Journal articles on the topic 'Representative upstream conditions'
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1
Cao, Ping, Xiangpeng Mu, Xiang Li, Baoligao Baiyin, Xiuying Wang, and Wanyue Zhen. "Relationship between Upstream Swimming Behaviors of Juvenile Grass Carp and Characteristic Hydraulic Conditions of a Vertical Slot Fishway." Water 13, no. 9 (May 6, 2021): 1299. http://dx.doi.org/10.3390/w13091299.
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The successful fish upstream movement through a dam/gate is closely associated with the hydraulic conditions of a fishway. To improve the passage efficiency, this study investigated the upstream swimming behaviors of juvenile grass carp, a representative fish of four major Chinese carps, under characteristic hydraulic conditions of a designed vertical slot fishway model. The impacts of different discharges and baffle lead angles on the successful movement of test fish were analyzed, and the selection of the movement trajectory was studied through overlay of their upstream swimming trajectories on the water flow field resulting from numerical modeling. We found that under the same discharge, the percentage of successful test fish movement with a lead angle of 45° was higher than 60° and 30°. Within a fixed lead angle, the higher the discharge, the lower the percentage of successful movement. During upstream movement, the test fish had a preferred water velocity of 0.01–0.45 m/s in the pool, and avoided areas where the turbulence kinetic energy (TKE) was greater than 0.012 m2/s2. These results provide a basis for the hydraulic design of vertical slot fishways and a reference for studying swimming behaviors of other fish species.
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Guardiola, Carlos, Benjamin Pla, Pau Bares, and Javier Mora. "An on-board method to estimate the light-off temperature of diesel oxidation catalysts." International Journal of Engine Research 21, no. 8 (December 16, 2018): 1480–92. http://dx.doi.org/10.1177/1468087418817965.
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Current diesel engine regulations include on-board diagnostic requirements so that after-treatment systems need on-board methods to detect their aging state through the available measurements. In a state-of-the-art diesel exhaust line, two temperature and [Formula: see text] measurements can be found upstream and downstream of the diesel oxidation catalyst. Thus, the strategy presented in this article makes use of these measurements to estimate the light-off temperature, which has been widely studied as a characteristic of diesel oxidation catalyst aging. The light-off temperature estimation potential is evaluated first under dynamic engine operating conditions, in which [Formula: see text] measurements are proved to be precise enough to detect oxidation. However, dynamic conditions make the association of a representative temperature with an oxidation event difficult. Therefore, the method makes use of more controlled conditions at idle, during which the exhaust temperature decreases avoiding dynamics of normal driving conditions. During the idle, post-injection pulses are applied to determine whether oxidation occurs at a representative temperature measured by the upstream temperature sensor. The result of each pulse is used to generate a database. Then, after a long enough time window, the database generated will allow characterizing non-oxidation and oxidation temperatures, with an intermediate interval of indefinition. This article shows how the temperatures of these ranges increase as the light-off temperature increases, thereby validating the proposed method for light-off temperature estimation.
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Chen, Yongping, Ninglin Jiang, and Changkuan Zhang. "RIVERBED EVOLUTION OF YANGTZE ESTUARY AND ITS RESPONSE TO THE HYDRODYNAMIC CHANGES AT UPSTREAM." Coastal Engineering Proceedings 1, no. 33 (December 13, 2012): 92. http://dx.doi.org/10.9753/icce.v33.sediment.92.
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The riverbed evolution of upper part of Yangtze estuary, Chengtong reach, is analyzed by comparison of 6 sets of bathymetry data during 1977~2011. The significant changes of water depth profiles along 6 representative cross-sections indicate the reach is still in the process of development. In order to get a better understanding of the effect of river discharge at upstream on the riverbed evolution of Chengtong reach, a series of numerical experiments are implemented by specifying different river discharge conditions at the upper boundary. The corresponding discharge ratio at main sub-reaches is compared to reveal the response of the riverbed evolution to the hydrodynamic changes at upstream. The results show that with the increase of river discharge, the discharge ratio in the main channels of Fujiangsha sub-reach and Rugaosha sub-reach increases, but it changes to decrease when the upstream river discharge becomes very large; however, the discharge ratio in the main channel of Tongzhousha sub-reach always decreases with the increase of river discharge at upstream.
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Bailey, D. W., K. M. Britchford, J. F. Carrote, and S. J. Stevens. "Performance Assessment of an Annular S-Shaped Duct." Journal of Turbomachinery 119, no. 1 (January 1, 1997): 149–56. http://dx.doi.org/10.1115/1.2841003.
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An experimental investigation has been carried out to determine the aerodynamic performance of an annular S-Shaped duct representative of that used to connect the compressor spools of aircraft gas turbine engines. For inlet conditions in which boundary layers are developed along an upstream entry length, the static pressure, shear stress and velocity distributions are presented. The data show that as a result of flow curvature, significant streamwise pressure gradients exist within the duct, with this curvature also affecting the generation and suppression of turbulence. The stagnation pressure loss within the duct is also assessed and is consistent with the measured distributions of shear stress. More engine representative conditions are provided by locating a single-stage compressor at inlet to the duct. Relative to the naturally developed inlet conditions, the flow within the duct is less likely to separate, but mixing out of the compressor blade wakes increases the measured duct loss. With both types of inlet conditions, the effect of a radial strut, such as that used for carrying loads and engine services, is also described both in terms of the static pressure distribution along the strut and its contribution to overall loss.
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DERZHO, OLEG, and ROGER GRIMSHAW. "Solitary waves with recirculation zones in axisymmetric rotating flows." Journal of Fluid Mechanics 464 (August 10, 2002): 217–50. http://dx.doi.org/10.1017/s0022112002008790.
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In this paper, we describe a theoretical asymptotic model for large-amplitude travelling solitary waves in an axially symmetric rotating flow of an inviscid incompressible fluid confined in an infinitely long circular tube. By considering the special, but important, case when the upstream flow is close to that of uniform axial flow and uniform rotation, we are able to construct analytical solutions which describe solitary waves with ‘bubbles’, that is, recirculation zones with reversed flow, located on the axis of the tube. Such waves have amplitudes which slightly exceed the critical amplitude, where there is incipient flow reversal. The effect of the recirculation zone is to introduce into the governing amplitude equation an extra nonlinear term, which is proportional to the square of the difference between the wave amplitude and the critical amplitude. We consider in detail a special, but representative, class of upstream inflow conditions. We find that although the structure of the recirculation zone is universal, the presence of such solitary waves is quite sensitive to the actual upstream axial and rotational velocity shear configurations. Our results are compared with previous theories and observations, and related to the well-known phenomenon of vortex breakdown.
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Nazrul-Islam, A. K. M., Fahmida Khan, Ambia Khatun, M. R. Khan, A. N. M. Abdullah, and P. K. Jha. "ECOLOGICAL CONDITIONS OF A TEMPORARY WETLAND IN BANGLADESH." Ecoprint: An International Journal of Ecology 18 (December 21, 2013): 71–76. http://dx.doi.org/10.3126/eco.v18i0.9413.
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Investigation has been done to gain evidence on certain chemical properties of water and vegetation in area representative of the various wetland habitats which go under water during rainy season. The measurements were done with edaphic condition, water chemistry, and floristic composition. Water was neutral to alkaline and pH varied from 6.97 to 7.20 and conductivity was in the range of 97.5 m mhos to 240 m mhos. Seasonal variation of chloride content was observed throughout the year and the highest chloride (104.96 mg/l) was in the month of October. Dissolved oxygen concentration was very low (2.99 mg/l) in the month of October. With the decrease of water, the value of alkalinity became double (76.0 mg/). No distinct variation in the content of hardness was observed in the three different locations. Temporary hardness varied from 0.1 0 to 0.56 mg/l. High value of total solids in the month of July (70 mg/l) indicated that high amount of sediment are coming with the flow of water from upstream. Total suspended solids were higher than dissolved solids. Exchangeable cations were low in the beginning and an increasing tendency of Na and Ca was observed in the later stages of marsh formation. DOI: http://dx.doi.org/10.3126/eco.v18i0.9413Ecoprint: An International Journal of EcologyVol. 18, 2011 Page: 71-76 Uploaded date: 12/22/2013
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Tang, Nanbo, Xiaogang Wang, Yun Li, Long Zhu, Zhushuan Tang, Hongze Li, Feifei He, Yongzeng Huang, and Zhengxian Zhang. "Laboratory Studies on the Rheotaxis of Fish under Different Attraction Flow Conditions." International Journal of Environmental Research and Public Health 19, no. 9 (May 9, 2022): 5744. http://dx.doi.org/10.3390/ijerph19095744.
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The damming of the river changes the structure of the original river ecosystem, and although fish passage plays an important role in maintaining the connectivity of the river ecosystem, the fish have difficulty finding the fish passage entrance during the upstream process. This paper studied the rheotaxis of fish under three different water flow conditions experimentally through recirculating water tanks. To better understand the response of Crucian carp (Carassius auratus) to water flow stimulation, the representative swimming trajectory, sensing success rate, attraction success rate, reaction time, and attraction time of the fish were analyzed by using a video monitoring system. The experimental results showed that fish responded differently to single-peak and lateral bimodal outflow conditions: (1) the single-peak outflow condition had a much better attraction effect than the lateral bimodal outflow condition, both in terms of sensing success rate and attraction success rate; (2) the fish swam mainly in the middle area of the lateral bimodal outflow condition, while the fish swam more evenly in the single-peak outflow condition. Therefore, setting the attraction current at the right time and near the entrance of the fish passage may help to improve the effect of fish attraction.
