180,255 research outputs found
A novel three-phase UPS system with a single-phase resonant HF link
No full textThis paper presents a new three-phase uninterruptible power supply (UPS) system based on a single-phase resonant high frequency (HF) link and a single-phase transformer. The three-phase output voltage is constructed and regulated from a three-phase cycloconverter fed from the constant amplitude, constant frequency link voltage. The generation of a novel switching stategy for the three-phase cycloconverter is presented. The simulation of the proposed system is carried out and verified with experimental results
Development of a novel fully coupled solver in OpenFOAM: Steady-state incompressible turbulent flows
No full textIn this work a block coupled algorithm for the solution of three-dimensional incompressible turbulent flows is presented. A cell-centered finite-volume method for unstructured grids is employed. The interequation coupling of the incompressible Navier-Stokes equations is obtained using a SIMPLE-type algorithm with a Rhie-Chow interpolation technique. Due to the simultaneous solution of momentum and continuity equations, implicit block coupling of pressure and velocity variables leads to faster convergence compared to classical, loosely coupled, segregated algorithms of the SIMPLE family of algorithms. This gain in convergence speed is accompanied by an improvement in numerical robustness. Additionally, a two-equation eddy viscosity turbulence model is solved in a segregated fashion. The substnatially improved performance of the block coupled approach compared to the segregated approach is demonstrated in a set of test cases. It is shown that the scalability of the coupled solution algorithm with increasing numbers of cells is nearly linear. To achieve this scalability, an algebraic multigrid solver for block coupled systems of equations has been implemented and used as linear solver for the system of block equations. The presented algorithm has been entirely embedded into the leading open-source computational fluid dynamics (CFD) library OpenFOAM. © 2014 Taylor and Francis Group, LLC.Benzi M, 2005, ACT NUMERIC, V14, P1, DOI 10.1017-S0962492904000212; Brandt A., 1977, MATH COMPUT; Casartelli E., 2012, INT C EXH INN APPR G; DACLESMARIANI J, 1995, AIAA J, V33, P1561, DOI 10.2514-3.12826; Darwish M., 2001, NUMER HEAT TRANSFE B; Darwish M., 2000, INT J NUMER METH FLU; Darwish M., 2003, INT J HEAT MASS TRAN; Darwish M., 2008, J COMPUT PHYS; Darwish M., 2004, NUMER HEAT TRANSFE B; de Lemos MJS, 2000, NUMER HEAT TR B-FUND, V37, P489; Doormaal J. V., 1986, NAT HEAT TRANSF C DE; Doormaal J. V., 1984, NUMER HEAT TRANSFER; Federenko R., ZH VYCHISL MAT MAT F, P922; Ferziger J., 1994, COMPUTATIONAL METHOD; Hutchinson B., 1986, NUMER HEAT TRANSFER; Keller S., 2004, P 10 BRAZ C THERM SC; Laia Y. G., 1997, NUMER HEAT TRANSFE B, V32, P267; Menter F., 1994, AIAA J; Menter F. R., 2003, TURBULENCE HEAT MASS; Moukalled F., 2000, NUMER HEAT TRANSFE B; Muzaferija S., 1994, THESIS U LONDON LOND; Patankar S., 1972, INT J HEAT MASS TRAN; Patankar S. V., 1980, NUMERICAL HEAT TRANS; Poussin F., 1968, SIAM J NUMER ANAL; Rhie C., 1983, AIAA J; Singh D., 2013, NUMER HEAT TRANSFE A; Vradis C., 1998, NUMERICAL HEAT TRANS, V33, P79; Weller H., 1998, COMPUT PHYS; Woodfield PL, 2003, NUMER HEAT TR B-FUND, V43, P403, DOI 10.1080-104077903901221223
Title: Laser Induced Self-Action Phenomena in a Photopolymerisable Medium, Author: Ana B. Villafranca, Location: Mills
