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Статті в журналах з теми "Complétive nominale":
1
Gołębiowski, Jerzy, and Marek Zaręba. "Analytical modelling of the transient thermal field of a tubular bus in nominal rating." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 38, no. 2 (March 4, 2019): 642–56. http://dx.doi.org/10.1108/compel-02-2018-0078.
Анотація:
Purpose The purpose of this paper is to analyse the dynamics of a thermal field generated in a tubular bus with rated current by using two models of electrical resistivity of copper. Design/methodology/approach The boundary-initial problem of the modified heat equation was formulated for the tubular bus. Analytical solutions were obtained by means of Green’s functions as the kernels of the integral operator inverse to the corresponding differential operator. The results were presented graphically and verified using the finite element method. The calculations were made by considering the example of the Storm Power Components tubular bus (USA). Findings Analytical field models were used to determine time- and space-variable heating curves, time constants and steady-state current ratings. Research limitations/implications This paper is related to the structure of a hollow cylinder. Other bus sections can be taken into account by using the coordinate systems of different curvilinear orthogonal symmetry. Originality/value Using the analytical method, the influence of the variable (temperature dependent) electrical resistivity on some important parameters and characteristics of the tubular bus was investigated. The system was considered as an element with distributed parameters.
2
Tasic, Bratislav, Jos J. Dohmen, E. Jan W. ter Maten, Theo G.J. Beelen, Wil H.A. Schilders, Alex de Vries, and Maikel van Beurden. "Robust DC and efficient time-domain fast fault simulation." COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 33, no. 4 (July 1, 2014): 1161–74. http://dx.doi.org/10.1108/compel-12-2012-0364.
Анотація:
Purpose – Imperfections in manufacturing processes may cause unwanted connections (faults) that are added to the nominal, “golden”, design of an electronic circuit. By fault simulation one simulates all situations. Normally this leads to a large list of simulations in which for each defect a steady-state (direct current (DC)) solution is determined followed by a transient simulation. The purpose of this paper is to improve the robustness and the efficiency of these simulations. Design/methodology/approach – Determining the DC solution can be very hard. For this the authors present an adaptive time-domain source stepping procedure that can deal with controlled sources. The method can easily be combined with existing pseudo-transient procedures. The method is robust and efficient. In the subsequent transient simulation the solution of a fault is compared to a golden, fault-free, solution. A strategy is developed to efficiently simulate the faulty solutions until their moment of detection. Findings – The paper fully exploits the hierarchical structure of the circuit in the simulation process to bypass parts of the circuit that appear to be unaffected by the fault. Accurate prediction and efficient solution procedures lead to fast fault simulation. Originality/value – The fast fault simulation helps to store a database with detectable deviations for each fault. If such a detectable output “matches” a result of a product that has been returned because of malfunctioning it helps to identify the subcircuit that may contain the real fault. One aims to detect as much as possible candidate faults. Because of the many options the simulations must be very efficient.
3
Athavale, M. M., and R. C. Hendricks. "A Small Perturbation CFD Method for Calculation of Seal Rotordynamic Coefficients." International Journal of Rotating Machinery 2, no. 3 (1996): 167–77. http://dx.doi.org/10.1155/s1023621x96000048.
Анотація:
Seal rotordynamic coefficients link the fluid reaction forces to the rotor motion, and hence are needed in the stability calculations for the overall rotating systems. Presented in this paper is a numerical method for calculations of rotordynamic coefficients of turbomachinery seals with rotors nominally at centered, eccentric and/or misaligned position. The rotor of the seal is assumed to undergo a prescribed small whirling motion about its nominal position. The resulting flow variable perturbations are expressed as Fourier functions in time. The N-S equations are used to generate the governing equations for the perturbation variables. Use of complex variables for the perturbations renders the problem quasi-steady. The fluid reaction forces are integrated on the rotor surface to obtain the fluid reaction forces at several different whirl frequencies. The rotordynamic coefficients are calculated using appropriate curve fitting. Details of the model are presented, and sample results for concentric and eccentric annular incompressible flow seals are included to demonstrate the capability and accuracy of the proposed method.
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McDaniel, James G., and Allison Kaminski. "Surrogate models of complex dynamic systems from energy distributions." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A134. http://dx.doi.org/10.1121/10.0015795.
Анотація:
Engineers who design complex dynamic systems do not have the luxury of iteration. Numerical analysis of a single design, typically by finite element analysis, requires enormous amounts of CPU time. Therefore, improving a design by trying out many design modifications is impossible. Moreover, it is also impossible to identify which subsystem designs have the largest effects on the dynamic response of the system. The present work addresses this challenge by constructing surrogate models from energy distributions in a nominal design. These surrogate models are surprisingly effective at identifying subsystems that have the largest effects on the dynamic response, and therefore guide engineers to design modifications that matter most. A significant advantage of these surrogate models is the very low cost of creating them, as they are created directly from the frequency response of a nominal design and therefore do not require additional linear solves or other time-intensive calculations. This presentation begins with an analytical justification for considering energy distributions as surrogate models. Next, Monte Carlo Simulations are presented to show strong correlations between energy distributions and the effects of design changes on dynamic responses. These simulations include random structures as well as beams. Work supported by ONR under Grant N00014-19-1-2100.
