bluuebunny/crossref_metadata_2025 huggingface dataset:
Convolutional neural network for classifying space target of the same shape by using RCS time series
Authors: Chen Jian , Xu Shiyou , Chen Zengping
Published: September 2018

Warhead and decoy classification is one of the most important and difficult technical problems in ballistic missile defence. The conventional methods extract features from the measured data and employ some classification algorithms. However, it is hard to extract all the information embedded in the raw data, and there might be contradictory features lowering the classification ability. A one‐dimensional convolutional neural network structure named RCSnet was proposed to classify the warhead and decoy targets of the same shape in midcourse, which directly utilises the radar cross‐section (RCS) time series. It was compared with 5 conventional classification algorithms which used 26 selected features on simulation dataset, and it outperformed them in both classification performance and predicting speed. Different training algorithms and networks of the RCSnet structure with different filter numbers were explored for better utilising the RCSnet.
Velocity profiles of [CII], [CI], CO, and [OI] and physical conditions in four star-forming regions in the Large Magellanic Cloud
Authors: Okada Yoko , Güsten Rolf , Requena-Torres Miguel Angel , Röllig Markus , Stutzki Jürgen , Graf Urs Ulrich , Hughes Annie
Published: September 2018

Aims. The aim of our study is to investigate the physical properties of the star-forming interstellar medium (ISM) in the Large Magellanic Cloud (LMC) by separating the origin of the emission lines spatially and spectrally. The LMC provides a unique local template to bridge studies in the Galaxy and high redshift galaxies because of its low metallicity and proximity, enabling us to study the detailed physics of the ISM in spatially resolved individual star-forming regions. Following Okada et al. (Okada, Y., Requena-Torres, M. A., Güsten, R., et al. 2015, A&A, 580, A54), we investigate different phases of the ISM traced by carbon-bearing species in four star-forming regions in the LMC, and model the physical properties using the KOSMA-τ PDR model.

Methods. We mapped 3–13 arcmin2 areas in 30 Dor, N158, N160, and N159 along the molecular ridge of the LMC in [C II] 158 μm with GREAT on board SOFIA. We also observed the same area with CO(2-1) to (6-5), 13CO(2-1) and (3-2), [C I] 3P1–3P0 and 3P2–3P1 with APEX. For selected positions in N159 and 30 Dor, we observed [O I] 145 μm and [O I] 63 μm with upGREAT. All spectra are velocity resolved.

Results. In all four star-forming regions, the line profiles of CO, 13CO, and [C I] emission are similar, being reproduced by a combination of Gaussian profiles defined by CO(3-2), whereas [C II] typically shows wider line profiles or an additional velocity component. At several positions in N159 and 30 Dor, we observed the velocity-resolved [O I] 145 and 63 μm lines for the first time. At some positions, the [O I] line profiles match those of CO, at other positions they are more similar to the [C II] profiles. We interpret the different line profiles of CO, [C II] and [O I] as contributions from spatially separated clouds and/or clouds in different physical phases, which give different line ratios depending on their physical properties. We modeled the emission from the CO, [C I], [C II], and [O I] lines and the far-infrared continuum emission using the latest KOSMA-τ PDR model, which treats the dust-related physics consistently and computes the dust continuum SED together with the line emission of the chemical species. We find that the line and continuum emissions are not well-reproduced by a single clump ensemble. Toward the CO peak at N159 W, we propose a scenario that the CO, [C II], and [O I] 63 μm emission are weaker than expected because of mutual shielding among clumps.
Accretion heated atmospheres of X-ray bursting neutron stars
Authors: Suleimanov V. F. , Poutanen J. , Werner K.
Published: September 2018

Some thermonuclear (type I) X-ray bursts at the neutron star surfaces in low-mass X-ray binaries take place during hard persistent states of the systems. Spectral evolution of these bursts is well described by the atmosphere model of a passively cooling neutron star when the burst luminosity is high enough. The observed spectral evolution deviates from the model predictions when the burst luminosity drops below a critical value of 20–70% of the maximum luminosity. The amplitude of the deviations and the critical luminosity correlate with the persistent luminosity, which leads us to suggest that these deviations are induced by the additional heating of the accreted particles. We present a method for computation of the neutron star atmosphere models heated by accreted particles assuming that their energy is released via Coulomb interactions with electrons. We computed the temperature structures and the emergent spectra of the atmospheres of various chemical compositions and investigate the dependence of the results on the velocity of accreted particles, their temperature and the penetration angle. We show that the heated atmosphere develops two different regions. The upper one is the hot (20–100 keV) corona-like surface layer cooled by Compton scattering, and the deeper, almost isothermal optically thick region with a temperature of a few keV. The emergent spectra correspondingly have two components: a blackbody with the temperature close to that of the isothermal region and a hard Comptonized component (a power law with an exponential decay). Their relative contribution depends on the ratio of the energy dissipation rate of the accreted particles to the intrinsic flux from the neutron star surface. These spectra deviate strongly from those of undisturbed, passively cooling neutron star atmospheres, with the main differences being the presence of a high-energy tail and a strong excess in the low-energy part of the spectrum. They also lack the iron absorption edge, which is visible in the spectra of undisturbed low-luminosity atmospheres with solar chemical composition. Using the computed spectra, we obtained the dependences of the dilution and color-correction factors as functions of relative luminosities for pure helium and solar abundance atmospheres. We show that the helium model atmosphere heated by accretion corresponding to 5% of the Eddington luminosity describes well the late stages of the X-ray bursts in 4U 1820−30.
Using tree-rings to determine large wood residence time and transport pulses in a gravel-bed river
Authors: Boivin Maxime , Buffin-Bélanger Thomas , Arseneault Dominique
Published: September 2018

