e-MMA.Data collection methods: Six participants using long-term polypharmacy and willing to try new technologies completed the 14-day trial and participated in the focus group. Inductive content analysis was performed to extract data.Principal findings: Participants rated ten of 17 general attributes as clearly applicable to the e-MMA and five as unsuitable. Attributes pertained to three interrelating themes: product design, patient support, and living conditions. Envisaged target groups were patients with time-sensitive medication regimens, patients with dementia, the visually impaired, and several patients living together to prevent accidental intake of the wrong medication.Conclusion: The evaluated e-MMA for prepackaged polypharmacy met the majority of the requirements set for an MMA. Patients' living conditions, such as mobility, remain the key determinants for acceptance of an e-MMA.Keywords: pharmaceutical care, medication adherence, medication management aids, automated drug dispensing

  14. Pitching effects of buoyancy during four competitive swimming strokes.

    Science.gov (United States)

    Cohen, Raymond C Z; Cleary, Paul W; Harrison, Simon M; Mason, Bruce R; Pease, David L

    2014-10-01

    The purpose of this study was to determine the pitching effects of buoyancy during all competitive swimming strokes--freestyle, backstroke, butterfly, and breaststroke. Laser body scans of national-level athletes and synchronized multiangle swimming footage were used in a novel markerless motion capture process to produce three-dimensional biomechanical models of the swimming athletes. The deforming surface meshes were then used to calculate swimmer center-of-mass (CoM) positions, center-of-buoyancy (CoB) positions, pitch buoyancy torques, and sagittal plane moments of inertia (MoI) throughout each stroke cycle. In all cases the mean buoyancy torque tended to raise the legs and lower the head; however, during part of the butterfly stroke the instantaneous buoyancy torque had the opposite effect. The swimming strokes that use opposing arm and leg strokes (freestyle and backstroke) had smaller variations in CoM positions, CoB positions, and buoyancy torques. Strokes with synchronized left-right arm and leg movement (butterfly and breaststroke) had larger variations in buoyancy torques, which impacts the swimmer's ability to maintain a horizontal body pitch for these strokes. The methodology outlined in this paper enables the rotational effects of buoyancy to be better understood by swimmers, allowing better control of streamlined horizontal body positioning during swimming to improve performance.

  15. Numerical investigation of the onset of centrifugal buoyancy in a rotating cavity

    Science.gov (United States)

    Pitz, Diogo B.; Marxen, Olaf; Chew, John

    2016-11-01

    Buoyancy-induced flows in a differentially heated rotating annulus present a multitude of dynamics when control parameters such as rotation rate, temperature difference and Prandtl number are varied. Whilst most of the work in this area has been motivated by applications involving geophysics, the problem of buoyancy-induced convection in rotating systems is also relevant in industrial applications such as the flow between rotating disks of turbomachinery internal air systems, in which buoyancy plays a major role and poses a challenge to accurately predict temperature distributions and heat transfer rates. In such applications the rotational speeds involved are very large, so that the centrifugal accelerations induced are much higher than gravity. In this work we perform direct numerical simulations and linear stability analysis of flow induced by centrifugal buoyancy in a sealed rotating annulus of finite gap with flat end-walls, using a canonical setup representative of an internal air system rotating cavity. The analysis focuses on the behaviour of small-amplitude disturbances added to the base flow, and how those affect the onset of Rossby waves and, ultimately, the transition to a fully turbulent state where convection columns no longer have a well-defined structure. Diogo B. Pitz acknowledges the financial support from the Capes foundation through the Science without Borders program.

  16. Microgravity Flow Regime Data: Buoyancy and Mixing Apparatus Effects

    Science.gov (United States)

    Shephard, Adam; Best, Frederick

    2010-01-01

    Zero-g two-phase flow data set qualification and flight experiment design have not been standardized and as a result, agreement among researchers has not been reached regarding what experimental conditions adequately approximate those of microgravity. The effects of buoyancy forces and mixing apparatus on the flow regime transitions are presented in this study. The gravity conditions onboard zero-g aircraft are at best 10-3 g which is used to approximate the 10-5 g conditions of microgravity, thus the buoyancy forces present on zero-g aircraft can become significantly large and unrepresentative of microgravity. When buoyancy forces approach those of surface tension forces, buoyancy induced coalescence occurs. When discussing flow regime transitions, these large buoyancy forces lead to flow regime transitions which otherwise would not occur. The buoyancy attributes of the two-phase flow data sets available in the literature are evaluated to determine which data sets exhibit buoyancy induced transitions. Upon comparison of the representative data sets, the affects of different mixing apparatus can be seen in the superficial velocity flow regime maps.

  17. Neutral Buoyancy Simulator- NB38 -Space Telescope

    Science.gov (United States)

    1980-01-01

    The Hubble Space Telescope (HST) is a cooperative program of the European Space Agency (ESA) and the National Aeronautical and Space Administration (NASA) to operate a long-lived space-based observatory. It was the flagship mission of NASA's Great Observatories program. The HST program began as an astronomical dream in the 1940s. During the 1970s and 1980s, the HST was finally designed and built becoming operational in the 1990s. The HST was deployed into a low-Earth orbit on April 25, 1990 from the cargo bay of the Space Shuttle Discovery (STS-31). The design of the HST took into consideration its length of service and the necessity of repairs and equipment replacement by making the body modular. In doing so, subsequent shuttle missions could recover the HST, replace faulty or obsolete parts and be re-released. Pictured is MSFC's Neutral Buoyancy Simulator (NBS) that served as the test center for shuttle astronauts training for Hubble related missions. Shown are astronauts Bruce McCandless and Sharnon Lucid being fitted for their space suits prior to entering the NBS to begin training on the space telescope axial scientific instrument changeout.

  18. Neutral Buoyancy Simulator- NB38 -Space Telescope

    Science.gov (United States)

    1980-01-01

    The Hubble Space Telescope (HST) is a cooperative program of the European Space Agency (ESA) and the National Aeronautical and Space Administration (NASA) to operate a long-lived space-based observatory. It was the flagship mission of NASA's Great Observatories program. The HST program began as an astronomical dream in the 1940s. During the 1970s and 1980s, the HST was finally designed and built becoming operational in the 1990s. The HST was deployed into a low-Earth orbit on April 25, 1990 from the cargo bay of the Space Shuttle Discovery (STS-31). The design of the HST took into consideration its length of service and the necessity of repairs and equipment replacement by making the body modular. In doing so, subsequent shuttle missions could recover the HST, replace faulty or obsolete parts and be re-released. Pictured is MSFC's Neutral Buoyancy Simulator (NBS) that served as the test center for shuttle astronauts training for Hubble related missions. Shown are astronauts Bruce McCandless and Sharnon Lucid being fitted for their space suits prior to entering the NBS to begin training on the space telescope axial scientific instrument changeout.

  19. Control of a Buoyancy-Based Pilot Underwater Lifting Body

    Directory of Open Access Journals (Sweden)

    Finn Haugen

    2010-04-01

    Full Text Available This paper is about position control of a specific small-scale pilot underwater lifting body where the lifting force stems from buoyancy adjusted with an air pocket in the lifting body. A mathematical model is developed to get a basis for a simulator which is used for testing and for designing the control system, including tuning controller parameters. A number of different position controller solutions were tried both on a simulator and on the physical system. Successful control on both the simulator and the physical system was obtained with cascade control based on feedback from measured position and height of the air pocket in the lifting body. The primary and the secondary controllers of the cascade control system were tuned using Skogestad's model-based PID tuning rules. Feedforward from estimated load force was implemented in combination with the cascade control system, giving a substantial improvement of the position control system, both with varying position reference and varying disturbance (load mass.

  20. Adherence of community caretakers of children to pre-packaged antimalarial medicines (HOMAPAK®) among internally displaced people in Gulu district, Uganda

    OpenAIRE

    Jan H Kolaczinski; Ojok, Naptalis; Opwonya, John; Meek, Sylvia; Collins, Andrew

    2006-01-01

    Abstract Background In 2002, home-based management of fever (HBMF) was introduced in Uganda, to improve access to prompt, effective antimalarial treatment of all fevers in children under 5 years. Implementation is through community drug distributors (CDDs) who distribute pre-packaged chloroquine plus sulfadoxine-pyrimethamine (HOMAPAK®) free of charge to caretakers of febrile children. Adherence of caretakers to this regimen has not been studied. Methods A questionnaire-based survey combined ...

  1. TAO/TRITON, RAMA, and PIRATA Buoys, Quarterly, Buoyancy Flux

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset has quarterly Buoyancy Flux data from the TAO/TRITON (Pacific Ocean, http://www.pmel.noaa.gov/tao/), RAMA (Indian Ocean,...

  2. TAO/TRITON, RAMA, and PIRATA Buoys, Daily, Buoyancy Flux

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset has daily Buoyancy Flux data from the TAO/TRITON (Pacific Ocean, http://www.pmel.noaa.gov/tao/), RAMA (Indian Ocean,...

  3. Semi-Empirical Models for Buoyancy-Driven Ventilation

    DEFF Research Database (Denmark)

    Terpager Andersen, Karl

    2015-01-01

    A literature study is presented on the theories and models dealing with buoyancy-driven ventilation in rooms. The models are categorised into four types according to how the physical process is conceived: column model, fan model, neutral plane model and pressure model. These models are analysed...... and compared with a reference model. Discrepancies and differences are shown, and the deviations are discussed. It is concluded that a reliable buoyancy model based solely on the fundamental flow equations is desirable....

  4. Rigorous buoyancy driven bubble mixing for centrifugal microfluidics.

    Science.gov (United States)

    Burger, S; Schulz, M; von Stetten, F; Zengerle, R; Paust, N

    2016-01-21

    We present batch-mode mixing for centrifugal microfluidics operated at fixed rotational frequency. Gas is generated by the disk integrated decomposition of hydrogen peroxide (H2O2) to liquid water (H2O) and gaseous oxygen (O2) and inserted into a mixing chamber. There, bubbles are formed that ascent through the liquid in the artificial gravity field and lead to drag flow. Additionaly, strong buoyancy causes deformation and rupture of the gas bubbles and induces strong mixing flows in the liquids. Buoyancy driven bubble mixing is quantitatively compared to shake mode mixing, mixing by reciprocation and vortex mixing. To determine mixing efficiencies in a meaningful way, the different mixers are employed for mixing of a lysis reagent and human whole blood. Subsequently, DNA is extracted from the lysate and the amount of DNA recovered is taken as a measure for mixing efficiency. Relative to standard vortex mixing, DNA extraction based on buoyancy driven bubble mixing resulted in yields of 92 ± 8% (100 s mixing time) and 100 ± 8% (600 s) at 130g centrifugal acceleration. Shake mode mixing yields 96 ± 11% and is thus equal to buoyancy driven bubble mixing. An advantage of buoyancy driven bubble mixing is that it can be operated at fixed rotational frequency, however. The additional costs of implementing buoyancy driven bubble mixing are low since both the activation liquid and the catalyst are very low cost and no external means are required in the processing device. Furthermore, buoyancy driven bubble mixing can easily be integrated in a monolithic manner and is compatible to scalable manufacturing technologies such as injection moulding or thermoforming. We consider buoyancy driven bubble mixing an excellent alternative to shake mode mixing, in particular if the processing device is not capable of providing fast changes of rotational frequency or if the low average rotational frequency is challenging for the other integrated fluidic operations.

  5. March of buoyancy elements during extreme rainfall over India

    Science.gov (United States)

    Krishnamurti, T. N.; Kumar, Vinay; Simon, Anu; Thomas, Aype; Bhardwaj, Amit; Das, Sweta; Senroy, Soma; Roy Bhowmik, S. K.

    2017-03-01

    A major rain storm in Uttarakhand (India) caused heavy rains and major loss of life from floods and land slide during 16-18 June, 2013. The observed daily maximum rainfall rates (3-hourly) during the 16th and 17th June were 220 and 340 mm respectively. This event is addressed via sensitivity studies using a cloud resolving non-hydrostatic model with detailed microphysics. The streaming of moist air from the east-south-east and warmer air from the south-west contributed to the sustained large population and amplitude of buoyancy and the associated CAPE contributed to the longer period of heavy rains. This study addresses the concept of Buoyancy as a means for large vertical accelerations, stronger vertical motions, extreme rain rates and the mechanisms that relate to the time rates of change. A post-processing algorithm provides an analysis of time rate of change for the buoyancy. Moist air streams and warm/moist air intrusions into heavily raining clouds are part of this buoyancy enhancement framework. Improvements in modeling of the extreme rain event came from adaptive observational strategy that showed lack of moisture data sets in these vital regions. We show that a moist boundary layer near the Bay of Bengal leads to moist rivers of moisture where the horizontal convergence confines a large population of buoyancy elements with large magnitudes of buoyancy that streams towards the region of extreme orographic rains. The areas covered in this study include: (i) Use of high resolution cloud modeling (1-km), (ii) Now casting of rains using physical initialization with a Newtonian relaxation, (iii) Use of an adaptive observational strategy, (iii) Sensitivity of the evolution of fields and population of buoyancy elements to boundary layer moisture, (iv) Role of orography and details of buoyancy budget.

  6. Buoyancy-Driven Polymerase Chain Reaction (PCR) Devices

    Energy Technology Data Exchange (ETDEWEB)

    Ness, K D; Wheeler, E K; Benett, W; Stratton, P; Christian, A; Chen, A; Ortega, J; Weisgraber, T H; Goodson, K E

    2004-09-28

    Polymerase chain reaction (PCR) facilitates DNA detection by significantly increasing the concentration of specific DNA segments. A new class of PCR instruments uses a buoyancy-driven re-circulating flow to thermally cycle the DNA sample and benefits from reduced cycle times, low sample volumes, a miniaturized format, and low power consumption. This paper analyzes a specific buoyancy PCR device in a micro-channel ''race-track'' geometry to determine key parameters about PCR cycle times and other figures of merit as functions of device dimensions. The 1-D model balances the buoyancy driving force with frictional losses. A hydrostatic pressure imbalance concept is used between the left and right sides of the fluid loop to calculate the buoyancy driving force. Velocity and temperature distributions within the channels are determined from two-dimensional analysis of the channel section, with developing region effects included empirically through scaled values of the local Nusselt number. Good agreement between four independent verification steps validate the 1-D simulation approach: (1) analytical expressions for the thermal entrance length are compared against, (2) comparison with a full 3-D finite element simulation, (3) comparison with an experimental flow field characterization, and (4) calculation of the minimum PCR runtime required to get a positive PCR signal from the buoyancy-driven PCR device. The 1-D approach closely models an actual buoyancy-driven PCR device and can further be used as a rapid design tool to simulate buoyancy PCR flows and perform detailed design optimizations studies.

  7. Mixing and dissipation in a geostrophic buoyancy-driven circulation

    Science.gov (United States)

    Vreugdenhil, Catherine A.; Gayen, Bishakhdatta; Griffiths, Ross W.

    2016-08-01

    Turbulent mixing and energy dissipation have important roles in the global circulation but are not resolved by ocean models. We use direct numerical simulations of a geostrophic circulation, resolving turbulence and convection, to examine the rates of dissipation and mixing. As a starting point, we focus on circulation in a rotating rectangular basin forced by a surface temperature difference but no wind stress. Emphasis is on the geostrophic regime for the horizontal circulation, but also on the case of strong buoyancy forcing (large Rayleigh number), which implies a turbulent convective boundary layer. The computed results are consistent with existing scaling theory that predicts dynamics and heat transport dependent on the relative thicknesses of thermal and Ekman boundary layers, hence on the relative roles of buoyancy and rotation. Scaling theory is extended to describe the volume-integrated rate of mixing, which is proportional to heat transport and decreases with increasing rotation rate or decreasing temperature difference. In contrast, viscous dissipation depends crucially on whether the thermal boundary layer is laminar or turbulent, with no direct Coriolis effect on the turbulence unless rotation is extremely strong. For strong forcing, in the geostrophic regime, the mechanical energy input from buoyancy goes primarily into mixing rather than dissipation. For a buoyancy-driven circulation in a basin comparable to the North Atlantic we estimate that the total rate of mixing accounts for over 95% of the mechanical energy supply, implying that buoyancy is an efficient driver of mixing in the oceans.

  8. Numerical and Experimental Study on Negative Buoyance Induced Vortices in N-Butane Jet Flames

    KAUST Repository

    Xiong, Yuan

    2015-07-26

    Near nozzle flow field in flickering n-butane diffusion jet flames was investigated with a special focus on transient flow patterns of negative buoyance induced vortices. The flow structures were obtained through Mie scattering imaging with seed particles in a fuel stream using continuous-wave (CW) Argon-ion laser. Velocity fields were also quantified with particle mage velocimetry (PIV) system having kHz repetition rate. The results showed that the dynamic motion of negative buoyance induced vortices near the nozzle exit was coupled strongly with a flame flickering instability. Typically during the flame flickering, the negative buoyant vortices oscillated at the flickering frequency. The vortices were distorted by the flickering motion and exhibited complicated transient vortical patterns, such as tilting and stretching. Numerical simulations were also implemented based on an open source C++ package, LaminarSMOKE, for further validations.

  9. Neutral Buoyancy Simulator - NB32 - Large Space Structure

    Science.gov (United States)

    1980-01-01

    The Hubble Space Telescope (HST) is a cooperative program of the European Space Agency (ESA) and the National Aeronautical and Space Administration (NASA) to operate a long-lived space-based observatory; it was the flagship mission of NASA's Great Observatories program. The HST program began as an astronomical dream in the 1940s. During the 1970s and 1980s, HST was finally designed and built; and it finally became operational in the 1990s. HST was deployed into a low-Earth orbit on April 25, 1990 from the cargo bay of the Space Shuttle Discovery (STS-31). The design of the HST took into consideration its length of service and the necessity of repairs and equipment replacement by making the body modular. In doing so, subsequent shuttle missions could recover the HST, replace faulty or obsolete parts and be re-released. MSFC's Neutral Buoyancy Simulator served as the training facility for shuttle astronauts for Hubble related missions. Shown is astronaut Sharnon Lucid having her life support system being checked prior to entering the NBS to begin training on the space telescope axial scientific instrument changeout.

  10. Neutral Buoyancy Simulator - NB32 - Large Space Structure

    Science.gov (United States)

    1980-01-01

    The Hubble Space Telescope (HST) is a cooperative program of the European Space Agency (ESA) and the National Aeronautical and Space Administration (NASA) to operate a long-lived space-based observatory; it was the flagship mission of NASA's Great Observatories program. The HST program began as an astronomical dream in the 1940s. During the 1970s and 1980s, HST was finally designed and built; and it finally became operational in the 1990s. HST was deployed into a low-Earth orbit on April 25, 1990 from the cargo bay of the Space Shuttle Discovery (STS-31). The design of the HST took into consideration its length of service and the necessity of repairs and equipment replacement by making the body modular. In doing so, subsequent shuttle missions could recover the HST, replace faulty or obsolete parts and be re-released. MSFC's Neutral Buoyancy Simulator served as the training facility for shuttle astronauts for Hubble related missions. Shown is astronaut Sharnon Lucid having her life support system being checked prior to entering the NBS to begin training on the space telescope axial scientific instrument changeout.

  11. Flow field topology of transient mixing driven by buoyancy

    Science.gov (United States)

    Duval, Walter M B.

    2004-01-01

    Transient mixing driven by buoyancy occurs through the birth of a symmetric Rayleigh-Taylor morphology (RTM) structure for large length scales. Beyond its critical bifurcation the RTM structure exhibits self-similarity and occurs on smaller and smaller length scales. The dynamics of the RTM structure, its nonlinear growth and internal collision, show that its genesis occurs from an explosive bifurcation which leads to the overlap of resonance regions in phase space. This event shows the coexistence of regular and chaotic regions in phase space which is corroborated with the existence of horseshoe maps. A measure of local chaos given by the topological entropy indicates that as the system evolves there is growth of uncertainty. Breakdown of the dissipative RTM structure occurs during the transition from explosive to catastrophic bifurcation; this event gives rise to annihilation of the separatrices which drives overlap of resonance regions. The global bifurcation of explosive and catastrophic events in phase space for the large length scale of the RTM structure serves as a template for which mixing occurs on smaller and smaller length scales. Copyright 2004 American Institute of Physics.

  12. Prevalence of Nutrition and Health-Related Claims on Pre-Packaged Foods: A Five-Country Study in Europe

    Science.gov (United States)

    Hieke, Sophie; Kuljanic, Nera; Pravst, Igor; Miklavec, Krista; Kaur, Asha; Brown, Kerry A.; Egan, Bernadette M.; Pfeifer, Katja; Gracia, Azucena; Rayner, Mike

    2016-01-01

    This study is part of the research undertaken in the EU funded project CLYMBOL (“Role of health-related CLaims and sYMBOLs in consumer behaviour”). The first phase of this project consisted of mapping the prevalence of symbolic and non-symbolic nutrition and health-related claims (NHC) on foods and non-alcoholic beverages in five European countries. Pre-packaged foods and drinks were sampled based on a standardized sampling protocol, using store lists or a store floor plan. Data collection took place across five countries, in three types of stores. A total of 2034 foods and drinks were sampled and packaging information was analyzed. At least one claim was identified for 26% (95% CI (24.0%–27.9%)) of all foods and drinks sampled. Six percent of these claims were symbolic. The majority of the claims were nutrition claims (64%), followed by health claims (29%) and health-related ingredient claims (6%). The most common health claims were nutrient and other function claims (47% of all claims), followed by disease risk reduction claims (5%). Eight percent of the health claims were children’s development and health claims but these were only observed on less than 1% (0.4%–1.1%) of the foods. The category of foods for specific dietary use had the highest proportion of NHC (70% of foods carried a claim). The prevalence of symbolic and non-symbolic NHC varies across European countries and between different food categories. This study provides baseline data for policy makers and the food industry to monitor and evaluate the use of claims on food packaging. PMID:26950149

  13. Prevalence of Nutrition and Health-Related Claims on Pre-Packaged Foods: A Five-Country Study in Europe.

    Science.gov (United States)

    Hieke, Sophie; Kuljanic, Nera; Pravst, Igor; Miklavec, Krista; Kaur, Asha; Brown, Kerry A; Egan, Bernadette M; Pfeifer, Katja; Gracia, Azucena; Rayner, Mike

    2016-03-03

    This study is part of the research undertaken in the EU funded project CLYMBOL ("Role of health-related CLaims and sYMBOLs in consumer behaviour"). The first phase of this project consisted of mapping the prevalence of symbolic and non-symbolic nutrition and health-related claims (NHC) on foods and non-alcoholic beverages in five European countries. Pre-packaged foods and drinks were sampled based on a standardized sampling protocol, using store lists or a store floor plan. Data collection took place across five countries, in three types of stores. A total of 2034 foods and drinks were sampled and packaging information was analyzed. At least one claim was identified for 26% (95% CI (24.0%-27.9%)) of all foods and drinks sampled. Six percent of these claims were symbolic. The majority of the claims were nutrition claims (64%), followed by health claims (29%) and health-related ingredient claims (6%). The most common health claims were nutrient and other function claims (47% of all claims), followed by disease risk reduction claims (5%). Eight percent of the health claims were children's development and health claims but these were only observed on less than 1% (0.4%-1.1%) of the foods. The category of foods for specific dietary use had the highest proportion of NHC (70% of foods carried a claim). The prevalence of symbolic and non-symbolic NHC varies across European countries and between different food categories. This study provides baseline data for policy makers and the food industry to monitor and evaluate the use of claims on food packaging.

  14. Prevalence of Nutrition and Health-Related Claims on Pre-Packaged Foods: A Five-Country Study in Europe

    Directory of Open Access Journals (Sweden)

    Sophie Hieke

    2016-03-01

    Full Text Available This study is part of the research undertaken in the EU funded project CLYMBOL (“Role of health-related CLaims and sYMBOLs in consumer behaviour”. The first phase of this project consisted of mapping the prevalence of symbolic and non-symbolic nutrition and health-related claims (NHC on foods and non-alcoholic beverages in five European countries. Pre-packaged foods and drinks were sampled based on a standardized sampling protocol, using store lists or a store floor plan. Data collection took place across five countries, in three types of stores. A total of 2034 foods and drinks were sampled and packaging information was analyzed. At least one claim was identified for 26% (95% CI (24.0%–27.9% of all foods and drinks sampled. Six percent of these claims were symbolic. The majority of the claims were nutrition claims (64%, followed by health claims (29% and health-related ingredient claims (6%. The most common health claims were nutrient and other function claims (47% of all claims, followed by disease risk reduction claims (5%. Eight percent of the health claims were children’s development and health claims but these were only observed on less than 1% (0.4%–1.1% of the foods. The category of foods for specific dietary use had the highest proportion of NHC (70% of foods carried a claim. The prevalence of symbolic and non-symbolic NHC varies across European countries and between different food categories. This study provides baseline data for policy makers and the food industry to monitor and evaluate the use of claims on food packaging.

  15. How did Archimedes discover the law of buoyancy by experiment?

    Science.gov (United States)

    Kuroki, Hidetaka

    2016-03-01

    After Archimedes and Vitruvius era, for more than 2000 years, it has been believed that the displaced water measurement of golden crown is impossible, and at his Eureka moment, Archimedes discovered the law of buoyancy (Proposition 7 of his principles) and proved the theft of a goldsmith by weighing the golden crown in water. A previous study showed that a small amount of displaced water was able to be measured with enough accuracy by the introduced method. Archimedes measured the weight of displaced water. He did not find the law of buoyancy but rather specific gravity of things at the moment. After which, Archimedes continued to measure the specific gravity of various solids and fluids. Through these measurements, he reached the discovery of the law of buoyancy directly by experiment. In this paper, the process to the discovery of Archimedes' principle (Proposition 5) is presented.

  16. Experimental study of buoyancy driven natural ventilation through horizontal openings

    DEFF Research Database (Denmark)

    Heiselberg, Per; Li, Zhigang

    2007-01-01

    An experimental study of buoyancy driven natural ventilation through single-sided horizontal openings was performed in a full-scale laboratory test rig. Measurements were made for opening ratios L/D range from 0.027 to 4.455, where L and D are the length and the diameter of the opening, respectiv......An experimental study of buoyancy driven natural ventilation through single-sided horizontal openings was performed in a full-scale laboratory test rig. Measurements were made for opening ratios L/D range from 0.027 to 4.455, where L and D are the length and the diameter of the opening...

  17. Problems and Countermeasures of Imported Pre-packaged Food Labels%进口预包装食品标签中存在的问题及对策建议

    Institute of Scientific and Technical Information of China (English)

    黄丹

    2015-01-01

    该文通过分析进口预包装食品标签现状,对照相关标准要求,对市场上进口预包装食品标签中存在的主要问题进行分析,主要存在的问题包括进口预包装食品缺少中文标签和进口预包装中文标签不规范,而中文标签不规范主要体现在宣传用语、营养成分表及版面不规范等方面,并提出了改进进口预包装食品标签现状的相关建议,以期对消费者在挑选进口预包装食品时起到一定的引导作用。%By analyzing the present situation of imported pre-packaged food labeling,this research is going to re-solve the main issues of imported pre-packaged food labels comparing with relevant standards. The main existing problems are the lack of Chinese imported pre-packaged food labels and the lack of standardization of imported pre-packaged Chinese labels. The lack of standardization of Chinese labels is mainly in publicity terms,nutrition and layout. Through the analysis of this article,forward recommendations to improve the status of imported pre-packaged food labels are raised,and hopefully it can play a guiding role to consumers in the selection of imported pre-packaged foods.

  18. Academic Buoyancy: Towards an Understanding of Students' Everyday Academic Resilience

    Science.gov (United States)

    Martin, Andrew J.; Marsh, Herbert W.

    2008-01-01

    Academic buoyancy is developed as a construct reflecting everyday academic resilience within a positive psychology context and is defined as students' ability to successfully deal with academic setbacks and challenges that are typical of the ordinary course of school life (e.g., poor grades, competing deadlines, exam pressure, difficult…

  19. An Analytic Model for Buoyancy Resonances in Protoplanetary Disks

    CERN Document Server

    Lubow, Stephen H

    2014-01-01

    Zhu, Stone, and Rafikov (2012) found in 3D shearing box simulations a new form of planet-disk interaction that they attributed to a vertical buoyancy resonance in the disk. We describe an analytic linear model for this interaction. We adopt a simplified model involving azimuthal forcing that produces the resonance and permits an analytic description of its structure. We derive an analytic expression for the buoyancy torque and show that the vertical torque distribution agrees well with results of Athena simulations and a Fourier method for linear numerical calculations carried out with the same forcing. The buoyancy resonance differs from the classic Lindblad and corotation resonances in that the resonance lies along tilted planes. Its width depends on damping effects and is independent of the gas sound speed. The resonance does not excite propagating waves. At a given large azimuthal wavenumber k_y > 1/h (for disk thickness h), the buoyancy resonance exerts a torque over a region that lies radially closer to...

  20. Using Surface Integrals for Checking Archimedes' Law of Buoyancy

    Science.gov (United States)

    Lima, F. M. S.

    2012-01-01

    A mathematical derivation of the force exerted by an "inhomogeneous" (i.e. compressible) fluid on the surface of an "arbitrarily shaped" body immersed in it is not found in the literature, which may be attributed to our trust in Archimedes' law of buoyancy. However, this law, also known as Archimedes' principle (AP), does not yield the force…

  1. Optimal design and control of buoyancy-driven ventilation

    DEFF Research Database (Denmark)

    Terpager Andersen, Karl

    2016-01-01

    Relationships between airflow rates and opening areas of importance for design and control are analysed for buoyancy-driven ventilation in a room with two openings and uniform temperature. The optimal ratio between the inlet and outlet areas is found. The consequences of deviations from the optimum...

  2. Bubble migration under the combined action of buoyancy and thermocapillarity

    Science.gov (United States)

    Merritt, Randy M.; Subramanian, R. S.

    1992-01-01

    The migration of a gas bubble under the combined action of buoyancy and a downward temperature gradient is analyzed. Inertial effects are considered negligible, but allowance is made for convective transport of energy in the model. Results from a numerical solution of the governing equations are presented and discussed.

  3. Using Surface Integrals for Checking Archimedes' Law of Buoyancy

    Science.gov (United States)

    Lima, F. M. S.

    2012-01-01

    A mathematical derivation of the force exerted by an "inhomogeneous" (i.e. compressible) fluid on the surface of an "arbitrarily shaped" body immersed in it is not found in the literature, which may be attributed to our trust in Archimedes' law of buoyancy. However, this law, also known as Archimedes' principle (AP), does not yield the force…

  4. Design of nutrition Labeling on pre-packaged foods%预包装快餐食品营养标签的制作

    Institute of Scientific and Technical Information of China (English)

    马丽萍; 王尔茂; 马立丽

    2014-01-01

    According to the requirements of National food safety Standard, Standard for the labeling of prepackaged foods (GB 28050-2011), and Management norm of food nutrition label, 4 kinds of core nutrients ingredients (protein, fat, carbohydrate, and sodium)and their energies in 19 servings of prepackaged snack food were determined and their nutrient label were designed. It is pressing need starting to use food nutrition label, which is for the consumer to select their suitable food according to their nutrition needs and for the company's enforcement activity to produce healthy and nutritious foods.%按照《食品安全国家标准预包装食品标签通则》及《食品营养标签管理规范》的要求测定了19种预包装快餐食品的4种核心营养成分(蛋白质、脂肪、碳水化合物、钠)及能量,并设计营养标签。快餐食品标示营养标签势在必行,可使消费者根据自身营养需求选择合适的食物,也可规范餐饮业生产行为,生产出健康、营养的美食。

  5. Bacteriological quality of aquacultured freshwater fish portions in prepackaged trays stored at 3 degrees C.

    Science.gov (United States)

    González-Rodríguez, M N; Sanz, J J; Santos, J A; Otero, A; García-López, M L

    2001-09-01

    Fresh trout fillets and salmon slices packed in trays were obtained from two multinational chain supermarkets and evaluated for freshness and bacteriological quality immediately after packaging and during storage at 3 degrees C. Initial aerobic counts at 30 and 25 degrees C were significantly (P fish was spoiled. Although initial presumptive Staphylococcus aureus counts were approximately 3 log CFU/g, only 4 of 84 selected colonies belonged to this species. Neither Salmonella nor antimicrobial residues were detected in any sample. Ethanol content in salmon slices did not significantly (P > 0.05) increase until they became inedible. Significant correlation (r = +0.72, P < 0.05) was observed between this chemical index and viable counts at 30 degrees C only when salmon slices were inedible. Trout fillets were acceptable for 7 days, and salmon slices showed signs of spoilage after 4 days. Although public health concerns associated with packed trout and salmon appear to be minimal, data on sensory quality, shelf life, and total viable and Enterobacteriaceae counts strongly suggest the need to improve the quality control systems used by European multinational retailers, especially for imported salmon.

  6. Experimental study of buoyancy-driven flow in a half-scale stairwell model

    Energy Technology Data Exchange (ETDEWEB)

    Zohrabian, A.S.; Mokhtarzadeh-Dehghan, M.R.; Reynolds, A.J. (Brunel Univ., Uxbridge (GB). Dept. of Mechanical Engineering); Marriott, B.S.T. (Logica EIS Ltd., London (GB))

    1989-01-01

    This paper describes an experimental study of buoyancy-driven flows of mass and energy in a half-scale model of a stairwell. Two different geometries are considered. The stairwell model forms a closed system, within which the circulation of air is maintained by the continuous operation of a heater placed in the lower floor. The rig, its instrumentation and the computerized data-logging system are described in detail. The overall features of the flow are also described. The results include the velocity and temperature distributions and the circulating volume flow. The effects of heat input rate on these parameters are also discussed. (author).

  7. 46 CFR 160.010-5 - Buoyant apparatus with plastic foam buoyancy.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 6 2010-10-01 2010-10-01 false Buoyant apparatus with plastic foam buoyancy. 160.010-5... Vessels § 160.010-5 Buoyant apparatus with plastic foam buoyancy. (a) Buoyant apparatus with plastic foam buoyancy must have a plastic foam body with an external protective covering. The body may be reinforced...

  8. The Effect of Buoyancy Force in Computational Fluid Dynamics Simulation of a Two-Dimensional Continuous Ohmic Heating Process

    Directory of Open Access Journals (Sweden)

    Elzubier A. Salih

    2009-01-01

    Full Text Available Problem statement: Earlier research on ohmic heating technique focused on viscous food and foods containing solid particles. In this study, use of ohmic heating on sterilization of guava juice is carried out. Computational fluid dynamics was used to model and simulate the system. Investigate the buoyancy effect on the CFD simulation of continuous ohmic heating systems of fluid foods. Approach: A two-dimensional model describing the flow, temperature and electric field distribution of non-Newtonian power law guava juice fluid in a cylindrical continuous ohmic heating cell was developed. The electrical conductivity, thermo physical and rheological properties of the fluid was temperature dependent. Numerical simulation was carried out using FLUENT 6.1 software package. A user defined functions available in FLUENT 6.1 was employed for the electric field equation. The heating cell used consisted of a cylindrical tube of diameter 0.05 m, height 0.50 m and having three collinear electrodes of 0.02 m width separated by a distance of 0.22 m. The sample was subjected to zero voltage at the top and bottom of electrodes while electrical potential of 90 volts (AC 50-60 Hz was set at the middle electrode. The inlet velocity is 0.003 m sec-1 and the temperature is in the range of 30-90°C. Results: Simulation was carried with and without buoyancy driven force effect. The ohmic heating was successfully simulated using CFD and the results showed that the buoyancy had a strong effect in temperature profiles and flow pattern of the collinear electrodes configuration ohmic heating. A more uniform velocity and temperature profiles were obtained with the buoyancy effect included. Conclusion: For accurate results, the inclusion of buoyancy effect into the CFD simulation is important.

  9. Buoyancy-corrected gravimetric analysis of lightly loaded filters.

    Science.gov (United States)

    Rasmussen, Pat E; Gardner, H David; Niu, Jianjun

    2010-09-01

    Numerous sources of uncertainty are associated with the gravimetric analysis of lightly loaded air filter samples (cut sizes (0.056-9.9 microm). By maintaining tight controls on humidity (within 0.5% RH of control setting) throughout pre- and postweighing at each stepwise increase in RH, it was possible to quantify error due to water absorption: 45% of the total mass change due to water absorption occurred between 16 and 50% RH, and 55% occurred between 50 and 60% RH. The buoyancy corrections ranged from -3.5 to +5.8 microg in magnitude and improved relative standard deviation (RSD) from 21.3% (uncorrected) to 5.6% (corrected) for a 7.2 microg sample. It is recommended that protocols for weighing low-mass particle samples (e.g., nanoparticle samples) should include buoyancy corrections and tight temperature/humidity controls. In some cases, conditioning times longer than 24 hr may be warranted.

  10. Buoyancy Effect on MHD Flow Past a Permeable Bed

    Directory of Open Access Journals (Sweden)

    S. Venkataramana

    1986-10-01

    Full Text Available In this paper, the effect of buoyancy force on the parallel flows bounded above by a rigid permeable plate which may be moving or stationary and below, by a permeable bed has been investigated. To discuss the solution, the flow region is divided into two zones. In Zone 1, the flow is laminar and is governed by the Navier-Stokes equations from the impermeable upper rigid plate to the permeable bed. In Zone 2, the flow is governed by the Darcy law in the permeable bed below the nominal surface. The expressions for velocity and temparature distributions, Slip velocity, slip temperature, mass flow rate and the rates of heat transfer coefficients are obtained. The effects of magnetic, porous, slip and buoyancy parameters and Biot number on the above physical quantities are investigated. The thickness of the boundary layer in Zone 2 has been evaluated.

  11. Capillary-driven two-dimensional buoyancy in vertical soap films

    Science.gov (United States)

    Adami, N.; Caps, H.

    2014-05-01

    The present study aims to investigate the capillary-driven buoyant effects in nearly two-dimensional systems. The case of rising rings in vertical soap films is studied both experimentally and theoretically. Since the pioneering works of Mysels and coworkers, the thickness differences and related two-dimensional densities are considered as the motor leading to two-dimensional buoyancy. We show how this effect can be re-interpreted in terms of the surface tension profiles present at the film interfaces. We propose a model involving surface tension profiles, as well as an adapted expression for the mass of the rising rings, and compare it to experimental data.

  12. Floating rings in vertical soap films : capillary driven bidimensional buoyancy

    CERN Document Server

    Adami, N

    2013-01-01

    The present study aims to investigate the motion of buoyant rings in vertical soap films. Thickness differences and related bi-dimensional densities are considered as the motor leading to bi-dimensional buoyancy. We show how this effect can be re-interpreted thanks to surface tension profiles in soap films. We propose a model involving surface tension profiles in order to describe the motion of buoyant particles in vertical soap films, and compare it to experimental data.

  13. Buoyancy-activated cell sorting using targeted biotinylated albumin microbubbles.

    Directory of Open Access Journals (Sweden)

    Yu-Ren Liou

    Full Text Available Cell analysis often requires the isolation of certain cell types. Various isolation methods have been applied to cell sorting, including fluorescence-activated cell sorting and magnetic-activated cell sorting. However, these conventional approaches involve exerting mechanical forces on the cells, thus risking cell damage. In this study we applied a novel isolation method called buoyancy-activated cell sorting, which involves using biotinylated albumin microbubbles (biotin-MBs conjugated with antibodies (i.e., targeted biotin-MBs. Albumin MBs are widely used as contrast agents in ultrasound imaging due to their good biocompatibility and stability. For conjugating antibodies, biotin is conjugated onto the albumin MB shell via covalent bonds and the biotinylated antibodies are conjugated using an avidin-biotin system. The albumin microbubbles had a mean diameter of 2 μm with a polydispersity index of 0.16. For cell separation, the MDA-MB-231 cells are incubated with the targeted biotin-MBs conjugated with anti-CD44 for 10 min, centrifuged at 10 g for 1 min, and then allowed 1 hour at 4 °C for separation. The results indicate that targeted biotin-MBs conjugated with anti-CD44 antibodies can be used to separate MDA-MB-231 breast cancer cells; more than 90% of the cells were collected in the MB layer when the ratio of the MBs to cells was higher than 70:1. Furthermore, we found that the separating efficiency was higher for targeted biotin-MBs than for targeted avidin-incorporated albumin MBs (avidin-MBs, which is the most common way to make targeted albumin MBs. We also demonstrated that the recovery rate of targeted biotin-MBs was up to 88% and the sorting purity was higher than 84% for a a heterogenous cell population containing MDA-MB-231 cells (CD44(+ and MDA-MB-453 cells (CD44-, which are classified as basal-like breast cancer cells and luminal breast cancer cells, respectively. Knowing that the CD44(+ is a commonly used cancer

  14. Hybrid Upwinding for Two-Phase Flow in Heterogeneous Porous Media with Buoyancy and Capillarity

    Science.gov (United States)

    Hamon, F. P.; Mallison, B.; Tchelepi, H.

    2016-12-01

    In subsurface flow simulation, efficient discretization schemes for the partial differential equations governing multiphase flow and transport are critical. For highly heterogeneous porous media, the temporal discretization of choice is often the unconditionally stable fully implicit (backward-Euler) method. In this scheme, the simultaneous update of all the degrees of freedom requires solving large algebraic nonlinear systems at each time step using Newton's method. This is computationally expensive, especially in the presence of strong capillary effects driven by abrupt changes in porosity and permeability between different rock types. Therefore, discretization schemes that reduce the simulation cost by improving the nonlinear convergence rate are highly desirable. To speed up nonlinear convergence, we present an efficient fully implicit finite-volume scheme for immiscible two-phase flow in the presence of strong capillary forces. In this scheme, the discrete viscous, buoyancy, and capillary spatial terms are evaluated separately based on physical considerations. We build on previous work on Implicit Hybrid Upwinding (IHU) by using the upstream saturations with respect to the total velocity to compute the relative permeabilities in the viscous term, and by determining the directionality of the buoyancy term based on the phase density differences. The capillary numerical flux is decomposed into a rock- and geometry-dependent transmissibility factor, a nonlinear capillary diffusion coefficient, and an approximation of the saturation gradient. Combining the viscous, buoyancy, and capillary terms, we obtain a numerical flux that is consistent, bounded, differentiable, and monotone for homogeneous one-dimensional flow. The proposed scheme also accounts for spatially discontinuous capillary pressure functions. Specifically, at the interface between two rock types, the numerical scheme accurately honors the entry pressure condition by solving a local nonlinear problem

  15. Sink or swim? Bone density as a mechanism for buoyancy control in early cetaceans.

    Science.gov (United States)

    Gray, Noel-Marie; Kainec, Kimberly; Madar, Sandra; Tomko, Lucas; Wolfe, Scott

    2007-06-01

    Previous analyses have shown that secondarily aquatic tetrapods, including whales, exhibit osteological adaptations to life in water as part of their complex buoyancy control systems. These structural specializations of bone span hyperostosis through osteoporosis. The past 15 years of paleontological effort has provided an unprecedented opportunity to examine the osteological transformation of whales as they make their transition to an obligate aquatic lifestyle over a 10-million-year period. It is hypothesized that whales manifest their osteological specialization in the same manner as extant semiaquatic and fully aquatic mammals. This study presents and analysis of the microstructural features of bone in early and late archaic cetaceans, and in a comparative sample of modern terrestrial, semiaquatic, and aquatic mammals. Bone histology was examined from the ribs of 10 fossilized individuals representing five early cetacean families, including Pakicetidae, Ambulocetidae, Protocetidae, Remintonocetidae, and Basilosauridae. Comparisons were then made with rib histology from nine genera of extant mammals including: Odocoileus (deer), Bos (cow), Equus (horse), Canis (dog), Lutra (river otter), Enhydra (sea otter), Choeropsis (pygmy hippo), Trichechus (sea cow), and Delphinus (dolphin). Results show that the transition from terrestrial, to semiaquatic, to obligate aquatic locomotion in archaeocetes involved a radical shift in bone function achieved by means of profound changes at the microstructural level. A surprising finding was that microstructural change predates gross anatomical shift in archaeocetes associated with swimming. Histological analysis shows that high bone density is an aquatic specialization that provides static buoyancy control (ballast) for animals living in shallow water, while low bone density is associated with dynamic buoyancy control for animals living in deep water. Thus, there was a shift from the typical terrestrial form, to osteopetrosis

  16. 预包装肉制品营养标签的制作%Making nutrition labeling of prepackaged meat products

    Institute of Scientific and Technical Information of China (English)

    冯吉

    2012-01-01

    How to make nutrition labeling of prepackaged meat products was introduced and dis- cussed in this paper. The status of nutrition labeling in China was described and enhancing knowledge of food nutrition was advised.%对预包装肉制品营养标签的制作提出建议,帮助生产者正确进行营养信息的标注。严格按照标准规定,讨论预包装肉制品营养标签的制作要点。生产者应当全面把握、正确理解营养标签的有关标准和知识,为消费者提供准确的营养信息。

  17. Dormitory Solar-Energy-System Economics

    Science.gov (United States)

    1982-01-01

    102-page report analyzes long-term economic performance of a prepackaged solar energy assembly system at a dormitory installation and extrapolates to four additional sites about the U.S. Method of evaluation is f-chart procedure for solar-heating and domestic hotwater systems.

  18. Using surface integrals for checking the Archimedes' law of buoyancy

    OpenAIRE

    Lima, F. M. S.

    2011-01-01

    A mathematical derivation of the force exerted by an \\emph{inhomogeneous} (i.e., compressible) fluid on the surface of an \\emph{arbitrarily-shaped} body immersed in it is not found in literature, which may be attributed to our trust on Archimedes' law of buoyancy. However, this law, also known as Archimedes' principle (AP), does not yield the force observed when the body is in contact to the container walls, as is more evident in the case of a block immersed in a liquid and in contact to the ...

  19. EXPERIMENTAL INVESTIGATION INTO HOT WATER SLOT JETS WITH NEGATIVELY BUOYANCY IN CROSS FLOW

    Institute of Scientific and Technical Information of China (English)

    YANG Zhong-hua; HUAI Wen-xin; DAI Hui-chao

    2005-01-01

    An experiment was conducted to examine the near-field behavior of negatively buoyant planar jets in flowing environment. Hot water jet was projected downwards at different angles from a slot into a uniform cross flow. Micro Acoustic Doppler Velocimeter (Micro ADV) system is used to measure the velocity and turbulent fluxes of Reynolds stresses. The whole field temperatures were measured with fast response thermocouples. Pure jets experiments were made also to study the effect of buoyancy in negatively buoyant jets. It is found that the influenced area of hot jets is larger than which of pure jets when the jet angle is 90° and the influenced area of hot jets is smaller than which of pure jets when the jet angle is 45°. The difference is not obvious at 60° angle jets. This means that the rising of temperature has effect not only on negatively buoyancy, but also on the intensity of turbulence. The contrast of these two influences dominates the trend of jet flow.

  20. Relations between morphology, buoyancy and energetics of requiem sharks

    Science.gov (United States)

    Papastamatiou, Yannis P.

    2016-01-01

    Sharks have a distinctive shape that remained practically unchanged through hundreds of millions of years of evolution. Nonetheless, there are variations of this shape that vary between and within species. We attempt to explain these variations by examining the partial derivatives of the cost of transport of a generic shark with respect to buoyancy, span and chord of its pectoral fins, length, girth and body temperature. Our analysis predicts an intricate relation between these parameters, suggesting that ectothermic species residing in cooler temperatures must either have longer pectoral fins and/or be more buoyant in order to maintain swimming performance. It also suggests that, in general, the buoyancy must increase with size, and therefore, there must be ontogenetic changes within a species, with individuals getting more buoyant as they grow. Pelagic species seem to have near optimally sized fins (which minimize the cost of transport), but the majority of reef sharks could have reduced the cost of transport by increasing the size of their fins. The fact that they do not implies negative selection, probably owing to decreased manoeuvrability in confined spaces (e.g. foraging on a reef). PMID:27853556

  1. On the general concept of buoyancy in sedimentation and ultracentrifugation

    Science.gov (United States)

    Piazza, Roberto; Buzzaccaro, Stefano; Secchi, Eleonora; Parola, Alberto

    2013-08-01

    Gravity or ultracentrifuge settling of colloidal particles and macromolecules usually involves several disperse species, either because natural and industrial colloids display a large size polydispersity, or because additives are put in on purpose to allow for density-based fractionation of the suspension. Such ‘macromolecular crowding’, however, may have surprising effects on sedimentation, for it strongly affects the buoyant force felt by a settling particle. Here we show that, as a matter of fact, the standard Archimedes' principle is just a limiting law, valid only for mesoscopic particles settling in a molecular fluid, and we obtain a fully general expression for the actual buoyancy force providing a microscopic basis to the general thermodynamic analysis of sedimentation in multi-component mixtures. The effective buoyancy also depends on the particle shape, being much more pronounced for thin rods and discs. Our model is successfully tested on simple colloidal mixtures, and used to predict rather unexpected effects, such as denser particles floating on top of a lighter fluid, which we actually observe in targeted experiments. This ‘generalized Archimedes principle’ may provide a tool to devise novel separation methods sensitive to particle size and shape.

  2. Equilibrium models of coronal loops that involve curvature and buoyancy

    CERN Document Server

    Hindman, Bradley W

    2013-01-01

    We construct magnetostatic models of coronal loops in which the thermodynamics of the loop is fully consistent with the shape and geometry of the loop. This is achieved by treating the loop as a thin, compact, magnetic fibril that is a small departure from a force-free state. The density along the loop is related to the loop's curvature by requiring that the Lorentz force arising from this deviation is balanced by buoyancy. This equilibrium, coupled with hydrostatic balance and the ideal gas law, then connects the temperature of the loop with the curvature of the loop without resorting to a detailed treatment of heating and cooling. We present two example solutions: one with a spatially invariant magnetic Bond number (the dimensionless ratio of buoyancy to Lorentz forces) and the other with a constant radius of curvature of the loop's axis. We find that the density and temperature profiles are quite sensitive to curvature variations along the loop, even for loops with similar aspect ratios.

  3. Equilibrium Models of Coronal Loops That Involve Curvature and Buoyancy

    Science.gov (United States)

    Hindman, Bradley W.; Jain, Rekha

    2013-12-01

    We construct magnetostatic models of coronal loops in which the thermodynamics of the loop is fully consistent with the shape and geometry of the loop. This is achieved by treating the loop as a thin, compact, magnetic fibril that is a small departure from a force-free state. The density along the loop is related to the loop's curvature by requiring that the Lorentz force arising from this deviation is balanced by buoyancy. This equilibrium, coupled with hydrostatic balance and the ideal gas law, then connects the temperature of the loop with the curvature of the loop without resorting to a detailed treatment of heating and cooling. We present two example solutions: one with a spatially invariant magnetic Bond number (the dimensionless ratio of buoyancy to Lorentz forces) and the other with a constant radius of the curvature of the loop's axis. We find that the density and temperature profiles are quite sensitive to curvature variations along the loop, even for loops with similar aspect ratios.

  4. Phenomenology of buoyancy-driven turbulence: recent results

    CERN Document Server

    Verma, Mahendra K; Pandey, Ambrish

    2016-01-01

    In this paper, we review the recent developments in the field of buoyancy-driven turbulence. Scaling and numerical arguments show that the stably-stratified turbulence with moderate stratification has kinetic energy spectrum $E_u(k) \\sim k^{-11/5}$ and the kinetic energy flux $\\Pi_u(k) \\sim k^{-4/5}$, which is called Bolgiano-Obukhov scaling. The energy flux for the Rayleigh-B\\'{e}nard convection (RBC) however is approximately constant in the inertial range that results in Kolmorogorv's spectrum ($E_u(k) \\sim k^{-5/3}$) for the kinetic energy. The phenomenology of RBC should apply to other flows where the buoyancy feeds the kinetic energy, e.g. bubbly turbulence and fully-developed Rayleigh Taylor instability. This paper also covers several models that predict the Reynolds and Nusselt numbers of RBC. Recent works show that the viscous dissipation rate of RBC scales as $\\sim \\mathrm{Ra}^{1.3}$, where $\\mathrm{Ra}$ is the Rayleigh number.

  5. Experimental study on the changes in coagulation and fibrinolysis system of the animals with decompression sickness induced by fast buoyancy ascent escape%快速上浮脱险致减压病动物凝血纤溶系统变化的实验研究

    Institute of Scientific and Technical Information of China (English)

    攸璞; 方以群; 唐瑛; 王海涛; 包晓辰; 李丹; 李娜; 袁恒荣; 马骏

    2015-01-01

    目的 研究快速上浮脱险致减压病动物凝血纤溶系统的变化,从而为快速上浮脱险减压病筛选能反映其损伤程度的敏感指标.方法 雄性SD大鼠80只,按数字表法随机分为2组,正常对照组(对照组)20只,快速上浮脱险实验组(实验组)60只,根据动物是否死亡进而分为死亡组和存活组.实验组以21/7指数速率加压至1.5 MPa(表压),停留4 min后匀速减压至常压.观察实验组大鼠出舱后30 min内的存活状况.如果大鼠30 min内死亡,则立即抽取其下腔静脉血;如果30 min内未死亡,则在30 min后抽取其下腔静脉血,血标本置于3.5%枸橼酸钾及1%肝素内抗凝,用于检测凝血6项指标和血小板计数.结果 实验组大鼠30 min内死亡率30只(50%).对照组、存活组与死亡组大鼠的血小板计数比较差异无统计学意义(P>0.05);存活组、死亡组及对照组大鼠的凝血酶时间分别为(28.00±1.69)s、(27.21 ±3.82)s与(30.91±2.82)s,组间比较差异均有统计学意义(P<0.01),对照组大鼠的纤维蛋白原(2.91±0.43)g/L和死亡组(3.72±1.55)g/L比较差异有统计学意义(P<0.05),存活组大鼠的D-二聚体(0.19±0.05) μg/L和死亡组(0.24±0.08) μg/L比较差异有统计学意义(P<0.05).结论 凝血酶时间、纤维蛋白原和D-二聚体可综合反映快速上浮脱险致减压病的发生以及造成损伤的严重程度,可作为反映损伤程度的指标.%Objective To study changes in coagulation and fibrinolysis system of animals with decompression sickness caused by fast buoyancy ascent escape.Methods Eighty male SD rats were randomly divided into 2 groups:the normal control group (n =20),the fast buoyancy ascent escape group (or simply the experimental group) (n =60) and the experimental group was further divided into the death and survival groups,based on whether the animals died or survived after escape.The animals in the experimental group were compressed to a pressure of 1.5 MPa

  6. On the role of buoyancy force in the ore genesis of SEDEX deposits: Example from Northern Australia

    Institute of Scientific and Technical Information of China (English)

    YANG JianWen; FENG ZuoHai; LUO XianRong; CHEN YuanRong

    2009-01-01

    Finite element modeling on a highly conceptualized 2-D model of fluid flow and heat transport is un-dertaken to simulate the paleo-hydrological system as if the Mount Ise deposits were being formed in the Mount Isa basin, Northern Australia, and to evaluate the potential of buoyancy force in driving ba-sin-scale fluid flow for the formation of sedimentary-exhalative (SEDEX) deposits. Our numerical case studies indicate that buoyancy-driven fluid flow is controlled mainly by the fault penetration depth and its spatial relation with the aquifer. Marine water recharges the basin via one fault and flows through the aquifer where it is heated from below. The heated metalliferous fluid discharges to the basin floor via the other fault. The venting fluid temperatures are computed to be in the range of 115 to 160℃, with fluid velocities of 2.6 to 4.1 m/year over a period of 1 Ma. These conditions are suitable for the formation of a Mount Isa-sized zinc deposit, provided a suitable chemical trap environment is present. Buoyancy force is therefore a viable driving mechanism for basin-scale ore-forming hydrothermal fluid migration, and it is strong enough to lead to the genesis of supergiant SEDEX deposits like the Mount Isa deposit, Northern Australia.

  7. Survey on Safe Management of Prepackaged Food in Restaurants in Haian County%海安县餐馆预包装食品安全管理现状调查

    Institute of Scientific and Technical Information of China (English)

    陈华; 王云飞

    2011-01-01

    Abstract Objective To understand the current status of safe management of prepackaged food in restaurants,and to provide the scientific evidence to improve the safe management. Methods Field questionnaire survey was conducted and prepackaged food in restaurants were checked. Results There were 989 restaurants in Haian county, 82. 31% of which were qualified in safe management of prepackaged foods, 14. 96% were unqualified in inspection of purchase records of prepackaged food, 7. 69% were unqualified in label and specification of prepackaged food, and 5. 56% were unqualified in guarantee period of prepackaged food. The qualified rate was higher in urban area than that in rural area, in large restaurants than in medium and small ones;The unqualified rate of inspection of purchase records of prepackaged food was lower in urban area than in rural area, in large and medium restaurants than in small ones; The unqualified rate of label, specification and guarantee period of prepackaged foods was lower in urban area than that in rural area, in large and small restaurants than in medium ones. All the differences were significant (P < 0. 01). Condiments ( prepackaged food) storage conditions : up to 51. 67% of restaurants had warehouses to store condiments, of which 83. 37% did condiments classification and placed them on shelf above the ground, 35. 19% stored condiments in the cooking rooms, and 13. 14% stored condiments in other places. Unqualified prepackaged food in restaurants were mainly from wholesale markets ( 84. 33% ) , and 90. 79% of prepackage food in wholesale markets were without qualified label and specification. Conclusion The management of prepackaged food in restaurants in Haian was generally good, but it is necessary to improved the management in those in rural area and with medium or small size. Food safety should be improved by strengthen the management.%目的 了解餐馆预包装食品管理现状,为今后有效开展食品安

  8. Buoyancy Instabilities in a Weakly Collisional Intracluster Medium

    CERN Document Server

    Kunz, Matthew W; Reynolds, Christopher S; Stone, James M

    2012-01-01

    The intracluster medium of galaxy clusters is a weakly collisional, high-beta plasma in which the transport of heat and momentum occurs primarily along magnetic-field lines. Anisotropic heat conduction allows convective instabilities to be driven by temperature gradients of either sign, the magnetothermal instability (MTI) in the outskirts of non-isothermal clusters and the heat-flux buoyancy-driven instability (HBI) in their cooling cores. We employ the Athena MHD code to investigate the nonlinear evolution of these instabilities, self-consistently including the effects of anisotropic viscosity (i.e. Braginskii pressure anisotropy), anisotropic conduction, and radiative cooling. We highlight the importance of the microscale instabilities that inevitably accompany and regulate the pressure anisotropies generated by the HBI and MTI. We find that, in all but the innermost regions of cool-core clusters, anisotropic viscosity significantly impairs the ability of the HBI to reorient magnetic-field lines orthogonal...

  9. Nonlinear optimization of buoyancy-driven ventilation flow

    Science.gov (United States)

    Nabi, Saleh; Grover, Piyush; Caulfield, C. P.

    2016-11-01

    We consider the optimization of buoyancy-driven flows governed by Boussinesq equations using the Direct-Adjoint-Looping method. We use incompressible Reynolds-averaged Navier-Stokes (RANS) equations, derive the corresponding adjoint equations and solve the resulting sensitivity equations with respect to inlet conditions. For validation, we solve a series of inverse-design problems, for which we recover known globally optimal solutions. For a displacement ventilation scenario with a line source, the numerical results are compared with analytically obtained optimal inlet conditions available from classical plume theory. Our results show that depending on Archimedes number, defined as the ratio of the inlet Reynolds number to the Rayleigh number associated with the plume, qualitatively different optimal solutions are obtained. For steady and transient plumes, and subject to an enthalpy constraint on the incoming flow, we identify boundary conditions leading to 'optimal' temperature distributions in the occupied zone.

  10. Study on buoyancy convection phenomenon in the crystal growth process

    Institute of Scientific and Technical Information of China (English)

    DUAN Li; KANG Qi

    2009-01-01

    Real-time phase shift Mach-Zehnder interference technique,imaging technique,and computer image processing technique were combined to perform a real-time diagnosis of NaCIO3 crystal,which described both the dissolution process end the crystallization process of the NaCIO3 crystal in real-time condition.The dissolution fringes and the growth fringes in the process were obtained.Moreover,a distribution of concentration field in this process was obtained by inversion calculation.Finally,the buoyancy convection phenomenon caused by gravity in the crystal growth process was analyzed.The results showed that this convection phenomenon directly influences the growth rate of each crystal face in the crystal.

  11. Study on buoyancy convection phenomenon in the crystal growth process

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Real-time phase shift Mach-Zehnder interference technique, imaging technique, and computer image processing technique were combined to perform a real-time diagnosis of NaClO3 crystal, which de- scribed both the dissolution process and the crystallization process of the NaClO3 crystal in real-time condition. The dissolution fringes and the growth fringes in the process were obtained. Moreover, a distribution of concentration field in this process was obtained by inversion calculation. Finally, the buoyancy convection phenomenon caused by gravity in the crystal growth process was analyzed. The results showed that this convection phenomenon directly influences the growth rate of each crystal face in the crystal.

  12. Field evidence for buoyancy-driven water flow in a Sphagnum dominated peat bog

    NARCIS (Netherlands)

    Adema, E.B.; Baaijens, G. J.; van Belle, J.; Rappoldt, C.; Grootjans, A. P.; Smolders, A. J. P.

    2006-01-01

    Nocturnal buoyancy-driven water flow in bogs is proposed as a mechanism to replenish the nutrient availability in the top of the acrotelm. In an earlier paper, we provided evidence for buoyancy-driven water flow on theoretical and experimental grounds. In this paper, field evidence is given for the

  13. Variation in seed buoyancy of species in wetland ecosystems with different flooding dynamics

    NARCIS (Netherlands)

    van den Broek, T; van Diggelen, R; Bobbink, R

    2005-01-01

    Question: Do species from communities with different flooding dynamics differ in seed buoyancy? Is there a trade-off between seed buoyancy and seed longevity? Methods: Seeds of 55 freshwater wetland species were collected and related to communities along the hydrological gradient, ranging from

  14. Buoyancy-driven instabilities of acid-base fronts: the case of a color indicator

    Science.gov (United States)

    Riolfo, L. A.; Kuster, S.; Trevelyan, P. M. J.; El Hasi, C.; Zalts, A.; Almarcha, C.; D'Onofrio, A.; de Wit, A.

