In Situ Determination of Long-Term Volcanic Glass Weathering: Implications for Nuclear Waste Storage over Geologic Time (open access)

In Situ Determination of Long-Term Volcanic Glass Weathering: Implications for Nuclear Waste Storage over Geologic Time

None
Date: July 20, 2000
Creator: Gordon, Steven J. & Brady, Patrick V.
Object Type: Article
System: The UNT Digital Library
Fast Through-Bond Diffusion of Nitrogen in Silicon (open access)

Fast Through-Bond Diffusion of Nitrogen in Silicon

The authors report first principles total energy calculations of interaction of nitrogen in silicon with silicon self-interstitials. Substitutional nitrogen captures a silicon interstitial with 3.5 eV binding energy forming a {l_angle}001{r_angle} split interstitial ground state geometry, with the nitrogen forming three bonds. The low energy migration path is through a bond bridge state having two bonds. Fast diffusion of nitrogen occurs through a pure interstitialcy mechanism; the nitrogen never has less than two bonds. Near-zero formation energy of the nitrogen interstitialcy with respect to the substitutional rationalizes the low solubility of substitutional nitrogen in silicon.
Date: July 12, 2000
Creator: Schultz, Peter A. & Nelson, Jeffrey S.
Object Type: Article
System: The UNT Digital Library
{sup 203,205}Tl NMR Studies of Crystallographically Characterized Thallium Alkoxides. X-Ray Structures of [Tl(OCH{sub 2}CH{sub 3})]4 and [Tl(OAr)]{sub infinity} where OAr = OC{sub 6}H{sub 3}(Me){sub 2}-2,6 and OC{sub 6}H{sub 3}(Pr{sup i}){sub 2}-2,6 (open access)

{sup 203,205}Tl NMR Studies of Crystallographically Characterized Thallium Alkoxides. X-Ray Structures of [Tl(OCH{sub 2}CH{sub 3})]4 and [Tl(OAr)]{sub infinity} where OAr = OC{sub 6}H{sub 3}(Me){sub 2}-2,6 and OC{sub 6}H{sub 3}(Pr{sup i}){sub 2}-2,6

[Tl(OCH{sub 2}CH{sub 3})]{sub 4}, (1) was reacted with excess HOR to prepare a series of [Tl(OR)]{sub n} where OR= OCHMe{sub 2} (2, n = 4), OCMe{sub 3} (3, n = 4), OCH{sub 2}CMe{sub 3} (4, n = 4), OC{sub 6}H{sub 3}(Me){sub 2}-2,6 (5, n = {infinity}), and OC{sub 6}H{sub 3}(Pr{sup i}){sub 2}-2,6 (6, n = {infinity}). Single crystal X-ray diffraction was used to determine the structure of compounds ligated by more sterically demanding ligands. Compound 4 was found to adopt a cubane structure, while 5 and 6 formed linear polymeric structures. These compounds were additionally characterized by {sup 203,205}Tl solution and {sup 205}Tl solid state NMR. Compounds 1--4 were found to remain intact in solution while the polymeric species, 5 and 6, appeared to be fluxional. While variations in the solution and solid state structures for the tetrameric [Tl(OR)]{sub 4} and polymeric [Tl(OAr)]{sub {infinity}} may be influenced by the steric hindrance of their respective ligands, the covalency of the species is believed to be more an effect of the parent alcohol acidity.
Date: July 25, 2000
Creator: Zechmann, Cecilia A.; Boyle, Timothy J.; Pedrotty, Dawn M.; Alam, Todd M.; Lang, David P. & Scott, Brain L.
Object Type: Article
System: The UNT Digital Library
Overview of the Flammability of Gases Generated in Hanford Waste Tanks (open access)

Overview of the Flammability of Gases Generated in Hanford Waste Tanks

This report presents an overview of what is known about the flammability of the gases generated and retained in Hanford waste tanks in terms of the gas composition, the flammability and detonability limits of the gas constituents, and the availability of ignition sources. The intrinsic flammability (or nonflammability) of waste gas mixtures is one major determinant of whether a flammable region develops in the tank headspace; other factors are the rate, surface area, volume of the release, and the tank ventilation rate, which are not covered in this report.
Date: July 21, 2000
Creator: Mahoney, L. A.; Huckaby, J. L.; Bryan, S. A. & Johnson, G. D.
Object Type: Report
System: The UNT Digital Library
High Shock, High Frequency Characteristics of a Mechanical Isolator for a Piezoresistive Accelerometer, the ENDEVCO 7270AM6* (open access)

