Wind Turbine Level Energy Storage for Low Voltage Ride Through (LVRT) Support

Renewable energy is a green source of energy that is clean, available and sustainable. Wind energy generation has been experiencing the largest growth among renewable sources due to lower cost and advanced technologies. Wind energy power plants or farms need low maintenance and last for a long time. The increasing higher penetration of wind energy in the grid has transformed wind energy into major player in grid operation and economics. Wind energy systems now have to participate in grid support and provide ancillary services. Variable wind speed leads to variable wind power generation, voltage fluctuations, and frequency deviations, which are the main problems related to wind energy integration into a grid. These problems become more evident in weak grids. In addition, wind farms have to take the grid problems into consideration and have to provide support during grid instability and transients. In this thesis, a PMSG wind turbine full energy conversion system design and modeling have been performed using Matlab Simulink. The system is grid integrated and applies MPPT control to extract the maximum power from the wind and utilizes full conversion circuitry to interface the unregulated generator AC power to the grid. Modules of Lithium-Ion Capacitors (LIC) have been placed on the DC bus in order to support the grid with wind energy power smoothing and LVRT. LICs offer high power density and reasonable energy density. During grid faults, wind energy can be stored in the LICs and discharged into the grid as soon as the voltage is restored. This feature will support the grid to stabilize the voltage. Detailed modeling of the architecture and controls has been performed to verify the viability of the proposed system

Robustness of Triple Sampling Inference Procedures to Underlying Distributions

In this study, the sensitivity of the sequential normal-based triple sampling procedure for estimatingthe population mean to departures from normality is discussed. We assume only that the underlyingpopulation has finite but unknown first six moments. Two main inferential methodologies areconsidered. First point estimation of the unknown population mean is investigated where a squarederror loss function with linear sampling cost is assumed to control the risk of estimating the unknownpopulation mean by the corresponding sample measure. We find that the behaviour of the estimatorsand of the sample size depends asymptotically on both the skewness and kurtosis of the underlyingdistribution and we quantify this dependence. Moreover, the asymptotic regret of using the triplesampling inference instead of the fixed sample size approach, had the nuisance parameter beenknown, is a finite but non-vanishing quantity that depends on the kurtosis of the underlyingdistribution. We also supplement our findings with a simulation experiment to study the performanceof the estimators and the sample size in a range of conditions and compare the asymptotic and finitesample results. The second part of the thesis deals with constructing a triple sampling fixed widthconfidence interval for the unknown population mean with a prescribed width and coverage whileprotecting the interval against Type II error. An account is given of the sensitivity of the normal-basedtriple sampling sequential confidence interval for the population when the first six moments areassumed to exist but are unknown. First, triple sampling sequential confidence intervals for the meanare constructed using Hall’s (1981) methodology. Hence asymptotic characteristics of the constructedinterval are discussed and justified. Then an asymptotic second order approximation of a continuouslydifferentiable and bounded function of the stopping time is given to calculate both asymptoticcoverage based on a second order Edgeworth asymptotic expansion and the Type II error probability.The impact of several parameters on the Type II error probability is explored for various continuousdistributions. Finally, a simulation experiment is performed to investigate the methods in finite samplecases and to compare the finite sample and asymptotic results

Akonni Biosystems: Wicking in Microchannels on Biochips

Microfluidics is the science of designing and manufacturing devices and processes for manipulation of extremely small volumes of fluid, typically micro to nanoliters.The most mature application of microfluidics technology is ink-jet printing, which uses orifices less than 100 μm in diameter to generate drops of ink. The complex devices now being developed for biological applications involving the analysis of DNA (in genetics and genomics) and proteins (in proteomics) and bio-defense typically involve aqueous solutions and channels 30 to 300 μm in diameter. Unlike microelectronics, in which the current emphasis is on reducing the size of transistors, microfluidics is focusing on making more complex systems of channels with more sophisticated fluid-handling capabilities, rather than reducing the size of the channels. Although micro- and macro-fluidic systems require similar components including pumps, valves, mixers, filters, and separators, the small size of microchannels causes their flow to behave differently. At micron scales, fluid motions are primarily dominated by surface tension and viscous forces. In the problem under consideration, the issue is one of wicking or leaking of the sample from the reaction reservoir to the waste region at elevated temperatures. A mechanism responsible for this phenomenon was thought to be the "wedge effect," which refers to the tendency of liquids to move along a sharp corner by capillary effects if the conditions are right. The analysis performed during the workshop also mainly focused on this effect. While a definitive solution to this challenging problem posed in the workshop was not identified, it was felt that using a manufacturing process that can affect the corner angles in the channels may hold the most promise, allowing the wicking mechanism to be controlled without surface treatments that insert hydrophobic stops in the channel. For instance by "rounding" the side walls to increase the corner angles from 90 toward 180 degrees, the leaking of the sample away from the reaction chamber might be delayed

