Thermochemical stability of Soviet macroporous sulfonated cation-exchangers

Energy Technology Data Exchange (ETDEWEB)

Rukhlyada, N.N.; Plotnikova, V.P.; Roginskaya, B.S.; Znamenskii, Yu.P.; Zavodovskaya, A.S.; Dobrova, E.I.

1988-10-20

The purpose of this work was to study the influence of macroporosity on the thermochemical stability of sulfonated cation-exchangers. The investigations were carried out on commercial macroporous sulfonated cation-exchangers based on styrene-divinylbenzene copolymers. Study of the thermochemical stability of macroporous sulfonated cation-exchangers in dilute hydrogen peroxide solutions showed that the type of macroporosity has virtually no influence on their stability. The determining factor in thermal stability of macroporous cation-exchangers, as of the gel type, is the degree of cross-linking of the polymer matrix. The capacity loss of macroporous cation-exchangers during oxidative thermolysis is caused by destruction of the macromolecular skeleton and elution of fragments of polar chains containing sulfo groups into the solution.

A NEW DOUBLE-SLIT CURVED WALL-JET (CWJ) BURNER FOR STABILIZING TURBULENT PREMIXED AND NON-PREMIXED FLAMES

KAUST Repository

Mansour, Morkous S.; Chung, Suk-Ho

2015-01-01

Mixing characteristics in the cold flow of non-premixed cases were first examined using acetone fluorescence technique, indicating substantial transport between the fuel and air by exhibiting appreciable premixing conditions.PIV measurements revealed that velocity gradients in the shear layers at the boundaries of the annularjets generate the turbulence, enhanced with the collisions in the interaction jet, IJ,region. Turbulent mean and rms velocities were influenced significantly by Re and high rms turbulent velocities are generated within the recirculation zone improving the flame stabilization in this burner.Premixed and non-premixed flames with high equivalence ratio were found to be more resistant to local extinction and exhibited a more corrugated and folded nature, particularly at high Re. For flames with low equivalence ratio, the processes of local quenching at IJ region and of re-ignition within merged jet region maintained these flames further downstream particularly for non-premixed methane flame, revealing a strong intermittency.

Optimization of Premix Powders for Tableting Use.

Science.gov (United States)

Todo, Hiroaki; Sato, Kazuki; Takayama, Kozo; Sugibayashi, Kenji

2018-05-08

Direct compression is a popular choice as it provides the simplest way to prepare the tablet. It can be easily adopted when the active pharmaceutical ingredient (API) is unstable in water or to thermal drying. An optimal formulation of preliminary mixed powders (premix powders) is beneficial if prepared in advance for tableting use. The aim of this study was to find the optimal formulation of the premix powders composed of lactose (LAC), cornstarch (CS), and microcrystalline cellulose (MCC) by using statistical techniques. Based on the "Quality by Design" concept, a (3,3)-simplex lattice design consisting of three components, LAC, CS, and MCC was employed to prepare the model premix powders. Response surface method incorporating a thin-plate spline interpolation (RSM-S) was applied for estimation of the optimum premix powders for tableting use. The effect of tablet shape identified by the surface curvature on the optimization was investigated. The optimum premix powder was effective when the premix was applied to a small quantity of API, although the function of premix was limited in the case of the formulation of large amount of API. Statistical techniques are valuable to exploit new functions of well-known materials such as LAC, CS, and MCC.

Gas turbine premixing systems

Science.gov (United States)

Kraemer, Gilbert Otto; Varatharajan, Balachandar; Evulet, Andrei Tristan; Yilmaz, Ertan; Lacy, Benjamin Paul

2013-12-31

Methods and systems are provided for premixing combustion fuel and air within gas turbines. In one embodiment, a combustor includes an upstream mixing panel configured to direct compressed air and combustion fuel through premixing zone to form a fuel-air mixture. The combustor includes a downstream mixing panel configured to mix additional combustion fuel with the fule-air mixture to form a combustion mixture.

Modified APEX model for Simulating Macropore Phosphorus Contributions to Tile Drains.

Science.gov (United States)

Ford, William I; King, Kevin W; Williams, Mark R; Confesor, Remegio B

2017-11-01

The contribution of macropore flow to phosphorus (P) loadings in tile-drained agricultural landscapes remains poorly understood at the field scale, despite the recognized deleterious impacts of contaminant transport via macropore pathways. A new subroutine that couples existing matrix-excess and matrix-desiccation macropore flow theory and a modified P routine is implemented in the Agricultural Policy Environmental eXtender (APEX) model. The original and modified formulation were applied and evaluated for a case study in a poorly drained field in Western Ohio with 31 months of surface and subsurface monitoring data. Results highlighted that a macropore subroutine in APEX improved edge-of-field discharge calibration and validation for both tile and total discharge from satisfactory and good, respectively, to very good and improved dissolved reactive P load calibration and validation statistics for tile P loads from unsatisfactory to very good. Output from the calibrated macropore simulations suggested median annual matrix-desiccation macropore flow contributions of 48% and P load contributions of 43%, with the majority of loading occurring in winter and spring. While somewhat counterintuitive, the prominence of matrix-desiccation macropore flow during seasons with less cracking reflects the importance of coupled development of macropore pathways and adequate supply of the macropore flow source. The innovative features of the model allow for assessments of annual macropore P contributions to tile drainage and has the potential to inform P site assessment tools. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Properties of calcium silicate-monobasic calcium phosphate materials for endodontics containing tantalum pentoxide and zirconium oxide.

Science.gov (United States)

Zamparini, Fausto; Siboni, Francesco; Prati, Carlo; Taddei, Paola; Gandolfi, Maria Giovanna

2018-05-08

The aim of the study was to evaluate chemical-physical properties and apatite-forming ability of three premixed calcium silicate materials containing monobasic calcium phosphate (CaH 4 P 2 O 8 ) bioceramic, tantalum pentoxide and zirconium oxide, recently marketed for endodontics (TotalFill BC-Sealer, BC-RRM-Paste, BC-RRM-Putty). Microchemical and micromorphological analyses, radiopacity, initial and final setting times, calcium release and alkalising activity were tested. The nucleation of calcium phosphates (CaPs) and/or apatite after 28 days ageing was evaluated by ESEM-EDX and micro-Raman spectroscopy. BC-Sealer and BC-RRM-Paste showed similar initial (23 h), prolonged final (52 h) setting times and good radiopacity (> 7 mm Al); BC-RRM-Putty showed fast initial (2 h) and final setting times (27 h) and excellent radiopacity (> 9 mm Al). All materials induced a marked alkalisation (pH 11-12) up to 28 days and showed the release of calcium ions throughout the entire test period (cumulative calcium release 641-806 ppm). After 28 days ageing, a well-distributed mineral layer was present on all samples surface; EDX demonstrated relevant calcium and phosphorous peaks. B-type carbonated apatite and calcite deposits were identified by micro-Raman spectroscopy on all the 28-day-aged samples; the deposit thickness was higher on BC-RRM-Paste and BC-RRM-Putty, in agreement with calcium release data. These materials met the required chemical and physical standards and released biologically relevant ions. The CaSi-CaH 4 P 2 O 8 system present in the materials provided Ca and OH ions release with marked abilities to nucleate a layer of B-type carbonated apatite favoured/accelerated by the bioceramic presence. The ability to nucleate apatite may lead many clinical advantages: In orthograde endodontics, it may improve the sealing ability by the deposition of CaPs at the material-root dentine interface, and in endodontic surgery, it could promote bone and

A NEW DOUBLE-SLIT CURVED WALL-JET (CWJ) BURNER FOR STABILIZING TURBULENT PREMIXED AND NON-PREMIXED FLAMES

KAUST Repository

Mansour, Morkous S.

2015-06-30

A novel double-slit curved wall-jet (CWJ) burner was proposed and employed, which utilizes the Coanda effect by supplying fuel and air as annular-inward jets over a curved surface. We investigated the stabilization characteristics and structure of methane/air, and propane/air turbulent premixed and non-premixed flames with varying global equivalence ratio, , and Reynolds number, Re. Simultaneous time-resolved measurements of particle image velocimetry and planar laser-induced fluorescence of OH radicals were conducted. The burner showed potential for stable operation for methane flames with relatively large fuel loading and overall rich conditions. These have a non-sooting nature. However, propane flames exhibit stable mode for a wider range of equivalence ratio and Re. Mixing characteristics in the cold flow of non-premixed cases were first examined using acetone fluorescence technique, indicating substantial transport between the fuel and air by exhibiting appreciable premixing conditions.PIV measurements revealed that velocity gradients in the shear layers at the boundaries of the annularjets generate the turbulence, enhanced with the collisions in the interaction jet, IJ,region. Turbulent mean and rms velocities were influenced significantly by Re and high rms turbulent velocities are generated within the recirculation zone improving the flame stabilization in this burner.Premixed and non-premixed flames with high equivalence ratio were found to be more resistant to local extinction and exhibited a more corrugated and folded nature, particularly at high Re. For flames with low equivalence ratio, the processes of local quenching at IJ region and of re-ignition within merged jet region maintained these flames further downstream particularly for non-premixed methane flame, revealing a strong intermittency.

Premixed and non-premixed generated manifolds in large-eddy simulation of Sandia flame D and F

NARCIS (Netherlands)

Vreman, A.W.; Albrecht, B.A.; Oijen, van J.A.; Goey, de L.P.H.; Bastiaans, R.J.M.

2008-01-01

Premixed and nonpremixed flamelet-generated manifolds have been constructed and applied to large-eddy simulation of the piloted partially premixed turbulent flames Sandia Flame D and F. In both manifolds the chemistry is parameterized as a function of the mixture fraction and a progress variable.

Multidimensional flamelet-generated manifolds for partially premixed combustion

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Phuc-Danh; Vervisch, Luc; Subramanian, Vallinayagam; Domingo, Pascale [CORIA - CNRS and INSA de Rouen, Technopole du Madrillet, BP 8, 76801 Saint-Etienne-du-Rouvray (France)

2010-01-15

Flamelet-generated manifolds have been restricted so far to premixed or diffusion flame archetypes, even though the resulting tables have been applied to nonpremixed and partially premixed flame simulations. By using a projection of the full set of mass conservation species balance equations into a restricted subset of the composition space, unsteady multidimensional flamelet governing equations are derived from first principles, under given hypotheses. During the projection, as in usual one-dimensional flamelets, the tangential strain rate of scalar isosurfaces is expressed in the form of the scalar dissipation rates of the control parameters of the multidimensional flamelet-generated manifold (MFM), which is tested in its five-dimensional form for partially premixed combustion, with two composition space directions and three scalar dissipation rates. It is shown that strain-rate-induced effects can hardly be fully neglected in chemistry tabulation of partially premixed combustion, because of fluxes across iso-equivalence-ratio and iso-progress-of-reaction surfaces. This is illustrated by comparing the 5D flamelet-generated manifold with one-dimensional premixed flame and unsteady strained diffusion flame composition space trajectories. The formal links between the asymptotic behavior of MFM and stratified flame, weakly varying partially premixed front, triple-flame, premixed and nonpremixed edge flames are also evidenced. (author)

Functionalization of 2D macroporous silicon under the high-pressure oxidation

Science.gov (United States)

Karachevtseva, L.; Kartel, M.; Kladko, V.; Gudymenko, O.; Bo, Wang; Bratus, V.; Lytvynenko, O.; Onyshchenko, V.; Stronska, O.

2018-03-01

Addition functionalization after high-pressure oxidation of 2D macroporous silicon structures is evaluated. X-ray diffractometry indicates formation of orthorhombic SiO2 phase on macroporous silicon at oxide thickness of 800-1200 nm due to cylindrical symmetry of macropores and high thermal expansion coefficient of SiO2. Pb center concentration grows with the splitting energy of LO- and TO-phonons and SiO2 thickness in oxidized macroporous silicon structures. This increase EPR signal amplitude and GHz radiation absorption and is promising for development of high-frequency devices and electronically controlled elements.

Use of macroporous plastics in extraction chromatography

International Nuclear Information System (INIS)

Braun, T.; Farac, A.B.

1978-01-01

Possibilities are analysed which the use of porous plastics (polyvinyl chloride, siloxane rubber, polyurethane, polystyrene and etc.) as carriers presents in extraction chromatography. Short characteristics of chemical and physical properties of macroporous carriers is given. The importance of correct chromatographic column packing is noted to obtain columns with good hydrodynamic characteristics and operational properties. Examples of using columns with macroporous carriers in radiochemistry and inorganic chemistry for element separation are given

Macroporous Hydrogel Scaffolds for Three-Dimensional Cell Culture and Tissue Engineering.

Science.gov (United States)

Fan, Changjiang; Wang, Dong-An

2017-10-01

Hydrogels have been promising candidate scaffolds for cell delivery and tissue engineering due to their tissue-like physical properties and capability for homogeneous cell loading. However, the encapsulated cells are generally entrapped and constrained in the submicron- or nanosized gel networks, seriously limiting cell growth and tissue formation. Meanwhile, the spatially confined settlement inhibits attachment and spreading of anchorage-dependent cells, leading to their apoptosis. In recent years, macroporous hydrogels have attracted increasing attention in use as cell delivery vehicles and tissue engineering scaffolds. The introduction of macropores within gel scaffolds not only improves their permeability for better nutrient transport but also creates space/interface for cell adhesion, proliferation, and extracellular matrix deposition. Herein, we will first review the development of macroporous gel scaffolds and outline the impact of macropores on cell behaviors. In the first part, the advantages and challenges of hydrogels as three-dimensional (3D) cell culture scaffolds will be described. In the second part, the fabrication of various macroporous hydrogels will be presented. Third, the enhancement of cell activities within macroporous gel scaffolds will be discussed. Finally, several crucial factors that are envisaged to propel the improvement of macroporous gel scaffolds are proposed for 3D cell culture and tissue engineering.

Controlled release of ibuprofen by meso-macroporous silica

Science.gov (United States)

Santamaría, E.; Maestro, A.; Porras, M.; Gutiérrez, J. M.; González, C.

2014-02-01

Structured meso-macroporous silica was successfully synthesized from an O/W emulsion using decane as a dispersed phase. Sodium silicate solution, which acts as a silica source and a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (EO19PO39EO19) denoted as P84 was used in order to stabilize the emulsion and as a mesopore template. The materials obtained were characterized through transmission electron microscopy (TEM), scanning electron microscopy (SEM), small-angle X-ray diffraction scattering (SAXS) and nitrogen adsorption-desorption isotherms. Ibuprofen (IBU) was selected as the model drug and loaded into ordered meso-macroporous materials. The effect of the materials’ properties on IBU drug loading and release was studied. The results showed that the loading of IBU increases as the macropore presence in the material is increased. The IBU adsorption process followed the Langmuir adsorption isotherm. A two-step release process, consisting of an initial fast release and then a slower release was observed. Macropores enhanced the adsorption capacity of the material; this was probably due to the fact that they allowed the drug to access internal pores. When only mesopores were present, ibuprofen was probably adsorbed on the mesopores close to the surface. Moreover, the more macropore present in the material, the slower the release behaviour observed, as the ibuprofen adsorbed in the internal pores had to diffuse along the macropore channels up to the surface of the material. The material obtained from a highly concentrated emulsion was functionalized with amino groups using two methods, the post-grafting mechanism and the co-condensation mechanism. Both routes improve IBU adsorption in the material and show good behaviour as a controlled drug delivery system.

Rainfall Simulator Experiments to Investigate Macropore Impacts on Hillslope Hydrological Response

Directory of Open Access Journals (Sweden)

Yvonne Smit

2016-11-01

Full Text Available Understanding hillslope runoff response to intense rainfall is an important topic in hydrology, and is key to correct prediction of extreme stream flow, erosion and landslides. Although it is known that preferential flow processes activated by macropores are an important phenomena in understanding runoff processes inside a hillslope, hydrological models have generally not embraced the concept of an extra parameter that represents ‘macropores’ because of the complexity of the phenomenon. Therefore, it is relevant to investigate the influence of macropores on runoff processes in an experimental small artificial hillslope. Here, we report on a controlled experiment where we could isolate the influence of macropores without the need for assumptions regarding their characteristics. Two identical hillslopes were designed, of which one was filled with artificial macropores. Twelve artificial rainfall events were applied to the two hillslopes and results of drainage and soil moisture were investigated. After the experiments, it could be concluded that the influence of macropores on runoff processes was minimal. The S90 sand used for this research caused runoff to respond fast to rainfall, leading to little or no development of saturation near the macropores. In addition, soil moisture data showed a large amount of pendular water in the hillslopes, which implies that the soil has a low air entry value, and, in combination with the lack of vertical flow, could have caused the pressure difference between the matrix and the macropores to vanish sooner and result in equilibrium being reached in a relatively short time. Nevertheless, a better outline is given to determine a correct sand type for these types of experiments and, by using drainage recession analysis to investigate the influences of macropores on runoff, heterogeneity in rainfall intensity can be overcome. This study is a good point of reference to start future experiments from concerning

Fully Premixed Low Emission, High Pressure Multi-Fuel Burner

Science.gov (United States)

Nguyen, Quang-Viet (Inventor)

2012-01-01

A low-emissions high-pressure multi-fuel burner includes a fuel inlet, for receiving a fuel, an oxidizer inlet, for receiving an oxidizer gas, an injector plate, having a plurality of nozzles that are aligned with premix face of the injector plate, the plurality of nozzles in communication with the fuel and oxidizer inlets and each nozzle providing flow for one of the fuel and the oxidizer gas and an impingement-cooled face, parallel to the premix face of the injector plate and forming a micro-premix chamber between the impingement-cooled face and the in injector face. The fuel and the oxidizer gas are mixed in the micro-premix chamber through impingement-enhanced mixing of flows of the fuel and the oxidizer gas. The burner can be used for low-emissions fuel-lean fully-premixed, or fuel-rich fully-premixed hydrogen-air combustion, or for combustion with other gases such as methane or other hydrocarbons, or even liquid fuels.

The influence of a mineral-vitamin premix on the metabolism of pregnant horses with microelemetosis

Directory of Open Access Journals (Sweden)

A. R. Shcherbatyy

2017-04-01

Full Text Available The article presents data on research into the influence of a mineral-vitamin premix on the clinical condition, erythropoiesis and the metabolism (macro- and micro-elemental, vitaminic, proteinaceous, enzymic of Hucul breed mares in the last trimester of pregnancy. The Marmix premix contains: vitamins – А, D3, Е, В1, В2, В12, pantothenic and ascorbic acids, niacin, biotin; nonorganic compounds of microelements – sulphate of cobalt, copper, zinc, iron, manganese; potassium iodide, sodium selenite; amino acids – lysine, threonine, methionine.The usage of the mineral-vitaminic premix Marmix on pregnant mares during 60 days causes recovery of clinical status, erythropoiesis, raises the level of the cobalt (by 45.9% and copper (by 2.15 times, normalizes the calcium-phosphorus ratio, raises the phosphorus level in the blood (by 17.7%, raises vitamin А (by 2.5 times and tocopherol (by 2.02 times, total protein (by 27.7%, decreases the level of urea (by 42.2%, activity of AspAT [aspartate transaminase or aspartate aminotransferase] (by 42.9% and AlAT [alanine transaminase] (by 44.9% and alkaline phosphatase (by 43.7%. The research conducted contributes to improvements in the study of the pathogenesis of microelementosis of mares and develops an efficient way of treating and preventing the development of microelementosis among these animals.

Fabrication and Characteristics of Macroporous TiO2 Photocatalyst

Directory of Open Access Journals (Sweden)

Guiyun Yi

2014-01-01

Full Text Available Macroporous TiO2 photocatalyst was synthesized by a facile nanocasting method using polystyrene (PS spherical particles as the hard template. The synthesized photocatalyst was characterized by transmission electron microscope (TEM, scanning electron microscopy (SEM, thermogravimetry-differential thermogravimetry (TG-DTG, X-ray diffraction (XRD, and N2-sorption. TEM, SEM, and XRD characterizations confirmed that the macroporous TiO2 photocatalyst is composed of anatase phase. The high specific surface area of 87.85 m2/g can be achieved according to the N2-sorption analysis. Rhodamine B (RhB was chosen as probe molecule to evaluate the photocatalytic activity of the TiO2 catalysts. Compared with the TiO2 materials synthesized in the absence of PS spherical template, the macroporous TiO2 photocatalyst sintered at 500°C exhibits much higher activity on the degradation of RhB under the UV irradiation, which can be assigned to the well-structured macroporosity. The macroporous TiO2 material presents great potential in the fields of environmental remediation and energy conversion and storage.

Simulation of lean premixed turbulent combustion

International Nuclear Information System (INIS)

Bell, J; Day, M; Almgren, A; Lijewski, M; Rendleman, C; Cheng, R; Shepherd, I

2006-01-01

There is considerable technological interest in developing new fuel-flexible combustion systems that can burn fuels such as hydrogen or syngas. Lean premixed systems have the potential to burn these types of fuels with high efficiency and low NOx emissions due to reduced burnt gas temperatures. Although traditional Scientific approaches based on theory and laboratory experiment have played essential roles in developing our current understanding of premixed combustion, they are unable to meet the challenges of designing fuel-flexible lean premixed combustion devices. Computation, with its ability to deal with complexity and its unlimited access to data, has the potential for addressing these challenges. Realizing this potential requires the ability to perform high fidelity simulations of turbulent lean premixed flames under realistic conditions. In this paper, we examine the specialized mathematical structure of these combustion problems and discuss simulation approaches that exploit this structure. Using these ideas we can dramatically reduce computational cost, making it possible to perform high-fidelity simulations of realistic flames. We illustrate this methodology by considering ultra-lean hydrogen flames and discuss how this type of simulation is changing the way researchers study combustion

Nonenzymatic free-cholesterol detection via a modified highly sensitive macroporous gold electrode with platinum nanoparticles.

Science.gov (United States)

Lee, Yi-Jae; Park, Jae-Yeong

2010-12-15

A sensitive macroporous Au electrode with a highly rough surface obtained through the use of with Pt nanoparticles (macroporous Au-/nPts) is reported. It has been designed for nonenzymatic free-cholesterol biosensor applications. A macroporous Au-/nPts electrode was fabricated by electroplating Pt nanoparticles onto a coral-like shaped macroporous Au electrode structure. The macroporous Au-/nPts electrode was physically characterized by field emission scanning electron microscopy (FESEM). It was confirmed that the Pt nanoparticles were well deposited on the surface of the macroporous Au electrode. The porosity and window pore size of the macroporous Au electrode were 50% and 100-300 nm, respectively. The electroplated Pt nanoparticle size was approximately 10-20 nm. Electrochemical experiments showed that the macroporous Au-/nPts exhibited a much larger surface activation area (roughness factor (RF)=2024.7) than the macroporous Au electrode (RF=46.07). The macroporous Au-/nPts also presented a much stronger electrocatalytic activity towards cholesterol oxidation than does the macroporous Au electrode. At 0.2 V, the electrode responded linearly up to a 5 mM cholesterol concentration in a neutral media, with a detection limit of 0.015 mM and detection sensitivity of 226.2 μA mM(-1) cm(-2). Meanwhile, interfering species such as ascorbic acid (AA), acetaminophen (AP), and uric acid (UA), were effectively avoided. This novel nonenzymatic detection electrode has strong applications as an electrochemically based cholesterol biosensor. Copyright © 2010 Elsevier B.V. All rights reserved.

Experience with the Large Eddy Simulation (LES) Technique for the Modelling of Premixed and Non-premixed Combustion

OpenAIRE

Malalasekera, W; Ibrahim, SS; Masri, AR; Gubba, SR; Sadasivuni, SK

2013-01-01

Compared to RANS based combustion modelling, the Large Eddy Simulation (LES) technique has recently emerged as a more accurate and very adaptable technique in terms of handling complex turbulent interactions in combustion modelling problems. In this paper application of LES based combustion modelling technique and the validation of models in non-premixed and premixed situations are considered. Two well defined experimental configurations where high quality data are available for validation is...

A new method to produce macroporous Mg-phosphate bone growth substitutes

Energy Technology Data Exchange (ETDEWEB)

Babaie, Elham, E-mail: Elham.Babaie@rockets.utoledo.edu [Department of Biomedical Engineering, University of Toledo, Toledo, OH 43606 (United States); Lin, Boren [Department of Biomedical Engineering, University of Toledo, Toledo, OH 43606 (United States); Bhaduri, Sarit B. [Department of Mechanical, Industrial and Manufacturing Engineering, University of Toledo, Toledo, OH 43606 (United States); Department of Surgery (Dentistry), University of Toledo, Toledo, OH 43614 (United States)

2017-06-01

This paper is a sequel to our previous effort in developing Mg-phosphate orthopedic cements using amorphous Mg-phosphate (AMP) as the precursor. In this paper, we report a new real-time in situ technique to create macroporous bone growth substitute (BGS). The method uses biodegradable Mg-particles as the porogen. As opposed to the conventional wisdom of providing corrosion protection layers to biodegradable Mg-alloys, the present method uses the fast corrosion kinetics of Mg to create macropores in real time during the setting of the cement. An aqueous solution of PVA was used as the setting solution. Using this technique, a macroporous cement containing up to 91% porosity is obtained, as determined by pycnometry. Due to formation of H{sub 2} gas bubbles from corrosion of Mg, the cement becomes macroporous. The pore sizes as big as 760 μm were observed. The results of SBF soaking indicated change in crystallinity as confirmed via scanning electron microscopy (SEM) and X-ray diffraction (XRD). Our in vitro cytocompatibility evaluation also revealed that the macroporous bone growth substitute composed of bobierrite is cytocompatible and can improve gene expression. - Highlights: • We report a new real time, in situ technique to fabricate macroporous bone grafts. • Self-corroding Mg granules act as porogens. • Compositions containing AMP and PVA self-set within a reasonable time. • The final bone graft substitute showed promising biocompatibility. • The results provide important information on the porosity content and bioactivity.

Soft-Template Construction of 3D Macroporous Polypyrrole Scaffolds.

Science.gov (United States)

Liu, Shaohua; Wang, Faxing; Dong, Renhao; Zhang, Tao; Zhang, Jian; Zheng, Zhikun; Mai, Yiyong; Feng, Xinliang

2017-04-01

A bottom-up approach toward 3D hierarchical macroporous polypyrrole aerogels is demonstrated via soft template-directed synthesis and self-assembly of ultrathin polypyrrole nanosheets in solution, which present interconnected macropores, ultrathin walls, and large specific surface areas, thereby exhibiting a high capacity, satisfactory rate capability, and excellent cycling stability for Na-ion storage. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Safety, cost, and clinical considerations for the use of premixed parenteral nutrition.

Science.gov (United States)

Hall, Jacob W

2015-06-01

Premixed parenteral nutrition (PN) can be used for PN therapy in place of traditional compounded or customized PN. Premixed PN may have a number of advantages over compounded PN such as decreased costs, decreased compounding time, reduced chance for error, and reduced incidence of bloodstream infections. However, premixed PN may not be appropriate for all patients and may have other additional costs associated with its use. This article discusses the data available with regard to the use of premixed PN, focusing on the potential advantages and disadvantages of using premixed PN, and also discusses the implementation of premixed PN in a large tertiary cancer center. © 2015 American Society for Parenteral and Enteral Nutrition.

Flow and transport processes in a macroporous subsurface-drained glacial till soil

DEFF Research Database (Denmark)

Villholth, Karen Grothe; Jensen, Karsten Høgh; Fredericia, Johnny

1998-01-01

of macropore structure and hydraulic efficiency, using image analysis and tension infiltration, and of soil water content, level of groundwater table, and chloride content of soil water within the soil profile yielded insights into small-scale processes and their associated variability. Macropore how...... into the soil profile. Dye infiltration experiments in the field as well as in the laboratory supported the recognition of the dominant contribution of macropores to the infiltration and transport process. The soil matrix significantly influenced the tracer distribution by acting as a source or sink...... for continuous solute exchange with the macropores. An average field-determined active macroporosity constituted 0.2% of the total porosity, or approximately 10% of the total macroporosity. (C) 1998 Elsevier Science B.V. All rights reserved....

Macropores and earthworm species affected by agronomic intensification

DEFF Research Database (Denmark)

Krogh, Paul Henning; Pérès, Guénola

project EcoFINDERS we investigated the relationsship between earthworm biodiversity, macropores and three agricultural landuse types. A field campaign was conducted in October-November 2011. Earthworm burrow distribution was quantified at 10, 20, 30, 50 and 100 20 cm horizontal layer intervals down...... the soil profile to 1 meter depth and correlated with the earthworm community consisting of 12 species dominated by the endogeics Aporrectodea caliginosa and Aporrectodea chlorotica and the anecics Aporrectodea longa and Lumbricus centralis. Medium-small macropores in the ploughing layer with diameters (Ø...

Early structure of LPG partially premixed conically stabilized flames

KAUST Repository

Elbaz, Ayman M.

2013-01-01

This paper presents experimental investigation of LPG partially premixed turbulent flames stabilized within a conical nozzle burner under constant degree of partial premixing. The stability limits and mean flame structure are presented based

Pembakaran Premixed Minyak Nabati Pada Bunsen Burner Type Silinder

OpenAIRE

La Muhaya, Syamsul Bahri; Wardana, ING; Widhiyanuriyawan, Denny

2015-01-01

In the premixed combustion wave propagation combustion occurs is called the flame front. Premixed flame will propagate at the speed of moving towards the reactants unique. If the speed of the reactants is equal to the speed of propagation of fire, the fire (reaction zone) will be stationary. It is necessary to follow up on the influence of equivalence ratio (φ) varied with laminar flame speed (SL) in the premixed combustion of vegetable oil (virgin coconut oil, jatropha and cotton seeds). Res...

Chemical structures and theoretical models of lean premixed ...

African Journals Online (AJOL)

To better understand the chemistry involved in the lean-fuel combustion, the chemical structure of lean premixed propene-oxygen-nitrogen flames stabilized on a flat-flame burner at atmospheric pressure was determined experimentally. The species mole fraction profiles were also computed by the Premix code and three ...

Quantification of extinction mechanism in counterflow premixed flames

KAUST Repository

Choi, Sangkyu; Cho, Eunseong; Chung, Suk-Ho

2014-01-01

The extinction mechanisms of stretched premixed flames have been investigated numerically for the fuels of CH4, C3H8, H2, CO and for the mixture fuels of CH4+H2 and CO+H2 by adopting symmetric double premixed flames in a counterflow configuration

Large eddy simulation of premixed and non-premixed combustion in a Stagnation Point Reverse Flow combustor

Science.gov (United States)

Undapalli, Satish

A new combustor referred to as Stagnation Point Reverse Flow (SPRF) combustor has been developed at Georgia Tech to meet the increasingly stringent emission regulations. The combustor incorporates a novel design to meet the conflicting requirements of low pollution and high stability in both premixed and non-premixed modes. The objective of this thesis work is to perform Large Eddy Simulations (LES) on this lab-scale combustor and elucidate the underlying physics that has resulted in its excellent performance. To achieve this, numerical simulations have been performed in both the premixed and non-premixed combustion modes, and velocity field, species field, entrainment characteristics, flame structure, emissions, and mixing characteristics have been analyzed. Simulations have been carried out first for a non-reactive case to resolve relevant fluid mechanics without heat release by the computational grid. The computed mean and RMS quantities in the non-reacting case compared well with the experimental data. Next, the simulations were extended for the premixed reactive case by employing different sub-grid scale combustion chemistry closures: Eddy Break Up (EBU), Artificially Thickened Flame (TF) and Linear Eddy Mixing (LEM) models. Results from the EBU and TF models exhibit reasonable agreement with the experimental velocity field. However, the computed thermal and species fields have noticeable discrepancies. Only LEM with LES (LEMLES), which is an advanced scalar approach, has been able to accurately predict both the velocity and species fields. Scalar mixing plays an important role in combustion, and this is solved directly at the sub-grid scales in LEM. As a result, LEM accurately predicts the scalar fields. Due to the two way coupling between the super-grid and sub-grid quantities, the velocity predictions also compare very well with the experiments. In other approaches, the sub-grid effects have been either modeled using conventional approaches (EBU) or need

Characteristics of immobilized aminoacylase from Aspergillus oryzae on macroporous copolymers.

Science.gov (United States)

He, B L; Jiang, P; Qiu, Y B

1990-01-01

Aminoacylase from Aspergillus oryzae was adsorbed on functionallized macroporous copolymers where the enzyme showed excellent catalyzing activity and operation stability. Various factors which effect the activity of the immobilized aminoacylase such as temperature, pH and ionic strength were investigated. The continuous operation of the enzyme immobilized on macroporous copolymers was compared with that of the enzyme immobilized on DEAE-Sephadex.

Representing macropore flow at the catchment scale: a comparative modeling study

Science.gov (United States)

Liu, D.; Li, H. Y.; Tian, F.; Leung, L. R.

2017-12-01

Macropore flow is an important hydrological process that generally enhances the soil infiltration capacity and velocity of subsurface water. Up till now, macropore flow is mostly simulated with high-resolution models. One possible drawback of this modeling approach is the difficulty to effectively represent the overall typology and connectivity of the macropore networks. We hypothesize that modeling macropore flow directly at the catchment scale may be complementary to the existing modeling strategy and offer some new insights. Tsinghua Representative Elementary Watershed model (THREW model) is a semi-distributed hydrology model, where the fundamental building blocks are representative elementary watersheds (REW) linked by the river channel network. In THREW, all the hydrological processes are described with constitutive relationships established directly at the REW level, i.e., catchment scale. In this study, the constitutive relationship of macropore flow drainage is established as part of THREW. The enhanced THREW model is then applied at two catchments with deep soils but distinct climates, the humid Asu catchment in the Amazon River basin, and the arid Wei catchment in the Yellow River basin. The Asu catchment has an area of 12.43km2 with mean annual precipitation of 2442mm. The larger Wei catchment has an area of 24800km2 but with mean annual precipitation of only 512mm. The rainfall-runoff processes are simulated at a hourly time step from 2002 to 2005 in the Asu catchment and from 2001 to 2012 in the Wei catchment. The role of macropore flow on the catchment hydrology will be analyzed comparatively over the Asu and Wei catchments against the observed streamflow, evapotranspiration and other auxiliary data.

Soil Susceptibility to Macropore Flow Across a Desert-Oasis Ecotone of the Hexi Corridor, Northwest China

Science.gov (United States)

Zhang, Yongyong; Zhao, Wenzhi; He, Jianhua; Fu, Li

2018-02-01

Macropore flow not only provides a fast pathway for water and solute transport and increases the risks of water and nutrient loss but also enhances soil aeration and groundwater recharge. However, macropore flow characteristics in irrigated oasis soils subject to continuous crop cultivation are poorly understood. This study was to investigate the effect of continuous cultivation on soil properties and macropore flow and to quantify the changes in macropore flow characteristics in an old oasis field (>50 years of cultivation, OOF), young oasis field (20 years, YOF), and adjacent uncultivated sandy area (0 year, USL) in Northwest China. Triplicate soil samples were collected from each site to investigate soil properties. Dye tracer experiments with also three replicates were conducted at each site. The degree of macropore flow (i.e., parameters of macropore flow) was highest at the OOF, intermediate at the YOF, and minimal at the USL. The macropore flow fraction (i.e., fraction of total infiltration flows through macropore flow pathways) at the OOF was 3.4 times greater than at the USL. The heterogeneous infiltration pattern at the OOF was dominated by macropore flow, while funnel flow was predominant at the USL. Long-term irrigation with silt-laden river water has increased silt + clay contents of the oasis soils. Irrigation and high-input crop cultivation also increased organic matter. These changes in soil properties contributed to the interaggregate voids formation. The conversion of native desert soils to irrigated croplands increases the degree of macropore flow, which might enhance groundwater recharge in the desert-oasis ecotone.

Accidental periapical extrusion of non-setting calcium hydroxide: Unusual bone response and management

Directory of Open Access Journals (Sweden)

Divya S Sharma

2014-01-01

Full Text Available Premixed non-setting calcium hydroxide is frequently used as interim root canal dressing in endodontically involved permanent teeth and as obturating paste in deciduous teeth in pediatric dentistry. Wide apex in both cases makes it more prone for deliberate extrusion especially when applied with pressure delivery systems. Contrary to common belief the mix was not resorbed in two years with the complaint of insufficiency in mastication. Large mass of calcium hydroxide in bone delayed healing process even after its removal. The present case report intends to demonstrate unusual behavior of bone in response to oily non-setting preparation of calcium hydroxide. Therefore its application with pressure syringe should be reconsidered in pediatric dentistry.

Biodiesel production from transesterification of palm oil with methanol over CaO supported on bimodal meso-macroporous silica catalyst.

Science.gov (United States)

Witoon, Thongthai; Bumrungsalee, Sittisut; Vathavanichkul, Peerawut; Palitsakun, Supaphorn; Saisriyoot, Maythee; Faungnawakij, Kajornsak

2014-03-01

Calcium oxide-loaded porous materials have shown promise as catalysts in transesterification. However, the slow diffusion of bulky triglycerides through the pores limited the activity of calcium oxide (CaO). In this work, bimodal meso-macroporous silica was used as a support to enhance the accessibility of the CaO dispersed inside the pores. Unimodal porous silica having the identical mesopore diameter was employed for the purpose of comparison. Effects of CaO content and catalyst pellet size on the yield of fatty acid methyl esters (FAME) were investigated. The basic strength was found to increase with increasing the CaO content. The CaO-loaded bimodal porous silica catalyst with the pellet size of 325μm achieved a high %FAME of 94.15 in the first cycle, and retained an excellent %FAME of 88.87 after five consecutive cycles. Copyright © 2014 Elsevier Ltd. All rights reserved.

Thermal Radiation Properties of Turbulent Lean Premixed Methane Air Flames

National Research Council Canada - National Science Library

Ji, Jun; Sivathanu, Y. R; Gore, J. P

2000-01-01

... of turbulent premixed flames. Reduced cooling airflows in lean premixed combustors, miniaturization of combustors, and the possible use of radiation sensors in combustion control schemes are some of the practical reasons...

Soot Formation in Freely-Propagating Laminar Premixed Flames

Science.gov (United States)

Lin, K.-C.; Hassan, M. I.; Faeth, G. M.

1997-01-01

Soot formation within hydrocarbon-fueled flames is an important unresolved problem of combustion science. Thus, the present study is considering soot formation in freely-propagating laminar premixed flames, exploiting the microgravity environment to simplify measurements at the high-pressure conditions of interest for many practical applications. The findings of the investigation are relevant to reducing emissions of soot and continuum radiation from combustion processes, to improving terrestrial and spacecraft fire safety, and to developing methods of computational combustion, among others. Laminar premixed flames are attractive for studying soot formation because they are simple one-dimensional flows that are computationally tractable for detailed numerical simulations. Nevertheless, studying soot-containing burner-stabilized laminar premixed flames is problematical: spatial resolution and residence times are limited at the pressures of interest for practical applications, flame structure is sensitive to minor burner construction details so that experimental reproducibility is not very good, consistent burner behavior over the lengthy test programs needed to measure soot formation properties is hard to achieve, and burners have poor durability. Fortunately, many of these problems are mitigated for soot-containing, freely-propagating laminar premixed flames. The present investigation seeks to extend work in this laboratory for various soot processes in flames by observing soot formation in freely-propagating laminar premixed flames. Measurements are being made at both Normal Gravity (NG) and MicroGravity (MG), using a short-drop free-fall facility to provide MG conditions.

Links between matrix bulk density, macropore characteristics and hydraulic behavior of soils

DEFF Research Database (Denmark)

Katuwal, Sheela; Møldrup, Per; Lamandé, Mathieu

2013-01-01

characteristics on soil hydraulic functions has rarely been studied. With the objective of studying the links between these parameters we quantified macropore characteristics of intact soil columns (19 cm diameter x 20 cm high) from two agricultural field sites (Silstrup and Faardrup) in Denmark using coarse...... resolution X-ray CT and linked them with laboratory measurements of air permeability and leaching experiment. In addition to macropore characteristics, we also quantified the CT-number of the matrix as a measure of the bulk density of the matrix, i.e., excluding macropores in the soil. Soils from the two...

Pesticide transport to tile-drained fields in SWAT model – macropore flow and sediment

DEFF Research Database (Denmark)

Lu, Shenglan; Trolle, Dennis; Blicher-Mathiesen, Gitte

2015-01-01

Tool (SWAT) to simulate transport of both mobile (e.g. Bentazon) and strongly sorbed (e.g. Diuron) pesticides in tile drains. Macropore flow is initiated when soil water content exceeds a threshold and rainfall intensity exceeds infiltration capacity. The amount of macropore flow is calculated...... to macropore sediment transport. Simulated tile drain discharge, sediment and pesticide loads are calibrated against data from intensively monitored tile-drained fields and streams in Denmark....

Premixed direct injection nozzle

Science.gov (United States)

Zuo, Baifang [Simpsonville, SC; Johnson, Thomas Edward [Greer, SC; Lacy, Benjamin Paul [Greer, SC; Ziminsky, Willy Steve [Simpsonville, SC

2011-02-15

An injection nozzle having a main body portion with an outer peripheral wall is disclosed. The nozzle includes a plurality of fuel/air mixing tubes disposed within the main body portion and a fuel flow passage fluidly connected to the plurality of fuel/air mixing tubes. Fuel and air are partially premixed inside the plurality of the tubes. A second body portion, having an outer peripheral wall extending between a first end and an opposite second end, is connected to the main body portion. The partially premixed fuel and air mixture from the first body portion gets further mixed inside the second body portion. The second body portion converges from the first end toward said second end. The second body portion also includes cooling passages that extend along all the walls around the second body to provide thermal damage resistance for occasional flame flash back into the second body.

[Studies on the process of Herba Clinopodii saponins purified with macroporous adsorption resin].

Science.gov (United States)

Zhang, Yi; Yan, Dan; Han, Yumei

2005-10-01

To study the technological parameters of the purification process of saponins with macroporous adsorption resin. The adsorptive characteristics and elutive parameters of the process were studied by taking the elutive and purified ratio of saponins as markers. 11.4 ml of the extraction of Herba Clinopodii (crude drugs 0.2 g/ml) was purified with a column of macroporous adsorption resin (phi15 mm x H90 mm, dry weight 2.5 g) and washed with 3BV of distilled water, then eluted with 3BV of 30% ethanol and 3BV of 70% ethanol. Most of saponins were collected in the 70% ethanol. With macroporous adsorption resin adsorbing and purifying,the elutive ratio of saponins is 86.8% and the purity reaches 153.2%. So this process of applying macroporous adsorption resin to adsorb and purify Saponins is feasible.

Deep Ultraviolet Macroporous Silicon Filters, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This SBIR Phase I proposal describes a novel method to make deep and far UV optical filters from macroporous silicon. This type of filter consists of an array of...

Comprehensive Validation of Skeletal Mechanism for Turbulent Premixed Methane–Air Flame Simulations

KAUST Repository

Luca, Stefano

2017-08-01

A new skeletal mechanism, consisting of 16 species and 72 reactions, has been developed for lean methane–air premixed combustion from the GRI-Mech 3.0. The skeletal mechanism is validated for elevated unburnt temperatures (800 K) and pressures up to 4 atm, thereby addressing realistic gas turbine conditions. The skeletal mechanism is obtained by applying the directed relation graph method and performing sensitivity analysis on the detailed mechanism. The mechanism has been validated for flame speed and flame structure in a wide range of conditions and configurations. A good agreement between the skeletal mechanism and GRI-3.0 was obtained. The configurations considered include one-dimension laminar premixed flames, laminar non-premixed counterflow burners, and two- and three-dimensional unsteady configurations with variations of temperature, pressure, and composition. The skeletal mechanism allows for the inclusion of accurate finite rate chemistry in large-scale direct numerical simulations of lean turbulent premixed flames. In a large-scale direct numerical simulation, the use of the skeletal mechanism reduces the memory requirements by more than a factor of 3 and accelerates the simulation by a factor of 7 compared with the detailed mechanism. The skeletal mechanism is suitable for unsteady three-dimensional simulations of methane turbulent premixed, non-premixed, and globally lean partially premixed flames and is available as supplementary material.

Quantification of extinction mechanism in counterflow premixed flames

International Nuclear Information System (INIS)

Choi, Sang Kyu; Cho, Eun Seong; Chung, Suk Ho

2014-01-01

The extinction mechanisms of stretched premixed flames have been investigated numerically for the fuels of CH 4 , C 3 H 8 , H 2 , CO and for the mixture fuels of CH 4 +H 2 and CO+H 2 by adopting symmetric double premixed flames in a counterflow configuration. The local equilibrium temperature concept was used as a measure of energy loss or gain in order to quantify the extinction mechanism by preferential diffusion and/or incomplete reaction. The energy loss ratio from preferential diffusion arising from non-unity Lewis number and the loss ratio from incomplete reaction were calculated at various equivalence ratios near flame extinction. The results showed that the extinction of lean H 2 , CH 4 , CH 4 +H 2 , CO+H 2 , and rich C 3 H 8 premixed flames was caused by incomplete reaction due to insufficient reaction time, indicating that the effective Lewis number was smaller than unity, while the effect of preferential diffusion resulted in energy gain. However, the extinction of rich H 2 , CH 4 , CH 4 +H 2 , CO+H 2 , and lean C 3 H 8 premixed flames was affected by the combined effects of preferential diffusion and incomplete reaction indicating that the effective Lewis number was larger than unity. In CO premixed flames, incomplete reaction was dominant in both lean and rich cases due to the effective Lewis number close to unity. The effect of H 2 mixing to CO is found to be quite significant as compared to CH 4 +H 2 cases, which can alter the flame behavior of CO flames to that of H 2 .

Quantification of extinction mechanism in counterflow premixed flames

KAUST Repository

Choi, Sangkyu

2014-09-01

The extinction mechanisms of stretched premixed flames have been investigated numerically for the fuels of CH4, C3H8, H2, CO and for the mixture fuels of CH4+H2 and CO+H2 by adopting symmetric double premixed flames in a counterflow configuration. The local equilibrium temperature concept was used as a measure of energy loss or gain in order to quantify the extinction mechanism by preferential diffusion and/or incomplete reaction. The energy loss ratio from preferential diffusion arising from non-unity Lewis number and the loss ratio from incomplete reaction were calculated at various equivalence ratios near flame extinction. The results showed that the extinction of lean H2, CH4, CH4+H2, CO+H2, and rich C3H8 premixed flames was caused by incomplete reaction due to insufficient reaction time, indicating that the effective Lewis number was smaller than unity, while the effect of preferential diffusion resulted in energy gain. However, the extinction of rich H2, CH4, CH4+H2, CO+H2, and lean C3H8 premixed flames was affected by the combined effects of preferential diffusion and incomplete reaction indicating that the effective Lewis number was larger than unity. In CO premixed flames, incomplete reaction was dominant in both lean and rich cases due to the effective Lewis number close to unity. The effect of H2 mixing to CO is found to be quite significant as compared to CH4+H2 cases, which can alter the flame behavior of CO flames to that of H2.

Chaos in an imperfectly premixed model combustor.

Science.gov (United States)

Kabiraj, Lipika; Saurabh, Aditya; Karimi, Nader; Sailor, Anna; Mastorakos, Epaminondas; Dowling, Ann P; Paschereit, Christian O

2015-02-01

This article reports nonlinear bifurcations observed in a laboratory scale, turbulent combustor operating under imperfectly premixed mode with global equivalence ratio as the control parameter. The results indicate that the dynamics of thermoacoustic instability correspond to quasi-periodic bifurcation to low-dimensional, deterministic chaos, a route that is common to a variety of dissipative nonlinear systems. The results support the recent identification of bifurcation scenarios in a laminar premixed flame combustor (Kabiraj et al., Chaos: Interdiscip. J. Nonlinear Sci. 22, 023129 (2012)) and extend the observation to a practically relevant combustor configuration.

Effects of macropores on groundwater flow and transport of radionuclides

International Nuclear Information System (INIS)

Huff, D.D.; DeAngelis, D.L.; Yeh, G.T.

1983-01-01

In humid environments, recent findings have shown that an important component of runoff and associated solute moves rapidly through large continuous voids. Thus, consideration of radionuclide transport in subsurface flow is incomplete without explicit treatment of continuous macropores and interaction between macropore flow and the soil matrix. A computer model, FRACPORT, that simulates the transport of a solute through a fractured porous matrix has been developed. The model employs the Integrated Compartment Method and uses the approach of dividing the porous media into compartments comprising fractures or porous material. The fracture region and a small portion of the porous matrix are simulated using a shorter time step than for the remaining porous matrix. This allows substantial savings in computational time. The model should be useful for analyses of generic problems associated with water and radionuclide transport in macropore systems at shallow-land disposal sites in humid environments. 14 references, 6 figures, 1 table

Three-dimensional macroporous nanoelectronic networks as minimally invasive brain probes

Science.gov (United States)

Xie, Chong; Liu, Jia; Fu, Tian-Ming; Dai, Xiaochuan; Zhou, Wei; Lieber, Charles M.

2015-12-01

Direct electrical recording and stimulation of neural activity using micro-fabricated silicon and metal micro-wire probes have contributed extensively to basic neuroscience and therapeutic applications; however, the dimensional and mechanical mismatch of these probes with the brain tissue limits their stability in chronic implants and decreases the neuron-device contact. Here, we demonstrate the realization of a three-dimensional macroporous nanoelectronic brain probe that combines ultra-flexibility and subcellular feature sizes to overcome these limitations. Built-in strains controlling the local geometry of the macroporous devices are designed to optimize the neuron/probe interface and to promote integration with the brain tissue while introducing minimal mechanical perturbation. The ultra-flexible probes were implanted frozen into rodent brains and used to record multiplexed local field potentials and single-unit action potentials from the somatosensory cortex. Significantly, histology analysis revealed filling-in of neural tissue through the macroporous network and attractive neuron-probe interactions, consistent with long-term biocompatibility of the device.

Novel macroporous amphoteric gels: Preparation and characterization

Directory of Open Access Journals (Sweden)

S. Kudaibergenov

2012-05-01

Full Text Available Macroporous amphoteric gels based on allylamine, methacrylic acid and acrylamide crosslinked by N,N'-methylenebisacrylamide were synthesized by radical copolymerization of monomers in cryoconditions. The composition of cryogels was determined by combination of potentiometric and conductimetric titrations. The morphology of cryogels was evaluated by scanning electron microscope (SEM. Cryogels exhibited sponge-like porous structure with pore size ranging from 50 to 200 μm. The values of the isoelectric points (IEPs determined from the swelling experiments arranged between 3.5 and 4.3. The high adsorption-desorption capacity of amphoteric cryogels with respect to mM and trace concentrations of copper, nickel, and cobalt ions was demonstrated. It was shown that the macroporous amphoteric cryogels are able to adsorb up to 99.9% of copper, nickel, and cobalt ions from 10–3 mol•L–1 aqueous solution.

Factorization of Transport Coefficients in Macroporous Media

DEFF Research Database (Denmark)

Shapiro, Alexander; Stenby, Erling Halfdan

2000-01-01

We prove the fundamental theorem about factorization of the phenomenological coefficients for transport in macroporous media. By factorization we mean the representation of the transport coefficients as products of geometric parameters of the porous medium and the parameters characteristic...

Organic matter composition of soil macropore surfaces under different agricultural management practices

Science.gov (United States)

Glæsner, Nadia; Leue, Marin; Magid, Jacob; Gerke, Horst H.

2016-04-01

Understanding the heterogeneous nature of soil, i.e. properties and processes occurring specifically at local scales is essential for best managing our soil resources for agricultural production. Examination of intact soil structures in order to obtain an increased understanding of how soil systems operate from small to large scale represents a large gap within soil science research. Dissolved chemicals, nutrients and particles are transported through the disturbed plow layer of agricultural soil, where after flow through the lower soil layers occur by preferential flow via macropores. Rapid movement of water through macropores limit the contact between the preferentially moving water and the surrounding soil matrix, therefore contact and exchange of solutes in the water is largely restricted to the surface area of the macropores. Organomineral complex coated surfaces control sorption and exchange properties of solutes, as well as availability of essential nutrients to plant roots and to the preferentially flowing water. DRIFT (Diffuse Reflectance infrared Fourier Transform) Mapping has been developed to examine composition of organic matter coated macropores. In this study macropore surfaces structures will be determined for organic matter composition using DRIFT from a long-term field experiment on waste application to agricultural soil (CRUCIAL, close to Copenhagen, Denmark). Parcels with 5 treatments; accelerated household waste, accelerated sewage sludge, accelerated cattle manure, NPK and unfertilized, will be examined in order to study whether agricultural management have an impact on the organic matter composition of intact structures.

Study on Combustion Oscillation of Premixed Flame with Pilot Fuel at Elevated Pressures

Science.gov (United States)

Ohtsuka, Masaya; Yoshida, Shohei; Hirata, Yoshitaka; Kobayashi, Nariyoshi

Acoustically-coupled combustion oscillation is studied for premixed flame with pilot fuel to be used in gas turbine combustors. Premixed gas is passed through swirl vanes and burnt with the centrally injected pilot fuel. The dependencies of pressure, fuel to air ratio, premixed fuel rate, inlet velocity and air temperature on the combustion oscillation are investigated. Two kinds of oscillation modes of ˜100Hz and ˜350Hz are activated according to inlet velocities. Fluctuating pressures are amplified when the premixed fuel rate is over ˜80% at elevated pressures. The fluctuating pressure peak moves to a higher premixed fuel ratio region with increased pressure or fuel to air ratio for the Helmholz type mode. Combustion oscillation occurs when the pilot fuel velocity is changed proportionally with the flame length.

Spatial structure and scaling of macropores in hydrological process at small catchment scale

Science.gov (United States)

Silasari, Rasmiaditya; Broer, Martine; Blöschl, Günter

2013-04-01

During rainfall events, the formation of overland flow can occur under the circumstances of saturation excess and/or infiltration excess. These conditions are affected by the soil moisture state which represents the soil water content in micropores and macropores. Macropores act as pathway for the preferential flows and have been widely studied locally. However, very little is known about their spatial structure and conductivity of macropores and other flow characteristic at the catchment scale. This study will analyze these characteristics to better understand its importance in hydrological processes. The research will be conducted in Petzenkirchen Hydrological Open Air Laboratory (HOAL), a 64 ha catchment located 100 km west of Vienna. The land use is divided between arable land (87%), pasture (5%), forest (6%) and paved surfaces (2%). Video cameras will be installed on an agricultural field to monitor the overland flow pattern during rainfall events. A wireless soil moisture network is also installed within the monitored area. These field data will be combined to analyze the soil moisture state and the responding surface runoff occurrence. The variability of the macropores spatial structure of the observed area (field scale) then will be assessed based on the topography and soil data. Soil characteristics will be supported with laboratory experiments on soil matrix flow to obtain proper definitions of the spatial structure of macropores and its variability. A coupled physically based distributed model of surface and subsurface flow will be used to simulate the variability of macropores spatial structure and its effect on the flow behaviour. This model will be validated by simulating the observed rainfall events. Upscaling from field scale to catchment scale will be done to understand the effect of macropores variability on larger scales by applying spatial stochastic methods. The first phase in this study is the installation and monitoring configuration of video

Spatial distribution of heterocyclic organic matter compounds at macropore surfaces in Bt-horizons

Science.gov (United States)

Leue, Martin; Eckhardt, Kai-Uwe; Gerke, Horst H.; Ellerbrock, Ruth H.; Leinweber, Peter

2017-04-01

The illuvial Bt-horizon of Luvisols is characterized by coatings of clay and organic matter (OM) at the surfaces of cracks, biopores and inter-aggregate spaces. The OM composition of the coatings that originate from preferential transport of suspended matter in macropores determines the physico-chemical properties of the macropore surfaces. The analysis of the spatial distribution of specific OM components such as heterocyclic N-compounds (NCOMP) and benzonitrile and naphthalene (BN+NA) could enlighten the effect of macropore coatings on the transport of colloids and reactive solutes during preferential flow and on OM turnover processes in subsoils. The objective was to characterize the mm-to-cm scale spatial distribution of NCOMP and BN+NA at intact macropore surfaces from the Bt-horizons of two Luvisols developed on loess and glacial till. In material manually separated from macropore surfaces the proportions of NCOMP and BN+NA were determined by pyrolysis-field ionization mass spectrometry (Py-FIMS). These OM compounds, likely originating from combustion residues, were found increased in crack coatings and pinhole fillings but decreased in biopore walls (worm burrows and root channels). The Py-FIMS data were correlated with signals from C=O and C=C groups and with signals from O-H groups of clay minerals as determined by Fourier transform infrared spectroscopy in diffuse reflectance mode (DRIFT). Intensive signals of C15 to C17 alkanes from long-chain alkenes as main components of diesel and diesel exhaust particulates substantiated the assumption that burning residues were prominent in the subsoil OM. The spatial distribution of NCOMP and BN+NA along the macropores was predicted by partial least squares regression (PLSR) using DRIFT mapping spectra from intact surfaces and was found closely related to the distribution of crack coatings and pinholes. The results emphasize the importance of clay coatings in the subsoil to OM sorption and stabilization

Coupling of Spinosad Fermentation and Separation Process via Two-Step Macroporous Resin Adsorption Method.

Science.gov (United States)

Zhao, Fanglong; Zhang, Chuanbo; Yin, Jing; Shen, Yueqi; Lu, Wenyu

2015-08-01

In this paper, a two-step resin adsorption technology was investigated for spinosad production and separation as follows: the first step resin addition into the fermentor at early cultivation period to decrease the timely product concentration in the broth; the second step of resin addition was used after fermentation to adsorb and extract the spinosad. Based on this, a two-step macroporous resin adsorption-membrane separation process for spinosad fermentation, separation, and purification was established. Spinosad concentration in 5-L fermentor increased by 14.45 % after adding 50 g/L macroporous at the beginning of fermentation. The established two-step macroporous resin adsorption-membrane separation process got the 95.43 % purity and 87 % yield for spinosad, which were both higher than that of the conventional crystallization of spinosad from aqueous phase that were 93.23 and 79.15 % separately. The two-step macroporous resin adsorption method has not only carried out the coupling of spinosad fermentation and separation but also increased spinosad productivity. In addition, the two-step macroporous resin adsorption-membrane separation process performs better in spinosad yield and purity.

Quantification of extinction mechanism in counterflow premixed flames

Energy Technology Data Exchange (ETDEWEB)

Choi, Sang Kyu [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of); Cho, Eun Seong [Doosan Heavy Industries and Construction, Changwon (Korea, Republic of); Chung, Suk Ho [Abdullah University of Science and Technology, Thuwal (Saudi Arabia)

2014-09-15

The extinction mechanisms of stretched premixed flames have been investigated numerically for the fuels of CH{sub 4}, C{sub 3}H{sub 8}, H{sub 2}, CO and for the mixture fuels of CH{sub 4}+H{sub 2} and CO+H{sub 2} by adopting symmetric double premixed flames in a counterflow configuration. The local equilibrium temperature concept was used as a measure of energy loss or gain in order to quantify the extinction mechanism by preferential diffusion and/or incomplete reaction. The energy loss ratio from preferential diffusion arising from non-unity Lewis number and the loss ratio from incomplete reaction were calculated at various equivalence ratios near flame extinction. The results showed that the extinction of lean H{sub 2} , CH{sub 4}, CH{sub 4}+H{sub 2}, CO+H{sub 2}, and rich C{sub 3}H{sub 8} premixed flames was caused by incomplete reaction due to insufficient reaction time, indicating that the effective Lewis number was smaller than unity, while the effect of preferential diffusion resulted in energy gain. However, the extinction of rich H{sub 2}, CH{sub 4}, CH{sub 4}+H{sub 2}, CO+H{sub 2}, and lean C{sub 3}H{sub 8} premixed flames was affected by the combined effects of preferential diffusion and incomplete reaction indicating that the effective Lewis number was larger than unity. In CO premixed flames, incomplete reaction was dominant in both lean and rich cases due to the effective Lewis number close to unity. The effect of H{sub 2} mixing to CO is found to be quite significant as compared to CH{sub 4}+H{sub 2} cases, which can alter the flame behavior of CO flames to that of H{sub 2}.

Development of rapid mixing fuel nozzle for premixed combustion

International Nuclear Information System (INIS)

Katsuki, Masashi; Chung, Jin Do; Kim, Jang Woo; Hwang, Seung Min; Kim, Seung Mo; Ahn, Chul Ju

2009-01-01

Combustion in high-preheat and low oxygen concentration atmosphere is one of the attractive measures to reduce nitric oxide emission as well as greenhouse gases from combustion devices, and it is expected to be a key technology for the industrial applications in heating devices and furnaces. Before proceeding to the practical applications, we need to elucidate combustion characteristics of non-premixed and premixed flames in high-preheat and low oxygen concentration conditions from scientific point of view. For the purpose, we have developed a special mixing nozzle to create a homogeneous mixture of fuel and air by rapid mixing, and applied this rapidmixing nozzle to a Bunsen-type burner to observe combustion characteristics of the rapid-mixture. As a result, the combustion of rapid-mixture exhibited the same flame structure and combustion characteristics as the perfectly prepared premixed flame, even though the mixing time of the rapid-mixing nozzle was extremely short as a few milliseconds. Therefore, the rapid-mixing nozzle in this paper can be used to create preheated premixed flames as far as the mixing time is shorter than the ignition delay time of the fuel

Effect of Sol-Gel Ageing Time on Three Dimensionally Ordered Macroporous Structure of 80SiO2-15CaO-5P2O5 Bioactive Glasses

Directory of Open Access Journals (Sweden)

Thanida CHAROENSUK

2014-04-01

Full Text Available Three dimensionally ordered macroporous bioactive glasses (3DOM-BGs, namely 80SiO2-15CaO-5P2O5, were synthesized by sol-gel method. PMMA colloidal crystals and non-ionic block copolymers P123 were used as cotemplates. The amorphous 3DOM-BGs had skeletal walls enclosing macropores. Such structure resulted from octahedral and tetrahedral holes of the face-centered cubic (fcc closest packed PMMA templates and windows interconnecting through macropores network. The thicknesses of the walls were around 50 nm – 80 nm and the windows were 90 nm – 110 nm in diameter. These wall thickness is increased by with an increase in ageing time up to 24 h and  then gradually reduced with further increase in aging time. Vibration bands of Si–O–Si and P–O were evident in infrared spectra which are in agreement with EDS spectra indicating Si, P and Ca compositions. After in vitro bioactivity testing by soaking 3DOM-BGs in simulated body fluid at 37 °C, the crystallization of amorphous calcium phosphate layers compatible to the bone component of hydroxyl carbonate apatite were rapidly formed within 3 h. These results indicated that these 3DOM-BGs resembled ideal bone implant materials.DOI: http://dx.doi.org/10.5755/j01.ms.20.1.4755

High energy density supercapacitors using macroporous kitchen sponges

KAUST Repository

Chen, Wei; Baby, Rakhi Raghavan; Alshareef, Husam N.

2012-01-01

Macroporous, low-cost and recyclable kitchen sponges are explored as effective electrode platforms for supercapacitor devices. A simple and scalable process has been developed to fabricate MnO 2-carbon nanotube (CNT)-sponge supercapacitor electrodes

A Macroporous TiO2 Oxygen Sensor Fabricated Using Anodic Aluminium Oxide as an Etching Mask

Directory of Open Access Journals (Sweden)

Sheng-Po Wu

2010-01-01

Full Text Available An innovative fabrication method to produce a macroporous Si surface by employing an anodic aluminium oxide (AAO nanopore array layer as an etching template is presented. Combining AAO with a reactive ion etching (RIE processes, a homogeneous and macroporous silicon surface can be effectively configured by modulating AAO process parameters and alumina film thickness, thus hopefully replacing conventional photolithography and electrochemical etch methods. The hybrid process integration is considered fully CMOS compatible thanks to the low-temperature AAO and CMOS processes. The gas-sensing characteristics of 50 nm TiO2 nanofilms deposited on the macroporous surface are compared with those of conventional plain (or non-porous nanofilms to verify reduced response noise and improved sensitivity as a result of their macroporosity. Our experimental results reveal that macroporous geometry of the TiO2 chemoresistive gas sensor demonstrates 2-fold higher (~33% improved sensitivity than a non-porous sensor at different levels of oxygen exposure. In addition, the macroporous device exhibits excellent discrimination capability and significantly lessened response noise at 500 °C. Experimental results indicate that the hybrid process of such miniature and macroporous devices are compatible as well as applicable to integrated next generation bio-chemical sensors.

Gravity Effects Observed In Partially Premixed Flames

Science.gov (United States)

Puri, Ishwar K.; Aggarwal, Suresh K.; Lock, Andrew J.; Gauguly, Ranjan; Hegde, Uday

2003-01-01

Partially premixed flames (PPFs) contain a rich premixed fuel air mixture in a pocket or stream, and, for complete combustion to occur, they require the transport of oxidizer from an appropriately oxidizer-rich (or fuel-lean) mixture that is present in another pocket or stream. Partial oxidation reactions occur in fuel-rich portions of the mixture and any remaining unburned fuel and/or intermediate species are consumed in the oxidizer-rich portions. Partial premixing, therefore, represents that condition when the equivalence ratio (phi) in one portion of the flowfield is greater than unity, and in another section its value is less than unity. In general, for combustion to occur efficiently, the global equivalence ratio is in the range fuel-lean to stoichiometric. These flames can be established by design by placing a fuel-rich mixture in contact with a fuel-lean mixture, but they also occur otherwise in many practical systems, which include nonpremixed lifted flames, turbulent nonpremixed combustion, spray flames, and unwanted fires. Other practical applications of PPFs are reported elsewhere. Although extensive experimental studies have been conducted on premixed and nonpremixed flames under microgravity, there is a absence of previous experimental work on burner stabilized PPFs in this regard. Previous numerical studies by our group employing a detailed numerical model showed gravity effects to be significant on the PPF structure. We report on the results of microgravity experiments conducted on two-dimensional (established on a Wolfhard-Parker slot burner) and axisymmetric flames (on a coannular burner) that were investigated in a self-contained multipurpose rig. Thermocouple and radiometer data were also used to characterize the thermal transport in the flame.

