Segui questo link per vedere altri tipi di pubblicazioni sul tema: Multiple cooling towers.
Articoli di riviste sul tema "Multiple cooling towers"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 articoli di riviste per l'attività di ricerca sul tema "Multiple cooling towers".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi gli articoli di riviste di molte aree scientifiche e compila una bibliografia corretta.
1
Rubio-Castro, Eusiel, Medardo Serna-González, José María Ponce-Ortega e Mahmoud M. El-Halwagi. "Synthesis of cooling water systems with multiple cooling towers". Applied Thermal Engineering 50, n. 1 (gennaio 2013): 957–74. http://dx.doi.org/10.1016/j.applthermaleng.2012.06.015.
Testo completo
2
CHENG, X. X., L. ZHAO e Y. J. GE. "MULTIPLE LOADING EFFECTS ON WIND-INDUCED STATIC PERFORMANCE OF SUPER-LARGE COOLING TOWERS". International Journal of Structural Stability and Dynamics 13, n. 08 (21 ottobre 2013): 1350039. http://dx.doi.org/10.1142/s0219455413500399.
Testo completoAbstract (sommario):
Currently, four grouped 177 m super-large cooling towers, i.e. column-supported hyperboloidal shells, are to be constructed in a typical electric power plant in Southeast China. To this end, simultaneous pressure measurements on 1:200 rigid tower models are carried out in an atmospheric boundary layer (ABL) wind tunnel, aimed at accurately obtaining the external/internal cladding wind loads on these shells. The wind-induced static behavior of the cooling towers is analyzed by applying the wind loads acquired via the pressure model tests, using both linear elastic and nonlinear elastic finite element (FE) analyses. The corresponding responses (structural deformation, internal force and local buckling state) are compared with those obtained by the traditional design approach, focused on the effects of internal suction and external pressure distribution. Besides, the tower group interference effects are studied by comparing the results computed of a freestanding tower, with those of the tower groups during two different construction stages. The main findings about the loading effects on the static performance of the super-large cooling towers are helpful for improving the current Chinese Codes that govern the design of super-large cooling towers.
3
Guo, Yong, e Zhi Yong Liu. "Study on the Cooling Water Systems with Multiple Cooling Water Supplies". Advanced Materials Research 610-613 (dicembre 2012): 2497–500. http://dx.doi.org/10.4028/www.scientific.net/amr.610-613.2497.
Testo completoAbstract (sommario):
Water pinch technology is a process integration technology used for enterprises water system optimization, in order to improve the water reuse rate. Application of water pinch point technology to the whole system analysis and design, to establish a feasible performance index, and then determine the detailed process of design and transformation to achieve the predetermined target performance. This paper presents a technique for simultaneous targeting and design in cooling water systems comprising of at least two cooling towers and several cooling water using operations. Through comprehensive analysis on the cooling water systems with multiple cooling water supplies, determine the corresponding heat transfer process to the cooling tower, obtained better results than literature.
4
Gololo, Khunedi Vincent, e Thokozani Majozi. "On Synthesis and Optimization of Cooling Water Systems with Multiple Cooling Towers". Industrial & Engineering Chemistry Research 50, n. 7 (6 aprile 2011): 3775–87. http://dx.doi.org/10.1021/ie101395v.
Testo completo
5
Barrette, Isabelle. "Comparison of Legiolert and a Conventional Culture Method for Detection of Legionella pneumophila from Cooling Towers in Québec". Journal of AOAC INTERNATIONAL 102, n. 4 (1 luglio 2019): 1235–40. http://dx.doi.org/10.5740/jaoacint.18-0245.
Testo completoAbstract (sommario):
Abstract Background: Legionnaires’ disease is a potentially lethal pneumonia contracted through inhalation of aerosolized water contaminated with Legionella bacteria. Detection and control of L. pneumophila, the primary species responsible for the disease, is critical to public health. In Québec, cooling towers and evaporative condensers are required to follow a maintenance and testing program to ensure L. pneumophila concentrations remain at acceptable levels. Objective: This study compared a new culture method based on the most probable number approach, Legiolert®, with the formal culture method used at EnvironeX for regulatory compliance testing to quantify L. pneumophila from cooling tower waters in Québec. Methods: A split-sample analysis was performed in which 401 samples from cooling towers in Québec were tested with both methods. Results: Results with 74 positive samples showed that Legiolert provided a significant increase in sensitivity for L. pneumophila compared with the agar plate method. Cooling tower samples often contain non-Legionella flora that necessitate multiple treatment and plating conditions to prevent interference with the test. Legiolert showed little to no impact from non-Legionella organisms in this study. Conclusions: Overall, Legiolert showed several advantages over the agar plate method, including increased sensitivity, reduced interference, a simplified test procedure, and an easy-to-read positive signal.
6
KOOL, J. L., U. BUCHHOLZ, C. PETERSON, E. W. BROWN, R. F. BENSON, J. M. PRUCKLER, B. S. FIELDS et al. "Strengths and limitations of molecular subtyping in a community outbreak of Legionnaires' disease". Epidemiology and Infection 125, n. 3 (dicembre 2000): 599–608. http://dx.doi.org/10.1017/s095026880000474x.
Testo completoAbstract (sommario):
An epidemiological and microbiological investigation of a cluster of eight cases of Legionnaires' disease in Los Angeles County in November 1997 yielded conflicting results. The epidemiological part of the investigation implicated one of several mobile cooling towers used by a film studio in the centre of the outbreak area. However, water sampled from these cooling towers contained L. pneumophila serogroup 1 of another subtype than the strain that was recovered from case-patients in the outbreak. Samples from two cooling towers located downwind from all of the case-patients contained a Legionella strain that was indistinguishable from the outbreak strain by four subtyping techniques (AP-PCR, PFGE, MAb, and MLEE). It is unlikely that these cooling towers were the source of infection for all the case-patients, and they were not associated with risk of disease in the case-control study. The outbreak strain also was not distinguishable, by three subtyping techniques (AP-PCR, PFGE, and MAb), from a L. pneumophila strain that had caused an outbreak in Providence, RI, in 1993. Laboratory cross-contamination was unlikely because the initial subtyping was done in different laboratories.In this investigation, microbiology was helpful for distinguishing the outbreak cluster from unrelated cases of Legionnaires' disease occurring elsewhere. However, multiple subtyping techniques failed to distinguish environmental sources that were probably not associated with the outbreak. Persons investigating Legionnaires' disease outbreaks should be aware that microbiological subtyping does not always identify a source with absolute certainty.
7
Hunt, D. A., K. A. V. Cartwright, M. C. Smith, J. Middleton, C. L. R. Bartlett, J. V. Lee, P. J. Dennis e D. Harper. "An outbreak of Legionnaires' disease in Gloucester". Epidemiology and Infection 107, n. 1 (agosto 1991): 133–41. http://dx.doi.org/10.1017/s0950268800048767.
Testo completoAbstract (sommario):
SUMMARYFourteen people living in or near the city of Gloucester fell ill with Legionnaires' disease caused by Legionella pneumophila serogroup (SG) 1 between 27 August and 27 October 1986. Another patient had fallen ill on 30 May. Nine of the 15 were diagnosed retrospectively during a case finding exercise. There were three deaths. Three cases of Pontiac fever were also diagnosed.The source was probably one or more wet cooling towers. Nineteen premises in the city with such towers were identified, and three just outside Gloucester. Samples from 11 of the 22 premises grew Legionella spp.; from nine of these L. pneumophila SG 1 (Pontiac) was isolated. The efficacy of regular addition of biocide in addition to hypochlorite added at the time of disinfection in inhibiting the growth of Legionella spp. was demonstrated.A survey of patients' movements during their likely incubation period showed that there was no single building that all patients had visited, but there were two areas of the city which nearly all had visited or passed through by car. A case-control study demonstrated an association with one of these areas.Cooling towers near both areas may have been sources but the evidence is insufficient to incriminate any single one. The unexpected finding of L. pneumophila SG 1 (Pontiac) in nine towers supports the hypothesis that there may have been multiple sources. Cooling towers may have been contaminated by mains water or by drift from other towers.
8
Young, Charlotte, Duncan Smith, Tim Wafer e Brian Crook. "Rapid Testing and Interventions to Control Legionella Proliferation following a Legionnaires’ Disease Outbreak Associated with Cooling Towers". Microorganisms 9, n. 3 (17 marzo 2021): 615. http://dx.doi.org/10.3390/microorganisms9030615.
Testo completoAbstract (sommario):
Most literature to date on the use of rapid Legionella tests have compared different sampling and analytical techniques, with few studies on real-world experiences using such methods. Rapid tests offer a significantly shorter feedback loop on the effectiveness of the controls. This study involved a complex of five factories, three of which had a history of Legionella contamination in their cooling water distribution system. Multiple sampling locations were utilised to take monthly water samples over 39 months to analyse for Legionella by both culture and quantitative polymerase chain reaction (qPCR). Routine monitoring gave no positive Legionella results by culture (n = 330); however, samples were frequently (68%) positive by qPCR for Legionella spp. (n = 1564). Legionella spp. qPCR assay was thus found to be a good indicator of cooling tower system health and suitable as a routine monitoring tool. An in-house qPCR limit of 5000 genomic units (GU)/L Legionella spp. was established to trigger investigation and remedial action. This approach facilitated swift remedial action to prevent Legionella proliferation to levels that may represent a public health risk. Cooling tower operators may have to set their own action levels for their own systems; however, in this study, 5000 GU/L was deemed appropriate and pragmatic.
9
Thornley, C., D. Harte, R. Weir, L. Allen e P. Wood. "Mixed species legionellosis outbreak linked to industrial cooling towers contaminated with multiple Legionella species, New Zealand, August-November 2015". International Journal of Infectious Diseases 53 (dicembre 2016): 138–39. http://dx.doi.org/10.1016/j.ijid.2016.11.341.
