Статті в журналах з теми "Drag showt"
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1
Bessen, Mark. "Drag Brunch." After Dinner Conversation 4, no. 11 (2023): 17–37. http://dx.doi.org/10.5840/adc2023411103.
Повний текст джерелаАнотація:
Are drags shows modern minstrel shows for straight party girls? Can defense of values be compromised for special occasions? In this work of philosophical short story fiction, Hannah is getting married and off to Miami for a girl’s weekend bachelorette party. Her longtime gay friend Kyle, is not invited. Hannah’s mother has budgeted $100,000 for the wedding and bachelorette party on the condition Kyle not be invited. Hannah’s wedding is her special day, the money will make it perfect, so she has her bridesmaid (who should have been Kyle!) message Kyle, last minute, to uninvite him. Of course, she supports, gay rights, but not at the cost of her special day. While in Miami the over-the-top bachelorette group goes to a gay night club, then for mimosa and a drag show the next morning to recover. Kyle tried to contact Hannah to talk to her about her reasoning, but she refuses to pick up the phone, so he flies to Miami and confronts her at the drag show about being a fair-weather liberal, in spectacular fashion.
2
Yakunin, Alexander F., Alexander S. Fedorov, Tatyana V. Laurinavichene, Vadim M. Glaser, Nikolay S. Egorov, Anatoly A. Tsygankov, Vladislav V. Zinchenko, and Patrick C. Hallenbeck. "Regulation of nitrogenase in the photosynthetic bacteriumRhodobacter sphaeroidescontainingdraTGandnifHDKgenes fromRhodobacter capsulatus." Canadian Journal of Microbiology 47, no. 3 (March 1, 2001): 206–12. http://dx.doi.org/10.1139/w00-144.
Повний текст джерелаАнотація:
The photosynthetic bacteria Rhodobacter capsulatus and Rhodospirillum rubrum regulate their nitrogenase activity by the reversible ADP-ribosylation of nitrogenase Fe-protein in response to ammonium addition or darkness. This regulation is mediated by two enzymes, dinitrogenase reductase ADP-ribosyl transferase (DRAT) and dinitrogenase reductase activating glycohydrolase (DRAG). Recently, we demonstrated that another photosynthetic bacterium, Rhodobacter sphaeroides, appears to have no draTG genes, and no evidence of Fe-protein ADP-ribosylation was found in this bacterium under a variety of growth and incubation conditions. Here we show that four different strains of Rba. sphaeroides are incapable of modifying Fe-protein, whereas four out of five Rba. capsulatus strains possess this ability. Introduction of Rba. capsulatus draTG and nifHDK (structural genes for nitrogenase proteins) into Rba. sphaeroides had no effect on in vivo nitrogenase activity and on nitrogenase switch-off by ammonium. However, transfer of draTG from Rba. capsulatus was sufficient to confer on Rba. sphaeroides the ability to reversibly modify the nitrogenase Fe-protein in response to either ammonium addition or darkness. These data suggest that Rba. sphaeroides, which lacks DRAT and DRAG, possesses all the elements necessary for the transduction of signals generated by ammonium or darkness to these proteins.Key words: nitrogenase regulation, nitrogenase modification, photosynthetic bacteria.
3
Whillans, I. M., Y. H. Chen, C. J. van der Veen, and T. J. Hughes. "Force Budget: Application to Three-Dimensional Flow of Byrd Glacier, Antarctica (Abstract)." Annals of Glaciology 11 (1988): 212. http://dx.doi.org/10.3189/s0260305500006741.
Повний текст джерелаАнотація:
Stresses at the surface and at depth are calculated for a stretch of Byrd Glacier, Antarctica. The calculations are based on photogrammetrically determined velocities and elevations (Brecher 1986) and on radio-echo-determined ice thicknesses. The results take the form of maps of drags from each valley wall, of normal forces laterally and longitudinally, and of basal drag. Special challenges in the calculation are the numerical gridding of velocity (ensuring that unreasonable short-wavelength features do not develop in the calculation) and inference of ice thicknesses where there are no data.The results show important variations in basal drag. For the floating part, basal drag is near zero, as expected. Within the grounded part, longitudinal components of basal drag are very variable, reaching 300 kPa, with a dominant wavelength of 10 km. Generally these drag maxima correlate with maxima in driving stress, and the across-glacier component of basal drag is usually small. An important exception occurs in the center of the grounded part of the glacier, where the flow shows major deviations from the axis of the valley.Results also show that side drag is roughly constant at 250 kPa along both margins of the glacier, tension from the ice shelf is about 100 kPa, and tension in the grounded part cycles between 250 and 150kPa. Calculated deep velocities are too large and this is attributed to deficiencies in the conventional isotropic flow law used.
4
Whillans, I. M., Y. H. Chen, C. J. van der Veen, and T. J. Hughes. "Force Budget: Application to Three-Dimensional Flow of Byrd Glacier, Antarctica (Abstract)." Annals of Glaciology 11 (1988): 212. http://dx.doi.org/10.1017/s0260305500006741.
Повний текст джерелаАнотація:
Stresses at the surface and at depth are calculated for a stretch of Byrd Glacier, Antarctica. The calculations are based on photogrammetrically determined velocities and elevations (Brecher 1986) and on radio-echo-determined ice thicknesses. The results take the form of maps of drags from each valley wall, of normal forces laterally and longitudinally, and of basal drag. Special challenges in the calculation are the numerical gridding of velocity (ensuring that unreasonable short-wavelength features do not develop in the calculation) and inference of ice thicknesses where there are no data. The results show important variations in basal drag. For the floating part, basal drag is near zero, as expected. Within the grounded part, longitudinal components of basal drag are very variable, reaching 300 kPa, with a dominant wavelength of 10 km. Generally these drag maxima correlate with maxima in driving stress, and the across-glacier component of basal drag is usually small. An important exception occurs in the center of the grounded part of the glacier, where the flow shows major deviations from the axis of the valley. Results also show that side drag is roughly constant at 250 kPa along both margins of the glacier, tension from the ice shelf is about 100 kPa, and tension in the grounded part cycles between 250 and 150kPa. Calculated deep velocities are too large and this is attributed to deficiencies in the conventional isotropic flow law used.
5
Whillans, I. M., Y. H. Chen, C. J. Van Der Veen, and T. J. Hughes. "Force Budget: III. Application to Three-dimensional Flow of Byrd Glacier, Antarctica." Journal of Glaciology 35, no. 119 (1989): 68–80. http://dx.doi.org/10.3189/002214389793701554.
Повний текст джерелаАнотація:
AbstractStresses at the surface and at depth are calculated for a stretch of Byrd Glacier, Antarctica. The calculations are based on photogrammetrically determined velocities and elevations, and on radio-echo-determined ice thicknesses. The results are maps of drags from each valley wall, of normal forces laterally and longitudinally, and of basal drag. Special challenges in the calculation are the numerical gridding of velocity, ensuring that unreasonable short-wavelength features do not develop in the calculation, and inference of ice thickness where there are no data.The results show important variations in basal drag. For the floating part, basal drag is near zero, as expected. Within the grounded part, longitudinal components of basal drag are very variable, reaching 300 kPa with a dominant wavelength of 13 km. Generally, these drag maxima correlate with maxima in driving stress. Usually the across-glacier component of basal drag is small. An important exception occurs in the center of the grounded part of the glacier where the flow shows major deviations from the axis of the valley.Other results are that side drag is roughly constant at 250 kPa along both margins of the glacier, tension from the ice shelf is about 100 kPa, and tension in the grounded part cycles between 250 and 150 kPa. Calculated deep velocities are too large and this is attributed to deficiencies in the conventional isotropic flow law used.