The Saint-Jean River (SRJ) in Eastern Canada is prone to the formation of very large rafts of wood. Managers of the SJR suspected these jams to influence salmon migration and carried out a dismantling operation to remove large wood accumulated in a 1.2 km long wood raft. This operation became a great opportunity to address key issues relating to large wood dynamics in a fluvial system: residence time and flood contribution to wood recruitment and transport. During the dismantling, we systematically sampled 319 trees from which year of death could be estimated from dendrochronology and year of accumulation in the raft could be obtained from satellite and aerial photos. These two dates allowed us to quantify the residence time for 262 datable large wood (LW) within the fluvial system, to examine the peak years of LW recruitment and to correlate the raft growth rate with hydrometeorological conditions since 1993. The results also emphasized four types of LW flood related to wood dynamics: 1) an erosive flood that produces a large amount of wood in river, 2) a mobilizing flood that carries large quantities of wood, 3) a flood mix that both recruits and transports large quantities of wood, and 4) an ice-breakup flood.
Numerical simulation of bedload tracer transport associated with sand bar formation, bank erosion, and channel migration
Authors: Iwasaki Toshiki , Yamaguchi Satomi , Yabe Hiroki
Published: September 2018

An understanding of bedload transport processes is an essential research goal for better prediction of river morphology and morphodynamics as well as the transport and fate of sediment-bound materials in river systems. Passive tracer particles have been used widely to monitor bedload transport processes in rivers by measuring the spatiotemporal distribution of the bedload tracers. Here, we propose a numerical model for reproducing the transport of bedload tracers in river systems, more specifically, the behaviours of bedload tracers under the influence of complex river morphodynamics. A two-dimensional morphodynamic model is combined with a flux-based bedload tracer model with use of the active layer approach. The model is applied to a laboratory experiment that demonstrates the transport processes within the channel of bedload tracers supplied from the floodplain. The numerical model effectively reproduces the main features of the experiment, namely, the bedload tracers supplied from the floodplain due to bank erosion deposit onto sand bars developed within the channel. Because the sand bars cause a very long residence time of the bedload tracers within the bed, the transport speed of the tracers is slowed significantly under the influence of bar formation and channel migration.
Transport and deposition of fine sediment in a channel partly covered by flexible vegetation
Authors: Box Walter , Västilä Kaisa , Järvelä Juha
Published: September 2018

Riparian plants exert flow resistance and largely influence the flow structure, which affects erosion, deposition and transport processes of fine sediments. Predicting these vegetative effects is important for flood, sediment and nutrient management. However, predictions on the fate of sediments are complicated by uncertainties associated with the suitable parameterization of natural plants and the associated effects on the turbulent flow field and on the variables in the transport equations. The aim of this study is to quantify deposition and transport of fine sandy sediment in a partly vegetated channel under laboratory conditions. Care was taken to reproduce conditions typical of vegetated floodplain flows including dense flexible grassy understory as a starting point. The experiments were conducted in a flume that is specifically designed to recirculate fine sediment. We measured suspended sediment concentrations with optical turbidity sensors and determined patterns of net deposition over the vegetated parts of the cross section. The flow field was determined with acoustic Doppler velocimetry. Our investigations are intended to improve future predictions of fine sediment storage and transport in natural or constructed vegetated channels, and the first results reported herein were useful in designing further, on-going experiments with complex combinations of vegetation and channel geometry. Key words: sediment transport, suspended sediment, deposition, riparian vegetation, flow field.
A flume study to investigate the contribution of main-channel bedforms on levee formation
Authors: Branß Till , Núñez-González Francisco , Dittrich Andreas , Aberle Jochen
Published: September 2018

Natural levees can be observed worldwide in nearly all river systems characterized by frequent flooding in combination with the transport of suspended bed material. Several parameters and processes have been suggested to explain the formation and the highly variable geometry of natural levees. However, the effect of bedforms migrating in the main-channel has not been amongst the studied parameters and processes. To fill this gap, this study investigates the relationship between bedforms and natural levee formation by flume experiments. Experiments were conducted in a 2 m wide and 30 m long sediment recirculating flume, monitoring the bed level elevation in the main channel by ultrasonic sensors as well as recording the levee development on the floodplain by a camera. The effect of different bed configurations on the developed levees is compared, and discussed, showing that bedforms could enhance levee formation.
Influence of hydrology, sediment supply and sediment gradation on river bar morphodynamics: application to the Loire River at Bréhémont (France)
Authors: Cordier Florian , Tassi Pablo , Claude Nicolas , Crosato Alessandra , Rodrigues Stephane , Van Bang Damien Pham
Published: September 2018