Testo completo
10
Sobral, D., P. Le Cann, A. Gerard, S. Jarraud, B. Lebeau, F. Loisy-Hamon, G. Vergnaud e C. Pourcel. "High-Throughput Typing Method To Identify a Non-Outbreak-Involved Legionella pneumophila Strain Colonizing the Entire Water Supply System in the Town of Rennes, France". Applied and Environmental Microbiology 77, n. 19 (5 agosto 2011): 6899–907. http://dx.doi.org/10.1128/aem.05556-11.
Testo completoAbstract (sommario):
ABSTRACTTwo legionellosis outbreaks occurred in the city of Rennes, France, during the past decade, requiring in-depth monitoring ofLegionella pneumophilain the water network and the cooling towers in the city. In order to characterize the resulting large collection of isolates, an automated low-cost typing method was developed. The multiplex capillary-based variable-number tandem repeat (VNTR) (multiple-locus VNTR analysis [MLVA]) assay requiring only one PCR amplification per isolate ensures a high level of discrimination and reduces hands-on and time requirements. In less than 2 days and using one 4-capillary apparatus, 217 environmental isolates collected between 2000 and 2009 and 5 clinical isolates obtained during outbreaks in 2000 and 2006 in Rennes were analyzed, and 15 different genotypes were identified. A large cluster of isolates with closely related genotypes and representing 77% of the population was composed exclusively of environmental isolates extracted from hot water supply systems. It was not responsible for the known Rennes epidemic cases, although strains showing a similar MLVA profile have regularly been involved in European outbreaks. The clinical isolates in Rennes had the same genotype as isolates contaminating a mall's cooling tower. This study further demonstrates that unknown environmental or genetic factors contribute to the pathogenicity of some strains. This work illustrates the potential of the high-throughput MLVA typing method to investigate the origin of legionellosis cases by allowing the systematic typing of any new isolate and inclusion of data in shared databases.
11
Takle, Eugene S., Daniel A. Rajewski e Samantha L. Purdy. "The Iowa Atmospheric Observatory: Revealing the Unique Boundary Layer Characteristics of a Wind Farm". Earth Interactions 23, n. 2 (1 marzo 2019): 1–27. http://dx.doi.org/10.1175/ei-d-17-0024.1.
Testo completoAbstract (sommario):
Abstract The Iowa Atmospheric Observatory was established to better understand the unique microclimate characteristics of a wind farm. The facility consists of a pair of 120-m towers identically instrumented to observe basic landscape–atmosphere interactions in a highly managed agricultural landscape. The towers, one within and one outside of a utility-scale low-density-array wind farm, are equipped to measure vertical profiles of temperature, wind, moisture, and pressure and can host specialized sensors for a wide range of environmental conditions. Tower measurements during the 2016 growing season demonstrate the ability to distinguish microclimate differences created by single or multiple turbines from natural conditions over homogeneous agricultural fields. Microclimate differences between the two towers are reported as contrasts in normalized wind speed, normalized turbulence intensity, potential temperature, and water vapor mixing ratio. Differences are analyzed according to conditions of no wind farm influence (i.e., no wake) versus wind farm influence (i.e., waked flow) with distance downwind from a single wind turbine or a large group of turbines. Differences are also determined for more specific atmospheric conditions according to thermal stratification. Results demonstrate agreement with most, but not all, currently available numerical flow-field simulations of large wind farm arrays and of individual turbines. In particular, the well-documented higher nighttime surface temperature in wind farms is examined in vertical profiles that confirm this effect to be a “suppression of cooling” rather than a warming process. A summary is provided of how the wind farm boundary layer differs from the natural boundary layer derived from concurrent measurements over the summer of 2016.
12
Kaya, A., e A. Sommer. "Energy Management of Chillers by Multilevel Control and Optimization". Journal of Dynamic Systems, Measurement, and Control 107, n. 4 (1 dicembre 1985): 270–77. http://dx.doi.org/10.1115/1.3140735.
Testo completoAbstract (sommario):
This paper deals with multilevel control and optimization of a chiller system. The system consists of multiple chillers, feed pumps, and cooling towers. A multilevel control structure is presented. The first level contains control loops for chilled water temperature, vane position, and condenser water temperature. Second level controls provide supervisory adjustments of set points of first level controls. Third level is optimum load allocation of chillers and pumps. A fourth level supervisory deals with the coordination of conflicting goals of subsystems to provide a load strategy. Performance analysis (monitoring, trouble shooting) are also presented. A digital and distributed control system is utilized for implementation. The distributed system has a flexible architecture compatible for each level of control sophistication. It offers simple function blocks for digital control of first-level loops, as well as, the higher levels without any need of computer programming.
13
Cheng, XX, X. Chen, YJ Ge, H. Jiang e L. Zhao. "A new atmospheric boundary layer wind tunnel simulation methodology for wind effects on large cooling towers considering wind environment variations". Advances in Structural Engineering 22, n. 5 (4 novembre 2018): 1194–210. http://dx.doi.org/10.1177/1369433218809899.
Testo completoAbstract (sommario):
The traditional atmospheric boundary layer wind tunnel model test practice employs wind fields, the flow characteristics of which are in accordance with the empirical formulae of the atmospheric turbulence presented in Codes of Practice and monographs. However, the empirical formulae presented in Codes of Practice and monographs cannot truthfully reflect the high variations of the realistic atmospheric turbulence which sometimes aggravates wind effects on structures. Based on model tests conducted in a multiple-fan actively controlled wind tunnel, it is found that most wind effects on large cooling towers change monotonically with the increase in free-stream turbulence, and the model test results are more unfavorable for a flow field of low turbulence intensity than for a flow field of high turbulence intensity with respect to the measured coherences. Thus, a new atmospheric boundary layer wind tunnel simulation methodology for wind effects on circular cylindrical structures is proposed to overcome the deficiency of the traditional atmospheric boundary layer wind tunnel model tests. The new simulation methodology includes the simulation of two realistic atmospheric boundary layer flow fields with the highest and the lowest turbulence intensities in the wind tunnel and the envelopment of model test results obtained in the two flow fields (e.g. the mean and fluctuating wind pressure distributions, the power spectral density, the coherence function, and the correlation coefficient). The superiority of the new atmospheric boundary layer wind tunnel simulation methodology over the traditional model test practice is demonstrated by comparing the model test results with the full-scale measurement data.
14
Dufton, D. R. L., e C. G. Collier. "Fuzzy logic filtering of radar reflectivity to remove non-meteorological echoes using dual polarization radar moments". Atmospheric Measurement Techniques 8, n. 10 (1 ottobre 2015): 3985–4000. http://dx.doi.org/10.5194/amt-8-3985-2015.
Testo completoAbstract (sommario):
Abstract. The ability of a fuzzy logic classifier to dynamically identify non-meteorological radar echoes is demonstrated using data from the National Centre for Atmospheric Science dual polarisation, Doppler, X-band mobile radar. Dynamic filtering of radar echoes is required due to the variable presence of spurious targets, which can include insects, ground clutter and background noise. The fuzzy logic classifier described here uses novel multi-vertex membership functions which allow a range of distributions to be incorporated into the final decision. These membership functions are derived using empirical observations, from a subset of the available radar data. The classifier incorporates a threshold of certainty (25 % of the total possible membership score) into the final fractional defuzzification to improve the reliability of the results. It is shown that the addition of linear texture fields, specifically the texture of the cross-correlation coefficient, differential phase shift and differential reflectivity, to the classifier along with standard dual polarisation radar moments enhances the ability of the fuzzy classifier to identify multiple features. Examples from the Convective Precipitation Experiment (COPE) show the ability of the filter to identify insects (18 August 2013) and ground clutter in the presence of precipitation (17 August 2013). Medium-duration rainfall accumulations across the whole of the COPE campaign show the benefit of applying the filter prior to making quantitative precipitation estimates. A second deployment at a second field site (Burn Airfield, 6 October 2014) shows the applicability of the method to multiple locations, with small echo features, including power lines and cooling towers, being successfully identified by the classifier without modification of the membership functions from the previous deployment. The fuzzy logic filter described can also be run in near real time, with a delay of less than 1 min, allowing its use on future field campaigns.
15
Dufton, D. R. L., e C. G. Collier. "Fuzzy logic filtering of radar reflectivity to remove non-meteorological echoes using dual polarization radar moments". Atmospheric Measurement Techniques Discussions 8, n. 5 (18 maggio 2015): 5025–63. http://dx.doi.org/10.5194/amtd-8-5025-2015.
Testo completoAbstract (sommario):
Abstract. The ability of a fuzzy logic classifier to dynamically identify non-meteorological radar echoes is demonstrated using data from the National Centre for Atmospheric Science dual polarisation, Doppler, X-band mobile radar. Dynamic filtering of radar echoes is required due to the variable presence of spurious targets, which can include insects, ground clutter and background noise. The fuzzy logic classifier described here uses novel multi-vertex membership functions which allow a range of distributions to be incorporated into the final decision. These membership functions are derived using empirical observations, from a subset of the available radar data. The classifier incorporates a threshold of certainty (25% of the total possible membership score) into the final fractional defuzzification to improve the reliability of the results. It is shown that the addition of linear texture fields, specifically the texture of the cross-correlation coefficient, differential phase shift and differential reflectivity, to the classifier along with standard dual polarisation radar moments enhances the ability of the fuzzy classifier to identify multiple features. Examples from the Convective Precipitation Experiment (COPE) show the ability of the filter to identify insects (18 August 2013) and ground clutter in the presence of precipitation (17 August 2013). Medium duration rainfall accumulations across the whole of the COPE campaign show the benefit of applying the filter prior to making quantitative precipitation estimates. A second deployment at a second field site (Burn Airfield, 6 October 2014) shows the applicability of the method to multiple locations, with small echo features, including power lines and cooling towers, being successfully identified by the classifier without modification of the membership functions from the previous deployment. The fuzzy logic filter described can also be run in near real time, with a delay of less than one minute, allowing its use on future field campaigns.