    2011-11-01

    Buoyancy-driven hydrodynamic instabilities of acid-base fronts are studied both experimentally and theoretically in the case where an aqueous solution of a strong acid is put above a denser aqueous solution of a color indicator in the gravity field. The neutralization reaction between the acid and the color indicator as well as their differential diffusion modifies the initially stable density profile in the system and can trigger convective motion both above and below the initial contact line. The type of patterns observed as well as their wavelength and the speed of the reaction front are shown to depend on the value of the initial concentrations of the acid and of the color indicator and on their ratio. A reaction-diffusion model explains how the hydrodynamic instability scenarios change when the concentration of the reactants are varied.

  15. Large eddy simulation of a buoyancy-aided flow in a non-uniform channel – Buoyancy effects on large flow structures

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Y. [Department of Mechanical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom); School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Manchester M13 9PL (United Kingdom); He, S., E-mail: s.he@sheffield.ac.uk [Department of Mechanical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom)

    2017-02-15

    Highlights: • Buoyancy may greatly redistribute the flow in a non-uniform channel. • Flow structures in the narrow gap are greatly changed when buoyancy is strong. • Large flow structures exist in wider gap, which is enhanced when heat is strong. • Buoyancy reduces mixing factor caused by large flow structures in narrow gap. - Abstract: It has been a long time since the ‘abnormal’ turbulent intensity distribution and high inter-sub-channel mixing rates were observed in the vicinity of the narrow gaps formed by the fuel rods in nuclear reactors. The extraordinary flow behaviour was first described as periodic flow structures by Hooper and Rehme (1984). Since then, the existences of large flow structures were demonstrated by many researchers in various non-uniform flow channels. It has been proved by many authors that the Strouhal number of the flow structure in the isothermal flow is dependent on the size of the narrow gap, not the Reynolds number once it is sufficiently large. This paper reports a numerical investigation on the effect of buoyancy on the large flow structures. A buoyancy-aided flow in a tightly-packed rod-bundle-like channel is modelled using large eddy simulation (LES) together with the Boussinesq approximation. The behaviour of the large flow structures in the gaps of the flow passage are studied using instantaneous flow fields, spectrum analysis and correlation analysis. It is found that the non-uniform buoyancy force in the cross section of the flow channel may greatly redistribute the velocity field once the overall buoyancy force is sufficiently strong, and consequently modify the large flow structures. The temporal and axial spatial scales of the large flow structures are influenced by buoyancy in a way similar to that turbulence is influenced. These scales reduce when the flow is laminarised, but start increasing in the turbulence regeneration region. The spanwise scale of the flow structures in the narrow gap remains more or

  16. Buoyancy Effects on Unsteady MHD Flow of a Reactive Third-Grade Fluid with Asymmetric Convective Cooling

    Directory of Open Access Journals (Sweden)

    Tirivanhu Chinyoka

    2015-01-01

    Full Text Available This article examines the combined effects of buoyancy force and asymmetrical convective cooling on unsteady MHD channel flow and heat transfer characteristics of an incompressible, reactive, variable viscosity and electrically conducting third grade fluid. The chemical kinetics in the flow system is exothermic and the asymmetric convective heat transfers at the channel walls follow the Newton’s law of cooling. The coupled nonlinear partial differential equations governing the problem are derived and solved numerically using a semi-implicit finite difference scheme. Graphical results are presented and physical aspects of the problem are discussed with respect to various parameters embedded in the system.

  17. Basal buoyancy and fast-moving glaciers: in defense of analytic force balance

    Science.gov (United States)

    van der Veen, C. J.

    2016-06-01

    The geometric approach to force balance advocated by T. Hughes in a series of publications has challenged the analytic approach by implying that the latter does not adequately account for basal buoyancy on ice streams, thereby neglecting the contribution to the gravitational driving force associated with this basal buoyancy. Application of the geometric approach to Byrd Glacier, Antarctica, yields physically unrealistic results, and it is argued that this is because of a key limiting assumption in the geometric approach. A more traditional analytic treatment of force balance shows that basal buoyancy does not affect the balance of forces on ice streams, except locally perhaps, through bridging effects.

  18. Buoyancy and shear characteristics of hurricane-tornado environments

    Science.gov (United States)

    Mccaul, Eugene W., Jr.

    1991-01-01

    This study presents detailed composite profiles of temperature, moisture, and wind constructed for tornado environments in tropical cyclones that affected the U.S. between 1948 and 1986. Winds are composited in components radial and tangential to the tropical cyclone center at observation time. Guided by observed patterns of tornado occurrence, composites are constructed for a variety of different stratifications of the data, including proximity to tornadoes, position relative to the cyclone center, time of day, time after cyclone landfall, cyclone translation speed, and landfall location. The composites are also compared to composite soundings from Great Plains tornado environments. A variety of sounding parameters are examined to see which are most closely related to the tornado distribution patterns. Lower-tropospheric vertical shears are found to be stronger in the tropical cyclone tornado environments than on the Great Plains. Buoyancy for the tropical cyclone tornado cases is much smaller than that seen with Great Plains tornado events and exhibits a weak negative correlation with tornado outbreak severity.

  19. Using surface integrals for checking the Archimedes' law of buoyancy

    CERN Document Server

    Lima, F M S

    2011-01-01

    A mathematical derivation of the force exerted by an \\emph{inhomogeneous} (i.e., compressible) fluid on the surface of an \\emph{arbitrarily-shaped} body immersed in it is not found in literature, which may be attributed to our trust on Archimedes' law of buoyancy. However, this law, also known as Archimedes' principle (AP), does not yield the force observed when the body is in contact to the container walls, as is more evident in the case of a block immersed in a liquid and in contact to the bottom, in which a \\emph{downward} force that \\emph{increases with depth} is observed. In this work, by taking into account the surface integral of the pressure force exerted by a fluid over the surface of a body, the general validity of AP is checked. For a body fully surrounded by a fluid, homogeneous or not, a gradient version of the divergence theorem applies, yielding a volume integral that simplifies to an upward force which agrees to the force predicted by AP, as long as the fluid density is a \\emph{continuous func...

  20. Buoyancy and Penrose Process Produce Jets from Rotating Black Holes

    CERN Document Server

    Semenov, V S; Heyn, M F

    2014-01-01

    The exact mechanism by which astrophysical jets are formed is still unknown. It is believed that necessary elements are a rotating (Kerr) black hole and a magnetised accreting plasma. We model the accreting plasma as a collection of magnetic flux tubes/strings. If such a tube falls into a Kerr black hole, then the leading portion loses angular momentum and energy as the string brakes, and to compensate for this loss, momentum and energy is redistributed to the trailing portion of the tube.} {We found that buoyancy creates a pronounced helical magnetic field structure aligned with the spin axis. Along the field lines, the plasma is centrifugally accelerated close to the speed of light. This process leads to unlimited stretching of the flux tube since one part of the tube continues to fall into the black hole and simultaneously the other part of the string is pushed outward. Eventually, reconnection cuts the tube, the inner part is filled with new material and the outer part forms a collimated bubble-structured...

  1. Particular uncertainties encountered in using a pre-packaged SEBS model to derive evapotranspiration in a heterogeneous study area in South Africa

    Directory of Open Access Journals (Sweden)

    L. A. Gibson

    2011-01-01

    Full Text Available The focus of this paper is on the pre-packaged version of SEBS in ILWIS and the sensitivity of SEBS to some parameters over which the user has some control when using this version of the model, in order to make informed choices to limit uncertainties. The sensitivities of SEBS to input parameters are related to daily ET rather than energy flux results since this is of interest to water managers and other users of the results of the SEBS model. This paper describes some of the uncertainties introduced by the sensitivity of the SEBS model to (a land surface temperature and air temperature gradient, (b the choice of fractional vegetation formula, (c displacement height and the height at which wind speed is measured, and (d study area heterogeneity. It was shown that SEBS is sensitive to land surface temperature and air temperature gradient and the magnitude of this sensitivity depended on the land cover and whether or not the wet-limit had been reached. The choice of fractional vegetation cover formula was shown to influence the daily ET results by up to 0.7 mm. It was shown that the height of the vegetation canopy should be considered in relation to the weather station reference height to avoid the sensible heat flux from becoming unsolvable due to a negative ln calculation. Finally the study area was shown to be heterogeneous although the resolution at which fluxes were calculated did not significantly impact on energy partitioning results. The differences in the upscaling from evaporative fraction to daily ET at varying resolutions observed implies that the heterogeneity may play the biggest role in the upscaling and the influence of albedo on this calculation should be studied.

  2. TAO/TRITON, RAMA, and PIRATA Buoys, 5-Day, Buoyancy Flux

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset has 5-day Buoyancy Flux data from the TAO/TRITON (Pacific Ocean, http://www.pmel.noaa.gov/tao/), RAMA (Indian Ocean,...

  3. The Role of Magnetic Buoyancy in a Babcock-Leighton Type Solar Dynamo

    Indian Academy of Sciences (India)

    Dibyendu Nandy; Arnab Rai Choudhuri

    2000-09-01

    We study the effects of incorporating magnetic buoyancy in a model of the solar dynamo—which draws inspiration from the Babcock-Leighton idea of surface processes generating the poloidal field. We present our main results here.

  4. An explanation for salinity- and SPM-induced vertical countergradient buoyancy fluxes

    NARCIS (Netherlands)

    De Nijs, M.A.J.; Pietrzak, J.D.

    2011-01-01

    Measurements of turbulent fluctuations of velocity, salinity, and suspended particulate matter (SPM) are presented. The data show persistent countergradient buoyancy fluxes. These countergradient fluxes are controlled by the ratio of vertical turbulent kinetic energy (VKE) and available potential

  5. Gravitaxis of Euglena gracilis depends only partially on passive buoyancy

    Science.gov (United States)

    Richter, Peter R.; Schuster, Martin; Lebert, Michael; Streb, Christine; Häder, Donat-Peter

    In darkness, the unicellular freshwater flagellate Euglena gracilis shows a pronounced negative gravitactic behavior, and the cells swim actively upward in the water column. Up to now it was unclear whether this behavior is based on a passive (physical) alignment mechanism (e.g., buoyancy due to a fore-aft asymmetry of the cell body) or on an active physiological mechanism. A sounding rocket experiment was performed in which the effect of sub-1g-accelerations (0.05, 0.08, 0.12, and 0.2g) on untreated living cells and immobilized (fixation with liquid nitrogen) cells was observed. By means of computerized image analysis the angles of the cells long axis with respect to the acceleration vector were analyzed in order to calculate and compare the reorientation kinetics of the immobilized cells versus that of the controls. In both groups, the reorientation kinetics depended on the dose, but the reorientation of the living cells was about five times faster than that of the immobilized cells. This indicates that in young cells gravitaxis can be explained by a physical mechanism only to a small extend. In older cultures, in which the cells often have a drop shaped cell body, the physical reorientation is considerably faster, and a more pronounced influence of passive alignment caused by fore/aft asymmetry (drag-gravity model) can not be excluded. In addition to these results, Euglena gracilis cells seem to respond very sensitively to small accelerations when they are applied after a longer microgravity period. The data indicate that gravitactic orientation occurred at an acceleration as low as 0.05g.

  6. Neutral Buoyancy Simultor (NBS) NB-1 Large Mass Transfer simulation

    Science.gov (United States)

    1980-01-01

    Once the United States' space program had progressed from Earth's orbit into outerspace, the prospect of building and maintaining a permanent presence in space was realized. To accomplish this feat, NASA launched a temporary workstation, Skylab, to discover the effects of low gravity and weightlessness on the human body, and also to develop tools and equipment that would be needed in the future to build and maintain a more permanent space station. The structures, techniques, and work schedules had to be carefully designed to fit this unique construction site. The components had to be lightweight for transport into orbit, yet durable. The station also had to be made with removable parts for easy servicing and repairs by astronauts. All of the tools necessary for service and repairs had to be designed for easy manipulation by a suited astronaut. And construction methods had to be efficient due to limited time the astronauts could remain outside their controlled environment. In lieu of all the specific needs for this project, an environment on Earth had to be developed that could simulate a low gravity atmosphere. A Neutral Buoyancy Simulator (NBS) was constructed by NASA Marshall Space Flight Center (MSFC) in 1968. Since then, NASA scientists have used this facility to understand how humans work best in low gravity and also provide information about the different kinds of structures that can be built. Pictured is a Massachusetts Institute of Technology (MIT) student working in a spacesuit on the Experimental Assembly of Structures in Extravehicular Activity (EASE) project which was developed as a joint effort between MFSC and MIT. The EASE experiment required that crew members assemble small components to form larger components, working from the payload bay of the space shuttle.

  7. Effects of body condition on buoyancy in endangered North Atlantic right whales.

    Science.gov (United States)

    Nousek-McGregor, Anna E; Miller, Carolyn A; Moore, Michael J; Nowacek, Douglas P

    2014-01-01

    Buoyancy is an important consideration for diving marine animals, resulting in specific ecologically relevant adaptations. Marine mammals use blubber as an energy reserve, but because this tissue is also positively buoyant, nutritional demands have the potential to cause considerable variation in buoyancy. North Atlantic right whales Eubalaena glacialis are known to be positively buoyant as a result of their blubber, and the thickness of this layer varies considerably, but the effect of this variation on buoyancy has not been explored. This study compared the duration and rate of ascending and descending glides, recorded with an archival tag, with blubber thickness, measured with an ultrasound device, in free-swimming right whales. Ascending whales with thicker blubber had shorter portions of active propulsion and longer passive glides than whales with thinner blubber, suggesting that blubber thickness influences buoyancy because the buoyant force is acting in the same direction as the animal's movement during this phase. Whales with thinner layers also used similar body angles and velocities when traveling to and from depth, while those with thicker layers used shallower ascent angles but achieved higher ascent velocities. Such alterations in body angle may help to reduce the cost of transport when swimming against the force of buoyancy in a state of augmented positive buoyancy, which represents a dynamic response to reduce the energetic consequences of physiological changes. These results have considerable implications for any diving marine animal during periods of nutritional stress, such as during seasonal migrations and annual variations in prey availability.

  8. Neutral Buoyancy Simulator-NB50B-SADE Training Exercises

    Science.gov (United States)

    1983-01-01

    One of the main components of the Hubble Space Telescope (HST) is the Solar Array Drive Electronics (SADE) system. This system interfaces with the Support System Module (SSM) for exchange of operational commands and telemetry data. SADE operates and controls the Solar Array Drive Mechanisms (SADM) for the orientation of the Solar Array Drive (SAD). It also monitors the position of the arrays and the temperature of the SADM. During the first HST servicing mission, the astronauts replaced the SADE component because of some malfunctions. This turned out to be a very challenging extravehicular activity (EVA). Two transistors and two diodes had been thermally stressed with the conformal coating discolored and charred. Soldered cornections became molten and reflowed between the two diodes. The failed transistors gave no indication of defective construction. All repairs were made and the HST was redeposited into orbit. Prior to undertaking this challenging mission, the orbiter's crew trained at Marshall Space Flight Center's (MSFC) Neutral Buoyancy Simulator (NBS) to prepare themselves for working in a low gravity environment. They also practiced replacing HST parts and exercised maneuverability and equipment handling. Pictured are crew members practicing on a space platform.

  9. Academic Buoyancy and Academic Outcomes: Towards a Further Understanding of Students with Attention-Deficit/Hyperactivity Disorder (ADHD), Students without ADHD, and Academic Buoyancy Itself

    Science.gov (United States)

    Martin, Andrew J.

    2014-01-01

    Background: Academic buoyancy is students' capacity to successfully overcome setback and challenge that is typical of the ordinary course of everyday academic life. It may represent an important factor on the psycho-educational landscape assisting students who experience difficulties in school and schoolwork. Aims: This study investigated the…

  10. System design package for SIMS prototype system 4, solar heating and domestic hot water

    Science.gov (United States)

    1978-01-01

    The system consisted of a modular designed prepackaged solar unit, containing solar collectors, a rock storage container, blowers, dampers, ducting, air-to-water heat exchanger, DHW preheat tank, piping, and system controls. The system was designed to be installed adjacent to a small single family dwelling. The description, performance specification, subsystem drawings, verification plan/procedure, and hazard analysis of the system were packaged for evaluation.

  11. Adherence of community caretakers of children to pre-packaged antimalarial medicines (HOMAPAK® among internally displaced people in Gulu district, Uganda

    Directory of Open Access Journals (Sweden)

    Opwonya John

    2006-05-01

    Full Text Available Abstract Background In 2002, home-based management of fever (HBMF was introduced in Uganda, to improve access to prompt, effective antimalarial treatment of all fevers in children under 5 years. Implementation is through community drug distributors (CDDs who distribute pre-packaged chloroquine plus sulfadoxine-pyrimethamine (HOMAPAK® free of charge to caretakers of febrile children. Adherence of caretakers to this regimen has not been studied. Methods A questionnaire-based survey combined with inspection of blister packaging was conducted to investigate caretakers' adherence to HOMAPAK®. The population surveyed consisted of internally displaced people (IDPs from eight camps. Results A total of 241 caretakers were interviewed. 95.0% (CI: 93.3% – 98.4% of their children had received the correct dose for their age and 52.3% of caretakers had retained the blister pack. Assuming correct self-reporting, the overall adherence was 96.3% (CI: 93.9% – 98.7%. The nine caretakers who had not adhered had done so because the child had improved, had vomited, did not like the taste of the tablets, or because they forgot to administer the treatment. For 85.5% of cases treatment had been sought within 24 hours. Blister packaging was considered useful by virtually all respondents, mainly because it kept the drugs clean and dry. Information provided on, and inside, the package was of limited use, because most respondents were illiterate. However, CDDs had often told caretakers how to administer the treatment. For 39.4% of respondents consultation with the CDD was their reported first action when their child has fever and 52.7% stated that they consult her/him if the child does not get better. Conclusion In IDP camps, the HBMF strategy forms an important component of medical care for young children. In case of febrile illness, most caretakers obtain prompt and adequate antimalarial treatment, and adhere to it. A large proportion of malaria episodes are thus

  12. Drag, but not buoyancy, affects swim speed in captive Steller sea lions

    Directory of Open Access Journals (Sweden)

    Ippei Suzuki

    2014-04-01

    Full Text Available Swimming at an optimal speed is critical for breath-hold divers seeking to maximize the time they can spend foraging underwater. Theoretical studies have predicted that the optimal swim speed for an animal while transiting to and from depth is independent of buoyancy, but is dependent on drag and metabolic rate. However, this prediction has never been experimentally tested. Our study assessed the effects of buoyancy and drag on the swim speed of three captive Steller sea lions (Eumetopias jubatus that made 186 dives. Our study animals were trained to dive to feed at fixed depths (10–50 m under artificially controlled buoyancy and drag conditions. Buoyancy and drag were manipulated using a pair of polyvinyl chloride (PVC tubes attached to harnesses worn by the sea lions, and buoyancy conditions were designed to fall within the natural range of wild animals (∼12–26% subcutaneous fat. Drag conditions were changed with and without the PVC tubes, and swim speeds were recorded and compared during descent and ascent phases using an accelerometer attached to the harnesses. Generalized linear mixed-effect models with the animal as the random variable and five explanatory variables (body mass, buoyancy, dive depth, dive phase, and drag showed that swim speed was best predicted by two variables, drag and dive phase (AIC = −139. Consistent with a previous theoretical prediction, the results of our study suggest that the optimal swim speed of Steller sea lions is a function of drag, and is independent of dive depth and buoyancy.

  13. Penguin lungs and air sacs: implications for baroprotection, oxygen stores and buoyancy.

    Science.gov (United States)

    Ponganis, P J; St Leger, J; Scadeng, M

    2015-03-01

    The anatomy and volume of the penguin respiratory system contribute significantly to pulmonary baroprotection, the body O2 store, buoyancy and hence the overall diving physiology of penguins. Therefore, three-dimensional reconstructions from computerized tomographic (CT) scans of live penguins were utilized to measure lung volumes, air sac volumes, tracheobronchial volumes and total body volumes at different inflation pressures in three species with different dive capacities [Adélie (Pygoscelis adeliae), king (Aptenodytes patagonicus) and emperor (A. forsteri) penguins]. Lung volumes scaled to body mass according to published avian allometrics. Air sac volumes at 30 cm H2O (2.94 kPa) inflation pressure, the assumed maximum volume possible prior to deep dives, were two to three times allometric air sac predictions and also two to three times previously determined end-of-dive total air volumes. Although it is unknown whether penguins inhale to such high volumes prior to dives, these values were supported by (a) body density/buoyancy calculations, (b) prior air volume measurements in free-diving ducks and (c) previous suggestions that penguins may exhale air prior to the final portions of deep dives. Based upon air capillary volumes, parabronchial volumes and tracheobronchial volumes estimated from the measured lung/airway volumes and the only available morphometry study of a penguin lung, the presumed maximum air sac volumes resulted in air sac volume to air capillary/parabronchial/tracheobronchial volume ratios that were not large enough to prevent barotrauma to the non-collapsing, rigid air capillaries during the deepest dives of all three species, and during many routine dives of king and emperor penguins. We conclude that volume reduction of airways and lung air spaces, via compression, constriction or blood engorgement, must occur to provide pulmonary baroprotection at depth. It is also possible that relative air capillary and parabronchial volumes are

  14. Importance of initial buoyancy field on evolution of mantle thermal structure: Implications of surface boundary conditions

    Directory of Open Access Journals (Sweden)

    Petar Glišović

    2015-01-01

    Full Text Available Although there has been significant progress in the seismic imaging of mantle heterogeneity, the outstanding issue that remains to be resolved is the unknown distribution of mantle temperature anomalies in the distant geological past that give rise to the present-day anomalies inferred by global tomography models. To address this question, we present 3-D convection models in compressible and self-gravitating mantle initialised by different hypothetical temperature patterns. A notable feature of our forward convection modelling is the use of self-consistent coupling of the motion of surface tectonic plates to the underlying mantle flow, without imposing prescribed surface velocities (i.e., plate-like boundary condition. As an approximation for the surface mechanical conditions before plate tectonics began to operate we employ the no-slip (rigid boundary condition. A rigid boundary condition demonstrates that the initial thermally-dominated structure is preserved, and its geographical location is fixed during the evolution of mantle flow. Considering the impact of different assumed surface boundary conditions (rigid and plate-like on the evolution of thermal heterogeneity in the mantle we suggest that the intrinsic buoyancy of seven superplumes is most-likely resolved in the tomographic images of present-day mantle thermal structure. Our convection simulations with a plate-like boundary condition reveal that the evolution of an initial cold anomaly beneath the Java-Indonesian trench system yields a long-term, stable pattern of thermal heterogeneity in the lowermost mantle that resembles the present-day Large Low Shear Velocity Provinces (LLSVPs, especially below the Pacific. The evolution of subduction zones may be, however, influenced by the mantle-wide flow driven by deeply-rooted and long-lived superplumes since Archean times. These convection models also detect the intrinsic buoyancy of the Perm Anomaly that has been identified as a unique

  15. Ceramic Spheres—A Novel Solution to Deep Sea Buoyancy Modules

    Directory of Open Access Journals (Sweden)

    Bo Jiang

    2016-06-01

    Full Text Available Ceramic-based hollow spheres are considered a great driving force for many applications such as offshore buoyancy modules due to their large diameter to wall thickness ratio and uniform wall thickness geometric features. We have developed such thin-walled hollow spheres made of alumina using slip casting and sintering processes. A diameter as large as 50 mm with a wall thickness of 0.5–1.0 mm has been successfully achieved in these spheres. Their material and structural properties were examined by a series of characterization tools. Particularly, the feasibility of these spheres was investigated with respect to its application for deep sea (>3000 m buoyancy modules. These spheres, sintered at 1600 °C and with 1.0 mm of wall thickness, have achieved buoyancy of more than 54%. As the sphere’s wall thickness was reduced (e.g., 0.5 mm, their buoyancy reached 72%. The mechanical performance of such spheres has shown a hydrostatic failure pressure above 150 MPa, corresponding to a rating depth below sea level of 5000 m considering a safety factor of 3. The developed alumina-based ceramic spheres are feasible for low cost and scaled-up production and show great potential at depths greater than those achievable by the current deep-sea buoyancy module technologies.

  16. Ceramic Spheres—A Novel Solution to Deep Sea Buoyancy Modules

    Science.gov (United States)

    Jiang, Bo; Blugan, Gurdial; Sturzenegger, Philip N.; Gonzenbach, Urs T.; Misson, Michael; Thornberry, John; Stenerud, Runar; Cartlidge, David; Kuebler, Jakob

    2016-01-01

    Ceramic-based hollow spheres are considered a great driving force for many applications such as offshore buoyancy modules due to their large diameter to wall thickness ratio and uniform wall thickness geometric features. We have developed such thin-walled hollow spheres made of alumina using slip casting and sintering processes. A diameter as large as 50 mm with a wall thickness of 0.5–1.0 mm has been successfully achieved in these spheres. Their material and structural properties were examined by a series of characterization tools. Particularly, the feasibility of these spheres was investigated with respect to its application for deep sea (>3000 m) buoyancy modules. These spheres, sintered at 1600 °C and with 1.0 mm of wall thickness, have achieved buoyancy of more than 54%. As the sphere’s wall thickness was reduced (e.g., 0.5 mm), their buoyancy reached 72%. The mechanical performance of such spheres has shown a hydrostatic failure pressure above 150 MPa, corresponding to a rating depth below sea level of 5000 m considering a safety factor of 3. The developed alumina-based ceramic spheres are feasible for low cost and scaled-up production and show great potential at depths greater than those achievable by the current deep-sea buoyancy module technologies. PMID:28773651

  17. Numerically quantifying the relative importance of topography and buoyancy in driving groundwater flow

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Both topography and buoyancy can drive groundwater flow;however,the interactions between them are still poorly understood.In this paper,the authors conduct numerical simulations of variable-density fluid flow and heat transport to quantify their relative importance.The finite element modeling experiments on a 2-D conceptual model reveal that the pattern of groundwater flow depends largely upon the relative magnitude of the flow rate due to topography alone and the flow rate due to buoyancy alone.When fluid velocity due to topography is greater than that due to buoyancy at large water table gradients,topography-driven ’forced convection’ overwhelms buoyancy-driven ’free convection’.When flow velocity due to buoyancy is greater than that due to topography at small water table gradients,mixed free and forced convection takes place.In this case,free convection becomes dominant,but topography-driven flow still plays an important role since it pushes the free convection cells to migrate laterally in the downhill direction.Consequently,hydrothermal fluid flow remains changing periodically with time and no steady state can be reached.The presence of a low-permeability layer near the surface helps eliminate the topography effect on the underlying free convection.

  18. Buoyancy increase and drag-reduction through a simple superhydrophobic coating.

    Science.gov (United States)

    Hwang, Gi Byoung; Patir, Adnan; Page, Kristopher; Lu, Yao; Allan, Elaine; Parkin, Ivan P

    2017-06-08

    A superhydrophobic paint was fabricated using 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES), TiO2 nanoparticles and ethanol. The paint has potential for aquatic application of a superhydrophobic coating as it induces increased buoyancy and drag reduction. Buoyance testing showed that the reduction of surface energy by superhydrophobic coating made it feasible that glass, a high density material, was supported by the surface tension of water. In a miniature boat sailing test, it was shown that the low energy surface treatment decreased the adhesion of water molecules to the surface of the boat resulting in a reduction of the drag force. Additionally, a robust superhydrophobic surface was fabricated through layer-by-layer coating using adhesive double side tape and the paint, and after a 100 cm abrasion test with sand paper, the surface still retained its water repellency, enhanced buoyancy and drag reduction.

  19. Buoyancy Instabilities in Galaxy Clusters: Convection Due to Adiabatic Cosmic Rays and Anisotropic Thermal Conduction

    CERN Document Server

    Sharma, P; Quataert, E; Parrish, I J

    2009-01-01

    Using a linear stability analysis and two and three-dimensional nonlinear simulations, we study the physics of buoyancy instabilities in a combined thermal and relativistic (cosmic ray) plasma, motivated by the application to clusters of galaxies. We argue that cosmic ray diffusion is likely to be slow compared to the buoyancy time on large length scales, so that cosmic rays are effectively adiabatic. If the cosmic ray pressure $p_{cr}$ is $\\gtrsim 25 %$ of the thermal pressure, and the cosmic ray entropy ($p_{\\rm cr}/\\rho^{4/3}$; $\\rho$ is the thermal plasma density) decreases outwards, cosmic rays drive an adiabatic convective instability analogous to Schwarzschild convection in stars. Global simulations of galaxy cluster cores show that this instability saturates by reducing the cosmic ray entropy gradient and driving efficient convection and turbulent mixing. At larger radii in cluster cores, the thermal plasma is unstable to the heat flux-driven buoyancy instability (HBI), a convective instability genera...

  20. Physostomous channel catfish, Ictalurus punctatus, modify swimming mode and buoyancy based on flow conditions.

    Science.gov (United States)

    Yoshida, Makoto A; Yamamoto, Daisuke; Sato, Katsufumi

    2017-02-15

    The employment of gliding in aquatic animals as a means of conserving energy has been theoretically predicted and discussed for decades. Several studies have shown that some species glide, whereas others do not. Freshwater fish species that widely inhabit both lentic and lotic environments are thought to be able to adapt to fluctuating flow conditions in terms of locomotion. In adapting to the different functional demands of lentic and lotic environments on fish energetics, physostomous (open swim bladder) fish may optimise their locomotion and activity by controlling their net buoyancy; however, few buoyancy studies have been conducted on physostomous fish in the wild. We deployed accelerometers on free-ranging channel catfish, Ictalurus punctatus, in both lentic and lotic environments to quantify their swimming activity, and to determine their buoyancy condition preferences and whether gliding conserves energy. Individual comparisons of swimming efforts between ascent and descent phases revealed that all fish in the lentic environment had negative buoyancy. However, all individuals showed many descents without gliding phases, which was contrary to the behaviour predicted to minimise the cost of transport. The fact that significantly fewer gliding phases were observed in the lotic environment, together with the existence of neutrally buoyant fish, indicated that channel catfish seem to optimise their locomotion through buoyancy control based on flow conditions. The buoyancy optimisation of channel catfish relative to the flow conditions that they inhabit not only reflects differences in swimming behaviour but also provides new insights into the adaptation of physostome fish species to various freshwater environments. © 2017. Published by The Company of Biologists Ltd.

  1. Origin of Domes on Europa: The Role of Thermally Induced Compositional Buoyancy,

    Science.gov (United States)

    Pappalardo, R. T.; Barr, A. C.

    2004-01-01

    The surface of Jupiter's moon Europa is peppered by topographic domes, interpreted as sites of intrusion and extrusion. Diapirism is consistent with dome morphology, but thermal buoyancy alone cannot produce sufficient driving pressures to create the observed dome elevations. Instead, diapirs may initiate by thermal convection that induces compositional segregation. Exclusion of impurities from warm upwellings allows sufficient buoyancy for icy plumes to create the observed surface topography, provided the ice shell has a small effective elastic thickness (0.2 to 0.5 km) and contains low-eutectic point impurities at the few percent level. This model suggests that the ice shell may be depleted in impurities over time.

  2. Effects of vehicle station-keeping and end-effector disturbance compensation on neutral-buoyancy teleoperation

    Science.gov (United States)

    Valdez, Michael S.

    1993-12-01

    Experiments were conducted with a neutral-buoyancy robot to test whether vehicle station keeping and end effector disturbance compensation significantly affect human teleoperation performance. The vehicle used for experiments, called the Submersible for Telerobotic Astronautical Research (STAR) is a free-flying underwater telerobot equipped with a three degree of freedom arm, a stereo pan/tilt camera platform, and a vision-based navigation system. Using visual feedback from a fixed onboard camera, test subject performed a Fitts- type tapping task with the arm while the vision navigator and control system held the vehicle steady relative to a visual reference target. This paper describes the testbed vehicle, experiments, data analysis, and conclusions.

  3. Buoyancy frequency profiles and internal semidiurnal tide turning depths in the oceans

    NARCIS (Netherlands)

    King, B.; Stone, M.; Zhang, H.P.; Gerkema, T.; Marder, M.; Scott, R.B.; Swinney, H.L.

    2012-01-01

    We examine the possible existence of internal gravity wave "turning depths," depths below which the local buoyancy frequency N(z) becomes smaller than the wave frequency. At a turning depth, incident gravity waves reflect rather than reaching the ocean bottom as is generally assumed. Here we conside

  4. Academic Buoyancy and Academic Resilience: Exploring "Everyday" and "Classic" Resilience in the Face of Academic Adversity

    Science.gov (United States)

    Martin, Andrew J.

    2013-01-01

    Academic buoyancy has been defined as a capacity to overcome setbacks, challenges, and difficulties that are part of everyday academic life. Academic resilience has been defined as a capacity to overcome acute and/or chronic adversity that is seen as a major threat to a student's educational development. This study is the first to examine the…

  5. 40 CFR 1065.690 - Buoyancy correction for PM sample media.

    Science.gov (United States)

    2010-07-01

    ...) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.690... mass uncorrected for buoyancy. ρ air = density of air in balance environment. ρ weight = density of... Where: p abs = absolute pressure in balance environment. M mix = molar mass of air in...

  6. Analysis of Buoyancy-Driven Ventilation of Hydrogen from Buildings: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Barley, C. D.; Gawlik, K.; Ohi, J.; Hewett, R.

    2007-08-01

    When hydrogen gas is used or stored within a building, as with a hydrogen-powered vehicle parked in a residential garage, any leakage of unignited H2 will mix with indoor air and may form a flammable mixture. One approach to safety engineering relies on buoyancy-driven, passive ventilation of H2 from the building through vents to the outside.

  7. Annual and seasonal mean buoyancy fluxes for the tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Prasad, T.G.

    . The fluxes of heat and freshwater across the air-sea interface, and hence the surface buoyancy flux, show strong spatial and temporal variability. The Bay of Bengal and eastern equatorial Indian Ocean are characterized by a net freshwater gain due to heavy...

  8. Buoyancy-driven flow in a peat moss layer as a mechanism for solute transport

    NARCIS (Netherlands)

    Rappoldt, C.; Pieters, G.J.J.M.; Adema, E.B.; Baaijens, G.J.; Grootjans, A.P.; Duijn, van C.J.

    2003-01-01

    Transport of nutrients, CO2, methane, and oxygen plays an important ecological role at the surface of wetland ecosystems. A possibly important transport mechanism in a water-saturated peat moss layer (usually Sphagnum cuspidatum) is nocturnal buoyancy flow, the downward flow of relatively cold surfa

  9. Investigating Students' Ideas About Buoyancy and the Influence of Haptic Feedback

    Science.gov (United States)

    Minogue, James; Borland, David

    2016-04-01

    While haptics (simulated touch) represents a potential breakthrough technology for science teaching and learning, there is relatively little research into its differential impact in the context of teaching and learning. This paper describes the testing of a haptically enhanced simulation (HES) for learning about buoyancy. Despite a lifetime of everyday experiences, a scientifically sound explanation of buoyancy remains difficult to construct for many. It requires the integration of domain-specific knowledge regarding density, fluid, force, gravity, mass, weight, and buoyancy. Prior studies suggest that novices often focus on only one dimension of the sinking and floating phenomenon. Our HES was designed to promote the integration of the subconcepts of density and buoyant forces and stresses the relationship between the object itself and the surrounding fluid. The study employed a randomized pretest-posttest control group research design and a suite of measures including an open-ended prompt and objective content questions to provide insights into the influence of haptic feedback on undergraduate students' thinking about buoyancy. A convenience sample (n = 40) was drawn from a university's population of undergraduate elementary education majors. Two groups were formed from haptic feedback (n = 22) and no haptic feedback (n = 18). Through content analysis, discernible differences were seen in the posttest explanations sinking and floating across treatment groups. Learners that experienced the haptic feedback made more frequent use of "haptically grounded" terms (e.g., mass, gravity, buoyant force, pushing), leading us to begin to build a local theory of language-mediated haptic cognition.

  10. CFD modelling of buoyancy-driven natural ventilation opposed by wind

    Energy Technology Data Exchange (ETDEWEB)

    Cook, M.; Ji, Y. [De Montfort Univ., Leceister (United Kingdom). Inst. of Energy and Sustainable Development; Hunt, G. [Imperial College of London, London (United Kingdom). Dept. of Civil and Environmental Engineering

    2005-07-01

    This study formed the basis for generating guidelines on how to use computational fluid dynamics (CFD) to model natural ventilation in low-energy building designs. Previous studies have investigated steady natural displacement ventilation in a single space driven by buoyancy alone. The simulations used an external flow domain which allowed airflow through inlets and outlets to be modelled without the need for boundary conditions at these locations. CFD methods were used successfully to model buoyancy-driven displacement ventilation in which wind forces oppose the flow. Simulations were then conducted for a wind assisted buoyancy-driven displacement ventilation flow. The use of boundary conditions was the basic differences in the way these simulations were modelled. It was emphasized that the simulations are for natural displacement ventilation in which wind forces oppose buoyancy. Results of analytical predictions and experimental measurements were found to be in good agreement. The small discrepancies in the interface height separating the warm stratified air from the cooler ambient layer below can be attributed to differences in the plume behaviour and performance of the gauze used for inhibiting horizontal momentum. The under-prediction in the reduced gravity of the upper layer may also be due to the small differences in plume structure. 12 refs., 1 tab., 11 figs.

  11. Investigating Students' Ideas about Buoyancy and the Influence of Haptic Feedback

    Science.gov (United States)

    Minogue, James; Borland, David

    2016-01-01

    While haptics (simulated touch) represents a potential breakthrough technology for science teaching and learning, there is relatively little research into its differential impact in the context of teaching and learning. This paper describes the testing of a haptically enhanced simulation (HES) for learning about buoyancy. Despite a lifetime of…

  12. Consistent Two-Equation Closure Modelling for Atmospheric Research: Buoyancy and Vegetation Implementations

    DEFF Research Database (Denmark)

    Sogachev, Andrey; Kelly, Mark C.; Leclerc, Monique Y.

    2012-01-01

    A self-consistent two-equation closure treating buoyancy and plant drag effects has been developed, through consideration of the behaviour of the supplementary equation for the length-scale-determining variable in homogeneous turbulent flow. Being consistent with the canonical flow regimes of gri...

  13. "'Sink or Swim': Buoyancy and Coping in the Cognitive Test Anxiety--Academic Performance Relationship"

    Science.gov (United States)

    Putwain, David W.; Daly, Anthony L.; Chamberlain, Suzanne; Sadreddini, Shireen

    2016-01-01

    This study explores the relationship between students' self-report levels of cognitive test anxiety (worry), academic buoyancy (withstanding and successfully responding to routine school challenges and setbacks), coping processes and their achieved grades in high-stakes national examinations at the end of compulsory schooling. The sample comprised…

  14. Core-annular flow through a horizontal pipe: Hydrodynamic counterbalancing of buoyancy force on core

    NARCIS (Netherlands)

    Ooms, G.; Vuik, C.; Poesio, P.

    2007-01-01

    A theoretical investigation has been made of core-annular flow: the flow of a high-viscosity liquid core surrounded by a low-viscosity liquid annular layer through a horizontal pipe. Special attention is paid to the question of how the buoyancy force on the core, caused by a density difference betwe

  15. Core-annular flow through a horizontal pipe: Hydrodynamic counterbalancing of buoyancy force on core

    NARCIS (Netherlands)

    Ooms, G.; Vuik, C.; Poesio, P.

    2007-01-01

    A theoretical investigation has been made of core-annular flow: the flow of a high-viscosity liquid core surrounded by a low-viscosity liquid annular layer through a horizontal pipe. Special attention is paid to the question of how the buoyancy force on the core, caused by a density difference

  16. Differential diffusion effects on buoyancy-driven instabilities of acid-base fronts: the case of a color indicator.

    Science.gov (United States)

    Kuster, S; Riolfo, L A; Zalts, A; El Hasi, C; Almarcha, C; Trevelyan, P M J; De Wit, A; D'Onofrio, A

    2011-10-14

    Buoyancy-driven hydrodynamic instabilities of acid-base fronts are studied both experimentally and theoretically in the case where an aqueous solution of a strong acid is put above a denser aqueous solution of a color indicator in the gravity field. The neutralization reaction between the acid and the color indicator as well as their differential diffusion modifies the initially stable density profile in the system and can trigger convective motions both above and below the initial contact line. The type of patterns observed as well as their wavelength and the speed of the reaction front are shown to depend on the value of the initial concentrations of the acid and of the color indicator and on their ratio. A reaction-diffusion model based on charge balances and ion pair mobility explains how the instability scenarios change when the concentration of the reactants are varied.

  17. A novel vehicle for transmission of Escherichia coli O157:H7 to humans: multistate outbreak of E. coli O157:H7 infections associated with consumption of ready-to-bake commercial prepackaged cookie dough--United States, 2009.

    Science.gov (United States)

    Neil, Karen P; Biggerstaff, Gwen; MacDonald, J Kathryn; Trees, Eija; Medus, Carlota; Musser, Kimberlee A; Stroika, Steven G; Zink, Don; Sotir, Mark J

    2012-02-15

     Escherichia coli O157:H7 is a Shiga toxin-producing E. coli (STEC) associated with numerous foodborne outbreaks in the United States and is an important cause of bacterial gastrointestinal illness. In May 2009, we investigated a multistate outbreak of E. coli O157:H7 infections.  Outbreak-associated cases were identified using serotyping and molecular subtyping procedures. Traceback investigation and product testing were performed. A matched case-control study was conducted to identify exposures associated with illness using age-, sex-, and state-matched controls.  Seventy-seven patients with illnesses during the period 16 March-8 July 2009 were identified from 30 states; 35 were hospitalized, 10 developed hemolytic-uremic syndrome, and none died. Sixty-six percent of patients were dough, compared with 4 of 36 controls (11%) (matched odds ratio = 41.3; P dough, 94% reported brand A. Three nonoutbreak STEC strains were isolated from brand A cookie dough. The investigation led to a recall of 3.6 million packages of brand A cookie dough and a product reformulation.  This is the first reported STEC outbreak associated with consuming ready-to-bake commercial prepackaged cookie dough. Despite instructions to bake brand A cookie dough before eating, case patients consumed the product uncooked. Manufacturers should consider formulating ready-to-bake commercial prepackaged cookie dough to be as safe as a ready-to-eat product. More effective consumer education about the risks of eating unbaked cookie dough is needed.

  18. Unexpected Positive Buoyancy in Deep Sea Sharks, Hexanchus griseus, and a Echinorhinus cookei.

    Directory of Open Access Journals (Sweden)

    Itsumi Nakamura

    Full Text Available We do not expect non air-breathing aquatic animals to exhibit positive buoyancy. Sharks, for example, rely on oil-filled livers instead of gas-filled swim bladders to increase their buoyancy, but are nonetheless ubiquitously regarded as either negatively or neutrally buoyant. Deep-sea sharks have particularly large, oil-filled livers, and are believed to be neutrally buoyant in their natural habitat, but this has never been confirmed. To empirically determine the buoyancy status of two species of deep-sea sharks (bluntnose sixgill sharks, Hexanchus griseus, and a prickly shark, Echinorhinus cookei in their natural habitat, we used accelerometer-magnetometer data loggers to measure their swimming performance. Both species of deep-sea sharks showed similar diel vertical migrations: they swam at depths of 200-300 m at night and deeper than 500 m during the day. Ambient water temperature was around 15°C at 200-300 m but below 7°C at depths greater than 500 m. During vertical movements, all deep-sea sharks showed higher swimming efforts during descent than ascent to maintain a given swimming speed, and were able to glide uphill for extended periods (several minutes, indicating that these deep-sea sharks are in fact positively buoyant in their natural habitats. This positive buoyancy may adaptive for stealthy hunting (i.e. upward gliding to surprise prey from underneath or may facilitate evening upward migrations when muscle temperatures are coolest, and swimming most sluggish, after spending the day in deep, cold water. Positive buoyancy could potentially be widespread in fish conducting daily vertical migration in deep-sea habitats.

  19. Unexpected Positive Buoyancy in Deep Sea Sharks, Hexanchus griseus, and a Echinorhinus cookei.

    Science.gov (United States)

    Nakamura, Itsumi; Meyer, Carl G; Sato, Katsufumi

    2015-01-01

    We do not expect non air-breathing aquatic animals to exhibit positive buoyancy. Sharks, for example, rely on oil-filled livers instead of gas-filled swim bladders to increase their buoyancy, but are nonetheless ubiquitously regarded as either negatively or neutrally buoyant. Deep-sea sharks have particularly large, oil-filled livers, and are believed to be neutrally buoyant in their natural habitat, but this has never been confirmed. To empirically determine the buoyancy status of two species of deep-sea sharks (bluntnose sixgill sharks, Hexanchus griseus, and a prickly shark, Echinorhinus cookei) in their natural habitat, we used accelerometer-magnetometer data loggers to measure their swimming performance. Both species of deep-sea sharks showed similar diel vertical migrations: they swam at depths of 200-300 m at night and deeper than 500 m during the day. Ambient water temperature was around 15°C at 200-300 m but below 7°C at depths greater than 500 m. During vertical movements, all deep-sea sharks showed higher swimming efforts during descent than ascent to maintain a given swimming speed, and were able to glide uphill for extended periods (several minutes), indicating that these deep-sea sharks are in fact positively buoyant in their natural habitats. This positive buoyancy may adaptive for stealthy hunting (i.e. upward gliding to surprise prey from underneath) or may facilitate evening upward migrations when muscle temperatures are coolest, and swimming most sluggish, after spending the day in deep, cold water. Positive buoyancy could potentially be widespread in fish conducting daily vertical migration in deep-sea habitats.

  20. Modeling the buoyancy-driven Black Sea Water outflow into the North Aegean Sea

    Directory of Open Access Journals (Sweden)

    Nikolaos Kokkos

    2016-04-01

    Full Text Available A three-dimensional numerical model was applied to simulate the Black Sea Water (BSW outflux and spreading over the North Aegean Sea, and its impact on circulation and stratification–mixing dynamics. Model results were validated against satellite-derived sea surface temperature and in-situ temperature and salinity profiles. Further, the model results were post-processed in terms of the potential energy anomaly, ϕ, analyzing the factors contributing to its change. It occurs that BSW contributes significantly on the Thracian Sea water column stratification, but its signal reduces in the rest of the North Aegean Sea. The BSW buoyancy flux contributed to the change of ϕ in the Thracian Sea by 1.23 × 10−3 W m−3 in the winter and 7.9 × 10−4 W m−3 in the summer, significantly higher than the corresponding solar heat flux contribution (1.41 × 10−5 W m−3 and 7.4 × 10−5 W m−3, respectively. Quantification of the ϕ-advective term crossing the north-western BSW branch (to the north of Lemnos Island, depicted a strong non-linear relation to the relative vorticity of Samothraki Anticyclone. Similar analysis for the south-western branch illustrated a relationship between the ϕ-advective term sign and the relative vorticity in the Sporades system. The ϕ-mixing term increases its significance under strong winds (>15 m s−1, tending to destroy surface meso-scale eddies.

  1. Passive urban ventilation by combined buoyancy-driven slope flow and wall flow: Parametric CFD studies on idealized city models

    Science.gov (United States)

    Luo, Zhiwen; Li, Yuguo

    2011-10-01

    This paper reports the results of a parametric CFD study on idealized city models to investigate the potential of slope flow in ventilating a city located in a mountainous region when the background synoptic wind is absent. Examples of such a city include Tokyo in Japan, Los Angeles and Phoenix in the US, and Hong Kong. Two types of buoyancy-driven flow are considered, i.e., slope flow from the mountain slope (katabatic wind at night and anabatic wind in the daytime), and wall flow due to heated/cooled urban surfaces. The combined buoyancy-driven flow system can serve the purpose of dispersing the accumulated urban air pollutants when the background wind is weak or absent. The microscopic picture of ventilation performance within the urban structures was evaluated in terms of air change rate (ACH) and age of air. The simulation results reveal that the slope flow plays an important role in ventilating the urban area, especially in calm conditions. Katabatic flow at night is conducive to mitigating the nocturnal urban heat island. In the present parametric study, the mountain slope angle and mountain height are assumed to be constant, and the changing variables are heating/cooling intensity and building height. For a typical mountain of 500 m inclined at an angle of 20° to the horizontal level, the interactive structure is very much dependent on the ratio of heating/cooling intensity as well as building height. When the building is lower than 60 m, the slope wind dominates. When the building is as high as 100 m, the contribution from the urban wall flow cannot be ignored. It is found that katabatic wind can be very beneficial to the thermal environment as well as air quality at the pedestrian level. The air change rate for the pedestrian volume can be as high as 300 ACH.

  2. Examination of Buoyancy-Reduction Effect in Induction-Heating Cookers by Using 3D Finite Element Method

    Science.gov (United States)

    Yonetsu, Daigo; Tanaka, Kazufumi; Hara, Takehisa

    In recent years, induction-heating (IH) cookers that can be used to heat nonmagnetic metals such as aluminum have been produced. Occasionally, a light pan moves on a glass plate due to buoyancy when heated by an IH cooker. In some IH cookers, an aluminum plate is mounted between the glass plate and the coil in order to reduce the buoyancy effect. The objective of this research is to evaluate the buoyancy-reduction effect and the heating effect of buoyancy-reduction plates. Eddy current analysis is carried out by 3D finite element method, and the electromagnetic force and the heat distribution on the heating plate are calculated. After this calculation is performed, the temperature distribution of the heating plate is calculated by heat transfer analysis. It is found that the shape, area, and the position of the buoyancy reduction plate strongly affect the buoyancy and the heat distribution. The impact of the shape, area, and position of the buoyancy reduction plate was quantified. The phenomena in the heating were elucidated qualitatively.

  3. Academic buoyancy, student's achievement, and the linking role of control: A cross-lagged analysis of high school students.

    Science.gov (United States)

    Collie, Rebecca J; Martin, Andrew J; Malmberg, Lars-Erik; Hall, James; Ginns, Paul

    2015-03-01

    Previous research has indicated that although academic buoyancy and student's achievement are associated, the relationship is relatively modest. We sought to determine whether another construct might link academic buoyancy and student's achievement. Based on prior theoretical and empirical work, we examined a sense of control as one possible linking mechanism. The study analysed data from 2,971 students attending 21 Australian high schools. We conducted a cross-lagged panel design as a first means of disentangling the relative salience of academic buoyancy, control, and achievement (Phase 1). Based upon these results, we proceeded with follow-up analyses of an ordered process model linking the constructs over time (Phase 2). Findings showed that buoyancy and achievement were associated with control over time, but not with one another (Phase 1). In addition, control appeared to play a role in how buoyancy influenced achievement and that a cyclical process may operate among the three factors over time (Phase 2). The findings suggest that control may play an important role in linking past experiences of academic buoyancy and achievement to subsequent academic buoyancy and achievement. © 2015 The British Psychological Society.

  4. The effects of buoyancy on turbulent nonpremixed jet flames in crossflow

    Science.gov (United States)

    Boxx, Isaac G.

    An experimental research study was conducted to investigate what effect buoyancy had on the mean and instantaneous flow-field characteristics of turbulent jet-flames in crossflow (JFICF). The study used an experimental technique wherein a series of normal-gravity, hydrogen-diluted propane JFICF were compared with otherwise identical ones in low-gravity. Experiments were conducted at the University of Texas Drop Tower Facility, a new microgravity science laboratory built for this study at the University of Texas at Austin. Two different diagnostic techniques were employed, high frame-rate digital cinematographic imaging and planar laser Mie scattering (PLMS). The flame-luminosity imaging revealed significant elongation and distortion of the large-scale luminous structure of the JFICF. This was seen to affect the flametip oscillation and burnout characteristics. Mean and root-mean-square (RMS) images of flame-luminosity were computed from the flame-luminosity image sequences. These were used to compare visible flame-shapes, flame chord-lengths and jet centerline-trajectories of the normal- and low-gravity flames. In all cases the jet-centerline penetration and mean luminous flame-width were seen to increase with decreasing buoyancy. The jet-centerline trajectories for the normal-gravity flames were seen to behave differently to those of the low-gravity flames. This difference led to the conclusion that the jet transitions from a momentum-dominated forced convection limit to a buoyancy-influenced regime when it reaches xiC ≈ 3, where xiC is the Becker and Yamazaki (1978) buoyancy parameter based on local flame chord-length. The mean luminous flame-lengths showed little sensitivity to buoyancy or momentum flux ratio. Consistent with the flame-luminosity imaging experiments, comparison of the instantaneous PLMS flow-visualization images revealed substantial buoyancy-induced elongation and distortion of the large-scale shear-layer vortices in the flow. This effect

  5. Optical Tracking Measurement on Vortex Induced Vibration of Flexible Riser with Short-Length Buoyance Module

    Science.gov (United States)

    Fan, Dixia; Du, Honglin; Triantafyllou, Michael

    2016-11-01

    We address experimentally the vortex induced vibrations (VIV) of long flexible cylinders. We employ optical tracking, using an array of high speed cameras. Compared to strain gauges and accelerometers, this non-intrusive approach, allows direct measurement of the flexible cylinder displacement with far denser spatial distribution. The measurements reveal essential features of flexible cylinder VIV, including complex geometries such as cylinders containing short-length buoyancy modules, with module to cylinder diameter ratio of 1:3.2 and module to bare cylinder length ratio of 1:1. The experiments are conducted with aspect ratio of 170 and 3 different coverage ratios, of 100%, 50% and 20%. The measurements demonstrate bi-frequency response due to excitation from both buoyancy module and bare cylinder, at low Strouhal number, down to values of 0.08, and the generation of traveling wave patterns.

  6. What buoyancy really is. A generalized Archimedes' principle for sedimentation and ultracentrifugation

    Science.gov (United States)

    Piazza, Roberto; Buzzaccaro, Stefano; Secchi, Eleonora; Parola, Alberto

    Particle settling is a pervasive process in nature, and centrifugation is a much versatile separation technique. Yet, the results of settling and ultracentrifugation experiments often appear to contradict the very law on which they are based: Archimedes Principle - arguably, the oldest Physical Law. The purpose of this paper is delving at the very roots of the concept of buoyancy by means of a combined experimental-theoretical study on sedimentation profiles in colloidal mixtures. Our analysis shows that the standard Archimedes' principle is only a limiting approximation, valid for mesoscopic particles settling in a molecular fluid, and we provide a general expression for the actual buoyancy force. This "Generalized Archimedes Principle" accounts for unexpected effects, such as denser particles floating on top of a lighter fluid, which in fact we observe in our experiments.

  7. BUOYANCY INSTABILITY IN THE NATURAL CONVECTION BOUNDARY LAYER AROUND A VERTICAL HEATED FLAT PLATE

    Institute of Scientific and Technical Information of China (English)

    颜大椿; 张汉勋

    2002-01-01

    A systematic research on the buoyancy instability in the natural convection boundary layer was conducted, including the basic characteristics such as its spectral components, wave length and velocity, the location of its critical layer,and amplitude distributions of the triple independent eigenmodes with the linear instability theory, the growth rates of its temperature and velocity fluctuations and the corresponding neutral curves for the buoyancy eigenmode were also obtained.Results indicated that the neutral curve of the velocity fluctuation had a nose shape consistent with that obtained in the numerical calculation, but for the temperature fluctuation, a ring-like region could be measured at a lower Grashof number before the nose-shaped main portion of the neutral curve.

  8. Buoyancy Limitation of Filamentous Cyanobacteria under Prolonged Pressure due to the Gas Vesicles Collapse

    Science.gov (United States)

    Abeynayaka, Helayaye Damitha Lakmali; Asaeda, Takashi; Kaneko, Yasuko

    2017-08-01

    Freshwater cyanobacterium Pseudanabaena galeata were cultured in chambers under artificially generated pressures, which correspond to the hydrostatic pressures at deep water. Variations occurred in gas vesicles volume, and buoyancy state of cells under those conditions were analyzed at different time intervals (5 min, 1 day, and 5 days). Variations in gas vesicles morphology of cells were observed by transmission electron microscopy images. Settling velocity ( Vs) of cells which governs the buoyancy was observed with the aid of a modified optical microscope. Moreover, effects of the prolonged pressure on cell ballast composition (protein and polysaccharides) were examined. Elevated pressure conditions reduced the cell ballast and caused a complete disappearance of gas vesicles in Pseudanabaena galeata cells. Hence cyanobacteria cells were not able to float within the study period. Observations and findings of the study indicate the potential application of hydrostatic pressure, which naturally occurred in hypolimnion of lakes, to inhibit the re-suspension of cyanobacteria cells.

  9. Buoyancy Effects on the Scaling Characteristics of Atmospheric Boundary Layer Wind Fields in the Mesoscale Range

    CERN Document Server

    Kiliyanpilakkil, V P; Ruiz-Columbié, A; Araya, G; Castillo, L; Hirth, B; Burgett, W

    2015-01-01

    We have analyzed long-term wind speed time-series from five field sites up to a height of 300 m from the ground. Structure function-based scaling analysis has revealed that the scaling exponents in the mesoscale regime systematically depend on height. This anomalous behavior is shown to be caused by the buoyancy effects. In the framework of the extended self-similarity, the relative scaling exponents portray quasi-universal behavior.

  10. What buoyancy really is. A Generalized Archimedes Principle for sedimentation and ultracentrifugation

    OpenAIRE

    Piazza, Roberto; Buzzaccaro, Stefano; Secchi, Eleonora; Parola, Alberto

    2012-01-01

    Particle settling is a pervasive process in nature, and centrifugation is a much versatile separation technique. Yet, the results of settling and ultracentrifugation experiments often appear to contradict the very law on which they are based: Archimedes Principle - arguably, the oldest Physical Law. The purpose of this paper is delving at the very roots of the concept of buoyancy by means of a combined experimental-theoretical study on sedimentation profiles in colloidal mixtures. Our analysi...

  11. Zero Power Buoyancy Control for Distributed Autonomous Sensor Networks Conducted During Crimson Viper 2010 Field Experiment

    Science.gov (United States)

    2011-03-04

    STATEMENT 13. SUPPLEMENTARY NOTES 14. ABSTRACT 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: a. REPORT 19a. NAME OF RESPONSIBLE PERSON 19b. TELEPHONE...producing simple, small, power-efficient data harvesting nodes with variable buoyancy, enabling unsupervised underwater sensing with subsequent surfacing...aerosol samples for subsequent analysis at NRL. At regular intervals, a hand-held hyperspectral sensor as to be used to collect near-water optical

  12. Neutral buoyancy testing of architectural and environmental concepts of space vehicle design

    Science.gov (United States)

    Lenda, J. A.; Rosener, A. A.; Stephenson, M. L.

    1972-01-01

    Design guidelines are presented that are applicable to providing habitability areas and furniture elements for extended periods in a zero gravity environment. This was accomplished by: (1) analyzing the existing habitability crew area requirements, mobility and restraint aids, cross-cultural design, and establishing a man model for zero gravity; (2) designing specific furniture elements, chair and table, and volumes for a stateroom, office, bathroom, galley, and wardroom; and (3) neutral buoyancy testing and evaluation of these areas.

  13. Buoyancy effect on the flow pattern and the thermal performance of an array of circular cylinders

    CERN Document Server

    Fornarelli, Francesco; Oresta, Paolo

    2016-01-01

    In this paper we found, by means of numerical simulations, a transition in the oscillatory character of the flow field for a particular combination of buoyancy and spacing in an array of six circular cylinders at a Reynolds number of 100 and Prandtl number of 0.7. The cylinders are iso-thermal and they are aligned with the Earth acceleration (g). According to the array orientation, an aiding or an opposing buoyancy is considered. The effect of natural convection with respect to the forced convection is modulated with the Richardson number, Ri, ranging between -1 and 1. Two values of center to center spacing (s=3.6d - 4d) are considered. The effects of buoyancy and spacing on the flow pattern in the near and far field are described. Several transitions in the flow patterns are found and a parametric analysis of the dependence of the force coefficients and Nusselt number with respect to the Richardson number is reported. For Ri=-1, the change of spacing ratio from 3.6 to 4 induces a transition in the standard d...

  14. Buoyancy effects on rotation and translation of large particles in turbulent flow

    Science.gov (United States)

    Byron, Margaret; Tao, Yiheng; Variano, Evan

    2013-11-01

    We use laboratory experiments to investigate the effects of homogeneous, isotropic turbulence on particles of varying buoyancy, size, and shape. The buoyancy is varied between a specific gravity of 1.001 and 1.05. All particles are roughly 1 cm, which in this flow is close to Taylor's turbulent microscale. We vary the shape to compare spherical particles to non-spherical particles while matching the settling velocity, volume, and/or surface area. Particles are fabricated in custom shapes using transparent hydrogels whose refractive index is close to water. We embed tracers within the particles and use PIV to image the interior of the particle simultaneously with the exterior flowfield of homogeneous isotropic turbulence, generated by two active-grid synthetic jet arrays. We find that the settling velocity of these particles, regardless of shape, is reduced relative to the quiescent settling velocity as predicted by the Clift-Gauvin model. We explore the distribution of rotation rates, as characterized by the variance of angular velocity. We find significant anisotropy in the angular velocities of negatively buoyant particles, which vanishes as particles approach neutral buoyancy. We also see differences in angular velocity distribution between particles of varying eccentricity.