Rivers inherently show heterogeneous sediment sizes and can also show a strong sediment supply variability in time because of natural episodic events or as a consequence of human activities, which alter the characteristics and dynamics of alluvial bars at the macro-scale. The impact of the combination between sediment size heterogeneity and sediment supply variation, or even with other forcings (i.e. hydrology, channel geometry) remains poorly documented. In this work, a physics-based numerical model is applied on a trained reach of a sandy-gravel bed river to investigate the combination of these parameters on bar morphodynamics. The morphodynamic computations are performed with a two-dimensional depth-averaged hydrodynamic solver, internally coupled to a sediment transport and bed evolution module, which estimate the transport of graded sediment and model bed stratigraphy, respectively. A 1 km long reach of the Loire River at Bréhémont (France) is selected to conduct the numerical investigations. The interaction between several forcing mechanisms induces highly complex bar morphodynamic processes in this area.A comprehensive set of high-definition data is available, which allows to study the river morphodynamics for a succession of three flooding events and a period of low flows. Based on this model, a variety of scenarios is presented with the aim of exploring the implications of sediment gradation, geometrical and boundary forcing effects on in situ bars morphodynamics.
Effect of riparian vegetation roots on development of meander bends in Tarim River, Northwest China
Authors: Yu Guo-An , Li Zhiwei , Huang He Qing , Yao Weiwei
Published: September 2018

Meandering channel with distorted bends develops along the Tarim River, the longest dryland river in China. The river bank and bed is majorly composed of coarse silt and fine sand and almost none clay content, making the bank strength very low. The development of meander bend in such environment hence is somehow irrational. We preliminarily investigate the effects of riparian vegetation root on bend development in this region through examining the root cohesion and its enhancement on bank stability. In-situ measurements and sampling of roots from local typical riparian vegetation (i.e., populous, Tamarix, and Phragmites Australis) were conducted to obtain root parameters like diameter and root area ratio. Local bend curvature corresponding to sampling sites are also obtained. BSTEM model is used to quantitatively estimate the effects of different root conditions on improving channel bank strength. Four vegetation root scenarios were modelled, i.e., tree (populous), shrub (Tamarix), grass (Phragmites Australis) and no root. The results show that root supplies effective cohesive reinforcement for the channel bank and enhances the bank safety factors (Fs). Riparian vegetation should be a necessary condition for development of meandering channel in Tarim River.
Evaluation of an acoustic Doppler technique for bed-load transport measurements in sand-bed Rivers
Authors: Conevski S. , Winterscheid A. , Ruther N. , Guerrero M. , Rennie C.
Published: September 2018

The bottom tracking (BT) feature of the acoustic Doppler current profilers (ADCP) have emerged as a promising technique in evaluating the bed load. Strong statistical correlations are reported between the ADCP BT velocity and the transport rate obtained by physical sampling or dune tracking; however, these relations are strictly site-specific and a local calibration is necessary. The direct physical sampling is very labor intensive and it is prone to high instrument uncertainty. The aim of this work is to develop a methodology for evaluating the bed load transport using commercial ADCPs without calibration with physical samples. Relatively long stationary measurements were performed in a sand-bed and sand gravel rivers, using three different ADCPs working at 3MHz, 1.2MHz and 0.6MHz. Simultaneously, bed load samples were collected with physical samplers, and the riverbed was closely observed with digital cameras mounted on the samplers. It is demonstrated that the kinematic transport model can yield a relatively good estimate of the transport rate by directly using filtered apparent velocity, the knowledge of the hydraulic conditions and instrument-related calibration coefficients. Additionally, the ADCP data can help in qualitative assessment of the physical sampling. Future investigation of the backscattering echo and further confirmation of the BT apparent velocity should be performed in laboratory-controlled conditions.
Near wake of emergent vegetation patches in shallow flow
Authors: Wunder Sina , Trevisson Michele , Heckele Christoph , Chagot Loïc , Murphy Brendan , McLelland Stuart , Moulin Frédéric , Eiff Olivier
Published: September 2018

Vegetation patches are particularly diffcult to quantify in terms of flow resistance due to their complex geometry and topological behaviour under hydrodynamic loading. They not only influence the water level and mean velocities due to the drag they exert, but they also affect the turbulence and hence all transfer processes such as the sediment transport dynamics in the surrounding area. Existing studies dealing with the interaction of flow and vegetation concern mostly measurements of the drag of single plants followed by analyses of the flow through and above homogeneous canopies. However, studies of the flow around single patches are uncommon and are mostly restricted to arrays of cylindrical elements. For leafy plants there is very limited information and understanding of how the flow evolves through and around the plants. This work aims at filling these gaps via complementary physical lab-scale and numerical experiments of the flow through and around an artificial vegetation patch. The experimental work focuses on PIV measurements in the wake of the patches whereas the method of large-eddy simulation is employed to provide additional insights of the flow inside the patch. Here we focus on results based on the PIV measurements.
Experimental Study of Submerged Vanes in Intakes under Sediment Feeding Conditions
Authors: Bor Türkben Aslı
Published: September 2018