6
Martin, Joseph D. "The Ether Drag Show." Endeavour 43, no. 3 (September 2019): 100693. http://dx.doi.org/10.1016/j.endeavour.2019.100693.
Повний текст джерела
7
Gurevich, V. L., and M. I. Muradov. "Shot noise of Coulomb drag current." Physical Review B 62, no. 3 (July 15, 2000): 1576–79. http://dx.doi.org/10.1103/physrevb.62.1576.
Повний текст джерела
8
Long, Thomas Lawrence. "Nature Is a Continual Drag Show." Harrington Gay Men's Literary Quarterly 8, no. 1 (September 2006): 1–2. http://dx.doi.org/10.1300/j510v08n01_01.
Повний текст джерела
9
Zhang, Xue Peng, Yong Hua Wang, and Lu Quan Ren. "Wind Tunnel Test for Drag Reduction of Airfoil Bionic Soft Surface." Applied Mechanics and Materials 461 (November 2013): 767–78. http://dx.doi.org/10.4028/www.scientific.net/amm.461.767.
Повний текст джерелаАнотація:
The soft surface of birds and aquatic organisms in the nature can effectively reduce the drag. Inspired by the fact,in this paper, an attempt is made to stick silicone rubber soft surface on the surfaces of NACA 4412 and NACA 6409 airfoils. The drags, lifts and lift-drag ratios of airfoils with soft and rigid surfaces in 5 different thickness were compared through wind tunnel test under the condition of α = 0 °. The results show that most of the bionic soft surfaces play the role of reducing the aerodynamic drag, and also increasing the lift at the same time, in which the soft surface of 0.6mm had the most significant effect of drag reduction and lift increasing.
10
Pavlov, Stanislav A. "INFLUENCE OF JET FAN INSTALLED ON A CUTTER-LOADER ON AIR DRAG IN VERY LONG LONGWALL PANELS." Interexpo GEO-Siberia 2, no. 4 (May 21, 2021): 32–40. http://dx.doi.org/10.33764/2618-981x-2021-2-4-32-40.
Повний текст джерелаАнотація:
The article presents studies into aerodynamic processes in very long longwall panels. The computations in ANSYS using the finite volume method show that air drag in longwalls varies versus position of the longwall mining system in the panel. Enhancement of ventilation efficiency in longwalls requires reduction in air drag. The longwall air drag is governed by the air drags of the powered roof support and cutter-loader. The latter have very large dimensions which are technologically unchangeable. For this reason, it is necessary to ensure forced air flow to by-pass the cutter-loader in the longwall panel. The estimate of advantages of the proposed method for the air drag reduction in very long longwall panels is presented. The method consists in increasing air flow rate in the longwall with the help of an axial jet fan mounted on the cutter-loader.
11
Hamrah Gharamaleki, Ali, and Amir Kevin. "Lateral and rotary light-drag enhancement in a vee+ladder configuration comprising a Rydberg state." Physica Scripta 96, no. 12 (November 16, 2021): 125524. http://dx.doi.org/10.1088/1402-4896/ac36eb.
Повний текст джерелаАнотація:
Abstract The lateral and rotary light-drag effects in a four-level vee+ladder configuration comprising a Rydberg state as the topmost level is theoretically investigated. We found that it is difficult to obtain enhanced lateral and rotary light drags accompanied by suppressed absorption in the three-level vee and ladder configurations. However, in the proposed four-level vee+ladder configuration both lateral and rotary light drags are significantly enhanced as well as suppressing the absorption of the weak probe field via electromagnetically induced transparency (EIT). The profound impacts of the intensity of the controlling fields on both the lateral and rotary light drags are discussed. It is demonstrated that intensifying the controlling fields leads to enhancing the lateral and rotary light-drag effects accompanied by negligible probe field absorption. Furthermore, it is shown that light is dragged opposite of the direction of the host medium motion while the superluminal light propagation dominates. Nevertheless, the light is dragged along the same direction of the host medium motion in the subluminal propagation condition. In addition, we present the real quantities of all the parameters used in this study for future empirical investigations.
12
Turton, R., and O. Levenspiel. "A short note on the drag correlation for spheres." Powder Technology 47, no. 1 (March 1986): 83–86. http://dx.doi.org/10.1016/0032-5910(86)80012-2.
Повний текст джерела
13
Dareing, D., J. Tlusty, and C. Zamudio. "Self-Excited Vibrations Induced by Drag Bits." Journal of Energy Resources Technology 112, no. 1 (March 1, 1990): 54–61. http://dx.doi.org/10.1115/1.2905713.
Повний текст джерелаАнотація:
Drillstring vibrations cause premature failure of downhole tools and the drillstring itself. Also, drill bits do not drill efficiently as a result of these vibrations and this inefficiency causes a significant reduction in penetration rate and a corresponding increase in footage cost. Drill bits are a primary source of excitation, but there has been no theory that adequately explains how drag bits excite drillstrings. The paper shows that these vibrations are self-excited by the interaction of drillstring, drill bit, and formation. The paper explains the mechanism for this self-excitation. Results show that drag bit design, shock absorber design and bit rotational speed dictate conditions of dynamic instability.
14
GOSSELIN, FRÉDÉRICK, EMMANUEL de LANGRE, and BRUNO A. MACHADO-ALMEIDA. "Drag reduction of flexible plates by reconfiguration." Journal of Fluid Mechanics 650 (March 18, 2010): 319–41. http://dx.doi.org/10.1017/s0022112009993673.
Повний текст джерелаАнотація:
Through an extensive and systematic experimental investigation of two geometries of flexible plates in air, it is shown that a properly defined scaled Cauchy number allows collapsing all drag measurements of the reconfiguration number. In the asymptotic regime of large deformation, it is shown that the Vogel exponents that scale the drag with the flow velocity for different geometries of plates can be predicted with a simple dimensional analysis reasoning. These predicted Vogel exponents are in agreement with previously published models of reconfiguration. The mechanisms responsible for reconfiguration, namely area reduction and streamlining, are studied with the help of a simple model for flexible plates based on an empirical drag formulation. The model predicts well the reconfiguration observed in the experiments and shows that for a rectangular plate, the effect of streamlining is prominent at the onset of reconfiguration, but area reduction dominates in the regime of large deformation. Additionally, the model demonstrates for both geometries of plates that the reconfiguration cannot be described by a single value of the Vogel exponent. The Vogel exponent asymptotically approaches constant values for small and for very large scaled Cauchy numbers, but in between both extremes it varies significantly over a large range of scaled Cauchy number.
15
Jung, Thomas, and Peter B. Rhines. "Greenland’s Pressure Drag and the Atlantic Storm Track." Journal of the Atmospheric Sciences 64, no. 11 (November 1, 2007): 4004–30. http://dx.doi.org/10.1175/2007jas2216.1.