Production and in vitro evaluation of macroporous, cell-encapsulating alginate fibres for nerve repair

Energy Technology Data Exchange (ETDEWEB)

Lin, Sharon Chien-Yu, E-mail: sharonlin114@gmail.com [The University of Queensland, Pharmacy Australia Centre of Excellence, 20 Cornwall Street, Woolloongabba, Brisbane QLD 4102 (Australia); Wang, Yiwei, E-mail: yiweiwang@anzac.edu.au [The University of Queensland, Pharmacy Australia Centre of Excellence, 20 Cornwall Street, Woolloongabba, Brisbane QLD 4102 (Australia); Wertheim, David F., E-mail: d.wertheim@kingston.ac.uk [Faculty of Science, Engineering and Computing, Kingston University, Kingston upon Thames, Surrey KT1 2EE (United Kingdom); Coombes, Allan G.A., E-mail: allancoombes@pharmacy.psu.ac.th [Faculty of Pharmaceutical Sciences, Prince of Songkla University, Hat Yai, Songkhla 90112 (Thailand)

2017-04-01

The prospects for successful peripheral nerve repair using fibre guides are considered to be enhanced by the use of a scaffold material, which promotes attachment and proliferation of glial cells and axonal regeneration. Macroporous alginate fibres were produced by extraction of gelatin particle porogens from wet spun fibres produced using a suspension of gelatin particles in 1.5% w/v alginate solution. Gelatin loading of the starting suspension of 40.0, 57.0, and 62.5% w/w resulted in gelatin loading of the dried alginate fibres of 16, 21, and 24% w/w respectively. Between 45 and 60% of the gelatin content of hydrated fibres was released in 1 h in distilled water at 37 °C, leading to rapid formation of a macroporous structure. Confocal laser scanning microscopy (CLSM) and image processing provided qualitative and quantitative analysis of mean equivalent macropore diameter (48–69 μm), pore size distribution, estimates of maximum porosity (14.6%) and pore connectivity. CLSM also revealed that gelatin residues lined the macropore cavities and infiltrated into the body of the alginate scaffolds, thus, providing cell adhesion molecules, which are potentially advantageous for promoting growth of glial cells and axonal extension. Macroporous alginate fibres encapsulating nerve cells [primary rat dorsal root ganglia (DRGs)] were produced by wet spinning alginate solution containing dispersed gelatin particles and DRGs. Marked outgrowth was evident over a distance of 150 μm at day 11 in cell culture, indicating that pores and channels created within the alginate hydrogel were providing a favourable environment for neurite development. These findings indicate that macroporous alginate fibres encapsulating nerve cells may provide the basis of a useful strategy for nerve repair. - Highlights: • Nerve cells were encapsulated in macroporous alginate fibres for use in nerve repair. • Fibres were produced from alginate solution containing gelatin porogens and cells. �

Macroporous synthetic hydroxyapatite bioceramics for bone substitute applications

CSIR Research Space (South Africa)

Thomas, ME

1999-08-01

Full Text Available An improved strategy is described for the manufacture of macroporous hydroxyapatite bioceramics for bone substitute applications. This is based on a modified fugitive phase technique, which allows production of relatively open, high-strength devices...

Polyacrylonitrile-Derived Sponge-Like Micro/Macroporous Carbon for Selective CO2 Separation.

Science.gov (United States)

Guo, Li-Ping; Hu, Qing-Tao; Zhang, Peng; Li, Wen-Cui; Lu, An-Hui

2018-03-25

CO 2 capture under a dynamical flow situation requires adsorbents possessing balanced proportion of macropores as diffusion path and micropores as adsorption reservoir. However, the construction of interconnected micro-/macropores structure coupled with abundant nitrogen species into one carbon skeleton remains a challenge. Here, we report a new approach to prepare sponge-like carbon with a well-developed micro-/macroporous structure and enriched nitrogen species through aqueous phase polymerization of acrylonitrile in the presence of graphene oxide. The tension stress caused by the uniform thermal shrinkage of polyacrylonitrile during the pyrolysis together with the favorable flexibility of graphene oxide sheets are responsible for the formation of the sponge-like morphology. The synergistic effect of micro-/macroporous framework and rich CO 2 -philic site enables such carbon to decrease resistance to mass transfer and show high CO 2 dynamic selectivity over N 2 (454) and CH 4 (11), as well as good CO 2 capacity at 298 K under low CO 2 partial pressure (0.17 bar, a typical CO 2 partial pressure in flue gas). The above attributes make this porous carbon a promising candidate for CO 2 capture from flue gas, methane sources and other relevant applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Macroporous silica–alumina composites with mesoporous walls

Indian Academy of Sciences (India)

Macroporous silica–alumina composites with mesopores have been prepared by employing polymethylmethacrylate beads as templates in the presence of the cationic surfactant, N-cetyl-N,N,N-trimethylammonium bromide. The Si/Al ratio in the composites has been varied between 4.5 and 48 and the occurrence of ...

In vitro biological characterization of macroporous 3D Bonelike structures prepared through a 3D machining technique

International Nuclear Information System (INIS)

Laranjeira, M.S.; Dias, A.G.; Santos, J.D.; Fernandes, M.H.

2009-01-01

3D bioactive macroporous structures were prepared using a 3D machining technique. A virtual 3D structure model was created and a computer numerically controlled (CNC) milling device machined Bonelike samples. The resulting structures showed a reproducible macroporosity and interconnective structure. Macropores size after sintering was approximately 2000 μm. In vitro testing using human bone marrow stroma showed that cells were able to adhere and proliferate on 3D structures surface and migrate into all macropore channels. In addition, these cells were able to differentiate, since mineralized globular structures associated with cell layer were identified. Results obtained showed that 3D structures of Bonelike successfully allow cell migration into all macropores, and allow human bone marrow stromal cells to proliferate and differentiate. This innovative technique may be considered as a step-forward preparation for 3D interconnective macroporous structures that allow bone ingrowth while maintaining mechanical integrity.

Silica-supported Macroporous Chitosan Bead for Affinity Purification of Trypsin Inhibitor

Institute of Scientific and Technical Information of China (English)

Feng Na XI; Jian Min WU; Ming Ming LUAN

2005-01-01

Macroporous cross-linking chitosan layer coated on silica gel (CTS-SiO2) was prepared by phase inversion and polyethylene glycol (PEG) molecular imprinting methods. Formation of macroporous surface was investigated by scanning electron microscopy (SEM) and BET analysis.The prepared bead was activated by reacting with 1,2-ethylene diglycidyl ether for introducing epoxy groups, and trypsin could be efficiently immobilized on the bead as a biospecific ligand.The bead bearing trypsin was employed to purify trypsin inhibitor (TIs) from egg white as affinity adsorbent.

Use of Piggyback Electrolytes for Patients Receiving Individually Prescribed vs Premixed Parenteral Nutrition.

Science.gov (United States)

Busch, Rebecca A; Curtis, Caitlin S; Leverson, Glen E; Kudsk, Kenneth A

2015-07-01

Parenteral nutrition (PN) is available as individualized prescriptions frequently prepared with an automated compounding device or as commercially prepared premixed solutions. Our institution exclusively used individualized PN until an amino acid shortage forced a temporary switch to premixed solutions. In general, premixed solutions contain lower electrolyte levels than individualized formulations prescribed for patients with normal organ function. We aimed to quantify supplemental intravenous piggyback (IVPB) electrolyte use in adult patients receiving individualized and premixed PN and to quantify any effect on difference in the cost of therapy. We compared use of supplemental IVPB electrolytes administered to patients receiving PN during consecutive periods prior to and during the amino acid shortage. Electrolyte IVPBs tabulated were potassium chloride, 10 and 20 mEq; magnesium sulfate, 2 g and 4 g; potassium phosphate, 7.5 and 15 mmol; and sodium phosphate, 7.5 and 15 mmol IVPB. There was no statistical difference in the number of PN formulations administered per day during each period (14.7 ± 3.9 vs 14.0 ± 2.6, individualized vs premixed, respectively). Total IVPB electrolytes prescribed per day increased significantly from the individualized PN period to the premixed PN period (7.03 ± 3.8 vs 13.8 ± 6.8; P Parenteral and Enteral Nutrition.

Buoyant Unstable Behavior of Initially Spherical Lean Hydrogen-Air Premixed Flames

Directory of Open Access Journals (Sweden)

Zuo-Yu Sun

2014-07-01

Full Text Available Buoyant unstable behavior in initially spherical lean hydrogen-air premixed flames within a center-ignited combustion vessel have been studied experimentally under a wide range of pressures (including reduced, normal, and elevated pressures. The experimental observations show that the flame front of lean hydrogen-air premixed flames will not give rise to the phenomenon of cellular instability when the equivalence ratio has been reduced to a certain value, which is totally different from the traditional understanding of the instability characteristics of lean hydrogen premixed flames. Accompanied by the smoothened flame front, the propagation mode of lean hydrogen premixed flames transitions from initially spherical outwardly towards upwardly when the flames expand to certain sizes. To quantitatively investigate such buoyant instability behaviors, two parameters, “float rate (ψ” and “critical flame radius (Rcr”, have been proposed in the present article. The quantitative results demonstrate that the influences of initial pressure (Pint on buoyant unstable behaviors are different. Based on the effects of variation of density difference and stretch rate on the flame front, the mechanism of such buoyant unstable behaviors has been explained by the competition between the stretch force and the results of gravity and buoyancy, and lean hydrogen premixed flames will display buoyant unstable behavior when the stretch effects on the flame front are weaker than the effects of gravity and buoyancy.

21 CFR 170.60 - Nitrites and/or nitrates in curing premixes.

Science.gov (United States)

2010-04-01

... premixes, may continue to be used under prior sanctions in the commercial curing of meat and meat products... that apply to meat curing preparations for the home curing of meat and meat products, including poultry and wild game. To assure safe use of such ingredients the labeling of the premixes shall bear...

A practical technique for the fabrication of highly ordered macroporous structures of inorganic oxides

International Nuclear Information System (INIS)

Tang Fengqiu; Uchikoshi, Tetsuo; Sakka, Yoshio

2006-01-01

Well-defined macroporous ceramics consisting of SiO 2 , TiO 2 and ZrO 2 have been fabricated via a template-assisted colloidal processing technique. Close-packed polymer spheres were first prepared as a template using centrifugation or gravitational sedimentation, followed by infiltration with alkoxide precursors. The centrifugation should be preferred because it is a less time-consuming process and the materials are better ordered. The removal of the template beads was achieved by calcination of the organic-inorganic hybrids at appropriate temperatures, yielding well-ordered macroporous ceramics. The arrangement of the porous structures could be changing the preparation of the packed polymer templates. Some novel arrangements of macropores were obtained in these macroporous ceramics: a simple square-packed arrangement for SiO 2 , the coexistence of hexagonal close-packed and simple close-packed arrangements for TiO 2 , and face-centered cubic packed arrangement for ZrO 2 . The resulting highly structured ceramics could have applications in areas ranging from quantum electronics to photocatalysis and battery materials

Effects of premixed diethyl ether (DEE) on combustion and exhaust emissions in a HCCI-DI diesel engine

International Nuclear Information System (INIS)

Cinar, Can; Can, Ozer; Sahin, Fatih; Yucesu, H. Serdar

2010-01-01

In this study, the effects of premixed ratio of diethyl ether (DEE) on the combustion and exhaust emissions of a single-cylinder, HCCI-DI engine were investigated. The experiments were performed at the engine speed of 2200 rpm and 19 N m operating conditions. The amount of the premixed DEE was controlled by a programmable electronic control unit (ECU) and the DEE injection was conducted into the intake air charge using low pressure injector. The premixed fuel ratio (PFR) of DEE was changed from 0% to 40% and results were compared to neat diesel operation. The percentages of premixed fuel were calculated from the energy ratio of premixed DEE fuel to total energy rate of the fuels. The experimental results show that single stage ignition was found with the addition of premixed DEE fuel. Increasing and phasing in-cylinder pressure and heat release were observed in the premixed stage of the combustion. Lower diffusion combustion was also occurred. Cycle-to cycle variations were very small with diesel fuel and 10% DEE premixed fuel ratio. Audible knocking occurred with 40% DEE premixed fuel ratio. NO x -soot trade-off characteristics were changed and improvements were found simultaneously. NO x and soot emissions decreased up to 19.4% and 76.1%, respectively, while exhaust gas temperature decreased by 23.8%. On the other hand, CO and HC emissions increased.

Effect of air-excess on blends of RON70 partially premixed combustion

NARCIS (Netherlands)

Wang, S.; Bakker, P.C.; Somers, L.M.T.; de Goey, L.P.H.

Partially Premixed Combustion (PPC) is a combustion concept that aims to provide combustion with low smoke and NOx emissions and a high thermal efficiency. Extending the ignition delay to enhance premixing, avoiding spray-driven combustion, and controlling temperature at an optimum level through use

A comparative experimental study on engine operating on premixed charge compression ignition and compression ignition mode

Directory of Open Access Journals (Sweden)

Bhiogade Girish E.

2017-01-01

Full Text Available New combustion concepts have been recently developed with the purpose to tackle the problem of high emissions level of traditional direct injection Diesel engines. A good example is the premixed charge compression ignition combustion. A strategy in which early injection is used causing a burning process in which the fuel burns in the premixed condition. In compression ignition engines, soot (particulate matter and NOx emissions are an extremely unsolved issue. Premixed charge compression ignition is one of the most promising solutions that combine the advantages of both spark ignition and compression ignition combustion modes. It gives thermal efficiency close to the compression ignition engines and resolves the associated issues of high NOx and particulate matter, simultaneously. Premixing of air and fuel preparation is the challenging part to achieve premixed charge compression ignition combustion. In the present experimental study a diesel vaporizer is used to achieve premixed charge compression ignition combustion. A vaporized diesel fuel was mixed with the air to form premixed charge and inducted into the cylinder during the intake stroke. Low diesel volatility remains the main obstacle in preparing premixed air-fuel mixture. Exhaust gas re-circulation can be used to control the rate of heat release. The objective of this study is to reduce exhaust emission levels with maintaining thermal efficiency close to compression ignition engine.

Direct Writing of Three-Dimensional Macroporous Photonic Crystals on Pressure-Responsive Shape Memory Polymers.

Science.gov (United States)

Fang, Yin; Ni, Yongliang; Leo, Sin-Yen; Wang, Bingchen; Basile, Vito; Taylor, Curtis; Jiang, Peng

2015-10-28

Here we report a single-step direct writing technology for making three-dimensional (3D) macroporous photonic crystal patterns on a new type of pressure-responsive shape memory polymer (SMP). This approach integrates two disparate fields that do not typically intersect: the well-established templating nanofabrication and shape memory materials. Periodic arrays of polymer macropores templated from self-assembled colloidal crystals are squeezed into disordered arrays in an unusual shape memory "cold" programming process. The recovery of the original macroporous photonic crystal lattices can be triggered by direct writing at ambient conditions using both macroscopic and nanoscopic tools, like a pencil or a nanoindenter. Interestingly, this shape memory disorder-order transition is reversible and the photonic crystal patterns can be erased and regenerated hundreds of times, promising the making of reconfigurable/rewritable nanooptical devices. Quantitative insights into the shape memory recovery of collapsed macropores induced by the lateral shear stresses in direct writing are gained through fundamental investigations on important process parameters, including the tip material, the critical pressure and writing speed for triggering the recovery of the deformed macropores, and the minimal feature size that can be directly written on the SMP membranes. Besides straightforward applications in photonic crystal devices, these smart mechanochromic SMPs that are sensitive to various mechanical stresses could render important technological applications ranging from chromogenic stress and impact sensors to rewritable high-density optical data storage media.

Highly ordered three-dimensional macroporous carbon spheres for determination of heavy metal ions

International Nuclear Information System (INIS)

Zhang, Yuxiao; Zhang, Jianming; Liu, Yang; Huang, Hui; Kang, Zhenhui

2012-01-01

Highlights: ► Highly ordered three dimensional macroporous carbon spheres (MPCSs) were prepared. ► MPCS was covalently modified by cysteine (MPCS–CO–Cys). ► MPCS–CO–Cys was first time used in electrochemical detection of heavy metal ions. ► Heavy metal ions such as Pb 2+ and Cd 2+ can be simultaneously determined. -- Abstract: An effective voltammetric method for detection of trace heavy metal ions using chemically modified highly ordered three dimensional macroporous carbon spheres electrode surfaces is described. The highly ordered three dimensional macroporous carbon spheres were prepared by carbonization of glucose in silica crystal bead template, followed by removal of the template. The highly ordered three dimensional macroporous carbon spheres were covalently modified by cysteine, an amino acid with high affinities towards some heavy metals. The materials were characterized by physical adsorption of nitrogen, scanning electron microscopy, and transmission electron microscopy techniques. While the Fourier-transform infrared spectroscopy was used to characterize the functional groups on the surface of carbon spheres. High sensitivity was exhibited when this material was used in electrochemical detection (square wave anodic stripping voltammetry) of heavy metal ions due to the porous structure. And the potential application for simultaneous detection of heavy metal ions was also investigated.

Occurrence of the macropore nucleation centers in silicon as result of ion implantation

CERN Document Server

Astrova, E V

2002-01-01

Instead of commonly used V-shaped pits the possibility of application of ion implantation for formation of the regular pattern of macropore nucleation centers has been studied. It is shown that selective radiative damage or local conductivity type conversion are sufficient for generation of macropore nucleation in certain regions and passivation in other ones. Results obtained can be of interest both for practical application and for explanation of pore origin in silicon

Computational aspects of premixing modelling

Energy Technology Data Exchange (ETDEWEB)

Fletcher, D.F. [Sydney Univ., NSW (Australia). Dept. of Chemical Engineering; Witt, P.J.

1998-01-01

In the steam explosion research field there is currently considerable effort being devoted to the modelling of premixing. Practically all models are based on the multiphase flow equations which treat the mixture as an interpenetrating continuum. Solution of these equations is non-trivial and a wide range of solution procedures are in use. This paper addresses some numerical aspects of this problem. In particular, we examine the effect of the differencing scheme for the convective terms and show that use of hybrid differencing can cause qualitatively wrong solutions in some situations. Calculations are performed for the Oxford tests, the BNL tests, a MAGICO test and to investigate various sensitivities of the solution. In addition, we show that use of a staggered grid can result in a significant error which leads to poor predictions of `melt` front motion. A correction is given which leads to excellent convergence to the analytic solution. Finally, we discuss the issues facing premixing model developers and highlight the fact that model validation is hampered more by the complexity of the process than by numerical issues. (author)

A Hierarchically Micro-Meso-Macroporous Zeolite CaA for Methanol Conversion to Dimethyl Ether

Directory of Open Access Journals (Sweden)

Yan Wang

2016-11-01

Full Text Available A hierarchical zeolite CaA with microporous, mesoporous and macroporous structure was hydrothermally synthesized by a ”Bond-Blocking” method using organo-functionalized mesoporous silica (MS as a silica source. The characterization by XRD, SEM/TEM and N2 adsorption/desorption techniques showed that the prepared material had well-crystalline zeolite Linde Type A (LTA topological structure, microspherical particle morphologies, and hierarchically intracrystalline micro-meso-macropores structure. With the Bond-Blocking principle, the external surface area and macro-mesoporosity of the hierarchical zeolite CaA can be adjusted by varying the organo-functionalized degree of the mesoporous silica surface. Similarly, the distribution of the micro-meso-macroporous structure in the zeolite CaA can be controlled purposely. Compared with the conventional microporous zeolite CaA, the hierarchical zeolite CaA as a catalyst in the conversion of methanol to dimethyl ether (DME, exhibited complete DME selectivity and stable catalytic activity with high methanol conversion. The catalytic performances of the hierarchical zeolite CaA results clearly from the micro-meso-macroporous structure, improving diffusion properties, favoring the access to the active surface and avoiding secondary reactions (no hydrocarbon products were detected after 3 h of reaction.

Response of partially premixed flames to acoustic velocity and equivalence ratio perturbations

Energy Technology Data Exchange (ETDEWEB)

Kim, K.T.; Lee, J.G.; Quay, B.D.; Santavicca, D.A. [Center for Advanced Power Generation, Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA (United States)

2010-09-15

This article describes an experimental investigation of the forced response of a swirl-stabilized partially premixed flame when it is subjected to acoustic velocity and equivalence ratio fluctuations. The flame's response is analyzed using phase-resolved CH{sup *} chemiluminescence images and flame transfer function (FTF) measurements, and compared with the response of a perfectly premixed flame under acoustic perturbations. The nonlinear response of the partially premixed flame is manifested by a partial extinction of the reaction zone, leading to rapid reduction of flame surface area. This nonlinearity, however, is observed only when the phase difference between the acoustic velocity and the equivalence ratio at the combustor inlet is close to zero. The condition, {delta}{phi}{sub {phi}}'-V'{approx}0 , indicates that reactant mixtures with high equivalence ratio impinge on the flame front with high velocity, inducing large fluctuations of the rate of heat release. It is found that the phase difference between the acoustic velocity and equivalence ratio nonuniformities is a key parameter governing the linear/nonlinear response of a partially premixed flame, and it is a function of modulation frequency, inlet velocity, fuel injection location, and fuel injector impedance. The results presented in this article will provide insight into the response of a partially premixed flame, which has not been well explored to date. (author)

Comparison Between Premixed and Compounded Parenteral Nutrition Solutions in Hospitalized Patients Requiring Parenteral Nutrition.

Science.gov (United States)

Beattie, Colleen; Allard, Johane; Raman, Maitreyi

2016-04-01

Parenteral nutrition (PN) may be provided through compounded or premixed solutions. To determine the proportion of stable custom-compounded PN prescriptions that would fit within a 20% deviance of an existing premixed PN solution. A retrospective study design was used. Inpatients who received PN in non-critical care units in the preceding year were screened for eligibility. Results are reported descriptively as means (95% confidence intervals) and proportions. We reviewed 97 PN prescriptions that met inclusion criteria. Stable hospital PN prescriptions compared with the reference premixed prescription provided 1838 (1777-1898) vs 1843 (1781-1905) kcal/d, P = .43; dextrose, 266 (254-277) vs 225 (216-234) g/d, P magnesium, 5.4 (4.8-5.4) vs 7.6 (7.4-7.9) mmol/L. Calories and protein were remarkably similar, but dextrose, lipid, and electrolytes differed between hospital PN and the reference premixed prescription. We believe that there may be a role for premixed solutions in quaternary centers in stable non-critically ill patients. © 2016 American Society for Parenteral and Enteral Nutrition.

Ion measurements in premixed methane-oxygen flames

KAUST Repository

Alquaity, Awad; Hourani, Nadim; Chahine, May; Selim, Hatem; Sarathy, Mani; Farooq, Aamir

2014-01-01

Mass Spectrometer (MBMS) is utilized to measure ion concentration profiles in premixed methane-oxygen-argon burner-stabilized flames. Lean, stoichiometric and rich flames at atmospheric pressure are used to study the dependence of ion chemistry

Highly ordered three-dimensional macroporous carbon spheres for determination of heavy metal ions

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yuxiao; Zhang, Jianming [Institute of Functional Nano and Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123 (China); Liu, Yang, E-mail: yangl@suda.edu.cn [Institute of Functional Nano and Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123 (China); Huang, Hui [Institute of Functional Nano and Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123 (China); Kang, Zhenhui, E-mail: zhkang@suda.edu.cn [Institute of Functional Nano and Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123 (China)

2012-04-15

Highlights: Black-Right-Pointing-Pointer Highly ordered three dimensional macroporous carbon spheres (MPCSs) were prepared. Black-Right-Pointing-Pointer MPCS was covalently modified by cysteine (MPCS-CO-Cys). Black-Right-Pointing-Pointer MPCS-CO-Cys was first time used in electrochemical detection of heavy metal ions. Black-Right-Pointing-Pointer Heavy metal ions such as Pb{sup 2+} and Cd{sup 2+} can be simultaneously determined. -- Abstract: An effective voltammetric method for detection of trace heavy metal ions using chemically modified highly ordered three dimensional macroporous carbon spheres electrode surfaces is described. The highly ordered three dimensional macroporous carbon spheres were prepared by carbonization of glucose in silica crystal bead template, followed by removal of the template. The highly ordered three dimensional macroporous carbon spheres were covalently modified by cysteine, an amino acid with high affinities towards some heavy metals. The materials were characterized by physical adsorption of nitrogen, scanning electron microscopy, and transmission electron microscopy techniques. While the Fourier-transform infrared spectroscopy was used to characterize the functional groups on the surface of carbon spheres. High sensitivity was exhibited when this material was used in electrochemical detection (square wave anodic stripping voltammetry) of heavy metal ions due to the porous structure. And the potential application for simultaneous detection of heavy metal ions was also investigated.

Large eddy simulation of turbulent premixed combustion flows over backward facing step

Energy Technology Data Exchange (ETDEWEB)

Park, Nam Seob [Yuhan University, Bucheon (Korea, Republic of); Ko, Sang Cheol [Jeju National University, Jeju (Korea, Republic of)

2011-03-15

Large eddy simulation (LES) of turbulent premixed combustion flows over backward facing step has been performed using a dynamic sub-grid G-equation flamelet model. A flamelet model for the premixed flame is combined with a dynamic sub-grid combustion model for the filtered propagation of flame speed. The objective of this study is to investigate the validity of the dynamic sub-grid G-equation model in a complex turbulent premixed combustion flow. For the purpose of validating the LES combustion model, the LES of isothermal and reacting shear layer formed at a backward facing step is carried out. The calculated results are compared with the experimental results, and a good agreement is obtained.

Large eddy simulation of turbulent premixed combustion flows over backward facing step

International Nuclear Information System (INIS)

Park, Nam Seob; Ko, Sang Cheol

2011-01-01

Large eddy simulation (LES) of turbulent premixed combustion flows over backward facing step has been performed using a dynamic sub-grid G-equation flamelet model. A flamelet model for the premixed flame is combined with a dynamic sub-grid combustion model for the filtered propagation of flame speed. The objective of this study is to investigate the validity of the dynamic sub-grid G-equation model in a complex turbulent premixed combustion flow. For the purpose of validating the LES combustion model, the LES of isothermal and reacting shear layer formed at a backward facing step is carried out. The calculated results are compared with the experimental results, and a good agreement is obtained

Estabilidade térmica das vitaminas A e E em rações e premixes vitamínicos para camarões Thermal stability of vitamins A and E in rations and vitamin premixes for shrimp

Directory of Open Access Journals (Sweden)

João Paulo de Sousa Prado

2011-03-01

Full Text Available O trabalho teve como objetivo avaliar a estabilidade térmica das vitaminas A e E em diferentes rações e premixes vitamínicos utilizados na carcinicultura. Foram utilizadas no experimento três rações comerciais peletilizadas e desintegradas em diferentes diâmetros e dois premixes vitamínicos. As amostras de cada dieta e de premixes foram acondicionadas em recipientes plásticos e armazenadas nas seguintes condições: ambiente refrigerado (6°C±2°C, ambiente climatizado (20°C±3°C e ambiente de estufa (40°C±3°C. Os teores das vitaminas foram determinados em triplicata nas amostras nos períodos 0 (controle, 5, 10, 15, 20, 25 e 30 dias, nas condições anteriormente descritas. Os resultados obtidos mostraram que o percentual médio das perdas de vitamina A nas rações foram de 65, 60 e 68% para os ambientes refrigerado, climatizado e em estufa, respectivamente. Para o premix vitamínico A, o percentual médio de degradação foi de 78 a 87%, observando maiores perdas nos ambiente climatizado e de estufa. Com relação à vitamina E, observou-se nas rações perdas de 88 a 100%, verificando-se perdas totais para o armazenamento em ambiente de refrigeração e estufa. Já o premix vitamínico E as perdas foram de 71 a 82%. Durante o armazenamento da ração e dos premixes vitamínicos, as perdas por degradação térmica demonstraram falta de estabilidade das vitaminas lipossolúveis na estrutura das rações e premixes, utilizados na alimentação de camarões.The study aimed to evaluate the thermal stability of vitamins A and E on different rations and vitamin premixes used in shrimp farming. Three commercial rations pelleted and disintegrated in two different diameters and two vitamin premixes were used in the experiment. Samples of each ration and premixes were placed in plastic containers and stored under the following conditions: refrigerated environment (6°C±2°C, acclimatized environment (20°C±3°C and greenhouse

Structure, MC3T3-E1 cell response, and osseointegration of macroporous titanium implants covered by a bioactive microarc oxidation coating with microporous structure.

Science.gov (United States)

Zhou, Rui; Wei, Daqing; Cheng, Su; Feng, Wei; Du, Qing; Yang, Haoyue; Li, Baoqiang; Wang, Yaming; Jia, Dechang; Zhou, Yu

2014-04-09

Macroporous Ti with macropores of 50-400 μm size is prepared by sintering Ti microbeads with different diameters of 100, 200, 400, and 600 μm. Bioactive microarc oxidation (MAO) coatings with micropores of 2-5 μm size are prepared on the macroporous Ti. The MAO coatings are composed of a few TiO2 nanocrystals and lots of amorphous phases with Si, Ca, Ti, Na, and O elements. Compared to compact Ti, the MC3T3-E1 cell attachment is prolonged on macroporous Ti without and with MAO coatings; however, the cell proliferation number increases. These results are contributed to the effects of the space structure of macroporous Ti and the surface chemical feature and element dissolution of the MAO coatings during the cell culture. Macroporous Ti both without and with MAO coatings does not cause any adverse effects in vivo. The new bone grows well into the macropores and micropores of macroporous Ti with MAO coatings, showing good mechanical properties in vivo compared to Ti, MAO-treated Ti, and macroporous Ti because of its excellent osseointegration. Moreover, the MAO coatings not only show a high interface bonding strength with new bones but also connect well with macroporous Ti. Furthermore, the pushing out force for macroporous Ti with MAO coatings increases significantly with increasing microbead diameter.

Premixed combustion on ceramic foam burners

NARCIS (Netherlands)

Bouma, P.H.; Goey, de L.P.H.

1999-01-01

Combustion of a lean premixed methane–air mixture stabilized on a ceramic foam burner has been studied. The stabilization of the flame in the radiant mode has been simulated using a one-dimensional numerical model for a burner stabilized flat-flame, taking into account the heat transfer between the

Fast plasma sintering delivers functional graded materials components with macroporous structures and osseointegration properties.

Science.gov (United States)

Godoy, R F; Coathup, M J; Blunn, G W; Alves, A L; Robotti, P; Goodship, A E

2016-04-13

We explored the osseointegration potential of two macroporous titanium surfaces obtained using fast plasma sintering (FPS): Ti macroporous structures with 400-600 µmØ pores (TiMac400) and 850-1000 µmØ pores (TiMac850). They were compared against two surfaces currently in clinical use: Ti-Growth® and air plasma spray (Ti-Y367). Each surface was tested, once placed over a Ti-alloy and once onto a CoCr bulk substrate. Implants were placed in medial femoral condyles in 24 sheep. Samples were explanted at four and eight weeks after surgery. Push-out loads were measured using a material-testing system. Bone contact and ingrowth were assessed by histomorphometry and SEM and EDX analyses. Histology showed early osseointegration for all the surfaces tested. At 8 weeks, TiMac400, TiMac850 and Ti-Growth® showed deep bone ingrowth and extended colonisation with newly formed bone. The mechanical push-out force was equal in all tested surfaces. Plasma spray surfaces showed greater bone-implant contact and higher level of pores colonisation with new bone than FPS produced surfaces. However, the void pore area in FPS specimens was significantly higher, yet the FPS porous surfaces allowed a deeper osseointegration of bone to implant. FPS manufactured specimens showed similar osseointegration potential to the plasma spray surfaces for orthopaedic implants. FPS is a useful technology for manufacturing macroporous titanium surfaces. Furthermore, its capability to combine two implantable materials, using bulk CoCr with macroporous titanium surfaces, could be of interest as it enables designers to conceive and manufacture innovative components. FPS delivers functional graded materials components with macroporous structures optimised for osseointegration.

Crossed-Plane Imaging of Premixed Turbulent Combustion Processes

National Research Council Canada - National Science Library

Gouldin, F

2003-01-01

.... Rayleigh scattering from premixed flames can be used for temperature imaging, and we have developed crossed-plane Rayleigh imaging in order to measure with high-resolution instantaneous temperature...

Thermal stability of vitamins A and E in rations and vitamin premixes for shrimp

OpenAIRE

Prado, João Paulo de Sousa; Cavalheiro, José Marcelino Oliveira; Silva, Fernanda Vanessa Gomes da; Queiroga Neto, Vicente; Bora, Pushkar Singh; Cavalheiro, Thiago Brandão

2011-01-01

O trabalho teve como objetivo avaliar a estabilidade térmica das vitaminas A e E em diferentes rações e premixes vitamínicos utilizados na carcinicultura. Foram utilizadas no experimento três rações comerciais peletilizadas e desintegradas em diferentes diâmetros e dois premixes vitamínicos. As amostras de cada dieta e de premixes foram acondicionadas em recipientes plásticos e armazenadas nas seguintes condições: ambiente refrigerado (6°C±2°C), ambiente climatizado (20°C&p...

Dense and porous titanium substrates with a biomimetic calcium phosphate coating

Energy Technology Data Exchange (ETDEWEB)

Ribeiro, A.A., E-mail: aantunesr@yahoo.com.br [Powder Technology Laboratory, Materials Processing and Characterization Division, National Institute of Technology, No. 82 Venezuela Avenue, Room 602, 20081-312 Rio de Janeiro, RJ (Brazil); Balestra, R.M. [Powder Technology Laboratory, Materials Processing and Characterization Division, National Institute of Technology, No. 82 Venezuela Avenue, Room 602, 20081-312 Rio de Janeiro, RJ (Brazil); Rocha, M.N. [Metallurgical and Materials Engineering Program, COPPE, Federal University of Rio de Janeiro, P.O. Box 68505, 21941-972 Rio de Janeiro, RJ (Brazil); Peripolli, S.B. [Materials Metrology Division, National Institute of Metrology, Normalization and Quality, No. 50 Nossa Senhora das Gracas Street, Building 3, 25250-020 Duque de Caxias, RJ (Brazil); Andrade, M.C. [Polytechnic Institute of Rio de Janeiro, Rio de Janeiro State University, s/n, Alberto Rangel Street, 28630-050 Nova Friburgo, RJ (Brazil); Pereira, L.C. [Metallurgical and Materials Engineering Program, COPPE, Federal University of Rio de Janeiro, P.O. Box 68505, 21941-972 Rio de Janeiro, RJ (Brazil); Oliveira, M.V. [Powder Technology Laboratory, Materials Processing and Characterization Division, National Institute of Technology, No. 82 Venezuela Avenue, Room 602, 20081-312 Rio de Janeiro, RJ (Brazil)

2013-01-15

Highlights: Black-Right-Pointing-Pointer A biomimetic coating method with simplified solution is proposed. Black-Right-Pointing-Pointer Titanium substrates are submitted to chemical and heat treatments. Black-Right-Pointing-Pointer Titanium substrates are coated with biocompatible calcium phosphate phases. Black-Right-Pointing-Pointer The simplified solution shows potential to be applied as a coating technique. - Abstract: The present work studied a biomimetic method using a simplified solution (SS) with calcium and phosphorus ions for coating titanium substrates, in order to improve their bioactivity. Commercially pure titanium dense sheet, microporous and macroporous titanium samples, both produced by powder metallurgy, were treated in NaOH solution followed by heat-treating and immersed in SS for 7, 14 or 21 days. The samples characterization was performed by quantitative metallographic analysis, confocal scanning optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and low angle X-ray diffraction. The results showed coatings with calcium phosphate precipitation in all samples, with globular or plate-like morphology, typical of hydroxyapatite and octacalcium phosphate, respectively, indicating that the solution (SS) has potential for coating titanium substrates. In addition, the different surfaces of substrates had an effect on the formed calcium phosphate phase and thickness of coatings, depending on the substrate type and imersion time in the simplified solution.

Effects of the hydraulic conductivity of the matrix/macropore interface on cumulative infiltrations into dual-permeability media

Science.gov (United States)

Lassabatere, L.; Peyrard, X.; Angulo-Jaramillo, R.; Simunek, J.

2009-12-01

Modeling of water infiltration into the vadose zone is important for better understanding of movement of water-transported contaminants. There is a great need to take into account the soil heterogeneity and, in particular, the presence of macropores or cracks that could generate preferential flow. Several mathematical models have been proposed to describe unsaturated flow through heterogeneous soils. The dual-permeability model (referred to as the 2K model) assumes that flow is governed by Richards equation in both porous regions (matrix and macropores). Water can be exchanged between the two regions following a first-order rate law. Although several studies have dealt with such modeling, no study has evaluated the influence of the hydraulic conductivity of the matrix/macropore interface on water cumulative infiltration. And this is the focus of this study. An analytical scaling method reveals the role of the following main parameters for given boundary and initial conditions: the saturated hydraulic conductivity ratio (R_Ks), the water pressure scale parameter ratio (R_hg), the saturated volumetric water content ratio (R_θs), and the shape parameters of the water retention and hydraulic conductivity functions. The last essential parameter is related to the interfacial hydraulic conductivity (Ka) between the macropore and matrix regions. The scaled 2K flow equations were solved using HYDRUS-1D 4.09 for the specific case of water infiltrating into an initially uniform soil profile and a zero pressure head at the soil surface. A sensitivity of water infiltration was studied for different sets of scale parameters (R_Ks, R_hg, R_θs, and shape parameters) and the scaled interfacial conductivity (Ka). Numerical results illustrate two extreme behaviors. When the interfacial conductivity is zero (i.e., no water exchange), water infiltrates separately into matrix and macropore regions, producing a much deeper moisture front in the macropore domain. In the opposite case

Large-scale synthesis of macroporous SnO2 with/without carbon and their application as anode materials for lithium-ion batteries

International Nuclear Information System (INIS)

Wang Fei; Yao Gang; Xu Minwei; Zhao Mingshu; Sun Zhanbo; Song Xiaoping

2011-01-01

Highlights: → A new hard template prepared from glucose was used to synthesize macroporous SnO 2 . → SnO 2 and SnO 2 /C were prepared in a simple and large-scale synthetic method. → Combining the nanostructure design and active/inactive nanocomposite concept. → The obtained SnO 2 /C composite exhibited superior cycling performance. - Abstract: The macroporous SnO 2 is prepared using close packed carbonaceous sphere template which synthesized from glucose by hydrothermal method. The structure and morphology of the macroporous SnO 2 are evaluated by XRD and FE-SEM. The average pore size of the macroporous SnO 2 is about 190 nm and its wall thickness is less than 10 nm. When the macroporous SnO 2 filled with carbon is used as an anode material for lithium-ion battery, the capacity is about 380 mAh g -1 after 70 cycles. The improved cyclability is attributed to the carbon matrix which is used as an effective physical buffer to prevent the collapse of the well dispersed macroporous SnO 2 .

Premixed burner experiments: Geometry, mixing, and flame structure issues

Energy Technology Data Exchange (ETDEWEB)

Gupta, A.K.; Lewis, M.J.; Gupta, M. [Univ of Maryland, College Park, MD (United States)] [and others

1995-10-01

This research program is exploring techniques for improved fuel-air mixing, with the aim of achieving combustor operations up to stoichiometric conditions with minimal NO x and maximum efficiency. The experimental studies involve the use of a double-concentric natural gas burner that is operable in either premixed or non-premixed modes, and the system allows systematic variation of equivalence ratio, swirl strength shear length region and flow momentum in each annulus. Flame structures formed with various combinations of swirl strengths, flow throughput and equivalence ratios in premixed mode show the significant impact of swirl flow distribution on flame structure emanating from the mixedness. This impact on flame structure is expected to have a pronounced effect on the heat release rate and the emission of NO{sub x}. Thus, swirler design and configuration remains a key factor in the quest for completely optimized combustion. Parallel numerical studies of the flow and combustion phenomena were carried out, using the RSM and thek-{epsilon} turbulence models. These results have not only indicated the strengths and limitations of CFD in performance and pollutants emission predictions, but have provided guidelines on the size and strength of the recirculation produced and the spatio-temporal structure of the combustion flowfield. The first stage of parametric studies on geometry and operational parameters at Morgan State University have culminated in the completion of a one-dimensional flow code that is integrated with a solid, virtual model of the existing premixed burner. This coupling will provide the unique opportunity to study the impact of geometry on the flowfield and vice-versa, with particular emphasis on concurrent design optimization.

Subgrid scale modeling in large-Eddy simulation of turbulent combustion using premixed fdlamelet chemistry

NARCIS (Netherlands)

Vreman, A.W.; Oijen, van J.A.; Goey, de L.P.H.; Bastiaans, R.J.M.

2009-01-01

Large-eddy simulation (LES) of turbulent combustion with premixed flamelets is investigated in this paper. The approach solves the filtered Navier-Stokes equations supplemented with two transport equations, one for the mixture fraction and another for a progress variable. The LES premixed flamelet

An Investigation of a Hybrid Mixing Model for PDF Simulations of Turbulent Premixed Flames

Science.gov (United States)

Zhou, Hua; Li, Shan; Wang, Hu; Ren, Zhuyin

2015-11-01

Predictive simulations of turbulent premixed flames over a wide range of Damköhler numbers in the framework of Probability Density Function (PDF) method still remain challenging due to the deficiency in current micro-mixing models. In this work, a hybrid micro-mixing model, valid in both the flamelet regime and broken reaction zone regime, is proposed. A priori testing of this model is first performed by examining the conditional scalar dissipation rate and conditional scalar diffusion in a 3-D direct numerical simulation dataset of a temporally evolving turbulent slot jet flame of lean premixed H2-air in the thin reaction zone regime. Then, this new model is applied to PDF simulations of the Piloted Premixed Jet Burner (PPJB) flames, which are a set of highly shear turbulent premixed flames and feature strong turbulence-chemistry interaction at high Reynolds and Karlovitz numbers. Supported by NSFC 51476087 and NSFC 91441202.

Monodispersed macroporous architecture of nickel-oxide film as an anode material for thin-film lithium-ion batteries

International Nuclear Information System (INIS)

Wu, Mao-Sung; Lin, Ya-Ping

2011-01-01

A nickel-oxide film with monodispersed open macropores was prepared on a stainless-steel substrate by electrophoretic deposition of a polystyrene-sphere monolayer followed by anodic electrodeposition of nickel oxy-hydroxide. The deposited films convert to cubic nickel oxide after annealing at 400 o C for 1 h. Galvanostatic charge and discharge results indicate that the nickel-oxide film with monodispersed open macropores is capable of delivering a higher capacity than the bare nickel-oxide film, especially in high-rate charge and discharge processes. The lithiation capacity of macroporous nickel oxide reaches 1620 mA h g -1 at 1 C current discharge and decreases to 990 mA h g -1 at 15 C current discharge. The presence of monodispersed open macropores in the nickel-oxide film might facilitate the electrolyte penetration, diffusion, and migration. Electrochemical reactions between nickel oxide and lithium ions are therefore markedly improved by this tailored film architecture.

Nanocrystals-based Macroporous Materials Synthesized by Freeze-drying Combustion

International Nuclear Information System (INIS)

Yan, Ruiqiang; Chen, Yu; Lin, Ye; Chen, Fanglin

2016-01-01

We present a novel freeze-drying combustion method for synthesis of macroporous powders with nano-network, using Sm 0.2 Ce 0.8 O 1.9 (SDC) as an example. The metal nitrate salt solution mixed with glycine is frozen to form homogeneous nitrate/glycine mixture and then freeze-dried through sublimation of ice crystals. Upon combustion of the freeze-dried mixture, SDC powders with macroporous microstructure consisting of 10–20 nm nanocrystals, high surface area and excellent sinterability are achieved. High resolution transmission electron microscopy (HRTEM) analysis indicates that nanodomains due to aggregation/segregation of dopants in the SDC powders obtained from freeze-drying combustion are much smaller than those in the SDC powders synthesized by the conventional nitrate solution combustion approach, demonstrating better elemental homogeneity and improved conductivity. Using low cost precursors and simple processing conditions, freeze-drying combustion can be a versatile method to synthesize nanocrystalline powders with excellent composition homogeneity for broad applications.

Dry low NOx combustion system with pre-mixed direct-injection secondary fuel nozzle

Science.gov (United States)

Zuo, Baifang; Johnson, Thomas; Ziminsky, Willy; Khan, Abdul

2013-12-17

A combustion system includes a first combustion chamber and a second combustion chamber. The second combustion chamber is positioned downstream of the first combustion chamber. The combustion system also includes a pre-mixed, direct-injection secondary fuel nozzle. The pre-mixed, direct-injection secondary fuel nozzle extends through the first combustion chamber into the second combustion chamber.

A combined single-multiphase flow formulation of the premixing phase using the level set method

International Nuclear Information System (INIS)

Leskovar, M.; Marn, J.

1999-01-01

The premixing phase of a steam explosion covers the interaction of the melt jet or droplets with the water prior to any steam explosion occurring. To get a better insight of the hydrodynamic processes during the premixing phase beside hot premixing experiments, where the water evaporation is significant, also cold isothermal premixing experiments are performed. The specialty of isothermal premixing experiments is that three phases are involved: the water, the air and the spheres phase, but only the spheres phase mixes with the other two phases whereas the water and air phases do not mix and remain separated by a free surface. Our idea therefore was to treat the isothermal premixing process with a combined single-multiphase flow model. In this combined model the water and air phase are treated as a single phase with discontinuous phase properties at the water air interface, whereas the spheres are treated as usually with a multiphase flow model, where the spheres represent the dispersed phase and the common water-air phase represents the continuous phase. The common water-air phase was described with the front capturing method based on the level set formulation. In the level set formulation, the boundary of two-fluid interfaces is modeled as the zero set of a smooth signed normal distance function defined on the entire physical domain. The boundary is then updated by solving a nonlinear equation of the Hamilton-Jacobi type on the whole domain. With this single-multiphase flow model the Queos isothermal premixing Q08 has been simulated. A numerical analysis using different treatments of the water-air interface (level set, high-resolution and upwind) has been performed for the incompressible and compressible case and the results were compared to experimental measurements.(author)

TRANSPLANTATION OF CRYOPRESERVED FETAL LIVER CELLS SEEDED INTO MACROPOROUS ALGINATE-GELATIN SCAFFOLDS IN RATS WITH LIVER FAILURE

Directory of Open Access Journals (Sweden)

D. V. Grizay

2015-01-01

Full Text Available Aim. To study the therapeutic potential of cryopreserved fetal liver cells seeded into macroporous alginategelatin scaffolds after implantation to omentum of rats with hepatic failure.Materials and methods.Hepatic failure was simulated by administration of 2-acetyl aminofl uorene followed partial hepatectomy. Macroporous alginate-gelatin scaffolds, seeded with allogenic cryopreserved fetal liver cells (FLCs were implanted into rat omentum. To prevent from colonization of host cells scaffolds were coated with alginate gel shell. Serum transaminase activity, levels of albumin and bilirubin as markers of hepatic function were determined during 4 weeks after failure model formation and scaffold implantation. Morphology of liver and scaffolds after implantation were examined histologically. Results. Macroporous alginate-gelatin scaffolds after implantation to healthy rats were colonized by host cells. Additional formation of alginate gel shell around scaffolds prevented the colonization. Implantation of macroporous scaffolds seeded with cryopreserved rat FLCs and additionally coated with alginate gel shell into omentum of rats with hepatic failure resulted in signifi cant improvement of hepatospecifi c parameters of the blood serum and positive changes of liver morphology. The presence of cells with their extracellular matrix within the scaffolds was confi rmed after 4 weeks post implantation.Conclusion. The data above indicate that macroporous alginate-gelatin scaffolds coated with alginate gel shell are promising cell carriers for the development of bioengineered liver equivalents.

Swozzle based burner tube premixer including inlet air conditioner for low emissions combustion

Science.gov (United States)

Tuthill, Richard Sterling; Bechtel, II, William Theodore; Benoit, Jeffrey Arthur; Black, Stephen Hugh; Bland, Robert James; DeLeonardo, Guy Wayne; Meyer, Stefan Martin; Taura, Joseph Charles; Battaglioli, John Luigi

2002-01-01

A burner for use in a combustion system of a heavy-duty industrial gas turbine includes a fuel/air premixer having an air inlet, a fuel inlet, and an annular mixing passage. The fuel/air premixer mixes fuel and air into a uniform mixture for injection into a combustor reaction zone. The burner also includes an inlet flow conditioner disposed at the air inlet of the fuel/air premixer for controlling a radial and circumferential distribution of incoming air. The pattern of perforations in the inlet flow conditioner is designed such that a uniform air flow distribution is produced at the swirler inlet annulus in both the radial and circumference directions. The premixer includes a swozzle assembly having a series of preferably air foil shaped turning vanes that impart swirl to the airflow entering via the inlet flow conditioner. Each air foil contains internal fuel flow passages that introduce natural gas fuel into the air stream via fuel metering holes that pass through the walls of the air foil shaped turning vanes. By injecting fuel in this manner, an aerodynamically clean flow field is maintained throughout the premixer. By injecting fuel via two separate passages, the fuel/air mixture strength distribution can be controlled in the radial direction to obtain optimum radial concentration profiles for control of emissions, lean blow outs, and combustion driven dynamic pressure activity as machine and combustor load are varied.

The effects of pre-mix on burn in ICF capsules

International Nuclear Information System (INIS)

Wilson, D C; Kyrala, G A; Jr, J F Benage; Wysocki, F J; Gunderson, M A; Herrman, H W; Cooley, J H; Welser-Sherrill, L; Garbett, W J; Horsfield, C J; Glebov, V Y; Yaakobi, B; Roberts, S A; Frenje, J

2008-01-01

Directly driven implosions at the Omega laser have tested the effects of pre-mix of Ar, Kr, and Xe in D 2 + 3 He filled glass micro-balloons. Diagnostics included: D+D and D+T neutron yields, D+ 3 He proton yields and spectra, Doppler broadened ion temperatures, time dependent neutron and proton burn rates, and time gated, high energy filtered, X-ray images. Yields are better calculated by XSN LTE than by non-LTE. Yields with a small amount of pre-mix, atom fractions of ∼5e-3 for Ar, 2e-3 Kr, and Xe for 5e-4, are more degraded than calculated, while the measured ion temperatures are the same as without pre-mix. There is also a decrease in fuel ρr. The neutron burn histories suggest that the early yield coming before the reflected shock strikes the incoming shell is un-degraded, with yield degradation occurring afterwards. Adding 20 atm % 3 He to pure D fuel seems to produce a similar degradation. Calculated gated X-ray images agree with observed when the reflected shock strikes the incoming shell, but are smaller than observed afterward. This partially explains yield degradation and both the low fuel and whole capsule ρr's observed in secondary T+D neutrons and slowing of the D+ 3 He protons. Neither LTE on non-LTE captures the degradation by 3 He or at low pre-mix levels, nor matches the large shell radii after impact of the reflected shock

Fate and transport of selected estrogen compounds in Hawaii soils: Effect of soil type and macropores

Science.gov (United States)

D'Alessio, Matteo; Vasudevan, Dharni; Lichwa, Joseph; Mohanty, Sanjay K.; Ray, Chittaranjan

2014-10-01

The fate and transport of estrogen compounds in the environment is of increasing concern due to their potential impact on freshwater organisms, ecosystems and human health. The behavior of these compounds in batch experiments suggests low mobility, while field studies indicate the persistence of estrogen compounds in the soil with the possibility of migration to surface water as well as groundwater. To better understand the movement of these chemicals through soils, we examined their transport in three different Hawaiian soils and two aqueous matrices. The three different soils used were an Oxisol, a Mollisol and a cinder, characterized by different mineralogical properties and collected at depths of 60-90 cm and 210-240 cm. Two liquid matrices were used; deionized (DI) water containing calcium chloride (CaCl2), and recycled water collected from a wastewater treatment facility. The experiments were conducted in packed and structured columns. Non-equilibrium conditions were observed during the study, especially in the structured soil. This is believed to be primarily related to the presence of macropores in the soil. The presence of macropores resulted in reduced contact time between soil and estrogens, which facilitated their transport. We found that the organic carbon content and mineralogical composition of the soils had a profound effect on the transport of the estrogens. The mobility of estrone (E1) and 17β-estradiol (E2) was greater in cinder than in the other soils. In column experiments with recycled water, earlier breakthrough peaks and longer tails of estrogens were produced compared to those observed using DI water. The use of recycled water for agricultural purposes and the siting of septic tanks and cesspools should be critically reviewed in light of these findings, especially in areas where groundwater is the primary source of potable water, such as Hawaii.

Fate and transport of selected estrogen compounds in Hawaii soils: effect of soil type and macropores.

Science.gov (United States)

D'Alessio, Matteo; Vasudevan, Dharni; Lichwa, Joseph; Mohanty, Sanjay K; Ray, Chittaranjan

2014-10-01

The fate and transport of estrogen compounds in the environment is of increasing concern due to their potential impact on freshwater organisms, ecosystems and human health. The behavior of these compounds in batch experiments suggests low mobility, while field studies indicate the persistence of estrogen compounds in the soil with the possibility of migration to surface water as well as groundwater. To better understand the movement of these chemicals through soils, we examined their transport in three different Hawaiian soils and two aqueous matrices. The three different soils used were an Oxisol, a Mollisol and a cinder, characterized by different mineralogical properties and collected at depths of 60-90 cm and 210-240 cm. Two liquid matrices were used; deionized (DI) water containing calcium chloride (CaCl2), and recycled water collected from a wastewater treatment facility. The experiments were conducted in packed and structured columns. Non-equilibrium conditions were observed during the study, especially in the structured soil. This is believed to be primarily related to the presence of macropores in the soil. The presence of macropores resulted in reduced contact time between soil and estrogens, which facilitated their transport. We found that the organic carbon content and mineralogical composition of the soils had a profound effect on the transport of the estrogens. The mobility of estrone (E1) and 17β-estradiol (E2) was greater in cinder than in the other soils. In column experiments with recycled water, earlier breakthrough peaks and longer tails of estrogens were produced compared to those observed using DI water. The use of recycled water for agricultural purposes and the siting of septic tanks and cesspools should be critically reviewed in light of these findings, especially in areas where groundwater is the primary source of potable water, such as Hawaii. Copyright © 2014 Elsevier B.V. All rights reserved.

Amphiphilic polymer promoted assembly of macroporous graphene/SnO2 frameworks with tunable porosity for high-performance lithium storage.

Science.gov (United States)

Huang, Yanshan; Wu, Dongqing; Wang, Jinzuan; Han, Sheng; Lv, Lu; Zhang, Fan; Feng, Xinliang

2014-06-12

3D macroporous graphene/SnO2 frameworks (MGTFs) are fabricated by amphiphilic polymer-promoted assembly method, which exhibit controllable macroporous structure and outstanding lithium storage performance. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ion measurements in premixed methane-oxygen flames

KAUST Repository

Alquaity, Awad

2014-07-25

Ions are formed as a result of chemi-ionization processes in combustion systems. Recently, there has been an increasing interest in understanding flame ion chemistry due to the possible application of external electric fields to reduce emissions and improve combustion efficiency by active control of combustion process. In order to predict the effect of external electric fields on combustion plasma, it is critical to gain a good understanding of the flame ion chemistry. In this work, a Molecular Beam Mass Spectrometer (MBMS) is utilized to measure ion concentration profiles in premixed methane-oxygen-argon burner-stabilized flames. Lean, stoichiometric and rich flames at atmospheric pressure are used to study the dependence of ion chemistry on equivalence ratio of premixed flames. The relative ion concentration profiles are compared qualitatively with previous methane-oxygen studies and show good agreement. The relative ion concentration data obtained in the present study can be used to validate and improve ion chemistry models for methane-oxygen flames.

[Investigation on the process of sapindus saponin purified with macroporous adsorption resin and screening of its bacteriostasis].

Science.gov (United States)

Fu, Yong; Lei, Peng; Han, Yu-mei; Yan, Dan

2010-02-01

To study the technological parameters of the purification process of saponins with macroporous adsorption resin. The adsorptive characteristics and elutive parameters of the process were studied by taking the elutive and purified ratio of saponins as markers. Bacteriostasis activity of each parts eluted was evaluated by the mean of cup-plate method. 13.6 mL of the extraction of sapindus saponin (crude drugs 0.01 g/mL) was purified with a column of macroporous adsorption resin (phi15 mm x H90 mm, dry weight 2.5 g) and washed with 3BV of distilled water, then eluted with 3BV of 30% ethanol and 3BV of 70% ethanol, most of saponins were collected in the 70% ethanol. With macroporous adsorption resin adsorbing and purifying, the elutive ratio of saponins was 93.8% and the purity reached 250.1%. So this process of applying macroporous adsorption resin to adsorb and purify saponins is feasible, and supplies reference to the purification of other types of saponin.

The flow field structure of highly stabilized partially premixed flames in a concentric flow conical nozzle burner with coflow

KAUST Repository

Elbaz, Ayman M.

2015-08-29

The stability limits, the stabilization mechanism, and the flow field structure of highly stabilized partially premixed methane flames in a concentric flow conical nozzle burner with air co-flow have been investigated and presented in this work. The stability map of partial premixed flames illustrates that the flames are stable between two extinction limits. A low extinction limit when partial premixed flames approach non-premixed flame conditions, and a high extinction limit, with the partial premixed flames approach fully premixed flame conditions. These two limits showed that the most stable flame conditions are achieved at a certain degree of partial premixed. The stability is improved by adding air co-flow. As the air co-flow velocity increases the most stable flames are those that approach fully premixed. The turbulent flow field of three flames at 0, 5, 10 m/s co-flow velocity are investigated using Stereo Particle Image Velocimetry (SPIV) in order to explore the improvement of the flame stability due to the use of air co-flow. The three flames are all at a jet equivalence ratio (Φj) of 2, fixed level of partial premixing and jet Reynolds number (Rej) of 10,000. The use of co-flow results in the formation of two vortices at the cone exit. These vortices act like stabilization anchors for the flames to the nozzle tip. With these vortices in the flow field, the reaction zone shifts toward the reduced turbulence intensity at the nozzle rim of the cone. Interesting information about the structure of the flow field with and without co-flow are identified and reported in this work.

Thermal-Conductivity Studies of Macro-porous Polymer-Derived SiOC Ceramics

Science.gov (United States)

Qiu, L.; Li, Y. M.; Zheng, X. H.; Zhu, J.; Tang, D. W.; Wu, J. Q.; Xu, C. H.

2014-01-01

A three-dimensional reticular macro-porous SiOC ceramics structure, made of spherical agglomerates, has been thermally characterized using a freestanding sensor-based method. The effective thermal conductivity of the macro-porous SiOC ceramics, including the effects of voids, is found to be to at room temperature, comparable with that of alumina aerogel or carbon aerogel. These results suggest that SiOC ceramics hold great promise as a thermal insulation material for use at high temperatures. The measured results further reveal that the effective thermal conductivity is limited by the low solid-phase volume fraction for the SiOC series processed at the same conditions. For SiOC ceramics processed under different pyrolysis temperatures, the contact condition between neighboring particles in the SiOC networks is another key factor influencing the effective thermal conductivity.

Preparation of thin layer materials with macroporous microstructure for SOFC applications

International Nuclear Information System (INIS)

Marrero-Lopez, D.; Ruiz-Morales, J.C.; Pena-Martinez, J.; Canales-Vazquez, J.; Nunez, P.

2008-01-01

A facile and versatile method using polymethyl methacrylate (PMMA) microspheres as pore formers has been developed to prepare thin layer oxide materials with controlled macroporous microstructure. Several mixed oxides with fluorite and perovskite-type structures, i.e. doped zirconia, ceria, ferrites, manganites, and NiO-YSZ composites have been prepared and characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption and mercury porosimetry. The synthesised materials are nanocrystalline and present a homogeneous pore distribution and relatively high specific surface area, which makes them interesting for SOFC and catalysis applications in the intermediate temperature range. - Graphical abstract: Thin films materials of mixed oxides with potential application in SOFC devices have been prepared with macroporous microstructure using PMMA microspheres as pore formers. Display Omitted

Micropore-induced capillarity enhances bone distribution in vivo in biphasic calcium phosphate scaffolds.

Science.gov (United States)

Rustom, Laurence E; Boudou, Thomas; Lou, Siyu; Pignot-Paintrand, Isabelle; Nemke, Brett W; Lu, Yan; Markel, Mark D; Picart, Catherine; Wagoner Johnson, Amy J

2016-10-15

The increasing demand for bone repair solutions calls for the development of efficacious bone scaffolds. Biphasic calcium phosphate (BCP) scaffolds with both macropores and micropores (MP) have improved healing compared to those with macropores and no micropores (NMP), but the role of micropores is unclear. Here, we evaluate capillarity induced by micropores as a mechanism that can affect bone growth in vivo. Three groups of cylindrical scaffolds were implanted in pig mandibles for three weeks: MP were implanted either dry (MP-Dry), or after submersion in phosphate buffered saline, which fills pores with fluid and therefore suppresses micropore-induced capillarity (MP-Wet); NMP were implanted dry. The amount and distribution of bone in the scaffolds were quantified using micro-computed tomography. MP-Dry had a more homogeneous bone distribution than MP-Wet, although the average bone volume fraction, BVF‾, was not significantly different for these two groups (0.45±0.03 and 0.37±0.03, respectively). There was no significant difference in the radial bone distribution of NMP and MP-Wet, but the BVF‾, of NMP was significantly lower among the three groups (0.25±0.02). These results suggest that micropore-induced capillarity enhances bone regeneration by improving the homogeneity of bone distribution in BCP scaffolds. The explicit design and use of capillarity in bone scaffolds may lead to more effective treatments of large and complex bone defects. The increasing demand for bone repair calls for more efficacious bone scaffolds and calcium phosphate-based materials are considered suitable for this application. Macropores (>100μm) are necessary for bone ingrowth and vascularization. However, studies have shown that microporosity (micropore-induced capillarity had the potential to enhance bone growth in vivo. This work illustrates the positive effects of capillarity on bone regeneration in vivo; it demonstrates that micropore-induced capillarity significantly

Large-scale synthesis of macroporous SnO{sub 2} with/without carbon and their application as anode materials for lithium-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Wang Fei; Yao Gang; Xu Minwei [MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, School of Science, Xi' an Jiaotong University, Shaan Xi 710049 (China); Zhao Mingshu, E-mail: zhaomshu@mail.xjtu.edu.cn [MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, School of Science, Xi' an Jiaotong University, Shaan Xi 710049 (China); Sun Zhanbo [MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, School of Science, Xi' an Jiaotong University, Shaan Xi 710049 (China); Song Xiaoping, E-mail: xpsong@mail.xjtu.edu.cn [MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, School of Science, Xi' an Jiaotong University, Shaan Xi 710049 (China)

2011-05-19

Highlights: > A new hard template prepared from glucose was used to synthesize macroporous SnO{sub 2}. > SnO{sub 2} and SnO{sub 2}/C were prepared in a simple and large-scale synthetic method. > Combining the nanostructure design and active/inactive nanocomposite concept. > The obtained SnO{sub 2}/C composite exhibited superior cycling performance. - Abstract: The macroporous SnO{sub 2} is prepared using close packed carbonaceous sphere template which synthesized from glucose by hydrothermal method. The structure and morphology of the macroporous SnO{sub 2} are evaluated by XRD and FE-SEM. The average pore size of the macroporous SnO{sub 2} is about 190 nm and its wall thickness is less than 10 nm. When the macroporous SnO{sub 2} filled with carbon is used as an anode material for lithium-ion battery, the capacity is about 380 mAh g{sup -1} after 70 cycles. The improved cyclability is attributed to the carbon matrix which is used as an effective physical buffer to prevent the collapse of the well dispersed macroporous SnO{sub 2}.

Intensifying existing premix therapy (BIAsp 30) with BIAsp 50 and BIAsp 70

DEFF Research Database (Denmark)

Brito, Miguel; Ligthelm, Robert Jan; Boemi, Massimo

2011-01-01

In 2009, consensus guidelines were published on intensification of insulin therapy using the premix analog biphasic insulin aspart (BIAsp) 30 in the treatment of type 2 diabetes, based on the recommendations of an international, independent expert panel. The guidelines included recommendations an...... assist physicians in introducing mid-/high-ratio premixes to optimize the insulin therapy of patients with type 2 diabetes who are failing to achieve glycemic targets on a BIAsp 30 BID or TID regimen....

ASSESSMENT OF FLOW AND TECHNOLOGICAL BEHAVIOR OF FRENCH BREAD PREMIXES

Directory of Open Access Journals (Sweden)

E. VALDUGA

2008-08-01

Full Text Available

In this work formulations of French bread premixes were investigated. The premixes were based on blends of Argentinean and Brazilian wheat. The bread produced with the mixtures was compared to the bread obtained with standard flour, which did not contain any additives. The flour was characterized by physico-chemical and biochemical analysis (humidity, ashes, water absorption, color, gluten index, flour strength and a-amylase activity. The bread rolls were prepared using a standard formulation (without additives and two different formulations, using ascorbic acid, a-amylase, esterlac, soybean flour and diacetyl tartaric acid emulsifier. The physico-chemical analysis results indicate that the standard flour is better than the formulations. Nevertheless bread-making tests showed that the premixes formulations have better performance concerning the specific volume and the sensory characteristics. Statistical analysis confirmed that there is a significant difference in the specific volume and the sensory characteristics between the formulations, proving that the use of additives can enhance the quality of the French bread.

Implementation of Premixed Equilibrium Chemistry Capability in OVERFLOW

Science.gov (United States)

Olsen, Mike E.; Liu, Yen; Vinokur, M.; Olsen, Tom

2004-01-01

An implementation of premixed equilibrium chemistry has been completed for the OVERFLOW code, a chimera capable, complex geometry flow code widely used to predict transonic flowfields. The implementation builds on the computational efficiency and geometric generality of the solver.

