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Tang, Long, Bo Li, Bin Zhao, Peng Li, Zhanbin Li i Yang Gao. "Invasive Smooth Cordgrass (Spartina alterniflora) Eradication and Native Crab Recovery". Invasive Plant Science and Management 11, nr 2 (czerwiec 2018): 89–95. http://dx.doi.org/10.1017/inp.2018.13.
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AbstractInvasive smooth cordgrass (Spartina alterniflora Loisel) eradication is important for the health of many coastal ecosystems. An integrated regime of continuous submergence after clear mowing, with three interval levels between mowing and submergence (5, 10, and 15 d) and three submergence depths (20, 30, and 50 cm), was implemented in cofferdams enclosing invader populations along a Chinese coast. In July of the following year, after the roots of mowed S. alterniflora had been submerged for 12 mo, some ramets grew under the regime with an interval of 15 d and the regime with a submergence depth of 20 cm, but no ramets occurred under the regimes with submergence depths of 30 or 50 cm and intervals of 5 or 10 d. Four crab species were documented: Helice tridens tientsinensis Rathbun, Sesarma dehaani H. Milne-Edwards, Ocypode stimpsoni Ortmann, and Chiromantes haematocheir de Haan. Biomass and abundance values of crab species in the cofferdams were similar to those in the mudflats but different from those in smooth cordgrass populations. Thus, the treatment of submergence after mowing, which was implemented in the cofferdams, can control S. alterniflora and provide a mudflat-like habitat that promotes crab recovery if this treatment uses the proper combination of submergence depth and interval between mowing and submergence.
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Aka, Mfoniso U., Okechukwu E. Agbasi, Okonna Nsidibe Ndaraka i Osu Azuanamibebi Derikuma. "Assessment of Geologic Effect of Road Submergence Depths on Soil Subgrade Strength in Eket, South-South Nigeria". International Journal of Scientific Research and Management 10, nr 06 (21.06.2022): 09–21. http://dx.doi.org/10.18535/ijsrm/v10i6.g1.
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Road submergence is a common occurrence in Eket, South-South Nigeria, resulting in massive outlays for road construction and alimony. Fundamentally, the delineation of roadway structures is based on the strength of consolidated soil avowed as the subgrade. Consequently, the subgrade is the in situ material upon which the roadway structure is placed. It is necessary to know the modes of damage to roads caused by submergence. This study assesses the effect of road submergence depths and the extent of submergences on the subgrade strength of soil samples carried out on the Uquo Eket road that was intensely defective by the deluge. Coherent and frictional soil material types were tested for California Bearing ratio (CBR), mechanical analysis, Atterberg limit determination, and moisture density tests, respectively. CBR tests were done at various elevations of submersion, including common drenching limit, elongated deluge, and resoluteness of its suitability. Atterberg limit determination and mechanical analysis tests categorized and determined the applicability of studious soil as subgrade substantial. For elongated duration deluges, the depth and extent of submergence of subgrade strength show a lower value. Moreover, mechanical and Atterberg limit determination tests indicate a rapid and high-resolution occurrence of delegation for the elongated duration.
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Kadhim, Ali F., i Hayder A. Al Thamiry. "Computation of Critical Submergence Depth to Avoid Surface Vortices at Vertical Pumps Intakes". Journal of Engineering 26, nr 8 (1.08.2020): 59–68. http://dx.doi.org/10.31026/j.eng.2020.08.05.
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The pumping station became widely used in many fields. Free surface vortices at intakes of pumps are not favorable. It may cause noise, excessive vibration, damage to the pumping structure, reduction in efficiency and flow for hydro-turbines, etc. One of the important problems encountered during the pump intake design is the depth of submergence and other design parameters to avoid strong free-surface vortices formation. This study aims to compute the critical submergence depth with some geometrical and hydraulic limitations by using Computational Fluid Dynamic (CFD) package. The mathematical model was validated with a laboratory model that had been conducted. The model of three intake pipes was investigated under five different submergence depth (S), three different spaces between intake pipes (b), and five different suction velocities (v). The results showed the best operation cases when the space between intake pipes (b) equal to 4D, the submergence depth of water is equal or greater than 1.25 from the bell mouth diameter of intake pipe (D), and the suction velocity less than 2 m/s. The worst case was when the space between the suction pipe (b) was (2D), in this case, the vortex appeared at submergence depth (S/D = 2) with suction velocity 3 m/s.
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Zhang, Hu Zhu, i Hui Min Li. "Influencing Factors Analysis on Sunken Greenbelt Design of Urban Road". Applied Mechanics and Materials 638-640 (wrzesień 2014): 1158–61. http://dx.doi.org/10.4028/www.scientific.net/amm.638-640.1158.
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In order to provide scientific basis for the design parameters’ selection of sunken greenbelt of urban road, computational formulae of critical sunken depth and sunken greenbelt plant’s submergence time were derived based on the storage-infiltration analysis of sunken greenbelt. And then the influence of various factors on the sunken greenbelt design of urban road were computed and analyzed. Results show that: soil infiltration coefficient, design recurrence interval of storm and sunken greenbelt plant’s submergence time are the key influencing factors on the sunken greenbelt design. Under the same condition, critical sunken depth decreases linearly with the increase of soil infiltration coefficient, and increases nonlinearly with the increase of design recurrence interval of storm. Sunken greenbelt plant’s submergence time is proportional to sunken depth of sunken greenbelt, and it is inversely proportional to soil infiltration coefficient. When the value of soil infiltration coefficient is greater than 10-6m/s and the sunken depth range from 0 to 0.25 meters, submergence time of sunken greenbelt plants is all within 70h, and the sunken greenbelt can most infiltrate the rainfall storage in 1d. Considering all the influencing factors, soil infiltration coefficient of sunken greenbelt of urban road should be greater than10-6m/s and the appropriate sunken depth should be range from 0 to 0.25 meters.
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Chu, Yuhang, Rui Li i Xiaozhang Li. "Analysis of Seismic Response of the Arch Bridge across Reservoir considering Fluid-Solid Coupling Effect". Shock and Vibration 2022 (26.12.2022): 1–15. http://dx.doi.org/10.1155/2022/3873935.
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Most of the deep-water bridges in Chinese reservoirs are concentrated on rivers in the southwest region. The unique structural characteristics of arch bridges are more in line with the geological topography requirements of deep reservoir areas, making them the bridge type of choice for bridges in deep reservoir areas. While the southwest region is an earthquake-prone area, in order to study the safety of arch bridges across deep water in the reservoir area, it is necessary to analyze the effect of water under seismic behavior on the box section arch ring and explore the effect of arch inundation depth on the dynamic response of arch bridges in the reservoir area. In this study, the effect of fluid-solid coupling is considered, the modified Morison equation is used to calculate the hydrodynamic pressure, and the effect of arch bridge inundation depth on the dynamic response is analyzed based on the Midas/civil finite element model of the arch bridge in the Yunnan reservoir area. The results show that the seismic response of the arch bridge across the reservoir is greatly influenced by the submergence depth of the arch bridge due to the fluid-solid coupling effect, and the influence of the hydrodynamic pressure on the longitudinal moment (My) and transverse moment (Mz) of the arch bridge increases with the increase of the submergence depth. There is a threshold value of the submergence depth. When the submergence depth is less than the threshold, the effect of fluid-solid coupling is negligible, and when the submergence depth is greater than the threshold, the fluid-solid coupling effect is significant. The thresholds for different parts of the main arch ring are different. The most unfavorable water depth in different parts of the main arch ring is not necessarily the water depth when the arch ring is completely submerged. Based on this result, for reservoir arch bridges in high intensity areas, it is recommended that the inundation depth of arch bridges crossing deep water reservoirs should be h/f less than or equal to 5/8 f.
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Petikidis, Nikos, i George Papadakis. "Investigation of Submergence Depth and Wave-Induced Effects on the Performance of a Fully Passive Energy Harvesting Flapping Foil Operating Beneath the Free Surface". Journal of Marine Science and Engineering 11, nr 8 (7.08.2023): 1559. http://dx.doi.org/10.3390/jmse11081559.