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Sun, Zhilin, Haolei Zheng, and Lixia Sun. "Analysis on the Characteristics of Bed Materials in the Jinghong Reservoir on the Lancang River." Sustainability 13, no. 12 (June 17, 2021): 6874. http://dx.doi.org/10.3390/su13126874.
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Nine samples of bed materials along the Jinghong reservoir on the Lancang River were obtained using a gravity sampler. The grain size characteristics of the samples were analyzed by the laser diffraction particle size analyzer. The results show that the median grain size of bed materials is in the range of 6.7 to 18.9 µm. From the upstream to the front of the dam, the overall grain size of the bed materials tends to decrease significantly; the sorting is poor but becomes better along the way; the skewness gradually changes from negative to near symmetrical; the kurtosis is platykurtic and mesokurtic with little change along the way. Based on the measured data, an exponential model is constructed to describe the distribution of representative grain size of bed materials along the way. Furthermore, the concept of representative particle Reynolds number is proposed. The relationship between representative particle Reynolds number and flow parameters with boundary conditions is established, and the coefficient and exponents in the equation are determined based on the measured data of the Jinghong reservoir. This study provides valuable first-hand information for reservoir sediment research and new ideas for sediment sorting and deposition studies.
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Kinney, Patrick, Gwi-Nam Bae, David Pui, and Benjamin Liu. "Particle Behavior in Vacuum Systems: Implications for In-Situ Particle Monitoring in Semiconductor Processing Equipment." Journal of the IEST 39, no. 6 (November 1, 1996): 40–48. http://dx.doi.org/10.17764/jiet.2.39.6.p7414773u18n5t20.
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The flow of aerosol in vacuum conditions representative of many semiconductor processes (100 sccm, 1 Torr). was investigated. The study was performed using aerosols with highly nonuniform spatial distributions. An ideally nonuniform aerosol was produced by generating an aerosol beam using an aerodynamic lens. The flow containing the aerosol beam was drawn through vacuum system components. The size of the beam was measured upstream and downstream of these components by collecting the aerosol on a filter and observing the deposition pattern. Very little mixing phenomenon was observed. These results point to a potential limitation in the methods employed by the semiconductor industry for in-situ particle monitoring in vacuum systems. A simple solution to this flaw is suggested.
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Jasek, Martin, and Amy Pryse-Phillips. "Influence of the proposed Site C hydroelectric project on the ice regime of the Peace River." Canadian Journal of Civil Engineering 42, no. 9 (September 2015): 645–55. http://dx.doi.org/10.1139/cjce-2014-0425.
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The objectives of the study were to describe the existing ice conditions in the Peace River and to predict changes as a result of the proposed Site C Clean Energy Project (the Project). The analyses of changes due to the Project were conducted using the CRISSP and PRTIGM models. Sixteen winters were simulated to provide a representative range of meteorological conditions on which to base the conclusions of the study. Potential changes are described in terms of the following ice characteristics: maximum upstream extent of ice cover; timing of ice cover formation and break-up; freeze-up and break-up water levels at the Town of Peace River; ice thickness; changes in ice conditions relevant for river ice crossings. The analyses also included predicting changes in these ice characteristics due to the combined influence of the Project and the proposed Dunvegan Hydro Project in Alberta. Two future climate scenarios were also considered.
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Meng, Ying, Xi Xu, Hongyu Luan, Lei Li, Wenhao Dai, Zhiyu Li, and Jinlei Bian. "The progress and development of GLUT1 inhibitors targeting cancer energy metabolism." Future Medicinal Chemistry 11, no. 17 (September 2019): 2333–52. http://dx.doi.org/10.4155/fmc-2019-0052.
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A major difference between glucose metabolism in cancer cells and normal cells is that glucose in cancer cells is preferably converted to lactate in aerobic conditions rather than oxidized in mitochondria. This process is called aerobic glycolysis, known as the ‘Warburg effect’. In this review, we focus on the energy-metabolism characteristics between tumor and normal cells, analyzing the regulation mechanism of energy metabolism based on glycolysis, and summarizing two targets on the upstream proteins of glycolysis, including glucose transporter (GLUT) and hexokinase. In addition, we proposed the risks and limitations of GLUT1-based drug research and summarized the current research progress of representative drugs, including natural and synthetic GLUT1 inhibitors. This will provide guidance for designing and synthesizing small molecule drugs targeting GLUT1 in glycolysis.
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Gumbel, J. "Rarefied gas flows through meshes and implications for atmospheric measurements." Annales Geophysicae 19, no. 5 (May 31, 2001): 563–69. http://dx.doi.org/10.5194/angeo-19-563-2001.
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Abstract. Meshes are commonly used as part of instruments for in situ atmospheric measurements. This study analyses the aerodynamic effect of meshes by means of wind tunnel experiments and numerical simulations. Based on the Direct Simulation Monte Carlo method, a simple mesh parameterisation is described and applied to a number of representative flow conditions. For open meshes freely exposed to the flow, substantial compression effects are found both upstream and downstream of the mesh. Meshes attached to close instrument structures, on the other hand, cause only minor flow disturbances. In an accompanying paper, the approach developed here is applied to the quantitative analysis of rocket-borne density measurements in the middle atmosphere.Key words. Atmospheric composition and structure (instruments and techniques; middle atmosphere – composition and chemistry)
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Wagner, Chad, Sharon Fitzgerald, and Matthew Lauffer. "Characterization of Stormwater Runoff from North Carolina Bridges and Determination of Effects on Selected Receiving Waters." Transportation Research Record: Journal of the Transportation Research Board 2309, no. 1 (January 2012): 178–99. http://dx.doi.org/10.3141/2309-18.
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The North Carolina Department of Transportation and the U.S. Geological Survey collaborated on a study to better understand the effects of stormwater runoff from bridges on receiving waters. The following tasks were performed: (a) characterizing the quality and quantity of stormwater runoff from a representative selection of bridges in North Carolina, (b) measuring the quality of stream water upstream of selected bridges to compare constituent concentrations and loads in bridge deck stormwater with those in the stream, (c) determining whether the chemistry of bed sediment upstream and downstream of selected bridges differed substantially according to the presence or absence of a best management practice for bridge runoff, and (d) estimating the rate at which bridge deck runoff mixed with the receiving stream. The investigation measured bridge deck runoff from 15 bridges for 12 to 15 storms, the quality of stream water for base flow and storm conditions at four of the bridge deck sites, and the chemistry of stream bed sediment upstream and downstream of 30 bridges across North Carolina. Runoff and stream samples were analyzed for a wide range of constituents, including dissolved and total recoverable metals and nutrients, major ions, total suspended solids, suspended sediment, oil and grease, petroleum hydrocarbons, and semi-volatile organic compounds. For 64% of comparisons, concentrations in bridge deck runoff were no different or were less than those measured in receiving waters, and the maximum concentrations of constituents in the bridge deck runoff were rapidly reduced to the ambient stream concentrations, generally within 50 ft downstream of the bridge.
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Miller, R. J., R. W. Moss, R. W. Ainsworth, and N. W. Harvey. "Wake, Shock, and Potential Field Interactions in a 1.5 Stage Turbine—Part II: Vane-Vane Interaction and Discussion of Results." Journal of Turbomachinery 125, no. 1 (January 1, 2003): 40–47. http://dx.doi.org/10.1115/1.1508387.
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The composition of the time-resolved surface pressure field around a high-pressure rotor blade caused by the presence of neighboring blade rows is investigated with the individual effects of wake, shock and potential field interaction being determined. Two test geometries are considered: first, a high-pressure turbine stage coupled with a swan-necked diffuser exit duct; secondly, the same high pressure stage but with a vane located in the downstream duct. Both tests were conducted at engine-representative Mach and Reynolds numbers and experimental data was acquired using fast-response pressure transducers mounted on the mid-height streamline of the HP rotor blades. The results are compared to time-resolved computational predictions of the flow field in order to aid interpretation of experimental results and to determine the accuracy with which the computation predicts blade interaction. In the first half of this paper it is shown that, in addition to the two main interaction mechanisms (upstream vane-rotor and rotor-downstream vane interactions, presented in Part I of this paper) a third interaction occurs. This new interaction mechanism is shown to be caused by the interaction between the downstream vane’s potential field and the upstream vane’s trailing edge potential field and shock. The unsteady rotor surface static pressure fluctuations caused by this interaction are shown to occur on the late rotor suction surface at a frequency corresponding to the difference in the numbers of upstream and downstream vanes. The second part to the paper discusses the mechanisms that cause vane-rotor-vane interaction. The rotor’s operating point is periodically altered as it passes the downstream vane. It is shown that for a large downstream vane, the flow conditions in the rotor passage, at any instant in time, are close to being steady state.
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Saleem, Mohammad, Omar L. Rodriguez, Aatresh Karnam, Ephraim Gutmark, and Junhui Liu. "Optical-acoustics source analysis of supersonic jet noise reduction using micro vortex generators." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A221. http://dx.doi.org/10.1121/10.0016074.
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A new supersonic jet noise reduction technology has been developed using Micro Vortex Generators (MVGs) by the collaboration between the University of Cincinnati and the Naval Research Laboratory. MVGs are used on model scale nozzles that are representative of GE F404 engine nozzles. Noise reductions up to −10 dB have been observed in both laboratory measurements and LES simulations at conditions related to take off in the overexpanded regime. Analysis of the acoustic field and flow field using Schlieren visualization reveal the noise reduction mechanisms associated with MVGs. Direct visualization of the changes in shock cell spacing, Large Coherent Structures (LCS) formation, and their convective velocity are identified and those changes modify the downstream propagating hydrodynamic waves and the upstream propagating acoustics waves. Spectral Proper Orthogonal Decomposition (SPOD) is utilized to examine the flow sources at frequencies associated with the noise components observed in the acoustic spectra to explain the noise reduction mechanisms of MVGs.
