Microbial Analysis of Drinking Water from Randomly Selected Boreholes and Shallow Wells around Hargeisa, Somaliland

Background: Shallow wells and boreholes are vital sources of potable water in Hargeisa. This water can be polluted by runoff, in particular during the rainy season, causing outbreaks of waterborne infections. Objectives: This research aimed at evaluating the microbial quality of shallow wells and boreholes water around Hargeisa, Somaliland. Methods: The total coliform and Escherichia coli count were done by using the membrane filtration method. Overall, 100 ml of each water sample was filtered via a 0.45 μm membrane filter, and then the filters were put on m-Endo agar plates that were incubated at 37°C for 24 to 48 hours. Results: The mean value of total coliform counts for the boreholes and shallow wells ranged from 1.288 × 103 to 8.8 × 103 CFU/100ml, while the mean value of total E. coli counts also ranged from 3.5 × 102 to 4.429 × 103 CFU/100ml. Results from this study have demonstrated that all water sources (Arabsiyo, Dararweyne, Darasalaam, Dabaraqas, and Jaleelo) don’t comply with the WHO guideline for drinking water. Results from the analysis of water samples of 28 wells demonstrated a significant correlation between total coliform and E. coli counts (P = 0.01). Therefore, this water is not fit for human consumption unless it is treated. Conclusion: This study has demonstrated that all results of both mean values of total coliform and E. coli counts from groundwater of selected shallow wells and boreholes were beyond WHO standards, so water from Arabsiyo, Jaleelo, Dabaraqas, Dararweyne, and Darasalaam requires treatment before human consumption.

GLOBAL WELL-POSEDNESS FOR A FIFTH-ORDER SHALLOW WATER EQUATION ON THE CIRCLE

The periodic initial value problem of a fifth-order shallow water equation t u 2 x t u ＋ 3 x u 5 x u ＋ 3u x u 2 x u 2 x u u 3 x u = 0 is shown to be globally well-posed in Sobolev spaces˙ H s （T） for s 〉 2/3 by I-method. For this equation lacks scaling invariance, we first reconsider the local result and pay special attention to the relationship between the lifespan of the local solution and the initial data, and then prove the almost conservation law, and finally obtain the global well-posedness by an iteration process.

BINDING ENERGY OF SHALLOW DONOR IN In_xGa_(1-x)As/GaAsSTRAINED QUANTUM WELL

The effect of the dielectric mismatch between the well and the barrier materials on the binding energies of shallow donor has been investigated in Inx Ga1-xAs/GaAsstrained quantum well. The binding energies as a function of the well widths and impurity positions in the well and the barriers are obtained by using a variational method. Calculation results show that the effect of the dielectric mismatch is quite sizable and such effect is larger for off-center impurity positions,but the effect of the lattice mismatch is small in general.

BINDING ENERGY OF THE SHALLOW DONOR IN （CdTe）_m／（ZnTe）_n STRAINED DOUBLE QUANTUM WELL

In this paper the binding energy of the shallow.donor in CdTe/ZnTe strained double quantum well was calculated.The effect of the finite well potential and strain,resulting from the lattice mismatch,on the binding energy of the impurity is included in a variational framework.The binding energy is obtained as a function of the well width,barrier width,and impurity position in the barrier by using a variational method.The result of the present calculation shows that the variational law of the binding energy is similar to that of unstrained materials.

THE LOCAL WELL-POSEDNESS OF A CHEMOTAXIS-SHALLOW WATER SYSTEM WITH VACUUM

In this paper we prove the local well-posedness of strong solutions to a chemotaxisshallow water system with initial vacuum in a bounded domainΩ■R^(2)without the standard compatibility condition for the initial data.This improves some results obtained in[J.Differential Equations 261(2016),6758-6789].

Shallow sea topography detection using fully Polarimetric Gaofen-3 SAR data based on swell patterns

Compared to single-polarization synthetic aperture radar(SAR)data,fully polarimetric SAR data can provide more detailed information of the sea surface,which is important for applications such as shallow sea topography detection.The Gaofen-3 satellite provides abundant polarimetric SAR data for ocean research.In this paper,a shallow sea topography detection method was proposed based on fully polarimetric Gaofen-3 SAR data.This method considers swell patterns and only requires SAR data and little prior knowledge of the water depth to detect shallow sea topography.Wave tracking was performed based on preprocessed fully polarimetric SAR data,and the water depth was then calculated considering the wave parameters and the linear dispersion relationships.In this paper,four study areas were selected for experiments,and the experimental results indicated that the polarimetric scattering parameterαhad higher detection accuracy than quad-polarization images.The mean relative errors were 14.52%,10.30%,12.56%,and 12.90%,respectively,in the four study areas.In addition,this paper also analyzed the detection ability of this model for different topographies,and the experiments revealed that the topography could be well recognized when the topography gradient is small,the topography gradient direction is close to the wave propagation direction,and the isobath line is regular.