Повний текст джерелаАнотація:
Abstract Some effects of Greenland on the Northern Hemisphere wintertime circulation are discussed. Inviscid pressure drag on Greenland’s slopes, calculated from reanalysis data, is related to circulation patterns. Greenland lies north of the core of the tropospheric westerly winds. Yet strong standing waves, which extend well into the stratosphere, produce a trough/ridge system with jet stream lying close to Greenland, mean Icelandic low in its wake, and storm track that interacts strongly with its topography. In the lower troposphere, dynamic height anomalies associated with strongly easterly pressure drag on the atmosphere are quite localized in space and relatively short-lived compared to upper levels, yet they involve a hemispheric-scale dislocation of the stratospheric polar vortex. It is a two-scale problem, however; the high-pass time-filtered part of the height field, responsible for 73% of the pressure drag, is quite different, and expresses propagating cyclonic development in the Atlantic storm track. Eliassen–Palm flux (EP flux) analysis shows that the atmospheric response is (counterintuitively) an acceleration of the westerly winds. The hemispheric influence is consistent with the model results of Junge et al. suggesting that Greenland affects the stationary waves in winter. This discussion shows that Greenland is not a simple “stirring rod” in the westerly circulation, yet involvement of Greenland’s topography with the shape, form, and intensity of the storm track is strong. Interaction of traveling storms, the jet stream, and the orographic wake frequently leads to increase of the lateral scale such that cyclonic system expands to the size of Greenland itself (∼2500 km). Using the global ECMWF general circulation model, the authors explore the effect of model resolution on these circulations. Statistically, in two case studies, and in higher-resolution global models at TL255 to TL799 resolution, intense tip jet, hydraulic downslope jet, and gravity wave radiation appear in strong flow events, in accord with the work of Doyle and Shapiro. Three-dimensional particle trajectories and vorticity maps show the nature and intensity of the summit-gap flow. Cyclonic systems in the lee of Greenland are strongly affected by the downslope jet. Penetration of the Arctic Basin by cyclonic systems arises from this source region, and the amplitude of the pressure drag is enhanced at high resolution. At the higher resolutions, storm-track analysis verifies the splitting of the storm track by Greenland with a substantial minority of storms moving northward through Baffin Bay. Finally, analysis of 20 winters of 40-yr ECMWF Re-Analysis (ERA-40) reforecasts shows little evidence that negative pressure-drag events are followed by anomalously large forecast errors over Europe, throughout the forecast. Forecast skill for the pressure drag is surprisingly good, with a correlation of 0.65 at 144 h.
16
Liang, Qimin, Bairu Xia, Baolin Liu, Zhen Nie, and Baokui Gao. "Experimental Study on the Local Drag of Completion String with Packers in Horizontal Wells." Coatings 10, no. 7 (July 8, 2020): 657. http://dx.doi.org/10.3390/coatings10070657.
Повний текст джерелаАнотація:
The multistage stimulation technology of horizontal wells has brought huge benefits to the development of oil and gas fields. However, the completion string with packers often encounters stuck due to the large drag in the horizontal section, causing huge economic losses. The local drag of the completion string with packers in the horizontal section is very complicated, and it has not been fully understood by theoretical calculations. A local drag experiment is designed to simulate the influence of microsteps and cuttings on the local drag of the completion string with packers in the inclined and horizontal sections. An obvious increase of the local drag of the packer is found at microsteps of the horizontal section, and the local drag is greatly affected by the amount of sand. In addition, the string with packers will vibrate during the tripping process in the deviated section, and the local drag is different when different amounts of sand are in the hole, but the change law is similar. The experimental results show that the friction coefficients of the packers with different materials in the horizontal section vary greatly, resulting in different local drags. It indicates that the local drag of the completion string not only depends on the microsteps and sand quantity in the wellbore, but also on the material difference of the packers. Only if microsteps and cuttings are removed can the completion string be tripped into horizontal wells smoothly.
17
Alsaedi, Sajda S., Zainab Yousif, Sheymaa Alazzawi, and Peter Filip. "Effect of Glycolic Acid Ethoxylate Lauryl Ether (GAL) Surfactant Solutions among Low and High Concentrations on Drag Reduction to Progress Flow in the Pipeline Networks Using RDA." Journal of Petroleum Research and Studies 12, no. 1 (March 20, 2022): 364–80. http://dx.doi.org/10.52716/jprs.v12i1.608.
Повний текст джерелаАнотація:
In the pipeline networks field, GAL surfactant can reduce drag forces relatively using a small quantity part per million (ppm). Accordingly, the drag reduction (DR) enhancement is highly recommended in many industrial applications specifically the crude oil transportation aspect. GAL solution was experimentally investigated at various concentrations. The experiments were performed at low concentrations range from 50 to 300 ppm, and high concentrations range from 1000 to 2000 ppm. The rotating disk apparatus (RDA) was used at various speeds range from 50 to 3000 rpm in all experiments. Torque values of the GAL solutions were compared with water alone. The results clearly show that the different concentrations of the Glycolic Acid Ethoxylate Lauryl Ether (GAL) are good drag reduction agents (DRAs), with clear and high torque reading differences. Further, GAL solutions have the same tendency at all concentrations. The torque finding was enhanced with increasing concentration.
18
Korte, Anne-Marie. "Between art and ritual." Approaching Religion 12, no. 3 (November 7, 2022): 94–114. http://dx.doi.org/10.30664/ar.115442.
Повний текст джерелаАнотація:
This article analyses the short performances of Drag Sethlas at the yearly Gran Canaria Drag Queen Contest in Spain (2017–20) from the perspective of religious studies and gender studies, following on from an earlier article in which this case was explored in light of the severe blasphemy accusations (by local and national bishops and lay organisations) against the 2017 show. These short performances consist of remarkable representations of Roman Catholic texts, saints, symbols and rituals acted out as prize-winning drag-queen shows that were aired on national television. At the same time, these acts are situated, by reference to famous earlier controversial acts by the pop artists Madonna, Lady Gaga and Ariana Grande, in a genealogy of provocations and blasphemy accusations that are currently made in North American and Western European countries. In exploring the forms of ritualisation (cf. Bell 1989) in the provocation that this type of popular artistic performance with strong religious connotations evokes, I show the presence of a double theatricality in Sethlas’s first and most controversial performance: on the one hand a ‘holy drama’ centred around a religious pattern of penance, repentance and redemption, and on the other hand a specific drag theatricality, with its parodies, mockery and daring erotic scenes. It is precisely the connection between both forms of theatricality, especially the representation of the Virgin Mary and Jesus, who play a large and special role in both forms of theatricality, that contributes most to the provocativeness of this scene.
19
Hedfors, Jim, Vincent Peyaud, Veijio A. Pohjola, Peter Jansson, and Rickard Pettersson. "Investigating the ratio of basal drag and driving stress in relation to bedrock topography during a melt season on Storglaciären, Sweden, using force-budget analysis." Annals of Glaciology 37 (2003): 263–68. http://dx.doi.org/10.3189/172756403781815861.
