Academic literature on the topic 'Passage Feature Variables'
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Journal articles on the topic "Passage Feature Variables"
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Mamirova, Malikaxon Xusravjon qizi. "THE WAYS OF CONSTRUCTING ITEMS IN READING TESTS." EURASIAN JOURNAL OF ACADEMIC RESEARCH 2, no. 4 (2022): 13–18. https://doi.org/10.5281/zenodo.6468362.
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In this article ways of constructing items in reading tests are demonstrated. The investigation of the effect of item test characteristics on the difficulty of reading comprehension item often involves an analysis of various variables including passage features, question type features and question format variables.The study is based on describing the process of developing an academic reading ability test undertaken as a class project and to evaluate its authenticity. The basic purpose of the test is to develop the ability of designing and developing a language test of the students of a class of English language teaching. Thus, in this way along with the learning of the principles of language testing and assessment, the students have also been given a practical experience of designing and developing a test.
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Belserene, Emilia Pisani. "Moving Through The Instability Strip." International Astronomical Union Colloquium 139 (1993): 419. http://dx.doi.org/10.1017/s025292110011810x.
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The purpose: To look at period changes in pulsating variables from the point of view of stellar evolution. Is there evidence of systematic, slow changes that might be caused by the changes in mean density during passage across the Instability Strip?The data: O – C diagrams for 67 RR Lyrae stars and Cepheids by student assistants at the Maria Mitchell Observatory, and for 88 northern Cepheids by L. SzabadosThe method: Least-squares lines and parabolae (unless the O – C diagram shows that the period has changed in both directions). The rate of change of period comes from the coefficient of the square term in the parabola. The principal feature of these analyses is that the rate is taken to be non-zero only if the parabola is significantly better than the linear fit, at the 2-sigma level.
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Sun, Yunpeng, Rafael Mendoza-Arriaga, and Vadim Linetsky. "Marshall–Olkin distributions, subordinators, efficient simulation, and applications to credit risk." Advances in Applied Probability 49, no. 2 (2017): 481–514. http://dx.doi.org/10.1017/apr.2017.10.
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Abstract In the paper we present a novel construction of Marshall–Olkin (MO) multivariate exponential distributions of failure times as distributions of the first-passage times of the coordinates of multidimensional Lévy subordinator processes above independent unit-mean exponential random variables. A time-inhomogeneous version is also given that replaces Lévy subordinators with additive subordinators. An attractive feature of MO distributions for applications, such as to portfolio credit risk, is its singular component that yields positive probabilities of simultaneous defaults of multiple obligors, capturing the default clustering phenomenon. The drawback of the original MO fatal shock construction of MO distributions is that it requires one to simulate 2n-1 independent exponential random variables. In practice, the dimensionality is typically on the order of hundreds or thousands of obligors in a large credit portfolio, rendering the MO fatal shock construction infeasible to simulate. The subordinator construction reduces the problem of simulating a rich subclass of MO distributions to simulating an n-dimensional subordinator. When one works with the class of subordinators constructed from independent one-dimensional subordinators with known transition distributions, such as gamma and inverse Gaussian, or their Sato versions in the additive case, the simulation effort is linear in n. To illustrate, we present a simulation of 100,000 samples of a credit portfolio with 1,000 obligors that takes less than 18 seconds on a PC.
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Horwitz, Rachel M., Alex E. Hay, William J. Burt, Richard A. Cheel, Joseph Salisbury, and Helmuth Thomas. "High-frequency variability of CO<sub>2</sub> in Grand Passage, Bay of Fundy, Nova Scotia." Biogeosciences 16, no. 2 (2019): 605–16. http://dx.doi.org/10.5194/bg-16-605-2019.
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Abstract. Assessing changes in the marine carbon cycle arising from anthropogenic CO2 emissions requires a detailed understanding of the carbonate system's natural variability. Coastal ecosystems vary over short spatial and temporal scales, so their dynamics are not well described by long-term and broad regional averages. A year-long time series of pCO2, temperature, salinity, and currents is used to quantify the high-frequency variability of the carbonate system at the mouth of the Bay of Fundy, Nova Scotia. The seasonal cycle of pCO2 is modulated by a diel cycle that is larger in summer than in winter and a tidal contribution that is primarily M2, with amplitude roughly half that of the diel cycle throughout the year. The interaction between tidal currents and carbonate system variables leads to lateral transport by tidal pumping, which moves alkalinity and dissolved inorganic carbon (DIC) out of the bay, opposite to the mean flow in the region, and constitutes a new feature of how this strongly tidal region connects to the larger Gulf of Maine and northwest Atlantic carbon system. These results suggest that tidal pumping could substantially modulate the coastal ocean's response to global ocean acidification in any region with large tides and spatial variation in biological activity, requiring that high-frequency variability be accounted for in assessments of carbon budgets of coastal regions.