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Du Clos, Kevin T., Amy Lang, Sean Devey, Philip J. Motta, Maria Laura Habegger, and Brad J. Gemmell. "Passive bristling of mako shark scales in reversing flows." Journal of The Royal Society Interface 15, no. 147 (October 2018): 20180473. http://dx.doi.org/10.1098/rsif.2018.0473.
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Shark skin has been shown to reduce drag in turbulent boundary layer flows, but the flow control mechanisms by which it does so are not well understood. Drag reduction has generally been attributed to static effects of scale surface morphology, but possible drag reduction effects of passive or active scale actuation, or ‘bristling’, have been recognized more recently. Here, we provide the first direct documentation of passive scale bristling due to reversing, turbulent boundary layer flows. We recorded and analysed high-speed videos of flow over the skin of a shortfin mako shark, Isurus oxyrinchus . These videos revealed rapid scale bristling events with mean durations of approximately 2 ms. Passive bristling occurred under flow conditions representative of cruise swimming speeds and was associated with two flow features. The first was a downward backflow that pushed a scale-up from below. The second was a vortex just upstream of the scale that created a negative pressure region, which pulled up a scale without requiring backflow. Both flow conditions initiated bristling at lower velocities than those required for a straight backflow. These results provide further support for the role of shark scale bristling in drag reduction.
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Czerniawski, Robert, and Monika Kowalska-Góralska. "Spatial changes in zooplankton communities in a strong human-mediated river ecosystem." PeerJ 6 (July 3, 2018): e5087. http://dx.doi.org/10.7717/peerj.5087.
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River damming causes a decrease in water current velocity which leads to an increase in richness and abundance of organisms atypical for running waters. Zooplankton is a representative example of such organisms. The influx of zooplankton from carp ponds is an additional factor that increases richness and abundance of zooplankton in rivers. We hypothesized that zooplankton dispersing from the carp ponds colonize the impoundments in river and the richness of zooplankton increase in impoundments by development of new species, not observed in the upstream. The zooplankton was collected monthly from April to September of 2013 and 2014. Sampling sites were located in the Barycz river (in the lotic sections and in the dam impoundments), as well as in its tributaries, which are the outlets of carp ponds. The most changes in zooplankton richness and abundance were observed at sites located within the dam impoundments, especially in relation to the lower values of the current velocity. Since the abundance of pelagic rotifers, cladocerans and copepods in the carp pond outlets was similar to that at lower sites in the Barycz, the influence of the carp pond outlets on the abundance in the dam and lotic sections was significant. The river itself in its impounded sections provides advantageous conditions for retention and colonization by a high abundance of zooplankton dispersing from the carp ponds, and for the development of species not occurred in the upstream, which, in turn, increases richness.
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Gilbert, Bettina, Ian R. McDonald, Ruth Finch, Graham P. Stafford, Allan K. Nielsen, and J. Colin Murrell. "Molecular Analysis of the pmo (Particulate Methane Monooxygenase) Operons from Two Type II Methanotrophs." Applied and Environmental Microbiology 66, no. 3 (March 1, 2000): 966–75. http://dx.doi.org/10.1128/aem.66.3.966-975.2000.
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ABSTRACT The particulate methane monooxygenase gene clusters,pmoCAB, from two representative type II methanotrophs of the α-Proteobacteria, Methylosinus trichosporium OB3b and Methylocystis sp. strain M, have been cloned and sequenced. Primer extension experiments revealed that the pmo cluster is probably transcribed from a single transcriptional start site located 300 bp upstream of the start of the first gene, pmoC, for Methylocystis sp. strain M. Immediately upstream of the putative start site, consensus sequences for ς70 promoters were identified, suggesting that thesepmo genes are recognized by ς70 and negatively regulated under low-copper conditions. The pmogenes were cloned in several overlapping fragments, since parts of these genes appeared to be toxic to the Escherichia colihost. Methanotrophs contain two virtually identical copies ofpmo genes, and it was necessary to use Southern blotting and probing with pmo gene fragments in order to differentiate between the two pmoCAB clusters in both methanotrophs. The complete DNA sequence of one copy of pmogenes from each organism is reported here. The gene sequences are 84% similar to each other and 75% similar to that of a type I methanotroph of the γ-Proteobacteria, Methylococcus capsulatus Bath. The derived proteins PmoC and PmoA are predicted to be highly hydrophobic and consist mainly of transmembrane-spanning regions, whereas PmoB has only two putative transmembrane-spanning helices. Hybridization experiments showed that there are two copies ofpmoC in both M. trichosporium OB3b andMethylocystis sp. strain M, and not three copies as found in M. capsulatus Bath.
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Georgiou, D. P., and J. F. Louis. "The Transpired Turbulent Boundary Layer in Various Pressure Gradients and the Blow-Off Condition." Journal of Engineering for Gas Turbines and Power 107, no. 3 (July 1, 1985): 636–41. http://dx.doi.org/10.1115/1.3239783.
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An experimental study of the reduction in heat transfer to a transpiration-cooled flat surface subjected to pressure gradients (zero, negative, and positive) is presented for flow conditions similar to those encountered in gas turbines. The investigation is carried out for high injection rates and determines the blow-off conditions under which the boundary layer is lifted away from the wall by the transpired coolant. The study was conducted in a hot blow-down wind tunnel facility. The transient nature of the facility ensures that the wall remains isothermal. The Reynolds number, the ratio of the gas to wall temperatures, and the pressure gradient parameters K are chosen to be representative of the conditions found in advanced gas turbines. The effect of the pressure gradient was found to be small. However, a local strong acceleration can reduce the cooling effectiveness. The heat transfer rates or Stanton numbers on a solid surface downstream of a transpiration cooled wall are found to be sensitive to the upstream injection ratio (b) and to the pressure gradient parameter. The data indicate that the ratio of Stanton numbers with and without cooling is nonzero for values of the injection parameters larger than values obtained theoretically by Kutateladze. The predicted value of the critical injection ratio (bcr) determined from this study agrees well with the experimental data of Liepmann and Laufer for a free mixing layer, which is similar to a transpired boundary layer near blow-off as pointed out by Coles.
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Zhao, Xinwei, Hongkun Li, Shuhua Yang, Zhenfang Fan, and Yang Wang. "Experimental determination of IGV preswirl effect on impeller blade vibration in an unshrouded centrifugal compressor." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 235, no. 6 (June 21, 2021): 1288–301. http://dx.doi.org/10.1177/09576509211024766.
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The unshrouded impeller is widely used in industrial centrifugal compressors and normally operates at high tip speed and large volume flow. However, this type of impeller can be very sensitive to flow excitations such as IGV wake, and hence encounters the challenge of high dynamic stress. Due to the lack of experimental vibration data, this paper aims to enhance the understanding of the IGV preswirl effect. The real operating representative data from strain gauges is acquired during the experiment. The blade transient and quasi-steady response due to upstream IGV wake under different configurations are investigated and quantified. Results show that the blade response increases with larger positive regulation. And under specific operating conditions, the vibration of the blade is quite large, which is comparable with synchronize resonance. This increment is attributed to the aerodynamic loading change due to enhanced distortion of the inlet flow. Based on the current findings, accurate numerical prediction of the blade forced vibration for a large shift of inlet flow condition is also needed for more reliable operating of the impeller.
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Kluwick, A., and M. Kornfeld. "Triple-deck analysis of transonic high Reynolds number flow through slender channels." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, no. 2020 (July 28, 2014): 20130346. http://dx.doi.org/10.1098/rsta.2013.0346.
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In this work, laminar transonic weakly three-dimensional flows at high Reynolds numbers in slender channels, as found in microsupersonic nozzles and turbomachines of micro-electro-mechanical systems, are considered. The channel height is taken so small that the viscous wall layers forming at the channel walls start to interact strongly rather than weakly with the inviscid core flow and, therefore, the classical boundary layer approach fails. The resulting viscous–inviscid interaction problem is formulated using matched asymptotic expansions and found to be governed by a triple-deck structure. As a consequence, the properties of the predominantly inviscid core region and the viscous wall layers have to be calculated simultaneously in the interaction region. Weakly three-dimensional effects caused by surface roughness, upstream propagating flow perturbations, boundary layer separation as well as bifurcating solutions are discussed. Representative results for subsonic as well as supersonic conditions are presented, and the importance of these flow phenomena in technical applications as, for example, a means to reduce shock losses through the use of deformed geometry is addressed.
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Ishar, Rishabh, Eurika Kaiser, Marek Morzyński, Daniel Fernex, Richard Semaan, Marian Albers, Pascal S. Meysonnat, Wolfgang Schröder, and Bernd R. Noack. "Metric for attractor overlap." Journal of Fluid Mechanics 874 (July 12, 2019): 720–55. http://dx.doi.org/10.1017/jfm.2019.447.
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We present the first general metric for attractor overlap (MAO) facilitating an unsupervised comparison of flow data sets. The starting point is two or more attractors, i.e. ensembles of states representing different operating conditions. The proposed metric generalizes the standard Hilbert-space distance between two snapshot-to-snapshot ensembles of two attractors. A reduced-order analysis for big data and many attractors is enabled by coarse graining the snapshots into representative clusters with corresponding centroids and population probabilities. For a large number of attractors, MAO is augmented by proximity maps for the snapshots, the centroids and the attractors, giving scientifically interpretable visual access to the closeness of the states. The coherent structures belonging to the overlap and disjoint states between these attractors are distilled by a few representative centroids. We employ MAO for two quite different actuated flow configurations: a two-dimensional wake with vortices in a narrow frequency range and three-dimensional wall turbulence with a broadband spectrum. In the first application, seven control laws are applied to the fluidic pinball, i.e. the two-dimensional flow around three circular cylinders whose centres form an equilateral triangle pointing in the upstream direction. These seven operating conditions comprise unforced shedding, boat tailing, base bleed, high- and low-frequency forcing as well as two opposing Magnus effects. In the second example, MAO is applied to three-dimensional simulation data from an open-loop drag reduction study of a turbulent boundary layer. The actuation mechanisms of 38 spanwise travelling transversal surface waves are investigated. MAO compares and classifies these actuated flows in agreement with physical intuition. For instance, the first feature coordinate of the attractor proximity map correlates with drag for the fluidic pinball and for the turbulent boundary layer. MAO has a large spectrum of potential applications ranging from a quantitative comparison between numerical simulations and experimental particle-image velocimetry data to the analysis of simulations representing a myriad of different operating conditions.