High Shock, High Frequency Characteristics of a Mechanical Isolator for a Piezoresistive Accelerometer, the ENDEVCO 7270AM6*

A mechanical isolator has been developed for a piezoresistive accelerometer. The purpose of the isolator is to mitigate high frequency shocks before they reach the accelerometer because the high frequency shocks may cause the accelerometer to resonate. Since the accelerometer is undamped, it often breaks when it resonates. The mechanical isolator was developed in response to impact test requirements for a variety of structures at Sandia National Laboratories (SNL). An Extended Technical Assistance Program (ETAP) with the accelerometer manufacturer has resulted in a commercial mechanically isolated accelerometer that is available to the general public, the ENDEVCO 7270AM6*, for three shock acceleration ranges of 6,000 g, 20,000 g, and 60,000 g. The in-axis response shown in this report has acceptable frequency domain performance from DC to 10 kHz and 10(XO)over a temperature range of {minus}65 F to +185 F. Comparisons with other isolated accelerometers show that the ENDEVCO 7270AM6 has ten times the bandwidth of any other commercial isolator. ENDEVCO 7270AM6 cross-axis response is shown in this report.
Date: July 1, 2000
Creator: Bateman, Vesta I.; Brown, Frederick A. & Nusser, Michael A.
Object Type: Report
System: The UNT Digital Library
UNFINISHED BUSINESS: The Economics of The Kyoto Protocol (open access)

UNFINISHED BUSINESS: The Economics of The Kyoto Protocol

The Kyoto Protocol to the Framework Convention on Climate Change (FCCC) was completed on the morning of December 11, 1997, following over two years of negotiations. The product of these deliberations is a complex and incomplete document knitting together the diversity of interests and perspectives represented by the more than 150 delegations. Because the document is complex, its implications are not immediately obvious. If it enters into force, the Kyoto Protocol will have far-reaching implications for all nations--both nations with obligations under the Protocol and those without obligations. National energy systems, and the world's energy system, could be forever changed. In this paper the authors develop an assessment of the energy and economic implications of achieving the goals of the Kyoto Protocol. They find that many of the details of the Protocol that remain to be worked out introduce critical uncertainties affecting the cost of compliance. There are also a variety of uncertainties that further complicate the analysis. These include future non-CO{sub 2} greenhouse gas emissions and the cost of their mitigation. Other uncertainties include the resolution of negotiations to establish rules for determining and allocating land-use emissions rights, mechanisms for Annex 1 trading, and participation by non-Annex 1 members …
Date: July 6, 2000
Creator: Edmonds, J. A.; MacCracken, C. N.; Sands, R. D. & Kim, S. H.
Object Type: Report
System: The UNT Digital Library
THE PLASMA FLUIDIZED BED. (open access)

THE PLASMA FLUIDIZED BED.

None
Date: July 18, 2000
Creator: Currier, Robert P.; Trkula, Mitchell & Snyder, Hans R.
Object Type: Report
System: The UNT Digital Library
Second Quarter Hanford Seismic Report for Fiscal Year 2000 (open access)

Second Quarter Hanford Seismic Report for Fiscal Year 2000

Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the US Department of Energy and its contractors. Hanford Seismic Monitoring also locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The HSN and the Eastern Washington Regional Network (EWRN) consist of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The HSN uses 21 sites and the EWRN uses 36 sites; both networks share 16 sites. The networks have 46 combined data channels because Gable Butte and Frenchman Hills East are three-component sites. The reconfiguration of the telemetry and recording systems was completed during the first quarter. All leased telephone lines have been eliminated and radio telemetry is now used exclusively. For the HSN, there were …
Date: July 17, 2000
Creator: Hartshorn, D. C.; Reidel, S. P. & Rohay, A. C.
Object Type: Report
System: The UNT Digital Library
Solvent Influences on the Molecular Aggregation of Magnesium Aryloxides (open access)