  15. CO$_2$ dissolution controlled by buoyancy driven shear dispersion in a background hydrological flow

    CERN Document Server

    Unwin, H Juliette T; Woods, Andrew W

    2015-01-01

    We present an analytical and numerical study of the long-time flow which controls the dissolution of a plume of CO$_2$ following injection into an anticline structure in a deep saline aquifer of finite vertical extent. Over times of tens to thousands of years, some of the CO$_2$ will dissolve into the underlying groundwater to produce a region of relatively dense, CO$_2$ saturated water directly below the plume of CO$_2$. Continued dissolution then requires the supply of CO$_2$ unsaturated aquifer water. This may be provided by a background hydrological flow or buoyancy driven flow caused by the density contrast between the CO$_2$ saturated and unsaturated water in the aquifer. At long times, the interaction of the cross-layer diffusive mixing with the buoyancy, leads to buoyancy driven shear dispersion of the CO$_2$. With a background hydrological flow, the upstream transport of dissolved CO$_2$ by this dispersion becomes balanced by the oncoming hydrological flow so that CO$_2$ rich water can only spread a ...

  16. Numerical Simulation on Floating Behavior of Buoyancy Tank Foundation of Anemometer Tower

    Institute of Scientific and Technical Information of China (English)

    丁红岩; 韩艳丽; 张浦阳

    2014-01-01

    The intact stability and damage stability of a model of an anemometer tower with buoyancy tank founda-tion are computed by the finite element software MOSES in this paper. The natural period of the anemometer tower is discussed through frequency domain analysis. The influence of a single factor, such as towing point position, wave height, wave direction and wave period, on towing stability is discussed through time domain analysis. At the same time, the towing stability under the condition of various combinations of many factors is analyzed based on the meas-ured data of the target area. Computer simulation results show that the intact stability is preferable and the damage stability is sufficient under the condition of plenty of subdivisions. Within the scope of the buoyancy tank foundation, the higher the towing point position is, the better the stability is. Wave height has a great impact on the motion ampli-tude of buoyancy tank foundation, but the effect on the acceleration is not obvious;wave period has a great impact on the acceleration, while the effect on the motion amplitude is not obvious;following-waves towing is more conducive to safety than atry.

  17. Use and understanding of the nutrition information panel of pre-packaged foods in a sample of Mexican consumers Uso y comprensión del etiquetado nutrimental posterior de los alimentos pre-empaquetados en una muestra de consumidores mexicanos

    OpenAIRE

    Vanessa De la Cruz-Góngora; Salvador Villalpando; Guadalupe Rodríguez-Oliveros; Marcia Castillo-García; Verónica Mundo-Rosas; Sergio Meneses-Navarro

    2012-01-01

    OBJECTIVE: To assess the use and understanding of the Nutritional information Panel (NIP) of pre-packaged foods by Mexican consumers. MATERIALS AND METHODS: A questionnaire and an understanding test for NIP were applied to adult consumers in supermarkets of six cities in the Northern, Central, and Southern regions of Mexico. Data were analyzed by frequencies and Poisson regression models. RESULTS: Interviewed 731 consumers; 71.5% were women, mean age 33 ± 9.7 (range: 18-60), 70% completed hig...

  18. Use and understanding of the nutrition information panel of pre-packaged foods in a sample of Mexican consumers Uso y comprensión del etiquetado nutrimental posterior de los alimentos pre-empaquetados en una muestra de consumidores mexicanos

    OpenAIRE

    Vanessa de la Cruz-Góngora; Salvador Villalpando; Guadalupe Rodríguez-Oliveros; Marcia Castillo-García; Verónica Mundo-Rosas; Sergio Meneses-Navarro

    2012-01-01

    OBJECTIVE: To assess the use and understanding of the Nutritional information Panel (NIP) of pre-packaged foods by Mexican consumers. MATERIALS AND METHODS: A questionnaire and an understanding test for NIP were applied to adult consumers in supermarkets of six cities in the Northern, Central, and Southern regions of Mexico. Data were analyzed by frequencies and Poisson regression models. RESULTS: Interviewed 731 consumers; 71.5% were women, mean age 33 ± 9.7 (range: 18-60), 70% completed hig...

  19. Young People's Academic Buoyancy and Adaptability: A Cross-Cultural Comparison of China with North America and the United Kingdom

    Science.gov (United States)

    Martin, Andrew J.; Yu, Kai; Ginns, Paul; Papworth, Brad

    2017-01-01

    We investigated academic buoyancy (a response to challenge) and adaptability (a response to change) among a sample of 12-16-year-olds in China (N = 3617) compared with same-aged youth from North America (N = 989) and the United Kingdom (UK; N = 1182). We found that Chinese students reported higher mean levels of buoyancy and adaptability. We also…

  20. Buoyancy under control: underwater locomotor performance in a deep diving seabird suggests respiratory strategies for reducing foraging effort.

    Directory of Open Access Journals (Sweden)

    Timothée R Cook

    Full Text Available BACKGROUND: Because they have air stored in many body compartments, diving seabirds are expected to exhibit efficient behavioural strategies for reducing costs related to buoyancy control. We study the underwater locomotor activity of a deep-diving species from the Cormorant family (Kerguelen shag and report locomotor adjustments to the change of buoyancy with depth. METHODOLOGY/PRINCIPAL FINDINGS: Using accelerometers, we show that during both the descent and ascent phases of dives, shags modelled their acceleration and stroking activity on the natural variation of buoyancy with depth. For example, during the descent phase, birds increased swim speed with depth. But in parallel, and with a decay constant similar to the one in the equation explaining the decrease of buoyancy with depth, they decreased foot-stroke frequency exponentially, a behaviour that enables birds to reduce oxygen consumption. During ascent, birds also reduced locomotor cost by ascending passively. We considered the depth at which they started gliding as a proxy to their depth of neutral buoyancy. This depth increased with maximum dive depth. As an explanation for this, we propose that shags adjust their buoyancy to depth by varying the amount of respiratory air they dive with. CONCLUSIONS/SIGNIFICANCE: Calculations based on known values of stored body oxygen volumes and on deep-diving metabolic rates in avian divers suggest that the variations of volume of respiratory oxygen associated with a respiration mediated buoyancy control only influence aerobic dive duration moderately. Therefore, we propose that an advantage in cormorants--as in other families of diving seabirds--of respiratory air volume adjustment upon diving could be related less to increasing time of submergence, through an increased volume of body oxygen stores, than to reducing the locomotor costs of buoyancy control.

  1. Silicate melts density, buoyancy relations and the dynamics of magmatic processes in the upper mantle

    Science.gov (United States)

    Sanchez-Valle, Carmen; Malfait, Wim J.

    2016-04-01

    Although silicate melts comprise only a minor volume fraction of the present day Earth, they play a critical role on the Earth's geochemical and geodynamical evolution. Their physical properties, namely the density, are a key control on many magmatic processes, including magma chamber dynamics and volcanic eruptions, melt extraction from residual rocks during partial melting, as well as crystal settling and melt migration. However, the quantitative modeling of these processes has been long limited by the scarcity of data on the density and compressibility of volatile-bearing silicate melts at relevant pressure and temperature conditions. In the last decade, new experimental designs namely combining large volume presses and synchrotron-based techniques have opened the possibility for determining in situ the density of a wide range of dry and volatile-bearing (H2O and CO2) silicate melt compositions at high pressure-high temperature conditions. In this contribution we will illustrate some of these progresses with focus on recent results on the density of dry and hydrous felsic and intermediate melt compositions (rhyolite, phonolite and andesite melts) at crustal and upper mantle conditions (up to 4 GPa and 2000 K). The new data on felsic-intermediate melts has been combined with in situ data on (ultra)mafic systems and ambient pressure dilatometry and sound velocity data to calibrate a continuous, predictive density model for hydrous and CO2-bearing silicate melts with applications to magmatic processes down to the conditions of the mantle transition zone (up to 2773 K and 22 GPa). The calibration dataset consist of more than 370 density measurements on high-pressure and/or water-and CO2-bearing melts and it is formulated in terms of the partial molar properties of the oxide components. The model predicts the density of volatile-bearing liquids to within 42 kg/m3 in the calibration interval and the model extrapolations up to 3000 K and 100 GPa are in good agreement

  2. Battleship Buoyancy

    Science.gov (United States)

    Dishaw, J. Patrick

    2010-04-01

    One of the most dramatic demonstrations of the Archimedes principle is the simple fact that battleships float. I estimate the depth of a battleship in seawater as an example in my physics classes. I use the battleship Arizona as an exemplar of a class of U.S. battleships used during World War II. The Arizona was 608 ft (185.3 m) long and 97 ft 1 in (29.6 m) wide at its widest dimension. The unloaded weight of the ship was 31,400 U.S. tons (2.79× 108 N). How deep would the Arizona sink into seawater of density 1028 kg/m3?

  3. Buoyancy Effects on Flow Structure and Instability of Low-Density Gas Jets

    Science.gov (United States)

    Pasumarthi, Kasyap Sriramachandra

    2004-01-01

    A low-density gas jet injected into a high-density ambient gas is known to exhibit self-excited global oscillations accompanied by large vortical structures interacting with the flow field. The primary objective of the proposed research is to study buoyancy effects on the origin and nature of the flow instability and structure in the near-field of low-density gas jets. Quantitative rainbow schlieren deflectometry, Computational fluid dynamics (CFD) and Linear stability analysis were the techniques employed to scale the buoyancy effects. The formation and evolution of vortices and scalar structure of the flow field are investigated in buoyant helium jets discharged from a vertical tube into quiescent air. Oscillations at identical frequency were observed throughout the flow field. The evolving flow structure is described by helium mole percentage contours during an oscillation cycle. Instantaneous, mean, and RMS concentration profiles are presented to describe interactions of the vortex with the jet flow. Oscillations in a narrow wake region near the jet exit are shown to spread through the jet core near the downstream location of the vortex formation. The effects of jet Richardson number on characteristics of vortex and flow field are investigated and discussed. The laminar, axisymmetric, unsteady jet flow of helium injected into air was simulated using CFD. Global oscillations were observed in the flow field. The computed oscillation frequency agreed qualitatively with the experimentally measured frequency. Contours of helium concentration, vorticity and velocity provided information about the evolution and propagation of vortices in the oscillating flow field. Buoyancy effects on the instability mode were evaluated by rainbow schlieren flow visualization and concentration measurements in the near-field of self-excited helium jets undergoing gravitational change in the microgravity environment of 2.2s drop tower at NASA John H. Glenn Research Center. The jet

  4. The Solar Vortex: Electric Power Generation using Anchored, Buoyancy-Induced Columnar Vortices

    Science.gov (United States)

    Glezer, Ari

    2015-04-01

    Naturally-occurring, buoyancy-driven columnar vortices (``dust devils'') that are driven by the instability of thermally stratified air layers and sustained by the entrainment of ground- heated air, occur spontaneously in the natural environment with core diameters of 1-50 m and heights up to 1 km. These vortices convert low-grade waste heat in the air layer overlying the warm surface into a solar-induced wind with significant kinetic energy. Unlike dust devil vortices that are typically free to wander laterally, the Solar Vortex (SoV) is deliberately triggered and anchored within a cylindrical domain bounded by an azimuthal array of stationary ground-mounted vertical vanes and sustained by continuous entrainment of the ground-heated air through these vanes. The mechanical energy of the anchored vortex is exploited for power generation by coupling the vortex to a vertical-axis turbine. This simple, low-cost electric power generating unit is competitive in cost, intermittency, and capacity factor with traditional solar power technologies. The considerable kinetic energy of the vortex column cannot be explained by buoyancy alone, and the fundamental mechanisms associated with the formation, evolution, and dynamics of an anchored, buoyancy-driven columnar vortex were investigated experimentally and numerically with specific emphasis on flow manipulation for increasing the available kinetic energy and therefore the generated power. These investigations have also considered the dependence of the vortex scaling and strength on the thermal resources and on the flow enclosure in the laboratory and in the natural environment. Preliminary outdoor tests of a two-meter scale prototype successfully demonstrated the ability to engender and anchor a columnar vortex using only solar radiation and couple the flow to a vertical axis wind turbine. A kilowatt-scale outer door prototype will be tested during the summer of 2015.

  5. Dynamic effects of plate-buoyancy subduction at Manila Trench, South China Sea

    Science.gov (United States)

    Jiang, L.; Zhan, W.; Sun, J.; Li, J.

    2015-12-01

    Bathymetric map of SCS plate shows two subducting buoyancies, the fossil ridge and the oceanic plateau, which are supposed to impact slab segmentation into the north from Taiwan to 18°N, and the south from 17°N to Mindoro. Hypocenter distribution show that slab dip angle turns lower southwards from 45° to 30° in the north segment, and relatively equals ~45° in the south segment at the depth of 100km. Moreover, volcano distribution can be segmented into Miocene WVC, Quaternary EVC in the north and combined SVC in the south (Fig. A). We found that WVC and SVC mostly locate in a parallel belt ~50km apart to Manila trench, however EVC turn father southwards from 50km to 100km (Fig. B). Above characters congruously indicate that SCS plate kept equal dip angle in Miocene; then the north segment shallowed at 18°N and developed northwards in Quaternary, resulting in lower dip angle than the invariant south segment. To check the transformation of slab dip angle from 45° to 30° between 17~18°N, focal mechanism solution nearby 17°N are found 90° in rake and dip angle, strike parallel to the fossil ridge, indicating a slab tear located coincident with the ridge, where is a weak zone of higher heat flow and lower plate coupling ratio than the adjacent zones and slab can be easily tore as an interface for SCS plate segmentation. Subduction of the two buoyancies within SCS plate is supposed as influential dynamic factor: It caused the trench retreat rate reduced, forming a cusp and a flat convex of Manila trench shape; Moreover, the buoyancies resisted subduction, resulting in shear stress heterogeneity of SCS plate, in consequence the fossil ridge as a fragile belt potentially became stress concentration zone that easily tore; Then the buoyant oceanic plateau might lead to shallowing of the northern SCS plate. To examine the hypothesis, dynamic effects of the two subducting buoyancies are being respectively investigated based on numerical models. (Grt. 41376063, 2013

  6. Effect of buoyancy and power design parameters on hybrid airship performance

    Science.gov (United States)

    Talbot, P. D.; Gelhausen, P. A.

    1983-01-01

    The effects of several design parameters on the performance of hybrid airships having rotors and propellers were examined with a simple mathematical model. The parameters included buoyancy ratio, Froude number, ratio of rotor power to total power, and rotor shaft tilt. Performance variations resulting from changes in these parameters were calculated, and are presented and discussed. Performance quantities included best climb rate, equivalent vehicle L/D, and maximum speed. Performance at all speeds between hover and maximum speed was found to be sensitive to power distribution between rotors and propellers, and to rotor shaft tilt.

  7. Effect of tracer buoyancy on tracer experiments conducted in fractured crystalline bedrock

    Science.gov (United States)

    Becker, Matthew W.

    2003-02-01

    Tracer buoyancy has been shown to influence breakthrough from two-well tracer experiments conducted in porous media. Two-well tracer experiments are presented from fractured crystalline bedrock, in which the specific gravity of the tracer injectate varied from 1.0002 to 1.0133. Under the forced hydraulic conditions imposed, no difference in breakthrough was noted for the three experiments. These results show that even relatively dense tracer injectate solutions may have an insignificant effect on breakthrough when imposed gradients are sufficiently large.

  8. Importance of initial buoyancy field on evolution of mantle thermal structure:Implications of surface boundary conditions

    Institute of Scientific and Technical Information of China (English)

    Petar Glisovic; Alessandro M. Forte

    2015-01-01

    Although there has been significant progress in the seismic imaging of mantle heterogeneity, the outstanding issue that remains to be resolved is the unknown distribution of mantle temperature anomalies in the distant geological past that give rise to the present-day anomalies inferred by global tomography models. To address this question, we present 3-D convection models in compressible and self-gravitating mantle initialised by different hypothetical temperature patterns. A notable feature of our forward convection modelling is the use of self-consistent coupling of the motion of surface tectonic plates to the underlying mantle flow, without imposing prescribed surface velocities (i.e., plate-like boundary condition). As an approximation for the surface mechanical conditions before plate tectonics began to operate we employ the no-slip (rigid) boundary condition. A rigid boundary condition dem-onstrates that the initial thermally-dominated structure is preserved, and its geographical location is fixed during the evolution of mantle flow. Considering the impact of different assumed surface boundary conditions (rigid and plate-like) on the evolution of thermal heterogeneity in the mantle we suggest that the intrinsic buoyancy of seven superplumes is most-likely resolved in the tomographic images of present-day mantle thermal structure. Our convection simulations with a plate-like boundary condition reveal that the evolution of an initial cold anomaly beneath the Java-Indonesian trench system yields a long-term, stable pattern of thermal heterogeneity in the lowermost mantle that resembles the present-day Large Low Shear Velocity Provinces (LLSVPs), especially below the Pacific. The evolution of sub-duction zones may be, however, influenced by the mantle-wide flow driven by deeply-rooted and long-lived superplumes since Archean times. These convection models also detect the intrinsic buoyancy of the Perm Anomaly that has been identified as a unique slow feature

  9. Transient laminar opposing mixed convection in a symmetrically heated duct with a plane symmetric sudden contraction-expansion: Buoyancy an inclination effects

    Science.gov (United States)

    Martínez-Suástegui, Lorenzo; Barreto, Enrique; Treviño, César

    2015-11-01

    Transient laminar opposing mixed convection is studied experimentally in an open vertical rectangular channel with two discrete protruded heat sources subjected to uniform heat flux simulating electronic components. Experiments are performed for a Reynolds number of Re = 700, Prandtl number of Pr = 7, inclination angles with respect to the horizontal of γ =0o , 45o and 90o, and different values of buoyancy strength or modified Richardson number, Ri* =Gr* /Re2 . From the experimental measurements, the space averaged surface temperatures, overall Nusselt number of each simulated electronic chip, phase-space plots of the self-oscillatory system, characteristic times of temperature oscillations and spectral distribution of the fluctuating energy have been obtained. Results show that when a threshold in the buoyancy parameter is reached, strong three-dimensional secondary flow oscillations develop in the axial and spanwise directions. This research was supported by the Consejo Nacional de Ciencia y Tecnología (CONACYT), Grant number 167474 and by the Secretaría de Investigación y Posgrado del IPN, Grant number SIP 20141309.

  10. Impacts of a wind stress and a buoyancy flux on the seasonal variation of mixing layer depth in the South China Sea

    Institute of Scientific and Technical Information of China (English)

    XIAO Xianjun; WANG Dongxiao; ZHOU Wen; ZHANG Zuqiang; QIN Yinghao; HE Na; ZENG Lili

    2013-01-01

    The seasonal variation of mixing layer depth (MLD) in the ocean is determined by a wind stress and a buoy-ance flux. A South China Sea (SCS) ocean data assimilation system is used to analyze the seasonal cycle of its MLD. It is found that the variability of MLD in the SCS is shallow in summer and deep in winter, as is the case in general. Owing to local atmosphere forcing and ocean dynamics, the seasonal variability shows a regional characteristic in the SCS. In the northern SCS, the MLD is shallow in summer and deep in winter, affected coherently by the wind stress and the buoyance flux. The variation of MLD in the west is close to that in the central SCS, influenced by the advection of strong western boundary currents. The eastern SCS presents an annual cycle, which is deep in summer and shallow in winter, primarily impacted by a heat flux on the air-sea interface. So regional characteristic needs to be cared in the analysis about the MLD of SCS.

  11. Large eddy simulation of pollutant gas dispersion with buoyancy ejected from building into an urban street canyon.

    Science.gov (United States)

    Hu, L H; Xu, Y; Zhu, W; Wu, L; Tang, F; Lu, K H

    2011-09-15

    The dispersion of buoyancy driven smoke soot and carbon monoxide (CO) gas, which was ejected out from side building into an urban street canyon with aspect ratio of 1 was investigated by large eddy simulation (LES) under a perpendicular wind flow. Strong buoyancy effect, which has not been revealed before, on such pollution dispersion in the street canyon was studied. The buoyancy release rate was 5 MW. The wind speed concerned ranged from 1 to 7.5m/s. The characteristics of flow pattern, distribution of smoke soot and temperature, CO concentration were revealed by the LES simulation. Dimensionless Froude number (Fr) was firstly introduced here to characterize the pollutant dispersion with buoyancy effect counteracting the wind. It was found that the flow pattern can be well categorized into three regimes. A regular characteristic large vortex was shown for the CO concentration contour when the wind velocity was higher than the critical re-entrainment value. A new formula was theoretically developed to show quantitatively that the critical re-entrainment wind velocities, u(c), for buoyancy source at different floors, were proportional to -1/3 power of the characteristic height. LES simulation results agreed well with theoretical analysis. The critical Froude number was found to be constant of 0.7.

  12. Vortex ring formation in starting forced plumes with negative and positive buoyancy

    Science.gov (United States)

    Gao, L.; Yu, S. C. M.

    2016-11-01

    The limiting process of vortex ring formation in starting forced plumes, with Richardson number in the range of -0.06 ≤ Ri ≤ 0.06, was studied numerically under the Boussinesq approximation. The examination of the dynamics of the starting flow evolution reveals that the plume-ambient density difference affects the vortex ring pinch-off mainly through three mechanisms, i.e., the baroclinic production of vorticity, the buoyancy acceleration (or deceleration) on the vortical structures, and its effect on the trailing shear layer instability. As Ri increases from negative to positive values, three regimes can be identified in terms of the vortex interaction patterns during the pinch-off process, i.e., the weak-interaction regime (-0.06 results show that the variation trends of formation number and separation number against Ri change near the critical value of Ric ≈ - 0.02. In the weak-interaction regime, both formation number and separation number increase rapidly against Ri. While in the transition and strong-interaction regimes alike, the formation number increases at a much slower rate than in the weak-interaction regime, and the separation number declines dramatically as Ri increases. Finally, a qualitative explanation on the variation patterns of formation number and separation number is proposed based on the buoyancy effects on the dynamic properties of the leading vortex ring and the vortex interaction patterns.

  13. Numerical Study of the Buoyancy-Driven Flow in a Four-Electrode Rectangular Electrochemical Cell

    Science.gov (United States)

    Sun, Zhanyu; Agafonov, Vadim; Rice, Catherine; Bindler, Jacob

    2009-11-01

    Two-dimensional numerical simulation is done on the buoyancy-driven flow in a four-electrode rectangular electrochemical cell. Two kinds of electrode layouts, the anode-cathode-cathode-anode (ACCA) and the cathode-anode-anode-cathode (CAAC) layouts, are studied. In the ACCA layout, the two anodes are placed close to the channel outlets while the two cathodes are located between the two anodes. The CAAC layout can be converted from the ACCA layout by applying higher electric potential on the two middle electrodes. Density gradient was generated by the electrodic reaction I3^-+2e^- =3I^-. When the electrochemical cell is accelerated axially, buoyancy-driven flow occurs. In our model, electro-neutrality is assumed except at the electrodes. The Navier-Stokes equations with the Boussinesq approximation and the Nernst-Planck equations are employed to model the momentum and mass transports, respectively. It is found that under a given axial acceleration, the electrolyte density between the two middle electrodes determines the bulk flow through the electrochemical cell. The cathodic current difference is found to be able to measure the applied acceleration. Other important electro-hydrodynamic characteristics are also discussed.

  14. A Review of Some Recent Studies on Buoyancy Driven Flows in an Urban Environment

    Directory of Open Access Journals (Sweden)

    Bodhisatta Hajra

    2014-01-01

    Full Text Available This paper reviews some recent studies (after 2000 pertaining to buoyancy driven flows in nature and thier use in reducing air pollution levels in a city (city ventilation. Natural convection flows occur due to the heating and cooling of various urban surfaces (e.g., mountain slopes, leading to upslope and downslope flows. Such flows can have a significant effect on city ventilation which has been the subject of study in the recent times due to increased pollution levels in a city. A major portion of the research reviewed here consists of natural convection flows occurring along mountain slopes, with a few studies devoted to flows along building walls. The studies discussed here primarily include field measurements and computational fluid dynamics (CFD models. This review shows that for densely populated cities with high pollution levels, natural convection flows (mountain slope or building walls can significantly aid the dispersion of pollutants. Additional studies in this area using CFD and water channel measurements can explain the physical processes involved in such flows and help improve CFD modelling. Future research should focus on a complete understanding of the mechanisms of buoyancy flows in nature and developing design guidelines for better planning of cities.

  15. Results of Buoyancy-gravity Effects in ITER Cable-in- Conduit Conductor with Dual Channel

    Science.gov (United States)

    Bruzzone, P.; Stepanov, B.; Zanino, R.; Richard, L. Savoldi

    2006-04-01

    The coolant in the ITER cable-in-conduit conductors (CICC) flows at significant higher speed in the central channel than in the strand bundle region due to the large difference of hydraulic impedance. When energy is deposited in the bundle region, e.g. by ac loss or radiation, the heat removal in vertically oriented dual channel CICC with the coolant flowing downward is affected by the reduced density of helium (buoyancy) in the bundle region, which is arising from the temperature gradient due to poor heat exchange between the two channels. At large deposited power, flow stagnation and back-flow can cause in the strand bundle area a slow temperature runaway eventually leading to quench. A new test campaign of the thermal-hydraulic behavior was carried out in the SULTAN facility on an instrumented section of the ITER Poloidal Field Conductor Insert (PFIS). The buoyancy-gravity effect was investigated using ac loss heating, with ac loss in the cable calibrated in separate runs. The extent of upstream temperature increase was explored over a broad range of mass flow rate and deposited power. The experimental behavior is partly reproduced by numerical simulations. The results from the tests are extrapolated to the likely operating conditions of the ITER Toroidal Field conductor with the inboard leg cooled from top to bottom and heat deposited by nuclear radiation from the burning plasma.

  16. On the mitigation of surf-riding by adjusting center of buoyancy in design stage

    Directory of Open Access Journals (Sweden)

    Liwei Yu

    2017-05-01

    Full Text Available High-speed vessels are prone to the surf-riding in adverse quartering seas. The possibility of mitigating the surf-riding of the ITTC A2 fishing vessel in the design stage is investigated using the 6-DOF weakly non-linear model developed for surf-riding simulations in quartering seas. The longitudinal position of the ship's center of buoyancy (LCB is chosen as the design parameter. The adjusting of LCB is achieved by changing frame area curves, and hull surfaces are reconstructed accordingly using the Radial Basis Function (RBF. Surf-riding motions in regular following seas for cases with different LCBs and Froude numbers are simulated using the numerical model. Results show that the surf-riding cannot be prevented by the adjusting of LCB. However, it occurs with a higher threshold speed when ship's center of buoyancy (COB is moved towards stem compared to moving towards stern, which is mainly due to the differences on wave resistance caused by the adjusting of LCB.

  17. Plate tectonics on the early Earth: Limitations imposed by strength and buoyancy of subducted lithosphere

    Science.gov (United States)

    van Hunen, Jeroen; van den Berg, Arie P.

    2008-06-01

    The tectonic style and viability of modern plate tectonics in the early Earth is still debated. Field observations and theoretical arguments both in favor and against the uniformitarian view of plate tectonics back until the Archean continue to accumulate. Here, we present the first numerical modeling results that address for a hotter Earth the viability of subduction, one of the main requirements for plate tectonics. A hotter mantle has mainly two effects: 1) viscosity is lower, and 2) more melt is produced, which in a plate tectonic setting will lead to a thicker oceanic crust and harzburgite layer. Although compositional buoyancy resulting from these thick crust and harzburgite might be a serious limitation for subduction initiation, our modeling results show that eclogitization significantly relaxes this limitation for a developed, ongoing subduction process. Furthermore, the lower viscosity leads to more frequent slab breakoff, and sometimes to crustal separation from the mantle lithosphere. Unlike earlier propositions, not compositional buoyancy considerations, but this lithospheric weakness could be the principle limitation to the viability of plate tectonics in a hotter Earth. These results suggest a new explanation for the absence of ultrahigh-pressure metamorphism (UHPM) and blueschists in most of the Precambrian: early slabs were not too buoyant, but too weak to provide a mechanism for UHPM and exhumation.

  18. Nonlinear waves in stratified Taylor--Couette flow. Part 2. Buoyancy flux

    CERN Document Server

    Leclercq, Colin; Caulfield, Colm-Cille P; Dalziel, Stuart B; Linden, Paul F

    2016-01-01

    This paper is the second part of a two-fold study of mixing, i.e. the formation of layers and upwelling of buoyancy, in axially stratified Taylor--Couette flow, with fixed outer cylinder. In a first paper, we showed that the dynamics of the flow was dominated by coherent structures made of a superposition of nonlinear waves. (Mixed)-ribbons and (mixed)-cross-spirals are generated by interactions between a pair of linearly unstable helical modes of opposite `handedness', and appear to be responsible for the formation of well-mixed layers and sharp density interfaces. In this paper, we show that these structures are also fully accountable for the upwards buoyancy flux in the simulations. The mechanism by which this occurs is a positive coupling between the density and vertical velocity components of the most energetic waves. This coupling is primarily caused by diffusion of density at low Schmidt number Sc, but can also be a nonlinear effect at larger Sc. Turbulence was found to contribute negatively to the buo...

  19. Simulation of buoyancy-induced turbulent flow from a hot horizontal jet

    KAUST Repository

    El-Amin, Mohamed

    2014-02-01

    Experimental visualizations and numerical simulations of a horizontal hot water jet entering cold water into a rectangular storage tank are described. Three different temperature differences and their corresponding Reynolds numbers are considered. Both experimental visualization and numerical computations are carried out for the same flow and thermal conditions. The realizable k - ε model is used for modeling the turbulent flow while the buoyancy is modeled using the Boussinesq approximation. Polynomial approximations of the water properties are used to compare with the Boussinesq approximation. Numerical solutions are obtained for unsteady flow while pressure, velocity, temperature and turbulence distributions inside the water tank as well as the Froude number are analyzed. The experimental visualizations are performed at intervals of five seconds for all different cases. The simulated results are compared with the visualized results, and both of them show the stratification phenomena and buoyancy force effects due to temperature difference and density variation. After certain times, depending on the case condition, the flow tends to reach a steady state. © 2014 Publishing House for Journal of Hydrodynamics.

  20. Laboratory experiments with a buoyancy forced circulation in a rotating basin

    Science.gov (United States)

    Vreugdenhil, Catherine; Griffiths, Ross; Gayen, Bishakhdatta

    2016-11-01

    We consider the relative influence of buoyancy forcing and Coriolis effects on convection forced by a differential in heating at a horizontal surface in a rectangular basin. Laboratory experiments with water are reported for a rotating f-plane basin and a range of Ekman number E = 2 ×10-7 - 1 ×10-5 . Heating is applied over half of the base as a uniform flux and cooling applied over the other half as a uniform temperature, resulting in a flux Rayleigh number RaF = O (1014) large enough to ensure turbulent convection, where RaF defined in terms of domain length L. Compared to the non-rotating circulation where Nusselt number (a measure of the convective to conductive heat transfer) scales as Nu RaF1 / 6 , the strongly rotating regime is determined by a geostrophic balance of the larger scales of horizontal flow in the inviscid thermal boundary with Nu Ro 1 / 6 , where Ro =B 1 / 2 / (f 3 / 2 L) is the natural Rossby number (B is buoyancy flux per unit area and f is Coriolis parameter). We also find evidence for a further transition into a regime where the circulation is dominated by deep 'chimney' convection in a field of small vortical plumes and Nu is more weakly dependent on rotation.

  1. Modeling and Assessment of Buoyancy-Driven Stratified Airflow in High-Space Industrial Hall

    Institute of Scientific and Technical Information of China (English)

    WANG Han-qing; CHEN Ke; HU Jian-jun; KOU Guang-xiao; WANG Zhi-yong

    2009-01-01

    In industrial environment,heat sources often are contaminant sources and health threatening con-taminants are mainly passive,so a detailed understanding of airflow mode can assist in work environment hy-giene measurement and prevention.This paper presented a numerical investigation of stratified airflow scenario in a high-space industrial hall with validated commercial code and experimentally acquired boundary conditions.Based upon an actually undergoing engineering project,this study investigated the performance of the buoyancy-driven displacement ventilation in a large welding hall with big components manufactured.The results have demonstrated that stratified airflow sustained by thermal buoyancy provides zoning effect in terms of clean and polluted regions except minor stagnant eddy areas.The competition between negative buoyant jets from displace-ment radial diffusers and positive buoyant plume from bulk object constitutes the complex transport characteris-tics under and above stratification interface.Entrainment,downdraft and turbulent eddy motion complicate the upper mixing zone,but the exhaust outlet plays a less important role in the whole field flow.And the corre-sponding suggestions concerning computational stability and convergence,further improvements in modeling and measurements were given.

  2. Simulation of buoyancy-induced turbulent flow from a hot horizontal jet

    Institute of Scientific and Technical Information of China (English)

    El-AMIN M. F.; SUN Shuyu; SALAM Amgad

    2014-01-01

    Experimental visualizations and numerical simulations of a horizontal hot water jet entering cold water into a rectangular storage tank are described. Three different temperature differences and their corresponding Reynolds numbers are considered. Both experimental visualization and numerical computations are carried out for the same flow and thermal conditions. The realizable k-e model is used for modeling the turbulent flow while the buoyancy is modeled using the Boussinesq approximation. Polynomial approximations of the water properties are used to compare with the Boussinesq approximation. Numerical solutions are obtained for unsteady flow while pressure, velocity, temperature and turbulence distributions inside the water tank as well as the Froude number are analyzed. The experimental visualizations are performed at intervals of five seconds for all different cases. The simulated results are compared with the visualized results, and both of them show the stratification phenomena and buoyancy force effects due to temperature difference and density variation. After certain times, depending on the case condition, the flow tends to reach a steady state.

  3. Southern Ocean buoyancy forcing of ocean ventilation and glacial atmospheric CO2

    Science.gov (United States)

    Watson, Andrew J.; Vallis, Geoffrey K.; Nikurashin, Maxim

    2015-11-01

    Atmospheric CO2 concentrations over glacial-interglacial cycles closely correspond to Antarctic temperature patterns. These are distinct from temperature variations in the mid to northern latitudes, so this suggests that the Southern Ocean is pivotal in controlling natural CO2 concentrations. Here we assess the sensitivity of atmospheric CO2 concentrations to glacial-interglacial changes in the ocean's meridional overturning circulation using a circulation model for upwelling and eddy transport in the Southern Ocean coupled with a simple biogeochemical description. Under glacial conditions, a broader region of surface buoyancy loss results in upwelling farther to the north, relative to interglacials. The northern location of upwelling results in reduced CO2 outgassing and stronger carbon sequestration in the deep ocean: we calculate that the shift to this glacial-style circulation can draw down 30 to 60 ppm of atmospheric CO2. We therefore suggest that the direct effect of temperatures on Southern Ocean buoyancy forcing, and hence the residual overturning circulation, explains much of the strong correlation between Antarctic temperature variations and atmospheric CO2 concentrations over glacial-interglacial cycles.

  4. The use of spirometry to evaluate pulmonary function in olive ridley sea turtles (Lepidochelys olivacea) with positive buoyancy disorders.

    Science.gov (United States)

    Schmitt, Todd L; Munns, Suzanne; Adams, Lance; Hicks, James

    2013-09-01

    This study utilized computed spirometry to compare the pulmonary function of two stranded olive ridley sea turtles (Lepidochelys olivacea) presenting with a positive buoyancy disorder with two healthy captive olive ridley sea turtles held in a large public aquarium. Pulmonary function test (PFT) measurements demonstrated that the metabolic cost of breathing was much greater for animals admitted with positive buoyancy than for the normal sea turtles. Positively buoyant turtles had higher tidal volumes and significantly lower breathing-frequency patterns with significantly higher expiration rates, typical of gasp-type breathing. The resulting higher energetic cost of breathing in the diseased turtles may have a significant impact on their long-term survival. The findings represent a method for clinical respiratory function analysis for an individual animal to assist with diagnosis, therapy, and prognosis. This is the first study, to our knowledge, to evaluate objectively sea turtles presenting with positive buoyancy and respiratory disease using pulmonary function tests.

  5. 某医学院大学生预包装食品营养标签认知度调查%An pre-packaged food nutrition labeling Awareness Survey of the College students

    Institute of Scientific and Technical Information of China (English)

    杨双波; 吴媛妮; 夏彦昌; 刘慧

    2013-01-01

    目的:了解某医学院大学生对预包装食品营养标签的认知情况,为指导大学生合理膳食提供科学理论依据,并通过调查为营养标签的完善及营养知识的普及教育积累资料。方法:分层整群随机抽样的方法抽取某医学院800名在校生,采用《某医学院大学生预包装食品营养标签认知度调查问卷》调查大学生对预包装食品营养标签的认知度。结果:该医学院大学生营养标签知识得分为(55.72±15.6),对营养标签知识总的认知度和意识度不够。不同性别、专业、年级及户籍等情况下高校学生对食品营养标签的认知存在统计学上的显著性差异(P<0.05)。结论:应采取多种形式对大学生加强营养健康教育,引导其合理膳食行为的形成,做到科学合理的安排膳食,促进身体健康。%Objective Understanding of college students' awareness of nutrition labeling on pre-packaged foods,and providing scientific theory by investigating the guidance of college students a reasonable diet,and accu-mulating the information to improve the nutrition labeling and nutrition labeling knowledge of universal educa-tion. Methods using stratified cluster random sampling method.Stratified in accordance with the faculties in the college(medical professionals and non-medical professionals from each of two),and then two classes were random-ly selected of each grade. Results College students on pre-packaged food nutrition awareness is not enough,and the nutrition labeling knowledge score is (55.72±15.6). Conclusion Should be taken to various forms of college students to strengthen nutrition and health education, and guide the formation of a reasonable diet behavior, to en-able them to improve their eating behavior, so that scientific and reasonable arrangements for meals, to promote good health.

  6. THE EFFECT OF BREATHING ON THE DISTANCE BETWEEN CENTER OF BUOYANCY AND CENTER OF MASS IN COMPETITIVE SWIMMERS

    Directory of Open Access Journals (Sweden)

    Yasunori Watanabe

    2014-06-01

    Full Text Available Introduction: Buoyancy is an important parameter in swimming. Previous studies suggested that gender, arm position, and lung volume influence natural buoyancy characteristics (Gagnon & Montpetit, 1981; McLean & Hinrichs, 2000. However, these data have not fully described the changes in natural buoyancy. For example, most previous studies measured center-of-buoyancy when participants held their breath. The purpose of this study was to examine the effect of breathing on the distance (d between Center-of-buoyancy (CB and Center-of-mass (CM, and its relation to glide-swimming performance. Method: The participants of this study were 14 male and 22 female Japanese Junior elite competitive swimmers. A reaction board (Hay, 1993 was used to locate CM for each participant while they lay in prone position with both arms held above the head (a streamline posture. The participant submerged and took the same posture for the measurement of CB. In both measurements, the changes of CM and CB were measured in relation to the changes of the lung volume which was measured by a flow instrument. The distance covered by glide-swimming was measured with the participant pushing off from the wall. Results: The result of d showed significant differences (p<.05 between the male (1.93 ± 0.21 cm and the female swimmers (1.36 ± 0.17 cm during hovering position (a neutral buoyancy. However there was no significant difference during full inspiration (male: 2.28 ± 0.44 cm, female: 2.01± 0.35 cm. The distance of the glide-swimming was not significantly different between the male and the female swimmers. Discussion: The results of this study showed that the change of CB with breathing was larger for the female swimmers than for the male swimmers. Also, the distance between CB and CM became smaller in the female swimmer during neutral buoyancy. These results indicated that the female swimmers have a potential to use buoyancy more effectively and could maintain a better

  7. Pre-packaged foods' nutritional ingredients analysis among 706 adult residents in cities in China%中国706名城市成年居民消费预包装食品营养成分分析

    Institute of Scientific and Technical Information of China (English)

    黄绯绯; 张继国; 王惠君; 翟凤英; 张兵

    2015-01-01

    Objective To analyze the nutritional ingredients of daily consumed pre-packaged foods in Chinese adult residents.Methods From October to December 2013,the nutrition labels of pre-packaged foods consumed in continuous 7 days by 706 adult residents were collected by multi-stage stratified cluster random sampling in 18 communities with 360 households in 9 cities in China including Beijing,Shanghai,Chongqing,Shenyang,Haerbin,Jinan,Zhengzhou,Changsha and Nanning.The contents of energy,protein,fat,carbohydrate,sodium and the percentages of low-fat and low-sodium foods were compared among 7 different kinds of foods including baked foods,convenient foods,leisure foods,puffed foods,milk,beverages and seasonings.Results 871 kinds of pre-packaged foods were collected.The median (min,max) of energy contents of puffed foods,baked foods and leisure foods were 2 155(1 638-2 785) kJ/100 g,1 980 (582-2 639) kJ/100 g,l 575 (353-3 015) kJ/100 g respectively.The median (min,max) of fat contents of puffed foods,baked foods and leisure foods were 30.0 (5.0-40.9) g/100 g,20.5 (0.3-40.5) g/100 g,15.1 (0-71.4) g/100 g respectively.The contents of carbohydrate of baked foods,convenient foods and puffed foods were high relatively,the medians(min,max) of which were 58.1 (19.8-82.5),56.5 (0-90.7),and 56.1 (42.6-75.8)g/100 g respectively.The sodium content of seasoning was the highest,which was 2 177 (20-12 000) mg/100 g.The protein content of beverage was the lowest,which was 0.4(0-17.8) g/100 ml.Conclusion The energy and fat contents of puffed foods,baked foods and leisure foods were high.The carbohydrate contents of baked foods,convenient foods and puffed foods were high relatively.The sodium content of seasonings was high.The protein contents of beverages were low.%目的 了解我国城市成年居民日常消费的预包装食品的营养成分.方法 2013年10-12月期间,采用多阶段分层整群随机抽样方法,收集北京、上海、重庆、沈阳、哈尔滨、济

  8. Modeling Diffusion and Buoyancy-Driven Convection with Application to Geological CO2 Storage

    KAUST Repository

    Allen, Rebecca

    2015-04-01

    ABSTRACT Modeling Diffusion and Buoyancy-Driven Convection with Application to Geological CO2 Storage Rebecca Allen Geological CO2 storage is an engineering feat that has been undertaken around the world for more than two decades, thus accurate modeling of flow and transport behavior is of practical importance. Diffusive and convective transport are relevant processes for buoyancy-driven convection of CO2 into underlying fluid, a scenario that has received the attention of numerous modeling studies. While most studies focus on Darcy-scale modeling of this scenario, relatively little work exists at the pore-scale. In this work, properties evaluated at the pore-scale are used to investigate the transport behavior modeled at the Darcy-scale. We compute permeability and two different forms of tortuosity, namely hydraulic and diffusive. By generating various pore ge- ometries, we find hydraulic and diffusive tortuosity can be quantitatively different in the same pore geometry by up to a factor of ten. As such, we emphasize that these tortuosities should not be used interchangeably. We find pore geometries that are characterized by anisotropic permeability can also exhibit anisotropic diffusive tortuosity. This finding has important implications for buoyancy-driven convection modeling; when representing the geological formation with an anisotropic permeabil- ity, it is more realistic to also account for an anisotropic diffusivity. By implementing a non-dimensional model that includes both a vertically and horizontally orientated 5 Rayleigh number, we interpret our findings according to the combined effect of the anisotropy from permeability and diffusive tortuosity. In particular, we observe the Rayleigh ratio may either dampen or enhance the diffusing front, and our simulation data is used to express the time of convective onset as a function of the Rayleigh ratio. Also, we implement a lattice Boltzmann model for thermal convective flows, which we treat as an analog for

  9. Swim bladder function and buoyancy control in pink snapper (Pagrus auratus) and mulloway (Argyrosomus japonicus).

    Science.gov (United States)

    Stewart, John; Hughes, Julian M

    2014-04-01

    Physoclist fish are able to regulate their buoyancy by secreting gas into their hydrostatic organ, the swim bladder, as they descend through the water column and by resorbing gas from their swim bladder as they ascend. Physoclists are restricted in their vertical movements due to increases in swim bladder gas volume that occur as a result of a reduction in hydrostatic pressure, causing fish to become positively buoyant and risking swim bladder rupture. Buoyancy control, rates of swim bladder gas exchange and restrictions to vertical movements are little understood in marine teleosts. We used custom-built hyperbaric chambers and laboratory experiments to examine these aspects of physiology for two important fishing target species in southern Australia, pink snapper (Pagrus auratus) and mulloway (Argyrosomus japonicus). The swim bladders of pink snapper and mulloway averaged 4.2 and 4.9 % of their total body volumes, respectively. The density of pink snapper was not significantly different to the density of seawater (1.026 g/ml), whereas mulloway were significantly denser than seawater. Pink snapper secreted gas into their swim bladders at a rate of 0.027 ± 0.005 ml/kg/min (mean ± SE), almost 4 times faster than mulloway (0.007 ± 0.001 ml/kg/min). Rates of swim bladder gas resorption were 11 and 6 times faster than the rates of gas secretion for pink snapper and mulloway, respectively. Pink snapper resorbed swim bladder gas at a rate of 0.309 ± 0.069 ml/kg/min, 7 times faster than mulloway (0.044 ± 0.009 ml/kg/min). Rates of gas exchange were not affected by water pressure or water temperature over the ranges examined in either species. Pink snapper were able to acclimate to changes in hydrostatic pressure reasonably quickly when compared to other marine teleosts, taking approximately 27 h to refill their swim bladders from empty. Mulloway were able to acclimate at a much slower rate, taking approximately 99 h to refill their swim bladders. We estimated that the

  10. Buoyancy driven flow in a hot water tank due to standby heat loss

    DEFF Research Database (Denmark)

    Fan, Jianhua; Furbo, Simon

    2012-01-01

    show that the CFD model predicts satisfactorily water temperatures at different levels of the tank during cooling by standby heat loss. It is elucidated how the downward buoyancy driven flow along the tank wall is established by the heat loss from the tank sides and how the natural convection flow......Results of experimental and numerical investigations of thermal behavior in a vertical cylindrical hot water tank due to standby heat loss of the tank are presented. The effect of standby heat loss on temperature distribution in the tank is investigated experimentally on a slim 150l tank...... parts of the tank is measured by experiments and used as input to the CFD model. Water temperatures at different levels of the tank are measured and compared to CFD calculated temperatures. The investigations focus on validation of the CFD model and on understanding of the CFD calculations.The results...

  11. Dispersion enhancement and damping by buoyancy driven flows in 2D networks of capillaries

    CERN Document Server

    D'Angelo, Maria Veronica; Allain, Catherine; Rosen, Marta; Hulin, Jean-Pierre

    2008-01-01

    The influence of a small relative density difference on the displacement of two miscible liquids is studied experimentally in transparent 2D networks of micro channels. Both stable displacements in which the denser fluid enters at the bottom of the cell and displaces the lighter one and unstable displacements in which the lighter fluid is injected at the bottom and displaces the denser one are realized. Except at the lowest mean flow velocity U, the average $C(x,t)$ of the relative concentration satisfies a convection-dispersion equation. The dispersion coefficient is studied as function of the relative magnitude of fluid velocity and of the velocity of buoyancy driven fluid motion. A model is suggested and its applicability to previous results obtained in 3D media is discussed.

  12. Buoyancy effects on the 3D MHD stagnation-point flow of a Newtonian fluid

    Science.gov (United States)

    Borrelli, A.; Giantesio, G.; Patria, M. C.; Roşca, N. C.; Roşca, A. V.; Pop, I.

    2017-02-01

    This work examines the steady three-dimensional stagnation-point flow of an electrically conducting Newtonian fluid in the presence of a uniform external magnetic field H0 under the Oberbeck-Boussinesq approximation. We neglect the induced magnetic field and examine the three possible directions of H0 which coincide with the directions of the axes. In all cases it is shown that the governing nonlinear partial differential equations admit similarity solutions. We find that the flow has to satisfy an ordinary differential problem whose solution depends on the Hartmann number M, the buoyancy parameter λ and the Prandtl number Pr. The skin-friction components along the axes are computed and the stagnation-point is classified. The numerical integration shows the existence of dual solutions and the occurrence of the reverse flow for some values of the parameters.

  13. Heart Rate Responses to Unaided Orion Side Hatch Egress in the Neutral Buoyancy Laboratory

    Science.gov (United States)

    English, Kirk L.; Hwang, Emma Y.; Ryder, Jeffrey W.; Kelly, Cody; Walker, Thomas; Ploutz-Snyder, Lori

    2016-01-01

    The Orion capsule will be the next NASA-built vehicle used for near and deep space exploration. The nominal landing scenario for Orion involves splashdown in the Pacific Ocean and subsequent aided crew egress conducted by military personnel. Contingency operations, however, require the crew to egress the capsule unaided, deploy an inflatable life raft, and to ingress the raft. Unaided egress is expected to be physiologically demanding, but no data exist to corroborate this. Thus, we evaluated the heart rate response to unaided Orion side hatch egress and raft ingress as par of the NASA crew Survival Engineering Team's evaluation of egress procedures using the Post-landing Orion Recovery Trainer (PORT) article in the Neutral Buoyancy Laboratory (NBL).

  14. Simulation of DPM distribution in a long single entry with buoyancy effect

    Institute of Scientific and Technical Information of China (English)

    Zheng Yi; Thiruvengadam Magesh; Lan Hai; Tien C. Jerry

    2015-01-01

    Diesel particulate matter (DPM) is considered carcinogenic after prolonged exposure. With more diesel-powered equipment used in underground mines, miners’ exposure to DPM has become an increasing concern. This paper used computational fluid dynamics (CFD) method to study DPM distribution based on an experiment conducted by the Diesel Emissions Evaluation Program (DEEP) in Canada. Twenty-four cases were simulated where the emissions from both truck and load-haul-dumps (LHDs) were examined. Each vehicle was placed in two stream wise locations, and the vehicles were oriented either facing or with the rear end toward the main fresh airflow. A species transport model with buoyancy effect was then used to examine the DPM dispersion pattern. High DPM regions were identified downstream, around, and even upstream of diesel engines. This can provide guidelines for good working practices and selection of diesel emission reduction technologies underground.

  15. Solving problems to learn concepts, how does it happen? A case for buoyancy

    Directory of Open Access Journals (Sweden)

    Laura Buteler

    2016-12-01

    Full Text Available Problem solving is a preferred activity teachers choose to help students learn concepts. At the same time, successful problem solving is widely regarded as a very good indicator of conceptual learning. Many studies have provided evidence that problem solving often improves students’ chances of learning concepts. Still, the question remains relatively unexplored as to how this activity is useful to promote concept learning. In this study we explore this question in the setting of three university students solving a problem on hydrostatics, in which the concept of buoyancy is involved. We use coordination class theory to study how these students progress on their conceptual understanding. We were able to describe how this progress is related to contextual traits, as well as to students’ particular epistemic stances. Finally, we discuss some implications for research and for teaching.

  16. Does size and buoyancy affect the long-distance transport of floating debris?

    Science.gov (United States)

    Ryan, Peter G.

    2015-08-01

    Floating persistent debris, primarily made from plastic, disperses long distances from source areas and accumulates in oceanic gyres. However, biofouling can increase the density of debris items to the point where they sink. Buoyancy is related to item volume, whereas fouling is related to surface area, so small items (which have high surface area to volume ratios) should start to sink sooner than large items. Empirical observations off South Africa support this prediction: moving offshore from coastal source areas there is an increase in the size of floating debris, an increase in the proportion of highly buoyant items (e.g. sealed bottles, floats and foamed plastics), and a decrease in the proportion of thin items such as plastic bags and flexible packaging which have high surface area to volume ratios. Size-specific sedimentation rates may be one reason for the apparent paucity of small plastic items floating in the world’s oceans.

  17. Safety divers prepare HST mockup in the Neutral Buoyancy Simulator at MSFC

    Science.gov (United States)

    1993-01-01

    Safety divers in the Neutral Buoyancy Simulator (NBS) at the Marshall Space Flight Center (MSFC) prepare a mockup of the Hubble Space Telescope (HST) for one of 32 separate training sessions conducted by four of the STS-61 crew members in June. The three-week process allowed mission trainers to refine the timelines for the five separate spacewalks scheduled to be conducted on the actual mission scheduled for December 1993. The HST is separated into two pieces since the water tank depth cannot support the entire structure in one piece. The full length payload bay mockup shows the Solar Array Carrier in the foreground and the various containers that will house replacement hardware that will be carried on the mission.

  18. Buoyancy leads to high productivity of the Changjiang diluted water: a note

    Institute of Scientific and Technical Information of China (English)

    CHEN Chen-Tung Arthur

    2008-01-01

    Being the mightiest river emptying into the East China Sea (ECS) and the Pacific Ocean,compounded with the large increase of nitrogen and phosphorus input due to anthropogenic activities,the Changjiang River (Yangtze River) has become a dominating source of these nutrients to the estuary.The high nutrient concentrations notwithstanding,however,outside of the estuary the high biological productivity of the Changjiang diluted water (CDW) are most probably fueled mainly by nutrient-rich subsurface waters originating from the upwelled Kuroshio waters.This is because while the buoyancy of the CDW spreads it out on the ECS continen-tal shelf,the CDW entrains subsurface waters along with the nutrients.Nutrients thus supplied are several times more than those supplied by the Changjiang River.

  19. Solving problems to learn concepts, how does it happen? A case for buoyancy

    Science.gov (United States)

    Buteler, Laura; Coleoni, Enrique

    2016-12-01

    Problem solving is a preferred activity teachers choose to help students learn concepts. At the same time, successful problem solving is widely regarded as a very good indicator of conceptual learning. Many studies have provided evidence that problem solving often improves students' chances of learning concepts. Still, the question remains relatively unexplored as to how this activity is useful to promote concept learning. In this study we explore this question in the setting of three university students solving a problem on hydrostatics, in which the concept of buoyancy is involved. We use coordination class theory to study how these students progress on their conceptual understanding. We were able to describe how this progress is related to contextual traits, as well as to students' particular epistemic stances. Finally, we discuss some implications for research and for teaching.

  20. Effects of buoyancy-driven convection on nucleation and growth of protein crystals.

    Science.gov (United States)

    Nanev, Christo N; Penkova, Anita; Chayen, Naomi

    2004-11-01

    Protein crystallization has been studied in presence or absence of buoyancy-driven convection. Gravity-driven flow was created, or suppressed, in protein solutions by means of vertically directed density gradients that were caused by generating suitable temperature gradients. The presence of enhanced mixing was demonstrated directly by experiments with crustacyanin, a blue-colored protein, and other materials. Combined with the vertical tube position the enhanced convection has two main effects. First, it reduces the number of nucleated hen-egg-white lysozyme (HEWL) crystals, as compared with those in a horizontal capillary. By enabling better nutrition from the protein in the solution, convection results in growth of fewer larger HEWL crystals. Second, we observe that due to convection, trypsin crystals grow faster. Suppression of convection, achieved by decreasing solution density upward in the capillary, can to some extent mimic conditions of growth in microgravity. Thus, impurity supply, which may have a detrimental effect on crystal quality, was avoided.

  1. Numerical experiments modeling the buoyancy of bubbles in a vertical plane layer of a magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Tsebers, A.O.

    1985-12-01

    The buoyancy of elliptical bubbles in the absence of surface tension are determined through a numerical experiment as a function of the semiaxis ratio, and the results are found to be in good agreement with the well-known Taylor-Saffman solution. Particular attention is given to the effect of the motion of bubbles on the development of a MHD instability in a transverse magnetic field, and it is shown that this motion stabilizes the development of perturbations in the motion direction and intensifies perturbations in the direction transverse to the motion. It is further shown that in the presence of a magnetic field, the configurations of the buoyant bubbles are not determined uniquely by physical parameters but also depend on their initial profiles. 6 references.

  2. The Enabling and Protective Role of Academic Buoyancy in the Appraisal of Fear Appeals Used Prior to High Stakes Examinations

    Science.gov (United States)

    Symes, Wendy; Putwain, David W.; Remedios, Richard

    2015-01-01

    Prior to high stakes examinations, teachers may engage in instructional practices to encourage their students to prepare well for their exams, including the use of "fear appeals". The current study examined whether academic buoyancy played a role in student appraisals of fear appeals as threatening or challenging. High school students…

  3. Spatio-temporal variability in western Baltic cod early life stage survival mediated by egg buoyancy, hydrography and hydrodynamics

    DEFF Research Database (Denmark)

    Hinrichsen, H-H.; Hüssy, K.; Huwer, B.

    2012-01-01

    Spatio-temporal variability in western Baltic cod early life stage survival mediated by egg buoyancy, hydrography and hydrodynamics. – ICES Journal of Marine Science, 69: 1744–1752.To disentangle the effects of different drivers on recruitment variability of marine fish, a spatially and temporally...

  4. A Closer Look at Boundary Layer Inversion in Large-Eddy Simulations and Bulk Models: Buoyancy-Driven Case

    NARCIS (Netherlands)

    Gentine, P.; Ballon, Gilles; Heerwaarden, van C.C.

    2015-01-01

    The inversion layer (IL) of a clear-sky, buoyancy-driven convective boundary layer is investigated using large-eddy simulations covering a wide range of convective Richardson numbers. A new model of the IL is suggested and tested. The model performs better than previous first-order models of the

  5. Academic Buoyancy Mediates Academic Anxiety's Effects on Learning Strategies: An Investigation of English- and Chinese-Speaking Australian Students

    Science.gov (United States)

    Collie, Rebecca J.; Ginns, Paul; Martin, Andrew J.; Papworth, Brad

    2017-01-01

    A primary goal our study was to explore whether relations between academic anxiety and students' use of a range of learning strategies (memorisation, elaboration, personal best [PB] goals and cooperation) were mediated by academic buoyancy. We were also interested in extending knowledge of anxiety and its role in students' learning strategy use.…

  6. The buoyancy of large siliceous magma chambers is sufficient to initiate supereruptions

    Science.gov (United States)

    Malfait, W.; Sanchez-Valle, C.; Seifert, R.; Petitgirard, S.; Perrillat, J.; Ota, T.; Nakamura, E.; Lerch, P.; Mezouar, M.

    2012-12-01

    The geological record shows abundant evidence for rare, but extremely large caldera-forming eruptions of siliceous magmas that dwarf all historical volcanic episodes in erupted volume [1] and environmental impact [2, 3]. Because of the large size of the magma chambers that feed these eruptions, the overpressure generated by magma recharge is insufficient to fracture the cap rock and trigger an eruption [4]. For these thick magma chambers, the buoyancy of the magma potentially creates a sufficient overpressure capable of fracturing the cap rock, but the lack of data on the density of rhyolite melts precludes the appropriate estimation of the overpressure and the role of buoyancy in initiating supervolcano eruptions. The density of rhyolite melts has not been determined at super-liquidus temperatures or elevated pressures because traditional techniques, including Archimedean methods, sink/float experiments and acoustic measurements, are limited by the high melt viscosity. Here, we measured the density of rhyolitic/granitic melts with 0, 4.5 and 7.7 wt% of dissolved water at geologically relevant conditions: 0.9 to 3.6 GPa, 1270 to 1950 K. High pressure and temperature conditions were generated in a Paris-Edinburgh large volume press. Before and after each density measurement, the molten state of the sample was verified by X-ray diffraction. The density of the melt (ρPT) was determined from the X-ray attenuation coefficient of the sample, determined in situ (μPT) and at room conditions (μ0), and the density at room conditions (ρ0): ρPT=ρ0.(μPT/μ0). The acquired data were combined with available ambient pressure data on super-cooled liquids [5, 6] to derive a third order Birch-Murnaghan equation of state that accurately predicts the density of rhyolite melts as a function of pressure, temperature and water content, and the partial molar volume of dissolved water. Application of the melt equation of state to calculate the overpressure at the roof of supervolcano

  7. Buoyancy-driven convection around chemical fronts traveling in covered horizontal solution layers.

    Science.gov (United States)

    Rongy, L; Goyal, N; Meiburg, E; De Wit, A

    2007-09-21

    Density differences across an autocatalytic chemical front traveling horizontally in covered thin layers of solution trigger hydrodynamic flows which can alter the concentration profile. We theoretically investigate the spatiotemporal evolution and asymptotic dynamics resulting from such an interplay between isothermal chemical reactions, diffusion, and buoyancy-driven convection. The studied model couples the reaction-diffusion-convection evolution equation for the concentration of an autocatalytic species to the incompressible Stokes equations ruling the evolution of the flow velocity in a two-dimensional geometry. The dimensionless parameter of the problem is a solutal Rayleigh number constructed upon the characteristic reaction-diffusion length scale. We show numerically that the asymptotic dynamics is one steady vortex surrounding, deforming, and accelerating the chemical front. This chemohydrodynamic structure propagating at a constant speed is quite different from the one obtained in the case of a pure hydrodynamic flow resulting from the contact between two solutions of different density or from the pure reaction-diffusion planar traveling front. The dynamics is symmetric with regard to the middle of the layer thickness for positive and negative Rayleigh numbers corresponding to products, respectively, lighter or heavier than the reactants. A parametric study shows that the intensity of the flow, the propagation speed, and the deformation of the front are increasing functions of the Rayleigh number and of the layer thickness. In particular, the asymptotic mixing length and reaction-diffusion-convection speed both scale as square root Ra for Ra>5. The velocity and concentration fields in the asymptotic dynamics are also found to exhibit self-similar properties with Ra. A comparison of the dynamics in the case of a monostable versus bistable kinetics is provided. Good agreement is obtained with experimental data on the speed of iodate-arsenous acid fronts

  8. Buoyed by geophysics : geophysics, just-in-time procurement help save millions on Ekwan pipeline buoyancy control

    Energy Technology Data Exchange (ETDEWEB)

    Roche, P.