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Ranjan, Pallav, Ketan Mittal, Leonardo P. Chamorro, and Rafael O. Tinoco. "Impact of gaps on the flow statistics in an emergent rigid canopy." Physics of Fluids 34, no. 6 (June 2022): 066601. http://dx.doi.org/10.1063/5.0088527.
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High-resolution large eddy simulations and complementary laboratory experiments using particle image velocimetry were performed to provide a detailed quantitative assessment of flow response to gaps in cylinder arrays. The base canopy consists of a dense array of emergent rigid cylinders placed in a regular staggered pattern. The gaps varied in length from [Formula: see text] to 24, in intervals of 4 d, where d is the diameter of the cylinders. The analysis was performed under subcritical conditions with Froude numbers [Formula: see text] and bulk Reynolds numbers [Formula: see text]. Results show that the gaps affect the flow statistics at the upstream and downstream proximity of the canopy. The affected zone was [Formula: see text] for the mean flow and [Formula: see text] for the second-order statistics. Dimensionless time-averaged streamwise velocity within the gap exhibited minor variability with gap spacing; however, in-plane turbulent kinetic energy, k, showed a consistent decay rate when normalized with that at [Formula: see text] from the beginning of the gap. The emergent canopy acts as a passive turbulence generator for the gap flow for practical purposes. The streamwise dependence of k follows an exponential trend within [Formula: see text] and transitions to a power-law at [Formula: see text]. The substantially lower maximum values of k within the gap compared to k within the canopy evidence a limitation of gap measurements representative of canopy flow statistics. We present a base framework for estimating representative in-canopy statistics from measurements in the gap.
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Miller, R. J., R. W. Moss, R. W. Ainsworth, and N. W. Harvey. "Wake, Shock, and Potential Field Interactions in a 1.5 Stage Turbine—Part I: Vane-Rotor and Rotor-Vane Interaction." Journal of Turbomachinery 125, no. 1 (January 1, 2003): 33–39. http://dx.doi.org/10.1115/1.1508386.
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The composition of the time-resolved surface pressure field around a high-pressure rotor blade caused by the presence of neighboring blade rows is investigated, with the individual effects of wake, shock and potential field interaction being determined. Two test geometries are considered: first, a high-pressure turbine stage coupled with a swan-necked diffuser exit duct; secondly, the same high-pressure stage but with a vane located in the downstream duct. Both tests were conducted at engine-representative Mach and Reynolds numbers, and experimental data was acquired using fast-response pressure transducers mounted on the mid-height streamline of the HP rotor blades. The results are compared to time-resolved computational predictions of the flowfield in order to aid interpretation of experimental results and to determine the accuracy with which the computation predicts blade interaction. The paper is split into two parts: the first investigating the effect of the upstream vane on the unsteady pressure field around the rotor (vane-rotor interaction), and the second investigating the effect of the downstream vane on the unsteady pressure field around the rotor (rotor-vane interaction). The paper shows that at typical design operating conditions shock interaction from the upstream blade row is an order of magnitude greater than wake interaction and that with the design vane-rotor inter-blade gap the presence of the rotor causes a periodic increase in the strength of the vane trailing edge shock. The presence of the potential field of the downstream vane is found to affect significantly the rotor pressure field downstream of the Mach one surface within each rotor passage.
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Cauteruccio, Arianna, Matteo Colli, Andrea Freda, Mattia Stagnaro, and Luca G. Lanza. "The Role of Free-Stream Turbulence in Attenuating the Wind Updraft above the Collector of Precipitation Gauges." Journal of Atmospheric and Oceanic Technology 37, no. 1 (January 2020): 103–13. http://dx.doi.org/10.1175/jtech-d-19-0089.1.
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AbstractIn operational conditions, wind is the main environmental source of measurement biases for catching-type precipitation gauges. The gauge geometry induces a deformation of the surrounding airflow pattern, which is generally characterized by relevant updraft zones in front of the collector and above it. This effect deviates the trajectories of the lighter hydrometeors away from the collector and thus is responsible for a significant reduction of the collection performance. Previous approaches to this problem, using computational fluid dynamics simulations and wind-tunnel tests, mostly assumed steady and uniform free-stream conditions. Wind is turbulent in nature, though. The role of natural free-stream turbulence on collection performance is investigated in this work for the case study of a calyx-shaped precipitation gauge and wind velocity between 10 and 18 m s−1. The unsteady Reynolds-averaged Navier–Stokes model was adopted. Turbulent conditions were simulated by imposing constant free-stream velocity and introducing a fixed solid fence upstream of the gauge to generate the desired turbulence intensity. Wind-tunnel measurements allowed validating numerical results by comparing measured and simulated velocity profiles in representative portions of the investigated domain. Results revealed that in the case of turbulent free-stream conditions both the normalized magnitude of the flow velocity and the updraft above the collector are reduced by approximately 20% and 12%, respectively. The dissipative effect of the turbulent fluctuations in the free stream has a damping role on the acceleration of the flow and on the updraft. This would result in a reduced undercatch with respect to literature simulations that employed the traditional uniform free-stream conditions.
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Brouwer, Ronald L., George P. Schramkowski, Yoeri M. Dijkstra, and Henk M. Schuttelaars. "Time Evolution of Estuarine Turbidity Maxima in Well-Mixed, Tidally Dominated Estuaries: The Role of Availability- and Erosion-Limited Conditions." Journal of Physical Oceanography 48, no. 8 (August 2018): 1629–50. http://dx.doi.org/10.1175/jpo-d-17-0183.1.
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AbstractUsing an idealized width-averaged process-based model, the role of a mud pool on the bed and time-varying river discharge on the trapping of fine sediment is systematically investigated. For this purpose, a dynamically and physically motivated description of erodibility is presented, which relates the amount of sediment on the bed to the suspended sediment concentration (SSC). We can distinguish between two states: in the availability-limited state, the SSC is limited by the amount of erodible sediment at the bed. Over time, under constant forcing conditions, the estuary evolves to morphodynamic equilibrium. In the erosion-limited state, there is an abundant amount of sediment at the bed so that sediment pickup occurs at the maximum possible rate. The SSC is then limited by the local hydrodynamic conditions. In this state, the estuary keeps importing sediment, forming an erodible bottom pool that grows in time. These two states can be used to explain the response of an estuary to changing river discharge. Under availability-limited conditions, periods of high river discharge push estuarine turbidity maxima (ETMs) downstream, while drier periods allow ETMs to move upstream. However, when the estuary is in an erosion-limited state during low river discharge, a bottom pool is formed. When the discharge then increases, it takes time to deplete this pool, so that an ETM located over a bottom pool moves with a significant time lag relative to changes in the river discharge. Good qualitative agreement is found between model results and observations in the Scheldt Estuary of surface SSC using a representative year of discharge conditions.
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Cho, He-Jin, Sung-Hun Son, Wanping Chen, Ye-Eun Son, Inhyung Lee, Jae-Hyuk Yu, and Hee-Soo Park. "Regulation of Conidiogenesis in Aspergillus flavus." Cells 11, no. 18 (September 7, 2022): 2796. http://dx.doi.org/10.3390/cells11182796.
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Aspergillus flavus is a representative fungal species in the Aspergillus section Flavi and has been used as a model system to gain insights into fungal development and toxin production. A. flavus has several adverse effects on humans, including the production of the most carcinogenic mycotoxin aflatoxins and causing aspergillosis in immune-compromised patients. In addition, A. flavus infection of crops results in economic losses due to yield loss and aflatoxin contamination. A. flavus is a saprophytic fungus that disperses in the ecosystem mainly by producing asexual spores (conidia), which also provide long-term survival in the harsh environmental conditions. Conidia are composed of the rodlet layer, cell wall, and melanin and are produced from an asexual specialized structure called the conidiophore. The production of conidiophores is tightly regulated by various regulators, including the central regulatory cascade composed of BrlA-AbaA-WetA, the fungi-specific velvet regulators, upstream regulators, and developmental repressors. In this review, we summarize the findings of a series of recent studies related to asexual development in A. flavus and provide insights for a better understanding of other fungal species in the section Flavi.
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Canepa, Edward, Davide Lengani, Alessandro Nilberto, Daniele Petronio, Daniele Simoni, Marina Ubaldi, and Pietro Zunino. "Flow Coefficient and Reduced Frequency Effects on Wake-Boundary Layer Interaction in Highly Accelerated LPT Cascade." International Journal of Turbomachinery, Propulsion and Power 6, no. 3 (August 4, 2021): 32. http://dx.doi.org/10.3390/ijtpp6030032.