Повний текст джерелаАнотація:
AbstractWe apply the force-budget technique using the isothermal block-flow model, on Storglaciaren, Sweden, to investigate the ratio between basal drag and driving stress in relation to a bedrock ridge in the bed topography during a peak melt season. The input data consist of glacier surface velocities collected using differential global positioning system surveying of a stake net and geometry from previous radar soundings and digitized ice surface maps. The study focuses on the effects of transverse bedrock ridges upon basal stress conditions. The pattern of the calculated ratio of basal drag and driving stress shows a rhythmical position of relatively high and low basal drags on the stoss and lee sides, respectively, of the bedrock thresholds. One of the zones of low basal drag corresponds to the location where the highest basal sliding rate has been measured previously by borehode deformation studies. This zone also aligns with the area where the drainage system is suggested to change from englacial to subglacial.
20
Darcie, Marina Paula, Juliano Ferreira Sousa, and Monique Dos Santos Nascimento. "“WE ALL BORN NAKED AND THE REST IS DRAG”: CULTURA E IDENTIDADE DA DRAG QUEEN NO AMBIENTE MIDIÁTICO DO REALITY SHOW RUPAUL’S DRAG RACE." Comunicologia - Revista de Comunicação da Universidade Católica de Brasília 13, no. 1 (October 11, 2020): 69. http://dx.doi.org/10.31501/comunicologia.v13i1.10457.
Повний текст джерелаАнотація:
O reality show RuPaul’s Drag Race, exibido originalmente pela TV norte-americana, é um espaço de manifestação e exposição da cultura drag queen, que explicita as múltiplas identidades existentes e discute os multitalentos necessários para uma estrela drag, a partir do que acredita o criador do programa RuPaul. O artigo tem como objetivo analisar quais são as características dessa cultura e quais são as identidades trabalhadas por esse reality show. A partir do estudo teórico, do acompanhamento de entrevistas, da observação do programa e de uma análise sobre as identidades presentes, o artigo propõe fazer uma reflexão sobre as identidades culturais da drag queen.
21
Zheng, Qiu Ya, and San Yang Liu. "Drag Prediction on DLR-F6 Wing-Body Configuration." Applied Mechanics and Materials 110-116 (October 2011): 1506–11. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.1506.
Повний текст джерелаАнотація:
This paper mainly investigate the accuracy of the computed drag on the DLR-F6 Wing-Body configuration, and analyze effect of grid and the turbulence models including the Spalart-Allmaras model, Wilcox’s k-ω model and Menter shear-stress transport model on aerodynamic forces for wing-body configuration. The computed results show that grid refinement has little effect on the pressure distributions, significant effect on drag. The turbulence models have certain effects on the pressure distributions, especially positions of the shock wave. They have obvious effects on drag, particularly friction drag. This study shows that performing the CFD calculation at the same angle-of-attack as experiment resulted in good comparisons with wing surface pressures.
22
Nifant’ev, Ilya E., Alexander N. Tavtorkin, Alexey A. Vinogradov, Sofia A. Korchagina, Maria S. Chinova, Roman S. Borisov, Grigory A. Artem’ev та Pavel V. Ivchenko. "Tandem Synthesis of Ultra-High Molecular Weight Drag Reducing Poly-α-Olefins for Low-Temperature Pipeline Transportation". Polymers 13, № 22 (14 листопада 2021): 3930. http://dx.doi.org/10.3390/polym13223930.
Повний текст джерелаАнотація:
Ultra-high molecular weight poly-α-olefins are widely used as drag reducing agents (DRAs) for pipeline transportation of oil and refined petroleum products. The synthesis of polyolefin DRAs is based on low-temperature Ziegler–Natta (ZN) polymerization of higher α-olefins. 1-Hexene based DRAs, the most effective at room temperature, typically lose DR activity at low temperatures. The use of 1-hexene copolymers with C8–C12 linear α-olefins appears to offer a solution to the problem of low-temperature drag reducing. The present work aims to develop two-stage synthesis of polyolefin DRAs that is based on selective oligomerization of ethylene in the presence of efficient chromium/aminodiphosphine catalysts (Cr-PNP), followed by polymerization of the olefin mixtures, formed at oligomerization stage, using efficient titanium–magnesium ZN catalyst. We have shown that oligomerization of ethylene in α-olefin reaction media proceeds faster than in saturated hydrocarbons, providing the formation of 1-hexene, 1-octene, and branched C10 and C12 olefins; the composition and the ratio of the reaction products depended on the nature of PNP ligand. Oligomerizates were used in ZN polymerization ‘as is’, without additional treatment. Due to branched character of C10+ hydrocarbons, formed during oligomerization of ethylene, resulting polyolefins demonstrate higher low-temperature DR efficiency at low polymer concentrations (~1 ppm) in comparison with benchmark polymers prepared from the mixtures of linear α-olefins and from pure 1-hexene. We assume that faster solubility and more efficient solvation of the polyolefins, prepared using ‘tandem’ ethylene-based process, represent an advantage of these type polymers over conventional poly(1-hexene) and linear α-olefin-based polymers when used as ‘winter’ DRAs.
23
R, Noor. "A Short Note on the General Aspects of Drug Designing." Open Access Journal of Microbiology & Biotechnology 6, no. 1 (2021): 1–4. http://dx.doi.org/10.23880/oajmb-16000184.
Повний текст джерелаАнотація:
Emerging and re-emerging diseases are expanding round the globe which drew the mass public health in dreadful condition. Microbial resistance to drugs is a complicated issue for the failure of treatment of a variety of diseases. In this circumstance, designing of appropriate drug(s) is essential which usually involves the computational modeling and simulation followed by cell culture/ animal model experiments, ending up to clinical trials. Current review briefly focused on the general aspects of drug manufacturing; and a short discussion on the fine tune basis of drug designing grounded on the previously published literature.
24
Bandyopadhyay, Promode R. "Stokes Mechanism of Drag Reduction." Journal of Applied Mechanics 73, no. 3 (September 20, 2005): 483–89. http://dx.doi.org/10.1115/1.2125974.
Повний текст джерелаАнотація:
The mechanism of drag reduction due to spanwise wall oscillation in a turbulent boundary layer is considered. Published measurements and simulation data are analyzed in light of Stokes’ second problem. A kinematic vorticity reorientation hypothesis of drag reduction is first developed. It is shown that spanwise oscillation seeds the near-wall region with oblique and skewed Stokes vorticity waves. They are attached to the wall and gradually align to the freestream direction away from it. The resulting Stokes layer has an attenuated nature compared to its laminar counterpart. The attenuation factor increases in the buffer and viscous sublayer as the wall is approached. The mean velocity profile at the condition of maximum drag reduction is similar to that due to polymer. The final mean state of maximum drag reduction due to turbulence suppression appears to be universal in nature. Finally, it is shown that the proposed kinematic drag reduction hypothesis describes the measurements significantly better than what current direct numerical simulation does.
25
HŒPFFNER, JÉRÔME, and KOJI FUKAGATA. "Pumping or drag reduction?" Journal of Fluid Mechanics 635 (September 10, 2009): 171–87. http://dx.doi.org/10.1017/s0022112009007629.