    2005-09-01

    Large-diameter natural gas pipelines buried in wet muskeg have the potential to rise to the surface due to buoyancy. Until recently, the most reliable method to prevent this was to attach specially manufactured bolt-on concrete weights at closely spaced intervals. However, these weights significantly increase capital budgets by millions of dollars because each weight weighs 2,540 kg and costs $1,000. A less costly alternative for buoyancy control in shallow muskeg is for the contractor to simply dig a deeper ditch. Another option is to hold down the pipeline by polyester straps attached to screw anchors. The challenge of applying these less costly options is that heavy equipment cannot be brought to the site to determine ground conditions until after all procurement, assessment and design is completed. Engineers must therefore select a buoyancy control measure based only on air photos and possibly a few drill holes. However, air photos do not indicate the depth of muskeg. Although some muskeg areas may turn out to be thick enough to avoid buoyancy control altogether, once construction is underway, it is too late to opt for cheaper alternatives. EnCana Corporation's 24-inch Ekwan pipeline was recently constructed through a remote area of British Columbia to connect the Greater Sierra natural gas discovery to a tie-in point on Nova Gas Transmission's northwest mainline. Air photos indicated that half of the route was through muskeg. AMEC E and C Services Inc. was responsible for the engineering and management of the project. The company used a combination of geophysical techniques to learn about the ground conditions. Toboggan mounted portable equipment was hauled by snowmobiles along trails made earlier by the survey crews. Ground penetrating radar assessed the muskeg thickness. Fixed frequency electromagnetic surveys also enhanced the results of the ground penetrating radar. The number of bolt-on weights was reduced from 9,000 to 3,700, a savings of $3

  9. Non-Boussinesq effects on buoyancy-driven variable-density turbulence

    Science.gov (United States)

    Aslangil, Denis; Livescu, Daniel; Banerjee, Arindam

    2016-11-01

    Non-Boussinesq effects on turbulent mixing of a heterogeneous mixture of two incompressible, miscible fluids with different densities are investigated in terms of properly normalized L2m-norms of density gradient by means of high-resolution Direct Numerical Simulations. In a triply periodic three-dimensional domain, the mixing occurs in response to stirring induced by buoyancy-generated motions between two fluids which are initially segregated in random patches. During the flow evolution, the density gradient can reach high values even at low Atwood numbers indicating that non-Boussinesq effects play a crucial role within the flow. The results cover a broad range of Reynolds numbers and non-dimensional density ratios (Atwood numbers, A) including small (A =0.05), moderate (A =0.25 and 0.5), and high (A =0.75) values. An asymmetric behavior is detected on the probability density function of the density gradient at high Atwood numbers. The evolution of the density gradient and the hierarchy of its higher order norms are also investigated by decomposing the flow into the different flow regions by using density as a fluid marker. It is found that the density gradient is much larger in regions of light fluid compared to regions occupied by the heavier fluid, indicating a strong mixing asymmetry between light and heavy fluids. This shows that Boussinesq models may not be adequate even at low density ratios; contrary to what statistics based on the entire domain. AB acknowledges NSF Career Award # 1453056.

  10. Buoyancy effects in vertical rectangular duct with coplanar magnetic field and single sided heat load

    Energy Technology Data Exchange (ETDEWEB)

    Kirillov, I.R. [NIIEFA – JSC “D.V. Efremov Institute of Electrophysical Apparatus”, St. Petersburg, 196641 (Russian Federation); Obukhov, D.M., E-mail: obukhov@sintez.niiefa.spb.su [NIIEFA – JSC “D.V. Efremov Institute of Electrophysical Apparatus”, St. Petersburg, 196641 (Russian Federation); Genin, L.G. [MPEI – National Research University “Moscow Power Engineering Institute”, 14 Krasnokazarmennaya str., Moscow (Russian Federation); Sviridov, V.G.; Razuvanov, N.G.; Batenin, V.M.; Belyaev, I.A. [JIHT – Joint Institute of High Temperatures of the Russian Academy of Science, 13/19, Igorskaya str., Moscow (Russian Federation); Poddubnyi, I.I. [MPEI – National Research University “Moscow Power Engineering Institute”, 14 Krasnokazarmennaya str., Moscow (Russian Federation); Pyatnitskaya, N.Yu. [JIHT – Joint Institute of High Temperatures of the Russian Academy of Science, 13/19, Igorskaya str., Moscow (Russian Federation)

    2016-03-15

    Highlights: • Heat transfer in vertical duct mercury flow in coplanar magnetic field is studied. • Mean velocity, temperature and temperature pulsations are measured. • Buoyancy influence on heat transfer is found. - Abstract: This article investigates an effect which was found out in downward flow of liquid metal (LM) in vertical rectangular duct in coplanar magnetic field (MF). The experiments have been performed on facility which located in JIHT. This facility is magneto hydrodynamic (MHD) mercury close-loop. The temperature field measurements have been performed at one side heating conditions in coplanar magnetic field. The averaged temperature fields, wall temperature distributions and statistical characteristics of temperature fluctuation have been obtained. The strong influence of counter thermo-gravitational convection (TGC) on average and fluctuation parameters has been observed. The influence of TGC in magnetic field leads to developing of temperature low-frequency fluctuations with high magnitude. The temperature fluctuation amplitude in a wide range of operating conditions is higher than turbulence level.

  11. Superhydrophobic treatment using atmospheric-pressure He/C4F8 plasma for buoyancy improvement

    Science.gov (United States)

    Noh, Sooryun; Moon, A.-Young; Moon, Se Youn

    2015-04-01

    A superhydrophobic miniature boat was fabricated with aluminum alloy plates treated with atmospheric-pressure helium (He)/octafluorocyclobutane (C4F8) plasma using 13.56 MHz rf power. When only 0.13% C4F8 was added to He gas, the contact angle of the surface increased to 140° and the surface showed superhydrophobic properties. On the basis of chemical and morphological analyses, fluorinated functional groups (CF, CF2, and CF3) and nano-/micro-sized particles were detected on the Al surface. These features brought about superhydrophobicity similar to the lotus effect. While the miniature boat, assembled with plasma-treated plates, was immersed in water, a layer of air (i.e., a plastron) surrounded the superhydrophobic surfaces. This effect contributed to the development of a 4.7% increase in buoyancy. In addition, the superhydrophobic properties lasted for two months under the submerged condition. These results demonstrate that treatment with atmospheric-pressure He/C4F8 plasma is a promising method of improving the load capacity and antifouling properties, and reducing the friction of marine ships through a fast and low-cost superhydrophobic treatment process.

  12. Hypergravity to Explore the Role of Buoyancy in Boiling in Porous Media

    Science.gov (United States)

    Lioumbas, John S.; Krause, Jutta; Karapantsios, Thodoris D.

    2013-02-01

    Boiling in porous media is an active topic of research since it is associated with various applications, e.g. microelectronics cooling, wetted porous media as thermal barriers, food frying. Theoretical expressions customary scale boiling heat and mass transfer rates with the value of gravitational acceleration. Information obtained at low gravity conditions show a deviation from the above scaling law but refers exclusively to non-porous substrates. In addition, the role of buoyancy in boiling at varying gravitational levels (i.e. from microgravity—important to satellites and future Lunar and Martial missions, to high-g body forces—associated with fast aerial maneuvers) is still unknown since most experiments were conducted over a limited range of g-value. The present work aims at providing evidence regarding boiling in porous media over a broad range of hypergravity values. For this, a special device has been constructed for studying boiling inside porous media in the Large Diameter Centrifuge (LDC at ESA/ESTEC). LDC offers the unique opportunity to cancel the shear stresses and study only the effect of increased normal forces on boiling in porous media. The device permits measurement of the temperature field beneath the surface of the porous material and video recordings of bubble activity over the free surface of the porous material. The preliminary results presented from experiments conducted at terrestrial and hypergravity conditions, reveal for the first time the influence of increased levels of gravity on boiling in porous media.

  13. Buoyancy-driven instability of a miscible horizontal displacement in a Hele-Shaw cell

    Science.gov (United States)

    Haudin, F.; Riolfo, L. A.; Knaepen, B.; de Wit, A.

    2012-11-01

    In Hele-Shaw cells, viscous fingers are forming when a fluid is injected into a more viscous one. If the two fluids are reversed, with the less mobile fluid injected into the low viscosity one, the situation is expected to be stable from a viscous point of view. Nevertheless, a destabilization of the interface can be observed due to a buoyancy-driven effect if a density difference exists between the two miscible fluids. As a result, the Poiseuille profile established in the gap of the cell locally destabilizes and convection rolls are forming. In a view from above, a striped pattern is observed at the miscible interface between the two fluids. To characterize the development of this instability, we have performed an experimental study of viscously stable miscible displacements in a Hele-Shaw cell with radial injection. The displacing fluids are aqueous solutions of glycerol and the displaced ones are either dyed water or dyed glycerol solutions. The way the relative properties of the two fluids is influencing the onset time of the instability and the characteristic size of the pattern is studied. The influence of the gap width and of the flow rate on the buoyantly unstable dynamics is also characterized.

  14. Influence of rheology on buoyancy driven instabilities of miscible displacements in 2D micromodels

    Science.gov (United States)

    D'Angelo, M. V.; Auradou, H.; Rosen, M.; Hulin, J. P.

    2009-05-01

    The stability of miscible displacements of Newtonian and shear-thinning fluids of slightly different densities (Δρ/ρ approx 3× 10-4) with a mean flow velocity U is investigated in a 2D transparent network of channels (average width = 0.33 mm). Concentration maps providing information at both the global and local scale are obtained through optical absorption measurements and compared in gravitationally stable and unstable vertical flow configurations; the influence of buoyant flows of typical velocity Ug is characterized by the gravity number Ng = Ug/|U|. For Ng glycerol solution, ld is only the same in the stable and unstable configurations for |Ng| 0.2, front spreading is not diffusive any more. In the stable configuration, in contrast, the front is flattened by buoyancy for Ng solution, both the concentration maps and the value of ld are the same in the stable and unstable configurations over the full range of U values investigated: this stabilization is explained by their high effective viscosity at low shear rates keeping Ng below the instability threshold even at the lowest velocities.

  15. Critical conditions for the buoyancy-driven detachment of a wall-bound pendant drop

    Science.gov (United States)

    Lamorgese, A.; Mauri, R.

    2016-03-01

    We investigate numerically the critical conditions for detachment of an isolated, wall-bound emulsion droplet acted upon by surface tension and wall-normal buoyancy forces alone. To that end, we present a simple extension of a diffuse-interface model for partially miscible binary mixtures that was previously employed for simulating several two-phase flow phenomena far and near the critical point [A. G. Lamorgese et al. "Phase-field approach to multiphase flow modeling," Milan J. Math. 79(2), 597-642 (2011)] to allow for static contact angles other than 90°. We use the same formulation of the Cahn boundary condition as first proposed by Jacqmin ["Contact-line dynamics of a diffuse fluid interface," J. Fluid Mech. 402, 57-88 (2000)], which accommodates a cubic (Hermite) interpolation of surface tensions between the wall and each phase at equilibrium. We show that this model can be successfully employed for simulating three-phase contact line problems in stable emulsions with nearly immiscible components. We also show a numerical determination of critical Bond numbers as a function of static contact angle by phase-field simulation.

  16. EFFECTS OF BUOYANCY RATIO ON CONVECTIVE HEAT AND SOLUTE TRANSFER IN NEWTONIAN FLUID SATURATED INCLINED POROUS CAVITY

    Directory of Open Access Journals (Sweden)

    A LATRECHE

    2014-12-01

    Full Text Available This paper summarizes a numerical study of the effects of buoyancy ratio on double-diffusive natural convection in square inclined cavity filled with fluid saturated porous media. Transverse gradients of heat and solute are applied on the two horizontal walls of the cavity, while the other two walls are impermeable and adiabatic. The Darcy model with the Boussinesq approximation is used to solve the governing equations. The flow is driven by a combined buoyancy effect due to both temperature and concentration variations. A finite volume approach has been used to solve the non-dimensional governing equations. The results are presented in streamline, isothermal, iso-concentration, Nusselt and Sherwood contours for different values of the non-dimensional governing parameters.

  17. Large eddy simulation of fire-induced buoyancy driven plume dispersion in an urban street canyon under perpendicular wind flow.

    Science.gov (United States)

    Hu, L H; Huo, R; Yang, D

    2009-07-15

    The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) x 18 m (height) x 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103-113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89-103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213-3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons--a large eddy simulation, Atmos. Environ. 38 (2004) 6883-6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934-949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire.

  18. Effects of salinity and sea salt type on egg activation, fertilization, buoyancy and early embryology of European eel, Anguilla anguilla

    DEFF Research Database (Denmark)

    Sørensen, Sune Riis; Butts, Ian; Munk, Peter;

    2016-01-01

    sizes, while the remaining four salt types resulted in smaller eggs. All salt types except NaCl treatments led to high fertilization rates and had no effect on fertilization success as well as egg neutral buoyancies at 7 h post-fertilization. The study points to the importance of considering ionic...... composition of the media when rearing fish eggs and further studies are encouraged...

  19. Geometric aspect and buoyancy effects on nature convection flow in the complex annuli filled with micropolar fluids

    Science.gov (United States)

    Chen, Wen Ruey

    2016-10-01

    This paper studies the steady laminar natural convection of micropolar fluids in the complex annuli between the inner sphere and outer vertical cylinder to present a numerical analysis of the flow and heat transfer characteristics with buoyancy effects. Computations were carried out systematically by the several different parameters of geometric ratio, micropolar material parameter and Rayleigh number to determine the average Nusselt number and the skin friction coefficient on the flow and the thermal fields.

  20. Velocity measurements and concentration field visualizations in copper electrolysis under the influence of Lorentz forces and buoyancy

    Science.gov (United States)

    Weier, T.; Cierpka, C.; Huller, J.; Gerbeth, G.

    2006-12-01

    Velocity measurements and shadowgraph visualizations for copper electrolysis under the influence of a magnetic field are reported. Experiments in a rectangular cell show the expected strong correlation between flow features and limiting current density. The flow can be understood as driven by the interplay of Lorentz force and buoyancy. For a cylindrical cell with only slightly non-parallel electric and magnetic field lines, the presence and importance of the Lorentz force is demonstrated by velocity measurements. Figs 6, Refs 13.

  1. Effects of buoyancy on lean premixed v-flames, Part II. VelocityStatistics in Normal and Microgravity

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, R.K.; Bedat, B.; Yegian, D.T.

    1999-07-01

    The field effects of buoyancy on laminar and turbulent premixed v-flames have been studied by the use of laser Doppler velocimetry to measure the velocity statistics in +1g, -1g and {micro}g flames. The experimental conditions covered mean velocity, Uo, of 0.4 to 2 m/s, methane/air equivalence ratio, f, of 0.62 to 0.75. The Reynolds numbers, from 625 to 3130 and the Richardson number from 0.05 to 1.34. The results show that a change from favorable (+1g) to unfavorable (-1g) mean pressure gradient in the plume create stagnating flows in the far field whose influences on the mean and fluctuating velocities persist in the near field even at the highest Re we have investigated. The use of Richardson number < 0.1 as a criterion for momentum dominance is not sufficient to prescribe an upper limit for these buoyancy effects. In {micro}g, the flows within the plumes are non-accelerating and parallel. Therefore, velocity gradients and hence mean strain rates in the plumes of laboratory flames are direct consequences of buoyancy. Furthermore, the rms fluctuations in the plumes of {micro}g flames are lower and more isotropic than in the laboratory flames to show that the unstable plumes in laboratory flames also induce velocity fluctuations. The phenomena influenced by buoyancy i.e. degree of flame wrinkling, flow acceleration, flow distribution, and turbulence production, can be subtle due to their close coupling with other flame flow interaction processes. But they cannot be ignored in fundamental studies or else the conclusions and insights would be ambiguous and not very meaningful.

  2. Pre-packaged applications in business reorganisations ...

    African Journals Online (AJOL)

    kirstam

    2015-01-20

    Jan 20, 2015 ... the company, usually to a new company (newco). ... Enterprise Act. This has addressed the risks pertaining to a lack of working capital ... uncertainty associated with selling a business after the process of insolvency had.

  3. Effects of buoyancy and thermal radiation on MHD flow over a stretching porous sheet using homotopy analysis method

    Directory of Open Access Journals (Sweden)

    Yahaya Shagaiya Daniel

    2015-09-01

    Full Text Available This paper investigates the theoretical influence of buoyancy and thermal radiation on MHD flow over a stretching porous sheet. The model which constituted highly nonlinear governing equations is transformed using similarity solution and then solved using homotopy analysis method (HAM. The analysis is carried out up to the 5th order of approximation and the influences of different physical parameters such as Prandtl number, Grashof number, suction/injection parameter, thermal radiation parameter and heat generation/absorption coefficient and also Hartman number on dimensionless velocity, temperature and the rate of heat transfer are investigated and discussed quantitatively with the aid of graphs. Numerical results obtained are compared with the previous results published in the literature and are found to be in good agreement. It was found that when the buoyancy parameter and the fluid velocity increase, the thermal boundary layer decreases. In case of the thermal radiation, increasing the thermal radiation parameter produces significant increases in the thermal conditions of the fluid temperature which cause more fluid in the boundary layer due to buoyancy effect, causing the velocity in the fluid to increase. The hydrodynamic boundary layer and thermal boundary layer thickness increase as a result of increase in radiation.

  4. Buoyancy-driven detachment of a wall-bound pendant drop: Interface shape at pinchoff and nonequilibrium surface tension

    Science.gov (United States)

    Lamorgese, A.; Mauri, R.

    2015-09-01

    We present numerical results from phase-field simulations of the buoyancy-driven detachment of an isolated, wall-bound pendant emulsion droplet acted upon by surface tension and wall-normal buoyancy forces alone. Our theoretical approach follows a diffuse-interface model for partially miscible binary mixtures which has been extended to include the influence of static contact angles other than 90∘, based on a Hermite interpolation formulation of the Cahn boundary condition as first proposed by Jacqmin [J. Fluid Mech. 402, 57 (2000), 10.1017/S0022112099006874]. In a previous work, this model has been successfully employed for simulating triphase contact line problems in stable emulsions with nearly immiscible components, and, in particular, applied to the determination of critical Bond numbers for buoyancy-driven detachment as a function of static contact angle. Herein, the shapes of interfaces at pinchoff are investigated as a function of static contact angle and distance to the critical condition. Furthermore, we show numerical results on the nonequilibrium surface tension that help to explain the discrepancy between our numerically determined static contact angle dependence of the critical Bond number and its sharp-interface counterpart based on a static stability analysis of equilibrium shapes after numerical integration of the Young-Laplace equation. Finally, we show the influence of static contact angle and distance to the critical condition on the temporal evolution of the minimum neck radius in the necking regime of drop detachment.

  5. Buoyancy-driven detachment of a wall-bound pendant drop: interface shape at pinchoff and nonequilibrium surface tension.

    Science.gov (United States)

    Lamorgese, A; Mauri, R

    2015-09-01

    We present numerical results from phase-field simulations of the buoyancy-driven detachment of an isolated, wall-bound pendant emulsion droplet acted upon by surface tension and wall-normal buoyancy forces alone. Our theoretical approach follows a diffuse-interface model for partially miscible binary mixtures which has been extended to include the influence of static contact angles other than 90^{∘}, based on a Hermite interpolation formulation of the Cahn boundary condition as first proposed by Jacqmin [J. Fluid Mech. 402, 57 (2000)JFLSA70022-112010.1017/S0022112099006874]. In a previous work, this model has been successfully employed for simulating triphase contact line problems in stable emulsions with nearly immiscible components, and, in particular, applied to the determination of critical Bond numbers for buoyancy-driven detachment as a function of static contact angle. Herein, the shapes of interfaces at pinchoff are investigated as a function of static contact angle and distance to the critical condition. Furthermore, we show numerical results on the nonequilibrium surface tension that help to explain the discrepancy between our numerically determined static contact angle dependence of the critical Bond number and its sharp-interface counterpart based on a static stability analysis of equilibrium shapes after numerical integration of the Young-Laplace equation. Finally, we show the influence of static contact angle and distance to the critical condition on the temporal evolution of the minimum neck radius in the necking regime of drop detachment.

  6. Analytical Investigation of Laminar Viscoelastic Fluid Flow over a Wedge in the Presence of Buoyancy Force Effects

    Directory of Open Access Journals (Sweden)

    B. Rostami

    2014-01-01

    Full Text Available An analytical strong method, the homotopy analysis method (HAM, is employed to study the mixed convective heat transfer in an incompressible steady two-dimensional viscoelastic fluid flow over a wedge in the presence of buoyancy effects. The two-dimensional boundary-layer governing partial differential equations (PDEs are derived by the consideration of Boussinesq approximation. By the use of similarity transformation, we have obtained the ordinary differential nonlinear (ODE forms of momentum and energy equations. The highly nonlinear forms of momentum and energy equations are solved analytically. The effects of different involved parameters such as viscoelastic parameter, Prandtl number, buoyancy parameter, and the wedge angle parameter, which is related to the exponent m of the external velocity, on velocity and temperature distributions are plotted and discussed. An excellent agreement can be seen between the results and the previously published papers for f′′(0 and θ′(0 in some of the tables and figures of the paper for velocity and temperature profiles for various values of viscoelastic parameter and Prandtl number. The effects of buoyancy parameter on the velocity and temperature distributions are completely illustrated in detail.

  7. Influence of various aspects of low Reynolds number k-ε turbulence models on predicting in-tube buoyancy affected heat transfer to supercritical pressure fluids

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Chen-Ru; Zhang, Zhen [Institute of Nuclear and New Energy Technology of Tsinghua University, Advanced Nuclear Energy Technology Cooperation Innovation Centre, Key Laboratory of Advanced Nuclear Engineering and Safety, Ministry of Education, Beijing 100084 (China); Jiang, Pei-Xue, E-mail: jiangpx@tsinghua.edu.cn [Beijing Key Laboratory of CO_2 Utilization and Reduction Technology/Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China); Bo, Han-Liang [Institute of Nuclear and New Energy Technology of Tsinghua University, Advanced Nuclear Energy Technology Cooperation Innovation Centre, Key Laboratory of Advanced Nuclear Engineering and Safety, Ministry of Education, Beijing 100084 (China)

    2017-03-15

    Highlights: • Understanding of the mechanism of buoyancy effect on supercritical heat transfer. • Turbulence related parameters in upward and downward flows were compared. • Turbulent Prandtl number affected the prediction insignificantly. • Buoyancy production was insignificant compared with shear production. • Damping function had the greatest effect and is a priority for further modification. - Abstract: Heat transfer to supercritical pressure fluids was modeled for normal and buoyancy affected conditions using several low Reynolds number k-ε models, including the Launder and Sharma, Myong and Kasagi, and Abe, Kondoh and Nagano, with the predictions compared with experimental data. All three turbulence models accurately predicted the cases without heat transfer deterioration, but failed to accurately predict the cases with heat transfer deterioration although the general trends were captured, indicating that further improvements and modifications are needed for the low Reynolds number k-ε turbulence models to better predict buoyancy deteriorated heat transfer. Further investigations studied the influence of various aspects of the low Reynolds number k-ε turbulence models, including the turbulent Prandtl number, the buoyancy production of turbulent kinetic energy, and the damping function to provide guidelines for model development to more precisely predict buoyancy affected heat transfer. The results show that the turbulent Prandtl number and the buoyancy production of turbulent kinetic energy have little influence on the predictions for cases in this study, while new damping functions with carefully selected control parameters are needed in the low Reynolds number k-ε turbulence models to correctly predict the buoyancy effect for heat transfer simulations in various applications such as supercritical pressure steam generators (SPSGs) in the high temperature gas cooled reactor (HTR) and the supercritical pressure water reactor (SCWR).

  8. Large Eddy simulation of turbulence: A subgrid scale model including shear, vorticity, rotation, and buoyancy

    Science.gov (United States)

    Canuto, V. M.

    1994-01-01

    The Reynolds numbers that characterize geophysical and astrophysical turbulence (Re approximately equals 10(exp 8) for the planetary boundary layer and Re approximately equals 10(exp 14) for the Sun's interior) are too large to allow a direct numerical simulation (DNS) of the fundamental Navier-Stokes and temperature equations. In fact, the spatial number of grid points N approximately Re(exp 9/4) exceeds the computational capability of today's supercomputers. Alternative treatments are the ensemble-time average approach, and/or the volume average approach. Since the first method (Reynolds stress approach) is largely analytical, the resulting turbulence equations entail manageable computational requirements and can thus be linked to a stellar evolutionary code or, in the geophysical case, to general circulation models. In the volume average approach, one carries out a large eddy simulation (LES) which resolves numerically the largest scales, while the unresolved scales must be treated theoretically with a subgrid scale model (SGS). Contrary to the ensemble average approach, the LES+SGS approach has considerable computational requirements. Even if this prevents (for the time being) a LES+SGS model to be linked to stellar or geophysical codes, it is still of the greatest relevance as an 'experimental tool' to be used, inter alia, to improve the parameterizations needed in the ensemble average approach. Such a methodology has been successfully adopted in studies of the convective planetary boundary layer. Experienc e with the LES+SGS approach from different fields has shown that its reliability depends on the healthiness of the SGS model for numerical stability as well as for physical completeness. At present, the most widely used SGS model, the Smagorinsky model, accounts for the effect of the shear induced by the large resolved scales on the unresolved scales but does not account for the effects of buoyancy, anisotropy, rotation, and stable stratification. The

  9. Tectonic controls on earthquake size distribution and seismicity rate: slab buoyancy and slab bending

    Science.gov (United States)

    Nishikawa, T.; Ide, S.

    2014-12-01

    There are clear variations in maximum earthquake magnitude among Earth's subduction zones. These variations have been studied extensively and attributed to differences in tectonic properties in subduction zones, such as relative plate velocity and subducting plate age [Ruff and Kanamori, 1980]. In addition to maximum earthquake magnitude, the seismicity of medium to large earthquakes also differs among subduction zones, such as the b-value (i.e., the slope of the earthquake size distribution) and the frequency of seismic events. However, the casual relationship between the seismicity of medium to large earthquakes and subduction zone tectonics has been unclear. Here we divide Earth's subduction zones into over 100 study regions following Ide [2013] and estimate b-values and the background seismicity rate—the frequency of seismic events excluding aftershocks—for subduction zones worldwide using the maximum likelihood method [Utsu, 1965; Aki, 1965] and the epidemic type aftershock sequence (ETAS) model [Ogata, 1988]. We demonstrate that the b-value varies as a function of subducting plate age and trench depth, and that the background seismicity rate is related to the degree of slab bending at the trench. Large earthquakes tend to occur relatively frequently (lower b-values) in shallower subduction zones with younger slabs, and more earthquakes occur in subduction zones with deeper trench and steeper dip angle. These results suggest that slab buoyancy, which depends on subducting plate age, controls the earthquake size distribution, and that intra-slab faults due to slab bending, which increase with the steepness of the slab dip angle, have influence on the frequency of seismic events, because they produce heterogeneity in plate coupling and efficiently inject fluid to elevate pore fluid pressure on the plate interface. This study reveals tectonic factors that control earthquake size distribution and seismicity rate, and these relationships between seismicity and

  10. Microliter-bioreactor array with buoyancy-driven stirring for human hematopoietic stem cell culture.

    Science.gov (United States)

    Luni, Camilla; Feldman, Hope C; Pozzobon, Michela; De Coppi, Paolo; Meinhart, Carl D; Elvassore, Nicola

    2010-08-11

    This work presents the development of an array of bioreactors where finely controlled stirring is provided at the microliter scale (100-300 mul). The microliter-bioreactor array is useful for performing protocol optimization in up to 96 parallel experiments of hematopoietic stem cell (HSC) cultures. Exploring a wide range of experimental conditions at the microliter scale minimizes cost and labor. Once the cell culture protocol is optimized, it can be applied to large-scale bioreactors for stem cell production at the clinical level. The controlled stirring inside the wells of a standard 96-well plate is provided by buoyancy-driven thermoconvection. The temperature and velocity fields within the culture volume are determined with numerical simulations. The numerical results are verified with experimental velocity measurements using microparticle image velocimetry (muPIV) and are used to define feasible experimental conditions for stem cell cultures. To test the bioreactor array's functionality, human umbilical cord blood-derived CD34(+) cells were cultured for 7 days at five different stirring conditions (0.24-0.58 mums) in six repeated experiments. Cells were characterized in terms of proliferation, and flow cytometry measurements of viability and CD34 expression. The microliter-bioreactor array demonstrates its ability to support HSC cultures under stirred conditions without adversely affecting the cell behavior. Because of the highly controlled operative conditions, it can be used to explore culture conditions where the mass transport of endogenous and exogenous growth factors is selectively enhanced, and cell suspension provided. While the bioreactor array was developed for culturing HSCs, its application can be extended to other cell types.

  11. Numerical analysis of two and three dimensional buoyancy driven water-exit of a circular cylinder

    Directory of Open Access Journals (Sweden)

    Moshari Shahab

    2014-06-01

    Full Text Available With the development of the technology of underwater moving bodies, the need for developing the knowledge of surface effect interaction of free surface and underwater moving bodies is increased. Hence, the two-phase flow is a subject which is interesting for many researchers all around the world. In this paper, the non-linear free surface deformations which occur during the water-exit of a circular cylinder due to its buoyancy are solved using finite volume discretization based code, and using Volume of Fluid (VOF scheme for solving two phase flow. Dynamic mesh model is used to simulate dynamic motion of the cylinder. In addition, the effect of cylinder mass in presence of an external force is studied. Moreover, the oblique exit and entry of a circular cylinder with two exit angles is simulated. At last, water-exit of a circular cylinder in six degrees of freedom is simulated in 3D using parallel processing. The simulation errors of present work (using VOF method for maximum velocity and height of a circular cylinder are less than the corresponding errors of level set method reported by previous researchers. Oblique exit shows interesting results; formation of waves caused by exit of the cylinder, wave motion in horizontal direction and the air trapped between the waves are observable. In 3D simulation the visualization of water motion on the top surface of the cylinder and the free surface breaking on the front and back faces of the 3D cylinder at the exit phase are observed which cannot be seen in 2D simulation. Comparing the results, 3D simulation shows better agreement with experimental data, specially in the maximum height position of the cylinder.

  12. Investing the role of buoyancy in iceberg calving dynamics from tidewater glaciers

    Science.gov (United States)

    Trevers, Matt; Payne, Tony; Cornford, Stephen

    2016-04-01

    The Greenland Ice Sheet (GIS) currently makes a major and accelerating contribution to sea level rise (SLR), with its contribution split roughly evenly between surface mass balance changes due to increased melting and dynamic ice loss through calving. In recent decades, many of Greenland's major outlet glaciers have retreated dramatically due to increased iceberg calving, associated with an increase in velocity and inland thinning. The potential contribution to SLR of a complete collapse of the GIS is ~7m. Iceberg calving is an important process not only as a major source of mass loss from the GIS, but also for the controlling influence it has on the dynamics of the grounding line and over the ice sheet as a whole. Despite plenty of scientific attention and a diverse body of literature, the processes involved in calving, their controlling factors and how it feeds back into glacier and ice sheet dynamics are still not fully understood. This presents a major uncertainty into projections of SLR over the coming decades and centuries. Using Elmer/Ice, a state-of-the-art full-Stokes finite-element model, we are able to resolve the stress distributions in high resolution at the calving front. Buoyancy forces have been proposed as a major influencing factor in inducing calving. By investigating the stress distributions induced in a buoyant calving front, we hope to gain an understanding of how environmental influences such as surface thinning and waterline notch-cutting influence the calving rate, and compare this to observations from calving glaciers in Greenland.

  13. Composition, buoyancy regulation and fate of ice algal aggregates in the Central Arctic Ocean.

    Directory of Open Access Journals (Sweden)

    Mar Fernández-Méndez

    Full Text Available Sea-ice diatoms are known to accumulate in large aggregates in and under sea ice and in melt ponds. There is recent evidence from the Arctic that such aggregates can contribute substantially to particle export when sinking from the ice. The role and regulation of microbial aggregation in the highly seasonal, nutrient- and light-limited Arctic sea-ice ecosystem is not well understood. To elucidate the mechanisms controlling the formation and export of algal aggregates from sea ice, we investigated samples taken in late summer 2011 and 2012, during two cruises to the Eurasian Basin of the Central Arctic Ocean. Spherical aggregates densely packed with pennate diatoms, as well as filamentous aggregates formed by Melosira arctica showed sign of different stages of degradation and physiological stoichiometries, with carbon to chlorophyll a ratios ranging from 110 to 66700, and carbon to nitrogen molar ratios of 8-35 and 9-40, respectively. Sub-ice algal aggregate densities ranged between 1 and 17 aggregates m(-2, maintaining an estimated net primary production of 0.4-40 mg C m(-2 d(-1, and accounted for 3-80% of total phototrophic biomass and up to 94% of local net primary production. A potential factor controlling the buoyancy of the aggregates was light intensity, regulating photosynthetic oxygen production and the amount of gas bubbles trapped within the mucous matrix, even at low ambient nutrient concentrations. Our data-set was used to evaluate the distribution and importance of Arctic algal aggregates as carbon source for pelagic and benthic communities.

  14. Thermo capillary and buoyancy flows instabilities; Instabilites d`ecoulements thermocapillaires et de thermogravite

    Energy Technology Data Exchange (ETDEWEB)

    Mercier, J.F.

    1997-10-22

    Fluid flows in which liquid layers are submitted to temperature gradient applied horizontally are studied. The thermo capillary and buoyancy effects are thus described. In the experiments, the form of the cell which contains the fluid is different and the fluid heating position too. Each of these experiments reveals a different aspect of the mechanism which is responsible of the flow instability. In the first experiment, the fluid is contained in a rectangular cell longer than larger and whose two longer vertical walls are differentially heated. The waves lengths, frequencies, propagation directions and instability thresholds of stationary, unsteady or oscillating modes obtained theoretically are compared to the structures observed experimentally. The instability mechanisms are essentially bound to the temperature vertical profile in the fluid and the heat exchanges between the fluid and the ambient air are particularly described. In the second experiment, the fluid is contained in an annular cell whose vertical cylindrical walls are differentially heated. The results obtained in the rectangular cell can be transposed to the annular cell substituting the constant thermal gradient of the rectangular geometry by those of the annular geometry, inversely proportional to the radial distance. The introduction of local parameters allows to show that the instability is developed at first near the inside cylinder. In the last experiment, the fluid layer is heated by an electric wire immersed in a parallel direction to the free surface. The development of an ascending vertical flow above the wire induces a deformation of the free surface which can be added to the instability mechanisms of the previous cells. (O.M.) 58 refs.

  15. Composition, buoyancy regulation and fate of ice algal aggregates in the Central Arctic Ocean.

    Science.gov (United States)

    Fernández-Méndez, Mar; Wenzhöfer, Frank; Peeken, Ilka; Sørensen, Heidi L; Glud, Ronnie N; Boetius, Antje

    2014-01-01

    Sea-ice diatoms are known to accumulate in large aggregates in and under sea ice and in melt ponds. There is recent evidence from the Arctic that such aggregates can contribute substantially to particle export when sinking from the ice. The role and regulation of microbial aggregation in the highly seasonal, nutrient- and light-limited Arctic sea-ice ecosystem is not well understood. To elucidate the mechanisms controlling the formation and export of algal aggregates from sea ice, we investigated samples taken in late summer 2011 and 2012, during two cruises to the Eurasian Basin of the Central Arctic Ocean. Spherical aggregates densely packed with pennate diatoms, as well as filamentous aggregates formed by Melosira arctica showed sign of different stages of degradation and physiological stoichiometries, with carbon to chlorophyll a ratios ranging from 110 to 66700, and carbon to nitrogen molar ratios of 8-35 and 9-40, respectively. Sub-ice algal aggregate densities ranged between 1 and 17 aggregates m(-2), maintaining an estimated net primary production of 0.4-40 mg C m(-2) d(-1), and accounted for 3-80% of total phototrophic biomass and up to 94% of local net primary production. A potential factor controlling the buoyancy of the aggregates was light intensity, regulating photosynthetic oxygen production and the amount of gas bubbles trapped within the mucous matrix, even at low ambient nutrient concentrations. Our data-set was used to evaluate the distribution and importance of Arctic algal aggregates as carbon source for pelagic and benthic communities.

  16. 2008年和2010年杭州市国产预包装食品营养标签标示变化调查%Change of nutrition labeling on domestie prepackaged food in Hangzhou in 2008 and 2010

    Institute of Scientific and Technical Information of China (English)

    王胜锋; 孙点剑一; 杜宇坤; 刘淼; 洪志恒; 刘庆敏; 任艳军; 吕筠; 李立明

    2011-01-01

    目的 了解《食品营养标签管理规范》实施前后预包装食品营养标签标示变化情况.方法2008年、2010年两次抄录超市预包装食品的营养标签,并判断其规范性.结果 两次分别调查国产预包装食品4 693种、5 526种,2008年标示营养成分表、营养声称和营养成分功能声称的分别为1 369种(27.6%)、643种(13.0%)和94种(1.9%),2010年分别为1 937种(35.1%)、424种(7.7%)和128种(2.3%).营养成分表中能量、蛋白质、脂肪、碳水化合物和钠均标示的分别为597种(43.8%)、1 661种(85.9%),其中形式全部规范的分别有134种(9.8%)、985种(51.0%).营养声称和营养成分功能声称主要涵盖维生素、钙、膳食纤维.结论 鼓励性规范对营养标签标示率的影响较小,但显著提高了标示规范性.营养标签强制标示势在必行,健康教育工作也应同步开展.%Objective To survey the change of nutrition labeling on prepackaged food in Hangzhou supermarkets before and two years after promulgating the Regulation for Food Nutrition Labeling. Methods Nutrition facts, nutrition claims and nutrient function claims on prepackaged food in a supermarket were copied with prepared questionnaire in 2008 and 2010, and a normative judgment was made. Results There were 4 693 and 5 526 kinds of domestic prepackaged food investigated in 2008 and 2010, respectively. The number of prepackaged foods labeled with nutrition facts, nutrition claims and nutrient function claims was 1 369 (27.6%), 643 (13.0%) and 94 (1.9%) in 2008, and that was 1 937 (35. 1% ) , 424 (7. 7% ) and 128 (2. 3% ) in 2010, respectively. The number of nutrition facts labeled with energy, protein, fat, carbohydrate and sodium was 597 (43. 8% ) and 1 661 (85. 9% ) in 2008 and 2010, respectively; but only 134 (9. 8% ) and 985 (51. 0% ) of labeling were normalized. Nutrition claims and nutrient function claims were focused on vitamin, calcium and fiber. Conclusion Although

  17. Buoyancy-induced squeezing of a deformable drop through an axisymmetric ring constriction

    Science.gov (United States)

    Ratcliffe, Thomas; Zinchenko, Alexander Z.; Davis, Robert H.

    2010-08-01

    Axisymmetric boundary-integral (BI) simulations were made for buoyancy-induced squeezing of a deformable drop through a ring constriction. The algorithm uses the Hebeker representation for the solid-particle contribution. A high-order, near-singularity subtraction technique is essential for near-critical squeezing. The drop velocity and minimum drop-solid spacing were determined for different ring and hole sizes, viscosity ratios, and Bond numbers, where the latter is a dimensionless ratio of gravitational to interfacial forces. The drop velocity decelerates typically 100-fold or more, and the drop-solid spacing reduces to typically 0.1%-1% of the nondeformed drop radius as the drop passes through the constriction. The critical Bond number (below which trapping occurs) was determined for different conditions. For supercritical conditions, the nondimensional time required for the drop to pass through the ring increases for a fixed drop-to-hole size with increasing viscosity ratio and decreasing Bond number, but it has a nonmonotonic dependence on the ratio of the radii of the drop and ring cross section. Numerical results indicate that the square of the drop squeezing time is inversely proportional to the Bond number minus the critical Bond number for near-critical squeezing. The critical Bond number, determined from dynamic BI calculations, compares favorably to that obtained precisely from a static algorithm. The static algorithm uses the Young-Laplace equation to calculate the pendant and sessile portions of the drop interface coupled through the conditions of global pressure continuity and total drop volume conservation. Over a limited parameter space, the critical Bond number increases almost linearly with the drop-to-hole ratio and is a weak function of the ratio of the ring cross-sectional radius to the hole radius. Another dynamic phenomenon, in addition to drop squeezing, is a drop "dripping" around the outer edge of the ring constriction, and a critical

  18. Buoyancy induced limits for nanoparticle synthesis experiments in horizontal premixed low-pressure flat-flame reactors

    Science.gov (United States)

    Weise, C.; Faccinetto, A.; Kluge, S.; Kasper, T.; Wiggers, H.; Schulz, C.; Wlokas, I.; Kempf, A.

    2013-06-01

    Premixed low-pressure flat-flame reactors can be used to investigate the synthesis of nanoparticles. The present work examines the flow field inside such a reactor during the formation of carbon (soot) and iron oxide (from Fe(CO)5) nanoparticles, and how it affects the measurements of nanoparticle size distribution. The symmetry of the flow and the impact of buoyancy were analysed by three-dimensional simulations and the nanoparticle size distribution was obtained by particle mass spectrometry (PMS) via molecular beam sampling at different distances from the burner. The PMS measurements showed a striking, sudden increase in particle size at a critical distance from the burner, which could be explained by the flow field predicted in the simulations. The simulation results illustrate different fluid mechanical phenomena which have caused this sudden rise in the measured particle growth. Up to the critical distance, buoyancy does not affect the flow, and an (almost) linear growth is observed in the PMS experiments. Downstream of this critical distance, buoyancy deflects the hot gas stream and leads to an asymmetric flow field with strong recirculation. These recirculation zones increase the particle residence time, inducing very large particle sizes as measured by PMS. This deviation from the assumed symmetric, one-dimensional flow field prevents the correct interpretation of the PMS results. To overcome this problem, modifications to the reactor were investigated; their suitability to reduce the flow asymmetry was analysed. Furthermore, 'safe' operating conditions were identified for which accurate measurements are feasible in premixed low-pressure flat-flame reactors that are transferrable to other experiments in this type of reactor. The present work supports experimentalists to find the best setup and operating conditions for their purpose.

  19. Solutions to Buoyancy-Drag Equation for Dynamical Evolution of Rayleigh-Taylor and Richtmyer-Meshkov Mixing Zone

    Institute of Scientific and Technical Information of China (English)

    Y.G. Cao; W.K. Chow; N.K. Fong

    2011-01-01

    With a self-similar parameter b(At) = Hi/λi, where At is the Atwood number, Hi and λi are the a.mplluae and wavelength of bubble (i = 1) and spike (i = 2) respectively, we derive analytically the solutions to the buoyancy-drag equation recently proposed for dynamical evolution of Rayleigh-Taylor and Richtmyer-Meshkov mixing zone. Numerical solutions are obtained with a simple form ofb(At)--- 1/(1 + At) and comparisons with recent LEM (linear electric motor) experiments are made, and an agreement is found with properly chosen initial conditions.

  20. Experimental study of gliding arc plasma channel motion: buoyancy and gas flow phenomena under normal and hypergravity conditions

    Science.gov (United States)

    Potočňáková, Lucia; Šperka, Jiří; Zikán, Petr; van Loon, Jack J. W. A.; Beckers, Job; Kudrle, Vít

    2017-04-01

    The details of plasma channel motion are investigated by frame-by-frame image analysis of high speed recording of a gliding arc. The gliding arc is operated in several noble gases at various flow rates, voltages and artificial gravity levels. Several peculiarities in evolution of individual glides are observed, described and discussed, such as accelerating motion of plasma channel or shortcutting events of various kinds. Statistics of averaged parameters are significantly different for buoyancy and gas drag dominated regimes, which is put into relation with differing flow patterns for hypergravity and high gas flow.

  1. Effect of Thermal Buoyancy on Fluid Flow and Inclusion Motion in Tundish without Flow Control Devices--Part Ⅱ: Inclusion Motion

    Institute of Scientific and Technical Information of China (English)

    ZHANG Li-feng

    2005-01-01

    Following up the fluid flow simulation in a 60 t tundish, the trajectories of inclusions in the 60 t tundish without flow control are simulated by considering the force balance between the drag force and the inertial buoyancy force. The Stochastic model yields more accurate inclusion motion than the non-Stochastic model due to including the effect of the turbulent fluctuation. The average residence time of inclusions decreases with increasing size. The thermal buoyancy favors inclusions removal especially the small inclusions. Using solute transport like the dye injection in water model and copper addition in the real steel tundish cannot accurately study the motion of the inclusions. In the simulation, more than 68% inclusions bigger than 10μm are removed to the top, and less than 32% enters the mold. The thermal buoyancy has little effect on the fraction of inclusions moved to the top of the inlet zone, and it mainly favors the removal of inclusions smaller than 100μm to the top surface of the outlet zone. For inclusions bigger than 100μm , the effect of thermal buoyancy on their motion can be ignored compared to the inertial buoyancy effect.

  2. Consumers’ understanding and use of nutrition labels on pre-packaged food in Taiyuan%太原市消费者预包装食品营养标签认知能力调查

    Institute of Scientific and Technical Information of China (English)

    唐海英; 马玲玲; 崔杉杉

    2013-01-01

    目的:了解太原市消费者对预包装食品营养标签的认知、使用现状及相关营养知识水平,为开展相关的营养教育和宣传提供依据。方法:采用自行设计的调查问卷,问卷的内容包括:被调查者的基本资料、对营养标签认知和使用状况、营养知识等,并采用随机分层抽样方法,于2013年4~5月,在太原市6个区内随机调查400名消费者,每区比例均衡。以调查员询问和被调查者自填相结合的问卷调查方法收集资料。由调查者对被调查者以面对面的方式进行,确保资料完整,数据符合要求。并应用SPSS软件对数据进行分析。结果:接受调查400人,有效问卷为390份,其中男性152人,女性238人,年龄(35.2±14.3)岁。食品营养标签的知晓率为79.3%;对标签内容和形式的满意度为83.3%;认为营养声称和营养成分功能声称有帮助的比例分别为68.7%和68.3%;43.3%的消费者总是经常阅读营养成分表,目的主要是了解食物的营养特性,合理膳食;有61.8%的消费者愿意依据营养标签提供的信息改变购买决策。分析食品营养标签对食品购买影响的相关因素进行Logistic回归建模,发现经常阅读营养成分表、认为营养声称有帮助的消费者更愿意依据标签所提供的信息决定购买选择。结论:消费者对营养标签的信任度和理解度较低,对营养标签认知和使用水平不高,为使消费者能够实际应用营养标签达到合理膳食的目的,建议加强对消费者使用营养标签的宣传教育。%OBJECTIVE:To study the cognition status and using of pre-packaged food nutrition labeling and related knowledge of nutrition in Taiyuan consumers and to provide basis for nutrition education and publicity. METHODS:A self-designed questionnaire included the basic data of respondents,nutrition labeling cognition and usage,nutrition knowledge. Using stratified

  3. Fatal nosocomial Legionnaires' disease: relevance of contamination of hospital water supply by temperature-dependent buoyancy-driven flow from spur pipes.

    Science.gov (United States)

    Patterson, W J; Seal, D V; Curran, E; Sinclair, T M; McLuckie, J C

    1994-06-01

    The investigation, epidemiology, and effectiveness of control procedures during an outbreak of Legionnaires' disease involving three immunosuppressed patients are described. The source of infection appeared to be a network of fire hydrant spurs connected directly to the incoming hospital mains water supply. Removal of these hydrants considerably reduced, but failed to eliminate, contamination of water storage facilities. As an emergency control procedure the incoming mains water was chlorinated continuously. Additional modifications to improve temperature regulation and reduce stagnation also failed to eliminate the legionellae. A perspex test-rig was constructed to model the pre-existing hospital water supply and storage system. This showed that through the hydraulic mechanism known as 'temperature buoyancy', contaminated water could be efficiently and quickly exchanged between a stagnant spur pipe and its mains supply. Contamination of hospital storage tanks from such sources has not previously been considered a risk factor for Legionnaires' disease. We recommend that hospital water storage tanks are supplied by a dedicated mains pipe without spurs.

  4. Analysis of Thermal-Hydraulic Gravity/ Buoyancy Effects in the Testing of the ITER Poloidal Field Full Size Joint Sample (PF-FSJS)

    Science.gov (United States)

    Zanino, R.; Bruzzone, P.; Ciazynski, D.; Ciotti, M.; Gislon, P.; Nicollet, S.; Savoldi Richard, L.

    2004-06-01

    The PF-FSJS is a full-size joint sample, based on the NbTi dual-channel cable-in-conduit conductor (CICC) design currently foreseen for the International Thermonuclear Experimental Reactor (ITER) Poloidal Field coil system. It was tested during the summer of 2002 in the Sultan facility of CRPP at a background peak magnetic field of typically 6 T. It includes about 3 m of two jointed conductor sections, using different strands but with identical layout. The sample was cooled by supercritical helium at nominal 4.5-5.0 K and 0.9-1.0 MPa, in forced convection from the top to the bottom of the vertical configuration. A pulsed coil was used to test AC losses in the two legs resulting, above a certain input power threshold, in bundle helium backflow from the heated region. Here we study the thermal-hydraulics of the phenomenon with the M&M code, with particular emphasis on the effects of buoyancy on the helium dynamics, as well as on the thermal-hydraulic coupling between the wrapped bundles of strands in the annular cable region and the central cooling channel. Both issues are ITER relevant, as they affect the more general question of the heat removal capability of the helium in this type of conductors.

  5. Heart Rate Responses to Unaided Orion Side Hatch Egress in the Neutral Buoyancy Laboratory

    Science.gov (United States)

    English, Kirk L.; Hwang Emma Y.; Ryder, Jeffrey W.; Kelly, Cody; Walker, Thomas; Ploutz-Snyder, Lori L.

    2016-01-01

    NASA is developing the Orion capsule as a vehicle for transporting crewmembers to and from the International Space Station (ISS) and for future human space exploration missions. Orion and other commercial vehicles are designed to splash down in the ocean where nominally support personnel will assist crewmembers in egressing the vehicle. However, off-nominal scenarios will require crewmembers to egress the vehicle unaided, deploy survival equipment, and ingress a life raft. PURPOSE: To determine the heart rate (HR) responses to unaided Orion side hatch egress and raft ingress as a part of the NASA Crew Survival Engineering Team's evaluation of the PORT Orion mockup in the Neutral Buoyancy Laboratory (NBL). METHODS: Nineteen test subjects, including four astronauts (N=19, 14 males/5 females, 38.6+/-8.4 y, 174.4+/-9.6 cm, 75.7+/-13.1 kg), completed a graded maximal test on a cycle ergometer to determine VO2peak and HRpeak and were divided into five crews of four members each; one subject served on two crews. Each crew was required to deploy a life raft, egress the Orion vehicle from the side hatch, and ingress the life raft with two 8 kg emergency packs per crew. Each crew performed this activity one to three times; a total of ten full egresses were completed. Subjects wore a suit that was similar in form, mass, and function to the Modified Advanced Crew Escape Suit (MACES) including helmet, gloves, boots, supplemental O2 bottles, and a CO2-inflated life preserver (approx.18 kg); subjects began each trial seated supine in the PORT Orion mockup with seat belts and mockup O2 and communication connections and ended each trial with all four crewmembers inside the life raft. RESULTS: VO2peak was 40.8+/-6.8 mL/kg/min (3.1+/-0.7 L/min); HRpeak was 181+/-10 bpm. Total egress time across trials was 5.0+/-1.6 min (range: 2.8-8.0 min); all subjects were able to successfully complete all trials. Average maximum HR at activity start, at the hatch opening, in the water, and in the

  6. Numerical investigation of double diffusive buoyancy forces induced natural convection in a cavity partially heated and cooled from sidewalls

    Directory of Open Access Journals (Sweden)

    Rasoul Nikbakhti

    2016-03-01

    Full Text Available This paper deals with a numerical investigation of double-diffusive natural convective heat and mass transfer in a cavity filled with Newtonian fluid. The active parts of two vertical walls of the cavity are maintained at fixed but different temperatures and concentrations, while the other two walls, as well as inactive areas of the sidewalls, are considered to be adiabatic and impermeable to mass transfer. The length of the thermally active part equals half of the height. The non-dimensional forms of governing transport equations that describe double-diffusive natural convection for two-dimensional incompressible flow are functions of temperature or energy, concentration, vorticity, and stream-function. The coupled differential equations are discretized via FDM (Finite Difference Method. The Successive-Over-Relaxation (SOR method is used in the solution of the stream function equation. The analysis has been done for an enclosure with different aspect ratios ranging from 0.5 to 11 for three different combinations of partially active sections. The results are presented graphically in terms of streamlines, isotherms and isoconcentrations. In addition, the heat and mass transfer rate in the cavity is measured in terms of the average Nusselt and Sherwood numbers for various parameters including thermal Grashof number, Lewis number, buoyancy ratio and aspect ratio. It is revealed that the placement order of partially thermally active walls and the buoyancy ratio influence significantly the flow pattern and the corresponding heat and mass transfer performance in the cavity.

  7. Numerical Investigation of Heat Transfer with Thermal Radiation in an Enclosure in Case of Buoyancy Driven Flow

    Directory of Open Access Journals (Sweden)

    Christoph Hochenauer

    2014-08-01

    Full Text Available The purpose of this paper is to investigate state of the art approaches and their accuracy to compute heat transfer including radiation inside a closed cavity whereas buoyancy is the only driving force. This research is the first step of an all-embracing study dealing with underhood airflow and thermal management of vehicles. Computational fluid dynamic (CFD simulation results of buoyancy driven flow inside a simplified engine compartment are compared to experimentally gained values. The test rig imitates idle condition without any working fan. Thus, the airflow is only driven by natural convection. A conventional method used for these applications is to compute the convective heat transfer coefficient and air temperature using CFD and calculate the wall temperature separately by performing a thermal analysis. The final solution results from coupling two different software tools. In this paper thermal conditions inside the enclosure are computed by the use of CFD only. The impact of the turbulence model as well as the results of various radiation models are analyzed and compared to the experimental data.

  8. Buoyancy and Dissolution of the Floating Crust Layer in Tank 241-SY-101 During Transfer and Back-Dilution

    Energy Technology Data Exchange (ETDEWEB)

    CW Stewart; JH Sukamto; JM Cuta; SD Rassat

    1999-11-22

    To remediate gas retention in the floating crust layer and the potential for buoyant displacement gas releases from below the crust, waste will be transferred out of Hanford Tank 241-SY-101 (SY-101) in the fall of 1999 and back-diluted with water in several steps of about 100,000 gallons each. To evaluate the effects of back-dilution on the crust a static buoyancy model is derived that predicts crust and liquid surface elevations as a function of mixing efficiency and volume of water added during transfer and back-dilution. Experimental results are presented that demonstrate the basic physics involved and verify the operation of the models. A dissolution model is also developed to evaluate the effects of dissolution of solids on crust flotation. The model includes dissolution of solids suspended in the slurry as well as in the crust layers. The inventory and location of insoluble solids after dissolution of the soluble fraction are also tracked. The buoyancy model is applied to predict the crust behavior for the first back-dilution step in SY-101. Specific concerns addressed include conditions that could cause the crust to sink and back-dilution requirements that keep the base of the crust well above the mixer pump inlet.

  9. Implementing Nonlinear Buoyancy and Excitation Forces in the WEC-Sim Wave Energy Converter Modeling Tool: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Lawson, M.; Yu, Y. H.; Nelessen, A.; Ruehl, K.; Michelen, C.

    2014-05-01

    Wave energy converters (WECs) are commonly designed and analyzed using numerical models that combine multi-body dynamics with hydrodynamic models based on the Cummins Equation and linearized hydrodynamic coefficients. These modeling methods are attractive design tools because they are computationally inexpensive and do not require the use of high performance computing resources necessitated by high-fidelity methods, such as Navier Stokes computational fluid dynamics. Modeling hydrodynamics using linear coefficients assumes that the device undergoes small motions and that the wetted surface area of the devices is approximately constant. WEC devices, however, are typically designed to undergo large motions in order to maximize power extraction, calling into question the validity of assuming that linear hydrodynamic models accurately capture the relevant fluid-structure interactions. In this paper, we study how calculating buoyancy and Froude-Krylov forces from the instantaneous position of a WEC device (referred to as instantaneous buoyancy and Froude-Krylov forces from herein) changes WEC simulation results compared to simulations that use linear hydrodynamic coefficients. First, we describe the WEC-Sim tool used to perform simulations and how the ability to model instantaneous forces was incorporated into WEC-Sim. We then use a simplified one-body WEC device to validate the model and to demonstrate how accounting for these instantaneously calculated forces affects the accuracy of simulation results, such as device motions, hydrodynamic forces, and power generation.

  10. Calculation of ice clearing resistance using normal vector of hull form and direct calculation of buoyancy force under the hull

    Directory of Open Access Journals (Sweden)

    Kyung-Duk Park

    2015-07-01

    Full Text Available The ice-resistance estimation technique for icebreaking ships had been studied intensively over recent years to meet the needs of designing Arctic vessels. Before testing in the ice model basin, the estimation of a ship’s ice resistance with high reliability is very important to decide the delivered power necessary for level ice operation. The main idea of previous studies came from several empirical formulas, such as Poznyak and Ionov (1981, Enkvist (1972 and Shimansky (1938 methods, in which ice resistance components such as icebreaking, buoyancy and clearing resistances were represented by the integral equations along the Design Load Water Line (DLWL. The current study proposes a few modified methods not only considering the DLWL shape, but also the hull shape under the DLWL. In the proposed methodology, the DLWL shape for icebreaking resistance and the hull shape under the DLWL for buoyancy and clearing resistances can be directly considered in the calculation. Especially, when calculating clearing resistance, the flow pattern of ice particles under the DLWL of ship is assumed to be in accordance with the ice flow observed during ice model testing. This paper also deals with application examples for a few ship designs and its ice model testing programs at the AARC ice model basin. From the comparison of results of the model test and the estimation, the reliability of this estimation technique has been discussed.

  11. Large-scale magnetic field in the accretion discs of young stars: the influence of magnetic diffusion, buoyancy and Hall effect

    CERN Document Server

    Khaibrakhmanov, Sergey A; Parfenov, Sergey Yu; Sobolev, Andrey M

    2016-01-01

    We investigate the fossil magnetic field in the accretion and protoplanetary discs using the Shakura and Sunyaev approach. The distinguishing feature of this study is the accurate solution of the ionization balance equations and the induction equation with Ohmic diffusion, magnetic ambipolar diffusion, buoyancy and the Hall effect. We consider the ionization by cosmic rays, X-rays and radionuclides, radiative recombinations, recombinations onto dust grains, and also thermal ionization. The buoyancy appears as the additional mechanism of magnetic flux escape in the steady-state solution of the induction equation. Calculations show that Ohmic diffusion and magnetic ambipolar diffusion constraint the generation of the magnetic field inside the `dead' zones. The magnetic field in these regions is quasi-vertical. The buoyancy constraints the toroidal magnetic field strength close to the disc inner edge. As a result, the toroidal and vertical magnetic fields become comparable. The Hall effect is important in the re...

  12. Multidisciplinary design approach and safety analysis of ADSR cooled by buoyancy driven flows

    NARCIS (Netherlands)

    Ceballos Castillo, C.A.

    2007-01-01

    Transmutation is useful to reduce the storing time and the amount of nuclear waste to be stored in the geological repository. Transmutation can be achieved in all types of reactors: thermal systems, fast systems, critical and subcritical systems. Fast spectrum systems have significant advantages bec

  13. Multidisciplinary design approach and safety analysis of ADSR cooled by buoyancy driven flows

    NARCIS (Netherlands)

    Ceballos Castillo, C.A.

    2007-01-01

    Transmutation is useful to reduce the storing time and the amount of nuclear waste to be stored in the geological repository. Transmutation can be achieved in all types of reactors: thermal systems, fast systems, critical and subcritical systems. Fast spectrum systems have significant advantages bec

  14. Multidisciplinary design approach and safety analysis of ADSR cooled by buoyancy driven flows

    NARCIS (Netherlands)

    Ceballos Castillo, C.A.

    2007-01-01

    Transmutation is useful to reduce the storing time and the amount of nuclear waste to be stored in the geological repository. Transmutation can be achieved in all types of reactors: thermal systems, fast systems, critical and subcritical systems. Fast spectrum systems have significant advantages

  15. Role of magnetic field strength and numerical resolution in simulations of the heat-flux driven buoyancy instability

    CERN Document Server

    Avara, Mark J; Bogdanović, Tamara

    2013-01-01

    The role played by magnetic fields in the intracluster medium (ICM) of galaxy clusters is complex. The weakly collisional nature of the ICM leads to thermal conduction that is channelled along field lines. This anisotropic heat conduction profoundly changes the stability of the ICM atmosphere, with convective stabilities being driven by temperature gradients of either sign. Here, we employ the Athena magnetohydrodynamic code to investigate the local non-linear behavior of the heat-flux driven buoyancy instability (HBI), relevant in the cores of cooling-core clusters where the temperature increases with radius. We study a grid of 2-d simulations that span a large range of initial magnetic field strengths and numerical resolutions. For very weak initial fields, we recover the previously known result that the HBI wraps the field in the horizontal direction thereby shutting off the heat flux. However, we find that simulations which begin with intermediate initial field strengths have a qualitatively different beh...

  16. Buoyancy-driven mixing of fluids in a confined geometry; Melange gravitationnel de fluides en geometrie confinee

    Energy Technology Data Exchange (ETDEWEB)

    Hallez, Y

    2007-12-15

    The present work based on Direct Numerical Simulations is devoted to the study of mixing between two miscible fluids of different densities. The movement of these fluids is induced by buoyancy. Three geometries are considered: a cylindrical tube, a square channel and a plane two-dimensional flow. For cylindrical tubes, the results of numerical simulations fully confirm previous experimental findings by Seon et al., especially regarding the existence of three different flow regimes, depending on the tilt angle. The comparison of the various geometries shows that tridimensional flows in tubes or channels are similar, whereas the two-dimensional model fails to give reliable information about real 3D flows, either from a quantitative point of view or for a phenomenological understanding. A peculiar attention is put on a joint analysis of the concentration and vorticity fields and allows us to explain several subtle aspects of the mixing dynamics. (author)

  17. Effects of Viscosity on the Gravi-kinesis Responses of Swimming Paramecia Studied Using Manetic Force Buoyancy Variation

    Science.gov (United States)

    Jung, Ilyong; Valles, James M.

