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Search Results: 1 - 10 of 18499 matches for " U. Greife "
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Decision-Aiding Transit-Tracker Methodology for Bus Scheduling Using Real Time Information to Ameliorate Traffic Congestion in the Kathmandu Valley of Nepal  [PDF]
Keshav Bhattarai, Mahmoud Yousef, Alice Greife, Sunil Lama
Journal of Geographic Information System (JGIS) , 2019, DOI: 10.4236/jgis.2019.112016
Abstract: The bustling urban environment of Kathmandu Valley is characterized by unprecedented traffic congestion. Due to its bowel-shaped geography, gusty winds rarely remove vehicular emissions from the urban atmosphere, making Kathmandu one of Asia’s most polluted cities, 100th city in global pollution index. Over 500,000 vehicles travel daily on over 1600 km of roads covering over 675 sq·km urban area. Thousands of low occupancy vehicles are added each year to the urban public transit system (UPTS). Kathmandu faces worse and unreliable traffic from the current UPTS mostly with low occupancy vehicles. Around 4.5 million urban denizens, both permanent and transient residents, suffer from unreliable UPTS. Traffic rules and daily transportation schedules are rarely followed, resulting in frequent traffic jams and accidents. Once experienced, visitors try avoiding the UPTS. Tourism, annually contributing almost 8 percent to Nepal’s total annual GDP, also suffers from poor UPTS. Planners, policy makers, and politicians (P-actors) are seeking ways to improve sustainable UPTS to ameliorate stresses to family life and working hours for the urban majority. Aiming to help P-actors, we propose a transit-tracker model that uses real time information (RTI) in mobile phones and web-embedded devices to inform travelers, drivers, government authorities, and sub-admins. We argue that unreliability in the UPTS motivates urban elites to add more low occupancy vehicles, which in turn reduces already shrunken urban spaces and contributes more per capita air pollution than multi-occupancy vehicles. Since mobile and smart phones are capable of processing RTI to generate meaningful information and inform various stakeholders in communicable languages, we argue that replacing low occupancy vehicles with multi-occupancy buses within a Bus Rapid Transit (BRT) system, on main roads with fixed schedules and strict traffic rules, would not only improve UPTS, but also reduce pollution in the Kathmandu Valley.
New Constraints on the 18F(p,alpha) 15O Rate in Novae from the (d,p) Reaction
R. L. Kozub,D. W. Bardayan,J. C. Batchelder,J. C. Blackmon,C. R. Brune,A. E. Champagne,J. A. Cizewski,T. Davinson,U. Greife,C. J. Gross,C. C. Jewett,R. J. Livesay,Z. Ma,B. H. Moazen,C. D. Nesaraja,L. Sahin,J. P. Scott,D. Shapira,M. S. Smith,J. S. Thomas,P. J. Woods
Physics , 2004, DOI: 10.1103/PhysRevC.71.032801
Abstract: The degree to which the (p,gamma) and (p,alpha) reactions destroy 18F at temperatures 1-4x10^8 K is important for understanding the synthesis of nuclei in nova explosions and for using the long-lived radionuclide 18F, a target of gamma-ray astronomy, as a diagnostic of nova mechanisms. The reactions are dominated by low-lying proton resonances near the 18F+p threshold (E_x=6.411 MeV in 19Ne). To gain further information about these resonances, we have used a radioactive 18F beam from the Holifield Radioactive Ion Beam Facility to selectively populate corresponding mirror states in 19F via the inverse d(18F,p)19F neutron transfer reaction. Neutron spectroscopic factors were measured for states in 19F in the excitation energy range 0-9 MeV. Widths for corresponding proton resonances in 19Ne were calculated using a Woods-Saxon potential. The results imply significantly lower 18F(p,gamma)19Ne and 18F(p,alpha)15O reaction rates than reported previously, thereby increasing the prospect of observing the 511-keV annihilation radiation associated with the decay of 18F in the ashes ejected from novae.