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This paper investigates the performance of a fully passive flapping foil device for energy harvesting in a free surface flow. The study uses numerical simulations to examine the effects of varying submergence depths and the impact of monochromatic waves on the foil’s performance. For the numerical simulations, a in-house artificial compressibility two-phase solver is employed and coupled with a rigid body dynamic solver. The results show that the fully passive flapping foil device can achieve high efficiency for submergence depths between 4 and 9 chords, with an “optimum” submergence depth where the flapping foil performance is maximised. The effects of regular waves on the foil’s performance were also investigated, showing that waves with a frequency close to that of the natural frequency of the flapping foil-aided energy harvesting. Overall, this study provides insights that could be useful for future design improvements for fully passive flapping foil devices for energy harvesting operating near the free surface.
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Poursorkhabi, Ramin Vafaei, i Roghayeh Ghasempour. "Possibilities to use the meta model and classical approaches to evaluate the impact of hydraulic conditions in prediction of the critical submergence depth ratio". Water Supply 19, nr 4 (10.09.2018): 1055–65. http://dx.doi.org/10.2166/ws.2018.153.
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Abstract One of the hydraulic phenomena that mainly occurs during the water withdrawal process of channels is the formation of vortices that can cause many problems for the hydro-mechanical facilities of intakes. In the current study, classical models and meta model approaches (i.e. Support Vector Machine and Gene Expression Programming) were applied to evaluate the impact of pipe diameter and hydraulic condition changes in prediction of the critical submergence depth ratio in horizontal intakes. In this regard, two types of critical submergence experiments, based on bottom clearance, were considered (i.e. c = 0 and c = d/2, in which c and d are the bottom clearance and diameter of the intake, respectively). Different models were developed and tested using experimental data series. The results indicated that in modeling the critical submergence depth ratio, meta model approaches led to better predictions compared to the classical approaches. It was observed that the developed models for the state of c = d/2 yielded better results. According to the outcome of sensitivity analysis, the ratio of velocities in the intake pipe and channel (Vi/Vc) had a key role in the modeling. It was also found that intake pipe diameter affected the critical submergence depth ratio in intake pipes. Increasing pipe diameter caused a decrease in model accuracy.
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TUCK, E. O., i D. C. SCULLEN. "Tandem submerged cylinders each subject to zero drag". Journal of Fluid Mechanics 364 (10.06.1998): 211–20. http://dx.doi.org/10.1017/s0022112098001141.
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Two identical circular cylinders are submerged to the same depth in tandem in a stream. There are separation distances between the cylinder centres such that the combination makes no downstream waves, and hence is subject to zero net wave drag. In general there is then a non-zero equal and opposite horizontal force on each cylinder. However, there are special depths of submergence such that this interaction force between the cylinders also vanishes, and hence each cylinder is separately free of horizontal force. The parameter range for this phenomenon is explored both by linear theory for cylinders of small radius, and by a fully nonlinear computer program. For example, a configuration with a separation distance of approximately one half-wavelength gives zero force on each cylinder when the depth of submergence is approximately three-quarters of the separation distance.
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Liu, Tianshi, Xue Tian, Liwen Liu, Xiaoyu Gu, Yun Zhao, Liumei Zhang i Xinai Song. "Modeling the Submergence Depth of Oil Well States and Its Applications". Applied Sciences 12, nr 23 (2.12.2022): 12373. http://dx.doi.org/10.3390/app122312373.
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Obtaining the liquid storage state of oil wells in real time is very important for oilfield production. In this paper, under the premise of fully considering the transformation factors of full-pumping and nonfull-pumping states of oil wells, submergence depth models suitable for full- and nonfull-pumping wells are constructed. To reduce the application complexity of the models, parameter-reduction processing is performed to enhance the usability of the models. By analyzing the change trend of the submergence depth during the rising, maintaining, and falling of the oil well in the full-pumping state and nonfull-pumping state models, the judgment criteria for the transition of the oil well state are provided. On this basis, the application methods of nonlinear interpolation and least squares curve-fitting numerical solutions of submergence depth models are studied, and the unique existence of the solution of the corresponding one-variable nonlinear characteristic equation in the (0, 1) open interval is proven. Finally, the error estimation of the numerical solution is carried out, the calculation formula of the number of iterations for the numerical solution of the dichotomy is provided, and the error of the relevant numerical solution is verified.
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Hays, G. C., S. Åkesson, A. C. Broderick, F. Glen, B. J. Godley, P. Luschi, C. Martin, J. D. Metcalfe i F. Papi. "The diving behaviour of green turtles undertaking oceanic migration to and from Ascension Island: dive durations, dive profiles and depth distribution". Journal of Experimental Biology 204, nr 23 (1.12.2001): 4093–98. http://dx.doi.org/10.1242/jeb.204.23.4093.
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SUMMARY Satellite telemetry was used to record the submergence duration of green turtles (Chelonia mydas) as they migrated from Ascension Island to Brazil (N=12 individuals) while time/depth recorders (TDRs) were used to examine the depth distribution and dive profiles of individuals returning to Ascension Island to nest after experimental displacement (N=5 individuals). Satellite telemetry revealed that most submergences were short (<5 min) but that some submergences were longer (>20 min), particularly at night. TDRs revealed that much of the time was spent conducting short (2–4 min), shallow (approximately 0.9–1.5 m) dives, consistent with predictions for optimisation of near-surface travelling, while long (typically 20–30 min), deep (typically 10–20 m) dives had a distinctive profile found in other marine reptiles. These results suggest that green turtles crossing the Atlantic do not behave invariantly, but instead alternate between periods of travelling just beneath the surface and diving deeper. These deep dives may have evolved to reduce silhouetting against the surface, which would make turtles more susceptible to visual predators such as large sharks.
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Zhang, Zhen, Yuan Zheng, Xiwang Xu i Bin Peng. "The Effect of Mixing Chamber Configuration and Submersion Depth on Centrifugal Aerator Performance". Sustainability 14, nr 18 (10.09.2022): 11355. http://dx.doi.org/10.3390/su141811355.
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Centrifugal aerators are a vital piece of equipment in water treatment. To improve the efficiency and economy of their operation, a study of their mixing chamber structure and submergence depth was carried out using a combination of numerical simulations and experiments. A centrifugal aerator dissolved oxygen (DO) test bench was built and the numerical simulation was compared with the experiment, the inlet air flow rate showing only a 2.23% error, which verifies the reliability of the numerical simulation. The results show that the capacity of oxygen dissolved in the aeration tank increases and then decreases as the relative area ratio (ð) of the mixing chamber increases, reaching the best capacity at ð = 8.38. In the case of different submergence coefficients (β), the gas volume fraction increased by 31.29% on average at β = 0.15; the standard oxygen transfer rate (SOTR) increased and then decreased with the increase of β, with an average increase of 56.6%. Moreover, the oxygenation performance of centrifugal aerators was significantly improved by the reasonable submergence depth and the structure of the mixing chamber.
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Liu, Y. L., B. Lv i W. L. Wei. "Investigation of the Submerged Depth of Aeration Impellers in an Oxidation Ditch by Numerical Simulation". Applied Mechanics and Materials 178-181 (maj 2012): 429–32. http://dx.doi.org/10.4028/www.scientific.net/amm.178-181.429.
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In this paper, the flow structure of the oxidation ditch was studied using numerical simulation method and different submerged depth of aeration impellers. The computed velocity fields were analyzed, which shows that under the same conditions, and by using the optimal submerged depth the average velocity of the flow in oxidation ditch is increased and the velocity near-bottom has increased significantly. The results of comparisons show that the velocity distribution is more uniform along the depth direction, and that the flow velocity distribution structure can prevent sludge from settling in the oxidation ditch processing system at the submergence ratio called the optimal submergence ratio, which helps to improve the efficiency of oxidation ditch sewage treatment system.
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Wagner, Martin R., i H. Johannes Pöpel. "Oxygen transfer and aeration efficiency - influence of diffuser submergence, diffuser density, and blower type". Water Science and Technology 38, nr 3 (1.08.1998): 1–6. http://dx.doi.org/10.2166/wst.1998.0163.