    2013-03-01

    Previous studies have shown that paramecia exhibit negative gravi-kinesis. They exert a stronger propulsive force when swimming up than when swimming down. This behavior is very surprising since it suggests they sense their tiny apparent weight of only ~ 80pN. In an effort to understand the mechanism of this sensing, we are testing how the viscosity of the swimming medium influences their gravi-kinetic response. We employ the technique of magnetic force buoyancy variation to simulate different effective gravity levels on swimming Paramecia. We are analyzing their swimming response employing a phenomenological model that relates the parameters describing their helical trajectories to the beating of their cilia. This work was supported by NSF PHY0750360 and at the NHMFL by NSF DMR-0084173

  18. Buoyancy-Driven Radiative Unsteady Magnetohydrodynamic Heat Transfer over a Stretching Sheet with non-Uniform Heat Source/sink

    Directory of Open Access Journals (Sweden)

    Dulal Pal

    2016-01-01

    Full Text Available In the present study an unsteady mixed convection boundary layer flow of an electrically conduct- ing fluid over an stretching permeable sheet in the presence of transverse magnetic field, thermal radiation and non-uniform heat source/sink effects is investigated. The unsteadiness in the flow and temperature fields is due to the time-dependent nature of the stretching velocity and the surface temperature. Both opposing and assisting flows are considered. The dimensionless governing or- dinary non-linear differential equations are solved numerically by applying shooting method using Runge-Kutta-Fehlberg method. The effects of unsteadiness parameter, buoyancy parameter, thermal radiation, Eckert number, Prandtl number and non-uniform heat source/sink parameter on the flow and heat transfer characteristics are thoroughly examined. Comparisons of the present results with previously published results for the steady case are found to be excellent.

  19. NUMERICAL MODELLING OF VELOCITY AND TEMPERATURE DISTRIBUTIONS OF THE BUOYANCY CONVECTION EFFECT IN KNbO3 MELT

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    @@ Numerical modelling of velocity and temperature fields in high-temperature KNbO3 melt of a loop-shaped Pt wire heater is carried out by using the commercial com putational code ANSYS for the mathematical solution of the governing equations.Based on the experimental boundary conditions and the Boussinesq approximation,the numerical modelling of a steady and two-dimensional model is applied to study the process under consideration of the buoyancy-driven convection condition. The result is compared with the previous experimental and theoretical data obtained in our laboratory, and the former is in agreement with the latter. Thus a theoretical guide for reasonable growth conditions is provided by studying in depth the real fluid flow effects in the crystal growth from the melt.

  20. Regulation of biofilm formation and cellular buoyancy through modulating intracellular cyclic di-GMP levels in engineered cyanobacteria.

    Science.gov (United States)

    Agostoni, Marco; Waters, Christopher M; Montgomery, Beronda L

    2016-02-01

    The second messenger cyclic dimeric (3'→5') GMP (cyclic di-GMP or c-di-GMP) has been implicated in the transition between motile and sessile lifestyles in bacteria. In this study, we demonstrate that biofilm formation, cellular aggregation or flocculation, and cellular buoyancy are under the control of c-di-GMP in Synechocystis sp. PCC 6803 (Synechocystis) and Fremyella diplosiphon. Synechocystis is a unicellular cyanobacterium and displays lower levels of c-di-GMP; F. diplosiphon is filamentous and displays higher intracellular c-di-GMP levels. We transformed Synechocystis and F. diplosiphon with a plasmid for constitutive expression of genes encoding diguanylate cylase (DGC) and phosphodiesterase (PDE) proteins from Vibrio cholerae or Escherichia coli, respectively. These engineered strains allowed us to modulate intracellular c-di-GMP levels. Biofilm formation and cellular deposition were induced in the DGC-expressing Synechocystis strain which exhibited high intracellular levels of c-di-GMP; whereas strains expressing PDE in Synechocystis and F. diplosiphon to drive low intracellular levels of c-di-GMP exhibited enhanced cellular buoyancy. In addition, the PDE-expressing F. diplosiphon strain showed elevated chlorophyll levels. These results imply roles for coordinating c-di-GMP homeostasis in regulating native cyanobacterial phenotypes. Engineering exogenous DGC or PDE proteins to regulate intracellular c-di-GMP levels represents an effective tool for uncovering cryptic phenotypes or modulating phenotypes in cyanobacteria for practical applications in biotechnology applicable in photobioreactors and in green biotechnologies, such as energy-efficient harvesting of cellular biomass or the treatment of metal-containing wastewaters.

  1. DNS of buoyancy-driven flows and Lagrangian particle tracking in a square cavity at high Rayleigh numbers

    Energy Technology Data Exchange (ETDEWEB)

    Puragliesi, R., E-mail: riccardo.puragliesi@psi.ch [Nuclear Energy and Safety Research Department, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Laboratoire d' Ingenierie Numerique, Ecole Polytechnique Federale de Lausanne, Station 9, CH-1015 Lausanne (Switzerland); Dehbi, A., E-mail: abdel.dehbi@psi.ch [Nuclear Energy and Safety Research Department, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Leriche, E., E-mail: emmanuel.leriche@univ-st-etienne.fr [Universite de Lyon, F-42023 Saint-Etienne, LMFA-UJM St-Etienne, CNRS UMR 5509 Universite de St-Etienne, 23 rue Docteur Paul Michelon, F-42023 Saint-Etienne (France); Soldati, A., E-mail: soldati@uniud.it [Dipartimento di Energetica e Macchine, Universita di Udine, Via delle Scienze 208, IT-33100 Udine (Italy); Deville, M.O., E-mail: michel.deville@epfl.ch [Laboratoire d' Ingenierie Numerique, Ecole Polytechnique Federale de Lausanne, Station 9, CH-1015 Lausanne (Switzerland)

    2011-10-15

    Highlights: > 2D study of micro-size particle depletion driven by chaotic natural convective flows in square domains. > Description of velocity and temperature first and second moments with changing in the Rayleigh number. > Strong decoupling between the turbulent kinetic energy and the dissipation rate. > Particle recirculation sustained by the vertical hot boundary layer. > Deposition mostly induced by gravity, thermophoretic and lift forces are negligible. - Abstract: In this work we investigate numerically particle deposition in the buoyancy driven flow of the differentially heated cavity (DHC). We consider two values of the Rayleigh number (Ra = 10{sup 9}, 10{sup 10}) and three values of the particle diameter (d{sub p} = 15, 25, 35 [{mu}m]). We consider the cavity filled with air and particles with the same density of water {rho}{sub w} = 1000 [kg/m{sup 3}] (aerosol). We use direct numerical simulations (DNS) for the continuous phase, and we solve transient Navier-Stokes and energy transport equations written in an Eulerian framework, under the Boussinesq approximation, for the viscous incompressible Newtonian fluid with constant Prandtl number (Pr = 0.71). First- and second-order statistics are presented for the continuous phase as well as important quantities like turbulent kinetic energy (TKE) and temperature variance with the associated production and dissipation fields. The TKE production shows different behaviour at the two Rayleigh numbers. The Lagrangian approach has been chosen for the dispersed phase description. The forces taken into account are drag, gravity, buoyancy, lift and thermophoresis. A first incursion in the sedimentation mechanisms is presented. Current results indicate that the largest contribution to particle deposition is caused by gravitational settling, but a strong recirculating zone, which liftoffs and segregates particles, contributes to decrease settling. Deposition takes place mostly at the bottom wall. The influence of lift

  2. It takes three to tango: 1. Simulating buoyancy-driven flow in the presence of large viscosity contrasts

    Science.gov (United States)

    Suckale, Jenny; Nave, Jean-Christophe; Hager, Bradford H.

    2010-07-01

    Buoyancy-driven flow is of fundamental importance for numerous geodynamic phenomena. Since the equations of motion governing multiphase flow are rarely amenable to analytical solutions, numerical simulations provide a compelling alternative. They offer the ability to carefully analyze flow phenomena under differing regimes, initial conditions, and flow dynamics. The three key challenges in these computations are (1) the accurate solution of the equations of motion in the presence of large viscosity contrasts, (2) the representation of strongly deforming interfaces between different fluids, and (3) the accurate coupling of fluid and interface solver. In three dimensions, these challenges become even more intricate, and the appropriate choice of numerical scheme has a profound influence on the tractability, accuracy, robustness, and efficiency of the computational simulation. This is the first paper of two that examine numerical simulations of buoyancy-driven flow in the presence of large viscosity contrasts. In this paper, we present our numerical approach which tackles the above three main challenges through a combination of three numerical methods, namely, (1) an extended ghost fluid type discretization which we developed specifically for the Stokes regime, (2) the level set method, and (3) the extension velocity technique. We find that all three components are crucial to obtain a versatile numerical tool for simulating complex structures in evolving flow. We validate our code by reproducing four benchmark problems in two and three dimensions. We devote special attention to comparing our method to other existing techniques, detailing the advantages of this approach. Finally, we highlight several types of geophysical flow problems for which we believe our method to be well suited.

  3. Buoyancy of Rigid Body in the Invariant Density and Static Fluid%匀质、静止流体中刚性物体所受的浮力

    Institute of Scientific and Technical Information of China (English)

    张丽辉; 谢颖; 吴永超

    2012-01-01

    根据流体静力学的结论,计算了重力场内匀质、静止流体中刚性物体在三种不同情形下所受的浮力,与阿基米德原理给出的结论一致.计算和讨论过程加深了对浮力本质的认识.%Principle of Archimedes is important way to compute buoyancy of object in the fluid. In gravitational field, we use basics principle of fluid statics, analyze buoyancy of object in the invariant density and static fluid , and obtain buoyancy of object in three different condition. It is indication that, we obtain buoyancy of object in three different condition agree with principle of Archimedes. In the process of calculation and discussion, we can understand the essence of buoyancy.

  4. The influence of different salinity conditions on egg buoyancy and development and yolk sac larval survival and morphometric traits of Baltic Sea sprat (Sprattus sprattus balticus Schneider

    Directory of Open Access Journals (Sweden)

    Christoph Petereit

    2009-10-01

    Full Text Available The small pelagic sprat (Sprattus sprattus is a key ecologic player in the Baltic Sea. However, there is long-term variability in recruitment which is thought to be influenced by fluctuations in abiotic and biotic conditions experienced during the early life stages. This study concentrates on the influence of different ambient salinities on sprat egg development, egg buoyancy and survival as well as early yolk sac larval morphometric traits. Egg buoyancy significantly decreased with increasing salinity experienced during fertilization and/or incubation experiments. Field egg buoyancy measurements in 2007 and 2008 exhibited annual and seasonal differences in specific gravity, potentially associated with changes in adult sprat vertical distribution. Neither egg development time nor the duration of the yolk sac phase differed among salinity treatments. At eye pigmentation, larval standard length exhibited high variance among individuals but did not differ among treatments. The largest ecological impact of salinity experienced during spawning was the modification the buoyancy of eggs and yolk sac larvae, which determines their vertical habitat in the Baltic Sea. There are strong thermo- and oxyclines in the Baltic Sea, and thus salinity can indirectly impact the survival of these early life stages by modifying the ambient temperatures and oxygen conditions experienced.

  5. Experimental study of the structure of flow regions with negative turbulent kinetic energy production in confined three-dimensional shear flows with and without buoyancy

    Science.gov (United States)

    Liberzon, A.; Lüthi, B.; Guala, M.; Kinzelbach, W.; Tsinober, A.

    2005-09-01

    Regions of negative turbulent kinetic energy (TKE) production are observed and studied in two different flows, namely in turbulent thermal Rayleigh-Bénard convection in a cubic cell, and in a mechanically agitated shear flow in absence of buoyancy, with a main focus on the small scale structure of the flow. The experimental investigation is performed using three-dimensional (3D) particle tracking velocimetry, which allows for measuring the three velocity components and the full tensor of velocity derivatives in a finite 3D volume. The capability to compute the TKE production term in its complete form P =-⟨uiuj⟩Sij is crucial due to the three dimensionality of the flows. A comparative analysis of four different flow situations is performed in regions with positive and negative TKE production with and without buoyancy effects. In both, convective shear flow and shear flow without buoyancy, negative TKE production is associated with the unusual, more pronounced alignment of the velocity vector u with the first eigenvector λ1S of the mean rate-of-strain tensor, related to the stretching eigenvalue, Λ1S, in contrast to the positive TKE production associated with the alignment with the third eigenvector (i.e., related to the negative, compressing eigenvalue). In the negative TKE production region of convective flow we find (i) increased values for mean strain, (ii) increased values of the first contribution PΛ1 in the eigenframe of the mean rate-of-strain tensor, and decreased values of the vertical contribution to the production term in a fixed frame of reference, (iii) stronger anisotropy of u, (iv) higher levels of fluctuating strain s2 and enstrophy ω2, as well as (v) higher rates of their production, -sijsjkski and ωiωjsij, compared to the respective values in positive TKE production region. In the shear flow without buoyancy, all the mentioned quantities are lower in the negative TKE production region than in the positive TKE production region. From this

  6. SIMS Prototype System 4: design data brochure

    Energy Technology Data Exchange (ETDEWEB)

    1978-08-01

    A pre-package prototype unit is described having domestic hot water and room solar heating capability that uses air as the collector fluid. This system is designed to be used with a small single-family dwelling where a roof mounted collector array is not feasible. The prototype unit is an assembly containing 203 square feet of effective collector surface with 113 cubic feet of rock storage. The design of structure and storage is modular, which permits expansion and reduction of the collector array and storage bed in 68 square feet and 37 cubic feet increments respectively. The system is designed to be transportable. This permitted assembly and certification testing in one area and installation in another area without tear down and reassembly. Design, installation, operation, performance and maintenance of this system are described.

  7. Numerical experiments on the role of buoyancy and rheology during the formation of extension-driven gneiss domes

    Science.gov (United States)

    Korchinski, Megan; Rey, Patrice; Teyssier, Christian; Whitney, Donna; Mondy, Luke

    2016-04-01

    Domal structures that are cored with crystallized partially melted crustal rocks are ubiquitous features in active and exhumed orogens. The exposure of these gneiss/migmatite domes at the Earth's surface represents an opportunity to study the mechanisms of flow within the deep crust, and the mode of emplacement of high-pressure rocks into the shallow crust. End-member gneiss dome types include (1) extension-driven domes that core metamorphic core complexes, and (2) buoyancy-driven domes that are exhumed by diapiric flow. Numerical models are ideally suited to test the relative roles of buoyancy and extension-driven mechanisms in dome dynamics, and therefore to explore the interaction of physical parameters involved in doming. To that end, this research utilizes a 2D visco-plastic thermomechanical modeling framework to undertake a parametric numerical experiment where the density (range of 2700-3100 kg.m3) and viscosity (range of 1E19-1E21 Pa.s) of the lower crust are systematically varied. The style and timing of "intrusion" of partially molten lower crust into non-molten lower crust is similar for densities of 2700-3100 kg.m3 across two lower crustal viscosities tested here (1E19 Pa.s, 1E21 Pa.s). However, dome development and upwards flow of lower crust material for a relatively high-density, middle-viscosity lower crust (2900-3100 kg.m^3; 1E20 Pa.s) involves a significant upward translation of the Moho, relative to the low-density, middle-viscosity model results. In addition, the high-density, middle-viscosity model shows a decrease in the volume of partial melt in the lower crust, and distributed brittle faulting in the upper crust. Thus, this experiment suite illustrates that variations in density and viscosity of the lower crust influence (1) faults distribution in the upper crust, (2) flow patterns within the lower crust, (3) upward translation of the solidus into the lower crust, and (4) upward displacement of the Moho. The style of extension within the

  8. Floating wind turbine system

    Science.gov (United States)

    Viterna, Larry A. (Inventor)

    2009-01-01

    A floating wind turbine system with a tower structure that includes at least one stability arm extending therefrom and that is anchored to the sea floor with a rotatable position retention device that facilitates deep water installations. Variable buoyancy for the wind turbine system is provided by buoyancy chambers that are integral to the tower itself as well as the stability arm. Pumps are included for adjusting the buoyancy as an aid in system transport, installation, repair and removal. The wind turbine rotor is located downwind of the tower structure to allow the wind turbine to follow the wind direction without an active yaw drive system. The support tower and stability arm structure is designed to balance tension in the tether with buoyancy, gravity and wind forces in such a way that the top of the support tower leans downwind, providing a large clearance between the support tower and the rotor blade tips. This large clearance facilitates the use of articulated rotor hubs to reduced damaging structural dynamic loads. Major components of the turbine can be assembled at the shore and transported to an offshore installation site.

  9. Coexisting contraction-extension consistent with buoyancy of the crust and upper mantle in North-Central Italy

    CERN Document Server

    Aoudia, A; Ismail-Zadeh, A T; Panza, G F; Pontevivo, A

    2002-01-01

    The juxtaposed contraction and extension observed in the crust of the Italian Apennines and elsewhere has, for a long time, attracted the attention of geoscientists and is a long-standing enigmatic feature. Several models, invoking mainly external forces, have been put forward to explain the close association of these two end-member deformation mechanisms clearly observed by geophysical and geological investigations. These models appeal to interactions along plate margins or at the base of the lithosphere such as back-arc extension or shear tractions from mantle flow or to subduction processes such as slab roll back, retreat or pull and detachment. We present here a revisited crust and upper mantle model that supports delamination processes beneath North-Central Italy and provides a new background for the genesis and age of the recent magmatism in Tuscany. Although external forces must have been important in the building up of the Apennines, we show that internal buoyancy forces solely can explain the coexist...

  10. Numerical Study of Buoyancy Convection of Air under Permanent Magnetic Field and Comparison with That under Gravity Field

    Directory of Open Access Journals (Sweden)

    Kewei Song

    2014-01-01

    Full Text Available Magnetothermal free convection of air in a square enclosure under a nonuniform magnetic field provided by a permanent neodymium-iron-boron magnet is numerically studied. The natural convection under the gravity field alone is also studied for comparison. The physical fields of magnetizing force, velocity, and temperature as well as the local distribution characteristic of Nusselt number are all presented in this paper. The results show that the buoyancy convection of air in the square enclosure under magnetic field is quite different from that under the gravity field. The local value of Nusselt number under the magnetic field supplied by a permanent magnet with a residual magnetic flux density of about 4.5 Tesla can reach a high value of about three times larger than the maximum local value of Nusselt number under the gravity field. Relatively uniform distributions of temperature gradient and Nusselt number can be obtained along the cold wall of the enclosure under the magnetic field. A permanent magnet with high magnetic energy product with Br reaching to 3.5 Tesla can play a comparative role on the averaged Nusselt number compared with that under the gravity environment.

  11. Analytical and experimental study of instabilities in buoyancy-driven convection in porous media

    Energy Technology Data Exchange (ETDEWEB)

    Georgiadis, J.G.; Behringer, R.; Johnson, G.A.

    1992-04-01

    During the second year of support under the DOE grant, significant progress was made in two directions: (1) Visualization of structure and tow field in randomly packed beds via Magnetic Resonance Imaging, and (2) Shadowgraphic visualization of natural convection in porous systems. This report describes the activities in detail, cite publications which resulted from this project, and conclude with plans for the last phase of the experimental investigation.

  12. CFD Study on Inter-Action and Heat Transfer between Non-Isothermal Airflow of Momentum Source and Plume of Buoyancy Force in an Air-Conditioned Space

    Directory of Open Access Journals (Sweden)

    Wuwei Cao

    2010-10-01

    Full Text Available This paper presents indoor airflow and thermal environment which is formed by a cooling jet and a local heat source in a ventilated room. To illustrate the effects of the combined the plume and the jet-flow, a series of simulated values with different calculated conditions such as different buoyancy flux are analysed by Fluent simulation software. This paper presents an index θ to describe the physical phenomenon by the thermal interaction between the cold jetflow and the plume. It is concluded that if the heat source is increasing considerably, the buoyancy source will be a leading factor of the indoor thermal field, though its initial momentum is considered to be zero.

  13. Effect of Thermal Buoyancy on Fluid Flow and Inclusion Motion in Tundish without Flow Control Devices--Part Ⅰ: Fluid Flow

    Institute of Scientific and Technical Information of China (English)

    ZHANG Li-feng; ZHI Jian-jun; MOU Ji-ning; CUI Jian

    2005-01-01

    The κ-ε two-equation model is used to simulate the fluid flow in the continuous casting tundish coupling with the effect of thermal buoyancy. The natural convection induced by the thermal buoyancy generates an upward flow pattern especially at the outlet zone, and has little effect on the fluid flow in the inlet zone. The maximum viscosity is 700 times larger than the laminar viscosity, which indicates the strong turbulent flow in the tundish. The maximum temperature difference in the whole tundish is 8.2 K. The temperature near the stopper rod and the short wall is obviously lower than that in the inlet zone. The existence of the stopper rod has a big effect on the fluid flow entering the SEN and the mold. All the characteristics of the tundish geometry should be considered to accurately simulate the fluid flow in the tundish.

  14. A method of evaluating efficiency during space-suited work in a neutral buoyancy environment

    Science.gov (United States)

    Greenisen, Michael C.; West, Phillip; Newton, Frederick K.; Gilbert, John H.; Squires, William G.

    1991-01-01

    The purpose was to investigate efficiency as related to the work transmission and the metabolic cost of various extravehicular activity (EVA) tasks during simulated microgravity (whole body water immersion) using three space suits. Two new prototype space station suits, AX-5 and MKIII, are pressurized at 57.2 kPa and were tested concurrently with the operationally used 29.6 kPa shuttle suit. Four male astronauts were asked to perform a fatigue trial on four upper extremity exercises during which metabolic rate and work output were measured and efficiency was calculated in each suit. The activities were selected to simulate actual EVA tasks. The test article was an underwater dynamometry system to which the astronauts were secured by foot restraints. All metabolic data was acquired, calculated, and stored using a computerized indirect calorimetry system connected to the suit ventilation/gas supply control console. During the efficiency testing, steady state metabolic rate could be evaluated as well as work transmitted to the dynamometer. Mechanical efficiency could then be calculated for each astronaut in each suit performing each movement.

  15. Experimental and Theoretical Studies on Velocity Field of Buoyancy Convection in KNbO3 Melt

    Institute of Scientific and Technical Information of China (English)

    JIN Wei-Qing; Shinichi YODA; JIANG Yuan-Fang; PAN Zhi-Lei; LIANG Xin-An

    2001-01-01

    The Schlieren technique coupling with a differential interference microscope was applied to visualize the KNbOa melt motion in a loop-shaped Pt wire heater. The natural convection in KNbOa melt was traced by observing themovement of the tiny KNbO3 crystals (~ 10 μm) and the stream velocities of these tracer crystals were measured. In theoretical analysis, the Navier-Stokes equation was solved as a stable field. The general solution for this system of the differential equation was expressed by an approximate power series of azimuth and radius vector. The expression was substituted in the differential equation; a non-trivial solution was obtained exactly. The velocity distribution in the vertical section was obtained which is in qualitative agreement with the experimental result.

  16. EXPERIMENTAL AND THEORETICAL STUDIES ON VELOCITY FIELD OF BUOYANCY CONVECTION IN KNbO3 MELT

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    @@ The Schlieren technique coupling with a differential interference microscope was applied to visualize the KNbO3 melt motion in a loop-shaped Pt wire heater. The natural convection in KNbO3 melt was traced by observing the movement of the tiny KNbO3 crystals (~10μm) and the stream velocities of these tracer crystals were measured. In theoretical analysis, the Navier-Stokes equation was solved as a stable field. The general solution for this system of the differential equation was expressed by an approximate power series of azimuth and radius vector. The expression was substituted in the differential equation; a non-trivial solution was obtained exactly.The velocity distribution in the vertical section was obtained which is in qualitative agreement with the experimental result.

  17. Thermo capillary and buoyancy convection in a fluid locally heated on its free surface; Convection thermocapillaire et thermogravitaire dans un fluide chauffe localement sur sa surface libre

    Energy Technology Data Exchange (ETDEWEB)

    Favre, E.

    1997-09-26

    coupled buoyancy and thermo-capillary convection lead to a convective motion of the interface liquid/gas which drastically changes the heat and mass transfer across the liquid layer. Two experiments were considered, depending on the fluid: oil or mercury. The liquid is set in a cooled cylindrical vessel, and heated by a heat flux across the center of the free surface. The basic flow, in the case of oil, is a torus. When the heat parameter increases, a stationary flow appears as petals or rays when the aspect ratio. The lateral confinement selects the azimuthal wavelength. In the case of petals-like flow, a sub-critical Hopf bifurcation is underlined. The turbulence is found to be `weak`, even for the largest values of the Marangoni number (Ma = 1.3 10{sup 5}). In the case of mercury, the thermo-capillary effect is reduced to zero to impurities at the surface which have special trajectories we describe and compare to a simpler experiment. Only the buoyancy forces induce a unstationary, weakly turbulent flow as soon as the heating power exceeds 4W (Ra = 4.5 10{sup 3}, calculated with h = 1 mm). The past part concerns the analysis of the effect on the flow of the boundary conditions, the geometry, the Prandtl number and the buoyancy force with the help of the literature. Results concerning heat transfer, in particular the exponent of the law Nusselt number vs. heating power, were compared with available data. (author) 115 refs.

  18. An Integrated Capillary, Buoyancy, and Viscous-Driven Model for Brine/CO2Relative Permeability in a Compositional and Parallel Reservoir Simulator

    KAUST Repository

    Kong, X.

    2012-11-03

    The effectiveness of CO2 storage in the saline aquifers is governed by the interplay of capillary, viscous, and buoyancy forces. Recent experimental study reveals the impact of pressure, temperature, and salinity on interfacial tension (IFT) between CO2 and brine. The dependence of CO2-brine relative permeability and capillary pressure on pressure (IFT) is also clearly evident in published experimental results. Improved understanding of the mechanisms that control the migration and trapping of CO2 in subsurface is crucial to design future storage projects that warrant long-term and safe containment. Simulation studies ignoring the buoyancy and also variation in interfacial tension and the effect on the petrophysical properties such as trapped CO2 saturations, relative permeability, and capillary pressure have a poor chance of making accurate predictions of CO2 injectivity and plume migration. We have developed and implemented a general relative permeability model that combines effects of pressure gradient, buoyancy, and IFT in an equation of state (EOS) compositional and parallel simulator. The significance of IFT variations on CO2 migration and trapping is assessed.

  19. To Float or Not to Float: How Interactions between Light and Dissolved Inorganic Carbon Species Determine the Buoyancy of Stratiotes aloides.

    Science.gov (United States)

    Harpenslager, Sarah F; Smolders, Alfons J P; Kieskamp, Ariët A M; Roelofs, Jan G M; Lamers, Leon P M

    2015-01-01

    Structural diversity formed by dense, floating Stratiotes aloides stands, generates hotspots of biodiversity of flora and fauna in wetlands. However, only part of the populations become emergent and provide this important facilitation. Since it has been hypothesised that its buoyancy depends on the rates of underwater photosynthesis, we investigated the role of dissolved CO2 availability and PAR on photosynthesis, biomass production and buoyancy in a controlled greenhouse experiment. Photosynthesis and growth were strongly influenced by both PAR and CO2 availability. At low PAR, plants formed less biomass and produced no emergent leaves, even when CO2 was abundant. At low CO2 levels, S. aloides switched to HCO3- use, resulting in a lower photosynthetic O2 production, decreased emergent leaf formation and increased CaCO3 precipitation on its leaves, all of which impaired buoyancy. At high PAR, low CO2 availability resulted in slower colonisation of the water layer, whereas CO2 availability did not influence PAR-limited plants. Our study shows that site conditions, rather than the sole abundance of potentially facilitating species, may strongly determine whether or not they form the structure necessary to act as a facilitator for biodiversity in aquatic environments.

  20. To Float or Not to Float: How Interactions between Light and Dissolved Inorganic Carbon Species Determine the Buoyancy of Stratiotes aloides.

    Directory of Open Access Journals (Sweden)

    Sarah F Harpenslager

    Full Text Available Structural diversity formed by dense, floating Stratiotes aloides stands, generates hotspots of biodiversity of flora and fauna in wetlands. However, only part of the populations become emergent and provide this important facilitation. Since it has been hypothesised that its buoyancy depends on the rates of underwater photosynthesis, we investigated the role of dissolved CO2 availability and PAR on photosynthesis, biomass production and buoyancy in a controlled greenhouse experiment. Photosynthesis and growth were strongly influenced by both PAR and CO2 availability. At low PAR, plants formed less biomass and produced no emergent leaves, even when CO2 was abundant. At low CO2 levels, S. aloides switched to HCO3- use, resulting in a lower photosynthetic O2 production, decreased emergent leaf formation and increased CaCO3 precipitation on its leaves, all of which impaired buoyancy. At high PAR, low CO2 availability resulted in slower colonisation of the water layer, whereas CO2 availability did not influence PAR-limited plants. Our study shows that site conditions, rather than the sole abundance of potentially facilitating species, may strongly determine whether or not they form the structure necessary to act as a facilitator for biodiversity in aquatic environments.

  1. Black carbon particulate matter emission factors for buoyancy-driven associated gas flares.

    Science.gov (United States)

    McEwen, James D N; Johnson, Matthew R

    2012-03-01

    Flaring is a technique used extensively in the oil and gas industry to burn unwanted flammable gases. Oxidation of the gas can preclude emissions of methane (a potent greenhouse gas); however, flaring creates other pollutant emissions such as particulate matter (PM) in the form of soot or black carbon (BC). Currently available PM emissionfactors for flares were reviewed and found to be questionably accurate, or based on measurements not directly relevant to open-atmosphere flares. In addition, most previous studies of soot emissions from turbulent diffusion flames considered alkene or alkyne based gaseous fuels, and few considered mixed fuels in detail and/or lower sooting propensity fuels such as methane, which is the predominant constituent of gas flared in the upstream oil and gas industry. Quantitative emission measurements were performed on laboratory-scale flares for a range of burner diameters, exit velocities, and fuel compositions. Drawing from established standards, a sampling protocol was developed that employed both gravimetric analysis of filter samples and real-time measurements of soot volume fraction using a laser-induced incandescence (LII) system. For the full range of conditions tested (burner inner diameter [ID] of 12.7-76.2 mm, exit velocity 0.1-2.2 m/sec, 4- and 6-component methane-based fuel mixtures representative of associated gas in the upstream oil industry), measured soot emission factors were less than 0.84 kg soot/10(3) m3 fuel. A simple empirical relationship is presented to estimate the PM emission factor as a function of the fuel heating value for a range of conditions, which, although still limited, is an improvement over currently available emission factors.

  2. Relationship between level of neutral buoyancy and dual-Doppler observed mass detrainment levels in deep convection

    Directory of Open Access Journals (Sweden)

    G. L. Mullendore

    2013-01-01

    Full Text Available Although it is generally accepted that the level of neutral buoyancy (LNB is only a coarse estimate of updraft depth, the LNB is still used to understand and predict storm structure in both observations and modeling. This study uses case studies to quantify the variability associated with using environmental soundings to predict detrainment levels. Nine dual-Doppler convective cases were used to determine the observed level of maximum detrainment (LMD to compare with the LNB. The LNB for each case was calculated with a variety of methods and with a variety of sources (including both observed and simulated soundings. The most representative LNB was chosen as the proximity sounding from NARR using the most unstable parcel and including ice processes.

    The observed cases were a mix of storm morphologies, including both supercell and multicell storms. As expected, the LMD was generally below the LNB, the mean offset for all cases being 2.2 km. However, there was a marked difference between the supercell and non-supercell cases. The two supercell cases had LMDs of 0.3 km and 0.0 km below the LNB. The remaining cases had LMDs that ranged from 4.0 km below to 1.6 km below the LNB, with a mean offset of 2.8 km below. Observations also showed that evolution of the LMD over the lifetime of the storm can be significant (e.g., >2 km altitude change in 30 min, and this time evolution is lacking from models with coarse time steps, missing significant changes in detrainment levels that may strongly impact the amount of boundary layer mass transported to the upper troposphere and lower stratosphere.

  3. 80-Myr history of buoyancy and volcanic fluxes along the trails of the Walvis and St. Helena hotspots (South Atlantic)

    Science.gov (United States)

    Vidal, V.; Adam, C.; Escartin, J.

    2007-12-01

    Walvis and St.~Helena are the only long-lived hotspot chains in the South Atlantic. Therefore, their characterization is important to constrain the processes associated with mantle plume formation, their temporal evolution, and the interaction with plate and mantle dynamics in the region. We study the temporal evolution of plume buoyancy and magma production rate along both hotspot chains, which are constrained from the swell and volume of volcanic materials emplaced along the chain. The regional depth anomaly is calculated by correcting the 2' bathymetry grid of Smith & Sandwell (1997) for thermal subsidence and sediment loading. We separate the topography associated with volcanism and the swell surrounding the hotspot chains using the MiFil filtering method (Adam et al., 2005). We then estimate the temporal variations associated with both parameters by computing volumes along the hotspot tracks. Neither Walvis nor St.~Helena show a 'classical' hotspot behavior. We find that two plumes are at the origin of the St.~Helena chain. This study also shows a swell associated with the Circe seamount, supporting the existence of a hotspot NW of the St.~Helena trail. The variation in swell and volcanic fluxes suggests temporal variability in the plume behavior at time scales of 10-20~m.y. and 5~m.y., which may be related to oscillations and instabilities of the plume conduit, respectively. Cumulative fluxes in the area are largest for Walvis and weakest for Circe, and all are significantly lower than that reported for the Hawai'i hotspot.

  4. Experiment Clarifies Buoyancy

    Science.gov (United States)

    Oguz, Ayse; Yurumezoglu, Kemal

    2008-01-01

    This article presents a simple activity using Archimedes' principle that helps students to develop their scientific thinking and also to identify and correct their misconceptions. The exercise consists of linear and reverse processes.

  5. Buoyancy Can-Can

    Science.gov (United States)

    Nelson, Jim; Nelson, Jane Bray

    2015-01-01

    In this paper, a discrepant event is used to initiate a learning cycle lesson to help students develop an understanding of the concept and equation for buoyant force. The data are gathered using readily available equipment and then graphically analyzed using a four-step analysis consistent with the modeling instructional approach. This laboratory…

  6. Buoyancy Can-Can

    Science.gov (United States)

    Nelson, Jim; Nelson, Jane Bray

    2015-05-01

    In this paper, a discrepant event is used to initiate a learning cycle1 lesson to help students develop an understanding of the concept and equation for buoyant force. The data are gathered using readily available equipment and then graphically analyzed using a four-step analysis consistent with the modeling instructional approach.2 This laboratory activity is appropriate for high school or first-year college physics, and provides the opportunity for review of free-body diagrams, experimental design, and graphical analysis. We use the "BSCS 5E" version of the Karplus learning cycle idea, popularized by Bybee, in which students are expected to Engage, Explore, Explain, Elaborate, and Evaluate.3

  7. Carbon Sinks in a Changing Climate: Relative Buoyancy and Sinking Potentials of Various Antarctic Phytoplankton and Ice Algae

    Science.gov (United States)

    Nirmel, S.; Selz, V.

    2016-12-01

    Polar phytoplankton play instrumental roles in global biogeochemical cycles, sometimes serving as massive carbon sinks via the biological pump. In addition to phytoplankton, sea ice supports a significant amount of ice algae, the essential primary producers for the ecosystem in winter and early spring. While sea ice habitat declines on regional scales, the fate of sea ice algae post-ice melt remains relatively unknown, despite its importance in understanding how the biological pump might be affected by sea ice loss. Through a series of settling column experiments on the icebreaker Nathaniel B. Palmer, we aimed to address the question: What controls the fate of the carbon-rich ice algae across the Western Antarctic Peninsula (WAP) during ice melt? We focused on whether species composition affects the sinking potential of ice algal communities. Using FlowCAM imagery, we classified samples collected from the buoyant, neutral, and negatively buoyant portions of the settling columns into genus-level taxonomic classes. We used image parameters and geometric shape equations to calculate the biovolume of each taxonomic group. We further explored relationships between taxa-specific sinking potentials, environmental parameters (temperature and nutrients), and physiological properties of associated algal communities (as described by Fast Rate Repetition fluorometry). Results indicate that colonial Phaeocystis antarctica tends to dominate lower regions of the settling column. Moreover, we observe strong correlations between geographic location and both nutrients and phytoplankton physiology. We found that these three factors are indeed related to taxa-specific buoyancy and sinking indices. An understanding of these relationships sheds more light on the role P. antarctica (a carbon-rich bloom-forming genus) plays in the biological pump; higher sinking rates suggest greater carbon export to depth, while lower sinking rates increase the likelihood of carbon being respired back

  8. Numerical investigation of mixed convection heat transfer from two isothermal circular cylinders in tandem arrangement: buoyancy, spacing ratio, and confinement effects

    Science.gov (United States)

    Salcedo, Erick; Cajas, Juan C.; Treviño, César; Martínez-Suástegui, Lorenzo

    2017-04-01

    This paper presents a two-dimensional numerical study for mixed convection in a laminar cross-flow with a pair of stationary equal-sized isothermal cylinders in tandem arrangement confined in a channel. The governing equations are solved using the control volume method on a nonuniform orthogonal Cartesian grid, and the immersed boundary method is employed to identify the cylinders placed in the flow field. The numerical scheme is first validated against standard cases of symmetrically confined isothermal circular cylinders in plane channels, and grid convergence tests were also examined. The objective of the present study was to investigate the influence of buoyancy and the blockage ratio constraint on the flow and heat transfer characteristics of the immersed cylinder array. Using a fixed Reynolds number based on cylinder diameter of ReD = 200, a fixed value of the Prandtl number of Pr = 7, and a blockage ratio of D/H = 0.2, all possible flow regimes are considered by setting the longitudinal spacing ratio (σ = L/D) between the cylinder axes to 2, 3, and 5 for values of the buoyancy parameter (Richardson number) in the range -1≤ Ri≤ 4. The interference effects and complex flow features are presented in the form of mean and instantaneous velocity, vorticity, and temperature distributions. The results demonstrate how the buoyancy, spacing ratio, and wall confinement affect the wake structure and vortex dynamics. In addition, local and average heat transfer characteristics of both cylinders are comprehensively presented for a wide range in the parametric space.

  9. Large-scale magnetic field in the accretion discs of young stars: the influence of magnetic diffusion, buoyancy and Hall effect

    Science.gov (United States)

    Khaibrakhmanov, S. A.; Dudorov, A. E.; Parfenov, S. Yu.; Sobolev, A. M.

    2017-01-01

    We investigate the fossil magnetic field in the accretion and protoplanetary discs using the Shakura and Sunyaev approach. The distinguishing feature of this study is the accurate solution of the ionization balance equations and the induction equation with Ohmic diffusion, magnetic ambipolar diffusion, buoyancy and the Hall effect. We consider the ionization by cosmic rays, X-rays and radionuclides, radiative recombinations, recombinations on dust grains and also thermal ionization. The buoyancy appears as the additional mechanism of magnetic flux escape in the steady-state solution of the induction equation. Calculations show that Ohmic diffusion and magnetic ambipolar diffusion constraint the generation of the magnetic field inside the `dead' zones. The magnetic field in these regions is quasi-vertical. The buoyancy constraints the toroidal magnetic field strength close to the disc inner edge. As a result, the toroidal and vertical magnetic fields become comparable. The Hall effect is important in the regions close to the borders of the `dead' zones because electrons are magnetized there. The magnetic field in these regions is quasi-radial. We calculate the magnetic field strength and geometry for the discs with accretion rates (10^{-8}-10^{-6}) {M}_{⊙} {yr}^{-1}. The fossil magnetic field geometry does not change significantly during the disc evolution while the accretion rate decreases. We construct the synthetic maps of dust emission polarized due to the dust grain alignment by the magnetic field. In the polarization maps, the `dead' zones appear as the regions with the reduced values of polarization degree in comparison to those in the adjacent regions.

  10. Numerical investigation of mixed convection heat transfer from two isothermal circular cylinders in tandem arrangement: buoyancy, spacing ratio, and confinement effects

    Science.gov (United States)

    Salcedo, Erick; Cajas, Juan C.; Treviño, César; Martínez-Suástegui, Lorenzo

    2016-11-01

    This paper presents a two-dimensional numerical study for mixed convection in a laminar cross-flow with a pair of stationary equal-sized isothermal cylinders in tandem arrangement confined in a channel. The governing equations are solved using the control volume method on a nonuniform orthogonal Cartesian grid, and the immersed boundary method is employed to identify the cylinders placed in the flow field. The numerical scheme is first validated against standard cases of symmetrically confined isothermal circular cylinders in plane channels, and grid convergence tests were also examined. The objective of the present study was to investigate the influence of buoyancy and the blockage ratio constraint on the flow and heat transfer characteristics of the immersed cylinder array. Using a fixed Reynolds number based on cylinder diameter of ReD = 200 , a fixed value of the Prandtl number of Pr = 7 , and a blockage ratio of D/H = 0.2 , all possible flow regimes are considered by setting the longitudinal spacing ratio (σ = L/D ) between the cylinder axes to 2, 3, and 5 for values of the buoyancy parameter (Richardson number) in the range -1≤ Ri≤ 4 . The interference effects and complex flow features are presented in the form of mean and instantaneous velocity, vorticity, and temperature distributions. The results demonstrate how the buoyancy, spacing ratio, and wall confinement affect the wake structure and vortex dynamics. In addition, local and average heat transfer characteristics of both cylinders are comprehensively presented for a wide range in the parametric space.

  11. Use and understanding of the nutrition information panel of pre-packaged foods in a sample of Mexican consumers Uso y comprensión del etiquetado nutrimental posterior de los alimentos pre-empaquetados en una muestra de consumidores mexicanos

    Directory of Open Access Journals (Sweden)

    Vanessa De la Cruz-Góngora

    2012-04-01

    Full Text Available OBJECTIVE: To assess the use and understanding of the Nutritional information Panel (NIP of pre-packaged foods by Mexican consumers. MATERIALS AND METHODS: A questionnaire and an understanding test for NIP were applied to adult consumers in supermarkets of six cities in the Northern, Central, and Southern regions of Mexico. Data were analyzed by frequencies and Poisson regression models. RESULTS: Interviewed 731 consumers; 71.5% were women, mean age 33 ± 9.7 (range: 18-60, 70% completed high-school or a higher degree. In total, 17% of consumers use the NIP for making purchase decisions; 49% did not understand the NIP. Only 1.2% of consumers answered correctly the five questions of the NIP understanding test. CONCLUSIONS: The use and understanding of the NIP are low despite a high proportion self-reported reading and understanding. The lack of previous knowledge of the technical language prevents use and interpretation of NIP nutritional information for purchasing decisions.OBJETIVO: Evaluar el uso y comprensión del etiquetado nutricional posterior (NIP, por sus siglas en inglés de alimentos preempacados por consumidores mexicanos. MATERIAL Y MÉTODOS: Se aplicaron un cuestionario y una prueba de comprensión del NIP a consumidores adultos en supermercados de seis ciudades de las regiones Norte, Centro y Sur de México. RESULTADOS: Se entrevistaron 731 consumidores; 71.5% eran mujeres, la media de edad 33 ± 9.7 años (intervalo 18-60; 70% terminaron preparatoria o un nivel más alto. El 17% usa la etiqueta nutrimental para elegir sus alimentos; 49% no comprendía la NIP. Sólo 1.2% de los consumidores respondió correctamente las cinco preguntas de la prueba de comprensión del NIP. CONCLUSIONES: El uso y comprensión del NIP fue bajo, a pesar de la gran proporción que autorreportó leerlo y comprenderlo. La falta de conocimiento previo del lenguaje técnico dificulta el uso e interpretación de la información nutricional de NIP para las

  12. Experimental study on buoyancy-driven exchange flows through breaches of a tokamak vacuum vessel in a fusion reactor under the loss-of-vacuum-event conditions

    Energy Technology Data Exchange (ETDEWEB)

    Takase, Kazuyuki; Tomoaki, Kunugi; Ogawa, Masurou; Seki, Yasushi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan)

    1997-02-01

    As one of thermofluid safety studies in the International Thermonuclear Experimental Reactor, buoyancy-driven exchange flow behavior through breaches of a vacuum vessel (VV) has been investigated quantitatively by using a preliminary loss-of-vacuum-event (LOVA) apparatus that simulated the tokamak VV of a fusion reactor with a small-scaled model. To carry out the present experiments under the atmospheric pressure condition, helium gas and air were provided as the working fluids. The inside of the VV was initially filled with helium gas and the outside was atmosphere. The breaches on the VV under the LOVA condition were simulated by opening six simulated breaches to which were set the different positions on the VV. When the buoyancy-driven exchange flow through the breach occurred, helium gas went out from the inside of the VV through the breach to the outside and air flowed into the inside of the VV through the breach from the outside. The exchange rate in the VV between helium gas and air was calculated from the measured weight change of the VV with time since the experiment has started. experimental parameters were breach position, breach number, breach length, breach size, and breach combination. The present study clarifies that the relation between the exchange rate and the breach position of the VV depended on the magnitude of the potential energy from the ground level to the breach position, and then, the exchange rate decreased as the breach length increased and as the breach size decreased.

  13. Thermal-solutal capillary-buoyancy flow of a low Prandtl number binary mixture with a -1 capillary ratio in an annular pool

    Science.gov (United States)

    Yu, Jia-Jia; Wu, Chun-Mei; Li, You-Rong; Chen, Jie-Chao

    2016-08-01

    A series of three-dimensional numerical simulations on thermal-solutal capillary-buoyancy flow in an annular pool were carried out. The pool was filled with silicon-germanium melt with an initial silicon mass fraction of 1.99%. The Prandtl number and the Lewis number of the working fluid are 6.37 × 10-3 and 2197.8, respectively. Both the radial temperature gradient and the solute concentration gradient were applied to the annular pool. The capillary ratio was assumed to be -1, which means that the solutal and thermal capillary effects were equal and opposite. Results show that the thermal-solutal capillary-buoyancy flow always occurs at this special case with the capillary ratio of -1, and even in a shallow annular pool with an aspect ratio of 0.05. With the increase of the thermal Marangoni number, four kinds of flow patterns appear orderly, including concentric rolls, petal-like, spoke, and rosebud-like patterns. These flow patterns are strongly influenced by the local interaction between the solutal and thermal capillary effects and the vertical solute concentration gradient near the outer cylinder. A small vortex driven by the dominant solutal capillary effect emerges near the inner cylinder, which is different from the flow pattern in a pure fluid. In addition, the critical thermal Marangoni number of the initial three-dimensional flow decreases with the increase of the aspect ratio of the annular pool.

  14. The Answer Doesn't Always Come Prepackaged

    Science.gov (United States)

    Boyer, Catherine M.

    1978-01-01

    The author states that a hospital inservice education department must function as a management tool in delivering quality care to patients and that the nursing inservice educator should provide input into administration decisions that have educational implications. She describes an ineffective packaged program used in one hospital without…

  15. The "Family Tree" of Air Distribution Systems

    DEFF Research Database (Denmark)

    Nielsen, Peter V.

    2011-01-01

    that all the known types of air distribution systems are interconnected in a “family tree”. The influence of supplied momentum flow versus buoyancy forces is discussed, and geometries for high ventilation effectiveness are indicated as well as geometries for fully mixed flow. The paper will also show...

  16. Research on the Self-balancing Sinking Pipe Technology by Temporary Buoyancy Plug%加临时浮力塞自平衡浮力法下管技术研究

    Institute of Scientific and Technical Information of China (English)

    余大有; 陈月化; 唐志宏

    2014-01-01

    Single-plug-buoyancy-method-was-used-to-sink-gas-pipe,-but-space-under-the-plug-was-small.-With-creasing-depth-of-the-gas-hole,-air-under-the-plug-had-been-compressed,-then-the-buoyancy-provided-by-air-decreased-too-much-to-meet-demand-of-sinking-pipe.-To-increase-the-length-of-air-column,-temporary-buoyancy-plug-was-been-made.-This-plug-has-been-placed-same-depth-of-the-single-plug-self-balancing-method-to-sink-pipe.-A-sealing-plate-was-welded-as-temporary-buoyancy-plug,-and-this-method-also-used-upon-empty-pipe-section-to-pro-duce-buoyancy.-When-the-upon-empty-pipe`s-length-reached-de-signed-length,-concrete-buoyancy-plug-was-going-to-be-installed.-And-air-will-be-aerated-into-the-empty-pipe-under-the-concrete-plug,-with-the-pressure-increasing,-the-steel-ball-which-was-placed-in-the-temporary-buoyancy-plug,-exfoliated-into-mud.-Air-was-aerated-into-space-under-the-temporary-buoyancy-plug.-Compared-to-single-plug-self-balancing-buoyancy-method,-tem-porary-buoyancy-plug-has-increased-length-of-air-column,-then-the-buoyancy-produced-by-air-was-also-increased.-Implementa-tion-is-that-all-steel-pipe-can-be-sinked-only-with-one-time-aera-tion.%现有单塞自平衡浮力法下管,塞下充气量较小,并且随着下管深度的增加,塞下空气进一步压缩,提供的浮力逐渐减小,无法满足下管要求。为增加管内储气段长度,设置临时浮力塞。所加临时浮力塞与单塞自平衡下管时的浮力塞处于同一深度,在此处焊接带加强筋的封板作为临时浮力塞,利用常规空管提供浮力。当临时浮力塞上部空管高度达到设计值时,加设混凝土材质浮力塞并充气,随着充气压力的增大,设置在临时浮力塞下部的钢球脱落,空气进入临时浮力塞下部空间。与单塞自平衡浮力法相比,增加了临时浮力塞下这段充气量,因此提供的浮力也增大,从而实现一次性充气下完全布钢管。

  17. Combined Effect of Buoyancy Force and Navier Slip on MHD Flow of a Nanofluid over a Convectively Heated Vertical Porous Plate

    Directory of Open Access Journals (Sweden)

    Winifred Nduku Mutuku-Njane

    2013-01-01

    Full Text Available We examine the effect of magnetic field on boundary layer flow of an incompressible electrically conducting water-based nanofluids past a convectively heated vertical porous plate with Navier slip boundary condition. A suitable similarity transformation is employed to reduce the governing partial differential equations into nonlinear ordinary differential equations, which are solved numerically by employing fourth-order Runge-Kutta with a shooting technique. Three different water-based nanofluids containing copper (Cu, aluminium oxide (Al2O3, and titanium dioxide (TiO2 are taken into consideration. Graphical results are presented and discussed quantitatively with respect to the influence of pertinent parameters, such as solid volume fraction of nanoparticles (φ, magnetic field parameter (Ha, buoyancy effect (Gr, Eckert number (Ec, suction/injection parameter (fw, Biot number (Bi, and slip parameter (β, on the dimensionless velocity, temperature, skin friction coefficient, and heat transfer rate.

  18. Some Exact Solutions of Boundary Layer Flows along a Vertical Plate with Buoyancy Forces Combined with Lorentz Forces under Uniform Suction

    Directory of Open Access Journals (Sweden)

    Asterios Pantokratoras

    2008-01-01

    Full Text Available Exact analytical solutions of boundary layer flows along a vertical porous plate with uniform suction are derived and presented in this paper. The solutions concern the Blasius, Sakiadis, and Blasius-Sakiadis flows with buoyancy forces combined with either MHD Lorentz or EMHD Lorentz forces. In addition, some exact solutions are presented specifically for water in the temperature range of 0∘C≤≤8∘C, where water density is nearly parabolic. Except for their use as benchmarking means for testing the numerical solution of the Navier-Stokes equations, the presented exact solutions with EMHD forces have use in flow separation control in aeronautics and hydronautics, whereas the MHD results have applications in process metallurgy and fusion technology. These analytical solutions are valid for flows with strong suction.

  19. Improving the buoyancy force and Archimedes principle experiment%对浮力实验和阿基米德实验的改进

    Institute of Scientific and Technical Information of China (English)

    陈风青

    2013-01-01

    An experiment of exploring the direction of buoyancy force was put forward ,which could be conducted by students independently . The Archimedes principle experiment was also im-proved .The experiment errors were reduced ,the experimental results were intuitive and clear .At the same time ,some suggestions and comments regarding the arrangement of teaching were proposed .%  通过学生自主实验,提出了相对简易的探究浮力方向的实验方法,同时对阿基米德实验进行了改进。改进后的阿基米德实验降低了实验偏差,实验效果直观、明显。本文还对教材的编排提出了建议和意见。

  20. The effects of lateral density gradients, slopes and buoyancy on channel flow: 1D analytical solutions and applications to the SE Canadian Cordillera

    Science.gov (United States)

    Gervais, Félix; Ranalli, Giorgio

    2017-08-01

    We present 1D analytical solutions for channel flow in orogens driven by various types of pressure gradients. Our calculations demonstrate that lateral density gradients in the upper crust, such as would occur across a suture zone separating arc rocks from pericratonic sediments provide a driving force for Poiseuille flow as large as topographic gradients observed in modern mountain belts. For cases for which the gradients are external (topographic and lateral density gradients) and internal (e.g. partial melting of channel material) to the channel, inclination decreases and increases the Poiseuille component of the average flow-velocity within the channel by the cosine and sine of the slope, respectively. The magnitude of the pressure gradient consequent upon the buoyancy generated by partial melting of metapelites in a channel with a 30° slope, such as would occur above an underthrusting basement ramp, is similar to that of topographic or lateral density gradients. Channel flow up a ramp could thus constitute an important exhumation mechanism in large hot orogens. Our calculations indicate that mid-crustal channel flow was a highly likely process in the Late Cretaceous-Paleocene setting of the southeastern Canadian Cordillera. The flow was first driven by the lateral density contrast between pericratonic sediments and the arc-related Intermontane terrane, then by combined effect of topographic gradient and melt-induced buoyancy of the Lower Selkirk Allochthon (part of the Shuswap Complex). Flow up the underthrusting basement ramp resulted in exhumation from mid- to upper-crustal levels. Channel flow then migrated downward to involve basement and overlying cover sequence rocks. Our results indicate that syn-convergent channel flow was a viable and very likely process in the southeastern Canadian Cordillera.

  1. Modeling and Analysis of a Buoyancy-Ballast Driven Airship%一类“浮力-压块”驱动飞艇建模与分析

    Institute of Scientific and Technical Information of China (English)

    邬依林; 刘屿

    2012-01-01

    In view of a new kind of buoyancy-ballast driven airship, the model and dynamics of a kind of buoyancy-ballast driven airship are studied. Based on Kirchhoff equations and Newton-Euler laws, we developed the six degree of freedom nonlinear dynamic model for an airship equipped with independent ballonets and moveable ballast by analysis its movement and stress. On the condition of little perturbation, the nonlinear dynamic model is divided into three group equations by restricting airship motion in longitudinal, lateral and e2-e3 planes respectively. Then the characteristics of mode and respond to input of airship are studied using linearization model and its related parameter. The results of simulation verify the correctness of established model and rationality of theoretical analysis on this kind of stratospheric airship, thus making itself a theoretical basis for the design of its control strategy.%针对一类新型“浮力-压块”驱动的自治飞艇,研究了该类飞艇的动力学建模和动力学特性.在Kirchhoff方程和Newton-Euler理论基础上,通过对飞艇运动及受力分析,建立了包括独立气囊和可运动压块的飞艇六自由度非线性动力学模型,并采用小扰动线性化方法,将飞艇运动分别限制在纵向、横侧向和e2-e3平面内,得到与之对应的三组飞艇线性化方程,其后基于飞艇相关参数和线性化模型,利用Matlab软件平台对飞艇运动模态和输入响应特性进行了分析研究.仿真结果验证了谊类飞艇模型的正确性和理论分析的合理性,为其后控制策略设计提供理论依据.

  2. Negative gravitactic behavior of Euglena gracilis can not be described by the mechanism of buoyancy-oriented upward swimming

    Science.gov (United States)

    Lebert, Michael; Häder, Donat-Peter

    1999-01-01

    Gravitactic behavior of microorganisms has been known for more than a hundred years. Euglena gracilis serves as a model system for gravity-triggered behavioral responses. Two basic mechanisms are discussed for gravitaxis: one is based on a physical mechanism where an asymmetric mass distribution pulls the cell passively in the correct orientation and, in contrast, the involvement of an active sensory system. A recently developed high-resolution motion-tracking system allows the analysis of single tracks during reorientation. The results are compared to a model developed by Fukui and Asai (1985) which describes gravitaxis of Paramecium caudatum on the basis of a physical mechanism. Taking into account the different size, different density, different mass distribution as well as the different velocity, results of the adapted model description of Paramecium were applied to measured data of Euglena. General shapes as well as the time scale of the predicted reorientational movement compared to measurements were different. The analysis clearly rules out the possibility that gravitaxis of Euglena gracilis is based on a pure physical phenomenon, and gives further support to the involvement of an active reorientational system. In addition, it could be shown that cell form changes during reorientation, even in an initial period where no angular change was observed.

  3. A new method for deriving analytical solutions of partial differential equations-Algebraically explicit analytical solutions of two-buoyancy natural convection in porous media

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Analytical solutions of governing equations of various phenomena have their irre-placeable theoretical meanings. In addition, they can also be the benchmark solu-tions to verify the outcomes and codes of numerical solutions, and even to develop various numerical methods such as their differencing schemes and grid generation skills as well. A hybrid method of separating variables for simultaneous partial differential equation sets is presented. It is proposed that different methods of separating variables for different independent variables in the simultaneous equa-tion set may be used to improve the solution derivation procedure, for example, using the ordinary separating method for some variables and using extraordinary methods of separating variables, such as the separating variables with addition promoted by the first author, for some other variables. In order to prove the ability of the above-mentioned hybrid method, a lot of analytical exact solutions of two-buoyancy convection in porous media are successfully derived with such a method. The physical features of these solutions are given.

  4. Development and Assessment of CFD Models Including a Supplemental Program Code for Analyzing Buoyancy-Driven Flows Through BWR Fuel Assemblies in SFP Complete LOCA Scenarios

    Science.gov (United States)

    Artnak, Edward Joseph, III

    This work seeks to illustrate the potential benefits afforded by implementing aspects of fluid dynamics, especially the latest computational fluid dynamics (CFD) modeling approach, through numerical experimentation and the traditional discipline of physical experimentation to improve the calibration of the severe reactor accident analysis code, MELCOR, in one of several spent fuel pool (SFP) complete loss-ofcoolant accident (LOCA) scenarios. While the scope of experimental work performed by Sandia National Laboratories (SNL) extends well beyond that which is reasonably addressed by our allotted resources and computational time in accordance with initial project allocations to complete the report, these simulated case trials produced a significant array of supplementary high-fidelity solutions and hydraulic flow-field data in support of SNL research objectives. Results contained herein show FLUENT CFD model representations of a 9x9 BWR fuel assembly in conditions corresponding to a complete loss-of-coolant accident scenario. In addition to the CFD model developments, a MATLAB based controlvolume model was constructed to independently assess the 9x9 BWR fuel assembly under similar accident scenarios. The data produced from this work show that FLUENT CFD models are capable of resolving complex flow fields within a BWR fuel assembly in the realm of buoyancy-induced mass flow rates and that characteristic hydraulic parameters from such CFD simulations (or physical experiments) are reasonably employed in corresponding constitutive correlations for developing simplified numerical models of comparable solution accuracy.

  5. Analytical and experimental study of instabilities in buoyancy-driven convection in porous media. Progress report, August 1991--April 1992

    Energy Technology Data Exchange (ETDEWEB)

    Georgiadis, J.G.; Behringer, R.; Johnson, G.A.

    1992-04-01

    During the second year of support under the DOE grant, significant progress was made in two directions: (1) Visualization of structure and tow field in randomly packed beds via Magnetic Resonance Imaging, and (2) Shadowgraphic visualization of natural convection in porous systems. This report describes the activities in detail, cite publications which resulted from this project, and conclude with plans for the last phase of the experimental investigation.

  6. A buoyancy-based screen of Drosophila larvae for fat-storage mutants reveals a role for Sir2 in coupling fat storage to nutrient availability.

    Directory of Open Access Journals (Sweden)

    Tânia Reis

    2010-11-01

    Full Text Available Obesity has a strong genetic component, but few of the genes that predispose to obesity are known. Genetic screens in invertebrates have the potential to identify genes and pathways that regulate the levels of stored fat, many of which are likely to be conserved in humans. To facilitate such screens, we have developed a simple buoyancy-based screening method for identifying mutant Drosophila larvae with increased levels of stored fat. Using this approach, we have identified 66 genes that when mutated increase organismal fat levels. Among these was a sirtuin family member, Sir2. Sirtuins regulate the storage and metabolism of carbohydrates and lipids by deacetylating key regulatory proteins. However, since mammalian sirtuins function in many tissues in different ways, it has been difficult to define their role in energy homeostasis accurately under normal feeding conditions. We show that knockdown of Sir2 in the larval fat body results in increased fat levels. Moreover, using genetic mosaics, we demonstrate that Sir2 restricts fat accumulation in individual cells of the fat body in a cell-autonomous manner. Consistent with this function, changes in the expression of metabolic enzymes in Sir2 mutants point to a shift away from catabolism. Surprisingly, although Sir2 is typically upregulated under conditions of starvation, Sir2 mutant larvae survive better than wild type under conditions of amino-acid starvation as long as sugars are provided. Our findings point to a Sir2-mediated pathway that activates a catabolic response to amino-acid starvation irrespective of the sugar content of the diet.

