Influence Of Advection Differencing Error Upon Large-Eddy Simulation Accuracy     

John W. Glendening  Tracy Haack 《Boundary-Layer Meteorology》2001,98(1):127-153

Accurate prediction of turbulent features by alarge-eddy simulation (LES) model requires accuratenumerical evaluation of the nonlinear advective terms. In the presence of a mean wind, use of second-order orfourth-order finite differencing produces large lossesof turbulent energy at high wavenumbers, an inaccuracyconsistent with idealized numerical properties ofthese schemes. The discrete differencing inaccuraciesalso affect the small wavenumber ``large eddy'structure and the horizontally-averaged turbulentquantities. With a high accuracy pseudospectraltechnique, this energy loss does not occur andspectral behaviour corresponds to filtered Kolmogorovtheory predictions out to the de-aliasing cutoffwavenumber. The inaccuracy of the finite differenceschemes is greatly ameliorated through a Galileantransformation of the advective term.  相似文献   

Combined Use of Flowmeter and Time-Drawdown Data to Estimate Hydraulic Conductivities in Layered Aquifer Systems     

R. T. Hanson  Tracy Nishikawa 《Ground water》1996,34(1):84-94

  相似文献   

Chemical contaminant exposure and effects in four fish species from Tampa Bay,Florida     

Bruce B. McCain  Donald W. Brown  Tom Hom  Mark S. Myers  Susan M. Pierce  Tracy K. Collier  John E. Stein  Sin-Lam Chan  Usha Varanasi 《Estuaries and Coasts》1996,19(1):86-104

Concentrations of selected anthropogenic chemical contaminants and levels of pollution-related biological effects were measured during three consecutive years (1990–1992) in hardhead catfish (Arius felis), Gulf killifish (Fundulus grandis), longnose killifish (F. majalis), and red drum (Scieaenops ocellatus) from 12 subtidal and intertidal sites in Tampa Bay and nearby Sarasota Bay. Each species was collected from at least four sites. Compared to nonindustrialized sites, concentrations of PCBs, DDTs, and alpha-chlordane in liver, and of fluorescent aromatic compounds in bile, were highest in fish from sites in or near Hillsborough Bay, the most industrialized portion of Tampa Bay. The results of analyses for two biochemical markers of contaminant-induced effects in fish, hepatic cytochrome P4501A activities and levels of hepatic DNA adducts, also showed the highest levels to be in all four fish species from sites in the vicinity of Hillsborough Bay. Liver lesions, considered to be pollution-associated in several other bottom-feeding fish species, were found in hardhead catfish and longnose killifish, exclusively from sites in Hillsborough Bay. Overall, concentrations of selected contaminants and their derivatives in the four target fish species generally reflected concentrations of these contaminants found in sediment. The biochemical and histopathological responses demonstrated that chemical contaminant concentrations in the vicinity of Hillsborough Bay are sufficiently high to cause adverse effects in indigenous fish species. The results, collectively, showed that the extent of contaminant exposure and biological effects in fish from sites in Tampa Bay were low to moderate compared to more urbanized coastal sites of the United States. *** DIRECT SUPPORT *** A01BY073 00009  相似文献   

Lead Contamination Adjacent to Roadways in Trujillo,Venezuela     

Tracy Newsome  Freddy Aranguren  Robert Brinkman 《The Professional geographer》1997,49(3):331-341

This study analyzes the extent and pattern of lead contamination along roadways in Trujillo, Venezuela, using traffic counts and soil samples collected in the field. The normalized mean lead level for frontyard samples along major traffic arteries was 200 μgg ^-1 versus 0 μgg^-1 for backyard samples. Furthermore 55%of the frontyard lead levels were hazardous, versus 7% of the backyard samples. This suggests a strong relationship between traffic and soil lead content. However, a relationship between lead level spatial patterns and traffic volume patterns was not established, suggesting that factors beyond traffic volume, such as slope and erosion, play a significant role in contamination patterns.  相似文献   

3rd ANtarctic Gravity Wave Instrument Network(ANGWIN)Science Workshop     

Tracy MOFFAT-GRIFFIN  Mike J. TAYLOR  Takuji NAKAMURA  Andrew J. KAVANAGH  J. Scott HOSKING  Andrew ORR 《大气科学进展》2017,34(1):1-3

<正>1.Overview The 3~(rd)ANtarctic Gravity Wave Instrument Network(ANGWIN)science workshop was held on 12–14 April 2016in Cambridge,UK.ANGWIN is a highly successful grassroots program that was started in 2011(in the Cornish English dialect ANGWIN means"the white").Although initially focused on the Antarctic,we now aim to develop collaborations in both polar regions.ANGWIN aims to use results from the network of instrumentation at international research  相似文献   

Investigation of Thulium and Other Rare Earth Element Mass Fractions in NIST SRM 1632a Bituminous Coal Reference Material by Quadrupole ICP‐MS          下载免费PDF全文

Elliot Roth  Tracy L. Bank  Evan Granite 《Geostandards and Geoanalytical Research》2018,42(2):263-269