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Dems, Maria, Krzysztof Komeza, Slawomir Wiak, and Sara Fernández Coya. "Influence of the closing rotor slots on the additional losses in the induction motor." COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 34, no. 2 (March 2, 2015): 531–49. http://dx.doi.org/10.1108/compel-07-2014-0183.
Анотація:
Purpose – The purpose of this paper is to present the distribution of the magnetic field and additional losses analysis of the induction motors (IM) with opened and closed rotor slots. Design/methodology/approach – In the field-circuit approach the distribution and changes of magnetic flux density in the motor are computed using a time-stepping finite element method. The additional losses in each element are evaluated at different frequencies. Findings – An approximate analytical formulation is derived for rapid losses computation confirmed by the results of field-circuit method. For high-voltage motors due to the size ratios of the core and relatively deep stator and rotor slots major role in causing loss of higher harmonics play a fundamental slot harmonics. Higher harmonics order bigger than 100 cause only small part of total higher harmonics core losses. Closed rotor slots construction influenced significantly on no-load losses mainly due to reduction of losses at slot upper part. For nominal load condition that influence is not so strong according to the saturation of slot tips by rotor leakage flux. Nevertheless, core losses at load are several times higher as at no-load. Research limitations/implications – In future research authors will take into account motors feed from PWM inverter, working in the frequency range up to 400 Hz. Practical implications – The results of investigation will be used in more detailed design of IMs especially for motors with closed rotor slots. Originality/value – The methods presented in the paper was not used before. Also results of additional losses in the motor core calculation, especially according motors with closed slots at no load and load conditions are new.
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Mason, Paul M., and Andres Gallo. "An Alternative Estimation Technique for Determining Discount Rates and Earnings Growth Rates in Wrongful Death and Personal Injury Cases." Journal of Forensic Economics 26, no. 2 (December 1, 2016): 181–92. http://dx.doi.org/10.5085/jfe-397.1.
Анотація:
Abstract Regardless of the time period studied since the 1970s ended, without adjustments for structural factors, both real and nominal interest rates across the spectrum of maturities exhibit non-stationary processes with a unit root. Consequently, simply employing past means of either real or nominal yields losses a degree of credibility. Focusing on the period of the “Great Moderation,” employing structural break analysis can remove the non-stationarity so that forensic economists can chose not to use more complex ARIMA models, stochastic properties of interest rates, or estimating methods more complex than these. Rather, following the analysis in this paper, forensic economists can employ one of a small number of discount rates from a not too distant past time period that reflect systematic variations more likely to be consistent with predictable future interest rates.
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Kim, Sang Su. "A Priching Model for Inflation-indexed Bonds." Journal of Derivatives and Quantitative Studies 19, no. 2 (May 31, 2011): 175–206. http://dx.doi.org/10.1108/jdqs-02-2011-b0003.
Анотація:
This paper derives the theoretical price of nominal bonds and inflation-indexed bonds through extracting the factors, which are assumed that their stochastic property follows the standard O-U process, in the term structure of nominal interest rates and yields of inflation-indexed bonds by the Principal Component Analysis (PCA). In particular, through reflecting the complex structure of inflation-indexed bonds by accurately applying theoretical price, it brought differentiation from other literatures, and applied this pricing model to Japanese Government Inflation-indexed Bond (JGB) data. The empirical results of above model show that explanation of time series and cross section of Janpan's real and nominal interest rates were outstanding and was found that Fisher hypothesis was rejected in further
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Fabbri, Massimo, Pier Luigi Ribani, and Davide Zuffa. "Design and testing of a magnetic suspension for a 90° horizontal bend conveyor." COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 34, no. 1 (January 5, 2015): 380–96. http://dx.doi.org/10.1108/compel-02-2014-0049.
Анотація:
Purpose – A conveyor device is studied with the aim to reduce the friction between the inner surface of the beam and the chain. The lower is the friction between the chain and the beam, the lower is the surface wear. The magnetic repulsion force among permanent magnets (PMs) placed on the beam and on the chain is utilized to reduce friction. The paper aims to discuss these issues. Design/methodology/approach – The considered magnetic suspension is realized with PMs in repulsive configuration; it is designed by solving a constrained optimization problem, with reference to the geometry of the 90° horizontal bend FlexLink WL322 conveyor. Flux density field and its gradient are evaluated using volume integral equation method, allowing to calculate the forces acting on the chain and the stiffness of the magnetic suspension. Findings – The magnetic suspension prototype was manufactured and tested. The experimental and calculated values of the forces acting on the chain compares well. A stable horizontal equilibrium of the chain was obtained during both static and dynamical tests. Research limitations/implications – The quasi-static model used neglects the dynamical interactions among the elements of the chain, the PMs and loads weight during motions and the eddy current losses in the aluminium beam. However the dynamical tests on the prototype show that the chain motion is regular up to the nominal velocity all along the conveyor with the exception of the trailing edge of the 90° curve. Practical implications – The tests on the prototype show the possibility of a removal or at least a reduction of the friction force between the chain and the inner side of the beam by means of a passive magnetic suspension. As a consequence a reduction of noise and vibrations and an increase of the mean-time-to-failure is expected. Originality/value – Prototype testing shows that the unavoidable vertical instability of the magnetic forces has no practical consequence since, reducing the allowed vertical gap, the chain is stabilized by the gravitational force.
