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1
van der Laan, Maarten Paul, Mads Baungaard, and Mark Kelly. "Brief communication: A clarification of wake recovery mechanisms." Wind Energy Science 8, no. 2 (February 24, 2023): 247–54. http://dx.doi.org/10.5194/wes-8-247-2023.
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Abstract. Understanding wind turbine wake recovery is important for developing models of wind turbine interaction employed in the design of energy-efficient wind farm layouts. Wake recovery is often assumed or explained to be a shear-driven process; however, this is generally not accurate. In this work we show that wind turbine wakes recover mainly due to the divergence (lateral and vertical gradients) of Reynolds shear stresses, which transport momentum from the freestream towards the wake center. The wake recovery mechanisms are illustrated using a simple analytic model and results of large-eddy simulation.
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Wei Ren, Hew, Fatimah Al Zahrah Mohd Saat, Fadhilah Shikh Anuar, Mohd Arizam Abdul Wahap, Ernie Mat Tokit, and Tee Boon Tuan. "Computational Fluid Dynamics Study of Wake Recovery for Flow Across Hydrokinetic Turbine at Different Depth of Water." CFD Letters 13, no. 2 (March 5, 2021): 62–76. http://dx.doi.org/10.37934/cfdl.13.2.6276.
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Depletion of fossil fuel caused mankind to look for sustainable and green energy resources. The characteristic of hydrokinetic turbine with ability to operate at low head stream and at low cost made it a good choice for use to harness hydro source of energy. As hydrokinetic turbine gain attention from the industry player, many experimental and Computational Fluid Dynamics (CFD) studies related to hydrokinetic turbine have been carried out. Yet the relationship of flow depth variation and wake recovery behind the turbine is still not fully understood. There is limited study about the effects of flow depth variations on the wake recovery behind the turbine. In this paper, a CFD model investigation was done based on published experimental work. A hydrokinetic water turbine was drawn using the MHKF1-180 and NACA4418 foils dimensions. The transient CFD study was conducted using SST k-w turbulence model and dynamic mesh method. The results showed that in near wake region, the wake at deeper depth will recover faster seemingly due to pressure change at that depth and the faster rate of momentum transfer of the fluid. It can be concluded that the deeper the placement of the turbine inside the water channel, the faster the wake recovers. The wake recovery results as presented in this paper should be considered when placing set of turbines especially in array arrangement to obtain a more efficient energy conversion.
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Krampa, F. N., and R. Balachandar. "Open channel flow recovery in the wake of a flat plate on rough beds." Canadian Journal of Civil Engineering 38, no. 6 (June 2011): 710–17. http://dx.doi.org/10.1139/l11-042.
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The flow recovery in the wake of a surface-mounted flat plate is investigated in an open channel. The plate with a thickness-to-chord ratio (t/c) of 0.12 is placed with the chord parallel to the flow. The characteristics of the mean velocity and higher-order statistics obtained along the wake axis upstream and downstream of the plate are discussed in the presence of bed roughness. Inner scaling of the mean velocity profile shows a depression in the outer region of the flow. The near-wall portion of the velocity profile in the plate wake region was found to recover faster to the upstream state. The profiles of the turbulent intensity in the plate wake deviate from the upstream profiles and recover gradually with downstream distance. The upstream turbulent intensities for the wire-mesh rough surface peak at farther wall normal locations compared to those of the sand grain and smooth surfaces. A similar roughness effect was observed at the downstream locations amidst the distorted flow, especially, in the intermediate and far wake regions. In the near- and intermediate-wake regions, both the velocity skewness and flatness factors data for the rough walls were higher compared to the data for the smooth surface. For all surfaces, even at the last measuring station (x = 200t) considered in the study, the skewness and flatness factors were found to be still recovering to the upstream condition.
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Ghaisas, Niranjan S., Aditya S. Ghate, and Sanjiva K. Lele. "Effect of tip spacing, thrust coefficient and turbine spacing in multi-rotor wind turbines and farms." Wind Energy Science 5, no. 1 (January 6, 2020): 51–72. http://dx.doi.org/10.5194/wes-5-51-2020.
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Abstract. Large eddy simulations (LESs) are performed to study the wakes of a multi-rotor wind turbine configuration comprising four identical rotors mounted on a single tower. The multi-rotor turbine wakes are compared to the wake of a conventional turbine comprising a single rotor per tower with the same frontal area, hub height and thrust coefficient. The multi-rotor turbine wakes are found to recover faster, while the turbulence intensity in the wake is smaller, compared to the wake of the conventional turbine. The differences with the wake of a conventional turbine increase as the spacing between the tips of the rotors in the multi-rotor configuration increases. The differences are also sensitive to the thrust coefficients used for all rotors, with more pronounced differences for larger thrust coefficients. The interaction between multiple multi-rotor turbines is contrasted with that between multiple single-rotor turbines by considering wind farms with five turbine units aligned perfectly with each other and with the wind direction. Similar to the isolated turbine results, multi-rotor wind farms show smaller wake losses and smaller turbulence intensity compared to wind farms comprised of conventional single-rotor turbines. The benefits of multi-rotor wind farms over single-rotor wind farms increase with increasing tip spacing, irrespective of the axial spacing and thrust coefficient. The mean velocity profiles and relative powers of turbines obtained from the LES results are predicted reasonably accurately by an analytical model assuming Gaussian radial profiles of the velocity deficits and a hybrid linear-quadratic model for the merging of wakes. These results show that a larger power density can be achieved without significantly increased fatigue loads by using multi-rotor turbines instead of conventional, single-rotor turbines.
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Song, Ke, and Yuchi Kang. "A Numerical Performance Analysis of a Rim-Driven Turbine in Real Flow Conditions." Journal of Marine Science and Engineering 10, no. 9 (August 25, 2022): 1185. http://dx.doi.org/10.3390/jmse10091185.
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The tidal turbines represent a new frontier for extracting energy from tides source. Despite the technology being mature, new solutions aimed at improving performance, reliability with reduced environmental impact, manufacturing and installation costs are currently under investigation. The Rim-driven turbine (abbreviated as RDT) was recently proposed. A RDT resembles a ducted turbine (abbreviated as DT), as both contain blades and a duct. The present study aims at investigating the detail performance and flow field of a RDT in a real flow based on the China Zhaitang Island’s tidal current data. To show the difference between the RDT and DT, simulations are also performed on the corresponding DT. It is found that the power and thrust for the two configurations exhibit time-periodic behavior that is consistent with the wave frequency. At axial flow, the fluctuation amplitude on the power and thrust increase with the increase of tip speed ratio. The RDT has higher power output when operating at lower tip speed ratio and has a potential reduction in flow resistance and disturbance with respect to the DT. At yawed flow, the fluctuation amplitude on the power and thrust decrease with the increase of yaw angle. The RDT has less capable of compensating the effect of yawed inflow in reducing the power than the DT at larger yaw angle. In addition, the power and thrust generates micro-amplitude fluctuation integrated into the main waveform, which the frequency is consistent with the turbine rotation frequency. The wake characteristics analysis reveals that the yawed flow field is more turbulent, and the two configurations suffer strong unsteady flow separation along the whole span. Strong interactions are observed between the rotor’s main wake and the duct’s upper wake. The yaw angle primarily determines the downstream wake deflection direction and significantly changes the wake shape and vortex structures. Meanwhile, the wake flow is found to recover more quickly at larger yaw angle. Besides, due to the open-center of RDT, a part free-stream flow is allowed to travel through and forms an obvious high velocity zone. The presence of open-center of RDT has avoided the low velocity zone, improved the wake structure and accelerated wakes recover, which seems to give an advantageous effect in operating a RDT.
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Rowell, Matthew, Martin Wosnik, Jason Barnes, and Jeffrey P. King. "Experimental Evaluation of a Mixer-Ejector Marine Hydrokinetic Turbine at Two Open-Water Tidal Energy Test Sites in NH and MA." Marine Technology Society Journal 47, no. 4 (July 1, 2013): 67–79. http://dx.doi.org/10.4031/mtsj.47.4.15.
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AbstractFor marine hydrokinetic energy to become viable, it is essential to develop energy conversion devices that are able to extract energy with high efficiency from a wide range of flow conditions and to field test them in an environment similar to the one they are designed to eventually operate in. FloDesign Inc. developed and built a mixer-ejector hydrokinetic turbine (MEHT) that encloses the turbine in a specially designed shroud that promotes wake mixing to enable increased mass flow through the turbine rotor. A scaled version of this turbine was evaluated experimentally, deployed below a purpose-built floating test platform at two open-water tidal energy test sites in New Hampshire and Massachusetts and also in a large cross-section tow tank. State-of-the-art instrumentation was used to measure the tidal energy resource and turbine wake flow velocities, turbine power extraction, test platform loadings, and platform motion induced by sea state. The MEHT was able to generate power from tidal currents over a wide range of conditions, with low-velocity start-up. The mean velocity deficit in the wake downstream of the turbine was found to recover more quickly with increasing levels of free stream turbulence, which has implications for turbine spacing in arrays.
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Plogmann, B., W. Würz, and E. Krämer. "On the disturbance evolution downstream of a cylindrical roughness element." Journal of Fluid Mechanics 758 (October 8, 2014): 238–86. http://dx.doi.org/10.1017/jfm.2014.499.