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Prasanta, Biswas. "Mathematical Differential Solution of Flow and Head loss in the Flow correction and Design of Distribution Network of Water Supply." International Journal of Trend in Scientific Research and Development 2, no. 3 (2018): 2711–15. https://doi.org/10.31142/ijtsrd12923.
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This study has explained a method of solution of general flow problem by mathematics. The flow problem is the Darcy Weisbach formula of the head loss, i.e., HL=KQx. This equation has been transformed into the Leibnitz's form of the differential equation and then solved subsequently, considering suitable functionary variables for the derivation as applicable. This way of solution takes the feature of inner variables of a problem to limelight which might not achieve the breakthrough instead by any other way of the available solution in mathematics. Ultimately, in this study, the flow correction has got to be a different dimension by the mode of application of mathematics. With the final form of the differential solution, the head loss estimation has been adjusted for the loops in a distribution network in order to get the given flows passing through the pipe loops made into the subsequent corrected values. Future scope of this study is enormous the following up of this study's initiative proceeding for the numerous subjective fields of concern and lastly not the least indeed, the further research on the outcomes determined in this study by such application of the mathematical passage to go to finding out its further implication. Prasanta Biswas "Mathematical Differential Solution of Flow & Head-loss in the Flow-correction & Design of Distribution Network of Water Supply" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-3 , April 2018, URL: https://www.ijtsrd.com/papers/ijtsrd12923.pdf
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Trace, Jonathan, James Dean Brown, Gerriet Janssen, and Liudmila Kozhevnikova. "Determining cloze item difficulty from item and passage characteristics across different learner backgrounds." Language Testing 34, no. 2 (2016): 151–74. http://dx.doi.org/10.1177/0265532215623581.
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Cloze tests have been the subject of numerous studies regarding their function and use in both first language and second language contexts (e.g., Jonz & Oller, 1994; Watanabe & Koyama, 2008). From a validity standpoint, one area of investigation has been the extent to which cloze tests measure reading ability beyond the sentence level. Using test data from 50 30-item cloze passages administered to 2,298 Japanese and 5,170 Russian EFL students, this study examined the degree to which linguistic features for cloze passages and items influenced item difficulty. Using a common set of 10 anchor items, all 50 tests were modeled in terms of person ability and item difficulty onto a single scale using many-faceted Rasch measurement ( k = 1314). Principle components analysis was then used to categorize 25 linguistic item- and passage-level variables for the 50 cloze tests and their respective items, from which three components for each passage- and item-level variables were identified. These six factors along with item difficulty were then entered into both a hierarchical structural equation model and a linear multiple regression to determine the degree to which difficulty in cloze tests could be explained separately by passage and item features. Comparisons were further made by looking at differences in models by nationality and by proficiency level (e.g., high and low). The analyses revealed noteworthy differences in mean item difficulties and in the variance structures between passage- and item-level features, as well as between different examinee proficiency groups.
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Kumar, Abhishek, and Meenakshi Bharkatiya. "A Review on Updates to Increase the Residence Time of Drug in the Stomach for Gastro Retentive Drug Delivery System." Indo Global Journal of Pharmaceutical Sciences 11, no. 02 (2021): 130–42. http://dx.doi.org/10.35652/igjps.2021.112008.
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Orally-administered controlled-release drug delivery systems are associated with the shortcomings of relatively short residence times in the human stomach as well as highly variable gastrointestinal (GI) transit times. Thus, considerable intra-individual and inter-individual differences in the bioavailability of drugs are observable. There are numerous drug substances which may benefit from prolonged and controlled GI passage times. As a solution to the problem, gastroretentive drug delivery systems (GRDDS), which feature an enhanced gastric residence time (GRT), were developed. Several approaches are currently used including Floating Drug Delivery System (FDDS), swelling and expanding system, polymeric bioadhesive systems, modified-shape systems, high density system and other delayed gastric emptying devices. The drugs having absorption window in the upper part of Gastro Intestinal Tract (GIT) have enhanced bioavailability when formulated through these techniques. The recent technological development for enhancing GRT including the physiological and formulation variables affecting gastric retention, patented delivery systems, approaches to design single-unit and multiple-unit floating systems, and their classification and formulation aspects are covered in detail. Despite the extensive research performed in the field of GRDDS, the development, the production, and the evaluation of floating devices are still challenging. The purpose of writing this review was to compile recent literature on pharmaceutical approaches used in enhancing the Gastric Residence Time (GRT). Enhancing the GRT may explore new potentials of stomach as drug-absorbing organ. © 2020 iGlobal Research and Publishing Foundation. All rights reserved.