16
Kuiper, Melanie W., Rinske M. Valster, Bart A. Wullings, Harry Boonstra, Hauke Smidt e Dick van der Kooij. "Quantitative Detection of the Free-Living Amoeba Hartmannella vermiformis in Surface Water by Using Real-Time PCR". Applied and Environmental Microbiology 72, n. 9 (settembre 2006): 5750–56. http://dx.doi.org/10.1128/aem.00085-06.
Testo completoAbstract (sommario):
ABSTRACT A real-time PCR-based method targeting the 18S rRNA gene was developed for the quantitative detection of Hartmannella vermiformis, a free-living amoeba which is a potential host for Legionella pneumophila in warm water systems and cooling towers. The detection specificity was validated using genomic DNA of the closely related amoeba Hartmannella abertawensis as a negative control and sequence analysis of amplified products from environmental samples. Real-time PCR detection of serially diluted DNA extracted from H. vermiformis was linear for microscopic cell counts between 1.14 � 10−1 and 1.14 � 104 cells per PCR. The genome of H. vermiformis harbors multiple copies of the 18S rRNA gene, and an average number (with standard error) of 1,330 � 127 copies per cell was derived from real-time PCR calibration curves for cell suspensions and plasmid DNA. No significant differences were observed between the 18S rRNA gene copy numbers for trophozoites and cysts of strain ATCC 50237 or between the copy numbers for this strain and strain KWR-1. The developed method was applied to water samples (200 ml) collected from a variety of lakes and rivers serving as sources for drinking water production in The Netherlands. Detectable populations were found in 21 of the 28 samples, with concentrations ranging from 5 to 75 cells/liter. A high degree of similarity (≥98%) was observed between sequences of clones originating from the different surface waters and between these clones and the reference strains. Hence, H. vermiformis, which is highly similar to strains serving as hosts for L. pneumophila, is a common component of the microbial community in fresh surface water.
17
Shim, Gyu-Jin, M. M. A. Sarker, Choon-Geun Moon, Ho-Saeng Lee e Jung-In Yoon. "Performance Characteristics of a Closed-Circuit Cooling Tower With Multiple Paths". Heat Transfer Engineering 31, n. 12 (ottobre 2010): 992–97. http://dx.doi.org/10.1080/01457631003638994.
Testo completo
18
Yamamoto, Toru, Hirofumi Hayama e Takao Hayashi. "Formulation of Coefficient of Performance Characteristics of Water-cooled Chillers and Evaluation of Composite COP for Combined Chillers". Energies 13, n. 5 (4 marzo 2020): 1182. http://dx.doi.org/10.3390/en13051182.
Testo completoAbstract (sommario):
The Coefficient of Performance of an ordinary water-cooled chiller is presented as a relationship with the chiller load factor and cooling water temperature. However, the cooling water temperature fluctuates according to the processed heat of the cooling tower originating in the cooling energy of the chiller and to the outside temperature and humidity. It is therefore difficult to obtain the cooling water temperature under the processed-heat and weather conditions at the time of evaluation. This, in turn, makes it difficult to determine the Coefficient of Performance of a water-cooled chiller at the evaluation time. In this research, we formulated the Coefficient of Performance of a water-cooled chiller as a relationship with the chiller load factor and specific enthalpy of outside air. Specifically, we used the Number of Transfer Units (NTU) model of a cooling tower to calculate the cooling water temperature corresponding to the cooling-tower load factor targeting a counterflow cooling tower for a range of values of outside-air specific enthalpy. This technique makes it possible to evaluate the Coefficient of Performance of a water-cooled chiller without determining the cooling water temperature. Furthermore, for the case of installing multiple units of chillers, it becomes possible to calculate the composite Coefficient of Performance of those chillers without having to determine the cooling water temperatures for the different operation load factors of those chillers. Moreover, since the composite Coefficient of Performance can be calculated by combining the different installation capacities of these chillers, the energy consumption of multiple chillers can be calculated at the basic planning stage.
19
Conibeer, Gavin, Yi Zhang, Stephen P. Bremner e Santosh Shrestha. "Towards an understanding of hot carrier cooling mechanisms in multiple quantum wells". Japanese Journal of Applied Physics 56, n. 9 (31 luglio 2017): 091201. http://dx.doi.org/10.7567/jjap.56.091201.
Testo completo
20
Dulinska, Joanna M. "Cooling Tower Shell under Asynchronous Kinematic Excitation Using Concrete Damaged Plasticity Model". Key Engineering Materials 535-536 (gennaio 2013): 469–72. http://dx.doi.org/10.4028/www.scientific.net/kem.535-536.469.
Testo completoAbstract (sommario):
The paper presents the analysis of the dynamic response of a cooling tower to moderate earthquake. To represent inelastic behavior of the concrete material of the tower under dynamic loading, the concrete damaged plasticity constitutive model was assumed. The model consists of the combination of non-associated multi-hardening plasticity and scalar damaged elasticity to describe the irreversible damage that occurs during the fracturing process. Two different models of seismic excitation were used. Initially, a classical model of uniform kinematic excitation was applied. In this model it was assumed that excitation at all supports was identical. Then, a model of non-uniform kinematic excitation, typical for large multiple-support structures, was introduced. In that model the wave passage along the foundation ring was taken into account. It occurred that the assumption of asynchronous excitation led to the increase of the dynamic response of the tower with respect to the assumption of uniform ground motion. The tensile damage (cracking) in some parts of the tower appeared and the stiffness of the concrete was degraded when non-uniformity of excitation was considered. This was due to the quasi-static effects resulting from changes of subsoil geometry during the shock. The analysis indicated that the classical assumption of uniform excitation may lead to non-conservative assessment of the dynamic response of the shell described with concrete damaged plasticity model.
21
Naveed, Syed, Satyasreet Jena, Sharma Kumar e Kumar Anil. "Performance investigation of multi-stage hydrogen-based sorption heat pump". FME Transactions 49, n. 1 (2021): 121–27. http://dx.doi.org/10.5937/fme2101121n.
Testo completoAbstract (sommario):
Metal hydrides are broadly investigated, for more than three decades, towards its application for cooling and heating applications. As a continuation of those works, in the present study, authors have investigated the performance of a multi-stage sorption heat pump for multiple cooling and heating outputs. The metal hydrides selected for the present study are Ti0.98Zr0.02V0.43Fe0.09Cr0.05Mn1.5, MmNi4.7Al0.3, LaNi4.8Al0.2 and Zr0.9Ti0.1 Cr0.9Fe1.1, with the operating temperature range as 20°C for cooling output, 45°C for heating output and 140°C for heat supply. The system produces three cooling and four heating outputs with only one heat input. The performance of the system is investigated, via finite volume approach, in terms of hydrogen interaction within the coupled beds, bed temperature variations and heat interactions during hydrogen transfer processes. The minimum temperature observed during the cooling process is 0.5°C, whereas the maximum temperature observed during the heating process is 60°C, which shows that the obtained temperature is capable of space air-conditioning. On the other hand, the maximum cooling and heating outputs, at a particular instant of time, are estimated at 361 W and 402 W, respectively with a heat supply of 23 W.
22
Ringel, Laidi e Djenouri. "Multiple Benefits through Smart Home Energy Management Solutions—A Simulation-Based Case Study of a Single-Family-House in Algeria and Germany". Energies 12, n. 8 (23 aprile 2019): 1537. http://dx.doi.org/10.3390/en12081537.
Testo completoAbstract (sommario):
From both global and local perspectives, there are strong reasons to promote energy efficiency. These reasons have prompted leaders in the European Union (EU) and countries of the Middle East and North Africa (MENA) to adopt policies to move their citizenry toward more efficient energy consumption. Energy efficiency policy is typically framed at the national, or transnational level. Policy makers then aim to incentivize microeconomic actors to align their decisions with macroeconomic policy. We suggest another path towards greater energy efficiency: Highlighting individual benefits at microeconomic level. By simulating lighting, heating and cooling operations in a model single-family home equipped with modest automation, we show that individual actors can be led to pursue energy efficiency out of enlightened self-interest. We apply simple-to-use, easily, scalable impact indicators that can be made available to homeowners and serve as intrinsic economic, environmental and social motivators for pursuing energy efficiency. The indicators reveal tangible homeowner benefits realizable under both the market-based pricing structure for energy in Germany and the state-subsidized pricing structure in Algeria. Benefits accrue under both the continental climate regime of Germany and the Mediterranean regime of Algeria, notably in the case that cooling energy needs are considered. Our findings show that smart home technology provides an attractive path for advancing energy efficiency goals. The indicators we assemble can help policy makers both to promote tangible benefits of energy efficiency to individual homeowners, and to identify those investments of public funds that best support individual pursuit of national and transnational energy goals.
23
Nelson, Ethan L., Tristan S. L’Ecuyer, Stephen M. Saleeby, Wesley Berg, Stephen R. Herbener e Susan C. van den Heever. "Toward an Algorithm for Estimating Latent Heat Release in Warm Rain Systems". Journal of Atmospheric and Oceanic Technology 33, n. 6 (giugno 2016): 1309–29. http://dx.doi.org/10.1175/jtech-d-15-0205.1.