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AbstractRoughness-induced transition is one of the main parameters contributing to performance loss of airfoils. Within this paper, the disturbance evolution downstream of a single, cylindrical roughness element, which is placed in a laminar boundary layer in an airfoil leading edge region, is investigated. The experiments focus on medium height roughness elements with respect to the local boundary layer displacement thickness. Hence, transition is not directly tripped at the roughness element. The roughness diameter is comparable to the streamwise wavelength of the most amplified (linear) disturbance eigenmodes. The vortical structures observed downstream of the roughness are in agreement with previous findings in the literature. In the near roughness wake, a distinct growth of high-frequency (fundamental) modes, that is modes with a high $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}n$-factor at the roughness location, is observed. In the far roughness wake, these fundamental modes recover linear stability characteristics due to a possible relaxation of the mean flow. However, an interaction of particularly two-dimensional fundamental modes and by the roughness interference excited oblique fundamental modes results in an excitation of subharmonic type, low-frequency combination modes, which are associated with a phase-locked interaction mechanism. Depending on the initial growth of the fundamental modes in the near wake, the low-frequency modes can experience a nonlinear growth in the far roughness wake and, thereby, trip turbulence. The fundamental mode growth rate in the near wake in turn is a weak function of the disturbance frequency and of the pressure gradient, whereas it is decisively increasing with the roughness height, that is with the mean flow distortion caused by the roughness.
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Pan, Hanxu, and Qing Ren. "Wake Up! Resuscitation of Viable but Nonculturable Bacteria: Mechanism and Potential Application." Foods 12, no. 1 (December 23, 2022): 82. http://dx.doi.org/10.3390/foods12010082.
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The viable but nonculturable (VBNC) state is a survival strategy for bacteria when encountered with unfavorable conditions. Under favorable environments such as nutrient supplementation, external stress elimination, or supplementation with resuscitation-promoting substances, bacteria will recover from the VBNC state, which is termed “resuscitation”. The resuscitation phenomenon is necessary for proof of VBNC existence, which has been confirmed in different ways to exclude the possibility of culturable-cell regrowth. The resuscitation of VBNC cells has been widely studied for the purpose of risk control of recovered pathogenic or spoilage bacteria. From another aspect, the resuscitation of functional bacteria can also be considered a promising field to explore. To support this point, the resuscitation mechanisms were comprehensively reviewed, which could provide the theoretical foundations for the application of resuscitated VBNC cells. In addition, the proposed applications, as well as the prospects for further applications of resuscitated VBNC bacteria in the food industry are discussed in this review.
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MAGNAUDET, JACQUES, and GUILLAUME MOUGIN. "Wake instability of a fixed spheroidal bubble." Journal of Fluid Mechanics 572 (January 23, 2007): 311–37. http://dx.doi.org/10.1017/s0022112006003442.
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Direct numerical simulations of the flow past a fixed oblate spheroidal bubble are carried out to determine the range of parameters within which the flow may be unstable, and to gain some insight into the instability mechanism. The bubble aspect ratio χ (i.e. the ratio of the major axis length over the minor axis length) is varied from 2.0 to 2.5 while the Reynolds number (based on the upstream velocity and equivalent bubble diameter) is varied in the range 102 ≤ Re ≤ 3 × 103. As vorticity generation at the bubble surface is at the root of the instability, theoretical estimates for the maximum of the surface vorticity and the surface vorticity flux are first derived. It is shown that, for large aspect ratios and high Reynolds numbers, the former evolves as χ8/3 while the latter is proportional to χ7/2Re−1/2. Then it is found numerically that the flow first becomes unstable for χ = χc ≈ 2.21. As the surface vorticity becomes independent of Re for large enough Reynolds number, the flow is unstable only within a finite range of Re, this range being an increasing function of χ − χc. An empirical criterion based on the maximum of the vorticity generated at the body surface is built to determine whether the flow is stable or not. It is shown that this criterion also predicts the correct threshold for the wake instability past a rigid sphere, suggesting that the nature of the body surface does not really matter in the instability mechanism. Also the first two bifurcations of the flow are similar in nature to those found in flows past rigid axisymmetric bluff bodies, such as a sphere or a disk. Wake dynamics become more complex at higher Reynolds number, until the Re−1/2-dependency of the surface vorticity flux makes the flow recover its steadiness and eventually its axisymmetry. A qualitative analysis of the azimuthal vorticity field in the base flow at the rear of the bubble is finally carried out to make some progress in the understanding of the primary instability. It is suggested that the instability originates in a thin region of the flow where the vorticity gradients have to turn almost at right angle to satisfy two different constraints, one at the bubble surface, the other within the standing eddy.
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Perre, Taylor, Arianna Stone, and Yuchi Young. "EXPLORING FIVE WISHES AND END-OF-LIFE CARE PLANNING IN YOUNG ADULTS." Innovation in Aging 6, Supplement_1 (November 1, 2022): 686. http://dx.doi.org/10.1093/geroni/igac059.2518.
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Abstract Introduction. Advance care planning (ACP) allows individuals to plan ahead and express their preferences for medical treatment and care options to health care providers, family, and loved ones before they are no longer able to make or voice decisions due to the event of a serious illness or injury. Advance directives (ADs) allow individuals to record their preferences. While unintentional injuries are the leading cause of death among young adults, limited studies focus on ACP, ADs, and end-of-life treatment and care. Our study aims to (1) examine the perspectives of young adults towards Five Wishes, and (2) measure their preferences related to personal, emotional, spiritual, and medical values in end-of-life care planning. Methods. Data were collected using Five Wishes and a one-time questionnaire. Participants include graduate students (n=30) at a New York State university. The average age was 24 years old (60% were female, 60% White, and 27% Black). Results. In the case of permanent and severe brain damage without expectation to wake up or recover, 63% do not want life-support treatment. In the event of coma without expectation to wake up or recover, 53% do not want life-support treatment. When close to death, 80% want to have religious or spiritual readings and well-loved - poems read aloud. Conclusions. Young adults are capable of making their decisions regarding appointing a health care proxy and giving specific instructions for personal, emotional, spiritual, and medical care. The present findings intend to make contributions in promoting population-based healthcare decision-making, education, and awareness.
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Demshuk, Andrew. "What was the “Right to the Heimat”? West German Expellees and the Many Meanings of Heimkehr." Central European History 45, no. 3 (September 2012): 523–56. http://dx.doi.org/10.1017/s0008938912000374.
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Twenty years and a day after Nazi Germany's unconditional surrender, Hanover county administrator Helmut Janssen declared to an assembly of East Prussian expellee leaders that Germany was still destined to recover all of the territory it had possessed in 1937. One day, he claimed, the roughly twelve million ethnic Germans expelled from the lost eastern territories and eastern Europe in the wake of the war would return home. Although by 1965 this political goal seemed “further away than ever before,” he repeated an expellee declaration of March 1960, which pledged that all expellees “still want to return to the Heimat [homeland]—now, in the future, and forever.”
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Miller, Mark J. "Reconstructing Citizenship: The Politics of Nationality Reform and Immigration in Contemporary France. By Miriam Feldblum. Albany, NY: SUNY Press, 1999. 227p. $54.50 cloth, $17.95 paper." American Political Science Review 95, no. 1 (March 2001): 234–35. http://dx.doi.org/10.1017/s0003055401582015.
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As recently as a quarter-century ago, virtually no one knew or cared about French nationality law and policy. But in the wake of the May-June events of 1968 there was a prise de conscience about international migration and its effects upon French society and the immigrants themselves. New Order, the then quite obscure extreme rightist group, began to organize protest rallies against illegal immigration. In 1974, the post of Secretary of State for Immigration was created to symbolize the growing concern accorded international migra- tion by the French government. Successive governments, whether rightist or leftist in orientation, pledged to recover control over migration.
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McLay, Geoff. "The Problem with Suing Sovereigns: Sloman (1876)." Victoria University of Wellington Law Review 41, no. 3 (November 1, 2010): 403. http://dx.doi.org/10.26686/vuwlr.v41i3.5222.
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In Sloman v The Governor and Government of New Zealand the plaintiff attempted to sue the New Zealand Government for failing to make good on emigration contracts concluded in Europe. This article analyses the decision in Sloman, that the New Zealand government could not be sued in English courts, both within its own historical context and with respect to 19th century concerns over the general inability of the Crown to be sued. The article points to archival documents which show that the New Zealand Government itself was concerned, in the wake of the earlier loss of the Cospatrick, as to its own ability to recover the passage monies it had paid, and whether that recovery might be prevented by a lack of legal personality in the English Courts. The article concludes that while Sloman is an important case in its own right, there is also a need for greater investigation of both the practical and theoretical legal difficulties that faced the New Zealand Government in its development and immigration projects of the 1870s.
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Reichenberger, D. A., S. M. Strayer, G. M. Mathew, O. M. Buxton, and A. Chang. "0303 Heart Rate and Systolic Blood Pressure Increase During Experimental Sleep Restriction." Sleep 43, Supplement_1 (April 2020): A114—A115. http://dx.doi.org/10.1093/sleep/zsaa056.300.
