Inland wetlands in Abu Dhabi Emirate are wintering and stopover sites for migratory birds of prey. We conducted long-term regular monitoring surveys in Al Wathba Wetland Reserve (AWWR) from January 1995 to December 20...Inland wetlands in Abu Dhabi Emirate are wintering and stopover sites for migratory birds of prey. We conducted long-term regular monitoring surveys in Al Wathba Wetland Reserve (AWWR) from January 1995 to December 2022. Both diurnal and occasionally nocturnal surveys were undertaken to record the migratory raptors and owls in the Wetland Reserve. During the study, a total of 1282 regular monitoring visits were undertaken and 27 species of diurnal raptors and owls representing five families and three orders were detected. These represent 57% of the total species of birds of prey recorded in the UAE. Overall, 63% of all the species that we observed were Accipitriformes followed by 26% Falconiformes and 11% Strigiformes. We found that changes in mean daily temperature have a positive effect on raptor species diversity and abundance in the Wetland Reserve. The species encounter rate was higher in low temperature as compared to high temperature and overall regression equation was statistically significant F (4, 1126) = 8.49), p = 0.00). However, the numbers of raptors did not vary significantly across the years (p = 0.51). Western Marsh-harrier (Circus aeruginosus) and Greater Spotted Eagle (Clanga clanga) were recorded to be the most abundant species in the wetland reserve followed by Common Kestrel (Falco tinnunculus). However, the encounter rate of globally threatened Greater Spotted Eagle was detected to have significantly decreased since 2016. Moreover, 63% of the species detected were uncommon and rarely recorded such as 1) Saker Falcon 2) Lanner Falcon 3) Long-eared Owl & Merlin, which were the rare records from the wetland reserve. Furthermore, 27 years of regular monitoring in the wetland have yielded diverse diurnal raptors and owl fauna (H) = 0.83, (E) = 1.43 (Shannon Diversity Index). The results demonstrate that long-term monitoring surveys in arid environments are essential to determine the trends in the raptor populations and to document rare and globally important species.展开更多
The relative intensities of L-subshell x-ray fluorescence(XRF)for elements with atomic numbers 62≤Z≤83 were measured at two excitation energies,18 keV and 23 keV,using a synchrotron radiation source at a beamline of...The relative intensities of L-subshell x-ray fluorescence(XRF)for elements with atomic numbers 62≤Z≤83 were measured at two excitation energies,18 keV and 23 keV,using a synchrotron radiation source at a beamline of the Synchrotron Light Center for Experimental Science and Applications in the Middle East(SESAME),Jordan.The experimentally measured results of the relative intensities were compared with the calculated results using the subshell fluorescence yield and the Coster-Kronig transition probabilities recommended by Campbell and the values based on the Dirac-Hartree-Slater model by Puri.The experimental and theoretical results are in agreement.In this work,L XRF relative intensities for the elements Sm,Gd,Tb,Er,Ta,W,Re,Hg,Pb and Bi at energies of 18 keV and 23 keV were measured.展开更多
The dipole-dipole interaction model is used to calculate the angular dependence of lateral and levitation forces on a small permanent magnet and a cylindrical superconductor in the Meissner state lying laterally off t...The dipole-dipole interaction model is used to calculate the angular dependence of lateral and levitation forces on a small permanent magnet and a cylindrical superconductor in the Meissner state lying laterally off the symmetric axis of the cylinder. Under the assumption that the lateral displacement of the magnet is small compared with the physical dimensions of the system, we obtain analytical expressions for the lateral and levitation forces as functions of geometrical parameters of the superconductor as well as the height, the lateral displacement and the orientation of magnetic moment of the magnet. The effect of thickness and radius of the superconductor on the levitation force is similar to that for a symmetric magnet/superconducting cylinder system, but within the range of lateral displacement. The splitting in the levitation force increases with the increasing angle of orientation of the magnetic moment of the magnet. For a given lateral displacement of the magnet, the lateral force vanishes when the magnetic moment is perpendicular to the surface of the superconductor and has a maximum value when the moment is parallel to the surface. For a given orientation of the magnetic moment, the lateral force has a linear relationship with the lateral displacement. The stability of the magnet above the superconducting cylinder is discussed in detail.展开更多