Solvent Influences on the Molecular Aggregation of Magnesium Aryloxides

Magnesium aryloxides were prepared in a variety of solvents through the reaction of dibutyl magnesium with sterically varied aryl alcohols: 2,6-dimethylphenol (H-DMP), 2,6-diisopropylphenol (H-DIP), and 2,4,6-trichlorophenol (H-TCP). Upon using a sufficiently strong Lewis-basic solvent, the monomeric species Mg(DMP){sub 2}(py){sub 3} (1, py = pyridine), Mg(DIP){sub 2}(THF){sub 3}, (2a, THF = tetrahydrofuran) Mg(TCP){sub 2}(THF){sub 3} (3) were isolated. Each of these complexes possesses a five-coordinate magnesium that adopts a trigonal bipyramidal geometry. In the absence of a Lewis base, the reaction with H-DIP yields a soluble trinuclear complex, [Mg(DIP){sub 2}]{sub 3} (2b). The Mg metal centers in 2b adopt a linear arrangement with a four-coordinate central metal while the outer metal centers are reduced to just three-coordinate. Solution spectroscopic methods suggest that while 2b remains intact, the monomeric species (1, 2a, and 3) are involved in equilibria, which facilitate intermolecular ligand transfer.
Date: July 14, 2000
Creator: Zechmann, Cecilia A.; Boyle, Timothy J.; Rodriguez, Mark A. & Kemp, Richard A.
Object Type: Article
System: The UNT Digital Library
Dynamics of Capillary Evaporation. II. Free Energy Barriers (open access)

Dynamics of Capillary Evaporation. II. Free Energy Barriers

None
Date: July 17, 2000
Creator: Leung, Kevin & Luzar, Alenka
Object Type: Article
System: The UNT Digital Library
Stability and transport in compact quasi-axisymmetric stellarators (open access)

Stability and transport in compact quasi-axisymmetric stellarators

The potential performance and flexibility of a compact, quasi-axisymmetric (QAS) stellarator design, has been addressed by studying the effects of varied pressure and rotational transform profiles on the global, ideal magnetohydrodynamic (MHD) stability and the energetic particle transport. The CAS3D and TERPSICHORE code packages were used in the MHD studies while the ORBITMN/ORBIT3D code package was used for the transport simulations of the three field period QAS. To assess robust performance in a medium-size experiment, the VMEC code was used to obtain magnetic flux surfaces for 30 equilibria near the design point, while keeping the boundary shape and the average beta fixed at 3.8%. The plasma equilibria obtained were designated P0X/I0Y as follows: P00/I00 was the baseline configuration. P01, P02 and P03 were defined so that P01 was similar to P00, P02 was more peaked than P01, while P03 was broader than P01. P04 was a very broad, parabolic pressure profile and P05 was the pressure profile used in helias reactor studies based on the W7-X design. The iota profiles were chosen as follows: I01 was linear, maintaining i(0) and i(a) the same as in I00. I02 and I03 were based on I01 and also kept i(0) and i(a) as …
Date: July 7, 2000
Creator: Redi, M. H.; Cooper, W. A.; Diallo, A.; Fu, G. Y.; Nuehrenberg, C.; Reiman, A. H. et al.
Object Type: Report
System: The UNT Digital Library
The ASCI Network for SC '99: A Step on the Path to a 100 Gigabit Per Second Supercomputing Network (open access)

The ASCI Network for SC '99: A Step on the Path to a 100 Gigabit Per Second Supercomputing Network

This document highlights the Discom{sup 2}'s Distance computing and communication team activities at the 1999 Supercomputing conference in Portland, Oregon. This conference is sponsored by the IEEE and ACM. Sandia, Lawrence Livermore and Los Alamos National laboratories have participated in this conference for eleven years. For the last four years the three laboratories have come together at the conference under the DOE's ASCI, Accelerated Strategic Computing Initiatives rubric. Communication support for the ASCI exhibit is provided by the ASCI DISCOM{sup 2} project. The DISCOM{sup 2} communication team uses this forum to demonstrate and focus communication and networking developments within the community. At SC 99, DISCOM built a prototype of the next generation ASCI network demonstrated remote clustering techniques, demonstrated the capabilities of the emerging Terabit Routers products, demonstrated the latest technologies for delivering visualization data to the scientific users, and demonstrated the latest in encryption methods including IP VPN technologies and ATM encryption research. The authors also coordinated the other production networking activities within the booth and between their demonstration partners on the exhibit floor. This paper documents those accomplishments, discusses the details of their implementation, and describes how these demonstrations support Sandia's overall strategies in ASCI networking.
Date: July 24, 2000
Creator: Pratt, Thomas J.; Tarman, Thomas D.; Martinez, Luis M.; Miller, Marc M.; Adams, Roger L.; Chen, Helen Y. et al.
Object Type: Report
System: The UNT Digital Library
Making connections: Case studies of interconnection barriers and their impact on distributed power projects (open access)