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Abstract Introduction Experimental sleep restriction is associated with elevated daytime cardiac activity, including heart rate (HR) and blood pressure (BP). However, some studies have found changes in systolic (SBP) but not diastolic blood pressure (DBP) or found changes in neither. Although findings are mixed, there may be a dose-response effect of cumulative sleep loss on daytime cardiac activity, such that HR and BP increase above basal levels with additional nights of insufficient sleep. This study examined changes in cardiac activity during experimental sleep restriction. Methods We used multilevel models with random effects for individuals to analyze data from 15 healthy males (M=22.3 years old, SD=2.8) in an 11-day inpatient protocol consisting of three nights of 10-hour/night baseline sleep opportunity, five nights of sleep restriction (5-hour/night sleep opportunity), and then two recovery nights (10-hour/night sleep opportunity). HR and BP were measured approximately every two hours during wake. Results HR increased 0.75 beats/minute with each successive night of sleep restriction (SE=0.18, p<0.001). HR was 5.13 beats/minute higher during the recovery condition than during baseline or sleep restriction (SE=1.05, p<0.001). During sleep restriction only, HR was lower in the later morning and evening compared to the earliest morning timepoint of the day, F(10, 743)=10.44, p<0.001. SBP increased 0.33 mmHg following each successive night of sleep restriction (SE=0.16, p=0.041); however, SBP was only marginally higher during the sleep restriction condition than during baseline (b=1.90, SE=1.09, p=0.082). Conclusion Our findings suggest that HR and SBP increase with each additional day of experimental sleep restriction, even after accounting for diurnal effects on HR and SBP. HR did not recover to baseline levels following a night of recovery sleep, suggesting that longer recovery sleep may be necessary to recover from a week of sleep restriction. Support Grant UL1TR000127 (Chang PI), Clinical and Translational Science Institute; College of Health and Human Development at Pennsylvania State University.
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Hu, Shufan, Chen Zhang, Hong Liu, and Fuxin Wang. "Study on vortex shedding mode on the wake of horn/ridge ice contamination under high-Reynolds conditions." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 13 (March 19, 2019): 5045–56. http://dx.doi.org/10.1177/0954410019835971.
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This paper studied the unsteadiness of vortex motion produced by a three-dimensional wing section with horn/ridge ice contamination. Using improved delayed detached eddy simulation method, multi-scale vortex and their associated flow structures were successfully captured. Results have shown a diversity of unsteadiness scales at different time series, including shear layer instability, vortex pairing, co-rotating and breaking up. Proper orthogonal decomposition was then introduced to extract the characteristic vortex shedding modes with scheduling the eigenvalues λi from large to small. The dominate and secondary proper orthogonal decomposition modes under horn ice condition were displayed, which could be illustrated as fluctuations near recirculation zone, and large-scale vortex shedding/reattaching motion, respectively. The proper orthogonal decomposition modal characteristics for ridge ice showed that vortex scales varied from large to small. The trajectory of large-scale vortex reattaching and co-rotating exist simultaneously with the pressure peak and recover, which also verified the association of proper orthogonal decomposition modes with different scales of vortices. Future works would be presented on demonstration of the complex structures and the dynamic features in such flow.
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D’Arcy, R., J. Chappell, J. Beinortaite, S. Diederichs, G. Boyle, B. Foster, M. J. Garland, et al. "Recovery time of a plasma-wakefield accelerator." Nature 603, no. 7899 (March 2, 2022): 58–62. http://dx.doi.org/10.1038/s41586-021-04348-8.
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AbstractThe interaction of intense particle bunches with plasma can give rise to plasma wakes1,2 capable of sustaining gigavolt-per-metre electric fields3,4, which are orders of magnitude higher than provided by state-of-the-art radio-frequency technology5. Plasma wakefields can, therefore, strongly accelerate charged particles and offer the opportunity to reach higher particle energies with smaller and hence more widely available accelerator facilities. However, the luminosity and brilliance demands of high-energy physics and photon science require particle bunches to be accelerated at repetition rates of thousands or even millions per second, which are orders of magnitude higher than demonstrated with plasma-wakefield technology6,7. Here we investigate the upper limit on repetition rates of beam-driven plasma accelerators by measuring the time it takes for the plasma to recover to its initial state after perturbation by a wakefield. The many-nanosecond-level recovery time measured establishes the in-principle attainability of megahertz rates of acceleration in plasmas. The experimental signatures of the perturbation are well described by simulations of a temporally evolving parabolic ion channel, transferring energy from the collapsing wake to the surrounding media. This result establishes that plasma-wakefield modules could be developed as feasible high-repetition-rate energy boosters at current and future particle-physics and photon-science facilities.
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Li, Jiagen, Han Zhang, Shanshan Liu, Xiuting Wang, and Liang Sun. "The Response and Feedback of Ocean Mesoscale Eddies to Four Sequential Typhoons in 2014 Based on Multiple Satellite Observations and Argo Floats." Remote Sensing 13, no. 19 (September 23, 2021): 3805. http://dx.doi.org/10.3390/rs13193805.
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Four sequential tropical cyclones generated and developed in the Northwest Pacific Ocean (NWP) in 2014, which had significant impacts on the oceanic environment and coastal regions. Based on a substantial dataset of multiple-satellite observations, Argo profiles, and reanalysis data, we comprehensively investigated the interactions between the oceanic environment and sequential tropical cyclones. Super typhoon Neoguri (2014) was the first typhoon-passing studied area, with the maximum sustained wind speed of 140 kts, causing strong cold wake along the track. The location of the strongest cold wake was consistent with the pre-existing cyclonic eddy (CE), in which the average sea surface temperature (SST) cooling exceeded −5 °C. Subsequently, three tropical cyclones passed the ocean environment left by Neoguri, namely, the category 2 typhoon Matmo (2014), the tropical cyclone Nakri (2014) and the category 5 typhoon Halong (2014), which caused completely different subsequent responses. In the CE, due to the fact that the ocean stratification was strongly destroyed by Neoguri and difficult to recover, even the weak Nakri could cause a secondary response, but the secondary SST cooling would be overridden by the first response and thus could cause no more serious ocean disasters. If the subsequent typhoon was super typhoon Halong, it could cause an extreme secondary SST cooling, exceeding −8 °C, due to the deep upwelling, exceeding 700 m, surpassing the record of the maximum cooling caused by the first typhoon. In the anti-cyclonic eddy (AE), since the first typhoon Neoguri caused strong seawater mixing, it was difficult for the subsequent weak typhoons to mix the deeper, colder and saltier water into the surface, thus inhibiting secondary SST cooling, and even the super typhoon Halong would only cause as much SST cooling as the first typhoon. Therefore, the ocean responses to sequential typhoons depended on not only TCs intensity, but also TCs track order and ocean mesoscale eddies. In turn, the cold wake caused by the first typhoon, Neoguri, induced different feedback effects on different subsequent typhoons.
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Coney, William B. "Optimum Circulation Distributions for a Class of Marine Propulsors." Journal of Ship Research 36, no. 03 (September 1, 1992): 210–22. http://dx.doi.org/10.5957/jsr.1992.36.3.210.
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A new method for determining the optimum circulation distributions for both single- and multiple-stage marine propulsors is developed. The lifting-line model for the propulsor is first discretized with a vortexlattice. Variational calculus is then applied to this discretized problem. The result is a general procedure for determining optimum circulation distributions. This procedure can be readily extended to increasingly complex combinations of interacting lifting lines. The propeller lifting-line, vortex-lattice model is described in some detail. Circulation optimization equations for a propeller are derived. The equations are shown to recover traditional results for both light and moderate propeller loading, as well as for wake adapted propellers. Optimization equations for the torque limited case are presented. The vortex-lattice model for multiple stage propulsors is described and the optimization equations are derived. Examples of optimum circulation distributions for contrarotating propellers, a vane-wheel propulsor, and a propeller with pre-swirl stator are presented.
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Rentner, Terry, and Cory Young. "Tumbling into a Crisis: Use of Corporate Apologia after USA Gymnastics Falls off the Balance Beam." Volume 2 2, no. 2019 (March 2019): 27–30. http://dx.doi.org/10.30658/icrcc.2019.8.
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In an open letter to U.S. gymnasts on Nov. 5, 2018, United States Olympic Committee (USOC) CEO Sarah Hirshland told its more than 150,000 members “You deserve better” as it launched the Nuclear Clause that would revoke USA Gymnastics (USAG) as a governing body for the sport at the Olympic level [1]. This announcement comes in the wake of USAG’s ongoing crisis that includes a failure to protect athletes from team doctor Larry Nassar, imprisoned for sexually abusing more than 350 female gymnasts; investigations tied to Michigan State University; and the turnover of several USAG CEO’s in just two years. The research question addressed in this study asks how gymnastics can recover from a crisis that was decades in the making and two years in the public spotlight. Benoit’s (1997) Image Repair theory as well as Hearit and Courtright’s (2004) social constructionist approach and apologia discourse inform our critical analysis on how and why USAG has tumbled.
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Liu, Xiaohao, Zhaobin Li, Xiaolei Yang, Duo Xu, Seokkoo Kang, and Ali Khosronejad. "Large-Eddy Simulation of Wakes of Waked Wind Turbines." Energies 15, no. 8 (April 15, 2022): 2899. http://dx.doi.org/10.3390/en15082899.
