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Brenneis, Björn, Sergej Gordeev, Sebastian Ruck, Leonid Stoppel i Wolfgang Hering. "Wake Shape and Height Profile Measurements in a Concave Open Channel Flow regarding the Target in DONES". Energies 14, nr 20 (11.10.2021): 6506. http://dx.doi.org/10.3390/en14206506.
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Wakes appearing downstream of disturbances on the surface of a water flow in a concave open channel were examined experimentally. The investigated channel geometry was similar to the liquid lithium target in DONES (Demonstration fusion power plant Oriented NEutron Source). The objective of the measurements was to analyze the effect of a disturbance on the downstream layer thickness. For measuring the height profiles in the channel, an optical measurement system based on laser triangulation was developed. It was shown that the wake of the undisturbed flow emerged from the nozzle corner, which was in accordance with analytical solutions. For sufficiently large disturbances at the nozzle edge, the height profiles located downstream showed symmetrical minima and maxima on both sides of the disturbance. The wake depth strongly depended on the diameter and penetration depth of the disturbance, as well as the circumferential position in the channel, which yields to a critical wake depth of one millimeter for the lithium target in DONES.
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Дубровин, К. А., А. Е. Зарвин, В. В. Каляда i А. С. Яскин. "Причины свечения аномального вторичного потока в сверхзвуковых кластированных струях, возбужденных высоковольтным электронным пучком". Письма в журнал технической физики 46, nr 7 (2020): 32. http://dx.doi.org/10.21883/pjtf.2020.07.49217.18011.
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The role of clustered particles in the formation of a secondary flow (“wake”) occuring at the gas expiring into a rarefied medium in condensation modes is established. The “wake” boundaries were found by comparing the spectral and photometric measurements. Possible mechanisms for initiating luminescence in "wake" are considered. The role of energy exchange of clusters with background gas in the afterglow of the "wake" has been found out. The wavelengths and corresponding transitions in the neutral (Ar-I) and once ionized (Ar-II) argon atoms, which determine the anomalous glow, were discovered. The lifetimes in the excited state of particles in the central part and on the periphery of the clustered flow are detected. The effect of condensation on the background gas penetration into the primary traditional supersonic jet and into the “wake” zone is found.
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Kim, Minju, Somi Jung, Than Van Chau i Won-Bae Na. "Correlation of the Structural Characteristics of an Artificial Oyster Reef with Its Wake Region". Journal of Marine Science and Engineering 11, nr 4 (3.04.2023): 775. http://dx.doi.org/10.3390/jmse11040775.
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Oyster reefs are currently at risk of severe decline due to dangerous human interference and its aftermath; hence, artificial oyster reefs (AORs) have been utilized for their restoration. AORs with high vertical reliefs interact with the surrounding flow, constitute a reverse flow, and create a wake region in which concentrated nutrients and food organisms exist. However, the correlations of the structural characteristics of an AOR with its wake regions have not been studied. Thus, we established 96 AOR models, carried out flow analyses, and obtained their wake volumes, considering shell orientation, composition, penetration depth, and growth stage. We found that the growth stage is the most critical parameter for establishing a normalized wake volume. This implies that the number of oyster shells (N) is the most critical factor in securing a normalized wake volume, in which their correlation was linear and significant (R2=0.89). We also found that the correlations of the normalized wake volume with blocking and surface complexity indices were linearly significant, respectively. Additionally, wake volume efficiency increased with the number of oyster shells; specifically, the criterion for wake volume efficiency of EI (efficiency index) ≥ 2.0 was satisfied when N≥50 per 900 cm2.
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Hu, Ye Zhou, Lin Zhang, Pai Liu, Xin Yuan Liu i Ming Zhou. "Modeling Large-Scale Wind Farms for Reliability Analysis Considering Wake Effect". Applied Mechanics and Materials 543-547 (marzec 2014): 647–52. http://dx.doi.org/10.4028/www.scientific.net/amm.543-547.647.
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Large scale wind power penetration has a significant impact on the reliability of the electric generation systems. A wind farm consists of a large number of wind turbine generators (WTGs). A major difficulty in modeling wind farms is that the WTG not have an independent capacity distribution due to the dependence of the individual turbine output on the same energy source, the wind. In this paper, a model of the wind farm output power considering multi-wake effects is established according to the probability distribution of the wind speed and the characteristic of the wind generator output power: based on the simple Jenson wake effect model, the wake effect with wind speed sheer model and the detail wake effect model with the detail shade areas of the upstream wind turbines are discussed respectively. Compared to the individual wake effect model, this model takes the wind farm as a whole and considers the multi-wakes effect on the same unit. As a result the loss of the velocity inside the wind farm is considered more exactly. Furthermore, considering the features of sequentially and self-correlation of wind speed, an auto-regressive and moving average (ARMA) model for wind speed is built up. Also the reliability model of wind farm is built when the output characteristics of wind power generation units, correlation of wind speeds among different wind farms, outage model of wind power generation units, wake effect of wind farm and air temperature are considered. Simulation results validate the effectiveness of the proposed models. These models can be used to research the reliability of power grid containing wind farms, wind farm capacity credit as well as the interconnection among wind farms
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Vermeulen, P. J., P. Grabinski i V. Ramesh. "Mixing of an Acoustically Excited Air Jet With a Confined Hot Crossflow". Journal of Engineering for Gas Turbines and Power 114, nr 1 (1.01.1992): 46–54. http://dx.doi.org/10.1115/1.2906306.
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The mixing of an acoustically pulsed air jet with a confined hot crossflow has been assessed by temperature profile measurements. These novel experiments were designed to examine the effects of acoustic driver power and Strouhal number on jet structure, penetration, and mixing. The results showed that excitation produced strong changes in the measured temperature profiles. This resulted in significant increases in mixing zone size, penetration (at least 100 percent increase), and mixing, and the length to achieve a given mixed state was shortened by at least 70 percent. There was strong modification to the jet-wake region. The increase in jet penetration and mixing was saturating near 90 W, the largest driving power tested. The jet response as determined by penetration and mixing was optimum at a Strouhal number of 0.27. Overall, pulsating the jet flow significantly improved the jet mixing processes in a controllable manner.
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Gretta, W. J., i C. R. Smith. "The Flow Structure and Statistics of a Passive Mixing Tab". Journal of Fluids Engineering 115, nr 2 (1.06.1993): 255–63. http://dx.doi.org/10.1115/1.2910133.
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Water channel flow visualization and anemometry studies were conducted to examine the flow structure and velocity statistics in the wake of a passive mixing tab designed for enhancement of cross-stream mixing by generation of flow structures characteristic of turbulent boundary layers. Flow visualization reveals that the mixing tab generates a wake comprising a combination of counter rotating, streamwise vortices enveloped by distinct hairpin vortex structures. The counter rotating streamwise vortices are observed to stimulate a strong ejection of fluid along the symmetry plane, which results in very rapid cross-stream mixing. The hairpin vortices are found to undergo successive amalgamation and coalescence downstream of the device, which aids in the streamwise mixing and outward penetration of ejected fluid. After an initially intense mixing process, the mixing tab wake rapidly develops mean velocity, turbulence intensity, and boundary layer integral properties characteristic of a significantly thickened turbulent boundary layer.
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Park, Rae-Jin, Jeong-Hwan Kim, Byungchan Yoo, Minhan Yoon i Seungmin Jung. "Verification of Prediction Method Based on Machine Learning under Wake Effect Using Real-Time Digital Simulator". Energies 15, nr 24 (14.12.2022): 9475. http://dx.doi.org/10.3390/en15249475.
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With the increase in the penetration rate of renewable energy sources, a machine-learning-based forecasting system has been introduced to the grid sector to improve the participation rate in the electricity market and reduce energy losses. In these studies, correlation analysis of mechanical and environmental variables, including geographical figures, is considered a crucial point to increase the prediction’s accuracy. Various models have been applied in terms of accuracy, speed calculation, and amount of data based on a mathematical model that can calculate the wake; however, it can be difficult to derive variables such as air density, roughness length, and the effect of turbulence on the structural characteristics of wind turbines. Furthermore, wake accuracy could decrease due to the excessive variables that come from the wake effect parameters. In this paper, we intend to conduct research to improve prediction accuracy by considering the wake effect of wind turbines using supervisory control and data acquisition (SCADA) data from the Dongbok wind farm. The wake divides the wind direction into four parts and then recognizes and predicts the affected wind turbine. The predicted result is the wake wind speed and its conversion to power generation by applying a power curve. We try to show the efficiency of machine learning by comparing the wake wind speed and the power generation in the wake model. This result shows the error rate using evaluation metrics of regression, such as mean squared error (MSE), root mean squared error (RMSE), and weighted absolute percentage error (WAPE), and attempts to verify power system impact and efficiency through a real-time digital simulator (RTDS).
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Depestele, Jochen, Ana Ivanović, Koen Degrendele, Moosa Esmaeili, Hans Polet, Marc Roche, Keith Summerbell, Lorna R. Teal, Bart Vanelslander i Finbarr G. O'Neill. "Measuring and assessing the physical impact of beam trawling". ICES Journal of Marine Science 73, suppl_1 (6.04.2015): i15—i26. http://dx.doi.org/10.1093/icesjms/fsv056.