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Młot, Adrian, and Marian Łukaniszyn. "Analysis of axial flux motor performance for traction motor applications." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 38, no. 4 (July 1, 2019): 1306–22. http://dx.doi.org/10.1108/compel-10-2018-0401.
Анотація:
Purpose Analysis of test data monitored for a number of electric machines from the low volume production line can lead to useful conclusions. The purpose of this paper is to trace the machine performance to find quality-related issues and/or identify assembly process ones. In this paper, the monitoring of experimental data is related to the axial flux motor (AFM) used in hybrid electric vehicle (HEV) and in electric vehicle (EV) traction motors in the global automobile market. Design/methodology/approach Extensive data analyses raised questions like what could be the causes of possible performance deterioration of the AFM and how many electric motors may not pass requirements during operation tests. In small and medium research units of AFM for HEV or EV, engineers came across a number of serious issues that must be resolved. A number of issues can be eliminated by implementing methods for reducing the number of failing AFMs. For example, improving the motor assembly precision leads to reduction of the machine parameters deterioration. Findings Assembly tolerances on electric motor characteristics should be investigated during motor design. The presented measurements can be usable and can point out the weakest parts of the motor that can be a reason for the reduced efficiency and/or lifetime of the AFM. Additionally, the paper is addressed to electric motor engineers designing and/or investigating electric AFMs. Originality/value Performance of AFM was monitored for a number of identical motors from low volume production line. All tested motors were operated continuously for a long period of time and the tests were repeated every few weeks for half a year to check the reliability of motor design and indicate how much the motor parameters may change. The final results point how many motors fail the requirements of motor performance. A few batches of AFM were selected for testing. Each batch represents a different size (nominal power) of the same type of AFM.
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Sinkevich, Mikhail, Eldar Ramazanov, and Anatoliy Kosoy. "Conceptual methods of starting and controlling operating modes of compressorless combined cycle gas turbine unit." E3S Web of Conferences 289 (2021): 02005. http://dx.doi.org/10.1051/e3sconf/202128902005.
Анотація:
A method for operation study of a compressorless combined-cycle gas turbine (CCCGT) unit during transients from one steady-state mode to another, including during start-up and shutdown, is proposed. As an example, studies of the transients of an energy complex with a capacity of 60 MW are given. A variant of an algorithm concept for start/stop and transients of such an energy complex is proposed. This concept includes algorithms for starting from the three initial states of the energy complex (cold, hot and standby). For these algorithms, the time and energy consumption characteristics are estimated. It is shown that from a cold state, such an energy complex can be started and brought to the nominal mode in 1.5-2 hours. At the same time, the energy costs will not exceed energy consumption for its own needs in a nominal mode. The start-up time from the hot state can be reduced to 20-25 minutes, and the start-up from the standby state can be 2.5-3 minutes. The proposed concept of control algorithms for transient modes is such, so that a temperature state of the main components and parts of the energy complex is provided at a constant temperature. Thus, the time of transients will be determined only by the speed of the regulatory authorities. Consequently, power systems operating on the CCCGT cycle can operate equally efficiently, both in the basic mode and in the power control mode.
Книги з теми "Complétive nominale":
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Back, Kerry E. Dynamic Securities Markets. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780190241148.003.0008.
Анотація:
The dynamic model with time‐additive utility is defined. The intertemporal budget constraint is explained. SDF processes are defined in terms of a martingale property. There is a strictly positive SDF process if and only if there are no arbitrage opportunities. Dynamic complete markets are explained. The difference between the price of an asset and its value calculated from an SDF process is called a bubble. There is no bubble if a transversality condition is satisfied. Some constraints on trading strategies are needed to rule out Ponzi schemes. SDF processes are derived for nominal asset prices and for asset prices denominated in a foreign currency.
Частини книг з теми "Complétive nominale":
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Ajanki, Rigina, Johanna Laakso, and Elena Skribnik. "Nominal predication." In The Oxford Guide to the Uralic Languages, 981–95. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780198767664.003.0052.
Анотація:
This chapter discusses the areal distribution of major strategies of nominal predication in Uralic: with an obligatory copula taking all necessary TAM and agreement markers, and without a copula (often in indicative present). The predicate nominal can in the latter case carry a) only markers of agreement in number, b) only markers in agreement in person and number, b) tense markers and agreement markers. Other important parameters are the number of copulas and the case-marking strategies for the predicate nominal: no marking (= only nominative), two-case opposition (e.g. nominative for static and translative for dynamic characterization in terms of ”relative time stability“), and more complex types of oppositions, coded with up to four possible cases (e.g. splitting of dynamic characterization in Ingrian into ‘beginning’, i.e. ’becoming something’, with the translative and ’ending’, i.e. ’stopping being something’, with the excessive case).
2
Lu, Guolin, Shihuan Zhang, and Jinhong Jiang. "Local Motion Planning Subject to Constrained State for Quadrotor with Model Predictive Control." In Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde221165.
Анотація:
As for the challenges of local motion planning subject to constrained state for quadrotor in evaluating the health status of photovoltaic power generation in complex environment, including fast replanning, limited onboard computational resources, a practical framework for constructing motion trajectory from the bounded states is proposed in this work. The references and nominal inputs are made by the scheme of receding horizon fashion of model predictive control (MPC) by means of gradient-based method in the continuous domain. In order to avoid the complex calculation of the optimal gradient, the ability of approximation of a neural network make it possible for the fast evaluation and online optimization. The simulations with variety types of trajectories are made by means of a quadrotor to demonstrate the good efficiency and real-time of the proposed approach.