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The wake dynamics of a wind turbine are influenced by the atmospheric turbulence and the wake of its upwind turbine. In this work, we investigate the wake characteristics of a waked wind turbine for four different downwind spacings and three different inflows using large-eddy simulation with a turbine parameterized using the actuator surface model. The wake statistics of the waked turbine are compared with those of the stand-alone wind turbine under the same inflow. The results show that the oncoming wake significantly affects the near wake of the waked turbine, where it accelerates the wake recovery by increasing the turbulent convection, and increases the turbulence kinetic energy. The velocity deficit and turbulence kinetic energy in the far wake, on the other hand, are fairly similar with each other for the considered different turbine spacings, and are close to those of the stand-alone wind turbine. As for the wake meandering of the waked wind turbines, it is initiated quickly and enhanced by the oncoming wake turbulence, as shown by the meandering amplitudes and the power spectral density of the instantaneous wake positions. The growth rates of the wake meandering from the waked wind turbines, on the other hand, are close to that of the stand-alone wind turbine, indicating the critical role of the atmospheric turbulence on wake meandering. The present work details how the oncoming wake influences the wake dynamics of the downwind turbine, and provides physical insights on developing engineering models to take into account such effects.
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Murawski, Christopher G., and Kambiz Vafai. "Effect of Wake Disturbance Frequency on the Secondary Flow Vortex Structure in a Turbine Blade Cascade." Journal of Fluids Engineering 122, no. 3 (March 27, 2000): 606–13. http://dx.doi.org/10.1115/1.1287792.
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An experimental study of the effect of wake disturbance frequency on the secondary flow vortices in a two-dimensional linear cascade is presented. The flow Reynolds numbers, based on exit velocity and suction side surface length were 25,000, 50,000 and 85,000. Secondary flow was visualized by injecting smoke into the boundary layer and illuminating it with a laser light sheet located at the exit of the cascade. To simulate wakes from upstream blade rows, a set of spanwise cylinders were traversed across the front of the blade row. The flow visualization results with a single wake disturbance reveal that the recovery time of the secondary flow vortex structure decreases as the wake traverse velocity is increased. The results of flow visualization with multiple wakes showed that wake disturbance frequencies below the axial chord flow frequency allowed complete recovery of the secondary flow vortex structure before the next wake encounters the blade leading edge. Wake disturbance frequencies that exceeded the axial chord flow frequency resulted in no observable recovery of the secondary flow vortex structure. Axial chord flow frequency is defined as the axial velocity in the cascade divided by the axial chord length of the turbine blade. [S0098-2202(00)02203-3]
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Shao, Zhenzhou, Ying Wu, Li Li, Shuang Han, and Yongqian Liu. "Multiple Wind Turbine Wakes Modeling Considering the Faster Wake Recovery in Overlapped Wakes." Energies 12, no. 4 (February 20, 2019): 680. http://dx.doi.org/10.3390/en12040680.
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In a wind farm some wind turbines may be affected by multiple upwind wakes. The commonly used approach in engineering to simulate the interaction effect of different wakes is to combine the single analytical wake model and the interaction model. The higher turbulence level and shear stress profile generated by upwind turbines in the superposed area leads to faster wake recovery. The existing interaction models are all analytical models based on some simple assumptions of superposition, which cannot characterize this phenomenon. Therefore, in this study, a mixing coefficient is introduced into the classical energy balance interaction model with the aim of reflecting the effect of turbulence intensity on velocity recovery in multiple wakes. An empirical expression is also given to calculate this parameter. The performance of the new model is evaluated using data from the Lillgrund and the Horns Rev I offshore wind farms, and the simulations agree reasonably with the observations. The comparison of different interaction model simulation results with measured data show that the calculation accuracy of this new interaction model is high, and the mean absolute percentage error of wind farm efficiency is reduced by 5.3% and 1.58%, respectively, compared to the most commonly used sum of squares interaction model.
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Van Zante, Dale E., John J. Adamczyk, Anthony J. Strazisar, and Theodore H. Okiishi. "Wake Recovery Performance Benefit in a High-Speed Axial Compressor." Journal of Turbomachinery 124, no. 2 (April 1, 2002): 275–84. http://dx.doi.org/10.1115/1.1445793.
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Rotor wakes are an important source of loss in axial compressors. The decay rate of a rotor wake is largely due to both mixing (results in loss) and stretching (no loss accrual). Thus, the actual loss associated with rotor wake decay will vary in proportion to the amounts of mixing and stretching involved. This wake stretching process, referred to by Smith (1996) as recovery, is reversible and for a 2-D rotor wake leads to an inviscid reduction of the velocity deficit of the wake. It will be shown that for the rotor/stator spacing typical of core compressors, wake stretching is the dominant wake decay process within the stator with viscous mixing playing only a secondary role. A model for the rotor wake decay process is developed and used to quantify the viscous dissipation effects relative to those of inviscid wake stretching. The model is verified using laser anemometer measurements acquired in the wake of a transonic rotor operated alone and in a stage configuration at near peak efficiency and near stall operating conditions. Results from the wake decay model exhibit good agreement with the experimental data. Data from the model and laser anemometer measurements indicate that rotor wake straining (stretching) is the primary decay process in the stator passage. Some implications of these results on compressor stage design are discussed.
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Kurzeja, Monika. "The Importance of Safety in Contemporary Consumer Behaviour in the Tourism Market." Socio-Economic Analyses 14, no. 1 (June 30, 2022): 113–19. http://dx.doi.org/10.54664/tmea3969.
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Until recently, the tourism industry was treated as the most dynamically developing sector of the economy. Tourism affects the national economies of many countries in the world by creating new jobs and stimulating GDP. However, the tourism sector has been hit hard by restrictions on the movement of tourists in the wake of the COVID-19 health crisis. The coronavirus outbreak has negatively impacted the travel industry around the world. Another phenomenon that weakens the tourism industry, mainly in the region of Central and Eastern Europe, is Russia’s invasion of Ukraine, which causes concern among consumers of the tourism market. Already in the first days of Russia’s aggression against Ukraine, tourists from Western Europe and the USA were looking for information on security in Poland. In addition, the war in Ukraine may also lead to a decline in demand for tourism services in the country. Fear wins, and the tourism industry is threatened with a crisis, now when it was just beginning to recover from its COVID debts. The aim of the article is to analyze the role of safety in contemporary consumer behaviour in the tourism market. The work is both theoretical and practical.
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Nakhutsrishvili, Luka. "Peasant Oaths, Furious Icons and the Quest for Agency: Tracing Subaltern Politics in Tsarist Georgia on the Eve of the 1905 Revolution. Part II: Agents and Items of (Counter)Insurgent Political Theology on the Imperial Borderland." Praktyka Teoretyczna 39, no. 1 (May 22, 2021): 43–72. http://dx.doi.org/10.14746/prt2021.1.3.
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This two-part transdisciplinary article elaborates on the autobiographical account of the Georgian Social-Democrat Grigol Uratadze regarding the oath pledged by protesting peasants from Guria in 1902. The oath inaugurated their mobilization in Tsarist Georgia in 1902, culminating in full peasant self-rule in the “Gurian Republic” by 1905. The study aims at a historical-anthropological assessment of the asymmetries in the alliance formed by peasants and the revolutionary intelligentsia in the wake of the oath as well as the tensions that crystallized around the oath between the peasants and Tsarist officials. In trying to recover the traces of peasant politics in relation to multiple hegemonic forces in a modernizing imperial borderland, the article invites the reader to reconsider the existing assumptions about historical agency, linguistic conditions of subjectivity, and the relationship between politics and the material and customary dimensions of religion. The ultimate aim is to set the foundations for a future subaltern reading of the practices specific to the peasant politics in the later “Gurian Republic”. The second part of the article delves into Uratadze’s account of the aftermath of the inaugural oath and the conflicts it triggered between peasants, intelligentsia and the Tsarist administration.
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Pan, Jiayi, and David A. Jay. "A Method for Processing Acoustic Doppler Current Profiler Velocity Data from Towed, Undulating Vehicles." Journal of Atmospheric and Oceanic Technology 25, no. 9 (September 1, 2008): 1710–16. http://dx.doi.org/10.1175/2008jtecho534.1.
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Abstract The utility of the acoustic Doppler current profiler (ADCP) for sampling small time and space scales of coastal environments can be enhanced by mounting a high-frequency (1200 kHz) ADCP on an oscillating towed body. This approach requires both an external reference to convert the measured shears to velocities in the earth coordinates and a method to determine the towed body velocities. During the River Influence on the Shelf Ecosystems (RISE) project cruise, a high-frequency (1200 kHz) and narrowbeam ADCP with mode 12 sampling was mounted on a TRIAXUS oscillating towfish, which steers a 3D path behind the ship. This deployment approach extended the vertical range of the ADCP and allowed it to sample near-surface waters outside the ship’s wake. The measurements from a ship-mounted 1200-kHz narrowbeam ADCP are used as references for TRIAXUS ADCP data, and a method of overlapping bins is employed to recover the entire vertical range of the TRIAXUS ADCP. The TRIAXUS vehicle horizontal velocities are obtained by removing the derived ocean current velocity from the TRIAXUS ADCP measurements. The results show that the method is practical.