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The paper presents a detailed analysis of particle image velocimetry (PIV) measurements performed in a turbine cascade representative of highly accelerated low-pressure turbine (LPT) blades. Two cameras have been simultaneously used to observe a great portion of the suction side boundary layer with the highest possible spatial resolution, thus allowing us to solve the interaction process between impinging upstream wakes and the blade boundary layer. Four unsteady inflow conditions, characterized by different incoming wake reduced frequencies and flow coefficients, have been examined at fixed Reynolds number. The highly resolved flow fields have been processed to explore reduced frequency and flow coefficient effects on the boundary layer unsteady transition process and, consequently, on loss production. For a deep physical insight on the mechanisms responsible for loss generation, proper orthogonal decomposition (POD) has been applied at different phases of the wake passing period. This has provided the dominant structures affecting the cascade aerodynamics during the wake period. Moreover, the examination of POD modes has allowed us to show the effects induced by the parameter variation on the turbulent kinetic energy production and thus to the unsteady loss production mechanisms.
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Pinelli, Lorenzo, Francesco Lori, Michele Marconcini, Roberto Pacciani, and Andrea Arnone. "Validation of a Modal Work Approach for Forced Response Analysis of Bladed Disks." Applied Sciences 11, no. 12 (June 11, 2021): 5437. http://dx.doi.org/10.3390/app11125437.
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The paper describes a numerical method based on a modal work approach to evaluate the forced response of bladed disks and its validation against numerical results obtained by a commercial FEM code. Forcing functions caused by rotor–stator interactions are extracted from CFD unsteady solutions properly decomposed in time and space to separate the spinning perturbation acting on the bladed disk in a cyclic environment. The method was firstly applied on a dummy test case with cyclic symmetry where the forcing function distributions were arbitrarily selected: comparisons for resonance and out of resonance conditions revealed an excellent agreement between the two numerical methods. Finally, the validation was extended to a more realistic test case representative of a low-pressure turbine bladed rotor subjected to the wakes of two upstream rows: an IGV with low blade count and a stator row. The results show a good agreement and suggest computing the forced response problem on the finer CFD blade surface grid to achieve a better accuracy. The successful validation of the method, closely linked to the CFD environment, creates the opportunity to include the tool in an integrated multi-objective procedure able to account for aeromechanical aspects.
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FERGASON, S. H., T. L. HO, B. M. ARGROW, and G. EMANUEL. "Theory for producing a single-phase rarefaction shock wave in a shock tube." Journal of Fluid Mechanics 445 (October 16, 2001): 37–54. http://dx.doi.org/10.1017/s0022112001005444.
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Although predicted early in the 20th century, a single-phase vapour rarefaction shock wave has yet to be demonstrated experimentally. Results from a previous shock tube experiment appear to indicate a rarefaction shock wave. These results are discussed and their interpretation challenged. In preparation for a new shock tube experiment, a global theory is developed, utilizing a van der Waals fluid, for demonstrating a single-phase vapour rarefaction shock wave in the incident flow of the shock tube. The flow consists of four uniform regions separated by three constant-speed discontinuities: a rarefaction shock, a compression shock, and a contact surface. Entropy jumps and upstream supersonic Mach number conditions are verified for both shock waves. The conceptual van der Waals model is applied to the fluid perfluoro-tripentylamine (FC-70, C15F33N) analytically, and verified with computational simulations. The analysis predicts a small region of initial states that may be used to unequivocally demonstrate the existence of a single-phase vapour rarefaction shock wave. Simulation results in the form of representative sets of thermodynamic state data (pressure, density, Mach number, and fundamental derivative of gas dynamics) are presented.
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Mughieda, Omer, Kenan Hazirbaba, Khaldoon Bani-Hani, and Wassim Daoud. "Numerical modelling of dynamic stability of RCC dam." MATEC Web of Conferences 195 (2018): 03021. http://dx.doi.org/10.1051/matecconf/201819503021.
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Stability and stress analyses are the most important elements that require rigorous consideration in design of a dam structure. In the current research, dynamic structural stability of a roller-compacted-concrete (RCC) dam was performed. The RCC dam was modeled using the finite element method to investigate the stability against sliding and the structural stability of the body of the dam. The commercially available finite element software (SAP 2000) was used to analyze stresses in the body of the dam and foundation. A linear finite element dynamic analysis was performed. Response spectrum and time history methods were used with different earthquake loads. The response spectrum of the 1995 Aqaba earthquake and a representative elastic-spectrum with smooth plateau for both Operating Basis Earthquake (OBE) and Maximum Credible Earthquake (MCE) were used in this study. The analysis was carried out assuming that no slip will occur at the interface between the dam and the foundation. The greatest tension was found to develop in the rock adjacent to the toe of the upstream slope. The factor of safety against sliding along the entire base of the dam was found to be greater than 1 (FS>1), for both loading conditions.
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Krishnababu, S. K., H. P. Hodson, W. N. Dawes, P. J. Newton, and G. D. Lock. "Numerical and experimental investigation of tip leakage flow and heat transfer using idealised rotor-tip models at transonic conditions." Aeronautical Journal 113, no. 1141 (March 2009): 165–75. http://dx.doi.org/10.1017/s0001924000011453.
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Abstract The effect of tip geometry on discharge coefficient and heat transfer is investigated both experimentally and numerically using idealised models of an unshrouded rotor blade. A flat tip was compared with two squealer-type geometries (a cavity and suction-side squealer) under the transonic conditions expected in the gas turbine engine. Heat transfer measurements were performed using a transient liquid crystal technique while a duplicate test section was used for measuring the pressure field. Computations were carried out using an unstructured, fully compressible, three-dimensional RANS (Reynolds averaged Navier Stokes) solver. Initial computations performed using a low Reynolds number k-ε model demonstrated the inability of the model to predict the Nusselt number with reasonable accuracy. Further computations performed using a low Reynolds number k-ω model improved the predictions dramatically. The computed discharge coefficient and the average Nusselt number over the blade tip agreed well with the experiments. Three upstream-total to exit-static pressure ratios were used to create a range of engine-representative Mach numbers. Both experimental and numerical studies at the lower pressure ratio of 1·3 (exit Mach number ~ 0·65) established the cavity geometry as the best performer from an aerodynamic perspective by reducing the discharge through the tip. However, from the heat transfer perspective, both the peak Nusselt number and the average heat transfer to the tip were higher than the flat tip. At the higher pressure ratios of 1·85 and 2·27 (corresponding to exit Mach numbers ~ 0·98 and 1·12) the discharge coefficient and heat transfer to the tip increases. This paper explores the fluid dynamics associated with these flows and shows that the highest heat transfer is caused by reattachment and flow impingement. The fluid dynamic computations provide insight into the experimental measurements and were successfully compared with simple analytical models.
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Wise, Adam S., James M. T. Neher, Robert S. Arthur, Jeffrey D. Mirocha, Julie K. Lundquist, and Fotini K. Chow. "Meso- to microscale modeling of atmospheric stability effects on wind turbine wake behavior in complex terrain." Wind Energy Science 7, no. 1 (February 17, 2022): 367–86. http://dx.doi.org/10.5194/wes-7-367-2022.
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Abstract. Terrain-induced flow phenomena modulate wind turbine performance and wake behavior in ways that are not adequately accounted for in typical wind turbine wake and wind plant design models. In this work, we simulate flow over two parallel ridges with a wind turbine on one of the ridges, focusing on conditions observed during the Perdigão field campaign in 2017. Two case studies are selected to be representative of typical flow conditions at the site, including the effects of atmospheric stability: a stable case where a mountain wave occurs (as in ∼ 50 % of the nights observed) and a convective case where a recirculation zone forms in the lee of the ridge with the turbine (as occurred over 50 % of the time with upstream winds normal to the ridgeline). We use the Weather Research and Forecasting Model (WRF), dynamically downscaled from the mesoscale (6.75 km resolution) to microscale large-eddy simulation (LES) at 10 m resolution, where a generalized actuator disk (GAD) wind turbine parameterization is used to simulate turbine wakes. We compare the WRF–LES–GAD model results to data from meteorological towers, lidars, and a tethered lifting system, showing good qualitative and quantitative agreement for both case studies. Significantly, the wind turbine wake shows different amounts of vertical deflection from the terrain and persistence downstream in the two stability regimes. In the stable case, the wake follows the terrain along with the mountain wave and deflects downwards by nearly 100 m below hub height at four rotor diameters downstream. In the convective case, the wake deflects above the recirculation zone over 40 m above hub height at the same downstream distance. Overall, the WRF–LES–GAD model is able to capture the observed behavior of the wind turbine wakes, demonstrating the model's ability to represent wakes over complex terrain for two distinct and representative atmospheric stability classes, and, potentially, to improve wind turbine siting and operation in hilly landscapes.
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Kaiktsis, Lambros, George Em Karniadakis, and Steven A. Orszag. "Onset of three-dimensionality, equilibria, and early transition in flow over a backward-facing step." Journal of Fluid Mechanics 231 (October 1991): 501–28. http://dx.doi.org/10.1017/s0022112091003488.
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A numerical study of three-dimensional equilibria and transition to turbulence in flow over a backward-facing step is performed using direct numerical solution of the incompressible Navier-Stokes equations. The numerical method is a high-order-accurate mixed spectral/spectral-element method with efficient viscous outflow boundary conditions. The appearance of three-dimensionality in nominally two-dimensional geometries is investigated at representative Reynolds numbers ranging from the onset of three-dimensional bifurcation to later transitional stages. Strongly three-dimensional regions are identified through standard correlation coefficients and new three-dimensionality indices, as well as through instantaneous and time-average streamline patterns and vorticity contours. Our results indicate that onset of three-dimensionality occurs at the boundaries between the primary and secondary recirculating zones with the main channel flow, the latter being the most stable flow component. There is. therefore, strong secondary instability in the shear layers, mainly due to the one emanating from the step corner.The flow further downstream is excited through the action of the upstream shear layers acquiring a wavy form closely resembling Tollmien–Schlichting waves both spatially and temporally with a characteristic frequency f1; upstream, at the shear layer another incommensurate frequency, f2, is present. The two-frequency flow locks-in to a single frequency if external excitations are imposed at the inflow at a frequency close to f1 or f2; the smaller amplitude excitations, however, may cause a strong quasi-periodic response. Such excitations may significantly increase or decrease (by more than 20%) the length of the primary separation zone XR at lock-in or quasi-periodic states. The equilibrium states resulting from the secondary instability at supercritical Reynolds numbers produce a flow modulated in the spanwise direction, with corresponding variations in the reattachment location XR. While three-dimensionality explains partially the discrepancy between numerical predictions and experimental results on XR at higher Reynolds number Re, the main source of discrepancy is attributed to the inflow conditions, and in particular to external disturbances superimposed on the mean flow, the latter being the main reason also for the somewhat earlier transition found in laboratory experiments.