No full textTitle: Shared Water Resources in the Great Lakes and in the Jordan River Basin: Comparative Models in Inter-Juristicational Water Management, Author: Abdel R Darwish, Location: MillsThe period from 1909 to 1987 could be characterized as achieving notable successes in the management of the Great Lakes waters. The successes during this interval provide important lessons for shared water resources elsewhere. However, the period from 1987 forward saw more obstacles in restoring and maintaining the waters in the Great Lakes
basin. Since 1987, progress toward delisting and restoring beneficial uses in the most degraded locations known as the geographic Areas of Concern (AOCs) (e.g. the St. Clair and Detroit Rivers) has been slow. Cleanup and restoration actions have been completed for only five of the 43 AOCs that were identified in the Great Lakes basin. Meanwhile, in the Jordan River basin, various bilateral agreements were signed to divide and manage
the water resources but with little success, with the exception of the successes achieved between Jordan and Israel on the Aqaba Gulf. These successes provide lessons for other parts in the world that are attempting to achieve effective transboundary environmental outcomes. This thesis examines the factors that impede progress in the restoration of the
beneficial uses in the St. Clair and Detroit Rivers AOCs and provides recommendations to advance implementation of the restoration process for the two rivers. This thesis also examines the conflict and the agreements over the shared water resources in the Jordan River basin and proposes a model consisting of three elements (political, socio-economic,
and scientific) to create sustainable solutions to the water problems and improve management of the shared water resources in the basin based on the historic successes achieved in the Great Lakes region. A comparative analysis of the management of sharedwater resources between the two basins provides a series of principles that are applicable to shared water resource management in other parts of the world.ThesisDoctor of Philosophy (PhD
Water pricing for optimal multi-sectoral allocation: The case of Tyre-Qasmieh area, Lebanon
No full textPerformance comparison of the NWF and DC methods for implementing High-Resolution schemes in a fully coupled incompressible flow solver
No full textThis paper reports on the use of the Normalized Weighting Factor (NWF) method and the Deferred Correction (DC) approach for the implementation of High Resolution (HR) convective schemes in an implicit, fully coupled, pressure-based flow solver. Four HR schemes are realized within the framework of the NWF and DC methods and employed to solve the following three laminar flow problems: (i) lid-driven flow in a square cavity, (ii) sudden expansion in a square cavity, and (iii) flow in a planar T-junction, over three grid systems with sizes of 104, 5 × 104, and 3 × 105 control volumes. The merit of both approaches is demonstrated by comparing the computational costs required to solve these problems using the various HR schemes on the different grid systems. Whereas previous attempts to use the NWF method in a segregated flow solver failed to produce converged solutions, current results clearly demonstrate that both methods are suitable for utilization in a coupled flow solver. In terms of CPU efficiency, there is no global and consistent superiority of any method over another even though the DC method outperformed the NWF method in two of the three test problems solved. © 2010 Elsevier Inc. All rights reserved.BRAATEN ME, 1985, THESIS U MINNESOTA; Caretto L. S., 1972, Computer Methods in Applied Mechanics and Engineering, V1, DOI 