Повний текст джерелаАнотація:
Two types of wall actuation in channel flow are considered: travelling waves of wall deformation (peristalsis) and travelling waves of blowing and suction. The flow response and its mechanisms are analysed using nonlinear and weakly nonlinear computations. We show that both actuations induce a flux in the channel in the absence of an imposed pressure gradient and can thus be characterized as pumping. In the context of flow control, pumping and drag reduction are strongly connected, and we seek to define them properly based on these two actuation examples. Movies showing the flow motion for the two types of actuation are available with the online version of this paper (journals.cambridge.org/FLM).
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Zhuchenko, M. A., N. V. Orlova, D. I. Zybin, V. V. Nikolaeva, A. A. Klishin, N. V. Lobanova, V. O. Soldatov, N. A. Romanova, and Y. A. Seregin. "Analytical comparison of Soliris® and its biosimilar, PRK-001." Biotekhnologiya 36, no. 1 (2020): 73–86. http://dx.doi.org/10.21519/0234-2758-2020-36-1-73-86.
Повний текст джерелаАнотація:
Soliris® (Eculizumab) was approved by regulatory authorities as the first drag for treatment of orphan disease, paroxysmal nocturnal hemoglobinuria, in 2007. Later its use was extended for treatment of atypical hemolytic-uremic syndrome and myasthenia gravis. The high cost, the unavailability of therapy for a number of patients, as well as the expiration of the patent protection period for Soliris®, these factors became the prerequisite for the development of biosimilar medicinal products. Here, comparative analysis of PRK-001 (LLC «Pharmapark») and reference drag product, Soliris® (Alexion Pharmaceuticals, USA), was carried out. Physicochemical biosimilarity assessment has shown complete comparability of both products in terms of protein sequence as well as higher order structures. Post-translation modifications as well as impurity profile were the same too. Neither biosimilar nor reference product had impurity amount exceeding threshold. Biological properties of the reference product and biosimilar were the same. Since the comparability of the both drags has been proven, it can be assumed that PRK-001 is biosimilar of Soliris®. Eculizumab, Soliris, paroxysmal nocturnal hemoglobinuria, physicochemical comparison, post-translational modifications, biosimilar, drag product
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Benham, G. P., J. P. Boucher, R. Labbé, M. Benzaquen, and C. Clanet. "Wave drag on asymmetric bodies." Journal of Fluid Mechanics 878 (September 4, 2019): 147–68. http://dx.doi.org/10.1017/jfm.2019.638.
Повний текст джерелаАнотація:
An asymmetric body with a sharp leading edge and a rounded trailing edge produces a smaller wave disturbance moving forwards than backwards, and this is reflected in the wave drag coefficient. This experimental fact is not captured by Michell’s theory for wave drag (Michell Lond. Edinb. Dubl. Phil. Mag. J. Sci., vol. 45 (272), 1898, pp. 106–123). In this study, we use a tow-tank experiment to investigate the effects of asymmetry on wave drag, and show that these effects can be replicated by modifying Michell’s theory to include the growth of a symmetry-breaking boundary layer. We show that asymmetry can have either a positive or a negative effect on drag, depending on the depth of motion and the Froude number.
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Gharib, M., and A. Roshko. "The effect of flow oscillations on cavity drag." Journal of Fluid Mechanics 177 (April 1987): 501–30. http://dx.doi.org/10.1017/s002211208700106x.
Повний текст джерелаАнотація:
An experimental investigation of flow over an axisymmetric cavity shows that self-sustained, periodic oscillations of the cavity shear layer are associated with low cavity drag. In this low-drag mode the flow regulates itself to fix the mean-shear-layer stagnation point at the downstream corner. Above a critical value of the cavity width-to-depth ratio there is an abrupt and large increase of drag due to the onset of the ‘wake mode’ of instability. It is also shown by measurement of the momentum balance how the drag of the cavity is related to the state of the shear layer, as defined by the mean momentum transport $\rho\overline{u}\overline{v}$ and the Reynolds stress $\rho\overline{u^{\prime}v^{\prime}}$, and how these are related to the amplifying oscillations in the shear layer. The cavity shear layer is found to be different, in several respects, from a free shear layer.
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Garshelis, Ivan J., Stijn P. L. Tollens, Marnix E. Hollander, Ryan J. Kari, and James M. Cuseo. "Assessment of shot peening uniformity by magnetic drag force measurements." Journal of Applied Physics 105, no. 7 (April 2009): 07E711. http://dx.doi.org/10.1063/1.3072378.
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Komori, Satoru, Koji Iwano, Naohisa Takagaki, Ryo Onishi, Ryoichi Kurose, Keiko Takahashi, and Naoya Suzuki. "Laboratory Measurements of Heat Transfer and Drag Coefficients at Extremely High Wind Speeds." Journal of Physical Oceanography 48, no. 4 (April 2018): 959–74. http://dx.doi.org/10.1175/jpo-d-17-0243.1.
Повний текст джерелаАнотація:
AbstractHeat and momentum transfer across the wind-driven breaking air–water interface at extremely high wind speeds was experimentally investigated using a high-speed wind-wave tank. An original multi-heat-balance method was utilized to directly measure latent and sensible heat transfer coefficients. The results show that both heat transfer coefficients level off at low and normal wind speeds but increase sharply at extremely high wind speeds. The coefficients have a similar shape for wind speeds at a height of 10 m. Therefore, the wind speed dependence on the latent and sensible heat transfer coefficients can be represented by that of the enthalpy coefficient even in the extremely high-speed region. To show how significantly the drag and enthalpy coefficients affect the intensity of tropical cyclones, the coefficients were applied to Emanuel’s analytic model. The analytic model shows that the difference between the present laboratory and conventional correlations significantly affects the maximum storm intensity predictions, and the present laboratory enthalpy and drag coefficients have the remarkable effect on intensity promotion at extremely high wind speeds. In addition, the simulations of strong tropical cyclones using the Weather Research and Forecasting (WRF) Model with the present and conventional correlations are shown for reference in the appendix. The results obtained from the models suggest that it is of great importance to propose more reliable correlations, verified not only by laboratory but also by field experiments at extremely high wind speeds.
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Nayeri, Christian Navid, Jonathan Tschepe, Harald Schulze, and Hanno Schell. "Aerodynamic Drag Reduction of Railroad Tank Wagons." Fluids 7, no. 8 (August 19, 2022): 283. http://dx.doi.org/10.3390/fluids7080283.
Повний текст джерелаАнотація:
Several geometrical modifications for passive flow control applied to a railroad tank wagon were investigated for the purpose of assessing the potential for the aerodynamic optimization of freight trains. The modifications were designed in accordance with applicable requirements and regulations. Four different modifications were investigated in the wind tunnel of the TU Berlin with 1:25 scaled wagon models: face radius, side skirts, fairing of the roof platform, and the newly introduced inter-wagon discs. In order to simulate the positions of the tested wagon at the end of a long train, the boundary layer on the train model setup was artificially thickened by spires. The Reynolds number was in the range of 0.4 × 106. The results of the experiments show that the proposed measures can reduce the aerodynamic drag of the individual wagon by up to 29%, depending on the location in the train consist. It was also shown that by combining different measures, the individual drag reductions add up. The device with the highest drag reduction was found to be the inter-wagon disc. Three different diameters of the inter-wagon disc were investigated. The largest diameter performed best and was less sensitive to the moving direction of the wagon in comparison to the smaller diameters.