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Berube, Paul M., Ram Samudrala, and David A. Stahl. "Transcription of All amoC Copies Is Associated with Recovery of Nitrosomonas europaea from Ammonia Starvation." Journal of Bacteriology 189, no. 11 (March 23, 2007): 3935–44. http://dx.doi.org/10.1128/jb.01861-06.
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ABSTRACT The chemolithotrophic ammonia-oxidizing bacterium Nitrosomonas europaea is known to be highly resistant to starvation conditions. The transcriptional response of N. europaea to ammonia addition following short- and long-term starvation was examined by primer extension and S1 nuclease protection analyses of genes encoding enzymes for ammonia oxidation (amoCAB operons) and CO2 fixation (cbbLS), a third, lone copy of amoC (amoC 3 ), and two representative housekeeping genes (glyA and rpsJ). Primer extension analysis of RNA isolated from growing, starved, and recovering cells revealed two differentially regulated promoters upstream of the two amoCAB operons. The distal σ70 type amoCAB promoter was constitutively active in the presence of ammonia, but the proximal promoter was only active when cells were recovering from ammonia starvation. The lone, divergent copy of amoC (amoC 3 ) was expressed only during recovery. Both the proximal amoC 1,2 promoter and the amoC 3 promoter are similar to gram-negative σE promoters, thus implicating σE in the regulation of the recovery response. Although modeling of subunit interactions suggested that a nonconservative proline substitution in AmoC3 may modify the activity of the holoenzyme, characterization of a ΔamoC 3 strain showed no significant difference in starvation recovery under conditions evaluated. In contrast to the amo transcripts, a delayed appearance of transcripts for a gene required for CO2 fixation (cbbL) suggested that its transcription is retarded until sufficient energy is available. Overall, these data revealed a programmed exit from starvation likely involving regulation by σE and the coordinated regulation of catabolic and anabolic genes.
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Rakhimova, Moldir, Tie Liu, Sanim Bissenbayeva, Yerbolat Mukanov, Khusen Sh Gafforov, Zhuldyzay Bekpergenova, and Aminjon Gulakhmadov. "Assessment of the Impacts of Climate Change and Human Activities on Runoff Using Climate Elasticity Method and General Circulation Model (GCM) in the Buqtyrma River Basin, Kazakhstan." Sustainability 12, no. 12 (June 18, 2020): 4968. http://dx.doi.org/10.3390/su12124968.
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The variations of climate and water resources in the Buqtyrma River Basin (BRB), which is located at the cross-section of the Altai Mountains, Eurasian Steppe and Tian Shan Mountains, have a great significance for agriculture and ecosystems in the region. Changing climatic conditions will change the hydrological cycle in the whole basin. In this study, we examined the historical trends and change points of the climate and hydrological variables, the contributions of climate change and human activities to runoff changes, and the relative changes in the runoff to the precipitation and potential evapotranspiration from 1950 to 2015 by using the Mann–Kendall trend test, Pettitt test, double cumulative curve and elasticities methods. In addition, a multi-model ensemble (MME) of the six general circulation models (GCMs) for two future periods (2036–2065 and 2071–2100) was assessed to estimate the spatio-temporal variations in precipitation and temperature under two representative concentration pathways (RCPs 4.5 and 8.5) scenarios. Our study detected that the runoff change-point occurred in 1982. The impacts induced by climate change on runoff change were as follows—70% in the upstream, 62.11% in the midstream and 15.34% in the downstream area. The impacts of human activity on runoff change were greater in the downstream area (84.66%) than in the upstream and midstream areas. A continuously increasing trend was indicated regarding average annual temperature under RCP 4.5 (from 0.37 to 0.33 °C/decade) and under RCP 8.5 (from 0.50 to 0.61 °C/decade) during two future periods. Additionally, an increasing trend in predicted precipitation was exhibited under RCP 4.5 (13.6% and 19.9%) and under RCP 8.5 (10.5% and 18.1%) during both future periods. The results of the relative runoff changes to the predicted precipitation and potential evapotranspiration were expected to increase during two future time periods under RCP 4.5 (18.53% and 25.40%) and under RCP 8.5 (8.91% and 13.38%) relative to the base period. The present work can provide a reference for the utilization and management of regional water resources and for ecological environment protection.
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Cui, Honglei, Mei Liu, and Chen Chen. "Ecological Restoration Strategies for the Topography of Loess Plateau Based on Adaptive Ecological Sensitivity Evaluation: A Case Study in Lanzhou, China." Sustainability 14, no. 5 (March 1, 2022): 2858. http://dx.doi.org/10.3390/su14052858.
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Existing studies related to ecological sensitivity evaluation are comparatively mature; however, few approaches are concerned with distinctive topographical conditions that enable response to specific environmental restoration requirements. In this paper, an adaptive ecological sensitivity evaluation framework is established according to a representative plateau topography (i.e., the Loess Plateau region) via a case study of Gaolan County, China. Through the process of factor selection, index system construction, formula adaption, factor weight determination by analytic hierarchy process (AHP) as well as the support of RS and GIS technology, the ecological sensitivity of the research region has been evaluated and analyzed in combination with land use types and typical gully problems. The results show that high sensitivity areas account for 11.16 percent of the total area in the research region and a tendency for fragmentation in spatial distribution. Forest lands with steep slopes in gullies’ upstream have the highest ecological sensitivity, the proportion of forest and garden land dominated by trees in the highest sensitivity area is around 80 percent. Evidence-based ecological restoration strategies are proposed in terms of the topography of Loess Plateau. This study shows possibilities to adapt existing sensitivity evaluation model for medium-scaled specific topography problems and provides useful clues as a basis for knowledge acquisition that can feed into spatial design, planning and restoration processes.
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Ottavy, Xavier, Stephane Vilmin, Howard Hodson, and Simon Gallimore. "The Effects of Wake-Passing Unsteadiness Over a Highly Loaded Compressor-Like Flat Plate." Journal of Turbomachinery 126, no. 1 (January 1, 2004): 13–23. http://dx.doi.org/10.1115/1.1643384.
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The present study is concerned with wake-induced unsteady effects in axial-compressor blade rows. The goal is to exploit these effects in order to design high-lift blades without increasing the profile loss, as has been achieved for low-pressure turbine blades. In the first part of this paper, the experimental means and the computational fluid dynamics tools are described. The rig features a flat plate that can be subjected to different velocity distributions representative of the suction side of a real compressor blade. Cylindrical bars mounted on a moving system simulate the incoming wakes from the upstream blade row in the compressor. Results are presented for steady flow and for unsteady compressor-like conditions. In all cases, the separation bubble of the steady flow is suppressed by the turbulence that is induced in the boundary layer by the wakes at approximately 10% of the suction side. Its reappearance is then delayed by a region of stable laminar-like flow and low loss due to the so-called calming effect that follows the wake-induced patch. The paper describes these phenomena in detail for one particular pressure distribution. It is then shown that it should be possible to increase the lift by 35% while keeping the same level of loss as the initial conventional pressure distribution of the study.
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Pérez-Sánchez, Eduardo J., Jose M. Garcia-Oliver, Ricardo Novella, and Jose M. Pastor. "Understanding the diesel-like spray characteristics applying a flamelet-based combustion model and detailed large eddy simulations." International Journal of Engine Research 21, no. 1 (July 24, 2019): 134–50. http://dx.doi.org/10.1177/1468087419864469.
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This investigation analyses the structure of spray A from engine combustion network (ECN), which is representative of diesel-like sprays, by means of large eddy simulations and an unsteady flamelet progress variable combustion model. A very good agreement between modelled and experimental measurements is obtained for the inert spray that supports further analysis. A parametric variation in oxygen concentration is carried out in order to describe the structure of the flame and how it is modified when mixture reactivity is changed. The most relevant trends for the flame metrics, ignition delay and lift-off length are well-captured by the simulations corroborating the suitability of the model for this type of configuration. Results show that the morphology of the flame is strongly affected by the boundary conditions in terms of the reactive scalar spatial fields and Z–T maps. The filtered instantaneous fields provided by the simulations allow investigation of the structure of the flame at the lift-off length, whose positioning shows low fluctuations, and how it is affected by turbulence. It is evidenced that small ignition kernels appear upstream and detached from the flame that eventually merge with its base in agreement with experimental observations, leading to state that auto-ignition plays a key role as one of the flame stabilization mechanisms of the flame.
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ŠORŠA, Ajka, Teja ČERU, Zsófia KOVÁCS, Gyozo JORDAN, Katalin Mária DUDÁS, and Peter SZABÓ. "ASSESSMENT OF RIVER SEDIMENT QUALITY ACCORDING TO THE EU WATER FRAMEWORK DIRECTIVE IN LOWLAND FLUVIAL CONDITIONS. A CASE STUDY IN THE DRAVA RIVER AREA, DANUBE RIVER BASIN." Carpathian Journal of Earth and Environmental Sciences 17, no. 2 (August 31, 2022): 459–68. http://dx.doi.org/10.26471/cjees/2022/017/235.