Covalently coating dextran on macroporous polyglycidyl methacrylate microsphere enabled rapid protein chromatographic separation

International Nuclear Information System (INIS)

Zhang, Rongyue; Li, Qiang; Li, Juan; Zhou, Weiqing; Ye, Peili; Gao, Yang; Ma, Guanghui; Su, Zhiguo

2012-01-01

Protein denaturation and nonspecific adsorption on polymer media as a chromatographic support have been a problem which needs to be overcome. Macroporous poly(glycidyl methacrylate–divinylbezene) (PGMA–DVB) microspheres prepared in this study were firstly covalently coated with dextran through a three-step method. The dextran was firstly adsorbed onto the microspheres and then covalently bound to the PGMA–DVB microsphere through ether bonds which were formed by hydroxyl group reacting with epoxy group at the presence of 4-(Dimethylamino) pyridine. Finally, the coating dextran layer was crosslinked by ethylene glycol diglycidyl ether to form the continuous network coating. The coated microspheres were characterized by Fourier transform infrared spectra, scanning electron microscope, mercury porosimetry measurements, laser scanning confocal microscope, and protein adsorption experiments. Results showed that PGMA–DVB microspheres coated with dextran successfully maintained the macroporous structure and high permeability. The backpressure was only 1.69 MPa at a high flow rate of 2891 cm/h. Consequently, the hydrophilicity and biocompatibility of modified microspheres were greatly improved, and the contact angle decreased from 184° to 13°, and nonspecific adsorption of proteins was decreased to little or none. The clad dextran coating with large amounts of hydroxyl group was easily derived to be various functional groups. The derived media have great potential applications in rapid protein chromatography. - Highlights: ► Macroporous PGMA–DVB microspheres were covalently coated with dextran. ► The hydrophilicity of the coated microspheres was significantly improved. ► The irreversible adsorption of proteins was reduced to zero. ► The coated microspheres can maintain the macropore structure. ► The coated microspheres were applied to rapid protein separation.

Direct Numerical Simulations of NOx formation in spatially developing turbulent premixed Bunsen flames with mixture inhomogeneity

KAUST Repository

Luca, Stefano

2017-01-05

Direct Numerical Simulation of three-dimensional spatially developing turbulent methane/air flames are performed. Four flames are simulated; they differ for the level of premixing of the fuel inlet: one has a fully premixed inlet, the other three have a partially premixed inlet that mimic a common injection strategy in stationary gas turbines. The jet consist of a methane/air mixture with global equivalence ratio ɸ = 0.7 and temperature of 800 K. The simulations are performed at 4 atm. The inlet velocity field and the fuel/air fields were extracted from a fully developed turbulent channel simulation. Chemistry is treated with a new skeletal chemical mechanism consisting of 33 species developed specifically for the DNS. The data are analyzed to study possible influences of partial premixing on the flame structure and the combustion efficiency. The results show that increasing the level of partial premixing, the fluctuations of heat release rate increase, due to the richer and leaner pockets of mixture in the flame, while the conditional mean decreases. Increasing the level of partial premixing, the peak of NO and the range of NO values for a given temperature increase. An analysis of NO production is performed categorizing the different initiation steps in the Ndecomposition through four pathways: thermal, prompt, NNH and NO. Different behaviour with respect to laminar flames is found for the NNH pathway suggesting that turbulence influences this pathway of formation of NO.

Experimental Investigation of Turbulence-Chemistry Interaction in High-Reynolds-Number Turbulent Partially Premixed Flames

Science.gov (United States)

2016-06-23

AFRL-AFOSR-VA-TR-2016-0277 Experimental Investigation of Turbulence-Chemistry Interaction in High- Reynolds -Number Turbulent Partially Premixed...4. TITLE AND SUBTITLE [U] Experimental investigation of turbulence-chemistry interaction in high- Reynolds -number 5a. CONTRACT NUMBER turbulent...for public release Final Report: Experimental investigation of turbulence-chemistry interaction in high- Reynolds -number turbulent partially premixed

Dynamic-Stability Characteristics of Premixed Methane Oxy-Combustion

KAUST Repository

Shroll, Andrew P.; Shanbhogue, Santosh J.; Ghoniem, Ahmed F.

2012-01-01

This work explores the dynamic stability characteristics of premixed CH 4/O 2/CO 2 mixtures in a 50 kW swirl stabilized combustor. In all cases, the methane-oxygen mixture is stoichiometric, with different dilution levels of carbon dioxide used

Direct numerical simulations of premixed autoignition in compressible uniformly-sheared turbulence

Science.gov (United States)

Towery, Colin; Darragh, Ryan; Poludnenko, Alexei; Hamlington, Peter

2017-11-01

High-speed combustion systems, such as scramjet engines, operate at high temperatures and pressures, extremely short combustor residence times, very high rates of shear stress, and intense turbulent mixing. As a result, the reacting flow can be premixed and have highly-compressible turbulence fluctuations. We investigate the effects of compressible turbulence on the ignition delay time, heat-release-rate (HRR) intermittency, and mode of autoignition of premixed Hydrogen-air fuel in uniformly-sheared turbulence using new three-dimensional direct numerical simulations with a multi-step chemistry mechanism. We analyze autoignition in both the Eulerian and Lagrangian reference frames at eight different turbulence Mach numbers, Mat , spanning the quasi-isentropic, linear thermodynamic, and nonlinear compressibility regimes, with eddy shocklets appearing in the nonlinear regime. Results are compared to our previous study of premixed autoignition in isotropic turbulence at the same Mat and with a single-step reaction mechanism. This previous study found large decreases in delay times and large increases in HRR intermittency between the linear and nonlinear compressibility regimes and that detonation waves could form in both regimes.

Gravitational Influences on Flame Propagation through Non-Uniform, Premixed Gas Systems

Science.gov (United States)

Miller, Fletcher J.; Easton, John; Ross, Howard D.; Marchese, Anthony; Perry, David; Kulis, Michael

2001-01-01

Flame propagation through non-uniformly premixed (or layered) gases has importance both in useful combustion systems and in unintentional fires. As summarized previously, non-uniform premixed gas combustion receives scant attention compared to the more usual limiting cases of diffusion or uniformly premixed flames, especially regarding the role gravity plays. This paper summarizes our progress on furthering the knowledge of layered combustion, in which a fuel concentration gradient exists normal to the direction of flame spread. We present experimental and numerical results for flame spread through propanol-air layers formed near the flash point temperature (25 C) or near the stoichiometric temperature (33 C). Both the model and experimental results show that the removal of gravity results in a faster spreading flame, by as much as 80% depending on conditions. This is exactly the opposite effect as that predicted by an earlier model reported. We also found that having a gallery lid results in faster flame spread, an effect more pronounced at normal gravity, demonstrating the importance of enclosure geometry. Also reported here is the beginning of our spectroscopic measurements of fuel vapor.

Wannier–Stark electro-optical effect, quasi-guided and photonic modes in 2D macroporous silicon structures with SiO_2 coatings

International Nuclear Information System (INIS)

Karachevtseva, L.; Goltviansky, Yu.; Sapelnikova, O.; Lytvynenko, O.; Stronska, O.; Bo, Wang; Kartel, M.

2016-01-01

Highlights: • The IR absorption spectra of oxidized macroporous silicon were studied. • The Wannier–Stark electro-optical effect on Si-SiO_2 boundary was confirmed. • An additional electric field of quasi-guided optical modes was evaluated. • The photonic modes and band gaps were measured as peculiarities in absorption spectra. - Abstract: Opportunities to enhance the properties of structured surfaces were demonstrated on 2D macroporous silicon structures with SiO_2 coatings. We investigated the IR light absorption oscillations in macroporous silicon structures with SiO2 coatings 0–800 nm thick. The Wannier–Stark electro-optical effect due to strong electric field on Si-SiO_2boundary and an additional electric field of quasi-guided optical modes were taken into account. The photonic modes and band gaps were also considered as peculiarities in absorbance spectra of macroporous silicon structures with a thick SiO_2 coating. The photonic modes do not coincide with the quasi-guided modes in the silicon matrix and do not appear in absorption spectra of 2D macroporous silicon structures with surface nanocrystals.

Large Eddy Simulation of High-Speed, Premixed Ethylene Combustion

Science.gov (United States)

Ramesh, Kiran; Edwards, Jack R.; Chelliah, Harsha; Goyne, Christopher; McDaniel, James; Rockwell, Robert; Kirik, Justin; Cutler, Andrew; Danehy, Paul

2015-01-01

A large-eddy simulation / Reynolds-averaged Navier-Stokes (LES/RANS) methodology is used to simulate premixed ethylene-air combustion in a model scramjet designed for dual mode operation and equipped with a cavity for flameholding. A 22-species reduced mechanism for ethylene-air combustion is employed, and the calculations are performed on a mesh containing 93 million cells. Fuel plumes injected at the isolator entrance are processed by the isolator shock train, yielding a premixed fuel-air mixture at an equivalence ratio of 0.42 at the cavity entrance plane. A premixed flame is anchored within the cavity and propagates toward the opposite wall. Near complete combustion of ethylene is obtained. The combustor is highly dynamic, exhibiting a large-scale oscillation in global heat release and mass flow rate with a period of about 2.8 ms. Maximum heat release occurs when the flame front reaches its most downstream extent, as the flame surface area is larger. Minimum heat release is associated with flame propagation toward the cavity and occurs through a reduction in core flow velocity that is correlated with an upstream movement of the shock train. Reasonable agreement between simulation results and available wall pressure, particle image velocimetry, and OH-PLIF data is obtained, but it is not yet clear whether the system-level oscillations seen in the calculations are actually present in the experiment.

Determination of appropriate models and parameters for premixing calculations

Energy Technology Data Exchange (ETDEWEB)

Park, Ik-Kyu; Kim, Jong-Hwan; Min, Beong-Tae; Hong, Seong-Wan

2008-03-15

The purpose of the present work is to use experiments that have been performed at Forschungszentrum Karlsruhe during about the last ten years for determining the most appropriate models and parameters for premixing calculations. The results of a QUEOS experiment are used to fix the parameters concerning heat transfer. The QUEOS experiments are especially suited for this purpose as they have been performed with small hot solid spheres. Therefore the area of heat exchange is known. With the heat transfer parameters fixed in this way, a PREMIX experiment is recalculated. These experiments have been performed with molten alumina (Al{sub 2}O{sub 3}) as a simulant of corium. Its initial temperature is 2600 K. With these experiments the models and parameters for jet and drop break-up are tested.

Determination of appropriate models and parameters for premixing calculations

International Nuclear Information System (INIS)

Park, Ik-Kyu; Kim, Jong-Hwan; Min, Beong-Tae; Hong, Seong-Wan

2008-03-01

The purpose of the present work is to use experiments that have been performed at Forschungszentrum Karlsruhe during about the last ten years for determining the most appropriate models and parameters for premixing calculations. The results of a QUEOS experiment are used to fix the parameters concerning heat transfer. The QUEOS experiments are especially suited for this purpose as they have been performed with small hot solid spheres. Therefore the area of heat exchange is known. With the heat transfer parameters fixed in this way, a PREMIX experiment is recalculated. These experiments have been performed with molten alumina (Al 2 O 3 ) as a simulant of corium. Its initial temperature is 2600 K. With these experiments the models and parameters for jet and drop break-up are tested

Partially premixed prevalorized kerosene spray combustion in turbulent flow

Energy Technology Data Exchange (ETDEWEB)

Chrigui, M.; Ahmadi, W.; Sadiki, A.; Janicka, J. [Institute for Energy and Powerplant Technology, TU Darmstadt, Petersenstr. 30, 64287 Darmstadt (Germany); Moesl, K. [Lehrstuhl fuer Thermodynamik, TU Muenchen, Boltzmannstr. 15, D-85747 Garching (Germany)

2010-04-15

A detailed numerical simulation of kerosene spray combustion was carried out on a partially premixed, prevaporized, three-dimensional configuration. The focus was on the flame temperature profile dependency on the length of the pre-vaporization zone. The results were analyzed and compared to experimental data. A fundamental study was performed to observe the temperature variation and flame flashback. Changes were made to the droplet diameter, kerosene flammability limits, a combustion model parameter and the location of the combustion initialization. Investigations were performed for atmospheric pressure, inlet air temperature of 90 C and a global equivalence ratio of 0.7. The simulations were carried out using the Eulerian Lagrangian procedure under a fully two-way coupling. The Bray-Moss-Libby model was adjusted to account for the partially premixed combustion. (author)

Covalently coating dextran on macroporous polyglycidyl methacrylate microsphere enabled rapid protein chromatographic separation

Energy Technology Data Exchange (ETDEWEB)

Zhang, Rongyue; Li, Qiang; Li, Juan; Zhou, Weiqing; Ye, Peili; Gao, Yang; Ma, Guanghui, E-mail: ghma@home.ipe.ac.cn; Su, Zhiguo

2012-12-01

Protein denaturation and nonspecific adsorption on polymer media as a chromatographic support have been a problem which needs to be overcome. Macroporous poly(glycidyl methacrylate-divinylbezene) (PGMA-DVB) microspheres prepared in this study were firstly covalently coated with dextran through a three-step method. The dextran was firstly adsorbed onto the microspheres and then covalently bound to the PGMA-DVB microsphere through ether bonds which were formed by hydroxyl group reacting with epoxy group at the presence of 4-(Dimethylamino) pyridine. Finally, the coating dextran layer was crosslinked by ethylene glycol diglycidyl ether to form the continuous network coating. The coated microspheres were characterized by Fourier transform infrared spectra, scanning electron microscope, mercury porosimetry measurements, laser scanning confocal microscope, and protein adsorption experiments. Results showed that PGMA-DVB microspheres coated with dextran successfully maintained the macroporous structure and high permeability. The backpressure was only 1.69 MPa at a high flow rate of 2891 cm/h. Consequently, the hydrophilicity and biocompatibility of modified microspheres were greatly improved, and the contact angle decreased from 184 Degree-Sign to 13 Degree-Sign , and nonspecific adsorption of proteins was decreased to little or none. The clad dextran coating with large amounts of hydroxyl group was easily derived to be various functional groups. The derived media have great potential applications in rapid protein chromatography. - Highlights: Black-Right-Pointing-Pointer Macroporous PGMA-DVB microspheres were covalently coated with dextran. Black-Right-Pointing-Pointer The hydrophilicity of the coated microspheres was significantly improved. Black-Right-Pointing-Pointer The irreversible adsorption of proteins was reduced to zero. Black-Right-Pointing-Pointer The coated microspheres can maintain the macropore structure. Black-Right-Pointing-Pointer The coated microspheres

Applying Lean Techniques to Reduce Intravenous Waste Through Premixed Solutions and Increasing Production Frequency.

Science.gov (United States)

Lin, Alex C; Penm, Jonathan; Ivey, Marianne F; Deng, Yihong; Commins, Monica

This study aims to use lean techniques and evaluate the impact of increasing the use of premixed IV solutions and increased IV production frequency on IV waste. Study was conducted at a tertiary hospital pharmacy department in three phases. Phase I included evaluation of IV waste when IV production occurred three times a day and eight premixed IV products were used. Phase II increased the number of premixed IV products to 16. Phase III then increased IV production to five times a day. During Phase I, an estimate of 2,673 IV doses were wasted monthly, accounting for 6.14% of overall IV doses. This accounted for 688 L that cost $60,135. During Phase II, the average monthly IV wastage reduced significantly to 1,069 doses (2.84%), accounting for 447 L and $34,003. During Phase III, the average monthly IV wastage was further decreased to 675 doses (1.69%), accounting for 78 L and $3,431. Hence, a potential annual saving of $449,208 could result from these changes. IV waste was reduced through the increased use of premixed solutions and increasing IV production frequency.

Acute toxicity study of Vilocym Premix (herbal growth promoter for Livestockin Wistar Albino Rat

Directory of Open Access Journals (Sweden)

A.H. Ahmad

2009-06-01

Full Text Available An experimental study with the objective of safety evaluation of Vilocym Premix, herbal growth promoter for Livestock (supplied by Ayurvet Ltd., Baddi, India, was done as per standard guidelines of OECD-423 for acute toxicity testing. Vilocym Premix is a scientifically developed combination of herbs that contains herbal ingredients namely Azadirachta indica, Curcuma longa & many more alongwith natural zeolites. The study was done in 3 males and 3 female Wistar Albino rats, which were administered an initial dose of 50 mg/kg body weight followed by dose rates of 300, 500 & 5000 mg/kg body weight of test compound. The animals were observed for signs of convulsions, tremors, circling, depression, excitement and mortality. Body weight was recorded at 0,7th and 14th day and plasma total protein, albumin; AST and ALT were measured after 3rd day of experiment. No abnormal sign of symptoms were observed in any of the animal fed with Vilocym Premix at the dose rate of 50, 300, 500 & 5000 mg/kg. No mortality was observed indicating safety of herbal premix. [Vet. World 2009; 2(3.000: 100-102

Rainfall Simulator Experiments to Investigate Macropore Impacts on Hillslope Hydrological Response

NARCIS (Netherlands)

Smit, Y.; Teuling, Adriaan J.; van der Ploeg, Martine J.

2016-01-01

Understanding hillslope runoff response to intense rainfall is an important topic in hydrology, and is key to correct prediction of extreme stream flow, erosion and landslides. Although it is known that preferential flow processes activated by macropores are an important phenomena in understanding

On the regimes of premixing

Energy Technology Data Exchange (ETDEWEB)

Angelini, S.; Theofanous, T.G.; Yuen, W.W. [California Univ., Santa Barbara, CA (United States). Center for Risk Studies and Safety

1998-01-01

The conditions of the MAGICO-2000 experiment are extended to more broadly investigate the regimes of premixing, and the corresponding internal structures of mixing zones. With the help of the data and numerical simulations using the computer code PM-ALPHA, we can distinguish extremes of behavior dominated by inertia and thermal effects - we name these the inertia and thermal regimes, respectively. This is an important distinction that should guide future experiments aimed at code verification in this area. Interesting intermediate behaviors are also delineated and discussed. (author)

A simple method for the production of large volume 3D macroporous hydrogels for advanced biotechnological, medical and environmental applications

Science.gov (United States)

Savina, Irina N.; Ingavle, Ganesh C.; Cundy, Andrew B.; Mikhalovsky, Sergey V.

2016-02-01

The development of bulk, three-dimensional (3D), macroporous polymers with high permeability, large surface area and large volume is highly desirable for a range of applications in the biomedical, biotechnological and environmental areas. The experimental techniques currently used are limited to the production of small size and volume cryogel material. In this work we propose a novel, versatile, simple and reproducible method for the synthesis of large volume porous polymer hydrogels by cryogelation. By controlling the freezing process of the reagent/polymer solution, large-scale 3D macroporous gels with wide interconnected pores (up to 200 μm in diameter) and large accessible surface area have been synthesized. For the first time, macroporous gels (of up to 400 ml bulk volume) with controlled porous structure were manufactured, with potential for scale up to much larger gel dimensions. This method can be used for production of novel 3D multi-component macroporous composite materials with a uniform distribution of embedded particles. The proposed method provides better control of freezing conditions and thus overcomes existing drawbacks limiting production of large gel-based devices and matrices. The proposed method could serve as a new design concept for functional 3D macroporous gels and composites preparation for biomedical, biotechnological and environmental applications.

Vortex combustor for low NOX emissions when burning lean premixed high hydrogen content fuel

Science.gov (United States)

Steele, Robert C; Edmonds, Ryan G; Williams, Joseph T; Baldwin, Stephen P

2012-11-20

A trapped vortex combustor. The trapped vortex combustor is configured for receiving a lean premixed gaseous fuel and oxidant stream, where the fuel includes hydrogen gas. The trapped vortex combustor is configured to receive the lean premixed fuel and oxidant stream at a velocity which significantly exceeds combustion flame speed in a selected lean premixed fuel and oxidant mixture. The combustor is configured to operate at relatively high bulk fluid velocities while maintaining stable combustion, and low NOx emissions. The combustor is useful in gas turbines in a process of burning synfuels, as it offers the opportunity to avoid use of diluent gas to reduce combustion temperatures. The combustor also offers the possibility of avoiding the use of selected catalytic reaction units for removal of oxides of nitrogen from combustion gases exiting a gas turbine.

The conditional moment closure method for modeling lean premixed turbulent combustion

Science.gov (United States)

Martin, Scott Montgomery

Natural gas fired lean premixed gas turbines have become the method of choice for new power generation systems due to their high efficiency and low pollutant emissions. As emission regulations for these combustion systems become more stringent, the use of numerical modeling has become an important a priori tool in designing clean and efficient combustors. Here a new turbulent combustion model is developed in an attempt to improve the state of the art. The Conditional Moment Closure (CMC) method is a new theory that has been applied to non-premixed combustion with good success. The application of the CMC method to premixed systems has been proposed, but has not yet been done. The premixed CMC method replaces the species mass fractions as independent variables with the species mass fractions that are conditioned on a reaction progress variable (RPV). Conservation equations for these new variables are then derived and solved. The general idea behind the CMC method is that the behavior of the chemical species is closely coupled to the reaction progress variable. Thus, species conservation equations that are conditioned on the RPV will have terms involving the fluctuating quantities that are much more likely to be negligible. The CMC method accounts for the interaction between scalar dissipation (micromixing) and chemistry, while de-coupling the kinetics from the bulk flow (macromixing). Here the CMC method is combined with a commercial computational fluid dynamics program, which calculates the large-scale fluid motions. The CMC model is validated by comparison to 2-D reacting backward facing step data. Predicted species, temperature and velocity fields are compared to experimental data with good success. The CMC model is also validated against the University of Washington's 3-D jet stirred reactor (JSR) data, which is an idealized lean premixed combustor. The JSR results are encouraging, but not as good as the backward facing step. The largest source of error is from

Linking air and water transport in intact soils to macropore characteristics inferred from X-ray computed tomography

DEFF Research Database (Denmark)

Katuwal, S.; Nørgaard, Trine; Møldrup, Per

2015-01-01

Soil macropores often control fluid flow and solute transport, and quantification of macropore characteristics including their variability in space and time are essential to predict soil hydraulic and hydrogeochemical functions. In this study, measurements of air and solute transport properties...... and direct macropore visualization by X-ray CT scanning were carried out on 17 large (19-cm diam.; 20-cm length) undisturbed soil columns sampled across a field site (Silstrup, Denmark) with natural gradients in texture and density. Air permeability (ka) at in-situ water content and -20 hPa of matric......-porosity, suggesting that density is the main control of functional soil structure and gas and solute transport at the Silstrup site. Linking gas transport and chemical tracer experiments with X-ray CT based visualization and quantification of macro-porosity was found to be a powerful method to understand field scale...

Experimental study of flame stability in biogas premix system

International Nuclear Information System (INIS)

Diaz G, Carlos A; Amell A Andres; Cardona Luis F

2008-01-01

Utilization of new renewable energy sources have had a special interest in last years looking for decrease the dependence of fossil fuels and the environmental impact generated for them. This work studies experimentally the flame stability of a simulated biogas with a volumetric composition of 60% methane and 40% carbon dioxide. The objective of this study is to obtain information about design and interchangeability of gases in premixed combustion systems that operate with different fuel gases. The critical velocity gradient was the stability criteria used. Utilization of this criteria and the experimental method followed, using a partial premixed burner, stability flame diagram of biogas studied had been obtained. Presence of carbon dioxide has a negative effect in flame stability, decreasing significantly the laminar flame speed and consequently, the stability range of biogas burners because of apparition of blow off.

Effect of hierarchical meso–macroporous alumina-supported copper catalyst for methanol synthesis from CO2 hydrogenation

International Nuclear Information System (INIS)

Witoon, Thongthai; Bumrungsalee, Sittisut; Chareonpanich, Metta; Limtrakul, Jumras

2015-01-01

Highlights: • CO 2 hydrogenation over Cu-loaded unimodal and hierarchical alumina catalysts. • Cu-loaded hierarchical catalyst exhibited higher methanol selectivity and stability. • The presence of macropores reduced the probability of side reaction. - Abstract: Effects of pore structures of alumina on the catalytic performance of copper catalysts for CO 2 hydrogenation were investigated. Copper-loaded hierarchical meso–macroporous alumina (Cu/HAl) catalyst exhibited no significant difference in terms of CO 2 conversion with copper-loaded unimodal mesoporous alumina (Cu/UAl) catalyst. However, the selectivity to methanol and dimethyl ether of the Cu/HAl catalyst was much higher than that of the Cu/UAl catalyst. This was attributed to the presence of macropores which diminished the occurrence of side reaction by the shortening the mesopores diffusion path length. The Cu/HAl catalyst also exhibited much higher stability than the Cu/UAl catalyst due to the fast diffusion of water out from the catalyst pellets, alleviating the oxidation of metallic copper to CuO

A simple method for preparation of macroporous polydimethylsiloxane membrane for microfluidic chip-based isoelectric focusing applications

Energy Technology Data Exchange (ETDEWEB)

Ou Junjie [Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Ave West, Waterloo, Ontario, N2L 3G1 (Canada); Department of Chemistry, University of Waterloo, 200 University Ave West, Waterloo, Ontario, N2L 3G1 (Canada); Ren, Carolyn L., E-mail: c3ren@mecheng1.uwaterloo.ca [Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Ave West, Waterloo, Ontario, N2L 3G1 (Canada); Pawliszyn, Janusz [Department of Chemistry, University of Waterloo, 200 University Ave West, Waterloo, Ontario, N2L 3G1 (Canada)

2010-03-10

A new, simple method was reported to prepare PDMS membranes with micrometer size pores for microfluidic chip applications. The pores were formed by adding polystyrene and toluene into PDMS prepolymer solution prior to spin-coating and curing. The resulting PDMS membrane has a thickness of around 10 {mu}m and macropores with a diameter ranging from 1 to 2 {mu}m measured using scanning electron microscope (SEM) imaging. This PDMS membrane was validated by integrating it with PDMS microfluidic chips for protein separation using isoelectric focusing mechanism coupled with whole channel imaging detection (IEF-WCID). It has been shown that five standard pI markers and a mixture of two proteins, myoglobin and {beta}-lactoglobulin, can be separated using these chips. The results indicated that this macroporous PDMS membrane can replace the dialysis membrane in PDMS chips for the IEF-WCID technique. The preparation method of macroporous PDMS membrane may be potentially applied in other fields of microfluidic chips.

Understanding premixed flame chemistry of gasoline fuels by comparing quantities of interest

KAUST Repository

Selim, Hatem

2016-07-23

Gasoline fuels are complex mixtures that vary in composition depending on crude oil feedstocks and refining processes. Gasoline combustion in high-speed spark ignition engines is governed by flame propagation, so understanding fuel composition effects on premixed flame chemistry is important. In this study, the combustion chemistry of low-pressure, burner-stabilized, premixed flames of two gasoline fuels was investigated under stoichiometric conditions. Flame speciation was conducted using vacuum-ultraviolet synchrotron photoionization time-of-flight molecular beam mass spectroscopy. Stable end-products, intermediate hydrocarbons, and free radicals were detected and quantified. In addition, several isomeric species in the reaction pool were distinguished and quantified with the help of the highly tunable synchrotron radiation. A comparison between the products of both flames is presented and the major differences are highlighted. Premixed flame numerical simulations were conducted using surrogate fuel kinetic models for each flame. Furthermore, a new approach was developed to elucidate the main discrepancies between experimental measurements and the numerical predictions by comparing quantities of interest. © 2016.

Flamelet Surface Density and Burning Rate Integral in Premixed Combustion

National Research Council Canada - National Science Library

Gouldin, F

1999-01-01

We have developed, tested and applied in V-flames and a spark ignition engine a new experimental method, crossed-plane laser imaging, for measuring flamelet surface normals in premixed turbulent flames...

LES of a laboratory-scale turbulent premixed bunsen flame using FSD, PCM-FPI and thickened flame models

NARCIS (Netherlands)

Hernandez Perez, F.E.; Yuen, F.T.C.; Groth, C.P.T.; Gülder, O.L.

2011-01-01

Large-eddy simulations (LES) of a turbulent premixed Bunsen flame were carried out with three subfilter-scale (SFS) modelling approaches for turbulent premixed combustion. One approach is based on the artificially thickened flame and power-law flame wrinkling models, the second approach is based on

Flow and transport processes in a macroporous subsurface-drained glacial till soil

DEFF Research Database (Denmark)

Villholth, Karen G.; Jensen, Karsten Høgh

1998-01-01

disturbance and compaction of the soil surface. Hypothetically introducing fully surface-connected macropores into the calibrated model resulted in a 22% increase in the loss of solute to the drain, indicating the significance of the hydraulic conditions at the soil surface and the model specification thereof......The experimental results from a field-scale tracer experiment in a subsurface-drained glacial till soil were analyzed by the application of a single/dual porosity model (MACRO), optionally accounting for concurrent and interacting flow and transport in the bulk soil porosity as well...... concentration. The exchange was overpredicted and too rapid when the soil aggregate size (distance between macropores) obtained from an image analysis of soil cores was used in the model. On this basis, the model assumption of instant equilibration of the solute across the matrix porosity, disregarding small...

Nitrogen Doped Macroporous Carbon as Electrode Materials for High Capacity of Supercapacitor

Directory of Open Access Journals (Sweden)

Yudong Li

2017-01-01

Full Text Available Nitrogen doped carbon materials as electrodes of supercapacitors have attracted abundant attention. Herein, we demonstrated a method to synthesize N-doped macroporous carbon materials (NMC with continuous channels and large size pores carbonized from polyaniline using multiporous silica beads as sacrificial templates to act as electrode materials in supercapacitors. By the nice carbonized process, i.e., pre-carbonization at 400 °C and then pyrolysis at 700/800/900/1000 °C, NMC replicas with high BET specific surface areas exhibit excellent stability and recyclability as well as superb capacitance behavior (~413 F ⋅ g−1 in alkaline electrolyte. This research may provide a method to synthesize macroporous materials with continuous channels and hierarchical pores to enhance the infiltration and mass transfer not only used as electrode, but also as catalyst somewhere micro- or mesopores do not work well.

Experimental study on flame propagation characteristics of Hydrogen premixed gas in gas pipeline

Science.gov (United States)

Ma, Danzhu; Li, Zhuang; Jia, Fengrui; Li, Zhou

2018-06-01

Hydrogen is the cleanest high-energy gas fuel, and also is the main industrial material. However, hydrogen is more explosive and more powerful than conventional gas fuels, which restricts its application. In particular, the expansion of premixed combustion under a strong constraint is more complicated, the reaction spreads faster. The flame propagation characteristics of premixed hydrogen/air were investigated by experiment. The mechanism of reaction acceleration is discussed, and then the speed of the flame propagation and the reaction pressure were tested and analysed.

Liftoff characteristics of partially premixed flames under normal and microgravity conditions

Energy Technology Data Exchange (ETDEWEB)

Lock, Andrew J.; Briones, Alejandro M.; Aggarwal, Suresh K. [Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL 60607 (United States); Qin, Xiao [Department of Mechanical & amp; Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States); Puri, Ishwar K. [Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 (United States); Hegde, Uday [National Center for Microgravity Research, Cleveland, OH 44135 (United States)

2005-11-01

An experimental and computational investigation on the liftoff characteristics of laminar partially premixed flames (PPFs) under normal (1-g) and microgravity ({mu}-g) conditions is presented. Lifted methane-air PPFs were established in axisymmetric coflowing jets using nitrogen dilution and various levels of partial premixing. The {mu}-g experiments were conducted in the 2.2-s drop tower at the NASA Glenn Research Center. A time-accurate, implicit algorithm that uses a detailed description of the chemistry and includes radiation effects is used for the simulations. The predictions are validated through a comparison of the flame reaction zone topologies, liftoff heights, lengths, and oscillation frequencies. The effects of equivalence ratio, gravity, jet velocity, and radiation on flame topology, liftoff height, flame length, base structure, and oscillation frequency are characterized. Both the simulations and measurements indicate that under identical conditions, a lifted {mu}-g PPF is stabilized closer to the burner compared with the 1-g flame, and that the liftoff heights of both 1-g and {mu}-g flames decrease with increasing equivalence ratio and approach their respective nonpremixed flame limits. The liftoff height also increases as the jet velocity is increased. In addition, the flame base structure transitions from a triple- to a double-flame structure as the flame liftoff height decreases. A modified flame index is developed to distinguish between the rich premixed, lean premixed, and nonpremixed reaction zones near the flame base. The 1-g lifted flames exhibit well-organized oscillations due to buoyancy-induced instability, while the corresponding {mu}-g flames exhibit steady-state behavior. The effect of thermal radiation is to slightly decrease the liftoff heights of both 1-g and {mu}-g flames under coflow conditions.

Fuel and combustion stratification study of Partially Premixed Combustion

NARCIS (Netherlands)

Izadi Najafabadi, M.; Dam, N.; Somers, B.; Johansson, B.

2016-01-01

Relatively high levels of stratification is one of the main advantages of Partially Premixed Combustion (PPC) over the Homogeneous Charge Compression Ignition (HCCI) concept. Fuel stratification smoothens heat release and improves controllability of this kind of combustion. However, the lack of a

Laser-saturated fluorescence of nitric oxide and chemiluminescence measurements in premixed ethanol flames

Energy Technology Data Exchange (ETDEWEB)

Marques, Carla S.T.; Barreta, Luiz G.; Sbampato, Maria E.; dos Santos, Alberto M. [Aerothermodynamic and Hypersonic Division, Institute of Advanced Studies - General Command of Aerospatial Technology, Rodovia dos Tamoios, km 5.5, 12228-001 Sao Jose dos Campos - SP (Brazil)

2010-11-15

In this study, nitric oxide laser-saturated fluorescence (LSF) measurements were acquired from premixed ethanol flames at atmospheric pressure in a burner. NO-LSF experimental profiles for fuel-rich premixed ethanol flames ({phi} = 1.34 and {phi} = 1.66) were determined through the excitation/detection scheme of the Q{sub 2}(26.5) rotational line in the A{sup 2}{sigma}{sup +} - X{sup 2}{pi} (0,0) vibronic band and {gamma}(0,1) emission band. A calibration procedure by NO doping into the flame was applied to establish the NO concentration profiles in these flames. Chemiluminescent emission measurements in the (0, 0) vibronic emission bands of the OH{sup *} (A{sup 2}{sigma}{sup +} - X{sup 2}{pi}) and CH{sup *}(A{sup 2}{delta} - X{sup 2}{pi}) radicals were also obtained with high spatial and spectral resolution for fuel-rich premixed ethanol flames to correlate them with NO concentrations. Experimental chemiluminescence profiles and the ratios of the integrated areas under emission spectra (A{sub CH*}/A{sub CH*}(max.) and A{sub CH*}/A{sub OH*}) were determined. The relationships between chemiluminescence and NO concentrations were established along the premixed ethanol flames. There was a strong connection between CH{sup *} radical chemiluminescence and NO formation and the prompt-NO was identified as the governing mechanism for NO production. The results suggest the optimum ratio of the chemiluminescence of two radicals (A{sub CH*}/A{sub OH*}) for NO diagnostic purposes. (author)

Effects of premixed flames on turbulence and turbulent scalar transport

Energy Technology Data Exchange (ETDEWEB)

Lipatnikov, A.N.; Chomiak, J. [Department of Applied Mechanics, Chalmers University of Technology, 412 75 Goeteborg (Sweden)

2010-02-15

Experimental data and results of direct numerical simulations are reviewed in order to show that premixed combustion can change the basic characteristics of a fluctuating velocity field (the so-called flame-generated turbulence) and the direction of scalar fluxes (the so-called countergradient or pressure-driven transport) in a turbulent flow. Various approaches to modeling these phenomena are discussed and the lack of a well-elaborated and widely validated predictive approach is emphasized. Relevant basic issues (the transition from gradient to countergradient scalar transport, the role played by flame-generated turbulence in the combustion rate, the characterization of turbulence in premixed flames, etc.) are critically considered and certain widely accepted concepts are disputed. Despite the substantial progress made in understanding the discussed effects over the past decades, these basic issues strongly need further research. (author)

Modeling of Dissipation Element Statistics in Turbulent Non-Premixed Jet Flames

Science.gov (United States)

Denker, Dominik; Attili, Antonio; Boschung, Jonas; Hennig, Fabian; Pitsch, Heinz

2017-11-01

The dissipation element (DE) analysis is a method for analyzing and compartmentalizing turbulent scalar fields. DEs can be described by two parameters, namely the Euclidean distance l between their extremal points and the scalar difference in the respective points Δϕ . The joint probability density function (jPDF) of these two parameters P(Δϕ , l) is expected to suffice for a statistical reconstruction of the scalar field. In addition, reacting scalars show a strong correlation with these DE parameters in both premixed and non-premixed flames. Normalized DE statistics show a remarkable invariance towards changes in Reynolds numbers. This feature of DE statistics was exploited in a Boltzmann-type evolution equation based model for the probability density function (PDF) of the distance between the extremal points P(l) in isotropic turbulence. Later, this model was extended for the jPDF P(Δϕ , l) and then adapted for the use in free shear flows. The effect of heat release on the scalar scales and DE statistics is investigated and an extended model for non-premixed jet flames is introduced, which accounts for the presence of chemical reactions. This new model is validated against a series of DNS of temporally evolving jet flames. European Research Council Project ``Milestone''.

The Effect of Premixed Al-Cu Powder on the Stir Zone in Friction Stir Welding of AA3003-H18

Science.gov (United States)

Abnar, B.; Kazeminezhad, M.; Kokabi, A. H.

2015-02-01

In this research, 3-mm-thick AA3003-H18 non-heat-treatable aluminum alloy plates were joined by friction stir welding (FSW). It was performed by adding pure Cu and premixed Cu-Al powders at various rotational speeds of 800, 1000, and 1200 rpm and constant traveling speeds of 100 mm/min. At first, the powder was filled into the gap (0.2 or 0.4 mm) between two aluminum alloy plates, and then the FSW process was performed in two passes. The microstructure, mechanical properties, and formation of intermetallic compounds were investigated in both cases of using pure Cu and premixed Al-Cu powders. The results of using pure Cu and premixed Al-Cu powders were compared in the stir zone at various rotational speeds. The copper particle distribution and formation of Al-Cu intermetallic compounds (Al2Cu and AlCu) in the stir zone were desirable using premixed Al-Cu powder into the gap. The hardness values were significantly increased by formation of Al-Cu intermetallic compounds in the stir zone and it was uniform throughout the stir zone when premixed Al-Cu powder was used. Also, longitudinal tensile strength from the stir zone was higher when premixed Al-Cu powder was used instead of pure Cu powder.

Properties of Ni-Mo steel prepared from premixed and prealloyed powder in sintered, forged and annealed state

International Nuclear Information System (INIS)

Salak, A.; Hrubjak, M.

Investigated were 2Ni-0.5Mo steel specimens made of premixed powder on the base of Hametag iron and of ATST-A prealloyed powder with graphite additives of 0.3% and 0.8%. In the sintered and forged state, specimens prepared from premixed powder exhibit better strength properties compared with those made of prealloyed ATST-A powder. After annealing, the carbon content has a different bearing on both systems. With premixed powder steel of 0.6% carbon content the tensile strength amounts to 1,800 MPa whilst that of prealloyed steel specimens with 0.2% carbon content is about 1,240 MPa. (author)

Modeling of pollutant formation in fully premixing surface burners using a verified practice-oriented experimental reaction-kinetic calculation method. Final report

International Nuclear Information System (INIS)

Ruy, C.; Kremer, H.

1996-01-01

The intent of the present study was to simulate quantitatively pollutant formation in premixing surface burners and to describe qualitatively the share of the premixing flame in pollut emissions from atmospheric burners. For this purpose reaction-kinetic programmes for one-dimensional premixing flames were extended by a terms describing heat discharge through gas radiation. Furthermore, the calculation range for the flame was extended far into the secondary reaction zone. Temperature, CO, and NO x profiles were measured in the secondary reaction zone of premixing burners at standard pressure. The air-fuel ratio was calculated within the practically relevant range between 0.5 and 1.5, as was load behaviour. (DG) [de

Evaluation of new macroporous resins for the removal of uranium and plutonium from waste streams

International Nuclear Information System (INIS)

Koenst, J.W.; Herald, W.R.

1976-01-01

Organic ion exchange resins were evaluated for 238 Pu(IV), 238 Pu(VI), and 233 U(VI) removal from water. The capacity of the resins and equilibrium coefficients (Kd) were compared with each other and to bone char--an inorganic adsorbent consisting of hydroxyapatite (HAP) for which data is available. Bone char gave the best results for the removal of 238 Pu(IV), Amberlite XE279 (one of the new macroporous resins) gave the best results for 238 Pu(VI), and another macroporous resin, Dowex-MSA-1, gave good results for 233 U(VI). Kd values were shown to be a function of pH

Honeycomb-like graphitic ordered macroporous carbon prepared by pyrolysis of ammonium bicarbonate

Energy Technology Data Exchange (ETDEWEB)

Wang, Liancheng [Key Laboratory of Colloid and Interface Chemistry, Shandong University, Jinan, Shandong 250100 (China); Zhang, Junhao, E-mail: jhzhang6@mail.ustc.edu.cn [Key Laboratory of Colloid and Interface Chemistry, Shandong University, Jinan, Shandong 250100 (China); School of Biology and Chemical Engineering, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu 212003 (China); Xu, Liqiang; Qian, Yitai [Key Laboratory of Colloid and Interface Chemistry, Shandong University, Jinan, Shandong 250100 (China)

2011-10-15

Graphical abstract: Honeycomb-like graphitic macroporous carbon (HGMC) with big pores centered at 1-3 {mu}m, has been prepared by controlling the reaction temperature and amount of NH{sub 4}HCO{sub 3} at 550 {sup o}C in a sealed reaction system. Possible formation processes of HGMC are discussed on the experimental results. It is believed that the in situ formed MgO microparticles play a template role during the preparation of HGMC. Highlights: {yields} Honeycomb-like graphitic carbon was synthesized at 550 {sup o}C. {yields} The honeycomb-like graphitic carbon is macroposous structures. {yields} The formed MgO microparticles play a template role during the HGMC formation. {yields} The method can be expended to synthesize other porous or hollow carbon material. -- Abstract: Honeycomb-like graphitic macroporous carbon (HGMC) was synthesized by means of pyrolysis of NH{sub 4}HCO{sub 3} using Mg powder as reductant in an autoclave at 550 {sup o}C. The characterization of structure and morphology was carried out by X-ray diffraction (XRD), Raman spectrum, field-emission scanning electron microscopy (FESEM), and (High-resolution) transmission electron microscope [(HR)TEM]. The results of nitrogen adsorption-desorption indicate that the products are macropore materials with the pore size of 1-3 {mu}m, and the Brunauer-Emett-Teller (BET) surface area was 14 m{sup 2}/g. As a typical morphology, the possible growth process of HGMC was also investigated and discussed. The experimental results show that the in situ formed MgO microparticles play a template role during the HGMC formation.

Honeycomb-like graphitic ordered macroporous carbon prepared by pyrolysis of ammonium bicarbonate

International Nuclear Information System (INIS)

Wang, Liancheng; Zhang, Junhao; Xu, Liqiang; Qian, Yitai

2011-01-01

Graphical abstract: Honeycomb-like graphitic macroporous carbon (HGMC) with big pores centered at 1-3 μm, has been prepared by controlling the reaction temperature and amount of NH 4 HCO 3 at 550 o C in a sealed reaction system. Possible formation processes of HGMC are discussed on the experimental results. It is believed that the in situ formed MgO microparticles play a template role during the preparation of HGMC. Highlights: → Honeycomb-like graphitic carbon was synthesized at 550 o C. → The honeycomb-like graphitic carbon is macroposous structures. → The formed MgO microparticles play a template role during the HGMC formation. → The method can be expended to synthesize other porous or hollow carbon material. -- Abstract: Honeycomb-like graphitic macroporous carbon (HGMC) was synthesized by means of pyrolysis of NH 4 HCO 3 using Mg powder as reductant in an autoclave at 550 o C. The characterization of structure and morphology was carried out by X-ray diffraction (XRD), Raman spectrum, field-emission scanning electron microscopy (FESEM), and (High-resolution) transmission electron microscope [(HR)TEM]. The results of nitrogen adsorption-desorption indicate that the products are macropore materials with the pore size of 1-3 μm, and the Brunauer-Emett-Teller (BET) surface area was 14 m 2 /g. As a typical morphology, the possible growth process of HGMC was also investigated and discussed. The experimental results show that the in situ formed MgO microparticles play a template role during the HGMC formation.

Macroporous 'bubble' graphene film via template-directed ordered-assembly for high rate supercapacitors.

Science.gov (United States)

Chen, Cheng-Meng; Zhang, Qiang; Huang, Chun-Hsien; Zhao, Xiao-Chen; Zhang, Bing-Sen; Kong, Qing-Qiang; Wang, Mao-Zhang; Yang, Yong-Gang; Cai, Rong; Sheng Su, Dang

2012-07-21

A three-dimensional bubble graphene film, with controllable and uniform macropores and tailorable microstructure, was fabricated by a facile hard templating strategy and exhibit extraordinary electrochemical capacitance with high rate capability (1.0 V s(-1)).

Optimization of instant dalia dessert pre-mix production by using response surface methodology.

Science.gov (United States)

Jha, Alok; Shalini, B N; Patel, Ashok Ambalal; Singh, Mithilesh; Rasane, Prasad

2015-02-01

Dalia, a wheat-based, particulate containing dairy dessert is popularly consumed as a breakfast food and is also considered as a health food. Though popular throughout Northern parts of the country, its limited shelf-life even under refrigeration imposes severe restrictions on its organized manufacture and marketing. In order to promote dalia dessert as a marketable product, in the present study, a process was developed for manufacture of instant dalia pre-mix, as a dry product with long shelf-life, which could be attractively packaged and easily reconstituted for consumption. During the investigation, the effect of different levels of milk solids and wheat solids was studied on dalia pre-mix quality by employing a central composite rotatable design (CCRD). The suggested formulation had 17.82 % milk solids and 2.87 % wheat solids. This formulation was found to be most appropriate for manufacture of instant dalia pre-mix with predicted sensory scores (Max. 100) of 85.35, 41.98 and 67.27 for mouthfeel, consistency and flavor, respectively; the viscosity of the product was 941.0 cp.

A parallel adaptive mesh refinement algorithm for predicting turbulent non-premixed combusting flows

International Nuclear Information System (INIS)

Gao, X.; Groth, C.P.T.

2005-01-01

A parallel adaptive mesh refinement (AMR) algorithm is proposed for predicting turbulent non-premixed combusting flows characteristic of gas turbine engine combustors. The Favre-averaged Navier-Stokes equations governing mixture and species transport for a reactive mixture of thermally perfect gases in two dimensions, the two transport equations of the κ-ψ turbulence model, and the time-averaged species transport equations, are all solved using a fully coupled finite-volume formulation. A flexible block-based hierarchical data structure is used to maintain the connectivity of the solution blocks in the multi-block mesh and facilitate automatic solution-directed mesh adaptation according to physics-based refinement criteria. This AMR approach allows for anisotropic mesh refinement and the block-based data structure readily permits efficient and scalable implementations of the algorithm on multi-processor architectures. Numerical results for turbulent non-premixed diffusion flames, including cold- and hot-flow predictions for a bluff body burner, are described and compared to available experimental data. The numerical results demonstrate the validity and potential of the parallel AMR approach for predicting complex non-premixed turbulent combusting flows. (author)

An Investigation of a Hybrid Mixing Timescale Model for PDF Simulations of Turbulent Premixed Flames

Science.gov (United States)

Zhou, Hua; Kuron, Mike; Ren, Zhuyin; Lu, Tianfeng; Chen, Jacqueline H.

2016-11-01

Transported probability density function (TPDF) method features the generality for all combustion regimes, which is attractive for turbulent combustion simulations. However, the modeling of micromixing due to molecular diffusion is still considered to be a primary challenge for TPDF method, especially in turbulent premixed flames. Recently, a hybrid mixing rate model for TPDF simulations of turbulent premixed flames has been proposed, which recovers the correct mixing rates in the limits of flamelet regime and broken reaction zone regime while at the same time aims to properly account for the transition in between. In this work, this model is employed in TPDF simulations of turbulent premixed methane-air slot burner flames. The model performance is assessed by comparing the results from both direct numerical simulation (DNS) and conventional constant mechanical-to-scalar mixing rate model. This work is Granted by NSFC 51476087 and 91441202.

Hollow hemisphere-shaped macroporous graphene/tungsten carbide/platinum nanocomposite as an efficient electrocatalyst for the oxygen reduction reaction

International Nuclear Information System (INIS)

Li, Zesheng; Liu, Zhisen; Li, Bolin; Liu, Zhenghui; Li, Dehao; Wang, Hongqiang; Li, Qingyu

2016-01-01

Graphical abstract: Newfashioned hollow hemisphere-shaped macroporous graphene/tungsten carbide/platinum (HMG/WC/Pt) nanocomposite with interesting three-dimensional architecture bas been successfully fabricated as an efficient electrocatalyst for the oxygen reduction reaction. - Highlights: • Hollow hemisphere-shaped macroporous graphene is proposed as ORR catalyst support. • Honeycomb-like macroporous graphene/WC/Pt electrocatalyst is firsy prepared for ORR. • The present electrocatalyst exhibited greatly enhanced ORR catalytic activity and stability. - Abstract: Hollow hemisphere-shaped macroporous graphene/tungsten carbide/platinum (HMG/WC/Pt) nanocomposite has been synthesized as an efficient electrocatalyst for the oxygen reduction reaction (ORR). The HMG/WC/Pt sample has been systematically characterized by the X-ray diffraction (XRD), Scanning electron microscope (SEM) and Transmission electron microscopy (TEM). The analysis results indicate that the sample has an interesting three-dimensional hollow hemisphere-shaped macroporous architecture. The results also demonstrate the successful integration of WC and Pt nanoparticles on the HMG, in which the WC nanoparticles are in size of about 10 nm and the Pt nanoparticles are in size of about 3 nm. The as-prepared HMG/WC/Pt electrode displays excellent electrocatalytic performances for the ORR in 0.1 mol L −1 HClO 4 electrolyte. The mass activity (i m at 0.9 V) of HMG/WC/Pt is 206 mA mg −1 Pt, which is about 85% higher than that of Pt/C (112 mA mg −1 Pt). It also displayed a very high activity retention of 84.5% after 2000 cyclic voltammetry cycles for the HMG/WC/Pt, while that of the Pt/C is only 70.5%. The HMG/WC/Pt nanocomposite would be a promising electrocatalytic material for the ORR in Fuel cell applications.

Effect of Different Routes of Vitamin/Mineral premix Administration ...

African Journals Online (AJOL)

An experiment was conducted to determine the best route of vitamin/mineral premix administration to broilers using a completely randomized design. The routes of administrations were through formulated diets, daily in drinking water, and daily mixing in feed ration. Histological examination of the liver did not reveal any ...

Structure of Unsteady Partially Premixed Flames and the Existence of State Relationships

Directory of Open Access Journals (Sweden)

Suresh K. Aggarwal

2009-09-01

Full Text Available In this study, we examine the structure and existence of state relationships in unsteady partially premixed flames (PPFs subjected to buoyancy-induced and external perturbations. A detailed numerical model is employed to simulate the steady and unsteady two-dimensional PPFs established using a slot burner under normal and zero-gravity conditions. The coflow velocity is parametrically varied. The methane-air chemistry is modeled using a fairly detailed mechanism that contains 81 elementary reactions and 24 species. Validation of the computational model is provided through comparisons of predictions with nonintrusive measurements. The combustion proceeds in two reaction zones, one a rich premixed zone and the other a nonpremixed zone. These reaction zones are spatially separated, but involve strong interactions between them due to thermochemistry and scalar transport. The fuel is mostly consumed in the premixed zone to produce CO and H2, which are transported to and consumed in the nonpremixed zone. The nonpremixed zone in turn provides heat and H-atoms to the premixed zone. For the range of conditions investigated, the zero-g partially premixed flames exhibit a stable behavior and a remarkably strong resistance to perturbations. In contrast, the corresponding normal-gravity flames exhibit oscillatory behavior at low coflow velocities but a stable behavior at high coflow velocities, and the behavior can be explained in terms of a global and convective instabilities. The effects of coflow and gravity on the flames are characterized through a parameter VR, defined as the ratio of coflow velocity to jet velocity. For VR ≤ 1 (low coflow velocity regime, the structures of both 0- and 1-g flames are strongly sensitive to changes in VR, while they are only mildly affected by coflow in the high coflow velocity regime (VR > 1. In addition, the spatio-temporal characteristics of the 0- and 1-g flames are markedly different in the first regime, but are

Investigation the effect of porosity on corrosion of macroporous silicon in 1.0 M sodium hydroxide solution using weight loss measurements, electrochemical methods and scanning electron microscope

International Nuclear Information System (INIS)

Lai, Chuan; Xiang, Zhen

2015-01-01

Highlights: • The dissolution of silicon wafers conforms Faraday’s laws of electrolysis. • The porosity effect on macroporous silicon corrosion was investigated. • The corrosion rate increase linearly with porosity increasing. • The porosity effect on activation parameters was obtained. - Abstract: In this study, the macroporous silicon has been fabricated by electrochemical anodization. The dissolution of n-type silicon wafers in etching solution conforms Faraday’s laws of electrolysis. The fabricated macroporous silicon with different porosity corrosion in 1.0 M NaOH was systemically investigated by weight loss measurements, electrochemical methods and scanning electron microscope. Results show that with the porosity increasing, the corrosion rate of macroporous silicon in 1.0 M NaOH increases linearly. In addition, the increase of corrosion rate of macroporous silicon with relative higher porosity was determined by the pre-exponential factor.

Non-lithographic method of forming ordered arrays of silicon pillars and macropores

International Nuclear Information System (INIS)

Mills, David; Kolasinski, Kurt W

2005-01-01

Micrometre-scale Si pillars are formed by chemically enhanced laser ablation using nanosecond excimer laser irradiation of a Si single crystal in the presence of SF 6 . We demonstrate the importance of precursor holes in determining the positioning of the pillars and show that we can control the initiation of precursor holes by ruling a grating into the Si substrate prior to irradiation. A rule defines an edge from which the laser light diffracts. Near-field amplification of the laser intensity enhances the formation of the precursor holes and aligns them parallel to the rule. The pillars can be thinned and eventually removed by wet chemical etching in aqueous KOH, resulting first in ordered arrays of extremely high aspect ratio pillars (e.g. tens of micrometres in length, with ∼ 10 nm tips) and then macropores. The shape of the macropore is determined by crystallography and the anisotropy of the wet etchant

An experimental and kinetic modeling study of premixed nitroethane flames at low pressure

DEFF Research Database (Denmark)

Zhang, Kuiwen; Zhang, Lidong; Xie, Mingfeng

2013-01-01

An experimental and kinetic modeling study is reported on three premixed nitroethane/oxygen/argon flames at low pressure (4.655kPa) with the equivalence ratios (Φ) of 1.0, 1.5 and 2.0. Over 30 flame species were identified with tunable synchrotron vacuum ultraviolet photoionization mass spectrome......An experimental and kinetic modeling study is reported on three premixed nitroethane/oxygen/argon flames at low pressure (4.655kPa) with the equivalence ratios (Φ) of 1.0, 1.5 and 2.0. Over 30 flame species were identified with tunable synchrotron vacuum ultraviolet photoionization mass...

The application of Flamelet Generated Manifolds in partailly-premixed flames

NARCIS (Netherlands)

Ramaekers, W.J.S.; Albrecht, B.A.; Oijen, van J.A.; Goey, de L.P.H.; Eggels, R.L.G.M.

2005-01-01

To reduce harmful emissions numerical models are developed to simulate combustion processes in engineering applications. In this paper a model for partially-premixed combustion used in Reynolds Averaged Navier-Stokes Simulations (RANS) is presented. A flamelet approach combined with a Probability

Premixer Design for High Hydrogen Fuels

Energy Technology Data Exchange (ETDEWEB)

Benjamin P. Lacy; Keith R. McManus; Balachandar Varatharajan; Biswadip Shome

2005-12-16

This 21-month project translated DLN technology to the unique properties of high hydrogen content IGCC fuels, and yielded designs in preparation for a future testing and validation phase. Fundamental flame characterization, mixing, and flame property measurement experiments were conducted to tailor computational design tools and criteria to create a framework for predicting nozzle operability (e.g., flame stabilization, emissions, resistance to flashback/flame-holding and auto-ignition). This framework was then used to establish, rank, and evaluate potential solutions to the operability challenges of IGCC combustion. The leading contenders were studied and developed with the most promising concepts evaluated via computational fluid dynamics (CFD) modeling and using the design rules generated by the fundamental experiments, as well as using GE's combustion design tools and practices. Finally, the project scoped the necessary steps required to carry the design through mechanical and durability review, testing, and validation, towards full demonstration of this revolutionary technology. This project was carried out in three linked tasks with the following results. (1) Develop conceptual designs of premixer and down-select the promising options. This task defined the ''gap'' between existing design capabilities and the targeted range of IGCC fuel compositions and evaluated the current capability of DLN pre-mixer designs when operated at similar conditions. Two concepts (1) swirl based and (2) multiple point lean direct injection based premixers were selected via a QFD from 13 potential design concepts. (2) Carry out CFD on chosen options (1 or 2) to evaluate operability risks. This task developed the leading options down-selected in Task 1. Both a GE15 swozzle based premixer and a lean direct injection concept were examined by performing a detailed CFD study wherein the aerodynamics of the design, together with the chemical kinetics of the

Linear Stability Analysis of Laminar Premixed Fuel-Rich Double-Spray Flames

Directory of Open Access Journals (Sweden)

Noam Weinberg

2014-03-01

Full Text Available This paper considers the stability of a double-spray premixed flame formed when both fuel and oxidizer are initially present in the form of sprays of evaporating liquid droplets. To simplify the inherent complexity that characterizes the analytic solution of multi-phase combustion processes, the analysis is restricted to fuel-rich laminar premixed double-spray flames, and assumes a single-step global chemical reaction mechanism. Steady-state solutions are obtained and the sensitivity of the flame temperature and the flame propagating velocity to the initial liquid fuel and/or oxidizer loads are established. The stability analysis revealed an increased proneness to cellular instability induced by the presence of the two sprays, and for the fuel-rich case considered here the influence of the liquid oxidizer was found to be more pronounced than that of the liquid fuel. Similar effects were noted for the neutral pulsating stability boundaries. The impact of unequal latent heats of vaporization is also investigated and found to be in keeping with the destabilizing influence of heat loss due to droplet evaporation. It should be noted that as far as the authors are aware no experimental evidence is available for (at least validation of the predictions. However, they do concur in a general and reasonable fashion with independent experimental evidence in the literature of the behavior of single fuel spray laminar premixed flames.

Soot Formation in Laminar Premixed Methane/Oxygen Flames at Atmospheric Pressure

Science.gov (United States)

Xu, F.; Lin, K.-C.; Faeth, G. M.

1998-01-01

Flame structure and soot formation were studied within soot-containing laminar premixed mc1hane/oxygen flames at atmospheric pressure. The following measurements were made: soot volume fractions by laser extinction, soot temperatures by multiline emission, gas temperatures (where soot was absent) by corrected fine-wire thermocouples, soot structure by thermophoretic sampling and transmission electron microscope (TEM), major gas species concentrations by sampling and gas chromatography, and gas velocities by laser velocimetry. Present measurements of gas species concentrations were in reasonably good agreement with earlier measurements due to Ramer et al. as well as predictions based on the detailed mechanisms of Frenklach and co-workers and Leung and Lindstedt: the predictions also suggest that H atom concentrations are in local thermodynamic equilibrium throughout the soot formation region. Using this information, it was found that measured soot surface growth rates could be correlated successfully by predictions based on the hydrogen-abstraction/carbon-addition (HACA) mechanisms of both Frenklach and co-workers and Colket and Hall, extending an earlier assessment of these mechanisms for premixed ethylene/air flames to conditions having larger H/C ratios and acetylene concentrations. Measured primary soot particle nucleation rates were somewhat lower than the earlier observations for laminar premixed ethylene/air flames and were significantly lower than corresponding rates in laminar diffusion flames. for reasons that still must be explained.

Understanding and predicting soot generation in turbulent non-premixed jet flames.

Energy Technology Data Exchange (ETDEWEB)

Wang, Hai (University of Southern California, Los Angeles, CA); Kook, Sanghoon; Doom, Jeffrey; Oefelein, Joseph Charles; Zhang, Jiayao; Shaddix, Christopher R.; Schefer, Robert W.; Pickett, Lyle M.

2010-10-01

This report documents the results of a project funded by DoD's Strategic Environmental Research and Development Program (SERDP) on the science behind development of predictive models for soot emission from gas turbine engines. Measurements of soot formation were performed in laminar flat premixed flames and turbulent non-premixed jet flames at 1 atm pressure and in turbulent liquid spray flames under representative conditions for takeoff in a gas turbine engine. The laminar flames and open jet flames used both ethylene and a prevaporized JP-8 surrogate fuel composed of n-dodecane and m-xylene. The pressurized turbulent jet flame measurements used the JP-8 surrogate fuel and compared its combustion and sooting characteristics to a world-average JP-8 fuel sample. The pressurized jet flame measurements demonstrated that the surrogate was representative of JP-8, with a somewhat higher tendency to soot formation. The premixed flame measurements revealed that flame temperature has a strong impact on the rate of soot nucleation and particle coagulation, but little sensitivity in the overall trends was found with different fuels. An extensive array of non-intrusive optical and laser-based measurements was performed in turbulent non-premixed jet flames established on specially designed piloted burners. Soot concentration data was collected throughout the flames, together with instantaneous images showing the relationship between soot and the OH radical and soot and PAH. A detailed chemical kinetic mechanism for ethylene combustion, including fuel-rich chemistry and benzene formation steps, was compiled, validated, and reduced. The reduced ethylene mechanism was incorporated into a high-fidelity LES code, together with a moment-based soot model and models for thermal radiation, to evaluate the ability of the chemistry and soot models to predict soot formation in the jet diffusion flame. The LES results highlight the importance of including an optically-thick radiation

Fabrication and properties of meso-macroporous electrodes screen-printed from mesoporous titania nanoparticles for dye-sensitized solar cells

International Nuclear Information System (INIS)

Ma Liang; Liu Min; Peng Tianyou; Fan Ke; Lu Lanlan; Dai Ke

2009-01-01

A meso-macroporous TiO 2 film electrode was fabricated by using mesoporous TiO 2 (m-TiO 2 ) nanoparticles through a screen-printing technique in order to efficiently control the main fabrication step of dye-sensitized solar cells (DSSCs). The qualities of the screen-printed m-TiO 2 films were characterized by means of spectroscopy, electron microscopy, nitrogen adsorption-desorption and photoelectrochemical measurements. Under the optimal paste composition and printing conditions, the DSSC based on the meso-macroporous m-TiO 2 film electrode exhibits an energy conversion efficiency of 4.14%, which is improved by 1.70% in comparison with DSSC made with commercially available nonporous TiO 2 nanoparticles (P25, Degussa) electrode printed with a similar paste composition. The meso-macroporous structure within the m-TiO 2 film is of great benefit to the dye adsorption, light absorption and the electrolyte transportation, and then to the improvement of the overall energy conversion efficiency of DSSC.

Methane combustion in catalytic premixed burners

International Nuclear Information System (INIS)

Cerri, I.; Saracco, G.; Specchia, V.

1999-01-01

Catalytic premixed burners for domestic boiler applications were developed with the aim of achieving a power modularity from 10 to 100% and pollutant emissions limited to NO x 2 , where the combustion took place entirely inside the burner heating it to incandescence and allowing a decrease in the flame temperature and NO x emissions. Such results were confirmed through further tests carried out in a commercial industrial-scale boiler equipped with the conical panels. All the results, by varying the excess air and the heat power employed, are presented and discussed [it

Experimental study of a premixed oscillating flame stabilized inside the tube

Energy Technology Data Exchange (ETDEWEB)

Choi, B.I.; Shin, H.D. [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

1998-04-01

An experimental study of premixed oscillating flame stabilized inside the tube has been conducted in order to examine the kinematic behavior of premixed flame under the flow oscillation and flame/flow interaction. Flow oscillation is accomplished by an acoustic excitation. Oscillating nature of flow has been studied with and without the flame using velocity and pressure measurements by a LDV and microphone, respectively Kinematic behavior of the oscillating flame is examined using triggered ICCD camera system. Velocity oscillation and flame oscillation is the same frequency as that produced by the acoustic excitation and flame shape has a similarity at various phase of oscillation. Upstream velocity field near the flame zone is greatly influenced by the flame oscillation. This is the typical example of flame/flow interaction. (author). 9 refs., 7 figs.

Optimization of gas mixing system of premixed burner based on CFD analysis

International Nuclear Information System (INIS)

Zhang, Tian-Hu; Liu, Feng-Guo; You, Xue-Yi

2014-01-01

Highlights: • New multi-ejectors gas mixing system for premixed combustion burner is provided. • Two measures are proposed to improve the flow uniformity at the outlet of GMS. • Small improvement of uniformity induces significant decrease of pollutant emission. • Uniformity of velocity and fuel–gas mixing of ejector increases 234.2% and 2.9%. • Uniformity of flow rate and fuel–gas mixing of ejectors increases 1.9% and 2.2%. - Abstract: The optimization of gas mixing system (GMS) of premixed burner is presented by Computational Fluid Dynamics (CFD) and the uniformity at the outlet of GMS is proved experimentally to have strong influence on pollutant emission. To improve the uniformity at the outlet of GMS, the eleven distribution orifice plates and a diversion plate are introduced. The quantified analysis shows that the uniformity at the outlet of GMS is improved significantly. With applying the distribution orifice plates, the uniformity of velocity and fuel–gas mixing of single ejector is increased by 234.2% and 2.9%, respectively. With applying the diversion plate, the uniformity of flow rate and fuel–gas mixing of different ejectors is increased by 1.9% and 2.2%, respectively. The optimal measures and geometrical parameters provide an applicable guidance for the design of commercial premixed burner

Cost analysis of premixed multichamber bags versus compounded parenteral nutrition: breakeven point.

Science.gov (United States)

Bozat, Erkut; Korubuk, Gamze; Onar, Pelin; Abbasoglu, Osman

2014-02-01

Industrially premixed multichamber bags or hospital-manufactured compounded products can be used for parenteral nutrition. The aim of this study was to compare the cost of these 2 approaches. Costs of compounded parenteral nutrition bags in an university hospital were calculated. A total of 600 bags that were administered during 34 days between December 10, 2009 and February 17, 2010 were included in the analysis. For quality control, specific gravity evaluation of the filled bags was performed. It was calculated that the variable cost of a hospital compounded bag was $26.15. If we take the annual fixed costs into consideration, the production cost reaches $36.09 for each unit. It was estimated that the cost for the corresponding multichamber bag was $37.79. Taking the fixed and the variable costs into account, the breakeven point of the hospital compounded and the premixed multichamber bags was seen at 5,404 units per year. In specific gravity evaluation, it was observed that the mean and interval values were inside the upper and lower control margins. In this analysis, usage of hospital-compounded parenteral nutrition bags showed a cost advantage in hospitals that treat more than 15 patients per day. In small volume hospitals, premixed multichamber bags may be more beneficial.