Testo completoAbstract (sommario):
AbstractThis paper outlines an approach for estimating latent heating, surface rainfall rate, and liquid water path in warm rain from downward-viewing W-band radar observations using a Bayesian Monte Carlo algorithm. The algorithm utilizes observed vertical and path-integrated characteristics of precipitating liquid clouds to identify the most appropriate hydrometeor and latent heating structures in a large database of profiles generated using a cloud-resolving model. These characteristics are selected by applying multiple performance metrics to synthetic retrievals. Analysis of the retrievals suggests that a combination of cloud-top, rain-top, and maximum reflectivity heights; vertically integrated reflectivity and attenuation; and a measure of near-surface intensity is sufficient to constrain bulk properties and the vertical structure of warm rain systems. When applied to observations at CloudSat resolution, biases in retrieved liquid water path and surface rainfall rate are small (less than 10%). The algorithm also captures the vertical structure of latent heating, although the magnitudes of integrated heating and cooling exhibit nearly compensating low biases. Random errors are larger owing to the limitations of single-frequency radar observations in constraining drop size distributions. Uncertainties in the altitudes of peak heating and cooling at the pixel scale are typically less than one vertical level, while uncertainties in vertically resolved estimates of heating and cooling rates are on the order of a factor of 2. The utility of the technique is illustrated through application to case studies from airborne radar data from the VAMOS Ocean–Cloud–Atmosphere–Land Study field campaign and satellite observations from CloudSat.
24
Gregg, Walter Boyd, David E. Werth e Carl Frizzell. "Determination of Discharge Coefficients for Hydraulic Sparger Design". Journal of Pressure Vessel Technology 126, n. 3 (1 agosto 2004): 354–59. http://dx.doi.org/10.1115/1.1762902.
Testo completoAbstract (sommario):
This paper provides design examples and summarizes a study on the determination of multiple free discharge orifice coefficients in a circular walled manifold for a variety of shapes and area projections. A simplified design procedure is presented which allows engineers to accurately maintain a given pressure and flow at the entrance to the sparger. The design provides for uniform flow across the cooling tower basin, and prevents an increase in back pressure or open channel flow within the sparger, minimizing the effect of surging or pressure fluctuations on upstream performance.
25
Thomas, Tibin M., Imdad Uddin Chowdhury, K. Dhivyaraja, Pallab Sinha Mahapatra, Arvind Pattamatta e Manish K. Tiwari. "Droplet Dynamics on a Wettability Patterned Surface during Spray Impact". Processes 9, n. 3 (22 marzo 2021): 555. http://dx.doi.org/10.3390/pr9030555.
Testo completoAbstract (sommario):
Wettability patterning of a surface is a passive method to manipulate the flow and heat transport mechanism in many physical processes and industrial applications. This paper proposes a rational wettability pattern comprised of multiple superhydrophilic wedges on a superhydrophobic background, which can continuously remove the impacted spray droplets from the horizontal surface. We observed that the spray droplets falling on the superhydrophilic wedge region spread and form a thin liquid film, which is passively transported away from the surface. However, most of the droplets falling on the superhydrophobic region move towards the wedge without any flooding. The physics of the passive transport of the liquid film on a wedge is also delved into using numerical modelling. In particular, we elucidate the different modes of droplet transport in the superhydrophobic region and the interaction of multiple droplets. The observed droplet dynamics could have profound implications in spray cooling systems and passive removal of liquid from a horizontal surface. This study’s findings will be beneficial for the optimization of efficient wettability patterned surfaces for spray cooling application.
26
Zhang, X., X. Lee, T. J. Griffis, J. M. Baker e W. Xiao. "Estimating greenhouse gas fluxes from an agriculture-dominated landscape using multiple planetary boundary layer methods". Atmospheric Chemistry and Physics Discussions 14, n. 3 (3 febbraio 2014): 3231–67. http://dx.doi.org/10.5194/acpd-14-3231-2014.
Testo completoAbstract (sommario):
Abstract. Quantification of regional greenhouse gas (GHG) fluxes is essential for establishing mitigation strategies and evaluating their effectiveness. Here, we used multiple top-down approaches and multiple trace gas observations at a tall tower to estimate GHG regional fluxes and evaluate the GHG fluxes derived from bottom-up approaches. We first applied the eddy covariance, equilibrium, inverse modeling (CarbonTracker), and flux aggregation methods using three years of carbon dioxide (CO2) measurements on a 244 m tall tower in the Upper Midwest, USA. We then applied the equilibrium method for estimating methane (CH4) and nitrous oxide (N2O) fluxes with one-month high-frequency CH4 and N2O gradient measurements on the tall tower and one-year concentration measurements on a nearby tall tower, and evaluated the uncertainties of this application. The results indicate that: (1) the flux aggregation, eddy covariance, the equilibrium method, and the CarbonTracker product all gave similar seasonal patterns of the regional CO2 flux (105–106 km2), but that the equilibrium method underestimated the July CO2 flux by 52–69%. (2) The annual budget varied among these methods from 74 to −131 g C-CO2 m−2 yr−1, indicating a large uncertainty in the annual CO2 flux estimation. (3) The regional CH4 and N2O emissions according to a top-down method were at least six and two times higher than the emissions from a bottom-up inventory (Emission Database for Global Atmospheric Research), respectively. (4) The global warming potentials of the CH4 and N2O emissions were equal in magnitude to the cooling benefit of the regional CO2 uptake. The regional GHG budget, including both biological and anthropogenic origins, is estimated at 7 ± 160 g CO2 eq m−2 yr−1.
27
He, Cheng. "Temperature Impact of the Industrial Cooling Water Discharges in a Long Boat Slip of Hamilton Harbour". Water Quality Research Journal 44, n. 3 (1 agosto 2009): 221–31. http://dx.doi.org/10.2166/wqrj.2009.024.
Testo completoAbstract (sommario):
Abstract The thermal structure of industrial cooling water discharged into a long, narrow and shallow, straight open boat slip (Ottawa Street Slip, [OSS]) was investigated by field measurements during the hottest summer month in 2006. Three-dimensional hydrodynamic and thermal transport models were established and verified with measurements. The main purposes of this study were to understand the mechanism of the thermal structure in the OSS during the hot summer season under the present cooling water discharge conditions, to investigate the influence of harbour water on the thermal structure in the slip, and to establish a means for scientific predictions of the impact of cooling water discharges in a future study. Toward this end, the water temperature at multiple locations along the OSS and meteorological data near the study site were collected during the summer period of 2006. The collected data reveal: (1) during the measured summer period, the water temperature in the slip can be higher than 30°C during a period of high air temperatures; (2) water temperature variations within short periods of 15, 30, 60, and 120 minutes were no more than 4°C during the entire measurement period; (3) water temperature in the slip is controlled by both air and cooling discharge temperatures, and the cooling water temperature's increase due to industrial cooling processing seems to be relatively independent of the intake water temperature; therefore, the water temperature in the slip varied mainly with the air temperature; (4) since water temperature in the slip seemed to closely follow the intake water temperature, the intake channel may need to be optimized to maximize the possibility of getting the coolest water available from Hamilton Harbour; and (5) the cooler harbour water could not penetrate deeply into the slip. The collected water temperature data were also used for verification of three-dimensional hydrodynamic and transport models. The simulation results showed that the established model could reasonably well reproduce general thermal structures in the entire slip. This achieved the ultimate goal of the study for establishing a model to assess the impacts of further increase of cooling water discharge into the OSS.
28
Dacre, Helen F., Simon A. Josey e Alan L. M. Grant. "Extratropical-cyclone-induced sea surface temperature anomalies in the 2013–2014 winter". Weather and Climate Dynamics 1, n. 1 (4 febbraio 2020): 27–44. http://dx.doi.org/10.5194/wcd-1-27-2020.
Testo completoAbstract (sommario):
Abstract. The 2013–2014 winter averaged sea surface temperature (SST) was anomalously cool in the mid-North Atlantic region. This season was also unusually stormy, with extratropical cyclones passing over the mid-North Atlantic every 3 d. However, the processes by which cyclones contribute towards seasonal SST anomalies are not fully quantified. In this paper a cyclone identification and tracking method is combined with European Centre for Medium-Range Weather Forecasts (ECMWF) atmosphere and ocean reanalysis fields to calculate cyclone-relative net surface heat flux anomalies and resulting SST changes. Anomalously large negative heat flux is located behind the cyclones' cold front, resulting in anomalous cooling up to 0.2 K d−1 when the cyclones are at maximum intensity. This extratropical-cyclone-induced “cold wake” extends along the cyclones' cold front but is small compared to climatological variability in the SSTs. To investigate the potential cumulative effect of the passage of multiple cyclone-induced SST cooling in the same location, we calculate Earth-relative net surface heat flux anomalies and resulting SST changes for the 2013–2014 winter period. Anomalously large winter averaged negative heat flux occurs in a zonally orientated band extending across the North Atlantic between 40 and 60∘ N. The 2013–2014 winter SST cooling anomaly associated with air–sea interactions (ASIs; anomalous heat flux, mixed layer depth and entrainment at the base of the ocean mixed layer) is estimated to be −0.67 K in the mid-North Atlantic (68 % of the total cooling anomaly). The role of cyclones is estimated using a cyclone-masking technique which encompasses each cyclone centre and its cold wake. The environmental flow anomaly in 2013–2014 sets the overall tripole pattern of heat flux anomalies over the North Atlantic. However, the presence of cyclones doubles the magnitude of the negative heat flux anomaly in the mid-North Atlantic. Similarly, the environmental flow anomaly determines the location of the SST cooling anomaly, but the presence of cyclones enhances the SST cooling anomaly. Thus air–sea interactions play a major part in determining the extreme 2013–2014 winter season SST cooling anomaly. The environmental flow anomaly determines where anomalous heat flux and associated SST changes occur, and the presence of cyclones influences the magnitude of those anomalies.
29
Zhang, Han, Xiaohui Liu, Renhao Wu, Fu Liu, Linghui Yu, Xiaodong Shang, Yongfeng Qi et al. "Ocean Response to Successive Typhoons Sarika and Haima (2016) Based on Data Acquired via Multiple Satellites and Moored Array". Remote Sensing 11, n. 20 (11 ottobre 2019): 2360. http://dx.doi.org/10.3390/rs11202360.
