Time filter

Source Type

Houston, TX, United States

Zamani N.,PE Inc. | Zamani N.,Southern Methodist University | El Shamy U.,Southern Methodist University
International Journal of Geomechanics | Year: 2013

In this study, a three-dimensional microscale framework utilizing the discrete-element method (DEM) is presented to analyze the seismic response of soil-foundation-structure systems subjected to three-directional base motion. The proposed approach is employed to investigate the response of a single lumped mass on a square spread footing founded on a dry granular deposit. The soil is idealized as a collection of spherical particles using DEM. The spread footing is modeled as a rigid block composed of clumped particles, and its motion is described by the resultant forces and moments acting upon it. The structure is modeled as a column made of clumped particles with a concentrated mass specified for the particle at the top. Analysis is done in a fully coupled scheme in time domain while taking into account the effects of soil nonlinear behavior, possible separation between the foundation base and soil because of rocking, possible sliding of the footing, and dynamic soilfoundation interactions.Atechnique to idealize several base boundary conditions to mimic rigid and elastic rock as well as an infinite medium is also presented. Microscale energy dissipation in the soil deposit in the free field and in the presence of the structure is quantified. Simulations were conducted to investigate the response of the deposit with and without the structure to various scenarios of multidirectional shaking patterns. Vertical motion amplification in the free field was similar to that of shear wave propagation. However, there was less nonlinearity for vertical motion than there was for horizontal motion. Lateral motion had a small impact on the amplification of the vertical input motion. The inclusion of vertical motion did not influence the amplification of horizontal motion at frequencies far from the resonance frequency of vertical motion. © 2013 American Society of Civil Engineers.

Huffmaster M.,PE Inc. | Maldonado F.,Criterion Catalysts
Sulphur 2014 30th International Conference and Exhibition | Year: 2014

The Tail Gas Unit (TGU) process has been developed to remove sulfur compounds from Claus tail gas in order to comply with stringent emission regulations. From the early 1970s to today TGUs have been improved to meet higher levels of performance for ever tighter environmental requirements and to reduce capital or operating cost. Reactor performance is a critical parameter in achieving TGU environmental performance. Conversion of sulfur species to H2S is a function of catalyst activity, reactor space velocity and temperature. Reactor modeling, process chemistry and chemical equilibrium influence tail gas unit performance and provide a framework to examine the effects of space velocity and temperature. Assessment of the impact of these principal variables on both catalyst bed design and performance is the subject of this paper. Copyright © 2012 CRI/Criterion Inc. All rights reserved.

Hubbard J.A.,University of Texas at Austin | Haglund J.S.,University of Texas at Austin | Ezekoye O.A.,University of Texas at Austin | McFarland A.R.,Texas A&M University | McFarland A.R.,PE Inc.
Aerosol Science and Technology | Year: 2011

Advances in microfluidic, lab on chip, and other near-real-time biological identification technologies have driven the desire to concentrate bioaerosols into hydrosol sample volumes on the order of tens of microliters (μL). However, typical wet biological aerosol collector outputs are an order or two of magnitude above this goal. The ultimate success of bioaerosol collectors and biological identifiers requires an effective coupling at the macro-to-micro interface. Liquid collection performance was studied experimentally for a family of dynamically scaled wetted wall bioaerosol sampling cyclones (WWCs). Steady-state liquid collection rates and system response times were measured for a range of environmental conditions (temperatures from 10°C to 50°C and relative humidities from 10% to 90%), liquid input rates, and WWC airflow configurations. A critical liquid input rate parameter was discovered that collapsed all experimental data to self-similar empirical performance correlations. A system algorithm was then developed from empirical correlations to provide control over the liquid output rate and resulting concentration factor for a cyclone with an airflow rate of 100 L/min. Desired liquid output rates of 25 to 50 μL/min were maintained while sampling outdoor air over diurnal ranges of environmental conditions. These flow rates are associated with concentration factors on the order of 1,000,000 to 2,000,000 and liquid outputs that are a steady stream of 10 to 30 drops/min of 7 to 10 μL droplets. These developments should allow wetted wall cyclones to be effectively coupled to advanced biological identification systems. © American Association for Aerosol Research.

King M.D.,Texas A&M University | McFarland A.R.,Texas A&M University | McFarland A.R.,PE Inc.
Aerosol Science and Technology | Year: 2012

Contemporary near-real-time bioaerosol identifiers that read labeled DNA require a minimum DNA length of about 500,000 base pairs; and for critical applications, instrumental identification results must be verified through the use of classical microbiological culturing techniques. A 300 L/min Wetted Wall Cyclone (WWC) and an 800 L/min inertial impactor were used in a comparative study to collect aerosolized single cells of Escherichia coli (E. coli) at temperatures of 24°C and 46°C. Classical microbiological plating techniques showed that the culturability of E. coli collected with a WWC is a factor of about 100 higher than that of the impactor when the sampled aerosol is at room temperature (RT) and a factor of about 4000 higher when the sampled aerosol is at 46°C. DNA integrity was qualitatively evaluated with pulsed field gel electrophoresis (PFGE) and photographic evidence shows a significant difference in the amount of high molecular weight DNA (molecules larger than 500,000 base pairs) collected with the WWC compared with the impactor. Extracted DNA was also digested by the NotI enzyme, and the qualitative results of the restriction analysis showed there to be high integrity of the WWC-collected DNA, whereas the impactor-collected DNA showed considerable fragmentation. Real-Time polymerase chain reaction (RT-PCR) showed samples required for E. coli identification need to be about 100 times more concentrated if they are collected with the impactor rather than that of the WWC. Also, it appears that only the intact genomic DNA of the culturable cells provides adequate templates for traditional and RT-PCR amplification. 2011 08 16.

Applera Corporation and PE Corporation | Date: 2006-08-08

Reagents for scientific or research use; reagents for forensics and human identification. Computer software used for collection, organization, analysis, integration and communication of scientific data; computer hardware; Pre-recorded CD-ROM, diskettes, audio and video tapes and cassettes featuring scientific information; computer software used to operate laboratory instrument; laboratory instruments, namely nucleic acid sequencers and synthesizers, electrophoresis machines, linkage analyzers, genetic mappers thermal cycler, cytometer, proteins and peptide synthesizers, mass spectrometer and chromatograph, high-throughput instrument for preparation of nucleic acid samples, laboratory robots, and accessories to and parts of the above instruments, laboratory supplies, namely, plastic consumables, rack, vials, caps, septa, needles, bottles, flask, filter, tubes, and seals, plastic tray cover, micro plate, pipette tips, reagent reservoir, optical heat field covers, plastic cards, and plastic capillary arrays; all aforesaid goods are for scientific and research use. Installation, maintenance and repair of laboratory instruments for scientific, research, medical, and diagnostics use; Installation, maintenance and repair of computer hardware instruments for scientific, research, medical, and diagnostics use.

Discover hidden collaborations