Development of Criteria for Flameholding Tendencies within Premixer Passages for High Hydrogen Content Fuels

Energy Technology Data Exchange (ETDEWEB)

Lewis, Elliot Sullivan- [Univ. of California, Irvine, CA (United States); McDonell, Vincent G. [Univ. of California, Irvine, CA (United States)

2014-12-01

Due to increasingly stringent air quality requirements stationary power gas turbines have moved to lean-premixed operation, which reduces pollutant emissions but can result in flashback. Flashback can cause serious damage to the premixer hardware. Curtailing flashback can be difficult with hydrocarbon fuels and becomes even more challenging when hydrogen is used as the fuel. The two main approaches for coping with flashback are either to design a combustor that is resistant to flashback, or to design a premixer that will not anchor a flame if flashback occurs. Even with a well-designed combustor flashback can occur under certain circumstances, thus it is necessary to determine how to avoid flameholding within the premixer passageways of a gas turbine. To this end, an experiment was designed that would determine the flameholding propensities at elevated pressures and temperatures of three different classes of geometric features commonly found in gas turbine premixers, with both natural gas and hydrogen fuel. Experiments to find the equivalence ratio at blow off were conducted within an optically accessible test apparatus with four flameholders: 0.25 and 0.50 inch diameter cylinders, a reverse facing step with a height of 0.25 inches, and a symmetric airfoil with a thickness of 0.25 inches and a chord length of one inch. Tests were carried out at temperatures between 300 K and 750 K, at pressures up to 9 atmospheres. Typical bulk velocities were between 40 and 100 m/s. The effect of airfoil’s angle of rotation was also investigated. Blow off for hydrogen flames was found to occur at much lower adiabatic flame temperatures than natural gas flames. Additionally it was observed that at high pressures and high turbulence intensities, reactant velocity does not have a noticeable effect on the point of blow off due in large part to corresponding increases in turbulent flame speed. Finally a semi empirical correlation was developed that predicts flame extinction for both

Influence of surface microstructure and chemistry on osteoinduction and osteoclastogenesis by biphasic calcium phosphate discs

Directory of Open Access Journals (Sweden)

NL Davison

2015-06-01

Full Text Available It has been reported that surface microstructural dimensions can influence the osteoinductivity of calcium phosphates (CaPs, and osteoclasts may play a role in this process. We hypothesised that surface structural dimensions of ≤ 1 μm trigger osteoinduction and osteoclast formation irrespective of macrostructure (e.g., concavities, interconnected macropores, interparticle space or surface chemistry. To test this, planar discs made of biphasic calcium phosphate (BCP: 80 % hydroxyapatite, 20 % tricalcium phosphate were prepared with different surface structural dimensions – either ~ 1 μm (BCP1150 or ~ 2-4 μm (BCP1300 – and no macropores or concavities. A third material was made by sputter coating BCP1150 with titanium (BCP1150Ti, thereby changing its surface chemistry but preserving its surface structure and chemical reactivity. After intramuscular implantation in 5 dogs for 12 weeks, BCP1150 formed ectopic bone in 4 out of 5 samples, BCP1150Ti formed ectopic bone in 3 out of 5 samples, and BCP1300 formed no ectopic bone in any of the 5 samples. In vivo, large multinucleated osteoclast-like cells densely colonised BCP1150, smaller osteoclast-like cells formed on BCP1150Ti, and osteoclast-like cells scarcely formed on BCP1300. In vitro, RAW264.7 cells cultured on the surface of BCP1150 and BCP1150Ti in the presence of osteoclast differentiation factor RANKL (receptor activator for NF-κB ligand proliferated then differentiated into multinucleated osteoclast-like cells with positive tartrate resistant acid phosphatase (TRAP activity. However, cell proliferation, fusion, and TRAP activity were all significantly inhibited on BCP1300. These results indicate that of the material parameters tested – namely, surface microstructure, macrostructure, and surface chemistry – microstructural dimensions are critical in promoting osteoclastogenesis and triggering ectopic bone formation.

Investigation of Scalar Filtered Density Function in Turbulent Partially Premixed Flames

National Research Council Canada - National Science Library

Tong, Chenning

2006-01-01

... using measurement data obtained in turbulent partially premixed methane/air (Sandia) flames. For SGS scalar variance small compared to its mean, the FMDF is not far from Gaussian and the SGS scalar is well mixed...

Quantification of trace metals in infant formula premixes using laser-induced breakdown spectroscopy

Science.gov (United States)

Cama-Moncunill, Raquel; Casado-Gavalda, Maria P.; Cama-Moncunill, Xavier; Markiewicz-Keszycka, Maria; Dixit, Yash; Cullen, Patrick J.; Sullivan, Carl

2017-09-01

Infant formula is a human milk substitute generally based upon fortified cow milk components. In order to mimic the composition of breast milk, trace elements such as copper, iron and zinc are usually added in a single operation using a premix. The correct addition of premixes must be verified to ensure that the target levels in infant formulae are achieved. In this study, a laser-induced breakdown spectroscopy (LIBS) system was assessed as a fast validation tool for trace element premixes. LIBS is a promising emission spectroscopic technique for elemental analysis, which offers real-time analyses, little to no sample preparation and ease of use. LIBS was employed for copper and iron determinations of premix samples ranging approximately from 0 to 120 mg/kg Cu/1640 mg/kg Fe. LIBS spectra are affected by several parameters, hindering subsequent quantitative analyses. This work aimed at testing three matrix-matched calibration approaches (simple-linear regression, multi-linear regression and partial least squares regression (PLS)) as means for precision and accuracy enhancement of LIBS quantitative analysis. All calibration models were first developed using a training set and then validated with an independent test set. PLS yielded the best results. For instance, the PLS model for copper provided a coefficient of determination (R2) of 0.995 and a root mean square error of prediction (RMSEP) of 14 mg/kg. Furthermore, LIBS was employed to penetrate through the samples by repetitively measuring the same spot. Consequently, LIBS spectra can be obtained as a function of sample layers. This information was used to explore whether measuring deeper into the sample could reduce possible surface-contaminant effects and provide better quantifications.

The route of liquid precursor to ZnO nanoparticles in premixed combustion spray pyrolysis

Science.gov (United States)

Widiyastuti, W.; Machmudah, Siti; Nurtono, Tantular; Winardi, Sugeng

2018-04-01

Zinc oxide nanoparticles had been successfully synthesized by premixed combustion spray pyrolysis. Zinc acetate was dissolved in distilled water was selected as a liquid precursor. Zinc nitrate was also used for comparison the effect of precursor type on the generated particles morphology and the crystallinity. The premixed combustion reaction used liquefied petroleum gas (LPG) mainly consisting of butane and propane as a fuel and compressed air used as an oxidizer. The liquid precursor was atomized using a custom two fluid nozzle to generate droplets. Then, the droplets were sprayed by the flow of air as a carrier gas into the premixed combustion reactor. The zinc precursor was decomposed to zinc oxide due to the high temperature as a result of combustion reaction inside the reactor resulting in nanoparticles formation. The particle size decreased with the increase of the fuel flow rate. In addition, it can be found that at the same flow rate of fuel, the particle size of zinc oxide synthesized using zinc nitrate is larger than that of the use of zinc acetate as a precursor.

Evaluation of partially premixed turbulent flame stability from mixture fraction statistics in a slot burner

KAUST Repository

Kruse, Stephan

2018-04-11

Partially premixed combustion is characterized by mixture fraction inhomogeneity upstream of the reaction zone and occurs in many applied combustion systems. The temporal and spatial fluctuations of the mixture fraction have tremendous impact on the combustion characteristics, emission formation, and flame stability. In this study, turbulent partially premixed flames are experimentally studied in a slot burner configuration. The local temperature and gas composition is determined by means of one-dimensional, simultaneous detection of Rayleigh and Raman scattering. The statistics of the mixture fraction are utilized to characterize the impact of the Reynolds number, the global equivalence ratio, the progress of mixing within the flame, as well as the mixing length on the mixing field. Furthermore, these effects are evaluated by means of a regime diagram for partially premixed flames. In this study, it is shown that the increase of the mixing length results in a significantly more stable flame. The impact of the Reynolds number on flame stability is found to be minor.

Evaluation of partially premixed turbulent flame stability from mixture fraction statistics in a slot burner

KAUST Repository

Kruse, Stephan; Mansour, Mohy S.; Elbaz, Ayman M.; Varea, Emilien; Grü nefeld, Gerd; Beeckmann, Joachim; Pitsch, Heinz

2018-01-01

Partially premixed combustion is characterized by mixture fraction inhomogeneity upstream of the reaction zone and occurs in many applied combustion systems. The temporal and spatial fluctuations of the mixture fraction have tremendous impact on the combustion characteristics, emission formation, and flame stability. In this study, turbulent partially premixed flames are experimentally studied in a slot burner configuration. The local temperature and gas composition is determined by means of one-dimensional, simultaneous detection of Rayleigh and Raman scattering. The statistics of the mixture fraction are utilized to characterize the impact of the Reynolds number, the global equivalence ratio, the progress of mixing within the flame, as well as the mixing length on the mixing field. Furthermore, these effects are evaluated by means of a regime diagram for partially premixed flames. In this study, it is shown that the increase of the mixing length results in a significantly more stable flame. The impact of the Reynolds number on flame stability is found to be minor.

Direct Numerical Simulations of Statistically Stationary Turbulent Premixed Flames

KAUST Repository

Im, Hong G.

2016-07-15

Direct numerical simulations (DNS) of turbulent combustion have evolved tremendously in the past decades, thanks to the rapid advances in high performance computing technology. Today’s DNS is capable of incorporating detailed reaction mechanisms and transport properties of hydrocarbon fuels, with physical parameter ranges approaching laboratory scale flames, thereby allowing direct comparison and cross-validation against laser diagnostic measurements. While these developments have led to significantly improved understanding of fundamental turbulent flame characteristics, there are increasing demands to explore combustion regimes at higher levels of turbulent Reynolds (Re) and Karlovitz (Ka) numbers, with a practical interest in new combustion engines driving towards higher efficiencies and lower emissions. The article attempts to provide a brief overview of the state-of-the-art DNS of turbulent premixed flames at high Re/Ka conditions, with an emphasis on homogeneous and isotropic turbulent flow configurations. Some important qualitative findings from numerical studies are summarized, new analytical approaches to investigate intensely turbulent premixed flame dynamics are discussed, and topics for future research are suggested. © 2016 Taylor & Francis.

Facile synthesis of radial-like macroporous superparamagnetic chitosan spheres with in-situ co-precipitation and gelation of ferro-gels.

Directory of Open Access Journals (Sweden)

Chih-Hui Yang

Full Text Available Macroporous chitosan spheres encapsulating superparamagnetic iron oxide nanoparticles were synthesized by a facile and effective one-step fabrication process. Ferro-gels containing ferrous cations, ferric cations and chitosan were dropped into a sodium hydroxide solution through a syringe pump. In addition, a sodium hydroxide solution was employed for both gelation (chitosan and co-precipitation (ferrous cations and ferric cations of the ferro-gels. The results showed that the in-situ co-precipitation of ferro-ions gave rise to a radial morphology with non-spheroid macro pores (large cavities inside the chitosan spheres. The particle size of iron oxide can be adjusted from 2.5 nm to 5.4 nm by tuning the concentration of the sodium hydroxide solution. Using Fourier Transform Infrared Spectroscopy and X-ray diffraction spectra, the synthesized nanoparticles were illustrated as Fe(3O(4 nanoparticles. In addition, the prepared macroporous chitosan spheres presented a super-paramagnetic behaviour at room temperature with a saturation magnetization value as high as ca. 18 emu/g. The cytotoxicity was estimated using cell viability by incubating doses (0∼1000 µg/mL of the macroporous chitosan spheres. The result showed good viability (above 80% with alginate chitosan particles below 1000 µg/mL, indicating that macroporous chitosan spheres were potentially useful for biomedical applications in the future.

Measurements of Positively Charged Ions in Premixed Methane-Oxygen Atmospheric Flames

KAUST Repository

Alquaity, Awad; Han, Jie; Chahine, May; Selim, Hatem; Belhi, Memdouh; Sarathy, Mani; Bisetti, Fabrizio; Farooq, Aamir

2016-01-01

chemistry models are needed to understand and predict the effect of external electric fields on combustion plasmas. In this work, a molecular beam mass spectrometer (MBMS) is utilized to measure ion concentration profiles in premixed methane–oxygen argon

Preparation of macroporous zirconia monoliths from ionic precursors via an epoxide-mediated sol-gel process accompanied by phase separation

International Nuclear Information System (INIS)

Guo, Xingzhong; Song, Jie; Lvlin, Yixiu; Yang, Hui; Nakanishi, Kazuki; Kanamori, Kazuyoshi

2015-01-01

Monolithic macroporous zirconia (ZrO 2 ) derived from ionic precursors has been successfully fabricated via the epoxide-mediated sol-gel route accompanied by phase separation in the presence of propylene oxide (PO) and poly(ethylene oxide) (PEO). The addition of PO used as an acid scavenger mediates the gelation, whereas PEO enhances the polymerization-induced phase separation. The appropriate choice of the starting compositions allows the production of a macroporous zirconia monolith with a porosity of 52.9% and a Brunauer–Emmett–Teller (BET) surface area of 171.9 m 2 · g −1 . The resultant dried gel is amorphous, whereas tetragonal ZrO 2 and monoclinic ZrO 2 are precipitated at 400 and 600 °C, respectively, without spoiling the macroporous morphology. After solvothermal treatment with an ethanol solution of ammonia, tetragonal ZrO 2 monoliths with smooth skeletons and well-defined mesopores can be obtained, and the BET surface area is enhanced to 583.8 m 2 · g −1 . (paper)

Effect of AC electric fields on the stabilization of premixed bunsen flames

KAUST Repository

Kim, Minkuk; Chung, Suk-Ho; Kim, Hwanho

2011-01-01

The stabilization characteristics of laminar premixed bunsen flames have been investigated experimentally for stoichiometric methane-air mixture by applying AC voltage to the nozzle with the single-electrode configuration. The detachment velocity

DNS of non-premixed combustion in a compressible mixing layer

NARCIS (Netherlands)

Bastiaans, R.J.M.; Somers, L.M.T.; Lange, de H.C.; Geurts, B.J.

2001-01-01

The non-premixed reaction of fuel with air in a mixing layer is studied using DNS. The situation is a model for the mixing-controlled combustion in a Diesel engine. We show that the combustion region can be comparably passive with respect to relatively large scale aerodynamic instabilities. However

Visualization of the heat release zone of highly turbulent premixed jet flames

Science.gov (United States)

Lv, Liang; Tan, Jianguo; Zhu, Jiajian

2017-10-01

Visualization of the heat release zone (HRZ) of highly turbulent flames is significantly important to understand the interaction between turbulence and chemical reactions, which is the foundation to design and optimize engines. Simultaneous measurements of OH and CH2O using planar laser-induced fluorescence (PLIF) were performed to characterize the HRZ. A well-designed piloted premixed jet burner was employed to generate four turbulent premixed CH4/air jet flames, with different jet Reynolds numbers (Rejet) ranging from 4900 to 39200. The HRZ was visualized by both the gradient of OH and the pixel-by-pixel product of OH and CH2O. It is shown that turbulence has an increasing effect on the spatial structure of the flame front with an increasing height above the jet exit for the premixed jet flames, which results in the broadening of the HRZ and the increase of the wrinkling. The HRZ remains thin as the Rejet increases, whereas the preheat zone is significantly broadened and thickened. This indicates that the smallest turbulent eddies can only be able to enter the flame front rather than the HRZ in the present flame conditions. The flame quenching is observed with Rejet = 39200, which may be due to the strong entrainment of the cold air from outside of the burned gas region.

Estabilidade térmica das vitaminas A e E em rações e premixes vitamínicos para camarões

OpenAIRE

Prado,João Paulo de Sousa; Cavalheiro,José Marcelino Oliveira; Silva,Fernanda Vanessa Gomes da; Queiroga Neto,Vicente; Bora,Pushkar Singh; Cavalheiro,Thiago Brandão

2011-01-01

O trabalho teve como objetivo avaliar a estabilidade térmica das vitaminas A e E em diferentes rações e premixes vitamínicos utilizados na carcinicultura. Foram utilizadas no experimento três rações comerciais peletilizadas e desintegradas em diferentes diâmetros e dois premixes vitamínicos. As amostras de cada dieta e de premixes foram acondicionadas em recipientes plásticos e armazenadas nas seguintes condições: ambiente refrigerado (6°C±2°C), ambiente climatizado (20°C&p...

Electrochemical study of nitrobenzene reduction using novel Pt nanoparticles/macroporous carbon hybrid nanocomposites

International Nuclear Information System (INIS)

Zhang Yufan; Zeng Lijun; Bo Xiangjie; Wang Huan; Guo Liping

2012-01-01

Graphical abstract: A one-step microwave-assisted route for rapidly synthesizing Pt nanoparticles ensemble on macroporous carbon hybrid nanocomposites (PNMPC) has been reported. As a novel electrode material, the excellent electrochemical behavior of nitrobenzene was investigated thoroughly at the PNMPC modified glassy carbon electrode. And moreover, the modified electrode was successfully applied to the determination of nitrobenzene in real samples. Highlights: ► One-step microwave-assisted heating synthesis Pt nanoparticles/macroporous carbon hybrid nanocomposites (PNMPC). ► Catalytic rate constant being 3.14 × 10 4 M −1 s −1 for NB in pH 7.0. ► Sensitive electrochemical detection of NB at the PNMPC/Nafion/GC electrode. ► The electrode showing excellent anti-interference ability and good stability for NB. - Abstract: Novel Pt nanoparticles (PN) ensemble on macroporous carbon (MPC) hybrid nanocomposites (PNMPC) were prepared through a rapidly and simple one-step microwave-assisted heating procedure. The obtained PNMPC was characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and electrochemical methods. The electrochemical reduction of nitrobenzene (NB) was thoroughly investigated at the PNMPC modified glassy carbon (GC) electrode, and the catalytic rate constant was calculated to be 3.14 × 10 4 M −1 s −1 for NB. A sensitive NB sensor was developed based on the PNMPC/GC electrode, which showed a wide linear range (1–200 μM), low detection limit (50 nM), high sensitivity (6.93 μA μM −1 ), excellent anti-interference ability and good stability. And moreover, the electrode was successfully applied to the determination of NB in real samples.

Synthesis and Textural Characterization of Mesoporous and Meso-/Macroporous Silica Monoliths Obtained by Spinodal Decomposition

Directory of Open Access Journals (Sweden)

Anne Galarneau

2016-04-01

Full Text Available Silica monoliths featuring either mesopores or flow-through macropores and mesopores in their skeleton are prepared by combining spinodal phase separation and sol-gel condensation. The macroporous network is first generated by phase separation in acidic medium in the presence of polyethyleneoxides while mesoporosity is engineered in a second step in alkaline medium, possibly in the presence of alkylammonium cations as surfactants. The mesoporous monoliths, also referred as aerogels, are obtained in the presence of alkylpolyethylene oxides in acidic medium without the use of supercritical drying. The impact of the experimental conditions on pore architecture of the monoliths regarding the shape, the ordering, the size and the connectivity of the mesopores is comprehensively discussed based on a critical appraisal of the different models used for textural analysis.

Flow Characteristics of Multi-circular Jet Plate in Premix Chamber of Air-Assist Atomizer for Burner System

Directory of Open Access Journals (Sweden)

Amirnordin Shahrin Hisham

2016-01-01

Full Text Available The flow characteristics of multi-circular jet (MCJ plate in the premix chamber of an atomizer were investigated using Computational Fluid Dynamics. Multiphase volume of fluid behavior inside the chamber was determined via steady simulations. The Eulerian–Eulerian two-fluid approach was used for execution mixing of diesel fuel and air. Spray simulation using the discrete phase with injection was generated from the nozzle hole into the ambient atmosphere. The behavior of three MCJ plates in the premix chamber was studied numerically. Results illustrated that plate open area, Ae, influenced the turbulence inside the chamber. MCJ 3, which had the lowest open area, generated the highest flow velocity and turbulence kinetic energy compared with MCJ 1 and 2. The MCJ plates could increase the turbulence in the premix chamber and contribute to the combustion efficiency.

PREMIXED FLAME PROPAGATION AND MORPHOLOGY IN A CONSTANT VOLUME COMBUSTION CHAMBER

Energy Technology Data Exchange (ETDEWEB)

Hariharan, A; Wichman, IS

2014-06-04

This work presents an experimental and numerical investigation of premixed flame propagation in a constant volume rectangular channel with an aspect ratio of six (6) that serves as a combustion chamber. Ignition is followed by an accelerating cusped finger-shaped flame-front. A deceleration of the flame is followed by the formation of a "tulip"-shaped flame-front. Eventually, the flame is extinguished when it collides with the cold wall on the opposite channel end. Numerical computations are performed to understand the influence of pressure waves, instabilities, and flow field effects causing changes to the flame structure and morphology. The transient 2D numerical simulation results are compared with transient 3D experimental results. Issues discussed are the appearance of oscillatory motions along the flame front and the influences of gravity on flame structure. An explanation is provided for the formation of the "tulip" shape of the premixed flame front.

Dynamics and Suppression Effectiveness of Monodisperse Water Droplets in Non-Premixed Counterflow Flames

National Research Council Canada - National Science Library

Zegers, E. J; Williams, B. A; Sheinson, R. S; Fleming, J. W

2000-01-01

...-premixed propane/air counterflow flames are reported. Droplets were generated piezoelectrically, and the size and velocity distributions and the number density were determined by phase-Doppler particle anemometry...

Study of possible reduction or withdrawal of vitamin premix during ...

African Journals Online (AJOL)

The effect of dietary vitamin premix withdrawal or reduction between 29 and 35, 36 and 42, and 29 and 42 days of age on broiler chicken performance and immunocompetence was evaluated. The diets were formulated based on wheat and barley, and the experiment was conducted in floor pens (experiment 1) and battery ...

Study of possible reduction or withdrawal of vitamin premix during ...

African Journals Online (AJOL)

Jane

2011-07-06

Jul 6, 2011 ... The effect of dietary vitamin premix withdrawal or reduction between 29 and 35, 36 and 42, and 29 and. 42 days of age on broiler chicken performance and immunocompetence was evaluated. The diets were formulated based on wheat and barley, and the experiment was conducted in floor pens ...

Dynamics of flow–soot interaction in wrinkled non-premixed ethylene–air flames

KAUST Repository

Arias, Paul G.; Lecoustre, Vivien R.; Roy, Somesh; Luo, Zhaoyu; Haworth, Daniel C.; Lu, Tianfeng; Trouvé , Arnaud; Im, Hong G.

2015-01-01

A two-dimensional simulation of a non-premixed ethylene–air flame was conducted by employing a detailed gas-phase reaction mechanism considering polycyclic aromatic hydrocarbons, an aerosol-dynamics-based soot model using a method of moments

Transient combustion modeling of an oscillating lean premixed methane/air flam

NARCIS (Netherlands)

Withag, J.A.M.; Kok, Jacobus B.W.; Syed, Khawar

2009-01-01

The main objective of the present study is to demonstrate accurate low frequency transient turbulent combustion modeling. For accurate flame dynamics some improvements were made to the standard TFC combustion model for lean premixed combustion. With use of a 1D laminar flamelet code, predictions

Low and High Temperature Combustion Chemistry of Butanol Isomers in Premixed Flames and Autoignition Systems

Energy Technology Data Exchange (ETDEWEB)

Sarathy, S M; Pitz, W J; Westbrook, C K; Mehl, M; Yasunaga, K; Curran, H J; Tsujimura, T; Osswald, P; Kohse-Hoinghaus, K

2010-12-12

Butanol is a fuel that has been proposed as a bio-derived alternative to conventional petroleum derived fuels. The structural isomer in traditional 'bio-butanol' fuel is n-butanol, but newer conversion technologies produce iso-butanol as a fuel. In order to better understand the combustion chemistry of bio-butanol, this study presents a comprehensive chemical kinetic model for all the four isomers of butanol (e.g., 1-, 2-, iso- and tert-butanol). The proposed model includes detailed high temperature and low temperature reaction pathways. In this study, the primary experimental validation target for the model is premixed flat low-pressure flame species profiles obtained using molecular beam mass spectrometry (MBMS). The model is also validated against previously published data for premixed flame velocity and n-butanol rapid compression machine and shock tube ignition delay. The agreement with these data sets is reasonably good. The dominant reaction pathways at the various pressures and temperatures studied are elucidated. At low temperature conditions, we found that the reaction of alphahydroxybutyl with O{sub 2} was important in controlling the reactivity of the system, and for correctly predicting C{sub 4} aldehyde profiles in low pressure premixed flames. Enol-keto isomerization reactions assisted by HO{sub 2} were also found to be important in converting enols to aldehydes and ketones in the low pressure premixed flames. In the paper, we describe how the structural features of the four different butanol isomers lead to differences in the combustion properties of each isomer.

Effects of Buoyancy on Laminar and Turbulent Premixed V-Flame

Science.gov (United States)

Cheng, Robert K.; Bedat, Benoit

1997-01-01

Turbulent combustion occurs naturally in almost all combustion systems and involves complex dynamic coupling of chemical and fluid mechanical processes. It is considered as one of the most challenging combustion research problems today. Though buoyancy has little effect on power generating systems operating under high pressures (e.g., IC engines and turbines), flames in atmospheric burners and the operation of small to medium furnaces and boilers are profoundly affected by buoyancy. Changes in burner orientation impacts on their blow-off, flash-back and extinction limits, and their range of operation, burning rate, heat transfer, and emissions. Theoretically, buoyancy is often neglected in turbulent combustion models. Yet the modeling results are routinely compared with experiments of open laboratory flames that are obviously affected by buoyancy. This inconsistency is an obstacle to reconciling experiments and theories. Consequently, a fundamental understanding of the coupling between turbulent flames and buoyancy is significant to both turbulent combustion science and applications. The overall effect of buoyancy relates to the dynamic interaction between the flame and its surrounding, i.e., the so-called elliptical problem. The overall flame shape, its flowfield, stability, and mean and local burning rates are dictated by both upstream and downstream boundary conditions. In steady propagating premixed flames, buoyancy affects the products region downstream of the flame zone. These effects are manifested upstream through the mean and fluctuating pressure fields to influence flame stretch and flame wrinkling. Intuitively, the effects buoyancy should diminish with increasing flow momentum. This is the justification for excluding buoyancy in turbulent combustion models that treats high Reynolds number flows. The objectives of our experimental research program is to elucidate flame-buoyancy coupling processes in laminar and turbulent premixed flames, and to

Tracking Single DNA Nanodevices in Hierarchically Meso-Macroporous Antimony-Doped Tin Oxide Demonstrates Finite Confinement.

Science.gov (United States)

Mieritz, Daniel; Li, Xiang; Volosin, Alex; Liu, Minghui; Yan, Hao; Walter, Nils G; Seo, Dong-Kyun

2017-06-27

Housing bio-nano guest devices based on DNA nanostructures within porous, conducting, inorganic host materials promise valuable applications in solar energy conversion, chemical catalysis, and analyte sensing. Herein, we report a single-template synthetic development of hierarchically porous, transparent conductive metal oxide coatings whose pores are freely accessible by large biomacromolecules. Their hierarchal pore structure is bimodal with a larger number of closely packed open macropores (∼200 nm) at the higher rank and with the remaining space being filled with a gel network of antimony-doped tin oxide (ATO) nanoparticles that is highly porous with a broad size range of textual pores mainly from 20-100 nm at the lower rank. The employed carbon black template not only creates the large open macropores but also retains the highly structured gel network as holey pore walls. Single molecule fluorescence microscopic studies with fluorophore-labeled DNA nanotweezers reveal a detailed view of multimodal diffusion dynamics of the biomacromolecules inside the hierarchically porous structure. Two diffusion constants were parsed from trajectory analyses that were attributed to free diffusion (diffusion constant D = 2.2 μm 2 /s) and to diffusion within an average confinement length of 210 nm (D = 0.12 μm 2 /s), consistent with the average macropore size of the coating. Despite its holey nature, the ATO gel network acts as an efficient barrier to the diffusion of the DNA nanostructures, which is strongly indicative of physical interactions between the molecules and the pore nanostructure.

Premixed direct injection disk

Science.gov (United States)

York, William David; Ziminsky, Willy Steve; Johnson, Thomas Edward; Lacy, Benjamin; Zuo, Baifang; Uhm, Jong Ho

2013-04-23

A fuel/air mixing disk for use in a fuel/air mixing combustor assembly is provided. The disk includes a first face, a second face, and at least one fuel plenum disposed therebetween. A plurality of fuel/air mixing tubes extend through the pre-mixing disk, each mixing tube including an outer tube wall extending axially along a tube axis and in fluid communication with the at least one fuel plenum. At least a portion of the plurality of fuel/air mixing tubes further includes at least one fuel injection hole have a fuel injection hole diameter extending through said outer tube wall, the fuel injection hole having an injection angle relative to the tube axis. The invention provides good fuel air mixing with low combustion generated NOx and low flow pressure loss translating to a high gas turbine efficiency, that is durable, and resistant to flame holding and flash back.

Combined Influence of Strain and Heat Loss on Turbulent Premixed Flame Stabilization

KAUST Repository

Tay-Wo-Chong, Luis

2015-11-16

The present paper argues that the prediction of turbulent premixed flames under non-adiabatic conditions can be improved by considering the combined effects of strain and heat loss on reaction rates. The effect of strain in the presence of heat loss on the consumption speed of laminar premixed flames was quantified by calculations of asymmetric counterflow configurations (“fresh-to-burnt”) with detailed chemistry. Heat losses were introduced by setting the temperature of the incoming stream of products on the “burnt” side to values below those corresponding to adiabatic conditions. The consumption speed decreased in a roughly exponential manner with increasing strain rate, and this tendency became more pronounced in the presence of heat losses. An empirical relation in terms of Markstein number, Karlovitz Number and a non-dimensional heat loss parameter was proposed for the combined influence of strain and heat losses on the consumption speed. Combining this empirical relation with a presumed probability density function for strain in turbulent flows, an attenuation factor that accounts for the effect of strain and heat loss on the reaction rate in turbulent flows was deduced and implemented into a turbulent combustion model. URANS simulations of a premixed swirl burner were carried out and validated against flow field and OH chemiluminescence measurements. Introducing the effects of strain and heat loss into the combustion model, the flame topology observed experimentally was correctly reproduced, with good agreement between experiment and simulation for flow field and flame length.

Macroporous Inverse Opal-like MoxC with Incorporated Mo Vacancies for Significantly Enhanced Hydrogen Evolution.

Science.gov (United States)

Li, Feng; Zhao, Xianglong; Mahmood, Javeed; Okyay, Mahmut Sait; Jung, Sun-Min; Ahmad, Ishfaq; Kim, Seok-Jin; Han, Gao-Feng; Park, Noejung; Baek, Jong-Beom

2017-07-25

The hydrogen evolution reaction (HER) is one of the most important pathways for producing pure and clean hydrogen. Although platinum (Pt) is the most efficient HER electrocatalyst, its practical application is significantly hindered by high-cost and scarcity. In this work, an Mo x C with incorporated Mo vacancies and macroporous inverse opal-like (IOL) structure (Mo x C-IOL) was synthesized and studied as a low-cost efficient HER electrocatalyst. The macroporous IOL structure was controllably fabricated using a facile-hard template strategy. As a result of the combined benefits of the Mo vacancies and structural advantages, including appropriate hydrogen binding energy, large exposed surface, robust IOL structure and fast mass/charge transport, the synthesized Mo x C-IOL exhibited significantly enhanced HER electrocatalytic performance with good stability, with performance comparable or superior to Pt wire in both acidic and alkaline solutions.

Direct numerical simulations of premixed turbulent flames with flamelet-generated manifolds

NARCIS (Netherlands)

Oijen, van J.A.; Bastiaans, R.J.M.; Goey, de L.P.H.

2005-01-01

Direct numerical simulation is a very powerful tool to evaluate the validity of new models and theories for turbulent combustion. In this paper, direct numerical simulations of spherically expanding premixed turbulent flames in the thin reaction zone regime and in the broken reaction zone regime are

Amperometric carbohydrate antigen 19-9 immunosensor based on three dimensional ordered macroporous magnetic Au film coupling direct electrochemistry of horseradish peroxidase

Energy Technology Data Exchange (ETDEWEB)

Zhang, Qi [College of Sciences, Nanjing Tech University, Nanjing 211816 (China); Chen, Xiaojun, E-mail: chenxj_njut@126.com [College of Sciences, Nanjing Tech University, Nanjing 211816 (China); State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 210009 (China); Tang, Yin [Zhangjiagang Hospital of Traditional Chinese Medicine, Zhangjiagang 215600 (China); Ge, Lingna; Guo, Buhua [College of Sciences, Nanjing Tech University, Nanjing 211816 (China); Yao, Cheng, E-mail: yaochengnjut@163.com [College of Sciences, Nanjing Tech University, Nanjing 211816 (China)

2014-03-01

Highlights: • Three dimensional ordered macroporous magnetic electrode was newly used in electrochemical immunosensor. • The large surface area of macroporous magnetic electrode could improve the immobilized amount of antibody. • Au nanoparticles functionalized SBA-15 was used to immobilize enzyme labeled Ab₂ and enzyme. • Macroporous magnetic electrode and Au nanoparticles composite facilitated the direct electron transfer of enzyme. • The immunoassay avoided adding electron transfer mediator, simplifying the procedure. Abstract: A sandwich-type electrochemical immunosensor for the detection of carbohydrate antigen 19-9 (CA 19-9) antigen based on the immobilization of primary antibody (Ab₁) on three dimensional ordered macroporous magnetic (3DOMM) electrode, and the direct electrochemistry of horseradish peroxidase (HRP) that was used as both the label of secondary antibody (Ab₂) and the blocking reagent. The 3DOMM electrode was fabricated by introducing core–shell Au–SiO₂@Fe₃O₄ nanospheres onto the surface of three dimensional ordered macroporous (3DOM) Au electrode via the application of an external magnet. Au nanoparticles functionalized SBA-15 (Au@SBA-15) was conjugated to the HRP labeled secondary antibody (HRP-Ab₂) through the Au–SH or Au–NH₃⁺ interaction, and HRP was also used as the block reagent. The formation of antigen–antibody complex made the combination of Au@SBA-15 and 3DOMM exhibit remarkable synergistic effects for accelerating direct electron transfer (DET) between HRP and the electrode. Under the optimal conditions, the DET current signal increased proportionally to CA 19-9 concentration in the range of 0.05 to 15.65 U mL⁻¹ with a detection limit of 0.01 U mL⁻¹. Moreover, the immunosensor showed high selectivity, good stability, satisfactory reproducibility and regeneration. Importantly, the developed method was used to assay clinical serum specimens, achieving a good relation with those obtained from

Study on the use of macroporous cation exchange resins for the separation and purification of uranium from thorium

International Nuclear Information System (INIS)

Rastogi, R.K.; Mahajan, M.A.; Chaudhuri, N.K.

1992-01-01

The possibility of using macroporous cation exchange resins for the purification of uranium from thorium relevant to the final purification of uranium after reprocessing thorium breeder fuel was explored. Two macroporous cation exchange resins were studied and compared with a commonly used gel type resin. Batch experiments and column experiments were performed to generate equilibrium data and to optimise the procedure for the separation of U from Th under process condition. Under the same condition Tulsion T-42 gave product U containing 0.1% of Th, while Amberlyst-15 gave the product U containing 1% of Th. Loading and washing rates were much higher (120 ml/hr) than those used for gel type resins (40 ml/hr). Though the volume of wash required for >90% recovery of U is more than that required with the gel type resin the disadvantage due to that is more than compensated by the use of high flow rate of loading and washing to give higher throughput. Thus there is a definite advantage of U purification with macroporous resins as compared to usual gel type resins. (author). 23 refs., 3 figs., 10 tabs

Synthesis of hierarchically meso-macroporous TiO2/CdS heterojunction photocatalysts with excellent visible-light photocatalytic activity.

Science.gov (United States)

Zhao, Haixin; Cui, Shu; Yang, Lan; Li, Guodong; Li, Nan; Li, Xiaotian

2018-02-15

Photocatalysts with a hierarchically porous structure have attracted considerable attention owing to their wide pore size distribution and high surface area, which enhance the efficiency of transporting species to active sites. In this study, hierarchically meso-macroporous TiO 2 photocatalysts decorated with highly dispersed CdS nanoparticles were synthesized via hydrolysis, followed by a hydrothermal treatment. The textural mesopores and interconnected pore framework provided more accessible active sites and efficient mass transport for the photocatalytic process. The light collection efficiency was enhanced because of multiple scattering of incident light in the macropores. Moreover, the formation of a heterojunction between the CdS and TiO 2 nanoparticles extended the photoresponse of TiO 2 to the visible-light range and enhanced the charge separation efficiency. Therefore, the hierarchically meso-macroporous TiO 2 /CdS photocatalysts exhibited excellent photocatalytic activity for the degradation of rhodaming B under visible-light irradiation. Trapping experiments demonstrated that superoxide radicals (O 2 - ) and hydroxyl radicals (OH) were the main active species in photocatalysis. A reasonable photocatalytic mechanism of TiO 2 /CdS heterojunction photocatalysts was also presented. Copyright © 2017 Elsevier Inc. All rights reserved.

Macroporous resin purification of peptides with umami taste from soy sauce.

Science.gov (United States)

Zhuang, Mingzhu; Zhao, Mouming; Lin, Lianzhu; Dong, Yi; Chen, Huiping; Feng, Mengying; Sun-Waterhouse, Dongxiao; Su, Guowan

2016-01-01

In this study, the performance and separation characteristics of four macroporous resins for purifying umami peptides from soy sauce were examined. Results showed that the resins could separate the peptides of soy sauce, and the particle diffusion kinetics model was suitable for describing the whole exothermic (ΔH sauce, and indicated that peptide may be the contributor to the umami taste in Chinese soy sauce. Copyright © 2015 Elsevier Ltd. All rights reserved.

Highly ordered macroporous woody biochar with ultra-high carbon content as supercapacitor electrodes

International Nuclear Information System (INIS)

Jiang, Junhua; Zhang, Lei; Wang, Xinying; Holm, Nancy; Rajagopalan, Kishore; Chen, Fanglin; Ma, Shuguo

2013-01-01

Woody biochar monolith with ultra-high carbon content and highly ordered macropores has been prepared via one-pot pyrolysis and carbonization of red cedar wood at 750 °C without the need of post-treatment. Energy-dispersive spectroscope (EDX) and scanning electron microscope (SEM) studies show that the original biochar has a carbon content of 98 wt% with oxygen as the only detectable impurity and highly ordered macroporous texture characterized by alternating regular macroporous regions and narrow porous regions. Moreover, the hierarchically porous biochar monolith has a high BET specific surface area of approximately 400 m 2 g −1 . We have studied the monolith material as supercapacitor electrodes under acidic environment using electrochemical and surface characterization techniques. Electrochemical measurements show that the original biochar electrodes have a potential window of about 1.3 V and exhibit typical rectangular-shape voltammetric responses and fast charging–discharging behavior with a gravimetric capacitance of about 14 F g −1 . Simple activation of biochar in diluted nitric acid at room temperature leads to 7 times increase in the capacitance (115 F g −1 ). Because the HNO 3 -activation slightly decreases rather than increases the BET surface area of the biochar, an increase in the coverage of surface oxygen groups is the most likely origin of the substantial capacitance improvement. This is supported by EDX, X-ray photoelectron spectroscopy (XPS), and Raman measurements. Preliminary life-time studies show that biochar supercapacitors using the original and HNO 3 -activated electrodes are stable over 5000 cycles without performance decays. These facts indicate that the use of woody biochar is promising for its low cost and it can be a good performance electrode with low environmental impacts for supercapacitor applications

On mathematical modeling and numerical simulation of chemical kinetics in turbulent lean premixed combustion

Energy Technology Data Exchange (ETDEWEB)

Lilleberg, Bjorn

2011-07-01

This thesis investigates turbulent reacting lean premixed flows with detailed treatment of the chemistry. First, the fundamental equations which govern laminar and turbulent reacting flows are presented. A perfectly stirred reactor numerical code is developed to investigate the role of unmixedness and chemical kinetics in driving combustion instabilities. This includes both global single-step and detailed chemical kinetic mechanisms. The single-step mechanisms predict to some degree a similar behavior as the detailed mechanisms. However, it is shown that simple mechanisms can by themselves introduce instabilities. Magnussens Eddy Dissipation Concept (EDC) for turbulent combustion is implemented in the open source CFD toolbox OpenFOAM R for treatment of both fast and detailed chemistry. RANS turbulence models account for the turbulent compressible flow. A database of pre-calculated chemical time scales, which contains the influence of chemical kinetics, is coupled to EDC with fast chemistry to account for local extinction in both diffusion and premixed flames. Results are compared to fast and detailed chemistry calculations. The inclusion of the database shows significantly better results than the fast chemistry calculations while having a comparably small computational cost. Numerical simulations of four piloted lean premixed jet flames falling into the 'well stirred reactor/broken reaction zones' regime, with strong finite-rate chemistry effects, are performed. Measured and predicted scalars compare well for the two jets with the lowest velocities. The two jets with the highest velocities experience extinction and reignition, and the simulations are able to capture the decrease and increase of the OH mass fractions, but the peak values are higher than in the experiments. Also numerical simulations of a lean premixed lifted jet flame with high sensitivity to turbulence modeling and chemical kinetics are performed. Limitations of the applied turbulence and

Flow structures in a lean-premixed swirl-stabilized combustor with microjet air injection

KAUST Repository

LaBry, Zachary A.; Shanbhogue, Santosh J.; Speth, Raymond L.; Ghoniem, Ahmed F.

2011-01-01

The major challenge facing the development of low-emission combustors is combustion instability. By lowering flame temperatures, lean-premixed combustion has the potential to nearly eliminate emissions of thermally generated nitric oxides

Bias-assisted KOH etching of macroporous silicon membranes

International Nuclear Information System (INIS)

Mathwig, K; Geilhufe, M; Müller, F; Gösele, U

2011-01-01

This paper presents an improved technique to fabricate porous membranes from macroporous silicon as a starting material. A crucial step in the fabrication process is the dissolution of silicon from the backside of the porous wafer by aqueous potassium hydroxide to open up the pores. We improved this step by biasing the silicon wafer electrically against the KOH. By monitoring the current–time characteristics a good control of the process is achieved and the yield is improved. Also, the etching can be stopped instantaneously and automatically by short-circuiting Si and KOH. Moreover, the bias-assisted etching allows for the controlled fabrication of silicon dioxide tube arrays when the silicon pore walls are oxidized and inverted pores are released.

Comprehensive Validation of Skeletal Mechanism for Turbulent Premixed Methane–Air Flame Simulations

KAUST Repository

Luca, Stefano; Al-Khateeb, Ashraf N.; Attili, Antonio; Bisetti, Fabrizio

2017-01-01

A new skeletal mechanism, consisting of 16 species and 72 reactions, has been developed for lean methane–air premixed combustion from the GRI-Mech 3.0. The skeletal mechanism is validated for elevated unburnt temperatures (800 K) and pressures up

Dynamics of Practical Premixed Flames, Part I: Model Structure and Identification

Directory of Open Access Journals (Sweden)

A. Huber

2009-06-01

Full Text Available For the analysis of thermoacoustic instabilities it is most important to determine the dynamic flame response to acoustic disturbances. Premixed flames are often modelled as single-input single-output system, where the “output” (the overall rate of heat release responds to a single “input” variable (often the velocity at the exit of the burner nozzle. However, for practical premixed flames, where perturbations of pressure or velocity at the fuel injector will modulate the fuel equivalence ratio, the heat release rate will respond to fluctuations of equivalence ratio as well as nozzle mass flow rate. In this case, a multiple-input, single-output (MISO model structure for the flame is appropriate. Such a model structure is developed in the present paper. Staged fuel injection as well as fuel line impedances can be taken into account, the integration with low-order or finite-element based models for stability analysis is straightforward. In order to determine unit impulse and frequency response functions for such a model structure, an identification scheme based on unsteady CFD calculation with broadband excitation followed by correlation analysis is proposed and validated successfully. Identification of MISO model coefficients is a challenging task, especially in the presence of noise. Therefore criteria are introduced which allow to ascertain a posteriori how well the identified model represents the true system dynamics. Using these criteria, it is investigated how excitation signal type, time series length and signal-to-noise ratio influence the results of the identification process. Consequences for passive design strategies based on multi-stage fuel injection and experimental work on practical premixed flame dynamics are discussed.

Response mechanisms of attached premixed flames subjected to harmonic forcing

Science.gov (United States)

Shreekrishna

The persistent thrust for a cleaner, greener environment has prompted air pollution regulations to be enforced with increased stringency by environmental protection bodies all over the world. This has prompted gas turbine manufacturers to move from nonpremixed combustion to lean, premixed combustion. These lean premixed combustors operate quite fuel-lean compared to the stochiometric, in order to minimize CO and NOx productions, and are very susceptible to oscillations in any of the upstream flow variables. These oscillations cause the heat release rate of the flame to oscillate, which can engage one or more acoustic modes of the combustor or gas turbine components, and under certain conditions, lead to limit cycle oscillations. This phenomenon, called thermoacoustic instabilities, is characterized by very high pressure oscillations and increased heat fluxes at system walls, and can cause significant problems in the routine operability of these combustors, not to mention the occasional hardware damages that could occur, all of which cumulatively cost several millions of dollars. In a bid towards understanding this flow-flame interaction, this research works studies the heat release response of premixed flames to oscillations in reactant equivalence ratio, reactant velocity and pressure, under conditions where the flame preheat zone is convectively compact to these disturbances, using the G-equation. The heat release response is quantified by means of the flame transfer function and together with combustor acoustics, forms a critical component of the analytical models that can predict combustor dynamics. To this end, low excitation amplitude (linear) and high excitation amplitude (nonlinear) responses of the flame are studied in this work. The linear heat release response of lean, premixed flames are seen to be dominated by responses to velocity and equivalence ratio fluctuations at low frequencies, and to pressure fluctuations at high frequencies which are in the

The role of reactant unmixedness, strain rate, and length scale on premixed combustor performance

Energy Technology Data Exchange (ETDEWEB)

Samuelsen, S.; LaRue, J.; Vilayanur, S. [Univ. of California, Irvine, CA (United States)] [and others

1995-10-01

Lean premixed combustion provides a means to reduce pollutant formation and increase combustion efficiency. However, fuel-air mixing is rarely uniform in space and time. This nonuniformity in concentration will lead to relative increases in pollutant formation and decreases in combustion efficiency. The nonuniformity of the concentration at the exit of the premixer has been defined by Lyons (1981) as the {open_quotes}unmixedness.{close_quotes} Although turbulence properties such as length scales and strain rate are known to effect unmixedness, the exact relationship is unknown. Evaluating this relationship and the effect of unmixedness in premixed combustion on pollutant formation and combustion efficiency are an important part of the overall goal of US Department of Energy`s Advanced Turbine Systems (ATS) program and are among the goals of the program described herein. The information obtained from ATS is intended to help to develop and commercialize gas turbines which have (1) a wide range of operation/stability, (2) a minimal amount of pollutant formation, and (3) high combustion efficiency. Specifically, with regard to pollutants, the goals are to reduce the NO{sub x} emissions by at least 10%, obtain less than 20 PPM of both CO and UHC, and increase the combustion efficiency by 5%.

DNS of turbulent premixed slot flames with mixture inhomogeneity: a study of NOx formation

Science.gov (United States)

Luca, Stefano; Attili, Antonio; Bisetti, Fabrizio

2016-11-01

A set of Direct Numerical Simulations of three-dimensional methane/air lean flames in a spatially developing turbulent slot burner are performed. The flames are in the thin-reaction zone regimes and the jet Reynolds number is 5600. This configuration is of interest since it displays turbulent production by mean shear as in real devices. The gas phase hydrodynamics are modeled with the reactive, unsteady Navier-Stokes equations in the low Mach number limit. Combustion is treated with finite-rate chemistry. The jet is characterized by a non-uniform equivalence ratio at the inlet and varying levels of incomplete premixing for the methane/air mixture are considered. The global equivalence ratio is 0.7 and temperature is 800 K. All simulations are performed at 4 atm. The instantaneous profiles of the mass fractions of methane and air at the inlet are sampled from a set of turbulent channel simulations that provide realistic, fully turbulent fields. The data are analyzed to study the influence of partial premixing on the flame structure. Particular focus is devoted to the assessment of heat release rate fluctuations and NOx formation. In particular, the effects of partial premixing on the production rates for the various pathways to NOx formation are investigated.

Fuel and combustion stratification study of Partially Premixed Combustion

OpenAIRE

Izadi Najafabadi, M.; Dam, N.; Somers, B.; Johansson, B.

2016-01-01

Relatively high levels of stratification is one of the main advantages of Partially Premixed Combustion (PPC) over the Homogeneous Charge Compression Ignition (HCCI) concept. Fuel stratification smoothens heat release and improves controllability of this kind of combustion. However, the lack of a clear definition of “fuel and combustion stratifications” is obvious in literature. Hence, it is difficult to compare stratification levels of different PPC strategies or other combustion concepts. T...

Study of Ni Metallization in Macroporous Si Using Wet Chemistry for Radio Frequency Cross-Talk Isolation in Mixed Signal Integrated Circuits.

Science.gov (United States)

Zhang, Xi; Xu, Chengkun; Chong, Kyuchul; Tu, King-Ning; Xie, Ya-Hong

2011-05-25

A highly conductive moat or Faraday cage of through-the-wafer thickness in Si substrate was proposed to be effective in shielding electromagnetic interference thereby reducing radio frequency (RF) cross-talk in high performance mixed signal integrated circuits. Such a structure was realized by metallization of selected ultra-high-aspect-ratio macroporous regions that were electrochemically etched in p - Si substrates. The metallization process was conducted by means of wet chemistry in an alkaline aqueous solution containing Ni 2+ without reducing agent. It is found that at elevated temperature during immersion, Ni 2+ was rapidly reduced and deposited into macroporous Si and a conformal metallization of the macropore sidewalls was obtained in a way that the entire porous Si framework was converted to Ni. A conductive moat was as a result incorporated into p - Si substrate. The experimentally measured reduction of crosstalk in this structure is 5~18 dB at frequencies up to 35 GHz.

Study of Ni Metallization in Macroporous Si Using Wet Chemistry for Radio Frequency Cross-Talk Isolation in Mixed Signal Integrated Circuits

Directory of Open Access Journals (Sweden)

King-Ning Tu

2011-05-01

Full Text Available A highly conductive moat or Faraday cage of through-the-wafer thickness in Si substrate was proposed to be effective in shielding electromagnetic interference thereby reducing radio frequency (RF cross-talk in high performance mixed signal integrated circuits. Such a structure was realized by metallization of selected ultra-high-aspect-ratio macroporous regions that were electrochemically etched in p− Si substrates. The metallization process was conducted by means of wet chemistry in an alkaline aqueous solution containing Ni2+ without reducing agent. It is found that at elevated temperature during immersion, Ni2+ was rapidly reduced and deposited into macroporous Si and a conformal metallization of the macropore sidewalls was obtained in a way that the entire porous Si framework was converted to Ni. A conductive moat was as a result incorporated into p− Si substrate. The experimentally measured reduction of crosstalk in this structure is 5~18 dB at frequencies up to 35 GHz.

Study of Ni Metallization in Macroporous Si Using Wet Chemistry for Radio Frequency Cross-Talk Isolation in Mixed Signal Integrated Circuits

Science.gov (United States)

Zhang, Xi; Xu, Chengkun; Chong, Kyuchul; Tu, King-Ning; Xie, Ya-Hong

2011-01-01

A highly conductive moat or Faraday cage of through-the-wafer thickness in Si substrate was proposed to be effective in shielding electromagnetic interference thereby reducing radio frequency (RF) cross-talk in high performance mixed signal integrated circuits. Such a structure was realized by metallization of selected ultra-high-aspect-ratio macroporous regions that were electrochemically etched in p− Si substrates. The metallization process was conducted by means of wet chemistry in an alkaline aqueous solution containing Ni2+ without reducing agent. It is found that at elevated temperature during immersion, Ni2+ was rapidly reduced and deposited into macroporous Si and a conformal metallization of the macropore sidewalls was obtained in a way that the entire porous Si framework was converted to Ni. A conductive moat was as a result incorporated into p− Si substrate. The experimentally measured reduction of crosstalk in this structure is 5~18 dB at frequencies up to 35 GHz. PMID:28879960

Ordered macroporous platinum electrode and enhanced mass transfer in fuel cells using inverse opal structure.

Science.gov (United States)

Kim, Ok-Hee; Cho, Yong-Hun; Kang, Soon Hyung; Park, Hee-Young; Kim, Minhyoung; Lim, Ju Wan; Chung, Dong Young; Lee, Myeong Jae; Choe, Heeman; Sung, Yung-Eun

2013-01-01

Three-dimensional, ordered macroporous materials such as inverse opal structures are attractive materials for various applications in electrochemical devices because of the benefits derived from their periodic structures: relatively large surface areas, large voidage, low tortuosity and interconnected macropores. However, a direct application of an inverse opal structure in membrane electrode assemblies has been considered impractical because of the limitations in fabrication routes including an unsuitable substrate. Here we report the demonstration of a single cell that maintains an inverse opal structure entirely within a membrane electrode assembly. Compared with the conventional catalyst slurry, an ink-based assembly, this modified assembly has a robust and integrated configuration of catalyst layers; therefore, the loss of catalyst particles can be minimized. Furthermore, the inverse-opal-structure electrode maintains an effective porosity, an enhanced performance, as well as an improved mass transfer and more effective water management, owing to its morphological advantages.

Prediction of biopore- and matrix-dominated flow from X-ray CT-derived macropore network characteristics

DEFF Research Database (Denmark)

Naveed, Muhammad; Møldrup, Per; Schaap, Marcel G

2016-01-01

was to investigate the predictive performance of previously developed empirical models for both water and air flow and to explore the potential applicability of X-ray computed tomography (CT)-derived macropore network characteristics. For this purpose, 65 cylindrical soil columns (6 cm diameter and 3.5 cm height......Prediction and modeling of localized flow processes in macropores is of crucial importance for sustaining both soil and water quality. However, currently there are no reliable means to predict preferential flow due to its inherently large spatial variability. The aim of this study......) were extracted from the topsoil (5 cm to 8.5 cm depth) in a 15m15m grid from an agricultural field located in Silstrup, Denmark. All soil columns were scanned with an industrial X-ray CT scanner (129 μm resolution) and later employed for measurement of saturated hydraulic conductivity, air permeability...

Combustion and radiation modeling of laminar premixed flames using OpenFOAM: A numerical investigation of radiative heat transfer in the RADIADE project

DEFF Research Database (Denmark)

Haider, Sajjad; Pang, Kar Mun; Ivarsson, Anders

2013-01-01

This paper presents the computational fluid dynamics modelling of a laminar premixed flame. A specific solver named ’rareLTSFoam’ is developed using OpenFOAM ® code. The solver is used to simulate experimental stoichiometric and rich laminar premixed flames. The modelling is carried out for thermal...

Impact of flame-wall interaction on premixed flame dynamics and transfer function characteristics

KAUST Repository

Kedia, K.S.; Altay, H.M.; Ghoniem, A.F.

2011-01-01

In this paper, we numerically investigate the response of a perforated-plate stabilized laminar methane-air premixed flame to imposed inlet velocity perturbations. A flame model using detailed chemical kinetics mechanism is applied and heat exchange

A numerical study of a premixed flame on a slit burner

NARCIS (Netherlands)

Somers, L.M.T.; Goey, de L.P.H.

1995-01-01

A numerical study of a premixed methane/air flame on a 4 mm slit burner is presented. A local grid refinement technique is used to deal with large gradients and curvature of all variables encountered in the flame, keeping the number of grid points within reasonable bounds. The method used here leads

The Impact of Variable Inlet Mixture Stratification on Flame Topology and Emissions Performance of a Premixer/Swirl Burner Configuration

Directory of Open Access Journals (Sweden)

P. Koutmos

2012-01-01

Full Text Available The work presents the assessment of a low emissions premixer/swirl burner configuration utilizing lean stratified fuel preparation. An axisymmetric, single- or double-cavity premixer, formed along one, two, or three concentric disks promotes propane-air premixing and supplies the combustion zone at the afterbody disk recirculation with a radial equivalence ratio gradient. The burner assemblies are operated with a swirl co-flow to study the interaction of the recirculating stratified flame with the surrounding swirl. A number of lean and ultra-lean flames operated either with a plane disk stabilizer or with one or two premixing cavity arrangements were evaluated over a range of inlet mixture conditions. The influence of the variation of the imposed swirl was studied for constant fuel injections. Measurements of turbulent velocities, temperatures, OH* chemiluminescence and gas analysis provided information on the performance of each burner set up. Comparisons with Large Eddy Simulations, performed with an 11-step global chemistry, illustrated the flame front interaction with the vortex formation region under the influence of the variable inlet mixture stratifications. The combined effort contributed to the identification of optimum configurations in terms of fuel consumption and pollutants emissions and to the delineation of important controlling parameters and limiting fuel-air mixing conditions.

Three-Dimensional Macroporous Polypyrrole-Derived Graphene Electrode Prepared by the Hydrogen Bubble Dynamic Template for Supercapacitors and Metal-Free Catalysts.

Science.gov (United States)

Yang, Xiaoqing; Liu, Anran; Zhao, Yuewu; Lu, Huijia; Zhang, Yuanjian; Wei, Wei; Li, Ying; Liu, Songqin

2015-10-28

We report a general method for the fabrication of three-dimensional (3D) macroporous graphene/conducting polymer modified electrode and nitrogen-doped graphene modified electrode. This method involves three consecutive steps. First, the 3D macroporous graphene (3D MG) electrode was fabricated electrochemically by reducing graphene oxide dispersion on different conducting substrates and used hydrogen bubbles as the dynamic template. The morphology and pore size of 3D MG could be governed by the use of surfactants and the dynamics of bubble generation and departure. Second, 3D macroporous graphene/polypyrrole (MGPPy) composites were constructed via directly electropolymerizing pyrrole monomer onto the networks of 3D MG. Due to the benefit of the good conductivity of 3D MG and pseudocapacitance of PPy, the composites manifest outstanding area specific capacitance of 196 mF cm(-2) at a current density of 1 mA cm(-2). The symmetric supercapacitor device assembled by the composite materials had a good capacity property. Finally, the nitrogen-doped MGPPy (N-MGPPy or MGPPy-X) with 3D macroporous nanostructure and well-regulated nitrogen doping was prepared via thermal treatment of the composites. The resultant N-MGPPy electrode was explored as a good electrocatalyst for the oxygen reduction reaction (ORR) with the current density value of 5.56 mA cm(-2) (-0.132 V vs Ag/AgCl). Moreover, the fuel tolerance and durability under the electrochemical environment of the N-MGPPy catalyst were found to be superior to the Pt/C catalyst.

Experimental and Numerical Study of Jet Controlled Compression Ignition on Combustion Phasing Control in Diesel Premixed Compression Ignition Systems

OpenAIRE

Qiang Zhang; Wuqiang Long; Jiangping Tian; Yicong Wang; Xiangyu Meng

2014-01-01

In order to directly control the premixed combustion phasing, a Jet Controlled Compression Ignition (JCCI) for diesel premixed compression ignition systems is investigated. Experiments were conducted on a single cylinder natural aspirated diesel engine without EGR at 3000 rpm. Numerical models were validated by load sweep experiments at fixed spark timing. Detailed combustion characteristics were analyzed based on the BMEP of 2.18 bar. The simulation results showed that the high temperature j...

Separation of scutellarin from crude extracts of Erigeron breviscapus (vant.) Hand. Mazz. by macroporous resins.

Science.gov (United States)

Gao, Min; Huang, Wei; Liu, Chun-Zhao

2007-10-15

Scutellarin, a flavone glycoside, popularly used in the treatment of heart disease, has been efficiently separated using macroporous resins from crude extracts of Chinese medicinal plant Erigeron breviscapus (vant.) Hand. Mazz. HPD-800 resin offered the best adsorption and desorption capacity for scutellarin among the eight macroporous resins tested, and its adsorption data at 25 degrees C fit best to the Langmuir isotherm. The dynamic adsorption and desorption experiments have been carried out on a HPD-800 resin packed column to optimize the separation process of scutellarin from the crude extracts of E. breviscapus. After one run treatment with HPD-800 resin, the scutellarin content in the product was increased 15.69-fold from 2.61% to 40.96% with a recovery yield of 95.01%. The preparative separation process via adsorption-desorption method developed in this study provides a new approach for scale-up separation and purification of scutellarin for its wide pharmaceutical use.

Industrial-scale preparation of akebia saponin D by a two-step macroporous resin column separation.

Science.gov (United States)

Wu, Yue; Ji, De; Liu, Yunfei; Zhang, Chunfeng; Yang, Zhonglin

2012-06-26

A simple and efficient procedure for the industrial preparation of akebia saponin D, one of the bioactive compounds commonly found in the well-known Chinese Medicinal herb Dipsaci Radix, was developed. First, HPD-722 was selected from among 10 kinds of macroporous absorption resins. Following this step, the purity of akebia saponin D was increased about 10 times from 6.27% to 59.41%. In order to achieve a higher purity, ADS-7 was chosen from among five kinds of macroporous absorption resins, and the purity of akebia saponin D was increased from 59.41% to 95.05%. The result indicated HPD-722 and ADS-7 were the most suitable resins to purify akebia saponin D from Dipsaci Radix. Under these conditions, large-scale preparation of akebia saponin D was carried out successfully. The preparation method is simple, efficient, and has been demonstrated to be effective for large scale preparations of akebia saponin D from Dipsaci Radix.

Process-based modelling of a headwater catchment in semi-arid conditions: the influence of macropore flow

NARCIS (Netherlands)

Schaik, N.L.M.B.; Bronstert, A.; Jong, S.M.; Jetten, V.G.; Dam, van J.C.; Ritsema, C.J.; Schnabel, S.

2014-01-01

Subsurface stormflow is thought to occur mainly in humid environments with steep terrains. However, in semi-arid areas, preferential flow through macropores can also result in a significant contribution of subsurface stormflow to catchment runoff for varying catchment conditions. Most hydrological

Inadequacy representation of flamelet-based RANS model for turbulent non-premixed flame

Science.gov (United States)

Lee, Myoungkyu; Oliver, Todd; Moser, Robert

2017-11-01

Stochastic representations for model inadequacy in RANS-based models of non-premixed jet flames are developed and explored. Flamelet-based RANS models are attractive for engineering applications relative to higher-fidelity methods because of their low computational costs. However, the various assumptions inherent in such models introduce errors that can significantly affect the accuracy of computed quantities of interest. In this work, we develop an approach to represent the model inadequacy of the flamelet-based RANS model. In particular, we pose a physics-based, stochastic PDE for the triple correlation of the mixture fraction. This additional uncertain state variable is then used to construct perturbations of the PDF for the instantaneous mixture fraction, which is used to obtain an uncertain perturbation of the flame temperature. A hydrogen-air non-premixed jet flame is used to demonstrate the representation of the inadequacy of the flamelet-based RANS model. This work was supported by DARPA-EQUiPS(Enabling Quantification of Uncertainty in Physical Systems) program.

Flame Structure and Dynamics for an Array of Premixed Methane-Air Jets

Science.gov (United States)

Nigam, Siddharth P.; Lapointe, Caelan; Christopher, Jason D.; Wimer, Nicholas T.; Hayden, Torrey R. S.; Rieker, Gregory B.; Hamlington, Peter E.

2017-11-01

Premixed flames have been studied extensively, both experimentally and computationally, and their properties are reasonably well characterized for a range of conditions and configurations. However, the premixed combustion process is potentially much more difficult to predict when many such flames are arranged in a closely spaced array. These arrays must be better understood, in particular, for the design of industrial burners used in chemical and heat treatment processes. Here, the effects of geometric array parameters (e.g., angle and diameter of jet inlets, number of inlets and their respective orientation) and operating conditions (e.g., jet velocities, fuel-air ratio) on flame structure and dynamics are studied using large eddy simulations (LES). The simulations are performed in OpenFOAM using multi-step chemistry for a methane-air mixture, and temperature and chemical composition fields are characterized for a variety of configurations as functions of height above the array. Implications of these results for the design and operation of industrial burners are outlined.

Management of Type 2 diabetes in Ramadan: Low-ratio premix insulin working group practical advice

Science.gov (United States)

Hassanein, Mohamed; Belhadj, Mohamed; Abdallah, Khalifa; Bhattacharya, Arpan D.; Singh, Awadhesh K.; Tayeb, Khaled; Al-Arouj, Monira; Elghweiry, Awad; Iraqi, Hinde; Nazeer, Mohamed; Jamoussi, Henda; Mnif, Mouna; Al-Madani, Abdulrazzaq; Al-Ali, Hossam; Ligthelm, Robert

2014-01-01

The challenge of insulin use during Ramadan could be minimized, if people with diabetes are metabolically stable and are provided with structured education for at least 2–3 months pre-Ramadan. Although, American diabetes association (ADA) recommendations 2010 and South Asian Consensus Guideline 2012 deal with management of diabetes in Ramadan and changes in insulin dosage, no specific guidance on widely prescribed low-ratio premix insulin is currently available. Hence, the working group for insulin therapy in Ramadan, after collective analysis, evaluation, and opinion from clinical practice, have formulated a practical advice to empower physicians with pre-Ramadan preparation, dose adjustment, and treatment algorithm for self-titration of low-ratio premix insulin. PMID:25364673

Management of Type 2 diabetes in Ramadan: Low-ratio premix insulin working group practical advice

Directory of Open Access Journals (Sweden)

Mohamed Hassanein

2014-01-01

Full Text Available The challenge of insulin use during Ramadan could be minimized, if people with diabetes are metabolically stable and are provided with structured education for at least 2-3 months pre-Ramadan. Although, American diabetes association (ADA recommendations 2010 and South Asian Consensus Guideline 2012 deal with management of diabetes in Ramadan and changes in insulin dosage, no specific guidance on widely prescribed low-ratio premix insulin is currently available. Hence, the working group for insulin therapy in Ramadan, after collective analysis, evaluation, and opinion from clinical practice, have formulated a practical advice to empower physicians with pre-Ramadan preparation, dose adjustment, and treatment algorithm for self-titration of low-ratio premix insulin.