Sediment is transported along the river flow and deposited in the mouth of the intake structure over time and reducing the water intake capacity. Nowadays, many water intake structures lose their function and are closed to operation. To deal with this problem, recently, submerged vane application has offered a practical and economical solution. The aim of this study was to evaluate the efficiency of three vane installations under sediment feeding conditions by comparing the bed topography before and after vanes were installed. For that purpose, experiments were carried out in a laboratory channel running for 90-degree intake angle. Three vanes were installed in one column at near the intake entrance. The vanes dimensions were equal to; 3cm height, 12cm long, 10 mm thick, and aligned with α = 20° angle to flow direction. The tests were run until equilibrium was reached, i.e. when the outgoing solid discharge was equal or larger than 90% of the incoming. Once the bed topography remained stable, bed and water level surfaces were measured. tests were carried out by feeding sediment from upstream of the main channel.
Experimental study on the performance analysis of river levee using new substance for improving earth surface resistance
Authors: Ko Dongwoo , Kang Joongu , Kim Sungjoong , Ryu Yonguk
Published: September 2018

The reasons why levee breaches during floods are largely due to overtopping, seepage, and structurally induced piping. According to an analysis of domestic and overseas reported cases of levee breaches, overtopping was found to be the cause for approximately 40% of all cases of breach. Despite such efforts of previous research to establish disaster prevention plans associated with levee breaches, to enhance our understanding of the processes and reasons, further research regarding the prediction of levee breaches must be undertaken by accumulating test data under several different conditions and further verification of the data using numerical models must also be undertaken. In this study, development of technologies regarding a new environmentally friendly bio-polymer capable of protecting levees from erosion is being undertaken. Breach mechanisms was assessed using an image measurement system that collected data regarding the breach progress of the levee, close-up views of the breaching surface, and the formation of the final breaching cross-sections. Further, levee slopes were covered with a bio-soil mixed with a new substance for the purpose of analyzing the stability and the time delay effect.
Impact Analysis of Sand Dredging from Alluvial Tidal River
Authors: Islam Md Kabirul , Al Kibriya Numan , Dustegir Md. Maruf
Published: September 2018

The Government of Bangladesh has planned to make a large build up area (BUA) in a newly developed sedimentary point bar (locally known as ‘Char’) at Lebukhali along the northern bank of Payra river in the southern part of the country. From a study it was revealed that, this sedimentary bar has to be raised by 3.45 meters from MSL to keep it free from any extreme events (like tidal and storm surge effects) for 100 years return period. Accordingly, it was planned to collect the required filling material (estimated 57.6 million m3 of sand/soil) by dredging the same river bed. In Bangladesh dredging of river is very popular and widely undertaken to collect filling and construction material, but its adverse impact on river bed, bank and adjacent areas are hardly probed. This study aimed at analyzing the adverse impacts of dredging from Payra River bed. Four alternative sand bars have been identified as dredging area at varying distances located both upstream and downstream of the proposed site. The dredging impacts were analyzed for different boundary conditions. The study is based on physical survey (topographic and bathymetric surveys), historical data and numerical model analysis. Numerical model is applied through Delf 3D to investigate the impact on flow parameters: flood depth and velocity magnitude. Continuous field visit and observations were made through last one year to observe real impact. The analysis revealed that dredging of any of the bars have resulted changes in flow field. The distance of dredging point does not control the flow field rather the dredging volume, depth and upstream conditions determine the effect on bank erosion. As such, the dredging locations have been prioritized considering the least possible effects on river bank erosion and founded that little erosion is taking place for both upstream and downstream region. However, the long term impacts in other areas of the river need to be investigated as the time pass.
Viscosity effects on local scour around vertical structures in clear-water conditions
Authors: Manes Costantino , Coscarella Francesco , Rogers Ashley , Gaudio Roberto
Published: September 2018

Local scour represents the erosion process that occurs at the base of hydraulic structures overlying sediment beds. Horseshoe vortices forming at the bed-structure junction are the main responsible for sediment removal and dictate erosion rates as well as the maximum erosion depth resulting from a significant flow event. In steady-flow conditions this is often referred to as the equilibrium scour depth, which, for many hydraulic structures, represents a key parameter for foundation-design and risk-assessment purposes. The equilibrium scour depth has been investigated for decades and many predictive formulae have been developed following the classical empirical approach, whereby numerous experimental datasets are used to isolate and identify the influence of non-dimensional groups emerging from dimensional analysis. Within this context, the influence of obstacle Reynolds numbers, and consequently of viscous forces, has always been neglected because of the large Re values normally encountered in engineering and laboratory conditions. The present paper demonstrates that this assumption is largely incorrect especially for beds made of sand or finer material. The theoretical analysis presented in Manes and Brocchini ([1]) is herein extended to include viscosity effects and investigate their importance on equilibrium scour depths forming around obstacles resembling bridge piers.
Measuring bedload grain-size distributions with passive acoustic measurements
Authors: Geay Thomas , Zanker Sébastien , Petrut Teodor , Recking Alain
Published: September 2018