  7. 空心微珠/环氧树脂高强浮力材料的性能及断裂分析%Performance and fracture of hollow glass microsphere/epoxy resin high-strength buoyancy material

    Institute of Scientific and Technical Information of China (English)

    林碧兰; 路新瀛; 陈勤

    2011-01-01

    The high-strength buoyancy material was synthesized with adhesive matrix of epoxy resin and filler of hollow glass microsphere (HGM) activated by silane coupling agent. The characteristics of HGM treated with silane were analyzed by XRD and FRIR. The effect of type and content of HGM on performance of buoyancy material was investigated through density test and uniaxial static compression test. The fracture characteristics and water absorption of buoyancy material were studied by SEM and water absorption test. The results show that the structure of HGM is amorphous. Silane is grafted on the surface of HGM after activation. HGM is perfectly combined with epoxy resin and there is no gap between their interface. The high specific compression strength of HGM is beneficial to the performance of buoyancy material. The density, compression strength and specific compression strength of buoyancy material are 0. 645 ~ 0. 850 g/cm3 , 60 ~ 93 MPa and 92 ~ 112 MPa · cm3 · g-1, respectively. On the fracture surface of buoyancy material with less HGM, HGM is destroyed and there is tailing in the matrix, while the damage degree of HGM increases with the increase of HGM content and finally HGM is destroyed thoroughly. The water absorption of buoyancy material is low.%以环氧树脂为基体,经硅烷活化处理的空心玻璃微珠(HGM)为填充剂,制备了高强浮力材料.采用XRD、FRIR分析了HGM的结构和硅烷处理效果,通过密度测试和单轴静态压缩试验研究了HGM的类型和含量对浮力材料性能的影响,利用SEM和吸水率试验研究了浮力材料的断裂特性和吸水性.结果表明:HGM为无定形结构;硅烷分子接枝在HGM表面,使得HGM与环氧树脂完好结合且两者界面没有间隙沟槽;HGM的较大比压缩强度有利于提高浮力材料的性能;高强浮力材料密度为0.645~0.850 g/cm3,抗压强度为60~93 MPa,比压缩强度为92~112 MPa·cm3·g-1;HGM 含量较少时,浮力材料断裂表面HGM破

  8. Dynamics of the Leeuwin Current: Part 2. Impacts of mixing, friction, and advection on a buoyancy-driven eastern boundary current over a shelf

    Science.gov (United States)

    Benthuysen, Jessica; Furue, Ryo; McCreary, Julian P.; Bindoff, Nathaniel L.; Phillips, Helen E.

    2014-03-01

    depth. When the timescale δt is sufficiently short, the poleward current is nearly barotropic. The current's spatial structure over the shelf is controlled by horizontal mixing, having the structure of a Munk layer. Increasing vertical diffusion deepens the upper layer thickness and strengthens the alongshore current speed. Bottom drag leads to an offshore flow along the bottom, reducing the net onshore transport and weakening the current's poleward acceleration. When δt is long, poleward advection of buoyancy forms a density front near the shelf break, intensifying poleward speeds near the surface. With bottom drag, a bottom Ekman flow advects density offshore, shifting the jet core offshore of the shelf break. The resulting cross-shelf density gradient reverses the meridional current's direction at depth, leading to an equatorward undercurrent.

  9. Implications of flexible work systems for work studies.

    Science.gov (United States)

    Kogi, K

    1997-12-01

    The relationship between changing work systems and work study methods is discussed by focusing on a recent trend toward more flexible work systems in different countries. These systems are commonly characterized by (a) uncoupling of working hours from business hours, (b) combining different atypical work forms and (c) individualized work patterns. Increased flexibility in working patterns is demanded because business hours may be covered by different workers and because special arrangements become necessary for unpopular shifts or linking separate jobs. Changes in work systems seem more successful when they are associated with (a) multiskilled work, (b) independent task implementation, (c) networked communication, (d) balanced or adjusted workload, and (e) accommodation of workers' preferences. Special attention is drawn to safety and health concerns and work-life effects. Many intervention studies done for work improvement are paying attention to multifaceted work aspects, locally available options, and participation by people. All these elements are important because prepackaged solutions do not exist. The following three views seem especially useful for action-oriented work studies: 1) Look at multiple aspects of the work, including work content and atypical work forms; 2) Know worker preferences and available options; and 3) Take into account work elements that may not be well defined, but important from local points of view. It is envisioned that these studies can provide support for a well-informed participatory process of work system changes in each local context.

  10. Análise da absorção de água em dois polímeros expandidos: desenvolvimento do módulo de flutuabilidade de um mini-robô submarino Study of expanded polymers water absorption for buoyancy modulus development of a submarine mini-robot

    Directory of Open Access Journals (Sweden)

    Nadège Bouchonneau

    2010-09-01

    Full Text Available Polímeros expandidos são bastante competitivos para serem utilizados como materiais de flutuabilidade, devido a sua baixa densidade. Em particular, eles se apresentam muito eficientes no desenvolvimento de módulos de flutuabilidade de robôs submarinos do tipo ROV (Remote Operated Vehicle. Este trabalho descreve um estudo da absorção de água em dois diferentes tipos de polímeros expandidos (poliuretano e poliestireno expandido, em diferentes meios aquosos (água do mar e água destilada. Estudo sobre o efeito da geometria das amostras com relação à cinética de absorção de água demonstrou que as amostras com maior área de contato com a água se apresentam mais susceptíveis à absorção de água. Os estudos também revelaram que o poliuretano expandido sofreu uma importante perda de material devido ao seu manuseio durante os ensaios de absorção. A influência do meio aquoso foi também bastante notável para este material, no qual apresentou uma maior taxa de absorção nos ensaios com água destilada em comparação com os ensaios utilizando água do mar. Os resultados das análises demonstraram que o melhor material para ser utilizado como módulo de flutuabilidade do robô submarino é o poliestireno expandido, pois este material não apresentou uma notável degradação e perda de material durante os ensaios de absorção.Owing to the low density and relative low price, expanded polymers appear to be competitive for buoyancy systems. Expanded polymers are particularly efficient to develop buoyancy modules of submarine robots such as ROV (Remote Operated Vehicle. This work describes water absorption mechanisms of two expanded polymers (expanded polyurethane and expanded polystyrene, in various aqueous media (seawater and distilled water. The influence of the samples geometry on the water absorption kinetics was studied. The samples with a larger contact area with water were found to be more susceptible to water absorption

  11. A System for Measurement of Convection Aboard Space Station

    Science.gov (United States)

    Bogatyrev, Gennady P.; Gorbunov, Aleksei V; Putin, Gennady F.; Ivanov, Alexander I.; Nikitin, Sergei A.; Polezhaev, Vadim I.

    1996-01-01

    A simple device for direct measurement of buoyancy driven fluid flows in a low-gravity environment is proposed. A system connecting spacecraft accelerometers data and results of thermal convection in enclosure measurements and numerical simulations is developed. This system will permit also to evaluate the low frequency microacceleration component. The goal of the paper is to present objectives and current results of ground-based experimental and numerical modeling of this convection detector.

  12. The use of salinity contrast for density difference compensation to improve the thermal recovery efficiency in high-temperature aquifer thermal energy storage systems

    NARCIS (Netherlands)

    van Lopik, J.H.; Hartog, N.; Zaadnoordijk, Willem Jan

    2016-01-01

    The efficiency of heat recovery in high-temperature (>60 °C) aquifer thermal energy storage (HT-ATES) systems is limited due to the buoyancy of the injected hot water. This study investigates the potential to improve the efficiency through compensation of the density difference by increased salinity

  13. The Atmospheric Imaging Array Feature and Event System (AFES) for SDO

    Science.gov (United States)

    Hurlburt, N.; Freeland, S.; Cheung, M.; Schrijver, C.

    2008-05-01

    The great data volumes involved in Solar Dynamics Observatory impose the need to have efficient means to access, process and transport data products that goes beyond basic data discovery. In order to reduce system requirements and to improve scientific productivity, we pre-package Ðinterestingî datasets and direct scientists to them through an event-based querying system. This will enable caching of commonly accessed datasets within the Joint Science Operations Center (JSOC) and reduces the (human) time spent searching for and downloading relevant data. This system leverages the infrastructure developed for the Hinode Observation System (http://sot.lmsal.com/sot-data) and incorporates elements of the evolving heliophysics knowledgebase (http://www.lmsal.com/helio-informatics/hpkb). We present the details of the AFES including the ingestion of images, automated and manual tools for identifying and annotation features within the images, and interfaces and webtools for querying and accessing events and their associated data. This work has been supported by NASA through contract NNG04AE00C and Lockheed Martin Research Funds.

  14. Bioregenerative Life Support Systems Test Complex (Bio-Plex) Food Processing System: A Dual System

    Science.gov (United States)

    Perchonok, Michele; Vittadini, Elena; Peterson, Laurie J.; Swango, Beverly E.; Toerne, Mary E.; Russo, Dane M. (Technical Monitor)

    2001-01-01

    A Bioregenerative Life Support Test Complex, BIO-Plex, is currently being constructed at the Johnson Space Center (JSC) in Houston, TX. This facility will attempt to answer the questions involved in developing a lunar or planetary base. The Food Processing System (FPS) of the BIO-Plex is responsible for supplying food to the crew in coordination with the chosen mission scenario. Long duration space missions require development of both a Transit Food System and of a Lunar or Planetary Food System. These two systems are intrinsically different since the first one will be utilized in the transit vehicle in microgravity conditions with mostly resupplied foods, while the second will be used in conditions of partial gravity (hypogravity) to process foods from crops grown in the facility. The Transit Food System will consist of prepackaged food of extended shelf life. It will be supplemented with salad crops that will be consumed fresh. Microgravity imposes significant limitation on the ability to handle food and allows only for minimal processing. The challenge is to develop food systems similar to the International Space Station or Shuttle Food Systems but with a shelf life of 3 - 5 years. The Lunar or Planetary Food System will allow for food processing of crops due to the presence of some gravitational force (1/6 to 1/3 that of Earth). Crops such as wheat, soybean, rice, potato, peanut, and salad crops, will be processed to final products to provide a nutritious and acceptable diet for the crew. Not only are constraints imposed on the FPS from the crops (e.g., crop variation, availability, storage and shelf-life) but also significant requirements are present for the crew meals (e.g., RDA, high quality, safety, variety). The FPS becomes a fulcrum creating the right connection from crops to crew meals while dealing with issues of integration within a closed self-regenerative system (e.g., safe processing, waste production, volumes, air contaminations, water usage, etc

  15. DESIGN AND RESEARCH FOR A NEW TYPE BUOYANCY-LIFTING ROW FLYING-WINGS%一种新型浮升一体化排式飞翼的设计与研究

    Institute of Scientific and Technical Information of China (English)

    李峰; 叶正寅

    2009-01-01

    It has important sciencfic and engineering applications for aircrafts of low speed to design the buoyancy-lifting aircraft with both bigger volume and higher aerodynamic efficiency. Based on the nero-foil NACA0030, some aerodynamic configurations of row flying-wings with the higher volume efficiency (vol-me/surface) were constructed. Different arrayed row flying-wings were calculated and investigated minutely. An aerodynamic configuration of row sweptback flying-wings with the better maneuverability and stability was educed. The numerical simulation results indicate that the lift-drag ratios of row straight flying-wings and row sweptback flying-wings increase by up to 40% and 20%, respectively, and the aerodynamic efficiency of aircrafts are improved obviously from the block of airflow under the anterior flying-wing by the posterior flying-wing. Meanwhile, the chordwise size of buoyancy-lifting row flying-wings is comparatively small so that the surface tension of skin material can be reduced availably. This characteristic provides the wider scope on the skin flexible material selection for high altitude aircrafts.%设计既有较大的内部容积、又有高气动效率的新型浮升一体化气动布局对此类低速飞行器的发展具有重要的科学研究价值和工程应用前景.以NAcA0030翼型为基础,构造了具有较高体积率(体积/表面积)的排式飞翼气动布局.对不同排列形式的排式飞翼进行了详细的计算和评估分析,并提出了具有更好操纵性和稳定性的排式后掠飞翼气动布局.数值模拟结果表明:通过排式飞翼中后翼对前翼下方气流的阻滞作用,排式直飞翼和排式后掠飞翼的升阻比分别增大40%和20%,整个飞行器的气动效率显著提高;同时,浮升一体化排式飞翼的弦向尺寸较小,可有效降低材料的表面张力,这为高空飞行器表面柔性材料提供了较宽的选择范围.

  16. Mooring System Diagnosis and Structural Reliability Control for Position Moored Vessels

    DEFF Research Database (Denmark)

    Fang, Shaoji; Blanke, Mogens; Leira, Bernt J.

    2015-01-01

    Early diagnosis and fault-tolerant control are essential for safe operation of oating platforms where mooring systems maintain vessel position and must withstand environmental loads. This paper considers two critical faults, line breakage and loss of a buoyancy element and employs vector statisti......Early diagnosis and fault-tolerant control are essential for safe operation of oating platforms where mooring systems maintain vessel position and must withstand environmental loads. This paper considers two critical faults, line breakage and loss of a buoyancy element and employs vector...... for monitoring the safety level of each mooring line and, a set-point chasing algorithm accommodates the eects of line failure, as an integral part of the reliability- based set-point chasing control algorithm. The feasibility of the diagnosis and of the fault-tolerant control strategy is veried in model basin...

  17. 浮标的双油囊浮力调节装置密封试验方法研究%Study of the Seal Test Method of the Double Oil Tanks Buoyancy Adjusting Device Based on the Autonomous Profiling Floats

    Institute of Scientific and Technical Information of China (English)

    杨江涛

    2014-01-01

    This paper briefly explain the function of the autonomous profiling floats and analyzed the advantages and disad-vantages of the buoyancy adjusting device which used by the floats.The paper advance the double oil tanks structure of the buoyancy adjusting device and also explain it. Then it has focused on the pressure seal test method and introduced the test process and inspection method. It has also provided the reference for the same kind of test method.%对剖面漂流浮标作了简要说明,并对目前常用的浮力调节装置结构形式优缺点进行了分析,介绍了双油囊结构形式的浮力调节装置,对其结构进行了说明,并阐述了对其耐压密封试验的方法。

  18. Mixed Convection Boundary-layer Flow of a Nanofluid Near Stagnation-point on a Vertical Plate with Effects of Buoyancy Assisting and Opposing Flows

    Directory of Open Access Journals (Sweden)

    Hossein Tamim

    2013-07-01

    Full Text Available In this study, the steady laminar mixed convection boundary layer flow of a nanofluid near the stagnation-point on a vertical plate with prescribed surface temperature is investigated. Here, both assisting and opposing flows are considered and studied. Using appropriate transformations, the system of partial differential equations is transformed into an ordinary differential system of two equations, which is solved numerically by shooting method, coupled with Runge-Kutta scheme. Three different types of nanoparticles, namely copper Cu, alumina Al2O3 and titania TiO2 with water as the base fluid are considered. Numerical results are obtained for the skin-friction coefficient and Nusselt number as well as for the velocity and temperature profiles for some values of the governing parameters, namely, the nanoparticle volume fraction parameter &Phiand mixed convection parameter &lambda It is found that the highest rate of heat transfer occurs in the mixed convection with assisting flow while the lowest one occurs in the mixed convection with opposing flow. Moreover, the skin friction coefficient and the heat transfer rate at the surface are highest for copper–water nanofluid compared to the alumina–water and titania–water nanofluids.

  19. FORMULATION AND EVALUATION OF ZIDOVUDINE CONTROLLED RELEASE GAS POWERED SYSTEM USING HYDROPHILLIC POLYMER

    Directory of Open Access Journals (Sweden)

    N. G. Raghavendra Rao

    2011-03-01

    Full Text Available Zidovudine is the first approved compound for the treatment of AIDS; however the main limitation to therapeutic effectiveness of zidovudine is its dose-dependent toxicity, short biological half-life and poor bioavailability. The present research work an attempt has been made to develop the Zidovudine gas powered drug delivery system for controlled release. The Zidovudine gas powered tablets were prepared by direct compression method by using the different grades of hydrophilic polymer like HPMC. The sodium bicarbonates and citric acid were also used as a gas generating agent. The power blend was subjected for pre-compressional parameters. The prepared gas powered tablets are evaluated to post-compressional analysis of parameter such as hardness, friability, weight variation , thickness, drug content, lag time subsequently buoyancy time and in-vitro dissolution studies and swelling index. All the pre and post-compressional parameter are evaluated the results were within acceptable limits. The results of in-vitro buoyancy time and lag time study, the values of in-vitro buoyancy time ranges from 38 to 960 min where as floating lag time ranges from 3.5 to 60 min. The formulation F4 shows the lag time 3.5 min and buoyancy time 960 min. The results of in-vitro buoyancy time and lag time study revealed that as the concentration of sodium bicarbonate increases there is increase in total buoyancy time and decrease in lag time. It is evident from the in-vitro dissolution data that increase in citric acid concentration increased the release rate but reduced the floating time, probably due to of excess carbon dioxide, disturbing the monolithic tablet. The citric acid level in the formulations greatly influenced the drug release. The formulation, F-4 shows maximum drug release at the end of 12 hrs. Form this study, it is concluded that, the formulation retained for longer periods of time in the stomach and provides controlled release of the drug. Hence it

  20. A Model of Secondary Hydrocarbon Migration As a Buoyancy-Driven Separate Phase Flow Un modèle de migration secondaire des hydrocarbures considéré comme un écoulement en phases séparées régi par la poussée d'Archimède

    Directory of Open Access Journals (Sweden)

    Lehner F. K.

    2006-11-01

    Full Text Available A mathematical model of secondary migration is described which permits the prediction of hydrocarbon migration and accumulation patterns in a sedimentary basin, if source rock expulsion rates and geometrical and hydraulic properties of major carrier systems are known through geological time. In this model, secondary migration is treated as buoyancy-driven, segregated flow of hydrocarbons in hydrostatic aquifers. Lateral, updip migration is conceived as a Boussinesq-type, free-surface flow, with source and sink terms representing supply from source rocks and leakage through cap rocks and faults. This permits a two-dimensional, map-view mathematical description of a three-dimensional, time-dependent secondary migration system. A nine-point finite difference approximation has been developed to minimize numerical dispersion, and upstream-weighting is used to obtain stable solutions. Example computations for simple, single carrier bed structures are presented. L'article décrit un modèle mathématique de migration secondaire prédisant la migration des hydrocarbures et leur accumulation dans un bassin sédimentaire, lorsque les taux d'expulsion des roches mères et les propriétés géométriques et hydrauliques des principaux systèmes de drainage sont connus à l'échelle du temps géologique. Dans ce modèle, la migration secondaire est traitée comme un écoulement des hydrocarbures en phase séparée, contrôlé par la poussée d'Archimède, dans des aquifères hydrostatiques. La migration latérale est considérée comme un écoulement de type Boussinesq, à surface libre, avec des termes sources et puits représentant les apports venant des roches mères et les fuites à travers les couvertures et les failles. Ceci permet une description mathématique bidimensionnelle cartographiable d'un système de migration secondaire tridimensionnel et dépendant du temps. On utilise une approximation type différences finies à neuf points pour minimiser

  1. Transport through Prince William Sound: numerical study in a nowcast/forecast system

    Science.gov (United States)

    Wu, Xinglong

    2011-04-01

    Using 1-year simulated data from extended Prince William Sound (PWS) nowcast/forecast system, both barotropic and baroclinic transports through two-strait, semi-enclosed PWS are examined. With major tidal constituents removed, hourly time series of volume transports through two straits are significantly correlated with net transport well balanced by the time rate of change of the PWS spatial-mean sea level. A transition frequency band occurs within the coherence function of hourly volume transports, which is characterized by a nearly 180° phase shift between low-frequency (>30 h) and high-frequency (exchange flow is determined to be mainly buoyancy-driven, geostrophic flow, and thus largely affected by seasonal variability of buoyancy over the shelf and PWS.

  2. Formulation of gastroretentive floating drug delivery system using hydrophilic polymers and its in vitro characterization

    Directory of Open Access Journals (Sweden)

    Venkata Srikanth Meka

    2014-04-01

    Full Text Available The aim of the present research is to formulate and evaluate the gastroretentive floating drug delivery system of antihypertensive drug, propranolol HCl. Gastroretentive floating tablets (GRFT were prepared by using a synthetic hydrophilic polymer polyethylene oxide of different grades such as PEO WSR N-12 K and PEO 18 NF as release retarding polymers and calcium carbonate as gas generating agent. The GRFT were compressed by direct compression strategy and the tablets were evaluated for physico-chemical properties, in vitro buoyancy, swelling studies, in vitro dissolution studies and release mechanism studies. From the dissolution and buoyancy studies, F 9 was selected as an optimized formulation. The optimized formulation followed zero order rate kinetics with non-Fickian diffusion mechanism. The optimized formulation was characterised with FTIR studies and observed no interaction between the drug and the polymers.

  3. 'Prepackaged symbioses': propagules on roots of the myco-heterotrophic plant Arachnitis uniflora.

    Science.gov (United States)

    Domínguez, Laura; Sérsic, Alicia; Melville, Lewis; Peterson, R Larry

    2006-01-01

    Arachnitis uniflora, a myco-heterotrophic plant species, has fleshy tuberous roots colonized by the arbuscular mycorrhizal fungal genus Glomus (Phylum Glomeromycota). These roots produce apical and lateral propagules, both reported here for the first time. The objective of the study was to characterize the ontogeny and structure of the propagules, and to determine their function. Scanning electron microscopy, laser scanning confocal microscopy and light microscopy were used to study the ontogeny and structure of the propagules. Propagules developed either from cortical parenchyma cells or from cells immediately beneath the root cap; they developed a shoot meristem and cells in the basal region which were colonized by various fungal structures including hyphae and vesicles. These propagules may detach from the roots, establishing new plants.

  4. Caffeine content of prepackaged national-brand and private-label carbonated beverages.

    Science.gov (United States)

    Chou, K-H; Bell, L N

    2007-08-01

    Caffeine is a well-known stimulant that is added as an ingredient to various carbonated soft drinks. Due to its stimulatory and other physiological effects, individuals desire to know the exact amount of caffeine consumed from these beverages. This study analyzed the caffeine contents of 56 national-brand and 75 private-label store-brand carbonated beverages using high-performance liquid chromatography. Caffeine contents ranged from 4.9 mg/12 oz (IGA Cola) to 74 mg/12 oz (Vault Zero). Some of the more common national-brand carbonated beverages analyzed in this study with their caffeine contents were Coca-Cola (33.9 mg/12 oz), Diet Coke (46.3 mg/12 oz), Pepsi (38.9 mg/12 oz), Diet Pepsi (36.7 mg/12 oz), Dr Pepper (42.6 mg/12 oz), Diet Dr Pepper (44.1 mg/12 oz), Mountain Dew (54.8 mg/12 oz), and Diet Mountain Dew (55.2 mg/12 oz). The Wal-Mart store-brand beverages with their caffeine contents were Sam's Cola (12.7 mg/12 oz), Sam's Diet Cola (13.3 mg/12 oz), Dr Thunder (30.6 mg/12 oz), Diet Dr Thunder (29.9 mg/12 oz), and Mountain Lightning (46.5 mg/12 oz). Beverages from 14 other stores were also analyzed. Most store-brand carbonated beverages were found to contain less caffeine than their national-brand counterparts. The wide range of caffeine contents in carbonated beverages indicates that consumers would benefit from the placement of caffeine values on food labels.

  5. 21 CFR 179.45 - Packaging materials for use during the irradiation of prepackaged foods.

    Science.gov (United States)

    2010-04-01

    ... PRODUCTION, PROCESSING AND HANDLING OF FOOD Packaging Materials for Irradiated Foods § 179.45 Packaging... chapter. (c) Ethylene-vinyl acetate copolymers complying with § 177.1350 of this chapter. The ethylene... exceed 1 pct by weight of the polymer. Triethylene glycol as described in § 178.3740(b) of this chapter...

  6. Design Analysis of a Prepackaged Nuclear Power Plant for an Ice Cap Location

    Science.gov (United States)

    1959-01-15

    manufacturers’ data and measured values durinp APPR-1 operation. The head loss due to frlctlon/lOO ft. of l/2n 16 BWG stainless steel tubing was calcu...A\\ ^rY/r-A*.-* prfi-crd Y WL&4& au td M.v: 357 &-235 TABI£ 10*1 DOSE RATES * FROM ACTIVATED COMPONENTS Shutdown Times Component 1 day...i^^L^l . 6.68 °F (T.-T^ = (178.020) (.020) . ^ ITc-Ti;^ ^^ ^ - 7.69 Td = 617.09 / 6.68 / 7.69 = 63l.46 0r 4.3

  7. Financial restructuring can be problematic under Chapter 11. Pre-packaged bankruptcy saves time and money.

    Energy Technology Data Exchange (ETDEWEB)

    Goffman, J.M.; Ashmead, J.R. [O`Sullivan, Graev & Karabell, NY (United States)

    1995-05-15

    For better or worse, deregulation is now a factor in the electric utility industry. As a general proposition, deregulation makes for increased competition, which in turn will trim costs for consumers. Deregulation of the electric industry means that utilities face the prospect of freezing or reducing rates to retain market share. Stranded investments and the burdens of above-market supply contracts and construction and development contracts (especially nuclear-related contracts) will place additional pressure on these utilities and further reduce their revenue. Ultimately these problems could hinder a utility`s ability to service its debt, invest for the future, and provide a reasonable rate of return to investors.

  8. 新型纸箱包装机PLC控制系统设计%Design of PLC Control System of New Type Carton Packaging Machine

    Institute of Scientific and Technical Information of China (English)

    赵汉雨; 姬少龙; 刘存祥; 罗飞

    2011-01-01

    Based on the designed mechanical, pneumatic system,the paper selected CP1H-X40DT-D PLC to study control system of the carton packaging machine. The paper assigned I / 0 addresses value, designed PLC exterior circuit and program control flow chart thus realized the automatic control functions of the cardboard feeding and pre-packaging product conveying, carton packaging forming, glue spraying, packaging sealing and shaping. This control system has realized high reliability and cost-effective. [ Ch, 5 fig. 1 tab. 10 ref. ]%基于已设计的机械及气动系统,选择欧姆龙公司CP1H-X40DT-D PLC研制纸箱包装机控制系统.并进行了L/O点分配、PLC外部接线图及程序控制流程图设计,实现了纸板供送、待装箱产品输送、纸箱装箱成形、喷胶封箱整形等工作过程的自动控制.具有很高的可靠性和性价比.图5表1参10

  9. How to influence Employees’ Business Process Compliance with Process-Enforcing Technological Agents : 3. post-ECIS JAIS Theory Development Workshop

    NARCIS (Netherlands)

    Hadasch, Frank; Maedche, Alexander; Mueller, Benjamin

    2013-01-01

    Business process compliance of individual employees is important in organizational environments to facilitate effective coordination among employees and to give managers insights into subordinates’ work outcomes. While the adoption of pre-packaged software application systems promises support for th

  10. Topology Optimization including Inequality Buoyancy Constraints

    NARCIS (Netherlands)

    Picelli, R.; Van Dijk, R.; Vicente, W.M.; Pavanello, R.; Langelaar, M.; Van Keuen, A.

    2014-01-01

    This paper presents an evolutionary topology optimization method for applications in design of completely submerged buoyant devices with design-dependent fluid pressure loading. This type of structures aid rig installations and pipeline transportation in all water depths in offshore structural

  11. Topology Optimization including Inequality Buoyancy Constraints

    NARCIS (Netherlands)

    Picelli, R.; Van Dijk, R.; Vicente, W.M.; Pavanello, R.; Langelaar, M.; Van Keuen, A.

    2014-01-01

    This paper presents an evolutionary topology optimization method for applications in design of completely submerged buoyant devices with design-dependent fluid pressure loading. This type of structures aid rig installations and pipeline transportation in all water depths in offshore structural engin

  12. DNA packaging induced by micellar aggregates: a novel in vitro DNA condensation system.

    Science.gov (United States)

    Ghirlando, R; Wachtel, E J; Arad, T; Minsky, A

    1992-08-11

    Evidence for a conceptually novel DNA packaging process is presented. X-ray scattering, electron microscopy, and circular dichroism measurements indicate that in the presence of positively charged micellar aggregates and flexible anionic polymers, such as negatively charged polypeptides or single-stranded RNA species, a complex is formed in which DNA molecules are partially embedded within a micellar scaffold and partially condensed into highly packed chiral structures. Based on studies of micelle-DNA and micelle-flexible anionic polymer systems, as well as on the known effects of a high charge density upon the micellar organization, a DNA packaging model is proposed. According to this model, the DNA induces the elongation of the micelles into rodlike aggregates, forming a closely packed matrix in which the DNA molecules are immobilized. In contrast, the flexible anionic polymers stabilize clusters of spherical micelles which are proposed to effect a capping of the rodlike micelles, thus arresting their elongation and creating surfactant-free segments of the DNA that are able to converge and collapse. Thus, unlike other in vitro DNA packaging systems, in which condensation follows encounters between charge-neutralized DNA molecules, a prepackaging phase where the DNA is immobilized within a matrix is proposed in this case. Cellular and nuclear membranes have been implicated in DNA packaging processes in vivo, and negatively charged polyelectrolytes were shown to be involved in the processes. These observations, combined with the basic tenets of the DNA condensation system described here, allow for the progression to the study of more elaborate model systems and thus might lead to insights into the nature and roles of the intricate in vivo DNA-membrane complexes.

  13. systems

    Directory of Open Access Journals (Sweden)

    Alexander Leonessa

    2000-01-01

    Full Text Available A nonlinear robust control-system design framework predicated on a hierarchical switching controller architecture parameterized over a set of moving nominal system equilibria is developed. Specifically, using equilibria-dependent Lyapunov functions, a hierarchical nonlinear robust control strategy is developed that robustly stabilizes a given nonlinear system over a prescribed range of system uncertainty by robustly stabilizing a collection of nonlinear controlled uncertain subsystems. The robust switching nonlinear controller architecture is designed based on a generalized (lower semicontinuous Lyapunov function obtained by minimizing a potential function over a given switching set induced by the parameterized nominal system equilibria. The proposed framework robustly stabilizes a compact positively invariant set of a given nonlinear uncertain dynamical system with structured parametric uncertainty. Finally, the efficacy of the proposed approach is demonstrated on a jet engine propulsion control problem with uncertain pressure-flow map data.

  14. Computational fluid dynamics for turbomachinery internal air systems.

    Science.gov (United States)

    Chew, John W; Hills, Nicholas J

    2007-10-15

    Considerable progress in development and application of computational fluid dynamics (CFD) for aeroengine internal flow systems has been made in recent years. CFD is regularly used in industry for assessment of air systems, and the performance of CFD for basic axisymmetric rotor/rotor and stator/rotor disc cavities with radial throughflow is largely understood and documented. Incorporation of three-dimensional geometrical features and calculation of unsteady flows are becoming commonplace. Automation of CFD, coupling with thermal models of the solid components, and extension of CFD models to include both air system and main gas path flows are current areas of development. CFD is also being used as a research tool to investigate a number of flow phenomena that are not yet fully understood. These include buoyancy-affected flows in rotating cavities, rim seal flows and mixed air/oil flows. Large eddy simulation has shown considerable promise for the buoyancy-driven flows and its use for air system flows is expected to expand in the future.

  15. 77 FR 19069 - Airworthiness Directives; Goodrich Evacuation Systems Approved Under Technical Standard Order...

    Science.gov (United States)

    2012-03-30

    ... inadequate buoyancy to support the raft's passenger capacity during ditching and increase the chance for... inadequate buoyancy to support the raft's passenger capacity during ditching and increase the chance...

  16. 76 FR 81885 - Airworthiness Directives; Goodrich Evacuation Systems Approved Under Technical Standard Order...

    Science.gov (United States)

    2011-12-29

    ... buoyancy to support the raft's passenger capacity during ditching and increase the chance for injury to... inadequate buoyancy to support the raft's passenger capacity during ditching and increase the chance...

  17. Work Systems Package/Pontoon Implacement Vehicle Operational Testing at San Clemente Island, 1979. Demonstration of a Technology for Remotely Controlled Deep-Water Recovery of Objects up to 5 Tons from Depths to 20000 Feet.

    Science.gov (United States)

    1980-06-06

    constant bag volume is maintained by a relief valve which keeps the internal bag pressure at 5 to 10 psi over ambient pressure. Buoyancy catl be...attachment devices and techniques by operators who \\ ere new to the system’s operational idiosyncrasies. When considering these facts, the reality of...derived from previous programs, and new , recoery techniques which were generated specifically for the San Clemente Island (SCI) operations. The ability to

  18. Investigation and Modelling of Thermal Conditions in Low Flow SDHW Systems

    DEFF Research Database (Denmark)

    Shah, Louise Jivan

    1999-01-01

    The purpose of this study was to characterise the thermal conditions in low flow SDHW systems. As the heat storage has proved to be the most important system component, there has been an emphasis on this component in the study. A literature survey revealed that the mantle tank heat storage type...... and compared with the CFD-predicted flow structures in the mantle. The results showed that the mantle flow was highly dominated by buoyancy and the CFD-models were able to model this flow. With a steel mantle tank, different dynamic thermal experiments were carried out in a heat storage test facility...

  19. Investigation of bubble behaviours in wet central heating systems

    Directory of Open Access Journals (Sweden)

    Shefik Ali

    2014-03-01

    Full Text Available A series of experimental measurements has been conducted in order to investigate the bubble behaviours through the horizontal pipe line of the domestic wet central heating systems. Obtained results exposed the effect of 90 degree bend, buoyancy forces on bubbly two phase flow patterns and effect of velocity on void fractions and bubble diameters. Distance chosen for the first sight glass (HSG0 was sufficient enough to note the effect of 90 degree bend on void fraction patterns. Due to the effect of 90 degree bend, position of the peak void fractions across the pipe section lowers, with an increase in bulk fluid velocity. Bubbles tend to flow for longer distance at the bottom of the pipe section. Buoyancy force effect is demonstrated with figures for highest bulk fluid velocity at three different positions. Analysis of four different flow rates at two different saturation ratios show reduction for average bubble diameters and void fractions when bulk fluid velocity increases. An attempt to predict bubble dissolution rates across the horizontal pipeline of the system is made, however results show some uncertainties.

  20. Investigation of bubble behaviours in wet central heating systems

    Science.gov (United States)

    Shefik, Ali; Ge, Yunting

    2014-03-01

    A series of experimental measurements has been conducted in order to investigate the bubble behaviours through the horizontal pipe line of the domestic wet central heating systems. Obtained results exposed the effect of 90 degree bend, buoyancy forces on bubbly two phase flow patterns and effect of velocity on void fractions and bubble diameters. Distance chosen for the first sight glass (HSG0) was sufficient enough to note the effect of 90 degree bend on void fraction patterns. Due to the effect of 90 degree bend, position of the peak void fractions across the pipe section lowers, with an increase in bulk fluid velocity. Bubbles tend to flow for longer distance at the bottom of the pipe section. Buoyancy force effect is demonstrated with figures for highest bulk fluid velocity at three different positions. Analysis of four different flow rates at two different saturation ratios show reduction for average bubble diameters and void fractions when bulk fluid velocity increases. An attempt to predict bubble dissolution rates across the horizontal pipeline of the system is made, however results show some uncertainties.

  1. systems

    Directory of Open Access Journals (Sweden)

    Patrick L. Brockett

    1978-01-01

    Full Text Available Suppose S={{Xnj,   j=1,2,…,kn}} is an infinitesimal system of random variables whose centered sums converge in law to a (necessarily infinitely divisible distribution with Levy representation determined by the triple (γ,σ2,M. If {Yj,   j=1,2,…} are independent indentically distributed random variables independent of S, then the system S′={{YjXnj,j=1,2,…,kn}} is obtained by randomizing the scale parameters in S according to the distribution of Y1. We give sufficient conditions on the distribution of Y in terms of an index of convergence of S, to insure that centered sums from S′ be convergent. If such sums converge to a distribution determined by (γ′,(σ′2,Λ, then the exact relationship between (γ,σ2,M and (γ′,(σ′2,Λ is established. Also investigated is when limit distributions from S and S′ are of the same type, and conditions insuring products of random variables belong to the domain of attraction of a stable law.

  2. system

    Science.gov (United States)

    Garcilazo, H.; Valcarce, A.; Vijande, J.

    2017-07-01

    Using local central Yukawa-type Malfliet-Tjon interactions reproducing the low-energy parameters and phase shifts of the nn system, and the latest updates of the nΛ and ΛΛ Nijmegen ESC08c potentials, we study the possible existence of a bound state. Our results indicate that the is unbound, being just above threshold. We discuss the role played by the 1 S 0 nn repulsive term of the Yukawa-type Malfliet-Tjon interaction. Supported by COFAA-IPN (México), Ministerio de Economía, Industria y Competitividad and EU FEDER (FPA2013-47443, FPA2015-69714-REDT, FPA2016-77177), Junta de Castilla y León (SA041U16) and Generalitat Valenciana PrometeoII/2014/066

  3. SYSTEM

    Directory of Open Access Journals (Sweden)

    K. Swarnalatha

    2013-01-01

    Full Text Available Risk analysis of urban aquatic systems due to heavy metals turns significant due to their peculiar properties viz. persis tence, non-degradab ility, toxicity, and accumulation. Akkulam Veli (AV, an urba n tropical lake in south India is subjected to various environmental stresses due to multiple waste discharge, sand mining, developmental activities, tour ism related activitie s etc. Hence, a comprehensive approach is adopted for risk assessment using modified degree of contamination factor, toxicity units based on numerical sediment quality guidelines (SQGs, and potentialecological risk indices. The study revealed the presence of toxic metals such as Cr, C d, Pb and As and the lake is rated under ‘low ecological risk’ category.

  4. Influence of zero-G on single-cell systems and zero-G fermenter design concepts

    Science.gov (United States)

    Mayeux, J. V.

    1977-01-01

    An analysis was made to identify potential gravity-sensitive mechanisms that may be present in the single-cell growth system. Natural convection (density gradients, induced sedimentation, and buoyancy) is important in microbial systems. The absence of natural convection in the space-flight environment could provide an opportunity for new approaches for developments in industrial fermentation and agriculture. Some of the potential influences of gravity (i.e., convection, sedimentation, etc.) on the cell were discussed to provide insight into what experimental areas may be pursued in future space-flight research programs.

  5. Calculation of the self-formation driving force for composite microstructure in liquid immiscible alloy system

    Institute of Scientific and Technical Information of China (English)

    LIU Xingjun; WANG Cuiping; Ikuo OHNUMA; Ryosuke KAINUMA; Kiyohito ISHIDA; CHEN Xiaohu

    2005-01-01

    Using Becker's method, we calculate the interfacial energy between two liquid phases in an immiscible system. Based on the Gibbs-Thomson equation, the force acting on the droplet towards the thermal center can be obtained by integrating the interfacial energy between the droplet and matrix liquid phase, which is related to both the radius of a droplet and the temperature gradient. In addition, the forces of gravitation and buoyancy also act on the droplet. The calculated results indicate that the resultant for these forces together mainly decides the microstructure morphology of the solidified alloy. The calculated results are in good agreement with the corresponding experimental results.

  6. Two lighter than air systems in opposing flight regimes: An unmanned short haul, heavy load transport balloon and a manned, light payload airship

    Science.gov (United States)

    Pohl, R. A.

    1975-01-01

    Lighter Than Air vehicles are generally defined or categorized by the shape of the balloon, payload capacity and operational flight regime. Two balloon systems that are classed as being in opposite categories are described. One is a cable guided, helium filled, short haul, heavy load transport Lighter Than Air system with a natural shaped envelope. The other is a manned, aerodynamic shaped airship which utilizes hot air as the buoyancy medium and is in the light payload class. While the airship is in the design/fabrication phase with flight tests scheduled for the latter part of 1974, the transport balloon system has been operational for some eight years.

  7. Boundary layer control of rotating convection systems.

    Science.gov (United States)

    King, Eric M; Stellmach, Stephan; Noir, Jerome; Hansen, Ulrich; Aurnou, Jonathan M

    2009-01-15

    Turbulent rotating convection controls many observed features of stars and planets, such as magnetic fields, atmospheric jets and emitted heat flux patterns. It has long been argued that the influence of rotation on turbulent convection dynamics is governed by the ratio of the relevant global-scale forces: the Coriolis force and the buoyancy force. Here, however, we present results from laboratory and numerical experiments which exhibit transitions between rotationally dominated and non-rotating behaviour that are not determined by this global force balance. Instead, the transition is controlled by the relative thicknesses of the thermal (non-rotating) and Ekman (rotating) boundary layers. We formulate a predictive description of the transition between the two regimes on the basis of the competition between these two boundary layers. This transition scaling theory unifies the disparate results of an extensive array of previous experiments, and is broadly applicable to natural convection systems.

  8. Risk of Performance Decrement and Crew Illness Due to an Inadequate Food System

    Science.gov (United States)

    Douglas, Grace L.; Cooper, Maya; Bermudez-Aguirre, Daniela; Sirmons, Takiyah

    2016-01-01

    NASA is preparing for long duration manned missions beyond low-Earth orbit that will be challenged in several ways, including long-term exposure to the space environment, impacts to crew physiological and psychological health, limited resources, and no resupply. The food system is one of the most significant daily factors that can be altered to improve human health, and performance during space exploration. Therefore, the paramount importance of determining the methods, technologies, and requirements to provide a safe, nutritious, and acceptable food system that promotes crew health and performance cannot be underestimated. The processed and prepackaged food system is the main source of nutrition to the crew, therefore significant losses in nutrition, either through degradation of nutrients during processing and storage or inadequate food intake due to low acceptability, variety, or usability, may significantly compromise the crew's health and performance. Shelf life studies indicate that key nutrients and quality factors in many space foods degrade to concerning levels within three years, suggesting that food system will not meet the nutrition and acceptability requirements of a long duration mission beyond low-Earth orbit. Likewise, mass and volume evaluations indicate that the current food system is a significant resource burden. Alternative provisioning strategies, such as inclusion of bioregenerative foods, are challenged with resource requirements, and food safety and scarcity concerns. Ensuring provisioning of an adequate food system relies not only upon determining technologies, and requirements for nutrition, quality, and safety, but upon establishing a food system that will support nutritional adequacy, even with individual crew preference and self-selection. In short, the space food system is challenged to maintain safety, nutrition, and acceptability for all phases of an exploration mission within resource constraints. This document presents the

  9. Floating and bioadhesive delivery system of metoprolol succinate: Formulation, development and in vitro evaluation

    Directory of Open Access Journals (Sweden)

    Mohan Rathi

    2012-01-01

    Full Text Available Aim of this study was to develop gastroretentive sustained release floating and bioadhesive drug delivery system (FBDDS to prolong the gastric retention time of Metoprolol succinate. Tablets were prepared employing hydroxypropyl methylcellulose (HPMC K100M as hydrophilic gel material, sodium bicarbonate as gas-generating agent and Sodium CMC (SCMC as bioadhesive polymer. A 3 2 full factorial design and response surface methodology were used for designing of experiment, mapping change in responses and deriving optimum formulation. Selected independent variables were amounts HPMC K100M and SCMC polymer while floating lag time (FLT, bioadhesive strength, t 50 (time taken to release 50% of drug and t90 (time taken to release 90% of drug were selected as dependent variables. Investigation of functionality of individual polymer to predict effect on dependent variable were statistically analyzed using the RSM. Tablets were also evaluated for physical properties, swelling and matrix erosion. Increase in concentration of HPMC and decrease in concentration of SCMC resulted in retardation of drug release. Furthermore, combination of HPMC K100M and sodium bicarbonate along with SCMC was found to affect buoyancy, bioadhesion strength and drug release. Optimized formulation showed values of dependent variables close to predicted values. Optimized formulation follows Higuchi kinetics with short buoyancy lag time, total buoyancy time of more than 24 hours and could maintain drug release for 24 hours. Content uniformity, hardness, friability, weight variation were all lying within limits. Hence, FBDDS was found to be very promising and alternative approach to increase gastric retention of dosage form and may improve bioavailability.

  10. Design and research on a variable ballast system for deep-sea manned submersibles

    Institute of Scientific and Technical Information of China (English)

    QIU Zhong-liang

    2008-01-01

    Variable ballast systems are necessary for manned submersibles to adjust their buoyancy. In this paper,the design of a variable ballast system for a manned submersible is described. The variable ballast system uses a super high pressure hydraulic seawater system. A super high pressure seawater pump and a deep-sea brushless DC motor are used to pump seawater into or from the variable ballast tank,increasing or decreasing the weight of the manned submersible. A magnetostrictive linear displacement transducer can detect the seawater level in the variable ballast tank. Some seawater valves are used to control pumping direction and control on-off states. The design and testing procedure for the valves is described. Finally,the future development of variable ballast systems and seawater hydraulic systems is projected.

  11. Foodborne pathogenic bacteria in prepackaged fresh retail portions of farmed rainbow trout and salmon stored at 3 degrees C.

    Science.gov (United States)

    González-Rodríguez, M N; Sanz, J J; Santos, J A; Otero, A; García-López, M L

    2002-06-05

    Twelve lots of fresh unskinned fillets of rainbow trout (Oncorhynchus mykiss) and 10 lots of fresh sliced salmon (Salmo salar) prepacked in trays wrapped with an oxygen-permeable film were obtained immediately after packing from two supermarkets having in-plant facilities for packaging wet fish. During storage at 3 degrees C, Listeria innocua was detected in eight lots of trout fillets after 4 days storage. L. monocytogenes was recovered from a single lot also contaminated with L. innocua. Initial numbers of aeromonads were significantly (p fish products, these bacteria significantly (p < 0.05) increased up until spoilage. Most Aeromonas spp. isolates from trout fillets were assigned to A. veronii biovar sobria HG8 (hybridisation group 8), A. caviae HG4, A. eucrenophila HG6, A. hydrophila HG1 and A. veronii biovar veronii HG10. Strains of HG12 (A. schubertii), HG4 and HG8 formed the majority of aeromonads recovered from salmon slices.

  12. Conveniently Pre-Tagged and Pre-Packaged: Extended Molecular Identification and Metagenomics Using Complete Metazoan Mitochondrial Genomes

    Science.gov (United States)

    Dettai, Agnes; Gallut, Cyril; Brouillet, Sophie; Pothier, Joel; Lecointre, Guillaume; Debruyne, Régis

    2012-01-01

    Background Researchers sorely need markers and approaches for biodiversity exploration (both specimen linked and metagenomics) using the full potential of next generation sequencing technologies (NGST). Currently, most studies rely on expensive multiple tagging, PCR primer universality and/or the use of few markers, sometimes with insufficient variability. Methodology/Principal Findings We propose a novel approach for the isolation and sequencing of a universal, useful and popular marker across distant, non-model metazoans: the complete mitochondrial genome. It relies on the properties of metazoan mitogenomes for enrichment, on careful choice of the organisms to multiplex, as well as on the wide collection of accumulated mitochondrial reference datasets for post-sequencing sorting and identification instead of individual tagging. Multiple divergent organisms can be sequenced simultaneously, and their complete mitogenome obtained at a very low cost. We provide in silico testing of dataset assembly for a selected set of example datasets. Conclusions/Significance This approach generates large mitogenome datasets. These sequences are useful for phylogenetics, molecular identification and molecular ecology studies, and are compatible with all existing projects or available datasets based on mitochondrial sequences, such as the Barcode of Life project. Our method can yield sequences both from identified samples and metagenomic samples. The use of the same datasets for both kinds of studies makes for a powerful approach, especially since the datasets have a high variability even at species level, and would be a useful complement to the less variable 18S rDNA currently prevailing in metagenomic studies. PMID:23251474

  13. Study on flow characteristics of solid/liquid system in lysozyme crystal growth

    Institute of Scientific and Technical Information of China (English)

    CUI HaiLiang; YU Yong; CHEN WanChun; KANG Qi

    2007-01-01

    During the process of lysozyme protein crystallization with batch method, the macroscopic flow field of solid/liquid system was observed by particle image velocimetry (PIV). Furthermore, a normal growth rate of (110) face and local flow field around a single protein crystal were obtained by a long work distance microscope. The experimental results showed that the average velocity, the maximal velocity of macroscopic solid/liquid system and the velooity of local flow field around single protein crystal were fluctuant. The effective boundary layer thickness δeff, the concentration at the interface Gi and the characteristic velocity V were calculated using a convection-diffusion model. The results showed that the growth of lysozyme crystal in this experiment was dominated by interfacial kinetics rather than bulk transport, and the function of buoyancy-driven flow in bulk transport was small, however, the effect of bulk transport in crystal growth had a tendency to increase with the increase of lysozyme concentration. The calculated results also showed that the order of magnitude of shear force was about 10-21 N,which was much less than the bond force between the lysozyme molecules. Therefore the shear force induced by buoyancy-driven flows cannot remove the protein molecules from the interface of crystal.

  14. Development of three-dimensional integrated microchannel-electrode system to understand the particles' movement with electrokinetics.

    Science.gov (United States)

    Yao, J; Obara, H; Sapkota, A; Takei, M

    2016-03-01

    An optical transparent 3-D Integrated Microchannel-Electrode System (3-DIMES) has been developed to understand the particles' movement with electrokinetics in the microchannel. In this system, 40 multilayered electrodes are embedded at the 2 opposite sides along the 5 square cross-sections of the microchannel by using Micro Electro-Mechanical Systems technology in order to achieve the optical transparency at the other 2 opposite sides. The concept of the 3-DIMES is that the particles are driven by electrokinetic forces which are dielectrophoretic force, thermal buoyancy, electrothermal force, and electroosmotic force in a three-dimensional scope by selecting the excitation multilayered electrodes. As a first step to understand the particles' movement driven by electrokinetic forces in high conductive fluid (phosphate buffer saline (PBS)) with the 3-DIMES, the velocities of particles' movement with one pair of the electrodes are measured three dimensionally by Particle Image Velocimetry technique in PBS; meanwhile, low conductive fluid (deionized water) is used as a reference. Then, the particles' movement driven by the electrokinetic forces is discussed theoretically to estimate dominant forces exerting on the particles. Finally, from the theoretical estimation, the particles' movement mainly results from the dominant forces which are thermal buoyancy and electrothermal force, while the velocity vortex formed at the 2 edges of the electrodes is because of the electroosmotic force. The conclusions suggest that the 3-DIMES with PBS as high conductive fluid helps to understand the three-dimensional advantageous flow structures for cell manipulation in biomedical applications.

  15. Acoustic field interaction with a boiling system under terrestrial gravity and microgravity.

    Science.gov (United States)

    Sitter, J S; Snyder, T J; Chung, J N; Marston, P L

    1998-11-01

    Pool boiling experiments from a platinum wire heater in FC-72 liquid were conducted under terrestrial and microgravity conditions, both with and without the presence of a high-intensity acoustic standing wave within the fluid. The purpose of this research was to study the interaction between an acoustic field and a pool boiling system in normal gravity and microgravity. The absence of buoyancy in microgravity complicates the process of boiling. The acoustic force on a vapor bubble generated from a heated wire in a standing wave was shown to be able to play the role of buoyancy in microgravity. The microgravity environment was achieved with 0.6 and 2.1-s drop towers. The sound was transmitted through the fluid medium by means of a half wavelength sonic transducer driven at 10.18 kHz. At high enough acoustic pressure amplitudes cavitation and streaming began playing an important role in vapor bubble dynamics and heat transfer. Several different fixed heat fluxes were chosen for the microgravity experiment and the effects of acoustics on the surface temperature of the heater were recorded and the vapor bubble movement was filmed. Video images of the pool boiling processes and heat transfer data are presented.

  16. Generation of free convection due to changes of the local circulation system

    Directory of Open Access Journals (Sweden)

    T. Foken

    2009-11-01

    Full Text Available Eddy-covariance and Sodar/RASS experimental measurement data of the COPS (Convective and Orographically-induced Precipitation Study field campaign 2007 are used to investigate the generation of near-ground free convection conditions (FCCs in the Kinzig valley, Black Forest, Southwest Germany. The measured high-quality turbulent flux data revealed that FCCs are initiated near the ground in situations where moderate to high buoyancy fluxes and a simultaneously occurring drop of the wind speed were present. The minimum in wind speed – observable by the Sodar measurements through the whole vertical extension of the valley atmosphere – is the consequence of a thermally-induced valley wind system, which changes its wind direction from down to up-valley winds in the morning hours. Buoyancy then dominates over shear within the production of turbulence kinetic energy near the ground. These situations are detected by the stability parameter (ratio of the measurement height to the Obukhov length when the level of free convection, which starts above the Obukhov length, drops below that of the sonic anemometer. An analysis of the scales of turbulent motions during FCCs using wavelet transform shows the occurrence of large-scale turbulence structures. Regarding the entire COPS measurement period, FCCs in the morning hours occur on about 50% of all days. Enhanced surface fluxes of latent and sensible heat are found on these days.

  17. Searching for the Origin through Central Nervous System: A Review and Thought which Related to Microgravity, Evolution, Big Bang Theory and Universes, Soul and Brainwaves, Greater Limbic System and Seat of the Soul.

    Science.gov (United States)

    Idris, Zamzuri

    2014-07-01

    Cerebrospinal fluid (CSF) serves buoyancy. The buoyancy thought to play crucial role in many aspects of the central nervous system (CNS). Weightlessness is produced mainly by the CSF. This manuscript is purposely made to discuss its significance which thought contributing towards an ideal environment for the CNS to develop and function normally. The idea of microgravity environment for the CNS is supported not only by the weightlessness concept of the brain, but also the noted anatomical position of the CNS. The CNS is positioned in bowing position (at main cephalic flexure) which is nearly similar to an astronaut in a microgravity chamber, fetus in the amniotic fluid at early gestation, and animals and plants in the ocean or on the land. Therefore, this microgravity position can bring us closer to the concept of origin. The hypothesis on 'the origin' based on the microgravity were explored and their similarities were identified including the brainwaves and soul. Subsequently a review on soul was made. Interestingly, an idea from Leonardo da Vinci seems in agreement with the notion of seat of the soul at the greater limbic system which has a distinctive feature of "from God back to God".

  18. Minimal Role of Basal Shear Tractions in Driving Nubia-Somalia Divergence Across the East African Rift System

    Science.gov (United States)

    Stamps, D. S.; Calais, E.; Iaffaldano, G.; Flesch, L. M.

    2012-12-01

    The Nubian and Somalian plates actively diverge along the topographically high, ~5000 km long East African Rift System (EARS). As no major subduction zones bound Africa, one can assume that the forces driving the Nubia-Somalia plate system result primarily from mantle buoyancies and lateral variation in lithospheric gravitational potential energy. Images from seismic tomography and convection models suggest active mantle flow beneath Africa. However, the contribution from large-scale convection to the force balance driving plate divergence across the EARS remains in question. In this work we investigate the impact of mantle shear tractions on the dynamics of Nubia-Somalia divergence across the EARS. We compare surface motions inferred from GPS observations with strain rates and velocities predicted from dynamic models where basal shear stresses are (1) derived from forward mantle circulation models and (2) inferred from stress field boundary conditions that balance buoyancy forces in the African lithosphere. Upper mantle anisotropy derived from seismic observations beneath Africa provide independent constraints for the latter. Preliminary results suggest that basal shear tractions play a minor role in the dynamics of Nubia-Somalia divergence along the EARS. This result implies mantle-lithosphere decoupling, possibly promoted by a low viscosity asthenosphere. We corroborate the robustness of our results with estimates of upper mantle viscosity based on local upper mantle temperature estimates and rheological parameters obtained from laboratory experiments.

  19. 模拟大深度快速上浮脱险兔血浆血管性血友病因子和一氧化氮水平变化%Experimental Study on the Changes of vWF and NO in Rabbits with Decompression Injury induced by Simulated Deep Fast Buoyancy Ascent Escape

    Institute of Scientific and Technical Information of China (English)

    许骥; 何佳; 陈锐勇; 顾靖华; 刘晓波; 陈新; 向导

    2015-01-01

    Objective:To investigate the changes of von Willebrand Factor(vWF)and Nitric oxide(NO)in rabbits with decompression injury induced by simulated deep fast buoyancy ascent escape and to evaluate their role in the pathogenesis of decompression sickness.Method:Sixteen male SD rabbits were compressed to a pressure of 1.5 MPa at an exponential rate of 2 t/4 with compressed air,after staying for 80s at the above pressure,the animals were decompressed to atmospheric pressure at linear speed (30KPa/s).Morbidity and symptoms of decompression sick-ness in animal model was monitored.The blood samples were collected before compression and after decompression respectively.vWF and NO were measured immediately.Results:The Morbidity of decompression sickness in animal model was 68.8%.Compared with those before compression,vWF levels[(2.65 ± 0.26 )μg/L]and NO levels[ (64.5 ± 26.6)μmol/L]in the of rabbits were increased significantly after decompression [(3.59 ± 0.31 )μg/L, (1 1 7.0±36.0)μmol/L](P <0.01).Conclusion:The changes of vWF and NO in the could be used as indicators for the occurrence of decompression injury induced by simulated deep fast buoyancy ascent escape.%目的::研究大深度快速上浮脱险兔血浆血管性血友病因子(vWF)和一氧化氮(NO)浓度变化及在减压损伤中的意义。方法:成年雄性新西兰兔16只,以2 t/4指数速率加压至1.5MPa(表压),稳压停留80s,以30kPa/s 匀速减压至常压。出舱后观察动物行为并统计减压病发病率。实验前及出舱后各采血2ml,4℃离心分离血浆,分别采用酶联免疫吸附法及硝酸还原酶法检测实验兔血浆 vWF 和 NO 浓度。结果:实验兔减压病发病率68.75%(11/16);实验后兔血浆 vWF 和 NO 浓度分别为3.59±0.31μg/L 和117.00±36.00μmol/L,较实验前(2.65±0.26μg/L 和64.50±26.60μmol/L)显著升高,差异有统计学意义(P <0.01)。结论:血浆 vWF、NO 浓度升高可以作为大深度快速上浮脱险机体减压

  20. Pick-and-Eat Salad-Crop Productivity, Nutritional Value, and Acceptability to Supplement the ISS Food System

    Science.gov (United States)

    Massa, G. D.; Wheeler, R. M.; Hummerick, M. E.; Morrow, R. C.; Mitchell, C. A.; Whitmire, A. M.; Ploutz-Snyder, R. J.; Douglas, G. L.

    2016-01-01

    treatments and one fertilizer treatment to test on ISS. Our work will help define light colors, levels, and horticultural best practices to achieve high yields of safe, nutritious leafy greens and tomatoes to supplement a space diet of prepackaged food. Our final deliverable will be the development of growth protocols for these crops in a spaceflight vegetable production system. With this work, and potentially with other pending joint projects, we will continue the synergistic research to help close gaps in the human research roadmap, and enable humans to venture to Mars and beyond. This research was co-funded by the Human Research Program and Space Biology (MTL1075) in the ILSRA 2015 NRA call.

  1. FORMULATION AND IN VITRO EVALUATION OF GLIPIZIDE AS FLOATING DRUG DELIVERY SYSTEM WITH NATURAL POLYMER (GUAR-GUM

    Directory of Open Access Journals (Sweden)

    Singh Amit Kumar

    2012-08-01

    Full Text Available The purpose of this investigation was to prepare a gastro retentive drug delivery system of Glipizide. Floating tablets of Glipizide were prepared employing different polymers like HPMC K15M, Guar-Gum, Carbopol 934p and Magnesium Stearate by effervescent technique. Sodium bicarbonate and citric acid were incorporated as a gas generating agent. The Floating tablets were evaluated for uniformity of weight, hardness, friability, drug content, in- vitro buoyancy, swelling study, dissolution studies and stability studies. The drug release profile and floating properties was investigated. The prepared tablets exhibited satisfactory physico-chemical characteristics. All the prepared batches showed good in vitro buoyancy. It was aimed to prepare for prolonged residence in the stomach over conventional Gastroretentive approaches. The tablets are produced by direct compression method. The release of the drug is concern from the nine formulations. F5 is a best formulation to determine the mode of release the data was subjected to Zero Order model. F5 optimized formulation released approximately 98.15% drug in 12 hours in vitro.

  2. Construction of a cooling water inlet system with settling basin of Derna power plant station (Libya)

    Energy Technology Data Exchange (ETDEWEB)

    Glissmann, R.; Heimburg, A.M. von; Sinner, H.

    1985-03-01

    Construction of a cooling water intake system with settling basin. The extension of the power station at Derna, in Libya, necessitated the construction of a new cooling water intake system including screening facilities and a settling basin. Construction based on extensive prefabrication (precast concrete) was chosen. The precast reinforced units, ranging up to about 4000 t in weight, were towed on barges to the site of erection. At Derna these units were temporarily stored on the sea bed for several months, during which they were exposed to winter storms and rough sea. The major precast portion of the settling basin was constructed direct on the barge. On arrival at the site, the barge was sunk, allowing the precast unit, which was designed with sufficient buoyancy, to be floated off. The open unprotected coast required special arrangements for the protection of personnel, structures and equipment.

  3. Positive-Buoyancy Rover for Under Ice Mobility

    Science.gov (United States)

    Leichty, John M.; Klesh, Andrew T.; Berisford, Daniel F.; Matthews, Jaret B.; Hand, Kevin P.

    2013-01-01

    A buoyant rover has been developed to traverse the underside of ice-covered lakes and seas. The rover operates at the ice/water interface and permits direct observation and measurement of processes affecting freeze- over and thaw events in lake and marine environments. Operating along the 2- D ice-water interface simplifies many aspects of underwater exploration, especially when compared to submersibles, which have difficulty in station-keeping and precision mobility. The buoyant rover consists of an all aluminum body with two aluminum sawtooth wheels. The two independent body segments are sandwiched between four actuators that permit isolation of wheel movement from movement of the central tether spool. For normal operations, the wheels move while the tether spool feeds out line and the cameras on each segment maintain a user-controlled fixed position. Typically one camera targets the ice/water interface and one camera looks down to the lake floor to identify seep sources. Each wheel can be operated independently for precision turning and adjustments. The rover is controlled by a touch- tablet interface and wireless goggles enable real-time viewing of video streamed from the rover cameras. The buoyant rover was successfully deployed and tested during an October 2012 field campaign to investigate methane trapped in ice in lakes along the North Slope of Alaska.