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Abstract Beam trawling causes physical disruption of the seabed through contact of the gear components with the sediment and the resuspension of sediment into the water column in the turbulent wake of the gear. To be able to measure and quantify these impacts is important so that gears of reduced impact can be developed. Here we assess the physical impact of both a conventional 4 m tickler-chain beam trawl and a “Delmeco” electric pulse beam trawl. We measure the changes in seabed bathymetry following the passage of these gears using a Kongsberg EM2040 multi-beam echosounder and use a LISST 100X particle size analyser to measure the concentration and particle size distribution of the sediment mobilized into the water column. We also estimate the penetration of the gears into the seabed using numerical models for the mechanical interaction between gears and seabed. Our results indicate that the seabed bathymetry changes between ∼1 and 2 cm and that it is further increased by higher trawling frequencies. Furthermore, our results suggest that the alteration following the passage of the conventional trawl is greater than that following the pulse trawl passage. There was no difference in the quantity of sediment mobilized in the wake of these two gears; however, the numerical model introduced in this study predicted that the tickler-chain trawl penetrates the seabed more deeply than the pulse gear. Hence, greater alteration to the seabed bathymetry by the tickler-chain beam trawling is likely to be a result of its greater penetration. The complimentary insights of the different techniques highlight the advantage of investigating multiple effects such as sediment penetration and resuspension simultaneously and using both field trials and numerical modelling approaches.
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Hsu, C. M., i R. F. Huang. "Comparisons of Flow and Mixing Characteristics between Unforced and Excited Elevated Transverse Jets". Journal of Mechanics 30, nr 1 (14.11.2013): 87–96. http://dx.doi.org/10.1017/jmech.2013.74.
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ABSTRACTThe influences of acoustic excitation on the velocity field and mixing characteristic of a jet in cross-flow were investigated in a wind tunnel. The acoustic excitation waves at resonance Strouhal number were generated by a loudspeaker. The time-averaged velocity field and streamlines of the excited elevated transverse jet in the symmetry plane were measured by a high-speed particle image velocimetry. The visual penetration height and spread width were obtained by using an image processing technique. The dispersion characteristics were obtained from the tracer-gas concentration measurement. The results showed that the streamline pattern of the non-excited transverse jet was significantly modified by the acoustic excitation—the bent streamlines evolved from the jet exit escalated and the vortex rings in the jet and tube wakes and the recirculation bubble in the jet wake disappeared. The time-averaged velocity distributions revealed that the excited transverse jet produces large momentum in the up-shooting direction so that the velocity trajectories were located at levels higher than those of the non-excited one. The mixing characteristics, which include the visual penetration height, spread width, and dispersion, were drastically improved by the acoustic excitation due to the changes in the flow structures. The excited transverse jet characterized at larger jet-to-crossflow momentum flux ratios presented larger improvement in the mixing characteristics than at lower jet-to-crossflow momentum flux ratios.
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Nawal, Taleb, Bentouati Bachir, Chettih Saliha, Harrouz Abdelkader i Ragab El-Sehiemy. "Renewable Energy Sources Scheduling Approach for Windfarm Layout Optimization by Using Ant Lion Optimization Algorithm". Applied Mechanics and Materials 905 (15.02.2022): 79–92. http://dx.doi.org/10.4028/p-1bvgm9.
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The increasing penetration of RES and the intermittent nature of various distributed power generation (DG) resources have created uncertainty in variable power production and power systems. The overall energy output of a wind farm may be optimized by strategically positioning wind turbines. This paper proposes a three-step strategy to dealing with the difficult-to-control problem of wind farm layout optimization. To construct the non-wake and wake impacts at various levels, three case scenarios are studied. The proposed strategy is used to a particular Ant-Lion Optimization Algorithm (ALOA) as a novel approach to producing highly efficient optimal output power, as well as case studies using actual wind data assessing potential turbine site. Finally, the simulation results demonstrate that the suggested approach is robust in ALOA design because it further reduces the objective function on the best new outcomes to implement all network restrictions acquired via the analysis.
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Abbas, Shah Rukh, Syed Ali Abbas Kazmi, Muhammad Naqvi, Adeel Javed, Salman Raza Naqvi, Kafait Ullah, Tauseef-ur-Rehman Khan i Dong Ryeol Shin. "Impact Analysis of Large-Scale Wind Farms Integration in Weak Transmission Grid from Technical Perspectives". Energies 13, nr 20 (21.10.2020): 5513. http://dx.doi.org/10.3390/en13205513.
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The integration of commercial onshore large-scale wind farms into a national grid comes with several technical issues that predominately ensure power quality in accordance with respective grid codes. The resulting impacts are complemented with the absorption of larger amounts of reactive power by wind generators. In addition, seasonal variations and inter-farm wake effects further deteriorate the overall system performance and restrict the optimal use of available wind resources. This paper presented an assessment framework to address the power quality issues that have arisen after integrating large-scale wind farms into weak transmission grids, especially considering inter-farm wake effect, seasonal variations, reactive power depletion, and compensation with a variety of voltage-ampere reactive (Var) devices. Herein, we also proposed a recovery of significant active power deficits caused by the wake effect via increasing hub height of wind turbines. For large-scale wind energy penetration, a real case study was considered for three wind farms with a cumulative capacity of 154.4 MW integrated at a Nooriabad Grid in Pakistan to analyze their overall impacts. An actual test system was modeled in MATLAB Simulink for a composite analysis. Simulations were performed for various scenarios to consider wind intermittency, seasonal variations across four seasons, and wake effect. The capacitor banks and various flexible alternating current transmission systems (FACTS) devices were employed for a comparative analysis with and without considering the inter-farm wake effect. The power system parameters along with active and reactive power deficits were considered for comprehensive analysis. Unified power flow controller (UPFC) was found to be the best compensation device through comparative analysis, as it maintained voltage at nearly 1.002 pu, suppressed frequency transient in a range of 49.88–50.17 Hz, and avoided any resonance while maintaining power factors in an allowable range. Moreover, it also enhanced the power handling capability of the power system. The 20 m increase in hub height assisted the recovery of the active power deficit to 48%, which thus minimized the influence of the wake effect.
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Tabas, Daniel, Jiannong Fang i Fernando Porté-Agel. "Wind Energy Prediction in Highly Complex Terrain by Computational Fluid Dynamics". Energies 12, nr 7 (5.04.2019): 1311. http://dx.doi.org/10.3390/en12071311.
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With rising levels of wind power penetration in global electricity production, the relevance of wind power prediction is growing. More accurate forecasts reduce the required total amount of energy reserve capacity needed to ensure grid reliability and the risk of penalty for wind farm operators. This study analyzes the Computational Fluid Dynamics (CFD) software WindSim regarding its ability to perform accurate wind power predictions in complex terrain. Simulations of the wind field and wind farm power output in the Swiss Jura Mountains at the location of the Juvent Wind Farm during winter were performed. The study site features the combined presence of three complexities: topography, heterogeneous vegetation including forest, and interactions between wind turbine wakes. Hence, it allows a comprehensive evaluation of the software. Various turbulence models, forest models, and wake models, as well as the effects of domain size and grid resolution were evaluated against wind and power observations from nine Vestas V90’s 2.0-MW turbines. The results show that, with a proper combination of modeling options, WindSim is able to predict the performance of the wind farm with sufficient accuracy.
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Teske, Milton E., i Harold W. Thistle. "The Influence of Forest Canopies on the Decay of Aircraft Wake Vortices and Downwash". Transactions of the ASABE 61, nr 6 (2018): 1857–66. http://dx.doi.org/10.13031/trans.12921.
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Abstract. The dominant mechanism driving aerially released spray material toward the ground is the flow field generated by the aircraft, in the form of either aircraft vortices or downwash. In AGDISP, the initial strength of this flow field is reduced over time by a simple damping mechanism tied to atmospheric turbulence. When these flow fields enter a forest canopy, the scrubbing impact of the canopy structure further reduces their strength and influences the behavior of spray droplets released into the canopy. This study uses a simple model to approximate the canopy damping mechanism and then applies this model to a recent canopy dataset in an effort to validate the approach proposed. Keywords: Aerial spray, AGDISP, Aircraft vortices, Canopy penetration, Damping, Downwash.
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Bentsen, Lars Ødegaard, Narada Dilp Warakagoda, Roy Stenbro i Paal Engelstad. "Wind Park Power Prediction: Attention-Based Graph Networks and Deep Learning to Capture Wake Losses". Journal of Physics: Conference Series 2265, nr 2 (1.05.2022): 022035. http://dx.doi.org/10.1088/1742-6596/2265/2/022035.