The effectiveness of non-regulated HSE cases in the drilling industry

Background and PurposeThe safety case regime, as a control measure to major accident hazard, was introduced to the oil and gas industry, three decades ago, following the Piper Alpha disaster. It appeared that safety cases had not passed the cost-benefit analysis, and its effectiveness had not been ascertained. This study investigated the effectiveness of non-regulated safety cases, within one of the oil and gas drilling companies, by determining its level of utilisation and examining its impact on the risks of major accidents and other rig incidents.MethodThe study design was cross sectional, retrospective and experimental. A questionnaire was administered electronically, after it had been tested and its validity and reliability had been assured, to five rig supervisors of 10 rigs that owned safety cases. Incidents were extracted from the company incident logs. The risk of major accidents and other rig incidents were compared and analysed before and after the introduction of safety cases, and against a control group.ResultsOut of 50 rig supervisors, 42 (84%) completed the questionnaire. The majority of the respondents indicated that they did not perceive a rig safety case as the most effective tool in reducing major accident risks; however, they agreed that safety cases were still required. Moreover, the introduction of safety cases to six rigs did not reduce the risk of major accidents or other rig incidents.Discussion and ConclusionsThe level of utilisation of non-regulated safety cases was evaluated to be below average. Furthermore, the evidence showed that safety cases did not reduce the risk of incidents. Conversely, the majority of the respondents indicated that safety cases were still needed in the drilling industry. The aim and objectives of the study were achieved; four hypotheses were tested, and recommendations were put forward for the company management and future researchers

Assessment of the Recycled Concrete Aggregates Structural Suitability for Road Construction

In most aspects of modem life, there is a consensus among practitioners and decision makers of the importance of preserving the environment, and to find alternatives to the scarce natural materials. This can be accomplished by better utilization of the natural materials and/or recycling or reclaiming their waste, specially, if they are of finite resources. The recycled material could be an attractive alternative (both environmentally and economically) if its characteristics are proven to be close to those of the natural material. Utilizing recycled mineral aggregates in the construction field in general and in highway pavement in specific is somehow governed by its ability to meet its intended function as carrying component within the structure. In the area of pavement construction, the suitability of the recycled aggregates is primarily judged by its ability to carry the high traffic loads effectively. The primary objective of this thesis is to study the suitability of using the Recycled Concrete Aggregates (RCA) for pavement construction or rehabilitation. The RCA is intended to replace the virgin material in one of the pavement layers, namely the subabse. The general characteristics of the RCA material (such as the grade distribution) are compared against the subbase material specifications. A testing model is built to quantify the RCA-layered pavement performance under various load levels, and to comparatively assess its behavior against the virgin mineral aggregates. The model dimensions are set large enough to replicate the pavement structures in reality to ensure accurate analysis. Several experimental settings are considered to account for the possible variability in the pavement loads (generated by the various vehicle types), material gradation, composition and thickness. The performance of the RCA material is captured through the resulting load-deflection relationships of the various settings. The results of these experiments indicated the good potential of the RCA as a subbase material. The resulting load-deflection relationships of both the RCA- and virgin-materials indicated the superiority of the RCA-material as a subbase material. In general the deflection results of the experiments indicated that the pavement deflection under load is generally lesser with the RCA material

Integrated marketing communications

The purpose of this project is to review the history of marketing following World War II and the changes taking place in the societies and the marketplace. The last decade of the 20th century brought many changes to the marketplace. Some changes were attributed to the introduction and use of technology while others relate to the expansion of the global marketplace. Customer demands and competitive forces require changes in market strategies

