scholarly journals Dynamic flood wave routing in prismatic channels with hydraulic and hydrologic methods

2019 ◽  
Vol 69 (3) ◽  
pp. 276-287 ◽  
Author(s):  
Eugene Retsinis ◽  
Erna Daskalaki ◽  
Panayiotis Papanicolaou
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Arrival Time ◽  
Peak Flow ◽  
Mass Conservation ◽  
Maximum Error ◽  
Flood Events ◽  
Flood Wave ◽  
Explicit Schemes ◽  
Lateral Inflow

Abstract Time-dependent, unsteady flow has been studied in prismatic open channels with symmetric trapezoidal and triangular cross sections and small bottom slope. The St Venant equations without lateral inflow have been discretized in explicit as well as in implicit form and solved numerically, for unsteady, subcritical flow. The inflow hydrograph used can be applied for different flood events by adjusting its parameters accordingly. The results presented are derived from the explicit schemes Lax-Diffusive, MacCormack, Lambda as well as the implicit Preissmann scheme, and are compared to those from the Muskingum-Cunge method and the widely used commercial software HEC-RAS. The peak flow computed by the Lax-Diffusive scheme was reduced at the downstream end of the channel and the arrival time of the peak increased if compared to the other methods. The Muskingun-Cunge method forecasted the shortest peak flow arrival time at the downstream end cross section. Mass conservation computed from inflow and outflow hydrographs has been confirmed, since the maximum error did not exceed 2.60%. All codes were implemented in house using Matlab®.

scholarly journals Current and Modified Flood Discharge Capacity of a Reach of Tigris River between Kut and Amarah Barrages

2020 ◽  
Vol 26 (2) ◽  
pp. 129-143
Author(s):  
Maysam S Abbas ◽  
Riyadh Z. Azzubaidi
Keyword(s):  
Cross Section ◽  
Discharge Capacity ◽  
Cross Sections ◽  
Flood Plain ◽  
Main Channel ◽  
Water Levels ◽  
Flood Wave ◽  
Tigris River ◽  
Flood Discharge ◽  
Lateral Inflow

This study was conducted to examine the discharge capacity of the reach of the Tigris River between Kut and Amarah Barrages of 250km in length. The examination includes simulation the current capacity of the reach by using HEC-RAS model. 247cross sections surveyed in 2012 were used in the simulation. The model was calibrated using observed discharges of 533, 800, 1025 and 3000m3/s discharged at Kut Barrage during 2013, 1995, 1995 and 1988, respectively, and its related water level at three gauge stations located along the reach. The result of calibration process indicated that the lowest Root Mean Square Error of 0.095 can be obtained when using Manning’s n coefficient of 0.026, 0.03 for the Kut- Ali Al Garbi and Ali Al Garbi- Amarah reaches respectively, and 0.03 for the flood plain of the whole reach under study. The reach under study has two lateral inflow streams, UmAljury, which joins Tigris River at station 51km, and Aljabab, which joins Tigris River at station 57km. The discharge of Aljabab varies between 0 and 400m3/s and the discharge of UmAljury varies between 0 and 50m3/s.                     The results showed that the current capacity of the main channel of the reach of the Tigris River between Kut and Amarah Barrages is 400m3/s. The water levels kept less 1m than both levees in case of discharging 1800m3/s from Kut Barrage, with no lateral inflows, and 1700m3/s with lateral inflow. The reach of Tigris River fails to accommodate the flood discharge of 3300m3/s which is the discharge of the flood of 1988 measured at Kut Barage. It can be concluded that the reach had large amount of sediment for the period from 1988 to 2012 and the reach capacity reduced to about half its capacity of 1988 during this period.                                                          The results of removing 12 islands and 2 sidebars by reshaping the current condition into trapezoidal cross-section will decrease the surface water levels by 20cm and flow of 1900m3/s can be discharged safely at Kut Barrage without any lateral inflow and 1800m3/s with lateral inflow from the tributaries. While, expand 58 narrow cross-sections that choking the flow, the water levels along the reach are lowered by an average of 20cm in addition to that 20cm when modifying the cross-sections at the islands and sidebars. In this case, flow of 2100m3/s can safely be discharged from Kut Barrage without any lateral inflow and 1900m3/s with lateral inflow. The result when modifying additional 111 cross-sections showed that the reach can safely accommodate a flood wave of 3300m3/s from Kut Barrage without any lateral inflow and 3000m3/s with lateral inflow.                                                                                                            