10.1016-0045-7825(72)90020-5; Chakravarthy S. R., 1983, 831943 AIAA; Darwish M, 2007, NUMER HEAT TR B-FUND, V52, P353, DOI 10.1080-10407790701372785; Darwish M., 2009, J COMPUT PHYS, V28, P180; Darwish MS, 1996, NUMER HEAT TR B-FUND, V30, P217, DOI 10.1080-10407799608915080; GASKELL PH, 1988, INT J NUMER METH FL, V8, P617, DOI 10.1002-fld.1650080602; HARTEN A, 1983, J COMPUT PHYS, V49, P357, DOI 10.1016-0021-9991(83)90136-5; HAYES RE, 1989, COMPUT FLUIDS, V17, P537, DOI 10.1016-0045-7930(89)90027-3; KARKI KC, 1990, INT J NUMER METH FL, V11, P1, DOI 10.1002-fld.1650110102; LEONARD BP, 1979, COMPUT METHOD APPL M, V19, P59, DOI 10.1016-0045-7825(79)90034-3; LEONARD BP, 1988, INT J NUMER METH FL, V8, P1291, DOI 10.1002-fld.1650081013; LEONARD BP, 1990, INT J NUMER METH ENG, V30, P729, DOI 10.1002-nme.1620300412; Mazhar Z, 2001, NUMER HEAT TR B-FUND, V39, P91, DOI 10.1080-104077901460704; Moukalled F, 2000, NUMER HEAT TR B-FUND, V37, P103; PATANKAR SV, 1972, INT J HEAT MASS TRAN, V15, P1787, DOI 10.1016-0017-9310(72)90054-3; RHIE CM, 1983, AIAA J, V21, P1525, DOI 10.2514-3.8284; Rubin S., 1982, J COMPUT PHYS, V27, P153; SHYY W, 1985, J COMPUT PHYS, V57, P415, DOI 10.1016-0021-9991(85)90188-3; SYE S, 1985, NASACR174776; van Leer B., 1977, J COMPUT PHYS, V23, P101; VANKA SP, 1986, J COMPUT PHYS, V65, P138, DOI 10.1016-0021-9991(86)90008-212
A fully coupled navier-stokes solver for fluid flow at all speeds
No full textThis article deals with the formulation and testing of a newly developed, fully coupled, pressure-based algorithm for the solution of fluid flow at all speeds. The new algorithm is an extension into compressible flows of a fully coupled algorithm developed by the authors for laminar incompressible flows. The implicit velocity-pressure-density coupling is resolved by deriving a pressure equation following a procedure similar to a segregated SIMPLE algorithm using the Rhie-Chow interpolation technique. The coefficients of the momentum and continuity equations are assembled into one matrix and solved simultaneously, with their convergence accelerated via an algebraic multigrid method. The performance of the coupled solver is assessed by solving a number of two-dimensional problems in the subsonic, transsonic, supersonic, and hypersonic regimes over several grid systems of increasing sizes. For a desired level of convergence, results for each problem are presented in the form of convergence history plots, tabulated values of the maximum number of required iterations, the total CPU time, and the CPU time per control volume. © 2014 Taylor and Francis Group, LLC.Abbasi R, 2013, COMPUT FLUIDS, V81, P68, DOI 10.1016-j.compfluid.2013.03.014; Acharya S, 2007, J HEAT TRANS-T ASME, V129, P407, DOI 10.1115-1.2716419; Anderson Jr J.D., 1982, MODERN COMPRESSIBLE; Anjorin V. A. O., 2001, INT J FLUID DYNAM, V5, P59; Barton IE, 1998, INT J NUMER METH FL, V26, P459, DOI 10.1002-(SICI)1097-0363(19980228)26:4459::AID-FLD6453.0.CO;2-U; BATINA JT, 1991, AIAA J, V29, P1836, DOI 10.2514-3.10808; Blokhin AM, 2009, SB MATH+, V200, P157, DOI 10.1070-SM2009v200n02ABEH003990; Cabboussat A., 2005, J COMPUT PHYS, V203, P626; Caretto L. S., 1972, Computer Methods in Applied Mechanics and Engineering, V1, DOI 10.1016-0045-7825(72)90020-5; Darwish M, 2001, NUMER HEAT TR B-FUND, V40, P99; Darwish M, 2007, NUMER HEAT TR B-FUND, V52, P353, DOI 10.1080-10407790701372785; Darwish M, 2004, NUMER HEAT TR B-FUND, V45, P49, DOI 10.1080-1040779049025487; Darwish M, 2009, J COMPUT PHYS, V228, P180, DOI 10.1016-j.jcp.2008.08.027; DEMIRDZIC I, 1993, INT J NUMER METH FL, V16, P1029, DOI 