Integrated marketing communications

The purpose of this project is to review the history of marketing following World War II and the changes taking place in the societies and the marketplace. The last decade of the 20th century brought many changes to the marketplace. Some changes were attributed to the introduction and use of technology while others relate to the expansion of the global marketplace. Customer demands and competitive forces require changes in market strategies

Proposing Robust LAD-Atan Penalty of Regression Model Estimation for High Dimensional Data

       لاقت قضية نموذج الانحدار اهتمامًا بالغ الأهمية لاختيار المتغيرات، إذ انه يؤدي دورًا أساسيًا في التعامل مع البيانات ذات  الابعاد العالية. يتم استخدام معكوس الظل الذي يشير إليه  دالة جزاء Atan في كل من التقدير والاختيار المتغير كطريقة فعالة. ومع ذلك ، فإن دالة الجزاء  Atan حساسة جدًا للقيم الشاذة لمتغيرات الاستجابة أو توزيع ملتوي للأخطاء أو توزيع ذو ذيل ثقيل. بينما  : LAD هي وسيلة جيدة للحصول على حصانة تقدير الانحدار. ان الهدف الاساس من هذا البحث هو اقتراح مُقدّر Atan يجمع بين هاتين الفكرتين في آن واحد. لقد اظهرت تجارب المحاكاة وتطبيق البيانات الحقيقية أن مقدّر LAD-Atan المقترح هو الافضل مقارنة بالمقدرات الاخرى.           The issue of penalized regression model has received considerable critical attention to variable selection. It plays an essential role in dealing with high dimensional data. Arctangent denoted by the Atan penalty has been used in both estimation and variable selection as an efficient method recently. However, the Atan penalty is very sensitive to outliers in response to variables or heavy-tailed error distribution. While the least absolute deviation is a good method to get robustness in regression estimation. The specific objective of this research is to propose a robust Atan estimator from combining these two ideas at once. Simulation experiments and real data applications show that the proposed LAD-Atan estimator has superior performance compared with other estimators. &nbsp

Performance Comparison Between CWDM-PON and DWDM-PON Over FTTH Technology

WDM-PON is being widely considered as a means to implement Fiber-To-The-Home (FTTH) and deliver broadband access to business and home users. This research examines a preliminary simulation of the implementation of WDM-PON technology and compares the network performance between CWDM-PON and DWDM-PON. Moreover different comparison scenarios will be considered in order to determine the suitable and reasonable technology in terms of three major categories: weighted spatial modal field, bit error rate (BER) and eye diagram. The result shows that DWDM-PON technology is superior to CWDM-PON technology in term of power modal coupling BER