UNIQUENESS FOR THE SOLUTIONS OF ELASTIC THIN PLATES AND SHALLOW SHELLS AS WELL AS THEIR CONTACT PROBLEM WITH HALF SPACE

The uniqueness for the solutions mentioned in the subject is proved by using the uniqueness of the solution for the internal boundary problem of Laplace and bi-Laplace equations of the first kind as well as of the second.

Shallow Convection Dataset Simulated by Three Different Large Eddy Models

Shallow convection plays an important role in transporting heat and moisture from the near-surface to higher altitudes,yet its parameterization in numerical models remains a great challenge,partly due to the lack of high-resolution observations.This study describes a large eddy simulation(LES)dataset for four shallow convection cases that differ primarily in inversion strength,which can be used as a surrogate for real data.To reduce the uncertainty in LES modeling,three different large eddy models were used,including SAM(System for Atmospheric Modeling),WRF(Weather Research and Forecasting model),and UCLA-LES.Results show that the different models generally exhibit similar behavior for each shallow convection case,despite some differences in the details of the convective structure.In addition to grid-averaged fields,conditionally sampled variables,such as in-cloud moisture and vertical velocity,are also provided,which are indispensable for calculation of the entrainment/detrainment rate.Considering the essentiality of the entraining/detraining process in the parameterization of cumulus convection,the dataset presented in this study is potentially useful for validation and improvement of the parameterization of shallow convection.

A Wave Superposition-Finite Element Method for Calculating the Radiated Noise Generated by Volumetric Targets in Shallow Water

A combined method of wave superposition and finite element is proposed to solve the radiation noise of targets in shallow sea.Taking the sound propagation of spherical sound source in shallow sea as an example,the radiation sound field of the spherical sound source is equivalent to the linear superposition of the radiation sound field of several internal point sound sources,and then the radiated noise induced by spherical sound source can be predicted quickly.The accuracy and efficiency of the method are verified by comparing with the numerical results of finite element method,and the rapid prediction of underwater radiated noise of cylindrical shell is carried out based on the method.The results show that compared with the finite element method,the relative error of the calculation results under different simulation conditions does not exceed 0.1%,and the calculation time is about 1/10 of the finite element method,so this method can be used to solve the radiated noise of shallow underwater targets.

Stable Production Technology for Horizontal Well Development in Shallow Water Delta Oilfield of Bohai Bay, China

BZ Oilfield is a medium-sized oilfield with shallow delta facies deposits in Bohai Bay of China,compared with fluvial and delta facies oilfields,there is no mature experience for reference of reservoir configuration,well pattern arrangement and development model in offshore oilfields in China.In view of the difficulty in describing the reservoir configuration of shallow water delta,the single distributary sand dam in shallow water delta is characterized by well-seismic combination and multi-attribute constraints.The mathematical mechanism model of pinch-out position of sand body is established,fine characterization of BZ shallow water delta reservoir is put forward.The horizontal well pattern arrangement type for shallow water delta reservoir is proposed and the method of well pattern optimization based on vertical displacement theory is put forward.A method of inversion of reservoir connectivity using production dynamic data by numerical well testing is proposed and a new method for optimizing water injection rate in water injection wells is proposed aiming at the difficulty of recognizing injection-production connectivity of shallow water delta reservoirs.The fine configuration of BZ shallow water delta reservoir based on distributary sand dam is proposed,which guides the recognition of remaining oil distribution law.By deploying adjustment wells,the water flooding coincidence degree of actual drilling is 86% compared with that of pre-drilling prediction,which indicates that the research results of reservoir configuration can effectively guide the understanding of oilfield geology.Through the theoretical well arrangement type of vertical displacement of single sand body in horizontal wells of shallow water delta reservoir,a high water flooding recovery rate of 35% is achieved in primary well pattern.The connectivity coefficients of injection-production boundary of shallow water delta reservoir configuration are calculated,and the water injection distribution coefficients are obtained by normalizing the directional coefficients.This paper presents a configuration method based on multi-attribute fusion under the constraints of sedimentary process.In this paper,a shallow water delta reservoir configuration method based on multi-attribute fusion constrained by sedimentary process is proposed,and the injection-production connectivity coefficient and injection well distribution coefficient of the configuration boundary are calculated.