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Abstract With the increased penetration of wind energy into the power grid, it has become increasingly important to be able to predict the expected power production for larger wind farms. Deep learning (DL) models can learn complex patterns in the data and have found wide success in predicting wake losses and expected power production. This paper proposes a modular framework for attention-based graph neural networks (GNN), where attention can be applied to any desired component of a graph block. The results show that the model significantly outperforms a multilayer perceptron (MLP) and a bidirectional LSTM (BLSTM) model, while delivering performance on-par with a vanilla GNN model. Moreover, we argue that the proposed graph attention architecture can easily adapt to different applications by offering flexibility into the desired attention operations to be used, which might depend on the specific application. Through analysis of the attention weights, it was showed that employing attention-based GNNs can provide insights into what the models learn. In particular, the attention networks seemed to realise turbine dependencies that aligned with some physical intuition about wake losses.
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Nirogi, Ramakrishna, Vijay Benade, Renny Abraham, Jagadeesh Babu Thentu, Surendra Petlu, Santosh Kumar Pandey, Rajesh Kumar Badange, Kumar Bojja i Ramkumar Subramanian. "0051 Samelisant, a H3 Receptor Inverse Agonist for the Potential Treatment of Excessive Daytime Sleepiness in Parkinson’s Disease". SLEEP 46, Supplement_1 (1.05.2023): A23—A25. http://dx.doi.org/10.1093/sleep/zsad077.0051.
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Abstract Introduction Samelisant (SUVN-G3031) is a potent and selective histamine 3 receptor (H3R) inverse agonist with hH3 Ki of 8.7 nM. Samelisant exhibited desired pharmacokinetic properties and favorable brain penetration in rodents. Preclinical studies demonstrated samelisant produced wake promoting and anticataplectic effects in orexin knockout mice. Additionally samelisant modulated neurotransmitters like histamine in brain indicating neurochemical basis for wake promoting effects. Excessive daytime sleepiness (EDS) estimated to affect 20-50% of patients with Parkinson’s disease (PD). Although non-treated PD patients exhibit EDS and sleep attacks, it is often associated with use of dopamine (DA) agonists, especially the recent non-ergot DA D2/3 agonists. Samelisant is currently being evaluated in a Phase-2 study as monotherapy for the treatment of EDS in patients with narcolepsy with or without cataplexy (ClinicalTrials.gov Identifier: NCT04072380). Methods Hemiparkinsonism was induced in male Wistar rats by injecting 6-OHDA (12 µg/4 µL) unilaterally into the medial forebrain bundle, and telemetric device was implanted to monitor EEG, EMG and activity. Animals were allowed to recover for 3 weeks prior to initiating EEG recordings. Basal EEG was recorded for 1 hour prior to samelisant administration and EEG acquisition was continued for 6 hours post treatment. After a washout period of 1 week, rats were administered with the quinpirole (30 µg/kg, i.p.) followed by samelisant and EEG acquisition was continued for 6 hours. EEG recordings were processed for sleep stages using NeuroScore and sleep sign software (DSI, MN, USA). Results Hemiparkinsonian animals showed decrease in wake and increase in sleep time during dark phase. Treatment with samelisant (10 and 30 mg/kg, p.o.) produced significant increase in cumulative wake period during first 3 hours post treatment. Treatment with quinpirole in hemiparkinsonian rats produced decrease in wake and increase in sleep time. Treatment with samelisant produced dose- dependent increase in wake with decrease in REM and NREM periods in quinpirole treated hemiparkinsonian rats. Conclusion The results from current preclinical studies indicate that samelisant may have a potential utility for the treatment of excessive daytime sleepiness in PD patients. Support (if any)
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Lopez-Aguilera, Elena, Ilker Demirkol, Eduard Garcia-Villegas i Josep Paradells. "IEEE 802.11-Enabled Wake-Up Radio: Use Cases and Applications". Sensors 20, nr 1 (21.12.2019): 66. http://dx.doi.org/10.3390/s20010066.
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IEEE 802.11 is one of the most commonly used radio access technologies, being present in almost all handheld devices with networking capabilities. However, its energy-hungry communication modes are a challenge for the increased battery lifetime of such devices and are an obstacle for its use in battery-constrained devices such as the ones defined by many Internet of Things applications. Wake-up Radio (WuR) systems have appeared as a solution for increasing the energy efficiency of communication technologies by employing a secondary low-power radio interface, which is always in the active state and switches the primary transceiver (used for main data communication) from the energy-saving to the active operation mode. The high market penetration of IEEE 802.11 technology, together with the benefits that WuR systems can bring to this widespread technology, motivates this article’s focus on IEEE 802.11-based WuR solutions. More specifically, we elaborate on the feasibility of such IEEE 802.11-based WuR solutions, and introduce the latest standardization efforts in this IEEE 802.11-based WuR domain, IEEE 802.11ba, which is a forthcoming IEEE 802.11 amendment, discussing its main features and potential use cases. As a use case consisting of green Wi-Fi application, we provide a proof-of-concept smart plug system implemented by a WuR that is activated remotely using IEEE 802.11 devices, evaluate its monetary and energy savings, and compare it with commercially available smart plug solutions. Finally, we discuss novel applications beyond the wake-up functionality that IEEE 802.11-enabled WuR devices can offer using a secondary radio, as well as applications that have not yet been considered by IEEE 802.11ba. As a result, we argue that the IEEE 802.11-based WuR solution will support a wide range of devices and deployments, for both low-rate and low-power communications, as well as high-rate transmissions.
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Showkat Ali, Syamir Alihan, Mahdi Azarpeyvand i Carlos Roberto Ilário da Silva. "Trailing-edge flow and noise control using porous treatments". Journal of Fluid Mechanics 850 (2.07.2018): 83–119. http://dx.doi.org/10.1017/jfm.2018.430.
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This paper is concerned with the application of porous treatments as a means of flow and aerodynamic noise reduction. An extensive experimental investigation is undertaken to study the effects of flow interaction with porous media, in particular in the context of the manipulation of flow over blunt trailing edges and attenuation of vortex shedding. Comprehensive boundary layer and wake measurements have been carried out for a long flat plate with solid and porous blunt trailing edges. Unsteady velocity and surface pressure measurements have also been performed to gain an in-depth understanding of the changes to the energy–frequency content and coherence of the boundary layer and wake structures as a result of the flow interaction with a porous treatment. Results have shown that permeable treatments can effectively delay the vortex shedding and stabilize the flow over the blunt edge via mechanisms involving flow penetration into the porous medium and discharge into the near-wake region. It has also been shown that the porous treatment can effectively destroy the spanwise coherence of the boundary layer structures and suppress the velocity and pressure coherence, particularly at the vortex shedding frequency. The flow–porous scrubbing and its effects on the near-wall and large coherent structures have also been studied. The emergence of a quasi-periodic recirculating flow field inside highly permeable surface treatments has also been investigated. Finally, the paper has identified several important mechanisms concerning the application of porous treatments for aerodynamic and aeroacoustic purposes, which can help more effective and tailored designs for specific applications.
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Zhou, Yao-zhi, Feng Xiao, Qing-lian Li i Chen-yang Li. "Simulation of Elliptical Liquid Jet Primary Breakup In Supersonic Crossflow". International Journal of Aerospace Engineering 2020 (5.06.2020): 1–12. http://dx.doi.org/10.1155/2020/6783038.
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The study of elliptical liquid jets in supersonic flow in a Mach 2.0 is performed numerically. The primary breakup process of the elliptical liquid jet is simulated for a Weber number 223, liquid/gas flux momentum 4.0. The aspect ratios of elliptical geometries are set to be 0.25, 0.5, 1, 2, and 5. The results show a remarkable difference in liquid jet disintegration morphology at different aspect ratios. Under supersonic crossflow conditions, the elliptical liquid jet shows more breakup characteristics than the round liquid jet. As the aspect ratio grows, the penetration depth decreases. The elliptical liquid jet with AR=0.25 has the largest penetration depth in all cases. Moreover, the round jet has a maximum spreading angle of 50.2°. The changing trends of the column breakup length both x direction and y direction are similar. The elliptical jet at a lower aspect ratio has a shorter breakup length due to the narrower windward area. The liquid jet has a pair of larger horseshoe vortex structure and a wider wake region at a higher aspect ratio. Two pairs of reversal vortex pairs with obvious characteristics can be observed in all the simulations.
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Gomez, Jishu Mary, i Prabhakar Karthikeyan Shanmugam. "Flexible Power Point Tracking Using a Neural Network for Power Reserve Control in a Grid-Connected PV System". Energies 15, nr 21 (4.11.2022): 8234. http://dx.doi.org/10.3390/en15218234.
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Renewable energy penetration in the global energy sector is in a state of steady growth. A major criterion imposed by the regulatory boards in the wake of electronic-driven power systems is frequency regulation capability. As more rooftop PV systems are under installation, the inertia response of the power utility system is descending. The PV systems are not equipped inherently with inertial or governor control for unseen frequency deviation scenarios. In the proposed method, inertial and droop frequency control is implemented by creating the necessary power reserve by the derated operation of the PV system. While, traditionally, PV systems operate in normal MPPT mode, a derated PV system follows a flexible power point tracking (FPPT) algorithm for creating virtual energy storage. The point of operation for the FPPT of the PV is determined by using a neural network block set available in MATLAB. For the verification of the controller, it is applied to a PV array in a modified IEEE-13 bus system modeled in the MATLAB/Simulink platform. The simulation results prove that when the proposed control is applied to the test network with renewable energy penetration, there is an improved system inertia response.