3D macroporous graphene frameworks for supercapacitors with high energy and power densities.

Science.gov (United States)

Choi, Bong Gill; Yang, Minho; Hong, Won Hi; Choi, Jang Wook; Huh, Yun Suk

2012-05-22

In order to develop energy storage devices with high power and energy densities, electrodes should hold well-defined pathways for efficient ionic and electronic transport. Herein, we demonstrate high-performance supercapacitors by building a three-dimensional (3D) macroporous structure that consists of chemically modified graphene (CMG). These 3D macroporous electrodes, namely, embossed-CMG (e-CMG) films, were fabricated by using polystyrene colloidal particles as a sacrificial template. Furthermore, for further capacitance boost, a thin layer of MnO(2) was additionally deposited onto e-CMG. The porous graphene structure with a large surface area facilitates fast ionic transport within the electrode while preserving decent electronic conductivity and thus endows MnO(2)/e-CMG composite electrodes with excellent electrochemical properties such as a specific capacitance of 389 F/g at 1 A/g and 97.7% capacitance retention upon a current increase to 35 A/g. Moreover, when the MnO(2)/e-CMG composite electrode was asymmetrically assembled with an e-CMG electrode, the assembled full cell shows remarkable cell performance: energy density of 44 Wh/kg, power density of 25 kW/kg, and excellent cycle life.

Tension free monofilament macropore polypropylene mesh (Gynemesh PS in female genital prolapse repair

Directory of Open Access Journals (Sweden)

Vicente Sola

2006-08-01

Full Text Available OBJECTIVES: To review intraoperative and postoperative complications associated to the correction of cystocele and rectocele with polypropylene mesh macropore monofilament (Gynemesh PS using transvaginal free tension technique. MATERIALS AND METHODS: Prospective study of patients that have been submitted to correction of cystocele and/or rectocele between November 2004 and August 2005 in the Urogynecology and Vaginal Surgery Unit of Gynecology and Obstetrics Department, Las Condes Clinic. Mesh was used in 31 patients: 9 for cystocele, 11 for rectocele, and 11 for concomitant meshes. Total mesh used 42. Media age 55 years old, weight 64 kilograms. In 7 patients we used a third mesh for correction of urinary incontinence by TVT-O technique. RESULTS: They did not present intraoperative complications, neither in immediate or delayed postoperative time. We did not observe hematoma, infection, erosion or exposition mesh. Healing of cystocele and rectocele was obtained in 100% of patients, with a pursuit between 1 and 8 months. DISCUSSION: The use of prosthetic polypropylene monofilament macropore mesh in the correction of cystocele and/or rectocele, by transvaginal route with tension free technique seems to be a safe and effective surgery procedure.

Study on laminar burning velocity of syngas-air premixed flames in various mixing conditions

International Nuclear Information System (INIS)

Lee, Kee Man; Jeong, Byeong Gyu; Lee, Seung Ro

2015-01-01

The laminar burning velocity of syngas-air premixed flames was measured with various equivalence ratios from 0.5 to 5.0 and a mole fraction of H 2 from 0.05 to 0.75. The laminar burning velocity was experimentally determined using a Bunsen flame according to the cone angle and surface area methods. A premixed code with a USC-II detailed reaction mechanism was used for the numerical calculations to predict the laminar burning velocity and to examine the relationship between the burning velocity enhancement and the hydrogen-related reactions. The results indicate that an appropriate method for the measurement of laminar burning velocity is necessary in the H 2 /CO/air syngas premixed flame. In addition, the burning velocity linearly increased with the increase of the H 2 mole fraction in the syngas mixture, although the burning velocity of H 2 was 10 times larger than that of CO. This result is attributed to the rapid production of H-radicals at the early stage of combustion. Furthermore, the predicted mole fractions of H and OH radicals increased with the increase of H 2 mole fraction for a lean syngas mixture. However, the mole fraction of OH radicals, an indicator of heat release rate, decreased for rich syngas mixture, resulting in a reduction of the laminar burning velocity, even with an increase of the H 2 mole fraction.

A composite chitosan-gelatin bi-layered, biomimetic macroporous scaffold for blood vessel tissue engineering.

Science.gov (United States)

Badhe, Ravindra V; Bijukumar, Divya; Chejara, Dharmesh R; Mabrouk, Mostafa; Choonara, Yahya E; Kumar, Pradeep; du Toit, Lisa C; Kondiah, Pierre P D; Pillay, Viness

2017-02-10

A composite chitosan-gelatin macroporous hydrogel-based scaffold with bi-layered tubular architecture was engineered by solvent casting-co-particulate leaching. The scaffold constituted an inner macroporous layer concealed by a non-porous outer layer mimicking the 3D matrix of blood vessels with cellular adhesion and proliferation. The scaffold was evaluated for its morphological, physicochemical, physicomechanical and biodurability properties employing SEM, FTIR, DSC, XRD, porositometry, rheology and texture analysis. The fluid uptake and biodegradation in the presence of lysozymes was also investigated. Cellular attachment and proliferation was analysed using human dermal fibroblasts (HDF-a) seeded onto the scaffold and evaluated by MTT assay, SEM, and confocal microscopy. Results demonstrated that the scaffold had a desirable tensile strength=95.81±11kPa, elongation at break 112.5±13%, porosity 82% and pores between 100 and 230μm, 50% in vitro biodegradation at day 16 and proliferated fibroblasts over 20 days. These results demonstrate that scaffold may be an excellent tubular archetype for blood vessel tissue engineering. Copyright © 2016 Elsevier Ltd. All rights reserved.

Flashback mechanisms in lean premixed gas turbine combustion

CERN Document Server

Benim, Ali Cemal

2014-01-01

Blending fuels with hydrogen offers the potential to reduce NOx and CO2 emissions in gas turbines, but doing so introduces potential new problems such as flashback.  Flashback can lead to thermal overload and destruction of hardware in the turbine engine, with potentially expensive consequences. The little research on flashback that is available is fragmented. Flashback Mechanisms in Lean Premixed Gas Turbine Combustion by Ali Cemal Benim will address not only the overall issue of the flashback phenomenon, but also the issue of fragmented and incomplete research.Presents a coherent review of f

Extinction of counterflow premixed laminar flames

International Nuclear Information System (INIS)

Smooke, M.D.; Giovangigli, V.

1987-01-01

Problems in combustion and heat and mass transfer often depend upon one or more physical/chemical parameters. In many cases the combustion scientist is interested in knowing how the solution will behave if one or more of these parameters is varied. For some parameter regimes the governing equations can produce multiple solutions and the branches of the solution curve are linked via singular points. It is at these singular points, however that the system exhibits special behavior. To be able to predict the solution structure in the neighborhood of these points, the authors employ a phase-space, pseudo arclength, continuation method that utilizes Newton-like iterations and adaptive gridding techniques. The authors apply the method in the solution of counterflow premixed laminar flames

Homogenization-assisted cavitation hybrid rotation extraction and macroporous resin enrichment of dihydroquercetin from Larix gmelinii.

Science.gov (United States)

Xia, Yu; Wang, Yinhang; Li, Wei; Ma, Chunhui; Liu, Shouxin

2017-12-01

Cavitation hybrid rotation, which was and is still looked upon as an unavoidable nuisance in the flow systems, for extraction processing intensification of active chemical compounds from natural products. In this study, a homogenization-assisted cavitation hybrid rotation extraction method was applied to extract dihydroquercetin (DHQ) from larch (Larix gmelinii) wood root. The extraction parameters were optimized in single factor experiments with the DHQ extraction yields as the response values. The optimum conditions were as follows: number of extractions, three; ethanol volume fraction for the extraction, 60%; liquid-solid ratio for homogenization, 10mL/g; homogenization time, 8min; liquid-solid ratio for cavitation extraction, 9mL/g, and cavitation extraction time, 35min. Under these conditions, the DHQ content in extract was 4.50±0.02mg/g, and the extraction efficiency was higher than those of traditional techniques. Cavitation can be effectively used to improve the extraction rate by increasing the mass transfer rates and possible rupture of cell wall due to formation of microcavities leading to higher product yields with reduced processing time and solvent consumption. After the extraction process, macroporous resin column chromatography was used to concentrate and purify the DHQ. Three resins were selected from fifteen macroporous resins for further investigation of their performance. Among these resins, AB-8 resin exhibited relatively better adsorption capacities and desorption ratios for DHQ. The ethanol volume fraction of the solutions for sample loading and desorption, and flow rates for loading and desorption were optimized for the macroporous resin column chromatography. Copyright © 2017 Elsevier B.V. All rights reserved.

Preparation of three-dimensional macroporous chitosan-gelatin B microspheres and HepG2-cell culture.

Science.gov (United States)

Huang, Fang; Cui, Long; Peng, Cheng-Hong; Wu, Xu-Bo; Han, Bao-San; Dong, Ya-Dong

2016-12-01

Chitosan-gelatin B microspheres with an open, interconnected, highly macroporous (100-200 µm) structure were prepared via a three-step protocol combining freeze-drying with an electrostatic and ionic cross-linking method. Saturated tripolyphosphate ethanol solution (85% ethanol) was chosen as the crosslinking agent to prevent destruction of the porous structure and to improve the biostability of the chitosan-gelatin B microspheres, with N-(3-dimethylaminopropyl)-N'-ethyl-carbodiimide/N-hydroxysuccinimide as a second crosslinking agent to react with gelatin A and fixed chitosan-gelatin B microspheres to attain improved biocompatibility. Water absorption of the three-dimensional macroporous chitosan-gelatin B microspheres (3D-P-CGMs) was 12.84, with a porosity of 85.45%. In vitro lysozyme degradation after 1, 3, 5, 7, 10, 14, and 21 days showed improved biodegradation in the 3D-P-CGMs. The morphology of human hepatoma cell lines (HepG2 cells) cultured on the 3D-P-CGMs was spherical, unlike that of cells cultured under traditional two-dimensional conditions. Scanning electron microscopy and paraffin sections were used to confirm the porous structure of the 3D-P-CGMs. HepG2 cells were able to migrate inside through the pore. Cell proliferation and levels of albumin and lactate dehydrogenase suggested that the 3D-P-CGMs could provide a larger specific surface area and an appropriate microenvironment for cell growth and survival. Hence, the 3D-P-CGMs are eminently suitable as macroporous scaffolds for cell cultures in tissue engineering and cell carrier studies. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.

Tip opening of premixed bunsen flames: Extinction with negative stretch and local Karlovitz number

KAUST Repository

Vu, Tranmanh; Cha, Min; Lee, Byeongjun; Chung, Suk-Ho

2015-01-01

The characteristics of tip openings in premixed bunsen flames have been studied experimentally by measuring OH radicals from laser-induced fluorescence and tip curvatures from chemiluminescent images. Results showed that the tip opening occurred

Cm-scale Heterogeneity in Degradation - Potential Impact on Leaching of MCPA through a Variably-Saturated Macroporous Clayey Till

DEFF Research Database (Denmark)

Rosenbom, Annette Elisabeth; Johnsen, Anders R.; Aamand, Jens

with no biodegradation of the MCPA at all nodes; 2) preferential flow (including a wormhole) of water with no biodegradation of the MCPA at all nodes; 3) simple matrix flow of water with average biodegradation of the MCPA at all nodes, which corresponds to results derived from a conventional homogenized soil sample; 4...... both flow and degradation are associated with macropores/wormholes. Results show that cm-scale heterogeneity in degradation potential with simple matrix flow has a negligible effect on MCPA leaching at one meter below soil surface. By introducing a wormhole in the low-permeable 3D-soil modeling domain......, however, the risk of MCPA-leaching below one meter depth increase drastically with low degradation potential along the wall of macropores/wormholes....

Modeling and simulation of combustion dynamics in lean-premixed swirl-stabilized gas-turbine engines

Science.gov (United States)

Huang, Ying

This research focuses on the modeling and simulation of combustion dynamics in lean-premixed gas-turbines engines. The primary objectives are: (1) to establish an efficient and accurate numerical framework for the treatment of unsteady flame dynamics; and (2) to investigate the parameters and mechanisms responsible for driving flow oscillations in a lean-premixed gas-turbine combustor. The energy transfer mechanisms among mean flow motions, periodic motions and background turbulent motions in turbulent reacting flow are first explored using a triple decomposition technique. Then a comprehensive numerical study of the combustion dynamics in a lean-premixed swirl-stabilized combustor is performed. The analysis treats the conservation equations in three dimensions and takes into account finite-rate chemical reactions and variable thermophysical properties. Turbulence closure is achieved using a large-eddy-simulation (LES) technique. The compressible-flow version of the Smagorinsky model is employed to describe subgrid-scale turbulent motions and their effect on large-scale structures. A level-set flamelet library approach is used to simulate premixed turbulent combustion. In this approach, the mean flame location is modeled using a level-set G-equation, where G is defined as a distance function. Thermophysical properties are obtained using a presumed probability density function (PDF) along with a laminar flamelet library. The governing equations and the associated boundary conditions are solved by means of a four-step Runge-Kutta scheme along with the implementation of the message passing interface (MPI) parallel computing architecture. The analysis allows for a detailed investigation into the interaction between turbulent flow motions and oscillatory combustion of a swirl-stabilized injector. Results show good agreement with an analytical solution and experimental data in terms of acoustic properties and flame evolution. A study of flame bifurcation from a stable

The global, centralized approach of the GAIN Premix Facility has made oil fortification in Indonesia more affordable.

Science.gov (United States)

Jallier, Vincent; Guyondet, Christophe; Provent, Adeline; Laillou, Arnaud; Soekirman; Moench-Pfanner, Regina

2013-06-01

Access to high-grade micronutrients is a recurring challenge that often threatens the long-term sustainability of food fortification programs. To assess the efficiency of the Global Alliance for Improved Nutrition (GAIN) Premix Facility in procuring quality, affordable vitamin A for fortification of edible oil in Indonesia. A global approach to procurement of standard items was used by combining volumes across various demand streams in order to reduce the total cost of acquisition through economies of scale. The GAIN Premix Facility undertook a detailed analysis of vitamin A requirements across its existing customer base, which served as a basis for developing a reliable demand forecast. A consolidated, competitive tender was launched that resulted in the setting up of a long-term commercial agreement with the selected supplier to lock in the most competitive price for a given period of time. The direct benefit to oil manufacturers of fortifying with vitamin A is that the cost of fortification went down significantly compared with prices they would have been offered had they ordered vitamin A individually. In Indonesia, this consolidated procurement approach has allowed a 14.5% decrease in the unit price of vitamin A. The GAIN Premix Facility demonstrated its effectiveness in acting as a global procurement platform by aggregating demand across different customers and leveraging improved prices through increased volumes. Building on the success of this effort, the GAIN Premix Facility is replicating this global approach for procurement of other standard items being procured across fortification programs worldwide.

Kecepatan Pembakaran Premixed Campuran Minyak Jarak - Liquefied Petroleum Gas (LPG pada Circular Tube Burner

Directory of Open Access Journals (Sweden)

Defmit B.N. Riwu

2016-10-01

Full Text Available This study was conducted to determine the characteristics of premixed combustion of a mixture of castor oil - LPG on a circular tube burner. Percentage of LPG fuel in a mixture of jatropha curcas oil - LPG varied as much as 10%, 20%, 30%, and 40% of the mass flow jatropha curcas oil vapor. Considering the flame of fire there are two angles formed which describe burning velocity. Also there are formed two cones of fire where the bright blue inside cone is a premixed flame, while the outer blue white cone is flame a diffusion flame. An increase in the percentage of LPG makes the value of top and bottom angle increase. So that the burning velocity on the upper angle decrease whilst on bottom angle increase.

Modeling of confined and unconfined laminar premixed flames on slit and tube burners

NARCIS (Netherlands)

Mallens, R.M.M.; Lange, de H.C.; Ven, van de C.J.H.; Goey, de L.P.H.

1995-01-01

A model is presented for laminar premixed Bunsen flames on slit and cylindrical burners burning in a surrounding atmosphere. A comparison between modeling and experimental results shows that the model can reproduce the experimental results within 10% accuracy. The influence of a surrounding

The Effect of Used of Soy Sauce Waste in the Ration on Yolk Chemical protein, fat and calcium of Mojosari Laying Duck

Directory of Open Access Journals (Sweden)

R. D. Jayanti

2017-10-01

Full Text Available The aim of this study was to examine the effect of soy sauce waste in the ration on protein, fat and calcium content in the yolk of Mojosari laying duck. The animals used were 240 Mojosari laying ducks at 20 weeks old with the average of body weight were 1,385.0 ± 130.85 g (CV = 9.44%. Feed materials used were corn, rice bran, soybean meal, fish meal, wheat pollard, premix and soy sauce waste. The experimental design used was a completely randomized design (CRD with 4 treatment and 6 replications so that there were 24 experimental units and each consists 10 ducks. The treatments were soy sauce waste at level T0 : 0%, T1: 5%, T2: 7,5% and T3: 10%. The data were analyzed using analysis of variance (ANOVA and Significant differences were denoted as P<0.05. There was no significant effect of soy sauce waste protein, fat, and calcium content. The conclusion of this study that soy sauce waste can be used up to 10% without adverse the content of protein, fat, and calcium in Mojosari laying ducks.

Activity and Spatial Distribution of Candida antarctica Lipase B Immobilized on Macroporous Organic Polymeric Adsorbents

DEFF Research Database (Denmark)

Nielsen, Anne Veller Friis; Andric, Pavle; Munk Nielsen, Per

2014-01-01

A systematic study of the influence of carrier particle size (500 − 850 μ m) and enzyme load (26 200 − 66 100 lipase activity units (LU)/g dry carrier) on the content and activity of Candida antarctica lipase B (CALB) immobilized by adsorption onto macroporous poly(methyl methacrylate) (PMM...

Effectiveness of insulin glargine in type 2 diabetes mellitus patients failing glycaemic control with premixed insulin: Adriatic countries data meta-analysis.

Science.gov (United States)

Cigrovski Berkovic, Maja; Petrovski, Goran; Grulovic, Natasa

2016-10-01

Type 2 diabetes mellitus (T2DM) is a progressive disease, often requiring exogenous insulin therapy and treatment intensification. Despite new therapies, most patients do not reach the recommended HbA1c targets, among them a significant proportion of patients on premixed insulins. The aim was to summarize published data in Adriatic countries on effectiveness of insulin glargine based therapy in type 2 diabetic patients suboptimally controlled on premix insulin. A meta-analysis was carried out in major medical databases up to April 2014, focusing on Adriatic region. We searched observational studies with duration of at least 6 months, evaluating effectiveness and safety of insulin glargine (IGlar), in combination with OAD or bolus insulin in patients with T2 failing premixed insulin therapy. Outcomes included values of HbA1c, fasting blood glucose and two hours post-prandial glucose concentration as well as changes in body mass index after at least 6 months of study duration. Three prospective, observational, multicentric trials (698 patients in total) were included. The basal bolus regimen with glargine significantly reduced HbA1c (Mean Difference, MD=2.27, CI [1.76, 2.78]), fasting glucose (MD=5.15, CI [4.86, 5.44]) and 2-hours postprandial glucose concentration (MD=6.94, CI [6.53, 7.34]). No significant changes were found in BMI after switching from premixes to IGlar based treatment. Insulin glargine based therapy following premix failure is efficacious and safe option of type 2 diabetes treatment intensification.

Design of pore size of macroporous ceramic substrates

International Nuclear Information System (INIS)

Szewald, O.; Kotsis, I.

2000-01-01

A method has been developed for the design of macro-porous ceramic substrates. Based on geometrical and regression models detailed technology was worked out for producing these 100% open porous filters, which were made using quasi homo-disperse fractions of corundum of diameters of several tens and hundreds microns and glassy binding material. Axial pressing was used as a forming process. Pore networks with size distribution that can be defined by a curve having one maximum were provided applying the above technology. Based on geometrical considerations and measurements it was proved that these maximums are at characteristic pore sizes that depend only on characteristic size of the original grain fractions and on the extent of the axial forming pressure. Copyright (2000) AD-TECH - International Foundation for the Advancement of Technology Ltd

Combustion and emission characteristics of a diesel engine with DME as port premixing fuel under different injection timing

International Nuclear Information System (INIS)

Wang, Ying; Zhao, Yuwei; Xiao, Fan; Li, Dongchang

2014-01-01

Highlights: • Combustion and emission of diesel engine with DME as premixing fuel were examined. • Injection timing has profound effect on HRR of diffusive combustion in PCCI engine. • DME introduction drastically influenced HRR of PCCI combustion, especially for HTR. • Effect of injection timing on emission of PCCI engine is similar to that of DICI engine. - Abstract: This work dealt with the combustion and exhaust performance of a DME premixed charge compression ignition diesel engine. With the port premixing DME, the heat-release process was made up of the premixed charge homogeneous charge compression ignition combustion and diffusion combustion. The in-cylinder fuel injection timing and port premixing DME quantity played the important roles in combustion and emission control. They had little impact on the peak position of heat-release rate (HRR) during LTR phase. However, they had great effects on the peak values and the crank-angle positions corresponding to the HRR peaks during HTR and diffusion combustion phase. The peak value of HRR increased and the crank-angle corresponding to the HRR peak advanced with an incremental DME quantity or an early injection during HTR phase. However, the peak value of HRR dropped with an incremental DME quantity or a late injection during the diffusion combustion phase. p max and T max increased with an incremental DME quantity or an early injection. At the fixed direct-injection timing, BSFC decreased slightly with a rise of DME quantity due to CA50 closer to TDC. At a fixed DME quantity, BSFC was lowest when diesel was injected into cylinder at 7°CA BTDC. Moreover, as more DME was aspirated from port, NO x emissions decreased firstly but this decreasing trend ceased later. Smoke reduced, but CO and HC increased with a rise of DME quantity. Meanwhile, like the conventional DICI operation, NO x increased, but smoke, CO and HC declined with an early direct-injection

Compression ignition of light naphtha and its multicomponent surrogate under partially premixed conditions

NARCIS (Netherlands)

Vallinayagam, R.; Vedharaj, S.; An, Y.; Dawood, A.; Izadi Najafabadi, M.; Somers, B.; Chang, J.; Sarathy, M.; Johansson, B.

2017-01-01

Light naphtha is the light distillate from crude oil and can be used in compression ignition (CI) engines; its low boiling point and octane rating (RON = 64.5) enable adequate premixing. This study investigates the combustion characteristics of light naphtha (LN) and its multicomponent surrogate

Study on laminar burning velocity of syngas-air premixed flames in various mixing conditions

Energy Technology Data Exchange (ETDEWEB)

Lee, Kee Man; Jeong, Byeong Gyu [Sunchon National University, Suncheon (Korea, Republic of); Lee, Seung Ro [Chonbuk National University, Jeonju (Korea, Republic of)

2015-07-15

The laminar burning velocity of syngas-air premixed flames was measured with various equivalence ratios from 0.5 to 5.0 and a mole fraction of H{sub 2} from 0.05 to 0.75. The laminar burning velocity was experimentally determined using a Bunsen flame according to the cone angle and surface area methods. A premixed code with a USC-II detailed reaction mechanism was used for the numerical calculations to predict the laminar burning velocity and to examine the relationship between the burning velocity enhancement and the hydrogen-related reactions. The results indicate that an appropriate method for the measurement of laminar burning velocity is necessary in the H{sub 2}/CO/air syngas premixed flame. In addition, the burning velocity linearly increased with the increase of the H{sub 2} mole fraction in the syngas mixture, although the burning velocity of H{sub 2} was 10 times larger than that of CO. This result is attributed to the rapid production of H-radicals at the early stage of combustion. Furthermore, the predicted mole fractions of H and OH radicals increased with the increase of H{sub 2} mole fraction for a lean syngas mixture. However, the mole fraction of OH radicals, an indicator of heat release rate, decreased for rich syngas mixture, resulting in a reduction of the laminar burning velocity, even with an increase of the H{sub 2} mole fraction.

Modification of macroporous membranes by graft co-polymerization induced by pre-irradiation with an electron accelerator

International Nuclear Information System (INIS)

Grasselli, M.; Yoshii, Fumio

1999-01-01

Glycidyl methacrylate (GMA) and N,N-dimethylacrylamide (DMAA) have been co-grafted on hollow fiber membranes of macroporous polyethylene. Grafted copolymers have been obtained with different ratios of the monomers (molar ratio between 0 and 2 DMAA/GMA). The properties of the modified membranes are studied

Supplementary Material for: Measurements of Positively Charged Ions in Premixed Methane-Oxygen Atmospheric Flames

KAUST Repository

Alquaity, Awad B. S.; Han, Jie; Chahine, May; Selim, Hatem; Belhi, Memdouh; Sarathy, Mani; Bisetti, Fabrizio; Farooq, Aamir

2017-01-01

chemistry models are needed to understand and predict the effect of external electric fields on combustion plasmas. In this work, a molecular beam mass spectrometer (MBMS) is utilized to measure ion concentration profiles in premixed methane–oxygen argon

Cellular burning in lean premixed turbulent hydrogen-air flames: Coupling experimental and computational analysis at the laboratory scale

International Nuclear Information System (INIS)

Day, M S; Bell, J B; Beckner, V E; Lijewski, M J; Cheng, R K; Tachibana, S

2009-01-01

One strategy for reducing US dependence on petroleum is to develop new combustion technologies for burning the fuel-lean mixtures of hydrogen or hydrogen-rich syngas fuels obtained from the gasification of coal and biomass. Fuel-flexible combustion systems based on lean premixed combustion have the potential for dramatically reducing pollutant emissions in transportation systems, heat and stationary power generation. However, lean premixed flames are highly susceptible to fluid-dynamical combustion instabilities making robust and reliable systems difficult to design. Low swirl burners are emerging as an important technology for meeting design requirements in terms of both reliability and emissions for next generation combustion devices. In this paper, we present simulations of a lean, premixed hydrogen flame stabilized on a laboratory-scale low swirl burner. The simulations use detailed chemistry and transport without incorporating explicit models for turbulence or turbulence/chemistry interaction. Here we discuss the overall structure of the flame and compare with experimental data. We also use the simulation data to elucidate the characteristics of the turbulent flame interaction and how this impacts the analysis of experimental measurements.

The premixing and propagation phases of fuel-coolant interactions: a review of recent experimental studies and code developments

Energy Technology Data Exchange (ETDEWEB)

Antariksawan, A.R. [Reactor Safety Technology Research Center of BATAN (Indonesia); Moriyama, Kiyofumi; Park, Hyun-sun; Maruyama, Yu; Yang, Yanhua; Sugimoto, Jun

1998-09-01

A vapor explosion (or an energetic fuel-coolant interactions, FCIs) is a process in which hot liquid (fuel) transfers its internal energy to colder, more volatile liquid (coolant); thus the coolant vaporizes at high pressure and expands and does works on its surroundings. Traditionally, the energetic fuel-coolant interactions could be distinguished in subsequent stages: premixing (or coarse mixing), triggering, propagation and expansion. Realizing that better and realistic prediction of fuel-coolant interaction consequences will be available understanding the phenomenology in the premixing and propagation stages, many experimental and analytical studies have been performed during more than two decades. A lot of important achievements are obtained during the time. However, some fundamental aspects are still not clear enough; thus the works are directed to that direction. In conjunction, the model/code development is pursuit. This is aimed to provide a scaling tool to bridge the experimental results to the real geometries, e.g. reactor pressure vessel, reactor containment. The present review intends to collect the available information on the recent works performed to study the premixing and propagation phases. (author). 97 refs.

The premixing and propagation phases of fuel-coolant interactions: a review of recent experimental studies and code developments

International Nuclear Information System (INIS)

Antariksawan, A.R.; Moriyama, Kiyofumi; Park, Hyun-sun; Maruyama, Yu; Yang, Yanhua; Sugimoto, Jun

1998-09-01

A vapor explosion (or an energetic fuel-coolant interactions, FCIs) is a process in which hot liquid (fuel) transfers its internal energy to colder, more volatile liquid (coolant); thus the coolant vaporizes at high pressure and expands and does works on its surroundings. Traditionally, the energetic fuel-coolant interactions could be distinguished in subsequent stages: premixing (or coarse mixing), triggering, propagation and expansion. Realizing that better and realistic prediction of fuel-coolant interaction consequences will be available understanding the phenomenology in the premixing and propagation stages, many experimental and analytical studies have been performed during more than two decades. A lot of important achievements are obtained during the time. However, some fundamental aspects are still not clear enough; thus the works are directed to that direction. In conjunction, the model/code development is pursuit. This is aimed to provide a scaling tool to bridge the experimental results to the real geometries, e.g. reactor pressure vessel, reactor containment. The present review intends to collect the available information on the recent works performed to study the premixing and propagation phases. (author). 97 refs

A simple one-step chemistry model for partially premixed hydrocarbon combustion

Energy Technology Data Exchange (ETDEWEB)

Fernandez-Tarrazo, Eduardo [Instituto Nacional de Tecnica Aeroespacial, Madrid (Spain); Sanchez, Antonio L. [Area de Mecanica de Fluidos, Universidad Carlos III de Madrid, Leganes 28911 (Spain); Linan, Amable [ETSI Aeronauticos, Pl. Cardenal Cisneros 3, Madrid 28040 (Spain); Williams, Forman A. [Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92093-0411 (United States)

2006-10-15

This work explores the applicability of one-step irreversible Arrhenius kinetics with unity reaction order to the numerical description of partially premixed hydrocarbon combustion. Computations of planar premixed flames are used in the selection of the three model parameters: the heat of reaction q, the activation temperature T{sub a}, and the preexponential factor B. It is seen that changes in q with equivalence ratio f need to be introduced in fuel-rich combustion to describe the effect of partial fuel oxidation on the amount of heat released, leading to a universal linear variation q(f) for f>1 for all hydrocarbons. The model also employs a variable activation temperature T{sub a}(f) to mimic changes in the underlying chemistry in rich and very lean flames. The resulting chemistry description is able to reproduce propagation velocities of diluted and undiluted flames accurately over the whole flammability limit. Furthermore, computations of methane-air counterflow diffusion flames are used to test the proposed chemistry under nonpremixed conditions. The model not only predicts the critical strain rate at extinction accurately but also gives near-extinction flames with oxygen leakage, thereby overcoming known predictive limitations of one-step Arrhenius kinetics. (author)

Negative plate macropore surfaces in lead-acid batteries: Porosity, Brunauer-Emmett-Teller area, and capacity

Energy Technology Data Exchange (ETDEWEB)

D' Alkaine, C.V.; de O. Brito, G.A. [Group of Electrochemistry and Polymers, DQ-UFSCar, Rodovia Washington Luis, Km 235, CP 676, 13565-905 Sao Carlos (SP) (Brazil)

2009-06-01

We propose an explanation for the production of an electrochemically active area during the electrochemical formation of lead-acid battery negative plates based on solid-state reactions. Our proposal is supported by experimental data. This study includes a critical review of the literature on charge/discharge mechanisms, porosity, and BET area. The critical review, through the latter two parameters, indicates the existence of both macro and micropores in positive plates, but only macropores in negative plates, with characteristic surface roughness. In the present paper the surface sulfation of the precursor is controlled using various acidic, neutral and alkaline solutions during an electrochemical formation process that does not include soaking. Our results confirm that variable roughness can be produced at the negative plate macropore surfaces. The morphological changes produced by different formation conditions are assessed by measuring the macroporosity, BET area, and capacity of single negative plates. Based on these concepts, a method was developed and applied to measure independently the contributions of geometrical surface macroporosity and roughness to the negative plate capacity. (author)

Effects of pressure fluctuations on the combustion process in turbulent premixed flames

Science.gov (United States)

Beardsell, Guillaume; Lapointe, Simon; Blanquart, Guillaume

2016-11-01

The need for a thorough understanding of turbulence-combustion interactions in compressible flows is driven by recent technological developments in propulsion as well as renewed interest in the development of next generation supersonic and hypersonic vehicles. In such flows, pressure fluctuations displaying a wide range of length and timescales are present. These fluctuations are expected to impact the combustion process to varying degrees, depending amongst other things on the amplitude of the pressure variations and the timescales of the chemical reactions taking place in the flame. In this context, numerical simulations of these flows can provide insight into the impact of pressure fluctuations on the combustion process. In the present work, we analyze data from simulations of statistically-flat premixed n-heptane/air flames at high Karlovitz numbers. The compressible Navier-Stokes equations are solved exactly (DNS) and results obtained with both detailed kinetic modeling and one-step chemistry are considered. The effects of pressure fluctuations on the fuel burning rate are investigated. The findings are compared with results obtained from simulations of one-dimensional premixed flames subjected to various pressure waves.

Transport of radionuclides by concentrated brine in a porous medium with micropore-macropore structure

International Nuclear Information System (INIS)

Hassanizadeh, S.M.

1987-01-01

This work concerns itself with the study of effects of soil aggregation and high salt concentrations on the transport of radionuclides by concentrated brine flowing through an aggregated porous medium. The medium is considered to be composed of porous rock aggregates separated by macropores through which the brine flows and transport of salt and radionuclides takes place. The aggregates contain dead-end pores, cracks, and stationary pockets collectively called micropores. The micropore space does not contribute to the flow, but it serves as a storage for salt and radionuclides. Adsorption of radionuclides takes place at internal surfaces of aggregates where they assume that a linear equilibrium isotherm describes the process. A one-dimensional numerical model is developed which is based on two sets of equations: one set for the flow and transport of salt and another set for transport of radionuclides. Results of numerical experiments clearly indicate that the existence of high salt concentrations markedly reduces the peak of nuclides concentration and slows down their movement. Also, it is found that diffusive mass exchange between macropores and aggregates results in a pronounced lowering of the radionuclides concentration peaks. 9 references, 7 figures

Preparative Separation and Purification of the Total Flavonoids in Scorzonera austriaca with Macroporous Resins.

Science.gov (United States)

Xie, Yang; Guo, Qiu-Shi; Wang, Guang-Shu

2016-06-13

The use of macroporous resins for the separation and purification of total flavonoids to obtain high-purity total flavonoids from Scorzonera austriaca was studied. The optimal conditions for separation and purification of total flavonoids in S. austriaca with macroporous resins were as follows: D4020 resin columns were loaded with crude flavonoid extract solution, and after reaching adsorptive saturation, the columns were eluted successively with 5 bed volumes (BV) of water, 5 BV of 5% (v/v) aqueous ethanol and 5 BV of 30% (v/v) aqueous ethanol at an elute flow rate of 2 BV·h(-1). Total flavonoids were obtained from the 30% aqueous ethanol eluate by vacuum distillation recovery. The content of flavonoid compounds in the total flavonoids was 93.5%, which represents an improvement by about 150%. In addition, five flavonoid compounds in the product were identified as 2″-O-β-d-xylopyranosyl isoorientin, 6-C-α-l-arabipyranosyl orientin, orientin, isoorientin and vitexin by LC-ESI-MS analysis and internal standard methods. The results in this study could represent a method for the large-scale production of total flavonoids from S. austriaca.

The Influence of Syndepositional Macropores on the Hydraulic Integrity of Thick Alluvial Clay Aquitards

Science.gov (United States)

Timms, Wendy A.; Acworth, R. Ian; Crane, Richard A.; Arns, Christoph H.; Arns, Ji-Youn; McGeeney, Dayna E.; Rau, Gabriel C.; Cuthbert, Mark O.

2018-04-01

Clay-rich deposits are commonly assumed to be aquitards which act as natural hydraulic barriers due to their low hydraulic connectivity. Postdepositional weathering processes are known to increase the permeability of aquitards in the near surface but not impact on deeper parts of relatively thick formations. However, syndepositional processes affecting the hydraulic properties of aquitards have previously received little attention in the literature. Here, we analyze a 31 m deep sediment core recovered from an inland clay-rich sedimentary sequence using a combination of techniques including particle size distribution and microscopy, centrifuge dye tracer testing and micro X-ray CT imaging. Subaerial deposition of soils within these fine grained alluvial deposits has led to the preservation of considerable macropores (root channels or animal burrows). Connected pores and macropores thus account for vertical hydraulic conductivity (K) of 4.2×10-9 m/s (geometric mean of 13 samples) throughout the thick aquitard, compared to a matrix K that is likely sediment was deposited must be considered when aquitards are investigated as potential natural hydraulic barriers and illustrate the value of combining multiple investigation techniques for characterizing clay-rich deposits.

Evaluation of resistant starch, glycemic index and fortificants content of premix rice coated with various concentrations and types of edible coating materials

Science.gov (United States)

Yulianto, W. A.; Susiati, A. M.; Adhini, H. A. N.

2018-01-01

The incidence of diabetes in Indonesia has been increasing year by year. Diets with a low glycemic index and high resistant starch foods can assist diabetics in controlling their blood glucose levels. Diabetics are known to have micro-nutrient deficiencies of chromium, magnesium and vitamin D that can be overcome by consuming parboiled rice fortified by use of a coating method. The fortification of parboiled rice (premix rice) can be achieved by coating with HPMC (hydroxypropyl methyl cellulose), MC (methyl cellulose), CMC (carboxyl methyl cellulose), gum arabic and rice starch. This research aimed to evaluate the levels of resistant starch, glycemic index and fortificants of premix rice coated with different concentrations and types of edible coating materials. This research used completely randomized design, with treatments to the concentrations and the types of edible coating (HPMC, CMC, MC, gum arabic and rice starch). The concentrations of edible coating were 0.15%, 0.2% and 0.25% for cellulose derivative coatings; 25%, 30%, 35% for gum arabic and 2%, 3.5% and 5% for rice starch. This research shows that fortified premix rice coated with various concentrations and types of edible coating materials is high in resistant starch and has a low glycemic index. The coating treatment affects the levels of magnesium and vitamin D, but does not affect the levels of chromium in parboiled rice. The premix rice with a low glycemic index and high nutrient content (chromium, magnesium and vitamin D) was premix rice coated by CMC 0.25% and HPMC 0.25% with glycemic indeces of 39.34 and 38.50, respectively.

Premixed autoignition in compressible turbulence

Science.gov (United States)

Konduri, Aditya; Kolla, Hemanth; Krisman, Alexander; Chen, Jacqueline

2016-11-01

Prediction of chemical ignition delay in an autoignition process is critical in combustion systems like compression ignition engines and gas turbines. Often, ignition delay times measured in simple homogeneous experiments or homogeneous calculations are not representative of actual autoignition processes in complex turbulent flows. This is due the presence of turbulent mixing which results in fluctuations in thermodynamic properties as well as chemical composition. In the present study the effect of fluctuations of thermodynamic variables on the ignition delay is quantified with direct numerical simulations of compressible isotropic turbulence. A premixed syngas-air mixture is used to remove the effects of inhomogeneity in the chemical composition. Preliminary results show a significant spatial variation in the ignition delay time. We analyze the topology of autoignition kernels and identify the influence of extreme events resulting from compressibility and intermittency. The dependence of ignition delay time on Reynolds and turbulent Mach numbers is also quantified. Supported by Basic Energy Sciences, Dept of Energy, United States.

Combustion stratification study of partially premixed combustion using Fourier transform analysis of OH* chemiluminescence images

KAUST Repository

Izadi Najafabadi, Mohammad; Somers, Bart; Johansson, Bengt; Dam, Nico

2017-01-01

A relatively high level of stratification (qualitatively: lack of homogeneity) is one of the main advantages of partially premixed combustion over the homogeneous charge compression ignition concept. Stratification can smooth the heat release rate

Ion chromatography for the analysis of salt splitting capacities of cation and anion resin in premixed resin sample

International Nuclear Information System (INIS)

Ghosh, Satinath; Kumar, Rakesh; Tripathy, M.K.; Dhole, K.; Sharma, R.S.; Varde, P.V.

2017-01-01

Mixed bed ion exchange resin is commonly used in various plants including nuclear reactors for the purpose of fine polishing. The analysis of ion exchange capacities of cation and anion resin in resin mixture is therefore an agenda in the context of purchasing of premixed resin from the manufacturer. An ion chromatographic method for assaying ion exchange capacities of pure as well as mixed resin has been optimized. The proposed method in contrast to the conventional ASTM method has been found to be quite encouraging to consider it as an alternate method for the analysis of premixed resin. (author)

Analysis of Hydrogen/Air Turbulent Premixed Flames at Different Karlovitz Numbers Using Computational Singular Perturbation

KAUST Repository

Manias, Dimitrios

2018-01-08

The dynamics and structure of two turbulent H2/air premixed flames, representative of the corrugated flamelet (Case 1) and thin reaction zone (Case 2) regimes, are analyzed and compared, using the computational singular perturbation (CSP) tools, by incorporating the tangential stretch rate (TSR) approach. First, the analysis is applied to a laminar premixed H2/air flame for reference. Then, a two-dimensional (2D) slice of Case 1 is studied at three time steps, followed by the comparison between two representative 2D slices of Case 1 and Case 2, respectively. Last, statistical analysis is performed on the full three-dimensional domain for the two cases. The dominant reaction and transport processes are identified for each case and the overall role of kinetics/transport is determined.

An experimental and kinetic modeling study of premixed nitromethane flames at low pressure

DEFF Research Database (Denmark)

Zhang, Kuiwen; Li, Yuyang; Yuan, Tao

2011-01-01

An experimental and modeling study is reported on three premixed nitromethane/oxygen/argon flames at low pressure (4.655kPa) with equivalence ratios (ϕ) of 1.0, 1.5 and 2.0. Flame species were identified with tunable synchrotron vacuum ultraviolet photoionization. The mole fraction profiles of more...

Enhanced Efficiency of Dye-Sensitized Solar Cells with Mesoporous-Macroporous TiO2 Photoanode Obtained Using ZnO Template

Science.gov (United States)

Pham, Trang T. T.; Mathews, Nripan; Lam, Yeng-Ming; Mhaisalkar, Subodh

2017-06-01

Improved light harvesting efficiency can be achieved by enhancing the optical properties of the titanium dioxide (TiO2) photoanode in dye-sensitized solar cells (DSSCs), leading to higher power conversion efficiency. By incorporating submicrometer cavities in TiO2 mesoporous film, using zinc oxide (ZnO) particles as a template, a bimodal pore size structure has been created, called a mesoporous-macroporous nanostructure. This photoanode structure consists of 20-nm TiO2 nanoparticles with two kinds of pores with size of 20 nm (mesopores) and 500 nm (macropores). Energy-dispersive x-ray spectroscopy and x-ray diffraction studies showed no trace of ZnO in the TiO2 after removal by TiCl4 treatment. Higher diffuse transmittance of this film compared with the standard transparent photoanode provides evidence of improved light scattering. When employed in a device, the incident-photon-to-current efficiency of ZnO-assisted devices showed enhancement at longer wavelengths, corresponding to the Mie light scattering effect with the macropores as scattering centers. This resulted in overall higher power conversion efficiency of the DSSC. In this work, a nonvolatile gel ionic liquid was used as the electrolyte to also demonstrate the benefit of this structure in combination with a viscous electrolyte and its promising application to prolong the stability of DSSCs.

Saturation mechanism of the heat release response of a premixed swirl flame using LES

NARCIS (Netherlands)

Krediet, H.J.; Beck, C. H.; Krebs, W.; Kok, J. B.W.

2013-01-01

The nonlinear heat release response of a premixed swirl flame to velocity perturbations is investigated using Large Eddy Simulation. The nonlinear heat release response is required for the prediction of thermoacoustic limit cycle pressure amplitudes and is represented here by the Flame Describing

Premixer assembly for mixing air and fuel for combustion

Science.gov (United States)

York, William David; Johnson, Thomas Edward; Keener, Christopher Paul

2016-12-13

A premixer assembly for mixing air and fuel for combustion includes a plurality of tubes disposed at a head end of a combustor assembly. Also included is a tube of the plurality of tubes, the tube including an inlet end and an outlet end. Further included is at least one non-circular portion of the tube extending along a length of the tube, the at least one non-circular portion having a non-circular cross-section, and the tube having a substantially constant cross-sectional area along its length

Study on biogas premixed charge diesel dual fuelled engine

International Nuclear Information System (INIS)

Duc, Phan Minh; Wattanavichien, Kanit

2007-01-01

This paper presents an experimental investigation of a small IDI biogas premixed charge diesel dual fuelled CI engine used in agricultural applications. Engine performance, diesel fuel substitution, energy consumption and long term use have been concerned. The attained results show that biogas-diesel dual fuelling of this engine revealed almost no deterioration in engine performance but lower energy conversion efficiency which was offset by the reduced fuel cost of biogas over diesel. The long term use of this engine with biogas-diesel dual fuelling is feasible with some considerations

Analysis of the flamelet concept in the numerical simulation of laminar partially premixed flames

Energy Technology Data Exchange (ETDEWEB)

Consul, R.; Oliva, A.; Perez-Segarra, C.D.; Carbonell, D. [Centre Tecnologic de Transferencia de Calor (CTTC), Universitat Politecnica de Catalunya (UPC), Colom 11, E-08222, Terrassa, Barcelona (Spain); de Goey, L.P.H. [Eindhoven University of Technology, Department of Mechanical Engineering, P.O. Box 513, 5600 MB Eindhoven (Netherlands)

2008-04-15

The aim of this work is to analyze the application of flamelet models based on the mixture fraction variable and its dissipation rate to the numerical simulation of partially premixed flames. Although the main application of these models is the computation of turbulent flames, this work focuses on the performance of flamelet concept in laminar flame simulations removing, in this way, turbulence closure interactions. A well-known coflow methane/air laminar flame is selected. Five levels of premixing are taken into account from an equivalence ratio {phi}={infinity} (nonpremixed) to {phi}=2.464. Results obtained using the flamelet approaches are compared to data obtained from the detailed solution of the complete transport equations using primitive variables. Numerical simulations of a counterflow flame are also presented to support the discussion of the results. Special emphasis is given to the analysis of the scalar dissipation rate modeling. (author)

Analysis of Hydrogen/Air Turbulent Premixed Flames at Different Karlovitz Numbers Using Computational Singular Perturbation

KAUST Repository

Manias, Dimitrios; Tingas, Alexandros-Efstathios; Hernandez Perez, Francisco E.; Im, Hong G.; Galassi, Riccardo Malpica; Ciottoli, Pietro Paolo; Valorani, Mauro

2018-01-01

The dynamics and structure of two turbulent H2/air premixed flames, representative of the corrugated flamelet (Case 1) and thin reaction zone (Case 2) regimes, are analyzed and compared, using the computational singular perturbation (CSP) tools

Optimization of operating conditions in the early direct injection premixed charge compression ignition regime

NARCIS (Netherlands)

Boot, M.D.; Luijten, C.C.M.; Rijk, E.P.; Albrecht, B.A.; Baert, R.S.G.

2009-01-01

Early Direct Injection Premixed Charge Compression Ignition (EDI PCCI) is a widely researched combustion concept, which promises soot and CO2 emission levels of a spark-ignition (SI) and compression-ignition (CI) engine, respectively. Application of this concept to a conventional CI engine using a

Inorganic and organic trace mineral supplementation in weanling pig diets

Directory of Open Access Journals (Sweden)

MARIA C. THOMAZ

2015-06-01

Full Text Available A study was conducted to evaluate the effects of dietary inorganic and organic trace minerals in two levels of supplementation regarding performance, diarrhea occurrence, hematological parameters, fecal mineral excretion and mineral retention in metacarpals and liver of weanling pigs. Seventy piglets weaned at 21 days of age with an average initial body weight of 6.70 ± 0.38 kg were allotted in five treatments: control diet (no added trace mineral premix; 50% ITMP (control diet with inorganic trace mineral premix supplying only 50% of trace mineral requirements; 50% OTMP (control diet with organic trace mineral premix supplying only 50% of trace mineral requirements; 100% ITMP (control diet with inorganic trace mineral premix supplying 100% of trace mineral requirements; and 100% OTMP (control diet with organic trace mineral premix supplying 100% of trace mineral requirements. Feed intake and daily weight gain were not affected by treatments, however, piglets supplemented by trace minerals presented better gain:feed ratio. No differences were observed at calcium, phosphorus, potassium, magnesium, sodium and sulfur excreted in feces per kilogram of feed intake. Treatments did not affect calcium, phosphorus, magnesium, sulfur and iron content in metacarpals. Trace mineral supplementation, regardless of level and source, improved the performance of piglets.

Turbulent piloted partially-premixed flames with varying levels of O2/N2: stability limits and PDF calculations

Science.gov (United States)

Juddoo, Mrinal; Masri, Assaad R.; Pope, Stephen B.

2011-12-01

This paper reports measured stability limits and PDF calculations of piloted, turbulent flames of compressed natural gas (CNG) partially-premixed with either pure oxygen, or with varying levels of O2/N2. Stability limits are presented for flames of CNG fuel premixed with up to 20% oxygen as well as CNG-O2-N2 fuel where the O2 content is varied from 8 to 22% by volume. Calculations are presented for (i) Sydney flame B [Masri et al. 1988] which uses pure CNG as well as flames B15 to B25 where the CNG is partially-premixed with 15-25% oxygen by volume, respectively and (ii) Sandia methane-air (1:3 by volume) flame E [Barlow et al. 2005] as well as new flames E15 and E25 that are partially-premixed with 'reconstituted air' where the O2 content in nitrogen is 15 and 25% by volume, respectively. The calculations solve a transported PDF of composition using a particle-based Monte Carlo method and employ the EMST mixing model as well as detailed chemical kinetics. The addition of oxygen to the fuel increases stability, shortens the flames, broadens the reaction zone, and shifts the stoichiometric mixture fraction towards the inner side of the jet. It is found that for pure CNG flames where the reaction zone is narrow (∼0.1 in mixture fraction space), the PDF calculations fail to reproduce the correct level of local extinction on approach to blow-off. A broadening in the reaction zone up to about 0.25 in mixture fraction space is needed for the PDF/EMST approach to be able to capture these finite-rate chemistry effects. It is also found that for the same level of partial premixing, increasing the O2/N2 ratio increases the maximum levels of CO and NO but shifts the peak to richer mixture fractions. Over the range of oxygenation investigated here, stability limits have shown to improve almost linearly with increasing oxygen levels in the fuel and with increasing the contribution of release rate from the pilot.

Delta-sleep inducing peptide entrapment in the charged macroporous matrices

International Nuclear Information System (INIS)

Sukhanova, Tatiana V.; Artyukhov, Alexander A.; Gurevich, Yakov M.; Semenikhina, Marina A.; Prudchenko, Igor A.; Shtilman, Mikhail I.; Markvicheva, Elena A.

2014-01-01

Various biomolecules, for example proteins, peptides etc., entrapped in polymer matrices, impact interactions between matrix and cells, including stimulation of cell adhesion and proliferation. Delta-sleep inducing peptide (DSIP) possesses numerous beneficial properties, including its abilities in burn treatment and neuronal protection. DSIP entrapment in two macroporous polymer matrices based on copolymer of dimethylaminoethyl methacrylate and methylen-bis-acrylamide (Co-DMAEMA-MBAA) and copolymer of acrylic acid and methylen-bis-acrylamide (Co-AA-MBAA) has been studied. Quite 100% of DSIP has been entrapped into positively charged Co-DMAEMA-MBAA matrix, while the quantity of DSIP adsorbed on negatively charged Co-AA-MBAA was only 2–6%. DSIP release from Co-DMAEMA-MBAA was observed in saline solutions (0.9% NaCl and PBS) while there was no DSIP release in water or 25% ethanol, thus ionic strength was a reason of this process. - Graphical abstract: Delta-sleep inducing peptide possessing neuroprotective and wound healing properties was adsorbed on positively charged polymer matrix Co-DMAEMA-MBAA for tissue engineering. The peptide released from Co-DMAEMA-MBAA matrix in function of ionic strength of solution, pH decreasing stimulated peptide release from Co-DMAEMA-MBAA matrix for 3 h. This construction could be a base of new bioactive implants. - Highlights: • Macroporous positively charged Co-DMAEMA-MBAA matrix pore size was 20–35 μm. • DSIP was adsorbed on Co-DMAEMA-MBAA totally in 16 h. • Its release depends on ionic strength of solution (no release in 25% ethanol or water). • Co-DMAEMA-MBAA matrix swelling depends on pH and ionic strength of solution. • DSIP is destroyed in PBS and 0.9% NaCl in 5 days, but in water it was more stable

Delta-sleep inducing peptide entrapment in the charged macroporous matrices

Energy Technology Data Exchange (ETDEWEB)

Sukhanova, Tatiana V., E-mail: sukhanovat@mail.ru [Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Laboratory of Cell Interactions, Miklukho-Maklaya st., 16/10 Moscow (Russian Federation); Artyukhov, Alexander A.; Gurevich, Yakov M.; Semenikhina, Marina A. [Mendeleyev University of Chemical Technology of Russia, Research and Teaching Center “Biomaterials”, Miusskaya sq., 9 Moscow (Russian Federation); Prudchenko, Igor A. [Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Laboratory of Peptide Chemistry, Miklukho-Maklaya st., 16/10 Moscow (Russian Federation); Shtilman, Mikhail I. [Mendeleyev University of Chemical Technology of Russia, Research and Teaching Center “Biomaterials”, Miusskaya sq., 9 Moscow (Russian Federation); Markvicheva, Elena A. [Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Laboratory Polymers for Biology, Miklukho-Maklaya st., 16/10 Moscow (Russian Federation)

2014-09-01

Various biomolecules, for example proteins, peptides etc., entrapped in polymer matrices, impact interactions between matrix and cells, including stimulation of cell adhesion and proliferation. Delta-sleep inducing peptide (DSIP) possesses numerous beneficial properties, including its abilities in burn treatment and neuronal protection. DSIP entrapment in two macroporous polymer matrices based on copolymer of dimethylaminoethyl methacrylate and methylen-bis-acrylamide (Co-DMAEMA-MBAA) and copolymer of acrylic acid and methylen-bis-acrylamide (Co-AA-MBAA) has been studied. Quite 100% of DSIP has been entrapped into positively charged Co-DMAEMA-MBAA matrix, while the quantity of DSIP adsorbed on negatively charged Co-AA-MBAA was only 2–6%. DSIP release from Co-DMAEMA-MBAA was observed in saline solutions (0.9% NaCl and PBS) while there was no DSIP release in water or 25% ethanol, thus ionic strength was a reason of this process. - Graphical abstract: Delta-sleep inducing peptide possessing neuroprotective and wound healing properties was adsorbed on positively charged polymer matrix Co-DMAEMA-MBAA for tissue engineering. The peptide released from Co-DMAEMA-MBAA matrix in function of ionic strength of solution, pH decreasing stimulated peptide release from Co-DMAEMA-MBAA matrix for 3 h. This construction could be a base of new bioactive implants. - Highlights: • Macroporous positively charged Co-DMAEMA-MBAA matrix pore size was 20–35 μm. • DSIP was adsorbed on Co-DMAEMA-MBAA totally in 16 h. • Its release depends on ionic strength of solution (no release in 25% ethanol or water). • Co-DMAEMA-MBAA matrix swelling depends on pH and ionic strength of solution. • DSIP is destroyed in PBS and 0.9% NaCl in 5 days, but in water it was more stable.

Characteristics of premixed flames stabilized in an axisymmetric curved-wall jet burner with tip modification

KAUST Repository

Kim, Daejoong; Gil, Y. S.; Chung, TaeWon; Chung, Suk-Ho

2009-01-01

The stabilization characteristics of premixed flames in an axisymmetric curved-wall jet burner have been experimentally investigated. This burner utilized the Coanda effect on top of a burner tip. The initially spherical burner tip was modified to a

Drug delivery properties of macroporous polystyrene solid foams.

Science.gov (United States)

Canal, Cristina; Aparicio, Rosa Maria; Vilchez, Alejandro; Esquena, Jordi; García-Celma, Maria José

2012-01-01

Polymeric porous foams have been evaluated as possible new pharmaceutical dosage forms. These materials were obtained by polymerization in the continuous phase of highly concentrated emulsions prepared by the phase inversion temperature method. Their porosity, specific surface and surface topography were characterized, and the incorporation and release of active principles was studied using ketoprofen as model lipophilic molecule. Solid foams with very high pore volume, mainly inside macropores, were obtained by this method. The pore morphology of the materials was characterized, and very rough topography was observed, which contributed to their nearly superhydrophobic properties. These solid foams could be used as delivery systems for active principles with pharmaceutical interest, and in the present work ketoprofen was used as a model lipophilic molecule. Drug incorporation and release was studied from solid foam disks, using different concentrations of the loading solutions, achieving a delayed release with short lag-time.

Risk predicting of macropore flow using pedotransfer functions, textural maps and modeling

DEFF Research Database (Denmark)

Iversen, Bo Vangsø; Børgesen, Christen Duus; Lægdsmand, Mette

2011-01-01

of this study were first to develop pedotransfer functions (PTFs) predicting near-saturated [k(−1)] and saturated (Ks) hydraulic conductivity using simple soil parameters as predictors and second to use this information and a newly developed rasterbased soil property map of Denmark to identify risk areas...... modeling were used to construct a new map dividing Denmark into risk categories for macropore flow. This map can be combined with other tools to identify areas where there is a high risk of contaminants leaching out of the root zone....

The anchoring mechanism of a bluff-body stabilized laminar premixed flame

KAUST Repository

Kedia, Kushal S.

2014-09-01

The objective of this work is to investigate the mechanism of the laminar premixed flame anchoring near a heat-conducting bluff-body. We use unsteady, fully resolved, two-dimensional simulations with detailed chemical kinetics and species transport for methane-air combustion. No artificial flame anchoring boundary conditions were imposed. Simulations show a shear-layer stabilized flame just downstream of the bluff-body, with a recirculation zone formed by the products of combustion. A steel bluff-body resulted in a slightly larger recirculation zone than a ceramic bluff-body; the size of which grew as the equivalence ratio was decreased. A significant departure from the conventional two-zone flame-structure is shown in the anchoring region. In this region, the reaction zone is associated with a large negative energy convection (directed from products to reactants) resulting in a negative flame-displacement speed. It is shown that the premixed flame anchors at an immediate downstream location near the bluff-body where favorable ignition conditions are established; a region associated with (1) a sufficiently high temperature impacted by the conjugate heat exchange between the heat-conducting bluff-body and the hot reacting flow and (2) a locally maximum stoichiometry characterized by the preferential diffusion effects. © 2014 The Combustion Institute.

Quantification and Purification of Mulberry Anthocyanins with Macroporous Resins

Directory of Open Access Journals (Sweden)

Xueming Liu

2004-01-01

Full Text Available Total anthocyanins in different cultivars of mulberry were measured and a process for the industrial preparation of mulberry anthocyanins as a natural food colorant was studied. In 31 cultivars of mulberry, the total anthocyanins, calculated as cyanidin 3-glucoside, ranged from 147.68 to 2725.46 mg/L juice. Extracting and purifying with macroporous resins was found to be an efficient potential method for the industrial production of mulberry anthocyanins as a food colorant. Of six resins tested, X-5 demonstrated the best adsorbent capability for mulberry anthocyanins (91 mg/mL resin. The adsorption capacity of resins increased with the surface area and the pore radius. Residual mulberry fruit juice after extraction of pigment retained most of its nutrients, except for anthocyanins, and may provide a substrate for further processing.

Subfilter Scale Modelling for Large Eddy Simulation of Lean Hydrogen-Enriched Turbulent Premixed Combustion

NARCIS (Netherlands)

Hernandez Perez, F.E.

2011-01-01

Hydrogen (H2) enrichment of hydrocarbon fuels in lean premixed systems is desirable since it can lead to a progressive reduction in greenhouse-gas emissions, while paving the way towards pure hydrogen combustion. In recent decades, large-eddy simulation (LES) has emerged as a promising tool to

Acetylene Black Induced Heterogeneous Growth of Macroporous CoV2O6 Nanosheet for High-Rate Pseudocapacitive Lithium-Ion Battery Anode.

Science.gov (United States)

Zhang, Lei; Zhao, Kangning; Luo, Yanzhu; Dong, Yifan; Xu, Wangwang; Yan, Mengyu; Ren, Wenhao; Zhou, Liang; Qu, Longbing; Mai, Liqiang

2016-03-23

Metal vanadates suffer from fast capacity fading in lithium-ion batteries especially at a high rate. Pseudocapacitance, which is associated with surface or near-surface redox reactions, can provide fast charge/discharge capacity free from diffusion-controlled intercalation processes and is able to address the above issue. In this work, we report the synthesis of macroporous CoV2O6 nanosheets through a facile one-pot method via acetylene black induced heterogeneous growth. When applied as lithium-ion battery anode, the macroporous CoV2O6 nanosheets show typical features of pseudocapacitive behavior: (1) currents that are mostly linearly dependent on sweep rate and (2) redox peaks whose potentials do not shift significantly with sweep rate. The macroporous CoV2O6 nanosheets display a high reversible capacity of 702 mAh g(-1) at 200 mA g(-1), excellent cyclability with a capacity retention of 89% (against the second cycle) after 500 cycles at 500 mA g(-1), and high rate capability of 453 mAh g(-1) at 5000 mA g(-1). We believe that the introduction of pseudocapacitive properties in lithium battery is a promising direction for developing electrode materials with high-rate capability.

Site selective generation of sol-gel deposits in layered bimetallic macroporous electrode architectures.

Science.gov (United States)

Lalo, Hélène; Bon-Saint-Côme, Yémima; Plano, Bernard; Etienne, Mathieu; Walcarius, Alain; Kuhn, Alexander

2012-02-07

The elaboration of an original composite bimetallic macroporous electrode containing a site-selective sol-gel deposit is reported. Regular colloidal crystals, obtained by a modified Langmuir-Blodgett approach, are used as templates for the electrogeneration of the desired metals in the form of a well-defined layered bimetallic porous electrode. This porous matrix shows a spatially modulated electroactivity which is subsequently used as a strategy for targeted electrogeneration of a sol-gel deposit, exclusively in one predefined part of the porous electrode.

Early structure of LPG partially premixed conically stabilized flames

KAUST Repository

Elbaz, Ayman M.

2013-01-01

This paper presents experimental investigation of LPG partially premixed turbulent flames stabilized within a conical nozzle burner under constant degree of partial premixing. The stability limits and mean flame structure are presented based on the mean gas temperature and the concentration of CO, O 2, NO, and HC at the flame early region of reaction. The investigation covered the influence of the nozzle cone angle, the jet exit velocity and the jet equivalence ratio. The stability results show that the flames with cone are more stable than those without cone. For conical stabilized flames, the stability results exhibit three different sensitivity regions between the jet velocity and equivalence ratio. The inflame measurements prove that the flame stability could be attributed to the triple flame structure at the flame leading edge. The data show that the triple flame structure is influenced by cone angle, the jet velocity and the equivalence ratio. The flame is believed to be controlled by the recirculation flow inside the cone. Increasing the cone angle induced higher air entrainment to the reaction zone as depicted by a higher O 2 concentration within the flame leading edge. Increasing the jet velocity to a certain limit enhances the intensity of combustion at the flame leading edge, while excessive increase in jet velocity reduces this intensity. At a fixed jet velocity the higher the equivalence ratio, the higher the amount of fuel diffused and engulfed to the reaction zone, the more delay of the combustion completion and the higher the emission concentrations of the flame. © 2012 Elsevier Inc.

The growth of high density network of MOF nano-crystals across macroporous metal substrates - Solvothermal synthesis versus rapid thermal deposition

Science.gov (United States)

Maina, James W.; Gonzalo, Cristina Pozo; Merenda, Andrea; Kong, Lingxue; Schütz, Jürg A.; Dumée, Ludovic F.

2018-01-01

Fabrication of metal organic framework (MOF) films and membranes across macro-porous metal substrates is extremely challenging, due to the large pore sizes across the substrates, poor wettability, and the lack of sufficient reactive functional groups on the surface, which prevent high density nucleation of MOF crystals. Herein, macroporous stainless steel substrates (pore size 44 × 40 μm) are functionalized with amine functional groups, and the growth of ZIF-8 crystals investigated through both solvothermal synthesis and rapid thermal deposition (RTD), to assess the role of synthesis routes in the resultant membranes microstructure, and subsequently their performance. Although a high density of well interconnected MOF crystals was observed across the modified substrates following both techniques, RTD was found to be a much more efficient route, yielding high quality membranes under 1 h, as opposed to the 24 h required for solvothermal synthesis. The RTD membranes also exhibited high gas permeance, with He permeance of up to 2.954 ± 0.119 × 10-6 mol m-2 s-1 Pa-1, and Knudsen selectivities for He/N2, Ar/N2 and CO2/N2, suggesting the membranes were almost defect free. This work opens up route for efficient fabrication of MOF films and membranes across macro-porous metal supports, with potential application in electrically mediated separation applications.

Nickel oxide film with open macropores fabricated by surfactant-assisted anodic deposition for high capacitance supercapacitors.

Science.gov (United States)

Wu, Mao-Sung; Wang, Min-Jyle

2010-10-07

Nickel oxide film with open macropores prepared by anodic deposition in the presence of surfactant shows a very high capacitance of 1110 F g(-1) at a scan rate of 10 mV s(-1), and the capacitance value reduces to 950 F g(-1) at a high scan rate of 200 mV s(-1).

An Efficient Protocol for Preparation of Gallic Acid from Terminalia bellirica (Gaertn.) Roxb by Combination of Macroporous Resin and Preparative High-Performance Liquid Chromatography.

Science.gov (United States)

Zou, Denglang; Chen, Tao; Chen, Chen; Li, Hongmei; Liu, Yongling; Li, Yulin

2016-08-01

In this article, macroporous resin column chromatography and preparative high-performance liquid chromatography were applied for preparation of gallic acid from Terminalia bellirica (Gaertn.) Roxb. In the first step, six kinds of resins were investigated by adsorption and desorption tests and AB-8 macroporous resin was selected for the enrichment of gallic acid. As a result, 20 g of gallic acid at a purity of 71% could be separated from 100 g of crude extract in which the content of gallic acid was 16.7% and the recovery of gallic acid reached 85.0%. In the second step, preparative high-performance liquid chromatography was selected to purify gallic acid. As a result, 640 mg of gallic acid at a purity of 99.1% was obtained from 1 g of sample in 35 min. The results demonstrated that macroporous resin coupled with preparative high-performance liquid chromatography was suitable for preparation of gallic acid from T. bellirica (Gaertn.) Roxb. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Combustion and radiation modeling of laminar premixed flames using OpenFOAM: A numerical investigation of radiative heat transfer in the RADIADE project

OpenAIRE

Haider, Sajjad; Pang, Kar Mun; Ivarsson, Anders; Schramm, Jesper

2013-01-01

This paper presents the computational fluid dynamics modelling of a laminar premixed flame. A specific solver named ’rareLTSFoam’ is developed using OpenFOAM ® code. The solver is used to simulate experimental stoichiometric and rich laminar premixed flames. The modelling is carried out for thermal flow and combusting flow cases. The results show that without including radiation modelling, the predicted flame temperature is higher than the measured values. P1 radiation Model is used with sub-...