<strong>Background:</strong> Keratoconus (KC) causes visual disability in young adults. To improve its early detection and compliance, improving the awareness of patients and their relatives is crucial. We...<strong>Background:</strong> Keratoconus (KC) causes visual disability in young adults. To improve its early detection and compliance, improving the awareness of patients and their relatives is crucial. We present the level of awareness about KC among the adult population of western Saudi Arabia and its determinants. <strong>Methods:</strong> This web-based survey was carried out from June to August 2020 in urban and semi-urban areas in western Saudi Arabia. Demographic and eye ailment profiles were collected. To generate responses on the presentation, causes, management and prevention of KC, a five-point Likert scale was used. The logit values were calculated and graded into good and poor awareness. Awareness was associated with other determinants. <strong>Results:</strong> We surveyed 420 Saudi adults. The median logit score of awareness about KC among participants was 2.86 (inter quartile range (IQR) 0.86;2.95). The median score of knowledge about the causes and presentation of KC was 2.86 (IQR 1.1;2.86) and for management, it was 0.00 (IQR 0.00;0.18). The level of awareness was good in 286 participants (68.1%) and poor in 134 (31.9%). Residents of major cities (P < 0.04) and women (P < 0.001) had significantly better awareness about KC. Knowledge about KC mainly came from friends and reading about it. The mass media and social media were rarely used to seek knowledge. <strong>Conclusions:</strong> Awareness about the presentation, causes and management of KC was good in two-thirds of adults but with some variation. Strategies to involve the community and stress health education need to be urgently implemented. Campaigns should target the male and semi-urban population in western Saudi Arabia.展开更多
The problem of a small magnet levitating above a very thin superconducting disc in the Meissner state is analysed. The dipole-dipole interaction model is employed to derive analytical expressions for the interaction e...The problem of a small magnet levitating above a very thin superconducting disc in the Meissner state is analysed. The dipole-dipole interaction model is employed to derive analytical expressions for the interaction energy, levitation force, magnetic stiffness and frequency of small vibrations about the equilibrium position in two different configurations, i.e. with the magnetic moment parallel and perpendicular to the superconductor. The results show that the frequency of small vibrations decreases with the increasing levitation height for a particular radius of the superconducting disc, which is in good agreement with the experimental results. However, the frequency increases monotonically up to saturation by increasing the radius of the disc for a particular height of the magnet. In addition, the frequency of vibrations is higher when the system is in the vertical configuration than that when the system is in the horizontal configuration.展开更多
Predicting the value of one or more variables using the values of other variables is a very important process in the various engineering experiments that include large data that are difficult to obtain using different...Predicting the value of one or more variables using the values of other variables is a very important process in the various engineering experiments that include large data that are difficult to obtain using different measurement processes.Regression is one of the most important types of supervised machine learning,in which labeled data is used to build a prediction model,regression can be classified into three different categories:linear,polynomial,and logistic.In this research paper,different methods will be implemented to solve the linear regression problem,where there is a linear relationship between the target and the predicted output.Various methods for linear regression will be analyzed using the calculated Mean Square Error(MSE)between the target values and the predicted outputs.A huge set of regression samples will be used to construct the training dataset with selected sizes.A detailed comparison will be performed between three methods,including least-square fit;Feed-Forward Artificial Neural Network(FFANN),and Cascade Feed-Forward Artificial Neural Network(CFFANN),and recommendations will be raised.The proposed method has been tested in this research on random data samples,and the results were compared with the results of the most common method,which is the linear multiple regression method.It should be noted here that the procedures for building and testing the neural network will remain constant even if another sample of data is used.展开更多
This study investigated the monthly variation of water quality in the Amman-Zarqa and Balqa regions in Jordan in terms of pH, ammonium, nitrate and conductivity. During 2004 there was no monthly variation in water qua...This study investigated the monthly variation of water quality in the Amman-Zarqa and Balqa regions in Jordan in terms of pH, ammonium, nitrate and conductivity. During 2004 there was no monthly variation in water quality for most of the tested parameters. All readings were above the accepted range except for pH, indicating that land use does have an impact on water quality irrespective of urban, industrial or agricultural usage. The water quality remained for the most part below the maximum levels for drinking standards in Jordan, but these standards are often below the WHO recommendations. The pH was found to fluctuate through the year. Nitrate levels were highly seasonal in irrigated lands but remained stable over basin covered by other land uses. Ammonium levels were high in areas of urbanisation and intensive animal husbandry as a consequence of effluent infiltration, peaking during the wet season due to increased infiltration. These results indicate that, over an annual cycle, the variation in water quality remains constant;however the continued drawdown of the aquifer system will inevitably lead to deterioration in the parameters investigated.展开更多