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The main factors of fine bubble aeration systems in uniform arrangement in clean water are the air flow rate, the depth of submergence of the diffusers, and the diffuser density. While the influence of the air flow rate on the oxygen transfer parameters is known, knowledge of the influence of the depth of submergence and the diffuser density on the specific oxygen transfer efficiency SOTE [%/m] and on the specific oxygen absorption SOA [g/m3·m at STP] is very limited. Both parameters are of great importance in dimensioning fine bubble aeration systems. Therefore, a literature review was conducted to show the influence of the diffuser submergence and density and the type of blower on oxygen transfer and aeration efficiency. The main review results are, that higher values of specific oxygen absorption can be obtained at higher diffuser density; secondly, the volumetric oxygen transfer rate VOTR [g/m3·h] is higher with increasing depth of submergence at the same air flow rate. Also it can be stated that with greater depth of submergence the specific oxygen absorption [g/m3·m at STP] is reduced. Dependent on the air flow rate and the pressure head, the energy consumption [Wh/m3·m at STP] of the blowers used in wastewater treatment plants is different. For example, the energy consumption varies from 4.3 [Wh/m3·m at STP] (positive displacement blower) to 3.0 [Wh/m3·m at STP] (turbo-compressors) at a pressure of 10 m and an air flow rate of 5,000 m3/h at STP. From the results of the literature review the following conclusions can be drawn: (1) High specific oxygen absorption values (SOA) [g/m3·m at STP] can be achieved applying shallow tanks, high diffuser densities and low specific air flow rates; (2) High aeration efficiencies (AE) [kg/kWh] can be obtained by applying high volumetric oxygen transfer rates and adequate selection of the blowers used at the wastewater treatment plants.
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Cui, Jin-tao, Guang-cheng Shao, Shuang-en Yu i Xi Cheng. "Influence of Controlled Drainage on the Groundwater Nitrogen and Phosphorus Concentration at Jointing-Booting Stage of Wheat". Journal of Chemistry 2016 (2016): 1–6. http://dx.doi.org/10.1155/2016/5280194.
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The effect of controlled drainage on nitrogen (N) and phosphorus (P) emission at jointing-booting stage of winter wheat was studied in 2007-2008. The conventional subsurface drainage was taken as the control (T5). The groundwater depth was naturally drained to 400 mm and 800 mm below the soil surface within 3 days at the jointing-booting stage, after the water level was kept at 100 mm for 1 day (T1, T2) and 3 days (T3, T4) from the soil surface. Results showed that controlled drainage could significantly reduce the concentration of P and N in groundwater. Compared to T5, the four controlled treatments could significantly decrease the concentration of TP,NH4+-N, andNO3--N. The highest concentration reduction for TP andNO3--N was observed under T4 and T1, which reached 64.9% and 73.2%, respectively. As for the concentration ofNH4+-N, the highest reduction was obtained under T2. The change of TP concentration was significantly affected by the interaction of submergence time and drain depth, while the influence of controlled drainage onNH4+-N concentration was not significant. The submergence time, drain depth, and the interaction of submergence time and drain depth had significant effect on the change of concentration ofNO3--N.
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Pernod, Laetitia, Matthieu Sacher, Jeroen Wackers, Benoit Augier i Patrick Bot. "Free-Surface Effects on Two-Dimensional Hydrofoils by RANS-VOF Simulations". Journal of Sailing Technology 8, nr 01 (27.01.2023): 24–38. http://dx.doi.org/10.5957/jst/2023.8.2.24.
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Foiling yachts and crafts are both very sensitive to the flying height in terms of stability and performance, raising the scientific issue of the influence of the free-surface when the foil is at low submergence. This work presents numerical simulations of a 2D hydrofoil section NACA0012 at 5° angle of attack in the vicinity of the free-surface, for different values of the submergence depth, for a chord-based Froude number of 0.571 and a Reynolds number of 159,000. Unsteady-Reynolds Averaged Navier-Stokes (URANS) equations are solved with a mixture model to capture the free surface (Volume Of Fluid method), and using an automatic grid refinement. Verification of the numerical model and validation with data from the literature are presented. Deformation of the free surface and alteration of the hydrodynamic forces compared to the deep immersion case are observed for a submergence depth-to-chord ratio ℎ/𝑐 lower than 2. The foil drag increases up to more than three times the infinite-depth value at ℎ/𝑐≈0.5. The lift force slightly increases until ℎ/𝑐 around 1, and then decreases sharply. For ℎ/𝑐<0.5, the pressure field around the foil is totally modified and the lift is swapped to downward. The study highlights the importance of considering the effect of finite submergence to compute foils’ hydrodynamic forces, for example to be used in Velocity Prediction Programs (VPP) of foiling crafts.
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Basack, Sudip, Ghritartha Goswami, Sumanpran Sonowal i Moses Karakouzian. "Influence of Saltwater Submergence on Geohydraulic Properties of Sand: A Laboratory Investigation". Hydrology 8, nr 4 (8.12.2021): 181. http://dx.doi.org/10.3390/hydrology8040181.
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Saline water intrusion into freshwater aquifers is a major geohydraulic problem relevant to coastal environment. Apart from contaminating the fresh groundwater resources, the saltwater intrusion alters the geotechnical properties of the aquifer materials, affecting the coastal water resource planning and management. The present study focuses on an in-depth laboratory investigation of the influence of saltwater submergence on the geohydraulic properties of sand. The fine sand sample was submerged under saline water of specified concentrations for specific periods, and the alteration in their engineering properties has been studied. It is observed that the specific gravity, dry density, and permeability of fine sand is significantly affected by the period of submergence and saline concentration. The specific gravity of sand particles was observed to increase almost linearly with period of submergence and saline concentration. While the sand dry density decreased fairly linearly with the period of submergence, the same is not being affected significantly by saline concentration. The permeability of sand increased nonlinearly with both period of submergence and saline concentration; for a submergence period of 14 days and saline concentration of 30,000 ppm, the permeability increased to a maximum value.
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Gualtieri, Paola, Sergio De Felice, Vittorio Pasquino i Guelfo Pulci Doria. "Use of conventional flow resistance equations and a model for the Nikuradse roughness in vegetated flows at high submergence". Journal of Hydrology and Hydromechanics 66, nr 1 (1.03.2018): 107–20. http://dx.doi.org/10.1515/johh-2017-0028.
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Abstract This study examines the problem of flow resistance due to rigid vegetation in open channel flow. The reliability of the conventional flow resistance equations (i.e. Keulegan, Manning and Chézy-Bazin) for vegetated flows at high submergence, i.e. h/k >5, (where h = flow depth and k = vegetation height) is assessed. Several modern flow resistance equations based on a two-layer approach are examined, showing that they transform into the conventional equations at high submergences. To compare the conventional flow resistance equations at high submergences, an experimental methodology is proposed and applied to the experimental data reported in the literature and collected for this study. The results demonstrate the reliability of the Keulegan equation in predicting the flow resistance. Based on the obtained results, a model to evaluate the Nikuradse equivalent sand-grain roughness, kN, starting from the vegetation height and density, is proposed and tested.
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Tyvand, Peder A., i Touvia Miloh. "Free-surface flow generated by a small submerged circular cylinder starting from rest". Journal of Fluid Mechanics 286 (10.03.1995): 103–16. http://dx.doi.org/10.1017/s0022112095000668.
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The impulsively starting motion of a small circular cylinder submerged horizontally below a free surface is studied analytically using a small-time expansion. The cylinder is considered small if the ratio between its radius and initial submergence depth is much smaller than one. The surface elevation is calculated up to third order. The hydrodynamic force on the small cylinder is also discussed. Certain inconsistencies in our small-cylinder approximation (assuming locally uniform flow around the cylinder) are found in the force prediction. The present work is an accompanying paper to Tyvand & Miloh (1995), where the same problem is studied for arbitrary radius versus submergence depth.
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(Derick) Nixon, J. F. "Thermal simulation of subsea saline permafrost". Canadian Journal of Earth Sciences 23, nr 12 (1.12.1986): 2039–46. http://dx.doi.org/10.1139/e86-188.