Inductively coupled plasma‐mass spectrometry after lithium metaborate fusion and digestion was used to measure the rare earth element (REE) mass fractions of several reference materials including NIST SRM 1632a, a historical bituminous Pennsylvania seam coal. While most of the REE mass fractions measured in this study were consistent with the published consensus data, the measured mass fraction of thulium for NIST SRM 1632a was consistently lower compared with the published data. Chondrite normalisation of the published consensus data for NIST SRM 1632a produced a positive thulium anomaly (Tm = 1.78), which is inconsistent with a terrestrial source of sediment. Normalisation of REE mass fractions collected in this study produced no significant Tm anomaly (Tm = 0.93), which agrees with the sedimentary depositional environment of coal. Therefore, a revised mass fraction of 0.16 mg kg^?1 Tm in NIST SRM 1632a is recommended.  相似文献   

GG Tau: the ringworld and beyond     

Anne?DutreyEmail author  Emmanuel?Di Folco  Tracy?Beck  Stéphane?Guilloteau 《Astronomy and Astrophysics Review》2016,24(1):5

In binary stellar systems, exoplanet searches have revealed planetary mass companions orbiting both in circumstellar and in circumbinary orbits. Modelling studies suggest increased dynamical complexity around the young stars that form such systems. Circumstellar and circumbinary disks likely exhibit different physical conditions for planet formation, which also depends on the stellar separation. Although binaries and higher order multiple stars are relatively common in nearby star-forming regions, surprisingly few systems with circumbinary distributions of proto-planetary material have been found. With its spectacular ring of dust and gas encircling the central triple star, one such system, GG Tau A, has become a unique laboratory for investigating the physics of circumsystem gas and dust evolution. We review here its physical properties.  相似文献   

The Haitian housing dilemma: can sustainability and hazard-resilience be achieved?     

Tracy Kijewski-Correa  Alexandros A. Taflanidis 《Bulletin of Earthquake Engineering》2012,10(3):765-771

The present danger in the Haitian rebuilding efforts, outside of the extreme level of need that often encourages temporary solutions at the expense of long-term capacity building, centers on the assumption that sustainability and resilience are mutually exclusive. They cannot be if this rare opportunity to achieve meaningful long-term change within a country that has suffered for far too long is to be fully seized. This change can be realized only with appropriate policies and incentives that do not simply fund the re-implementation of vulnerable construction modes in an effort to meet immediate needs, but that foster the introduction of alternative structural systems with the requirement that they build genuine local capacity to deliver sustainable and resilient homes that meet Haiti’s cultural and economic constraints. This short communication reviews the important housing dilemma Haiti now faces, a dilemma with international extensions since researchers and construction firms from all over the world (including France, Germany, Italy, Greece, Japan, Canada, US) are involved, and presents thoughts for the importance of offering solutions that serve both ends of the economic spectrum, are hazard-resilient and truly sustainable.  相似文献   

Minimal‐disturbance seismic rehabilitation of steel moment‐resisting frames using light‐weight steel elements          下载免费PDF全文

Masahiro Kurata  Miho Sato  Lei Zhang  Oren Lavan  Tracy Becker  Masayoshi Nakashima 《地震工程与结构动力学》2016,45(3):383-400

This paper presents a rehabilitation technique developed under a design and construction scheme, termed minimal‐disturbance seismic rehabilitation. This scheme pursues enhancing the seismic performance of buildings with the intention of improving the continuity of business while minimizing obstruction of the visual and physical space of building users and the use of heavy construction equipment and hot work (welding/cutting). The developed rehabilitation technique consists of light‐weight steel elements and aims to decrease demands to beam‐ends of steel moment‐resisting frames. The behavior of the baseline model was verified through numerical analysis and proof‐of‐concept testing. Furthermore, the effectiveness of rehabilitation is studied through retrofitting a four‐story steel moment‐resisting frame originally designed with Japanese design guidelines. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

On board short-time high temperature heat treatment of ballast water: a field trial under operational conditions   总被引：2，自引：1，他引：1  

Quilez-Badia G  McCollin T  Josefsen KD  Vourdachas A  Gill ME  Mesbahi E  Frid CL 《Marine pollution bulletin》2008,56(1):127-135

A ballast water short-time high temperature heat treatment technique was applied on board a car-carrier during a voyage from Egypt to Belgium. Ballast water from three tanks was subjected for a few seconds to temperatures ranging from 55 degrees C to 80 degrees C. The water was heated using the vessel's heat exchanger steam and a second heat exchanger was used to pre-heat and cool down the water. The treatment was effective at causing mortality of bacteria, phytoplankton and zooplankton. The International Maritime Organization (IMO) standard was not agreed before this study was carried out, but comparing our results gives a broad indication that the IMO standard would have been met in some of the tests for the zooplankton, in all the tests for the phytoplankton; and probably on most occasions for the bacteria. Passing the water through the pump increased the kill rate but increasing the temperature above 55 degrees C did not improve the heat treatment's efficacy.  相似文献