Dynamic Location Method for Shallow Ocean Bottom Nodes Using the Levenberg-Marquart Algorithm

Ocean bottom node(OBN)data acquisition is the main development direction of marine seismic exploration;it is widely promoted,especially in shallow sea environments.However,the OBN receivers may move several times because they are easily affected by tides,currents,and other factors in the shallow sea environment during long-term acquisition.If uncorrected,then the imaging quality of subsequent processing will be affected.The conventional secondary positioning does not consider the case of multiple movements of the receivers,and the accuracy of secondary positioning is insufficient.The first arrival wave of OBN seismic data in shallow ocean mainly comprises refracted waves.In this study,a nonlinear model is established in accordance with the propagation mechanism of a refracted wave and its relationship with the time interval curve to realize the accurate location of multiple receiver movements.In addition,the Levenberg-Marquart algorithm is used to reduce the influence of the first arrival pickup error and to automatically detect the receiver movements,identifying the accurate dynamic relocation of the receivers.The simulation and field data show that the proposed method can realize the dynamic location of multiple receiver movements,thereby improving the accuracy of seismic imaging and achieving high practical value.

Harnessing machine learning tools for water quality assessment in the Kebili shallow aquifers,Southwestern Tunisia

An integrated method that implements multivariate statistical analysis and ML methods to evaluate groundwater quality of the shallow aquifers of the Djerid and Kebili district,Southern Tunisia,was adopted.An evaluation of their suitability for irrigation and/or drinking purposes is necessary.A comprehensive hydrochemical assessment of 52 samples with entropy weighted water quality index(EWQI)was also proposed.Eleven water parameters were calculated to ascertain the potential use of those resources in irrigation and drinking.Multivariate analysis showed two main components with Dim1(variance=62.3%)and Dim.2(variance=22%),due to the bicarbonate,dissolution,and evaporation and the intrusion of drainage water.The evaluation of water quality has been carried out using EWQI model.The calculated EWQI for the Djerid and Kebili waters(i.e.,52 samples)varied between 7.5 and 152.62,indicating a range of 145.12.A mean of 79.12 was lower than the median(88.47).From the calculation of EWQI,only 14 samples are not suitable for irrigation because of their poor to extremely poor quality(26.92%).The bivariate plot showed high correlation for EWQI~TH(r=0.93),EWQI~SAR(r=0.87),indicating that water quality depended on those parameters.Diff erent ML algorithms were successfully applied for the water quality classifi cation.Our results indicated high prediction accuracy(SVM>LDA>ANN>kNN)and perfect classifi cation for kNN,LDA and Naive Bayes.For the purposes of developing the prediction models,the dataset was divided into two groups:training(80%)and testing(20%).To evaluate the models’performance,RMSE,MSE,MAE and R^(2) metrics were used.kNN(R^(2)=0.9359,MAE=6.49,MSE=79.00)and LDA(accuracy=97.56%;kappa=96.21%)achieved high accuracy.Moreover,linear regression indicated high correlation for both training(R^(2)=0.9727)and testing data(0.9890).This well confi rmed the validity of LDA algorithm in predicting water quality.Cross validation showed a high accuracy(92.31%),high sensitivity(89.47%)and high specifi city(95%).These fi ndings are fundamentally important for an integrated water resource management in a larger context of sustainable development of the Kebili district.

An isogeometric analysis approach for dynamic response of doubly-curved magneto electro elastic composite shallow shell subjected to blast loading

For the first time, the isogeometric analysis(IGA) approach is used to model and analyze free and forced vibrations of doubly-curved magneto-electro-elastic(MEE) composite shallow shell resting on the visco-Pasternak foundation in a hygro-temperature environment. The doubly-curved MEE shallow shell types include spherical shallow shell, cylindrical shallow shell, saddle shallow shell, and elliptical shallow shell subjected to blast load are investigated. The Maxwell equation and electromagnetic boundary conditions are used to determine the vary of the electric and magnetic potentials. The MEE shallow shell's equations of motion are derived from Hamilton's principle and refined higher-order shear theory. Then, the IGA method is used to derive the laws of natural frequencies and dynamic responses of the shell under various boundary conditions. The accuracy of the model and method is verified through reliable numerical comparisons. Aside from this, the impact of the input parameters on the free and forced vibration of the doubly-curved MEE shallow shell is examined in detail. These results may be useful in the design and manufacture of military structures such as warships, fighter aircraft, drones and missiles.