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Ali, Irfan, Mohd Haizal Jamaluddin, Abinash Gaya, and Hasliza A. Rahim. "A Dielectric Resonator Antenna with Enhanced Gain and Bandwidth for 5G Applications." Sensors 20, no. 3 (January 26, 2020): 675. http://dx.doi.org/10.3390/s20030675.
Повний текст джерелаАнотація:
In this paper, a dielectric resonator antenna (DRA) with high gain and wide impedance bandwidth for fifth-generation (5G) wireless communication applications is proposed. The dielectric resonator antenna is designed to operate at higher-order T E δ 15 x mode to achieve high antenna gain, while a hollow cylinder at the center of the DRA is introduced to improve bandwidth by reducing the quality factor. The DRA is excited by a 50 Ω microstrip line with a narrow aperture slot. The reflection coefficient, antenna gain, and radiation pattern of the proposed DRAs are analyzed using the commercially available full-wave electromagnetic simulation tool CST Microwave Studio (CST MWS). In order to verify the simulation results, the proposed antenna structures were fabricated and experimentally validated. Measured results of the fabricated prototypes show a 10-dB return loss impedance bandwidth of 10.7% (14.3–15.9GHz) and 16.1% (14.1–16.5 GHz) for DRA1 and DRA2, respectively, at the operating frequency of 15 GHz. The results show that the designed antenna structure can be used in the Internet of things (IoT) for device-to-device (D2D) communication in 5G systems.
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Chabroux, Vincent, Caroline Barelle, and Daniel Favier. "Aerodynamics of Cyclist Posture, Bicycle and Helmet Characteristics in Time Trial Stage." Journal of Applied Biomechanics 28, no. 3 (July 2012): 317–23. http://dx.doi.org/10.1123/jab.28.3.317.
Повний текст джерелаАнотація:
The present work is focused on the aerodynamic study of different parameters, including both the posture of a cyclist’s upper limbs and the saddle position, in time trial (TT) stages. The aerodynamic influence of a TT helmet large visor is also quantified as a function of the helmet inclination. Experiments conducted in a wind tunnel on nine professional cyclists provided drag force and frontal area measurements to determine the drag force coefficient. Data statistical analysis clearly shows that the hands positioning on shifters and the elbows joined together are significantly reducing the cyclist drag force. Concerning the saddle position, the drag force is shown to be significantly increased (about 3%) when the saddle is raised. The usual helmet inclination appears to be the inclination value minimizing the drag force. Moreover, the addition of a large visor on the helmet is shown to provide a drag coefficient reduction as a function of the helmet inclination. Present results indicate that variations in the TT cyclist posture, the saddle position and the helmet visor can produce a significant gain in time (up to 2.2%) during stages.
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Tavares, Jeremias Lucas, and Sinara De Oliveira Branco. "A tradução da linguagem drag em RuPaul’s Drag Race: um estudo sobre representação através de legendas." Revista Letras Raras 10, no. 1 (January 31, 2021): 210. http://dx.doi.org/10.35572/rlr.v1i1.1890.
Повний текст джерелаАнотація:
Desde 2009, o reality show RuPaul’s Drag Race vêm disseminando a cultura e a linguagem drag dos Estados Unidos. Essa cultura e linguagem são disseminadas não apenas nos Estados Unidos, mas em diversos países do mundo, como Brasil. Por meio da legendagem e da dublagem, o público não falante da língua inglesa pode ter acesso a RuPaul’s Drag Race. A tradução desse reality show é um ponto relevante para discussão, uma vez que em governos opressivos contra minorias, como o Brasil e os Estados Unidos, é indispensável que haja produção acadêmica sobre/por mulheres, pretos ou LGBTQIs. Assim, discute-se sobre a tradução da linguagem drag através das legendas do reality show RuPaul’s Drag Race, estudando a linguagem presente no programa, seus aspectos culturais e significados, e analisando a representação da tradução da linguagem drag para o português brasileiro. O arcabouço teórico deste artigo é formado pelas teorias da Tradução Audiovisual, com foco na legendagem. Além disso, há também uma discussão sobre a cultura e a linguagem drag dos Estados Unidos e do Brasil. O corpus da pesquisa é construído por seis imagens e legendas retiradas de três temporadas de RuPaul’s Drag Race. Ao todo, são analisadas seis expressões e suas traduções nas legendas. A análise mostra legendas que traduzem a linguagem drag em inglês através de expressões da linguagem LGBTQ+ do Brasil, assim como legendas não usam uma linguagem semelhante a apresentada no reality show. Os/as tradutores/as parecem cientes da cultura e da linguagem apresentadas no reality show ao legenda-lo.
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Nazemi, Siamak, Ramin Khajavi, Hamidreza Rabie Far, Mohammad Esmail Yazdanshenas, and Manouchehr Raad. "Effect of hydrophobic finishing on drag force of swimwear." International Journal of Clothing Science and Technology 30, no. 1 (March 5, 2018): 2–15. http://dx.doi.org/10.1108/ijcst-09-2016-0109.
Повний текст джерелаАнотація:
Purpose During 2008 Olympics, Michael Phelps had a record-breaking performance. One contributing factor to his success was the full-body swimsuit he was wearing. Cases like these were the reason for the initiation of study and research for improvement in the new generation of sport gears. The purpose of this paper is to show that drag force plays a significant role in swimmers’ speed through the water; thus, using swimsuit with minimized drag force becomes imperative for Olympians like Michael Phelps. Design/methodology/approach This paper shows a comparative evaluation of hydrodynamics of three PET fabrics with different finishings that have hydrophobic behavior over a range of Reynolds number 1.0218×103 and 1.365×103 in the air medium at 20°C ambient temperature, and Reynolds number ranging from 15.68856×103 to 20.958×103 in the water medium at 20°C ambient temperature under stable stretch conditions. Findings The results show that hydrophobic finishing reduces the drag force by 1.5 percent at the angles of attack of 0 and 90 degrees. Originality/value If all the factors are considered to be stable for the swimmer, the drag force reduces by 1.5 percent, thereby increasing the speed of swimmer by 1.22 percent, which means that the record of the swimmer improves by 0.819 seconds.
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Zhang Meng, Geng Xing-Guo, Zhang Yao, and Wang Xiao-Na. "Mechanism analysis of one-dimensional short groove quasicrystal structure drag-reduction." Acta Physica Sinica 61, no. 19 (2012): 194702. http://dx.doi.org/10.7498/aps.61.194702.
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Lang Sha-Sha, Geng Xing-Guo, and Zang Du-Yang. "Drag reduction mechanisms of 8-fold quasi-periodic short groove structures." Acta Physica Sinica 63, no. 8 (2014): 084704. http://dx.doi.org/10.7498/aps.63.084704.
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Javadi, Kh, F. Kiani, and M. Tahaye Abadi. "Utilising flags to reduce drag around a short finite circular cylinder." Journal of Turbulence 19, no. 3 (January 29, 2018): 229–51. http://dx.doi.org/10.1080/14685248.2017.1414225.
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Lee, Jaecheong, Hyoung Jin Lee, and Hwanil Huh. "Drag reduction analysis of counterflow jets in a short penetration mode." Aerospace Science and Technology 106 (November 2020): 106065. http://dx.doi.org/10.1016/j.ast.2020.106065.
