PFC Topologies for AC to DC Converters in DC Micro-Grid

With increasing dominance of renewable energy resources and DC household appliances, the novelty of DC micro grid is attracting significant attention. The key interface between the main supply grid and DC micro grid is AC to DC converter. The conventional AC to DC converter with large output capacitor introduces undesirable power quality problems in the main supply current. It reduces system efficiency due to low power factor and high harmonic distortion. Power Factor Correction (PFC) circuits are used to make supply currents sinusoidal and in-phase with supply voltages. This paper presents different PFC topologies for single phase AC to DC converters which are analyzed for power factor (PF), total harmonic distortion (THD) and system efficiency by varying output power. Two-quadrant shunt active filter topology attains a power factor of 0.999, 3.03% THD and 98% system efficiency. Output voltage regulation of the presented active PFC topologies is simulated by applying a step load. Two-quadrant shunt active filter achieves better output voltage regulation compared to other topologies and can be used as grid interface

Interception capacity of curb opening inlets

Curb inlets are sized and placed along a road to maintain a safe spread of water from the curb to reduce the chances of vehicle hydroplaning and flood hazards at assets near the roadway. The accepted curb inlet design standard is the Hydraulic Engineering Circular No.22 (HEC-22), which contains the FHWA's guidelines and recommended design procedures. However, the source and assumptions in the design equations are not well-documented in the HEC-22 report. This dissertation uses full-scale physical model and experimental data reported in the literature to evaluate the HEC-22 design approach and prepare updated guidance for the sizing of curb inlets. The studies presented herein provide key insights into the hydraulics of curb inlet flow. The first study provides a detailed derivation and discussion of the assumptions in HEC-22 equations for depressed and undepressed inlets, at 100% interception and bypass flow conditions. The derivation shows that the 100% interception equations from HEC-22 deviate from their supposed theoretical basis through significant rounding up of numerical coefficients in the equations and by introducing a parameter to model depressed inlets without providing any justification. The inconsistencies in the 100% interception equations led HEC-22 to deviate from theory once more by introducing a bias in the partial interception equation in an attempt to compensate for the bias in the 100% equations. The second study shows that HEC-22 significantly underestimates the 100% interception of undepressed inlets. Experimental data reported in the literature was used to provide a new design equation that reduced the relative error by a factor of 2 compared to HEC-22. The data was used as well to propose a modification to the partial interception equation and to show that Froude scaling in physical models of undepressed inlets only provides accurate results at smooth roadway surface with minimal effects of friction. In the third study, a full-scale model is modified and operated to assess the assumptions in HEC-22 equations for depressed inlets, such as the inaccurate assumption of a linear water profile along the inlet length. Data from this study was then combined with data from five other studies to provide a correction factor for the 100% interception as computed by HEC-22, and the correction factor reduced the RMSE by a factor of 3.75. A new approach was proposed as well for partial interception condition that has the advantage of providing better predictions and being structured in a way that facilitate checking and updating it using experimental data. The Fourth study modifies the depressed inlet model to test a 10 ft model of an inlet with a channel extension. The inlet was found to be robust towards flow restriction when installed on-grade. However, the capacity of the inlet extension when submerged regresses into only 23% of the expected capacity. Experimental data from this study and data reported in the literature was provided in the Appendix to facilitate future research on curb inlets hydraulics. Finally, an analysis is provided for the interception of recessed inlets in the Appendix as well. All these studies have important implications in the safe and economical design of urban stormwater drainage.Civil, Architectural, and Environmental Engineerin

Designing Prototype of Acoustic & Resistivity Transducer

A seismic wave is acoustic energy transmitted by vibration of rock particles. Low energy waves are approximately elastic, leaving the rock mass unchanged by their passage, but close to a seismic source the rock may be shattered and permanently distorted. Reservoir characterization and monitoring using seismic technology has seen tremendous progress and recognition in recent years. In theory, time-lapse seismology measures the spatial and temporal changes related to reservoir changes and processes and it provide data on whether these changes are large enough to resolve seismically. Other than seismic method, resistivity is one of alternative for geophysicist to characterize and monitoring the reservoir. Seismic and resistivity test normally done in different stages which create errors. This method affect the feasibility during test or experiment thus resulting in wrong interpretation for reservoir characteristic especially while monitoring water flooding. A device is being designed which has the capability to run seismic and resistivity monitoring on reservoir characterization at one time and feasibility will be the focus objective for this research by implementing several experiment with the new device designed. As a result of completing the research project, it expected for author to learn as much possible about geophysics application and able to apply while monitoring the devices. The author will focus on the application of seismic and resistivity test during water flooding monitoring. As the conclusion, implication of findings will be the feasibility of device by applying two geophysics principals which are seismic and resistivity during water flooding monitoring

Monetary policy restriction and dividend behavior of Pakistani firms: an empirical analysis