Evaluation of the Shallow Gas Hydrate Production Based on the Radial Drilling-Heat Injection-Back Fill Method

It has been evidenced that shallow gas hydrate resources are abundant in deep oceans worldwide.Their geological back-ground,occurrence,and other characteristics differ significantly from deep-seated hydrates.Because of the high risk of well construction and low production efficiency,they are difficult to be recovered by using conventional oil production methods.As a result,this paper proposes an alternative design based on a combination of radial drilling,heat injection,and backfilling methods.Multi-branch holes are used to penetrate shallow gas hydrate reservoirs to expand the depressurization area,and heat injection is utilized as a supplement to improve gas production.Geotechnical information collected from an investigation site close to the offshore production well in the South China Sea is used to assess the essential components of this plan,including well construction stability and gas production behavior.It demonstrates that the hydraulic fracturing of the 60mbsf overburden layer can be prevented by regulating the drilling fluid densities.However,the traditional well structure is unstable,and the suction anchor is advised for better mechanical performance.The gas produc-tion rate can be significantly increased by combining hot water injection and depressurization methods.Additionally,the suitable produc-tion equipment already in use is discussed.

A CFD Model to Evaluate Near-Surface Oil Spill from a Broken Loading Pipe in Shallow Coastal Waters

Oil spills continue to generate various issues and concerns regarding their effect and behavior in the marine environment,owing to the related potential for detrimental environmental,economic and social implications.It is essential to have a solid understanding of the ways in which oil interacts with the water and the coastal ecosystems that are located nearby.This study proposes a simplified model for predicting the plume-like transport behavior of heavy Bunker C fuel oil discharging downward from an acutely-angled broken pipeline located on the water surface.The results show that the spill overall profile is articulated in three major flow areas.The first,is the source field,i.e.,a region near the origin of the initial jet,followed by the intermediate or transport field,namely,the region where the jet oil flow transitions into an underwater oil plume flow and starts to move horizontally,and finally,the far-field,where the oil re-surface and spreads onto the shore at a significant distance from the spill site.The behavior of the oil in the intermediate field is investigated using a simplified injection-type oil spill model capable of mimicking the undersea trapping and lateral migration of an oil plume originating from a negatively buoyant jet spill.A rectangular domain with proper boundary conditions is used to implement the model.The Projection approach is used to discretize a modified version of the Navier-Stokes equations in two dimensions.A benchmark fluid flow issue is used to verify the model and the results indicate a reasonable relationship between specific gravity and depth as well as agreement with the aerial data and a vertical temperature profile plot.

ANALYSIS OF NONLINEAR PIEZOELECTRIC CIRCULAR SHALLOW SPHERICAL SHELLS BY DIFFERENTIAL QUADRATURE ELEMENT METHOD

The static behavior of piezoelectric circular spherical shallow shells under both electrical and mechanical loads is studied by using the differential quadrature element method (DQEM). Geometrical nonlinearity effect is considered. Detailed formulations and procedures are given for the first time. Several examples are analyzed and accurate results are obtained by the DQEM. Based on the results in this paper, one may conclude that the DQEM is a useful tool for obtaining solutions of structural elements. It can be seen that the shell shape may be theore tically controlled and snap through may occur when the applied voltage reaches a critical value even without mechanical load for certain geometric configurations.

Geochemical Forms of Phosphorus in Sediments of Three Large, Shallow Lakes of China

A sequential extraction method for the fractionation of phosphorus （P） in lake sediments was used to analyze phos- phorus fractions of sediments taken from three large, shallow. eutrophic freshwater lakes of China-Talhu Lake. Chaohu Lake, and Long.an Lake. All three lakes are located in the lower reaches of the Changjiang River （Yangtze River）. In Taihu Lake and Chaohu Lake, algae blooms occurred every year, while Longgan Lake was a macrophyte-dominated lake. Results showed that exchangeable phosphorus fractions were much higher in the eutrophic lake sediments than in the macrophyte-flourishing lake sediment. Also, the ratio of Fe：P in the sediments of the algae-predomlnant lakes was generally much lower than that in the macrophyte-predominant lakes. Thus, the geochemical fractions of phosphorus in sediments had a closer relationship with the type of aquatic vegetation.

