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Search Results: 1 - 10 of 325561 matches for " Abdulrahman S. Alharbi "
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Synthetic Approach for Novel Fluorine Substituted α-Aminophosphonic Acids Containing 1,2,4-Triazin-5-One Moiety as Antioxidant Agents  [PDF]
Mohammed S. T. Makki, Reda M. Abdel-Rahman, Abdulrahman S. Alharbi
International Journal of Organic Chemistry (IJOC) , 2018, DOI: 10.4236/ijoc.2018.81001
Abstract: Novel fluorine substituted α-amino phosphonic acids containing 1,2,4-triazin- 5-one (6a-f) have been obtained from fluoroacylation of 6-(2-amino-5-nitrophenyl)-3-thioxo-1,2,4-triazin-5(4H)-one (1) followed by ammonilysis to give the corresponding 3-amino-derivative 3. Condensation of compound 3 with nitro/halogenated aromatic aldehydes yielded the Schiff bases 4. The simple addition of diethyl phosphonate to compound 4 produced the α-amino phosphonates 5. Acidic hydrolysis of compound 5 produced the fluorine substituted α-amino acids derivatives 6. Structures of the new compounds have been established with the help of elemental analysis and spectral measurements. Also, the products evaluated as antioxidants, where the fluorinated α-amino phosphonic acids 6 are more active than the other synthesized systems.
Synthesis of Novel 4-Thiazolidinone and Bis-Thiazalidin-4-One Derivatives Derived from 4-Amino-Antipyrine and Evaluated as Inhibition of Purine Metabolism Enzymes by Bacteria  [PDF]
Reda M. Abdel Rahman, Abdulrahman S. Alharbi, Nawaa A. Alshammari
International Journal of Organic Chemistry (IJOC) , 2019, DOI: 10.4236/ijoc.2019.92008
Abstract: Novel 4-thiazolidione and 1,4-bis-thiazolidinone derivatives bearing antipyrine moiety have been obtained from condensation of 4-aminoantipyrine 1 with aromatic/heteroaldehydes followed by cycloaddition with mercaptoacetic acid in nonpolar solvents. Structure of the products has been deduced upon their elemental analysis and spectral measurements. Most of the targets evaluated as enzymatic effect towards some bacteria (E. coli) in compare with Xanthine oxidase (from buttermilk) where the role of compounds is an inhibition of purine metabolism enzymes caused by E. coli.
Waveguide Design Optimization for Long Wavelength Semiconductor Lasers with Low Threshold Current and Small Beam Divergence  [PDF]
Abdulrahman Al-Muhanna, Abdullah Alharbi, Abdelmajid Salhi
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.24031
Abstract: Long wavelength GaSb-based quantum well lasers have been optimized for high coupling efficiency into an optical system. Two approaches were used to reduce the vertical far-field. In the first approach we showed the use of V-shaped Weaker Waveguide in the n-cladding layer dramatically reduces vertical beam divergence without any performance degradation compared to a conventional broad-waveguide laser structure. Starting from a broad waveguide laser structure design which gives low threshold current and a large vertical far-field (VFF), the structure was modified to decrease the VFF while maintaining a low threshold-current density. In a first step the combination of a narrow optical waveguide and reduced refractive index step between the waveguide and the cladding layers reduce the VFF from 67? to 42?. The threshold current density was kept low to a value of ~190 A/cm2 for 1000 × 100 µm2 devices by careful adjustment of the doping profile in the p-type cladding layer. The insertion of a V-Shaped Weaker Waveguide in the n-cladding layer is shown to allow for further reduction of the VFF to a value as low as 35? for better light-coupling efficiency into an optical system without any degradation of the device performance. In the second approach, we showed that the use of a depressed cladding structure design also allows for the reduction of the VFF while maintaining low the threshold current density (210 A/cm2), slightly higher value compare to the first design.
Observations “Detections” of Shallow Unconventional Qusaiba Shale Gas Reservoirs North Part of Saudi Arabia  [PDF]
Mamdoh Alajmi, Abdulrahman Alotaibi, Essam Aboud, Aqeel Alharbi, Majed Almalki
Journal of Geoscience and Environment Protection (GEP) , 2018, DOI: 10.4236/gep.2018.65022
Abstract:
There are many oil and gas conventional reservoirs in Saudi Arabia have been exploited, but still there are also need to be explored and produced especially in the fields of unconventional shale gas. Investigation the extending of rock source of the hot shale gas Qusaiba formation in North part of Saudi Arabia, the most important rock source in the word, is crucial for one of the most promising shallow shale gas reservoir in the region. Most previous studies in the area were a geological, petrographical, petrophysical, geochemical characteristics or well logs studies which are not enough to show the continuously of the reservoir and map the diverse of the depth changes. The lack of the geophysical studies in the area inspiring to perform such study and image how the continuously and behavior of the reservoir subsurface. Imaging the geological stratigraphy of area utilizing a multiple geophysical methods is a crucial step to disclosure the unconventional reservoir and understand the source rock extending underneath the North region of Saudi Arabia. A good achievement is shown in this study using this integration of seismic migrated image and gravity geological model. This integration provides a robust and true subsurface geological formations, structures, and determined thickness and depth of the Lower Silurian Sharawra Qusaiba and Sarah formations. This work would be a valuable contribution in unconventional reservoirs exploration in shale gas in Saudi Arabia.