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Eckermann, Stephen D. "Explicitly Stochastic Parameterization of Nonorographic Gravity Wave Drag." Journal of the Atmospheric Sciences 68, no. 8 (August 1, 2011): 1749–65. http://dx.doi.org/10.1175/2011jas3684.1.
Повний текст джерелаАнотація:
Abstract A straightforward methodology is presented for converting the deterministic multiwave parameterizations of nonorographic gravity wave drag, currently used in general circulation models (GCMs), to stochastic analogs that use fewer waves (in the example herein, a single wave) within each grid box. Deterministic discretizations of source-level momentum flux spectra using a fixed spectrum of many waves with predefined phase speeds are replaced by sampling these source spectra stochastically using waves with randomly assigned phase speeds. Using simple conversion formulas, it is shown that time-mean wave-induced drag, diffusion, and heating-rate profiles identical to those from the deterministic scheme are produced by the stochastic analog. Furthermore, in these examples the need for bulk intermittency factors of small value is largely obviated through the explicit incorporation of stochastic intermittency into the scheme. When implemented in a GCM, the single-wave stochastic analog of an existing deterministic scheme reproduces almost identical time-mean middle-atmosphere climate and drag as its deterministic antecedent but with an order of magnitude reduction in computational expense. The stochastically parameterized drag is also accompanied by inherent variability about the time-mean profile that forces the smallest space–time scales of the GCM. Studies of mean GCM kinetic energy spectra show that this additional stochastic forcing does not lead to excessive increases in dynamical variability at these smallest GCM scales. The results show that the expensive deterministic schemes currently used in GCMs are easily modified and replaced by cheap stochastic analogs without any obvious deleterious impacts on GCM climate or variability, while offering potential advantages of computational savings, reduction of systematic climate biases, and greater and more realistic ensemble spread.
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McKinnon, Sean. "“Building a thick skin for each other”." Journal of Language and Sexuality 6, no. 1 (June 17, 2017): 90–127. http://dx.doi.org/10.1075/jls.6.1.04mck.
Повний текст джерелаАнотація:
Abstract Although queer linguistics has long acknowledged the playful use of potentially impolite utterances by LGBT people to build in-group solidarity these practices have not been analyzed from a sociopragmatic approach, nor have they been mentioned in the general pragmatics literature. Responding to these two gaps, the present study examines the functional use of the interactional practice ‘reading’ in the backstage talk of four drag queen performers. By employing a mock impoliteness analytical framework (Haugh & Bousfield 2012) this study shows how these utterances, which could potentially be evaluated as genuine impoliteness outside of the appropriate context, are positively evaluated by in-group members who recognize the importance of “building a thick skin” to face a hostile environment from LGBT and non-LGBT people. This study also seeks to draw attention to the use of backstage talk, and supplemental interview data, to uncover drag queen cultural practices through language use.
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Wu, J., and H. C. Juvkam-Wold. "Helical Buckling of Pipes in Extended Reach and Horizontal Wells—Part 2: Frictional Drag Analysis." Journal of Energy Resources Technology 115, no. 3 (September 1, 1993): 196–201. http://dx.doi.org/10.1115/1.2905993.
Повний текст джерелаАнотація:
This paper studies the frictional drag of helically buckled pipes (drillstring and tubing) in extended reach and horizontal wells to correctly predict the actual bit weight or packer load, in cases where helical buckling of pipes may have occurred. Helical buckling of pipes in such wells may occur, since large axial loads are often required. The differential equation of axial force balance with consideration of the axial friction for helically buckled pipes is resolved, and the solution shows that when the pipes are helically buckled, the frictional drag will become very large. The actual bit weight for drilling or packer load for well completion may therefore become much smaller than estimated under the unbuckled pipe conditions. The analytical solution is also shown to agree with the results from laboratory experiments, which simulate the real wellbore-pipe conditions. An example is provided to show the calculation procedure and the importance of the results.
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Wang, Yue, Wei-Hua Cai, Xin Zheng, Hong-Na Zhang, and Feng-Chen Li. "Experimental study on two oscillating grid turbulence with viscoelastic fluids based on PIV." Canadian Journal of Physics 95, no. 12 (December 2017): 1271–77. http://dx.doi.org/10.1139/cjp-2017-0038.
Повний текст джерелаАнотація:
In this paper, to study the viscoelastic effect on isotropic turbulence without wall effects, a two oscillating grid turbulence is built to investigate this phenomenon using particle image velocimetry. In the experiments, the classical drag-reducing additives are chosen: polyacrylamide (PAM) and cetyltrimethyl ammonium chloride (CTAC), which have shown remarkable drag-reducing effect in wall-bounded turbulent flows. The results show that the existence of drag-reducing additives makes velocity field more anisotropic and reduces turbulent kinetic energy. We propose an intuitive and natural definition for a reduction rate of turbulent kinetic energy to show viscoelastic effect. It suggests that there exists a critical concentration for the reduction rate of turbulent kinetic energy in the CTAC solution case. Also, the small-scale vortex structures are inhibited, which suggests the drag-reducing mechanism in grid turbulence without wall effect.
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Gilbert, Sky. "Drag and Popular Culture." Canadian Theatre Review 58 (March 1989): 42–44. http://dx.doi.org/10.3138/ctr.58.009.
Повний текст джерелаАнотація:
In this discussion of drag and popular culture, I should make it very clear at the outset that I will be discussing drag in the context of gay culture. This does not mean to say that drag does not exist outside of gay culture, or that every person who dresses in drag (male or female) is gay or lesbian. But, first of all, my specialty is gay culture, and secondly, much of the drag we see in popular or avant-garde art comes from that world. And finally, I’m just dreadfully tired of turning on the television and watching drag artistes on interview shows who are asked whether or not they are gay, replying “I really don’t think sex is that important, do you, that it has to enter into everything? I love women very much, and I’m dating a very lovely woman at the moment, thank you.” The fact of the matter is that many drag artists are gay and this is quite simply because drag is a significant element in gay culture. So much time is wasted (as is always wasted around gay matters) with men defending their so-called “masculinity” that it’s time to redress the imbalance and talk of drag in the context of its roots. (Keep in mind that when I suggest that drag has its roots in gay culture I am referring to modern western culture of the last 500 years. Obviously in Asian cultures and ancient cultures there are different cultural and sociological factors involved.)
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Song, Wuchao, Cong Wang, Yingjie Wei, Lirui Lu, and Hao Xu. "The characteristics and mechanism of microbubble drag reduction on the axisymmetric body." Modern Physics Letters B 32, no. 18 (June 27, 2018): 1850206. http://dx.doi.org/10.1142/s0217984918502068.
