Characterization of Asphalt Mixtures in Qatar

The State of Qatar went through a massive road construction program in the last decade as part of the ongoing development of its infrastructure and road transport network. Construction of roads in Qatar generally utilizes imported materials such as aggregate and binders as a result of the scarcity of local construction materials. Characteristics of asphalt mixtures are studied in this research program in order to evaluate mixtures properties in terms of aggregate packing, binder content, voids, mixture density, maximum density and Marshall Stability. Actual mixtures used in the Public Works Authority road projects were analyzed in the research program. Mixtures were prepared following the Qatar Construction Specifications (QCS, 2014). Combined aggregate gradations for different asphalt mixtures were compared with maximum density envelopes for different maximum aggregate sizes. Moreover, regression analysis was used to evaluate the strength of correlations established between different asphalt mixtures properties. The analysis of these mixtures is outlined in terms of general characteristics and consequently, recommendations are given to improve asphalt mixtures performance

Personalized Quantification of Facial Normality using Artificial Intelligence

While congenital facial deformities are not rare, and surgeons typically perform operations to improve these deformities, currently the success of the surgical reconstruction operations can only be “measured” subjectively by surgeons and specialists. No efficient objective mechanisms of comparing the outcomes of plastic reconstruction surgeries or the progress of different surgery techniques exist presently. The aim of this research project is to develop an efficient software application that can be used by plastic surgeons as an objective measurement tool for the success of an operation. The long-term vision is to develop a software application that is user-friendly and can be downloaded on a regular laptop and used by doctors and patients to assess the progress of their surgical reconstruction procedures. The application would work by first scanning a face before and after an operation and providing the surgeon with a normality score of the face from 0 to 3 where 3 represents normal and 0 represents extreme abnormality. A score will be given when the face is scanned before and after surgery. The difference between those scores is what we will call the delta. A high delta value would point to a high improvement in the normality of a face post-surgery, and a low delta value would indicate a small improvement. The first chapter of the thesis represents the introduction which describes the general aspects of the project. The second chapter presents the methodology employed for building the application and the existing solutions and proposed functional model structure. The results chapter presents the process behind collecting and labeling the image database and analyzes the scores produced by the program when fed with new images from the database. Finally, the last chapter of this thesis presents the conclusions. The list of references completes this work

Development and Performance of Cement Bound Materials in Road Pavements

The use of cement bound materials (CBMs) for road construction in Qatar is relatively new. CBM improves the structural capacity and durability of pavement, but considerations should be made to the setting time and strength development in hot arid environment, such as in Qatar. The paper presents a laboratory development and performance characteristics of CBM mixtures, with environmental and economic benefits through the use of local and recycled materials. The developed mixtures showed full compliance with the grading, strength and durability requirements of the Qatar Construction Specifications (QCS, 2014). Site data from Ashghal projects indicated the difficulty of producing consistent strength in practice, with the potential of increased strength and associated risk of reflection cracking in the asphalt overlaying. Recommendations are made to improve the construction practice and specification of cement and other hydraulically bound materials to enhance the service life of pavement and support the government strategy of sustainable construction

Challenges for the Use of Local Materials in Unbound Road Subbase in Qatar

Current practice in Qatar is to blend local limestone with dune sand for use in unbound pavement applications. Dune sand is used to improve the properties of fine aggregate and compliance with the QCS 2014 requirements of plasticity and sand equivalent. The material has been successfully used for many years but currently facing the challenge of limited dune sand supply and recent government restrictions on its use in construction. The paper presents data on the properties of limestone obtained from different sources, tested in accordance with the QCS 2014 requirements. Variation of limestone source and the presence of clay particles greatly affected its suitability for use in unbound pavement applications. Improvement could be achieved by adjusting the grading of the material. Recommendations are made to revise the QCS 2014 specifications within the context of international specifications, when the unbound material is placed in a dry environment and away from the water level to enhance the wider utilization of local materials and sustainable construction in Qatar

Test Procedures for Advanced Characterization of Bituminous Binders Employed for Pavement Construction in Public Works Authority Road Projects - State of Qatar

This paper illustrates the approach adopted by the Public Works Authority (Ashghal) of the State of Qatar for the advanced chemical and rheological characterization of bituminous binders (both neat and modified). The ultimate objective of testing is to create a database of employed binders, which may be meaningful for the optimization of the selection of materials and for the consequent enhancement of pavement performance. This paper provides an illustration of employed testing procedure and briefly discusses typical experimental results