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Patel, M., V. Darade, C. Solanki i T. Thaker. "Development of Empirical Correlation between Standard Penetration Test and Shear Wave Velocity for Dahej Region". Disaster Advances 15, nr 10 (25.09.2022): 1–9. http://dx.doi.org/10.25303/1510da01009.
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The earthquake that took place at Bhuj in 2001 acted as a wake-up call that triggered a review of the seismic risk in several areas of the nation. Seismic microzonation analysis benefits greatly from in-depth investigations of both geotechnical and geophysical conditions. This study aims to create correlations between the conventional SPT-N value and the s - wave velocity for different soil conditions in the Dahej port. For the geophysical site characterization, the shear wave velocity models were created using the MASW method and the bundle of software known as SeisImager/SW was used to perform an analysis of the test results. Moreover, the correlations are compared to the relationships established by other scientists. The suggested correlations will be beneficial for the congested areas of the vibrant area, where testing is neither practical nor cost-effective. Such empirical correlations will be used for other similar geological and geophysical site conditions when they have gone through the essential validation stages. To analyze the ground response and a hazard assessment of the study region, the obtained correlations can be used.
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Raju, M. S., i W. A. Sirignano. "Spray Computations in a Centerbody Combustor". Journal of Engineering for Gas Turbines and Power 111, nr 4 (1.10.1989): 710–18. http://dx.doi.org/10.1115/1.3240317.
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A hybrid Eulerian–Lagrangian method is employed to model the reactive flow field of a centerbody combustor. The unsteady two-dimensional gas-phase equations are represented in Eulerian coordinates and liquid-phase equations are formulated in Lagrangian coordinates. The gas-phase equations based on the conservation of mass, momentum, and energy are supplemented by turbulence and combustion models. The vaporization model takes into account the transient effects associated with the droplet heating and liquid-phase internal circulation. The integration scheme is based on the TEACH algorithm for gas-phase equations, the Runge-Kutta method for liquid-phase equations, and linear interpolation between the two coordinate systems. The calculations show that the droplet penetration and recirculation characteristics are strongly influenced by the gas- and liquid-phase interaction in such a way that most of the vaporization process is confined to the wake region of the centerbody, thereby improving the flame stabilization properties of the flow field.
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Rahman, Imran, Pandian M. Vasant, Balbir Singh Mahinder Singh i M. Abdullah-Al-Wadud. "Swarm Intelligence-Based Smart Energy Allocation Strategy for Charging Stations of Plug-In Hybrid Electric Vehicles". Mathematical Problems in Engineering 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/620425.
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Recent researches towards the use of green technologies to reduce pollution and higher penetration of renewable energy sources in the transportation sector have been gaining popularity. In this wake, extensive participation of plug-in hybrid electric vehicles (PHEVs) requires adequate charging allocation strategy using a combination of smart grid systems and smart charging infrastructures. Daytime charging stations will be needed for daily usage of PHEVs due to the limited all-electric range. Intelligent energy management is an important issue which has already drawn much attention of researchers. Most of these works require formulation of mathematical models with extensive use of computational intelligence-based optimization techniques to solve many technical problems. In this paper, gravitational search algorithm (GSA) has been applied and compared with another member of swarm family, particle swarm optimization (PSO), considering constraints such as energy price, remaining battery capacity, and remaining charging time. Simulation results obtained for maximizing the highly nonlinear objective function evaluate the performance of both techniques in terms of best fitness.
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MORI, YOSHITAKA, SHYUJI FUKUMOCHI, YOSHIKAZU HAMA, KIMINORI KONDO, YASUHIKO SENTOKU i YONEYOSHI KITAGAWA. "PRESENT STATUS OF TABLE-TOP SHORT-PULSE BEAT WAVE ELECTRON ACCELERATION LASER SYSTEM". International Journal of Modern Physics B 21, nr 03n04 (10.02.2007): 572–78. http://dx.doi.org/10.1142/s0217979207042379.
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Development status of a double-line table top beat wave electron laser acceleration system is discussed. The advantage of beat wave driven laser accelerator is described here using 1D-PIC simulation comparing with a single laser wake-field acceleration concerning an electric field excitation. As for experimental status, double line different color pulses (central wavelength with 795 nm and 805 nm, respectively) were successfully amplified to 30 mJ as a single overlapping beam with a hybrid chirped pulse amplification system, Optical Parametric Chirped Pulse Amplification (OPCPA) and Ti -Sap multi-pass amplifier pumped by YAG lasers, and then compressed into ps time duration. Amplified double-color pulse drove beating pulse bunches of 300 fs time duration which was identified by an autocorrelation trace. In order to investigate plasma sustainment in cm order, amplified beam illuminated a 2 cm in-length glass capillary and then the laser penetration in the capillary was confirmed.
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Gao, Tianyun, Jianhan Liang, Mingbo Sun i Zhan Zhong. "Dynamic combustion characteristics in a rectangular supersonic combustor with single-side expansion". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 231, nr 10 (3.08.2016): 1862–72. http://dx.doi.org/10.1177/0954410016662062.
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Dynamic combustion characteristics of a rectangular scramjet combustor with single-side expansion were studied experimentally and numerically. Experiments were implemented with an isolator entrance Mach number of 3.46, and an air stagnation temperature of 1430 K. Ethylene was utilized to fuel the combustor over an equivalence ratio range of 0.20 < φ < 0.63. Results indicated that the combustion modes varied from different equivalence ratios. For an intermediate φ = 0.375, an intermittent dynamic combustion occurred. During the dynamic process, the flame sometimes stabilized in the jet wake of the top cavity, and at other time it oscillated between dual parallel cavities. The pseudo-shock train traveled periodically along the length of the combustor, and the penetration depths of the two injectors exchanged. Quantitative analysis illustrated that the average frequency of unsteady combustion was approximately 200 Hz. The reason for the occurrence of the self-sustained dynamic process was related to the interactions between the shock-induced separated region and heat release.
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Wu, Yuan-Kang, Wen-Chin Wu i Jyun-Jie Zeng. "Key Issues on the Design of an Offshore Wind Farm Layout and Its Equivalent Model". Applied Sciences 9, nr 9 (9.05.2019): 1911. http://dx.doi.org/10.3390/app9091911.
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Offshore wind farms will have larger capacities in the future than they do today. Thus, the costs that are associated with the installation of wind turbines and the connection of power grids will be much higher, thus the location of wind turbines and the design of internal cable connections will be even more important. A large wind farm comprises of hundreds of wind turbines. Modeling each using a complex model leads to long simulation times—especially in transient response analyses. Therefore, in the future, simulations of power systems with a high wind power penetration must apply the equivalent wind-farm model to reduce the burden of calculation. This investigation examines significant issues around the optimal design of a modern offshore wind farm layout and its equivalent model. According to a review of the literature, the wake effect and its modeling, layout optimization technologies, cable connection design, and wind farm reliability, are significant issues in offshore wind farm design. This investigation will summarize these important issues and present a list of factors that strongly influence the design of an offshore wind farm.
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Olivera, Gabriela C., Leonie Vetter, Chiara Tesoriero, Federico Del Gallo, Gustav Hedberg, Juan Basile i Martin E. Rottenberg. "Role of T cells during the cerebral infection with Trypanosoma brucei". PLOS Neglected Tropical Diseases 15, nr 9 (29.09.2021): e0009764. http://dx.doi.org/10.1371/journal.pntd.0009764.
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The infection by Trypanosoma brucei brucei (T.b.b.), a protozoan parasite, is characterized by an early-systemic stage followed by a late stage in which parasites invade the brain parenchyma in a T cell-dependent manner. Here we found that early after infection effector-memory T cells were predominant among brain T cells, whereas, during the encephalitic stage T cells acquired a tissue resident memory phenotype (TRM) and expressed PD1. Both CD4 and CD8 T cells were independently redundant for the penetration of T.b.b. and other leukocytes into the brain parenchyma. The role of lymphoid cells during the T.b.b. infection was studied by comparing T- and B-cell deficient rag1-/- and WT mice. Early after infection, parasites located in circumventricular organs, brain structures with increased vascular permeability, particularly in the median eminence (ME), paced closed to the sleep-wake regulatory arcuate nucleus of the hypothalamus (Arc). Whereas parasite levels in the ME were higher in rag1-/- than in WT mice, leukocytes were instead reduced. Rag1-/- infected mice showed increased levels of meca32 mRNA coding for a blood /hypothalamus endothelial molecule absent in the blood-brain-barrier (BBB). Both immune and metabolic transcripts were elevated in the ME/Arc of WT and rag1-/- mice early after infection, except for ifng mRNA, which levels were only increased in WT mice. Finally, using a non-invasive sleep-wake cycle assessment method we proposed a putative role of lymphocytes in mediating sleep alterations during the infection with T.b.b. Thus, the majority of T cells in the brain during the early stage of T.b.b. infection expressed an effector-memory phenotype while TRM cells developed in the late stage of infection. T cells and parasites invade the ME/Arc altering the metabolic and inflammatory responses during the early stage of infection and modulating sleep disturbances.
