On the criteria for the initiation of motion in tidal inlets,deterministic and stochastic approaches

Details are given herein of the refinement and application of a three-dimensional layer integrated numerical model to predict morphological changes in tidal basins. The solution of governing differential equations, which consist of the conservation of mass and momentum for the hydrodynamics, the transport equation for the suspended sediment fluxes and the sediment mass conservation equation for the bed level changes are carried out by the use of Alternating Direction Implicit (ADI) Finite Difference Method (FDM). The model includes different criteria for the initiation of motion namely Shields (1936, Application of Similarity Principles and Turbulence Research to Bed load Movement, Hydrodynamics Laboratory, California Institute of Technology, Pub. No. 167), Kolahdoozan (1999, Numerical Modelling of Geomorphological Processes in Estuarine Waters, PhD Thesis, Department of Civil and Environmental Engineering, University of Bradford, Bradford, UK, 288) and Zanke (2003, On the Influence of Turbulence on the Initiation of Sediment Motion, International Journal of Sediment Research, 18(1), 17–31), to compare different aspects of flow conditions. As the flow is highly turbulent with the random nature of its components, many researchers have tried to express sediment transport processes by using stochastic approaches. In the current study both deterministic and stochastic methods are included in the numerical model to evaluate their accuracy and efficiency. To validate the numerical model results, laboratory measurements are used, with these being obtained from an earlier experimental program undertaken by the authors. Results of a short term bed level changes in a laboratory model harbor are included for the model verification purposes. Comparisons are undertaken using different criteria for the initiation of motion, with the results highlighting that the unsteadiness in the flow parameters included in the numerical model has a major effect on the bed level changes inside the harbor, in compare with the turbulence structure of the flow. The model is then applied to a real case study of the Humber Estuary, located in the UK, with comparisons being undertaken for different criteria for the initiation of motion, using both deterministic and stochastic approaches for the long term bed level predictions.     

Axisymmetric transient waves in transversely isotropic half-space

A transversely isotropic material in the sense of Green is considered. Using a series of potential functions proposed in [Eskandari-Ghadi M. A complete solution of the wave equations for transversely isotropic media. J Elasticity 2005; 81:1–19], the solutions of the transient wave equations within a half-space under surface load are obtained in the Laplace–Hankel domain for axisymmetric problems. The solutions are investigated in detail in the special case of a surface point force pulse varying with time as Heaviside function. Using Cagniard–De Hoop method, the inverse Laplace transform and inverse Hankel transform of the solutions are then obtained in the form of integrals with finite limits. For validity of the analytical results, the final formulations for surface waves are degenerated for an isotropic material and compared with the existing formulation obtained by Pekeris [The seismic surface pulse. Proc Natl Acad Sci USA 1955;41:469–80], to show that they are exactly the same. The numerical evaluations of the integrals for some transversely isotropic materials as well as an isotropic one are obtained. The present approach is then numerically verified by comparing a particular case of displacements for the surface of an isotropic half-space subjected to a point load of Heaviside function with the solutions obtained by Pekeris [The seismic surface pulse. Proc Natl Acad Sci USA 1955;41:469–80]. In addition, the wave equations for the mentioned medium are obtained on the vertical line directly under the applied surface load. The final formulations are degenerated for an isotropic material and compared with the existing formulation given in Graff [Wave motion in elastic solids. New York: Dover Publications Inc; 1975 [New Ed edition, November 1991]], to show that they are also exactly the same. Then equations are presented in graphical forms using an appropriate numerical evaluation.     

Using uncertainty and sensitivity analysis for finding the best rainfall-runoff model in mountainous watersheds(Case study: the Navrood watershed in Iran)