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Vlassopoulos, Kostas. "Enslaved Persons." In Historicising Ancient Slavery, 92–112. Edinburgh University Press, 2021. http://dx.doi.org/10.3366/edinburgh/9781474487214.003.0005.
Анотація:
Chapter 5 aims to construct a new framework for approaching the complex phenomenon of slave identity. The first part of the chapter distinguishes between categorical and relational modes of slave identification and examines their implications. The second part of the chapter examines three key aspects of slave identities: the categorisation of people as slaves; the various self-understandings of the slaves; and the forms of slave groupness. This conceptual framework highlights the complex and contradictory phenomenon of slave identities; while slave categorisation had undoubtedly major consequences for the lives of slaves, at the same time slaves could see themselves as free people in captivity, or build identities and groups on the basis of other factors: gender, kinship, ethnicity, religion and profession. Ultimately, the major struggle that slaves engaged in concerned the gap between the nominal slave identity imposed on slaves and its real impact in shaping slave lives. The concept of ‘enslaved persons’ allows us to capture the complex and contradictory character of slave identities.
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André, Maina, and Rudy Calif. "Temporal Fluctuations Scaling Analysis: Power Law of Ramp Rate’s Variance for PV Power Output." In Solar Radiation - Measurement, Modeling and Forecasting Techniques for Photovoltaic Solar Energy Applications [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.99072.
Анотація:
The characterization of irradiance variability needs tools to describe and quantify variability at different time scales in order to optimally integrate PV onto electrical grids. Recently in the literature, a metric called nominal variability defines the intradaily variability by the ramp rate’s variance. Here we will concentrate on the quantification of this parameter at different short time scales for tropical measurement sites which particularly exhibit high irradiance variability due to complex microclimatic context. By analogy with Taylor law performed on several complex processes, an analysis of temporal fluctuations scaling properties is proposed. The results showed that the process of intradaily variability obeys Taylor’s power law for every short time scales and several insolation conditions. The Taylor power law for simulated PV power output has been verified for very short time scale (30s sampled data) and short time scale (10 min sampled data). The exponent λ presents values between 0.5 and 0.8. Consequently, the results showed a consistency of Taylor power law for simulated PV power output. These results are a statistical perspective in solar energy area and introduce intradaily variability PV power output which are key properties of this characterization, enabling its high penetration.
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Ricketts, James, and Roger Jones. "Severe Testing and Characterization of Change Points in Climate Time Series." In Recent Advances in Numerical Simulations. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.98364.
Анотація:
This paper applies misspecification (M-S) testing to the detection of abrupt changes in climate regimes as part of undertaking severe testing of climate shifts versus trends. Severe testing, proposed by Mayo and Spanos, provides severity criteria for evaluating statistical inference using probative criteria, requiring tests that would find any flaws present. Applying M-S testing increases the severity of hypothesis testing. We utilize a systematic approach, based on well-founded principles that combines the development of probative criteria with error statistical testing. Given the widespread acceptance of trend-like change in climate, especially temperature, tests that produce counter-examples need proper specification. Reasoning about abrupt shifts embedded within a complex times series requires detection methods sensitive to level changes, accurate in timing, and tolerant of simultaneous changes of trend, variance, autocorrelation, and red-drift, given that many of these measures may shift together. Our preference is to analyse the raw data to avoid pre-emptive assumptions and test the results for robustness. We use a simple detection method, based on the Maronna-Yohai (MY) test, then re-assess nominated shift-points using tests with varied null hypotheses guided by M-S testing. Doing so sharpens conclusions while avoiding an over-reliance on data manipulation, which carries its own assumptions.
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Posner, Eric A. "Noncompetes." In How Antitrust Failed Workers, 91–114. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780197507629.003.0007.
Анотація:
Employee covenants not to compete, which bar workers who leave their jobs from working for a competing employer for a period of time, should be subject to heightened antitrust enforcement. While noncompetes may serve legitimate purposes, they also create entry barriers and reduce labor market competition. The threat to competition has been highlighted by new research, which suggests that employers overuse noncompetes and that noncompetes reduce labor market competition. A likely explanation is the inadequacy of the existing legal regime. Antitrust law nominally applies to noncompetes, but courts have eviscerated it by imposing an excessive burden of proof on plaintiffs who challenge noncompetes. An appropriate doctrinal framework for evaluating noncompetes under antitrust law would shift the burden of proof to employers. Employers would be permitted to rebut challenges to their noncompetes only by showing that the noncompetes raise wages for their own workers and workers in the broader labor market.
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Sornicola, Rosanna. "A diachronic perspective on polymorphism, overabundance, and polyfunctionalism." In Periphrasis and Inflexion in Diachrony, 305–32. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780198870807.003.0012.
Анотація:
This chapter investigates the traditional notions of polymorphism and polyfunctionalism, comparing and contrasting them with the more recent concept of overabundance. These ideas are set in the context of a broader view of developments in morphological theory, in particular those associated with functionalism and natural morphology. The issues are addressed through a study of nominal inflexion in a body of legal texts from Cava dei Tirreni in Campania and a comparison of the patterns discernible there with those of the system of noun declensions encoded in traditional grammars. Variation can be shown to depend not only on the different inflexional patterns associated with different noun classes and on the syntactic context but also on the linguistic competence of the individual scribes and notaries. The reduced paradigm structure to be seen here goes together with an increase in intra-cell variation and argues for the existence of a more complex sequence of historical developments from Latin to Romance than is traditionally assumed. At a theoretical level, these data support the view that morphology is autonomous, while at the same time indicating the need to rethink the core concepts of cell and paradigm and the relations between them. The chapter also underscores the fundamental importance of both diachronic and synchronic considerations in any such theoretical enterprise.