Verification of flood wave arrival time predictions using remote sensing-derived water levels

2020 ◽  
Author(s):  
Stefania Grimaldi ◽  
Ashley J. Wright ◽  
Jeffrey P. Walker ◽  
Valentijn R.N. Pauwles
Keyword(s):  
Remote Sensing ◽  
Water Level ◽  
Model Calibration ◽  
Arrival Time ◽  
Performance Metrics ◽  
Flood Events ◽  
Flood Wave ◽  
Hydraulic Models ◽  
Spatially Distributed ◽  
Wave Arrival

<p>Two-dimensional (2-D) hydraulic models are used for the prediction of floodplain inundation spatio-temporal patterns to improve flood risk estimation, and support emergency and land management. Accurate model calibration is pivotal to enable adequate representation of flood dynamics and requires the comparison between model predictions and observed data.</p><p>Remote sensing (RS) observations of inundation extent and water level allow model evaluation at a large number of locations in the floodplain, providing opportunities for a thorough understanding of inundation dynamics. However, RS instruments provide information at a snapshot in time and so the existing performance metrics generally compare model results and observations at the acquisition time. Nevertheless, explicitly differentiating between model parameterizations which underpredict or overpredict the flood wave arrival time is valuable to assess models’ predictive skill.</p><p>In 2-D hydraulic models, roughness values are considered to be the most important parameters controlling the flow characteristics and so they are used for model calibration. Although RS-derived spatially distributed information allows the tuning of a large number of spatially distributed roughness values, the calibration framework must enable parameter identifiability while avoiding overfitting and equifinality problems. Another challenge affecting the calibration exercise is the computational burden of 2D-hydraulic models, which generally hampers the application of frameworks requiring a large number of model realizations.</p><p>This presentation introduces a novel framework for the calibration of 2D hydraulic models. Specifically, the calibration framework was designed to (1) make exclusive use of RS-derived observations and consequently enable model calibration in ungauged catchments; (2) allow discriminating between underprediction and overprediction of flood wave arrival time; (3) identify a parameter configuration which is robust for different flood events; and (4) require a limited number of model realizations.</p><p>A novel performance metric, the Space-Time-Score, is therefore proposed to compare modelled and observed water level and discriminate between underestimation and overestimation of flood wave arrival time, with binary performance metrics used to compare modelled and observed inundation extents. These performance metrics allow quantifying the capability of different parameter sets to reproduce the observed data.  A novel set of river roughness values is then computed to minimise the discrepancy between model results and observations.</p><p>The 2011 and the 2013 flood events in the Clarence catchment (Australia) were used as test cases. The 2D hydraulic model was LISFLOOD-FP; available remote sensing data included both Synthetic Aperture Radar and optical acquisitions. Gauged data were used as an independent validation dataset and demonstrated the effectiveness of the proposed framework to identify a spatially distributed parameter set which is robust for different flood events.   </p><p>Despite the promising results of this initial testing, it is imperative to underline that the proposed framework was designed to minimise the discrepancies between model results and observations. Consequently, RS accuracy, timing and spatial coverage are expected to affect the performance of the calibration. For this reason, extensive further testing is essential to investigate the impacts of RS features on the effectiveness of the proposed methodology for a number of catchments with different morphologies and flooding dynamics.</p>

Electron Irradiation Effects in Polyoxymethylene Crystals Grown Inside Trioxane Crystals

1971 ◽  
Vol 29 ◽  
pp. 78-79
Author(s):  
J. P. Colson ◽  
D. H. Reneker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Detailed Examination ◽  
The Other ◽  
Electron Micrograph ◽  
Irradiation Effects ◽  
Threefold Axis ◽  
Typical Sample ◽  
Polymer Crystals ◽  
Chain Axis

Polyoxymethylene (POM) crystals grow inside trioxane crystals which have been irradiated and heated to a temperature slightly below their melting point. Figure 1 shows a low magnification electron micrograph of a group of such POM crystals. Detailed examination at higher magnification showed that three distinct types of POM crystals grew in a typical sample. The three types of POM crystals were distinguished by the direction that the polymer chain axis in each crystal made with respect to the threefold axis of the trioxane crystal. These polyoxymethylene crystals were described previously.At low magnifications the three types of polymer crystals appeared as slender rods. One type had a hexagonal cross section and the other two types had rectangular cross sections, that is, they were ribbonlike.