In watersheds that have not sufficient meteorological and hydrometric data for simulating rainfall-runoff events, using geomorphologic and geomorphoclimatic characteristics of watershed is a conventional method for the simulation. A number of rainfall-runoff models utilize these characteristics such as Nash-IUH, Clark-IUH, Geomorphologic Instantaneous Unit Hydrograph(GIUH), Geomorphoclimatic Instantaneous Unit Hydrograph(GcIUH), GIUH-based Nash(GIUH-Nash) and GcIUH-based Clark(GcIUH-Clark). But all these models are not appropriate for mountainous watersheds. Therefore, the objective of this study is to select the best of them for the simulation. The procedure of this study is: a) selecting appropriate rainfall-runoff events for calibration and validation of six hybrid models, b) distinguishing the best model based on different performance criteria(Percentage Error in Volume(PEV); Percentage Error in Peak(PEP); Percentage Error in Time to Peak(PETP); Root Mean Square Error(RMSE) and Nash-Sutcliffe model efficiency coefficient(ENS)), c) Sensitivity analysis for determination of the most effective parameter at each model, d) Uncertainty determination of different parameters in each model and confirmation of the obtained results by application of the performance criteria. For application of this procedure, the Navrood watershed in the north of Iran as a mountainous watershed has been considered. The results showed that the ClarkIUH and GcIUH-Clark are suitable models for simulation of flood hydrographs, while other models cannot simulate flood hydrographs appropriately. The sensitivity analysis shows that the most sensitive parameters are the infiltration constant rate and time of concentration in the Clark-IUH model. Also, the most sensitive parameters include the infiltration constant rate and storage coefficient in the GcIUHClark model. The Clark-IUH and GcIUH-Clark models are more sensitive to their parameters. The Latin Hypercube Sampling(LHS) on Monte Carlo(MC) simulation method was used for evaluation of uncertainty of data in rainfall-runoff models. In this method 500 sets of data values are produced and then the peak discharge of flood hydrographs for each produced data set is simulated with rainfall-runoff models. The uncertainty of data changes the value of simulated peak discharge of flood hydrograph. The uncertainty analysis shows that the observed peak discharges of different rainfall-runoff events are within the range of values of simulated by the six hybrid rainfall-runoff models and IUH that inputs of these models were the produced data sets. The range of the produced peak discharge of flood hydrographs by the Clark-IUH and GcIUH-Clark models is wider than those of other models.     

Application of the Dynamic Cone Penetrometer (DCP) for determination of the engineering parameters of sandy soils

Determination of the in situ engineering properties of foundation materials has always been a challenge for geotechnical engineers and, thus, several methods have been developed so far. Dynamic Cone Penetration (DCP) test is one of the most versatile amongst them. In the present research, a light weight simple DCP device was developed and used for evaluation of the engineering properties of sandy soils in laboratory conditions. The device consisted of an 8-kg hammer that drops over a height of 575 mm, and drives a 60° cone tip with 20 mm base diameter into the ground. To control the validation of the results, laboratory direct shear and plate load tests were used as reference tests. The soil sample was a poorly graded sandy soil (SP) taken from alluvial deposits of the Tehran plain. All DCP tests and PLTs were undertaken on compacted soil in a mould with 700 mm diameter and 700 mm height. Based on the results of the experiments, the relationships between Dynamic Penetration Index (DPI), relative density (D_r), modulus of elasticity (E), shear modulus (G), modulus of subgrade reaction (K_S), and the friction angle of the soil were obtained with a high coefficient of determination (> 90%). The repeatability of the test results was also evaluated by calculating the coefficient of variations (C_v), which was less than 30% for all tests.     

Forced vertical and horizontal movements of a rectangular rigid foundation on a transversely isotropic half‐space

An analytical investigation of a half‐space containing transversely isotropic material under forced vertical and horizontal displacements applied on a rectangular rigid foundation is presented in this paper. With the goal of a rigorous solution to the shape‐ and rigidity‐ induced singular mixed boundary value problem, the formulation employs scalar potential representation, the Fourier expansion and the Hankel integral transforms method to obtain the surface arbitrary point‐load solution in cylindrical coordinate system. The obtained Green's functions are rewritten in rectangular coordinate system, allowing the response of the half‐space because of an arbitrary distributed load on a rectangular surface area be given in terms of a double integral. The numerical evaluations of stresses are done with the use of an element, which is singular at the edge and the corner of the rectangle. Upon the imposition of the rigidity displacement boundary condition for a rigid foundation and the use of a set of two‐dimensional adaptive‐gradient elements, which can capture the singular behavior in the contact stress effectively, a set of new numerical results are presented to illustrate the effect of transverse isotropy on the foundation response. Copyright © 2012 John Wiley & Sons, Ltd.     

Hydroclimatic variations over the last two glacial/interglacial cycles at Lake Urmia,Iran