The dipole–dipole interaction model is employed to investigate the angular dependence of the levitation and lateral forces acting on a small magnet in an anti-symmetric magnet/superconducting sphere system. Breaking ...The dipole–dipole interaction model is employed to investigate the angular dependence of the levitation and lateral forces acting on a small magnet in an anti-symmetric magnet/superconducting sphere system. Breaking the symmetry of the system enables us to study the lateral force which is important in the stability of the magnet above a superconducting sphere in the Meissner state. Under the assumption that the lateral displacement of the magnet is small compared to the physical dimensions of our proposed system, analytical expressions are obtained for the levitation and lateral forces as a function of the geometrical parameters of the superconductor as well as the height, the lateral displacement, and the orientation of the magnetic moment of the magnet. The dependence of the levitation force on the height of the levitating magnet is similar to that in the symmetric magnet/superconducting sphere system within the range of proposed lateral displacements. It is found that the levitation force is linearly dependent on the lateral displacement whereas the lateral force is independent of this displacement. A sinusoidal variation of both forces as a function of the polar and azimuthal angles specifying the orientation of the magnetic moment is observed. The relationship between the stability and the orientation of the magnetic moment is discussed for different orientations.展开更多
We obtain analytical relations for the levitation force as a function of dimensions of the superconductor-magnet system. The force has been calculated on the basis of the dipole-dipole interaction model. The effect of...We obtain analytical relations for the levitation force as a function of dimensions of the superconductor-magnet system. The force has been calculated on the basis of the dipole-dipole interaction model. The effect of thickness of the superconductor on the levitation force is investigated. The results show that the influence of geometry and thickness of the magnet becomes significantly large at small levitation distances. Furthermore, approximating the permanent magnet as a point dipole results in an inaccurate estimation of the levitation force.展开更多
The vertical stability of a magnetic tip over a superconducting material is investigated by using the critical state and the frozen image models. The analytical expressions of the stiffness and the vibration frequency...The vertical stability of a magnetic tip over a superconducting material is investigated by using the critical state and the frozen image models. The analytical expressions of the stiffness and the vibration frequency about the equilibrium position are derived in term of the geometrical parameters of the magnet/superconductor system. It is found that the stability of the system depends on the shape of the superconductor as well as its thickness.展开更多
The stability of the magnetic dipole and the metamaterial with negative permeability are investigated. Analytical expressions of the interaction force and stiffness of the magnetic line and metamaterial with negative ...The stability of the magnetic dipole and the metamaterial with negative permeability are investigated. Analytical expressions of the interaction force and stiffness of the magnetic line and metamaterial with negative permeability are derived. The repulsive force between the magnetic line and the metamaterial exceeds the value of the maximum force in the magnet-superconductor system.展开更多
文摘Inland wetlands in Abu Dhabi Emirate are wintering and stopover sites for migratory birds of prey. We conducted long-term regular monitoring surveys in Al Wathba Wetland Reserve (AWWR) from January 1995 to December 2022. Both diurnal and occasionally nocturnal surveys were undertaken to record the migratory raptors and owls in the Wetland Reserve. During the study, a total of 1282 regular monitoring visits were undertaken and 27 species of diurnal raptors and owls representing five families and three orders were detected. These represent 57% of the total species of birds of prey recorded in the UAE. Overall, 63% of all the species that we observed were Accipitriformes followed by 26% Falconiformes and 11% Strigiformes. We found that changes in mean daily temperature have a positive effect on raptor species diversity and abundance in the Wetland Reserve. The species encounter rate was higher in low temperature as compared to high temperature and overall regression equation was statistically significant F (4, 1126) = 8.49), p = 0.00). However, the numbers of raptors did not vary significantly across the years (p = 0.51). Western Marsh-harrier (Circus aeruginosus) and Greater Spotted Eagle (Clanga clanga) were recorded to be the most abundant species in the wetland reserve followed by Common Kestrel (Falco tinnunculus). However, the encounter rate of globally threatened Greater Spotted Eagle was detected to have significantly decreased since 2016. Moreover, 63% of the species detected were uncommon and rarely recorded such as 1) Saker Falcon 2) Lanner Falcon 3) Long-eared Owl & Merlin, which were the rare records from the wetland reserve. Furthermore, 27 years of regular monitoring in the wetland have yielded diverse diurnal raptors and owl fauna (H) = 0.83, (E) = 1.43 (Shannon Diversity Index). The results demonstrate that long-term monitoring surveys in arid environments are essential to determine the trends in the raptor populations and to document rare and globally important species.