  4. The cognitive development of Galileo's theory of buoyancy

    Science.gov (United States)

    Palmieri, Paolo

    2005-01-01

    Some thirty years ago, in a seminal book, William Shea argued that between 1610 and 1632 Galileo worked out "the methodology of his intellectual revolution", and that hydrostatics was one fundamental area of research Galileo concerned himself with at that time. According to Shea, that methodology was deeply rooted in Archimedean mathematics and basically consisted in mathematically investigating classes of phenomena, such as floating bodies, under certain idealized conditions. I believe that Shea's view is fundamentally correct. I will develop it further, by reconsidering Galileo's methodology in finer detail, specifically in relation to the development of his theory of floating bodies.

  5. Buoyancy-driven flow excursions in fuel assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Laurinat, J.E.; Paul, P.K.; Menna, J.D.

    1995-12-31

    A power limit criterion was developed for a postulated Loss of Pumping Accident (LOPA) in one of the recently shut down heavy water production reactors at the Savannah River Site. These reactors were cooled by recirculating moderator downward through channels in cylindrical fuel tubes. Powers were limited to prevent a flow excursion from occurring in one or more of these parallel channels. During full-power operation, limits prevented a boiling flow excursion from taking place. At low flow rates, during the addition of emergency cooling water, buoyant forces reverse the flow in one of the coolant channels before boiling occurs. As power increases beyond the point of flow reversal, the maximum wall temperature approaches the fluid saturation temperature, and a thermal excursion occurs. The power limit criterion for low flow rates was the onset of flow reversal. To determine conditions for flow reversal, tests were performed in a mock-up of a fuel assembly that contained two electrically heated concentric tubes surrounded by three flow channels. These tests were modeled using a finite difference thermal-hydraulic code. According to code calculations, flow reversed in the outer flow channel before the maximum wall temperature reached the local fluid saturation temperature. Thermal excursions occurred when the maximum wall temperature approximately equaled the saturation temperature. For a postulated LOPA, the flow reversal criterion for emergency cooling water addition was more limiting than the boiling excursion criterion for full power operation. This criterion limited powers to 37% of historical levels.

  6. Microbial Gas Production Used to Achieve Autonomous Buoyancy Control

    Science.gov (United States)

    2010-09-01

    counter weight. The microbe used is cultured in the Erlenmeyer flask. Clostridium acetobutylicum for micro1bial ballast In order to utilize microbial...34 20 0 --100% 0 20 40 60 80 Time(hr) Figure 6. Gas production by different S()lid-phase agar cultures of C. acetobutvlicum. Clostridium ... acetobutylicum as our model microbe; a gram-positive anaerobic bacterium known for its ability to produce hydrogen gas 4,5 To determine if there

  7. Buoyancy-driven flow excursions in fuel assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Laurinat, J.E.; Paul, P.K.; Menna, J.D. [Westinghouse Savannah River Company, Aiken, SC (United States)

    1995-09-01

    A power limit criterion was developed for a postulated Loss of Pumping Accident (LOPA) in one of the recently shut down heavy water production reactors at the Savannah River Site. These reactors were cooled by recirculating heavy water moderator downward through channels in cylindrical fuel tubes. Powers were limited to safeguard against a flow excursion in one of more of these parallel channels. During-full-power operation, limits safeguarded against a boiling flow excursion. At low flow rates, during the addition of emergency cooling water, buoyant forces reverse the flow in one of the coolant channels before boiling occurs. As power increased beyond the point of flow reversal, the maximum wall temperature approaches the fluid saturation temperature, and a thermal excursion occurs. The power limit criterion for low flow rates was the onset of flow reversal. To determine conditions for flow reversal, tests were performed in a mock-up of a fuel assembly that contained two electrically heated concentric tubes surrounded by three flow channels. These tests were modeled using a finite difference thermal-hydraulic code. According to code calculations, flow reversed in the outer flow channel before the maximum wall temperature reached the local fluid saturation temperature. Thermal excursions occurred when the maximum wall temperature approximately equaled the saturation temperature. For a postulated LOPA, the flow reversal criterion for emergency cooling water addition was more limiting than the boiling excursion criterion for full power operation. This criterion limited powers to 37% of the limiting power for previous long-term reactor operations.

  8. Experiments on buoyancy and surface tension following Galileo Galilei

    Science.gov (United States)

    Straulino, S.; Gambi, C. M. C.; Righini, A.

    2011-01-01

    We analyze passages of Galileo's writings on aspects of floating. Galileo encountered peculiar effects such as the "floating" of light objects made of dense material and the creation of large drops of water that were difficult to explain because they are related to our current understanding of surface tension. Even though Galileo could not understand the phenomenon, his proposed explanations and experiments are interesting from an educational point of view. We replicate the experiment on water and wine that was described by Galileo in his Two New Sciences.

  9. Buoyancy induced MHD transient mass transfer flow with thermal radiation

    Directory of Open Access Journals (Sweden)

    N. Ahmed

    2016-09-01

    Full Text Available The problem of a transient MHD free convective mass transfer flow past an infinite vertical porous plate in presence of thermal radiation is studied. The fluid is considered to be a gray, absorbing-emitting radiating but non-scattered medium. Analytical solutions of the equations governing the flow problem are obtained. The effects of mass transfer, suction, radiation and the applied magnetic field on the flow and transport characteristics are discussed through graphs.

  10. Validation of buoyancy driven spectral tensor model using HATS data

    DEFF Research Database (Denmark)

    Chougule, A.; Mann, Jakob; Kelly, Mark C.

    2016-01-01

    We present a homogeneous spectral tensor model for wind velocity and temperature fluctuations, driven by mean vertical shear and mean temperature gradient. Results from the model, including one-dimensional velocity and temperature spectra and the associated co-spectra, are shown in this paper. Th...

  11. Heat Transfer in Boiling Dilute Emulsion with Strong Buoyancy

    Science.gov (United States)

    Freeburg, Eric Thomas

    Little attention has been given to the boiling of emulsions compared to that of boiling in pure liquids. The advantages of using emulsions as a heat transfer agent were first discovered in the 1970s and several interesting features have since been studied by few researchers. Early research focuses primarily on pool and flow boiling and looks to determine a mechanism by which the boiling process occurs. This thesis looks at the boiling of dilute emulsions in fluids with strong buoyant forces. The boiling of dilute emulsions presents many favorable characteristics that make it an ideal agent for heat transfer. High heat flux electronics, such as those seen in avionics equipment, produce high heat fluxes of 100 W/cm2 or more, but must be maintained at low temperatures. So far, research on single phase convection and flow boiling in small diameter channels have yet to provide an adequate solution. Emulsions allow the engineer to tailor the solution to the specific problem. The fluid can be customized to retain the high thermal conductivity and specific heat capacity of the continuous phase while enhancing the heat transfer coefficient through boiling of the dispersed phase component. Heat transfer experiments were carried out with FC-72 in water emulsions. FC-72 has a saturation temperature of 56 °C, far below that of water. The parameters were varied as follows: 0% ≤ epsilon ≤ 1% and 1.82 x 1012 ≤ RaH ≤ 4.42 x 1012. Surface temperatures along the heated surface reached temperature that were 20 °C in excess of the dispersed phase saturation temperature. An increase of ˜20% was seen in the average Nusselt numbers at the highest Rayleigh numbers. Holography was used to obtain images of individual and multiple FC-72 droplets in the boundary layer next to the heated surface. The droplet diameters ranged from 0.5 mm to 1.3 mm. The Magnus effect was observed when larger individual droplets were injected into the boundary layer, causing the droplets to be pushed outside the boundary layer. Vaporization of FC-72 droplets in the boundary layer next to the heated surface was not observed.

  12. Diving into buoyancy: exploring the Archimedes principle through engineering

    OpenAIRE

    Thiam, Mouhamadou

    2016-01-01

    In our daily lives, we observe objects sinking, floating, or rising when immersed in a fluid. The Archimedes principle, which explains an object's behavior when immersed in a fluid, is important in fluid mechanics; however, it is a relatively complex concept for middle school students to grasp, as they often harbor misconceptions. To initiate conceptual change among students regarding the misconception "heavy objects sink and light objects float," I created a project during which students bui...

  13. Buoyancy and g-modes in young superfluid neutron stars

    CERN Document Server

    Passamonti, A; Ho, W C G

    2015-01-01

    We consider the local dynamics of a realistic neutron star core, including composition gradients, superfluidity and thermal effects. The main focus is on the gravity g-modes, which are supported by composition stratification and thermal gradients. We derive the equations that govern this problem in full detail, paying particular attention to the input that needs to be provided through the equation of state and distinguishing between normal and superfluid regions. The analysis highlights a number of key issues that should be kept in mind whenever equation of state data is compiled from nuclear physics for use in neutron star calculations. We provide explicit results for a particular stellar model and a specific nucleonic equation of state, making use of cooling simulations to show how the local wave spectrum evolves as the star ages. Our results show that the composition gradient is effectively dominated by the muons whenever they are present. When the star cools below the superfluid transition, the support fo...

  14. Ground-based diffusion experiments on liquid Sn-In systems using the shear cell technique of the satellite mission Foton-M1.

    Science.gov (United States)

    Suzuki, Shinsuke; Kraatz, Kurt-Helmut; Frohberg, Günter

    2004-11-01

    This study reported in this paper was aimed at testing the shear cell that was developed for the satellite mission Foton-M1 to measure diffusion coefficients in liquid metals under microgravity (microg)-conditions. Thick Layer diffusion experiments were performed in the system Sn90In10 versus Sn under 1 g-conditions. For this system several microg-diffusion results are available as reference data. This combination provides a low, but sufficiently stable, density layering throughout the entire experiment, which is important to avoid buoyancy-driven convection. The experimental results were corrected for the influences of the shear-induced convection and mixing after the final shearing, both of which are typical for the shear cell technique. As the result, the reproducibility and the reliability of the diffusion coefficients in the ground-based experiments were within the limits of error of microg-data. Based on our results we discuss the necessary conditions to avoid buoyancy-driven convection.

  15. Hydrogen mitigation Gas Characterization System: System design description

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, T.C.

    1998-07-17

    The Gas Characterization System (GCS) design is described for flammable gas monitoring. Tank 241-SY-101 (SY-101) is known to experience periodic tank level increases and decreases during which hydrogen gas is released. It is believed that the generated gases accumulate in the solids-containing layer near the bottom of the tank. Solids and gases are also present in the crust and may be present in the interstitial liquid layer. The accumulation of gases creates a buoyancy that eventually overcomes the density and bonding strength of the bottom layer. When this happens, the gas from the bottom layer is released upward through the liquid layer to the vapor space above the tank crust. Previous monitoring of the vapor space gases during such an event indicates hydrogen release concentrations greater than the lower flammability limit (LFL) of hydrogen in a partial nitrous oxide atmosphere. Tanks 241-AN-105, 241-AW-101, and 241-SY-103 have been identified as having the potential to behave similar to SY-101. These waste tanks have been placed on the flammable gas watch list (FGWL). All waste tanks on the FGWL will have a standard hydrogen monitoring system (SHMS) installed to measure hydrogen. In the event that hydrogen levels exceed 0.75% by volume, additional characterization will be required. The purpose of this additional vapor space characterization is to determine the actual lower flammability limit of these tanks, accurately measure low baseline gas release concentrations, and to determine potential hazards associated with larger Gas Release Events (GREs). The instruments to be installed in the GCS for vapor monitoring will allow accurate analysis of samples from the tank vapor space. It will be possible to detect a wide range of hydrogen from parts per million to percent by volume, as well as other gas species suspected to be generated in waste tanks.

  16. Multiple steady states of exhaust airflow in a multi-branch tunnel with the combined effects of buoyancy and fan power%热压与风机动力共同作用下多分支隧道内排烟气流的多解性

    Institute of Scientific and Technical Information of China (English)

    阳东; 赵成梅

    2015-01-01

    The multi‐branch tunnel has multiple routes for smoke extraction and air supply ,consequently its ventilation and smoke control modes could have multiple solutions owing to the competitive effects of buoyancy and fan power .For the smoke control of a multi‐branch tunnel ,the mass and energy balance equations for every possible flow pattern were established ,and the corresponding multiple solutions were obtained using mathematical methods .The results demonstrate that ,even though the exhaust ventilation mode and fan type have been determined in accordance with the anticipation ,multiple states of exhausted flow remain and the operation point of the fans will drift away from the design accordingly .This could cause a totally different direction of smoke route from the anticipated one .It is also shown that the type of fan has significant effects on the existence of multiple solutions .%多分支隧道的排烟与补风路径较多,热压与风机动力的竞争可能造成其通风排烟模式具有多解性。针对某一多分支隧道的防排烟工况,利用理论分析建立了各种气流模式的控制方程,通过数学方法获得了理论解。结果证明,在按照预期设计选定通风排烟模式与风机以后,多分支隧道内的排烟气流仍然可能存在多种状态,风机的运行工况点也会随之漂移,导致排烟方向可能与设计预期完全相反。研究还发现,通过改变风机选型能起到抑制排烟气流出现多解的作用。

  17. Lifting Entry & Atmospheric Flight (LEAF) System Concept Applications at Solar System Bodies With an Atmosphere

    Science.gov (United States)

    Lee, Greg; Polidan, Ronald; Ross, Floyd; Sokol, Daniel; Warwick, Steve

    2015-11-01

    Northrop Grumman and L’Garde have continued the development of a hypersonic entry, semi-buoyant, maneuverable platform capable of performing long-duration (months to a year) in situ and remote measurements at any solar system body that possesses an atmosphere.The Lifting Entry & Atmospheric Flight (LEAF) family of vehicles achieves this capability by using a semi-buoyant, ultra-low ballistic coefficient vehicle whose lifting entry allows it to enter the atmosphere without an aeroshell. The mass savings realized by eliminating the heavy aeroshell allows significantly more payload to be accommodated by the platform for additional science collection and return.In this presentation, we discuss the application of the LEAF system at various solar system bodies: Venus, Titan, Mars, and Earth. We present the key differences in platform design as well as operational differences required by the various target environments. The Venus implementation includes propulsive capability to reach higher altitudes during the day and achieves full buoyancy in the mid-cloud layer of Venus’ atmosphere at night.Titan also offers an attractive operating environment, allowing LEAF designs that can target low or medium altitude operations, also with propulsive capabilities to roam within each altitude regime. The Mars version is a glider that descends gradually, allowing targeted delivery of payloads to the surface or high resolution surface imaging. Finally, an Earth version could remain in orbit in a stowed state until activated, allowing rapid response type deployments to any region of the globe.

  18. 76 FR 15229 - Airworthiness Directives; Goodrich Evacuation Systems Approved Under Technical Standard Order...

    Science.gov (United States)

    2011-03-21

    ... inadequate buoyancy to support the raft's passenger capacity during ditching and increase the chance for... ditching and increase the chance for injury to raft passengers. Actions Since Existing AD Was Issued Since... inadequate buoyancy to support the raft's passenger capacity during ditching and increase the chance...

  19. Research on the effect of preoxygenation on the prevention of decompression sickness induced by fast buoyancy ascent escape at a pressure of 30 m%30 m高压预吸氧对快速上浮脱险致减压病的预防作用研究

    Institute of Scientific and Technical Information of China (English)

    攸璞; 方以群; 马骏; 李丹; 沈泉; 张师; 王芳芳

    2016-01-01

    Objective To investigate the effect of preoxygenation on the DCS morbidity and cardiopulmonary injury induced by fast buoyancy ascent escape at a pressure of 30 m.Methods Sixty male Wistar rats were randomly divided into 3 groups (the experimental group,the control group and the blank group),each consisting of 20 rats.The experimental group was pressurized to 30 m with 10 minutes of preoxygenation in the animal chamber,the control group in the small animal chamber inside the large animal chamber was exposed to atmospheric pressure for 10 minutes,and the blank control group just stayed in the chamber without any pressurization.Then,both the experimental group and the control group were pressurized by air to a pressure of 1 .5 MPa at an exponential rate of 2 t/7 ,remained at the said pressure for 4 minutes and then were decompressed to normal pressure at linear pressure.Half an hour after the animals were out of the chamber,close observation was made on the mortality and the morbidity of DCS,and detection was also made on the pathological changes of the heart and lungs.Results The morbidity and mortality of the control group were respectively 80% and 75%,and those of the experimental group were all 40%.Alveolar and interstitial hemorrhage,as well as broadened interstitial lung could clearly be seen in the lung tissue of the survival animals in the control group.Edema or even rupture was obviously noticeable in the myocardial fibers of the cardiac apex in the survival animals of the control group.However,hemorrhage and oozing of blood could hardly be seen in the lung tissue of the experimental group,and pulmonary interstitium was normal.Only mild edema was noticeable in the myocardial fibers of the cardiac apex.Conclusions Ten minutes of preoxygenation at a pressure of 30 m could produce protective effect on cardiopulmonary injury induced by DCS in fast buoyancy ascent escape.With this reason,preoxygenation could prevent the occurrence of DCS.%目的:研究30 m高

  20. Establishment of a rat model of decompression sickness induced by simulated deep fast buoyancy ascent of submariners%模拟大深度潜艇艇员快速上浮脱险致减压病大鼠模型的建立

    Institute of Scientific and Technical Information of China (English)

    张师; 包晓辰; 方以群; 攸璞; 袁恒荣; 王芳芳

    2012-01-01

    Objective To establish a rat model of decompression sickness induced by simulated deep fast buoyancy ascent of submariners.Methods Eighty male SD rats were randomly divided into 4 groups,each consisting of 20 animals:the control group,the 2-min exposure group,the 4-min exposure group,and the 8-min exposure group.The latter 3 groups were compressed to 150 m at an exponential rate of 2 t/8s in the air chamber,stayed at the said pressure respectively for 2,4 and 8 mins.Then,they were decompressed to atmospheric pressure at a linear speed of 3 m/s.Behavior and pathological changes in lungs,brain,spinal cord of all the animal groups were closely observed.Results After they came out of the chamber,the animals of all the groups displayed the following behaviors:hair erection,scratching and slow reaction.Pathological examination indicated that there were edema and hemorrhage in the alveolar and pulmonary interstitial tissue,and in the spinal cord as well.However,no significant pathological changes in the brain tissue could be noted.Mobidity of 2,4,8-min profile SD rats were 20.07%,55.0% and 10.0%,respectiuely,At the same time,mortality of which were 0,20.0% and 85.0%,respectively.Significant differences could also be seen in the morbidity and mortality of the animals in various exposure groups with different exposure time(P<0.01).As the exposure time of the 8-min profile was too long,mortality 3 of the developed rat model was relatively higher,when they came out of the chamber.Nevertheless,the exposure time of the 2-min profile was obviously inadequate,morbidity of the developed rat model was relatively lower.Thus,the 4-min profile with a low mortality and high morbidity of decompression sickness might be appropriate for submarine escape.Conclusions The experiment has successfully established 4-min exposure profile was the animal model of decompression sickness induced by deep fast buoyancy ascent of submariners.%目的 建立稳定的模拟大深度潜艇艇

  1. Study of the circulation theory of the cooling system in vertical evaporative cooling generator

    Institute of Scientific and Technical Information of China (English)

    YU; Shunzhou; CAI; Jing; GUO; Chaohong

    2006-01-01

    The article briefly states the current development of evaporative cooling generator and its advantages comparing with generators of traditional cooling. Vertical evaporative cooling generator, which adopts Close-Loop-Self-Cycle with no-pump and free convection boil in the hollow stator bar, is one of the great developments in generator design. This article emphasizes the importance of cooling system in generator; expatiates the circulation theory in two aspects, energy and flow; and analyzes the essential reason,motivity and stability of Close-Loop-Self-Cycle. The article points out that the motivity of the circulation is the heat absorbed by coolant. After absorbing heat the coolant will have the ability of doing work because of the phase change. In another words, it is the buoyancy causing by density difference leads to the Close-Loop-Self-Cycle. This conclusion is validated by experimental data.

  2. Pressure compensated transducer system with constrained diaphragm

    Science.gov (United States)

    Percy, Joseph L.

    1992-08-01

    An acoustic source apparatus has an acoustic transducer that is enclosed in a substantially rigid and watertight enclosure to resist the pressure of water on the transducer and to seal the transducer from the water. The enclosure has an opening through which acoustic signals pass and over which is placed a resilient, expandable and substantially water-impermeable diaphragm. A net stiffens and strengthens the diaphragm as well as constrains the diaphragm from overexpansion or from migrating due to buoyancy forces. Pressurized gas, regulated at slightly above ambient pressure, is supplied to the enclosure and the diaphragm to compensate for underwater ambient pressures. Gas pressure regulated at above ambient pressure is used to selectively tune the pressure levels within the enclosure and diaphragm so that diaphragm resonance can be achieved. Controls are used to selectively fill, as well as vent the enclosure and diaphragm during system descent and ascent, respectively. A signal link is used to activate these controls and to provide the driving force for the acoustic transducer.

  3. Dynamic analysis of multibodies system with a floating base for rolling of ro-ro ship caused by wave and slip of heavy load

    Institute of Scientific and Technical Information of China (English)

    SHEN Qing; LI Yue; CHEN Xu-jun

    2003-01-01

    Common effect of wave and slip of internal heavy load will make rolling of the roll-on ship serious. This is one of the important reasons for overturn of ro-ro ships. The multibodies System with a floating base is composed of ro-ro ship and slipping heavy load. This paper takes the rolling angle of the ship and the transverse displacement of the heavy load on desk as two freedoms. Making use of analysis of apparent gravitation and apparent buoyancy, the wave rolling moment is derived. By use of dynamic method of multibodies system with a floating base, dynamic equations of the system are established. Taking a certain channel ferry as an example, a set of numerical calculation have been carried out for rolling response of the ship and displacement response of the slipping heavy load under common effect of synchro-slipping heavy loads and wave.

  4. CFD Analysis of the Effect on Buoyancy Due to Terrain Temperature Based on an Integrated DEM and Landsat Infrared Imagery Análisis CFD de vientos convectivos naturales debidos a la temperatura de un terreno basado en un modelo DEM integrado con imágenes infrarrojas Landsat

    Directory of Open Access Journals (Sweden)

    Santiago Giraldo

    2008-12-01

    Full Text Available This paper deals with the influence of concrete structures on atmospheric temperatureand the convection winds generated in the Aburra Valley in Medell´ın,Colombia. This area is characterised by low wind velocities with a high industrydensity. A digital elevation model was used from the Radar ShuttleTopography Mission and post-processed in order to obtain a valid volumetricCFD domain. The construction process includes hole-filling due to imperfectionsin the original radar data, decimation of the original cloud-of-points to reduce the excess of detail in regions with low curvature, and the introductionof a volume of air over the terrain surface (CFD domain. Landsat satellitedata was used to set the terrain temperatures for various material compositions.The converted infrared image was then registered into the CFD domainusing an interpolation technique.Navier–Stokes Equations were solved for buoyant, turbulent flow of compressiblefluids accounting for convection and heat transfer effects. Simulationincludes buoyancy and turbulence flow through the k–epsilon model using thehigh-performance computing facilities of Westgrid (Western Canada ResearchGrid. Preliminary results show wind distributions that compare to the oneobserved at low–altitude in the region.El presente trabajo estudia la influencia de estructuras de concreto en la temperatura atmosférica y los vientos convectivos generados en el Valle de Aburrá en Medellín, Colombia. Esta zona se caracteriza por vientos de bajas velocidades con alta densidad industrial. Un modelo de elevación digital fue obtenido de la misión topográfica del radar Shuttle y post-procesado en aras de obtener un dominio volumétrico CFD válido. El proceso de construcción incluye el parchado de agujeros debidos a imperfectos en los datos originarios del radar, decimación de la nube de puntos original para reducir el exceso de detalle en regiones con baja curvatura y la generación de un volumen de

  5. Integration of Product, Package, Process, and Environment: A Food System Optimization

    Science.gov (United States)

    Cooper, Maya R.; Douglas, Grace L.

    2015-01-01

    The food systems slated for future NASA missions must meet crew nutritional needs, be acceptable for consumption, and use resources efficiently. Although the current food system of prepackaged, moderately stabilized food items works well for International Space Station (ISS) missions, many of the current space menu items do not maintain acceptability and/or nutritive value beyond 2 years. Longer space missions require that the food system can sustain the crew for 3 to 5 years without replenishment. The task "Integration of Product, Package, Process, and Environment: A Food System Optimization" has the objective of optimizing food-product shelf life for the space-food system through product recipe adjustments, new packaging and processing technologies, and modified storage conditions. Two emergent food processing technologies were examined to identify a pathway to stable, wet-pack foods without the detrimental color and texture effects. Both microwave-assisted thermal sterilization (MATS) and pressure-assisted thermal stabilization (PATS) were evaluated against traditional retort processing to determine if lower heat inputs during processing would produce a product with higher micronutrient quality and longer shelf life. While MATS products did have brighter color and better texture initially, the advantages were not sustained. The non-metallized packaging film used in the process likely provided inadequate oxygen barrier. No difference in vitamin stability was evident between MATS and retort processed foods. Similarly, fruit products produced using PATS showed improved color and texture through 3 years of storage compared to retort fruit, but the vitamin stability was not improved. The final processing study involved freeze drying. Five processing factors were tested in factorial design to assess potential impact of each to the quality of freeze-dried food, including the integrity of the microstructure. The initial freezing rate and primary freeze drying

  6. Assessing the viability of microsponges as gastro retentive drug delivery system of curcumin: optimization and pharmacokinetics.

    Science.gov (United States)

    Arya, Priyanka; Pathak, Kamla

    2014-01-01

    The work was aimed to validate the gastroretentive potential of microsponges via optimization of targeted floating curcumin microsponges for improved site specific absorption for gastric cancer Modified quasi emulsion solvent diffusion method was used to formulate microsponges using 3(2) full factorial design. The effect of different levels of ethyl cellulose and polyvinyl alcohol concentration, selected as independent variables was determined on the % entrapment efficiency, % buoyancy and % cumulative drug release. Modified rosette rise apparatus was used for in vitro release and the release data best fitted Higuchi's model and mechanism of drug release was diffusion (n). The optimized formulation (MS5) demonstrated favourable % entrapment efficiency (90.7 ± 1.7), % buoyancy (82.0 ± 2.0) and % cumulative drug release (85.2 ± 1.07) with maximum desirability factor of 0.816. SEM revealed spherical and porous microsponges. DSC confirmed molecular dispersion of the drug in the microsponges polymeric matrix. DRIFT revealed no chemical interaction between the drug and polymer used. The in vitro permeation of curcumin through gastric mucin gel layer affirmed the capability of microsponges to deliver drug across mucin r and reach the target site to treat gastric cancer. Anticancer oral dose of microsponges was calculated as 50mg by cytotoxicity assay in human cancer cell line KB. The pharmacokinetic evaluation of MS5 in rabbits revealed 10-fold increase in bioavailability as compared to native curcumin, demonstrated the superiority of microsponges over native curcumin as gastro retentive drug delivery system. This study presents a new approach based on floating ability of microsponges for treatment of gastric cancer.

  7. Impacts of the representation of riverine freshwater input in the community earth system model

    Science.gov (United States)

    Tseng, Yu-heng; Bryan, Frank O.; Whitney, Michael M.

    2016-09-01

    The impacts of the representation of riverine freshwater input on the simulated ocean state are investigated through comparison of a suite of experiments with the Community Earth System Model (CESM). The aspects of river and estuary processes investigated include lateral spreading of runoff, runoff contribution to the surface buoyancy flux within the K-Profile Parameterization (KPP), the use of a local salinity in the virtual salt flux (VSF) formulation, and the vertical redistribution of runoff. The horizontal runoff spreading distribution plays an important role in the regional salinity distribution and significantly changes the vertical stratification and mixing. When runoff is considered to be a contribution to the surface buoyancy flux, the calculation of turbulent length and velocity scales in the KPP can be significantly impacted near larger discharge rivers, resulting in local surface salinity changes of up to 12 ppt. Using the local surface salinity instead of a globally constant reference salinity in the conversion of riverine freshwater flux to VSF can reduce biases in the simulated salinity near river mouths but leads to drift in global mean salinity. This is remedied through a global correction approach. We also explore the sensitivity to the vertical redistribution of runoff, which partially mimics the impacts of vertical mixing process within estuaries and coastal river plumes. The impacts of the vertical redistribution of runoff are largest when the runoff effective mixing depth is comparable with the mixed layer depth, resulting from the enhanced vertical mixing and the increase of the available potential energy. The impacts in all sensitivity experiments are predominantly local, but the regional circulation can advect the influences downstream.

  8. Migration behavior of supercritical and liquid CO2 in a stratified system: Experiments and numerical simulations

    Science.gov (United States)

    Oh, Junho; Kim, Kue-Young; Han, Weon Shik; Park, Eungyu; Kim, Jeong-Chan

    2015-10-01

    Multiple scenarios of upward CO2 migration driven by both injection-induced pressure and buoyancy force were investigated in a horizontally and vertically stratified core utilizing a core-flooding system with a 2-D X-ray scanner. Two reservoir-type scenarios were considered: (1) the terrestrial reservoir scenario (10 MPa and 50°C), where CO2 exists in a supercritical state and (2) the deep-sea sediment reservoir scenario (28 MPa and 25°C), where CO2 is stored in the liquid phase. The core-flooding experiments showed a 36% increase in migration rate in the vertical core setting compared with the horizontal setting, indicating the significance of the buoyancy force under the terrestrial reservoir scenario. Under both reservoir conditions, the injected CO2 tended to find a preferential flow path (low capillary entry pressure and high-permeability (high-k) path) and bypass the unfavorable pathways, leaving low CO2 saturation in the low-permeability (low-k) layers. No distinctive fingering was observed as the CO2 moved upward, and the CO2 movement was primarily controlled by media heterogeneity. The CO2 saturation in the low-k layers exhibited a more sensitive response to injection rates, implying that the increase in CO2 injection rates could be more effective in terms of storage capacity in the low-k layers in a stratified reservoir. Under the deep-sea sediment condition, the storage potential of liquid CO2 was more than twice as high as that of supercritical CO2 under the terrestrial reservoir scenario. In the end, multiphase transport simulations were conducted to assess the effects of heterogeneity on the spatial variation of pressure buildup, CO2 saturation, and CO2 flux. Finally, we showed that a high gravity number (Ngr) tended to be more influenced by the heterogeneity of the porous media.

  9. Lifting Entry & Atmospheric Flight (LEAF) Applications at Solar System Bodies.

    Science.gov (United States)

    Lee, G.; Sen, B.; Polidan, R. S.

    2015-12-01

    Introduction: Northrop Grumman and L'Garde have continued the development of a hypersonic entry, maneuverable platform capable of performing long-duration (months to a year) in situ and remote measurements at any solar system body that possesses an atmosphere. The Lifting Entry & Atmospheric Flight (LEAF) family of vehicles achieve this capability by using a semi-buoyant, ultra-low ballistic coefficient vehicle whose lifting entry allows it to enter the atmosphere without an aeroshell. In this presentation, we discuss the application of the LEAF system at various solar system bodies: Venus, Titan, Mars, and Earth. We present the key differences in platform design as well as operational differences required by the various target environments. The Venus implementation includes propulsive capability to reach higher altitudes during the day and achieves full buoyancy in the "habitable layers" of Venus' atmosphere at night. Titan also offers an attractive operating environment, allowing LEAF designs that can target low, medium, or high altitude operations, also with propulsive capabilities to roam within each altitude regime. The Mars version is a glider that descends gradually, allowing targeted delivery of payloads to the surface. Finally, an Earth version could remain in orbit in a stowed state until activated, allowing rapid response type deployments to any region of the globe.

  10. DESIGN OF GASTRO RETENTIVE DRUG DELIVERY SYSTEM OF DILTIAZEM HYDROCHLORIDE

    Directory of Open Access Journals (Sweden)

    L. K. Omray

    2014-02-01

    Full Text Available Gastro retentive drug delivery system of diltiazem hydrochloride was designed and evaluated for its effectiveness for the management of mild to moderate hypertension. Gastro retentive drug delivery system were prepared using polyvinyl alcohol and sodium carboxy methyl cellulose as the polymers and sodium bicarbonate as a gas generating agent for the reduction of floating lag time. Gastro retentive drug delivery system tablets were prepared by wet granulation method by compression in tablet compression machine. Formulations DL1, DL2, DL3, DL4 and DL5 were developed which differed in the ratio of polyvinyl alcohol and sodium carboxy methyl cellulose polymers. All the formulations were evaluated for hardness, weight variation, friability, drug content, swelling index, buoyancy studies and in vitro drug release study. In vitro drug release study was performed using United State Pharmacopoeia 23 type 2 dissolution test apparatus employing paddle stirrer at 50 r/pm. Dissolution medium was 900 ml of 0.1N hydrochloric acid at 37ºC ± 3ºC. Formulations DL3 was found to be better as compared to other formulation.

  11. Archimedes' principle in fluidized granular systems.

    Science.gov (United States)

    Huerta, D A; Sosa, Victor; Vargas, M C; Ruiz-Suárez, J C

    2005-09-01

    We fluidize a granular bed in a rectangular container by injecting energy through the lateral walls with high-frequency sinusoidal horizontal vibrations. In this way, the bed is brought to a steady state with no convection. We measured buoyancy forces on light spheres immersed in the bed and found that they obey Archimedes' principle. The buoyancy forces decrease when we reduce the injected energy. By measuring ascension velocities as a function of gamma, we can evaluate the frictional drag of the bed; its exponential dependence agrees very well with previous findings. Rising times of the intruders ascending through the bed were also measured, they increase monotonically as we increase the density.

  12. Effects of Mg on diamond growth and properties in Fe-C system under high pressure and high temperature condition

    Science.gov (United States)

    Huang, Guo-Feng; Zheng, You-Jin; Li, Zhan-Chang; Gao, Qiang; Ma, Zhuo; Shi, Si-Ming; Jiang, Bao-Gang; Zhao, He

    2016-08-01

    Diamond crystal crystallized in Fe-Mg-C system with Archimedes buoyancy as a driving force is established under high pressure and high temperature conditions. The experimental results indicate that the addition of the Mg element results in the nitrogen concentration increasing from 87 ppm to 271 ppm in the diamond structure. The occurrence of the {100} plane reveals that the surface character is remarkably changed due to the addition of Mg. Micro-Raman spectra indicate that the half width of full maximum is in a range of 3.01 cm-1-3.26 cm-1, implying an extremely good quality of diamond specimens in crystallization. Project supported by the Natural Science Foundation of Inner Mongolia Autonomous Region, China (Grant No. 2013MS0809) and the Open Project of Key Laboratory of Functional Materials Physics and Chemistry (Jilin Normal University) of the Ministry of Education of China (Grant No. 201608).

  13. Characteristic of Starch-Poly(N-Vinyl-Pyrrolidone) for an encapsulation material in floating drug delivery system

    Science.gov (United States)

    Rositaningsih, N.; Budianto, E.

    2017-04-01

    Modified starch has been widely used in many studies in the field of drug delivery for gastrointestinal drug release. In this study, the starch was modified with poly(N-vinyl-pyrrolidone) by interpenetrating polymer network (IPN) method. Characterizations were done to observe its characteristics in floating drug delivery applications. Three modified starch-based hydrogels were synthesized, i.e. crosslinked starch, semi-IPN, and full-IPN hydrogels. Non-modified starch hydrogel was also synthesized for benchmark purpose. All materials were characterized and analysed by Swelling Test, Buoyancy Test, Differential Scanning Calorimetry (DSC), Thermal Gravimetric Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR). Swelling test showed that the crosslinked-starch hydrogel has the lowest swelling percentage compared to other hydrogels, whereas non-modified hydrogels tend to have similar swelling percentage to Semi-IPN. Morphology and visual analysis results showed that non-modified hydrogels were physically the most fragile, followed by a crosslinked-starch, semi-IPN-starch, and full-IPN-starch hydrogel. Therefore, full-IPN-starch hydrogel had the highest elasticity. From IR spectrum result, it can be seen that a wavenumbers shift was observed for the modified starch compared with the IR spectrum of pure starch powder. TGA and DSC characterizations showed the degradation temperature for non-modified hydrogel was at 250°C. The degradation temperature for both crosslinked and semi-IPN starch were at 275°C. For full-IPN, however, the degradation temperature was at 225°C. On the other hand, the degradation level could be observed from DSC and TGA results as well. Full-IPN appeared to be the slowest, while non-modified hydrogel seem to be the fastest to degrade. CaCO3 was used as the pore forming agent (PFA) in this research for buoyancy characterization. Buoyancy test showed that the full-IPN had the fastest floating lag and longest floating time followed by

  14. Cross-diffusion-driven hydrodynamic instabilities in a double-layer system: General classification and nonlinear simulations

    Science.gov (United States)

    Budroni, M. A.

    2015-12-01

    Cross diffusion, whereby a flux of a given species entrains the diffusive transport of another species, can trigger buoyancy-driven hydrodynamic instabilities at the interface of initially stable stratifications. Starting from a simple three-component case, we introduce a theoretical framework to classify cross-diffusion-induced hydrodynamic phenomena in two-layer stratifications under the action of the gravitational field. A cross-diffusion-convection (CDC) model is derived by coupling the fickian diffusion formalism to Stokes equations. In order to isolate the effect of cross-diffusion in the convective destabilization of a double-layer system, we impose a starting concentration jump of one species in the bottom layer while the other one is homogeneously distributed over the spatial domain. This initial configuration avoids the concurrence of classic Rayleigh-Taylor or differential-diffusion convective instabilities, and it also allows us to activate selectively the cross-diffusion feedback by which the heterogeneously distributed species influences the diffusive transport of the other species. We identify two types of hydrodynamic modes [the negative cross-diffusion-driven convection (NCC) and the positive cross-diffusion-driven convection (PCC)], corresponding to the sign of this operational cross-diffusion term. By studying the space-time density profiles along the gravitational axis we obtain analytical conditions for the onset of convection in terms of two important parameters only: the operational cross-diffusivity and the buoyancy ratio, giving the relative contribution of the two species to the global density. The general classification of the NCC and PCC scenarios in such parameter space is supported by numerical simulations of the fully nonlinear CDC problem. The resulting convective patterns compare favorably with recent experimental results found in microemulsion systems.

  15. 预包装食品中维生素D强化情况调查%Investigation on the pre-packaged food fortified with vitamin D

    Institute of Scientific and Technical Information of China (English)

    周明; 殷璐; 陈楠; 蔡云清

    2015-01-01

    目的 了解预包装食品中维生素D强化的情况.方法 根据GB 14880-2012的规定,在南京5家大型超市进行调查.结果 有36个品牌、共110种食品进行了维生素D的强化,65.5%的食品属于调制乳粉、调制乳、豆粉类;食品维生素D强化剂量均符合食品营养强化剂使用标准,人造黄油的添加量最高,最低的为糊状食品;九大知名品牌产品数约占所有维生素D强化食品的58.2%;76.4%的维生素D强化食品未明确标注维生素D2或维生素D3.结论 结果显示维生素D强化食品种类仍然不多且关于维生素D的标示信息不全.应增加维生素D的强化食品种类,并考虑强制性对一些食品进行维生素D强化.

  16. Development of DMC controllers for temperature control of a room deploying the displacement ventilation HVAC system

    Directory of Open Access Journals (Sweden)

    Zhicheng Li, Ramesh K. Agarwal, Huijun Gao

    2013-01-01

    Full Text Available In this paper, by developing a new Dynamic Matrix Control (DMC method, we develop a controller for temperature control of a room cooled by a displacement ventilation HVAC system. The fluid flow and heat transfer inside the room are calculated by solving the Reynolds-Averaged Navier-Stokes (RANS equations including the effects of buoyancy in conjunction with a two-equation realizable k - epsilon turbulence model. Thus the physical environment is represented by a nonlinear system of partial differential equations. The system also has a large time delay because of the slowness of the heat exchange. The goal of the paper is to develop a controller that will maintain the temperature at three points near three different walls in a room within the specified upper and lower bounds. In order to solve this temperature control problem at three different points in the room, we develop a special DMC method. The results show that the newly developed DMC controller is an effective controller to maintain temperature within desired bounds at multiple points in the room and also saves energy when compared to other controllers. This DMC method can also be employed to develop controllers for other HVAC systems such as the overhead VAV (Variable Air Volume system and the radiant cooling hydronic system.

  17. Development of DMC controllers for temperature control of a room deploying the displacement ventilation HVAC system

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhicheng; Agarwal, Ramesh K. [Department of Mechanical Engineering and Materials Science, Washington University in Saint Louis, MO 63130 (United States); Gao, Huijun [Research Institute of Intelligent Control and Systems, Harbin Institute of Technology, Harbin 150001 (China)

    2013-07-01

    In this paper, by developing a new Dynamic Matrix Control (DMC) method, we develop a controller for temperature control of a room cooled by a displacement ventilation HVAC system. The fluid flow and heat transfer inside the room are calculated by solving the Reynolds-Averaged Navier-Stokes (RANS) equations including the effects of buoyancy in conjunction with a two-equation realizable k - epsilon turbulence model. Thus the physical environment is represented by a nonlinear system of partial differential equations. The system also has a large time delay because of the slowness of the heat exchange. The goal of the paper is to develop a controller that will maintain the temperature at three points near three different walls in a room within the specified upper and lower bounds. In order to solve this temperature control problem at three different points in the room, we develop a special DMC method. The results show that the newly developed DMC controller is an effective controller to maintain temperature within desired bounds at multiple points in the room and also saves energy when compared to other controllers. This DMC method can also be employed to develop controllers for other HVAC systems such as the overhead VAV (Variable Air Volume) system and the radiant cooling hydronic system.

  18. CFD Analysis of a Hybrid Heat Pipe for In-Core Passive Decay Heat Removal System

    Energy Technology Data Exchange (ETDEWEB)

    Jeong Yeong Shin; Kim, Kyung Mo; Bang, In Cheol [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

    2014-05-15

    Station blackout (SBO) accident is the event that all AC power is totally lost from the failure of offsite and onsite power sources. Although electricity was provided from installed batteries for active system after shutdown, they were failed due to flooding after tsunami. The vulnerability of the current operating power plant's cooling ability during extended station blackout events is demonstrated and the importance of passive system becomes emphasized. Numerous researches about passive system have been studied for proper cooling residual heat after Fukushima nuclear power plant accident. Heat pipe is the effective passive heat transfer device that latent heat of vaporization is used to transport heat over long distance with even small temperature difference. Since liquid flows due to capillary force from wick structure and steam flows up due to buoyancy force, power is not necessary. Heat pipe is widely used in removal of local hot spot heat fluxes in CPU and thermal management in space crafts and satellites. Hybrid control rod, which consists of heat pipe with B{sub 4}C for wick structure material can be used for removing residual heat after. It can be applied to both for shutdown and cooling of decay heat in reactor. This concept is independent of external reactor situation like operator's mistake or malfunction of active cooling system. Heat pipe cooling system can be applied to Emergency Core Cooling System, In-Vessel Retention, containment and spent fuel cooling, contributing to decrease Core Damage Frequency.

  19. Instability of coupled gravity-inertial-Rossby waves on a β-plane in solar system atmospheres

    Directory of Open Access Journals (Sweden)

    J. F. McKenzie

    2009-11-01

    Full Text Available This paper provides an analysis of the combined theory of gravity-inertial-Rossby waves on a β-plane in the Boussinesq approximation. The wave equation for the system is fifth order in space and time and demonstrates how gravity-inertial waves on the one hand are coupled to Rossby waves on the other through the combined effects of β, the stratification characterized by the Väisälä-Brunt frequency N, the Coriolis frequency f at a given latitude, and vertical propagation which permits buoyancy modes to interact with westward propagating Rossby waves. The corresponding dispersion equation shows that the frequency of a westward propagating gravity-inertial wave is reduced by the coupling, whereas the frequency of a Rossby wave is increased. If the coupling is sufficiently strong these two modes coalesce giving rise to an instability. The instability condition translates into a curve of critical latitude Θc versus effective equatorial rotational Mach number M, with the region below this curve exhibiting instability. "Supersonic" fast rotators are unstable in a narrow band of latitudes around the equator. For example Θc~12° for Jupiter. On the other hand slow "subsonic" rotators (e.g. Mercury, Venus and the Sun's Corona are unstable at all latitudes except very close to the poles where the β effect vanishes. "Transonic" rotators, such as the Earth and Mars, exhibit instability within latitudes of 34° and 39°, respectively, around the Equator. Similar results pertain to Oceans. In the case of an Earth's Ocean of depth 4km say, purely westward propagating waves are unstable up to 26° about the Equator. The nonlinear evolution of this instability which feeds off rotational energy and gravitational buoyancy may play an important role in atmospheric dynamics.

  20. The mechanics of granitoid systems and maximum entropy production rates.

    Science.gov (United States)

    Hobbs, Bruce E; Ord, Alison

    2010-01-13

    A model for the formation of granitoid systems is developed involving melt production spatially below a rising isotherm that defines melt initiation. Production of the melt volumes necessary to form granitoid complexes within 10(4)-10(7) years demands control of the isotherm velocity by melt advection. This velocity is one control on the melt flux generated spatially just above the melt isotherm, which is the control valve for the behaviour of the complete granitoid system. Melt transport occurs in conduits initiated as sheets or tubes comprising melt inclusions arising from Gurson-Tvergaard constitutive behaviour. Such conduits appear as leucosomes parallel to lineations and foliations, and ductile and brittle dykes. The melt flux generated at the melt isotherm controls the position of the melt solidus isotherm and hence the physical height of the Transport/Emplacement Zone. A conduit width-selection process, driven by changes in melt viscosity and constitutive behaviour, operates within the Transport Zone to progressively increase the width of apertures upwards. Melt can also be driven horizontally by gradients in topography; these horizontal fluxes can be similar in magnitude to vertical fluxes. Fluxes induced by deformation can compete with both buoyancy and topographic-driven flow over all length scales and results locally in transient 'ponds' of melt. Pluton emplacement is controlled by the transition in constitutive behaviour of the melt/magma from elastic-viscous at high temperatures to elastic-plastic-viscous approaching the melt solidus enabling finite thickness plutons to develop. The system involves coupled feedback processes that grow at the expense of heat supplied to the system and compete with melt advection. The result is that limits are placed on the size and time scale of the system. Optimal characteristics of the system coincide with a state of maximum entropy production rate.

  1. Mooring System of Ocean Turbulence Observation Based on Submerged Buoy

    Institute of Scientific and Technical Information of China (English)

    SONG Da-lei; SUN Jing-jing; XUE Bing; JIANG Qian-li; WU Bing-wei

    2013-01-01

    A comparison experiment has been taken in the Kiaochow Bay between a newly designed mooring turbulence observation instrument (MTOI) and microstructure profiler MSS60 made by Sea & Sun.The whole observing system is based on a submerged buoy,in which the turbulence observation instrument is embedded,with a streamline-shape floating body,which is made of buoyancy material of glass microsphere.For the movement of seawater and the cable shaking strongly anytime influence the behaviors of the floating body,the accelerate sensors are used for the vibration measurement in the instrument together with the shear probe sensor.Both the vibration data and the shear data are acquired by the instrument at the same time.During data processing,the vibration signals can be removed and leave the shear data which we really need.In order to prove the reliability of the new turbulence instrument MTOI,a comparison experiment was designed.The measuring conditions are the same both in time and space.By this way,the two groups of data are comparable.In this paper,the conclusion gives a good similarity of 0.93 for the two groups of shear data in dissipation rate.The processing of the data acquired by MTOI is based on the cross-spectrum analysis,and the dissipation rate of it matches the Nasmyth spectrum well.

  2. Supplementary safety system 1/4 scale testing

    Energy Technology Data Exchange (ETDEWEB)

    Garrett, R.L.; Paik, I.K.

    1993-09-01

    During the course of updating the K-Reactor Safety Analysis Report Chapter 15 in 1990, it was identified that the current Supplementary Safety System (SSS) may not be adequate in protecting the reactor during the process water pump coastdown initiated by a loss of AC power when the safety rods are assumed to fail. A SSS modification project was initiated to add an additional ink injection pathway near the pump suction. In addition, the Department of Energy raised a question on the thermal buoyancy effects on moderator flow pattern and ink dispersion in the moderator space. The development and documentation of a two-dimensional code called MODFLOW was undertaken to describe the problem. This report discusses the results of the moderator flow and ink (Gadolinium Poison Solution - GPS) dispersion tests designed to provide qualified data for validation and benchmarking of the MODFLOW computer code with the secondary objectives being the development of concentration profiles and video footage of simulated GPS dispersion under steady-state and transient flow conditions.

  3. Mooring system of ocean turbulence observation based on submerged buoy

    Science.gov (United States)

    Song, Da-lei; Sun, Jing-jing; Xue, Bing; Jiang, Qian-li; Wu, Bing-wei

    2013-06-01

    A comparison experiment has been taken in the Kiaochow Bay between a newly designed mooring turbulence observation instrument (MTOI) and microstructure profiler MSS60 made by Sea & Sun. The whole observing system is based on a submerged buoy, in which the turbulence observation instrument is embedded, with a streamline-shape floating body, which is made of buoyancy material of glass microsphere. For the movement of seawater and the cable shaking strongly anytime influence the behaviors of the floating body, the accelerate sensors are used for the vibration measurement in the instrument together with the shear probe sensor. Both the vibration data and the shear data are acquired by the instrument at the same time. During data processing, the vibration signals can be removed and leave the shear data which we really need. In order to prove the reliability of the new turbulence instrument MTOI, a comparison experiment was designed. The measuring conditions are the same both in time and space. By this way, the two groups of data are comparable. In this paper, the conclusion gives a good similarity of 0.93 for the two groups of shear data in dissipation rate. The processing of the data acquired by MTOI is based on the cross-spectrum analysis, and the dissipation rate of it matches the Nasmyth spectrum well.

  4. In vitro Evaluation of Acyclovir/Chitosan Floating Systems.

    Science.gov (United States)

    Ruiz-Caro, Roberto; Veiga, María D

    2010-12-06

    Chitosan (CS) floating lyophilized formulations (L) for gastric drug delivery of acyclovir (ACV) have been developed. The freeze-dried formulations were obtained from acidic aqueous suspensions prepared with different ACV/CS ratios. No changes in ACV crystallinity were observed during X-ray diffraction powder studies as a consequence of the manufacturing process. Considering that fed and fasted states modified the intragastric pH, swelling and in vitro dissolution studies were carried out in different acidic media (0.1 M HCl and progressive pH medium) in order to understand the influence of these physiological states on ACV/CS formulations. Swelling behavior of the floating lyophilized formulations was dependent on CS and ACV proportions within L and on medium nature due to pH dependent CS solubility. Furthermore, no interactions between ACV and CS were detected in solid state according to the X-ray studies. In vitro dissolution of ACV from L was influenced by the swelling behavior. However, it is feasible to optimize the ACV/CS ratios to achieve a desired formulation that releases the total quantity of ACV at a specific time. Moreover, floatability was assessed by buoyancy tests. The results demonstrated that the freeze-drying process achieved effective floating systems capable of remaining within the stomach while the total amount of ACV is released from L.

  5. Design and optimization of floating drug delivery system of acyclovir

    Directory of Open Access Journals (Sweden)

    Kharia A

    2010-01-01

    Full Text Available The purpose of the present work was to design and optimize floating drug delivery systems of acyclovir using psyllium husk and hydroxypropylmethylcellulose K4M as the polymers and sodium bicarbonate as a gas generating agent. The tablets were prepared by wet granulation method. A 32 full factorial design was used for optimization of drug release profile. The amount of psyllium husk (X1 and hydroxypropylmethylcellulose K4M (X2 were selected as independent variables. The times required for 50% (t 50% and 70% (t 70% drug dissolution were selected as dependent variables. All the designed nine batches of formulations were evaluated for hardness, friability, weight variation, drug content uniformity, swelling index, in vitro buoyancy, and in vitro drug release profile. All formulations had floating lag time below 3 min and constantly floated on dissolution medium for more than 24 h. Validity of the developed polynomial equation was verified by designing two check point formulations (C1 and C2. The closeness of predicted and observed values for t 50% and t 70% indicates validity of derived equations for the dependent variables. These studies indicated that the proper balance between psyllium husk and hydroxypropylmethylcellulose K4M can produce a drug dissolution profile similar to the predicted dissolution profile. The optimized formulations followed Higuchi′s kinetics while the drug release mechanism was found to be anomalous type, controlled by diffusion through the swollen matrix.

  6. Modelling internal air systems in gas turbine engines

    Institute of Scientific and Technical Information of China (English)

    J Michael Owen

    2007-01-01

    Rotating-disc systems can be used to model,experimentally and computationally,the flow and heat transfer that occur inside the internal cooling-air systems of gas turbine engines.These rotating-disc systems have been used successfully to simplify and understand some of the complex flows that occur in internal-air systems,and designers have used this insight to improve the cooling effectiveness,thereby increasing the engine efficiency and reducing the emissions.In this review paper,three important cases are considered:hot-gas ingress;the pre-swirl system;and buoyancy-induced flow.Ingress,or ingestion,occurs when hot gas from the mainstream gas path is ingested into the wheel-space between the turbine disc and its adjacent casing.Rim seals are fitted at the periphery of the system,and sealing flow is used to reduce or prevent ingress.However,too much sealing air reduces the engine efficiency,and too little can cause serious overheating,resulting in damage to the turbine rim and blade roots.Although the flow is three-dimensional and unsteady,there are encouraging signs that simple 'orifice models' could be used to estimate the amount of ingress into the wheel-space.In a pre-swirl system,the cooling air for the gas-turbine blades is swirled by stationary nozzles,and the air is delivered to the blades via receiver holes in the rotating turbine disc.Swirling the air reduces its temperature relative to the rotating blades,and the designer needs to calculate the air temperature and pressure drop in the system.The designer also needs to calculate the effect of this swirling flow on the heat transfer from the turbine disc to the air,as this has a significant effect on the temperature distribution and stresses in the disc.Recent experimental and computational studies have given a better understanding of the flow and heat transfer in these systems.Buoyancy-induced flow occurs in the cavity between two co-rotating compressor discs when the temperature of the discs is higher

  7. The physical oceanography of upwelling systems and the development of harmful algal blooms

    Science.gov (United States)

    Pitcher, G.C.; Figueiras, F.G.; Hickey, B.M.; Moita, M.T.

    2011-01-01

    The upwelling systems of the eastern boundaries of the world’s oceans are susceptible to harmful algal blooms (HABs) because they are highly productive, nutrient-rich environments, prone to high-biomass blooms. This review identifies those aspects of the physical environment important in the development of HABs in upwelling systems through description and comparison of bloom events in the Benguela, California and Iberia systems. HAB development is dictated by the influence of wind stress on the surface boundary layer through a combination of its influence on surface mixed-layer characteristics and shelf circulation patterns. The timing of HABs is controlled by windstress fluctuations and buoyancy inputs at the seasonal, event and interannual scales. Within this temporal framework, various mesoscale features that interrupt typical upwelling circulation patterns, determine the spatial distribution of HABs. The inner shelf in particular provides a mosaic of shifting habitats, some of which favour HABs. Changes in coastline configuration and orientation, and bottom topography are important in determining the distribution of HABs through their influence on water stratification and retention. A spectrum of coastline configurations, including headlands, capes, peninsulas, Rías, bays and estuaries, representing systems of increasing isolation from the open coast and consequent increasing retention times, are assessed in terms of their vulnerability to HABs. PMID:22053120

  8. Investigations on the dynamic coupling in AUV-manipulator system and the manipulator trajectory errors using bond graph method

    Science.gov (United States)

    Periasamy, T.; Asokan, T.; Singaperumal, M.

    2012-06-01

    This article presents the modelling and simulation of the dynamic coupling in an autonomous underwater vehicle (AUV)-manipulator system, used for subsea intervention tasks. Bond graph, a powerful tool in multi-domain dynamic system modelling, is used for the first time to model the coupled dynamics of the AUV-manipulator system. This method enables the development of the system model in a modular form by creating sub-system models and connecting these models together at energy interactions ports, thus overcoming many of the computational difficulties encountered in conventional modelling methods. The effects of gravity, buoyancy, added mass and fluid drag on the dynamics of a 3 degrees of freedom (DoF) manipulator mounted on a 6 DoF AUV are analysed. The manipulator trajectory errors due to the interaction forces and moments between the vehicle and the manipulator have also been investigated and the results are presented. The dynamic model predicts the reaction forces on the vehicle under various operating conditions of the manipulator and their influence on the manipulator trajectory. The percentage errors of manipulator tip trajectory for different initial configurations and operating conditions are analysed. The estimation of resulting errors in the manipulator path due to dynamic coupling effect on the manipulator trajectory helps in the design of suitable trajectory controller for the system. Cartesian space transpose Jacobian controller for trajectory control of manipulator has been implemented and results are presented.

  9. The relationship between latent heating, vertical velocity, and precipitation processes: The impact of aerosols on precipitation in organized deep convective systems

    Science.gov (United States)

    Tao, Wei-Kuo; Li, Xiaowen

    2016-06-01

    A high-resolution, two-dimensional cloud-resolving model with spectral-bin microphysics is used to study the impact of aerosols on precipitation processes in both a tropical oceanic and a midlatitude continental squall line with regard to three processes: latent heating (LH), cold pool dynamics, and ice microphysics. Evaporative cooling in the lower troposphere is found to enhance rainfall in low cloud condensation nuclei (CCN) concentration scenarios in the developing stages of a midlatitude convective precipitation system. In contrast, the tropical case produced more rainfall under high CCN concentrations. Both cold pools and low-level convergence are stronger for those configurations having enhanced rainfall. Nevertheless, latent heat release is stronger (especially after initial precipitation) in the scenarios having more rainfall in both the tropical and midlatitude environment. Sensitivity tests are performed to examine the impact of ice and evaporative cooling on the relationship between aerosols, LH, and precipitation processes. The results show that evaporative cooling is important for cold pool strength and rain enhancement in both cases. However, ice microphysics play a larger role in the midlatitude case compared to the tropics. Detailed analysis of the vertical velocity-governing equation shows that temperature buoyancy can enhance updrafts/downdrafts in the middle/lower troposphere in the convective core region; however, the vertical pressure gradient force (PGF) is of the same order and acts in the opposite direction. Water loading is small but of the same order as the net PGF-temperature buoyancy forcing. The balance among these terms determines the intensity of convection.

  10. Experimentally determined rock-fluid interactions applicable to a natural hot dry rock geothermal system

    Energy Technology Data Exchange (ETDEWEB)

    Charles, R.W.; Holley, C.E. Jr.; Tester, J.W.; Blatz, L.A.; Grigsby, C.O.

    1980-02-01

    The Los Alamos Scientific Laboratory is pursuing laboratory and field experiments in the development of the Hot Dry Rock concept of geothermal energy. The field program consists of experiments in a hydraulically fractured region of low permeability in which hot rock is intercepted by two wellbores. These experiments are designed to test reservoir engineering parameters such as: heat extraction rates, water loss rates, flow characteristics including impedance and buoyancy, seismic activity and fluid chemistry. Laboratory experiments have been designed to provide information on the mineral reactivity which may be encountered in the field program. Two experimental circulation systems have been built to study the rates of dissolution and alteration in dynamic flow. Solubility studies have been done in agitated systems. To date, pure minerals, samples of the granodiorite from the actual reservoir and Tijeras Canyon granite have been reacted with distilled water and various solutions of NaCl, NaOH, and Na/sub 2/CO/sub 3/. The results of these experimental systems are compared to observations made in field experiments done in a hot dry rock reservoir at a depth of approximately 3 km with initial rock temperatures of 150 to 200/sup 0/C.

  11. Natural convection heat exchangers for solar water heating systems. Technical progress report, September 15, 1996--November 14, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Davidson, J.H.

    1998-06-01

    The goals of this project are: (1) to develop guidelines for the design and use of thermosyphon side-arm heat exchangers in solar domestic water heating systems, and (2) to establish appropriate modeling and testing criteria for evaluating the performance of systems using this type of heat exchanger. The tasks for the project are as follows: (1) Develop a model of the thermal performance of thermosyphon heat exchangers in solar water heating applications. A test protocol will be developed which minimizes the number of tests required to adequately account for mixed convection effects. The TRNSYS component model will be fully integrated in a system component model and will use data acquired with the specified test protocol. (2) Conduct a fundamental study to establish friction and heat transfer correlations for conditions and geometries typical of thermosyphon heat exchangers in solar systems. Data will be obtained as a function of a buoyancy parameter based on Grashof and Reynolds numbers. The experimental domain will encompass the ranges expected in solar water heating systems.

  12. The development of a under-water robot system for inspection of the contaminated inner wall of nuclear research reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyung Hoon; Kim, Byung Man; Cho, Hyung Suk; Park, Ki Yong [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of); Park, Young Soo; Yoon, Ji Sup; Lee, Byung Jik [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1997-12-31

    In this paper, an under-water robot system is developed in order to inspect the radiation level and decontaminate the contaminated inner wall of nuclear research reactor, TRIGA MARK III. This system is composed of the mobile robot which navigates autonomously under the water and the ground control unit which monitors and commands the motion of mobile robot. The mobile robot can move on the wall surface with five thruster systems and is composed of three parts, i.e., mechanical, control, and sensory parts. The five thruster system is configured such as one main thruster, two wall adhesion thruster, and two turning/buoyancy compensation thruster. The control part has 4 CPU boards and each board is configured such that one is in charge of supervisory control mode which controls the position of mobile robot and communicates with the ground control unit and the other board is designed to have motor control mode which drives two motors simultaneously. In secondary part, the laser scanner and fluorescent reflectors and the incilinometer are designed. The laser scanner with fluorescent reflectors provides the current position of the mobile robot on the wall surface and by incilinometer, the moving direction can be obtained. This paper describes the design and configuration procedures of under-water robot in detail and presents the experimental results for characteristic test of the thruster system. 11 refs., 4 tabs., 7 figs.