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Magee, Patrick, and Mark Tooley. "Statistics." In The Physics, Clinical Measurement and Equipment of Anaesthetic Practice for the FRCA. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199595150.003.0006.
Анотація:
This chapter will provide background to enable the reader to understand basic statistics and be able then to follow more complex statistical ideas. Although statistics is more than the mere analysis of data, it is a subject largely about data, so this will be discussed first. Data can be categorical or numerical, and in these two classifications there are various different types of data. This is the allocation of the individual to one of two categories. Often these relate to the presence or absence of some attribute. These data also have many other names such as binary, dichotomous and attribute data. Examples of such categorisations for patients include: ◆ Male/Female ◆ Smoker/Non-smoker ◆ Anaesthetist/Surgeon ◆ Married/Single. Each of these can be only be one or the other – they could be coded ‘1’ or ‘0’ to be binary (or on, off). For example male = 0, female = 1, or vice versa. Many classifications require more than two categories, such as: blood group, type of doctor, country of birth. Also the two categories, such as described previously, might be expanded into several categories. For example the married/single could be expanded to: married/single/divorced/separated/ widowed. This sort of data is called nominal data where there are several categories, but with no logical order. When there is a natural order (such as in seniority), the data are then called ordinal data. For example, anaesthetists could be divided into: ‘Foundation year 1’, ‘Foundation year 2’, ‘speciality doctor’, consultants’, ‘senior consultants’ and ‘clinical directors’. Ordinal data can be reduced to two categories, with possibly a considerable loss of information (e.g. ‘senior doctors’, ‘junior doctors’). Discrete numerical data are where the observation takes exact numerical values. Counts or events are discrete values. For example: number of children, number of ectopic beats in a time period and so on. Continuous (or analogue) data are usually obtained by some form of measurement. Examples are body temperature, blood pressure, height and weight. These values have an infinite number of possibilities, depending on the measurement interval, and variation. Although there are infinite possibilities, measurement systems usually round the continuous data up, or down, to discrete values. Blood pressure is often rounded up to the nearest 5 mmHg, for example.
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Blow, David. "Electron-density maps." In Outline of Crystallography for Biologists. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780198510512.003.0016.
Анотація:
When everything has been done to make the phases as good as possible, the time has come to examine the image of the structure in the form of an electron-density map. The electron-density map is the Fourier transform of the structure factors (with their phases). If the resolution and phases are good enough, the electron-density map may be interpreted in terms of atomic positions. In practice, it may be necessary to alternate between study of the electron-density map and the procedures mentioned in Chapter 10, which may allow improvements to be made to it. Electron-density maps contain a great deal of information, which is not easy to grasp. Considerable technical effort has gone into methods of presenting the electron density to the observer in the clearest possible way. The Fourier transform is calculated as a set of electron-density values at every point of a three-dimensional grid labelled with fractional coordinates x, y, z. These coordinates each go from 0 to 1 in order to cover the whole unit cell. To present the electron density as a smoothly varying function, values have to be calculated at intervals that are much smaller than the nominal resolution of the map. Say, for example, there is a protein unit cell 50 Å on a side, at a routine resolution of 2Å. This means that some of the waves included in the calculation of the electron density go through a complete wave cycle in 2 Å. As a rule of thumb, to represent this properly, the spacing of the points on the grid for calculation must be less than one-third of the resolution. In our example, this spacing might be 0.6 Å. To cover the whole of the 50 Å unit cell, about 80 values of x are needed; and the same number of values of y and z. The electron density therefore needs to be calculated on an array of 80×80×80 points, which is over half a million values. Although our world is three-dimensional, our retinas are two-dimensional, and we are good at looking at pictures and diagrams in two dimensions.
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Kupchuk, Ihor, and Natalia Telekalo. "TECHNICAL AND TECHNOLOGICAL PREREQUISITES FOR THE INTRODUCTION OF AUTONOMOUS ENERGY SYSTEMS OF AGRO-INDUSTRIAL ENTERPRISES USING RENEWABLE ENERGY SOURCES." In Theoretical and practical aspects of the development of modern scientific research. Publishing House “Baltija Publishing”, 2022. http://dx.doi.org/10.30525/978-9934-26-195-4-16.