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Thermal analyses of the response of offshore permafrost to emergence and submergence have traditionally employed simple closed-form solutions, where phase change is confined to a discrete freezing temperature. These have led to rather rapid rates of return to thermal equilibrium, which have proved difficult to explain in the light of recent deep temperature measurements in offshore permafrost profiles. This paper reviews the need for an appropriate unfrozen-water-content relationship for a saline frozen soil and describes some simulations of long-term thermal response in offshore permafrost using the author's geothermal simulator. Simulations of submergence assumed an initial permafrost thickness of 600 m and a mean soil-surface temperature of −9.0 °C. The salinity was assumed constant at 30‰. The initial-temperature profile was linear, varying between −9.0 °C and a freezing point of −1.8 °C at the bottom of ice-bonded permafrost. The temperature of the ground surface was assumed to have changed to −0.8 °C following submergence. After a period of 10 000 years, the predicted ground temperature at a depth of 300 m was −3.55 °C and was still rising. The equivalent temperature in a soil with a discrete freezing point would be 0.25 °C below the freezing point.Following permafrost submergence, for example, the rate of thaw in saline soils is somewhat faster than that predicted for discrete-freezing-point soils. However, more importantly, the rate at which the ground temperatures at depth rise in response to submergence is very much slower than that predicted by simpler closed-form solutions for freshwater soils. This means that for any given period since submergence, a cooler temperature profile would be predicted for a saline soil than for a soil with a discrete freezing point. This has far-reaching implications for geologists interpreting deep permafrost temperature records and for engineers involved with the design of structures in the arctic offshore.
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Hassan, Md Juiceball, Md Masudul Karim, Md Amirul Islam, Md Habibur Rahman Pramanik i Md Alamgir Hossain. "Changes in root porosity and water soluble carbohydrates in rice (Oryza sativa L.) under submergence stress". Journal of the Bangladesh Agricultural University 17, nr 4 (31.12.2019): 539–44. http://dx.doi.org/10.3329/jbau.v17i4.44623.
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Submergence stress at early vegetative stage is one of the most important constraints in the productivity of rice in Bangladesh. Submergence causes yield loss of rice at Aman season in Bangladesh and therefore, it is necessary to develop submergence tolerant rice cultivars. A pot experiment was conducted at the net house of Department of Crop Botany, Bangladesh Agricultural University, during Aman season from July to December, 2017 to evaluate the changes in root porosity and water soluble carbohydrates (WSCs) associated with submergence tolerance in rice. The experiment consisted of two factors—(i) Rice cultivars (Binadhan-11, Binadhan-12, BRRI dhan51 and BRRI dhan52 as tolerant and BRRI dhan49 as susceptible) and(ii) Submergence stress: Submergence for 14 days at vegetative stage and control. Submergence stress was imposed by dipping of pots into a water tank with about 90 cm depth of water while the control plants are maintained in the pot house of the field laboratory. The plants were sampled at seven days interval during submergence to determine the changes in root porosity and to examine the contribution of shoot reserves for their survival. The root porosity was measured by pycnometer method and water soluble carbohydrate was measured by the anthrone method. Tolerant cultivars showed greater root porosity development in both control and stress condition but the susceptible cultivar showed significantly lower root development in stress condition. Higher root porosity might help tolerant cultivars to survive in submergence stress more efficiently. Tolerant rice cultivars had high initial soluble carbohydrate than the susceptible one. Under submergedcondition, the tolerant cultivars showed slow depletion of water soluble carbohydrate compared to susceptible cultivar. Higher carbohydrate contents in tolerant cultivars might act as buffer stock during submergence for their better survival and growth.
J Bangladesh Agril Univ 17(4): 539–544, 2019
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Teh, Hee Min, Vengatesan Venugopal i Tom Bruce. "HYDRODYNAMIC PERFORMANCE OF A FREE SURFACE SEMICIRCULAR PERFORATED BREAKWATER". Coastal Engineering Proceedings 1, nr 32 (29.01.2011): 20. http://dx.doi.org/10.9753/icce.v32.structures.20.
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The increasing importance of the sustainability challenge in coastal engineering has led to the development of free surface breakwaters of various configurations. In this study, the hydrodynamic characteristics of a perforated semicircular free surface breakwater (SCB) are investigated for irregular wave conditions. The hydrodynamic performance of the breakwater is evaluated in the form of transmission, reflection and energy dissipation coefficients, which are then presented as a function of the relative submergence depth (D/d) and the relative breakwater width (B/Lp), where D = the depth of immersion, d = the water depth, B = the breakwater width and Lp = the wavelength corresponding to the peak wave period. It is found that the wave attenuation ability of the SCB model improves with the increase of D/d and B/Lp. The SCB performs better as an energy dissipater than as a wave reflector. Based on the analysis of measured data, some empirical equations are proposed to predict the performance of the breakwater under varying submergence depths. The behaviour of wave transformation around and within the breakwater’s chamber is discussed. Also, the measured horizontal wave forces acting on the SCB are reported.
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Yan, Bin, Ming Gao, Zhenwei Gao i Shengli Yan. "A farmland immersion evaluation method based on grey clustering". E3S Web of Conferences 199 (2020): 00014. http://dx.doi.org/10.1051/e3sconf/202019900014.
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As we all know, the degree of farmland immersion is affected by many factors such as soil moisture content, natural pore ratio, saturation, soil lithology and so on. However, the conventional submergence assessment method only uses the relative relationship between the depth of phreatic water and the rising height of capillary water to judge the degree of submergence, which is obviously unreasonable. Therefore, in this paper, a method of farmland immersion evaluation based on trigonometric whiteness weight function grey clustering is proposed. The physical properties of soil, surface soil lithology of vadose zone and groundwater level elevation are included in the evaluation index system, and the degree of submergence is classified, and then the weight function is constructed to determine the degree of submergence hazard of each observation point in the immersion area. Case study shows that the method is reasonable and feasible for farmland immersion evaluation.
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Zhang, S., Y. Liu, J. Zhang i Y. Liu. "Simulation study of anisotropic flow resistance of farmland vegetation". Soil and Water Research 12, No. 4 (9.10.2017): 220–28. http://dx.doi.org/10.17221/50/2016-swr.
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Farmland vegetation is commonly cultivated with uniform planting spacing and heights. The effect of these features on resistance to hydraulic erosion is unclear. Hydraulic model experiments with the angle between the crop rows and the water flow direction set at 15°, 30°, 45° or 90° were conducted to analyze variation in the law of water flow resistance under partial or complete submergence of the crop. Cultivation can impact the flow resistance on slopes and this effect was greater when the crop was partially submerged. When planting spacing, slope, and water depth were constant, the change of the water flow Darcy-Weisbach resistance coefficient f with crop row-water flow angle was f<sub>15</sub>° > f<sub>30</sub>° > f<sub>45</sub>° > f<sub>90</sub>°. This suggests that flow resistance of farmland vegetation is anisotropic. The water flow resistance coefficient of crops that were partly submerged increased with water depth, but decreased with water depth when the crop was completely submerged. At the critical change from partial submergence to complete submergence, the water flow resistance coefficient was the highest when water depth was equal to crop height. These results may be useful for optimizing farmland planting and soil and water conservation.
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Jamieson, Alan J., Patrick Lahey, Rob MacCallum, Stuart Buckle, Tim Macdonald i Victor Vescovo. "Recovery of a Lost Subsea Asset at Full Ocean Depth in the Mariana Trench (10,925 m ± 4) Using a Crewed Submersible". Marine Technology Society Journal 57, nr 1 (27.02.2023): 151–55. http://dx.doi.org/10.4031/mtsj.57.1.4.
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Abstract In 2019, the Deep Submergence Support Vessel Pressure Drop embarked on the third leg of the Five Deeps Expedition. Over the course of 10 days, the full ocean depth submersible Deep Submergence Vehicle Limiting Factor made a record five dives to the bottom of the Mariana Trench: four to the Challenger Deep, one to the Sirena Deep. The submersible was supported by three scientific landers, one of which became stuck on the seafloor at 10,925 m depth. Here we describe how, during the third dive of the campaign, the expedition utilized the submersible to rescue this lost asset from full ocean depth. The expedition was not only significant for its operational jump from single full ocean depth dives to multiple dives in a short space of time, but demonstrated that assets lost in the deepest 45% of the oceans are no longer irretrievable.
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Hough, G. R., i J. P. Moran. "Froude Number Effects on Two-Dimensional Hydrofoils". Journal of Ship Research 13, nr 01 (14.12.2022): 53–60. http://dx.doi.org/10.5957/jsr.1969.13.1.53.
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The performance of a two-dimensional hydrofoil of arbitrary camber, moving at arbitrary Froude number at a constant depth below a free surface, is considered. The treatment is based upon the use of singularity distributions and thin foil theory. By assuming an appropriate series form for the vortex distribution representing the hydrofoil, it is shown that the problem can be reduced to the solution of a set of linear algebraic equations. These are solved by a collocation procedure. Numerical results for the performance characteristics are then given for several hydrofoil configurations, submergence depths, and Froude numbers. These indicate that operation at Froude numbers greater than about ten is practically equivalent to operation at infinite Froude number. However, at lower values of the Froude number and for all the configurations considered, Froude number effects are important, even at submergence depths of several chord lengths.