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Gamba, Mirko, i M. Godfrey Mungal. "Ignition, flame structure and near-wall burning in transverse hydrogen jets in supersonic crossflow". Journal of Fluid Mechanics 780 (3.09.2015): 226–73. http://dx.doi.org/10.1017/jfm.2015.454.
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We have investigated the properties of transverse sonic hydrogen jets in high-temperature supersonic crossflow at jet-to-crossflow momentum flux ratios$J$between 0.3 and 5.0. The crossflow was held fixed at a Mach number of 2.4, 1400 K and 40 kPa. Schlieren and$\text{OH}^{\ast }$chemiluminescence imaging were used to investigate the global flame structure, penetration and ignition points;$\text{OH}$planar laser-induced fluorescence imaging over several planes was used to investigate the instantaneous reaction zone. It is found that$J$indirectly controls many of the combustion processes. Two regimes for low (${<}1$) and high (${>}3$)$J$are identified. At low$J$, the flame is lifted and stabilizes in the wake close to the wall possibly by autoignition after some partial premixing occurs; most of the heat release occurs at the wall in regions where$\text{OH}$occurs over broad regions. At high$J$, the flame is anchored at the upstream recirculation region and remains attached to the wall within the boundary layer where$\text{OH}$remains distributed over broad regions; a strong reacting shear layer exists where the flame is organized in thin layers. Stabilization occurs in the upstream recirculation region that forms as a consequence of the strong interaction between the bow shock, the jet and the boundary layer. In general, this interaction – which indirectly depends on$J$because it controls the jet penetration – dominates the fluid dynamic processes and thus stabilization. As a result, the flow field may be characterized by a flame structure characteristic of multiple interacting combustion regimes, from (non-premixed) flamelets to (partially premixed) distributed reaction zones, thus requiring a description based on a multi-regime combustion formulation.
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RODGERS, JEAN. "Trypanosomiasis and the brain". Parasitology 137, nr 14 (23.12.2009): 1995–2006. http://dx.doi.org/10.1017/s0031182009991806.
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SUMMARYNeurological involvement following trypanosome infection has been recognised for over a century. However, there are still many unanswered questions concerning the mechanisms used by the parasite to gain entry to the CNS and the pathogenesis of the resulting neuroinflammatory reaction. There is a paucity of material from human cases of the disease therefore the majority of current research relies on the use of animal models of trypanosome infection. This review reports contemporary knowledge, from both animal models and human samples, regarding parasite invasion of the CNS and the neuropathological changes that accompany trypanosome infection and disease progression. The effects of trypanosomes on the blood-brain barrier are discussed and possible key molecules in parasite penetration of the barrier highlighted. Changes in the balance of CNS cytokines and chemokines are also described. The article closes by summarising the effects of trypanosome infection on the circadian sleep-wake cycle, and sleep structure, in relation to neuroinflammation and parasite location within the CNS. Although a great deal of progress has been made in recent years, the advent and application of sophisticated analysis techniques, to decipher the complexities of HAT pathogenesis, herald an exciting and rewarding period for advances in trypanosome research.
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Benade, V., S. Daripelli, S. Petlu, R. Subramanian, G. Bhyrapuneni, A. Shinde, M. Rasheed, P. Jayarajan, P. Choudakari i R. Nirogi. "0008 SUVN-G3031, A Histamine H3 Receptor Inverse Agonist Produces Robust Wake Promoting and Anticataplectic Activity in Orexin Knockout Mice". Sleep 43, Supplement_1 (kwiecień 2020): A3. http://dx.doi.org/10.1093/sleep/zsaa056.007.
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Abstract Introduction Narcolepsy is a sleep disorder characterized by excessive daytime sleepiness, sleep paralysis, hallucinations, and in some cases episodes of cataplexy. Results from animal studies indicate the involvement of deficient orexin transmission in narcolepsy which can be circumvented by the activation of histaminergic neurons. SUVN-G3031 is a potent and selective histamine H3 receptor inverse agonist with hKi of 8.7 nM and shows less than 50% inhibition at 1 µM against 70 other targets. SUVN-G3031 exhibited excellent pharmacokinetic properties and brain penetration in preclinical species. Oral administration of SUVN-G3031 produces significant increase in histamine, dopamine and norepinephrine levels in the rat cortex. Long-term safety studies in animals have been successfully completed without any concern for further development of SUVN-G3031. In the present study, the effects of SUVN-G3031 were evaluated in orexin knockout mice, a reliable animal model of narcolepsy as a proof-of-concept study for the treatment of narcolepsy with and without cataplexy. Methods Male orexin knockout mice (10 - 15 weeks old, 25 - 35 g at the time of surgery) were implanted with telemetric device for simultaneous monitoring of electroencephalography (EEG) and electromyography. Animals were allowed surgical recovery of 3 weeks prior to EEG recording. Effects of SUVN-G3031 (3 and 10 mg/kg, p.o.) were evaluated during active period of animals. Results SUVN-G3031 produced significant increase in wakefulness with concomitant decrease in non-rapid eye movement sleep in orexin knockout mice. SUVN-G3031 also significantly decreased the number of cataplectic episodes in orexin knockout mice. Conclusion Results from the current preclinical study provide a strong basis for the utility of SUVN-G3031 for the treatment of narcolepsy with and without cataplexy. SUVN-G3031 is currently being evaluated in a Phase 2 study as monotherapy for the treatment of narcolepsy with and without cataplexy (ClinicalTrials.gov Identifier: NCT04072380). Support None
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Dai, Jianfeng, Yi Tang i Jun Yi. "Adaptive Gains Control Scheme for PMSG-Based Wind Power Plant to Provide Voltage Regulation Service". Energies 12, nr 4 (24.02.2019): 753. http://dx.doi.org/10.3390/en12040753.
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High-penetration wind power will count towards a significant portion of future power grid. This significant role requires wind turbine generators (WTGs) to contribute to voltage and reactive power support. The maximum reactive power capacity (MRPC) of a WTG depends on its current input wind speed, so that the reactive power regulating ability of the WTG itself and adjacent WTGs are not necessarily identical due to the variable wind speed and the wake effect. This paper proposes an adaptive gains control scheme (AGCS) for a permanent magnet synchronous generator (PMSG)-based wind power plant (WPP) to provide a voltage regulation service that can enhance the voltage-support capability under load disturbance and various wind conditions. The droop gains of the voltage controller for PMSGs are spatially and temporally dependent variables and adjusted adaptively depending on the MRPC which are a function of the current variable wind speed. Thus, WTGs with lower input wind speed can provide greater reactive power capability. The proposed AGCS is demonstrated by using a PSCAD/EMTDC simulator. It can be concluded that, compared with the conventional fixed-gains control scheme (FGCS), the proposed method can effectively improve the voltage-support capacity while ensuring stable operation of all PMSGs in WPP, especially under high wind speed conditions.
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Mohammed, Ali Abdulwahhab, i Haitham A. Anwer. "A New Method Encryption and Decryption". Webology 18, nr 1 (1.01.2021): 20–31. http://dx.doi.org/10.14704/web/v18i1/web18002.
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In all times manual investigation and decryption of enciphered archives is a repetitive and mistake inclined work. Regularly considerably in the wake of investing a lot of energy in a specific figure, no decipherment can be found. Computerizing the unscrambling of different kinds of figures makes it conceivable to filter through the huge number of encoded messages found in libraries and files. We propose in this paper new algorithm has been made to encrypt the information; this algorithm works to shield information from robbery and can't be decrypted in the text. It is taken care of precisely to very accurately to avoid any penetration to arrive at the first text. It tends to be used in companies or some other system; however, it takes a long time to encrypt it. To the first text when encryption to ensure the assurance of information in full and security. Encrypted text contains a unique key, even when stolen. The private key can't be decrypted by the specialist and licensed by the maker of the code in order to protect the data in an excellent manner. While demonstrating in addition much stronger security guarantees with regards to Differential/ direct assaults. Specifically, we are can to provide new Method Encryption and Decryption with strong bounds for all versions.
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Sivaccumar, Jwala P., Emanuela Iaccarino, Angela Oliver, Maria Cantile, Pierpaolo Olimpieri, Antonio Leonardi, Menotti Ruvo i Annamaria Sandomenico. "Production in Bacteria and Characterization of Engineered Humanized Fab Fragment against the Nodal Protein". Pharmaceuticals 16, nr 8 (10.08.2023): 1130. http://dx.doi.org/10.3390/ph16081130.
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Drug development in recent years is increasingly focused on developing personalized treatments based on blocking molecules selective for therapeutic targets specifically present in individual patients. In this perspective, the specificity of therapeutic targets and blocking agents plays a crucial role. Monoclonal antibodies (mAbs) and their surrogates are increasingly used in this context thanks to their ability to bind therapeutic targets and to inhibit their activity or to transport bioactive molecules into the compartments in which the targets are expressed. Small antibody-like molecules, such as Fabs, are often used in certain clinical settings where small size and better tissue penetration are required. In the wake of this research trend, we developed a murine mAb (3D1) neutralizing the activity of Nodal, an oncofetal protein that is attracting an ever-increasing interest as a selective therapeutic target for several cancer types. Here, we report the preparation of a recombinant Fab of 3D1 that has been humanized through a computational approach starting from the sequence of the murine antibody. The Fab has been expressed in bacterial cells (1 mg/L bacterial culture), biochemically characterized in terms of stability and binding properties by circular dichroism and bio-layer interferometry techniques and tested in vitro on Nodal-positive cancer cells.
