22 research outputs found
The design and engineering of innovative mobile data services: An ontological framework founded on business model thinking
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This research investigates mobile service design and engineering in the mobile telecommunications industry. The mobile telecommunication business is shifting from one that was voice-centric to one that is almost all data-centric; thanks to recent rapid advances in Information and Communication Technologies (ICTs). The underlying reasons behind this shift can be traced back to two main issues that are interlinked. The first and major reason is that telecoms (telecommunication companies) are trying to generate new revenue streams based on data and information transmissions, given the saturation of the voice market. This is rational given the market opportunities in one direction and the pressures being generated by the current economic downturn from the other direction. The second reason relates to the flexibility of data, compared to voice. Indeed, the number of services that can be developed on the basis of data are much greater than those that can be developed on the basis of voice. However, the design and engineering of successful and innovative mobile data services has proven to be a complex undertaking. The number of effective mobile data services is relatively small and the revenue generated from such offerings has generally been below expectations. This research develops an ontological framework to help in changing this situation, and making mobile services engineering more effective and successful, following the design-science research paradigm.
Design-science research, in general, aims to solve unstructured but relevant organizational or social problems through the development of novel and useful artefacts. As the current research aims to help in solving the mobile data services engineering dilemma by developing a purposeful ontological framework, the design-science research paradigm is deemed fitting. Within this paradigm, the author develops a novel design approach specified for ontology engineering, termed “OntoEng”. This design approach is used in this research for developing the ontological framework.
The developed ontological framework is founded on business model thinking. The idea is that creating innovative mobile data services requires developing innovative business models. Indeed, innovative business models can help translate technological potential into economic value and allow telecoms to achieve their strategic objectives. The ontological framework includes the development of an ontology, termed “V4 Mobile Service BM Ontology” as well as “Mobile Key Value Drivers” for designing and engineering innovative mobile data services. The V4 Mobile Service BM Ontology incorporates four design dimensions: (1) value proposition including targeting; (2) value architecture including technological and organizational infrastructure; (3) value network dealing with aspects relating to partnerships and co-operations; and finally (4) value finance relating to costs, pricing, and revenue structures. Within these four dimensions, sixteen design concepts are identified along with their constituent elements. Relationships and interdependencies amongst the identified design constructs are established and clear semantics are produced. The research then derives six key value drivers for mobile service engineering as follows: (a) Market Alignment; (b) Cohesion; (c) Dynamicity; (d) Uniqueness; (e) Fitting Network-Mode; and (f) Explicitness.
The developed ontological framework in this research is evaluated to ensure that it can be successfully implemented and performs correctly in the real world. The research mainly utilizes case analysis methods to ensure the semantic correctness of the ontological framework. Indeed, the developed ontological framework is employed as an analytical lens to examine the design and engineering of three key real-life cases in the mobile telecommunications industry. These cases are: (1) Apple’s iPhone Services and Applications; (2) NTT DoCoMo’s i-mode Services; and (3) Orange Business Services. For further validation, the developed ontological framework is evaluated against a set of criteria synthesized from ontology engineering and evaluation literature. These criteria are: Clarity; Coherence; Conciseness; Preciseness; Completeness; and Customizability.