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Pramanik, MHR, IJ Shelley, D. Adhikary i MO Islam. "Carbohydrate reserve and aerenchyma formation enhance submergence tolerance in rice". Progressive Agriculture 27, nr 3 (28.12.2016): 256–64. http://dx.doi.org/10.3329/pa.v27i3.30805.
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An attempt was made to evaluate the submergence tolerance in rice using four Aman rice varieties viz. FR13A (local flood resistant, check), BRRI dhan 51 (HYV flood tolerant, check), BR 5 (HYV, susceptible) and a local aromatic rice,Ukunimadhu (local susceptible). Twenty days old seedlings of the rice varieties raised in earthen pots were submerged under 90 cm water depth in a submergence tank for 12 days and data were recorded on plant height, tiller number, carbohydrate reserve and internal anatomical structure of roots of the submerged and control (ambient) plants. Under submergence treatment Ukunimadhu showed rapid stem elongation with taller plants than the HYVs which showed shorter plant height. Tillering pattern was almost similar both in submergence treated and control plants in all the varieties. Variation in carbohydrate reserve was negligible among the varieties at ambient condition but the submergence treatment brought significant variation in carbohydrate content in them. Submergence treated FR13A and BRRI dhan 51 had the highest sugar and starch conservation ability while BR 5 and Ukunimadhu had the lowest. The higher reserved carbohydrate in the tolerant varieties might assist them to regenerate their normal growth rapidly after desubmergence. The cellular morphology of root tissue showed that intensity of aerenchyma development in submergence treated FR13A and BRRI dhan 51 was more pronounced compared to the local aromatic rice Ukunimadhu and perhaps this cellular large aerenchymatous development might be associated with the submergence tolerance of FR13A and BRRI dhan 51 than the local variety, Ukunimadhu.Progressive Agriculture 27 (3): 256-264, 2016
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Li, Gaohui, Ting Lu, Funan Chen, Shaojia Yang, Lei Jiang i Haolei Zhen. "Experimental study of a hydraulic model of the side inlet and outlet of a pumped storage power station". Journal of Physics: Conference Series 2565, nr 1 (1.08.2023): 012031. http://dx.doi.org/10.1088/1742-6596/2565/1/012031.
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Abstract Inlets/outlets have bi-directional characteristics and complex structures, which have important implications for practical operational safety and efficiency. In this paper, the hydraulic characteristics of the lateral inlet/outlet of a pumped storage power station are studied by means of model tests. The flow velocity distribution at the leading edge of the inlet/outlet orifice and the barrage section is more uniform, and the flow velocity distribution at the left, middle, and right of each orifice is the same. The formation of swirl is related to the relative submergence depth s/d and the Froude number Fr, with the inlet/outlet Fr< 0.23, relative submergence depth s/d> 0.5 and it has no harmful eddies.
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Johnstone, H. W., i F. Zangrando. "Mixing Depth of a Submerged, Horizontally Injected Buoyant Jet". Journal of Solar Energy Engineering 110, nr 2 (1.05.1988): 125–31. http://dx.doi.org/10.1115/1.3268242.
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Tests in the laboratory were conducted to determine the effective mixing depth of turbulent buoyant fluid injected horizontally into an initially unstratified environment through a radial, deeply submerged diffuser. The diffuser was moved slowly during the experiments, at a rate much smaller than the entrainment and mixing process. The effective mixing depth is defined as the relative position between the initial injector level and the lowest position of the resulting mixed layer over which the injected fluid is deposited. Results have applications to discharge of contaminants and heat into large reservoirs (sewage disposal, power plants, OTEC systems) and establishment of a stratified region as is required for operation of salt gradient solar ponds. A functional dependence between mixing depth, scaled by the injector slot size, and injector Froude number was found. Dependence on submergence was not found for the large submergence values tested; dependence on diffuser radius was not investigated. The laboratory data compare well with results obtained in a reservoir of 3355 m2 surface area and indicate a strong dependence of effective mixing depth on the Froude number.
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Zhang, Shang Hong, Yan Liu i Zhong Xi Xia. "Flood Submergence Processes Simulation Based on Virtual Reality". Advanced Materials Research 403-408 (listopad 2011): 4210–15. http://dx.doi.org/10.4028/www.scientific.net/amr.403-408.4210.
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Flood submergence process simulation has important practical significance for flood control and disaster alleviation. An integrated information expression was developed to simulate flooding submergence. The Songhua River and urban area in Harbin, China were used as an example with the terrain described by a triangular mesh to describe the topological relations. A hydrodynamic model was used to calculate the water level of Songhua River, and submerged areas along the river were calculated by grid adjusting method for levees. The flooding process of levee-breach flow in Harbin city was simulated by using two methods: hydrodynamic model calculations method and water depth comparison method. Comparison of the two methods in terms of advantages and disadvantages were made. Combining hydrodynamic modeling method and domain searching method realized smooth simulation of flood routing process in three-dimensional virtual environment. The study presents the integrated information such as the geographical environment, flooded areas, flooding extent, and water depth distribution in the three-dimensional virtual environment, thus, can help improve flood submergence forecasting and decision.
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Manzur, M. E., A. A. Grimoldi i G. G. Striker. "The forage grass Paspalum dilatatum tolerates partial but not complete submergence caused by either deep water or repeated defoliation". Crop and Pasture Science 71, nr 2 (2020): 190. http://dx.doi.org/10.1071/cp19303.
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Grazing, flooding and their combination are major disturbances that could affect plant performance in humid grasslands. We performed two experiments to study the tolerance of the forage grass Paspalum dilatatum Poir. to different submergence depths and defoliation frequencies. First, we addressed whether this species can shift from the escape strategy to ‘quiescence’ when completely submerged for 30 days. Second, we explored to what extent partial or complete submergence produced by defoliation compromises plant regrowth. The results showed that regardless of the depth of water at submergence, P. dilatatum always responded by attempting to expose its leaf area above water, by increasing the tiller angle and/or blade length (i.e. tiller height). Partially submerged plants showed a reduction in starch concentration (89%) but biomass was unaffected, whereas completely submerged plants did not survive. After one defoliation event, 77% of aerial biomass of partially submerged plants was removed and the concentration of carbon reserves (water-soluble carbohydrates and starch) decreased to half that of control plants. A second event of defoliation (20 days later) of plants with few reserves removed 50–52% of shoot biomass and compromised plant survival, with plants dying before the end of the experiment. In conclusion, P. dilatatum does not tolerate prolonged conditions of complete submergence caused by either deep water columns or repeated defoliation.
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Taha, Nesreen, Maged M. El-Feky, Atef A. El-Saiad, Martina Zelenakova, Frantisek Vranay i Ismail Fathy. "Study of Scour Characteristics Downstream of Partially-Blocked Circular Culverts". Water 12, nr 10 (13.10.2020): 2845. http://dx.doi.org/10.3390/w12102845.
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Debris accumulations upstream and through crossing hydraulic structures such as culverts cause the upstream water level and the downstream scour depth to increase, which can lead to structure failure. This experimental study aimed to investigate the effects of various inlet blockage ratios on culvert efficiency and scour hole depth. In a non-blocked case, various submergence ratios (S = 1.06, 1.33, 1.60, and 1.90) were tested with different discharge rates. In a blocked case, the effects of inlet blockage with various blockage ratios (Ar = 10%, 20%, and 30%) were seen as sediment blockage on the pipe bed or floating debris upstream of the culvert. The results show that as the submergence ratio increases, the maximum scour depth decreases at the same discharge rate, and the relative energy loss also decreases in the non-blocked case. In the sediment blockage (Ar d) case, the relative maximum depth increases with increasing densimetric Froude number and with an increasing blockage ratio. An empirical equation was developed to predict the relative scour depth under the present study conditions.
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Wu, Huiyu, Jiayi He, Hui Liang i Francis Noblesse. "Influence of Froude number and submergence depth on wave patterns". European Journal of Mechanics - B/Fluids 75 (maj 2019): 258–70. http://dx.doi.org/10.1016/j.euromechflu.2018.10.018.
