New method for square root of non-singular M-matrix

Square root of a matrix play an important role in many applications of matrix theory. In this paper, we propose a new iterative method for square root of a non-singular M-matrix. We first transform the matrix equation X2 – A=0 into special form of a non-symmetric algebraic Riccati equation (NARE), and then solve this special NARE by Newton method. Efficiency and effectiveness proved by theoretical analysis and numerical experiments. Keywords: - Matrix square root, M-matrix, Non-symmetric algebraic Riccati equation, Newton method

Factors Affecting the Labour Productivity in Construction Projects of Pakistan

Construction projects are considered crucial in every developed and developing country from the perspective of economic and social development. Thus, it is mandatory to achieve successful completion of the project. Efficient production is one of the significant criteria in ensuring the success of projects. An efficient production, labour productivity is considered an important aspect. Labour productivity is affected by several factors which are essential to study for productivity improvements. Since in Pakistan, labour productivity is one of the least studied areas within the construction industry. Hence, this paper focused on determining the common factors which have influenced the labour productivity. A survey among the construction practitioners included 33 identified factors from literature. A total of 150 questionnaire forms were distributed, and only 54 completed data forms were received back. These forms were used to analyse statistically using frequency analysis with SPSS software and weighted average (WA) calculation with Microsoft Excel application. The results indicated 1 factor as very often occurring, and other 32 factors were reported as often occurring during construction works while WA value for significance revealed that there are seven factors which have extremely significant while other 26 factors lie in the category of very significant. Those seven dominating factors reported as extremely significant are the misuse of schedule, the increase of labourer age, weather changes, tool and equipment shortages, violation of safety precautions, working seven days per week without taking a holiday and lack of financial motivation system

Structural model of cost overrun factors affecting Pakistani construction projects

Cost overruns are a global challenge to successfully completing construction projects. Cost overrun has a substantial impact resulting in most construction projects failing to be completed. Several factors have contributed significantly to the industry's decline. The factors were discovered in the literature, assessed, and applied to the construction industry in Pakistan. This study scrutinized and identified the relationships between the factors causing cost overruns in the Pakistani construction industry using the Partial Least Squares Structural Equation Modelling (PLS-SEM) approach. The structural model was created and tested with Smart-PLS software using data from a questionnaire survey of 131 construction practitioners. Six constructs were used to categorise the factors. The model identifies 21 critical factors in Pakistani construction projects, with resource management ranking first. Contract management issues can also contribute significantly to project cost overruns. Model assessment results indicate that the developed model has a substantial power of explaining the factors of cost performance while R2 value showed that 45.7% variance is explained by the model. The model developed model will serve as a jumping-off point for academics, researchers, and practitioners in developing a cost-control system. It is suggested that establishing an efficient and effective contract management protocol among stakeholders throughout the design and supervision stages is extremely beneficial for improving project cost performance and significantly reducing time overruns

Contractor's Perception on Factors Causing Cost Overrun in Construction Works of Pakistan

This paper assessed the occurrence and severity level of various factors causing time and cost overrun in construction projects of Pakistan. Investigation was carried out through questionnaire form prepared based on 55 common factors identified from literature. Survey was done amongst the representatives of the contractors involved in handling construction activities in Pakistan. A total of 46 responses gathered against 100 distributed forms were analysed statistically. The results obtained from the analyses based on Average Index values revealed that delay in obtaining permits from the governmental agencies, financial difficulties are common issue faced in construction works of Pakistan. The study also revealed that high cost of machinery & its maintenance, inadequate planning & scheduling and slow information flow between parties have significant effect on time overrun cost while critical factors affecting cost overrun are high cost of machinery & its maintenance, unsuitable construction methods and lack of experience of contractors in affecting project cost. The findings of this study will be helpful for the practitioner in planning for achieving timely completion of the projects and also within the estimated cost

Simulation Techniques for Porous Media Confined in Silo Geometry

Granular materials have vast applications both in industry and in daily life. They display quite interesting and exceptional properties different from the other known forms of matter. To investigate the complex properties of particulate materials, experimental, analytical and simulation techniques have been employed. In this paper the results of large-scale discrete element molecular dynamics (DEM) simulations in three dimensions are reported. It deals with the investigation of stress deflection due to various grain sizes. Moreover, the influence of coefficient of friction between granules and cylindrical walls on the mass measured at bottom of container i.e. apparent mass is thoroughly investigated. It is revealed that apparent mass varies linearly with the grain size. In addition to that, it is also found that the apparent mass variation is strongly dependent on bead diameter rather than the silo. The results reveal that conversion of vertical stresses into horizontal in silo is mainly due to the friction between the grain and system boundary