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Usry, W. R., J. A. C. Humphrey, and R. Greif. "Unsteady Flow in the Obstructed Space Between Disks Corotating in a Cylindrical Enclosure." Journal of Fluids Engineering 115, no. 4 (December 1, 1993): 620–26. http://dx.doi.org/10.1115/1.2910189.
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Time-resolved measurements of the circumferential velocity component were obtained with a laser-Doppler velocimeter in the space between the center pair of four disks corotating in air in an axisymmetric cylindrical enclosure. The separate influences on the flow of two obstructions of similar shapes but having different lengths were investigated. The results show that both obstructions significantly alter the mean and rms distributions of velocity in quantitatively different but qualitatively similar ways. Both obstructions also alter the characteristic frequencies of flow oscillations associated with large scale motions present in the flow, apparently of the type that arise in unobstructed configurations. The measurements suggest that an obstruction can induce bimodal states of motion over frequency ranges that depend on the obstruction’s length. The presence of an obstruction increases the strength of the cross-stream secondary motion in the inter-disk space by redirecting fluid moving in the circumferential direction towards the radial direction. While this reduced the magnitude of the velocity deficit in the obstruction wake, for the cases investigated the flow did not recover within one revolution from the effects of either obstruction.
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Hodgkin, Amy, Sylvain Laizet, and Georgios Deskos. "Do ambient shear and thermal stratification impact wind turbine tip-vortex breakdown?" Journal of Physics: Conference Series 2265, no. 2 (May 1, 2022): 022061. http://dx.doi.org/10.1088/1742-6596/2265/2/022061.
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Abstract Modern wind turbines experience uneven inflow conditions across the rotor, due to the ambient flow’s shear and thermal stratification. Such conditions alter the shape and length of turbine wakes and thus impact the loads and power generation of downstream turbines. To this end, understanding the spatial evolution of the individual wakes under different atmospheric conditions is key to controlling and optimising turbine arrays. With this numerical study we aim to obtain a better understanding of the fundamental physics governing the near-wake dynamics of wind turbines under shear and thermal stability, by examining their tip-vortex breakup mechanisms. Our approach considers scale-resolving simulations of a single turbine wake under a linear shear profile as well as the application of harmonic tip perturbations to trigger flow instabilities. For the subsequent analysis we use the proper orthogonal decomposition (POD) method to extract coherent structures from the flow, and we also calculate mean kinetic energy fluxes to quantify each coherent structure’s contribution to wake recovery. The wake’s helical spiral is found to hinder wake recovery for all studied ambient flow conditions, whereas the mutual inductance instability has positive MKE flux leading to an enhanced wake recovery. Finally, the ambient shear has the largest impact on the local MKE flux with respect to downstream location by changing the shape of the curve and location of extrema, whereas thermal stratification has only a minimal impact on the magnitude of the near-wake local MKE flux distribution.
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Iungo, Giacomo Valerio, and Fernando Porté-Agel. "Volumetric Lidar Scanning of Wind Turbine Wakes under Convective and Neutral Atmospheric Stability Regimes." Journal of Atmospheric and Oceanic Technology 31, no. 10 (October 1, 2014): 2035–48. http://dx.doi.org/10.1175/jtech-d-13-00252.1.
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Abstract Optimization of a wind farm’s layout is a strategic task to reduce wake effects on downstream turbines, thus maximizing wind power harvesting. However, downstream evolution and recovery of each wind turbine wake are strongly affected by the characteristics of the incoming atmospheric boundary layer (ABL) flow, such as the vertical profiles of the mean wind velocity and the turbulence intensity, which are in turn affected by the ABL thermal stability. Therefore, the characterization of the variability of wind turbine wakes under different ABL stability regimes becomes fundamental to better predict wind power harvesting and to improve wind farm efficiency. To this aim, wind velocity measurements of the wake produced by a 2-MW Enercon E-70 wind turbine were performed with three scanning Doppler wind lidars. One lidar was devoted to the characterization of the incoming wind—in particular, wind velocity, shear, and turbulence intensity at the height of the rotor disc. The other two lidars performed volumetric scans of the wind turbine wake under different atmospheric conditions. Through the evaluation of the minimum wake velocity deficit as a function of the downstream distance, it is shown that the ABL stability regime has a significant effect on the wake evolution; in particular, the wake recovers faster under convective conditions. This result suggests that atmospheric inflow conditions, and particularly thermal stability, should be considered for improved wake models and predictions of wind power harvesting.
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Yang, Xiaolei, and Fotis Sotiropoulos. "A Review on the Meandering of Wind Turbine Wakes." Energies 12, no. 24 (December 11, 2019): 4725. http://dx.doi.org/10.3390/en12244725.
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Meandering describes the large-scale, low frequency motions of wind turbine wakes, which could determine wake recovery rates, impact the loads exerted on turbine structures, and play a critical role in the design and optimal control of wind farms. This paper presents a comprehensive review of previous work related to wake meandering. Emphasis is placed on the origin and characteristics of wake meandering and computational models, including both the dynamic wake meandering models and large-eddy simulation approaches. Future research directions in the field are also discussed.
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Lequerica, A., J. Lengenfelder, H. Genova, H. A. Shoval, C. Marchetta, K. Yalamanchi, and J. DeLuca. "0985 Utility Of A Rest-activity Ratio In A Pediatric Brain Injury Rehabilitation Sample: A Pilot Study." Sleep 43, Supplement_1 (April 2020): A374. http://dx.doi.org/10.1093/sleep/zsaa056.981.
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Abstract Introduction Sleep is an important element of health that can impact daytime performance in brain injury rehabilitation. Actigraphy in a pediatric inpatient setting can pose challenges when there are increased amounts of time spent in a hospital bed. A rest-activity ratio (Duclos et al., 2013) has demonstrated utility in adult brain injury populations, showing sensitivity to improved regulation of the sleep-wake cycle as individuals recover during their hospitalization. The present study sought to examine the utility of this ratio in differentiating children with and without acquired brain injury (ABI). Methods Sixteen individuals, ages 8-16 (M=12.6, SD=2.4) admitted to an inpatient pediatric rehabilitation hospital wore an actigraph over a 7-day period. Eight inpatients were being treated for ABI whereas another 8 inpatients treated for other, non-neurological conditions served as a control. Raw activity counts across the 24-hour period were analyzed to derive a rest-activity ratio. Results Those with ABI had lower average ratios (0.73) compared with patients without ABI (0.84), F(1,14)=4.3, p=0.058. Individuals with ratios of 0.85 or higher were rated by their physical therapists as being more alert during therapy using a 5-point Likert scale, F(1,14)=4.1, p=0.061. While these results were marginally significant, this pilot sample was small, and the effect sizes were large (eta squared = 0.234 and 0.229 respectively). Conclusion The rest-activity ratio successfully distinguished those with ABI from a non-ABI sample. This preliminary evidence in a pediatric sample suggests that this ratio, shown to be sensitive to the effects of brain injury on sleep-wake regulation, may be a useful metric in the inpatient pediatric rehabilitation setting when sleep diaries may be difficult to obtain and patients may be spending more time in bed while awake. Future studies with larger sample sizes are needed to explore the correlates of this ratio with other aspects of rehabilitation after pediatric brain injury. Support This study was funded in part through a generous grant from the Church & Dwight Employee Giving Fund
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Kurz, Rainer. "Wake Behavior behind Turbine Cascades in Compressible Two-Dimensional Flows." International Journal of Rotating Machinery 2005, no. 1 (2005): 30–35. http://dx.doi.org/10.1155/ijrm.2005.30.
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The goal of the paper is to describe wake parameters of wakes from turbine cascades in compressible flows especially in planes where the leading edge of the following blade row would be located. Data from experiments with turbine cascades in compressible flow will be used to derive a theoretical approach which describes the wake growth and the recovery of the velocity deficit. The theory is based on similarity assumptions. The derived equations depend on simple and readily available parameters such as overall losses, exit angle, and Mach or Laval number. In compressible turbine flows, the influence of the inviscid flow field is of great importance. In this paper, an approach to take this influence into account when determining the behavior of the wake is presented. Correlations for basic characteristics of wakes in compressible flows are not readily available. Such correlations are necessary as input to unsteady flow and heat transfer calculation procedures for turbomachine blades. Based on available data on wake behavior in the compressible flow behind turbine blades, the correlations presented describe the wake behavior from the trailing edge to the confluence of the wakes of adjacent blades.
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Spaeth, Andrea, and Emily Glavin. "0302 Recovery Sleep in University Students." Sleep 45, Supplement_1 (May 25, 2022): A135—A136. http://dx.doi.org/10.1093/sleep/zsac079.300.