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IVANOV, Vladimir Mikhaylovich, i Tatyana Yur'evna IVANOVA. "IMPROVING METHODS OF CALCULATING HYDRODYNAMIC LOADS FOR WATER OUTLETS AT THE BOTTOM MODE OF POOLS BLENDING". Urban construction and architecture 5, nr 3 (15.09.2015): 64–72. http://dx.doi.org/10.17673/vestnik.2015.03.9.
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The article presents the results of new methods of calculating hydrodynamic loads on the fastening of a spillway dam. The dam described has a smooth blending of its spillway face and its apron. Different submergence coefficients of the hydraulic jump at the bottom mode are calculated. The research yielded calculation values and graphs which make possible to estimate the average hydrodynamic load on the fastening with account of pressure pulsations at different submergence coefficients of the hydraulic jump as well as to estimate the second sequent depth on a upturned apron.
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Ting, Chao-Lung, i Ming-Chung Lin. "Generation of Harmonics by Non-Breaking Water Waves Over Permeable Submerged Breakwaters". Journal of Mechanics 20, nr 1 (marzec 2004): 57–67. http://dx.doi.org/10.1017/s1727719100004044.
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ABSTRACTThis work examines the interesting phenomenon of the generation of harmonics by non-breaking waves over permeable submerged obstacles. Nine model geometries, each with six different porosities, from 0.421 to 0.912, were considered to examine the effects of model width, porosity, and submergence depth on harmonic generation. The results revealed coupled effects on harmonic generation. A modified Ursell number was proposed to analyze experimental data. Almost no harmonic generation occurs at a modified Ursell number of less than five and/or a model width to wavelength ratio of over 1.6. After harmonics have been generated, wave profiles become dimpled, and the energy of the fundamental mode is transferred to higher-frequency components. Furthermore, the higher harmonics become more pronounced as the models widen, the depth of submergence becomes shallower, and model porosity declines.
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Hamed, A. M., M. J. Sadowski, H. M. Nepf i L. P. Chamorro. "Impact of height heterogeneity on canopy turbulence". Journal of Fluid Mechanics 813 (27.01.2017): 1176–96. http://dx.doi.org/10.1017/jfm.2017.22.
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The flow development above and within homogeneous and heterogeneous canopies was experimentally studied using particle image velocimetry in a refractive-index-matching channel. The experiments were designed to gain insight into the effect of height heterogeneity on the structure and spatial distribution of the turbulence. The homogeneous model (base case) is constituted of elements of height $h$ arranged in a staggered configuration; whereas the heterogeneous canopy resembled a row canopy and consisted of elements of two heights $h_{1}=h+(1/3)h$ and $h_{2}=h-(1/3)h$ alternated every two rows. Both canopies had the same density, element geometry and mean height. The flow was studied under three submergences $H/h=2$, 3 and 4, where $H$ denotes the flow depth. The experiments were performed at Reynolds number $Re_{H}\simeq 6500$, 11 300 and 12 300 and nearly constant Froude number $Fr\simeq 0.1$. Turbulence statistics complemented with quadrant analysis and proper orthogonal decomposition reveal richer flow dynamics induced by height heterogeneity. Topography-induced spatially periodic mean flows are observed for the heterogeneous canopy. Furthermore, and in contrast to the homogeneous case, non-vanishing vertical velocity is maintained across the entire length of the heterogeneous canopy with increased levels at lower submergence depths. Further alternations were induced in the magnitude and distribution of the turbulent kinetic energy, Reynolds shear stress and characteristics of the canopy mixing layer, evidencing enhanced mixing and turbulent transport for the heterogeneous canopy especially at lower submergence depths. Overall, the results indicate that heterogeneous canopies exhibit greater vertical turbulent exchange at the canopy interface, suggesting a potential for greater scalar exchange and a greater impact on channel hydraulic resistance than a homogeneous canopy of similar roughness density.
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Yang, Shengmu, Jiuxing Xing, Daoyi Chen i Shengli Chen. "A modelling study of eddy-splitting by an island/seamount". Ocean Science 13, nr 5 (25.10.2017): 837–49. http://dx.doi.org/10.5194/os-13-837-2017.
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Abstract. A mesoscale eddy's trajectory and its interaction with topography under the planetary β and nonlinear effects in the South China Sea are examined using the MIT General Circulation Model (MITgcm). Warm eddies propagate to the southwest while cold eddies propagate to the northwest. The propagation speed of both warm and cold eddies is about 2.4 km day−1 in the model. The eddy trajectory and its structure are affected by an island or a seamount, in particular, under certain conditions, the eddy may split during the interaction with an island/seamount. We focus this research on two parameters R and S (where R and S are two dimensionless parameters of the island size and submergence depth; R is the ratio of the island radius to the eddy radius, and S is the ratio of the seamount submergence depth to the eddy vertical length). The results of sensitivity experiments with varying island or seamount geometry indicate that the eddy would split in the qualitative range of 1∕4 < R < 2 and S < 1∕5. The scale of the secondary eddy split-off decreases as the island diameter or the seamount submergence depth increases. In the splitting process, besides the off-spring eddy, there are also some filaments or eddies with opposite vorticity appearing around the eddy. Eddy-splitting, therefore, is an important way to transform energy from the mesoscale to sub-mesoscale in the ocean.
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Nurrahma, Arinal Haq Izzawati, Shin Yabuta, Ahmad Junaedi i Jun-Ichi Sakagami. "Characterizing the photosynthetic ability of the submergence-tolerant rice variety of Inpari30 via maximum quantum yield performance during transient flooding stress and recovery". JANUARY 2021, nr 15(01):2021 (2.01.2021): 107–13. http://dx.doi.org/10.21475/ajcs.21.15.01.2889.
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Submergence is an environmental challenge for crop cultivation which causes physiological perturbation and yield loss. Tolerant genotypes are characterized by the ability to maintain physiological processes, especially photosynthesis, minimizing the negative effects of flooding stress. This experiment was aimed to examine the photosynthetic ability during submergence and a recovery period in rice variety of Inpari30 (carrying gene Sub1) compared to IR72442 (an elongation type) under control and submergence treatment. A randomized complete block design was employed in this experiment with three replications. The first factor was the environmental condition consisting of control and submergence. The second factor was rice varieties consisting of Inpari30 and IR72442. Fourteen-day-old seedlings were submerged under 35 cm of water depth for 6 days and re-aerated by lowering the water level up to the stem base for 6 days of recovery. Measurement of plant height, SPAD, Fv/Fm and photosynthetic rate were taken continuously from the same plant sample following the experimental stage. The results showed that shoot length increased significantly more in IR72442 than in the quiescent Inpari30. The noticeable decline was observed in the photosynthetic rate of both varieties during submergence with chlorophyll content and chlorophyll fluorescence (Fv/Fm) decreased more severely in IR72442 than in Inpari30. After flooding, Inpari30 adapted quickly to the aerobic environment, as shown by a recovery in Fv/Fm and accumulated dry weight more quickly than IR72442. We concluded that the Sub1 genotype of Inpari30 confers the ability to maintain maximum quantum yield of PSII under conditions of limiting gas exchange for photosynthesis for adapting post submergence
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Karim, Md Masudul, Md Juiceball Hassan, Md Habibur Rahman Pramanik i Md Alamgir Hossain. "Morpho-phenological traits and yield performance of rice cultivars as affected by submergence stress". Journal of the Bangladesh Agricultural University 17, nr 4 (31.12.2019): 545–50. http://dx.doi.org/10.3329/jbau.v17i4.44624.
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Complete submergence up to 1-2 weeks of low land rice crops during flash floods occurs in large areas of South-East Asia including Bangladesh, resulting in increased mortality of plants as well as low productivity of rice crops. A pot experiment was conducted at the Net House, Department of Crop Botany, Bangladesh Agricultural University, Mymensingh, during Aman season from July 2017 to December 2017 to evaluate morphological and phenological traits associated with submergence tolerance in rice. The experiment consisted of two factors—Rice cultivars (Binadhan-11, Binadhan-12, BRRI dhan51 and BRRI dhan52 as tolerant and BRRI dhan49 as susceptible) and submergence stress for 14 days at vegetative stage and control. Submergence stress was imposed by dipping of pots into a water tank with about 90 cm depth of water. After desubmergence, the plants were grown with proper care till maturity. Control plants are maintained in the pot house of field laboratory. Leaf greenness was measured after desubmergence to physiological maturity. The tolerant cultivars maintain higher leaf greenness for a long time than the susceptible cultivar after desubmergence. Reduction of grain filling rate and yield was significantly higher in susceptible cultivar than the tolerant cultivars. Among the five cultivars, BRRI dhan51 contributed the highest yield under stress treatment. Submergence tolerant rice cultivars (Binadhan-11, Binadhan-12, BRRI Dhan51 and BRRI Dhan52) had maintained higher tiller number, 1000-grain weight and the higher number of grains per panicle during submergence, as compared to susceptible rice cultivar BRRI Dhan49.