Bedload Self-Generated Noise (SGN) measurements consist in deploying an underwater microphone (i.e. a hydrophone) in the water course and to record the ambient noise of a river. The use of hydrophones is of interest as it can be easily deployed and can provide a continuous monitoring of bedload transport. However, developments are still required to fully understand how bedload characteristics (e.g. specific flux or granulometry) are related to bedload SGN parameters (e.g. acoustic power and spectrum). Laboratory experiments have shown that central and peak frequencies of bedload noise decrease as the particle size increases, just like in string instruments where the tone frequency decreases from a narrow string to a broader string. In this paper, we propose to test a new inverse method enabling the estimation of bedload grain size distributions from SGN measurements. The inverse method is based on a theoretical modelling of the noise generated by a bedload mixture. SGN and physical sampling measurements have been made in 5 French alpine rivers having several transport conditions (bedload D50 from 1 to 40 mm) and varying slopes (0.05 to 1%). Measurements were made for specific bedload flux varying from 10 to 150 g.m-1s-1. The proposed inverse method was used to estimate the bedload grain size distributions. SGN results are compared to bedload samples and are found to largely overestimate sampled granulometries. Finally, it is observed that the spectral characteristics of bedload SGN are not related to bedload GSD but rather to the roughness of the river bed, acting as a source of attenuation and shaping bedload SGN spectra.
Experimental bed active-layer survey with active RFID scour chains: Example of two braided rivers (the Drac and the Vénéon) in the French Alps
Authors: Brousse Guillaume , Liébault Frédéric , Arnaud-Fassetta Gilles , Vazquez-Tarrio Daniel
Published: September 2018

An innovative scour chains device composed of active UHF RFID tags is proposed to survey the bed active layer. This device is tested on three cross-sections deployed along two large Alpine braided rivers: the Drac and the Vénéon. A specific field deployment procedure is developed, using a technique of drilling with a tube and a jack-hammer. After each flood, the device allows recording presence/absence of active tags inside a scour chain column. This provides the maximum scouring depth of the bed at the position of the column, and the topographic resurvey of the channel provides the net fill depth. Results show that bed active layer can reach up to 1.43 m during high flow conditions and remains <0.1 m during low and moderate flows. The main advantage of this technology against traditional scour chains is the rapidity and easiness with which the scouring depth is obtained after a flow event, notably under conditions of massive net deposition after the flow. This technology is therefore particularly suitable for large braided rivers, where traditional scour chains necessitate too much field efforts for their relocation, and can be rapidly lost under deep active layers.
Getting information on suspended sediments in a large river from acoustic backscatter
Authors: Vergne Adrien , Berni Céline , Le Coz Jérôme
Published: September 2018

There has been a growing interest in the last decade in extracting information on Suspended Sediment Concentration (SSC) from acoustic backscatter in rivers. Quantitative techniques are not yet effective, but acoustic backscatter already provides qualitative information on suspended sediments. In particular, in the common case of a bi-modal sediment size distribution, corrected acoustic backscatter can be used to look for sand particles in suspension and provide spatial information on their distribution throughout a river crosssection. This paper presents a case-study where these techniques have been applied.
Development of a method for suspended sediment transport monitoring by means of ADCP measurements
Authors: Aleixo Rui , Guerrero Massimo , Ruther Nils , Stokseth Siri
Published: September 2018

Monitoring stations in rivers and water courses are an important mean to obtain critical data about the different variables that play a role in the hydrodynamics and ecological processes. Measuring suspended sediment concentration often requires the displacement of equipment and manpower to the field. This is often expensive and not practical, in particular during severe weather and flow conditions. A method to determine the suspended sediment concentration as a result of ADCP remote measurements is here presented. This method relies on the relationship between the attenuation to backscatter ratio and the normalized attenuation coefficient. To test this method, data from a field monitoring station in Kokel, on the banks of the Devoll river in Albania, is used.
Experimental Studies on the Formation of Air-core inside the Drop Shaft
Authors: Rhee Dong Sop , Seong Hoje , Park Inhwan , Kim Hyung-jun
Published: September 2018

In this study, the drainage efficiency of the multi-stage intake structure, which transports flood to the underground storage, was investigated from the laboratory experiments. The multi-stage intake structure was designed based on the tangential intake and the steps on the bed were purposes to decrease the energy of approaching flow. The experimental results show that the maximum water depth was effectively decreased in the entrance of the drop shaft. The measurements results of the air core width in the drop shaft show that the flow was stably drained without the choking. Furthermore, the air core width tends to increase with the Froude number, and these results indicate that the multi-stage intake structure is applicable to convey the approaching flow with relatively high velocity.
Impact of bed surface arrangement on bedload rate: comparisons between loose, armored and water-worked beds
Authors: Perret Emeline , Berni Céline , Camenen Benoît
Published: September 2018