A coarse-resolution, absolutely dated isotope record spanning the last 180 ka was constructed from aragonite-rich fecal pellets in a sediment core from Lake Urmia, Iran. The isotope record is not continuous as a consequence of detrital calcite that contaminates the pellets at certain depths. An isotopic correction was applied to samples > 50% aragonite, using the δ¹⁸O values of calcite-only pellets. Absolute dates were derived from U-Th analyses on pellets > 80% aragonite. The resultant δ¹⁸O record and sediment lithofacies confirm that the Penultimate Glacial was cold and dry, with pronounced interstadials at ca. 150 and >175 ka. Deglaciation began at ca. 130 ka, but climate was unstable and supported a probable no-analog vegetation assemblage. The onset of true interglacial conditions occurred at ca. 126 ka. Peak moisture conditions lasted for 5–6 ka before the climate became drier, with the loss of some tree taxa towards the end of the Last Interglacial. A period of greater moisture occurred between 116 and 108 ka, overlapping in timing with interstadial conditions recorded in the Soreq Cave speleothem record. In general, stadial to interstadial transitions (OIS 5d-5c, 5b-5a) are marked by decreasing δ¹⁸O values and rising lake levels. The nature of the OIS 5 to OIS 4 transition cannot be resolved in this study because of the loss of 5 m of core and imprecise dates. According to the present chronology, δ¹⁸O values, and inferred lake levels, arid conditions began at 60 ka and persisted until Termination I. Episodic increases in moisture, characterized by layers of aragonite-rich pellets, ostracodes, and the pollen of trees and/or aquatic plants, occurred during the Last Glacial. Deglaciation associated with the Late-glacial Interstadial began at 14 ka but was interrupted by a marked Younger Dryas event that resulted in renewed aridity. The Holocene began at approximately 10 ka. Despite large errors in the chronology, the overall timing and pattern of effective moisture matches the record from Soreq Cave, Israel, suggesting that the two regions were climatically in-phase.     

Site selection and cost-benefit analysis for artificial recharge in the Baghmalek plain, Khuzestan Province, southwest Iran

Available hydrogeological data for the Baghmalek aquifer, southwest Iran, suggest that in order to counter progressive depletion of groundwater, but at the same time meet the growing demand on groundwater resources, artificial recharge should be considered. The success of artificial recharge schemes requires the integration of many types of data and information. The prime prerequisite in establishing an artificial recharge scheme using the surface spreading technique is identification of a suitable site. Therefore, an integrated investigation, including a detailed assessment of surface and sub-surface geology, and hydrogeological surveys were undertaken. The potential of harvesting storm waters, considering their quality and suspended loads, has been evaluated. Using this background, three sites (including basins and check dam) for artificial recharge are suggested in the north and northeast of the area, where the thickness of coarse alluvium is greatest. On the basis of the collected data, (1) the rate of recharge that can be achieved at the three sites is approximately 2.2 million m³ per year, (2) the cost–benefit ratio is 1:1.32, and (3) the analysis suggests that the project could recover the investment within 3 years.     

An analysis of the optical light curve of the X-ray binary 3U 1653+35

The purpose of this paper is to provide an estimate of several parameters of X-ray binary system 3U 1653+35, based a study of the optical light curve of the companion of HZ Her.The introductory section gives a general outline of the problem and deals with the general method of estimation of the parameters. In Section 2, the reflection effect in close binary systems is demonstrated in the end of this section we first introduce a new method of evaluation of reflection effect in close binary systems. Section 3 gives an analysis of the optical curve of the X-ray binary system 3U 1653+35, and general discussion.     

Leaching of an oxide gold ore with chloride/hypochlorite solutions

An oxide gold ore was subjected to chloride/hypochlorite leaching at room temperature. The effects of three factors, including Ca(OCl)₂ vs. NaOCl, OCl⁻ concentration, and HCl concentration on gold leaching performance were investigated. Due to formation of CaOCl⁺ complex in solution and hence less reactivity, calcium hypochlorite produces a sluggish gold leaching kinetics, taking twice the time (46 h) to achieve maximum gold recovery of 58% compared to sodium hypochlorite. 10 g/L of total initial hypochlorite species in solution produces reasonable gold recoveries. The amount of added HCl and hence the initial pH was found to have a major effect on gold leaching kinetics and maximum gold recovery. A high level of 9 g/L of added HCl causes HClO to be very reactive, producing very fast kinetics, reaching 67% gold extraction in 4 h. It also causes a faster consumption of hypochlorous acid, through catalytic decomposition (by NiO and CuO) and disproportionation. Hypochlorous acid reactions with sulfide and ferrous content of ore proceed very slowly in the pH range of 4–11. Gold–chloro complexes are strongly adsorbed on quartz component of ore. To minimize this undesirable adsorption of gold–chloro species, the aging time must be limited to a few hours only.     

Microwave links: The future for urban rainfall measurement?

Microwave links are ideally suited to the urban environment, since there are many suitable vandal-free locations to which the receiver and transmitter can be attached. A signal sent along a link is received with reduced power as a consequence of scattering and absorption by intervening water droplets. Thus a measurement of the power loss can be transformed into a measure of total path rainfall. This paper discusses the requirements for the estimation process to be accurate. The paper presents results using a single frequency, together with the improved results from a dual-frequency link. Potential future applications of microwave links are presented.