Making connections: Case studies of interconnection barriers and their impact on distributed power projects

Distributed power is modular electric generation or storage located close to the point of use. Based on interviews of distributed generation project proponents, this report reviews the barriers that distributed generators of electricity are encountering when attempting to interconnect to the electrical grid. Descriptions of 26 of 65 case studies are included in the report. The survey found and the report describes a wide range of technical, business-practice, and regulatory barriers to interconnection. An action plan for reducing the impact of these barriers is also included.
Date: July 25, 2000
Creator: Alderfer, B.; Eldridge, M. & Starrs, T.
Object Type: Report
System: The UNT Digital Library
Optical studies of the {beta}{double_prime}-(ET){sub 2}SF{sub 5}RSO{sub 3} R = CH{sub 2}CF{sub 2}, CHFCF{sub 2} and CHF system: Chemical tuning of the counterion (open access)

Optical studies of the {beta}{double_prime}-(ET){sub 2}SF{sub 5}RSO{sub 3} R = CH{sub 2}CF{sub 2}, CHFCF{sub 2} and CHF system: Chemical tuning of the counterion

The authors compare the polarized optical spectra of the organic metal {beta}{double_prime}-(ET){sub 2}SF{sub 5}CHFSO{sub 3} and the {beta}{double_prime}-ET{sub 2}SF{sub 5}CHFCF{sub 2}SO{sub 3} metal/insulator material with those of the first fully organic superconductor {beta}{double_prime}-ET{sub 2}SF{sub 5}CH{sub 2}SO{sub 3}. The small chemical modification of the counterion has a dramatic effect on the spectral and charge transport properties of these materials, and they discuss their electronic structure in terms of band structure, many-body effects, and disorder. Based on structural differences in the anion pocket of the three salts, they conclude that the unusual electronic excitations observed in the {beta}{double_prime}-(ET){sub 2}SF{sub 5}CHFCF{sub 2}SO{sub 3} metal/insulator material are caused by disorder-related localization.
Date: July 24, 2000
Creator: Olejniczak, I.; Jones, B. R.; Dong, J.; Pigos, J. M.; Zhu, Z.; Garlach, A. D. et al.
Object Type: Article
System: The UNT Digital Library
Surveys of Organizational Culture and Safety Culture in Nuclear Power (open access)

Surveys of Organizational Culture and Safety Culture in Nuclear Power

The results of a survey of organizational culture at a nuclear power plant are summarized and compared with those of a similar survey which has been described in the literature on high-reliability organizations. A general-purpose cultural inventory showed a profile of organizational style similar to that reported in the literature; the factor structure for the styles was also similar to that of the plant previously described. A specialized scale designed to measure safety culture did not distinguish among groups within the organization that would be expected to differ.
Date: July 30, 2000
Creator: Brown, B. S.
Object Type: Article
System: The UNT Digital Library
Report of official foreign travel to France, June 7--20, 2000 (open access)

Report of official foreign travel to France, June 7--20, 2000

The Department of Energy (DOE) has moved rapidly toward electronic production, management, and dissemination of scientific and technical information. The World-Wide Web (WWW) has become a primary means of information dissemination. Electronic commerce (EC) is becoming the preferred means of procurement. DOE, like other government agencies, depends on and encourages the use of international standards in data communications. Like most government agencies, DOE has expressed a preference for openly developed standards over proprietary designs promoted as ``standards'' by vendors. In particular, there is a preference for standards developed by organizations such as the International Organization for Standardization (ISO) and the American National Standards Institute (ANSI) that use open, public processes to develop their standards. Among the most widely adopted international standards is the Standard Generalized Markup Language (SGML, ISO 8879:1986, FIPS 152), to which DOE long ago made a commitment. Besides the official commitment, which has resulted in several specialized projects, DOE makes heavy use of coding derived from SGML: Most documents on the WWW are coded in HTML (Hypertext Markup Language), which is an application of SGML. The World-Wide Web Consortium (W3C), with the backing of major software houses like Adobe, IBM, Microsoft, Netscape, Oracle, and Sun, is promoting …
Date: July 11, 2000
Creator: Mason, J. D.
Object Type: Report
System: The UNT Digital Library
A high-precision cryogenically-cooled crystal monochromator for the APS diagnostics beamline (open access)

A high-precision cryogenically-cooled crystal monochromator for the APS diagnostics beamline