Анотація:
The research is devoted to solving important tasks of interdisciplinary research work on the topic: «Development of scientific and technical support for energy autonomy of the agro-industrial complex based on environmentally efficient use of agrobiomass for biofuel production», state registration number 0122U000844, implementation of which is planned for 2022–2024 at the expense of the state budget of Ukraine. The main purpose of the planned research is to increase the level of energy independence of agricultural enterprises through renewable energy sources through the use of the principles of dispersed hybrid energy supply, development of energy-efficient and environmentally friendly technologies for growing and processing agrobiomas for biofuel production, as well as modernization of means of control and monitoring of parameters of energy generating equipment. Given the complexity and interdisciplinarity of the planned research, the authors set a task, the solution will be an intermediate stage to achieve the overall goal of research. Such tasks are assessing the potential and identifying promising ways of decentralized power supply of agro-industrial producers based on the analysis of modern technical and technological solutions in the field of electrical engineering and synthesis of promising schemes of combined autonomous power supply of agricultural enterprises. Research of technical and technological prerequisites for the development of a combined system of autonomous energy supply and its components was carried out using the methods of analysis, generalization and systems approach. The potential benefits and effects of the proposed scheme are based on the laws of development of technical and power systems. The technical and technological aspects of the use of wind power generation in combination with solar energy conversion were evaluated. Also, the known methods of accumulating electrical energy received from autonomous electrical installations were analyzed. For efficient generation of electrical energy by modern wind turbines (vertical and ridge), wind speeds from 1.0-1.5 m/s are sufficient, and the nominal operating mode starts at 2-3 m/s, which corresponds to the meteorological indicators of the Vinnitsa region and confirms the possibility use of wind power generation. Also, a scheme was developed for a combined wind-solar autonomous power supply system for small and medium-sized agricultural enterprises and priority areas for further research were formed to improve the efficiency of such a system. At the same time, the most functionally and economically viable option is the use of energy storage systems based on flywheels with partial use of a backup lithium-ion battery pack. A flywheel scheme with a variable dynamic moment of inertia has also been developed, the use of which will improve the maneuverability of the autonomous power supply, and increase its performance.
Тези доповідей конференцій з теми "Complétive nominale":
1
Rzadkowski, Romuald, Vitaly Gnesin, and Lubov Kolodyazhnaya. "Numerical Modelling of Fluid-Structure Interaction in a Turbine Stage for 3D Viscous Flow in Nominal and Off- Design Regimes." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-23779.
Анотація:
In recent years there have been major developments in turbomachinery aeroelasticity methods. There are now greater possibilities to predict blade vibrations arising from self-excitation or inlet flow distortion. This is not only important with regard to aircraft compressor and fan blade rows, but also in the case of the last stages of steam and gas turbines working in highly loaded off-design conditions. In order to predict the unsteady pressure loads and aeroelastic behaviour of blades (including the computation of shock waves, shock/boundary layer interaction and boundary layer separation), complete Reynolds-averaged Navier-Stokes (RANS) equations are used in modelling complex and off-design cases of turbomachinery flows. In this paper the 3D RANS solver, including a modified Baldwin and Lomax algebraic eddy viscous turbulence model, is presented to calculate unsteady viscous flow through the turbine stage, while taking into account the blade oscillations but without the separating of outer excitation and unsteady effects caused by blade motion. The numerical method uses the second order by time and coordinates an explicit finite-volume Godunov’s type difference scheme and a moving H-O structured grid. The structure analysis uses the modal approach and a 3D finite element model of blade. To validate the numerical viscous code, the numerical calculation results were compared with the 11th Standard Configuration measurements. Presented here are the numerical analysis results for the aeroelastic behaviour of a steam turbine last stage with 760 mm rotor blades in a nominal and an off-design regime.
2
Togayev, Adil, Mario G. Perhinschi, Dia Al Azzawi, Hever Moncayo, Israel Moguel, and Andres E. Perez. "Immunity-Based Abnormal Condition Accommodation of Aircraft Sub-System Failures." In ASME 2014 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/dscc2014-5899.
Анотація:
This paper describes the design, development, and flight-simulation testing of an artificial immune-system-based approach for accommodation of different aircraft sub-system failures/damages. The accommodation of abnormal flight conditions is regarded as part of a complex integrated artificial immune system scheme, which consists of four major components: detection, identification, evaluation, and accommodation. The accommodation part consists of providing compensatory commands under upset conditions for specific maneuvers. The approach is based on building an artificial memory, which represents the self (nominal conditions) and the non-self (abnormal conditions) within the artificial immune system paradigm. Self and non-self are structured as a set of memory cells consisting of measurement strings, over pre-defined time windows. Each string is a set of features values at each sample time of the flight including pilot inputs, system states, and other variables. The accommodation algorithm is based on the cell in the memory that is the most similar to the in-coming measurement. Once the best match is found, control commands corresponding to this match will be extracted from the memory and used for control purposes. The proposed methodology is illustrated through simulation of simple maneuvers at nominal flight conditions and under locked actuator. The results demonstrate the possibility of extracting pilot compensatory commands from the self/non-self structure and capability of the artificial-immune-system-based scheme to accommodate an actuator malfunction, maintain control, and complete the task.
3
Waldherr, Christian U., and Damian M. Vogt. "An Extension of the Classical Subset of Nominal Modes Method for the Model Order Reduction of Gyroscopic Systems." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76742.
Анотація:
In the structural dynamics design process of turbomachines, Coriolis effects are usually neglected. This assumption holds true if no pronounced interaction between the shaft and disk occurs or if the radial blade displacements are negligible. For classical rotordynamic investigations or for machines where the disk is comparatively thin or weak, Coriolis effects as well as centrifugal effects like stress stiffening and spin softening have to be taken into account. For the analysis of complex structures the finite element method is today the most commonly used modeling approach. To handle the numerical effort in such an analysis, the aim of the present work is the further development of an existing reduced order model, which also allows the consideration of Coriolis effects without the loss of accuracy for a wide range of rotational speeds. In addition to the investigation of the tuned design of the bladed disk using cyclic boundary conditions, the described method is also appropriate to investigate mistuning phenomena including Coriolis effects. Due to the fact that the computation time can be reduced by two orders of magnitude, the method also opens up the possibility for performing probabilistic mistuning investigations including Coriolis effects.