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Reinhard, M., A. A. Korobkin i M. J. Cooker. "Water entry of a flat elastic plate at high horizontal speed". Journal of Fluid Mechanics 724 (29.04.2013): 123–53. http://dx.doi.org/10.1017/jfm.2013.155.
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AbstractThe two-dimensional problem of an elastic-plate impact onto an undisturbed surface of water of infinite depth is analysed. The plate is forced to move with a constant horizontal velocity component which is much larger than the vertical velocity component of penetration. The small angle of attack of the plate and its vertical velocity vary in time, and are determined as part of the solution, together with the elastic deflection of the plate and the hydrodynamic loads within the potential flow theory. The boundary conditions on the free surface and on the wetted part of the plate are linearized and imposed on the initial equilibrium position of the liquid surface. The wetted part of the plate depends on the plate motion and its elastic deflection. To determine the length of the wetted part we assume that the spray jet in front of the advancing plate is negligible. A smooth separation of the free-surface flow from the trailing edge is imposed. The wake behind the moving body is included in the model. The plate deflection is governed by Euler’s beam equation, subject to free–free boundary conditions. Four different regimes of plate motion are distinguished depending on the impact conditions: (a) the plate becomes fully wetted; (b) the leading edge of the plate touches the water surface and traps an air cavity; (c) the free surface at the forward contact point starts to separate from the plate; (d) the plate exits the water. We could not detect any impact conditions which lead to steady planing of the free plate after the impact. It is shown that a large part of the total energy in the fluid–plate interaction leaves the main bulk of the liquid with the spray jet. It is demonstrated that the flexibility of the plate may increase the hydrodynamic loads acting on it. The impact loads can cause large bending stresses, which may exceed the yield stress of the plate material. The elastic vibrations of the plate are shown to have a significant effect on the fluid flow in the wake.
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Cramer, Christina, Brandi Page, Jeffrey S. Wefel, Emily Dressler, Edward Ip, Steve Rapp, Edward Shaw, Kathryn Weaver, Glenn Lesser i Michael Chan. "NCOG-24. WAKE FOREST NCORP RESEARCH BASE FEASIBILITY STUDY OF RAMIPRIL FOR PREVENTING COGNITIVE DECLINE IN GLIOBLASTOMA PATIENTS RECEIVING BRAIN RADIOTHERAPY (WF-1801)". Neuro-Oncology 22, Supplement_2 (listopad 2020): ii134. http://dx.doi.org/10.1093/neuonc/noaa215.562.
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Abstract INTRODUCTION Chronic neuro-inflammation after brain radiotherapy (RT) contributes to radiation-induced cognitive decline (RICD). The renin angiotensin system (RAS) may mediate this inflammatory cascade after RT. Ramipril is an angiotensin-converting enzyme inhibitor used to treat hypertension and has good blood-brain barrier penetration. By blocking RAS activation, ramipril reduces neuro-inflammation and preclinical data show that ramipril administration during RT can prevent RICD. METHODS WF-1801 is an ongoing feasibility study that will enroll a total of 75 patients. Patients ≥ 18 with newly diagnosed and pathologically confirmed GBM who will receive chemoradiation are eligible. All participants take ramipril daily during RT and for 4 months thereafter. Ramipril is titrated from 1.25mg to 5mg daily over 3 weeks. A cognitive battery that includes the Hopkins Verbal Learning Test-Revised (HVLT-R), Trail Making Test (TMT), and Controlled Oral Word Association test (COWA) is administered at baseline, end of RT, and 1-month and 4-months post-RT. The co-primary endpoints are retention rate (with retention defined as compliance with > 75% of drug therapy doses) and neurocognitive function at 1-month post-RT. To estimate the effect of ramipril on cognitive function, performance on the cognitive battery will be compared to a historical control (cognitive data from the control arm of RTOG 0825). ApoE genotyping is being performed as a correlative study. RESULTS 31 of a planned 75 participants have been enrolled over 14 months. 20 of 31 (64.5%) are male. 21 (67.7%) are between the age of 40-64. 20 (95.6%) are white and 29 (93.6%) are not Hispanic or Latino. CONCLUSION Despite a pause in accrual due to COVID-19, we are easily meeting planned accrual goals. Community oncology-based clinical trials of interventions to prevent cognitive toxicity appear to be feasible. GBM patients seem eager to enroll in studies seeking to prevent cognitive decline. Supported by NCI grant UG1CA189824.
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Dai, Jianfeng, Lei Wan, Ping Chang, Lin Liu i Xia Zhou. "Reactive Voltage Control Strategy for PMSG-Based Wind Farm Considering Reactive Power Adequacy and Terminal Voltage Balance". Electronics 11, nr 11 (2.06.2022): 1766. http://dx.doi.org/10.3390/electronics11111766.
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To improve the ability of the power system to accommodate high penetration wind power, wind turbines (WTs) need to realize the mode transformation from grid-following to grid-forming, thus actively participating in the voltage regulation of the power grid with a high proportion of wind power. In this work, a reactive voltage control strategy for wind farms considering reactive power adequacy and terminal voltage balance is proposed. Firstly, the expression of the maximum reactive power regulation capacity of WT, namely reactive power adequacy, is derived under the complete wind condition based on the mathematical model and operating characteristics of WT, to study the influence of wake effect on reactive power adequacy of a wind farm. Then, the point of common coupling (PCC) voltage and terminal voltage are expressed analytically based on the radiative topology equivalent model of a wind farm, to analyze the influence of electrical distance on active power loss of wind farm. Finally, the calculation method of the adaptive gain coefficient of WT is put forward, which comprehensively considers the input wind speed and the electrical distance, to regulate the PCC voltage and terminal voltage simultaneously. The comprehensive effectiveness of the proposed strategy is demonstrated on a permanent magnet synchronous generator (PMSG)-based wind farm integration simulation model. While supporting the PCC voltage, the proposed strategy maintains the balance of the terminal voltage in the wind farm, thereby improving the friendliness of wind power grid connection.
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Zhang, Jincheng, Zhenguo Wang, Mingbo Sun, Hongbo Wang, Chaoyang Liu i Jiangfei Yu. "Effect of the Backward Facing Step on a Transverse Jet in Supersonic Crossflow". Energies 13, nr 16 (12.08.2020): 4170. http://dx.doi.org/10.3390/en13164170.
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A transverse jet in the supersonic crossflow is one of the most promising injection schemes in scramjet, where the control or enhancement of jet mixing is a critical issue. In this paper, the effect of the backward facing step on the characteristics of jet mixing was investigated by three-dimensional large eddy simulation (LES). The simulation in the flat plate configuration (step height of 0) was performed as the baseline case to verify the computation framework. The distribution of the velocity and pressure obtained by the LES agreed well with the experiment, which shows the reliability of the LES code. Then, two steps with a height of 1.0D and 1.58D (D is the injector diameter) were numerically compared to the non-step baseline case. The comparison of the three cases illustrates the effect of the large-scale recirculation region on the variable distribution, and shock and vortex structures in the flow field. In the windward region, the shear layers become thicker, and the convection velocity of the shear vortexes reduces. In the leeward region, the wake vortices almost disappear while the counterrotating vortex pairs (CVPs) expand in the spanwise direction. In the area upstream of the jet, the separation bubble works with the upstream large-scale recirculation zone to entrain the jet into the upstream near-wall zone. At last, a comparison of the overall mixing performance of the three cases revealed that the penetration depth and mixing efficiency increased with the step height increasing.
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Philip, Reni, Farah Naaz Fathima, Twinkle Agarwal i Aman Andews. "Mobile phone usage among adults with type 2 diabetes mellitus in an urban sub-center in India: a cross sectional study". International Journal Of Community Medicine And Public Health 6, nr 9 (27.08.2019): 3829. http://dx.doi.org/10.18203/2394-6040.ijcmph20193979.
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Background: Diabetes education enables patients to be more involved in their care and helps in delaying complications. Mobile phone penetration in rural India is high and provides us with an opportunity to use mobile phones in delivering diabetes education messages. So the objective of the study is to study mobile phone usage among adults with type 2 diabetes mellitus in an urban sub-center.Methods: A list of all the patients with type 2 diabetes mellitus was obtained from the health management information system records of the rural health and center and structured interview schedule was administered. Universal sampling method was used.Results: Around half of the diabetic patients included in the study (55.6%) owned a personal mobile phone, 44.4% had access to a smart phone in the household and 35.4% had internet connectivity on their phone. Predominant mobile phone usages included making phone calls (54.4%), short messaging services (44.8%), listening to music (17.6), wake up alarm (14.4%) and capturing photos/videos (12.8%). Very few participants reported using mobile phone for health-related purposes (12.8%) and usage of health-related apps (10%). A large proportion of participant reported that they would like to receive reminders for clinic visits (54.0%), set alarms as reminders to improve adherence to medication (53.6). Chi-square test was used to find associations.Conclusions:Two-thirds of the patients with known diabetes have access to a mobile phone at the household level. Mobile phones have potential application to be used as channel for health education, reminders for clinic visits and to improve adherence to medication among patients with diabetes in urban India.