On a Problem of an Infinite Plate with a Curvilinear Hole inside the Unit Circle  [PDF]
F. S. Bayones, B. M. Alharbi
Applied Mathematics (AM) , 2015, DOI: 10.4236/am.2015.61020
Abstract: In this work, we used the complex variable methods to derive the Goursat functions for the first and second fundamental problem of an infinite plate with a curvilinear hole C. The hole is mapped in the domain inside a unit circle by means of the rational mapping function. Many special cases are discussed and established of these functions. Also, many applications and examples are considered. The results indicate that the infinite plate with a curvilinear hole inside the unit circle is very pronounced.
High-Order Finite Difference Schemes for the First Derivative in Von Mises Coordinates  [PDF]
S. O. Alharbi, M. H. Hamdan
Journal of Applied Mathematics and Physics (JAMP) , 2016, DOI: 10.4236/jamp.2016.43059
Abstract: Third- and fourth-order accurate finite difference schemes for the first derivative of the square of the speed are developed, for both uniform and non-uniform grids, and applied in the study of a two-dimensional viscous fluid flow through an irregular domain. The von Mises transformation is used to transform the governing equations, and map the irregular domain onto a rectangular computational domain. Vorticity on the solid boundary is expressed in terms of the first partial derivative of the square of the speed of the flow in the computational domain, and the schemes are used to calculate the vorticity at the computational boundary grid points using up to five computational domain grid points. In all schemes developed, we study the effect of coordinate clustering on the computed results.
Framework to Classify and Analyze Social Media Content  [PDF]
Hayfa Aleid, Amjad Abdulrahman Alkhalaf, Aseel Helal Taemees, Hanan Saeed Almurished, Khawla Abdullah Alharbi, Nawal Hussein Alanazi
Social Networking (SN) , 2018, DOI: 10.4236/sn.2018.72006
Abstract:
In the last decade, a large amount of data has been published in different fields and can be used as a data source for research and study. However, identifying a specific type of data requires processing, which involves machine learning classifying techniques. To facilitate this, we propose a general framework that can be applied to any social media content to develop an intelligent system. The framework consists of three main parts: an interface, classifier and ana-lyzer. The analyzer uses media recognition to identify specific features. Then, the classifier uses these features and involves them in the classification process. The interface organizes the interaction between the system compo-nents. We tested the framework and developed a system to be applied to im-age-based social media networks (Instagram). The system was implemented as a mobile application (My Interests) that works as a recommendation and filtering system for Instagram users and reduces the time they spend on irre-levant information. It analyzes the images, categorizes them, identifies the in-teresting ones, and finally, reports the results. We used the Cloud Vision API as a tool to analyze the images and extract their features. Furthermore, we adapted support vector machine (SVM), a machine learning method, to classify images and to predict the preferred ones.
Further Evidence for Arabic Basic Colour Categories  [PDF]
Abdulrahman S. Al-rasheed
Psychology (PSYCH) , 2014, DOI: 10.4236/psych.2014.515179
Abstract: The aim of this study was to describe the basic colour terms (BCTs) of Arabic and, in particular, clarify the relationship among the three Arabic terms for blue: azrock, samawee, and khuhlie that suggested a BCTs in Arabic language in Al-rasheed et al. (2013). Data were collected from adult native Arabic speakers (30 male and 27 female) age between 18 and 34 years old, with a mean age of 21.67 years (SD = 2.98). All were under and postgraduate students at King Saud University. Participants task was to group the 320 colours by similarity. Based on this result, Arabic probably has eleven basic colour terms and these correspond with Berlin and Kay’s eleven universal categories. The terms are that ahmar “red”, akhdar “green”, asfer, “yellow”, azrock “blue”, asswed “black”, abiyadh “white”, banafsagee “purple”, boartoogaalee “orange”, bonee “brown”, wardee “pink” and rassasee. In addition, the terms of particular interest—samawee (“light blue”) had the next highest claim to being basic and may deserve further investigating.
Characteristics of Students with Emotional/Behavioral Disorders: Perspectives of General Education Teachers in Saudi Arabia  [PDF]
Abdulrahman A. Abaoud, Nabil S. Almalki
Psychology (PSYCH) , 2015, DOI: 10.4236/psych.2015.65050
Abstract: Students with emotional/behavioral disorders (EBDs) have a number of characteristics that distinguish them from other students with special needs. Some teachers may be aware of these problems through their teaching level, level of education, and/or experience in education but others are not. This study was conducted through a survey to determine teachers’ perspectives of students with EBDs because an important relationship exists between what is believed by teachers about such students and what is practiced concerning them. Participants in this study included 296 general education teachers from Saudi Arabia. The results showed that the participants who responded to the survey have neutral perspectives on the characteristics of students with EBDs. The study has found additional significant differences between male and female teachers regarding their perceptions of characteristics of students with EBDs. No significant differences were discovered in the level of education, the number of years of teaching experience, or the school level taught. Implications and conclusions are discussed.
The Development of Curriculum for Girls in Saudi Arabia  [PDF]
Fahad Alharbi
Creative Education (CE) , 2014, DOI: 10.4236/ce.2014.524226
Abstract: This paper illustrates the development of curriculum for girls in Saudi Arabia and how it has changed and been challenged over time. Several factors have played important roles on impeding girls’ education. Society was the main impediment, as it used to refuse any change and fight that change. Girls in Saudi Arabia are segregated from boys in different schools, but in the past, they also had to take different subjects and curriculum that what boys were studying. There are three major challenges that girls’ education faced until they were given the same quality of education that boys received. The first challenge started during King Faisal’s era when girls were allowed to go to public schools but under different directors than boys’ institutions. The second time was in 2002, when the girls’ education was moved under the Ministry of Education. The last challenge began with King Abdullah’s project for developing education, whereupon girls received the same quality of education as men.
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