A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

Oxygen K near edge structures studied with multiple scattering calculations

1988 ◽  
Vol 46 ◽  
pp. 504-505
Author(s):  
Xudong Weng ◽  
Peter Rez
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Partial Cross Section ◽  
Energy Window ◽  
Edge Structure ◽  
Fine Structures ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
Quantitative Chemical

In electron energy loss spectroscopy, quantitative chemical microanalysis is performed by comparison of the intensity under a specific inner shell edge with the corresponding partial cross section. There are two commonly used models for calculations of atomic partial cross sections, the hydrogenic model and the Hartree-Slater model. Partial cross sections could also be measured from standards of known compositions. These partial cross sections are complicated by variations in the edge shapes, such as the near edge structure (ELNES) and extended fine structures (ELEXFS). The role of these solid state effects in the partial cross sections, and the transferability of the partial cross sections from material to material, has yet to be fully explored. In this work, we consider the oxygen K edge in several oxides as oxygen is present in many materials. Since the energy window of interest is in the range of 20-100 eV, we limit ourselves to the near edge structures.

Absolute inner-shell cross section determination for EELS analysis

1988 ◽  
Vol 46 ◽  
pp. 534-535
Author(s):  
P.A. Crozier
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absolute Cross Section ◽  
Specimen Thickness ◽  
Mass Thickness ◽  
Scattering Cross ◽  
Before And After ◽  
Estimated Error ◽  
Scattering Cross Sections ◽  
Electron Microscopist

Absolute inelastic scattering cross sections or mean free paths are often used in EELS analysis for determining elemental concentrations and specimen thickness. In most instances, theoretical values must be used because there have been few attempts to determine experimental scattering cross sections from solids under the conditions of interest to electron microscopist. In addition to providing data for spectral quantitation, absolute cross section measurements yields useful information on many of the approximations which are frequently involved in EELS analysis procedures. In this paper, experimental cross sections are presented for some inner-shell edges of Al, Cu, Ag and Au.Uniform thin films of the previously mentioned materials were prepared by vacuum evaporation onto microscope cover slips. The cover slips were weighed before and after evaporation to determine the mass thickness of the films. The estimated error in this method of determining mass thickness was ±7 x 107g/cm2. The films were floated off in water and mounted on Cu grids.

A technique for preparing semiconductor cross sections for both TEM and SEM analysis

1989 ◽  
Vol 47 ◽  
pp. 712-713
Author(s):  
Stanley J. Klepeis ◽  
J.P. Benedict ◽  
R.M Anderson
Keyword(s):  
Sample Preparation ◽  
Cross Section ◽  
Cross Sections ◽  
Sem Analysis ◽  
Preparation Technique ◽  
Ion Milling ◽  
Tem Analysis ◽  
Polished Cross Section ◽  
Area Of Interest ◽  
Polished Side

The ability to prepare a cross-section of a specific semiconductor structure for both SEM and TEM analysis is vital in characterizing the smaller, more complex devices that are now being designed and manufactured. In the past, a unique sample was prepared for either SEM or TEM analysis of a structure. In choosing to do SEM, valuable and unique information was lost to TEM analysis. An alternative, the SEM examination of thinned TEM samples, was frequently made difficult by topographical artifacts introduced by mechanical polishing and lengthy ion-milling. Thus, the need to produce a TEM sample from a unique,cross-sectioned SEM sample has produced this sample preparation technique.The technique is divided into an SEM and a TEM sample preparation phase. The first four steps in the SEM phase: bulk reduction, cleaning, gluing and trimming produces a reinforced sample with the area of interest in the center of the sample. This sample is then mounted on a special SEM stud. The stud is inserted into an L-shaped holder and this holder is attached to the Klepeis polisher (see figs. 1 and 2). An SEM cross-section of the sample is then prepared by mechanically polishing the sample to the area of interest using the Klepeis polisher. The polished cross-section is cleaned and the SEM stud with the attached sample, is removed from the L-shaped holder. The stud is then inserted into the ion-miller and the sample is briefly milled (less than 2 minutes) on the polished side. The sample on the stud may then be carbon coated and placed in the SEM for analysis.