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Whiteman, C. David, Manuela Lehner, Sebastian W. Hoch, Bianca Adler, Norbert Kalthoff i Thomas Haiden. "Katabatically Driven Cold Air Intrusions into a Basin Atmosphere". Journal of Applied Meteorology and Climatology 57, nr 2 (luty 2018): 435–55. http://dx.doi.org/10.1175/jamc-d-17-0131.1.
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AbstractThe interactions between a katabatic flow on a plain and a circular basin cut into the plain and surrounded by an elevated rim were examined during a 5-h steady-state period during the Second Meteor Crater Experiment (METCRAX II) to explain observed disturbances to the nocturnal basin atmosphere. The approaching katabatic flow split horizontally around Arizona’s Meteor Crater below a dividing streamline while, above the dividing streamline, an ~50-m-deep stable layer on the plain was carried over the 30–50-m rim of the basin. A flow bifurcation occurred over or just upwind of the rim, with the lowest portion of the stable layer having negative buoyancy relative to the air within the crater pouring continuously over the crater’s upwind rim and accelerating down the inner sidewall. The cold air intrusion was deepest and coldest over the direct upwind crater rim. Cold air penetration depths varied around the inner sidewall depending on the temperature deficit of the inflow relative to the ambient environment inside the crater. A shallow but extremely stable cold pool on the crater floor could not generally be penetrated by the inflow and a hydraulic jump–like feature formed on the lower sidewall as the flow approached the cold pool. The upper nonnegatively buoyant portion of the stable layer was carried horizontally over the crater, forming a neutrally stratified, low–wind speed cavity or wake in the lee of the upwind rim that extended downward into the crater over the upwind sidewall.
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Ostermann, Florian, Rene Woszidlo, C. Navid Nayeri i C. Oliver Paschereit. "The interaction between a spatially oscillating jet emitted by a fluidic oscillator and a cross-flow". Journal of Fluid Mechanics 863 (23.01.2019): 215–41. http://dx.doi.org/10.1017/jfm.2018.981.
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This experimental study investigates the fundamental flow field of a spatially oscillating jet emitted by a fluidic oscillator into an attached cross-flow. Dominant flow structures, such as the jet trajectory and dynamics of streamwise vortices, are discussed in detail with the aim of understanding the interaction between the spatially oscillating jet and the cross-flow. The oscillating jet is ejected perpendicular to the cross-flow. A moveable stereoscopic particle image velocimetry (PIV) system is employed for the plane-by-plane acquisition of the flow field. The three-dimensional, time-resolved flow field is obtained by phase averaging the PIV results based on a pressure signal from inside the fluidic oscillator. The influence of velocity ratio and Strouhal number is assessed. Compared to a common steady wall-normal jet, the spatially oscillating jet penetrates to a lesser extent into the cross-flow’s wall-normal direction in favour of a considerable spanwise penetration. The flow field is dominated by streamwise-oriented vortices, which are convected downstream at the speed of the cross-flow. The vortex dynamics exhibits a strong dependence on the Strouhal number. For small Strouhal numbers, the spatially oscillating jet acts similar to a vortex-generating jet with a time-dependent deflection angle. Accordingly, it forms time-dependent streamwise vortices. For higher Strouhal numbers, the cross-flow is not able to follow the motion of the jet, which results in a quasi-steady wake that forms downstream of the jet. The results suggest that the flow field approaches a quasi-steady behaviour when further increasing the Strouhal number.
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MUSCULUS, MARK P. B. "Entrainment waves in decelerating transient turbulent jets". Journal of Fluid Mechanics 638 (1.10.2009): 117–40. http://dx.doi.org/10.1017/s0022112009990826.
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A simplified one-dimensional partial differential equation for the integral axial momentum flux during the deceleration phase of single-pulsed transient incompressible jets is derived and solved analytically. The wave speed of the derived first-order nonlinear wave equation shows that the momentum flux transient from the deceleration phase propagates downstream at twice the initial jet penetration rate. Transient-jet velocity data from the existing literature is shown to be consistent with this derivation, and an algebraic analytical solution matches the measured timing and decay of axial velocity after the deceleration transient. The solution also shows that a wave of increased entrainment accompanies the deceleration transient as it travels downstream through the jet. In the long-time limit, the peak entrainment rate at the leading edge of this ‘entrainment wave’ approaches an asymptotic value of three times that of the initial steady jet. The rate of approach to the asymptotic behaviour is controlled by the deceleration rate, which suggests that rate-shaping may be tailored to achieve a desired mixing state at a given time after the end of a single-pulsed jet. In the wake of the entrainment wave, the absolute entrainment rate eventually decays to zero. The local injected fluid concentration also decays, however, so that entrainment rate relative to the local concentration of injected fluid remains higher than in the initial steady jet. An analysis of diesel engine fuel-jets is provided as one example of a transient-jet application in which the considerable increase in the mixing rate after the deceleration phase has important implications.
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Kotova, G. Yu, i K. V. Krasnobaev. "Interaction of an accelerating layer with a cloud: formation of tails and cumulative jets". Monthly Notices of the Royal Astronomical Society 492, nr 2 (26.12.2019): 2229–35. http://dx.doi.org/10.1093/mnras/stz3604.
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ABSTRACT We consider the penetration of spherical dense cloud into a planar layer of gas that is in gravitational equilibrium in a constant field of gravity with acceleration W. We take into account the compressibility of the medium in contrast to the classical problem of a drop falling on the surface of an incompressible fluid. Our goal is to study the formation of cumulative jets in relation to the conditions on the borders of H ii regions. We determine those features of motion that would distinguish jet streams from inhomogeneities of a different origin. Our simulation has shown that cumulative jets may arise in the presence of an acceleration layer W. The gas in jet moves in the direction opposite to the initial velocity Vc. At the same time, there are both a cumulative jet and tails, teardrop-shaped condensations, caused, respectively, by gas inflow in the wake behind the cloud and the classical Rayleigh–Taylor instability. We assume the model, according to which the H ii RCW 82 region formed in an initially homogeneous cloud. In framework of this model, we estimated the characteristic time of a cumulative jet formation ts ≈ 0.15 Myr. This is less than the present age of the H ii RCW 82 region, which is about 0.4 Myr. From the obtained estimates, it follows that the conditions at the periphery of the H ii RCW 82 region are favourable for the manifestation of cumulative effects on scales of ∼1.4 × 1017 cm, which are significantly smaller than the layer thickness.
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Samuel, Kesiya Elizabeth, Beena Mary John i Rajesh P. Nair. "Soil Structure interaction of Laterally Loaded Piles". IOP Conference Series: Earth and Environmental Science 1161, nr 1 (1.04.2023): 012016. http://dx.doi.org/10.1088/1755-1315/1161/1/012016.
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Abstract The rapid development of the global economy has led to an increased energy demand throughout the world. More than 70% of the world’s energy consumption is from the use of fossil fuels. In the wake of rising global temperatures and increased carbon emissions, policymakers across the globe think about alternate and renewable ways of energy generation, among which wind energy is a promising energy source. Offshore wind turbines are new technologies and are challenging when it comes to their installation in harsh ocean environment as they are subjected to environmental loads caused by wind, wave and currents. These loads are then transferred to foundation. Monopiles are the most common foundations used in offshore wind turbines today and therefore its analysis is important. Monopiles are single large diameter tubular steel piles of diameter 3–7 m driven into the seabed with typical penetration depth of 25–30 m, and are subjected to lateral dynamic loads. Soil structure interaction of monopile is an important aspect to be considered in its design and for the present study, PLAXIS 3D geotechnical software is used for the soil-pile interaction and the corresponding displacement behaviour of the pile under study. The dynamic analysis due to the wave forces on the monopile is carried out using wave data off Gulf of Mannar, near the Tamil Nadu coast, and the embedment length of the pile is varied to study the effect of diameter of pile and embedment length on the displacement characteristics of the pile.
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Salah, Wa'el, i A. B. Hallak. "Analysis of ultrashort accelerated electron beam using the short-range monopole wake fields driven by the beam during its penetration in the drift tube of the laser-driven rf electron gun". Journal of Physics D: Applied Physics 38, nr 13 (17.06.2005): 2292–97. http://dx.doi.org/10.1088/0022-3727/38/13/031.
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Hague, Mark, i Marcello Vichi. "Southern Ocean Biogeochemical Argo detect under-ice phytoplankton growth before sea ice retreat". Biogeosciences 18, nr 1 (4.01.2021): 25–38. http://dx.doi.org/10.5194/bg-18-25-2021.