基金supported by the Jordan University of Science and Technology(Grant No.20180167)the SESAME Synchrotron Center Jordan(Grant No.20185004)。
文摘The relative intensities of L-subshell x-ray fluorescence(XRF)for elements with atomic numbers 62≤Z≤83 were measured at two excitation energies,18 keV and 23 keV,using a synchrotron radiation source at a beamline of the Synchrotron Light Center for Experimental Science and Applications in the Middle East(SESAME),Jordan.The experimentally measured results of the relative intensities were compared with the calculated results using the subshell fluorescence yield and the Coster-Kronig transition probabilities recommended by Campbell and the values based on the Dirac-Hartree-Slater model by Puri.The experimental and theoretical results are in agreement.In this work,L XRF relative intensities for the elements Sm,Gd,Tb,Er,Ta,W,Re,Hg,Pb and Bi at energies of 18 keV and 23 keV were measured.
文摘The dipole-dipole interaction model is used to calculate the angular dependence of lateral and levitation forces on a small permanent magnet and a cylindrical superconductor in the Meissner state lying laterally off the symmetric axis of the cylinder. Under the assumption that the lateral displacement of the magnet is small compared with the physical dimensions of the system, we obtain analytical expressions for the lateral and levitation forces as functions of geometrical parameters of the superconductor as well as the height, the lateral displacement and the orientation of magnetic moment of the magnet. The effect of thickness and radius of the superconductor on the levitation force is similar to that for a symmetric magnet/superconducting cylinder system, but within the range of lateral displacement. The splitting in the levitation force increases with the increasing angle of orientation of the magnetic moment of the magnet. For a given lateral displacement of the magnet, the lateral force vanishes when the magnetic moment is perpendicular to the surface of the superconductor and has a maximum value when the moment is parallel to the surface. For a given orientation of the magnetic moment, the lateral force has a linear relationship with the lateral displacement. The stability of the magnet above the superconducting cylinder is discussed in detail.
文摘<strong>Background:</strong> Keratoconus (KC) causes visual disability in young adults. To improve its early detection and compliance, improving the awareness of patients and their relatives is crucial. We present the level of awareness about KC among the adult population of western Saudi Arabia and its determinants. <strong>Methods:</strong> This web-based survey was carried out from June to August 2020 in urban and semi-urban areas in western Saudi Arabia. Demographic and eye ailment profiles were collected. To generate responses on the presentation, causes, management and prevention of KC, a five-point Likert scale was used. The logit values were calculated and graded into good and poor awareness. Awareness was associated with other determinants. <strong>Results:</strong> We surveyed 420 Saudi adults. The median logit score of awareness about KC among participants was 2.86 (inter quartile range (IQR) 0.86;2.95). The median score of knowledge about the causes and presentation of KC was 2.86 (IQR 1.1;2.86) and for management, it was 0.00 (IQR 0.00;0.18). The level of awareness was good in 286 participants (68.1%) and poor in 134 (31.9%). Residents of major cities (P < 0.04) and women (P < 0.001) had significantly better awareness about KC. Knowledge about KC mainly came from friends and reading about it. The mass media and social media were rarely used to seek knowledge. <strong>Conclusions:</strong> Awareness about the presentation, causes and management of KC was good in two-thirds of adults but with some variation. Strategies to involve the community and stress health education need to be urgently implemented. Campaigns should target the male and semi-urban population in western Saudi Arabia.
文摘The problem of a small magnet levitating above a very thin superconducting disc in the Meissner state is analysed. The dipole-dipole interaction model is employed to derive analytical expressions for the interaction energy, levitation force, magnetic stiffness and frequency of small vibrations about the equilibrium position in two different configurations, i.e. with the magnetic moment parallel and perpendicular to the superconductor. The results show that the frequency of small vibrations decreases with the increasing levitation height for a particular radius of the superconducting disc, which is in good agreement with the experimental results. However, the frequency increases monotonically up to saturation by increasing the radius of the disc for a particular height of the magnet. In addition, the frequency of vibrations is higher when the system is in the vertical configuration than that when the system is in the horizontal configuration.