Повний текст джерелаАнотація:
To investigate the characteristics and mechanism of microbubble drag reduction on the axisymmetric body, both experiments and the numerical simulation of microbubble drag reduction have been conducted in this paper. Based on the experiments, the morphology of microbubble flow and the characteristics of microbubble drag reduction were analyzed. The size distribution of microbubbles and the influence of microbubble size on the drag reduction efficiency were quantitatively investigated. Based on the numerical simulation, the influences of microbubbles on the turbulence intensity and vorticity were analyzed to investigate the mechanism of microbubble drag reduction. The results indicate that the diameters of microbubbles basically obey the normal distribution at various conditions, and the microbubble flow presents the uniform microbubble, roll-up and cavity. As the air injection rate increases, the drag reduction respectively shows microbubble drag reduction, mixture drag reduction and air-layer drag reduction. Besides, the drag reduction ratio correspondingly presents the increasing stage, rapidly increasing stage and stable stage. At the same void ratio, the smaller microbubbles show the higher efficiency in drag reduction. The microbubbles injected into the boundary layer can reduce the turbulence intensity and the frequency of the bursting events in the flow field, which results in the drag reduction.
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Fruman, D. H., and S. S. Aflalo. "Tip Vortex Cavitation Inhibition by Drag-Reducing Polymer Solutions." Journal of Fluids Engineering 111, no. 2 (June 1, 1989): 211–16. http://dx.doi.org/10.1115/1.3243625.
Повний текст джерелаАнотація:
This paper presents previous and recent results obtained by the authors concerning the modification of the tip vortex cavitation of a finite span hydrofoil by drag-reducing polymer solutions. Experiments were conducted with homogeneous solutions and with semidilute solutions ejected at the tip of the wing. Measurements of the onset cavitation number for tip vortex cavitation, hydrodynamic forces on the hydrofoil and tangential velocities in the tip vortex have been conducted. The results show that tip vortex cavitation is inhibited in all cases but for different reasons. In homogeneous polymer solutions the lift of the hydrofoil, and hence the circulation, is considerably reduced leading to a less intense vortex as shown by tangential velocity measurements. With semidilute polymer solution ejections there is no noticeable change of the hydrodynamic forces but a significant modification of the tangential velocities in the core region. The mechanism for tip vortex cavitation inhibition is thus completely different in these two situations.
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Bauer, Florian, and Ralph M. Kennel. "Fault-Tolerant Power Electronic System for Drag Power Kites." Journal of Renewable Energy 2018 (2018): 1–37. http://dx.doi.org/10.1155/2018/1306750.
Повний текст джерелаАнотація:
An approach for a fault-tolerant power electronic system for drag power kites is proposed. The key idea is to use a high number of electrical cables in the tether and leave rotor drivetrains in groups isolated on the kite, in the tether, and on the ground. The power flow is paralleled behind an uninterruptible power supply of each drivetrain group on the ground. It is shown that this approach hardly affects the overall system performance, for example, due to the anyways high optimal number of electrical cables in the tether. With this approach, a fault in one drivetrain group does only affect the same drivetrain group and a fault between two drivetrain groups affects only the same two drivetrain groups. A fuse system and a fault shut-off control for the power converters are proposed, with which also faults between two drivetrain groups lead at most to unavailability of only one drivetrain group. In particular also open circuit faults and short circuit faults in the tether are mitigated and are overall not harmful for the system and a usual multicopter-like landing is still possible. Therefore, the proposed power electronic system design has no single point of failure. A generalization and a number of variants are discussed. In detail, a number of power electronic topologies and both tether power transmission types, DC and AC, are possible. The proposed approach was verified by a high number of circuit simulations and by a proof-of-principle demonstrator. In all cases it was confirmed that any open circuit fault and any short circuit fault lead at the most to unavailability of only one rotor drivetrain group.
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Mollicone, J. P., F. Battista, P. Gualtieri, and C. M. Casciola. "Superhydrophobic surfaces to reduce form drag in turbulent separated flows." AIP Advances 12, no. 7 (July 1, 2022): 075003. http://dx.doi.org/10.1063/5.0098365.
Повний текст джерелаАнотація:
The drag force acting on a body moving in a fluid has two components, friction drag due to fluid viscosity and form drag due to flow separation behind the body. When present, form drag is usually the most significant between the two, and in many applications, streamlining efficiently reduces or prevents flow separation. As studied here, when the operating fluid is water, a promising technique for form drag reduction is to modify the walls of the body with superhydrophobic surfaces. These surfaces entrap gas bubbles in their asperities, avoiding the direct contact of the liquid with the wall. Superhydrophobic surfaces have been vastly studied for reducing friction drag. We show they are also effective in reducing flow separation in turbulent flow and therefore in reducing the form drag. Their conceptual effectiveness is demonstrated by performing direct numerical simulations of turbulent flow over a bluff body, represented by a bump inside a channel, which is modified with different superhydrophobic surfaces. The approach shown here contributes to new and powerful techniques for drag reduction on bluff bodies.
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Chang, Ailian, Le Huang, Song Wei, and Minglu Shao. "Analysis of the Drag Reduction Performance and Rheological Properties of Drag-Reducing Additives." Polymers 16, no. 9 (April 29, 2024): 1247. http://dx.doi.org/10.3390/polym16091247.
Повний текст джерелаАнотація:
In the practical application of hydraulic rotating machinery, it is essential to thoroughly explore drag reduction and rheological characteristics of drag-reducing additives to optimize machinery efficiency and reduce equipment consumption. This paper combines simulation and experimental approaches to investigate the drag-reduction performance and rheological properties of drag-reducing additives. Numerical simulations are initially conducted to investigate the shear-thinning properties of drag-reducing fluid and explore variations in drag-reduction rate. Turbulent phenomena characteristics are described by analyzing turbulent statistical quantities. Subsequently, the rheological behaviors of polyethylene oxide (PEO), cetyltrimethyl ammonium chloride (CTAC), and their mixed solutions under different conditions are scrutinized using a rotational rheometer. The findings indicate that the drag reduction effect amplifies as the rheological index n and characteristic time λ decrease. The numerical simulations show a maximum drag reduction rate of 20.18%. In rheological experiments, a three-stage viscosity variation is observed in single drag-reducing additives: shear thickening, shear thinning, and eventual stabilization. Composite drag-reducing additives significantly reduce the apparent viscosity at low shear rates, thereby strengthening the shear resistance of the system.
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Obara, Clifford J., and C. P. van Dam. "Keel Design for Low Viscous Drag." Journal of Ship Research 33, no. 02 (June 1, 1989): 145–55. http://dx.doi.org/10.5957/jsr.1989.33.2.145.
Повний текст джерелаАнотація:
Foil and planform parameters which govern the level of viscous drag produced by the keel of a sailing yacht are discussed. It is shown that the application of laminar boundary-layer flow offers great potential for increased boat speed resulting from the reduction in viscous drag. Three foil shapes have been designed and it is shown that their hydrodynamic characteristics are very much dependent on location and mode of boundary-layer transition. The planform parameter which strongly affects the capabilities of the keel to achieve laminar flow is leading-edge sweep angle. The two significant phenomena related to keel sweep angle which can cause premature transition of the laminar boundary layer are crossflow instability and turbulent contamination of the leading-edge attachment line. These flow phenomena and methods to control them are discussed in detail. The remaining factors that affect the maintainability of laminar flow include surface roughness, surface waviness, and freestream turbulence. Recommended limits for these factors are given to insure achievability of laminar flow on the keel. In addition, the application of a simple trailing-edge flap to improve the hydrodynamic characteristics of a foil at moderate-to-high leeway angles is studied.