A high-precision cryogenically-cooled crystal monochromator has been developed for the APS diagnostics beamline. The design permits simultaneous measurements of the particle beam size and divergence. It provides for a large rotation angle, {minus}15{degree} to 180{degree}, with a resolution of 0.0005{degree}. The roll angle of the crystal can be adjusted by up to {+-}3{degree} with a resolution of 0.0001{degree}. A vertical translational stage, with a stroke of {+-}25 mm and resolution of 8 {micro}m, is provided to enable using different parts of the same crystal or to retract the crystal from the beam path. The modular design will allow optimization of cooling schemes to minimize thermal distortions of the crystal under high heat loads.
Date: July 24, 2000
Creator: Rotela, E.; Yang, B.; Sharma, S. & Barcikowski, A.
Object Type: Article
System: The UNT Digital Library
Notes on a search for optimal lattice rules (open access)

Notes on a search for optimal lattice rules

In this paper some of the results of a recent computer search [CoLy99] for optimal three- and four-dimensional lattice rules of specified trigonometric degree are discussed. The theory is presented in a general frame emphasizing the special nature of lattice rules among the rules of specified trigonometric degree.
Date: July 5, 2000
Creator: Lyness, J. & Cools, R.
Object Type: Article
System: The UNT Digital Library
A Two-Stage Model of Radiological Inspection: Spending Time (open access)

A Two-Stage Model of Radiological Inspection: Spending Time

The paper describes a model that visually portrays radiological survey performance as basic parameters (surveyor efficiency and criteria, duration of pause, and probe speed) are varied; field and laboratory tests provided typical parameter values. The model is used to illustrate how practical constraints on the time allotted to the task can affect radiological inspection performance. Similar analyses are applicable to a variety of other tasks (airport baggage inspection, and certain types of non-destructive testing) with similar characteristics and constraints.
Date: July 30, 2000
Creator: Brown, W. S.
Object Type: Article
System: The UNT Digital Library
Organically-Templated Zinc Hydrogen Phosphites: Syntheses, Structures and Properties of {alpha}- and {Beta}-ZnHOP{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4} (open access)

Organically-Templated Zinc Hydrogen Phosphites: Syntheses, Structures and Properties of {alpha}- and {Beta}-ZnHOP{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4}

The syntheses, crystal structures and some properties of {alpha}- and {beta}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4} are reported. These two polymorphs are the first organically-templated hydrogen phosphites. They are built up from vertex-sharing HPO{sub 3} pseudo pyramids and ZnO{sub 3}N tetrahedra, where the Zn-N bond represents a direct link between zinc and the neutral 2-cyanoguanidine template. {alpha}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4} is built up from infinite layers of vertex-sharing ZnO{sub 3}N and HPO{sub 3} groups forming 4-rings and 8-rings. {beta}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4} has strong one-dimensional character, with the polyhedral building units forming 4-ring ladders. Similarities and differences to related zinc phosphates are discussed. Crystal data: {alpha}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4}, M{sub r} = 229.44, monoclinic, P2{sub 1}/c, a = 9.7718 (5) {angstrom}, b = 8.2503 (4) {angstrom}, c = 9.2491 (5) {angstrom}, {beta} = 104.146 (1){sup 0}, V = 723.1 (1) {angstrom}{sup 3}, R(F) = 2.33%, wR(F) = 2.52%. {beta}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4}, M{sub r} = 229.44, monoclinic, C2/c, a = 14.5092 (9) {angstrom}, b = 10.5464 (6) {angstrom}, c = 10.3342 (6) {angstrom}, {beta} = 114.290 (1){sup 0}, V = 1441.4 (3) {angstrom}{sup 3}, R(F) = 3.01%, wR(F) = 3.40%.
Date: July 14, 2000
Creator: HARRISON,WILLIAM T.A.; PHILLIPS,MARK L.F.; STANCHFIELD,JESSE & NENOFF,TINA M.
Object Type: Article
System: The UNT Digital Library
Liquid fuel reformer development: Autothermal reforming of Diesel fuel (open access)