文摘Predicting the value of one or more variables using the values of other variables is a very important process in the various engineering experiments that include large data that are difficult to obtain using different measurement processes.Regression is one of the most important types of supervised machine learning,in which labeled data is used to build a prediction model,regression can be classified into three different categories:linear,polynomial,and logistic.In this research paper,different methods will be implemented to solve the linear regression problem,where there is a linear relationship between the target and the predicted output.Various methods for linear regression will be analyzed using the calculated Mean Square Error(MSE)between the target values and the predicted outputs.A huge set of regression samples will be used to construct the training dataset with selected sizes.A detailed comparison will be performed between three methods,including least-square fit;Feed-Forward Artificial Neural Network(FFANN),and Cascade Feed-Forward Artificial Neural Network(CFFANN),and recommendations will be raised.The proposed method has been tested in this research on random data samples,and the results were compared with the results of the most common method,which is the linear multiple regression method.It should be noted here that the procedures for building and testing the neural network will remain constant even if another sample of data is used.
文摘This study investigated the monthly variation of water quality in the Amman-Zarqa and Balqa regions in Jordan in terms of pH, ammonium, nitrate and conductivity. During 2004 there was no monthly variation in water quality for most of the tested parameters. All readings were above the accepted range except for pH, indicating that land use does have an impact on water quality irrespective of urban, industrial or agricultural usage. The water quality remained for the most part below the maximum levels for drinking standards in Jordan, but these standards are often below the WHO recommendations. The pH was found to fluctuate through the year. Nitrate levels were highly seasonal in irrigated lands but remained stable over basin covered by other land uses. Ammonium levels were high in areas of urbanisation and intensive animal husbandry as a consequence of effluent infiltration, peaking during the wet season due to increased infiltration. These results indicate that, over an annual cycle, the variation in water quality remains constant;however the continued drawdown of the aquifer system will inevitably lead to deterioration in the parameters investigated.
文摘The dipole–dipole interaction model is employed to investigate the angular dependence of the levitation and lateral forces acting on a small magnet in an anti-symmetric magnet/superconducting sphere system. Breaking the symmetry of the system enables us to study the lateral force which is important in the stability of the magnet above a superconducting sphere in the Meissner state. Under the assumption that the lateral displacement of the magnet is small compared to the physical dimensions of our proposed system, analytical expressions are obtained for the levitation and lateral forces as a function of the geometrical parameters of the superconductor as well as the height, the lateral displacement, and the orientation of the magnetic moment of the magnet. The dependence of the levitation force on the height of the levitating magnet is similar to that in the symmetric magnet/superconducting sphere system within the range of proposed lateral displacements. It is found that the levitation force is linearly dependent on the lateral displacement whereas the lateral force is independent of this displacement. A sinusoidal variation of both forces as a function of the polar and azimuthal angles specifying the orientation of the magnetic moment is observed. The relationship between the stability and the orientation of the magnetic moment is discussed for different orientations.
文摘We obtain analytical relations for the levitation force as a function of dimensions of the superconductor-magnet system. The force has been calculated on the basis of the dipole-dipole interaction model. The effect of thickness of the superconductor on the levitation force is investigated. The results show that the influence of geometry and thickness of the magnet becomes significantly large at small levitation distances. Furthermore, approximating the permanent magnet as a point dipole results in an inaccurate estimation of the levitation force.
文摘The vertical stability of a magnetic tip over a superconducting material is investigated by using the critical state and the frozen image models. The analytical expressions of the stiffness and the vibration frequency about the equilibrium position are derived in term of the geometrical parameters of the magnet/superconductor system. It is found that the stability of the system depends on the shape of the superconductor as well as its thickness.
文摘The stability of the magnetic dipole and the metamaterial with negative permeability are investigated. Analytical expressions of the interaction force and stiffness of the magnetic line and metamaterial with negative permeability are derived. The repulsive force between the magnetic line and the metamaterial exceeds the value of the maximum force in the magnet-superconductor system.