Existing formulas for predicting bedload rate may be not adapted for mountain rivers with poorly sorted sediments, partly because they were often established using laboratory data with conditions far from those found in such rivers. Natural bed arrangement is particularly difficult to reproduce in flumes, although recent studies highlighted its importance on bedload dynamics. This study aims to quantify bed arrangement impact on bedload rate using original laboratory tests and to improve existing bedload formulas. Three types of bed composed with the same material but having different bed arrangements were studied: loose beds were installed manually in the flume and the others, packed and water-worked beds, were created using water power. Packed beds were assimilated to flat beds composed of a static armor layer whereas water-worked beds exhibited stronger bed organization, including large-scale bed forms. Laser-scanner surveys were used to characterize differences in bed morphology. Similar unsteady hydraulic conditions were applied over these beds. Results showed that bedload dynamics varies significantly depending on the initial arrangement. Compared to loose bed, bedload was enhanced over water-worked bed and reduced over packed bed. Bed surface indicators are thus important parameters to take into account when predicting gravel transport.
Large and very large scale motions in roughbed open-channel flow
Authors: Cameron Stuart , Nikora Vladimir , Stewart Mark , Zampiron Andrea
Published: September 2018

Long duration PIV measurements in rough-bed (glass beads) open-channel flow (OCF) reveal that the pre-multiplied spectra of the streamwise velocity has a bimodal distribution due to the presence of large and very large scale motions (LSMs and VLSMs, respectively). The existence of VLSMs in boundary layers, pipes and closed channels has been acknowledged for some time, but strong supporting evidence for their presence in OCF has been lacking. Length scales of the large and very large scale motions in OCF exhibit different scaling properties; whereas the streamwise length of the LSM scales with the flow depth, the VLSM streamwise length does not scale purely with flow depth and may additionally depend on other scales such as the channel width, roughness height, or viscous length. Supplementary data for flows over self-affine fractal rough beds support these findings and additionally indicate that the length of VLSMs may grow along the extensive distance from the channel entrance. The origin and nature of LSMs and VLSMs are still to be resolved, but differences in their scaling suggest that VLSMs in rough-bed open-channel flows form independently rather than as a spatial alignment of LSMs.
Advanced characterization techniques of the scour hole around a bridge pier model
Authors: Bento Ana Margarida , Couto Lúcia , Pêgo João Pedro , Viseu Teresa
Published: September 2018

Local scouring around bridge foundations is a major reason for bridge collapse worldwide. It occurs due to the formation of vortices around bridge foundations as a result of changing the unidirectional approach flow into the three-dimensional field in an erodible channel bed, leading to the development of a scour hole in its vicinity. In the present work, two different techniques were applied for a full characterization of the scour hole geometry developed in a sand bed flume experiment by means of a Kinect sensor and a close-range photogrammetry. These advanced survey and sensor technologies offer efficient techniques of deriving point clouds and Digital Elevation Models (DEMs), respectively. The potential, limitations and results of both techniques are herein examined and conveniently compared, including a description of measurement devices, reference points and respective software. Reliable and accurate estimates of the topographic representation of the scour hole and inherent features were obtained. The design of the bridge pier used, with a 0.14 m wide rectangular round-nose concrete column (henceforth termed as oblong pier), replicates the typical shape used in the 19th and 20th centuries, and are the most common in Portugal.
Scale model of a training dam using lightweight granulates
Authors: Vermeulen Bart , Boersema Matthijs , Hoitink Ton , Sieben Arjan , Sloff Kees , van der Wal Maarten
Published: September 2018

Longitudinal training dams (LTDs) are a promising alternative for river groynes. Here we summarize findings of a recent study focused on the along river transition from a series of river groynes to an LTD, where the flow divides between the fairway and the side channel between the LTD and the river bank. A scale model is setup using lightweight granulates made of polystyrene to create conditions that are dynamically similar to a prototype situation in the River Waal. The key advantage of using lightweight granulates is that both the Shields number and the Froude number are similar in the model and the prototype. A high flow and a low flow experiment were carried out. The bedforms in the physical model have dimensions that correspond to theoretical dune height predictions, and also the channel incision due to width reduction is in accordance with expectations. The scour holes that develop near the tip of the groynes, however, are too deep, which may relate to improper scaling of the local turbulent vortices, initiated at the groynes. The morphodynamic developments in the flow divergence zone are subtle, and are overwhelmed by the mobile bed response to the presence of groynes. Considering that the physical model over-predicts the erosion caused by groynes, this suggests that the LTD configuration subject to study results in a comparatively stable bed morphology.
Flood hazard mapping techniques with LiDAR in the absence of river bathymetry data
Authors: Choné Guénolé , Biron Pascale M. , Buffin-Bélanger Thomas
Published: September 2018

In many areas of the world, flood risk assessment is either out of date or completely lacking. In Quebec (Canada), one of the challenges to map flood risk is the very large territory combined with very few datasets on river bathymetry, which are required to run hydraulic models. The objective of this study is to assess the precision and accuracy of 2D flood hydraulic modelling exclusively based on LiDAR elevation data which do not include information on in-channel river bathymetry. Hydraulic simulations (HEC-RAS 5.0) are carried out, for discharges of 20-, 100- and 500-year recurrence intervals, using two techniques that do not require bathymetry data, either subtracting discharge of the LiDAR survey from the flood discharge or estimating flow depth from the water surface slope. These techniques are compared to a traditional approach using bed topography obtained from detailed field surveys, on two long reaches (several kilometers). Sensitivity tests were conducted to assess the impacts of the main sources of error on simulated flood levels. Results show that both techniques can be applied with limited introduction of error in the modelled flood stages, and that errors are greatly reduced if calibration data are available.
1D/2D porosity model for urban flood modeling: case of a dense street networks
Authors: Finaud-Guyot Pascal , Garambois Pierre-André , Chen Shangzhi , Dellinger Guilhem , Ghenaim Abdellah , Terfous Abdellali
Published: September 2018

