1,849 research outputs found
Deriving Regression Lines Without Calculus
No full textThis article, C.W. Puritz of the Royal Grammar School - High Wycombe, describes a method to calculate the least squares line algebraically. First, the author uses a numeric example, which uses calculus, then describes a simpler algebraic method. This is a great lesson plan for those instructors attempting to teach this method with having students with prior knowledge of calculus. The author uses a step by step approach to help best describe both the technique and subsequent ways to best teach this method
Equity and Foreign Exchange Hybrid Models for Pricing Long-Maturity Financial Derivatives
No full textModelling derivative products in Finance usually starts with the specification of a system of Stochastic Differential Equations (SDEs), that corresponds to state variables like stock, interest rate, Foreign Exchange (FX) rate and volatility. By correlating the SDEs for the different asset classes one can define the hybrid models, and use them for pricing multi-asset derivatives. Even if each of the individual SDEs yields a closed-form solution, a non-zero correlation structure between the processes may cause difficulties for efficient product pricing. Typically, a closed-form solution of hybrid models is not known, and numerical approximation by means of Monte Carlo (MC) simulation or discretization of the corresponding Partial Differential Equations (PDEs) has to be employed for pricing. The speed of pricing European derivative products is crucial, especially for the calibration of the SDEs. Several theoretically attractive SDE models, that cannot fulfil the speed requirements, are not used in practice.Numerical AnalysisElectrical Engineering, Mathematics and Computer Scienc
Development and optimisation of a duplex real-time reverse transcription quantitative PCR assay targeting the VP7 and NS2 genes of African horse sickness virus
No full textNucleotide sequences of 52 South African isolates of African horse sickness virus (AHSV) collected during 2004–2005 and including viruses of all nine AHSV serotypes, were used to design and develop a duplex real-time reverse transcription quantitative PCR (RT-PCR) assay targeting the VP7 (S8) and NS2 (S9) genes of AHSV. The assay was optimized for detection of AHSV in fresh and frozen blood of naturally infected horses. Assay performance was enhanced using random hexamers rather than gene-specific primers for RT, and with denaturation of double-stranded RNA in the presence of random hexamers. The assay was efficient with a linear range of at least five orders of magnitude. The analytical sensitivity of the assay was 132 copies of the target genes (4125 copies per ml of blood), and the assay was at least 10-fold more sensitive than virus isolation on BHK-21 cells. The assay was also highly specific because it did not detect related orbiviruses, such as bluetongue and equine encephalosis viruses.ID: S0166093410000893; M3: Article; Accession Number: S0166093410000893; Author: M. Quan (a, b, ⁎); Author: C.W. Lourens (a, b); Author: N.J. MacLachlan (c); Author: I.A. Gardner (d); Author: A.J. Guthrie (a); Affiliation: Equine Research Centre, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa; Affiliation: Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa; Affiliation: Equine Viral Disease Laboratory, Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA; Affiliation: Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA; Keyword: African horse sickness virus; Keyword: Real-time quantitative RT-PCR; Keyword: VP7 gene; Keyword: NS2 gene; Keyword: Duplex; Number of Pages: 8; Language: English
Introduction to special issue on high speed solar wind streams and geospace interactions (HSS-GI)
No full textThis special issue of the Journal of Atmospheric and Solar-Terrestrial Physics is devoted to research into high speed solar wind streams (HSSs) and their effects on the region of near-Earth space commonly known as ‘geospace’. Interest in the effects of HSSs has increased during the last solar cycle and, following the successful meeting focusing on corotating solar wind streams in Manaus, Brazil (Tsurutani et al., 2006), we recognised the need for further work on the topic, with particular focus on HSSs and their effects in the inner magnetosphere, ionosphere, and neutral atmosphere. As a result the High Speed Solar Wind Streams and Geospace Interactions (HSS–GI) Workshop was held at Hilltop, St. Martin's College in Ambleside, UK, from 2 to 7 September, 2007 (Kavanagh and Denton, 2007; Denton et al., 2008 M.H. Denton, J.E. Borovsky, R.B. Horne, R.L. McPherron, S.K. Morley and B.T. Tsurutani, High speed solar wind streams: a call for key research, EOS Trans. AGU 89 (7) (2008), pp. 62–63. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (7)Denton et al., 2009), sponsored by the Department of Communication Systems at Lancaster University. The majority of the work presented in this special issue was prompted by discussion and interaction at the workshop. It is indeed an indication of the importance of HSSs that the papers in this issue cover the entire region from the Sun and solar wind, through the magnetosphere, and into the ionosphere, thermosphere, and down to the stratosphere. It is hoped that this research will stimulate more understanding, appreciation, and research, into these important drivers of physical phenomena within geospace
Does a video speed task predict risky speeding behaviour in young and inexperienced drivers?