4
Horner, Jim W. "Modeling Multi-Product Pipeline Hydraulics With a Spreadsheet." In 2008 7th International Pipeline Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/ipc2008-64106.
Анотація:
Steady state computations have traditionally been used for liquid pipeline hydraulic design. The hydraulic behavior of multiproduct pipelines is more complex than single-product lines because the throughput varies with time as the different batches move through the system. Designing a multiproduct pipeline involves hydraulic simulation to ensure that the system can meet a specified time-average throughput for the design batch line-up. To calculate the time-averaged throughput, the hydraulic simulation determines the total time it takes to ship the complete design batch cycle and the methodology must account for the time-varying throughput of the pipeline. Two basic methods available to accomplish this are: the fully-transient method, and the simpler succession-of-steady-state method. A fully-transient model would rigorously solve the time-dependent equations of energy, mass and momentum conservation to determine operating capacity. A succession-of-steady-state (SSS) model is one where batches are moved through the system in small volume increments, and the steady-state capacity is calculated at each step. Fully-transient type software models are powerful, but expensive, complex and usually require lengthy simulation run times. An SSS spreadsheet model would not be used to evaluate transient phenomena, but is adequate for determination of nominal pipeline capacities. This paper discusses the development of a trans-thermal, SSS spreadsheet based model that was created as a design tool to determine pipeline capacity and evaluate the impact of design alternatives or changes.
5
Watts, Travis J., Jerry G. Rose, and Ethan J. Russell. "Relationships Between Wheel/Rail Surface Impact Loadings and Correspondingly Transmitted Tie/Ballast Impact Pressures for Revenue Train Operations." In 2018 Joint Rail Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/jrc2018-6184.
Анотація:
A series of specially designed granular material pressure cells were precisely positioned directly below the rail at the tie/ballast interface to measure typical interfacial pressures exerted by revenue freight trains. These vertical pressures were compared to the recorded wheel/rail nominal and peak forces for the same trains traversing nearby mainline wheel impact load detectors (WILDs). The cells were imbedded within the bottom of new wood ties so that the surfaces of the pressure cells were even with the bottoms of the ties and the underlying ballast. The cells were inserted below consecutive rail seats of one rail to record pressures for a complete wheel rotation. The stability and tightness of the ballast support influenced the magnitudes and consistencies of the recorded ballast pressures. Considerable effort was required to provide consistent ballast conditions for the instrumented ties and adjacent undisturbed transition ties. Norfolk Southern (NS) crews surfaced and tamped through the test section and adjacent approach ties. This effort along with normal accruing train traffic subsequently resulted in reasonably consistent pressure measurements throughout the test section. The impact ratio (impact factor) and peak force values recorded by the WILDs compared favorably with the resulting magnitudes of the transferred pressures at the tie/ballast interface. High peak force and high impact ratio WILD readings indicate the presence of wheel imperfections that increase nominal forces at the rail/wheel interface. The resulting increased dynamic impact forces can contribute to higher degradation rates for the track component materials and more rapid degradation rates of the track geometry. The paper contains comparative WILD force measurements and tie/ballast interfacial pressure measurements for loaded and empty trains. Typical tie/ballast pressures for locomotives and loaded freight cars ranges from 20 to 30 psi (140 to 210 kPa) for smooth wheels producing negligible impacts. The effect of increased wheel/rail impacts and peak force values on the correspondingly transmitted pressures at the tie/ballast interface is significant, with increased pressures of several orders of magnitude compared to nominal impact forces from wheels.
6
Kerdok, Amy E., Robert D. Howe, and Simona Socrate. "Viscoelastic Characterization of Perfused Liver: Indentation Testing and Preliminary Modeling." In ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-176645.
Анотація:
Computer-aided medical technologies are currently restricted by the limited understanding of the mechanical response of solid abdominal organs to finite loading conditions typical of surgical manipulation [5]. This limitation is a result of the difficulty in acquiring the necessary data on whole organs. To develop a constitutive model capable of predicting complex surgical scenarios, multiple testing modalities need to be simultaneously obtained to capture the fundamental nature of the tissue’s behavior under such conditions. In vivo tests are essential to obtain a realistic response, but their inherent difficulty and unknown boundary conditions makes them an impractical approach. Ex vivo tests are easy to control, but the response is unrealistic. A perfusion apparatus was previously developed that obtained near in vivo conditions for whole livers while allowing the ease of ex vivo testing [3]. This work presents the results from complete viscoelastic testing of whole-perfused livers with surgically relevant time-dependant indentation loading profiles to 35% nominal strain. These results will aid in the development of a constitutive model for the liver whose parameters can be related to the physical constituents of the tissue. As an intermediate modeling step, a 1D rheological modeling tool was used to identify the form and initial parameters for a constitutive model.
7
Marko, Kenneth. "Machine Learning and Model Based Reasoning for Prognostics of Complex Systems." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81625.