Testo completoAbstract (sommario):
Tropical cyclones (TCs) are natural disasters for coastal regions. TCs with maximum wind speeds higher than 32.7 m/s in the north-western Pacific are referred to as typhoons. Typhoons Sarika and Haima successively passed our moored observation array in the northern South China Sea in 2016. Based on the satellite data, the winds (clouds and rainfall) biased to the right (left) sides of the typhoon tracks. Sarika and Haima cooled the sea surface ~4 and ~2 °C and increased the salinity ~1.2 and ~0.6 psu, respectively. The maximum sea surface cooling occurred nearly one day after the two typhoons. Station 2 (S2) was on left side of Sarika’s track and right side of Haima’s track, which is studied because its data was complete. Strong near-inertial currents from the ocean surface toward the bottom were generated at S2, with a maximum mixed-layer speed of ~80 cm/s. The current spectrum also shows weak signal at twice the inertial frequency (2f). Sarika deepened the mixed layer, cooled the sea surface, but warmed the subsurface by ~1 °C. Haima subsequently pushed the subsurface warming anomaly into deeper ocean, causing a temperature increase of ~1.8 °C therein. Sarika and Haima successively increased the heat content anomaly upper than 160 m at S2 to ~50 and ~100 m°C, respectively. Model simulation of the two typhoons shows that mixing and horizontal advection caused surface ocean cooling, mixing and downwelling caused subsurface warming, while downwelling warmed the deeper ocean. It indicates that Sarika and Haima sequentially modulated warm water into deeper ocean and influenced internal ocean heat budget. Upper ocean salinity response was similar to temperature, except that rainfall refreshed sea surface and caused a successive salinity decrease of ~0.03 and ~0.1 psu during the two typhoons, changing the positive subsurface salinity anomaly to negative
30
Szakáll, Miklós, Michael Debertshäuser, Christian Philipp Lackner, Amelie Mayer, Oliver Eppers, Karoline Diehl, Alexander Theis, Subir Kumar Mitra e Stephan Borrmann. "Comparative study on immersion freezing utilizing single-droplet levitation methods". Atmospheric Chemistry and Physics 21, n. 5 (4 marzo 2021): 3289–316. http://dx.doi.org/10.5194/acp-21-3289-2021.
Testo completoAbstract (sommario):
Abstract. Immersion freezing experiments were performed utilizing two distinct single-droplet levitation methods. In the Mainz vertical wind tunnel, supercooled droplets of 700 µm diameter were freely floated in a vertical airstream at constant temperatures ranging from −5 to −30 ∘C, where heterogeneous freezing takes place. These investigations under isothermal conditions allow the application of the stochastic approach to analyze and interpret the results in terms of the freezing or nucleation rate. In the Mainz acoustic levitator, 2 mm diameter drops were levitated while their temperature was continuously cooling from +20 to −28 ∘C by adapting to the ambient temperature. Therefore, in this case the singular approach was used for analysis. From the experiments, the densities of ice nucleation active sites were obtained as a function of temperature. The direct comparison of the results from two different instruments indicates a shift in the mean freezing temperatures of the investigated drops towards lower values that was material-dependent. As ice-nucleating particles, seven materials were investigated; two representatives of biological species (fibrous and microcrystalline cellulose), four mineral dusts (feldspar, illite NX, montmorillonite, and kaolinite), and natural Sahara dust. Based on detailed analysis of our results we determined a material-dependent parameter for calculating the freezing-temperature shift due to a change in cooling rate for each investigated particle type. The analysis allowed further classification of the investigated materials to be described by a single- or a multiple-component approach. From our experiences during the present synergetic studies, we listed a number of suggestions for future experiments regarding cooling rates, determination of the drop temperature, purity of the water used to produce the drops, and characterization of the ice-nucleating material. The observed freezing-temperature shift is significantly important for the intercomparison of ice nucleation instruments with different cooling rates.
31
Zhang, X., X. Lee, T. J. Griffis, J. M. Baker e W. Xiao. "Estimating regional greenhouse gas fluxes: an uncertainty analysis of planetary boundary layer techniques and bottom-up inventories". Atmospheric Chemistry and Physics 14, n. 19 (10 ottobre 2014): 10705–19. http://dx.doi.org/10.5194/acp-14-10705-2014.
Testo completoAbstract (sommario):
Abstract. Quantification of regional greenhouse gas (GHG) fluxes is essential for establishing mitigation strategies and evaluating their effectiveness. Here, we used multiple top-down approaches and multiple trace gas observations at a tall tower to estimate regional-scale GHG fluxes and evaluate the GHG fluxes derived from bottom-up approaches. We first applied the eddy covariance, equilibrium, inverse modeling (CarbonTracker), and flux aggregation methods using 3 years of carbon dioxide (CO2) measurements on a 244 m tall tower in the upper Midwest, USA. We then applied the equilibrium method for estimating CH4 and N2O fluxes with 1-month high-frequency CH4 and N2O gradient measurements on the tall tower and 1-year concentration measurements on a nearby tall tower, and evaluated the uncertainties of this application. The results indicate that (1) the flux aggregation, eddy covariance, the equilibrium method, and the CarbonTracker product all gave similar seasonal patterns of the regional CO2 flux (105−106 km2, but that the equilibrium method underestimated the July CO2 flux by 52–69%. (2) The annual budget varied among these methods from −54 to −131 g C–CO2 m−2 yr−1, indicating a large uncertainty in the annual CO2 flux estimation. (3) The regional CH4 and N2O emissions according to a top-down method were at least 6 and 2 times higher than the emissions from a bottom-up inventory (Emission Database for Global Atmospheric Research), respectively. (4) The global warming potentials of the CH4 and N2O emissions were equal in magnitude to the cooling benefit of the regional CO2 uptake. The regional GHG budget, including both biological and anthropogenic origins, is estimated at 7 ± 160 g CO2 equivalent m−2 yr−1.
32
Heidrich, Tobias, Jonathan Grobe, Henning Meschede e Jens Hesselbach. "Economic Multiple Model Predictive Control for HVAC Systems—A Case Study for a Food Manufacturer in Germany". Energies 11, n. 12 (11 dicembre 2018): 3461. http://dx.doi.org/10.3390/en11123461.
Testo completoAbstract (sommario):
The following paper describes an economical, multiple model predictive control (EMMPC) for an air conditioning system of a confectionery manufacturer in Germany. The application consists of a packaging hall for chocolate bars, in which a new local conveyor belt air conditioning system is used and thus the temperature and humidity limits in the hall can be significantly extended. The EMMPC calculates the optimum energy or cost humidity and temperature set points in the hall. For this purpose, time-discrete state space models and an economic objective function with which it is possible to react to flexible electricity prices in a cost-optimised manner are created. A possible future electricity price model for Germany with a flexible Renewable Energies levy (EEG levy) was used as a flexible electricity price. The flexibility potential is determined by variable temperature and humidity limits in the hall, which are oriented towards the comfort field for easily working persons, and the building mass. The building mass of the created room model is used as a thermal energy store. Considering the electricity price and weather forecasts as well as an internal, production plan-dependent load forecasts, the model predictive controller directly controls the heating and cooling register and the humidifier of the air conditioning system.
33
Gajewski, K. "Late Holocene Climate Changes in Eastern North America Estimated from Pollen Data". Quaternary Research 29, n. 3 (maggio 1988): 255–62. http://dx.doi.org/10.1016/0033-5894(88)90034-8.
Testo completoAbstract (sommario):
Well-dated pollen profiles from six sites from Maine to Minnesota record vegetation changes indicative of summer temperature and annual precipitation variations over the past 2000 yr. Laminations in the sediment provide accurate time control. Multiple regression techniques were used to calculate calibration functions from a spatial network of modern pollen and climate data. When applied to the six pollen diagrams, these calibration functions yielded estimates that show a long-term trend toward lower summer temperature. Superimposed on this long-term trend are short-term fluctuations that are frequently in phase at the sites. Departures from the long-term cooling trend are positive around 1500 yr ago (indicating relative warmth) and negative between 200 and 500 yr ago (indicating relative cold). Annual precipitation showed a slight increase at several sites during the past 1000 yr relative to the previous 1000 yr.
34
Xue, Y. P., Jia Rong Li, Jin Qian Zhao e J. C. Xiong. "The Precipitation Behavior of γ′ Phase in Single Crystal Ni-Based DD6 Superalloy for Turbine Blade". Materials Science Forum 898 (giugno 2017): 534–44. http://dx.doi.org/10.4028/www.scientific.net/msf.898.534.
Testo completoAbstract (sommario):
The precipitation behavior of γ′ precipitates in typical section dimensions of DD6 single crystal superalloy turbine blade was investigated experimentally during directional solidification process. The phase transformation temperatures in the single crystal Ni-based DD6 superalloy from DSC analysis and JmatPro simulation were basically in consistent with the isothermal solidification experiments. The solidification route of DD6 single crystal superalloy could be described as follows: L1 → γ + L2; L2 → (γ + γ′)eutectic + MC; γ → γ′/γ. With increasing continuous cooling rates, the primary γ′ precipitates tended to be refined, and the size distributions of the primary γ′ precipitates at every temperature measuring position followed the normal distribution. In comparison to the interdendritic regions, nearly a 60% reduction in the average sizes of the primary γ′ precipitates was measured in the dendritic core regions. The result of the primary γ′ size difference was strongly affected by the multi-component segregations between the interdendritic and dendritic regions, where the γ′ forming elements of Al and Ta segregated towards the interdendritic regions. Furthermore, the secondary γ′ precipitation was found to occur within a relatively wide corridor of γ matrix for low cooling rates (12.6, 23.3 and 29.7 °C/min) during the directional solidification process. The occurrence of the secondary γ′ precipitation resulted from the complex interaction of multiple thermodynamic and kinetic factors in the γ′ nucleation and the diffusion rate of γ′ forming elements.