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Pan, Hong, Jie Yang, Yang Yu, Yuan Zheng, Xiaonan Zheng, and Chenyang Hang. "Intelligent Low-Consumption Optimization Strategies: Economic Operation of Hydropower Stations Based on Improved LSTM and Random Forest Machine Learning Algorithm." Mathematics 12, no. 9 (2024): 1292. http://dx.doi.org/10.3390/math12091292.
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The economic operation of hydropower stations has the potential to increase water use efficiency. However, there are some challenges, such as the fixed and unchangeable flow characteristic curve of the hydraulic turbines, and the large number of variables in optimal load distribution, which limit the progress of research. In this paper, we propose a new optimal method of the economic operation of hydropower stations based on improved Long Short-Term Memory neural network (I-LSTM) and Random Forest (RF) algorithm. Firstly, in order to accurately estimate the water consumption, the LSTM model’s hyperparameters are optimized using improved particle swarm optimization, and the I-LSTM method is proposed to fit the flow characteristic curve of the hydraulic turbines. Secondly, the Random Forest machine learning algorithm is introduced to establish a load-distribution model with its powerful feature extraction and learning ability. To improve the accuracy of the load-distribution model, we use the K-means algorithm to cluster the historical data and optimize the parameters of the Random Forest model. A Hydropower Station in China is selected for a case study. It is shown that (1) the I-LSTM method fits the operating characteristics under various working conditions and actual operating characteristics of hydraulic turbines, ensuring that they are closest to the actual operating state; (2) the I-LSTM method is compared with Support Vector Machine (SVM), Extreme Learning Machine (ELM) and Long Short-Term Memory neural network (LSTM). The prediction results of SVM have a large error, but compared with ELM and LSTM, MSE is reduced by about 46% and 38% respectively. MAE is reduced by about 25% and 21%, respectively. RMSE is reduced by about 27% and 24%, respectively; (3) the RF algorithm performs better than the traditional dynamic programming algorithm in load distribution. With the passage of time and the increase in training samples, the prediction accuracy of the Random Forest model has steadily improved, which helps to achieve optimal operation of the units, reducing their average total water consumption by 1.24%. This study provides strong support for the application of intelligent low-consumption optimization strategies in hydropower fields, which can bring higher economic benefits and resource savings to renewable energy production.
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Gattulli, Lofrano, Paolone, and Potenza. "Measured properties of structural damping in railway bridges." Journal of Civil Structural Health Monitoring 9 (October 14, 2019): 639–53. https://doi.org/10.5281/zenodo.6671677.
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Dissipative properties of a structural system are difficult to be characterized in real structure. Nevertheless, damping features may be dominant in several operating conditions of railway bridges influencing fatigue life or passenger comfort during train passage. Observations treating real data acquired in operational condition on steel and concrete railway bridges belonging to the Italian network permits to highlight dissipative sources and features. Consequently, linearized modal damping ratios are evaluated through a recursive process on the acceleration signals acquired before, during and after train passages and/or in environmental conditions. Stochastic Subspace Identification has been used to identify state-space dynamical models able to reproduce the vibrations. Through these models, characterized by an increasing number of state-space variables, it is possible to extract modal damping ratios. A mechanical interpretation of damping characteristics is pursued through the evaluation of the differences with respect to a classical Rayleigh proportional damping matrix of the viscous matrix belonging to the identified state-space models determined through the system spectral features. A non-proportional damping index is presented as a basis to determine the influence of different sources of non-proportionality in the damping matrix (as the ballast layer under the track) and to justify the high value of damping observed in specific experimental campaigns.
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Binding, Paul, D. R. Farenick, and Chi-Kwong Li. "A Dilation and Norm in Several Variable Operator Theory." Canadian Journal of Mathematics 47, no. 3 (1995): 449–61. http://dx.doi.org/10.4153/cjm-1995-025-5.