An increasing urbanization of floodplains has led to higher vul- nerability of urban areas and building a new generation of robust, accurate and computationally affordable models dedicated to urban floods is highly re- quired for improving prediction systems and mitigation measures. A better understanding of urban floods hydrodynamics may also be required. In view to achieve computationally affordable and reliable simulations a new 1D/2D parsimonious hydraulic model Flood1D2D is introduced for flood modeling in complex branched urban networks. It takes advantage of a cut-cell technique and a new effective model able to take into account some essential sub-grid flow features such as flow vein contractions due to recirculations downstream of a crossroad. It is shown that this local phenomenon can be correctly repro- duced thanks to this 1D/2D coupled SW model parameterized with roughness and porosity. The ability of the model to reproduce realistic flood discharge distributions at the subdistrict scale is also tested on a part of the branched net- work of ICUBE experimental rig. Further studies should tackle the issues of calibration and unsteady modeling.
Shore-based monitoring of flow dynamics in a steep bedrock canyon river
Authors: Ansari Saber , Rennie Colin D. , Venditti Jeremy G. , Kwoll Eva , Fairweather Kirsti
Published: September 2018

The pace of landscape evolution is set by bedrock erosion in canyons. This phenomenon occurs by various geological processes including plucking of bedrock blocks and abrasion by saltating bedload and suspended load in highly turbulent flows. For a better understanding of the river flow characteristics in bedrock rivers, a comprehensive study of flow dynamics was undertaken in Black Canyon in the Fraser River, British Columbia. We used shore-based video imagery of the river to study surface flow dynamics. The shore-based monitoring system consisted of a Campbell Scientific camera mounted at the top of the canyon walls. We monitored the water surface boils due to upwelling and determined river surface flow velocities from the shore-based imagery. Automatic detection of the upwelling surface boils leads to a better understanding of the secondary circulation patterns and flow structures in this large steep river bedrock canyon. The data collection and analytical procedures developed in this research are cost-effective tools for remotely determining flow dynamics, which can be applied to other rivers.
Experimental validation of transient source term in porosity-based shallow water models
Authors: Guinot Vincent , Soares-Frazão Sandra , Delenne Carole
Published: September 2018

Porosity-based shallow water models for the simulation of urban floods incorporate additional energy dissipation terms compared to the usual two-dimensional shallow water equations. These terms account for head losses stemming from building drag. They are usually modelled using turbulence-based equations of state (drag proportional to the squared velocity). However, refined numerical simulations of wave propagation in periodic urban layouts indicate that such drag models do not suffice to reproduce energy dissipation properly. Correct wave propagation speeds, energy dissipation rates and flow fields are obtained by incorporating a new type of source term, active only under transient situations involving positive waves. This source term does not take the form of an equation of state. It can be modelled as an artificial increase in water inertia. In this communication, an experimental validation of this source term model is presented by means of new dam-break flow experiments in idealized, periodic urban layouts. The experimental results validate both the existence and the proposed formulation of this new source term.
Nonintrusive approximation of parametrized limits of matrix power algorithms – application to matrix inverses and log-determinants
Authors: Casenave Fabien , Akkari Nissrine , Charles Alexandre , Rey Christian
Published: September 2018

We consider in this work quantities that can be obtained as limits of powers of parametrized matrices, for instance the inverse matrix or the logarithm of the determinant. Under the assumption of affine dependence in the parameters, we use the Empirical Interpolation Method (EIM) to derive an approximation for powers of these matrices, from which we derive a nonintrusive approximation for the aforementioned limits. We derive upper bounds of the error made by the obtained formula. Finally, numerical comparisons with classical intrusive and nonintrusive approximation techniques are provided: in the considered test-cases, our algorithm performs well compared to the nonintrusive ones.
Therapie der Sternumosteomyelitis nach medianer Sternotomie bei 130 Patienten mittels gestielter myokutaner Latissimuslappenplastik
Authors: Pech Thomas , Kania Alexander , Fehlberg Wiebke , Kalff Jörg , Walgenbach Klaus-Jürgen , Busch Kay-Hendrik
Published: September 2018

Hintergrund Nach medianer Sternotomie kommt es bei 0,8 – 8% der Patienten nach herzchirurgischer Operation zu tiefreichenden Wundheilungsstörungen des Sternums, die mit einem deutlich verlängerten Krankenhausaufenthalt sowie einer deutlich erhöhten Morbidität und Letalität einhergehen. Zur plastisch-chirurgischen Defektdeckung wird in unserer Klinik nach radikalem chirurgischen Débridement, Entfernung von Fremdmaterial sowie Vakuumkonditionierung bei großen und tiefreichenden Defekten eine gestielte M.-latissimus-dorsi-Lappenplastik durchgeführt. Ziel der Arbeit war es, durch retrospektive Analyse von Patientencharakteristika und prä- und perioperativen Daten Risikofaktoren für das Auftreten von Wundheilungsstörungen und Nachblutungen nach Lappenplastik herauszuarbeiten.

Material und Methoden Es wurden Charakteristika (Alter, BMI, Geschlecht), Vorerkrankungen (Diabetes mellitus, chronisch obstruktive Lungenerkrankung [COPD], Niereninsuffizienz sowie prä- und postoperative Daten (perioperative Antikoagulation, Keimspektrum bei Muskellappenplastik) von 130 Patienten gesammelt, die in den Jahren 2009 – 2015 eine Latissimuslappenplastik zur sternalen Defektdeckung erhielten.

Ergebnisse Bei einem Anteil weiblicher Patienten von 37% betrug das mittlere Alter 68,72 ± 9,53 Jahre. Die In-Hospital-Letalität betrug 3,8%. Revisionspflichtige Wundheilungsstörungen oder Nachblutungen traten bei 21,5 bzw. 10,8% der Patienten auf. Die am häufigsten nachgewiesenen Keime bei der plastischen Deckung sind Staphylococcus (S.) aureus und S. epidermidis. Alter > 80 Jahre (p = 0,04), weibliches Geschlecht (p = 0,002) sowie der Nachweis von Fäkalkeimen (p = 0,006), multiresistenten Keimen (p = 0,007) und Klebsiellen (p = 0,026) sind signifikante Risikofaktoren für das Auftreten revisionspflichtiger Wundheilungsstörungen nach Muskellappenplastik. Eine therapeutische perioperative Antikoagulation mit Danaparoid/Fondaparinux stellt einen signifikanten Risikofaktor für eine revisionspflichtige Nachblutung dar.

Schlussfolgerung Die gestielte Latissimuslappenplastik ist bei großen sternalen Wunden die Methode der Wahl, um eine suffiziente Defektauskleidung zu erzielen. Die Keimbesiedelung zum Zeitpunkt der plastischen Defektdeckung beeinflusst das Risiko für Wundheilungsstörungen signifikant, sodass keimreduzierende Maßnahmen im Fokus weiterer Untersuchungen stehen.
Fertilitätserhalt bei Frauen mit Krebserkrankungen
Authors: Nawroth Frank
Published: September 2018

Experten-Interview | Die Diagnose Krebs löst bei vielen Menschen eine existenzielle Krise aus. Umso härter trifft es Frauen im gebärfähigen Alter, wenn sie in diesem Zustand von Schock, Wut und Verzweiflung vor der Frage stehen, ob sie noch Kinder bekommen möchten. Krebstherapien können die Fertilität einschränken. Im Interview mit Die Hebamme verrät Prof. Dr. med. Frank Nawroth, welche Möglichkeiten es gibt, die Fruchtbarkeit zu schützen und warum Frauen darüber rechtzeitig aufgeklärt werden sollten.
Die symptomatische Harnstauungsniere beim metastasierten Malignom
Authors: Heidegger Isabel , Steinkohl Fabian , Horninger Wolfgang , Pichler Renate
Published: September 2018

Die symptomatische Harnstauungsniere, welche durch einen verminderten oder fehlenden Abfluss von Urin bedingt ist, ist eine häufige Begleiterkrankung bei Patienten/innen mit metastasierten Karzinomen im Abdominal- und Urogenitalbereich. Während die akute Harnstauungsniere mit kolikartigen Beschwerden einhergeht, ist die chronische Harnstauungsniere vielfach lange Zeit unbemerkt. Neben intrinsischen Ursachen wie Harnleitertumore kommt es häufig zu einer externen Kompression von Tumormassen auf den Harnleiter. Durch die Anlage einer Harnleiterschiene oder einer perkutanen Nephrostomie kann zügig eine Deobstruktion erzielt werden. Je nach Prognose der Grunderkrankung kann eine definitive chirurgische Sanierung angedacht werden.
Dichlorodioxomolybdenum(VI) Complexes: Useful and Readily Available Catalysts in Organic Synthesis
Authors: Sanz Roberto , Hernández-Ruiz Raquel
Published: September 2018

Molybdenum(VI) dichloride dioxide (MoO2Cl2), and its addition complexes [MoO2Cl2(L)n; L = neutral ligand], are commercially or easily available and inexpensive transition-metal complexes based on a non-noble metal that can be applied as catalysts for various organic transformations. This short review aims to present the most significant breakthroughs in this field.

1 Introduction

2 Preparation and Reactivity of MoO2Cl2(L)n Complexes

2.1 Synthesis and Structure

2.2 Reactivity of Dichlorodioxomolybdenum(VI) Complexes

3 Redox Processes Catalyzed by MoO2Cl2(L)n Complexes

3.1 Deoxygenation Reactions Using Phosphorus Compounds

3.2 Deoxygenation and Hydrosilylation Reactions Using Silanes

3.3 Reduction Reactions Using Hydrogen

3.4 Deoxygenation Reactions with Boranes and Thiols

3.5 Reduction Reactions with Glycols

3.6 Oxidation Reactions

4 Ambiphilic Reactivity of MoO2Cl2

4.1 Amphoteric Lewis Acid–Lewis Base Catalyzed Reactions

4.2 Lewis Acid Type Catalyzed Reactions

5 Conclusion and Perspective