Simulation Techniques for Porous Media Confined in Silo Geometry

Granular materials have vast applications both in industry and in daily life. They display quite interesting and exceptional properties different from the other known forms of matter. To investigate the complex properties of particulate materials, experimental, analytical and simulation techniques have been employed. In this paper the results of large-scale discrete element molecular dynamics (DEM) simulations in three dimensions are reported. It deals with the investigation of stress deflection due to various grain sizes. Moreover, the influence of coefficient of friction between granules and cylindrical walls on the mass measured at bottom of container i.e. apparent mass is thoroughly investigated. It is revealed that apparent mass varies linearly with the grain size. In addition to that, it is also found that the apparent mass variation is strongly dependent on bead diameter rather than the silo. The results reveal that conversion of vertical stresses into horizontal in silo is mainly due to the friction between the grain and system boundary

A Symmetric RZ-DPSK Based Colorless NG-PON using Optical Carrier Suppression Scheme

In this paper a simultaneous transmission of a 10 Gbps RZ-DPSK data signal for downstream as well as for upstream is proposed and successfully simulated. An OCS (Optical Carrier Suppression) scheme for generation of second order dual side-band optical carrier is utilized by quadrupling a 10 GHz clockfrequency with a 10 GHz LN-MZM (Lithium-Niobate Mach-Zehnder-Modulator). The upper side second order band is used to generate a RZ-DPSK (Return to Zero-Differential Phase Shift Keying) data signal at the OLT (Optical Line Terminal). At the receiving ONU (Optical Network Unit) 50 km away from the OLT the unmodulated lower side second order band coupled with the downlink transmitted signal is utilized for the uplink modulation of 10 Gbps data in RZ-DPSK format. The simulation results show that the performance of the single-tone RZ-DPSK data modulation format is a suitable choice for the WDMPON (Wavelength Division Multiplexing-Passive Optical Network) link with a transmission span of 50 km. The proposed architecture eliminates the need of any pulse carver and mid-span power amplifiers along with the requirement of any power splitting device used in the ONU for colorless uplink transmission. In this scheme, high data rate transmission over long distance is achieved. This scheme merges the boundaries of local access networks and MAN (Metropolitan Area Networks). The proposed scheme is a highly robust, cost effective, backward compatible as well as future proof WDM-PON architecture

Optimizing WiMAX: Mitigating Co-Channel Interference for Maximum Spectral Efficiency

The efficient use of radio spectrum is one of the most important issues in wireless networks because spectrum is generally limited and wireless environment is constrained to channel interference. To cope up and for increased usefulness of radio spectrum wireless networks use frequency reuse technique. The frequency reuse technique allows the use of same frequency band in different cells of same network considering inter-cell distance and resulting interference level. WiMAX (Worldwide Interoperability for Microwave Access) PHY profile is designed to use FRF (Frequency Reuse Factor) of one. When FRF of one is used it results in an improved spectral efficacy but also results in CCI (Co-Channel interference) at cell boundaries. The effect of interference is always required to be measured so that some averaging/ minimization techniques may be incorporated to keep the interference level up to some acceptable threshold in wireless environment. In this paper, we have analyzed, that how effectively CCI impact can be mitigated by using different subcarrier permutation types presented in IEEE 802.16 standard. A simulation based analysis is presented wherein impact of using same and different permutation base in adjacent cells in a WiMAX network on CCI, under varying load conditions is analyzed. We have further studied the effect of permutation base in environment where frequency reuse technique is used in conjunction with cell sectoring for better utilization of radio spectrum

Validity of the Janssen Model for Layered Structures in a Silo

Granular materials are found every where despite they are poorly understood at microscopic level. The main hindrance is how to connect the microscopic properties with the macroscopic behavior and propose a rigorous unified theory. One method is to test the existing theoretical models in various configurations. In this connection we have performed experiments in different configurations of granules in a silo to determine the validity of the Janssen model under such arrangements. Two and four layered structures of different bead diameters are prepared. The effective mass at the bottom of the container in such cases have been measured. Moreover, the investigation of layered structures reveals that such configurations also follow well the Janssen model. An interesting percolation phenomenon was observed when smaller beads were stacked on larger ones, despite the model remained valid. Furthermore, it is demonstrated that Janssen law holds for larger bead diameters

Effects of Moving Side Walls on Confined Granular Packings

Granular materials have numerous industrial and geophysical applications. However, many phenomenon exhibited by granular media are not yet fully explained. Nowadays simulation has emerged as an important tool to investigate the complex properties exhibited by granular media. The influence of side walls movement of a granular column is investigated by discrete element, molecular dynamics simulations. The evolution of stress profile and deflection of vertical stresses is due to different bead sizes, coefficient of friction between grains and confining wall is investigated by using large-scale discrete element MD simulations in 3D. In such a configuration, it is found that apparent mass systemically increases with the increase in diameter of granules. As soon as the wall stops moving, the column attains equilibrium. The stress profiles are in good agreement with the Janssen form for high friction coefficient, while some deviations remain for smaller values of friction coefficient. The wall movement augments the number of particle-wall and particle-particle forces at the Coulomb criterion. The results indicate the variation in shielding of vertical stresses in granular column; it can be attributed to the fiction between the beads and the confining walls of the container