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The EU Water Framework Directive requires the monitoring and evaluation of surface water sediment quality based on the assessment of risk posed by contamination on the biotic receptors. Fluvial sediments are important receptors of hazardous substances (HSs) pollution from the upstream catchment areas in the Danube River Basin (DRB). For the development of systematic sediment quality monitoring and evaluation, the Drava River region on the border of Hungary and Croatia was selected as a test area representative of lowland hydromorphological conditions. Overbank (floodplain) sediments and river bottom sediments (stream sediments) were sampled at two depths at 9 locations in the test area. Eight heavy metal(oid)s were analyzed As, Cd, Cr, Cu, Hg, Ni, and Zn as hazardous substances. The sediment quality assessment was carried out according to the 2013/39/EU Directive and EU Water Framework Directive standards. Most of the analysed HS concentrations in river bottom sediment and overbank (floodplain) sediments fall within the limits of environmental quality standards (EQS). Results show that there is no significant differences in metal(oid) HS concentrations among the various sediment types and between shallow (0-5cm) and deeper (stream sediment: 5-10cm; floodplain sediment: 40-50cm) sediment which suggests that the large lowland Drava River fluvial system is an extensive single fluvial system with homogeneous distribution of sediments and the associated contaminants. Specifically, the studied sediments in the tributaries of the Drava River do not seem to be contaminated with metal(oid) hazardous substances but at certain sites concentrations are elevated above the environmental limit values, especially for As and Zn, and to lesser extent for Cr. The data analysis techniques used enabled the identification of sites with anthropogenic pollution and the recognition of regional pattern in HSs distribution.
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Basen, Timo, Albert Ros, Christoph Chucholl, Sarah Oexle, and Alexander Brinker. "Who will be where: Climate driven redistribution of fish habitat in southern Germany." PLOS Climate 1, no. 5 (May 2, 2022): e0000006. http://dx.doi.org/10.1371/journal.pclm.0000006.
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To improve the robustness of projections of freshwater fish distributions under climate change, species distribution models (SDMs) were calculated for six fish species in southwestern Germany with different ecological requirements along an upstream-downstream gradient in a multi-general circulation model (GCM) approach. Using the maximum entropy (Maxent) algorithm and a high number of occurrence records (N = 4684), species distributions were projected to future climate conditions derived from 13 GCMs across the most likely representative carbon pathways (RCP4.5 and 8.5) and two time spans (near future 2050, and far future 2070), resulting in 104 distribution maps per species that were then used for the statistical analysis of future trends. Climate change is likely to affect the distribution of four of the six fish species. The potential ranges of salmonids are predicted to decline by up to 92% (brown trout) and 75% (grayling). In contrast, habitat suitability for perch and roach is predicted to increase by up to 108% and 53%, respectively. Even when accounting for broad variation in GCMs and realistic RCPs, these results suggest climate change will drive a significant redistribution of fish habitat. Salmonid-dominated communities in headwaters seem more sensitive to climate change than the fish communities of downstream sections. Because headwaters are a prevailing element of the hydrographic network in southwestern Germany, such changes may result in large-scale regressions of valuable fish communities that currently occupy broad geographic niches.
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Szeto, Kit K. "On the Extreme Variability and Change of Cold-Season Temperatures in Northwest Canada." Journal of Climate 21, no. 1 (January 1, 2008): 94–113. http://dx.doi.org/10.1175/2007jcli1583.1.
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Abstract The Mackenzie River basin (MRB) in northwestern Canada is a climatologically important region that exerts significant influences on the weather and climate of North America. The region exhibits the largest cold-season temperature variability in the world on both the intraseasonal and interannual time scales. In addition, some of the strongest recent warming signals have been observed over the basin. To understand the nature of these profound and intriguing observed thermal characteristics of the region, its atmospheric heat budget is assessed by using the NCEP–NCAR reanalysis dataset. The composite heat budgets and large-scale atmospheric conditions that are representative of anomalous winters in the region are examined in unison to study the processes that are responsible for the development of extreme warm/cold winters in the MRB. It is shown that the large winter temperature variability of the region is largely a result of the strong variability of atmospheric circulations over the North Pacific, the selective enhancement/weakening of latent heating of the cross-barrier flow for various onshore flow configurations, and synoptic-scale feedback processes that accentuate the thermal response of the basin to the changes in upwind conditions. The improved understanding of mechanisms that govern the thermal response of the basin to changes in the upstream environment provides a theoretical basis to interpret the climate change and modeling results for the region. In particular, the large recent warming trend observed for the region can be understood as the enhanced response of the basin to the shift in North Pacific circulation regime during the mid-1970s. The strong cold bias that affected the region in some climate model results can be attributed to the underprediction of orographic precipitation and associate latent heating of the cross-barrier flow, and the subsequent weakening of mean subsidence and warming over the basin in the models.
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Ma, W., Y. Ma, Z. Hu, Z. Su, J. Wang, and H. Ishikawa. "Estimating surface fluxes over middle and upper streams of the Heihe River Basin with ASTER imagery." Hydrology and Earth System Sciences 15, no. 5 (May 6, 2011): 1403–13. http://dx.doi.org/10.5194/hess-15-1403-2011.
Full textAbstract:
Abstract. Land surface heat fluxes are essential measures of the strengths of land-atmosphere interactions involving energy, heat and water. Correct parameterization of these fluxes in climate models is critical. Despite their importance, state-of-the-art observation techniques cannot provide representative areal averages of these fluxes comparable to the model grid. Alternative methods of estimation are thus required. These alternative approaches use (satellite) observables of the land surface conditions. In this study, the Surface Energy Balance System (SEBS) algorithm was evaluated in a cold and arid environment, using land surface parameters derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. Field observations and estimates from SEBS were compared in terms of net radiation flux (Rn), soil heat flux (G0), sensible heat flux (H) and latent heat flux (λE) over a heterogeneous land surface. As a case study, this methodology was applied to the experimental area of the Watershed Allied Telemetry Experimental Research (WATER) project, located on the mid-to-upstream sections of the Heihe River in northwest China. ASTER data acquired between 3 May and 4 June 2008, under clear-sky conditions were used to determine the surface fluxes. Ground-based measurements of land surface heat fluxes were compared with values derived from the ASTER data. The results show that the derived surface variables and the land surface heat fluxes furnished by SEBS in different months over the study area are in good agreement with the observed land surface status under the limited cases (some cases looks poor results). So SEBS can be used to estimate turbulent heat fluxes with acceptable accuracy in areas where there is partial vegetation cover in exceptive conditions. It is very important to perform calculations using ground-based observational data for parameterization in SEBS in the future. Nevertheless, the remote-sensing results can provide improved explanations of land surface fluxes over varying land coverage at greater spatial scales.
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El Khalki, El Mahdi, Yves Tramblay, Christian Massari, Luca Brocca, Vincent Simonneaux, Simon Gascoin, and Mohamed El Mehdi Saidi. "Challenges in flood modeling over data-scarce regions: how to exploit globally available soil moisture products to estimate antecedent soil wetness conditions in Morocco." Natural Hazards and Earth System Sciences 20, no. 10 (October 5, 2020): 2591–607. http://dx.doi.org/10.5194/nhess-20-2591-2020.
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Abstract. The Mediterranean region is characterized by intense rainfall events giving rise to devastating floods. In Maghreb countries such as Morocco, there is a strong need for forecasting systems to reduce the impacts of floods. The development of such a system in the case of ungauged catchments is complicated, but remote-sensing products could overcome the lack of in situ measurements. The soil moisture content can strongly modulate the magnitude of flood events and consequently is a crucial parameter to take into account for flood modeling. In this study, different soil moisture products (European Space Agency Climate Change Initiative, ESA-CCI; Soil Moisture and Ocean Salinity, SMOS; Soil Moisture and Ocean Salinity by the Institut National de la Recherche Agronomique and Centre d'Etudes Spatiales de la Biosphère, SMOS-IC; Advanced Scatterometer, ASCAT; and ERA5 reanalysis) are compared to in situ measurements and one continuous soil-moisture-accounting (SMA) model for basins located in the High Atlas Mountains, upstream of the city of Marrakech. The results show that the SMOS-IC satellite product and the ERA5 reanalysis are best correlated with observed soil moisture and with the SMA model outputs. The different soil moisture datasets were also compared to estimate the initial soil moisture condition for an event-based hydrological model based on the Soil Conservation Service curve number (SCS-CN). The ASCAT, SMOS-IC, and ERA5 products performed equally well in validation to simulate floods, outperforming daily in situ soil moisture measurements that may not be representative of the whole catchment soil moisture conditions. The results also indicated that the daily time step may not fully represent the saturation state before a flood event due to the rapid decay of soil moisture after rainfall in these semiarid environments. Indeed, at the hourly time step, ERA5 and in situ measurements were found to better represent the initial soil moisture conditions of the SCS-CN model by comparison with the daily time step. The results of this work could be used to implement efficient flood modeling and forecasting systems in semiarid regions where soil moisture measurements are lacking.
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Jackson, Emma L., Nathan B. English, Andrew D. Irving, Andrew M. Symonds, Gordon Dwane, Owen T. Nevin, and Damien T. Maher. "A Multifaceted Approach for Determining Sediment Provenance to Coastal Shipping Channels." Journal of Marine Science and Engineering 7, no. 12 (November 29, 2019): 434. http://dx.doi.org/10.3390/jmse7120434.