An Exploratory Analysis of Vegetation Strategies to Reduce Shallow Landslide Activity on Loess Hillslopes, Northeast Qinghai-Tibet Plateau, China

Heavy summer rainfall induces significant soil erosion and shallow landslide activity on the loess hillslopes of the Xining Basin at the northeast margin of the Qinghai-Tibet Plateau. This study examines the mechanical effects of five native shrubs that can be used to reduce shallow landslide activity. We measured single root tensile resistance and shear resistance, root anatomical structure and direct shear and triaxial shear for soil without roots and five root- soil composite systems. Results show that Atriplex canescens （Pursh） Nutt. possessed the strongest roots, followed by Caragana korshinskii Kom., Zygophyllum xanthoxylon （Bunge） Maxim., Nitraria tangutorum Bobr. and Lycium chinense Mill. Single root strength and shear resistance relationships with root diameter are characterized by power or exponential relations, consistent with the Mohr- Coulomb law. Root mechanical strength reflects their anatomical structure, especially the percentage of phloem and xylem cells, and the degree and speed of periderm lignifications. The cohesion force of root- soil composite systems is notably higher than that of soil without roots, with increasing amplitudes of cohesion force for A. canescens, C. korshinskii, Z. xanthoxylon, N. tangutorurn and L. chinense of 75.9%, 75.1%, 36.2%, 24.6% and 17.0 % respectively. When subjected to shear forces, the soil without root samples show much greater lateral deformation thanthe root-soil composite systems, reflecting the restraining effects of roots. Findings from this paper indicate that efforts to reduce shallow landslides in this region by enhancing root reinforcement will be achieved most effectively using A. canescens and C. korshinskii.

Coupling Effects on Gold Mineralization of Deep and Shallow Structures in the Northwestern Jiaodong Peninsula, Eastern China

For understanding the possible deep-seated processes and geodynamic constrains on gold mineralization, comprehensive physicochemical and geochemical studies of gold mineralization have been undertaken within the paleo-lithosphere framework during the metailogenic epoch from the northwestern part of the Jiaodong Peninsula in this paper. A general image of the paleo-crust has been remained although it has been superimposed and reformed by post-metailogenic tectonic movements. The gold ore deposits occur usually in local uplifts and gradient belts featuring a turn from steep to gentle in granite-metamorphic contact zones, relative uplifts of gradient zones of the Curier isothermal interfaces, depressions of the Moho discontinuity and areas where depth contours are cut by isotherms perpendicularly. Gold mineralization and lithogenesis are characterized by high temperature, low pressure and high strength of thermal flux. The depth of mineralization ranges from 0.8 to 4.5 km. The depth of the top interface of the granitic complex in the metallogenic epoch is about 3 km. There is a low-velocity layer （LVL） at the bottom of the upper crust with a depth close to 19.5 km, which may be a detachment belt in the crust. The appearance of the LVL indicates the existence of paleo-hyperthermal fluid or relics of molten magma chambers, which reflects partial melting within the crust during the diagenetic and metallogenic epochs and the superposition effects of strike-slip shearing of the Taulu fault zone. The subsidence of the Moho is probably attributed to the coupling process of the NW-SE continental collision between North China and the Yangtze Block and the strike-slip movement of the Tanlu fault accompanied with underplating of mantle magma in the northwestern part of the Jiaodong Peninsula. The underplating of mantle magma may result in partial melting and make granite magma transfer upwards. This is favorable for the migration of metallogenic materials from deep to shallow to be enriched to form deposits. Coupling interactions between the strike-slip of the Taulu fault, the underplating of mantle magma, partial melting within the crust, and hyperthermal fluid, etc. may be the important factors controlling the gold mineralization and spatial structures in the metailogenic system.

Upper bound solutions for supporting pressures of shallow tunnels with nonlinear failure criterion

Linear failure criterion is widely used in calculation of earth pressure acting on shallow tunnels. However, experimental evidence shows that nonlinear failure criterion is able to represent fairly well the failure of almost all types of rocks, A nonlinear Hock-Brown failure criterion is employed to estimate the supporting pressures of shallow tunnels in limit analysis framework. Two failure mechanisms are proposed for calculating the work rate of extemal force and the internal energy dissipation. A tangential line to the nonlinear failure criterion is used to formulate the supporting pressure problem as a nonlinear programming problem. The objective function formulated in this way is minimized with respect to the failure mechanism and the location of tangency point. In order to assess the validity, the supporting pressures for the proposed failure mechanisms are calculated and compared with each other, and the present results are compared with previously published solutions when the nonlinear criterion is reduced to linear criterion. The agreement supports the validity of the proposed failure mechanisms. An experiment is conducted to investigate the influences of the nonlinear criterion on collapse shape and supporting pressures of shallow tunnels.