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Search Results: 1 - 10 of 52983 matches for " David Boteler "
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On Choosing Fourier Transforms for Practical Geoscience Applications  [PDF]
David Boteler
International Journal of Geosciences (IJG) , 2012, DOI: 10.4236/ijg.2012.325096
Abstract: The variety of definitions of Fourier transforms can create confusion for practical applications. This paper examines the choice of formulas for Fourier transforms and determines the appropriate choices for geoscience applications. One set of Discrete Fourier Transforms can be defined that approximate Fourier integrals and provide transforms between sampled continuous functions in both domains. For applications involving transforms between a continuous function and a discrete function a second set of Discrete Fourier Transforms is needed with different scaling factors. Two classes of application are presented: those where either form of transforms can be used and those where it is necessary to use a particular transform to obtain the correct results.
Modelling of geomagnetic induction in pipelines
L. Trichtchenko,D. H. Boteler
Annales Geophysicae (ANGEO) , 2003,
Abstract: Geomagnetic field variations induce telluric currents in pipelines, which modify the electrochemical conditions at the pipe/soil interface, possibly contributing to corrosion of the pipeline steel. Modelling of geomagnetic induction in pipelines can be accomplished by combining several techniques. Starting with geomagnetic field data, the geoelectric fields in the absence of the pipeline were calculated using the surface impedance derived from a layered-Earth conductivity model. The influence of the pipeline on the electric fields was then examined using an infinitely long cylinder (ILC) model. Pipe-to-soil potentials produced by the electric field induced in the pipeline were calculated using a distributed source transmission line (DSTL) model. The geomagnetic induction process is frequency dependent; therefore, the calculations are best performed in the frequency domain, using a Fourier transform to go from the original time domain magnetic data, and an inverse Fourier transform at the end of the process, to obtain the pipe-to-soil potential variation in the time domain. Examples of the model calculations are presented and compared to observations made on a long pipeline in the auroral zone. Key words. Geomagnetism and paleomagnetism (geo-magnetic induction)
Case studies of space weather events from their launching on the Sun to their impacts on power systems on the Earth
H.-L. Lam,D. H. Boteler,L. Trichtchenko
Annales Geophysicae (ANGEO) , 2003,
Abstract: Active geomagnetic conditions on 12–13, 15–16, and 22–23 September 1999 resulted in geomagnetically induced currents (GIC) measurable in power systems in Canada and the United States. Different solar origins for these three events gave rise to dissimilar interplanetary signatures. We used these events to present three case studies, each tracing an entire space weather episode from its inception on the Sun, propagation through the interplanetary medium, manifestation on the ground as intense magnetic and electric fluctuations, and its eventual impact on technological systems. Key words. Geomagnetism and paleomagnetism (rapid time variations) – Interplanetary physics (interplanetary magnetic fields) – Solar physics, astrophysics, and astronomy (flares and mass ejections)
Earth conductivity structures and their effects on geomagnetic induction in pipelines
P. A. Fernberg, C. Samson, D. H. Boteler, L. Trichtchenko,P. Larocca
Annales Geophysicae (ANGEO) , 2007,
Abstract: Anomalous, large pipe-to-soil potentials (PSP) have been observed along a natural gas pipeline in eastern Ontario, Canada, where there is a major geological contact between the highly resistive rocks of the Precambrian Shield to the west and the more conductive Paleozoic sediments to the east. This study tested the hypothesis that large variations of PSP are related to lateral changes of Earth conductivity under the pipeline. Concurrent and co-located PSP and magnetotelluric (MT) geophysical data were acquired in the study area. Results from the MT survey were used to model PSP variations based on distributed-source transmission line theory, using a spatially-variant surface geoelectric field. Different models were built to investigate the impact of different subsurface features. Good agreement between modelled and observed PSP was reached when impedance peaks related to major changes of subsurface geological conditions were included. The large PSP could therefore be attributed to the presence of resistive intrusive bodies in the upper crust and/or boundaries between tectonic terranes. This study demonstrated that combined PSP-MT investigations are a useful tool in the identification of potential hazards caused by geomagnetically induced currents in pipelines.