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Abstract Introduction Poor sleep hygiene is common in American college students, with the majority reporting insufficient sleep. Previous studies suggest that many students extend sleep during the weekend to recover sleep debt accrued during the week. In the current study we objectively measured sleep to determine if weekend catch-up sleep was practiced. We also provided students with a 9h sleep opportunity in order to observe how an extended sleep period affected sleep architecture. Methods Students (N=36, 20 women, 19.9±1.7 years) participated in the study from September 2019-March 2020. Sleep-wake behavior was assessed for two weeks using wrist actigraphy and a twice-daily diary. During this two-week period, participants wore at-home polysomnography (PSG) on two non-consecutive nights. For these two nights, in counterbalanced order, participants were instructed to follow their typical sleep pattern or to extend their sleep opportunity to 9h. Within-subjects ANOVA were used to compare sleep between week (Sunday-Thursday) and weekend (Friday and Saturday) nights as well as between typical and 9h PSG nights. Results Compared to week nights, participants went to bed 35 minutes later and woke up 58 minutes later on weekend nights (ps<0.01). Measures of sleep duration and sleep continuity were comparable (ps>0.10) between week and weekend nights and indicated that students averaged less than 7h of sleep per night (6.3±1.0h on week nights and 6.7±1.1h on weekend nights). Self-report measures of sleep quality and daytime sleepiness were also comparable between week and weekend nights (ps>0.05). When instructed to extend their sleep opportunity to 9h, participants exhibited high adherence and increased total sleep time by 88 minutes compared to the typical night (p<0.05). This increase in sleep was due to significant increases in time spent in all four stages of sleep (NREM S1-3 and REM sleep, ps<0.05). Conclusion In this study, students did not utilize weekend nights to extend sleep in order to recover accumulated sleep debt from the week. When provided with a 9h sleep opportunity, participants were physically able to extend sleep and exhibited high quality sleep, suggesting that the primary driver of insufficient sleep in this population is a lack of sleep opportunity rather than impaired sleep ability. Support (If Any)
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Morwood, James. "Euripides’ Suppliant Women, Theseus and Athenocentrism." Mnemosyne 65, no. 4-5 (2012): 552–64. http://dx.doi.org/10.1163/156852511x547947.
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Abstract In Euripides’ Suppliant Women, Theseus at first rejects Adrastos’ supplication to recover the bodies of the Argive dead. Later he changes his mind. This article discusses the initial failure of the supplication, both examining the failings in Adrastos’ appeal and suggesting that a strong case can be made for Theseus’ rejection: neither he nor Athens would have suffered from gods or from men had he stood by it. Why then did he have the change of heart that the play clearly approves? The article links his rejection with a narrow nationalism evinced in his response to the exogamous marriages Adrastos had contracted for his daughters. His attitude looks back to Perikles’ marriage law of 451 BC and reflects the chauvinism that it brought in its wake. Theseus must unlearn this limited mind-set and become a truly Panhellenic hero. The article traces how this in fact happens in the course of the play, above all through the developing relationship between Theseus and Adrastos. His jingoism and isolationism melt away, though in her ex machina appearance Athena undermines the great-heartedness that both kings have displayed. Despite that, the play ends affirmatively, endorsing the theme of the inadequacy of a narrow Athenocentrism.
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Nash, Paul B. "Susceptibility to Low Dose Influenza in Mice is Increased by Administration of Ketamine/Xylazine." Journal of Immunology 206, no. 1_Supplement (May 1, 2021): 20.25. http://dx.doi.org/10.4049/jimmunol.206.supp.20.25.
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Abstract Ketamine/xylazine is an anesthetic commonly used in both research and practice. This study demonstrates a side effect that may have important ramifications. Mice where ketamine/xylazine was used compared to mice not administered the anesthetic were more susceptible to illness caused by administration of low pathogenic preparations of influenza strain A/Puerto Rico/8/34 (PR8). When using one lot of virus, severity of illness as measured by weight loss was increased dramatically by the use of the anesthetic. A slightly more pathogenic lot of virus in other experiments showed that mice with no anesthetic had very mild if any signs of disease, while those with anesthetic succumbed to the illness. In weight loss experiments, mice were affected by the anesthetic even if they were allowed to wake up before inoculation with virus, showing that it was exposure to the drugs that caused the effect, not simply them being asleep. The asleep mice however did recover more slowly from the infection. These results suggest that anesthesia with ketamine/xylazine for treatments may increase the likelihood of post-treatment illness. Likewise experimental results could be affected by using this drug combination such that the immune responses analyzed could be suppressed or the diseases investigated could be more severe.
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Balatbat-Paglinawan, Karen Cristina, and William Mel Paglinawan. "Life Experiences in the New Normal: Interpersonal Communication, Work Values and Job Commitment of Young Professionals." Journal of Humanities and Education Development 4, no. 2 (2022): 69–75. http://dx.doi.org/10.22161/jhed.4.2.9.
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The pandemic has hit every single employee detrimentally, leaving each one feeling worried about how to make ends meet especially in this new normal. Using qualitative measures to probe the living experiences of the young professionals in the highly affected economic sectors of General Santos City - Philippines, eight-core themes were extracted using Moustakas’ (1994) modified van Kaam phenomenological analysis. Results revealed that the economic uncertainty, as well as the psychological and personal consequences brought by the pandemic, have kept young professionals staying in their existing jobs; thus, allowing them to seek multiple employment. It was found out that young professionals developed a certain perspective towards employment, making job security a central aspect in staying committed to their jobs. More so, the participants manifested a dynamic communication style which became one of the essential aspects of expressing concern in the organization and they also regarded family values as a driving force in striving to live. Findings also revealed that it was not the nature of adversity, such as the threat brought by the pandemic, that was most important, but how individuals dealt with it. In this paper, when young professionals faced adversity or frustration in this new normal, protective factors of resilience, work values, commitment and communication helped them survive, recover, and even thrive in the face and wake of misfortunes.
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Li, Ning, Li Li, Yongqian Liu, Yulu Wu, Hang Meng, Jie Yan, and Shuang Han. "Effects of the Parameter C4ε in the Extended k-ε Turbulence Model for Wind Farm Wake Simulation Using an Actuator Disc." Journal of Marine Science and Engineering 10, no. 4 (April 15, 2022): 544. http://dx.doi.org/10.3390/jmse10040544.
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The actuator disc model (ADM) incorporated into the k-ε turbulence model of EI Kasmi is able to simulate the wind farm wakes with high fidelity, which is essential for layout optimization and the evaluation of power production in modern wind farms. However, the effects of the parameter C4ε in the k-ε model of EI Kasmi on turbulent kinetic energy (TKE) in the superposition areas and the recovery of wind farm wake velocity have rarely been studied. To this end, the k-ε model of EI Kasmi is coupled with the advanced ADM in PHOENICS to investigate the influence of the parameter C4ε on the wake simulation of wind farms (e.g., two offshore wind farms, one onshore wind farm). It is concluded that a decreased parameter C4ε makes the generation range of TKE in the vicinity of the rotor smaller, but the TKE near the rotor becomes larger, and the wake recovery rate of the downstream turbine is less affected by the near wake. As the interwind turbine spacing increases, the influence area of TKE in the wake region of each downstream machine gradually reduces, and atmospheric turbulence plays a dominant role in wake recovery. A decreased parameter C4ε can effectively promote the inflow wind velocity and power output of downstream turbines. The power output simulated compares well with the measured power value when the parameter C4ε = 0.15.
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Kushida, Clete, Andrew Cotton-Clay, Susan Baron, Laura Fava, Venkat Easwar, Arthur Kinsolving, Philippe Kahn, Jennifer Zitser, Anil Rama, and Feihong Ding. "0284 Repetitive Weekly REM Sleep Deprivation-Recovery Cycle Obtained from a Large U.S. Sample by Home-Based Under-Mattress Monitoring Devices." Sleep 45, Supplement_1 (May 25, 2022): A128—A129. http://dx.doi.org/10.1093/sleep/zsac079.282.
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Abstract Introduction American adults are typically sleep deprived during weekdays and attempt to recover sleep on the weekends. Technological advances in home sleep monitoring have provided the opportunity to analyze sleep patterns on a scale much larger than previously imaginable. This study explores the weekly REM sleep deprivation–recovery cycle in a large U.S. sample. Methods Estimated total sleep time (TST) and REM/TST (R%) were analyzed by a commercially-available home-sleep-monitoring device (Sleeptracker-AI Monitor, Fullpower Technologies, California, USA). The device passively monitors sleep using piezo-electric sensors that register the forces exerted through the mattress. The de-identified data from the devices were analyzed following review and exemption of the study (#57681) from the Stanford University IRB. Data from 07/2020–06/2021, from 101,442 individuals with 14,277,964 recorded nights, were available. The analytic dataset included individuals with at least 300 nights of sleep per year and 26 of 52 nights per each day of the week (excluding nights abutting federal holidays). Results A total of 21,543 individuals (11,095 men, 51±14 years; 9,821 women, 50±15 years; 627 unspecified genders) and 6,850,717 recorded nights met the inclusion criteria. There is a stepwise increase in R% from Sunday night to Friday night and a decrease back to Sunday night, following a cycle of weekday sleep deprivation and weekend recovery. The means and standard deviations (across individuals’ averages) of TST in hours and R% for each night were: Sunday (TST*:7.21±0.885, R%*:24.20±3.09), Monday (TST*:7.18±0.853, R%*:24.56±3.10), Tuesday (TST*:7.16±0.847, R%*:24.67±3.13), Wednesday (TST*:7.16±0.845, R%*:24.80±3.15), Thursday (TST*:7.18±0.845, R%*:24.87±3.15), Friday (TST*:7.51±0.904, R%*:25.05±3.15), and Saturday (TST*:7.59±0.897, R%*:24.83±3.12). Each statistic, when compared with the previous night of the week, was significant (p < 0.05/7, Bonferroni corrected) by paired t-test (denoted by an asterisk). Conclusion The use of advanced technology to estimate sleep-wake patterns in a large sample permits the validation of a repetitive REM sleep deprivation–recovery cycle. Individuals are, on average, partially sleep deprived starting Sunday night, which leads to a progressive REM sleep rebound that transitions into a REM recovery cycle on Friday and Saturday nights. Further work will focus on studying this cycle within different groups (e.g., age, gender), across seasons, and including other sleep parameters. Support (If Any)
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Shamsoddin, Sina, and Fernando Porté-Agel. "Wind turbine wakes over hills." Journal of Fluid Mechanics 855 (September 19, 2018): 671–702. http://dx.doi.org/10.1017/jfm.2018.653.