Study on the combustion characteristics of a premixed combustion system with exhaust gas recirculation

International Nuclear Information System (INIS)

Yu, Byeonghun; Kum, Sung-Min; Lee, Chang-Eon; Lee, Seungro

2013-01-01

The boiler of a premixed combustion system with EGR (exhaust gas recirculation) is investigated to explore the potential for increasing thermal efficiency and lowering pollutant emissions. To achieve this purpose, a thermodynamic analysis is performed to predict the effect of EGR on the thermodynamic efficiency for various equivalence ratios. Experiments of a preheated air condensing boiler with EGR were conducted to measure the changes in the thermal efficiency and the characteristics of the pollutant emission. Finally, a 1-D premixed code was calculated to understand the effect of the EGR method on the NO reduction mechanism. The results of the thermodynamic analysis show that the thermodynamic efficiency is not changed because the temperature and the amount of the exhaust gas are unchanged, even though the EGR method is implemented in the system. However, when the EGR method is used with an equivalence ratio near 1.00, it is experimentally verified that the thermal efficiency increases and the NO x concentration decreases. Based on the results from numerical calculations, it is shown that the NO production rates of N + O 2 ↔ NO + O and N + OH ↔ NO + H are remarkably changed due to the decrease in the flame temperature and the NO mole fraction is decreased. - Highlights: • Premixed combustion system with EGR is studied for a high efficiency and low NO x . • All research is performed with various EGR and equivalence ratios. • It verified that efficiency increases and the NO x emission decreases with EGR method. • NO production rates are remarkably changed by N + O 2 ↔ NO + O and N + OH ↔ NO + H with EGR

Emission noise spectrum in a premixed H2-O2-N2 flame

NARCIS (Netherlands)

Alkemade, C.T.J.; Hooymayers, H.P.; Lijnse, P.L.; Vierbergen, T.J.M.J.

Experimental noise spectra in the frequency range of 15–105 Hz are reported for the thermal emission of the first resonance doublet of Na and K in a premixed H2-O2-N2 flame, and for the flame background emission. Under certain conditions, low-frequency peaks arise in the noise spectrum below 100 Hz,

Effects of Driving Frequency on Propagation Characteristics of Methane - Air Premixed Flame Influenced by Ultrasonic Standing Wave

Energy Technology Data Exchange (ETDEWEB)

Bae, Dae Seok; Kim, Jeong Soo [Pukyong National University, Busan (Korea, Republic of); Seo, Hang Seok [Hanwha Corporation, DaeJeon (Korea, Republic of)

2015-02-15

An experimental study was conducted to scrutinize the influence of the frequency of an ultrasonic standing wave on the variation in the behavior of a methane-air premixed flame. The evolutionary features of the propagating flame were captured by a high-speed camera, and the macroscopic flame behavior, including the flame structure and local velocities, was investigated in detail using a post-processing analysis of the high-speed images. It was found that a structural variation and propagation-velocity augmentation of the methane-air premixed flame were caused by the intervention of the ultrasonic standing wave, which enhanced the combustion reaction. Conclusive evidence for the dependency of the flame behaviors on the driving frequency of the ultrasonic standing wave and equivalence ratio of the reactants is presented.

Interaction of adsorption of reactive yellow 4 from aqueous solutions onto synthesized calcium phosphate

Directory of Open Access Journals (Sweden)

H. El Boujaady

2017-01-01

Full Text Available The interaction of reactive yellow 4 with Apatitic Tricalcium Phosphate (PTCa has been investigated in aqueous medium to understand the mechanism of adsorption and explore the potentiality of this phosphate toward controlling pollution resulting from textile dyes. Transmission electron microscopy (TEM analysis demonstrates that the adsorbent is composed of needle-like nanoparticles and the SAED pattern exhibits spotted sharp and continuous rings that evidence polycrystalline grains. X-ray diffraction results showed that, the crystallinity of the dye decreased after interaction with RY4 indicatating incorporation of the dye into the micropores and macropores of the adsorbent. The results of Fourier transform infrared (FTIR spectroscopy indicate that the adsorption is due to the electrostatic interaction between the –SO3- groups of dye and the surface of the Phosphate. The desorption efficiency was very high at about 99.4%. The presence of calcium ions favored the adsorption of the dye, while the phosphate ions inhibited it.

Experimental study on fuel economies and emissions of direct-injection premixed combustion engine fueled with gasoline/diesel blends

International Nuclear Information System (INIS)

Du, Jiakun; Sun, Wanchen; Guo, Liang; Xiao, Senlin; Tan, Manzhi; Li, Guoliang; Fan, Luyan

2015-01-01

Highlights: • A compound combustion concept was proposed and investigated. • Premixed combustion near the top dead center was investigated using blended fuels. • Increasing gasoline blend ratio was found to enhance the mixture preparation. • Too much addition of gasoline decreases indicated thermal efficiency. • Gasoline/diesel blends may be a promising alternative for premixed combustion. - Abstract: The effects of gasoline/diesel blended fuel composed of diesel fuel with gasoline as additives in volume basis, on combustion, fuel economies and exhaust emissions were experimentally investigated. Tests were carried out based on a turbocharged Common-rail Direct Injection engine at a constant engine speed of 1800 r/min and different loads of 3.2 bar, 5.1 bar Indicated Mean Effective Pressure. Additionally, the effect of combustion phasing and Exhaust Gas Recirculation were evaluated experimentally for various fuels. The results indicated that with the fraction of gasoline increasing in blends, the ignition delay was prolonged and the combustion phasing was retarded with the common injection timing. This led to a significant increase of premixed burning phase, which was in favor of smoke reduction; although, too much gasoline might be adverse to fuel consumption. An optimum combustion phasing was identified, leading to a higher thermal efficiency and better premixed combustion with blended fuels. A combined application of Exhaust Gas Recirculation and blended fuel with a high gasoline fraction was confirmed effective in reducing the oxides of nitrogen and smoke emissions simultaneously at the optimum combustion phasing without giving significant penalty of fuel consumption. A compound combustion mode with its emission lower than the conventional Compression Ignition engines, and efficiency higher than the typical Spark Ignition engines, could be achieved with a cooperative control of Exhaust Gas Recirculation and combustion phasing of the gasoline

Effects of elliptical burner geometry on partially premixed gas jet flames in quiescent surroundings

Science.gov (United States)

Baird, Benjamin

This study is the investigation of the effect of elliptical nozzle burner geometry and partial premixing, both 'passive control' methods, on a hydrogen/hydrocarbon flame. Both laminar and turbulent flames for circular, 3:1, and 4:1 aspect ratio (AR) elliptical burners are considered. The amount of air mixed with the fuel is varied from fuel-lean premixed flames to fuel-rich partially premixed flames. The work includes measurements of flame stability, global pollutant emissions, flame radiation, and flame structure for the differing burner types and fuel conditions. Special emphasis is placed on the near-burner region. Experimentally, both conventional (IR absorption, chemiluminecent, and polarographic emission analysis,) and advanced (laser induced fluorescence, planar laser induced fluorescence, Laser Doppler Velocimetry (LDV), Rayleigh scattering) diagnostic techniques are used. Numerically, simulations of 3-dimensional laminar and turbulent reacting flow are conducted. These simulations are run with reduced chemical kinetics and with a Reynolds Stress Model (RSM) for the turbulence modeling. It was found that the laminar flames were similar in appearance and overall flame length for the 3:1 AR elliptical and the circular burner. The laminar 4:1 AR elliptical burner flame split into two sub-flames along the burner major axis. This splitting had the effect of greatly shortening the 4:1 AR elliptical burner flame to have an overall flame length about half of that of the circular and 3:1 AR elliptical burner flames. The length of all three burners flames increased with increasing burner exit equivalence ratio. The blowout velocity for the three burners increased with increase in hydrogen mass fraction of the hydrogen/propane fuel mixture. For the rich premixed flames, the circular burner was the most stable, the 3:1 AR elliptical burner, was the least stable, and the 4:1 AR elliptical burner was intermediate to the two other burners. This order of stability was due

Premixing and steam explosion phenomena in the tests with stratified melt-coolant configuration and binary oxidic melt simulant materials

Energy Technology Data Exchange (ETDEWEB)

Kudinov, Pavel, E-mail: pavel@safety.sci.kth.se; Grishchenko, Dmitry, E-mail: dmitry@safety.sci.kth.se; Konovalenko, Alexander, E-mail: kono@kth.se; Karbojian, Aram, E-mail: karbojan@kth.se

2017-04-01

Highlights: • Steam explosion in stratified melt-coolant configuration is studied experimentally. • Different binary oxidic melt simulant materials were used. • Five spontaneous steam explosions were observed. • Instability of melt-coolant interface and formation of premixing layer was observed. • Explosion strength is influenced by melt superheat and water subcooling. - Abstract: Steam explosion phenomena in stratified melt-coolant configuration are considered in this paper. Liquid corium layer covered by water on top can be formed in severe accident scenarios with (i) vessel failure and release of corium melt into a relatively shallow water pool; (ii) with top flooding of corium melt layer. In previous assessments of potential energetics in stratified melt-coolant configuration, it was assumed that melt and coolant are separated by a stable vapor film and there is no premixing prior to the shock wave propagation. This assumption was instrumental for concluding that the amount of energy that can be released in such configuration is not of safety importance. However, several recent experiments carried out in Pouring and Under-water Liquid Melt Spreading (PULiMS) facility with up to 78 kg of binary oxidic corium simulants mixtures have resulted in spontaneous explosions with relatively high conversion ratios (order of one percent). The instability of the melt-coolant interface, melt splashes and formation of premixing layer were observed in the tests. In this work, we present results of experiments carried out more recently in steam explosion in stratified melt-coolant configuration (SES) facility in order to shed some light on the premixing phenomena and assess the influence of the test conditions on the steam explosion energetics.

[Methods quantitative for determination of water-soluble vitamins in premixes and fortified food products by micellar electrokinetic chromatography on short end of the capillary].

Science.gov (United States)

Bogachuk, M N; Bessonov, V V; Perederiaev, O I

2011-01-01

It was purposed new technique by micellar electrokinetic chromatography on short end of the capillary (capillary electrophoresis system Agilent 3D CE, DAD, quartz capillary HPCE stndrd cap 56 cm, 50 microm, 50 mM borate buffer pH=9,3, 100 mM sodium dodecil sulfate) for simultaneous determination of water-soluble vitamins (B1, B2, B6, B12, PP, B5, B9, C, B8) in fortified food products and premixes. It was observed on 6 samples of vitamin premixes and 28 samples of fortified food products using this technique. Our findings are consistent with the results of research on certain vitamins, conducted by other methods. The developed technique can be used in analysis of water-soluble vitamins in premixes and fortified food products.

Combustion stratification study of partially premixed combustion using Fourier transform analysis of OH* chemiluminescence images

KAUST Repository

Izadi Najafabadi, Mohammad

2017-11-06

A relatively high level of stratification (qualitatively: lack of homogeneity) is one of the main advantages of partially premixed combustion over the homogeneous charge compression ignition concept. Stratification can smooth the heat release rate and improve the controllability of combustion. In order to compare stratification levels of different partially premixed combustion strategies or other combustion concepts, an objective and meaningful definition of “stratification level” is required. Such a definition is currently lacking; qualitative/quantitative definitions in the literature cannot properly distinguish various levels of stratification. The main purpose of this study is to objectively define combustion stratification (not to be confused with fuel stratification) based on high-speed OH* chemiluminescence imaging, which is assumed to provide spatial information regarding heat release. Stratification essentially being equivalent to spatial structure, we base our definition on two-dimensional Fourier transforms of photographs of OH* chemiluminescence. A light-duty optical diesel engine has been used to perform the OH* bandpass imaging on. Four experimental points are evaluated, with injection timings in the homogeneous regime as well as in the stratified partially premixed combustion regime. Two-dimensional Fourier transforms translate these chemiluminescence images into a range of spatial frequencies. The frequency information is used to define combustion stratification, using a novel normalization procedure. The results indicate that this new definition, based on Fourier analysis of OH* bandpass images, overcomes the drawbacks of previous definitions used in the literature and is a promising method to compare the level of combustion stratification between different experiments.

Effect of energetic electrons on combustion of premixed burner flame

Science.gov (United States)

Sasaki, Koichi

2011-10-01

In many studies of plasma-assisted combustion, authors superpose discharges onto flames to control combustion reactions. This work is motivated by more fundamental point of view. The standpoint of this work is that flames themselves are already plasmas. We irradiated microwave power onto premixed burner flame with the intention of heating electrons in it. The microwave power was limited below the threshold for a discharge. We obtained the enhancement of burning velocity by the irradiation of the microwave power, which was understood by the shortening of the flame length. At the same time, we observed the increases in the optical emission intensities of OH and CH radicals. Despite the increases in the optical emission intensities, the optical emission spectra of OH and CH were not affected by the microwave irradiation, indicating that the enhancement of the burning velocity was not attributed to the increase in the gas temperature. On the other hand, we observed significant increase in the optical emission intensity of the second positive system of molecular nitrogen, which is a clear evidence for electron heating in the premixed burner flame. Therefore, it is considered that the enhancement of the burning velocity is obtained by nonequilibrium combustion chemistry which is driven by energetic electrons. By irradiating pulsed microwave power, we examined the time constants for the increases and decreases in the optical emission intensities of N2, OH, CH, and continuum radiation.

Streamline segment statistics of premixed flames with nonunity Lewis numbers

Science.gov (United States)

Chakraborty, Nilanjan; Wang, Lipo; Klein, Markus

2014-03-01

The interaction of flame and surrounding fluid motion is of central importance in the fundamental understanding of turbulent combustion. It is demonstrated here that this interaction can be represented using streamline segment analysis, which was previously applied in nonreactive turbulence. The present work focuses on the effects of the global Lewis number (Le) on streamline segment statistics in premixed flames in the thin-reaction-zones regime. A direct numerical simulation database of freely propagating thin-reaction-zones regime flames with Le ranging from 0.34 to 1.2 is used to demonstrate that Le has significant influences on the characteristic features of the streamline segment, such as the curve length, the difference in the velocity magnitude at two extremal points, and their correlations with the local flame curvature. The strengthenings of the dilatation rate, flame normal acceleration, and flame-generated turbulence with decreasing Le are principally responsible for these observed effects. An expression for the probability density function (pdf) of the streamline segment length, originally developed for nonreacting turbulent flows, captures the qualitative behavior for turbulent premixed flames in the thin-reaction-zones regime for a wide range of Le values. The joint pdfs between the streamline length and the difference in the velocity magnitude at two extremal points for both unweighted and density-weighted velocity vectors are analyzed and compared. Detailed explanations are provided for the observed differences in the topological behaviors of the streamline segment in response to the global Le.

Mechanisms of stabilization and blowoff of a premixed flame downstream of a heat-conducting perforated plate

KAUST Repository

Kedia, Kushal S.; Ghoniem, Ahmed F.

2012-01-01

The objective of this work is to investigate the flame stabilization mechanism and the conditions leading to the blowoff of a laminar premixed flame anchored downstream of a heat-conducting perforated-plate/multi-hole burner, with overall nearly

Calcium paradox and calcium entry blockers

NARCIS (Netherlands)

Ruigrok, T.J.C.; Slade, A.M.; Nayler, W.G.; Meijler, F.L.

1984-01-01

Reperfusion of isolated hearts with calcium-containing solution after a short period of calcium-free perfusion results in irreversible cell damage (calcium paradox). This phenomenon is characterized by an excessive influx of calcium into the cells, the rapid onset of myocardial contracture,

NO{sub x} formation in lean premixed combustion of methane at high pressures

Energy Technology Data Exchange (ETDEWEB)

Bengtsson, K U.M.; Griebel, P; Schaeren, R [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1999-08-01

High pressure experiments in a jet-stirred reactor have been performed to study the NO{sub x} formation in lean premixed combustion of methane/air mixtures. The experimental results are compared with numerical predictions using four well known reaction mechanisms and a model which consists of a series of two perfectly stirred reactors and a plug flow reactor. (author) 2 figs., 7 refs.

SOLVENT EFFECTS IN THE LIQUID-PHASE HYDRATION OF CYCLOHEXENE CATALYZED BY A MACROPOROUS STRONG ACID ION-EXCHANGE RESIN

NARCIS (Netherlands)

PANNEMAN, HJ; BEENACKERS, AACM

1992-01-01

The liquid-phase hydration of cyclohexene, a pseudo first order reversible reaction catalyzed by a strong acid ion exchange resin, macroporous Amberlite XE 307, was investigated in solvent mixtures of water and sulfolane. A decrease by a factor of 3 and 6 is observed in the experimentally measured

Separation and purification of both tea seed polysaccharide and saponin from camellia cake extract using macroporous resin.

Science.gov (United States)

Yang, Pengjie; Zhou, Mingda; Zhou, Chengyun; Wang, Qian; Zhang, Fangfang; Chen, Jian

2015-02-01

A novel method to separate and purify tea seed polysaccharide and tea seed saponin from camellia cake extract by macroporous resin was developed. Among four kinds of resins (AB-8, NKA-9, XDA-6, and D4020) tested, AB-8 macroporous resin possessed optimal separating capacity for the two substances and thus was selected for the separation, in which deionized water was used to elute tea seed polysaccharide, 0.25% NaOH solution to remove the undesired pigments, and 90% ethanol to elute tea seed saponin. Further dynamic adsorption/desorption experiments on AB-8 resin-based column chromatography were conducted to obtain the optimal parameters. Under optimal dynamic adsorption and desorption conditions, 18.7 and 11.8% yield of tea seed polysaccharide and tea seed saponin were obtained with purities of 89.2 and 96.0%, respectively. The developed method provides a potential approach for the large-scale production of tea seed polysaccharide and tea seed saponin from camellia cake. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Combustion characteristics of lemongrass (Cymbopogon flexuosus oil in a partial premixed charge compression ignition engine

Directory of Open Access Journals (Sweden)

Avinash Alagumalai

2015-09-01

Full Text Available Indeed, the development of alternate fuels for use in internal combustion engines has traditionally been an evolutionary process in which fuel-related problems are met and critical fuel properties are identified and their specific limits defined to resolve the problem. In this regard, this research outlines a vision of lemongrass oil combustion characteristics. In a nut-shell, the combustion phenomena of lemongrass oil were investigated at engine speed of 1500 rpm and compression ratio of 17.5 in a 4-stroke cycle compression ignition engine. Furthermore, the engine tests were conducted with partial premixed charge compression ignition-direct injection (PCCI-DI dual fuel system to profoundly address the combustion phenomena. Analysis of cylinder pressure data and heat-release analysis of neat and premixed lemongrass oil were demonstrated in-detail and compared with conventional diesel. The experimental outcomes disclosed that successful ignition and energy release trends can be obtained from a compression ignition engine fueled with lemongrass oil.

EXPERIMENTAL AND MODELING STUDY OF PREMIXED LAMINAR FLAMES OF ETHANOL AND METHANE.

Science.gov (United States)

Tran, Luc-Sy; Glaude, Pierre-Alexandre; Fournet, René; Battin-Leclerc, Frédérique

2013-04-18

To better understand the chemistry of the combustion of ethanol, the structure of five low pressure laminar premixed flames has been investigated: a pure methane flame (φ=1), three pure ethanol flames (φ=0.7, 1.0, and 1.3), and an ethanol/methane mixture flames (φ=1). The flames have been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 64.3 cm/s at 333 K. The results consist of mole fraction profiles of 20 species measured as a function of the height above the burner by probe sampling followed by online gas chromatography analyses. A mechanism for the oxidation of ethanol was proposed. The reactions of ethanol and acetaldehyde were updated and include recent theoretical calculations while that of ethenol, dimethyl ether, acetone, and propanal were added in the mechanism. This mechanism was also tested against experimental results available in the literature for laminar burning velocities and laminar premixed flame where ethenol was detected. The main reaction pathways of consumption of ethanol are analyzed. The effect of the branching ratios of reaction C 2 H 5 OH+OH→Products+H 2 O is also discussed.

Dynamics of premixed hydrogen/air flames in mesoscale channels

Energy Technology Data Exchange (ETDEWEB)

Pizza, Gianmarco [Paul Scherrer Institute, Combustion Research, CH-5232, Villigen PSI (Switzerland); Aerothermochemistry and Combustion Systems Laboratory, Swiss Federal Institute of Technology, CH-8092, Zurich (Switzerland); Frouzakis, Christos E.; Boulouchos, Konstantinos [Aerothermochemistry and Combustion Systems Laboratory, Swiss Federal Institute of Technology, CH-8092, Zurich (Switzerland); Mantzaras, John [Paul Scherrer Institute, Combustion Research, CH-5232, Villigen PSI (Switzerland); Tomboulides, Ananias G. [Department of Engineering and Management of Energy Resources, University of Western Macedonia, 50100 Kozani (Greece)

2008-10-15

Direct numerical simulation with detailed chemistry and transport is used to study the stabilization and dynamics of lean ({phi}=0.5) premixed hydrogen/air atmospheric pressure flames in mesoscale planar channels. Channel heights of h=2, 4, and 7 mm, and inflow velocities in the range 0.3{<=}U{sub IN}{<=}1100cm/ s are investigated. Six different burning modes are identified: mild combustion, ignition/extinction, closed steady symmetric flames, open steady symmetric flames, oscillating and, finally, asymmetric flames. Chaotic behavior of cellular flame structures is observed for certain values of U{sub IN}. Stability maps delineating the regions of the different flame types are finally constructed. (author)

Effects of porous insert on flame dynamics in a lean premixed swirl-stabilized combustor

Science.gov (United States)

Brown, Marcus; Agrawal, Ajay; Allen, James; Kornegay, John

2016-11-01

In this study, we investigated different methods of determining the effect a porous insert has on flame dynamics during lean premixed combustion. A metallic porous insert is used to mitigate instabilities in a swirl-stabilized combustor. Thermoacoustic instabilities are seen as negative consequences of lean premixed combustion and eliminating them is the motivation for our research. Three different diagnostics techniques with high-speed Photron SA5 cameras were used to monitor flame characteristics. Particle image velocimetry (PIV) was used to observe vortical structures and recirculation zones within the combustor. Using planar laser induced fluorescence (PLIF), we were able to observe changes in the reaction zones during instabilities. Finally, utilizing a color high-speed camera, visual images depicting a flame's oscillations during the instability were captured. Using these monitoring techniques, we are able to support the claims made in previous studies stating that the porous insert in the combustor significantly reduces the thermoacoustic instability. Funding for this research was provided by the NSF REU site Grant EEC 1358991 and NASA Grant NNX13AN14A.

Soot Particle Size Distribution Functions in a Turbulent Non-Premixed Ethylene-Nitrogen Flame

KAUST Repository

Boyette, Wesley

2017-02-21

A scanning mobility particle sizer with a nano differential mobility analyzer was used to measure nanoparticle size distribution functions in a turbulent non-premixed flame. The burner utilizes a premixed pilot flame which anchors a C2H4/N2 (35/65) central jet with ReD = 20,000. Nanoparticles in the flame were sampled through a N2-filled tube with a 500- μm orifice. Previous studies have shown that insufficient dilution of the nanoparticles can lead to coagulation in the sampling line and skewed particle size distribution functions. A system of mass flow controllers and valves were used to vary the dilution ratio. Single-stage and two-stage dilution systems were investigated. A parametric study on the effect of the dilution ratio on the observed particle size distribution function indicates that particle coagulation in the sampling line can be eliminated using a two-stage dilution process. Carbonaceous nanoparticle (soot) concentration particle size distribution functions along the flame centerline at multiple heights in the flame are presented. The resulting distributions reveal a pattern of increasing mean particle diameters as the distance from the nozzle along the centerline increases.

Soot Particle Size Distribution Functions in a Turbulent Non-Premixed Ethylene-Nitrogen Flame

KAUST Repository

Boyette, Wesley; Chowdhury, Snehaunshu; Roberts, William L.

2017-01-01

A scanning mobility particle sizer with a nano differential mobility analyzer was used to measure nanoparticle size distribution functions in a turbulent non-premixed flame. The burner utilizes a premixed pilot flame which anchors a C2H4/N2 (35/65) central jet with ReD = 20,000. Nanoparticles in the flame were sampled through a N2-filled tube with a 500- μm orifice. Previous studies have shown that insufficient dilution of the nanoparticles can lead to coagulation in the sampling line and skewed particle size distribution functions. A system of mass flow controllers and valves were used to vary the dilution ratio. Single-stage and two-stage dilution systems were investigated. A parametric study on the effect of the dilution ratio on the observed particle size distribution function indicates that particle coagulation in the sampling line can be eliminated using a two-stage dilution process. Carbonaceous nanoparticle (soot) concentration particle size distribution functions along the flame centerline at multiple heights in the flame are presented. The resulting distributions reveal a pattern of increasing mean particle diameters as the distance from the nozzle along the centerline increases.

Novel method of separating macroporous arrays from p-type silicon substrate

International Nuclear Information System (INIS)

Peng Bobo; Wang Fei; Liu Tao; Yang Zhenya; Wang Lianwei; Fu, Ricky K. Y.; Chu, Paul K.

2012-01-01

This paper presents a novel method to fabricate separated macroporous silicon using a single step of photo-assisted electrochemical etching. The method is applied to fabricate silicon microchannel plates in 100 mm p-type silicon wafers, which can be used as electron multipliers and three-dimensional Li-ion microbatteries. Increasing the backside illumination intensity and decreasing the bias simultaneously can generate additional holes during the electrochemical etching which will create lateral etching at the pore tips. In this way the silicon microchannel can be separated from the substrate when the desired depth is reached, then it can be cut into the desired shape by using a laser cutting machine. Also, the mechanism of lateral etching is proposed. (semiconductor materials)

Cholesterol-imprinted macroporous monoliths: Preparation and characterization.

Science.gov (United States)

Stepanova, Mariia А; Kinziabulatova, Lilia R; Nikitina, Anna A; Korzhikova-Vlakh, Evgenia G; Tennikova, Tatiana B

2017-11-01

The development of sorbents for selective binding of cholesterol, which is a risk factor for cardiovascular disease, has a great importance for analytical science and medicine. In this work, two series of macroporous cholesterol-imprinted monolithic sorbents differing in the composition of functional monomers (methacrylic acid, butyl methacrylate, 2-hydroxyethyl methacrylate and ethylene dimethacrylate), amount of a template (4, 6 and 8 mol%) used for molecular imprinting, as well as mean pore size were synthesized by in situ free-radical process in stainless steel housing of 50 mm × 4.6 mm i.d. All prepared materials were characterized regarding to their hydrodynamic permeability and porous properties, as well as examined by BET and SEM methods. Imprinting factors, apparent dynamic dissociation constants, the maximum binding capacity, the number of theoretical plates and the height equivalent to a theoretical palate of MIP monoliths at different mobile phase flow rates were determined. The separation of a mixture of structural analogues, namely, cholesterol and prednisolone, was demonstrated. Additionally, the possibility of using the developed monoliths for cholesterol solid-phase extraction from simulated biological solution was shown. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The instability characteristics of lean premixed hydrogen and syngas flames stabilized on meso-scale bluff-body

KAUST Repository

Kim, Yu Jeong

2017-01-05

Bluff-body flame stabilization has been used as one of main flame stabilization schemes to improve combustion stability in both large and small scale premixed combustion systems. The detailed investigation of instability characteristics is needed to understand flame stability mechanism. Direct numerical simulations are conducted to investigate flame dynamics on the instability of lean premixed hydrogen/air and syngas/air flames stabilized on a meso-scale bluff-body. A two-dimensional channel of 10 mm height and 10 mm length with a square bluff-body stabilizer of 0.5 mm is considered. The height of domain is chosen as an unconfined condition to minimize the effect of the blockage ratio. Flame/flow dynamics are observed by increasing the mean inflow velocity from a steady stable to unsteady asymmetrical instability, followed by blowoff. Detailed observations between hydrogen and syngas flames with a time scale analysis are presented.

Turbulent Premixed Flame Propagation in Microgravity

Science.gov (United States)

Menon, S.; Disseau, M.; Chakravarthy, V. K.; Jagoda, J.

1997-01-01

A facility in which turbulent Couette flow could be generated in a microgravity environment was designed and built. To fit into the NASA Lewis drop tower the device had to be very compact. This means that edge effects and flow re-circulation were expected to affect the flow. The flow was thoroughly investigated using LDV and was found to be largely two dimensional away from the edges with constant turbulence intensities in the core. Slight flow asymmetries are introduced by the non symmetric re-circulation of the fluid outside the test region. Belt flutter problems were remedied by adding a pair of guide plates to the belt. In general, the flow field was found to be quite similar to previously investigated Couette flows. However, turbulence levels and associated shear stresses were higher. This is probably due to the confined re-circulation zone reintroducing turbulence into the test section. An estimate of the length scales in the flow showed that the measurements were able to resolve nearly all the length scales of interest. Using a new LES method for subgrid combustion it has been demonstrated that the new procedure is computational feasible even on workstation type environment. It is found that this model is capable of capturing the propagation of the premixed names by resolving the flame in the LES grid within 2-3 grid points. In contrast, conventional LES results in numerical smearing of the flame and completely inaccurate estimate of the turbulent propagation speed. Preliminary study suggests that there is observable effect of buoyancy in the 1g environment suggesting the need for microgravity experiments of the upcoming experimental combustion studies. With the cold flow properties characterized, an identical hot flow facility is under construction. It is assumed that the turbulence properties ahead of the flame in this new device will closely match the results obtained here. This is required since the hot facility will not enable LDV measurements. The

A model of propagating calcium-induced calcium release mediated by calcium diffusion

NARCIS (Netherlands)

Backx, P. H.; de Tombe, P. P.; van Deen, J. H.; Mulder, B. J.; ter Keurs, H. E.

1989-01-01

The effect of sudden local fluctuations of the free sarcoplasmic [Ca++]i in cardiac cells on calcium release and calcium uptake by the sarcoplasmic reticulum (SR) was calculated with the aid of a simplified model of SR calcium handling. The model was used to evaluate whether propagation of calcium

Experimental study on a comparison of typical premixed combustible gas-air flame propagation in a horizontal rectangular closed duct.

Science.gov (United States)

Jin, Kaiqiang; Duan, Qiangling; Liew, K M; Peng, Zhongjing; Gong, Liang; Sun, Jinhua

2017-04-05

Research surrounding premixed flame propagation in ducts has a history of more than one hundred years. Most previous studies focus on the tulip flame formation and flame acceleration in pure gas fuel-air flame. However, the premixed natural gas-air flame may show different behaviors and pressure dynamics due to its unique composition. Natural gas, methane and acetylene are chosen here to conduct a comparison study on different flame behaviors and pressure dynamics, and to explore the influence of different compositions on premixed flame dynamics. The characteristics of flame front and pressure dynamics are recorded using high-speed schlieren photography and a pressure transducer, respectively. The results indicate that the compositions of the gas mixture greatly influence flame behaviors and pressure. Acetylene has the fastest flame tip speed and the highest pressure, while natural gas has a faster flame tip speed and higher pressure than methane. The Bychkov theory for predicting the flame skirt motion is verified, and the results indicate that the experimental data coincide well with theory in the case of equivalence ratios close to 1.00. Moreover, the Bychkov theory is able to predict flame skirt motion for acetylene, even outside of the best suitable expansion ratio range of 6

Experimental and Numerical Study of Jet Controlled Compression Ignition on Combustion Phasing Control in Diesel Premixed Compression Ignition Systems

Directory of Open Access Journals (Sweden)

Qiang Zhang

2014-07-01

Full Text Available In order to directly control the premixed combustion phasing, a Jet Controlled Compression Ignition (JCCI for diesel premixed compression ignition systems is investigated. Experiments were conducted on a single cylinder natural aspirated diesel engine without EGR at 3000 rpm. Numerical models were validated by load sweep experiments at fixed spark timing. Detailed combustion characteristics were analyzed based on the BMEP of 2.18 bar. The simulation results showed that the high temperature jets of reacting active radical species issued from the ignition chamber played an important role on the onset of combustion in the JCCI system. The combustion of diesel pre-mixtures was initiated rapidly by the combustion products issued from the ignition chamber. Moreover, the flame propagation was not obvious, similar to that in Pre-mixed Charge Compression Ignition (PCCI. Consequently, spark timing sweep experiments were conducted. The results showed a good linear relationship between spark timing in the ignition chamber and CA10 and CA50, which indicated the ability for direct combustion phasing control in diesel PCCI. The NOx and soot emissions gradually changed with the decrease of spark advance angle. The maximum reduction of NOx and soot were both over 90%, and HC and CO emissions were increased.

A LES-CMC formulation for premixed flames including differential diffusion

Science.gov (United States)

Farrace, Daniele; Chung, Kyoungseoun; Bolla, Michele; Wright, Yuri M.; Boulouchos, Konstantinos; Mastorakos, Epaminondas

2018-05-01

A finite volume large eddy simulation-conditional moment closure (LES-CMC) numerical framework for premixed combustion developed in a previous studyhas been extended to account for differential diffusion. The non-unity Lewis number CMC transport equation has an additional convective term in sample space proportional to the conditional diffusion of the progress variable, that in turn accounts for diffusion normal to the flame front and curvature-induced effects. Planar laminar simulations are first performed using a spatially homogeneous non-unity Lewis number CMC formulation and validated against physical-space fully resolved reference solutions. The same CMC formulation is subsequently used to numerically investigate the effects of curvature for laminar flames having different effective Lewis numbers: a lean methane-air flame with Leeff = 0.99 and a lean hydrogen-air flame with Leeff = 0.33. Results suggest that curvature does not affect the conditional heat release if the effective Lewis number tends to unity, so that curvature-induced transport may be neglected. Finally, the effect of turbulence on the flame structure is qualitatively analysed using LES-CMC simulations with and without differential diffusion for a turbulent premixed bluff body methane-air flame exhibiting local extinction behaviour. Overall, both the unity and the non-unity computations predict the characteristic M-shaped flame observed experimentally, although some minor differences are identified. The findings suggest that for the high Karlovitz number (from 1 to 10) flame considered, turbulent mixing within the flame weakens the differential transport contribution by reducing the conditional scalar dissipation rate and accordingly the conditional diffusion of the progress variable.

Enrichment and Purification of Syringin, Eleutheroside E and Isofraxidin from Acanthopanax senticosus by Macroporous Resin

Directory of Open Access Journals (Sweden)

Yuangang Zu

2012-07-01

Full Text Available In order to screen a suitable resin for the preparative simultaneous separation and purification of syringin, eleutheroside E and isofraxidin from Acanthopanax senticosus, the adsorption and desorption properties of 17 widely used commercial macroporous resins were evaluated. According to our results, HPD100C, which adsorbs by the molecular tiers model, was the best macroporous resin, offering higher adsorption and desorption capacities and higher adsorption speed for syringin, eleutheroside E and isofraxidin than other resins. Dynamic adsorption and desorption tests were carried out to optimize the process parameters. The optimal conditions were as follows: for adsorption, processing volume: 24 BV, flow rate: 2 BV/h; for desorption, ethanol–water solution: 60:40 (v/v, eluent volume: 4 BV, flow rate: 3 BV/h. Under the above conditions, the contents of syringin, eleutheroside E and isofraxidin increased 174-fold, 20-fold and 5-fold and their recoveries were 80.93%, 93.97% and 93.79%, respectively.

Direct Numerical Simulations of NOx formation in spatially developing turbulent premixed Bunsen flames with mixture inhomogeneity

KAUST Repository

Luca, Stefano; Attili, Antonio; Bisetti, Fabrizio

2017-01-01

have a partially premixed inlet that mimic a common injection strategy in stationary gas turbines. The jet consist of a methane/air mixture with global equivalence ratio ɸ = 0.7 and temperature of 800 K. The simulations are performed at 4 atm. The inlet

PREMIX, documentation of the results of experiments PM01 to PM06

International Nuclear Information System (INIS)

Huber, F.; Kaiser, A.; Steinbrueck, M.; Will, H.

1996-03-01

A series of so-called PREMIX experiments is being performed in which the mixing behaviour is investigated of a hot alumina melt which is discharged into water. The tests are part of a multi-lateral programme carried out in support of the licencing procedure of LWR. The programme, which aims at the safety of the reactor, includes relevant experiments and the numerical simulation by computer codes. The parameters of the 1st experimental series were: Melt masses of 10 and 20 kg, released through nozzles of 40 and 56 mm in diameter, resp., the type of melt discharge, a slender size of the water pool, and the degree of sub-cooling. The phenomena of mixing can well be described by means of both high speed and video films and a variety of measurements. The results show that it is the period up to about 0.4 to 0.5 s in which the decisive processes of premixing occur. The very first material release generally occurs as single droplets. In 3 of the first 6 tests, a more or less compact stream of melt formed soon after that. In the other tests, the spray-type discharge of melt continued. A funnel-shaped interaction region is formed in the water pool. Its radial and axial growth rates are determined by the discharge mode and mass flux of the melt. A vapour explosion did not occur. The test results are well suited to be used in the verification and validation of computer models. The results of the measurements and the post-test examination of the debris give an indication of a possible inherent limitation of the masses involved in premixing. Consequently, the probability of a steam explosion to occur would also be limited. This limitation is anticipated to occur in 2 stages: 1. The bulk portion of the water is displaced far enough by the growing interaction region and is prevented from taking part immediately in the thermal interaction. Vapour is the continuous phase in the interaction region. 2. In case of a compact melt stream, the major part of the melt quickly flows down

Calcium Phosphate as a Key Material for Socially Responsible Tissue Engineering

Directory of Open Access Journals (Sweden)

Vuk Uskoković

2016-06-01

; (d intracellularly deliver bioactive compounds; (e accommodate an array of functional ions; (f be processed into macroporous constructs for tissue engineering; and (g be naturally antimicrobial. All in all, we see in calcium phosphates the presence of a protean nature whose therapeutic potentials have been barely tapped into.

High energy density supercapacitors using macroporous kitchen sponges

KAUST Repository

Chen, Wei

2012-01-01

Macroporous, low-cost and recyclable kitchen sponges are explored as effective electrode platforms for supercapacitor devices. A simple and scalable process has been developed to fabricate MnO 2-carbon nanotube (CNT)-sponge supercapacitor electrodes using ordinary kitchen sponges. Two organic electrolytes (1 M of tetraethylammonium tetrafluoroborate (Et 4NBF 4) in propylene carbonate (PC), 1 M of LiClO 4 in PC) are utilized with the sponge-based electrodes to improve the energy density of the symmetrical supercapacitors. Compared to aqueous electrolyte (1 M of Na 2SO 4 in H 2O), the energy density of supercapacitors tripled in Et 4NBF 4 electrolyte, and further increased by six times in LiClO 4 electrolyte. The long-term cycling performance in different electrolytes was examined and the morphology changes of the electrode materials were also studied. The good electrochemical performance in both aqueous and organic electrolytes indicates that the MnO 2-CNT-sponge is a promising low-cost electrode for energy storage systems. © 2012 The Royal Society of Chemistry.

Mammary-Specific Ablation of the Calcium-Sensing Receptor During Lactation Alters Maternal Calcium Metabolism, Milk Calcium Transport, and Neonatal Calcium Accrual

Science.gov (United States)

Mamillapalli, Ramanaiah; VanHouten, Joshua; Dann, Pamela; Bikle, Daniel; Chang, Wenhan; Brown, Edward

2013-01-01

To meet the demands for milk calcium, the lactating mother adjusts systemic calcium and bone metabolism by increasing dietary calcium intake, increasing bone resorption, and reducing renal calcium excretion. As part of this adaptation, the lactating mammary gland secretes PTHrP into the maternal circulation to increase bone turnover and mobilize skeletal calcium stores. Previous data have suggested that, during lactation, the breast relies on the calcium-sensing receptor (CaSR) to coordinate PTHrP secretion and milk calcium transport with calcium availability. To test this idea genetically, we bred BLG-Cre mice with CaSR-floxed mice to ablate the CaSR specifically from mammary epithelial cells only at the onset of lactation (CaSR-cKO mice). Loss of the CaSR in the lactating mammary gland did not disrupt alveolar differentiation or milk production. However, it did increase the secretion of PTHrP into milk and decreased the transport of calcium from the circulation into milk. CaSR-cKO mice did not show accelerated bone resorption, but they did have a decrease in bone formation. Loss of the mammary gland CaSR resulted in hypercalcemia, decreased PTH secretion, and increased renal calcium excretion in lactating mothers. Finally, loss of the mammary gland CaSR resulted in decreased calcium accrual by suckling neonates, likely due to the combination of increased milk PTHrP and decreased milk calcium. These results demonstrate that the mammary gland CaSR coordinates maternal bone and calcium metabolism, calcium transport into milk, and neonatal calcium accrual during lactation. PMID:23782944

Aerodynamic features of flames in premixed gases

Science.gov (United States)

Oppenheim, A. K.

1984-01-01

A variety of experimentally established flame phenomena in premixed gases are interpreted by relating them to basic aerodynamic properties of the flow field. On this basis the essential mechanism of some well known characteristic features of flames stabilized in the wake of a bluff-body or propagating in ducts are revealed. Elementary components of the flame propagation process are shown to be: rotary motion, self-advancement, and expansion. Their consequences are analyzed under a most strict set of idealizations that permit the flow field to be treated as potential in character, while the flame is modelled as a Stefan-like interface capable of exerting a feed-back effect upon the flow field. The results provide an insight into the fundamental fluid-mechanical reasons for the experimentally observed distortions of the flame front, rationalizing in particular its ability to sustain relatively high flow velocities at amazingly low normal burning speeds.

Studies on the absorption of uranium and plutonium on macroporous anion-exchange resins from mixed solvent media

International Nuclear Information System (INIS)

Chetty, K.V.; Mapara, P.M.; Godbole, A.G.; Swarup, Rajendra

1995-01-01

The ion-exchange studies on uranium and plutonium using macroporous anion-exchange resins from an aqueous-organic solvent mixed media were carried out to develop a method for their separation. Out of the several water miscible organic solvents tried, methanol and acetone were found to be best suited. Distribution data for U(VI) and Pu(IV) for three macroporous resins Tulsion A-27(MP) (strong base), Amberlyst A-26(MP) (strong base) and Amberlite XE-270(MP) (weak base) as a function of (i) nitric acid concentration (ii) organic solvent concentration were obtained. Based on the data separation factors for Pu/U were calculated. Column experiments using Tulsion A-27(MP) from a synthetic feed (HNO 3 - methanol and HNO 3 - acetone) containing Pu and U in different ratios were carried out. Plutonium was recovered from the bulk of the actual solution generated during the dissolution of plutonium bearing fuels. The method has the advantage of loading plutonium from as low as 1M nitric acid in presence of methanol or acetone and could be used satisfactorily for its recovery from solutions containing plutonium and uranium. (author). 11 refs., 4 figs., 16 tabs

Premixed Flames Under Microgravity and Normal Gravity Conditions

Science.gov (United States)

Krikunova, Anastasia I.; Son, Eduard E.

2018-03-01

Premixed conical CH4-air flames were studied experimentally and numerically under normal straight, reversed gravity conditions and microgravity. Low-gravity experiments were performed in Drop tower. Classical Bunsen-type burner was used to find out features of gravity influence on the combustion processes. Mixture equivalence ratio was varied from 0.8 to 1.3. Wide range of flow velocity allows to study both laminar and weakly turbulized flames. High-speed flame chemoluminescence video-recording was used as diagnostic. The investigations were performed at atmospheric pressure. As results normalized flame height, laminar flame speed were measured, also features of flame instabilities were shown. Low- and high-frequency flame-instabilities (oscillations) have a various nature as velocity fluctuations, preferential diffusion instability, hydrodynamic and Rayleigh-Taylor ones etc., that was explored and demonstrated.

Numerical simulation of nitrogen oxide formation in lean premixed turbulent H2/O2/N2 flames

DEFF Research Database (Denmark)

Day, Marc S.; Bell, John B.; Gao, Xinfeng

2011-01-01

Lean premixed hydrogen flames are thermodiffusively unstable and burn in cellular structures. Within these cellular structures the flame is locally enriched by preferential diffusion of hydrogen, leading to local hotspots that burn more intensely than an idealized flat steady flame at comparable ...

Experimental study on the potential of higher octane number fuels for low load partially premixed combustion

NARCIS (Netherlands)

Wang, S.; van der Waart, K.; Somers, B.; de Goey, P.

2017-01-01

The optimal fuel for partially premixed combustion (PPC) is considered to be a gasoline boiling range fuel with an octane number around 70. Higher octane number fuels are considered problematic with low load and idle conditions. In previous studies mostly the intake air temperature did not exceed 30

Microjet Injection Strategies for Mitigating Dynamics in a Lean Premixed Swirl-Stabilized Combustor

KAUST Repository

LaBry, Zachary; Shanbhogue, Santosh; Ghoniem, Ahmed

2011-01-01

Combustion dynamics remain a challenge in the development of low-emission, air-breathing combustors for power generation and aircraft propulsion. In this paper, we presenta parametric study on the use of microjet injectors for suppressing or mitigating the combustion dynamics that energize the thermoacoustic instability in a swirl-stabilized, premixed combustor. Microjet injectors consist of small inlet ports intended to inject flow with high momentum at relatively low mass flow rates into the flame-anchoring region. The microjets were configured to inject flow either axially, into the outer recirculation zone, or radially into the inner recirculation zone. Additionally, different injectors were tested with different relative senses of swirl (signs of angular momentum)with respect to the main flow: co-swirling, not swirling, or counter-swirling. We observed that injecting air or premixed fuel/air into the inner recirculation zone via counter-swirling radial microjets, we were able to reduce the overall sound pressure level in the combustor by over 20 dB in the lean end of the operating range. Other injector configurations were not observed to positively influence the combust or stability. Detailed PIV measurements are used to examine possible mechanisms of how the microjets impact the combustion dynamics, and the technology implications of our experiments are discussed.

Microjet Injection Strategies for Mitigating Dynamics in a Lean Premixed Swirl-Stabilized Combustor

KAUST Repository

LaBry, Zachary

2011-01-04

Combustion dynamics remain a challenge in the development of low-emission, air-breathing combustors for power generation and aircraft propulsion. In this paper, we presenta parametric study on the use of microjet injectors for suppressing or mitigating the combustion dynamics that energize the thermoacoustic instability in a swirl-stabilized, premixed combustor. Microjet injectors consist of small inlet ports intended to inject flow with high momentum at relatively low mass flow rates into the flame-anchoring region. The microjets were configured to inject flow either axially, into the outer recirculation zone, or radially into the inner recirculation zone. Additionally, different injectors were tested with different relative senses of swirl (signs of angular momentum)with respect to the main flow: co-swirling, not swirling, or counter-swirling. We observed that injecting air or premixed fuel/air into the inner recirculation zone via counter-swirling radial microjets, we were able to reduce the overall sound pressure level in the combustor by over 20 dB in the lean end of the operating range. Other injector configurations were not observed to positively influence the combust or stability. Detailed PIV measurements are used to examine possible mechanisms of how the microjets impact the combustion dynamics, and the technology implications of our experiments are discussed.

Insight into the cryopolymerization to form a poly(N-isopropylacrylamide)/clay macroporous gel: structure and phase evolution

Czech Academy of Sciences Publication Activity Database

Strachota, Beata; Matějka, Libor; Sikora, Antonín; Spěváček, Jiří; Konefal, Rafal; Zhigunov, Alexander; Šlouf, Miroslav

2017-01-01

Roč. 13, č. 6 (2017), s. 1244-1256 ISSN 1744-683X R&D Projects: GA ČR(CZ) GA13-23392S; GA MŠk(CZ) LD14010 Grant - others:European Commission(XE) COST Action MP1202 HINT Institutional support: RVO:61389013 Keywords : macroporous gels * nanocomposite cryogels * polymer-clay hydrogel Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 3.889, year: 2016

Meso-Molding Three-Dimensional Macroporous Perovskites: A New Approach to Generate High-Performance Nanohybrid Catalysts

DEFF Research Database (Denmark)

Arandiyan, Hamidreza; Scott, Jason; Wang, Yuan

2016-01-01

Newly designed 3D highly ordered macro/mesoporous multifunctional La1-xCexCoO3 nanohybrid frameworks with a 2D hexagonal mesostructure were fabricated via facile meso-molding in a three-dimensionally macroporous perovskite (MTMP) route. The nanohybrid framework exhibited excellent catalytic...... activity for methane combustion, which derived from the MTMP providing a larger surface area and pore volume, uniform pore sizes, higher accessible surface oxygen concentration, better low-temperature reducibility, and a unique nanovoid 3D structure....

[Calcium suppletion for patients who use gastric acid inhibitors: calcium citrate or calcium carbonate?].

NARCIS (Netherlands)

Jonge, H.J. de; Gans, R.O.; Huls, G.A.

2012-01-01

Various calcium supplements are available for patients who have an indication for calcium suppletion. American guidelines and UpToDate recommend prescribing calcium citrate to patients who use antacids The rationale for this advice is that water-insoluble calcium carbonate needs acid for adequate

Impact of fuel composition on the recirculation zone structure and its role in lean premixed flame anchoring

KAUST Repository

Hong, Seunghyuck; Shanbhogue, Santosh J.; Ghoniem, Ahmed F.

2015-01-01

) and chemiluminescence measurements for C3H8/H2/air lean premixed flames stabilized in a backward-facing step combustor. Results show an intricate coupling between the flame anchoring and the RZ structure and length. For a fixed fuel composition, at relatively low

Purification of bioactive phenolics from Phanerochaete chysosporium biomass extract on selected macroporous resins

Science.gov (United States)

Idris, Z. M.; Dzahir, M. I. H. M.; Jamal, P.; Barkat, A. A.; Xian, R. L. W.

2017-06-01

In this study, two different types of macroporous resins known as XAD-7HP and HP-20 were evaluated for the adsorption and desorption properties against bioactive phenolics extracted from Phanerochaete chrysosporium. From the previous static sorption studies, it was found that the adsorption capacity for both resins had has no significant difference. Then, the kinetic adsorption data were analyzed with both pseudo-first-order and pseudo-second-order equations and the later performed better. The adsorption isotherm data were fitted well by both Langmuir and Freundlich models. Meanwhile in desorption study, HP-20 and XAD-7HP gave 90.52% and 88.28% recoveries, respectively. Considering the desorption results of the macroporous resins, HP-20 and XAD-7HP were packed in chromatography column to further purify the phenolics. For dynamic adsorption, breakthrough capacity of HP-20 (0.522) was found to be higher than XAD-7HP (0.131). Different ethanol concentrations (30% to 50% (v/v)) were investigated at fixed flowrate (1 ml/min) on phenolics recovery from both types of resins. The highest recovery of bioactive phenolics was 94.3% using XAD-7HP resins at 50% (v/v) of ethanol. Only 77.1% of bioactive phenolics were recovered using HP-20 resin at the same experimental conditions. The purified extract subsequently was analyzed using HPLC. The results showed that three phenolics (gallic acid 3,4-dihydroxybenzoic acid and 4-hydroxybenzoic acid) were identified with higher concentrations as compared to non-purified extract. Finally, the purified extract was tested for scavenging activity against DPPH, and it showed that the activity increased significantly to 90.80% from 59.94% in non-purified extract.

Nutrient composition of premixed and packaged complementary foods for sale in low- and middle-income countries: Lack of standards threatens infant growth.

Science.gov (United States)

Masters, William A; Nene, Marc D; Bell, Winnie

2017-10-01

Premixed flours for infant porridge are increasingly produced and sold in developing countries to complement continued breastfeeding. Such complementary food (CF) products have known efficacy against malnutrition in children from 6 to 24 months of age, but ingredient ratios and production processes may vary. This study provides the first systematic measurement of their actual nutrient composition. We purchased samples of 108 premixed CF products in 22 low- and middle-income countries, and commissioned blind laboratory measurement of each product's macronutrients and micronutrients. We compared measured contents to nutrient claims on their packaging and to CF standards from the Codex Alimentarius, the Super Cereal Plus product used in nutrition assistance programs, and the Lutter and Dewey (2003) recommendations, as well as our own modeled nutrient requirements for a healthy breastfed child. Actual densities are significantly different from nutrient claims for protein (p = .013) and fat (p = .000). Only 15% of samples met two of the three benchmarks for fat, 32% met the most stringent protein standard, while only 22% met them for iron, and 21% for zinc. The median healthy child consuming breast milk plus enough of these solid foods to meet energy needs would experience deficits of zinc at 6 months, iron at 6 and 9 months, and dietary fat from 12 months of age. In summary, premixed CF products can provide adequate nutrient density but usually do not, revealing the need and opportunity for independent monitoring and quality assurance to help grain millers making premixed foods maintain uniform ingredient ratios and production practices. © 2016 John Wiley & Sons Ltd.

Three-dimensional simulations of cellular non-premixed jet flames

Energy Technology Data Exchange (ETDEWEB)

Valaer, A.L.; Frouzakis, C.E.; Boulouchos, K. [Aerothermochemistry and Combustion System Laboratory, Swiss Federal Institute of Technology, CH-8092 Zurich (Switzerland); Papas, P. [Division of Engineering, Colorado School of Mines, Golden, CO 80401 (United States); Tomboulides, A.G. [Department of Engineering and Management of Energy Resources, University of Western Macedonia, 50100 Kozani (Greece)

2010-04-15

The formation, dynamics and structure of cellular flames in circular non-premixed jets are examined with three-dimensional numerical simulations incorporating detailed descriptions of chemistry and transport. Similar to past experiments reported in the literature, CO{sub 2}-diluted hydrogen in diluted or pure oxygen co-flowing streams in the proximity of the extinction limit are considered. As in the experiments, several preferred cellular states are found to co-exist with the particular state realized depending on initial conditions as well as on the jet characteristics. The simulations provide additionally the temporal transitions to different stationary or rotating cellular flames, their detailed structure, and the dependence of the scaling of the realized number of cells with the vorticity thickness. (author)

Exchange of Th, U and Pu on macroporous ion exchange resins

International Nuclear Information System (INIS)

Nadkarni, M.N.; Mayankutty, P.C.; Pillai, N.S.; Shinde, S.S.

1977-01-01

Absorption of Th, U and Pu on macroporous ion exchangers, Amberlyst 15 (cationic) and Amberlyst A-26 (anionic) were studied in nitric acid solutions and the results were found comparable with those on their microreticular counter parts, Dowex 50x8 and Dowex IX4. With a view to evalute the efficiency of Amberlyst A-26 for the final purification of plutonium from the purex process stream, detailed studies conducted to determine the breakthrough capacity of Pu(IV) from 7.2 M nitric acid, elution by 0.5 M nitric acid and the decontamination factors for uranium and zirconium-95. Because of its faster kinetics, Amberlyst A-26 exhibited a much more efficient elution of Pu(IV) by 0.5 M nitric acid than Dowex IX4. (author)

The challenge of modeling fuel–coolant interaction: Part I – Premixing

Energy Technology Data Exchange (ETDEWEB)

Meignen, Renaud, E-mail: renaud.meignen@irsn.fr [Institut de Radioprotection et de Sûreté Nucléaire, IRSN/PSN-RES/SAG, BP 3, 13115 Saint-Paul-Lez-Durance Cedex (France); Picchi, Stephane; Lamome, Julien [Communication and Systèmes, 22 avenue Galilée, 92350 Le Plessis Robinson (France); Raverdy, Bruno [IRSN/PSN-RES/SAG, BP3, 92362 Fontenay aux Roses Cedex (France); Escobar, Sebastian Castrillon [Institut de Radioprotection et de Sûreté Nucléaire, IRSN/PSN-RES/SAG, BP 3, 13115 Saint-Paul-Lez-Durance Cedex (France); Nicaise, Gregory [IRSN/PSN-RES/SAG, BP3, 92362 Fontenay aux Roses Cedex (France)

2014-12-15

Highlights: • We present the status modeling of the fuel–coolant interaction premixing stage in the computer code MC3D. • We also propose a general state of the art, highlighting recent improvements in understanding and modeling, remaining difficulties, controversies and needs. • We highlight the need for improving the understanding of the melt fragmentation and oxidation. • The verification basis is presented. - Abstract: Fuel–coolant interaction is a complex mixing process that can occur during the course of a severe accident in a nuclear power plant involving core melting and relocation. Under certain circumstances, a steam explosion might develop during the mixing of the melt and the water and induce a loss of integrity of the containment. Even in the absence of an explosion, studying the mixing phenomenon is also of high interest due to its strong impact on the progression of the accident (debris bed formation, hydrogen production). This article is the first of two aiming at presenting both a status of research and understanding of fuel–coolant interaction and the main characteristics of the model developed in the 3-dimensional computer code MC3D. It is devoted to the premixing phase whereas the second is related to the explosion phase. A special attention is given to major difficulties, uncertainties and needs for further improvements in knowledge and modeling. We discuss more particularly the major phenomena that are melt fragmentation and film boiling heat transfer and the challenges related to modeling melt solidification and oxidation. Some highlights related to the code verification are finally given.

Nanoporous Calcium Silicate and PLGA Bio composite for Bone Repair

International Nuclear Information System (INIS)

Su, J.; Wang, Z.; Wu, Y.; Cao, L.; Ma, Y.; Yu, B.; Li, M.; Yan, Y.

2010-01-01

Nanoporous calcium silicate (n-CS) with high surface area was synthesized using the mixed surfactants of EO20PO70EO20 (polyethylene oxide)20(polypropylene oxide)70(polyethylene oxide)20, P123) and hexadecyltrimethyl ammonium bromide (CTAB) as templates, and its composite with poly(lactic acid-co-glycolic acid) (PLGA) were fabricated. The results showed that the n-CS/PLGA composite (n-CPC) with 20 wt% n-CS could induce a dense and continuous layer of apatite on its surface after soaking in simulated body fluid (SBF) for 1 week, suggesting the excellent in vitro bioactivity. The n-CPC could promote cell attachment on its surfaces. In addition, the proliferation ratio of MG63 cells on n-CPC was significantly higher than PLGA; the results demonstrated that n-CPC had excellent cytocompatibility. We prepared n-CPC scaffolds that contained open and interconnected macroporous ranging in size from 200 to 500 μ m. The n-CPC scaffolds were implanted in femur bone defect of rabbits, and the in vivo biocompatibility and osteogenicity of the scaffolds were investigated. The results indicated that n-CPC scaffolds exhibited good biocompatibility, degradability, and osteogenesis in vivo. Collectively, these results suggested that the incorporation of n-CS in PLGA produced biocomposites with improved bioactivity and biocompatibility.

21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium pantothenate, calcium chloride double salt... FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.330 Calcium pantothenate, calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may...

Numerical and experimental investigation of NO{sub x} formation in lean premixed combustion of methane

Energy Technology Data Exchange (ETDEWEB)

Bengtsson, K; Benz, P; Marti, T; Schaeren, R; Schlegel, A [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-06-01

A high pressure jet-stirred reactor has been built and employed to investigate NO{sub x} formation in lean premixed combustion of methane/air. Experimental results are compared with numerical predictions using the model of a perfectly stirred reactor and elementary reaction mechanisms. Four reaction mechanisms are considered with respect to NO{sub x} formation. (author) 3 figs., 6 refs.

The influence of plutonium concentration and solution flow rate on the effective capacity of macroporous anion exchange resin

International Nuclear Information System (INIS)

Marsh, S.F.; Gallegos, T.D.

1987-07-01

The principal aqueous process used to recover and purify plutonium at the Los Alamos Plutonium Facility is anion exchange in nitric acid. Previous studies with gel-type anion exchange resin have shown an inverse relationship between plutonium concentration in the feed solution and the optimum flow rate for this process. Because gel-type resin has been replaced with macroporous resin at Los Alamos, the relationship between plutonium concentration and solution flow rate was reexamined with the selected Lewatit MP-500-FK resin using solutions of plutonium in nitric acid and in nitric acid with high levels of added nitrate salts. Our results with this resin differ significantly from previous data obtained with gel-type resin. Flow-rate variation from 10 to 80 liters per hour had essentially no effect on the measured quantities of plutonium sorbed by the macroporous resin. However, the effect of plutonium concentration in the feed solutions was pronounced, as feed solutions that contained the highest concentrations of plutonium also produced the highest resin loadings. The most notable effect of high concentrations of dissolved nitrate salts in these solutions was an increased resin capacity for plutonium at low flow rates. 16 refs., 7 figs., 2 tabs

Computational Enhancements for Direct Numerical Simulations of Statistically Stationary Turbulent Premixed Flames

KAUST Repository

Mukhadiyev, Nurzhan

2017-05-01

Combustion at extreme conditions, such as a turbulent flame at high Karlovitz and Reynolds numbers, is still a vast and an uncertain field for researchers. Direct numerical simulation of a turbulent flame is a superior tool to unravel detailed information that is not accessible to most sophisticated state-of-the-art experiments. However, the computational cost of such simulations remains a challenge even for modern supercomputers, as the physical size, the level of turbulence intensity, and chemical complexities of the problems continue to increase. As a result, there is a strong demand for computational cost reduction methods as well as in acceleration of existing methods. The main scope of this work was the development of computational and numerical tools for high-fidelity direct numerical simulations of premixed planar flames interacting with turbulence. The first part of this work was KAUST Adaptive Reacting Flow Solver (KARFS) development. KARFS is a high order compressible reacting flow solver using detailed chemical kinetics mechanism; it is capable to run on various types of heterogeneous computational architectures. In this work, it was shown that KARFS is capable of running efficiently on both CPU and GPU. The second part of this work was numerical tools for direct numerical simulations of planar premixed flames: such as linear turbulence forcing and dynamic inlet control. DNS of premixed turbulent flames conducted previously injected velocity fluctuations at an inlet. Turbulence injected at the inlet decayed significantly while reaching the flame, which created a necessity to inject higher than needed fluctuations. A solution for this issue was to maintain turbulence strength on the way to the flame using turbulence forcing. Therefore, a linear turbulence forcing was implemented into KARFS to enhance turbulence intensity. Linear turbulence forcing developed previously by other groups was corrected with net added momentum removal mechanism to prevent mean

Hydrogen-enriched non-premixed jet flames : analysis of the flame surface, flame normal, flame index and Wobbe index

NARCIS (Netherlands)

Ranga Dinesh, K.K.J.; Jiang, X.; Oijen, van J.A.

2014-01-01

A non-premixed impinging jet flame is studied using three-dimensional direct numerical simulation with detailed chemical kinetics in order to investigate the influence of fuel variability on flame surface, flame normal, flame index and Wobbe index for hydrogen-enriched combustion. Analyses indicate

The flow field structure of highly stabilized partially premixed flames in a concentric flow conical nozzle burner with coflow

KAUST Repository

Elbaz, Ayman M.; Zayed, M.F.; Samy, M.; Roberts, William L.; Mansour, Mohy S.

2015-01-01

The stability limits, the stabilization mechanism, and the flow field structure of highly stabilized partially premixed methane flames in a concentric flow conical nozzle burner with air co-flow have been investigated and presented in this work

AN ASSESSMENT OF THE USE OF VARYING LEVELS OF MORINGA OLEIFERA LEAF MEAL AS A SUBSTITUTE FOR VITAMIN + MINERAL PREMIX IN FINISHER BROILER DIET.

Directory of Open Access Journals (Sweden)

2016-11-01

Full Text Available One hundred and twenty (120 4 weeks old unsexed broiler chicken were used in a twenty eight days feeding trial to evaluate the use of Moringa oleifera leaf meal as a replacement for vitamin + mineral premix in finisher broilers. The birds were assigned to four treatment group with three replicates per group .The treatment groups includes T1, T2, T3, and T4 representing 0, 2.5, 5.0 and 7.5% inclusion levels of Moringa oleifera leaf meal as a replacement for vitamin + mineral premix. The result of the study showed that average final weight gain, average feed intake and feed conversion ratio differed significantly (P and lt;0.05 in favour of T4 and T3 .The dressing percentage as well as organ (gizzard, liver and heart weights also differed significantly(p and lt;0.05. The study thus indicate that the inclusion of Moringa oleifera leaf meal at 5% and 7.5% can successfully be used to replace vitamin + mineral premix in finisher diet.

Low-cost removal of organic pollutants with nickel nanoparticle loaded ordered macroporous hydrogel as high performance catalyst

Energy Technology Data Exchange (ETDEWEB)

Tang, Mingyi, E-mail: tmyi@tjcu.edu.cn [Department of Applied Chemistry, School of Science, Tianjin University of Commerce, Tianjin 300134 (China); Huang, Guanbo, E-mail: gbhuang2007@hotmail.com [Department of Chemistry, School of Science, Tianjin University, Tianjin 300072 (China); Zhang, Sai [Department of Applied Chemistry, School of Science, Tianjin University of Commerce, Tianjin 300134 (China); Liu, Yue [Department of Chemistry, School of Science, Tianjin University, Tianjin 300072 (China); Li, Xianxian [Department of Applied Chemistry, School of Science, Tianjin University of Commerce, Tianjin 300134 (China); Wang, Xingrui [Department of Chemistry, School of Science, Tianjin University, Tianjin 300072 (China); Pang, Xiaobo [Department of Applied Chemistry, School of Science, Tianjin University of Commerce, Tianjin 300134 (China); Qiu, Haixia, E-mail: qhx@tju.edu.cn [Department of Chemistry, School of Science, Tianjin University, Tianjin 300072 (China)

2014-06-01

A facile route for the in situ preparation of catalytically active Ni nanoparticles (NPs) in ordered macroporous hydrogel (OMH) has been developed. The hydrogel was fabricated based on polystyrene colloid template. The electronegativity of amide and carboxyl groups on the poly(acrylamide-co-acryl acid) chains of the hydrogel caused strong binding of Ni{sup 2+} ions which made them distribute uniformly inside the hydrogel. When immersed in NaBH{sub 4} aqueous solution, the Ni{sup 2+} ions on the hydrogel were reduced to Ni NPs. The resultant Ni NPs loaded OMH showed good catalytic activity for the reduction of a common organic pollutant, 4-nitrophenol, with NaBH{sub 4}. A kinetic study of the catalytic reaction was carried out. The rate constant per unit weight could reach 0.53 s{sup −1} g{sup −1}, which is much better than many common hydrogel loaded nickel catalysts. Moreover, the current catalyst can be easily separated and recovered with stable catalytic activity. - Highlights: • A new poly(acrylamide-co-acryl acid) hydrogel with ordered macropores. • A simple in situ fabrication of nickel nanoparticles under mild conditions. • High-performance heterogeneous catalyst for removal of nitrophenol from water. • Good recyclability of catalyst without any complicated regeneration process.