Coulomb dissociation of 8B and the low-energy cross section of the 7Be(p,gamma)8B solar fusion reaction
F. Schuemann,F. Hammache,S. Typel,F. Uhlig,K. Suemmerer,I. Boettcher,D. Cortina,A. Foerster,M. Gai,H. Geissel,U. Greife,N. Iwasa,P. Koczon,B. Kohlmeyer,R. Kulessa,H. Kumagai,N. Kurz,M. Menzel,T. Motobayashi,H. Oeschler,A. Ozawa,M. Ploskon,W. Prokopowicz,E. Schwab,P. Senger,F. Strieder,C. Sturm,Zhi-Yu Sun,G. Surowka,A. Wagner,W. Walus
Physics , 2003, DOI: 10.1103/PhysRevLett.90.232501
Abstract: An exclusive measurement of the Coulomb breakup of 8B into 7Be+p at 254 A MeV allowed to study the angular correlations of the breakup particles. These correlations demonstrate clearly that E1 multipolarity dominates and that E2 multipolarity can be neglected. By using a simple single-particle model for 8B and treating the breakup in first-order perturbation theory, we extract a zero-energy S factor of S-(17)(0) = 18.6 +- 1.2 +- 1.0 eV b.
Background identification and suppression for the measurement of (n,g) reactions with the DANCE array at LANSCE
R. Reifarth,T. A. Bredeweg,A. Alpizar-Vicente,J. C. Browne,E. -I. Esch,U. Greife,R. C. Haight,R. Hatarik,A. Kronenberg,J. M. O'Donnell,R. S. Rundberg,J. L. Ullmann,D. J. Vieira,J. B. Wilhelmy,J. M. Wouters
Physics , 2013, DOI: 10.1016/j.nima.2004.05.096
Abstract: In the commissioning phase of the DANCE project (Detector for Advanced Neutron Capture Experiments) measurements have been performed with special emphasis on the identification and suppression of possible backgrounds for the planned (n,g) experiments. This report describes several background sources, observed in the experiment or anticipated from simulations, which will need to be suppressed in this and in similar detectors that are planned at other facilities. First successes are documented in the suppression of background from scattered neutrons captured in the detector as well as from the internal radiation. Experimental results and simulations using the GEANT code are compared.
The Cross Section of 3He(3He,2p)4He measured at Solar Energies
The LUNA Collaboration,M. Junker,A. D'Alessandro,S. Zavatarelli,C. Arpesella,E. Bellotti,C. Broggini,P. Corvisiero,G. Fiorentini,A. Fubini,G. Gervino,U. Greife,C. Gustavino,J. Lambert,P. Prati,W. S. Rodney,C. Rolfs,F. Strieder,H. P. Trautvetter,D. Zahnow
Physics , 1997, DOI: 10.1103/PhysRevC.57.2700
Abstract: We report on the results of the \hethet\ experiment at the underground accelerator facility LUNA (Gran Sasso). For the first time the lowest projectile energies utilized for the cross section measurement correspond to energies below the center of the solar Gamow peak ($E_{\rm 0}$=22 keV). The data provide no evidence for the existence of a hypothetical resonance in the energy range investigated. Although no extrapolation is needed anymore (except for energies at the low-energy tail of the Gamow peak), the data must be corrected for the effects of electron screening, clearly observed the first time for the \hethet\ reaction. The effects are however larger than expected and not understood, leading presently to the largest uncertainty on the quoted $S_{\rm b}(E_{\rm 0})$ value for bare nuclides (=5.40 MeV b).
The 21Na(p,gamma)22Mg Reaction and Oxygen-Neon Novae
S. Bishop,R. E. Azuma,L. Buchmann,A. A. Chen,M. L. Chatterjee,J. M. D'Auria,S. Engel,D. Gigliotti,U. Greife,M. Hernanz,D. Hunter,A. Hussein,D. Hutcheon,C. Jewett,J. Jose,J. King,S. Kubono,A. M. Laird,M. Lamey,R. Lewis,W. Liu,S. Michimasa,A. Olin,D. Ottewell,P. D. Parker,J. G. Rogers,F. Strieder,C. Wrede
Physics , 2003, DOI: 10.1103/PhysRevLett.90.162501
Abstract: The 21Na(p,gamma)22Mg reaction is expected to play an important role in the nucleosynthesis of 22Na in Oxygen-Neon novae. The decay of 22Na leads to the emission of a characteristic 1.275 MeV gamma-ray line. This report provides the first direct measurement of the rate of this reaction using a radioactive 21Na beam, and discusses its astrophysical implications. The energy of the important state was measured to be E$_{c.m.}$= 205.7 $\pm$ 0.5 keV with a resonance strength $\omega\gamma = 1.03\pm0.16_{stat}\pm0.14_{sys}$ meV.