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Understanding and predicting the behaviour of wind turbine wake flows over hills is important for optimal design of wind-farm configurations on topography. In this study, we present an analytical modelling framework together with large-eddy simulation (LES) results to investigate turbine wakes over two-dimensional hills. The analytical model consists of two steps. In the first step, we deal with the effect of the pressure gradient on the wake evolution; and in the second step, we consider the effect of the hill-induced streamline distortion on the wake. This model enables us to obtain the wake recovery rate, the mean velocity and velocity deficit profiles and the wake trajectory in the presence of the hill. Moreover, we perform LES to test our model and also to obtain new complementary insight about such flows. Especially, we take advantage of the LES data to perform a special analysis of the behaviour of the wake on the leeward side of the hill. It is found that the mainly favourable pressure gradient on the windward side of the hill accelerates the wake recovery and the adverse pressure gradient on the leeward side decelerates it. The wake trajectory for a hill of the same height as the turbine’s hub height is found to closely follow the hill profile on the windward side, but it maintains an almost constant elevation (a horizontal line) downstream of the hilltop. The trajectory of the wake on the leeward side is also studied for a limiting case of an escarpment, and it is shown that an internal boundary layer forms on the plateau which leads to an upward displacement of the wake centre. Finally, a parametric study of the position of the turbine with respect to the hill is performed to further elucidate the effect of the hill-induced pressure gradient on the wind turbine wake recovery.
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Blondel, Frédéric, and Marie Cathelain. "An alternative form of the super-Gaussian wind turbine wake model." Wind Energy Science 5, no. 3 (September 28, 2020): 1225–36. http://dx.doi.org/10.5194/wes-5-1225-2020.
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Abstract. A new analytical wind turbine wake model, based on a super-Gaussian shape function, is presented. The super-Gaussian function evolves from a nearly top-hat shape in the near wake to a Gaussian shape in the far wake, which is consistent with observations and measurements of wind turbine wakes. Using such a shape function allows the recovery of the mass and momentum conservation that is violated when applying a near-wake regularization function to the expression of the maximum velocity deficit of the Gaussian wake model. After a brief introduction of the theoretical aspects, an easy-to-implement model with a limited number of parameters is derived. The super-Gaussian model predictions are compared to wind tunnel measurements, full-scale measurements, and a large-eddy simulation (LES), showing a good agreement and an improvement compared with predictions based on the Gaussian model.
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Chen, Pin-Wei, Megan O’Brien, Amy Nguyen, Sara Prokup, Kristen Knutson, Hyun Sik Yang, Alejandro Hucker, et al. "0597 The Relationship Between Sleep Quality and Functional Outcomes Following Acute Stroke and Inpatient Rehabilitation." Sleep 45, Supplement_1 (May 25, 2022): A262—A263. http://dx.doi.org/10.1093/sleep/zsac079.594.
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Abstract Introduction There is mounting evidence that sleep plays an important role in the rehabilitation and recovery process following acute stroke. Following acute care, many patients with stroke are admitted to inpatient rehabilitation facilities (IRFs), where they undergo intensive, interdisciplinary therapy to recover or relearn functional skills to minimize long-term disability. The role and impact of sleep in this early stage of stroke rehabilitation, however, is poorly understood. The purpose of this study is to investigate the relationship between sleep quality and clinical outcomes in the IRF setting following acute stroke. Methods Patients wore a collection of wearable sensors to measure sleep and wake throughout their IRF stay. Linear mixed-effect models (LMEMs) were built to determine the relationship between functional outcomes and sleep quality. Independent variables were total sleep time (TST) and sleep efficiency (SE) derived from wearable sensors, calculated between two clinical measures. Dependent variables included scores from repeated measures of the 6-Minute Walk Test (6MWT), 10-Meter Walk Test (10MWT), Berg Balance Scale (BBS), and Action Research Arm Test (ARAT). Covariates included demographics such as age and stroke type. Results Fifty-three individuals with stroke (age: 58.26±15.57 years; BMI: 28.27±6.16 kg/m2) consented to participate during their IRF program within 7 days of admission. All individuals were recruited from a single-site IRF between July 2020 and August 2021. The average length of stay was 17.85±6.99 days. There were no significant differences in TST between the first three nights and the last three nights (5.1±1.9 hours vs. 5.2±2.0 hours) or SE (67.8±17.7% vs. 69.0±17.8%). The greater standard deviation of TST was associated with lower 6MWT scores (R2=0.77, beta=−0.48, p=0.06), while the greater standard deviation of SE was associated with lower 10MWT scores (R2=0.80, beta=−0.20, p=0.18). Conclusion Our preliminary findings indicate that greater variability in TST and SE are associated with walking endurance and mobility recovery. Future analyses will investigate additional measures of sleep and activity in IRF settings and their relationship with patient outcomes. This work can inform novel sleep interventions to optimize post-stroke recovery. Support (If Any) This work is supported by the Eunice Kennedy Shriver National Institute of Child Health & Human Development (NIH R01HD097786-01A1).
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Zhao, Donghui. "ESG Strategies and Practices of Chinese Listed Companies." Frontiers in Management Science 1, no. 3 (December 2022): 29–36. http://dx.doi.org/10.56397/fms.2022.12.03.
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In the wake of the global outbreak of the new coronavirus, many organizations have been subjected to stress tests, including companies and some contractual organizations. This, coupled with challenges ranging from economic inequality to racial inequality to climate change and those already closely tied to business, has combined to create an extraordinary test for business. Capital market investors are also re-examining traditional growth models and placing greater emphasis on sustainability, with a new surge in global ESG investment and practice. China’s economy has benefited from a combination of sustainable development strategies and high-quality development strategies, making it the world’s first major economy to recover from the epidemic. The government has introduced a series of initiatives on carbon emissions, anti-monopoly, and corporate governance to positively transform to a low-carbon economy. When asked about how to handle the deep-rooted problems facing society, companies often say that they cannot afford to invest in environmental protection, high employee compensation, or other social issues because they must return sufficient profits to shareholders. To address this issue, this paper will use the ROSI model developed by the Stern Center for Sustainable Business (CSB) to embed ESG strategies into corporate development strategies to better integrate, track report on the financial performance of companies owing the implementation of ESG strategies, which will improve management decisions related to ESG and sustainable practices and provide investors with more actionable information.
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Gooshki, Hossein Shamsi, Seyyed Hassan Abedian Kalkhoran, Seyyed Mohammad Mahdi Ahmadi, Abolfazl Khoshi, and Hassan Goodarzi. "Vegetative State from the Perspective of Islamic Law." Journal of Ecophysiology and Occupational Health 19, no. 3&4 (December 26, 2019): 102. http://dx.doi.org/10.18311/jeoh/2019/23817.
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<p>The death of the cerebral cortex is a particular type of brain death that occurs after the destruction of the cerebral cortex (the hemispheres of the brain). It is said that the individual has gone through a vegetative state. This cortex is responsible for controlling voluntary activities of the body. This condition is caused by a coma (anesthesia), and sometimes the individual remains in this state for several years. Although the person looks awake, his/her eyes are open and has some involuntary movements, there is no signs of mental and cognitive function. Moreover, the individual is physically in a state of dementia. Coma is a state in which a person cannot be awakened and does not respond to any stimulation including pain. Generally it lasts few days to a few weeks, after which some patients gradually recover, but some permanently lose all brain function (brain death), while others evolve to a vegetative state (VS). Patients in VS are unconscious and unaware of their surroundings, but they continue to have a sleep-wake cycle and can have periods of consciousness. They are able to breathe spontaneously, retain their gag, cough, sucking, and swallowing reflexes. They often look fairly “normal” to families and friends who hope and pray for their full recovery. Laws and regulations in Islamic countries originate from popular jurisprudence. Therefore, by arguing that the well-known principles of Islam are necessarily legitimate, the phenomenon of vegetative state has been recognized. Jurisprudents have conflicting opinions on brain deaths and these perspectives cannot be considered as a widespread legal basis at the level of macro policy for administrative, medical and judicial affairs. In criminal law, maniac has no criminal responsibility because the punishment is not in line with the purpose of punishment. Consequently, restrictions will be imposed on the patients. Therefore, it can be concluded that a person with vegetative state is compatible with the insanity.</p>
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YANG, XIANGSHENG, NING ZHAO, LINLIN TIAN, and JUN ZHU. "WAKE NUMERICAL SIMULATION BASED ON THE PARK-GAUSS MODEL AND CONSIDERING ATMOSPHERIC STABILITY." International Journal of Modern Physics: Conference Series 42 (January 2016): 1660175. http://dx.doi.org/10.1142/s2010194516601757.