Studies upon impact of macro variables on firm’s dividend policy are very limited and specifically rare in Pakistan perspective. Main purpose of this research paper is to observe impact of restricted monetary policy on dividend behavior of Pakistani firms. During restricted monetary policy, cost of external funds increases and firms prefer to utilize internal funds leading to reduction in dividend payout. Behaviour of 100 listed firms, selected purposefully, has been observed for the period from 2001 to 2009 by using Lintner’ modified model.. During the research period of nine years, monetary policy has been gone through both loose and tight phases. Proposed model is dynamic one as lagged dependent variable has been used as explanatory variable. Due to certain limitations with selection of monetary policy instrument, overall stance of State Bank of Pakistan (SBP) in its annual reports has been used as a dummy variable in the model. Results of all the three estimations reveal almost same results. First lagged dividend has been proved to be most deterministic factor of dividend policy followed by current earnings. Monetary policy and lagged dividends interactive variables provide mixed results. First interactive variable has negative coefficients in all three, fixed effect, random effects and GMM, models but with insignificant p values. Second monetary policy interactive variable has positive coefficients with significant values in random effects and GMM model. Firms seem to follow relatively stable dividend policies with lower adjustment factor. As model is dynamic, GMM estimation is preferred. Monetary policy has not been observed as significant determinant of dividend policy of Pakistani firms.Dividend payment, Monetary Policy

Dark tourism: a bibliometric review of the past, present and future trends

Purpose – The purpose of this study is to critically review the knowledge structure of dark tourism. It is an emerging tourism attraction, but one that has received less attention in the literature. The fundamental difference between dark tourism and other forms of tourism is the deeply rooted association with death and mortality, which is considered a distinctive element of the tourist attraction. Despite the role that gloom tourism plays in the economic development of tourism, its function as an economic resource for the local community needs to be further explored and evaluated. With this in mind, this study conducts a science mapping based on a bibliometric analysis to uncover the knowledge structure of the phenomenon based on recognized publications in the field. Methodology/Design/Approach – Drawing from the opportunity of dark tourism, this paper analyzes the knowledge structure based on two bibliometric analyses to uncover the past, present and future trends in dark tourism. 592 journal publications were extracted and analyzed from the Web of Science (WoS) core collection database. Findings – The results indicate that the clusters that emerged from the analyzes focus on the foundations of dark tourism, motivations for visiting dark sites, and specific interest in war/ battlefield tourism. This research shows that dark tourism benefits each segment of society in different ways by making it possible to experience the pain and suffering of the dead, the dark and agonizing events of past generations. Implications for theory and practice are discussed to further develop the field into a sustainable tourism segment. Originality of the research – This study provides the state-of-the-art knowledge structure analysis of the dark tourism phenomenon

Analyzing Behavior of Polymer Modified Asphalt Using Master Curve Approach

In Pakistan, asphalt pavements are experiencing a high rate of deterioration due to rutting and fatigue cracking. These problems arise in asphalt pavements due to the use of improper binder characterization and mix design. It is believed that polymer modification can be employed to improve binder ductility and durability. Therefore, the objective of this study is to analyze the behavior of virgin and polymer modified asphalt at a range of temperature and rate of loading. Two virgin and seven polymer modified asphalt (PMA) samples were tested using Dynamic Shear Rheometer. Master curves were developed for complex shear modulus by applying a shift factor to log of time at each temperature to the reference temperature. The major finding is that a decrease in the temperature susceptibility was observed for PMA samples; that is relatively lower stiffness at lower temperature and relatively higher stiffness at higher temperature. These polymer modification results are beneficial in improving the performance of flexible pavements

Measuring the Impact of Factors Affecting Game Development in Distributed Software Development

A software game is an application that is not only applicable for entertainment purposes but also used in domains like business, education and health care. Software game development is a multidisciplinary process that involves art, sound, artificial intelligence (AI), control systems and human factors which makes it different from traditional software development practice.  Distributed software development (DSD) facilitates decentralized zones for the availability of multidisciplinary human resources at less cost. Past studies explored many influencing factors for game development, however, how these factors majorly affect the game development in Distributed Software Development (DSD) environment yet not been studied as per our knowledge. In this research, we not only identified the most influencing factors for game development in DSD but also gauge a relationship matrix between these factors with games’ technical requirements. In our evaluation, we took twenty-nine top-rated animated games to establish a mapping of these factors present in these games. To calculate the variation in a given project budget, we execute Monte-Carlo simulations between the independent variable (influencing factors) and dependent variable (overall cost) that forecast the valuation of each variable impact on the overall nominal cost of the project. Empirical results of our research conclude that among all identified factors, ‘Physical Resources’ and ‘Freelancers’ have a significant impact on the overall project cost. Our research findings quantitatively assist the software project managers to estimate the cost deviations due to influencing factors in Distributed Software Development (DSD) environment.   &nbsp