35
Fernández, José A., Roman Skryma, Gabriel Bidaux, Karl L. Magleby, C. Norman Scholfield, J. Graham McGeown, Natalia Prevarskaya e Alexander V. Zholos. "Voltage- and cold-dependent gating of single TRPM8 ion channels". Journal of General Physiology 137, n. 2 (31 gennaio 2011): 173–95. http://dx.doi.org/10.1085/jgp.201010498.
Testo completoAbstract (sommario):
Transient receptor potential (TRP) channels play critical roles in cell signaling by coupling various environmental factors to changes in membrane potential that modulate calcium influx. TRP channels are typically activated in a polymodal manner, thus integrating multiple stimuli. Although much progress has been made, the underlying mechanisms of TRP channel activation are largely unknown. The TRPM8 cation channel has been extensively investigated as a major neuronal cold sensor but is also activated by voltage, calcium store depletion, and some lipids as well as by compounds that produce cooling sensations, such as menthol or icilin. Several models of TRPM8 activation have been proposed to explain the interaction between these diverse stimuli. However, a kinetic scheme is not yet available that can describe the detailed single-channel kinetics to gain further insight into the underlying gating mechanism. To work toward this goal, we investigated voltage-dependent single-channel gating in cell-attached patches at two different temperatures (20 and 30°C) using HEK293 cells stably expressing TRPM8. Both membrane depolarization and cooling increased channel open probability (Po) mainly by decreasing the duration of closed intervals, with a smaller increase in the duration of open intervals. Maximum likelihood analysis of dwell times at both temperatures indicated gating in a minimum of five closed and two open states, and global fitting over a wide range of voltages identified a seven-state model that described the voltage dependence of Po, the single-channel kinetics, and the response of whole-cell currents to voltage ramps and steps. The major action of depolarization and cooling was to accelerate forward transitions between the same two sets of adjacent closed states. The seven-state model provides a general mechanism to account for TRPM8 activation by membrane depolarization at two temperatures and can serve as a starting point for further investigations of multimodal TRP activation.
36
Hutchinson, David K., Helen K. Coxall, Daniel J. Lunt, Margret Steinthorsdottir, Agatha M. de Boer, Michiel Baatsen, Anna von der Heydt et al. "The Eocene–Oligocene transition: a review of marine and terrestrial proxy data, models and model–data comparisons". Climate of the Past 17, n. 1 (28 gennaio 2021): 269–315. http://dx.doi.org/10.5194/cp-17-269-2021.
Testo completoAbstract (sommario):
Abstract. The Eocene–Oligocene transition (EOT) was a climate shift from a largely ice-free greenhouse world to an icehouse climate, involving the first major glaciation of Antarctica and global cooling occurring ∼34 million years ago (Ma) and lasting ∼790 kyr. The change is marked by a global shift in deep-sea δ18O representing a combination of deep-ocean cooling and growth in land ice volume. At the same time, multiple independent proxies for ocean temperature indicate sea surface cooling, and major changes in global fauna and flora record a shift toward more cold-climate-adapted species. The two principal suggested explanations of this transition are a decline in atmospheric CO2 and changes to ocean gateways, while orbital forcing likely influenced the precise timing of the glaciation. Here we review and synthesise proxy evidence of palaeogeography, temperature, ice sheets, ocean circulation and CO2 change from the marine and terrestrial realms. Furthermore, we quantitatively compare proxy records of change to an ensemble of climate model simulations of temperature change across the EOT. The simulations compare three forcing mechanisms across the EOT: CO2 decrease, palaeogeographic changes and ice sheet growth. Our model ensemble results demonstrate the need for a global cooling mechanism beyond the imposition of an ice sheet or palaeogeographic changes. We find that CO2 forcing involving a large decrease in CO2 of ca. 40 % (∼325 ppm drop) provides the best fit to the available proxy evidence, with ice sheet and palaeogeographic changes playing a secondary role. While this large decrease is consistent with some CO2 proxy records (the extreme endmember of decrease), the positive feedback mechanisms on ice growth are so strong that a modest CO2 decrease beyond a critical threshold for ice sheet initiation is well capable of triggering rapid ice sheet growth. Thus, the amplitude of CO2 decrease signalled by our data–model comparison should be considered an upper estimate and perhaps artificially large, not least because the current generation of climate models do not include dynamic ice sheets and in some cases may be under-sensitive to CO2 forcing. The model ensemble also cannot exclude the possibility that palaeogeographic changes could have triggered a reduction in CO2.
37
Torresin, Simone, Rossano Albatici, Francesco Aletta, Francesco Babich, Tin Oberman e Jian Kang. "Acoustic Design Criteria in Naturally Ventilated Residential Buildings: New Research Perspectives by Applying the Indoor Soundscape Approach". Applied Sciences 9, n. 24 (10 dicembre 2019): 5401. http://dx.doi.org/10.3390/app9245401.
Testo completoAbstract (sommario):
The indoor-outdoor connection provided by ventilation openings has been so far a limiting factor in the use of natural ventilation (NV), due to the apparent conflict between ventilation needs and the intrusion of external noise. This limiting factor impedes naturally ventilated buildings meeting the acoustic criteria set by standards and rating protocols, which are reviewed in this paper for residential buildings. The criteria reflect a general effort to minimize noise annoyance by reducing indoor sound levels, typically without a distinction based on a ventilation strategy. Research has developed a number of solutions, discussed here, that try to guarantee ventilation without compromising façade noise insulation, but, currently, none have been adopted on a large scale. This concept paper highlights the main limits of the current approach. First, a fragmented view towards indoor environmental quality has not included consideration of the following acoustic criteria: (i) how buildings are designed and operated to meet multiple needs other than acoustical ones (e.g., ventilation, visual, and cooling needs) and (ii) how people respond to multiple simultaneous environmental factors. Secondly, the lack of a perceptual perspective has led acoustic criteria to neglect the multiple cognitive and behavioral factors impinging on comfort in naturally ventilated houses. Indeed, factors such as the connection with the outside and the sense of control over one’s environment may induce “adaptive acoustic comfort” opportunities that are worth investigating. The mere use of different sound level limits would not be enough to define criteria tailored to the complex user–building interaction that occurs under NV conditions. More holistic and human-centered approaches are required to guarantee not only neutrally but even positively perceived indoor acoustic environments. For this reason, this paper considers this apparent conflict from a soundscape viewpoint, in order to expose still unexplored lines of research. By underpinning a perceptual perspective and by contextualizing it, the indoor soundscape approach provides a framework capable of overcoming the limits of the traditional noise control approach. This could provide the opportunity to foster a wider adoption of NV as a passive design strategy that enhances user health and well-being, while enabling low-cost, and low-energy cooling and ventilation, thereby contributing to current climate change challenges.
38
Gupta, Mukund, e John Marshall. "The Climate Response to Multiple Volcanic Eruptions Mediated by Ocean Heat Uptake: Damping Processes and Accumulation Potential". Journal of Climate 31, n. 21 (novembre 2018): 8669–87. http://dx.doi.org/10.1175/jcli-d-17-0703.1.
Testo completoAbstract (sommario):
A hierarchy of models is used to explore the role of the ocean in mediating the response of the climate to a single volcanic eruption and to a series of eruptions by drawing cold temperature anomalies into its interior, as measured by the ocean heat exchange parameter q (W m−2 K−1). The response to a single (Pinatubo-like) eruption comprises two primary time scales: one fast (year) and one slow (decadal). Over the fast time scale, the ocean sequesters cooling anomalies induced by the eruption into its depth, enhancing the damping rate of sea surface temperature (SST) relative to that which would be expected if the atmosphere acted alone. This compromises the ability to constrain atmospheric feedback rates measured by λ (~1 W m−2 K−1) from study of the relaxation of SST back toward equilibrium, but yields information about the transient climate sensitivity proportional to λ + q. Our study suggests that q can significantly exceed λ in the immediate aftermath of an eruption. Shielded from damping to the atmosphere, the effect of the volcanic eruption persists on longer decadal time scales. We contrast the response to an “impulse” from that of a “step” in which the forcing is kept constant in time. Finally, we assess the “accumulation potential” of a succession of volcanic eruptions over time, a process that may in part explain the prolongation of cold surface temperatures experienced during, for example, the Little Ice Age.
39
Zhao, Mengmeng, e Xiaoying Wang. "A Synthetic Approach for Datacenter Power Consumption Regulation towards Specific Targets in Smart Grid Environment". Energies 14, n. 9 (2 maggio 2021): 2602. http://dx.doi.org/10.3390/en14092602.
Testo completoAbstract (sommario):
With the large-scale grid connection of renewable energy sources, the frequency stability problem of the power system has become increasingly prominent. At the same time, the development of cloud computing and its applications has attracted people’s attention to the high energy consumption characteristics of datacenters. Therefore, it was proposed to use the characteristics of the high power consumption and high flexibility of datacenters to respond to the demand response signal of the smart grid to maintain the stability of the power system. Specifically, this paper establishes a synthetic model that integrates multiple methods to precisely control and regulate the power consumption of the datacenter while minimizing the total adjustment cost. First, according to the overall characteristics of the datacenter, the power consumption models of servers and cooling systems were established. Secondly, by controlling the temperature, different kinds of energy storage devices, load characteristics and server characteristics, the working process of various regulation methods and the corresponding adjustment cost models were obtained. Then, the cost and penalty of each power regulation method were incorporated. Finally, the proposed dynamic synthetic approach was used to achieve the goal of accurately adjusting the power consumption of the datacenter with least adjustment cost. Through comparative analysis of evaluation experiment results, it can be observed that the proposed approach can better regulate the power consumption of the datacenter with lower adjustment cost than other alternative methods.