Experimental Studies Of Multilayer Glass Structures On Compression, Compression With Bending And Simple Bending

2019 ◽  
pp. 22-30
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Applied Load ◽  
Experimental Studies ◽  
Strength Properties ◽  
Research Topic ◽  
Normative Values ◽  
Laminated Glass ◽  
The Cross ◽  
Experimental Values

The work of multilayer glass structures for central and eccentric compression and bending are considered. The substantiation of the chosen research topic is made. The description and features of laminated glass for the structures investigated, their characteristics are presented. The analysis of the results obtained when testing for compression, compression with bending, simple bending of models of columns, beams, samples of laminated glass was made. Overview of the types and nature of destruction of the models are presented, diagrams of material operation are constructed, average values of the resistance of the cross-sections of samples are obtained, the table of destructive loads is generated. The need for development of a set of rules and guidelines for the design of glass structures, including laminated glass, for bearing elements, as well as standards for testing, rules for assessing the strength, stiffness, crack resistance and methods for determining the strength of control samples is emphasized. It is established that the strength properties of glass depend on the type of applied load and vary widely, and significantly lower than the corresponding normative values of the strength of heat-strengthened glass. The effect of the connecting polymeric material and manufacturing technology of laminated glass on the strength of the structure is also shown. The experimental values of the elastic modulus are different in different directions of the cross section and in the direction perpendicular to the glass layers are two times less than along the glass layers.

Cross Section Analysis of Cu Filled TSVs Based on High Throughput Plasma-FIB Milling

2012 ◽  
Author(s):  
Frank Altmann ◽  
Jens Beyersdorfer ◽  
Jan Schischka ◽  
Michael Krause ◽  
German Franz ◽  
...  
Keyword(s):  
High Resolution ◽  
Cross Section ◽  
High Throughput ◽  
Cross Sections ◽  
Electron Backscatter Diffraction ◽  
Grain Structure ◽  
Electron Backscatter ◽  
Section Surface ◽  
Backscatter Diffraction ◽  
Section Analysis

Abstract In this paper the new Vion™ Plasma-FIB system, developed by FEI, is evaluated for cross sectioning of Cu filled Through Silicon Via (TSV) interconnects. The aim of the study presented in this paper is to evaluate and optimise different Plasma-FIB (P-FIB) milling strategies in terms of performance and cross section surface quality. The sufficient preservation of microstructures within cross sections is crucial for subsequent Electron Backscatter Diffraction (EBSD) grain structure analyses and a high resolution interface characterisation by TEM.

Automated 3D measurement of fiber cross section morphology in handsheets

2012 ◽  
Vol 27 (2) ◽  
pp. 264-269 ◽  
Author(s):  
Christian Lorbach ◽  
Ulrich Hirn ◽  
Johannes Kritzinger ◽  
Wolfgang Bauer
Keyword(s):  
Image Analysis ◽  
Cross Section ◽  
Cross Sections ◽  
Image Plane ◽  
3D Measurement ◽  
Cross Sectional ◽  
Fiber Cross Section ◽  
Fiber Wall ◽  
Sectional Shape ◽  
Cross Section Geometry

Abstract We present a method for 3D measurement of fiber cross sectional morphology from handsheets. An automated procedure is used to acquire 3D datasets of fiber cross sectional images using an automated microtome and light microscopy. The fiber cross section geometry is extracted using digital image analysis. Simple sample preparation and highly automated image acquisition and image analysis are providing an efficient tool to analyze large samples. It is demonstrated that if fibers are tilted towards the image plane the images of fiber cross sections are always larger than the true fiber cross section geometry. In our analysis the tilting angles of the fibers to the image plane are measured. The resulting fiber cross sectional images are distorted to compensate the error due to fiber tilt, restoring the true fiber cross sectional shape. We use an approximated correction, the paper provides error estimates of the approximation. Measurement results for fiber wall thickness, fiber coarseness and fiber collapse are presented for one hardwood and one softwood pulp.

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