The Single-Particle Structure of Neutron-Rich Nuclei of Astrophysical Interest at the Ornl Hribf
D. W. Bardayan,J. C. Batchelder,J. C. Blackmon,C. R. Brune,A. E. Champagne,J. A. Cizewski,T. Davinson,U. Greife,A. N. James,M. Johnson,R. L. Kozub,J. F. Liang,R. J. Livesay,Z. Ma,C. D. Nesaraja,D. C. Radford,D. Shapira,M. S. Smith,J. S. Thomas,P. J. Woods,E. Zganjar,the Unirib Collaboration
Physics , 2002,
Abstract: The rapid nuetron-capture process (r process) produces roughly half of the elements heavier than iron. The path and abundances produced are uncertain, however, because of the lack of nuclear strucure information on important neutron-rich nuclei. We are studying nuclei on or near the r-process path via single-nucleon transfer reactions on neutron-rich radioactive beams at ORNL's Holifield Radioactive Ion Beam Facility (HRIBF). Owing to the difficulties in studying these reactions in inverse kinematics, a variety of experimental approaches are being developed. We present the experimental methods and initial results.
First Measurement of the He3+He3-->He4+2p Cross Section down to the Lower Edge of the Solar Gamow Peak
The LUNA Collaboration,R. Bonetti,C. Broggini,L. Campajola,P. Corvisiero,A. D'Alessandro,M. Dessalvi,A. D'Onofrio,A. Fubini,G. Gervino,L. Gialanella,U. Greife,A. Guglielmetti,C. Gustavino,G. Imbriani,M. Junker,P. Prati,V. Roca,C. Rolfs,M. Romano,F. Schuemann,F. Strieder,F. Terrasi,H. P. Trautvetter,S. Zavatarelli
Physics , 1999, DOI: 10.1103/PhysRevLett.82.5205
Abstract: We give the LUNA results on the cross section measurement of a key reaction of the proton-proton chain strongly affecting the calculated neutrino luminosity from the Sun: He3+He3-->He4+2p. Due to the cosmic ray suppression provided by the Gran Sasso underground laboratory it has been possible to measure the cross section down to the lower edge of the solar Gamow peak, i.e. as low as 16.5 keV centre of mass energy. The data clearly show the cross section increase due to the electron screening effect but they do not exhibit any evidence for a narrow resonance suggested to explain the observed solar neutrino flux.
The NIFFTE project
Ruz J.,Asner D. M.,Baker R. G.,Bundgaard J.,Burgett E.,Cunningham M.,Deaven J.,Duke D. L.,Greife U.,Grimes S.,Heffner M.,Hill T.,Isenhower D.,Klay J. L.,Kleinrath V.,Kornilov N.,Laptev A. B.,Loveland W.,Masseyf T. N.,Meharchand R.,Qu H.,Sangiorgio S.,Seilhan B.,Snyder L.,Stave S.,Tatishvili G.,Thornton R. T.,Tovesson F.,Towell D.,Towell R. S.,Watson S.,Wendt B.,Wood L
Physics , 2013, DOI: 10.1088/1748-0221/8/12/C12018
Abstract: The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) is a double-sided Time Projection Chamber (TPC) with micromegas readout designed to measure the energy-dependent neutron-induced fission cross sections of the major and minor actinides with unprecedented accuracy. The NIFFTE project addresses the challenge of minimizing major sources of systematic uncertainties from previous fission chamber measurements such as: target and beam non-uniformities, misidentification of alpha and light charged particles as fission fragments, and uncertainties inherent to the reference standards used. In-beam tests of the NIFFTE TPC at the Los Alamos Neutron Science Center (LANSCE) started in 2010 and have continued in 2011, 2012 and 2013. An overview of the NIFFTE TPC status and performance at LANSCE will be presented.
Targets for Precision Measurements
W. Loveland,L. Yao,David M. Asner,R. G. Baker,J. Bundgaard,E. Burgett,M. Cunningham,J. Deaven,D. L. Duke,U. Greife,S. Grimes,M. Heffer,T. Hill,D. Isenhower,J. L. Klay,V. Kleinrath,N. Kornilov,A. B. Laptev,T. N. Massey,R. Meharchand,H. Qu,J. Ruz,S. Sangiorgio,B. Selhan,L. Snyder,S. Stave,G. Tatishvili,R. T. Thornton,F. Tovesson,D. Towell,R. S. Towell,S. Watson,B. Wendt,L. Wood
Physics , 2013,
Abstract: The general properties needed in targets (sources) for high precision, high accuracy measurements are reviewed. The application of these principles to the problem of developing targets for the Fission TPC is described. Longer term issues, such as the availability of actinide materials, improved knowledge of energy losses and straggling and the stability of targets during irradiation are also discussed.
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