40
Schwenkel, Johannes, e Björn Maronga. "Towards a Better Representation of Fog Microphysics in Large-Eddy Simulations Based on an Embedded Lagrangian Cloud Model". Atmosphere 11, n. 5 (5 maggio 2020): 466. http://dx.doi.org/10.3390/atmos11050466.
Testo completoAbstract (sommario):
The development of radiation fog is influenced by multiple physical processes such as radiative cooling and heating, turbulent mixing, and microphysics, which interact on different spatial and temporal scales with one another. Once a fog layer has formed, the number of fog droplets and their size distribution have a particularly large impact on the development of the fog layer due to their feedback on gravitational settling and radiative cooling at the fog top, which are key processes for fog. However, most models do not represent microphysical processes explicitly, or parameterize them rather crudely. In this study we simulate a deep radiation fog case with a coupled large-eddy simulation (LES)–Lagrangian cloud model (LCM) approach for the first time. By simulating several hundred million fog droplets as Lagrangian particles explicitly (using the so-called superdroplet approach), we include a size-resolved diffusional growth including Köhler theory and gravitational sedimentation representation. The results are compared against simulations using a state of the art bulk microphysics model (BCM). We simulate two different aerosol backgrounds (pristine and polluted) with each microphysics scheme. The simulations show that both schemes generally capture the key features of the deep fog event, but also that there are significant differences: the drop size distribution produced by the LCM is broader during the formation and dissipation phase than in the BCM. The LCM simulations suggest that its spectral shape, which is fixed in BCMs, exhibits distinct changes during the fog life cycle, which cannot be taken into account in BCMs. The picture of the overall fog droplet number concentration is twofold: For both aerosol environments, the LCM shows lower concentrations of larger fog droplets, while we observe a higher number of small droplets and swollen aerosols reducing the visibility earlier than in the BCM. As a result of the different model formulation we observe higher sedimentation rates and lower liquid water paths for the LCM. The present work demonstrates that it is possible to simulate fog with the computational demanding approach of LCMs to assess the advantages of high-resolution cloud models and further to estimate errors of traditional parameterizations.
41
Chou, Chihchung, Dongryeol Ryu, Min-Hui Lo, Hao-Wei Wey e Hector M. Malano. "Irrigation-Induced Land–Atmosphere Feedbacks and Their Impacts on Indian Summer Monsoon". Journal of Climate 31, n. 21 (novembre 2018): 8785–801. http://dx.doi.org/10.1175/jcli-d-17-0762.1.
Testo completoAbstract (sommario):
From the 1980s, Indian summer monsoon rainfall (ISMR) shows a decreasing trend over north and northwest India, and there was a significant observed reduction in July over central and south India in 1982–2003. The key drivers of the changed ISMR, however, remain unclear. It was hypothesized that the large-scale irrigation development that started in the 1950s has resulted in land surface cooling, which slowed large-scale atmospheric circulation, exerting significant influences on ISMR. To test this hypothesis, a fully coupled model, the CESM v1.0.3, was used with a global irrigation dataset. In this study, spatially varying irrigation-induced feedback mechanisms are investigated in detail at different stages of the monsoon. Results show that soil moisture and evapotranspiration increase significantly over India throughout the summertime because of the irrigation. However, 2-m air temperature shows a significant reduction only in a limited region because the temperature change is influenced simultaneously by surface incoming shortwave radiation and evaporative cooling resulting from the irrigation, especially over the heavily irrigated region. Irrigation also induces a 925-hPa northeasterly wind from 30°N toward the equator. This is opposite to the prevailing direction of the Indian summer monsoon (ISM) wind that brings moist air to India. The modeled rainfall in the irrigated case significantly decreases up to 1.5 mm day−1 over central and north India from July to September. This paper reveals that the irrigation can contribute to both increasing and decreasing the surface temperature via multiple feedback mechanisms. The net effect is to weaken the ISM with the high spatial and temporal heterogeneity.
42
Brennan, Ian G., e J. Scott Keogh. "Miocene biome turnover drove conservative body size evolution across Australian vertebrates". Proceedings of the Royal Society B: Biological Sciences 285, n. 1889 (17 ottobre 2018): 20181474. http://dx.doi.org/10.1098/rspb.2018.1474.
Testo completoAbstract (sommario):
On deep time scales, changing climatic trends can have a predictable influence on macroevolution. From evidence of mass extinctions, we know that rapid climatic oscillations can indirectly open niche space and precipitate adaptive radiation, changing the course of ecological diversification. These dramatic shifts in the global climate, however, are rare events relative to extended periods of protracted climate change and biome turnover. It remains unclear whether during gradually changing periods, shifting habitats may instead promote non-adaptive speciation by facilitating allopatry and phenotypic conservatism. Using fossil-calibrated, species-level phylogenies for five Australian radiations comprising more than 800 species, we investigated temporal trends in biogeography and body size evolution. Here, we demonstrate that gradual Miocene cooling and aridification correlates with the restricted phenotypic diversification of multiple ecologically diverse vertebrate groups. This probably occurred as species ranges became fractured and isolated during continental biome restructuring, encouraging a shift towards conservatism in body size evolution. Our results provide further evidence that abiotic changes, not only biotic interactions, may act as selective forces influencing phenotypic macroevolution.
43
Pant, Stuti, Maya Annie Elias, Kerry Woolfall, Maria Moreno Morales, Bensitta Lincy, Ismat Jahan, Samanmali P. Sumanasena, Siddarth Ramji, Seetha Shankaran e Sudhin Thayyil. "Parental and professional perceptions of informed consent and participation in a time-critical neonatal trial: a mixed-methods study in India, Sri Lanka and Bangladesh". BMJ Global Health 6, n. 5 (maggio 2021): e005757. http://dx.doi.org/10.1136/bmjgh-2021-005757.
Testo completoAbstract (sommario):
IntroductionTime-critical neonatal trials in low-and-middle-income countries (LMICs) raise several ethical issues. Using a qualitative-dominant mixed-methods design, we explored informed consent process in Hypothermia for encephalopathy in low and middle-income countries (HELIX) trial conducted in India, Sri Lanka and Bangladesh.MethodsTerm infants with neonatal encephalopathy, aged less than 6 hours, were randomly allocated to cooling therapy or usual care, following informed parental consent. The consenting process was audio-video (A-V) recorded in all cases. We analysed A-V records of the consent process using a 5-point Likert scale on three parameters—empathy, information and autonomy. In addition, we used exploratory observation method to capture relevant aspects of consent process and discussions between parents and professionals. Finally, we conducted in-depth interviews with a subgroup of 20 parents and 15 healthcare professionals. A thematic analysis was performed on the observations of A-V records and on the interview transcripts.ResultsA total of 294 A-V records of the HELIX trial were analysed. Median (IQR) score for empathy, information and autonomy was 5 (0), 5 (1) and 5 (1), respectively. However, thematic analysis suggested that the consenting was a ceremonial process; and parental decision to participate was based on unreserved trust in the treating doctors, therapeutic misconception and access to an expensive treatment free of cost. Most parents did not understand the concept of a clinical trial nor the nature of the intervention. Professionals showed a strong bias towards cooling therapy and reported time constraints and explaining to multiple family members as key challenges.ConclusionDespite rigorous research governance and consent process, parental decisions were heavily influenced by situational incapacity and a trust in doctors to make the right decision on their behalf. Further research is required to identify culturally and context-appropriate strategies for informed trial participation.
44
Longridge, Luke, Roger L. Gibson e Paul A. M. Nex. "Structural controls on melt segregation and migration related to the formation of the diapiric Schwerin Fold in the contact aureole of the Bushveld Complex, South Africa". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 100, n. 1-2 (marzo 2009): 61–76. http://dx.doi.org/10.1017/s1755691009016119.
Testo completoAbstract (sommario):
ABSTRACTPartial melting of metapelitic rocks beneath the mafic–ultramafic Rustenburg Layered Suite of the Bushveld Complex in the vicinity of the periclinal Schwerin Fold resulted in a structurally controlled distribution of granitic leucosomes in the upper metamorphic aureole. In the core of the pericline, subvertical structures facilitated the rise of buoyant leucosome through the aureole towards the contact with the Bushveld Complex, with leucosomes accumulating in en-echelon tension gashes. In a subhorizontal syn-metamorphic shear zone to the southeast of the pericline, leucosomes accumulated in subhorizontal dilational structural sites. The kinematics of this shear zone are consistent with slumping of material off the southeastern limb of the rising Schwerin pericline. The syndeformational timing of leucosome emplacement supports a syn-intrusive, density-driven origin for the Schwerin Fold. Modelling of the cooling of the Rustenburg Layered Suite and heating of the floor rocks using a multiple intrusion model indicates that temperatures above the solidus were maintained for >600,000 years up to 300 m from the contact, in agreement with rheological modelling of floor-rock diapirs that indicate growth rates on the order of 8 mm/year for the Schwerin Fold.
45
Zainal, Nurul Amira, Roslinda Nazar, Kohilavani Naganthran e Ioan Pop. "Unsteady MHD Mixed Convection Flow in Hybrid Nanofluid at Three-Dimensional Stagnation Point". Mathematics 9, n. 5 (5 marzo 2021): 549. http://dx.doi.org/10.3390/math9050549.