Low-cost removal of organic pollutants with nickel nanoparticle loaded ordered macroporous hydrogel as high performance catalyst

International Nuclear Information System (INIS)

Tang, Mingyi; Huang, Guanbo; Zhang, Sai; Liu, Yue; Li, Xianxian; Wang, Xingrui; Pang, Xiaobo; Qiu, Haixia

2014-01-01

A facile route for the in situ preparation of catalytically active Ni nanoparticles (NPs) in ordered macroporous hydrogel (OMH) has been developed. The hydrogel was fabricated based on polystyrene colloid template. The electronegativity of amide and carboxyl groups on the poly(acrylamide-co-acryl acid) chains of the hydrogel caused strong binding of Ni 2+ ions which made them distribute uniformly inside the hydrogel. When immersed in NaBH 4 aqueous solution, the Ni 2+ ions on the hydrogel were reduced to Ni NPs. The resultant Ni NPs loaded OMH showed good catalytic activity for the reduction of a common organic pollutant, 4-nitrophenol, with NaBH 4 . A kinetic study of the catalytic reaction was carried out. The rate constant per unit weight could reach 0.53 s −1  g −1 , which is much better than many common hydrogel loaded nickel catalysts. Moreover, the current catalyst can be easily separated and recovered with stable catalytic activity. - Highlights: • A new poly(acrylamide-co-acryl acid) hydrogel with ordered macropores. • A simple in situ fabrication of nickel nanoparticles under mild conditions. • High-performance heterogeneous catalyst for removal of nitrophenol from water. • Good recyclability of catalyst without any complicated regeneration process

Surface plasmon resonance sensor for femtomolar detection of testosterone with water-compatible macroporous molecularly imprinted film.

Science.gov (United States)

Zhang, Qingwen; Jing, Lijing; Zhang, Jinling; Ren, Yamin; Wang, Yang; Wang, Yi; Wei, Tianxin; Liedberg, Bo

2014-10-15

A novel water-compatible macroporous molecularly imprinted film (MIF) has been developed for rapid, sensitive, and label-free detection of small molecule testosterone in urine. The MIF was synthesized by photo copolymerization of monomers (methacrylic acid [MAA] and 2-hydroxyethyl methacrylate [HEMA]), cross-linker (ethylene glycol dimethacrylate, EGDMA), and polystyrene nanoparticles (PS NPs) in combination with template testosterone molecules. The PS NPs and template molecules were subsequently removed to form an MIF with macroporous structures and the specific recognition sites of testosterone. Incubation of artificial urine and human urine on the MIF and the non-imprinted film (NIF), respectively, indicated undetectable nonspecific adsorption. Accordingly, the MIF was applied on a surface plasmon resonance (SPR) sensor for the detection of testosterone in phosphate-buffered saline (PBS) and artificial urine with a limit of detection (LOD) down to 10(-15)g/ml. To the best of our knowledge, the LOD is considered as one of the lowest among the SPR sensors for the detection of small molecules. The control experiments performed with analogue molecules such as progesterone and estradiol demonstrated the good selectivity of this MIF for sensing testosterone. Furthermore, this MIF-based SPR sensor shows high stability and reproducibility over 8months of storage at room temperature, which is more robust than protein-based biosensors. Copyright © 2014 Elsevier Inc. All rights reserved.

Determination of percent calcium carbonate in calcium chromate

International Nuclear Information System (INIS)

Middleton, H.W.

1979-01-01

The precision, accuracy and reliability of the macro-combustion method is superior to the Knorr alkalimetric method, and it is faster. It also significantly reduces the calcium chromate waste accrual problem. The macro-combustion method has been adopted as the official method for determination of percent calcium carbonate in thermal battery grade anhydrous calcium chromate and percent calcium carbonate in quicklime used in the production of calcium chromate. The apparatus and procedure can be used to measure the percent carbonate in inorganic materials other than calcium chromate. With simple modifications in the basic apparatus and procedure, the percent carbon and hydrogen can be measured in many organic material, including polymers and polymeric formulations. 5 figures, 5 tables

Large eddy simulation of n-heptane spray combustion in partially premixed combustion regime with linear eddy model

International Nuclear Information System (INIS)

Xiao, Gang; Jia, Ming; Wang, Tianyou

2016-01-01

Spray combustion of n-heptane in a constant-volume vessel under engine-relevant conditions was investigated using linear eddy model in the framework of large eddy simulation. In this numerical approach, turbulent mixing was traced by an innovative stochastic approach instead of the conventional gradient diffusion model. Chemical reaction rates were calculated with the consideration of the sub-grid scale spatial fluctuations of reactive scalars. Turbulence-chemistry interactions were represented by the separated treatments of the underlying processes including turbulent stirring, chemical reaction, and molecular diffusion. The model was validated against the experimental data of ignition delay times, chemiluminescence images, and soot images from Sandia National Laboratories. Numerical results showed that the ignition process changed from the temperature-controlled regime to the mixing-controlled regime as the initial ambient temperature increased from 800 K to 1000 K. The premixed flame and the diffusion flame coexisted, while the gross heat release rate was found to be dominated by the premixed flame. The temperature fluctuation was mainly observed around the spray jet due to the cooling effect of the fuel vaporization. The fluctuations were more significantly smoothed out by the high-temperature flame than the low-temperature flame. The mean temperature would be overpredicted if the sub-grid temperature fluctuation was neglected. - Highlights: • Turbulent mixing is traced by stochastic method instead of gradient diffusion model. • Sub-grid scale fluctuations of reactive scalars are captured. • Ignition process varies from temperature-controlled to mixing-controlled regime. • Temperature fluctuation can be smoothed out by high-temperature flame. • The heat release rate is dominated by the premixed flame.

Rayleigh/Raman/LIF measurements in a turbulent lean premixed combustor

Energy Technology Data Exchange (ETDEWEB)

Nandula, S.P.; Pitz, R.W. [Vanderbilt Univ., Nashville, TN (United States); Barlow, R.S. [Sandia National Labs., Livermore, CA (United States)] [and others

1995-10-01

Much of the industrial electrical generation capability being added worldwide is gas-turbine engine based and is fueled by natural gas. These gas-turbine engines use lean premixed (LP) combustion to meet the strict NO{sub x} emission standards, while maintaining acceptable levels of CO. In conventional, diffusion flame gas turbine combustors, large amount of NO{sub x} forms in the hot stoichiometric zones via the Zeldovich (thermal) mechanism. Hence, lean premixed combustors are rapidly becoming the norm, since they are specifically designed to avoid these hot stoichiometric zones and the associated thermal NO, However, considerable research and development are still required to reduce the NO{sub x} levels (25-40 ppmvd adjusted to 15% O{sub 2} with the current technology), to the projected goal of under 10 ppmvd by the turn of the century. Achieving this objective would require extensive experiments in LP natural gas (or CH{sub 4}) flames for understanding the combustion phenomena underlying the formation of the exhaust pollutants. Although LP combustion is an effective way to control NO{sub x}, the downside is that it increases the CO emissions. The formation and destruction of the pollutants (NO{sub x} and CO) are strongly affected by the fluid mechanics, the finite-rate chemistry, and their (turbulence-chemistry) interactions. Hence, a thorough understanding of these interactions is vital for controlling and reducing the pollutant emissions. The present research is contributing to this goal by providing a detailed nonintrusive laser based data set with good spatial and temporal resolutions of the pollutants (NO and CO) along with the major species, temperature, and OH. The measurements reported in this work, along with the existing velocity data on a turbulent LP combustor burning CH{sub 4}, would provide insight into the turbulence-chemistry interactions and their effect on pollutant formation.

Flame holding tolerant fuel and air premixer for a gas turbine combustor

Science.gov (United States)

York, William David; Johnson, Thomas Edward; Ziminsky, Willy Steve

2012-11-20

A fuel nozzle with active cooling is provided. It includes an outer peripheral wall, a nozzle center body concentrically disposed within the outer wall in a fuel and air pre-mixture. The fuel and air pre-mixture includes an air inlet, a fuel inlet and a premixing passage defined between the outer wall in the center body. A gas fuel flow passage is provided. A first cooling passage is included within the center body in a second cooling passage is defined between the center body and the outer wall.

Investigation of Turbulent Hydrogen Premixed Flame Topologies at Different Combustion Regimes Using Computational Singular Perturbation

Science.gov (United States)

Tingas, Efstathios-Alexandros; Hernandez Perez, Francisco; Im, Hong

2017-11-01

The investigation of turbulent flames at higher Reynolds and Karlovitz numbers has been gaining research interest, due to the advances in the computational power that has facilitated the use of direct numerical simulations (DNS). One of the additional challenges associated with highly turbulent premixed flames is the difficulties in identifying the turbulent flame topologies as the flame structures become severely corrugated or even disrupted by the small scale turbulent eddies. In these conditions, the conventional methods using a scalar iso-surface may lead to uncertainties in describing the flame front dynamics. In this study, the computational singular perturbation (CSP) is utilized as an automated tool to identify the flame front topologies based on the dynamical time scales and eigenvalues. In particular, the tangential stretch rate (TSR) approach, an extended generalized method to depict the dynamics of chemical and transport processes, is used for the flame front identification. The CSP/TSR approach and tools are used to compare the flame fronts of two turbulent H2/air premixed flames and to identify their similarities/differences, from a dynamical point of view. The results for two different combustion regimes are analyzed and compared.

Effects of diluents on cellular instabilities in outwardly propagating spherical syngas-air premixed flames

Energy Technology Data Exchange (ETDEWEB)

Vu, Tran Manh; Park, Jeong; Kwon, Oh Boong; Bae, Dae Seok [School of Mechanical Engineering, Pukyong National University, San 100, Yongdang-dong, Nam-gu, Busan 608-739 (Korea); Yun, Jin Han; Keel, Sang In [Environment and Energy Research Division, Korea Institute of Machinery and Materials, 171 Jang-dong, Yuseong-gu, Daejeon 305-343 (Korea)

2010-04-15

Experiments were conducted in a constant pressure combustion chamber using schlieren system to investigate the effects of carbon dioxide-nitrogen-helium diluents on cellular instabilities of syngas-air premixed flames at room temperature and elevated pressures. The cellular instabilities for the diluted syngas-air flames were interpreted and evaluated in the viewpoint of the hydrodynamic and diffusional-thermal instabilities. Laminar burning velocities and Markstein lengths were calculated by analyzing high-speed schlieren images at various diluent concentrations and equivalence ratios. The measured unstretched laminar burning velocities were compared with the predicted results computed using the PREMIX code with the kinetic mechanism developed by Sun et al. Also, experimentally measured Peclet numbers were compared with the predicted results for fuel-lean flames. Experimental results showed substantial reduction of the laminar burning velocities and of the Markstein lengths with the diluent additions in the fuel blends. Effective Lewis numbers of helium-diluted syngas-air flames increased but those of carbon dioxide- and nitrogen-diluted syngas-air flames decreased in increase of diluents in the reactant mixtures. With helium diluent, the propensity for cells formation was significantly diminished, whereas the cellular instabilities for carbon dioxide- and nitrogen-diluted syngas-air flames were not suppressed. (author)

Enstrophy transport conditional on local flow topologies in different regimes of premixed turbulent combustion

KAUST Repository

Papapostolou, Vassilios

2017-09-11

Enstrophy is an intrinsic feature of turbulent flows, and its transport properties are essential for the understanding of premixed flame-turbulence interaction. The interrelation between the enstrophy transport and flow topologies, which can be assigned to eight categories based on the three invariants of the velocity-gradient tensor, has been analysed here. The enstrophy transport conditional on flow topologies in turbulent premixed flames has been analysed using a Direct Numerical Simulation database representing the corrugated flamelets (CF), thin reaction zones (TRZ) and broken reaction zones (BRZ) combustion regimes. The flame in the CF regime exhibits considerable flame-generated enstrophy, and the dilatation rate and baroclinic torque contributions to the enstrophy transport act as leading order sink and source terms, respectively. Consequently, flow topologies associated with positive dilatation rate values, contribute significantly to the enstrophy transport in the CF regime. By contrast, enstrophy decreases from the unburned to the burned gas side for the cases representing the TRZ and BRZ regimes, with diminishing influences of dilatation rate and baroclinic torque. The enstrophy transport in the TRZ and BRZ regimes is governed by the vortex-stretching and viscous dissipation contributions, similar to non-reacting flows, and topologies existing for all values of dilatation rate remain significant contributors.

The evaluation/application of Hydrus-2D model for simulating macro-pores flow in loess soil

OpenAIRE

Xuexuan Xu; Shahmir Ali Kalhoro; Wen yuan Chen; Sajjad Raza

2017-01-01

Soil hydraulic properties were mainly governed by soil structures especially when the structures is full of the connected soil macro-pores. Therefore, the good hydrological models need to be well documented for revealing the process of soil water movement affected by soil medium. The Hydrus-2D model with double domain was recommended in simulating water movement in a heterogeneous medium of soil. To evaluate the performance of the double domain Hydrus-2D model in loess soil, the dynamic of so...

Analyzing of in-cylinder flow structures and cyclic variations of partially premixed combustion in a light duty engine

NARCIS (Netherlands)

Tanov, S.; Johansson, B,; Izadi Najafabadi, M.; Wang, H.

2016-01-01

Partially Premixed Combustion (PPC) strategy offers the potential for simultaneously reduction of NOx and soot emissions with high efficiency. This low temperature combustion strategy involves a proper mixing of fuel and air prior to auto-ignition. During ignition delay (ID) the exact amount of

Direct numerical simulations of turbulent lean premixed combustion

International Nuclear Information System (INIS)

Sankaran, Ramanan; Hawkes, Evatt R; Chen, Jacqueline H; Lu Tianfeng; Law, Chung K

2006-01-01

In recent years, due to the advent of high-performance computers and advanced numerical algorithms, direct numerical simulation (DNS) of combustion has emerged as a valuable computational research tool, in concert with experimentation. The role of DNS in delivering new Scientific insight into turbulent combustion is illustrated using results from a recent 3D turbulent premixed flame simulation. To understand the influence of turbulence on the flame structure, a 3D fully-resolved DNS of a spatially-developing lean methane-air turbulent Bunsen flame was performed in the thin reaction zones regime. A reduced chemical model for methane-air chemistry consisting of 13 resolved species, 4 quasi-steady state species and 73 elementary reactions was developed specifically for the current simulation. The data is analyzed to study possible influences of turbulence on the flame thickness. The results show that the average flame thickness increases, in qualitative agreement with several experimental results

Extraction of anthocyanins from black bean canning wastewater with macroporous resins.

Science.gov (United States)

Wang, Xiaoxi; Hansen, Conly; Allen, Karin

2014-02-01

This study investigated purification of anthocyanins from black bean canning wastewater by column chromatography with 5 types of macroporous resins (Diaion Hp20, Sepabeads Sp70, Sepabeads Sp207, Sepabeads Sp700, and Sepabeads Sp710). By-product of canned black beans was partially purified by filtration, in anticipation of higher performance during column chromatography. Equilibrium adsorption isotherms were measured and analyzed using Langmuir and Freundlich isotherm models. Both Langmuir (all R² ≥ 0.98) and Freundlich (all R² ≥ 0.97) models can describe the adsorption process of anthocyanins from black bean canning wastewater using the tested resins. The adsorption and desorption behaviors of anthocyanins were studied using a dynamic method on the 5 types of resins, and Sp700 presented the highest adsorption capacity (39 ± 4 mg/g; P canning wastewater. © 2014 Institute of Food Technologists®

Internal combustion engine using premixed combustion of stratified charges

Science.gov (United States)

Marriott, Craig D [Rochester Hills, MI; Reitz, Rolf D [Madison, WI

2003-12-30

During a combustion cycle, a first stoichiometrically lean fuel charge is injected well prior to top dead center, preferably during the intake stroke. This first fuel charge is substantially mixed with the combustion chamber air during subsequent motion of the piston towards top dead center. A subsequent fuel charge is then injected prior to top dead center to create a stratified, locally richer mixture (but still leaner than stoichiometric) within the combustion chamber. The locally rich region within the combustion chamber has sufficient fuel density to autoignite, and its self-ignition serves to activate ignition for the lean mixture existing within the remainder of the combustion chamber. Because the mixture within the combustion chamber is overall premixed and relatively lean, NO.sub.x and soot production are significantly diminished.

Role of the outer-edge flame on flame extinction in nitrogen-diluted non-premixed counterflow flames with finite burner diameters

KAUST Repository

Chung, Yong Ho; Park, Daegeun; Park, Jeong; Kwon, Oh Boong; Yun, Jin Han; Keel, Sang In

2013-01-01

This study of nitrogen-diluted non-premixed counterflow flames with finite burner diameters investigates the important role of the outer-edge flame on flame extinction through experimental and numerical analyses. It explores flame stability diagrams

QUEOS, an experimental investigation of the premixing phase with hot spheres

Energy Technology Data Exchange (ETDEWEB)

Meyer, L. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Neutronenphysik und Reaktortechnik

1998-01-01

A second series of experiments with hot spheres to investigate the premixing phase of a steam explosion has been performed in the QUEOS facility at FZK. The diameter of the sphere jet plunging into the water has been reduced from 180 mm to 100 mm and larger masses have been employed. Both changes led to longer pours, compared to the short pours in the first series. The data of seven experiments are presented using three types of spheres at 1800 K and total volumes of approximately two and four liters, respectively. High speed films were taken, pressures, water temperatures and the steaming rate were measured. (author)

THE EFFECTS OF EQUIVALENCE RATIO ON THE FORMATION OF POLYCYCLIC AROMATIC HYDROCARBONS AND SOOT IN PREMIXED ETHANE FLAMES. (R825412)

Science.gov (United States)

AbstractThe formation of polycyclic aromatic hydrocarbons (PAH) and soot has been investigated in atmospheric-pressure, laminar, ethane/oxygen/argon premixed flames as a function of mixture equivalence ratio. Mole fraction profiles of major products, trace aromatics, ...

Ordered nanoporous silica as carriers for improved delivery of water insoluble drugs: a comparative study between three dimensional and two dimensional macroporous silica

Directory of Open Access Journals (Sweden)

Wang Y

2013-10-01

Full Text Available Ying Wang, Qinfu Zhao, Yanchen Hu, Lizhang Sun, Ling Bai, Tongying Jiang, Siling WangDepartment of Pharmaceutics, Shenyang Pharmaceutical University, Liaoning Province, People’s Republic of ChinaAbstract: The goal of the present study was to compare the drug release properties and stability of the nanoporous silica with different pore architectures as a matrix for improved delivery of poorly soluble drugs. For this purpose, three dimensional ordered macroporous (3DOM silica with 3D continuous and interconnected macropores of different sizes (200 nm and 500 nm and classic mesoporous silica (ie, Mobil Composition of Matter [MCM]-41 and Santa Barbara Amorphous [SBA]-15 with well-ordered two dimensional (2D cylindrical mesopores were successfully fabricated and then loaded with the model drug indomethacin (IMC via the solvent deposition method. Scanning electron microscopy (SEM, N2 adsorption, differential scanning calorimetry (DSC, and X-ray diffraction (XRD were applied to systematically characterize all IMC-loaded nanoporous silica formulations, evidencing the successful inclusion of IMC into nanopores, the reduced crystallinity, and finally accelerated dissolution of IMC. It was worth mentioning that, in comparison to 2D mesoporous silica, 3DOM silica displayed a more rapid release profile, which may be ascribed to the 3D interconnected pore networks and the highly accessible surface areas. The results obtained from the stability test indicated that the amorphous state of IMC entrapped in the 2D mesoporous silica (SBA-15 and MCM-41 has a better physical stability than in that of 3DOM silica. Moreover, the dissolution rate and stability of IMC loaded in 3DOM silica was closely related to the pore size of macroporous silica. The colorimetric 3-(4,5-Dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT and Cell Counting Kit (CCK-8 assays in combination with direct morphology observations demonstrated the good biocompatibility of nanoporous

Evolution of the Calcium Paradigm: The Relation between Vitamin D, Serum Calcium and Calcium Absorption

Directory of Open Access Journals (Sweden)

Borje E. Christopher Nordin

2010-09-01

Full Text Available Osteoporosis is the index disease for calcium deficiency, just as rickets/osteomalacia is the index disease for vitamin D deficiency, but there is considerable overlap between them. The common explanation for this overlap is that hypovitaminosis D causes malabsorption of calcium which then causes secondary hyperparathyroidism and is effectively the same thing as calcium deficiency. This paradigm is incorrect. Hypovitaminosis D causes secondary hyperparathyroidism at serum calcidiol levels lower than 60 nmol/L long before it causes malabsorption of calcium because serum calcitriol (which controls calcium absorption is maintained until serum calcidiol falls below 20 nmol/L. This secondary hyperparathyroidism, probably due to loss of a “calcaemic” action of vitamin D on bone first described in 1957, destroys bone and explains why vitamin D insufficiency is a risk factor for osteoporosis. Vitamin D thus plays a central role in the maintenance of the serum (ionised calcium, which is more important to the organism than the preservation of the skeleton. Bone is sacrificed when absorbed dietary calcium does not match excretion through the skin, kidneys and bowel which is why calcium deficiency causes osteoporosis in experimental animals and, by implication, in humans.

Effects of injection timing on fluid flow characteristics of partially premixed combustion based on high-speed particle image velocimetry

NARCIS (Netherlands)

Izadi Najafabadi, M.; Tanov, S.; Wang, H.; Somers, L.M.T.; Johansson, B.; Dam, N.J.

2017-01-01

Partially premixed combustion (PPC) is a promising combustion concept to meet the increasing demands of emission legislation and to improve fuel efficiency. Longer ignition delay of PPC in comparison with conventional diesel combustion provide better fuel/air mixture which decreases soot and NOx

Calcium absorption

International Nuclear Information System (INIS)

Carlmark, B.; Reizenstein, P.; Dudley, R.A.

1976-01-01

The methods most commonly used to measure the absorption and retention of orally administered calcium are reviewed. Nearly all make use of calcium radioisotopes. The magnitude of calcium absorption and retention depends upon the chemical form and amount of calcium administered, and the clinical and nutritional status of the subject; these influences are briefly surveyed. (author)

Analgesic efficacy of equimolar 50% nitrous oxide/oxygen gas premix (Kalinox®) as compared with a 5% eutectic mixture of lidocaine/prilocaine (EMLA®) in chronic leg ulcer debridement.

Science.gov (United States)

Traber, Juerg; Held, Ulrike; Signer, Maria; Huebner, Tobias; Arndt, Stefan; Neff, Thomas A

2017-08-01

Chronic foot and leg ulcers are a common health problem worldwide. A mainstay of chronic ulcer therapy is sharp mechanical wound debridement requiring potent analgesia. In this prospective, controlled, single-centre, crossover design study, patients were assigned to either the administration of topical analgesia with 5% lidocaine/prilocaine cream or the inhalation of an analgesic 50% N 2 O/O 2 gas premix. Primary outcome parameter was level of pain at maximum wound depth during debridement as measured by a visual analogue scale. Secondary outcomes included level of pain after debridement, overall duration of treatment session, duration and completeness of debridement, and the patient's subjective perception of analgesic quality during debridement. Pain level increased from 0·60/0·94 (first/second debridement; baseline) to 1·76/2·50 (debridement) with 5% lidocaine/prilocaine and from 1·00/1·35 (baseline) to 3·95/3·29 (debridement) with 50% N 2 O/O 2 gas premix. Patient satisfaction was 90·48%/94·44% (first/second debridement) with topical 5% lidocaine/prilocaine analgesia and 90·48%/76·47% with the inhalation of 50% N 2 O/O 2 gas premix. Debridement was completed in a significantly higher percentage of 85·71%/88·89% (first/second debridement) with 5% lidocaine/prilocaine than with 50% N 2 O/O 2 gas premix (42·86%/58·82%) (odds ratio 6·7; P = 0·001). This study provides sound evidence that analgesia with topically administered 5% lidocaine/prilocaine cream is superior to the use of inhaled 50% N 2 O/O 2 gas premix in chronic leg ulcer debridement. © 2016 Medicalhelplines.com Inc and John Wiley & Sons Ltd.

Experimental validation of large-eddy simulation for swirling methane-air non-premixed combustion

Energy Technology Data Exchange (ETDEWEB)

Hu, L.Y.; Luo, Y.H.; Xu, C.S. [Shanghai Jiaotong Univ. (China). School of Mechanical Engineering; Zhou, L.X. [Tsinghua Univ., Beijing (China). Dept. of Engineering Mechanics

2013-07-01

Large-eddy simulation of swirling methane-air non-premixed combustion was carried out using a Smagorinsky-Lilly subgrid scale stress model and a presumed-PDF fast-chemistry combustion model. The LES statistical results are validated by PIV, temperature and species concentration measurements made by the present authors. The results indicate that in the present case the presumed-PDF fast-chemistry combustion model is a fairish one. The instantaneous vorticity and temperature maps show clearly the development and the interaction between coherent structures and combustion.

Nonorthogonality analysis of a thermoacoustic system with a premixed V-shaped flame

International Nuclear Information System (INIS)

Ji, Chenzhen; Zhao, Dan; Li, Xinyan; Li, Shihuai; Li, Junwei

2014-01-01

Highlights: • Nonorthogonality analysis of a choked thermoacoustic system is conducted. • A thermoacoustic model of a premixed V-shaped flame is developed. • Nonorthogonality is identified to arise from the boundary condition and the flame. • The contribution from the flame is shown to play a dominant role. • Eigenmodes nonorthogonality leads to transient growth of acoustic disturbances. - Abstract: Thermoacoustic instability occurs in many combustion systems, such as aero-engine afterburners, rocket motors, ramjets and gas turbines. It most often arises due to the coupling between unsteady heat release and acoustic waves. In this work, nonorthogonality analysis of a choked combustor with a gutter confined is conducted. Such configuration is used as a simplified model of the afterburner of an aero-engine. A thermoacoustic model is developed first to study the nonnormal interaction between acoustic disturbances and a premixed V-shaped flame anchored to the tip of the gutter. Eigenmode nonorthogonality analysis is then conducted. The thermoacoustic system is shown to be nonnormal and characterized by nonorthogonal eigenmodes. The nonorthogonality is identified to arise from both the complex boundary condition and the monopole-like flame. However, the contribution from the Robin-type boundary is approximately 1.5% of that from the flame. Thus the flame is identified to play a dominant role. One practical conclusions is that acoustic disturbances undergo transient growth in a combustion system with nonorthogonal eigenmodes. Such finite-time growth, which cannot be predicted by using classical linear theory might trigger high-amplitude self-sustained oscillations

An analytical model for the prediction of the dynamic response of premixed flames stabilized on a heat-conducting perforated plate

KAUST Repository

Kedia, Kushal S.; Ghoniem, Ahmed F.

2013-01-01

The dynamic response of a premixed flame stabilized on a heat-conducting perforated plate depends critically on their coupled thermal interaction. The objective of this paper is to develop an analytical model to capture this coupling. The model

Effects of combined dimension reduction and tabulation on the simulations of a turbulent premixed flame using a large-eddy simulation/probability density function method

Science.gov (United States)

Kim, Jeonglae; Pope, Stephen B.

2014-05-01

A turbulent lean-premixed propane-air flame stabilised by a triangular cylinder as a flame-holder is simulated to assess the accuracy and computational efficiency of combined dimension reduction and tabulation of chemistry. The computational condition matches the Volvo rig experiments. For the reactive simulation, the Lagrangian Large-Eddy Simulation/Probability Density Function (LES/PDF) formulation is used. A novel two-way coupling approach between LES and PDF is applied to obtain resolved density to reduce its statistical fluctuations. Composition mixing is evaluated by the modified Interaction-by-Exchange with the Mean (IEM) model. A baseline case uses In Situ Adaptive Tabulation (ISAT) to calculate chemical reactions efficiently. Its results demonstrate good agreement with the experimental measurements in turbulence statistics, temperature, and minor species mass fractions. For dimension reduction, 11 and 16 represented species are chosen and a variant of Rate Controlled Constrained Equilibrium (RCCE) is applied in conjunction with ISAT to each case. All the quantities in the comparison are indistinguishable from the baseline results using ISAT only. The combined use of RCCE/ISAT reduces the computational time for chemical reaction by more than 50%. However, for the current turbulent premixed flame, chemical reaction takes only a minor portion of the overall computational cost, in contrast to non-premixed flame simulations using LES/PDF, presumably due to the restricted manifold of purely premixed flame in the composition space. Instead, composition mixing is the major contributor to cost reduction since the mean-drift term, which is computationally expensive, is computed for the reduced representation. Overall, a reduction of more than 15% in the computational cost is obtained.

Adsorption and desorption properties of macroporous resins for anthocyanins from the calyx extract of roselle (Hibiscus sabdariffa L.).

Science.gov (United States)

Chang, Xiu-Lian; Wang, Dong; Chen, Bi-Yun; Feng, Yong-Mei; Wen, Shao-Hong; Zhan, Peng-Yuan

2012-03-07

Adsorption of roselle anthocynins, a natural pigment, onto various macroporous resins was optimized to develop a simple and efficient process for industrial separation and purification of roselle anthocyanins. Nine different macroporous resins (AB-8, X-5, HPD-100, SP-207, XAD-4, LS-305A, DM-21, LS-610B, and LS-305) were evaluated for the adsorption properties of the anthocyanins extracted from the calyx extract of Hibiscus sabdariffa L. The influences of phase contact time, solution pH, initial anthocyanin concentration, and ethanol concentration with different citric acid amounts were studied by the static adsorption/desorption method. The adsorption isotherm data were fitted well to the Langmuir isotherm, and according to this model, LS-610B and LS-305 exhibited the highest monolayer sorption capacities of 31.95 and 38.16 mg/g, respectively. The kinetic data were modeled using pseudo-first-order, pseudo-second-order, and intraparticle diffusion equations. The experimental data were well described by the pseudo-second-order kinetic model. Continuous column adsorption-regeneration cycles indicated negligible capacity loss of LS-305 during operation. The overall yield of pigment product was 49.6 mg/g dried calyces. The content of roselle anthocynins in the pigment product was 4.85%.

Molecularly imprinted macroporous monoliths for solid-phase extraction: Effect of pore size and column length on recognition properties.

Science.gov (United States)

Vlakh, E G; Stepanova, M A; Korneeva, Yu M; Tennikova, T B

2016-09-01

The series of macroporous monolithic molecularly imprinted monoliths differed by pore size, column length (volume) and amount of template used for imprinting was synthesized using methacrylic acid and glycerol dimethacrylate as co-monomers and antibiotic ciprofloxacin as a template. The prepared monoliths were characterized regarding to their permeability, pore size, porosity, and resistance to the flow of a mobile phase. The surface morphology was also analyzed. The slight dependence of imprinting factor on flow rate, as well as its independence on pore size of macroporous molecularly imprinted monolithic media was observed. The column obtained at different conditions exhibited different affinity of ciprofloxacin to the imprinted sites that was characterized with Kdiss values in the range of 10(-5)-10(-4)M. The solid-phase extraction of ciprofloxacin from such biological liquids as human blood serum, human urine and cow milk serum was performed using the developed monolithic columns. In all cases, the extraction was found to be 95.0-98.6%. Additionally, the comparison of extraction of three fluoroqinolone analogues, e.g. ciprofloxacin, levofloxacin and moxifloxacin, from human blood plasma was carried out. Contrary to ciprofloxacin extracted with more than 95%, this parameter did not exceed 40% for its analogues. Copyright © 2016 Elsevier B.V. All rights reserved.

LES of explosions in venting chamber: A test case for premixed turbulent combustion models

OpenAIRE

Vermorel , Olivier; Quillatre , Pierre; Poinsot , Thierry

2017-01-01

International audience; This paper presents a new experimental and Large Eddy Simulation (LES) database to study upscaling effects in vented gas explosions. The propagation of premixed flames in three setups of increasing size is investigated experimentally and numerically. The baseline model is the well-known laboratory-scale combustion chamber from Sydney (Kent et al., 2005; Masri et al., 2012); two exact replicas at scales 6 and 24.4 were set up by GexCon (Bergen, Norway). The volume ratio...

Soil macropores: Control on infiltration, hillslope and surface hydrology on a reclaimed surface-mined watershed

International Nuclear Information System (INIS)

Guebert, M.D.; Gardner, T.W.

1992-01-01

The hydrologic response of a surface-mined watershed in central Pennsylvania is controlled by rapid macropore flow within the unsaturated man-made topsoil. Newly reclaimed surface-mined watersheds in central Pennsylvania exhibit low steady-state infiltration rates (1--2 cm/hr) and produce runoff dominated by infiltration-excess overland flow. However, within four years after reclamation, infiltration rates on some mine surfaces approach premined rates (8 cm/hr). As infiltration rate increases, the volume of infiltrated water increases, but the total porosity of minesoil matrix remains constant. There is little change in the surface discharge volume, indicating that infiltrated water continues to contribute to the basin surface discharge by the processes of throughflow and return flow. Throughflow in the topsoil horizon occurs in rapid response to rainfall input, producing large volumes of water with throughflow rates closely related to rainfall rates and with throughflow peaks following rainfall peaks by only minutes. Increased return flow alters the shape of the surface runoff hydrograph by slightly lagging behind infiltration excess overland flow. These changes in the shape of the surface runoff hydrograph reduce the potential for severe gully erosion on the reclaimed site. In addition, throughflow water remains predominantly in the topsoil horizon, and therefore has limited contact with potentially acid-producing backfill. Better understanding of macropore flow processes in reclaimed minesoils will help investigators evaluate past strategies and develop new reclamation techniques that will minimize the short-term surface erosional effects of mining and reclamation, while optimizing the long-term effluent and groundwater quality

Qualitative Analysis of Polyphenols in Macroporous Resin Pretreated Pomegranate Husk Extract by HPLC-QTOF-MS.

Science.gov (United States)

Abdulla, Rahima; Mansur, Sanawar; Lai, Haizhong; Ubul, Ablikim; Sun, Guangying; Huang, Guozheng; Aisa, Haji Akber

2017-09-01

Pomegranate (Punica granatum L.) husk is a traditional herbal medicine abundant in phenolic compounds and plays some roles in the treatment of oxidative stress, bacterial and viral infection, diabetes mellitus, and acute and chronic inflammation. Identification and determination of polyphenols in macroporous resin pretreated pomegranate husk extract by high performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (HPLC-QTOF-MS). The total polyphenols of pomegranate husk were prepared by ethanol extraction followed by pretreatment with HPD-300 macroporous resin. The polyphenolic compounds were qualitatively analysed by HPLC-QTOF-MS in negative electrospray ionisation (ESI) mode at different collision energy (CE) values. A total of 50 polyphenols were detected in the extract of pomegranate husk, including 35 hydrolysable tannins and 15 flavonoids with distinct retention time, fragmentation behaviours and characteristics, and the accurate mass-to-charge ratios at low, moderate and high CE values. Of these, we identified nine compounds for the first time in the pomegranate husk, including hexahydroxydiphenoyl-valoneoyl-glucoside (HHDP-valoneyl-glucoside), galloyl-O-punicalin, rutin, hyperoside, quercimeritrin, kaempferol-7-O-rhahmano-glucoside, luteolin-3'-O-arabinoside, luteolin-3'-O-glucoside, and luteolin-4'-O-glucoside. To validate the specificity and accuracy of mass spectrometry in the detection of polyphenols, as compared to the fragmentation pathways of granatin B in detail, including the HHDP-valoneyl- glucoside was first identified from pomegranate husk. The study provides evidence for the quality control and development of novel drugs based on polyphenols from the pomegranate husk. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Radioisotope 45Ca labeling four calcium chemical compounds and tracing calcium bioavailability

International Nuclear Information System (INIS)

Zheng Hui; Zhen Rong; Niu Huisheng; Li Huaifen

2004-01-01

Objective: To build up a new method of the radioisotope 45 Ca labeling four calcium chemical compounds, observe and tracing bioavailability change of calcium labeled with radioisotope 45 Ca. Methods: The calcium gluconate (Ca-Glu), calcium citrate (Ca-Cit), calcium carbonate (Ca-Car) and calcium L-threonate (Ca-Thr)were labeled by radioisotope 45 Ca. Four calcium chemical compounds of 45 Ca labeling were used of calcium content 200 mg/kg in the rats and measure the absorption content and bioavailability of calcium in tissue of heart, lever spleen, stomach, kidney, brain, intestine, whole blood, urine, faeces. Results: 1) Radioisotope 45 Ca labeling calcium chemical compound has high radio intensity, more steady standard curve and recover rate. 2) The absorption of organic calcium chemical compounds is higher than the inorganic calcium chemical compound in the study of calcium bioavailability. Conclusion: The method of tracing with radioisotope 45 Ca labeling calcium chemical compounds has the characteristic of the sensitive, objective, accurate and steady in the study of calcium bioavailability

The impact of calcium assay change on a local adjusted calcium equation.

Science.gov (United States)

Davies, Sarah L; Hill, Charlotte; Bailey, Lisa M; Davison, Andrew S; Milan, Anna M

2016-03-01

Deriving and validating local adjusted calcium equations is important for ensuring appropriate calcium status classification. We investigated the impact on our local adjusted calcium equation of a change in calcium method by the manufacturer from cresolphthalein complexone to NM-BAPTA. Calcium and albumin results from general practice requests were extracted from the Laboratory Information Management system for a three-month period. Results for which there was evidence of disturbance in calcium homeostasis were excluded leaving 13,482 sets of results for analysis. The adjusted calcium equation was derived following least squares regression analysis of total calcium on albumin and normalized to the mean calcium concentration of the data-set. The revised equation (NM-BAPTA calcium method) was compared with the previous equation (cresolphthalein complexone calcium method). The switch in calcium assay resulted in a small change in the adjusted calcium equation but was not considered to be clinically significant. The calcium reference interval differed from that proposed by Pathology Harmony in the UK. Local adjusted calcium equations should be re-assessed following changes in the calcium method. A locally derived reference interval may differ from the consensus harmonized reference interval. © The Author(s) 2015.

Self-floating carbon nanotube membrane on macroporous silica substrate for highly efficient solar-driven interfacial water evaporation

KAUST Repository

Wang, Yuchao

2016-01-22

Given the emerging energy and water challenges facing the mankind, solar-driven water evaporation has been gaining renewed research attention from both academia and industry as an energy efficient means of wastewater treatment and clean water production. In this project, a bi-layered material, consisting of a top self-floating hydrophobic CNT membrane and a bottom hydrophilic macroporous silica substrate, was rationally designed and fabricated for highly energy-efficient solar driven water evaporation based on the concept of interfacial heating. The top thin CNT membrane with excellent light adsorption capability, acted as photothermal component, which harvested and converted almost the entire incident light to heat for exclusively heating of interfacial water. On the other hand, the macroporous silica substrate provided multi-functions toward further improvement of operation stability and water evaporation performance of the material, including water pumping, mechanical support and heat barriers. The silica substrate was conducive in forming the rough surface structures of the CNT top layers during vacuum filtration and thus indirectly contributed to high light adsorption by the top CNT layers. With optimized thicknesses of the CNT top layer and silica substrate, a solar thermal conversion efficiency of 82 % was achieved in this study. The bi-layered material also showed great performance toward water evaporation from seawater and contaminated water, realizing the separation of water from pollutants, and indicating its application versatility.

Self-floating carbon nanotube membrane on macroporous silica substrate for highly efficient solar-driven interfacial water evaporation

KAUST Repository

Wang, Yuchao; Zhang, Lianbin; Wang, Peng

2016-01-01

Given the emerging energy and water challenges facing the mankind, solar-driven water evaporation has been gaining renewed research attention from both academia and industry as an energy efficient means of wastewater treatment and clean water production. In this project, a bi-layered material, consisting of a top self-floating hydrophobic CNT membrane and a bottom hydrophilic macroporous silica substrate, was rationally designed and fabricated for highly energy-efficient solar driven water evaporation based on the concept of interfacial heating. The top thin CNT membrane with excellent light adsorption capability, acted as photothermal component, which harvested and converted almost the entire incident light to heat for exclusively heating of interfacial water. On the other hand, the macroporous silica substrate provided multi-functions toward further improvement of operation stability and water evaporation performance of the material, including water pumping, mechanical support and heat barriers. The silica substrate was conducive in forming the rough surface structures of the CNT top layers during vacuum filtration and thus indirectly contributed to high light adsorption by the top CNT layers. With optimized thicknesses of the CNT top layer and silica substrate, a solar thermal conversion efficiency of 82 % was achieved in this study. The bi-layered material also showed great performance toward water evaporation from seawater and contaminated water, realizing the separation of water from pollutants, and indicating its application versatility.

Propagation of a premixed flame in a divided-chamber combustor

Science.gov (United States)

Cattolica, R. J.; Barr, P. K.; Mansour, N. N.

1989-01-01

Experimental observations on the propagation of lean premixed ethylene-air flames in a divided-chamber combustion vessel have been compared with the results of numerical simulations based on a flame sheet-vortex dynamics model in axisymmetric coordinates. Flame speeds were found to increase from 10-24 cm/s as the equivalence ratio was varied from 0.5-0.65 in the experiments. Using the associated increase in gas velocity with equivalence ratio, the estimated Reynolds number in the experiment was changed from 1870 to 8090. Good agreement between experimental and theoretical results was obtained for the prechamber flame propagation rates and for the spatial and temporal development of the flame in the main combustion chamber at the lowest Reynolds number.

Turbulent premixed flames on fractal-grid-generated turbulence

Energy Technology Data Exchange (ETDEWEB)

Soulopoulos, N; Kerl, J; Sponfeldner, T; Beyrau, F; Hardalupas, Y; Taylor, A M K P [Mechanical Engineering Department, Imperial College London, London SW7 2AZ (United Kingdom); Vassilicos, J C, E-mail: ns6@ic.ac.uk [Department of Aeronautics, Imperial College London, London SW7 2AZ (United Kingdom)

2013-12-15

A space-filling, low blockage fractal grid is used as a novel turbulence generator in a premixed turbulent flame stabilized by a rod. The study compares the flame behaviour with a fractal grid to the behaviour when a standard square mesh grid with the same effective mesh size and solidity as the fractal grid is used. The isothermal gas flow turbulence characteristics, including mean flow velocity and rms of velocity fluctuations and Taylor length, were evaluated from hot-wire measurements. The behaviour of the flames was assessed with direct chemiluminescence emission from the flame and high-speed OH-laser-induced fluorescence. The characteristics of the two flames are considered in terms of turbulent flame thickness, local flame curvature and turbulent flame speed. It is found that, for the same flow rate and stoichiometry and at the same distance downstream of the location of the grid, fractal-grid-generated turbulence leads to a more turbulent flame with enhanced burning rate and increased flame surface area. (paper)

Forced and self-excited oscillations in a natural gas fired lean premixed combustor

Energy Technology Data Exchange (ETDEWEB)

Kim, Daesik; Park, Sung Wook

2010-11-15

An experimental study of the flame response in a premixed gas turbine combustor has been conducted at room temperature and under atmospheric pressure inlet conditions using natural gas. The fuel is premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. Therefore the observed flame response is only the result of the imposed velocity fluctuations, which are produced using a variable-speed siren. Also, a variable length combustor is designed for investigating characteristics of self-excited instabilities. Measurements are made of the velocity fluctuation in the mixing section using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The results are analyzed to determine the phase and gain of the flame transfer function. The results show that the gain of flame transfer function is closely associated both with inlet flow forcing conditions such as frequency and amplitude of modulation as well as the operating conditions such as equivalence ratio. In order to predict the operating conditions where the combustor goes stable or unstable at given combustor and nozzle designs, time-lag analysis was tried using convection time delay measured from the phase information of the transfer function. The model prediction was in very good agreement with the self-excited instability measurement. However, spatial heat release distribution became more significant in long flames than in short flames and also had an important influence on the system damping procedure. (author)

Emission characteristics and axial flame temperature distribution of producer gas fired premixed burner

Energy Technology Data Exchange (ETDEWEB)

Bhoi, P.R. [Department of Mechanical Engineering, L and T-Sargent and Lundy Limited, L and T Energy Centre, Near Chhani Jakat Naka, Baroda 390 002 (India); Channiwala, S.A. [Department of Mechanical Engineering, Sardar Vallabhbhai National Institute of Technology, Deemed University, Ichchhanath, Surat 395 007, Gujarat (India)

2009-03-15

This paper presents the emission characteristics and axial flame temperature distribution of producer gas fired premixed burner. The producer gas fired premixed burner of 150 kW capacity was tested on open core throat less down draft gasifier system in the present study. A stable and uniform flame was observed with this burner. An instrumented test set up was developed to evaluate the performance of the burner. The conventional bluff body having blockage ratio of 0.65 was used for flame stabilization. With respect to maximum flame temperature, minimum pressure drop and minimum emissions, a swirl angle of 60 seems to be optimal. The experimental results also showed that the NO{sub x} emissions are inversely proportional to swirl angle and CO emissions are independent of swirl angle. The minimum emission levels of CO and NO{sub x} are observed to be 0.167% and 384 ppm respectively at the swirl angle of 45-60 . The experimental results showed that the maximum axial flame temperature distribution was achieved at A/F ratio of 1.0. The adiabatic flame temperature of 1653 C was calculated theoretically at A/F ratio of 1.0. Experimental results are in tune with theoretical results. It was also concluded that the CO and UHC emissions decreases with increasing A/F ratio while NO{sub x} emissions decreases on either side of A/F ratio of 1.0. (author)

The Effect of Heat Treatments on Alloying of Pre-mixed Al + 4.5 wt. % Cu Powders

Directory of Open Access Journals (Sweden)

Kübra KÖPRÜLÜ

2018-06-01

Full Text Available In this study, 4.5 wt. % Cu powder was added to Al powder and mixed for 45 minutes to produce premixed metal powders. Premixed powders were compacted by cold pressing at 20 MPa. After that these samples were pressed at 500℃ under 200 MPa for 30 minutes by hot pressed method. Hot pressed block samples were subjected to diffusion annealing at 540 ℃ for 2, 4, 8, 16, 32 hours. These samples, produced by powder metallurgy, are used at metallographic and microscopic researches to investigate the diffusion process. During the diffusion annealing, it was determined that significant amount of copper powder particles was dissolved in the Al matrix by diffusion. Diffusion annealing was followed by aging heat treatment, characterized by metallographic and mechanical tests. According to the increasing the annealing time, the homogeneity of the chemical composition is not provided, however the increasing of the heat treatment (T6 capability of the produced parts, and partial porosity which is believed to be due to atomic diffusion, have been observed. Moreover, in the XRD analyses, it was determined that the phases of -Al,  and  were formed in the microstructure.

Calcium supplements

Science.gov (United States)

... this page: //medlineplus.gov/ency/article/007477.htm Calcium supplements To use the sharing features on this page, please enable JavaScript. WHO SHOULD TAKE CALCIUM SUPPLEMENTS? Calcium is an important mineral for the ...

Combustion Characteristics for Turbulent Prevaporized Premixed Flame Using Commercial Light Diesel and Kerosene Fuels

Directory of Open Access Journals (Sweden)

Mohamed S. Shehata

2014-01-01

Full Text Available Experimental study has been carried out for investigating fuel type, fuel blends, equivalence ratio, Reynolds number, inlet mixture temperature, and holes diameter of perforated plate affecting combustion process for turbulent prevaporized premixed air flames for different operating conditions. CO2, CO, H2, N2, C3H8, C2H6, C2H4, flame temperature, and gas flow velocity are measured along flame axis for different operating conditions. Gas chromatographic (GC and CO/CO2 infrared gas analyzer are used for measuring different species. Temperature is measured using thermocouple technique. Gas flow velocity is measured using pitot tube technique. The effect of kerosene percentage on concentration, flame temperature, and gas flow velocity is not linearly dependent. Correlations for adiabatic flame temperature for diesel and kerosene-air flames are obtained as function of mixture strength, fuel type, and inlet mixture temperature. Effect of equivalence ratio on combustion process for light diesel-air flame is greater than for kerosene-air flame. Flame temperature increases with increased Reynolds number for different operating conditions. Effect of Reynolds number on combustion process for light diesel flame is greater than for kerosene flame and also for rich flame is greater than for lean flame. The present work contributes to design and development of lean prevaporized premixed (LPP gas turbine combustors.

Considerations and calculations on the breakup of jets and drops of melt related to premixing

Energy Technology Data Exchange (ETDEWEB)

Buerger, M.; Berg, E. von; Buck, M. [Inst. fuer Kernenergetik und Energiesysteme (IKE), Univ. of Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart (Germany)

1998-01-01

Various descriptions of jet and drop breakup are applied in premixing codes, presently. The main task is to check these descriptions over a wide range of conditions in order to assure extrapolation capabilities for the codes. Jet breakup under non-boiling conditions is relatively well described by IKEJET, based on Conte/Miles (CM) instability description and a relatively detailed stripping model, in contrast to using Kelvin/Helmholtz (KH) theory. Remaining open questions are elaborated. Especially, thick jet behavior with dominance of stripping even at small relative velocities must be distinguished from thin jets with coarse breakup. The application of IKEJET to cases with jet breakup under strong film boiling yielded significantly too little fragmentation. As a possible explanation line, multiphase effects on the wave growth and stripping are considered, due to entrainment of melt and water. Parametric checking calculations are performed with a strongly simplified approach for PREMIX and FARO experiments in order to reveal main effects and the possible physical explanation features as a basis for extended modelling. The results indicate that jet breakup may be essentially sufficient to explain the experimental behavior. Rather coalescence than further drop breakup may be expected. This is also indicated by calculations with IKE drop breakup models. (author)

Numerical and Experimental Investigation of Computed Tomography of Chemiluminescence for Hydrogen-Air Premixed Laminar Flames

Directory of Open Access Journals (Sweden)

Liang Lv

2016-01-01

Full Text Available Computed tomography of chemiluminescence (CTC is a promising technique for combustion diagnostics, providing instantaneous 3D information of flame structures, especially in harsh circumstance. This work focuses on assessing the feasibility of CTC and investigating structures of hydrogen-air premixed laminar flames using CTC. A numerical phantom study was performed to assess the accuracy of the reconstruction algorithm. A well-designed burner was used to generate stable hydrogen-air premixed laminar flames. The OH⁎ chemiluminescence intensity field reconstructed from 37 views using CTC was compared to the OH⁎ chemiluminescence distributions recorded directly by a single ICCD camera from the side view. The flame structures in different flow velocities and equivalence ratios were analyzed using the reconstructions. The results show that the CTC technique can effectively indicate real distributions of the flame chemiluminescence. The height of the flame becomes larger with increasing flow velocities, whereas it decreases with increasing equivalence ratios (no larger than 1. The increasing flow velocities gradually lift the flame reaction zones. A critical cone angle of 4.76 degrees is obtained to avoid blow-off. These results set up a foundation for next studies and the methods can be further developed to reconstruct 3D structures of flames.

Impact of computerized order entry and pre-mixed dialysis solutions for continuous veno-venous hemodiafiltration on selection of therapy for acute renal failure.

Science.gov (United States)

Saadulla, Lawand; Reeves, W Brian; Irey, Brittany; Ghahramani, Nasrollah

2012-02-01

To investigate the impacts of availability of pre-mixed solutions and computerized order entry on nephrologists' choice of the initial mode of renal replacement therapy in acute renal failure. We studied 898 patients with acute renal failure in 3 consecutive eras: era 1 (custom-mixed solution; n = 309), era 2 (pre-mixed commercial solution; n = 324), and era 3 (post-computerized order entry; n = 265). The proportion of patients treated with renal replacement therapy and the time from consult to initiation of continuous renal replacement therapy was similar in the 3 eras. Following introduction of the pre-mixed solution, the proportion of patients treated with continuous renal replacement therapy increased (20% vs. 33%; p mixed solution increases the likelihood of initiating continuous renal replacement therapy in acute renal failure, initiating it at a lower creatinine and for older patients, use of continuous veno-venous hemodialysis and higher prescribed continuous renal replacement therapy dose. Computerized order entry implementation is associated with an additional increase in the use of continuous veno-venous hemodialysis, higher total prescribed dialysis dose, and use of CRRT among an increasing number of patients not on mechanical ventilation. The effect of these changes on patient survival is not significant.

Attempt of multiple stage injection with EGR for high load operation of a premixed compression ignition engine; Tadan funsha ni yoru yokongo asshuku chakka kikan no unten ryoiki kakudai

Energy Technology Data Exchange (ETDEWEB)

Hashizume, T.; Miyamoto, T.; Akagawa, H. [New ACE Institute Co. Ltd., Tsukuba (Japan); Tsujimura, K. [Chiba Institute of Technology, Chiba (Japan)

2000-01-25

By injecting fuel at the very early stage of compression stroke and thus creating homogeneous lean mixture before ignition, (PREDIC ; PREmixed lean DIesel Combustion), simultaneous reduction of NO{sub x} and smoke was obtained. However, since increasing the mixture equivalence ratio cause knocking, it was difficult to operate at higher load conditions. In this study, in order to reduce combustion rate at high load conditions in a premixed compression ignition engine, multiple stage injection method and EGR were combined, and heterogeneous mixture was made before ignition. The engine test results showed that NO{sub x} emissions could be reduced to less than 50 ppm, without knocking even at full load conditions. In addition, smoke emissions were also maintained below invisible level. It can be understood that the premixing of fuel was advanced, smoke was reduced, and EGR rate was increased, resulting lower heat release rate and NO{sub x} emissions. (author)

Flame Front Detection Using Formaldehyde Laser Induced Fluorescence In Turbulent Lean Premixed Flames

Energy Technology Data Exchange (ETDEWEB)

Schenker, S.; Tylli, N.; Bombach, R.

2005-03-01

The present work aims at suggesting the excitation-detection scheme best suited for laser-induced fluorescence measurements of formaldehyde in turbulent lean premixed flames. In the literature, three different excitation schemes within the A{sup 1} X{sup 1} electronic transition have been suggested, with excitation into the 2{sup 1}{sub 0} 4{sup 1}{sub 0} , 4{sup 1}{sub 0} , and 4{sup 0}{sub 1} vibratoric bands, respectively. These excitation schemes were tested systematically and both advantages and disadvantages for each scheme are discussed. (author)

Experiments for the premixing phase (QUEOS)

International Nuclear Information System (INIS)

Meyer, L.; Huber, R.; Haessler, M.; Kirstahler, M.; Kuhn, D.; Rehme, K.; Schumacher, G.; Schwall, M.; Wachter, E.; Woerner, G.

1995-01-01

Experiments are performed with solid spheres at high temperatures to establish a data base for the premixing phase of a steam explosion, which will be used for code improvement and validation. The hot spheres (T≤2600 K) are being dropped into saturated water at 1 bar pressure. The objective of the experiments is to obtain data on the cooling rate of the spheres, their distribution in the water, the amount of generated steam and its distribution with respect to the spheres. The spheres have a diameter of 4.2 mm, 4.8 mm and 10 mm, respectively, depending on the material used. Molybdenum coated with Rhenium to inhibit oxidation and ZrO 2 are used. The experimental parameters are the mass flow of the spheres, their density and their temperature. The QUEOS test facility has been set up and tested. A series of first tests has been performed with cold spheres and spheres at 1000 C. The main results are the distribution of the spheres during the fall through the water and their distribution at the bottom of the water vessel. A large air bubble is being entrained into the water in both the cold and hot tests. (orig./HP)

Calcium waves.

Science.gov (United States)

Jaffe, Lionel F

2008-04-12

Waves through living systems are best characterized by their speeds at 20 degrees C. These speeds vary from those of calcium action potentials to those of ultraslow ones which move at 1-10 and/or 10-20 nm s(-1). All such waves are known or inferred to be calcium waves. The two classes of calcium waves which include ones with important morphogenetic effects are slow waves that move at 0.2-2 microm s(-1) and ultraslow ones. Both may be propagated by cycles in which the entry of calcium through the plasma membrane induces subsurface contraction. This contraction opens nearby stretch-sensitive calcium channels. Calcium entry through these channels propagates the calcium wave. Many slow waves are seen as waves of indentation. Some are considered to act via cellular peristalsis; for example, those which seem to drive the germ plasm to the vegetal pole of the Xenopus egg. Other good examples of morphogenetic slow waves are ones through fertilizing maize eggs, through developing barnacle eggs and through axolotl embryos during neural induction. Good examples of ultraslow morphogenetic waves are ones during inversion in developing Volvox embryos and across developing Drosophila eye discs. Morphogenetic waves may be best pursued by imaging their calcium with aequorins.

Flame kernel generation and propagation in turbulent partially premixed hydrocarbon jet

KAUST Repository

Mansour, Mohy S.

2014-04-23

Flame development, propagation, stability, combustion efficiency, pollution formation, and overall system efficiency are affected by the early stage of flame generation defined as flame kernel. Studying the effects of turbulence and chemistry on the flame kernel propagation is the main aim of this work for natural gas (NG) and liquid petroleum gas (LPG). In addition the minimum ignition laser energy (MILE) has been investigated for both fuels. Moreover, the flame stability maps for both fuels are also investigated and analyzed. The flame kernels are generated using Nd:YAG pulsed laser and propagated in a partially premixed turbulent jet. The flow field is measured using 2-D PIV technique. Five cases have been selected for each fuel covering different values of Reynolds number within a range of 6100-14400, at a mean equivalence ratio of 2 and a certain level of partial premixing. The MILE increases by increasing the equivalence ratio. Near stoichiometric the energy density is independent on the jet velocity while in rich conditions it increases by increasing the jet velocity. The stability curves show four distinct regions as lifted, attached, blowout, and a fourth region either an attached flame if ignition occurs near the nozzle or lifted if ignition occurs downstream. LPG flames are more stable than NG flames. This is consistent with the higher values of the laminar flame speed of LPG. The flame kernel propagation speed is affected by both turbulence and chemistry. However, at low turbulence level chemistry effects are more pronounced while at high turbulence level the turbulence becomes dominant. LPG flame kernels propagate faster than those for NG flame. In addition, flame kernel extinguished faster in LPG fuel as compared to NG fuel. The propagation speed is likely to be consistent with the local mean equivalence ratio and its corresponding laminar flame speed. Copyright © Taylor & Francis Group, LLC.

Absorbability of calcium from calcium-bound phosphoryl oligosaccharides in comparison with that from various calcium compounds in the rat ligated jejunum loop.

Science.gov (United States)

To-o, Kenji; Kamasaka, Hiroshi; Nishimura, Takahisa; Kuriki, Takashi; Saeki, Shigeru; Nakabou, Yukihiro

2003-08-01

Calcium-bound phosphoryl oligosaccharides (POs-Ca) were prepared from potato starch. Their solubility and in situ absorbability as a calcium source were investigated by comparing with the soluble calcium compounds, calcium chloride and calcium lactate, or insoluble calcium compounds, calcium carbonate and dibasic calcium phosphate. The solubility of POs-Ca was as high as that of calcium chloride and about 3-fold higher than that of calcium lactate. An in situ experiment showed that the intestinal calcium absorption rate of POs-Ca was almost comparable with that of the soluble calcium compounds, and was significantly higher (pcalcium groups. Moreover, the total absorption rate of a 1:1 mixture of the calcium from POs-Ca and a whey mineral complex (WMC) was significantly higher (psoluble calcium source with relatively high absorption in the intestinal tract.

Fabrication of cell-benign inverse opal hydrogels for three-dimensional cell culture.

Science.gov (United States)

Im, Pilseon; Ji, Dong Hwan; Kim, Min Kyung; Kim, Jaeyun

2017-05-15

Inverse opal hydrogels (IOHs) for cell culture were fabricated and optimized using calcium-crosslinked alginate microbeads as sacrificial template and gelatin as a matrix. In contrast to traditional three-dimensional (3D) scaffolds, the gelatin IOHs allowed the utilization of both the macropore surface and inner matrix for cell co-culture. In order to remove templates efficiently for the construction of 3D interconnected macropores and to maintain high cell viability during the template removal process using EDTA solution, various factors in fabrication, including alginate viscosity, alginate concentration, alginate microbeads size, crosslinking calcium concentration, and gelatin network density were investigated. Low viscosity alginate, lower crosslinking calcium ion concentration, and lower concentration of alginate and gelatin were found to obtain high viability of cells encapsulated in the gelatin matrix after removal of the alginate template by EDTA treatment by allowing rapid dissociation and diffusion of alginate polymers. Based on the optimized fabrication conditions, gelatin IOHs showed good potential as a cell co-culture system, applicable to tissue engineering and cancer research. Copyright © 2017 Elsevier Inc. All rights reserved.

Preparation of Macroporous Poly (vinyl alcohol-co-triallyl isocyanurate) Beads Bearing Aminocarboxylic Acid as Functional Groups by Suspension Polymerization

Institute of Scientific and Technical Information of China (English)

无

2003-01-01

Macroporous poly (vinyl acetate-co-triallyl isocyanurate) beads were prepared with suspension polymerization method. The copolymer beads were then transformed into poly (vinyl alcohol-co-triallyl isocyanurate) by ester exchange reaction. Aminocarboxylic acids were immobilized on the copolymer beads by the esterification of hydroxyl groups with diethyl-lenetriaminepentaacetic bisanhydride. The weak acid exchange capacities, specific surface areas and mean pore diameters of the resultant resin beads were measured.

Get Enough Calcium

Science.gov (United States)

... Calcium Print This Topic En español Get Enough Calcium Browse Sections The Basics Overview Foods and Vitamins ... women, don't get enough calcium. How much calcium do I need every day? Women: If you ...

The Effects of Dietary Calcium and/or Iron Deficiency upon Murine Intestinal Calcium Binding Protein Activity and Calcium Absorption

OpenAIRE

McDonald, Catherine M.

1980-01-01

Iron deficiency has been shown to impair calcium absorption, leading to decreased bone mass. Vitamin D3-dependent calcium binding protein (CaBP) has been demonstrated to be necessary for the active transport of calcium in the intestine of numerous species. Iron deficiency might affect the activity of the calcium binding protein. Four experimental diets were formulated as follows: Diet 1, iron adequate, calcium adequate; Diet 2, iron deficient, calcium adequate; Diet 3, iron adequate, calci...

Effects of diphosphonate on kidney calcium content and duodenal absorption of 45calcium

International Nuclear Information System (INIS)

Goulding, A.; Cameron, V.

1978-01-01

In rats the relationships between EHDP-induced changes in serum calcium concentration, kidney calcium content and duodenal transport of 45 calcium were studied. Body weights and kidney weights were similar in all groups. EHDP administration was associated with an increase in serum calcium concentration and kidney calcium content, and a decrease in duodenal 45 calcium transport. In the EHDP-treated rats, there was a significant negative correlation between kidney calcium concentration and duodenal 45 calcium transport but no correlation between either kidney calcium content and serum calcium concentration (r = 0.116) or between serum calcium concentration and duodenal 45 calcium transport (r = 0.02). Further experiments will be needed to determine whether the demonstrated increase in kidney calcium content induced by EHDP administration was the cause of, or was secondary to, inhibition of 1, 25(OH) 2 D 3 synthesis. (orig./AJ) [de

Effect of lowering dietary calcium intake on fractional whole body calcium retention

International Nuclear Information System (INIS)

Dawson-Hughes, B.; Stern, D.T.; Shipp, C.C.; Rasmussen, H.M.

1988-01-01

Although fractional calcium absorption is known to vary inversely with calcium intake, the extent and timing of individual hormonal and calcium absorption responses to altered calcium intake have not been defined. We measured fractional whole body retention of orally ingested 47 Ca, an index of calcium absorption, in nine normal women after they had eaten a 2000-mg calcium diet for 8 weeks and a 300-mg calcium diet for 1, 2, 4, and 8 weeks. After the diet change, serum intact PTH (32.2% increase; P = 0.005), serum 1,25-dihydroxyvitamin D [1,25-(OH)2D; 43.8% increase; P = 0.003], and fractional whole body calcium retention (42.8% increase; P = 0.004) increased within 1 week. Although the PTH and calcium retention responses remained fairly constant throughout the low calcium intake period, serum 1,25-(OH)2D concentrations declined toward baseline after week 1. Thus, the late increase in calcium retention may have resulted from calcium absorption that was independent of 1,25-(OH)2D stimulation

CFD Analysis of Fuel Atomization, Secondary Droplet Breakup and Spray Dispersion in the Premix Duct of a LPP Combustor

NARCIS (Netherlands)

Schmehl, R.; Maier, G.; Wittig, S.

2000-01-01

The two phase flow in the premix duct of a LPP combustor is computed using a Lagrangian droplet tracking method. To reproduce the characteristic spray structure of an air-assisted pressure-swirl atomizer, a sheet spray model is de-rived from measured sheet parameters and combined with an advanced

Hierarchically Macroporous Graphitic Nanowebs Exhibiting Ultra-fast and Stable Charge Storage Performance

Science.gov (United States)

Yun, Young Soo

2018-02-01

The macro/microstructures of carbon-based electrode materials for supercapacitor applications play a key role in their electrochemical performance. In this study, hierarchically macroporous graphitic nanowebs (HM-GNWs) were prepared from bacterial cellulose by high-temperature heating at 2400 °C. The HM-GNWs were composed of well-developed graphitic nanobuilding blocks with a high aspect ratio, which was entangled as a nanoweb structure. The morphological and microstructural characteristics of the HM-GNWs resulted in remarkable charge storage performance. In particular, the HM-GNWs exhibited very fast charge storage behaviors at scan rates ranging from 5 to 100 V s-1, in which area capacitances ranging from 8.9 to 3.8 mF cm-2 were achieved. In addition, 97% capacitance retention was observed after long-term cycling for more than 1,000,000 cycles.