No full textVehicle crashes account for the highest number of fatalities for persons aged between 17 and 25 years of age in New Zealand. Despite a myriad of factors precipitating vehicle crashes, excess or inappropriate vehicle speed has been identified as the greatest predictor of crash likelihood and severity. Excess or inappropriate speed reduces a driver’s control over the vehicle, while exaggerating both collision force and the distances required in stopping or safely manoeuvring. One of the major differences identified between young and inexperienced and older more experienced drivers is the ability to adapt driving behaviour to road conditions. Young drivers are more prone to speeding through both a lack of awareness of risks and a desire to seek out novel and stimulating experiences. Recent developments in cognitive models of risk taking propose that older more experienced drivers may adapt their speed by “feeling out” the road conditions, where as young drivers may depend more upon posted limits to determine their speed. A video speed task was developed to measure speed preferences on a selection of road conditions (or ‘environments’) commonly confronting New Zealand motorists. Analyses of speed preferences revealed that young and inexperienced drivers preferred speeds close to the road-limit irrespective of conditions, whereas older and more experienced drivers preferred speeds clearly below the road limit, and demonstrated greater variation in speed preferences on different road environments. This suggests that young and inexperienced drivers both prefer faster speeds and may use the road limit as a target in determining an appropriate speed. Older and more experienced drivers prefer slower speeds, and adapt driving to changing road conditions. Faster preferred speeds were found to be related to a riskier attitudes towards driving in general, and more lenient attitudes toward speeding in particular. In addition, faster preferred speeds were found to be related to a heightened enjoyment of risk taking, as well as the number of speeding convictions issued in the previous 12 months. The used video speed task provided a convenient measure of speeding behaviour in natural driving scenarios, and appeared to be sensitive to differences in the way drivers adjust their behaviour across changing driving conditions. The video speed task might be useful in determining differences in speed choice between day and night time driving scenarios, as well as expanding the road conditions to including wet or foggy driving situations. This may be particularly useful in determining the pre- and post-effectiveness of driver training programs
Nota, betreffende berekeningen omtrent rivierverbeteringen: opgemaakt door den ingenieur van den Rijkswaterstaat C.W. Lely
No full textHydraulische basis voor de normalisatiewerken van de grote rivieren. Berekingen van optimale breedte en diepte
Onderzoek naar signaalgeneratie met behulp van fasedraaiers ten behoeve van reflectie-compensatie in een F.M.-C.W. radarsysteem
No full textVoor onderzoek aan de troposfeer wordt gebruik gemaakt van een F.M.-C.W. radarsysteem. Een aspect van het radarsysteem waarnaar nog onderzoek gewenst is, is de onderdrukking van de overspraak van zender naar ontvanger, en van sterke reflecties aan nabije obstakels: deze signalen houden nl. het gevaar in van oversturing van de ontvanger. Dit aspect is met name van belang voor een mogelijk nog te realiseren F.M. -C.V. radarsysteem met één antenne…Applied SciencesElectrotechniekTelecommunicatie- en Verkeersbegeleidingssysteme
Reduced-Order Modelling for Production Optimisation
No full textProduction optimisation of a reservoir simulation problem can be very computationally demanding as the reservoir model may contain many variables and nonlinearities, thus many iterations may be needed to obtain an optimal production schedule. Using Proper Orthogonal Decomposition and Trajectory Piecewise Linearization (POD-TPWL) developed in [1] and [2], simulations were performed on the Delft Egg model 100-200 times faster than the high-fidelity simulation with reasonable accuracy, depending on the distance from the trained solution. Production optimisation was performed using the gradient-based adjoint method. A reduced version of the adjoint equation was used by incorporating POD, as presented in [3] and by performing a first-order Taylor series expansion around a training point (similar to TPWL). This method allowed for time gains of 50-100 times when compared to the high-fidelity adjoint method. The results from the high-fidelity production optimisation compared with POD-TPWL showed a similar Net Present Value (NPV) for both optimisation methods, with an error of 0.1% between the two-values. However, the optimal injection schedules were not the same. When the high-fidelity model was run using the input schedules from POD-TPWL optimisation, the error in NPV was 4%. The speed-up observed for the optimisation loop using POD-TPWL was 6 times faster than the high-fidelity model. This is due to the number of snapshots that needed to be generated and the processing of the data from these snapshots. Robust optimisation was performed on the Egg model ensemble using a POD-TPWL model incorporating geological model parameters, states and well controls. Results showed a 0.7% deviation from the mean NPV value calculated in MoReS and a 4 million dollar increase in the standard deviation of the NPV. POD-TPWL was able to complete the robust optimisation 25 times faster than a high-fidelity simulation. POD-TPWL shows promise as a reduced-order modelling application for reservoir simulation and production optimisation. The accuracy needs to be improved in order to move to an operational application.Petroleum EngineeringGeoscience & EngineeringCivil Engineering and Geoscience
Advanced Systems Theory Applied to AMB Systems
No full textIn this thesis we look at the application of advanced systems theoretic algorithms for an experimental Active Magnetic Bearing System (AMB). These systems are inherently unstable and therefore require a feedback controller. Accurate modeling of these systems with input-output data is hindered due to the strong correlation between the inputs and noise. Recently a predictor based subspace identification algorithm has been developed specially catered to data from closed-loop experiments. We use this algorithm to build models for a flexible AMB spindle. In order to improve the accuracy of the model, we use frequency domain method which leads to a nonlinear optimization problem. We consider a variety of problem scenarios for designing controllers for rejecting disturbances that are caused due to mass imbalances. For ensuring performance against an uncertainty in the rotational speed we use a robust synthesis algorithm that is known to be convex. We synthesize H-infinity controllers and observe that for a model with flexible dynamics the resulting controllers are unstable. To realize the performance benefits of an unstable controller, we use a switching method based on the Youla parameters of the stabilizing controllers. We also design and implement LPV controllers for rejecting disturbances over a range of rotational speeds.Delft Center for Systems and ControlMechanical, Maritime and Materials Engineerin
A Fourier-Based Valuation Method for Bermudan and Barrier Options under Heston’s Model
No full textWe develop an efficient Fourier-based numerical method for pricing Bermudan and discretely monitored barrier options under the Heston stochastic volatility model. The two-dimensional pricing problem is dealt with by a combination of a Fourier cosine series expansion, as in [F. Fang and C.W. Oosterlee, SIAM J. Sci. Comput., 31 (2008), pp. 826–848, F. Fang and C. W. Oosterlee, Numer. Math., 114 (2009), pp. 27–62], and high-order quadrature rules in the other dimension. Error analysis and experiments confirm a fast error convergence.Delft Institute of Applied MathematicsElectrical Engineering, Mathematics and Computer Scienc
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