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In this paper, a new Park-Gauss model based on the assumption of the Park model and the Eddy-viscosity model is investigated to conduct the wake numerical simulation for solving a single wind turbine problem. The initial wake radius has been modified to improve the model’s numerical accuracy. Then the impact of the atmospheric stability based on the Park-Gauss model has been studied in the wake region. By the comparisons and the analyses of the test results, it turns out that the new Park-Gauss model could achieve better effects of the wind velocity simulation in the wake region. The wind velocity in the wake region recovers quickly under the unstable atmospheric condition provided the wind velocity is closest to the test result, and recovers slowly under stable atmospheric condition in case of the wind velocity is lower than the test result. Meanwhile, the wind velocity recovery falls in between the unstable and stable neutral atmospheric conditions.
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Stallard, T., R. Collings, T. Feng, and J. Whelan. "Interactions between tidal turbine wakes: experimental study of a group of three-bladed rotors." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, no. 1985 (February 28, 2013): 20120159. http://dx.doi.org/10.1098/rsta.2012.0159.
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It is well known that a wake will develop downstream of a tidal stream turbine owing to extraction of axial momentum across the rotor plane. To select a suitable layout for an array of horizontal axis tidal stream turbines, it is important to understand the extent and structure of the wakes of each turbine. Studies of wind turbines and isolated tidal stream turbines have shown that the velocity reduction in the wake of a single device is a function of the rotor operating state (specifically thrust), and that the rate of recovery of wake velocity is dependent on mixing between the wake and the surrounding flow. For an unbounded flow, the velocity of the surrounding flow is similar to that of the incident flow. However, the velocity of the surrounding flow will be increased by the presence of bounding surfaces formed by the bed and free surface, and by the wake of adjacent devices. This paper presents the results of an experimental study investigating the influence of such bounding surfaces on the structure of the wake of tidal stream turbines.
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Ouro, Pablo, Peter K. Stansby, and Tim Stallard. "Analysis of the kinetic energy recovery behind a tidal stream turbine for various submergence levels." International Marine Energy Journal 5, no. 3 (December 19, 2022): 265–72. http://dx.doi.org/10.36688/imej.5.265-272.
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Tidal turbines are commonly deployed at sea sites with water depths of up to 50 m to ease their deployment and quick maintenance operations. In these relatively shallow water depth conditions, the vertical expansion of tidal stream turbine wakes is restricted by the proximity of the rotor blades to the bottom bed and free-surface layer. These physical constrains can lead to changes in the flow mechanisms that drive momentum recovery behind the turbines, e.g. limiting the vertical fluxes of velocity. Understanding how the wake recovers depending on the submergence ratio is of utmost importance to designing the future multi-row tidal turbine arrays. Here, we adopt high-fidelity Large-Eddy Simulations (LES) with an Actuator Line Method (ALM) to represent the turbine's rotor to analyse the mean flow and transport equation for mean kinetic energy (MKE) behind a single bottom-fixed tidal turbine for four water depth values. Our results show that the close proximity of the turbine blade tip to the free-surface can notably constrain the wake expansion, with very shallow conditions leading to a limited contribution to the MKE replenishment of the turbulent momentum exchange over the vertical direction. Conversely, under such shallow conditions, the horizontal flux of MKE is enhanced over the lateral boundaries of the downstream wake. Our study evidences that the ratio of water depth to turbine diameter plays a relevant role in future tidal arrays and needs to be correctly accounted for in numerical models to provide reliable results.
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Iungo, G. V., and F. Porté-Agel. "Measurement procedures for characterization of wind turbine wakes with scanning Doppler wind LiDARs." Advances in Science and Research 10, no. 1 (May 30, 2013): 71–75. http://dx.doi.org/10.5194/asr-10-71-2013.
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Abstract. The wake flow produced from an Enercon E-70 wind turbine is investigated through three scanning Doppler wind LiDARs. One LiDAR is deployed upwind to characterize the incoming wind, while the other two LiDARs are located downstream to carry out wake measurements. The main challenge in performing measurements of wind turbine wakes is represented by the varying wind conditions, and by the consequent adjustments of the turbine yaw angle needed to maximize power production. Consequently, taking into account possible variations of the relative position between the LiDAR measurement volume and wake location, different measuring techniques were carried out in order to perform 2-D and 3-D characterizations of the mean wake velocity field. However, larger measurement volumes and higher spatial resolution require longer sampling periods; thus, to investigate wake turbulence tests were also performed by staring the LiDAR laser beam over fixed directions and with the maximum sampling frequency. The characterization of the wake recovery along the downwind direction is performed. Moreover, wake turbulence peaks are detected at turbine top-tip height, which can represent increased fatigue loads for downstream wind turbines within a wind farm.
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Valkov, T. V., and C. S. Tan. "Effect of Upstream Rotor Vortical Disturbances on the Time-Averaged Performance of Axial Compressor Stators: Part 1—Framework of Technical Approach and Wake–Stator Blade Interactions." Journal of Turbomachinery 121, no. 3 (July 1, 1999): 377–86. http://dx.doi.org/10.1115/1.2841330.
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In a two-part paper, key computed results from a set of first-of-a-kind numerical simulations on the unsteady interaction of axial compressor stators with upstream rotor wakes and tip leakage vortices are employed to elucidate their impact on the time-averaged performance of the stator. Detailed interrogation of the computed flow field showed that for both wakes and tip leakage vortices, the impact of these mechanisms can be described on the same physical basis. Specifically, there are two generic mechanisms with significant influence on performance: reversible recovery of the energy in the wakes/tip vortices (beneficial) and the associated nontransitional boundary layer response (detrimental). In the presence of flow unsteadiness associated with rotor wakes and tip vortices, the efficiency of the stator under consideration is higher than that obtained using a mixed-out steady flow approximation. The effects of tip vortices and wakes are of comparable importance. The impact of stator interaction with upstream wakes and vortices depends on the following parameters: axial spacing, loading, and the frequency of wake fluctuations in the rotor frame. At reduced spacing, this impact becomes significant. The most important aspect of the tip vortex is the relative velocity defect and the associated relative total pressure defect, which is perceived by the stator in the same manner as a wake. In Part 1, the focus will be on the framework of technical approach, and the interaction of stator with the moving upstream rotor wakes.
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Tepper-García, Thor, Joss Bland-Hawthorn, Marcel S. Pawlowski, and Tobias K. Fritz. "The Magellanic System: the puzzle of the leading gas stream." Monthly Notices of the Royal Astronomical Society 488, no. 1 (June 14, 2019): 918–38. http://dx.doi.org/10.1093/mnras/stz1659.
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ABSTRACT The Magellanic Clouds (MCs) are the most massive gas-bearing systems falling into the Galaxy at the present epoch. They show clear signs of interaction, manifested in particular by the Magellanic Stream, a spectacular gaseous wake that trails from the MCs extending more than 150° across the sky. Ahead of the MCs is the ‘Leading Arm’ usually interpreted as the tidal counterpart of the Magellanic Stream, an assumption we now call into question. We revisit the formation of these gaseous structures in a first-infall scenario, including for the first time a Galactic model with a weakly magnetized, spinning hot corona. In agreement with previous studies, we recover the location and the extension of the Stream on the sky. In contrast, we find that the formation of the Leading Arm – that is otherwise present in models without a corona – is inhibited by the hydrodynamic interaction with the hot component. These results hold with or without coronal rotation or a weak, ambient magnetic field. Since the existence of the hot corona is well established, we are led to two possible interpretations: (i) the Leading Arm survives because the coronal density beyond 20 kpc is a factor ≳10 lower than required by conventional spheroidal coronal X-ray models, in line with recent claims of rapid coronal rotation; or (ii) the ‘Leading Arm’ is cool gas trailing from a frontrunner, a satellite moving ahead of the MCs, consistent with its higher metallicity compared to the trailing stream. Both scenarios raise issues that we discuss.
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Baskett, Peter J. F. "Immediate Care for the Private Pilot." Journal of the World Association for Emergency and Disaster Medicine 1, no. 2 (1985): 148. http://dx.doi.org/10.1017/s1049023x00065353.
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Private aviation being popular, there are many light planes in regular use. Several of these are operated by pilots in training through local flying clubs. There is naturally a risk every time a plane takes to the air, but the statistics show that the risk is actually quite small. Most insurance companies do not increase their premiums for private pilots flying for pleasure. The most common emergencies which arise in light aircraft are caused by deteriorating weather conditions, fuel shortage, engine failure or pilot error.Accidents caused by the inept pilot usually occur during take-off or landing. Gusting wind conditions can produce an unexpectd stall position when there is inadequate height to recover. The strong vortices generated in the wake of high powered jet engines can turn over a light plane which is following too closely at take-off or landing in the circuit. Accidents may also occur during flight because of the pilot's failure to fly at the correct height on the correct course and communicate properly to the local air traffic control. Fear of being made to look incompetent often results in the inexperienced pilot failing to ask for help when he is in doubt or in trouble.If problems such as engine failure or fuel starvation occur, however, all is not lost since, unlike their enormous commercial counterparts, light planes have excellent gliding characteristics and can usually make an emergency landing. Requiring only a relatively short landing run if full flaps are used, they can often find a suitable site free from buildings and people.