Large-eddy simulation of a bluff-body stabilised turbulent premixed flame using the transported flame surface density approach

Science.gov (United States)

Lee, Chin Yik; Cant, Stewart

2017-07-01

A premixed propane-air flame stabilised on a triangular bluff body in a model jet-engine afterburner configuration is investigated using large-eddy simulation (LES). The reaction rate source term for turbulent premixed combustion is closed using the transported flame surface density (TFSD) model. In this approach, there is no need to assume local equilibrium between the generation and destruction of subgrid FSD, as commonly done in simple algebraic closure models. Instead, the key processes that create and destroy FSD are accounted for explicitly. This allows the model to capture large-scale unsteady flame propagation in the presence of combustion instabilities, or in situations where the flame encounters progressive wrinkling with time. In this study, comprehensive validation of the numerical method is carried out. For the non-reacting flow, good agreement for both the time-averaged and root-mean-square velocity fields are obtained, and the Karman type vortex shedding behaviour seen in the experiment is well represented. For the reacting flow, two mesh configurations are used to investigate the sensitivity of the LES results to the numerical resolution. Profiles for the velocity and temperature fields exhibit good agreement with the experimental data for both the coarse and dense mesh. This demonstrates the capability of LES coupled with the TFSD approach in representing the highly unsteady premixed combustion observed in this configuration. The instantaneous flow pattern and turbulent flame behaviour are discussed, and the differences between the non-reacting and reacting flow are described through visualisation of vortical structures and their interaction with the flame. Lastly, the generation and destruction of FSD are evaluated by examining the individual terms in the FSD transport equation. Localised regions where straining, curvature and propagation are each dominant are observed, highlighting the importance of non-equilibrium effects of FSD generation and

Carbon nanotube-coated macroporous sponge for microbial fuel cell electrodes

KAUST Repository

Xie, Xing

2012-01-01

The materials that are used to make electrodes and their internal structures significantly affect microbial fuel cell (MFC) performance. In this study, we describe a carbon nanotube (CNT)-sponge composite prepared by coating a sponge with CNTs. Compared to the CNT-coated textile electrodes evaluated in prior studies, CNT-sponge electrodes had lower internal resistance, greater stability, more tunable and uniform macroporous structure (pores up to 1 mm in diameter), and improved mechanical properties. The CNT-sponge composite also provided a three-dimensional scaffold that was favorable for microbial colonization and catalytic decoration. Using a batch-fed H-shaped MFC outfitted with CNT-sponge electrodes, an areal power density of 1.24 W m -2 was achieved when treating domestic wastewater. The maximum volumetric power density of a continuously fed plate-shaped MFC was 182 W m -3. To our knowledge, these are the highest values obtained to date for MFCs fed domestic wastewater: 2.5 times the previously reported maximum areal power density and 12 times the previously reported maximum volumetric power density. © 2011 The Royal Society of Chemistry.

Dual-Function Electrocatalytic and Macroporous Hollow-Fiber Cathode for Converting Waste Streams to Valuable Resources Using Microbial Electrochemical Systems

KAUST Repository

Katuri, Krishna; Kalathil, Shafeer; Ragab, Ala'a; Bian, Bin; AlQahtani, Manal Faisal; Pant, Deepak; Saikaly, Pascal

2018-01-01

Dual-function electrocatalytic and macroporous hollow-fiber cathodes are recently proposed as promising advanced material for maximizing the conversion of waste streams such as wastewater and waste CO2 to valuable resources (e.g., clean freshwater, energy, value-added chemicals) in microbial electrochemical systems. The first part of this progress report reviews recent developments in this type of cathode architecture for the simultaneous recovery of clean freshwater and energy from wastewater. Critical insights are provided on suitable materials for fabricating these cathodes, as well as addressing some challenges in the fabrication process with proposed strategies to overcome them. The second and complementary part of the progress report highlights how the unique features of this cathode architecture can solve one of the intrinsic bottlenecks (gas-liquid mass transfer limitation) in the application of microbial electrochemical systems for CO2 reduction to value-added products. Strategies to further improve the availability of CO2 to microbial catalysts on the cathode are proposed. The importance of understanding microbe-cathode interactions, as well as electron transfer mechanisms at the cathode-cell and cell-cell interface to better design dual-function macroporous hollow-fiber cathodes, is critically discussed with insights on how the choice of material is important in facilitating direct electron transfer versus mediated electron transfer.

Mechanosensation across borders: fibroblasts inside a macroporous scaffold sense and respond to the mechanical environment beyond the scaffold walls.

Science.gov (United States)

Könnig, D; Herrera, A; Duda, G N; Petersen, A

2018-01-01

In tissue defects, cells face distinct mechanical boundary conditions, but how this influences early stages of tissue regeneration remains largely unknown. Biomaterials are used to fill defects but also to provide specific mechanical or geometrical signals. However, they might at the same time shield mechanical information from surrounding tissues that is relevant for tissue functionalisation. This study investigated how fibroblasts in a soft macroporous biomaterial scaffold respond to distinct mechanical environments while they form microtissues. Different boundary stiffnesses counteracting scaffold contraction were provided via a newly developed in vitro setup. Online monitoring over 14 days revealed 3.0 times lower microtissue contraction but 1.6 times higher contraction force for high vs. low stiffness. This difference was significant already after 48 h, a very early stage of microtissue growth. The microtissue's mechanical and geometrical adaptation indicated a collective cellular behaviour and mechanical communication across scaffold pore walls. Surprisingly, the stiffness of the environment influenced cell behaviour even inside macroporous scaffolds where direct cell-cell contacts are hindered. Mechanical communication between cells via traction forces is essential for tissue adaptation to the environment and should not be blocked by rigid biomaterials. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Dual-Function Electrocatalytic and Macroporous Hollow-Fiber Cathode for Converting Waste Streams to Valuable Resources Using Microbial Electrochemical Systems

KAUST Repository

Katuri, Krishna

2018-04-30

Dual-function electrocatalytic and macroporous hollow-fiber cathodes are recently proposed as promising advanced material for maximizing the conversion of waste streams such as wastewater and waste CO2 to valuable resources (e.g., clean freshwater, energy, value-added chemicals) in microbial electrochemical systems. The first part of this progress report reviews recent developments in this type of cathode architecture for the simultaneous recovery of clean freshwater and energy from wastewater. Critical insights are provided on suitable materials for fabricating these cathodes, as well as addressing some challenges in the fabrication process with proposed strategies to overcome them. The second and complementary part of the progress report highlights how the unique features of this cathode architecture can solve one of the intrinsic bottlenecks (gas-liquid mass transfer limitation) in the application of microbial electrochemical systems for CO2 reduction to value-added products. Strategies to further improve the availability of CO2 to microbial catalysts on the cathode are proposed. The importance of understanding microbe-cathode interactions, as well as electron transfer mechanisms at the cathode-cell and cell-cell interface to better design dual-function macroporous hollow-fiber cathodes, is critically discussed with insights on how the choice of material is important in facilitating direct electron transfer versus mediated electron transfer.

Rhombohedral iron trifluoride with a hierarchized macroporous/mesoporous texture from gaseous fluorination of iron disilicide

Energy Technology Data Exchange (ETDEWEB)

Guérin, Katia, E-mail: katia.araujo_da_silva@univ-bpclermont.fr [Université Clermont Auvergne, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6296, ICCF, F-63171 Aubière (France); Delbègue, Diane; Louvain, Nicolas; Doubtsof, Léa; Hamwi, André [Université Clermont Auvergne, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6296, ICCF, F-63171 Aubière (France); Laik, Barbara; Pereira-Ramos, Jean-Pierre [Université Paris Est Créteil, Institut de Chimie et des Matériaux Paris-Est, UMR CNRS 7182, Thiais (France); Tahar-sougrati, Moulay; Jumas, Jean-Claude [Université Montpellier II, Institut Charles Gerhardt de Montpellier, UMR CNRS 5253, Montpellier (France); Willmann, Patrick; Cénac-Morthe, Céline [Centre National d' Etudes Spatiales, Toulouse (France)

2016-04-15

Stable low temperature rhombohedral iron trifluoride has been obtained by the fluorination under the pure fluorine gas of iron disilicide. The combination of both unusual fluorination process and precursor avoids to get unhydrated crystalline FeF{sub 3} particles and allows the formation of hierarchized channels of mesoporous/macroporous texture favorable for lithium diffusion. The fluorination mechanism proceeds by temperature steps from the formation, for a fluorination temperature below 200 °C, of an amorphous phase and an intermediate iron difluoride identified mainly by {sup 57}Fe Mössbauer spectroscopy before getting, as soon as a fluorination temperature of 260 °C is reached, the rhombohedral FeF{sub 3}. Both amorphous and crystallized samples display good ability for electrochemical process when used as cathode in lithium-ion battery. The low diameter of rhombohedral structure channels is balanced by an appropriate mesoporous texture and a capacity of 225 mAh.g{sup −1} after 5 cycles for a discharge cut-off of 2.5 V vs. Li{sup +}/Li at a current density of C/20 has been obtained and stabilized at 95 mAh.g{sup −1} after 116 cycles. - Highlights: • We investigated the synthesis of rhombohedral FeF{sub 3} by solid–gas reaction from iron disilicide. • We demonstrated that depending on the fluorination temperature various phases are stabilized. • We got a hierarchized macroporous/mesoporous texture. • We studied the electrochemical performances of amorphous and crystallized FeF{sub 3}. • Crystallized FeF{sub 3} presents a high faradic yield at first cycle focusing on insertion process.

Angiogenesis in calcium phosphate scaffolds by inorganic copper ion release.

Science.gov (United States)

Barralet, Jake; Gbureck, Uwe; Habibovic, Pamela; Vorndran, Elke; Gerard, Catherine; Doillon, Charles J

2009-07-01

Angiogenesis in a tissue-engineered device may be induced by incorporating growth factors (e.g., vascular endothelial growth factor [VEGF]), genetically modified cells, and=or vascular cells. It represents an important process during the formation and repair of tissue and is essential for nourishment and supply of reparative and immunological cells. Inorganic angiogenic factors, such as copper ions, are therefore of interest in the fields of regenerative medicine and tissue engineering due to their low cost, higher stability, and potentially greater safety compared with recombinant proteins or genetic engineering approaches. The purpose of this study was to compare tissue responses to 3D printed macroporous bioceramic scaffolds implanted in mice that had been loaded with either VEGF or copper sulfate. These factors were spatially localized at the end of a single macropore some 7 mm from the surface of the scaffold. Controls without angiogenic factors exhibited only poor tissue growth within the blocks; in contrast, low doses of copper sulfate led to the formation of microvessels oriented along the macropore axis. Further, wound tissue ingrowth was particularly sensitive to the quantity of copper sulfate and was enhanced at specific concentrations or in combination with VEGF. The potential to accelerate and guide angiogenesis and wound healing by copper ion release without the expense of inductive protein(s) is highly attractive in the area of tissue-engineered bone and offers significant future potential in the field of regenerative biomaterials.

Calcium signals can freely cross the nuclear envelope in hippocampal neurons: somatic calcium increases generate nuclear calcium transients

Directory of Open Access Journals (Sweden)

Bading Hilmar

2007-07-01

Full Text Available Abstract Background In hippocampal neurons, nuclear calcium signaling is important for learning- and neuronal survival-associated gene expression. However, it is unknown whether calcium signals generated by neuronal activity at the cell membrane and propagated to the soma can unrestrictedly cross the nuclear envelope to invade the nucleus. The nuclear envelope, which allows ion transit via the nuclear pore complex, may represent a barrier for calcium and has been suggested to insulate the nucleus from activity-induced cytoplasmic calcium transients in some cell types. Results Using laser-assisted uncaging of caged calcium compounds in defined sub-cellular domains, we show here that the nuclear compartment border does not represent a barrier for calcium signals in hippocampal neurons. Although passive diffusion of molecules between the cytosol and the nucleoplasm may be modulated through changes in conformational state of the nuclear pore complex, we found no evidence for a gating mechanism for calcium movement across the nuclear border. Conclusion Thus, the nuclear envelope does not spatially restrict calcium transients to the somatic cytosol but allows calcium signals to freely enter the cell nucleus to trigger genomic events.

Calcium hydroxide isotope effect in calcium isotope enrichment by ion exchange

International Nuclear Information System (INIS)

Jepson, B.E.; Shockey, G.C.

1984-01-01

The enrichment of calcium isotopes has been observed in ion-exchange chromatography with an aqueous phase of calcium hydroxide and a solid phase of sulfonic acid resin. The band front was exceedingly sharp as a result of the acid-base reaction occuring at the front of the band. Single-stage separation coefficients were found to be epsilon( 44 Ca/ 40 Ca) = 11 x 10 -4 and epsilon( 48 Ca/ 40 Ca) = 18 x 10 -4 . The maximum column separation factors achieved were 1.05 for calcium-44 and 1.09 for calcium-48 with the heavy isotopes enriching in the fluid phase. The calcium isotope effect between fully hydrated aqueous calcium ions and undissociated aqueous calcium hydroxide was estimated. For the calcium-44/40 isotope pair the separation coefficient was 13 x 10 -4 . 20 references, 2 figures

Novel three-dimensionally ordered macroporous Fe{sup 3+}-doped TiO{sub 2} photocatalysts for H{sub 2} production and degradation applications

Energy Technology Data Exchange (ETDEWEB)

Yan, Xiaoqing; Xue, Chao; Yang, Bolun; Yang, Guidong, E-mail: guidongyang@xjtu.edu.cn

2017-02-01

Highlights: • 3DOM Fe{sup 3+}-doped TiO{sub 2} photocatalyst was prepared. • 3DOM structure showed high activity for decomposition of the RhB and the generation of H{sub 2}. • 3DOM structure provided interfacial reaction sites and optical absorption active sites. • The energy level from Fe{sup 3+} centers were existed in the band gap of TiO{sub 2}. • 3DOM structure promoted the separation of charge carriers. - Abstract: Novel three-dimensionally ordered macroporous (3DOM) Fe{sup 3+}-doped TiO{sub 2} photocatalysts were prepared using a colloidal crystal template method with low-cost raw material including ferric trichloride, isopropanol, tetrabutyl titanate and polymethyl methacrylate. The as-prepared 3DOM Fe{sup 3+}-doped TiO{sub 2} photocatalysts were characterized by various analytical techniques. TEM and SEM results showed that the obtained photocatalysts possess well-ordered macroporous structure in three dimensional orientations. As proved by XPS and EDX analysis that Fe{sup 3+} ions have been introduced TiO{sub 2} lattice and the doped Fe{sup 3+} ions can act as the electron acceptor/donor centers to significantly enhance the electron transfer from the bulk to surface of TiO{sub 2}, resulting in more electrons could take part in the oxygen reduction process thereby decreasing the recombination rate of photogenerated charges. Meanwhile, the 3DOM architecture with the feature of interfacial chemical reaction active sites and optical absorption active sites is remarkably favorable for the reactant transfer and light trapping in the photoreaction process. As a result, the 3DOM Fe{sup 3+}-doped TiO{sub 2} photocatalysts show the considerably higher photocatalytic activity for decomposition of the Rhodamine B (RhB) and the generation of hydrogen under visible light irradiation due to the synergistic effects of open, interconnected macroporous network and metal ion doping.

Hydrogen-hydrocarbon turbulent non-premixed flame structure

Energy Technology Data Exchange (ETDEWEB)

Tabet, F. [ANSYS-Benelux, 4 Avenue Pasteur, B-1300 Wavre (Belgium); Sarh, B.; Goekalp, I. [Institut de Combustion, Aerothermique, Reactivite et Environnement (ICARE), Centre National de la Recherche Scientifique (CNRS), 1 C avenue de la recherche scientifique, Orleans 45071 Cedex 2 (France)

2009-06-15

In this study, the structure of turbulent non-premixed CH{sub 4}-H{sub 2}/air flames is analyzed with a special emphasis on mixing and air entrainment. The amount of H{sub 2} in the fuel mixture varies under constant volumetric fuel flow. Mixing is described by mixture fraction and its variance while air entrainment is characterized by the ratio of gas mass flow to fuel mass flow at the inlet section. The flow field and the chemistry are coupled by the flamelet assumption. Mixture fraction and its variance are transported by the computational fluid dynamics (CFD) code. The slow chemistry aspect of NO{sub x} is handled by solving an additional transport equation with a source term derived from flamelet library. The results obtained show an improvement of mixing with hydrogen addition leading to a strong consumption of CH{sub 4} and a high air entrainment into the centerline region. As a global effect of this, the composite fuels burn faster and thereby reduce the residence time which ultimately shortens the flame length and thickness. On the other hand, hydrogen is found to increase NO{sub x} level. (author)

Measurements of Turbulent Flame Speed and Integral Length Scales in a Lean Stationary Premixed Flame

OpenAIRE

Klingmann, Jens; Johansson, Bengt

1998-01-01

Turbulent premixed natural gas - air flame velocities have been measured in a stationary axi-symmetric burner using LDA. The flame was stabilized by letting the flow retard toward a stagnation plate downstream of the burner exit. Turbulence was generated by letting the flow pass through a plate with drilled holes. Three different hole diameters were used, 3, 6 and 10 mm, in order to achieve different turbulent length scales. Turbulent integral length scales were measured using two-point LD...

Management of Type 2 diabetes in Ramadan: Low-ratio premix insulin working group practical advice

OpenAIRE

Mohamed Hassanein; Mohamed Belhadj; Khalifa Abdallah; Arpan D Bhattacharya; Awadhesh K Singh; Khaled Tayeb; Monira Al-Arouj; Awad Elghweiry; Hinde Iraqi; Mohamed Nazeer; Henda Jamoussi; Mouna Mnif; Abdulrazzaq Al-Madani; Hossam Al-Ali; Robert Ligthelm

2014-01-01

The challenge of insulin use during Ramadan could be minimized, if people with diabetes are metabolically stable and are provided with structured education for at least 2–3 months pre-Ramadan. Although, American diabetes association (ADA) recommendations 2010 and South Asian Consensus Guideline 2012 deal with management of diabetes in Ramadan and changes in insulin dosage, no specific guidance on widely prescribed low-ratio premix insulin is currently available. Hence, the working group for i...

An experimental and kinetic modeling study of premixed NH3/CH4/O-2/Ar flames at low pressure

DEFF Research Database (Denmark)

Tian, Z.Y.; Li, Y. Y.; Zhang, L. D.

2009-01-01

An experimental and modeling study of 11 premixed NH3/CH4/O-2/Ar flames at low pressure (4.0 kPa) with the same equivalence ratio of 1.0 is reported. Combustion intermediates and products are identified using tunable synchrotron vacuum Ultraviolet (VUV) photoionization and molecular-beam mass...

Calcium

Science.gov (United States)

... You can get decent amounts of calcium from baked beans, navy beans, white beans, and others. Canned fish. You're in luck if you like sardines and canned salmon with bones. Almond milk. Working Calcium Into Your ...

Influence of dietary calcium on bone calcium utilization

International Nuclear Information System (INIS)

Farmer, M.; Roland, D.A. Sr.; Clark, A.J.

1986-01-01

In Experiment 1, 10 microCi 45 Ca/day were administered to 125 hens for 10 days. Hens were then allocated to five treatments with calcium levels ranging from .08 to 3.75% of the diet. In Experiment 2, hens with morning oviposition times were randomly allocated to 11 treatments that were periods of time postoviposition ranging from 6 hr to 24 hr, in 2-hr increments (Experiment 2). At the end of each 2-hr period, eggs from 25 hens were removed from the uterus. The 18-, 20-, and 22-hr treatments were replicated three times. In Experiment 3, hens were fed either ad libitum or feed was withheld the last 5 or 6 hr before oviposition. In Experiment 4, hens were fed 10 microCi of 45 Ca for 15 days to label skeletal calcium. Hens were divided into two groups and fed a .08 or 3.75% calcium diet for 2 days. On the second day, 25 hens fed the 3.75% calcium diet were intubated with 7 g of the same diet containing .5 g calcium at 1700, 2100, 0100, 0500, and 0700 hr. The measurements used were egg weight, shell weight, and 45 Ca content of the egg shell. Results indicated a significant linear or quadratic regression of dietary calcium levels on 45 Ca accumulation in eggshells and eggshell weight (Experiment 1). As the calcium level of the diet increased, eggshell weight increased and 45 Ca recovery decreased. Utilization of skeletal calcium for shell formation ranged from 28 to 96%. In Experiment 2, the rate of shell calcification was not constant throughout the calcification process but varied significantly

Calcium D-saccharate

DEFF Research Database (Denmark)

Garcia, André Castilho; Hedegaard, Martina Vavrusova; Skibsted, Leif Horsfelt

2016-01-01

Molar conductivity of saturated aqueous solutions of calcium d-saccharate, used as a stabilizer of beverages fortified with calcium d-gluconate, increases strongly upon dilution, indicating complex formation between calcium and d-saccharate ions, for which, at 25 °C, Kassoc = 1032 ± 80, ΔHassoc......° = -34 ± 6 kJ mol-1, and ΔSassoc° = -55 ± 9 J mol-1 K-1, were determined electrochemically. Calcium d-saccharate is sparingly soluble, with a solubility product, Ksp, of (6.17 ± 0.32) × 10-7 at 25 °C, only moderately increasing with the temperature: ΔHsol° = 48 ± 2 kJ mol-1, and ΔSassoc° = 42 ± 7 J mol-1...... K-1. Equilibria in supersaturated solutions of calcium d-saccharate seem only to adjust slowly, as seen from calcium activity measurements in calcium d-saccharate solutions made supersaturated by cooling. Solutions formed by isothermal dissolution of calcium d-gluconate in aqueous potassium d...

CSP-based chemical kinetics mechanisms simplification strategy for non-premixed combustion: An application to hybrid rocket propulsion

KAUST Repository

Ciottoli, Pietro P.

2017-08-14

A set of simplified chemical kinetics mechanisms for hybrid rocket applications using gaseous oxygen (GOX) and hydroxyl-terminated polybutadiene (HTPB) is proposed. The starting point is a 561-species, 2538-reactions, detailed chemical kinetics mechanism for hydrocarbon combustion. This mechanism is used for predictions of the oxidation of butadiene, the primary HTPB pyrolysis product. A Computational Singular Perturbation (CSP) based simplification strategy for non-premixed combustion is proposed. The simplification algorithm is fed with the steady-solutions of classical flamelet equations, these being representative of the non-premixed nature of the combustion processes characterizing a hybrid rocket combustion chamber. The adopted flamelet steady-state solutions are obtained employing pure butadiene and gaseous oxygen as fuel and oxidizer boundary conditions, respectively, for a range of imposed values of strain rate and background pressure. Three simplified chemical mechanisms, each comprising less than 20 species, are obtained for three different pressure values, 3, 17, and 36 bar, selected in accordance with an experimental test campaign of lab-scale hybrid rocket static firings. Finally, a comprehensive strategy is shown to provide simplified mechanisms capable of reproducing the main flame features in the whole pressure range considered.

Study on the Enhancement Effect of Dielectric Barrier Discharge on the Premixed Methane/Oxygen/Helium Flame Velocity

International Nuclear Information System (INIS)

Mu Haibao; Yu Lin; Li Ping; Zhang Guanjun; Tang Chenglong; Wang Jinhua

2015-01-01

Recently, plasma-assisted combustion has become a potentially applicable technology in many combustion scenarios. In this paper, a dielectric barrier discharge (DBD) plasma generator is designed to explore the effect of plasma on the CH4 oxidation process, and several properties of combustion are considered. First, in the presence or absence of plasma discharge, physical appearance of the flame is examined and analyzed. Second, the flame propagation velocity is calculated by the flame front extracted from the imaging data with the Bunsen burner method. Finally, the main molecular components and their intensity variation in the flame and the plasma zones are identified with an emission spectrograph to analyze the effect of active species on the combustion process. We also discuss the possible kinetic regime of plasma-assisted combustion. Experimental results imply that plasma discharge applied to the premixed CH4/O2/He mixture significantly raises the flame speed with equivalence ratios ranging from 0.85 to 1.10, with the flame speed improved by 17% to 35%. It can be seen that plasma can improve methane oxidation efficiency in the premixed fuel/oxidizer, especially at a low equivalence ratio. (paper)

Effects of CT Number-Derived Matrix Density on Preferential Flow 1 and Transport in a Macroporous Agricultural Soil

DEFF Research Database (Denmark)

Katuwal, Sheela; Moldrup, Per; Lamandé, Mathieu

2015-01-01

risks to public health. This study was focused on establishing links between the structural pore space and preferential transport using a combination of standard physical measurement methods for air and water permeabilities, breakthrough experiments, and X-ray Computed Tomography (CT) on large soil...... columns. Substantial structural heterogeneity that resulted in significant variations of flow and tracer transport was observed, despite the textural similarity of investigated samples. Quantification of macropore characteristics with X-ray CT was useful but not sufficient to explain the variability...

Sub-grid scale combustion models for large eddy simulation of unsteady premixed flame propagation around obstacles.

Science.gov (United States)

Di Sarli, Valeria; Di Benedetto, Almerinda; Russo, Gennaro

2010-08-15

In this work, an assessment of different sub-grid scale (sgs) combustion models proposed for large eddy simulation (LES) of steady turbulent premixed combustion (Colin et al., Phys. Fluids 12 (2000) 1843-1863; Flohr and Pitsch, Proc. CTR Summer Program, 2000, pp. 61-82; Kim and Menon, Combust. Sci. Technol. 160 (2000) 119-150; Charlette et al., Combust. Flame 131 (2002) 159-180; Pitsch and Duchamp de Lageneste, Proc. Combust. Inst. 29 (2002) 2001-2008) was performed to identify the model that best predicts unsteady flame propagation in gas explosions. Numerical results were compared to the experimental data by Patel et al. (Proc. Combust. Inst. 29 (2002) 1849-1854) for premixed deflagrating flame in a vented chamber in the presence of three sequential obstacles. It is found that all sgs combustion models are able to reproduce qualitatively the experiment in terms of step of flame acceleration and deceleration around each obstacle, and shape of the propagating flame. Without adjusting any constants and parameters, the sgs model by Charlette et al. also provides satisfactory quantitative predictions for flame speed and pressure peak. Conversely, the sgs combustion models other than Charlette et al. give correct predictions only after an ad hoc tuning of constants and parameters. Copyright 2010 Elsevier B.V. All rights reserved.

Estimation of presynaptic calcium currents and endogenous calcium buffers at the frog neuromuscular junction with two different calcium fluorescent dyes.

Science.gov (United States)

Samigullin, Dmitry; Fatikhov, Nijaz; Khaziev, Eduard; Skorinkin, Andrey; Nikolsky, Eugeny; Bukharaeva, Ellya

2014-01-01

At the frog neuromuscular junction, under physiological conditions, the direct measurement of calcium currents and of the concentration of intracellular calcium buffers-which determine the kinetics of calcium concentration and neurotransmitter release from the nerve terminal-has hitherto been technically impossible. With the aim of quantifying both Ca(2+) currents and the intracellular calcium buffers, we measured fluorescence signals from nerve terminals loaded with the low-affinity calcium dye Magnesium Green or the high-affinity dye Oregon Green BAPTA-1, simultaneously with microelectrode recordings of nerve-action potentials and end-plate currents. The action-potential-induced fluorescence signals in the nerve terminals developed much more slowly than the postsynaptic response. To clarify the reasons for this observation and to define a spatiotemporal profile of intracellular calcium and of the concentration of mobile and fixed calcium buffers, mathematical modeling was employed. The best approximations of the experimental calcium transients for both calcium dyes were obtained when the calcium current had an amplitude of 1.6 ± 0.08 pA and a half-decay time of 1.2 ± 0.06 ms, and when the concentrations of mobile and fixed calcium buffers were 250 ± 13 μM and 8 ± 0.4 mM, respectively. High concentrations of endogenous buffers define the time course of calcium transients after an action potential in the axoplasm, and may modify synaptic plasticity.

Kinetic parameters, collision rates, energy exchanges and transport coefficients of non-thermal electrons in premixed flames at sub-breakdown electric field strengths

KAUST Repository

Bisetti, Fabrizio; El Morsli, Mbark

2014-01-01

The effects of an electric field on the collision rates, energy exchanges and transport properties of electrons in premixed flames are investigated via solutions to the Boltzmann kinetic equation. The case of high electric field strength, which

Effect of the superposition of a dielectric barrier discharge onto a premixed gas burner flame

Science.gov (United States)

Zaima, Kazunori; Takada, Noriharu; Sasaki, Koichi

2011-10-01

We are investigating combustion control with the help of nonequilibrium plasma. In this work, we examined the effect of dielectric barrier discharge (DBD) on a premixed burner flame with CH4/O2/Ar gas mixture. The premixed burner flame was covered with a quartz tube. A copper electrode was attached on the outside of the quartz tube, and it was connected to a high-voltage power supply. DBD inside the quartz tube was obtained between the copper electrode and the grounded nozzle of the burner which was placed at the bottom of the quartz tube. We clearly observed that the flame length was shortened by superposing DBD onto the bottom part of the flame. The shortened flame length indicates the enhancement of the burning velocity. We measured the optical emission spectra from the bottom region of the flame. As a result, we observed clear line emissions from Ar, which were never observed from the flame without DBD. We evaluated the rotational temperatures of OH and CH radicals by spectral fitting. As a result, the rotational temperature of CH was not changed, and the rotational temperature of OH was decreased by the superposition of DBD. According to these results, it is considered that the enhancement of the burning velocity is not caused by gas heating. New reaction pathways are suggested.

Measurement of OH radical density in DBD-enhanced premixed burner flame by laser-induced fluorescence

Science.gov (United States)

Zaima, Kazunori; Sasaki, Koichi

2013-09-01

We examined OH density in DBD-enhanced premixed burner flame by laser-induced fluorescence (LIF). We ignited a premixed flame with CH4 /O2 / Ar mixture using a burner which worked as the ground electrode. The upper part of the flame was covered with a quartz tube, and we attached an aluminum electrode on the outside of the quartz tube. DBD inside the quartz tube was obtained between the aluminum electrode and the burner nozzle. The planar beam from a pulsed tunable laser excited OH in X2 Π (v'' = 0) to A2Σ+ (v' = 0) , and we captured two-dimensional distribution of the LIF intensity using an ICCD camera. We employed three pump lines of Q1(J=4, 8 and 10), and the rotational temperature of OH(X) was deduced from the ratio of the LIF intensities. The total density of OH was obtained from the LIF intensities and the rotational temperature. A principal experimental result was that no remarkable increase was observed in the OH density by the superposition of DBD. The correlation between the pulsed discharge current and the temporal variation of the OH density was not clear, suggesting that the oscillation of the OH density with a small amplitude is related to the transittion time constant between equilibrium and nonequilibrium combustion chemistries.

Adsorption kinetics, isotherm, and thermodynamics studies of acetyl-11-keto-β-boswellic acids (AKBA) from Boswellia serrata extract using macroporous resin.

Science.gov (United States)

Niphadkar, Sonali S; Rathod, Virendra K

2017-09-14

An acetyl-11-keto-β-boswellic acid (AKBA) is potent anti-inflammatory agent found in Boswellia serrata oleogum resin. Adsorption characteristics of AKBA from B. serrata were studied using macroporous adsorbent resin to understand separation and adsorption mechanism of targeted molecules. Different macroporous resins were screened for adsorption and desorption of AKBA and Indion 830 was screened as it showed higher adsorption capacity. The kinetic equations were studied and results showed that the adsorption of AKBA on Indion 830 was well fitted to the pseudo first-order kinetic model. The influence of two parameters such as temperature (298, 303, and 308 K) and pH (5-8) on the adsorption process was also studied. The experimental data was further investigated using Langmuir, Freundlich, and Temkin isotherm models. It was observed that Langmuir isotherm model was found to be the best fit for AKBA adsorption by Indion 830 and highest adsorption capacity (50.34 mg/g) was obtained at temperature of 303 K. The values of thermodynamic parameters such as the change of Gibbs free energy (ΔG*), entropy (ΔS*), and enthalpy (ΔH*), indicated that the process of adsorption was spontaneous, favourable, and exothermic.

A multi-scaled hybrid orthopedic implant: bone ECM-shaped Sr-HA nanofibers on the microporous walls of a macroporous titanium scaffold.

Science.gov (United States)

Han, Yong; Zhou, Jianhong; Zhang, Lan; Xu, Kewei

2011-07-08

We report here, for the first time, a novel multi-scaled hybrid orthopedic implant material consisting of a macroporous Ti scaffold, whose macropores' walls have a microporous titania layer which is fully covered with nanofibers of Sr-doped hydroxyapatite (Sr-HA). The microporous titania layer is formed on and within the Ti scaffold by micro-arc oxidation, which firmly binds to the Ti substrate and contains Ca2+, Sr2+ and PO4(3-) ions. It is then hydrothermally treated to form Sr-HA nanofibers. During the hydrothermal treatment, Sr-HA nanoprisms nucleate from Ca0.5Sr0.5TiO3 pre-formed on the TiO2 and grow in length to nanofibers at the expense of Ca2+, Sr2+ and PO4(3-) ions that migrate from the TiO2. These Sr-HA nanofibers construct a network structure similar to the hierarchical organization of bone extracellular matrix (ECM), and the resulting nanofibrous surface displays a firm adhesion to substrate, superhydrophilicity and apatite-inducing ability. The induced apatite prefers to nucleate on the basal-faceted surfaces of Sr-HA nanofibers. The nanofiber-walled scaffold has a great potential for load-bearing orthotopic use.

Research of calcium oxide hydration in calcium nitrate solutions

Directory of Open Access Journals (Sweden)

M.A. Oliynyk

2016-09-01

Full Text Available Mineral fertilizers are one of the important factors of agriculture intensification and increasing of food products quantity. The volume of fertilizers production and its domestic consumption in Ukraine indicate that nitrogen fertilizer using only comes nearer to the required number of science-based. One of the most widespread artificial fertilizers is the calcium nitrate. Aim: The aim is to study and theoretically substantiate the processes occurring in the preparation of suspensions of calcium hydroxide Са(ОН2 in solution of calcium nitrate Ca(NО32. Materials and Methods: The technical calcium oxide (quicklime DSTU BV.2.7-90-99, solutions of calcium nitrate of 15, 20, 25, 30, 35 and 40% Ca(NО32 concentrations were used in the work. The content of lime in the preparation of a suspension in the solution changed (in terms of calcium oxide CaO from 150 g/dm3 to the maximum possible. Each of these solutions saturated at 40°С in lime to maximum concentration. Suitable for use in these experiments and in the technology of calcium nitrate obtaining are considered the solutions (suspensions that within 12 hours did not lose their mobility (transportability. Results: The experimental results show that increasing of the concentration of calcium nitrate in solution within the range 15...40%, the amount of lime that you can put into the solution without loss of transportability decreases. Further increasing of lime quantity in solutions concentrations causes to its solidifying, loss of mobility (transportability. Calculations showed that in the presence of calcium nitrate the solubility of Са(ОН2 is reduced nearly by order that can lead to the formation of calcium oxide CaO the solid phase Са(ОН2 on the surface, which also can form hydrogen bonds with the components of the solution. As the probability of formation of hydrogen bonds in solutions is high, there is a possibility of formation of clusters.

Effect of the mixing fields on the stability and structure of turbulent partially premixed flames in a concentric flow conical nozzle burner

KAUST Repository

Mansour, Mohy S.; Elbaz, Ayman M.; Roberts, William L.; Senosy, Mohamed S.; Zayed, Mohamed F.; Juddoo, Mrinal; Masri, Assaad R.

2016-01-01

of partially premixed methane flames. The mixing field in a concentric flow conical nozzle (CFCN) burner with well-controlled mechanism of the mixing is investigated using Rayleigh scattering technique. The flame stability, structure and flow field of some

Fabrication of porous bioceramics for bone tissue applications using luffa cylindrical fibres (LCF as template

Directory of Open Access Journals (Sweden)

Mazen Alshaaer

2017-03-01

Full Text Available Three-dimensionally ordered macroporous biomaterials containing hydroxyapatite were synthesized using natural luffa cylindrical fibres (with diameter of 100–400 µm as templates. The preliminary evaluation of this novel method for production of porous bioceramics showed promising potential applications in bone tissue engineering. The produced bioceramics were subjected to microstructural, physical, mechanical, and in vitro characterisation. Mercury intrusion porosimetry, supported by SEM analysis, showed the presence of bimodal porosity (smaller pores with diameters of 10 to 30 µm and cylindrical macropores with diameters from 100 to 400 µm and 60% of the interconnected porosity. These porous calcium phosphate ceramics proved to be bioactive and exhibited mechanical properties comparable to those of natural spongy bones with compressive strength up to 3 MPa and elastic modulus in compression around 0.05 GPa. In vitro characterization of the porous ceramics showed cells attaching to the apatite crystals that make up the scaffold matrix. Cell adhesion resulted in elongated and highly stretched cells within the macropores with focal adhesion points on the scaffolds. Moreover, the cells adhered to the calcium phosphate cement (CPC and developed cytoplasmic extensions as shown by SEM imagery. Their proliferation in the scaffolds in culture demonstrates that the scaffold architecture is suitable for Mesenchymal stem cells seeding and growth.

Production of precipitated calcium carbonate from calcium silicates and carbon dioxide

International Nuclear Information System (INIS)

Teir, Sebastian; Eloneva, Sanni; Zevenhoven, Ron

2005-01-01

The possibilities for reducing carbon dioxide emissions from the pulp and paper industry by calcium carbonation are presented. The current precipitated calcium carbonate (PCC) production uses mined, crushed calcium carbonate as raw materials. If calcium silicates were used instead, carbon dioxide emissions from the calcination of carbonates would be eliminated. In Finland, there could, thus, be a potential for eliminating 200 kt of carbon dioxide emissions per year, considering only the PCC used in the pulp and paper industry. A preliminary investigation of the feasibility to produce PCC from calcium silicates and the potential to replace calcium carbonate as the raw material was made. Calcium carbonate can be manufactured from calcium silicates by various methods, but only a few have been experimentally verified. The possibility and feasibility of these methods as a replacement for the current PCC production process was studied by thermodynamic equilibrium calculations using HSC software and process modelling using Aspen Plus[reg]. The results from the process modelling showed that a process that uses acetic acid for extraction of the calcium ions is a high potential option for sequestering carbon dioxide by mineral carbonation. The main obstacle seems to be the limited availability and relatively high price of wollastonite, which is a mineral with high calcium silicate content. An alternative is to use the more common, but also more complex, basalt rock instead

Estimation of presynaptic calcium currents and endogenous calcium buffers at the frog neuromuscular junction with two different calcium fluorescent dyes

Directory of Open Access Journals (Sweden)

Dmitry eSamigullin

2015-01-01

Full Text Available At the frog neuromuscular junction, under physiological conditions, the direct measurement of calcium currents and of the concentration of intracellular calcium buffers—which determine the kinetics of calcium concentration and neurotransmitter release from the nerve terminal—has hitherto been technically impossible. With the aim of quantifying both Ca2+ currents and the intracellular calcium buffers, we measured fluorescence signals from nerve terminals loaded with the low-affinity calcium dye Magnesium Green or the high-affinity dye Oregon Green BAPTA-1, simultaneously with microelectrode recordings of nerve-action potentials and end-plate currents. The action-potential-induced fluorescence signals in the nerve terminals developed much more slowly than the postsynaptic response. To clarify the reasons for this observation and to define a spatiotemporal profile of intracellular calcium and of the concentration of mobile and fixed calcium buffers, mathematical modeling was employed. The best approximations of the experimental calcium transients for both calcium dyes were obtained when the calcium current had an amplitude of 1.6 ± 0.08 рА and a half-decay time of 1.2 ± 0.06 ms, and when the concentrations of mobile and fixed calcium buffers were 250 ± 13 µM and 8 ± 0.4 mM, respectively. High concentrations of endogenous buffers define the time course of calcium transients after an action potential in the axoplasm, and may modify synaptic plasticity.

Calcium electroporation in three cell lines; a comparison of bleomycin and calcium, calcium compounds, and pulsing conditions

DEFF Research Database (Denmark)

Frandsen, Stine Krog; Gissel, Hanne; Hojman, Pernille

2013-01-01

offers several advantages over standard treatment options: calcium is inexpensive and may readily be applied without special precautions, as is the case with cytostatic drugs. Therefore, details on the use of calcium electroporation are essential for carrying out clinical trials comparing calcium...

The Utilization of Premix Flour with Sorghum Mutant Lines Zh-30 Based as Material For Dough Making And Dry Noodle Industry

International Nuclear Information System (INIS)

Dwi Djoko Slamet Santosa

2009-01-01

Sorghum mutant line Zh-30 is a breeding line developed at the Center for the Application of Isotope and Radiation Technology, BATAN by using mutation techniques. Gamma irradiation with the dose of 300 Gy was used to induced plant genetic variability. Through selection processes on several generations, the mutant line Zh-30 was identified to have better agronomic characteristics, better grain quality and higher yield than the original variety. Research on flour quality of this mutant line was done to identify its potential use in dry noodle. Subsequent experiments, i.e. the effect of kansui (alkaline salt Na 2 CO 3 and K 2 CO 3 ) on rheological properties of dough, the effect of egg addition on rheological properties of dough and cooked noodles. Observations were done on dough which were premix flour I, II and III with 10.2 %, 14.5 % and 17.4 % protein content respectively. The influence of each alkaline salt and their mixture on dough rheology i.e., dough consistency and resistant to extension and extensibility. The kansui Concentration applied were 0, 0.5, 1.0 and 1.5 %. Obviously premix flour I + 0.5 % kansui gave optimal consistency, resistance and extensibility of the dough. The addition of five ml egg to premix I dough + 0.5 % kansui gave optimal results. The increase of egg mellowed the dough, and increase noodle texture and reduce stickiness. Addition of five ml egg already gave significant increase of elasticity, with the highest elasticity was reached by addition of 35 ml egg, although no difference was found for 5 - 35 ml.. (author)

Transcellular transport of calcium

Energy Technology Data Exchange (ETDEWEB)

Terepka, A R; Coleman, J R; Armbrecht, H J; Gunter, T E

1976-01-01

Studies of two calcium transporting epithelia, embryonic chick chorioallantoic membrane and the small intestine of rat and chick, have strongly suggested that the transfer of calcium across a cell involves processes distinctly different from intracellular calcium ion regulation. In the proposed model, transcellular calcium transport is considered as a specialized process developed only by certain cells in those tissues charged with bulk transfer of calcium. The overall effect of the endocytotic mechanism is bulk calcium movement across a cell, protection of mitochondria from exposure to high concentrations of calcium, and the avoidance of wide and potentially toxic fluctuations in cytosol ionic calcium levels. (MFB)

Incipient Soot Formation in Rich Partially Premixed Flames under High Pressure Conditions of Relevance to Compression-Ignition Engines

Science.gov (United States)

2017-09-09

a Laminar Premixed Flame, Aerosol Reaction Engineering , Center for Aerosol science and Engineering (CASE) Workshop 2016, Saint Louis, Missouri, May...Publication Type: Conference Paper or Presentation Conference Name: Aerosol Reaction Engineering , Center for Aerosol science and Engineering (CASE...measurements of critical soot precursors up to 3-ring aromatics is available online to modelers to improve the chemical reaction mechanism [24]. To give a

Calcium hydroxide poisoning

Science.gov (United States)

Hydrate - calcium; Lime milk; Slaked lime ... Calcium hydroxide ... These products contain calcium hydroxide: Cement Limewater Many industrial solvents and cleaners (hundreds to thousands of construction products, flooring strippers, brick cleaners, cement ...

Study of the synthesis of TiO2 layers on macroporous ceramic supports in supercritical (SC) CO2 for processing radioactive aqueous effluents in dynamic mode

International Nuclear Information System (INIS)

Duchateau, Maxime

2014-01-01

Public and military nuclear industry generates a significant amount of radioactive liquid waste which must be treated before being released into the environment. Decontamination methods alternative to the industrial techniques (evaporation, chemical treatment) are being developed, such as column treatments or coupled filtration/sorption processes. Current researches mainly focus on the development and shaping of specific sorbents. In this context, the objectives of this thesis were first to study the synthesis of TiO 2 layers on macroporous ceramic supports in supercritical (SC) CO 2 and then to evaluate their potential for radionuclide extraction in these alternative processes. A robust synthesis method has been developed, based on the thermal decomposition of titanium isopropoxide in SC CO 2 in the temperature range between 150 C and 350 C. Nano-structured TiO 2 films were formed on the macroporous supports (ceramic foams, tubular α-alumina supports) with good adhesion, already at 150 C. The effect of the synthesis temperature on sorbents physico-chemical characteristics and sorption properties has been studied with TiO 2 powders prepared under the same conditions as the supported films. The best sorption performance were observed for the powder prepared at 150 C, owing to its higher density of surface sites in comparison with powders prepared at either 250 C or 350 C. Consequently, this synthesis temperature (150 C) was selected for a detailed study of the composite sorbents (TiO 2 /support), in order to assess their sorption performance in continuous treatment processes. The sorption experiments have shown that a column of alumina macroporous foam (Φpore = 400μm) coated with TiO 2 was suitable for processing effluents in dynamic mode with high throughputs. Both macro-pore sizes and column height were revealed as important parameters to be controlled. For the coupled filtration/sorption treatment, TiO 2 membranes exhibit good mechanical strength and are able

Kinetics of calcium sulfoaluminate formation from tricalcium aluminate, calcium sulfate and calcium oxide

International Nuclear Information System (INIS)

Li, Xuerun; Zhang, Yu; Shen, Xiaodong; Wang, Qianqian; Pan, Zhigang

2014-01-01

The formation kinetics of tricalcium aluminate (C 3 A) and calcium sulfate yielding calcium sulfoaluminate (C 4 A 3 $) and the decomposition kinetics of calcium sulfoaluminate were investigated by sintering a mixture of synthetic C 3 A and gypsum. The quantitative analysis of the phase composition was performed by X-ray powder diffraction analysis using the Rietveld method. The results showed that the formation reaction 3Ca 3 Al 2 O 6 + CaSO 4 → Ca 4 Al 6 O 12 (SO 4 ) + 6CaO was the primary reaction 4 Al 6 O 12 (SO 4 ) + 10CaO → 6Ca 3 Al 2 O 6 + 2SO 2 ↑ + O 2 ↑ primarily occurred beyond 1350 °C with an activation energy of 792 ± 64 kJ/mol. The optimal formation region for C 4 A 3 $ was from 1150 °C to 1350 °C and from 6 h to 1 h, which could provide useful information on the formation of C 4 A 3 $ containing clinkers. The Jander diffusion model was feasible for the formation and decomposition of calcium sulfoaluminate. Ca 2+ and SO 4 2− were the diffusive species in both the formation and decomposition reactions. -- Highlights: •Formation and decomposition of calcium sulphoaluminate were studied. •Decomposition of calcium sulphoaluminate combined CaO and yielded C 3 A. •Activation energy for formation was 231 ± 42 kJ/mol. •Activation energy for decomposition was 792 ± 64 kJ/mol. •Both the formation and decomposition were controlled by diffusion

Why Calcium? How Calcium Became the Best Communicator*

Science.gov (United States)

Carafoli, Ernesto; Krebs, Joachim

2016-01-01

Calcium carries messages to virtually all important functions of cells. Although it was already active in unicellular organisms, its role became universally important after the transition to multicellular life. In this Minireview, we explore how calcium ended up in this privileged position. Most likely its unique coordination chemistry was a decisive factor as it makes its binding by complex molecules particularly easy even in the presence of large excesses of other cations, e.g. magnesium. Its free concentration within cells can thus be maintained at the very low levels demanded by the signaling function. A large cadre of proteins has evolved to bind or transport calcium. They all contribute to buffer it within cells, but a number of them also decode its message for the benefit of the target. The most important of these “calcium sensors” are the EF-hand proteins. Calcium is an ambivalent messenger. Although essential to the correct functioning of cell processes, if not carefully controlled spatially and temporally within cells, it generates variously severe cell dysfunctions, and even cell death. PMID:27462077

Codissolution of calcium hydrogenphosphate and sodium hydrogencitrate in water. Spontaneous supersaturation of calcium citrate increasing calcium bioavailability

DEFF Research Database (Denmark)

Hedegaard, Martina Vavrusova; Danielsen, Bente Pia; Garcia, André Castilho

2018-01-01

The sparingly soluble calcium hydrogenphosphate dihydrate, co-dissolving in water during dissolution of freely soluble sodium hydrogencitrate sesquihydrate as caused by proton transfer from hydrogencitrate to hydrogenphosphate, was found to form homogenous solutions supersaturated by a factor up...... to 8 in calcium citrate tetrahydrate. A critical hydrogencitrate concentration for formation of homogeneous solutions was found to depend linearly on dissolved calcium hydrogenphosphate: [HCitr2-] = 14[CaHPO4] - 0.05 at 25 °C. The lag phase for precipitation of calcium citrate tetrahydrate......, as identified from FT-IR spectra, from these spontaneously formed supersaturated solutions was several hours, and the time to reach solubility equilibrium was several days. Initial calcium ion activity was found to be almost independent of the degree of supersaturation as determined electrochemically...

Calcium blood test

Science.gov (United States)

... page: //medlineplus.gov/ency/article/003477.htm Calcium blood test To use the sharing features on this page, please enable JavaScript. The calcium blood test measures the level of calcium in the blood. ...

A study on the amount of pilot injection and its effects on rich and lean boundaries of the premixed CNG/air mixture for a CNG/diesel dual-fuel engine

Energy Technology Data Exchange (ETDEWEB)

Zhiqiang Lin; Wanhua Su [Tianjin University (China). State Key Laboratory of Engines

2003-07-01

A sequential port injection, lean-burn, fully electronically-controlled compressed natural gas (CNG)/diesel dual-fuel engine has been developed based on a turbo-charged and inter-cooled direct injection (D.I.) diesel engine. During the optimisation of engine overall performance, the effects of pilot diesel and premixed CNG/air mixture equivalence ratio on emissions (CO, HC, NO{sub x}, soot), knocking, misfire and fuel economy are studied. The rich and lean boundaries of the premixed CNG/air mixture versus engine load are also provided, considering the acceptable values of NO{sub x} and THC emissions, respectively. It is interesting to find that there is a critical amount of pilot diesel for each load and speed point, which proved to be the optimum amount of pilot fuel. Any decrease in the amount of pilot diesel from this optimum amount results in an increase of NO{sub x} emissions, because the premixed CNG/air mixture must be made richer, otherwise THC emissions would increase. However, the soot emissions remain almost unchanged at a very low level. (author)

Formation of photoluminescent n-type macroporous silicon: Effect of magnetic field and lateral electric potential

Energy Technology Data Exchange (ETDEWEB)

Antunez, E.E. [Centro de Investigación en Ingeniería y Ciencias Aplicadas, UAEM, Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos, CP 62210 (Mexico); Estevez, J.O. [Instituto de Física, B. Universidad Autónoma de Puebla, A.P. J-48, Puebla 72570 (Mexico); Campos, J. [Instituto de Energías Renovables, UNAM, Priv. Xochicalco S/N, Temixco, Morelos, CP 62580 (Mexico); Basurto-Pensado, M.A. [Centro de Investigación en Ingeniería y Ciencias Aplicadas, UAEM, Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos, CP 62210 (Mexico); Agarwal, V., E-mail: vagarwal@uaem.mx [Centro de Investigación en Ingeniería y Ciencias Aplicadas, UAEM, Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos, CP 62210 (Mexico)

2014-11-15

Metal electrode-free electrochemical etching of low doped n-type silicon substrates, under the combined effect of magnetic and lateral electric field, is used to fabricate photoluminescent n-type porous silicon structures in dark conditions. A lateral gradient in terms of structural characteristics (i.e. thickness and pore dimensions) along the electric field direction is formed. Enhancement of electric and magnetic field resulted in the increase of pore density and a change in the shape of the macropore structure, from circular to square morphology. Broad photoluminescence (PL) emission from 500 to 800 nm, with a PL peak wavelength ranging from 571 to 642 nm, is attributed to the wide range of microporous features present on the porous silicon layer.

Analysis of Flavonoids in Lotus (Nelumbo nucifera Leaves and Their Antioxidant Activity Using Macroporous Resin Chromatography Coupled with LC-MS/MS and Antioxidant Biochemical Assays

Directory of Open Access Journals (Sweden)

Ming-Zhi Zhu

2015-06-01

Full Text Available Lotus (Nelumbo nucifera leaves, a traditional Chinese medicinal herb, are rich in flavonoids. In an effort to thoroughly analyze their flavonoid components, macroporous resin chromatography coupled with HPLC-MS/MS was employed to simultaneously enrich and identify flavonoids from lotus leaves. Flavonoids extracted from lotus leaves were selectively enriched in the macroporous resin column, eluted subsequently as fraction II, and successively subjected to analysis with the HPLC-MS/MS and bioactivity assays. Altogether, fourteen flavonoids were identified, four of which were identified from lotus leaves for the first time, including quercetin 3-O-rhamnopyranosyl-(1→2-glucopyranoside, quercetin 3-O-arabinoside, diosmetin 7-O-hexose, and isorhamnetin 3-O-arabino- pyranosyl-(1→2-glucopyranoside. Further bioactivity assays revealed that these flavonoids from lotus leaves possess strong antioxidant activity, and demonstrate very good potential to be explored as food supplements or even pharmaceutical products to improve human health.

Calcium carbonate overdose

Science.gov (United States)

Tums overdose; Calcium overdose ... Calcium carbonate can be dangerous in large amounts. ... Products that contain calcium carbonate are certain: Antacids (Tums, Chooz) Mineral supplements Hand lotions Vitamin and mineral supplements Other products may also contain ...

3D-macroporous chitosan-based scaffolds with in situ formed Pd and Pt nanoparticles for nitrophenol reduction.

Science.gov (United States)

Berillo, Dmitriy; Cundy, Andrew

2018-07-15

3D-macroporous chitosan-based scaffolds (cryogels) were produced via growth of metal-polymer coordinated complexes and electrostatic interactions between oppositely charged groups of chitosan and metal ions under subzero temperatures. A mechanism of reduction of noble metal complexes inside the cryogel walls by glutaraldehyde is proposed, which produces discrete and dispersed noble metal nanoparticles. 3D-macroporous scaffolds prepared under different conditions were characterised using TGA, FTIR, nitrogen adsorption, SEM, EDX and TEM, and the distribution of platinum nanoparticles (PtNPs) and palladium nanoparticles (PdNPs) in the material assessed. The catalytic activity of the in situ synthesised PdNPs, at 2.6, 12.5 and 21.0 μg total mass, respectively, was studied utilising a model system of 4-nitrophenol reduction. The kinetics of the reaction under different conditions (temperature, concentration of catalyst) were examined, and a decrease of catalytic activity was not observed over 17 treatment cycles. Increasing the temperature of the catalytic reaction from 10 to 22 and 35 °C by PdNPs supported within the cryogel increased the kinetic rate by 44 and 126%, respectively. Turnover number and turnover frequency of the PdNPs catalysts at room temperature were in the range 0.20-0.53 h -1 . The conversion degree of 4-nitrophenol at room temperature reached 98.9% (21.0 μg PdNPs). Significantly less mass of palladium nanoparticles (by 30-40 times) was needed compared to published data to obtain comparable rates of reduction of 4-nitrophenol. Copyright © 2018 Elsevier Ltd. All rights reserved.

Calcium: the molecular basis of calcium action in biology and medicine

National Research Council Canada - National Science Library

Pochet, Roland; Donato, Rosario

2000-01-01

... of Calcium Calcium Signalling in Excitable Cells Ca2+ Release in Muscle Cells by N. Macrez and J. Mironneau Calcium Signalling in Neurons Exemplified by Rat Sympathetic Ganglion Cells by S.J. M...

Study of the structure of 3D-ordered macroporous GaN-ZnS:Mn nanocomposite films

Energy Technology Data Exchange (ETDEWEB)

Kurdyukov, D. A., E-mail: kurd@gvg.ioffe.ru; Shishkin, I. I.; Grudinkin, S. A.; Sitnikova, A. A.; Zamoryanskaya, M. V.; Golubev, V. G. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

2015-05-15

A film-type 3D-ordered macroporous GaN-ZnS:Mn nanocomposite with the structure of an inverted opal is fabricated. Structural studies of the nanocomposite are performed, and it is shown that GaN and ZnS:Mn introduced into the pores of the silica opal are nanocrystallites misoriented with respect to each other. It is shown that the nanocomposite is a structurally perfect 3D photonic crystal. The efficiency of using a buffer of GaN crystallites to preclude interaction between the surface of the spherical a-SiO{sub 2} particles forming the opal matrix and chemically active substances introduced into the pores is demonstrated.

Calcium source (image)

Science.gov (United States)

Getting enough calcium to keep bones from thinning throughout a person's life may be made more difficult if that person has ... as a tendency toward kidney stones, for avoiding calcium-rich food sources. Calcium deficiency also effects the ...

Study of high load operation limit for premixed compression ignition engine; Yokongo asshuku chakka kikan no kofuka unten genkai ni kansuru kosatsu

Energy Technology Data Exchange (ETDEWEB)

Shimazaki, N. [Isuzu Advanced Engineering Center Ltd., Kanagawa (Japan); Akagawa, H. [Nissan Diesel Motor Co. Ltd., Saitama (Japan); Tsujimura, K. [Chiba Institute of Technology, Chiba (Japan); Miyamoto, T.

2000-11-25

NO{sub x} emission was remarkably reduced by PREDIC (PREmixed lean DIesel Combustion) system in which fuel was injected at very early stage of compression stroke and the major part of the fuel is considered to be burned with self-ignition of premixed charge around TDC. However PREDIC system had some problems, a restriction of a high load operation was one of these problems. In order to investigate the combustion characteristics of PREDIC at the richer operation limit, a test engine was operated with gaseous fuel-air mixture where less heterogeneous mixture can be formed than that of conventional diesel engines. A steep pressure rise or the abrupt increase in NO{sub x} emission determined the richer operation limit. This was at 2 to 2.4 of excess air ratio. Supercharging operation enabled the high load operation more than 2.4 of excess air ratio. (author)

Numerical Investigation of Soot Formation in Non-premixed Flames

KAUST Repository

Abdelgadir, Ahmed Gamaleldin

2017-05-01

Soot is a carbon particulate formed as a result of the combustion of fossil fuels. Due to the health hazard posed by the carbon particulate, government agencies have applied strict regulations to control soot emissions from road vehicles, airplanes, and industrial plants. Thus, understanding soot formation and evolution is critical. Practical combustion devices operate at high pressure and in the turbulent regime. Elevated pressures and turbulence on soot formation significantly and fundamental understanding of these complex interactions is still poor. In this study, the effects of pressure and turbulence on soot formation and growth are investigated numerically. As the first step, the evolution of the particle size distribution function (PSDF) and soot particles morphology are investigated in turbulent non-premixed flames. A Direct Simulation Monte Carlo (DSMC) code is developed and used. The stochastic reactor describes the evolution of soot in fluid parcels following Lagrangian trajectories in a turbulent flow field. The trajectories are sampled from a Direct Numerical Simulation (DNS) of an n-heptane turbulent non-premixed flame. Although individual trajectories display strong bimodality as in laminar flames, the ensemble-average PSDF possesses only one mode and a broad tail, which implies significant polydispersity induced by turbulence. Secondly, the effect of the flow and mixing fields on soot formation at atmospheric and elevated pressures is investigated in coflow laminar diffusion flames. The experimental observation and the numerical prediction of the spatial distribution are in good agreement. Based on the common scaling methodology of the flames (keeping the Reynolds number constant), the scalar dissipation rate decreases as pressure increases, promoting the formation of PAH species and soot. The decrease of the scalar dissipation rate significantly contributes to soot formation occurring closer to the nozzle and outward on the flames wings as pressure

LES of the interaction between a premixed flame and complex turbulent swirling flow

International Nuclear Information System (INIS)

Iudiciani, P; Duwig, C; Szasz, R Z; Fuchs, L; Gutmark, E

2011-01-01

In this paper the Triple Annular Research Swirler, a fuel injector characterized by complex design with three concentric air passages, has been studied numerically. A swirl-stabilized lean premixed flame has been simulated by means of Large Eddy Simulation. The computations characterize successfully the dynamics of the flame and their interactions with the complex swirling flow. The flame is stabilized upstream the fuel injector exit, and the dynamics are led by a Precessing Vortex Core which seems to originate in the inner air passage. The results obtained by Proper Orthogonal Decomposition analysis are in agreement with previous findings in the context of swirling flows/flames.

Calcium ferrite formation from the thermolysis of calcium tris (maleato)

Indian Academy of Sciences (India)

For preparing calcium ferrite, calcium tris (maleato) ferrate(III) precursor was prepared by mixing aqueous solutions of iron(III) maleate, calcium maleate and maleic acid. Various physico-chemical techniques i.e. TG, DTG, DTA, Mössbauer, XRD, IR etc have been used to study the decomposition behaviour from ambient to ...

Numerical study of the effect of inlet geometry on combustion instabilities in a lean premixed swirl combustor

Energy Technology Data Exchange (ETDEWEB)

Lee, Chang Eon [Dept. of Mechanical Engineering, Inha University, Incheon (Korea, Republic of); Park, Seul Hyun [Dept. of Mechanical Systems Engineering, Chosun University, Gwangju (Korea, Republic of); Hwang, Cheol Hong [Dept. of Fire and Disaster Prevention, Daejeon University, Daejeon (Korea, Republic of)

2016-11-15

The effects of flow structure and flame dynamics on combustion instabilities in a lean premixed swirl combustor were numerically investigated using Large eddy simulation (LES) by varying the inlet geometry of combustor. The dynamic ksgs-equation and G-equation flamelet models were respectively employed as the LES subgrid models of turbulence and combustion. The divergent half angle (α) in the combustor inlet was varied systematically from 30° to 90° to quantify the effect of inlet geometry on the combustion instabilities. This variation caused considerable deformation in recirculation zones in terms of their size and location, leading to significant changes in flame dynamics. Analysis of unsteady pressure distributions in the combustor showed that the largest damping caused by combustion instabilities takes place at α = 45°, and the amplitude of acoustic pressure oscillation is largest at α = 30°. Examination of local Rayleigh parameters indicated that controlling flame-vortex interactions by modifying inlet geometry can change the local characteristics of combustion instabilities in terms of their amplification and suppression, and thus serve as a useful approach to reduce the instabilities in a lean premixed swirl combustor. These phenomena were studied in detail through unsteady analysis associated with flow and flame dynamics.

Numerical study of the effect of inlet geometry on combustion instabilities in a lean premixed swirl combustor

International Nuclear Information System (INIS)

Lee, Chang Eon; Park, Seul Hyun; Hwang, Cheol Hong

2016-01-01

The effects of flow structure and flame dynamics on combustion instabilities in a lean premixed swirl combustor were numerically investigated using Large eddy simulation (LES) by varying the inlet geometry of combustor. The dynamic ksgs-equation and G-equation flamelet models were respectively employed as the LES subgrid models of turbulence and combustion. The divergent half angle (α) in the combustor inlet was varied systematically from 30° to 90° to quantify the effect of inlet geometry on the combustion instabilities. This variation caused considerable deformation in recirculation zones in terms of their size and location, leading to significant changes in flame dynamics. Analysis of unsteady pressure distributions in the combustor showed that the largest damping caused by combustion instabilities takes place at α = 45°, and the amplitude of acoustic pressure oscillation is largest at α = 30°. Examination of local Rayleigh parameters indicated that controlling flame-vortex interactions by modifying inlet geometry can change the local characteristics of combustion instabilities in terms of their amplification and suppression, and thus serve as a useful approach to reduce the instabilities in a lean premixed swirl combustor. These phenomena were studied in detail through unsteady analysis associated with flow and flame dynamics

Chemiluminescence-based multivariate sensing of local equivalence ratios in premixed atmospheric methane-air flames

Energy Technology Data Exchange (ETDEWEB)

Tripathi, Markandey M.; Krishnan, Sundar R.; Srinivasan, Kalyan K.; Yueh, Fang-Yu; Singh, Jagdish P.

2011-09-07

Chemiluminescence emissions from OH*, CH*, C2, and CO2 formed within the reaction zone of premixed flames depend upon the fuel-air equivalence ratio in the burning mixture. In the present paper, a new partial least square regression (PLS-R) based multivariate sensing methodology is investigated and compared with an OH*/CH* intensity ratio-based calibration model for sensing equivalence ratio in atmospheric methane-air premixed flames. Five replications of spectral data at nine different equivalence ratios ranging from 0.73 to 1.48 were used in the calibration of both models. During model development, the PLS-R model was initially validated with the calibration data set using the leave-one-out cross validation technique. Since the PLS-R model used the entire raw spectral intensities, it did not need the nonlinear background subtraction of CO2 emission that is required for typical OH*/CH* intensity ratio calibrations. An unbiased spectral data set (not used in the PLS-R model development), for 28 different equivalence ratio conditions ranging from 0.71 to 1.67, was used to predict equivalence ratios using the PLS-R and the intensity ratio calibration models. It was found that the equivalence ratios predicted with the PLS-R based multivariate calibration model matched the experimentally measured equivalence ratios within 7%; whereas, the OH*/CH* intensity ratio calibration grossly underpredicted equivalence ratios in comparison to measured equivalence ratios, especially under rich conditions ( > 1.2). The practical implications of the chemiluminescence-based multivariate equivalence ratio sensing methodology are also discussed.

Application of polymeric macroporous supports for temperature-responsive chromatography of pharmaceuticals.

Science.gov (United States)

Lamprou, Alexandros; Gavriilidou, Agni-Faviola-Mika; Storti, Giuseppe; Soos, Miroslav; Morbidelli, Massimo

2015-08-14

A macroporous particulate support prepared previously by reactive gelation under shear and functionalized with poly(N-isopropylacrylamide), PNIPAM, brushes of variable length is applied for temperature-responsive chromatography, whereby temperature modulates hydrophobic interactions. Several different analytes, including small pharmaceuticals, peptides, proteins and monoclonal antibodies are employed. Contrary to the most commonly observed behavior in conventional chromatography, increasing retention is observed at elevated temperatures. Peak broadening is quantified using the peak standard deviation, which depends on both the polymer chain conformation and analyte adsorptivity. The favorable effect of grafted polymer thickness on retention becomes progressively less pronounced for thicker grafted PNIPAM layers. The effect of eluent composition on solute-sorbent interactions was investigated by introducing NaCl, methanol, dioxane and by varying the pH. Salt or organic solvent addition affects apart from the analytes solution properties, the hydrophobicity of the stationary phase itself. Frontal analyses performed at different temperatures to determine dynamic binding capacities, indicate small mass transfer resistances imposed by this novel packing material. Copyright © 2015 Elsevier B.V. All rights reserved.