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Abstract. The seasonality of sea ice in the Southern Ocean has profound effects on the life cycle (phenology) of phytoplankton residing under the ice. The current literature investigating this relationship is primarily based on remote sensing, which often lacks data for half of the year or more. One prominent hypothesis holds that, following ice retreat in spring, buoyant meltwaters enhance available irradiance, triggering a bloom which follows the ice edge. However, an analysis of Biogeochemical Argo (BGC-Argo) data sampling under Antarctic sea ice suggests that this is not necessarily the case. Rather than precipitating rapid accumulation, we show that meltwaters enhance growth in an already highly active phytoplankton population. Blooms observed in the wake of the receding ice edge can then be understood as the emergence of a growth process that started earlier under sea ice. Indeed, we estimate that growth initiation occurs, on average, 4–5 weeks before ice retreat, typically starting in August and September. Novel techniques using on-board data to detect the timing of ice melt were used. Furthermore, such growth is shown to occur under conditions of substantial ice cover (>90 % satellite ice concentration) and deep mixed layers (>100 m), conditions previously thought to be inimical to growth. This led to the development of several box model experiments (with varying vertical depth) in which we sought to investigate the mechanisms responsible for such early growth. The results of these experiments suggest that a combination of higher light transfer (penetration) through sea ice cover and extreme low light adaptation by phytoplankton can account for the observed phenology.
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Benade, Vijay, Renny Abraham, Raghava Chowdary Palacharla, Jagadeesh Babu Thentu, Surendra Petlu, Venkat Reddy Mekala, Santosh Kumar Pandey i in. "0265 Samelisant (SUVN-G3031), a Histamine H3 Receptor Inverse Agonist in Animal Models of Narcolepsy". Sleep 45, Supplement_1 (25.05.2022): A119—A120. http://dx.doi.org/10.1093/sleep/zsac079.263.
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Abstract Introduction Samelisant (SUVN-G3031) is a potent and selective H3 receptor (H3R) inverse agonist with hKi of 8.7 nM. It lacks measurable affinity against 70 other targets which includes GPCRs, ion channels, transporters, enzymes, peptides, steroids, second messengers, growth factors and prostaglandins. Samelisant exhibited desired pharmacokinetic properties and favorable brain penetration in preclinical species. Samelisant blocked R-α-methylhistamine induced dipsogenia in rats and increased tele-methylhistamine levels in brain and cerebrospinal fluid as well. Samelisant is currently being evaluated in a Phase-2 study as monotherapy for the treatment of excessive daytime sleepiness (EDS) in patients with narcolepsy with and without cataplexy (ClinicalTrials.gov Identifier: NCT04072380). Methods In brain microdialysis, samelisant was evaluated for its effects on modulation of neurotransmitters like histamine and norepinephrine in prefrontal cortex. In male orexin knockout mice, electroencephalography (EEG), electromyography and activity were monitored using telemetric device. Effects of samelisant on sleep/ wake profile and cataplexy episodes were evaluated during active period of animals. Animals were allowed three weeks of recovery from surgery prior to EEG recording. Results Samelisant significantly increased histamine, dopamine and norepinephrine levels in the prefrontal cortex. Samelisant did not change dopamine levels in the striatal and accumbal. These suggest that samelisant may not have propensity to induce abuse liability. Samelisant produced a significant increase in wakefulness with concomitant decrease in non-rapid eye movement sleep in orexin knockout mice. It also significantly decreased number of cataplectic episodes in orexin knockout mice. Conclusion The results from non-clinical studies presented here provide a strong evidence for the potential utility of samelisant for the treatment of EDS and cataplexy in patients with narcolepsy. Support (If Any) None
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Ho, Hao-Che, Ying-Tien Lin i Marian Muste. "Velocimetry Based on Self-Generated Surface Wave Patterns". Water 12, nr 9 (20.08.2020): 2342. http://dx.doi.org/10.3390/w12092342.
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This paper introduces an image analysis technique applied to an artificially-created disturbance at the free surface of a moving water body as a means of quantifying the average velocity of the water stream for shallow flows. The disturbance was created by a thin object penetrating the free surface with different submerged distances. A V-shaped wake pattern was created by the object of interest through its variation with the water body velocity, the submergence and shape of the piercing body. The angle of the wake pattern decreased with the increase of the velocity for a depth-based Froude number ranging from 0.15 to 0.96. The proof-of-concept experiments presented in this paper, therefore, are usable to quantify the velocity based on the wake angle only in subcritical flow conditions. The results showed the shape of the wake was only slightly influenced by the shape of the object geometry and its submergence. Observations on various types of surface wakes have been documented before, but it is the conversion of these observations into a relatively inexpensive and robust method to estimate the velocity of the moving body that is deemed innovative.
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Mehta, Ritu, i Mahima Mathur. "Vakrangee: changing lives in rural India". Emerald Emerging Markets Case Studies 12, nr 4 (18.10.2022): 1–21. http://dx.doi.org/10.1108/eemcs-11-2021-0376.
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Learning outcomes The learning outcomes are as follows: to design an appropriate strategy for firms to succeed in low-income, price-sensitive markets; to appreciate how business model innovation can help to overcome the obstacles faced by firms when serving rural and semi-urban markets in an emerging economy; to identify possible threats to the business model and evaluate strategies to sustain growth in a dynamic environment; and to allow students to consider sources for competitive advantage and how to build a sustainable business model in low-income markets. Case overview/synopsis The case details the growth story of Vakrangee Limited (Vakrangee) from a technology consultancy firm to a technology-driven firm focused on creating the largest last-mile retail network providing various services in underserved parts of India, mainly rural India. The firm launched retail outlets called Vakrangee Kendras (VKs) in 2011 that evolved from non-exclusive stores offering a single line of e-governance services into technology-enabled franchisee-based exclusive stores that offered a multiple line of services such as banking, finance, insurance, ATM, e-commerce and logistics. VK however is witnessing competition from different players in different segments. Additionally, the dynamic business environment such as the growing penetration of smartphones and internet usage, heterogeneous needs of customers and government policies pose further threat to the company’s growth in the future. In the wake of these challenges, what should Vakrangee do to sustain its growth? Should it focus on cost-leadership or differentiation for strategic positioning? Complexity academic level This case can be used in an MBA or an executive management program, in courses on strategic management, entrepreneurship, services marketing and rural marketing. Supplementary materials Teaching notes are available for educators only. Subject code CSS 3: Entrepreneurship.
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Jung, Thomas, i Peter B. Rhines. "Greenland’s Pressure Drag and the Atlantic Storm Track". Journal of the Atmospheric Sciences 64, nr 11 (1.11.2007): 4004–30. http://dx.doi.org/10.1175/2007jas2216.1.
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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.
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Wu, Yuan-Kang, Deng-Yue Gau i Trinh-Duc Tung. "Overview of Various Voltage Control Technologies for Wind Turbines and AC/DC Connection Systems". Energies 16, nr 10 (16.05.2023): 4128. http://dx.doi.org/10.3390/en16104128.
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Wind power generation is one of the mainstream renewable energy resources. Voltage stability is as important as the frequency stability of a power system with a high penetration of wind power generation. The advantages of high-voltage direct current (HVDC) transmission systems become more significant with the increase of both installed capacity and transmission distance in offshore wind farms. Therefore, this study discusses various voltage control methods for wind turbines and HVDC transmission systems. First, various voltage control methods of a wind farm were introduced, and they include QV control and voltage droop control. The reactive power of a wind turbine varies with active power, while the active power from each wind turbine may be different owing to wake effects. Thus, QV and voltage droop control with varying gain values are also discussed in this paper. Next, the voltage control methods for an HVDC transmission system, such as power factor control, voltage control, and Vac-Q control, are also summarized and tested in this study. When a three-phase short circuit fault occurs or a sudden reactive power load increases, the system voltage would drop immediately. Thus, various voltage control methods for wind turbines or HVDC can make the system’s transient response more stable. Therefore, this study implemented the simulation scenarios, including a three-phase short circuit fault at the point of common coupling (PCC) or a sudden increase of reactive power load, and adopted various voltage control methods, which aim to verify whether additional voltage control methods are effective to improve the performance of transient voltage. The voltage control method has been implemented in PSCAD/EMTDC, and the simulation results show that the QV control performs better than the droop control. In addition, when applying the voltage control technique during a three-phase fault, transient voltage nadir can be improved through either an HVDC transmission system or an AC transmission system.
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Paz, Lourenco S. "Chinese imports’ impacts on Brazil’s inter-industry wage premium". Journal of Economic Studies 46, nr 5 (29.08.2019): 1052–64. http://dx.doi.org/10.1108/jes-12-2017-0382.
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Purpose The purpose of this paper is to investigate the effects of Chinese and non-Chinese import penetration on the inter-industry wage premium, and how such effects vary according to the unskilled-labor intensity of the industry and to the implementation of the Nova Matriz Economica policy in 2008. Design/methodology/approach The paper empirically examines the effects of the Chinese and non-Chinese import penetration on the wage premium using a linear instrumental variables model and data from Brazilian household surveys and censuses. Findings The estimates show the Chinese import penetration positively affecting the wage premium in unskilled-labor intensive. And the implementation of the new macroeconomic policy strengthened this effect. Originality/value To the best of the author’s knowledge, this is the first paper to study the effects of Chinese and non-Chinese import penetration on the inter-industry wage premium.