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AbstractFor every m-tuple of operators acting on a Hilbert space, it is shown that there exists a common dilation of these operators to mcommuting normal operators on some larger Hilbert space. We then introduce a norm on the m-fold cartesian product of ℬ(ℋ) that is defined to be, for a given w-tuple, the infimum of the joint spectral radii of all joint normal dilations of the m operators. This norm has several good features, one of which is that it is invariant under the passage to adjoints.
Book chapters on the topic "Passage Feature Variables"
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Weir, Bryce. "Anatomic Features of Aneurysms." In Subarachnoid Hemorrhage: Causes And Cures. Oxford University PressNew York, NY, 1998. http://dx.doi.org/10.1093/oso/9780195128758.003.0004.
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Abstract Saccular aneurysms are located much more frequently on the anterior circulation (85% to 95%) than on the posterior circulation (5% to 15%) (Fig. 4-1). Aneurysms can occur at almost any arterial point in the intracranial or intraspinal space, but are rarely located anywhere other than the anterior and posterior circulations. About one-third of aneurysms occur in the midline, and about one-third on each of the sides. Subarachnoid hemorrhage (SAH) occurs because most aneurysms are located within the subarachnoid space. The su!Jarachnoid space is located between the arachnoid layer abutting the dura and the pia mater lying on the brain’s surface. Continuous sheets of cells from the arachnoid and pial layers completely invest the collagenous trabeculae, strands that run between them, as well as the vascular and neural structures traversing the space. The subarachnoid space is highly variable in width and configuration, but consistently large chambers are identified as named cisterns (e.g., interpeduncular, carotid). The pia mater is a physical barrier to the passage of erythrocytes into the potential periadventitial spaces around blood vessels perforating the brain’s surface.
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Seuren, Pieter A. M. "Internal variability in competence †." In A View of Language. Oxford University PressOxford, 2002. http://dx.doi.org/10.1093/oso/9780199244812.003.0005.
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Abstract To the non-linguist one of the most obvious facts about natural languages is the availability of ranges of, often subtly, differing ways of expressing the same linguistic meaning, where the differences correlate with values on non-linguistic parameters. Every speaker of a language knows that certain features in his or other persons’ speech indicate, not the linguistic meaning carried by the message, but associations with geographical area, with social class, with kinds of interactional situation, with age, with a profession, with a religion, etc. The differences show themselves in lexical selection, choice of grammatical construction, choice of pronunciation-i.e. choices throughout the grammar. Even though most speakers are not aware, and cannot make themselves aware, of the precise features carrying the variable associations (except, sometimes, for a few prominent features which then acquire a special symbolic value),1 the associations are nevertheless registered by listeners.2 To know a language does not only mean having the ability of converting meanings into well-formed strings of symbols and vice versa, but also being able to distinguish, to some extent, between standard, substandard, formal, informal, dialectally and sociolectally marked forms of speech. An ideal speaker-listener would have command, both active and passive, of all varieties occurring in the community where the language in question is spoken. Obviously, such ideally competent people hardly occur in real life. But equally obviously, real people hardly ever have a linguistic competence which is entirely homogeneous: we all have active and passive command of a fairly wide range of varieties. A foreign learner whose competence is restricted to one variety
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Nedecky, Jason. "Special Pronunciation Considerations." In French Lyric Diction. Oxford University PressNew York, 2023. http://dx.doi.org/10.1093/oso/9780197573839.003.0008.
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Abstract Idiosyncracies are to be encountered in every language; French is no exception. When it comes to singing in French, several features constitute topics particularly worthy of exploration. This chapter provides instruction on the most important of these topics. Emphatic stress (l’acccent d’insistance) involves shifting stress to a new syllable in the phonetic group in order to create a sense of urgency. This practice is widespread both in speech and in fine French singing. Another special topic is vocalic harmonization (l’harmonisation vocalique). Here, a relatively open vowel in an unstressed syllable closes to match the more closed vowel of the following, stressed syllable. This occurs in everyday French speech, but is applied much more cautiously in French vocal music. Unlike the other main singing languages, French rarely features consonant doubling (gémination consonantique). It is however possible in a few important scenarios, namely: in certain prefixes, with doubled (rolled) r in passages of heightened expressivity and in particular verb tenses, and as phrasal doubling of the same consonant in two words. An account is given for all of these cases. Several words with variable pronunciation are treated, including toujours, tous, and the infamously tricky word donc. The pronunciation of French numbers ends the chapter. Explanations and musical examples provide context.
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Chu, C. