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n-Absorbing Ideals of Commutative Rings and Recent Progress on Three Conjectures: A Survey
No full textLet R be a commutative ring with 1 ≠ 0. Recall that a proper ideal I of R is called a 2-absorbing ideal of R if a,b,c ∈ R and abc ∈ I, then ab ∈ I or ac ∈ I or bc ∈ I . A more general concept than 2-absorbing ideals is the concept of n-absorbing ideals. Let n ≥ 1 be a positive integer. A proper ideal I of R is called an n-absorbing ideal of R if a1,a2,…an+1 ∈ R and a1a2…an+1 ∈ I, then there are n of the ai's whose product is in I. The concept of n-absorbing ideals is a generalization of the concept of prime ideals (note that a prime ideal of R is a 1-absorbing ideal of R). In this survey article, we collect some old and recent results on n-absorbing ideals of commutative rings
Solving Fourth Order Differential Non-Linear Equations, Existence and Uniqueness
No full textA Master of Science thesis in Mathematics by Amer Mahmoud Malbanji entitled, "Solving Fourth Order Differential Non-Linear Equations, Existence and Uniqueness," submitted in May 2017. Thesis advisor is Dr. Suheil A. Khoury. Soft and hard copy available.The aim of this thesis is to present a novel numerical approach for the solution of a class of non-linear fourth-order boundary value problems. The method is based on embedding Green's function into some fixed point iteration schemes, an idea previously used in other works to investigate nonlinear boundary value problems of lower order. To this end, the thesis is divided in 6 chapters. The first chapter is a short description of the main ideas of this thesis. The second chapter represents a review on Green's functions for differential equations. In Chapter 3 some existence and uniqueness results for the fourth order boundary value problems are presented. The proposed numerical method is then explained and applied on numerical examples in Chapter 4, where a comparison with the Spline method is also given, demonstrating thus that our method yields accurate results up to 10 e-20, compared to the Spline method, where the results are accurate up to 10 e-13. The results obtained by our method were achieved within a reasonable time limit compared with other methods. Chapter 5 is concerned with the convergence analysis of our method. More precisely, some conditions which guarantees the convergence of the solution under specific conditions is given. For the proof we used the Banach-Picard theorem along with the Green's function. Finally, in Chapter 6 we present a short conclusions and a summary of the whole thesis.College of Arts and SciencesDepartment of Mathematics and StatisticsMaster of Science in Mathematics (MSMTH
Dynamics of a four-bar mechanism with clearance and springs - Modeling and experimental analysis
No full textThis paper presents a study of the dynamic behavior of a planar four-bar mechanism with clearance. A spring is added to improve the dynamic response of the mechanism with clearance. Simulations and experimental tests are carried out to show the improvement of the dynamic behavior using this simple yet effective solution. The simulation is performed under MATLAB and ADAMS. An experimental set-up is designed and built to achieve the experimental validations. The presented results show that the added spring improved the dynamic behavior of the mechanism by keeping a continuous contact between the journal and the sleeve despite the presence of the clearance. The effect of the spring on the input torque is also investigated. It is shown that the spring increases the maximum value of the torque. An optimization is performed to determine the best parameters of the spring that reduce the effect of the clearance while minimizing the increase of the input torque. The optimized system is tested at different speeds to show the effect of the speed on the dynamic behavior of the optimized system
Dynamic Spectrum Scheduling and Management in Centralized Cognitive Radio Networks
No full textA Master of Science thesis in Electrical Engineering by Omar Khalid Sweileh entitled, "Dynamic Spectrum Scheduling and Management in Centralized Cognitive Radio Networks," submitted in November 2017. Thesis advisor is Dr. Mohamed Hassan and thesis co-advisor is Dr. Hasan Mir. Soft and hard copy available.As the demand for wireless radio spectrum increases, spectrum regulatory authorities expect to face a spectrum scarcity problem.As the demand for wireless radio spectrum increases, spectrum regulatory authorities expect to face a spectrum scarcity problem. Dynamic Spectrum Access (DSA) was recently proposed to enable efficient utilization of the radio spectrum. Cognitive Radio (CR)s are used to help in the realization of efficient DSA techniques. An integral component in Cognitive Radio Network (CRN), and in DSA in general, is scheduling, which has to do with the Secondary User (SU)’s ability to decide on the available spectrum that best meets its Quality of Service (QoS) requirements. Switching delay, which is defined as the time needed by a SU to hop among available channels, is a major factor that affects the performance of CRNs. This study is motivated by the fact that the literature is in need for efficient schedulers that can maximize the CRN’s through-put while maintaining a minimum spectrum switching delay for the SUs. Specifically, two scheduling techniques are introduced with the aim of minimizing the switching de-lay and hence maximizing the amount of transmitted information over the underlying CRN. The first scheduler is an opportunistic spectrum and switching-delay aware scheduler with the objective of maximizing the total number of transmitted packets over the span of multiple time-slots. From the simulation results, the opportunistic scheduler, in highly dynamic channels, was able to transmit up to 20% more packets compared to the benchmark scheduling algorithm where the scheduling problem is done every timeslot. Moreover, the scheduler was able to reduce the effect of both switching and scheduling delays. On the other hand, the second proposed scheduler maximizes spectrum exploitation by allowing unscheduled SUs to utilize any idle spectrum during the switching delay. From the results, the proposed scheduler allowed for≈38% more SUs to be scheduled in an overpopulated CRN. Moreover, by utilizing the switching delay, the proposed scheduler was able to deliver around 4.5% more packets compared to the benchmark algorithm without sacrificing any complexity. In conclusion, both of the implemented schedulers delivered a higher amount of transmitted packets compared to the benchmark scheduling algorithms and both schedulers were able to reduce the effect of switching delay.College of EngineeringDepartment of Electrical EngineeringMaster of Science in Electrical Engineering (MSEE
Evaluation of sustainable concrete produced with desalinated reject brine
No full textThe worldwide demand for new concrete buildings is increasing at a rapid pace to keep up with urban development. Despite the need, concrete production and its use have a number of environmental consequences. The production of concrete creates a substantial need for water that directly causes a burden on the already scare natural resource. In United Arab Emirates the majority of the water used for concrete production is obtained through desalination of the seawater. Desalination of seawater produces highly saline wastewater commonly known as reject brine or concentrated brine that has numerous negative environmental effects. The production of cement, the primary ingredient in the production of concrete is responsible for the generation of nearly 5% of the global carbon dioxide that is a potent greenhouse gas. With the intent of reducing the carbon footprint of concrete production, a study was carried out to determine the effect of using reject brine as the source of water and the use of ground granulated blast furnace slag (GGBS) as a replacement for cement. Concrete samples having three different cement contents were prepared with normal tap water and reject brine. Results showed that the use of GGBS and reject brine improved the strength of concrete produced by 16.5%. Replacing 50% of the cement with GGBS and using reject brine as the source of water has a potential for reducing 176 kg CO2 and 1.7–3.4 kg of CO2 equivalents per one cubic meter of concrete, respectively. The use of the waste reject brine can potentially save USD 170–340 per cubic meter of concrete produced
A conversation for now and later
No full textEssay for the 'New Chapter' catalogue in conjunction with an exhibition of new photographs by HH Lateefa bint Maktoum, held at the Tashkeel Gallery Dubai, 18 January - 23 February 2017
Civil Engineering Volunteerism: Assisting Developing Countries Stem the Tide of Economic Migration
No full textForum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal
Tunable CPW Ring Resonator-Based Bandpass Filters Utilizing RF MEMS Varactors
No full textA Master of Science thesis in Electrical Engineering by Ahlam Mohammad Ebrahim Pish Dast entitled, "Tunable CPW Ring Resonator-Based Bandpass Filters Utilizing RF MEMS Varactors," submitted in January 2017. Thesis advisor is Dr. Maher Bakri Kassem. Soft and hard copy available.Radio Frequency (RF) Micro-Electro-Mechanical Systems (MEMS) switches are mostly used in many applications such as: tunable filters, phase shifters and oscillators because they offer wide bandwidth, low insertion loss, excellent isolation and outstanding linearity in comparison with their electronic counterparts. The objective of this research is to design and implement tunable RF MEMS based bandpass filters (BPF) using coplanar waveguide (CPW) ring resonator with both frequency control, and to achieve tunable BPF that demonstrate low insertion loss, high return loss, high quality factor, and compact size. Tunable