多电压等级电网的GIC-Benchmark建模方法
郑宽,刘连光,DavidH.Boteler,RistoJ.Pirjola
中国电机工程学报 , 2013,
Abstract: 准确计算电网地磁感应电流(geomagneticallyinducedcurrents,GIC)对评估磁暴灾害至关重要。以往的电网GIC建模集中于高压线路,即只考虑最高一级电压线路而忽略了低压部分。这种简化忽略了与高压线路有联系的变压器绕组支路及低压系统,降低了电网GIC的计算精度从而影响电网磁暴灾害的风险评估。以美国电科院(EPRI)等单位新设计的GIC-Benchmark算例为基础,在GIC节点导纳矩阵的算法上,通过对不同电压等级线路、不同变压器绕组支路模型的分析与研究,提出用于多电压等级并存的电网GIC全节点模型和简化模型建模方法。算例及其结果表明,所提建模方法能有效解决多电压等级电网GIC的计算问题,提高GIC的计算精度。
The influence of the different elements of an organic molecule structure on the main kinetic parameters of its unimolecular reaction in the high-pressure region  [PDF]
David Krinkin
Natural Science (NS) , 2011, DOI: 10.4236/ns.2011.38090
Abstract: The most general dynamic tendencies of the energy redistribution in the high-pressure region are considered. Their influence on the possible deviations from the kinetic conceptions, which is now generally accepted, is examined. In this way, the structural elements of an organic molecule that promote internal energy mobilization in the high-pressure region and, conversely, hamper it, are defined. The first of these elements reduces both the Arrhenius parameters of the unimolecular reactions while the second leads to the opposite results. Some well-known exceptions to existing kinetic theories, which find an explanation in the framework of these proposed concepts, is considered. The proposed concept is very general as distinct from the existing dynamic studies, which investigate more particular details of the separate bond behaviors. The proposed general concept can broaden the study of chemical kinetics.
Raising Engagement and Enhancing Learning: School Community Partnerships That Work for Students at Promise  [PDF]
David Zyngier
Creative Education (CE) , 2011, DOI: 10.4236/ce.2011.24053
Abstract: This paper reports on a pilot study that investigates the widely reported issue of underachievement of students from Culturally Linguistically and Economically Diverse (CLED) backgrounds. It involves 15 university education faculty student volunteers and over 40 students and their families in primary (elementary) schools situated in disadvantaged communities of Victoria whose students come from 40 different nationalities, speaking 36 languages and with 75 per cent of its student cohort coming from Non English Speaking Backgrounds. A partnership was formed to focus on the problem of CLED children’s disengagement from their academic learning. We focus on how a productive partnership between schools and a university impact on inclusive teaching and learning practices both at the school and the university level. We investigate whether such an intervention can have an impact on engagement levels and the learning and social outcomes of students from refugee, migrant and working class families. Privileging participant voice we analyze data from interviews, surveys and focus groups with students, teachers and parents to argue that such a program has the capacity to re-engage underachieving students at a minimal cost to the community as an alternative model to other expensive and unsuccessful intervention programs. We conclude that at the core of this successful program is the need for both participants to feel they are empowered in the process. We know that student outcomes can be enhanced when the students feel connected to and involved in their community. Through this project, the students have the opportunity to experience greater community engagement leading to improved school attendance and retention, as well as better academic outcomes.
A Simple Proof That the Curl Defined as Circulation Density Is a Vector-Valued Function, and an Alternative Approach to Proving Stoke’s Theorem  [PDF]
David McKay
Advances in Pure Mathematics (APM) , 2012, DOI: 10.4236/apm.2012.21007
Abstract: This article offers a simple but rigorous proof that the curl defined as a limit of circulation density is a vector-valued function with the standard Cartesian expression.
“Your Guide to Paediactric Anesthesia” by Sims and Johnson: A Book Review  [PDF]
David Faraoni
Open Journal of Anesthesiology (OJAnes) , 2012, DOI: 10.4236/ojanes.2012.21003
Abstract: “Your Guide to Paediatric Anaesthesia”by Sims and Johnson is the first edition of a book written for fellow or non-pediatric anesthetists. The authors give a practical approach for daily practice in pediatric anesthesia. This \"book review\" describes a general presentation and an objective evaluation of this recently published book.
Investment Incentives under Price-Cap Regulation  [PDF]
David Bartolini
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.25105
Abstract: In the literature on price regulation, the price-cap mechanism is seen as a very powerful incentive mechanism towards efficiency improvements. What about quality investments? The empirical literature is not univocal: Some studies suggest a deterioration of quality, while others do not find any statistically significant impact. We analyze the incentive provided by price-cap regulation in a setting in which the investment decisions of the regulated firm suffer from hold-up, and contacts are incomplete. We show that the incentives to invest in cost-saving innovations can be fostered by a price-cap contract with a “sufficient” regulatory lag, while for other types of investments, such as quality enhancement, the same contract does not help. Furthermore, we show that if the firm faces a binding resource constraint the price-cap contract generates a crowding-out effect between the two types of investment. This might explain the non univocal empirical evidence.


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