National University of Computer and Emerging Sciences

About: National University of Computer and Emerging Sciences is a education organization based out in Islamabad, Pakistan. It is known for research contribution in the topics: Computer science & The Internet. The organization has 1506 authors who have published 2438 publications receiving 26786 citations.

Improving the performance of OCL constraint solving with novel heuristics for logical operations: a search-based approach

Abstract: A common practice to specify constraints on the Unified Modeling Language (UML) models is using the Object Constraint Language (OCL). Such constraints serve various purposes, ranging from simply providing precise meaning to the models to supporting complex verification and validation activities. In many applications, these constraints have to be solved to obtain values satisfying the constraints, for example, in the case of model-based testing (MBT) to generate test data for the purpose of generating executable test cases. In our previous work, we proposed novel heuristics for various OCL constructs to efficiently solve them using search algorithms. These heuristics are enhanced in this paper to further improve the performance of OCL constraint solving. We performed an empirical evaluation comprising of three case studies using three search algorithms: Alternating Variable Method (AVM), (1ź+ź1) Evolutionary Algorithm (EA), and a Genetic Algorithm (GA) and in addition Random Search (RS) was used as a comparison baseline. In the first case study, we evaluated each heuristics using carefully designed artificial problems. In the second case study, we evaluated the heuristics on various constraints of Cisco's Video Conferencing Systems defined to support MBT. Finally, the third case study is about EU-Rent Car Rental specification and is obtained from the literature. The results of the empirical evaluation showed that (1ź+ź1) EA and AVM with the improved heuristics significantly outperform the rest of the algorithms.

Design of Modular Power Management and Attitude Control Subsystems for a Microsatellite

Abstract: The Electric Power System (EPS) and attitude control system (ACS) are the essential components of any satellite. EPS and ACS efficiency and compactness are substantial for the proper operation and performance of the satellite’s entire mission life. So, realizing the significance of EPS and ACS subsystems for any satellite, they have been assimilated and developed in modular forms focusing on efficiency and compactness. The EPS is comprised of three modules called the solar panel module (SPM), power conditioning module (PCM), and power distribution module (PDM) while the ACS has an embedded magnetorquer coil. For compactness and miniaturization purposes, the magnetorquer coil is embedded inside the SPM. The components used are commercial off-the-shelf (COTS) components emphasizing on their power efficiency, small dimensions, and weight. Latch-up protection systems have been designed and analyzed for CMOS-based COTS components, in order to make them suitable for space radioactive environment. The main design features are modularity, redundancy, power efficiency, and to avoid single component failure. The modular development of the EPS and ACS helps to reuse them for future missions, and as a result, the overall budget, development, and testing time and cost are reduced. A specific satellite mission can be achieved by reassembling the required subsystems.

Design of a simple and effective object-to-relational mapping technique

Abstract: Currently, most object-oriented applications use relational databases to meet their needs for persistent storage However, object-oriented and relational paradigms represent information in manners that are quite different from each other This results in two different models for representing the same information, thus increasing the design and maintenance efforts Several attempts have been made to overcome this impedance mismatch but all of them have fallen short of providing satisfactory results from one aspect or the other This paper outlines a simple and straightforward approach to effectively overcome this challenge Our methodology yields a data model that is mechanically derived from the object model without compromising the performance of the system The physical schema and the basic object persistence and population operations are automatically generated, thus, resulting in a system that makes design and maintenance much easier tasks than before

Structural equation modeling of public transport use with COVID-19 precautions: An extension of the norm activation model.

Abstract: This study aims to identify the travelers' attitudes and preferences towards the use of public transport during COVID-19 through the Norm-Activation Model (NAM). A questionnaire survey was designed to assess the traveler's awareness, sense of responsibility, and moral obligations to comply with safety norms or guidelines while using public transport in Lahore, Pakistan. The Structural Equation Modeling method was applied to analyze the collected 1516 complete responses. The survey results and measurement equations confirmed the association between observed and corresponding latent variables. The results of SEM revealed that the travelers' Awareness of Consequences (AC) and Ascription of Responsibility (AR) are positively correlated with Personal Norms (PN), whereas attitudes towards public transport are negatively related to the PN. The perceived behavioral control (PBC) and PN have negative structural correlations with public transport use. However, the attitudes towards public transport are strong predictors of travelers' behavior towards public transport. The current motorcycle users and high-income people have low preferences, whereas current users of public transport modes and middle-income people have high preferences to choose public transport during a pandemic. The travelers' perceived difficulty of complying with safety guidelines while traveling, such as wearing a facemask, use of sanitizers, and maintaining a social distance, have a significant impact on their public transport use. The travelers' better awareness, responsibility, and trust in using public transport may have a strong influence on their preferences towards public transport during a pandemic situation.