The isotopic composition of Zn in natural materials

This work represents the most recent development of Zn isotopic measurements, and the first identification of Zn isotopic fractionation in natural materials using Thermal Ionisation Mass Spectrometry (TIMS). The procedures developed in this research systematically evaluates and solves several critical analytical issues involved in TIMS Zn isotopic measurements such as, reducing the size of sample needed to perform an accurate and precise measurement, minimizing the effect of interferences on the Zn fractionation, reducing the blank associated with the analyses, dissolution and purification of different natural samples, and the generally ignored issue of the effect of the ion exchange chemistry (Zn separation) to the fractionation of Zn. These procedures have allowed sub-permil fractionations in the isotopic composition of Zn to be revealed in small Zn sample (1µg), and the determination of low level (ng) elemental abundance of Zn in samples to be measured accurately by the means of isotope dilution mass spectrometry IDMS. This thesis uses the rigorous double spike technique to measure fractionation, relative to the internationally proposed absolute Zn isotopic reference material (δ zero), based on a high purity Alfa Aesar 10759, now available to the international isotope community. All the isotopic measurements in natural materials were performed on bulk samples purified by ion exchange chemistry.The isotopic composition of the Zn minerals and igneous rocks agreed with that of the absolute reference material, which makes it possible to consider this reference material as being representative of “bulk Earth” Zn. Significant and consistent fractionation of ~+0.3 ‰ per amu were found in 5 sediments from a range of localities. The consistency of this is attributed to conveyor type oceanic circulations effects. The results from the two metamorphic samples indicate that the fractionation of Zn in these rocks is the same as found in igneous rocks but are different from the Zn found in sedimentary rocks. This supports the widely held assumption that high temperature and pressure processes do not fractionate the isotopic composition of chalcophile elements, such as has been found for Cd. Clay sample TILL-3 appears to exhibit a consistently slightly positive Zn fractionation of +0.12 ± 0.10 ‰ amu-1, although inside the uncertainties of both igneous and sedimentary rocks, which is not surprising since Till is thought to be a formed from a range of mixed glacial sediments The isotopic composition of Zn was measured in two plants and one animal sample. The fractionation of (-0.088 ± 0.070 ‰ amu-1) of Zn in the Rice (a C3 type plant material) sample suggested that Zn may be used to study Zn systematics in plants. The result obtained for MURST-Iss-A2 (Antarctic Krill) was +0.21 ± 0.11 ‰ amu-1 relative to the laboratory standard which is similar to the average Zn fractionation results of +0.281 ± 0.083 ‰ amu-1 obtained for marine sediments.In this work, the isotopic composition of Zn was measured in five stone and two iron meteorites. The range of Zn fractionation in stone meteorites was between -0.287 ± 0.098 and + 0.38 ± 0.16 ‰ amu-1, and was consistent with previous work, although more measurements would be needed to generalize this to all stone meteorites. In iron meteorites; Canyon Diablo was found to have the greatest fractionation of +1.11 ± 0.11 ‰ amu-1 relative to the laboratory standard. Of all the meteorites studied, Redfields clearly showed an anomalous isotopic composition indicating that this meteorite possesses a significantly different Zn isotopic composition compared to all of the other natural materials measured. Using 64Zn as a reference isotope, significant differences relative to the laboratory standard were found of +5.6 ± 0.4‰, +4.4 ± 3.6 ‰, and +21.0± 0.9 ‰ and +27.4 ± 18.8 ‰ on 66Zn and 67Zn, 68Zn and 70Zn respectively. These significant “Redfields anomalies” can be interpreted in a number of ways in relation to their nucleosynthetic production. Whether Redfields is a primitive type of iron meteorite or not, the Redfields anomaly strongly suggests wide spread isotopic heterogeneity of at least one part of the Solar System and does not support the suggestion that “Zn was derived from an initially single homogeneous reservoir in the early Solar System”. A pilot study to determine the concentration and the isotopic composition of Zn in River and tap water was performed.The concentration of Zn in River water averaged 6.9 ± 0.8 ngg-1, while for tap water it ranged from 13.1 ngg-1 to 5.2 μgg-1. River water was fractionated by -1.09 ± 0.70 ‰ amu-1, while restrained tap water yielded the maximum fractionation of -6.39 ± 0.62 ‰ amu-1 relative to the laboratory standard. The Zn fractionation of tap water is much larger than all other natural samples, although the uncertainty is also significantly greater due to the use of the less precise Daly detector used for these preliminary experimental measurements. The fractionation of Zn in seven ultra pure Zn standard materials was measured relative to the laboratory standard and found to range from -5.11 ± 0.36 ‰ amu-1 for AE 10760 to +0.12 ± 0.16 ‰ amu-1 for Zn IRMM 10440. There appears to be some evidence for a relationship between Zn fractionation and its purity. As well as natural materials, the fractionation of Zn was measured in a number of processed materials. None of these results or those obtained for natural materials impact on the currently IUPAC accepted value for the atomic weight of Zn. Along with fractionation determinations, the concentration of Zn was also measured by Isotope Dilution Mass Spectrometry in all of the samples. The concentration of Zn in five stony meteorites ranged from 26 ± 13 to 302 ± 14 μgg-1 for Plainview and Orgueil respectively. For ordinary Chondrites, the concentration of Zn in the three samples analysed ranged from 26 ± 13 to 64 ± 34 μgg-1 for Plainview and Brownfield 1937 respectively.The concentration of Zn was measured in two metamorphic rocks standard materials; the maximum concentration was 101.5 ± 1.7 µgg-1 in SDC-1. The concentration of Zn present in plant samples studied in this research was 22.15 ± 0.42, 14.62 ± 0.27 µgg-1 for Rice IMEP-19 and Sargasso NIES-Number 9 respectively which is within the normal range of Zn concentrations. Except for meteorites, the final uncertainties consistently cover the ranges of individual concentration measurements and indicate the homogeneity of the samples, including samples from different bottles where available. The final fractional uncertainties obtained for SRMs were all less than 2.8 %, demonstrating the high level of precision possible using IDMS