Liquid fuel reformer development: Autothermal reforming of Diesel fuel

Argonne National Laboratory is developing a process to convert hydrocarbon fuels to clean hydrogen feeds for a polymer electrolyte fuel cell. The process incorporates an autothermal reforming catalyst that can process hydrocarbon feeds at lower temperatures than existing commercial catalysts. The authors have tested the catalyst with three diesel-type fuels: hexadecane, certified low-sulfur grade 1 diesel, and a standard grade 2 diesel. Hexadecane yielded products containing 60% hydrogen on a dry, nitrogen-free basis at 850 C, while maximum hydrogen product yields for the two diesel fuels were near 50%. Residual products in all cases included CO, CO{sub 2}, ethane, and methane. Further studies with grade 1 diesel showed improved conversion as the water:fuel ratio was increased from 1 to 2 at 850 C. Soot formation was reduced when the oxygen:carbon ratio was maintained at 1 at 850 C. There were no significant changes in hydrogen yield as the space velocity and the oxygen:fuel ratio were varied. Tests with a microchannel monolithic catalyst yielded similar or improved hydrogen levels at higher space velocities than with extruded pellets in a packed bed.
Date: July 24, 2000
Creator: Pereira, C.; Bae, J-M.; Ahmed, S. & Krumpelt, M.
Object Type: Article
System: The UNT Digital Library
Unique Rock-n-Roll Dynamic Appearance of a Ge-Si Ad-Dimer on Si(001) (open access)

Unique Rock-n-Roll Dynamic Appearance of a Ge-Si Ad-Dimer on Si(001)

The authors carry out a comparative study of the energetic and dynamics of Si-Si, Ge-Ge, and Ge-Si ad-dimers on top of a dimer row in the Si(001) surface, using first-principles calculations. The dynamic appearance of a Ge-Si dimer is distinctively different from that of a Si-Si or Ge-Ge dimer, providing a unique way for its identification by scanning tunneling microscopy (STM). Its rocking motion, observed in STM, actually reflects a 180{degree} rotation of the dimer, involving a piecewise-rotation mechanism. The calculated energy barrier of 0.74 eV is in good agreement with the experimental value of 0.82 eV.
Date: July 24, 2000
Creator: Lu, Zhong-Yi; Liu, Feng; Wang, Cai-Zhuang; Qin, X. R.; Swartzentruber, Brian S.; Lagally, M. G. et al.
Object Type: Article
System: The UNT Digital Library
Recent B-physics results at CDF (open access)

Recent B-physics results at CDF

Between 1992 and 1996 CDF collected about 100 pb{sup {minus}1} of data at a {radical}s = 1.8 TeV at the Fermilab Tevatron collider. This data sample led to a large number of precision measurements of B hadrons properties including their masses, lifetimes and neutral B meson oscillation parameters and the discovery of the B{sub c} meson. Here the author reports on three recent results: the measurement of the B{sup +} production cross section, the search for radiative penguin B hadron decays and the measurement of the CP violating parameter sin 2{beta}. These results are significant examples of the breadth of the CDF program. In 2001 the main injector will allow the Tevatron initially to deliver 1 fb{sup {minus}1} per year at {radical}s = 2 TeV. The CDF detector will undergo major upgrades which will further increase the B physics reach.
Date: July 27, 2000
Creator: Bortoletto, Daniela
Object Type: Article
System: The UNT Digital Library
Modeling of on-line catalyst addition effects in a short contact time reactor (open access)

Modeling of on-line catalyst addition effects in a short contact time reactor

Recently developed short-contact-time reactors (SCTR), consisting of porous alumina monoliths coated with platinum, have been shown to produce ethylene from rich ethane/oxygen(hydrogen) mixtures with yields and selectivities comparable to conventional steam cracking, using a reactor of much smaller size. Although the overall mechanism is clearly autothermal and catalytic, the details, in particular the relative contributions of heterogeneous and homogeneous chemistry, are a matter of considerable debate. Recent experiments show that reactor performance can be further enhanced by dripping a dilute platinum solution onto the SCTR front face during reaction, resulting in catalyst deposition within only a short (several millimeter) zone of the reactor. The authors have undertaken a computational study of this system, using two-dimensional computational fluid dynamics simulations with full heat and mass transport and detailed heterogeneous and homogeneous kinetic mechanisms. The results indicate that front-face catalyst loading enhances reactor performance by limiting the opportunity for heterogeneous ethane reactions that produce methane. As a result, ethylene selectivity increases and CH{sub 4} selectivity decreases. The results strongly support a mechanism recently proposed by the authors, in which rapid, heterogeneous oxidation of adsorbed hydrogen consumes most of the oxygen. The resulting heat is then released to the gas phase, causing homogeneous …
Date: July 30, 2000
Creator: Zerkle, D. K.; Allendorf, M. d.; Wolf, M. & Deutschmann, O.
Object Type: Article
System: The UNT Digital Library