J Bangladesh Agril Univ 17(4): 545–550, 2019
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Reddy, M. D., A. R. Sharma i M. M. Panda. "Flood tolerance of rice grown under intermediate deepwater conditions (15–50 cm) as affected by phosphorus fertilization". Journal of Agricultural Science 117, nr 3 (grudzień 1991): 319–24. http://dx.doi.org/10.1017/s0021859600067058.
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SUMMARYThe effect of phosphorus fertilizer on the performance of an improved semi-dwarf (100 cm), long duration (170 days), photosensitive rice variety CR 1016, grown under conditions of intermediate deepwater (15–50 cm) and simulated flash flooding (80 cm), was investigated at Cuttack, India in 1985, 1987 and 1988. Growth and yield of rice subjected to overhead flash flooding (complete submergence) at the vegetative stage for 10 days was decreased significantly compared with partial submergence in water of intermediate depth. The adverse effect of complete submergence was due to greater tiller mortality and lower number and/or weight of panicles at maturity. Rice plants fertilized with P tolerated flooding better and produced significantly higher grain yields than when no P was applied. There was no significant effect of P application on the crop grown under natural unsubmerged conditions, except when it was raised in the same plots as the previous year and may therefore have benefited from residual effects. Therefore, application of 8.7–17.5 kg P/ha along with 60 kg N and 16.7 kg K/ha at sowing was essential to overcome the deleterious effects of submergence on rice grown under waterlogged conditions.
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Syafiqah Alia Sazali, Mohd Shukor Nordin, Noraziyah Abd. Aziz Shamsudin, Rozilawati Shahari, Mohd Rafii Yusop, Mohd Shahril Firdaus Ab Razak, Rahiniza Kamaruzaman i Mohd Syahmi Salleh. "Susceptibility of Malaysian Rice (Oryza sativa L.) Cultivar to Saline Water Submergence Based on the Morphological Traits". Journal Of Agrobiotechnology 12, nr 2 (4.09.2021): 47–55. http://dx.doi.org/10.37231/jab.2021.12.2.257.
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Saline water submergence is a newly emerge abiotic stress jeopardizing rice production especially for the rice fields located nearby or alongside coastal areas. The stress was caused by the intrusion of sea water into those rice fields causing flash flood mainly during monsoon season. The present study was conducted to evaluate susceptibility level of selected Malaysian rice cultivars to saline water submergence at seedling stage based on the morphological traits and survival rate. There were six genotypes involved in the study mainly IR64-Sub1 as submergence tolerant control, Pokkali as salinity tolerant control, IR64 as susceptible control and MR297, MR284 and MR253 as local rice cultivars, respectively. The experiment was conducted using split plot design with three replications. On the day 14 after germination, all rice seedlings were totally submerged of about one-meter depth in a polyethylene tank containing saline water at 0, 4, 8 and 12 dS/m for 14 days while the non-submerged plant was control of the experiment. Seedling growth attributes and survival rate were recorded before, right after de-submerged and 14 days after de-submerged. All genotypes however were susceptible to saline water submergence at 4, 8 and 12 dS/m. In contrast, under 0 dS/m, IR64-Sub1 recorded significantly higher survival rate at 83% as compared to MR284 (17%), MR297 (17%), Pokkali (8%), MR253 (0%) and IR64 (0%). All genotypes were not survived under saline submergence. Therefore, further phenotypic screening of rice genetic resources originated from or nearby coastal areas could be suggested in order to increase chance of identifying potentially tolerant genotype to saline water submergence.
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Yuan, Jian Hong, i Xi Zhu. "Dynamic Response of a Ring-Stiffened Cylindrical Shell Subjected to Underwater Explosive Loading". Applied Mechanics and Materials 105-107 (wrzesień 2011): 931–36. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.931.
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Choosing scaled stiffened cylindrical shell model as simulation object, the simulation model of stiffened cylindrical shell subjected to underwater explosion load is built by using MSC-DYTRAN finite element analysis software, the typical test conditions which shock factor is 1.1 is simulated, the damage properties of stiffened cylindrical Shell is analyzed, numerical results are compared with experimental data, it is proved that the simulation method is effective and feasible. By performing a series of numerical experiments, the influence of attack angle of explosive and submergence depth of model on the elastic-plastic dynamic response were investigated. It is shown that angle of 90 degrees is the most serious attack angle, angle of 0 degrees is less serious than other angle, the submergence depth of stiffened cylindrical shell has obvious influence on dynamic response, the more deep cylindrical shell is, the more serious cylindrical shell is damaged.
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Bhaduri, Debarati, Koushik Chakraborty, A. K. Nayak, Mohammad Shahid, Rahul Tripathi, Rashmita Behera, Sudhanshu Singh i Ashish K. Srivastava. "Alteration in plant spacing improves submergence tolerance in Sub1 and non-Sub1 rice (cv. IR64) by better light interception and effective carbohydrate utilisation under stress". Functional Plant Biology 47, nr 10 (2020): 891. http://dx.doi.org/10.1071/fp19364.
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Besides genetic improvement for developing stress-tolerant cultivars, agronomic management may also add considerable tolerance against different abiotic stresses in crop plants. In the present study, we evaluated the effect of six different spacing treatments (S1: 10 × 10 cm; S2: 15 × 10 cm; S3:15 × 15 cm; S4:20 × 10 cm; S5: 20 × 15 cm; S6: 20 × 20 cm (row-row × plant-plant)) for improving submergence tolerance in rice. A high yielding submergence intolerant rice cultivar IR64 was tested against its SUB1 QTL introgressed counterpart (IR64-Sub1) for 12 days of complete submergence for different spacing treatments in field tanks. Relatively wider spaced plants showed higher individual plant biomass and early seedling vigour, which was particularly helpful for IR64 in increasing plant survival (by 150% in S6 over S1) under 12 days of submergence, whereas the improvement was less in IR64-Sub1 (13%). Underwater radiation inside the plant canopy, particularly beyond 40 cm water depth, was significantly greater in wider spacing treatments. Leaf senescence pattern captured by SPAD chlorophyll meter reading and chlorophyll fluorescence imaging data (Fm, Fv/Fm) taken at different time intervals after stress imposition suggested that there was lesser light penetration inside the canopy of closer spaced plants, and that it might hasten leaf senescence and damage to the photosynthetic system. The initial content of total non-structural carbohydrate (NSC) was higher in wider spaced plants of IR64, and also the rate of depletion of NSC was lesser compared with closer spaced plants. In contrast, there was not much difference in NSC depletion rate under different spacing in IR64-Sub1. Further, higher antioxidant enzyme activities in wider spaced plants (both IR64 and IR64-Sub1) after de-submergence indicated better stress recovery and improved tolerance. Taken together we found that wider spacing (row-row: 20 cm and plant-plant: 15 cm and more) can significantly improve submergence tolerance ability in rice, particularly in submergence intolerant non-Sub1 cultivar like IR64, perhaps due to better underwater light penetration, delayed leaf senescence and slower depletion of NSC reserve.
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Tyvand, Peder A. "Impulsive Motion of a Wide Torus Submerged Below a Free Surface". Journal of Ship Research 41, nr 03 (1.09.1997): 195–209. http://dx.doi.org/10.5957/jsr.1997.41.3.195.
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The impulsively starting motion of a torus submerged horizontally below a free surface is studied analytically, using a small-time expansion. The torus is assumed wide, i.e., the torus radius is much larger than its initial submergence depth. A quasi-two-dimensional theory is applied. Its accuracy is checked by comparing the first-order surface elevation with slender-body theory. The hydrodynamic force and torque are investigated in the first three orders of the small-time expansion. The ratio between the cross-section radius and submergence depth is arbitrary (between 0 and 1). The general motion of the torus consists of all six degrees of freedom. Special emphasis is put on the five different leading-order nonlinear interactions that may occur between these modes: surge/heave, surge/roll, sway/roll, heave/roll, and roll/yaw. These leading-order nonlinear interactions give rise to zeroth-order forces and torques. The leading-order gravitational effects are investigated.