Анотація:
Model based reasoning (MBR) has been shown to be an effective means of providing condition based maintenance for many high-value assets for which accurate first principle models have been developed. Yet, many low-cost complex computer controlled systems are mass-produced without the concurrent provision of precise physics based models. We wish to utilize new developments in machine learning coupled with model based reasoning methods to address this deficiency. In particular, we shall demonstrate that for an important class of these systems, the extremely large number of mass produced, complex engine systems which power vehicles and small power generation plants, effective means of providing MBR for condition based maintenance exists. It will be recognized that the methodology also has much broader applicability. We will show that a class of dynamic neural networks can be used to provide high-fidelity models of these complex systems that permit an analysis of differences between predicted normal behavior and actual plant behavior to be analyzed to detect deviations from nominal behavior which will be shown to be valuable in estimating time-to-failure for such systems. The realization of this capability is dependent upon the development of extremely efficient and powerful training algorithms for these dynamics neural networks. While many simple training schemes have been in use for many years, they generally fail to provide the needed model accuracy when they are applied to training the relatively “large” multi-layered dynamic networks that are needed to precisely mimic plant behavior over all operating conditions. Our approach has several advantages over these simpler, but less effective methods. Three major improvements are the rate at which learning proceeds, the provision of a means to optimize the learning rate through-out the process, and the dramatic improvements observed in learning in the final stages of training when the error feedback from training examples are extremely small and the associated error covariance matrices almost vanish. We shall demonstrate with data drawn from production vehicles, that for several important problems in analyzing system performance in these vehicles, sufficient model fidelity can be attained to meet the requirements on detection efficiency, false alarm immunity and alarm response time which are required for effective diagnostics and prognostics. Finally we shall discuss the manner in which the deviations are analyzed to not only identify that a failure has been detected but also the means by which the probable root cause may be isolated.
8
Nagy, Doug, and Gerry Bergstaller. "LPM™ Composite Overlay for Erosion Protection of Turbine Nozzles." In ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-69019.
Анотація:
Aircraft turbine engines, particularly those of helicopter and turboprops tend to suffer hot gas path erosion in service. When the service environment includes operation from “un-improved” airstrips, component life is limited by erosion to times well less than the nominal time between overhaul (TBO). In response, an engineered material overlay was applied to the critical areas on turbine nozzles in overhaul. The overlay both “repaired” and “reinforced” the nozzles leading to a longer time on wing and less damage upon removal. No performance penalty was detected during test cell operation or flight service. The engineered material overlay was fabricated by powder metallurgical methods and consisted of a nickel superalloy matrix containing a rigid “skeleton” of chromium carbide hard particles. In the raw form, the overlay material was pliable to allow forming to complex geometries, but after diffusion bonding it was rigid and refractory.
9
Bladh, Ronnie, Qingyuan Zhuang, Jiasen Hu, and Johan Hammar. "Leakage-Induced Compressor Blade Excitation due to Inter-Segment Gaps." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-70040.
Анотація:
A comprehensive investigation is presented related to leakage-induced blade excitation from shrouded vane segments found in industrial gas turbine compressors. The focus of the investigation is to explore the excitation mechanism acting on downstream rotor blades that stem from the particularly complex leakage flows around the hub inter-segment gaps. The aerodynamic forces are here determined using 3D nonlinear time-marching CFD simulations. The employed computational model encompasses the two rear-most stages in an existing industrial gas turbine compressor. The inter-segment gap is implemented in the next-to-last stator, varying from no gap to twice the nominal gap size. Obtained results indicate that the excitation induced by the inter-segment gap leakage flows is distinctly multi-harmonic and unexpectedly strong. As much as five times the excitation strength of upstream wakes was observed already for the nominal gap. The induced unsteady forces were found to derive from two different sources: (i) a large separation producing local forcing in the hub region; and (ii) circumferentially varying flow speed resulting in distributed forcing over the entire blade. The findings imply that the excitation induced by inter-segment gap leakage flows can be a significant contributor to blade vibratory responses in the intermediate engine order range, and thereby add to the knowledge base related to blade dynamic integrity.
10
Smith, Joel, Jaehee Chae, Shawn Learn, Ron Hugo, and Simon Park. "Pipeline Rupture Detection Using Real-Time Transient Modelling and Convolutional Neural Networks." In 2018 12th International Pipeline Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/ipc2018-78426.
Анотація:
Demonstrating the ability to reliably detect pipeline ruptures is critical for pipeline operators as they seek to maintain the social license necessary to construct and upgrade their pipeline systems. Current leak detection systems range from very simple mass balances to highly complex models with real-time simulation and advanced statistical processing with the goal of detecting small leaks around 1% of the nominal flow rate. No matter how finely-tuned these systems are, however, they are invariably affected by noise and uncertainties in a pipeline system, resulting in false alarms that reduce system confidence. This study aims to develop a leak detection system that can detect leaks with high reliability by focusing on sudden-onset leaks of various sizes (ruptures), as opposed to slow leaks that develop over time. The expected outcome is that not only will pipeline operators avoid the costs associated with false-alarm shut downs, but more importantly, they will be able to respond faster and more confidently in the event of an actual rupture. To accomplish these goals, leaks of various sizes are simulated using a real-time transient model based on the method of characteristics. A novel leak detection model is presented that fuses together several different preprocessing techniques, including convolution neural networks. This leak detection system is expected to increase operator confidence in leak alarms, when they occur, and therefore decrease the amount of time between leak detection and pipeline shutdown.