bandpass filters that are RF MEMS based have the potential to advance wireless communications and radar systems due to their superior RF performance in comparison with conventional tunable filters. Four new types of bandpass filters using CPW technology with open ring resonators are proposed in this work which being tuned using RF MEMS capacitive switches to achieve wide tuning range with multiple DC biasing circuits. The advantage of designing the filter with CPW structure is having the ground plane and the signal conductor on the same level. This feature allows achieving compact structures in comparison with microstrip technology and will allow the integration with other technology such as RF MEMS. Two tunable ring resonators and two second order BPF are introduced in this thesis. The ring resonator that is the basic block of the proposed tunable filters is of a circular shape and open type where the RF MEMS capacitive switches are placed in the open area of the ring resonator between the edges to tune the electrical length and achieve tunability. For the second order BPF, two ring resonators are coupled with two couplers and a CPW waveguide. All proposed filters are built on an Aluminum Oxide (Al2-O3) ceramic substrate with the thickness of 675 μm. The first and second designs of tunable ring resonator are designed at 2 GHz. These two designs are used in wireless communications, WiMAX (Worldwide interoperability Microwave Access), mobile GSM and ISM bands. The third and fourth designs of tunable bandpass filter are designed at 20 GHz, and they can be used in mobile satellite applications.College of EngineeringDepartment of Electrical EngineeringMaster of Science in Electrical Engineering (MSEE
An IOT-Based Context-Aware Wearable Assessment Platform for Smart Watches
No full textA Master of Science project in Computer Engineering by Mohamad Naeem Al Solh entitled, “An IOT-Based Context-Aware Wearable Assessment Platform for Smart Watches”, submitted in November 2017. Thesis advisor is Dr. Imran Ahmed Zualkernan. Soft and hard copy available.College of EngineeringDepartment of Computer Science and EngineeringMaster of Science in Computer Engineering (MSCoE
Dynamic Power Characteristics of Selective Buried Oxide (SELBOX) MOSFET
No full textA Master of Science thesis in Electrical Engineering by Rana Mahmoud entitled, "Dynamic Power Characteristics of Selective Buried Oxide (SELBOX) MOSFET," submitted in February 2017. Thesis advisors are Dr. Hasan Al-Nashash and Dr. Narayanan Madathumpadical. Soft and hard copy available.The ever-increasing number of devices and electronic systems resulted in increasing the die size to satisfy the increasing demand. Moreover, the shrinking size of transistors according to the scaling theory became a contributor to increasing the leakage current. Many efforts have been made to reduce power dissipation by introducing new circuit designs and new device architectures, which is the main scope of this thesis, such as the Silicon-On-Insulator (SOI) and the Selective Buried Oxide (SELBOX) structures. The bulk Metal-Oxide-Semiconductor Field-Effect-Transistor (MOSFET) structure has relatively high power dissipation, in addition to its poor frequency response due to its internal capacitances. As a result, SOI MOSFET has been introduced as an alternative to the bulk MOSFET to minimize power dissipation as well as to tackle the existing problems of the bulk MOSFET. The SOI MOSFET transistor active region is isolated from the substrate and hence device parasitic capacitances are reduced resulting in a faster operation and lower leakage power dissipation. Unfortunately, results showed that the fully-depleted SOI (FD-SOI) and partially-depleted SOI (PD-SOI) suffer from self-heating effect and the PD-SOI has the kink effect problem. Therefore, the concerns towards fabricating a new device that combines the advantages of the bulk and SOI MOSFETs and eliminating their drawbacks have been raised again. The proposed device is called the SELBOX MOSFET and has structural features identical to SOI MOSFET structure with the only difference which is the gap in the isolation layer. Our results showed that the existing gap in the BOX layer has eliminated the self-heating and the kink effects which are the major drawbacks of the SOI MOSFET. The main objective of this thesis is to investigate the dynamic power dissipation of the CMOS SELBOX structure and compare it with that of the CMOS bulk and SOI structures. The devices' fabrication simulation have been conducted using Silvaco TCAD tools. The simulation results show that the dynamic power dissipation of the CMOS bulk, SOI and SELBOX are almost the same at high frequencies. However, at low frequencies, the dynamic power dissipation of the CMOS bulk is the highest and that of CMOS SOI and SELBOX is very close.College of EngineeringDepartment of Electrical EngineeringMaster of Science in Electrical Engineering (MSEE