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Orakwe, Luis Chukwuemeka, Kingsley Nnaemeka Ogbu, Joseph Ikenna Ubah, Chike Pius Nwachukwu, Chinaza Rosemary Akamonye i Uchenna Peter Okoro. "Determination of Hydraulic Roughness Coefficients of Some Vegetated Species in Awka, Nigeria". ASM Science Journal 17 (5.12.2022): 1–8. http://dx.doi.org/10.32802/asmscj.2022.1008.
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In this study, selected types of grasses were studied to determine their hydraulic roughness coefficient and to select the most suitable grass for erosion control. The experiments were performed in twelve trapezoidal open channels measuring 5 m x 0.12 m x 0.03 m at different flow depths (0.001m, 0.002m, 0.003m, 0.004m and 0.005m) and at varying bed slope (0.2%, 0.3%, and 0.4%). Overall, Bahama grass showed the highest Manning’s n-value due to its deep root system and creeping nature. For each slope, the degree of submergence, Reynolds number, and flow depth increases as Manning’s n decreases. As the flow depth increases, the Reynolds number increased while the drag coefficient, Cd decreases.
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Singh, Balwinder, i M. S. Bajwa. "Studies on the leaching of urea in sodic soils". Journal of Agricultural Science 106, nr 2 (kwiecień 1986): 323–30. http://dx.doi.org/10.1017/s0021859600063917.
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SUMMARYLaboratory experiments were conducted in PVC columns to study the leaching and transformation of applied urea in sodic soils (Gharachon loam-Aquic Natrustalf and Domeli silty clay loam-Aquic Camborthid) reclaimed by gypsum application and kept submerged for 7 or 14 days after fertilizer application. The effect of different depths of irrigation water (5, 7·5, 10, 20 and 30 cm) on urea leaching was studied in a sandy loam sodic soil. In another experiment, the effect of time interval (0 or 4 days) between urea application and initiation of submergence with distilled water (for 7 or 14 days) was investigated involving two recently reclaimed sodic soils (Gharachon loam and Domeli silty clay loam). The results showed that the extent of urea leaching mainly depended upon soil texture. In Domeli silty clay loam, urea penetrated to 20 cm depth with peaks in concentration at 12·5 cm at both 7 and 14 days of submergence. In Gharachon loam urea-N moved to 25 cm depth after 7 days and to 35 cm after 14 days. In the sandy loam sodic soil peaks of urea-N concentration were observed at 12·5, 22·5 and 27·5 cm depths after infiltration of 5, 7·5 and 10 cm depth of water, respectively. Leaching with 20 and 30 cm depths of water moved urea deeper (below 50 and 70 cm, respectively). In recently reclaimed soils, leaching initiated immediately after fertilizer application displaced urea to slightly deeper layers compared with leaching initiated 4 days after urea application. Leaching may not be an important loss mechanism of urea-N in loam or silty clay loam sodic soils. However, in light-textured sandy loam sodic soils leaching beyond the root zone can be expected to create fertilizer management problems.
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Zhou, Rui Fen, Lin Bai, Kang Xing Dong i Yu Xin Dai. "Suspended Load Prediction on Sucker Rod Suspension Load Based on Artificial Neural Network". Advanced Materials Research 217-218 (marzec 2011): 1040–43. http://dx.doi.org/10.4028/www.scientific.net/amr.217-218.1040.
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Using the test data of suspendsion load on socker rod from oilfield database, a prediction model is presented, which adapted the improved L-M neural network algorithm and explored the 6 effect factors’ relationship: the rod stroke, frequency of strokes, rod diameter, pump diameter, submergence depth and pump setting depth. With training the model,and higher training accuracy is acquired, which shows using this method to predict the suspendsion load is effective.
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Lumpkin, Rick, Semyon A. Grodsky, Luca Centurioni, Marie-Helene Rio, James A. Carton i Dongkyu Lee. "Removing Spurious Low-Frequency Variability in Drifter Velocities". Journal of Atmospheric and Oceanic Technology 30, nr 2 (1.02.2013): 353–60. http://dx.doi.org/10.1175/jtech-d-12-00139.1.
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Abstract Satellite-tracked drifting buoys of the Global Drifter Program have drogues, centered at 15-m depth, to minimize direct wind forcing and Stokes drift. Drogue presence has historically been determined from submergence or tether strain records. However, recent studies have revealed that a significant fraction of drifters believed to be drogued have actually lost their drogues, a problem that peaked in the mid-2000s before the majority of drifters in the global array switched from submergence to tether strain sensors. In this study, a methodology is applied to the data to automatically reanalyze drogue presence based on anomalous downwind ageostrophic motion. Results indicate that the downwind slip of undrogued drifters is approximately 50% higher than previously believed. The reanalyzed results no longer exhibit the dramatic and spurious interannual variations seen in the original data. These results, along with information from submergence/tether strain and transmission frequency variations, are now being used to conduct a systematic manual reevaluation of drogue presence for each drifter in the post-1992 dataset.
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Juraeva, Makhsuda, i Dong Jin Kang. "Mixing Enhancement of a Passive Micromixer with Submerged Structures". Micromachines 13, nr 7 (30.06.2022): 1050. http://dx.doi.org/10.3390/mi13071050.
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A passive micromixer combined with two different mixing units was designed by submerging planar structures, and its mixing performance was simulated over a wider range of the Reynolds numbers from 0.1 to 80. The two submerged structures are a Norman window and rectangular baffles. The mixing performance was evaluated in terms of the degree of mixing (DOM) at the outlet and the required pressure load between inlet and outlet. The amount of submergence was varied from 30 μm to 70 μm, corresponding to 25% to 58% of the micromixer depth. The enhancement of mixing performance is noticeable over a wide range of the Reynolds numbers. When the Reynolds number is 10, the DOM is improved by 182% from that of no submergence case, and the required pressure load is reduced by 44%. The amount of submergence is shown to be optimized in terms of the DOM, and the optimum value is about 40 μm. This corresponds to a third of the micromixer depth. The effects of the submerged structure are most significant in the mixing regime of convection dominance from Re = 5 to 80. In a circular passage along the Norman window, one of the two Dean vortices burst into the submerged space, promoting mixing in the cross-flow direction. The submerged baffles in the semi-circular mixing units generate a vortex behind the baffles that contributes to the mixing enhancement as well as reducing the required pressure load.
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Filippas, Evangelos S., George P. Papadakis i Kostas A. Belibassakis. "Free-Surface Effects on the Performance of Flapping-Foil Thruster for Augmenting Ship Propulsion in Waves". Journal of Marine Science and Engineering 8, nr 5 (19.05.2020): 357. http://dx.doi.org/10.3390/jmse8050357.
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Flapping foils located beneath or to the side of the hull of the ship can be used as unsteady thrusters, augmenting ship propulsion in waves. The basic setup is composed of a horizontal wing, which undergoes an induced vertical motion due to the ship’s responses in waves, while the self-pitching motion of the wing is controlled. Flapping foil thrusters can achieve high level of thrust as indicated by measurements and numerical simulations. Due to the relatively small submergence of the above biomimetic ship thrusters, the free-surface effects become significant. In the present work, the effect of the free surface on the performance of flapping foil thruster is assessed by means of two in-house developed computational models. On one hand, a cost-effective time-domain boundary element method (BEM) solver exploiting parallel programming techniques and general purpose programming on graphics processing units (GPGPU) is employed, while on the other hand a higher fidelity RANSE finite volume solver implemented for high performance computing (HPC) is used, and comparative results are presented. BEM and RANSE calculations present quite similar trends with respect to mean submergence depth, presenting 12%, 28%, and 18% of differences concerning the mean values of lift, thrust, and moment coefficients, respectively. The latter differences become very small after enhancement of the BEM model to include viscous corrections. Useful information and data are derived supporting the design of the considered biomimetic thrusters, for moderate submergence depths and conditions characterized by minor flow separation effects.
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Wei, Wenli, Yuling Liu i Bin Lv. "Numerical simulation of optimal submergence depth of impellers in an oxidation ditch". Desalination and Water Treatment 57, nr 18 (13.03.2015): 8228–35. http://dx.doi.org/10.1080/19443994.2015.1021840.
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