  13. Simulation of the performance of a hybrid ventilation system in different climates

    Energy Technology Data Exchange (ETDEWEB)

    Charvat, P.; Jicha, M. [Brno Univ. of Technology, Brno (Czech Republic). Faculty of Mechanical Engineering; Niachou, A.; Santamouris, M. [National and Kapodistrian Univ. of Athens, Athens (Greece)

    2005-07-01

    Four different concepts of hybrid ventilation systems for 4 climates in Europe have been developed within the Framework of the European Union project called Residential Hybrid Ventilation (RESHYVENT). This study involved computational simulations to examine the performance of the hybrid ventilation system for a moderate climate in an urban environment under various climatic conditions. A hybrid ventilation system refers to a ventilation system that uses natural driving forces as long as possible and which switches to mechanical forces when needed. It therefore minimizes energy consumption while maintaining good indoor air quality and thermal comfort for occupants. The RESHYVENT hybrid ventilation system consists of a self-regulating air inlet, DC fan, motorized damper, flow meter, central control unit, carbon dioxide sensors and ductwork. If natural driving forces are not sufficient, the fan engages and its speed adjusts to match the demanded flow rate. This paper presents a case study in which the TRNSYS type 15 software package was used with the TRNFlow air flow network module to simulate natural driving forces such as wind and buoyancy in an apartment building situated in an urban canyon. Results were obtained for a specific geometry, occupancy scheme and other factors. The study showed that the hybrid ventilation system was able to maintain required indoor air quality regardless of weather conditions. As such, it was better than the natural ventilation system and holds promise for use in office and residential buildings. The complexity of hybrid and natural ventilation systems is due to the fact that air flow rates depend greatly on climatic conditions. Therefore, simulations must consider thermal and air flow models. Experiments conducted at a demonstration house in Brno, Czech Republic show that the RESHYVENT hybrid ventilation system could maintain the level of carbon dioxide concentration in rooms below 1200 ppm. refs., 7 tabs., 3 figs.

  14. System Budgets

    DEFF Research Database (Denmark)

    Jeppesen, Palle

    1996-01-01

    The lecture note is aimed at introducing system budgets for optical communication systems. It treats optical fiber communication systems (six generations), system design, bandwidth effects, other system impairments and optical amplifiers.......The lecture note is aimed at introducing system budgets for optical communication systems. It treats optical fiber communication systems (six generations), system design, bandwidth effects, other system impairments and optical amplifiers....

  15. Enhanced geothermal systems (EGS) using CO2 as working fluid - Anovelapproach for generating renewable energy with simultaneoussequestration of carbon

    Energy Technology Data Exchange (ETDEWEB)

    Pruess, Karsten

    2006-06-07

    Responding to the need to reduce atmospheric emissions of carbon dioxide, Donald Brown (2000) proposed a novel enhanced geothermal systems (EGS) concept that would use CO{sub 2} instead of water as heat transmission fluid, and would achieve geologic sequestration of CO{sub 2} as an ancillary benefit. Following up on his suggestion, we have evaluated thermophysical properties and performed numerical simulations to explore the fluid dynamics and heat transfer issues in an engineered geothermal reservoir that would be operated with CO{sub 2}. We find that CO{sub 2} is superior to water in its ability to mine heat from hot fractured rock. CO{sub 2} also has certain advantages with respect to wellbore hydraulics, where larger compressibility and expansivity as compared to water would increase buoyancy forces and would reduce the parasitic power consumption of the fluid circulation system. While the thermal and hydraulic aspects of a CO{sub 2}-EGS system look promising, major uncertainties remain with regard to chemical interactions between fluids and rocks. An EGS system running on CO{sub 2} has sufficiently attractive features to warrant further investigation.

  16. Implementation of unscented transform to estimate the uncertainty of a liquid flow standard system

    Energy Technology Data Exchange (ETDEWEB)

    Chun, Sejong; Choi, Hae-Man; Yoon, Byung-Ro; Kang, Woong [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)

    2017-03-15

    First-order partial derivatives of a mathematical model are an essential part of evaluating the measurement uncertainty of a liquid flow standard system according to the Guide to the expression of uncertainty in measurement (GUM). Although the GUM provides a straightforward method to evaluate the measurement uncertainty of volume flow rate, the first-order partial derivatives can be complicated. The mathematical model of volume flow rate in a liquid flow standard system has a cross-correlation between liquid density and buoyancy correction factor. This cross-correlation can make derivation of the first-order partial derivatives difficult. Monte Carlo simulation can be used as an alternative method to circumvent the difficulty in partial derivation. However, the Monte Carlo simulation requires large computational resources for a correct simulation because it considers the completeness issue whether an ideal or a real operator conducts an experiment to evaluate the measurement uncertainty. Thus, the Monte Carlo simulation needs a large number of samples to ensure that the uncertainty evaluation is as close to the GUM as possible. Unscented transform can alleviate this problem because unscented transform can be regarded as a Monte Carlo simulation with an infinite number of samples. This idea means that unscented transform considers the uncertainty evaluation with respect to the ideal operator. Thus, unscented transform can evaluate the measurement uncertainty the same as the uncertainty that the GUM provides.

  17. A novel system for embryo-larval toxicity testing of pelagic fish: Applications for impact assessment of Deepwater Horizon crude oil.

    Science.gov (United States)

    Stieglitz, John D; Mager, Edward M; Hoenig, Ronald H; Alloy, Matthew; Esbaugh, Andrew J; Bodinier, Charlotte; Benetti, Daniel D; Roberts, Aaron P; Grosell, Martin

    2016-11-01

    Key differences in the developmental process of pelagic fish embryos, in comparison to embryos of standard test fish species, present challenges to obtaining sufficient control survival needed to successfully perform traditional toxicity testing bioassays. Many of these challenges relate to the change in buoyancy, from positive to negative, of pelagic fish embryos that occurs just prior to hatch. A novel exposure system, the pelagic embryo-larval exposure chamber (PELEC), has been developed to conduct successful bioassays on the early life stages (ELSs; embryos/larvae) of pelagic fish. Using this unique recirculating upwelling system, it was possible to significantly improve control survival in pelagic fish ELS bioassays compared to commonly used static exposure methods. Results demonstrate that control performance of mahi-mahi (Coryphaena hippurus) embryos in the PELEC system, measured as percent survival after 96-hrs, significantly outperformed agitated static exposure and static exposure systems. Similar significant improvements in 72-hr control survival were obtained with yellowfin tuna (Thunnus albacares). The PELEC system was subsequently used to test the effects of photo-induced toxicity of crude oil to mahi-mahi ELSs over the course of 96-hrs. Results indicate a greater than 9-fold increase in toxicity of Deepwater Horizon (DWH) crude oil during co-exposure to ambient sunlight compared to filtered ambient sunlight, revealing the importance of including natural sunlight in 96-hr DWH crude oil bioassays as well as the PELEC system's potential application in ecotoxicological assessments.

  18. Development and evaluation of gastroretentive raft forming systems incorporating curcumin-Eudragit® EPO solid dispersions for gastric ulcer treatment.

    Science.gov (United States)

    Kerdsakundee, Nattha; Mahattanadul, Sirima; Wiwattanapatapee, Ruedeekorn

    2015-08-01

    Novel raft forming systems incorporating curcumin-Eudragit® EPO solid dispersions were developed to prolong the gastric residence time and provide for a controlled release therapy of curcumin to treat gastric ulcers. The solid dispersions of curcumin with Eudragit® EPO were prepared by the solvent evaporation method at various ratios to improve the solubility and the dissolution of curcumin. The optimum weight ratio of 1:5 for curcumin to Eudragit® EPO was used to incorporate into the raft forming systems. The raft forming formulations were composed of curcumin-Eudragit® EPO solid dispersions, sodium alginate as a gelling polymer and calcium carbonate for generating divalent Ca(2+) ions and carbon dioxide to form a floating raft. All formulations formed a gelled raft in 1min and sustained buoyancy on the 0.1N hydrochloric acid (pH 1.2) surface with a 60-85% release of curcumin within 8h. The curative effect on the acetic acid-induced chronic gastric ulcer in rats was determined. The curcumin raft forming formulations at 40mg/kg once daily showed a superior curative effect on the gastric ulcer in terms of the ulcer index and healing index than the standard antisecretory agent: lansoprazole (1mg/kg, twice daily) and a curcumin suspension (40mg/kg, twice daily). These studies demonstrated that the new raft forming systems containing curcumin solid dispersions are promising carriers for a stomach-specific delivery of poorly soluble lipophilic compounds.

  19. System Identification

    NARCIS (Netherlands)

    Keesman, K.J.

    2011-01-01

    Summary System Identification Introduction.- Part I: Data-based Identification.- System Response Methods.- Frequency Response Methods.- Correlation Methods.- Part II: Time-invariant Systems Identification.- Static Systems Identification.- Dynamic Systems Identification.- Part III: Time-varying

  20. Design and construction of an automatic system for minimizing the risk of sinking of water vehicle

    Science.gov (United States)

    Sutradhar, Amit; Rashid, Md. Mahbubur; Helal-An-Nahiyan, Md.; Mandal, Manash Kumar

    2016-07-01

    This paper focuses on the reduction of the risk of water vehicle like launch, ferry, ship and boat from sinking which is a burning problem of Bangladesh now-a-days. Every year death toll is rising by leaps and bounds due to this unexpected phenomenon. The sinking mostly occurs due to overloading and lack of consciousness. That's why, an automated system is introduced here to make the travelers warned about the overloading situation through raising alarm before the vehicle starts to move on. The tolerance limit of the vehicle is determined based on the theory of buoyancy and floatation. Moreover, while moving on the water, the vehicle may get victim of sinking due to rough weather, low visibility or machineries breakdown. So water level indicator is used to determine the safe level of water. When water level rises up to the safe limit or just before crossing the safe limit, another alarm will warn the passengers which will sound quite different from the first alarm as stated before. And at once the on board GPS sensor will record the current position of the vehicle and transmit the location to the nearest rescue authority via GSM module in the form of text message which will help them to take necessary steps for the rescue of the passengers as soon as possible. Effective implementation of this method can reduce the accident as well as this research can also be a helpful tool to organize further researches in this field for the sake of humanity.

  1. Basic development of a small balloon-mounted telemetry and its operation system by university students

    Science.gov (United States)

    Yamamoto, Masa-yuki; Kakinami, Yoshihiro; Kono, Hiroki

    In Japan, the high altitude balloon for scientific observation has been continuously launched by JAXA. The balloon has a possibility to reach 50 km altitude without tight environmental condition for onboard equipments, operating with a cost lower than sounding rockets, however, development of the large-scale scientific observation balloons by university laboratories is still difficult. Being coupled with recent improvement of semiconductor sensors, laboratory-basis balloon experiments using small weather balloons has been becoming easily in these years. Owing to an advantage of wide land fields in continental regions, the launch of such small balloons has become to be carried out many times especially in continental countries (e.g. Near Space Ventures, Inc., 2013). Although the balloon is very small as its diameter of 6 feet, excluding its extra buoyancy and the weight of the balloon itself, it is expected that about 2 kg loading capacity is remained for payloads to send it up to about 35 km altitude. However, operation of such balloons in Japan is not in general because precise prediction of a landing area of the payload is difficult, thus high-risk situation for balloon releases is remained. In this study, we aim to achieve practical engineering experiments of weather balloons in Japan to be used for scientific observation within university laboratory level as an educational context. Here we report an approach of developing many devices for a small tethered balloon currently in progress. We evaluated an accuracy of altitude measurement by using a laboratory developed altitude data logger system that consists of a GPS-module and a barometric altimeter. Diameter of the balloon was about 1.4 m. Being fulfilled with about 1440 L helium, it produced buoyancy of about 15.7 N. Taking into account of total weight including the mooring equipments, available payload mass becomes to be about 1100 g. Applying an advantage of a 3D printer of FDM (Fused Deposition Modeling

  2. Origin of salt giants in abyssal serpentinite systems

    Science.gov (United States)

    Scribano, Vittorio; Carbone, Serafina; Manuella, Fabio C.; Hovland, Martin; Rueslåtten, Håkon; Johnsen, Hans-K.

    2017-03-01

    Worldwide marine salt deposits ranging over the entire geological record are generally considered climate-related evaporites, derived from the precipitation of salts (mainly chlorides and sulfates) from saturated solutions driven by solar evaporation of seawater. This explanation may be realistic for a salt thickness ≤100 m, being therefore inadequate for thicker (>1 km) deposits. Moreover, sub-seafloor salt deposits in deep marine basins are difficult to reconcile with a surface evaporation model. Marine geology reports on abyssal serpentinite systems provide an alternative explanation for some salt deposits. Seawater-driven serpentinization consumes water and increases the salinity of the associated aqueous brines. Brines can be trapped in fractures and cavities in serpentinites and the surrounding `country' rocks. Successive thermal dehydration of buried serpentinites can mobilize and accumulate the brines, forming highly saline hydrothermal solutions. These can migrate upwards and erupt onto the seafloor as saline geysers, which may form salt-saturated water pools, as are currently observed in numerous deeps in the Red Sea and elsewhere. The drainage of deep-seated saline brines to seafloor may be a long-lasting, effective process, mainly occurring in areas characterized by strong tectonic stresses and/or igneous intrusions. Alternatively, brines could be slowly expelled from fractured serpentinites by buoyancy gradients and, hence, separated salts/brines could intrude vertically into surrounding rocks, forming salt diapirs. Serpentinization is an ubiquitous, exothermic, long-lasting process which can modify large volumes of oceanic lithosphere over geological times. Therefore, buried salt deposits in many areas of the world can be reasonably related to serpentinites.

  3. Effects of aerosol on evaporation, freezing and precipitation in a multiple cloud system

    Science.gov (United States)

    Lee, Seoung Soo; Kim, Byung-Gon; Yum, Seong Soo; Seo, Kyong-Hwan; Jung, Chang-Hoon; Um, Jun Shik; Li, Zhanqing; Hong, JinKyu; Chang, Ki-Ho; Jeong, Jin-Yim

    2017-02-01

    Aerosol effects on clouds and precipitation account for a large portion of uncertainties in the prediction of the future course of global hydrologic circulations and climate. As a process of a better understanding of interactions between aerosol, clouds and precipitation, simulations are performed for a mixed-phase convective multiple-cloud system over the tropics. Studies on single-cloud systems have shown that aerosol-induced increases in freezing, associated increases in parcel buoyancy and thus the intensity of clouds (or updrafts) are a main mechanism which controls aerosol-cloud-precipitation interactions in convective clouds. However, in the multiple-cloud system that plays much more important roles in global hydrologic circulations and thus climate than single-cloud systems, aerosol effects on condensation play the most important role in aerosol-induced changes in the intensity of clouds and the effects on freezing play a negligible role in those changes. Aerosol-induced enhancement in evaporation intensifies gust fronts and increases the number of subsequently developing clouds, which leads to the substantial increases in condensation and associated intensity of convection. Although aerosol-induced enhancement in freezing takes part in the increases in condensation by inducing stronger convergence around cloud bottom, the increases in condensation are one order of magnitude larger than those in freezing. It is found that while aerosol-induced increases in freezing create intermittent extremely heavy precipitation, aerosol-induced increases in evaporation enhance light and medium precipitation in the multiple-cloud system here. This increase in light and medium precipitation makes it possible that cumulative precipitation increases with increasing aerosol concentration, although the increase is small. It is interesting that the altitude of the maximum of the time- and domain-averaged hydrometeor mass densities is quite robust to increases in aerosol

  4. Gradient systems and mechanical systems

    Institute of Scientific and Technical Information of China (English)

    Fengxiang Mei; Huibin Wu

    2016-01-01

    All types of gradient systems and their properties are discussed. Two problems connected with gradient sys-tems and mechanical systems are studied. One is the direct problem of transforming a mechanical system into a gradi-ent system, and the other is the inverse problem, which is transforming a gradient system into a mechanical system.

  5. Design of push-pull system to control diesel particular matter inside a dead-end entry.

    Science.gov (United States)

    Zheng, Yi; Thiruvengadam, Magesh; Lan, Hai; Tien, Jerry C

    Diesel particulate matter (DPM) is considered to be carcinogenic after prolonged exposure. With more diesel-powered equipment used in underground mines, miners' exposure to DPM has become an increasing concern. This paper used computational fluid dynamics method to study the DPM dispersion in a dead-end entry with loading operation. The effects of different push-pull ventilation systems on DPM distribution were evaluated to improve the working conditions for underground miners. The four push-pull systems considered include: long push and short pull tubing; short push and long pull tubing, long push and curved pull tubing, and short push and curved pull tubing. A species transport model with buoyancy effect was used to examine the DPM dispersion pattern with unsteady state analysis. During the 200 s of loading operation, high DPM levels were identified in the face and dead-end entry regions. This study can be used for mining engineer as guidance to design and setup local ventilation, select DPM control strategies and for DPM annual training for underground miners.

  6. Design of push-pull system to control diesel particular matter inside a dead-end entry

    Institute of Scientific and Technical Information of China (English)

    Yi Zheng; Magesh Thiruvengadam; Hai Lan; Jerry C Tien

    2015-01-01

    Diesel particulate matter (DPM) is considered to be carcinogenic after prolonged exposure. With more diesel-powered equipment used in underground mines, miners’ exposure to DPM has become an increasing concern. This paper used computational fluid dynamics method to study the DPM dispersion in a dead-end entry with loading operation. The effects of different push–pull ventilation systems on DPM distribution were evaluated to improve the working conditions for underground miners. The four push–pull systems considered include:long push and short pull tubing;short push and long pull tubing, long push and curved pull tubing, and short push and curved pull tubing. A species transport model with buoyancy effect was used to examine the DPM dispersion pattern with unsteady state analysis. During the 200 s of loading operation, high DPM levels were identified in the face and dead-end entry regions. This study can be used for mining engineer as guidance to design and setup local ventilation, select DPM control strategies and for DPM annual training for underground miners.

  7. Thermal systems; Systemes thermiques

    Energy Technology Data Exchange (ETDEWEB)

    Lalot, S. [Valenciennes Univ. et du Hainaut Cambresis, LME, 59 (France); Lecoeuche, S. [Ecole des Mines de Douai, Dept. GIP, 59 - Douai (France)]|[Lille Univ. des Sciences et Technologies, 59 - Villeneuve d' Ascq (France); Ahmad, M.; Sallee, H.; Quenard, D. [CSTB, 38 - Saint Martin d' Heres (France); Bontemps, A. [Universite Joseph Fourier, LEGI/GRETh, 38 - Grenoble (France); Gascoin, N.; Gillard, P.; Bernard, S. [Laboratoire d' Energetique, Explosion, Structure, 18 - Bourges (France); Gascoin, N.; Toure, Y. [Laboratoire Vision et Robotique, 18 - Bourges (France); Daniau, E.; Bouchez, M. [MBDA, 18 - Bourges (France); Dobrovicescu, A.; Stanciu, D. [Bucarest Univ. Polytechnique, Faculte de Genie Mecanique (Romania); Stoian, M. [Reims Univ. Champagne Ardenne, Faculte des Sciences, UTAP/LTM, 51 (France); Bruch, A.; Fourmigue, J.F.; Colasson, S. [CEA Grenoble, Lab. Greth, 38 (France); Bontemps, A. [Universite Joseph Fourier, LEGI/GRETh, 38 - Grenoble (France); Voicu, I.; Mare, T.; Miriel, J. [Institut National des Sciences Appliquees (INSA), LGCGM, IUT, 35 - Rennes (France); Galanis, N. [Sherbrooke Univ., Genie Mecanique, QC (Canada); Nemer, M.; Clodic, D. [Ecole des Mines de Paris, Centre Energetique et Procedes, 75 (France); Lasbet, Y.; Auvity, B.; Castelain, C.; Peerhossaini, H. [Nantes Univ., Ecole Polytechnique, Lab. de Thermocinetiquede Nantes, UMR-CNRS 6607, 44 (France)

    2005-07-01

    This session about thermal systems gathers 26 articles dealing with: neural model of a compact heat exchanger; experimental study and numerical simulation of the thermal behaviour of test-cells with walls made of a combination of phase change materials and super-insulating materials; hydraulic and thermal modeling of a supercritical fluid with pyrolysis inside a heated channel: pre-dimensioning of an experimental study; energy analysis of the heat recovery devices of a cryogenic system; numerical simulation of the thermo-hydraulic behaviour of a supercritical CO{sub 2} flow inside a vertical tube; mixed convection inside dual-tube exchangers; development of a nodal approach with homogenization for the simulation of the brazing cycle of a heat exchanger; chaotic exchanger for the cooling of low temperature fuel cells; structural optimization of the internal fins of a cylindrical generator; a new experimental approach for the study of the local boiling inside the channels of exchangers with plates and fins; experimental study of the flow regimes of boiling hydrocarbons on a bundle of staggered tubes; energy study of heat recovery exchangers used in Claude-type refrigerating systems; general model of Carnot engine submitted to various operating constraints; the free pistons Stirling cogeneration system; natural gas supplied cogeneration system with polymer membrane fuel cell; influence of the CRN coating on the heat flux inside the tool during the wood unrolling process; transport and mixture of a passive scalar injected inside the wake of a Ahmed body; control of a laser welding-brazing process by infrared thermography; 2D self-adaptative method for contours detection: application to the images of an aniso-thermal jet; exergy and exergy-economical study of an 'Ericsson' engine-based micro-cogeneration system; simplified air-conditioning of telephone switching equipments; parametric study of the 'low-energy' individual dwelling; brief synthesis of

  8. Data Systems vs. Information Systems

    OpenAIRE

    Amatayakul, Margret K.

    1982-01-01

    This paper examines the current status of “hospital information systems” with respect to the distinction between data systems and information systems. It is proposed that the systems currently existing are incomplete data dystems resulting in ineffective information systems.

  9. Data Systems vs. Information Systems

    OpenAIRE

    Amatayakul, Margret K.

    1982-01-01

    This paper examines the current status of “hospital information systems” with respect to the distinction between data systems and information systems. It is proposed that the systems currently existing are incomplete data dystems resulting in ineffective information systems.

  10. Multibody Systems

    DEFF Research Database (Denmark)

    Wagner, Falko Jens

    1999-01-01

    Multibody Systems is one area, in which methods for solving DAEs are of special interst. This chapter is about multibody systems, why they result in DAE systems and what kind of problems that can arise when dealing with multibody systems and formulating their corresponding DAE system....

  11. Lymph system

    Science.gov (United States)

    Lymphatic system ... neck, under the arms, and groin. The lymph system includes the: Tonsils Adenoids Spleen Thymus ... JE, Flynn JA, Solomon BS, Stewart RW. Lymphatic system. In: Ball JW, Dains JE, Flynn JA, Solomon ...

  12. Buoyancy-driven leakage of oil from a ruptured submarine pipeline

    NARCIS (Netherlands)

    Kranenburg, C.

    1983-01-01

    The rupture of a submarine oil pipeline starts various mechanisms leading to an oil spill. Among these mechanisms the leakage of oil driven by the difference in specific gravities of oil and sea-water is difficult to estimate. A simple mathematical model has been developed and laboratory experiments

  13. Modeling Atmospheric Turbulence via Rapid Distortion Theory: Spectral Tensor of Velocity and Buoyancy

    DEFF Research Database (Denmark)

    Chougule, Abhijit S.; Mann, Jakob; Kelly, Mark C.

    2017-01-01

    A spectral tensor model is presented for turbulent fluctuations of wind velocity components and temperature, assuming uniform vertical gradients in mean temperature and mean wind speed. The model is built upon rapid distortion theory (RDT) following studies by Mann and by Hanazaki and Hunt, using...... the eddy lifetime parameterization of Mann to make the model stationary. The buoyant spectral tensor model is driven via five parameters: the viscous dissipation rate epsilon, length scale of energy-containing eddies L, a turbulence anisotropy parameter Gamma, gradient Richardson number (Ri) representing...... separation. Finally, it is shown that the RDT output can deviate from Monin-Obukhov similarity theory....

  14. The selective advantage of buoyancy provided by gas vesicles for planktonic cyanobacteria in the Baltic Sea

    NARCIS (Netherlands)

    Walsby, A.E.; Hayes, P.K.; Boje, R.; Stal, L.J.

    1997-01-01

    Observations were made on the vertical distribution of colonies of Aphanizomenon flos-aquae for 9 d at a drift-station east of Bornholm Island in the Baltic Sea. The buoyant colonies were dispersed in the upper layers of the water column during periods of wind-induced mixing but floated up during

  15. In-Situ Production of Hydrogen for Buoyancy on Titan Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Resupply of materials in space applications is a significant logistical problem. Historically the replacement materials have been carried with the spacecraft. This...

  16. Microliter-bioreactor array with buoyancy-driven stirring for human hematopoietic stem cell culture

    OpenAIRE

    Luni, Camilla; Feldman, Hope C.; Pozzobon, Michela; De Coppi, Paolo; Meinhart, Carl D.; Elvassore, Nicola

    2010-01-01

    This work presents the development of an array of bioreactors where finely controlled stirring is provided at the microliter scale (100–300 μl). The microliter-bioreactor array is useful for performing protocol optimization in up to 96 parallel experiments of hematopoietic stem cell (HSC) cultures. Exploring a wide range of experimental conditions at the microliter scale minimizes cost and labor. Once the cell culture protocol is optimized, it can be applied to large-scale bioreactors for ste...

  17. Design of a Lighter Than Air Vehicle That Achieves Positive Buoyancy in Air Using a Vacuum

    Science.gov (United States)

    2012-06-01

    calculated for the frame. The skin was predicted to add approximately 0.37 to the W/B if Zylon was used to reinforce a Mylar membrane, which would...stiffening the skin are Zylon and Vectran as shown in Table 6. If graphene could be made in usable sizes and attached to the structure, it would far exceed...Graphene 250 ∙ 109 100 130 0.02 Only Available in small sheets Zylon 303 ∙ 109 1560 5.8 2.5 Fiber Vectran 75 ∙ 109 1400 3.2 3.6 Fiber

  18. Buoyancy effects on upward brine displacement caused by CO2 injection

    Energy Technology Data Exchange (ETDEWEB)

    Oldenburg, C.M.; Rinaldi, A.

    2010-01-15

    Upward displacement of brine from deep reservoirs driven by pressure increases resulting from CO{sub 2} injection for geologic carbon sequestration may occur through improperly sealed abandoned wells, through permeable faults, or through permeable channels between pinch-outs of shale formations. The concern about upward brine flow is that, upon intrusion into aquifers containing groundwater resources, the brine may degrade groundwater. Because both salinity and temperature increase with depth in sedimentary basins, upward displacement of brine involves lifting fluid that is saline but also warm into shallower regions that contain fresher, cooler water. We have carried out dynamic simulations using TOUGH2/EOS7 of upward displacement of warm, salty water into cooler, fresher aquifers in a highly idealized two-dimensional model consisting of a vertical conduit (representing a well or permeable fault) connecting a deep and a shallow reservoir. Our simulations show that for small pressure increases and/or high-salinity-gradient cases, brine is pushed up the conduit to a new static steady-state equilibrium. On the other hand, if the pressure rise is large enough that brine is pushed up the conduit and into the overlying upper aquifer, flow may be sustained if the dense brine is allowed to spread laterally. In this scenario, dense brine only contacts the lower-most region of the upper aquifer. In a hypothetical case in which strong cooling of the dense brine occurs in the upper reservoir, the brine becomes sufficiently dense that it flows back down into the deeper reservoir from where it came. The brine then heats again in the lower aquifer and moves back up the conduit to repeat the cycle. Parameter studies delineate steady-state (static) and oscillatory solutions and reveal the character and period of oscillatory solutions. Such oscillatory solutions are mostly a curiosity rather than an expected natural phenomenon because in nature the geothermal gradient prevents the cooling in the upper aquifer that occurs in the model. The expected effect of upward brine displacement is either establishment of a new hydrostatic equilibrium or sustained upward flux into the bottom-most region of the upper aquifer.

  19. Developing Buoyancy Driven Flow of a Nanofluid in a Vertical Channel Subject to Heat Flux

    Directory of Open Access Journals (Sweden)

    Nirmal C. Sacheti

    2014-01-01

    Full Text Available The developing natural convective flow of a nanofluid in an infinite vertical channel with impermeable bounding walls has been investigated. It is assumed that the nanofluid is dominated by two specific slip mechanisms and that the channel walls are subject to constant heat flux and isothermal temperature, respectively. The governing nonlinear partial differential equations coupling different transport processes have been solved numerically. The variations of velocity, temperature, and nanoparticles concentration have been discussed in relation to a number of physical parameters. It is seen that the approach to the steady-state profiles of velocity and temperature in the present work is different from the ones reported in a previous study corresponding to isothermal wall conditions.

  20. Response of the Atlantic overturning circulation to South Atlantic sources of buoyancy

    NARCIS (Netherlands)

    Weijer, W.; Ruijter, W.P.M. de; Sterl, A.; Drijfhout, S.

    2002-01-01

    The heat and salt input from the Indian to Atlantic Oceans by Agulhas Leakage is found to influence the Atlantic overturning circulation in a low-resolution Ocean General Circulation Model. The model used is the Hamburg Large-Scale Geostrophic (LSG) model, which is forced by mixed boundary condition

  1. In-situ Production of Hydrogen for Buoyancy on Titan Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Based on current observations Titan is believed to have a rich, dense atmosphere. If the findings of the Cassini and Huygens missions corroborate this, the next...

  2. Particle fluid interactivity deteriorates buoyancy driven thermal transport in nanosuspensions : A multi component lattice Boltzmann approach

    CERN Document Server

    S, Savithiri; Pattamatta, Arvind; Das, Sarit K

    2015-01-01

    Severe contradictions exist between experimental observations and computational predictions regarding natural convective thermal transport in nanosuspensions. The approach treating nanosuspensions as homogeneous fluids in computations has been pin pointed as the major contributor to such contradictions. To fill the void, inter particle and particle fluid interactivities (slip mechanisms), in addition to effective thermophysical properties, have been incorporated within the present formulation. Through thorough scaling analysis, the dominant slip mechanisms have been identified. A Multi Component Lattice Boltzmann Model (MCLBM) approach has been proposed, wherein the suspension has been treated as a non homogeneous twin component mixture with the governing slip mechanisms incorporated. The computations based on the mathematical model can accurately predict and quantify natural convection thermal transport in nanosuspensions. The role of slip mechanisms such as Brownian diffusion, thermophoresis, drag, Saffman ...

  3. Particle fluid interactivity deteriorates buoyancy driven thermal transport in nanosuspensions : A multi component lattice Boltzmann approach

    OpenAIRE

    S, Savithiri; Dhar,Purbarun; Pattamatta, Arvind; Das, Sarit K

    2015-01-01

    Severe contradictions exist between experimental observations and computational predictions regarding natural convective thermal transport in nanosuspensions. The approach treating nanosuspensions as homogeneous fluids in computations has been pin pointed as the major contributor to such contradictions. To fill the void, inter particle and particle fluid interactivities (slip mechanisms), in addition to effective thermophysical properties, have been incorporated within the present formulation...

  4. Floating along buoyancy levels: dispersal and survival of western Baltic fish eggs

    DEFF Research Database (Denmark)

    Petereit, C.; Hinrichsen, H.-H.; Franke, A.

    2014-01-01

    Vertical distribution is an important feature of pelagic fish eggs and yolk sac larvae impacting their survival and dispersal, especially in heterogeneous and highly variable estuarine environments like the Baltic Sea. Egg densities determining the vertical distribution pattern were experimentally...... ascertained for cod (Gadus morhua), plaice (Pleuronectes platessa) and flounder (Platichthys flesus) from the western Baltic Sea. Plaice eggs floated at lower mean (± standard deviation) density range (1.0136 ± 0.0007 g cm-3) compared to cod (1.0146 ± 0.0009 g cm-3) and flounder eggs (1.0160 ± 0.0015 g cm-3...... for any of the species. Available egg density data for Baltic Sea cod, plaice and flounder are summarized considering ICES subdivisions and stock management units. A hydrodynamic drift modeling approach was applied releasing drifters in the Belt Sea continuously from December to May, covering the species...

  5. Dynamo action and magnetic buoyancy in convection simulations with vertical shear

    CERN Document Server

    Guerrero, G

    2011-01-01

    A hypothesis for sunspot formation is the buoyant emergence of magnetic flux tubes created by the strong radial shear at the tachocline. In this scenario, the magnetic field has to exceed a threshold value before it becomes buoyant and emerges through the whole convection zone. We follow the evolution of a random seed magnetic field with the aim of study under what conditions it is possible to excite the dynamo instability and whether the dynamo generated magnetic field becomes buoyantly unstable and emerges to the surface as expected in the flux-tube context. We perform numerical simulations of compressible turbulent convection that include a vertical shear layer. Like the solar tachocline, the shear is located at the interface between convective and stable layers. We find that shear and convection are able to amplify the initial magnetic field and form large-scale elongated magnetic structures. The magnetic field strength depends on several parameters such as the shear amplitude, the thickness and location ...

  6. Buoyancy-driven leakage of oil from a ruptured submarine pipeline

    NARCIS (Netherlands)

    Kranenburg, C.

    1983-01-01

    The rupture of a submarine oil pipeline starts various mechanisms leading to an oil spill. Among these mechanisms the leakage of oil driven by the difference in specific gravities of oil and sea-water is difficult to estimate. A simple mathematical model has been developed and laboratory experiments

  7. Recruitment of benthic Microcystis (Cyanophyceae) to the water column: internal buoyancy changes or resuspension?

    NARCIS (Netherlands)

    Verspagen, J.M.H.; Snelder, E.O.F.M.; Visser, P.M.; Huisman, J.; Mur, L.R.; Ibelings, B.W.

    2004-01-01

    In some lakes, large amounts of the potentially toxic cyanobacterium Microcystis overwinter in the sediment. This overwintering population might inoculate the water column in spring and promote the development of dense surface blooms of Microcystis during summer. In the Dutch Lake Volkerak, we found

  8. Influence of buoyancy forces on the flow of gases through packed beds at elevated pressures

    NARCIS (Netherlands)

    Benneker, A.H.; Benneker, A.H.; Kronberg, Alexandre E.; Westerterp, K.R.

    1998-01-01

    The flow of gases through packed-bed columns at elevated pressures was investigated by displacement experiments with a stepwise change in the tracer concentration. The experiments with different tracers, flow rates, pressures, particle sizes, tube diameters, and flow directions were used to

  9. Composition, Buoyancy Regulation and Fate of Ice Algal Aggregates in the Central Arctic Ocean

    DEFF Research Database (Denmark)

    Fernandez-Mendez, Mar; Wenzhöfer, Frank; Peeken, Ilka

    2014-01-01

    Arctic Ocean. Spherical aggregates densely packed with pennate diatoms, as well as filamentous aggregates formed by Melosira arctica showed sign of different stages of degradation and physiological stoichiometries, with carbon to chlorophyll a ratios ranging from 110 to 66700, and carbon to nitrogen...

  10. Buoyancy storms in a zonal stream on the polar beta-plane: experiments with altimetry

    CERN Document Server

    Sui, Yi

    2013-01-01

    Results from a new series of experiments on flows generated by localized heating in the presence of a background zonal current on the polar beta-plane are presented. The flow induced by a heater without the background zonal flow is in the form of a beta-plume. Zonal jets of alternating directions are formed within the plume. The westward transport velocity in the plume is proportional to the upwelling velocity above the heater in agreement with linear theory. When the background flow in the form of the eastward zonal current is present, the beta-plume can be overwhelmed by the eastward current. The main control parameters of the experiment are the strength of the heater and strength of the sink which is used to create the background flow. The regime diagram shows the area where a beta-plume can exist in the parameter space. The critical value of the velocity of the zonal flow below which the beta-plume can exist is obtained by considering barotropic Rossby waves emitted by the baroclinic eddies in the heated ...

  11. Algebraically explicit analytical solutions of two-buoyancy natural convection in porous media

    Institute of Scientific and Technical Information of China (English)

    CAI Ruixian; ZHANG Na; LIU Weiwei

    2003-01-01

    Analytical solutions of governing equations of various physical phenomena have their own irreplaceable theoretical meaning. In addition, they can also be the benchmark solutions to verify the outcomes and codes of numerical solution, and to develop various numerical methods such as their differencing schemes and grid generation skills as well. In order to promote the development of the discipline of natural convection, three simple algebraically explicit analytical solution sets are derived for a non-linear simultaneous partial differential equation set with five dependent unknown variables, which represents the natural convection in porous media with both temperature and concentration gradients. An extraordinary method separating variables with addition is applied in this paper to deduce solutions.

  12. Dynamic regimes of buoyancy-affected two-phase flow in unconsolidated porous media

    Science.gov (United States)

    Stöhr, M.; Khalili, A.

    2006-03-01

    The invasion and subsequent flow of a nonwetting fluid (NWF) in a three-dimensional, unconsolidated porous medium saturated with a wetting fluid of higher density and viscosity have been studied experimentally using a light-transmission technique. Distinct dynamic regimes have been found for different relative magnitudes of viscous, capillary, and gravity forces. It is shown that the ratio of viscous and hydrostatic pressure gradients can be used as a relevant dimensionless number K for the characterization of the different flow regimes. For low values of K , the invasion is characterized by the migration and fragmentation of isolated clusters of the NWF resulting from the prevalence of gravity and capillary forces. At high values of K , the dominance of viscous and gravity forces leads to an anisotropic fingerlike invasion. When the invasion stops after the breakthrough of the NWF at the open upper boundary, the invasion structure retracts under the influence of gravity and transforms into stable vertical channels. It is shown that the stability of these channels is the result of a balance between hydrostatic and viscous pressure gradients.

  13. Influence of Orientation and Radiative Heat Transfer on Aluminum Foams in Buoyancy-Induced Convection

    Directory of Open Access Journals (Sweden)

    Marijn Billiet

    2015-10-01

    Full Text Available Two differently-produced open-cell aluminum foams were compared to a commercially available finned heat sink. Further, an aluminum plate and block were tested as a reference. All heat sinks have the same base plate dimensions of four by six inches. The first foam was made by investment casting of a polyurethane preform and has a porosity of 0.946 and a pore density of 10 pores per linear inch. The second foam is manufactured by casting over a solvable core and has a porosity of 0.85 and a pore density of 2.5 pores per linear inch. The effects of orientation and radiative heat transfer are experimentally investigated. The heat sinks are tested in a vertical and horizontal orientation. The effect of radiative heat transfer is investigated by comparing a painted/anodized heat sink with an untreated one. The heat flux through the heat sink for a certain temperature difference between the environment and the heat sink’s base plate is used as the performance indicator. For temperature differences larger than 30 °C, the finned heat sink outperforms the in-house-made aluminum foam heat sink on average by 17%. Furthermore, the in-house-made aluminum foam dissipates on average 12% less heat than the other aluminum foam for a temperature difference larger than 40 °C. By painting/anodizing the heat sinks, the heat transfer rate increased on average by 10% to 50%. Finally, the thermal performance of the horizontal in-house-made aluminum foam heat sink is up to 18% larger than the one of the vertical aluminum foam heat sink.

  14. Onshore Wind Stress and Buoyancy Flux Observed on a Dissipative Mediterranean Beach

    Science.gov (United States)

    2015-12-01

    and terrestrial radiation. On April 11, 2015, a second sonic anemometer was added at a height of 3m. All sensors were wired to a Campbell Scientific...from mixing upward while under unstable conditions when thermal instability and convection work to enhance turbulent mixing. Studies have... convective sublayer, 1.20  z / L  0.12 , describes conditions where thermal instabilities become significant but do not yet dominate mechanical

  15. INFLUENCE OF VISCOUS AND BUOYANCY FORCES ON THE MOBILIZATION OF RESIDUAL TETRACHLOROETHYLENE DURING SURFACTANT FLUSHING

    Science.gov (United States)

    The potential for nonaqueous phase liquid (NAPL) mobilization is one of the most important considerations in the development and implementation of surfactant-based remediation technologies. Column experiments were performed to investigate the onset and extent of tetrachloroethyle...

  16. Rubber Balloons, Buoyancy and the Weight of Air: A Look Inside

    Science.gov (United States)

    Calza, G.; Gratton, L. M.; Lopez-Arias, T.; Oss, S.

    2009-01-01

    We discuss three methods of measuring the density of air most commonly used in a teaching context. Emphasis is put on the advantages and/or difficulties of each method. In particular, we show that the 'rubber balloon' method can still be performed with meaningful physical insight, but it requires a very careful approach. (Contains 4 figures and 3…

  17. Buoyancy effects on thermal behavior of a flat-plate solar collector

    DEFF Research Database (Denmark)

    Fan, Jianhua; Furbo, Simon

    2008-01-01

    Theoretical and experimental investigations of the flow and temperature distribution in a 12.53 m(2) solar collector panel with an absorber consisting of two vertical manifolds interconnected by 16 parallel horizontal fins have been carried out. The investigations are focused on overheating and b...

  18. Psycho-Educational Factors in the Prediction of Academic Buoyancy in Second Life®

    Science.gov (United States)

    Carrington, Cheril C.

    2013-01-01

    Academic resilience has been widely researched in traditional and online educational settings, but it has not been sufficiently studied in three-dimensional (3D) virtual learning environments (VLEs). This inferential research used multiple regression to quantitatively investigate the extent to which psycho-educational factors including academic…

  19. Investigations of Physical Processes in Microgravity Relevant to Space Electrochemical Power Systems

    Science.gov (United States)

    Lvovich, Vadim F.; Green, Robert; Jakupca, Ian

    2015-01-01

    NASA has performed physical science microgravity flight experiments in the areas of combustion science, fluid physics, material science and fundamental physics research on the International Space Station (ISS) since 2001. The orbital conditions on the ISS provide an environment where gravity driven phenomena, such as buoyant convection, are nearly negligible. Gravity strongly affects fluid behavior by creating forces that drive motion, shape phase boundaries and compress gases. The need for a better understanding of fluid physics has created a vigorous, multidisciplinary research community whose ongoing vitality is marked by the continuous emergence of new fields in both basic and applied science. In particular, the low-gravity environment offers a unique opportunity for the study of fluid physics and transport phenomena that are very relevant to management of fluid - gas separations in fuel cell and electrolysis systems. Experiments conducted in space have yielded rich results. These results provided valuable insights into fundamental fluid and gas phase behavior that apply to space environments and could not be observed in Earth-based labs. As an example, recent capillary flow results have discovered both an unexpected sensitivity to symmetric geometries associated with fluid container shape, and identified key regime maps for design of corner or wedge-shaped passive gas-liquid phase separators. In this presentation we will also briefly review some of physical science related to flight experiments, such as boiling, that have applicability to electrochemical systems, along with ground-based (drop tower, low gravity aircraft) microgravity electrochemical research. These same buoyancy and interfacial phenomena effects will apply to electrochemical power and energy storage systems that perform two-phase separation, such as water-oxygen separation in life support electrolysis, and primary space power generation devices such as passive primary fuel cell.

  20. Comparison of Model and Experimental Results for Material and Energy Flow in a Titanium Evaporation System with Deforming Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    McClelland, M A; Westerberg, K W; Meier, T C; Braun, D G; Frischknecht, K D; Anklam, T M

    2003-05-12

    Finite element calculations and measurements are compared for material and energy flow in a system to evaporate pure titanium. A 40 kW electron beam is used to heat the end of a 7.62 cm diameter cylindrical rod which is fed vertically through a water-cooled crucible. Vapor emanates from a liquid pool in which flow is driven strongly by buoyancy and capillary forces. At high evaporation rates, the vapor exerts strong shear and normal forces on the liquid-vapor interface. The MELT finite element code is used to calculate steady-state, axisymmetric flow and temperature fields along with liquid-solid and liquid-vapor interface locations. The influence of the vapor on the liquid top surface is treated using boundary conditions with parameters derived from Monte Carlo simulations. The upper and lower interfaces of the liquid pool are tracked using a mesh structured with rotating spines. Experimental evaporation rates are obtained from measured feed rates, and heat flow rates are determined from measured temperature rises in the cooling water. The finite element model provides a good representation of the measured evaporation rates, heat flows, and lower pool boundary locations.

  1. Finite element analysis of flow, heat transfer, and free interfaces in an electron-beam vaporization system for metals

    Science.gov (United States)

    Westerberg, K. W.; McClelland, M. A.; Finlayson, B. A.

    1998-03-01

    A numerical analysis is made of the liquid flow and energy transport in a system to evaporate metals. The energy from an electron-beam heats an axisymmetric metal disk supported by a water-cooled platform. Metal evaporates from the surface of a hot pool of liquid which is surrounded by a shell of its own solid. Flow in the pool is strongly driven by temperature-induced buoyancy and capillary forces, and is located in the transition region between laminar and turbulent flow. The evaporation rate is strongly influenced by the locations of the free boundaries. A modified finite element method is used to calculate the steady state flow and temperature fields coupled with the interface locations. The mesh is structured with spines that stretch and pivot as the interfaces move. The discretized equations are arranged in an arrow matrix and are solved using the Newton-Raphson method. The electron-beam power and platform contact resistance are varied for cases involving the evaporation of aluminum. The results reveal the interaction of liquid flow, heat transfer and free interfaces.

  2. Systems effectiveness

    CERN Document Server

    Habayeb, A R

    1987-01-01

    Highlights three principal applications of system effectiveness: hardware system evaluation, organizational development and evaluation, and conflict analysis. The text emphasizes the commonality of the system effectiveness discipline. The first part of the work presents a framework for system effectiveness, partitioning and hierarchy of hardware systems. The second part covers the structure, hierarchy, states, functions and activities of organizations. Contains an extended Appendix on mathematical concepts and also several project suggestions.

  3. Design and gamma-scintigraphic evaluation of a floating and pulsatile drug delivery system based on an impermeable cylinder.

    Science.gov (United States)

    Zou, Hao; Jiang, Xuetao; Kong, Lingshan; Gao, Shen

    2007-04-01

    A blend of floating and pulsatile principles of drug delivery system seems to present the advantage that a drug can be released in the upper GI tract after a definite time period of no drug release. The objective of this study was to develop and evaluate a floating and pulsatile drug delivery system based on an impermeable cylinder. Pulsatile capsule was prepared by sealing the drug tablet and the buoyant material filler inside the impermeable capsule body with erodible plug. The drug delivery system showed typical floating and pulsatile release profile with a lag time followed by a rapid release phase. The lag time prior to the pulsatile drug release correlated well with the erosion properties of plugs and the composition of the plug could be controlled by the weight of the plug. The buoyancy of the whole system depended on the bulk density of the dosage form. Gamma-scintigraphic evaluation in humans was used to establish methodology capable of showing the subsequent in vivo performance of the floating and pulsatile release capsule. Developed formulations showed instantaneous floating with no drug release during the lag time followed by a pulse drug release. From the gamma-scintigraphic results, the pulsatile release capsule we prepared could achieve a rapid release after lag time in vivo, which was longer than that in vitro. The scintigraphic evaluation could confirm qualitatively that the system with in vitro lag time of 4.0 h provided, with relatively high reproducibility, a pulsatile release occurred around 5.0 h after administration.

  4. Bitcoin System

    Directory of Open Access Journals (Sweden)

    Jan Lánský

    2017-06-01

    Full Text Available Cryptocurrency systems are purely digital and decentralized systems that use cryptographic principles to confirm transactions. Bitcoin is the first and also the most widespread cryptocurrency. The aim of this article is to introduce Bitcoin system using a language understandable also to readers without computer science education. This article captures the Bitcoin system from three perspectives: internal structure, network and users. Emphasis is placed on brief and clear definitions (system components and their mutual relationships. A new system view of the stated terms constitutes author’s own contribution.

  5. Intelligent Systems

    Data.gov (United States)

    National Aeronautics and Space Administration — The autonomous systems (AS) project, led by NASA Ames, is developing software for system operation automation. AS technology will help astronauts make more decisions...

  6. Three-phase-flow dynamics in the upper plumbing system at Stromboli volcano

    Science.gov (United States)

    Suckale, J.; Cashman, K. V.

    2013-12-01

    With the potential exception of paroxysms and major explosions, eruptive activity at Stromboli volcano is thought to be driven by gas, as evidenced by the relative masses of erupted gas and pyroclastic rocks. The insight that degassing drives eruptions led to the development of models that explain the observed eruptive activity with reference to diverse two-phase flow regimes in gas-rich fluids. Numerous petrological studies, however, have established the existence of two different types of magma at Stromboli that vary drastically in crystallinity. Highly-porphyritic (HP) and water-poor magma is confined to the upper few hundred meters of the plumbing system; low-porphyritic (LP) and water-rich magma originates much deeper. This observational evidence raises the question of how the presence of a third phase, the solid fraction, affects degassing at Stromboli. The goal of this study is to develop a three-phase-flow model for degassing processes in the upper plumbing system at Stromboli, where the HP magma resides. Contrary to previous two-phase flow models, we do not assume the existence of pipe-like conduits that traverse the upper plumbing system. To explore whether the relative stability of the three-crater morphology can be understood self-consistently in our modeling framework, we devise a numerical model that couples stress and gas flux in the HP magma. We approximate the crater terrace as an elliptic surface and assume that the HP magma extends several hundred meters below. The drastic contrast in crystallinity between HP and LP magma is represented as a similarly drastic transition from a highly nonlinear creep rheology to a Newtonian rheology. One important ramification of this rheological transition is that ascending gas will accumulate underneath the HP magma. The HP magma is thus reminiscent of a plug that slows gas flux, although the prevalence of passive degassing at Stromboli shows that the plug does not inhibit gas invasion entirely. At high gas

  7. Systems Engineering

    Science.gov (United States)

    Pellerano, Fernando

    2015-01-01

    This short course provides information on what systems engineering is and how the systems engineer guides requirements, interfaces with the discipline leads, and resolves technical issues. There are many system-wide issues that either impact or are impacted by the thermal subsystem. This course will introduce these issues and illustrate them with real life examples.

  8. Retrofitting Systems

    DEFF Research Database (Denmark)

    Rose, Jørgen

    1997-01-01

    This report gives an overview of the different retrofitting possibilities that are available today. The report looks at both external and internal systems for external wall constructions, roof constructions, floor constructions and foundations. All systems are described in detail in respect to use...... and methods, and the efficiency of the different systems are discussed....

  9. Operating systems

    CERN Document Server

    Tsichritzis, Dionysios C; Rheinboldt, Werner

    1974-01-01

    Operating Systems deals with the fundamental concepts and principles that govern the behavior of operating systems. Many issues regarding the structure of operating systems, including the problems of managing processes, processors, and memory, are examined. Various aspects of operating systems are also discussed, from input-output and files to security, protection, reliability, design methods, performance evaluation, and implementation methods.Comprised of 10 chapters, this volume begins with an overview of what constitutes an operating system, followed by a discussion on the definition and pr

  10. Cryogenic Systems

    Science.gov (United States)

    Hosoyama, Kenji

    2002-02-01

    In this lecture we discuss the principle of method of cooling to a very low temperature, i.e. cryogenic. The "gas molecular model" will be introduced to explain the mechanism cooling by the expansion engine and the Joule-Thomson expansion valve. These two expansion processes are normally used in helium refrigeration systems to cool the process gas to cryogenic temperature. The reverse Carnot cycle will be discussed in detail as an ideal refrigeration cycle. First the fundamental process of liquefaction and refrigeration cycles will be discussed, and then the practical helium refrigeration system. The process flow of the system and the key components; -compressor, expander, and heat exchanger- will be discussed. As an example of an actual refrigeration system, we will use the cryogenic system for the KEKB superconducting RF cavity. We will also discuss the liquid helium distribution system, which is very important, especially for the cryogenic systems used in accelerator applications. 1 Principles of Cooling and Fundamental Cooling Cycle 2 Expansion engine, Joule-Thomson expansion, kinetic molecular theory, and enthalpy 3 Liquefaction Systems 4 Refrigeration Systems 5 Practical helium liquefier/refrigeration system 6 Cryogenic System for TRISTAN Superconducting RF Cavity

  11. Expert System

    DEFF Research Database (Denmark)

    Hildebrandt, Thomas Troels; Cattani, Gian Luca

    2016-01-01

    An expert system is a computer system for inferring knowledge from a knowledge base, typically by using a set of inference rules. When the concept of expert systems was introduced at Stanford University in the early 1970s, the knowledge base was an unstructured set of facts. Today the knowledge...... base of expert systems is often given in terms of an ontology, extracted and built from various data sources by employing natural language-processing and statistics. To emphasize such capabilities, the term “expert” is now often replaced by “cognitive,” “knowledge,” “knowledge-based,” or “intelligent......” system. With very few exceptions, general-purpose expert systems have failed to emerge so far. However, expert systems are applied in specialized domains, particularly in healthcare. The increasing availability of large quantities of data to organizations today provides a valuable opportunity...

  12. Research into the Physiology of Cerebrospinal Fluid Reaches a New Horizon: Intimate Exchange between Cerebrospinal Fluid and Interstitial Fluid May Contribute to Maintenance of Homeostasis in the Central Nervous System

    Science.gov (United States)

    MATSUMAE, Mitsunori; SATO, Osamu; HIRAYAMA, Akihiro; HAYASHI, Naokazu; TAKIZAWA, Ken; ATSUMI, Hideki; SORIMACHI, Takatoshi

    2016-01-01

    Cerebrospinal fluid (CSF) plays an essential role in maintaining the homeostasis of the central nervous system. The functions of CSF include: (1) buoyancy of the brain, spinal cord, and nerves; (2) volume adjustment in the cranial cavity; (3) nutrient transport; (4) protein or peptide transport; (5) brain volume regulation through osmoregulation; (6) buffering effect against external forces; (7) signal transduction; (8) drug transport; (9) immune system control; (10) elimination of metabolites and unnecessary substances; and finally (11) cooling of heat generated by neural activity. For CSF to fully mediate these functions, fluid-like movement in the ventricles and subarachnoid space is necessary. Furthermore, the relationship between the behaviors of CSF and interstitial fluid in the brain and spinal cord is important. In this review, we will present classical studies on CSF circulation from its discovery over 2,000 years ago, and will subsequently introduce functions that were recently discovered such as CSF production and absorption, water molecule movement in the interstitial space, exchange between interstitial fluid and CSF, and drainage of CSF and interstitial fluid into both the venous and the lymphatic systems. Finally, we will summarize future challenges in research. This review includes articles published up to February 2016. PMID:27245177

  13. Plate Tectonics as a Far-From-Equilibrium Self-Organized Dissipative System

    Science.gov (United States)

    Anderson, D. L.

    2001-12-01

    A fluid above the critical Rayleigh number is far from equilibrium and spontaneously organizes itself into patterns involving the collective motion of large numbers of molecules which are resisted by the viscosity of the fluid. No external template is involved in forming the pattern. In 1928 Pearson showed that Bénard's experiments were driven by variations in surface tension at the top of the fluid and the surface motions drove convection in the fluid. In this case, the surface organized itself AND the underlying fluid. Both internal buoyancy driven flow and flow driven by surface forces can be far-from-equilibrium self-organized open systems that receive energy and matter from the environment. In the Earth, the cold thermal boundary layer at the surface drives plate tectonics and introduces temperature, shear and pressure gradients into the mantle that drive mantle convection. The mantle provides energy and material but may not provide the template. Plate tectonics is therefore a candidate for a far-from-equilibrium dissipative self-organizing system. Alternatively, one could view mantle convection as the self-organized system and the plates as simply the surface manifestation. Lithospheric architecture also imposes lateral temperature gradients onto the mantle which can drive and organize flow. Far-from-equilibrium self-organization requires; an open system, interacting parts, nonlinearities or feedbacks, an outside steady source of energy or matter, multiple possible states and a source of dissipation. In uniform fluids viscosity is the source of dissipation. Sources of dissipation in the plate system include bending, breaking, folding, shearing, tearing, collision and basal drag. These can change rapidly, in contrast to plate driving forces, and introduce the sort of fluctuations that can reorganize far-from-equilibrium systems. Global plate reorganizations can alternatively be thought of as convective overturns of the mantle, or thermal weakening of plates

  14. Recommender systems

    CERN Document Server

    Kembellec, Gérald; Saleh, Imad

    2014-01-01

    Acclaimed by various content platforms (books, music, movies) and auction sites online, recommendation systems are key elements of digital strategies. If development was originally intended for the performance of information systems, the issues are now massively moved on logical optimization of the customer relationship, with the main objective to maximize potential sales. On the transdisciplinary approach, engines and recommender systems brings together contributions linking information science and communications, marketing, sociology, mathematics and computing. It deals with the understan

  15. Material Systems

    DEFF Research Database (Denmark)

    Jensen, Mads Brath; Mortensen, Henrik Rubæk; Mullins, Michael;

    2009-01-01

    This paper describes and reflects upon the results of an investigative project which explores the setting up of a material system - a parametric and generative assembly consisting of and taking into consideration material properties, manufacturing constraints and geometric behavior. The project...... approaches the subject through the construction of a logic-driven system aiming to explore the possibilities of a material system that fulfills spatial, structural and performative requirements concurrently and how these are negotiated in situations where they might be conflicting....

  16. Material Systems

    DEFF Research Database (Denmark)

    Jensen, Mads Brath; Mortensen, Henrik Rubæk; Mullins, Michael

    2009-01-01

    This paper describes and reflects upon the results of an investigative project which explores the setting up of a material system - a parametric and generative assembly consisting of and taking into consideration material properties, manufacturing constraints and geometric behavior. The project...... approaches the subject through the construction of a logic-driven system aiming to explore the possibilities of a material system that fulfills spatial, structural and performative requirements concurrently and how these are negotiated in situations where they might be conflicting....

  17. Conceptual design of a passive moderator cooling system for a pressure tube type natural circulation boiling water cooled reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Mukesh [Reactor Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Pal, Eshita, E-mail: eshi.pal@gmail.com [Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094 (India); Nayak, Arun K.; Vijayan, Pallipattu K. [Reactor Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

    2015-09-15

    Highlights: • Passive moderator cooling system is designed to cool moderator passively during SBO. • PMCS is a system of two natural circulation loops, coupled via a heat exchanger. • RELAP5 analyses show that PMCS maintains moderator within safe limits for 7 days. - Abstract: The recent Fukushima accident has raised strong concern and apprehensions about the safety of reactors in case of a prolonged Station Black Out (SBO) continuing for several days. In view of this, a detailed study was performed simulating this condition in Advanced Heavy Water Reactor. In this study, a novel concept of moderator cooling by passive means has been introduced in the reactor design. The Passive Moderator Cooling System (PMCS) consists of a shell and tube heat exchanger designed to remove 2 MW heat from the moderator inside Calandria. The heat exchanger is located at a suitable elevation from the Calandria of the reactor, such that the hot moderator rises due to buoyancy into the heat exchanger and upon cooling from shell side water returns to Calandria forming a natural circulation loop. The shell side of the heat exchanger is also a natural circulation loop connected to an overhead large water reservoir, namely the GDWP. The objective of the PMCS is to remove the heat from the moderator in case of an SBO and maintaining its temperature below the permissible safe limit (100 °C) for at least 7 days. The paper first describes the concept of the PMCS. The concept has been assessed considering a prolonged SBO for at least 7 days, through an integrated analysis performed using the code RELAP5/MOD3.2 considering all the major components of the reactor. The analysis shows that the PMCS is able to maintain the moderator temperature below boiling conditions for 7 days.

  18. Intelligent systems

    CERN Document Server

    Irwin, J David

    2011-01-01

    Technology has now progressed to the point that intelligent systems are replacing humans in the decision making processes as well as aiding in the solution of very complex problems. In many cases intelligent systems are already outperforming human activities. Artificial neural networks are not only capable of learning how to classify patterns, such images or sequence of events, but they can also effectively model complex nonlinear systems. Their ability to classify sequences of events is probably more popular in industrial applications where there is an inherent need to model nonlinear system

  19. Energetic Systems

    Data.gov (United States)

    Federal Laboratory Consortium — The Energetic Systems Division provides full-spectrum energetic engineering services (project management, design, analysis, production support, in-service support,...

  20. Systemic darwinism.

    Science.gov (United States)

    Winther, Rasmus Grønfeldt

    2008-08-19

    Darwin's 19th century evolutionary theory of descent with modification through natural selection opened up a multidimensional and integrative conceptual space for biology. We explore three dimensions of this space: explanatory pattern, levels of selection, and degree of difference among units of the same type. Each dimension is defined by a respective pair of poles: law and narrative explanation, organismic and hierarchical selection, and variational and essentialist thinking. As a consequence of conceptual debates in the 20th century biological sciences, the poles of each pair came to be seen as mutually exclusive opposites. A significant amount of 21st century research focuses on systems (e.g., genomic, cellular, organismic, and ecological/global). Systemic Darwinism is emerging in this context. It follows a "compositional paradigm" according to which complex systems and their hierarchical networks of parts are the focus of biological investigation. Through the investigation of systems, Systemic Darwinism promises to reintegrate each dimension of Darwin's original logical space. Moreover, this ideally and potentially unified theory of biological ontology coordinates and integrates a plurality of mathematical biological theories (e.g., self-organization/structure, cladistics/history, and evolutionary genetics/function). Integrative Systemic Darwinism requires communal articulation from a plurality of perspectives. Although it is more general than these, it draws on previous advances in Systems Theory, Systems Biology, and Hierarchy Theory. Systemic Darwinism would greatly further bioengineering research and would provide a significantly deeper and more critical understanding of biological reality.