Full textAbstract:
Maintenance dredging for shipping channels is required to maintain safe and efficient navigational channels and berths in ports around the world. Sediment that refills dredged channels can enter ports via alluvial transport of eroded materials from upstream and adjacent catchments, from marine transport due to tidal currents and wind driven currents and from longshore drift. Identifying the provenance of sediment infilling navigational channels allows port operators to mitigate and manage sediment transport, potentially reducing dredging requirements and costs. Further, understanding sediment sources can inform options for beneficial reuse or disposal of dredged sediments. A multi-faceted approach was used to assess whether sediment provenance in the Port of Gladstone could be characterized. A combination of particle size analysis, rare earth element composition, carbon stable isotope ratios, strontium isotopes, and beryllium-7 radioisotopes was employed. Samples were collected at accumulation locations within the navigational channel. Potential sediment sources were sampled from sites of longshore drift to the south of the Port of Gladstone, and intertidal sand and mud representative of transport from currents. Fluvial sediment samples were collected during dry and wet season conditions and from the three main local catchments. Potential source sediment samples yielded identifiable differences with respect to rare earth elements, while beryllium-7 isotope analysis indicated recent deposition of sediments from mudflats or catchment within the channels. The approach used here provided insights into the source of recently deposited sediments to the dredged channels, enabling managers to make informed decisions on mitigation and management strategies.
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Buetti, E. "Stably integrated mouse mammary tumor virus long terminal repeat DNA requires the octamer motifs for basal promoter activity." Molecular and Cellular Biology 14, no. 2 (February 1994): 1191–203. http://dx.doi.org/10.1128/mcb.14.2.1191-1203.1994.
Full textAbstract:
In the mouse mammary tumor virus promoter, a tandem of octamer motifs, recognized by ubiquitous and tissue-restricted Oct transcription factors, is located upstream of the TATA box and next to a binding site for the transcription factor nuclear factor I (NF-I). Their function was investigated with mutant long terminal repeats under different transfection conditions in mouse Ltk- cells and quantitative S1 nuclease mapping of the transcripts. In stable transfectants, which are most representative of the state of proviral DNA with respect to both number of integrated DNA templates and chromatin organization, a long terminal repeat mutant of both octamer sites showed an average 50-fold reduction of the basal transcription level, while the dexamethasone-stimulated level was unaffected. DNase I in vitro footprinting assays with L-cell nuclear protein extracts showed that the mutant DNA was unable to bind octamer factors but had a normal footprint in the NF-I site. I conclude that mouse mammary tumor virus employs the tandem octamer motifs of the viral promoter, recognized by the ubiquitous transcription factor Oct-1, for its basal transcriptional activity and the NF-I binding site, as previously shown, for glucocorticoid-stimulated transcription. A deletion mutant with only one octamer site showed a marked base-level reduction at high copy number but little reduction at low copies of integrated plasmids. The observed transcription levels may depend both on the relative ratio of transcription factors to DNA templates and on the relative affinity of binding sites, as determined by oligonucleotide competition footprinting.
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Vericat, Damià, Fanny Ville, Antonio Palau-Ibars, and Ramon J. Batalla. "Effects of Hydropeaking on Bed Mobility: Evidence from a Pyrenean River." Water 12, no. 1 (January 8, 2020): 178. http://dx.doi.org/10.3390/w12010178.
Full textAbstract:
Hydropower production involves significant impacts on the dynamics and continuity of river systems. In this paper we analyse the effects of hydropeaks on river-bed particle mobility along a 2-km river channel. For this, a total of four study reaches were stablished: one considered a control reach (no impact by hydropeaking) and three impacted (upstream and downstream from the confluence of tributaries). Mobility related to three hydrological scenarios considered representative of the entire flow conditions in the control and impacted reaches was investigated. Results indicate that sediment availability and dynamics proved different in the control reach to those observed downstream in reaches daily affected by hydropeaks. In the absence of large floods capable of resetting the system from a sedimentary point-of-view, only the role of tributaries during small flow events reduces the effects of hydropeaks on river-bed particles’ availability and mobility. The effects of a hydropeaked regime are not observed for the whole spectrum of grain-sizes present in the river-bed. While the structural large elements (i.e., boulders) in the channel do not move, sand and fine gravel stored in patches of the bed are constantly entrained, transported and depleted whereas, in between, medium and large gravel are progressively winnowed. Our results point out that hydropeaked flows, which are generally not considered as disturbances in geomorphic terms, initiate frequent episodes of (selected) bed mobility and, consequently, the river-bed becomes depleted of fine sediments from patches and progressively lacks other fractions such as medium gravels, all of which are highly relevant from the ecological point of view.
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Buetti, E. "Stably integrated mouse mammary tumor virus long terminal repeat DNA requires the octamer motifs for basal promoter activity." Molecular and Cellular Biology 14, no. 2 (February 1994): 1191–203. http://dx.doi.org/10.1128/mcb.14.2.1191.
Full textAbstract:
In the mouse mammary tumor virus promoter, a tandem of octamer motifs, recognized by ubiquitous and tissue-restricted Oct transcription factors, is located upstream of the TATA box and next to a binding site for the transcription factor nuclear factor I (NF-I). Their function was investigated with mutant long terminal repeats under different transfection conditions in mouse Ltk- cells and quantitative S1 nuclease mapping of the transcripts. In stable transfectants, which are most representative of the state of proviral DNA with respect to both number of integrated DNA templates and chromatin organization, a long terminal repeat mutant of both octamer sites showed an average 50-fold reduction of the basal transcription level, while the dexamethasone-stimulated level was unaffected. DNase I in vitro footprinting assays with L-cell nuclear protein extracts showed that the mutant DNA was unable to bind octamer factors but had a normal footprint in the NF-I site. I conclude that mouse mammary tumor virus employs the tandem octamer motifs of the viral promoter, recognized by the ubiquitous transcription factor Oct-1, for its basal transcriptional activity and the NF-I binding site, as previously shown, for glucocorticoid-stimulated transcription. A deletion mutant with only one octamer site showed a marked base-level reduction at high copy number but little reduction at low copies of integrated plasmids. The observed transcription levels may depend both on the relative ratio of transcription factors to DNA templates and on the relative affinity of binding sites, as determined by oligonucleotide competition footprinting.
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Göttlich, E., J. Woisetschläger, P. Pieringer, B. Hampel, and F. Heitmeir. "Investigation of Vortex Shedding and Wake-Wake Interaction in a Transonic Turbine Stage Using Laser-Doppler-Velocimetry and Particle-Image-Velocimetry." Journal of Turbomachinery 128, no. 1 (February 1, 2005): 178–87. http://dx.doi.org/10.1115/1.2103092.
Full textAbstract:
The current paper presents a time-resolved experimental flow investigation in a highly loaded transonic gas turbine stage operating continuously under engine representative conditions. The measurement was performed with a two-component laser-doppler-velocimeter (LDV) and a three-component stereoscopic particle-image-velocimeter (3C-PIV). Unsteady velocity data were obtained in axis perpendicular planes (LDV) and tangential planes (3C-PIV) between stator and rotor as well as downstream of the rotor. The results of the time-resolved investigation at several radii show the vortex shedding process from the trailing edges of nozzle guide vanes and rotor blades. This vortex shedding was found to be phase locked to higher harmonics of the blade passing frequency. Pressure waves evoked by reflection of the trailing edge shocks of the vanes on the passing rotor blades interact with the boundary layers on the rear suction side of the vanes and on the rotor blade surfaces while running upstream and downstream the flow. They are responsible for this phase-locking phenomenon of the shedding vortices. At midspan, the vortices shedding from stator and rotor blades were also observed by PIV. The in-plane vorticity distribution was used to discuss the wake-wake interaction indicating that wake segments from the nozzle guide vanes were chopped by the rotor blades. These chopped segments are still visible in the distributions as a pair of counter rotating vortices. The nozzle wake segments are transported through the rotor passages by the flow, influencing the vortex street of the rotor blades as they pass by with the higher velocity of the main flow. A comparison with a numerical simulation is also given.
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Onda, Chihaya, Tetsuya Sumi, and Tsuyoshi Asahi. "Planning and Analysis of Sedimentation Countermeasures in Hydropower Dams Considering Properties of Reservoir Sedimentation." Journal of Disaster Research 13, no. 4 (August 1, 2018): 702–8. http://dx.doi.org/10.20965/jdr.2018.p0702.
Full textAbstract:
Sedimentation in hydropower reservoirs is one of the most important problems facing power generation. Many of the reservoirs our company’s dams, built in the postwar reconstruction period, have been storing up sedimentation for decades. The percentage of sedimentation is now considerable, about 9%, because of a combination of a high degree of sediment production and the river flow regime. We have been trying to excavate the sedimentation from the reservoirs to avoid aggradations of upstream riverbeds and to eliminate obstacles to intake and outlet functions. Considering sediment properties, we have carried out representative five different ways of managing reservoir sediment. At the Sakuma dam, which is comparatively large, provisional transporting inside the reservoir is the main countermeasure, but radical management will be required in the near future. At the Futatsuno dam and Taki dam, which are medium-sized, the current volume of sedimentation excavation is not sufficient to maintain the size of the reservoir, due to flow sedimentation. Sediment routing methods, such as bypassing, will therefore be urgently planned. At the Setoishi and Yambara dams, the testing of sediment sluicing or hydro-suction sediment removal systems has already started. Regarding sedimentation sluicing, we have studied the feasibility of sediment bypass tunnels and gated outlets in the dam reservoir that is unsuitable for sluicing with the existing spillway. We found that gated outlet will be effective. Although there are no quick remedies that can reduce reservoir sedimentation dramatically, there are some methods that may be suitable, considering the size, life and basin of each reservoir. Not only the technical feasibility, but also the economic advantages and ecological acceptability should be considered. To sustain reservoirs and hydropower, sedimentation should be managed effectively and adaptively, based on the specific conditions of each reservoir.