Testo completoAbstract (sommario):
There has been significant interest in exploring a stagnation point flow due to its numerous potential uses in engineering applications such as cooling of nuclear reactors. Hence, this study proposed a numerical analysis on the unsteady magnetohydrodynamic (MHD) mixed convection at three-dimensional stagnation point flow in Al2O3–Cu/H2O hybrid nanofluid over a permeable sheet. The ordinary differential equations are accomplished by simplifying the governing partial differential equations through suitable similarity transformation. The numerical computation is established by the MATLAB system software using the bvp4c technique. The bvp4c procedure is excellent in providing more than one solution once sufficient predictions are visible. The influence of certain functioning parameters is inspected, and notable results exposed that the rate of heat transfer is exaggerated along with the skin friction coefficient while the suction/injection and magnetic parameters are intensified. The results also signified that the rise in the volume fraction of the nanoparticle and the decline of the unsteadiness parameter demonstrates a downward attribution towards the heat transfer performance and skin friction coefficient. Conclusively, the observations are confirmed to have multiple solutions, which eventually contribute to an investigation of the analysis of the solution stability, thereby justifying the viability of the first solution.
46
Lasemi, Niusha, Günther Rupprechter, Gerhard Liedl e Dominik Eder. "Near-Infrared Femtosecond Laser Ablation of Au-Coated Ni: Effect of Organic Fluids and Water on Crater Morphology, Ablation Efficiency and Hydrodynamic Properties of NiAu Nanoparticles". Materials 14, n. 19 (24 settembre 2021): 5544. http://dx.doi.org/10.3390/ma14195544.
Testo completoAbstract (sommario):
Scanning electron microscopy (SEM) and profilometry of the crater morphology and ablation efficiency upon femtosecond laser ablation of Au-coated Ni targets in various fluids revealed a pronounced dependence on the ablation medium. For ethanol, a sufficient ablation efficiency was obtained, whereas for 2-butanol a higher efficiency indicated stronger laser–target interaction. Hierarchical features in the crater periphery pointed to asymmetrical energy deposition or a residual effect of the Coulomb-explosion-initiating ablation. Significant beam deviation in 2-butanol caused maximum multiple scattering at the crater bottom. The highest values of microstrain and increased grain size, obtained from Williamson–Hall plots, indicated the superposition of mechanical stress, defect formation and propagation of fatigue cracks in the crater circumference. For n-hexane, deposition of frozen droplets in the outer crater region suggested a femtosecond-laser-induced phase explosion. A maximum ablation depth occurred in water, likely due to its high cooling efficiency. Grazing incidence micro X-ray diffraction (GIXRD) of the used target showed residual carbon and partial surface oxidation. The produced nanoparticle colloids were examined by multiangle dynamic light scattering (DLS), employing larger scattering angles for higher sensitivity toward smaller nanoparticles. The smallest nanoparticles were obtained in 2-butanol and ethanol. In n-hexane, floating carbon flakes originated from femtosecond-laser-induced solvent decomposition.
47
Hansen, Katrine Elnegaard, Jacques Giraudeau, Lukas Wacker, Christof Pearce e Marit-Solveig Seidenkrantz. "Reconstruction of Holocene oceanographic conditions in eastern Baffin Bay". Climate of the Past 16, n. 3 (22 giugno 2020): 1075–95. http://dx.doi.org/10.5194/cp-16-1075-2020.
Testo completoAbstract (sommario):
Abstract. Baffin Bay is a semi-enclosed basin connecting the Arctic Ocean and the western North Atlantic, thus making out a significant pathway for heat exchange. Here we reconstruct the alternating advection of relatively warmer and saline Atlantic waters versus the incursion of colder Arctic water masses entering Baffin Bay through the multiple gateways in the Canadian Arctic Archipelago and the Nares Strait during the Holocene. We carried out benthic foraminiferal assemblage analyses, X-ray fluorescence scanning, and radiocarbon dating of a 738 cm long marine sediment core retrieved from eastern Baffin Bay near Upernavik, Greenland (Core AMD14-204C; 987 m water depth). Results reveal that eastern Baffin Bay was subjected to several oceanographic changes during the last 9.2 kyr. Waning deglacial conditions with enhanced meltwater influxes and an extensive sea-ice cover prevailed in eastern Baffin Bay from 9.2 to 7.9 ka. A transition towards bottom water amelioration is recorded at 7.9 ka by increased advection of Atlantic water masses, encompassing the Holocene Thermal Maximum. A cold period with growing sea-ice cover at 6.7 ka interrupts the overall warm subsurface water conditions, promoted by a weaker northward flow of Atlantic waters. The onset of the neoglaciation at ca. 2.9 ka is marked by an abrupt transition towards a benthic fauna dominated by agglutinated species, likely in part explained by a reduction of the influx of Atlantic Water, allowing an increased influx of the cold, corrosive Baffin Bay Deep Water originating from the Arctic Ocean to enter Baffin Bay through the Nares Strait. These cold subsurface water conditions persisted throughout the Late Holocene, only interrupted by short-lived warmings superimposed on this cooling trend.
48
Rewatkar, Kishor G. "Magnetic Nanoparticles: Synthesis and Properties". Solid State Phenomena 241 (ottobre 2015): 177–201. http://dx.doi.org/10.4028/www.scientific.net/ssp.241.177.
Testo completoAbstract (sommario):
The discovery of novel materials, processes, and phenomena at the nanoscale and the development of new experimental and theoretical techniques for research provide fresh opportunities for the development of innovative nanosystems and nanostructured materials. Nanomaterials with tailored unique properties have limitless possibilities in materials science. The most widely used synthesis routes for iron oxide nanoparticles are based on precipitation from solution. Most of the nanoparticles available to date have been prepared using chemical route. Physical processes have also been recently developed to produce high quality monodisperse and monocrystalline iron oxide nanoparticles. Magnetite has recently attracted attention because bulk Fe3O4has a high Curie temperature of 850 K and nearly full spin polarization at room temperature, and due to its wide range of applications in almost all branches of science and technology. Clearly, nanoscale magnetite offers potential for creation of novel technology in multiple fields of study. Opportunities for magnetite nanoparticles to be effectively incorporated into environmental contaminant removal and cell separation magnetically guided drug delivery, imaging of tissue and organs, magnetocytolysis, sealing agents (liquid O-rings), dampening and cooling mechanisms in loudspeakers, high gradient magnetic separation (HGMS) techniques and contrasting agents for magnetic resonance imaging (MRI). Advancement of synthesis and stabilization procedures towards production of uniformly sized, dispersed (potentially embedded) magnetite nanoparticles has clearly inspired creative imagination and application in various fields.
49
Ellwood, Brooks B., Lawrence Febo, Laurie Anderson, Rebecca T. Hackworth, Guy H. Means, Jonathon A. Bryan, Jonathan Tomkin, Harry Rowe e Luigi Jovane. "Regional to global correlation of Eocene–Oligocene boundary transition successions using biostratigraphic, geophysical and geochemical methods". Geological Magazine 157, n. 1 (12 luglio 2019): 80–100. http://dx.doi.org/10.1017/s0016756819000578.
Testo completoAbstract (sommario):
AbstractRegional to global high-resolution correlation and timing is critical when attempting to answer important geological questions, such as the greenhouse to icehouse transition that occurred during the Eocene–Oligocene boundary transition. Timing of these events on a global scale can only be answered using correlation among many sections, and multiple correlation proxies, including biostratigraphy, lithostratigraphy, geochemistry and geophysical methods. Here we present litho- and biostratigraphy for five successions located in the southeastern USA. To broaden the scope of correlation, we also employ carbon and oxygen stable isotope and magnetic susceptibility (χ) data to interpret these sections regionally, and correlate to the Global Boundary Stratotype Section and Point (GSSP) near Massignano in central Italy. Our results indicate that approaching the Eocene–Oligocene boundary, climate warmed slightly, but then δ18O data exhibit an abrupt c. +5 ‰ positive shift towards cooling that reached a maximum c. 1 m below the boundary at St Stephens Quarry, Alabama. This shift was accompanied by a c. −3 ‰ negative shift in δ13C interpreted to indicate environmental changes associated with the onset of the Eocene–Oligocene boundary planktonic foraminiferal extinction event. The observed cold pulse may be responsible for the final extinction of Hantkeninidae, used to define the beginning of the Rupelian Stage. Immediately preceding the boundary, Hantkeninidae species dropped significantly in abundance and size (pre-extinction dwarfing occurring before the final Eocene–Oligocene extinctions), and these changes may be the reason for inconsistencies in past Eocene–Oligocene boundary placement in the southeastern USA.
50
Newman, Andrew J., e Richard H. Johnson. "Dynamics of a Simulated North American Monsoon Gulf Surge Event". Monthly Weather Review 141, n. 9 (28 agosto 2013): 3238–53. http://dx.doi.org/10.1175/mwr-d-12-00294.1.
Testo completoAbstract (sommario):
Abstract Gulf surges are transient disturbances that propagate along the Gulf of California (GoC) from south to north, transporting cool moist air toward the deserts of northwest Mexico and the southwest United States during the North American monsoon. They have been shown to modulate precipitation and have been linked to severe weather and flooding in northern Mexico and the southwest United States. The general features and progression of surge events are well documented but their detailed dynamical evolution is still unclear. In this study, a convection-permitting simulation is performed over the core monsoon region for the 12–14 July 2004 gulf surge event and the dynamics of the simulated surge are examined. Initially, convection associated with the tropical easterly wave precursor to Tropical Cyclone Blas creates a disturbance in the southern GoC on early 12 July. This disturbance is a precursor to the gulf surge on 13 July and is a Kelvin shock (internal bore under the influence of rotation) that dissipates in the central GoC. The surge initiates from inflow from the mouth of the GoC along with convective outflow impinging on the southern GoC. Continued convective outflow along the GoC generates multiple gravity currents and internal bores while intensifying the simulated surge as it propagates up the GoC. As the core of the surge reaches the northern GoC, a Kelvin shock is again the best dynamical fit to the phenomenon. Substantial low-level cooling and moistening are associated with the modeled surge along the northern GoC as is observed.