The developed ontological framework is argued to make significant contributions for theory, practice, and methodology. For theory, this research provides (1) a novel ontological framework for designing and engineering mobile data services; (2) a unified framework of the business model concept; and (3) a new design approach for ontology engineering in information systems. For practice, the current research provides practitioners in the telecommunications industry with systematic and customizable means to design, implement, analyze, evaluate, and change new and existing mobile data services to make them more manageable, effective, and creative. For methodology, the use of the design- science research paradigm for ontology engineering signifies the focal methodological contribution in this research given its novelty. This research also contributes to the understanding of the design-science research paradigm in information systems as it is relatively new. It provides a working example in which the author illustrates how recognizing design-science research as a paradigm is essential and useful to the research in information systems discipline
Control of teleoperation systems in the presence of cyber attacks: A survey
No full textThe teleoperation system is often composed of a human operator, a local master manipulator, and a remote slave manipulator that are connected by a communication network. This paper proposes a survey on feedback control design for the bilateral teleoperation systems (BTSs) in nominal situations and in the presence of cyber-attacks. The main idea of the presented methods is to achieve the stability of a delayed bilateral teleoperation system in the presence of several kinds of cyber attacks. In this paper, a comprehensive survey on control systems for BTSs under cyber-attacks is discussed. Finally, we discuss the current and future problems in this field. The teleoperation system is often composed of a human operator, a local master manipulator, and a remote slave manipulator that are connected by a communication network. This paper proposes a survey on feedback control design for the bilateral teleoperation systems (BTSs) in nominal situations and in the presence of cyber-attacks. The main idea of the presented methods is to achieve the stability of a delayed bilateral teleoperation system in the presence of several kinds of cyber attacks. In this paper, a comprehensive survey on control systems for BTSs under cyber-attacks is discussed. Finally, we discuss the current and future problems in this field
Analysis and Challenges in Wireless Networked Control System: A Survey
No full textA wireless networked control system (WNCS) consists of a dynamic system to be controlled, sensors, actuators, and a remote controller. A WNCS has two types of wireless transmissions, i.e., the sensor's measurement transmission to the controller and the controller's command transmission to the actuator. In this paper, we are surveying the literature on the communication networks in WNCSs and the challenges related to them, such as the communication standards, delay, Packet dropout, and delay jitter. Then, the control approaches in the design of a WNCS are presented, including the interactive design approaches and the joint design approaches. Also, several applications of WNCSs have been discussed in terms of their structure, functionality, and control design. These applications include Intra-Vehicle Wireless networks, Wireless Avionics Intra-Communication, Building Automation, and Water pumping. After that, security issues in WNCSs from a control engineering point of view are detailed while focusing on the major kinds of cyber attacks affecting WNCSs. Finally, future directions and conclusions are summarized at the end of the paper
Cyberphysical infrastructures in power systems architectures and vulnerabilities
No full textIn an uncertain and complex environment, to ensure secure and stable operations of large-scale power systems is one of the biggest challenges that power engineers have to address today. Traditionally, power system operations and decision-making in controls are based on power system computations of physical models describing the behavior of power systems. Largely, physical models are constructed according to some assumptions and simplifications, and such is the case with power system models. However, the complexity of power system stability problems, along with the system's inherent uncertainties and nonlinearities, can result in models that are impractical or inaccurate. This calls for adaptive or deep-learning algorithms to significantly improve current control schemes that solve decision and control problems.Cyberphysical Infrastructures in Power Systems: Architectures and Vulnerabilities provides an extensive overview of CPS concepts and infrastructures in power systems with a focus on the current state-of-the-art research in this field. Detailed classifications are pursued highlighting existing solutions, problems, and developments in this area.- Gathers the theoretical preliminaries and fundamental issues related to CPS architectures.- Provides coherent results in adopting control and communication methodologies to critically examine problems in various units within smart power systems and microgrid systems.- Presents advanced analysis under cyberphysical attacks and develops resilient control strategies to guarantee safe operation at various power level
An Adaptive Sliding Mode Control for Single Machine Infinite Bus System under Unknown Uncertainties
No full textThe inherent uncertainties in a Single Machine Infinite Bus System (SMIBS) are governed by unmodeled dynamics or large disturbances such as the system's faults. The existence of these uncertainties demands robust controllers to guarantee the system's asymptotic stability under such exacting conditions. In this work, we propose an Adaptive Sliding Mode Control (ASMC) design implemented on a fifth-order nonlinear SMIBS to handle those uncertainties without prior knowledge about its upper bounds. We develop the ASMC with gains of two nested adaptive layers to asymptotically stabilize the system's internal states, the machine's terminal voltage, and power angle within a region of unknown bounded uncertainties while mitigating the chattering phenomena associated with conventional Sliding Mode Control (SMC). To verify the design's effectiveness and prove the conducted Lyapunov theoretical stability analysis, we simulate the occurrence of a large disturbance represented by a 3-phase fault at the system's universal bus. The results show that the ASMC can successfully achieve asymptotic stable output errors and stabilizing the SMIBS internal states after the clearance of the fault. Moreover, the ASMC noticeably outperforms the SMC in chattering mitigation, where the ASMC's signal is significantly smoother than that of the SMC
Effect of Ion Sizes on Separation Characteristics of Nanofiltration Membrane Systems
No full textThe effect of the ion size on salt rejection is investigated using the Donnan steric pore model (DSPM). This model accounts for the transport phenomena occurring inside the membrane through the appropriate ion sizes. Four hydrated ions (Na+, Mg2+, Cl-, SO42-) are considered. The ion radius is determined from Stokes-Einstein relationship (Stokes radius), the Born’s theory (Born’s effective radius), and the strength of hydration (Pauling radius). Experimental data validate predictions of ion rejections. It was found that ionic hydration has strong influence on the diffusion properties of ions, which affects significantly the ion rejections. The charge density across the surface of the membrane varies according to the choice of radius of solute, causes remarkable variations in the model prediction. It was also found that the charge density should be predicted accurately to obtain the surface potential which will aid in the improvement of membrane performance and also give approximate index for fabrication of thin film composite layer membrane.