10.1002-fld.1650161202; Deng GB, 2001, COMPUT FLUIDS, V30, P445, DOI 10.1016-S0045-7930(00)00025-6; Dettmer W, 2006, COMPUT METHOD APPL M, V195, P3038, DOI 10.1016-j.cma.2004.07.057; Elling V, 2008, COMMUN PUR APPL MATH, V61, P1347, DOI 10.1002-cpa.20231; Favini B, 1996, INT J NUMER METH FL, V23, P589, DOI 10.1002-(SICI)1097-0363(19960930)23:6589::AID-FLD4443.3.CO;2-R; Grismer M. J., 1994, THESIS NOTRE DAME U; Hirsch C., 1990, NUMERICAL COMPUTATIO; HWANG CJ, 1993, AIAA J, V31, P61, DOI 10.2514-3.11319; Karlci K. C., 1986, THESIS U MINNESOTA; Khalid M. S., 2009, P WORLD C ENG 2009 W; Kissling K., 2010, 5 EUR C COMP FLUID D; Langtry RB, 2005, 2005522 AIAA; LIEN FS, 1993, J FLUID ENG-T ASME, V115, P717, DOI 10.1115-1.2910204; LIEN FS, 1994, COMPUT METHOD APPL M, V114, P123, DOI 10.1016-0045-7825(94)90165-1; MARCHI CH, 1994, NUMER HEAT TR B-FUND, V26, P293, DOI 10.1080-10407799408914931; Menter F, 2003, TURBULENCE HEAT MASS, V4, P2003; Modesto-Madera N. A., 2010, THESIS RENSSELAER PO; Moguen Y, 2013, J COMPUT APPL MATH, V246, P136, DOI 10.1016-j.cam.2012.10.029; Montero R. S., 2000, 200027 NASA ICASE; Moukalled F, 2003, J COMPUT PHYS, V190, P550, DOI 10.1016-S0021-9991(03)00297-3; Moukalled F, 2004, NUMER HEAT TR B-FUND, V45, P343, DOI 10.1080-10407790490268841; Darwish M, 2003, INT J NUMER METH FL, V41, P1221, DOI 10.1002-fld.490; Moukalled F, 2000, NUMER HEAT TR B-FUND, V37, P103; Moukalled F, 2002, NUMER HEAT TR B-FUND, V42, P259, DOI 10.1080-10407790190053941; Moukalled F, 2001, J COMPUT PHYS, V168, P101, DOI 10.1006-jcph.2000.6683; Muzaferija S, 1997, J COMPUT PHYS, V138, P766, DOI 10.1006-jcph.1997.5853; PATANKAR SV, 1972, INT J HEAT MASS TRAN, V15, P1787, DOI 10.1016-0017-9310(72)90054-3; Rhie C., 1983, AIAA J, V17, P1525; Rispoli F., 2009, ASME J APPL MECH, V76, DOI [10.1115-1.3062969, DOI 10.1115-1.3062969]; Rossow CC, 2007, J COMPUT PHYS, V220, P879, DOI 10.1016-j.jcp.2006.05.034; Shapiro A. H., 1953, DYNAMICS THERMODYNAM; Shapiro E, 2005, J COMPUT PHYS, V210, P584, DOI 10.1016-j.jcp.2005.05.001; Shterev KS, 2010, J COMPUT PHYS, V229, P461, DOI 10.1016-j.jcp.2009.09.042; Tao WQ, 2004, NUMER HEAT TR B-FUND, V45, P1, DOI 10.1080-1040779049025485; Tezduyar TE, 2006, COMPUT MECH, V38, P469, DOI 10.1007-s00466-005-0025-6; VANDOORMAAL JP, 1984, NUMER HEAT TRANSFER, V7, P147, DOI 10.1080-10407798408546946; van Wachem B. G. M., 2006, EUR C COMP FLUID DYN; van Wachem B. G. M., 2007, 6 INT C MULT FLOW IC; Yaldin Y., 1991, AIAA J, V29, P712; Yang JY, 2001, AIAA J, V39, P2082, DOI 10.2514-2.1231; ZHANG LX, 2011, J HYDRODYN, V23, P421
Water pricing for multi-sectoral allocation: a case study
No full textThis paper presents a case study for the allocation pattern of available water resources within and among competing sectors that would achieve the highest economic return from water use. For this purpose, an optimization model using linear programming was developed. Considering constraints on greenhouse area, crop production and seasonal per capita water requirements along with the area-specific conditions and potential growth, the optimal water allocation pattern between the prevailing and future consuming sectors was determined. The results indicated that, at present, water resources are misallocated as well as under-priced; current municipal and agricultural water prices represent 61% and 69%, respectively, of the actual water cost. With the development of tourism in the area, the agricultural sector is expected to diminish as more profitable uses of water evolve
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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