Use of Crumb Rubber Modified Binders and Asphalt Mixtures in Public Works Authority Road Projects - State of Qatar

This paper illustrates the approach adopted by the Public Works Authority (Ashghal) of the State of Qatar for the widespread implementation in road projects of paving technologies related to the use of crumb rubber modified binders (CRMBs). Such an approach has entailed the monitoring of a full-scale preliminary trial, the definition of a prequalification system for crumb rubber and CRMB producers, and the development of mix design and quality control guidelines applicable to CRMB asphalt mixtures. Experimental results obtained in the preparatory phases of work and during the approval process of materials and mixtures are critically presented

Differential Flatness-Based Performance Enhancement of a Vector Controlled VSC with an LCL-Filter for Weak Grids

In this paper, a novel single-loop flatness-based controller (FBC) is proposed to control the grid-side current in a shunt converter connected to a weak grid through an LCL-filter. After its mathematical description, the paper reports controller implementation and some performance comparisons with two distinct implementations of the widely diffused vector current control approach, during balanced and unbalanced grid voltages, and weak grid conditions. Obtained results highlight higher tracking capability and better dynamic response of the proposed FBC. Moreover, because of its reduced negative conductance region, unstable behaviors that can be observed in weak grids appear significantly improved due to a reduced influence of the phase-locked loop system

A novel DSTATCOM with 5-level CHB architecture and selective harmonic mitigation algorithm

This paper proposes a five level cascaded converter for Distribution Static Compensator (DSTATCOM) implementing a novel modulation algorithm with harmonic mitigation and a PI controller with phase shift modulation for reactive power control. The modulator operates at fundamental frequency and the whole system satisfies grid code requirements using a simple passive output filter tuned with 11th harmonic. The behavior of the proposed system has been successfully compared with another one with multilevel space vector pulse width modulation. Results show its capability of ensuring satisfactory dynamic response at low frequency operations, resulting improved efficiency and reduced output filter requirements over more conventional systems. All rights reserved.Scopu

A novel model predictive control with an integrated SOC and floating DC-link voltage balancing for 3-phase 7-level PUC converter-based MV BESS

Compared to conventional multilevel topologies, the Packed U-Cell multilevel topology utilizes the minimum number of components and provides both maximum voltage levels and high reliability. When used in a battery energy storage system, its dc-link consists of a top branch battery storage and bottom branch flying capacitors, whose state of charge and voltages must be balanced.This paper proposes a novel control scheme with two cascaded controllers: the inner loop regulates the output filter current and dc-link voltages using a novel finite-set model predictive control, the outer one is fully integrated with the model predictive controller and regulates the battery state of charge by injecting a zero-sequence voltage. The proposed control scheme was successfully implemented and tested through simulation and real-time testing. The obtained results highlight good dynamic performance and robustness of the proposed scheme during active power injection/absorption and low voltage ride-through capability

A novel control scheme for three-phase seven-level packed U-Cell based DSTATCOM

With the advent of SiC devices, the packed U-Cell converter has become a promising topology among the multilevel converters for medium voltage DSTATCOM application. It utilizes fewer components while achieving the maximum voltage levels with higher reliability. However, as a reactive power compensator, its dc-link consists of flying capacitors, whose voltages must be balanced which presents a challenging problem for a seven-level packed U-Cell inverter, as there are no-redundant switching states. This paper proposes a novel control scheme to keep these flying capacitors balanced under normal/abnormal grid conditions. It consists of a standard cascaded: inner and outer controllers. The inner current controller regulates both the active and reactive currents and the outer controller regulates the upper flying capacitor voltage. In parallel with the cascaded controllers, a novel model predictive voltage balancing controller is proposed to maintain the lower flying capacitor voltage at a given setpoint. To cope with the unbalance grid conditions, an additional zero-sequence injection regulator is also integrated into the designed control scheme. The proposed control scheme was simulated and real-time tested on the Hardware-In-the-Loop system. The results show that the proposed controller effectively balances the two flying capacitor voltages while controlling the reactive power.Qatar University Internal Grant no. QUCP-CENG-EE-15 16-