Keywords: Membrane, Mathematical modeling, Nanofiltration, Ion sizeCorresponding Author:
Mr. M. E. E. Abashar
Chemical Engineering Department, College of Engineering, King Saud University,
P.O. Box 800, Riyadh 11421, Saudi Arabia, E-mail address: [email protected]
Wide area monitoring system operations in modern power grids: A median regression function-based state estimation approach towards cyber attacks
No full textModern power grid is a generation mix of conventional generation facilities and variable renewable energy resources (VRES). The complexity of such a power grid with generation mix has routed the utilization of infrastructures involving phasor measurement units (PMUs). This is to have access to real-time grid information. However, the traffic of digital information and communication is potentially vulnerable to data-injection and cyber attacks. To address this issue, a median regression function (MRF)-based state estimation is presented in this paper. The algorithm was stationed at each monitoring node using interacting multiple model (IMM)-based fusion architecture. An exogenous variable-driven representation of the state is considered for the system. A mapping function-based initial regression analysis is made to depict the margins of state estimate in the presence of data-injection. A median regression function is built on top of it while generating and evaluating the residuals. The tests were conducted on a revisited New England 39-Bus system with large scale photovoltaic (PV) power plant. The system was affected with multiple system disturbances and severe data-injection attacks. The results show the effectiveness of the proposed MRF method against the mainstream and regression methods. The proposed scheme can accurately estimate the states and evaluate the contaminated measurements while improving the situation awareness of wide area monitoring systems (WAMS) operations in modern power grids 2023 The Author(s)The publication of this article was funded by Qatar National Library .Scopu
Stability Analysis of Cyber-physical System Under Transmission Delay
No full textWith the intimate integration of power grids and cyber networks, limited bandwidth and packet delay have a rapidly expanding negative impact on power system performance. The presented multi-area interconnected power system consists of four areas, each including thermal and hydro-generation plants. This paper investigates the stability analysis problem for cyber-physical systems with a round-robin communication protocol under mixed cyberattacks and load changes. The objective is to stabilize a multi-area interconnected power system (MAIPS) using a static feedback controller while minimizing the defined performance function. Then, the stability of the MAIPS is characterized when the system is subjected to a transmission delay while considering predetermined limits for the duration and the frequency of the delay. Our findings indicate that time delays can influence system stability and that choosing an appropriate sampling interval is necessary to ensure the stability of the system. Finally, an illustrative example of three areas of interconnected power systems with several scenarios is presented to verify the effectiveness of the proposed method
Second ever reported case of central cause of unilateral foot drop due to cervical disc herniation : Case report and review of literature
No full textBackground: Foot drop is defined as a weakness in the ankle and foot dorsiflexors. A disruption of the neural pathway starting from the motor prefrontal cortex and ending in the peroneal nerve can lead to foot drop. Foot drop due to lower motor neuron injury is well documented. However, foot drop due to a central cause of cervical disc prolapse is very rare. Case presentation: A 55-year-old male presenting with neck pain, right and left arms radicular pain and numbness, and unilateral right foot drop following cervical disc prolapse. The patient presented with upper motor neuron lesion signs. MRI showed cervical disc prolapse at two levels, confirming central cause of foot drop. The patient underwent anterior cervical decompression and fusion surgery. Discussion: Following decompression and fusion of involved cervical spine disc pathology, the patient had complete recovery of his right foot drop. Conclusions: Central causes, although rare, should be considered in the differential diagnosis of foot drop. Causes could be due to the compression effect of the cortico-spinal tract of the cervical spinal cord. Satisfactory results can be achieved upon correcting the causative lesion. CC BY 4.0© 2021 The Author(s)Guarantor Prof Dr. Walid El Ansari: [email protected]</p
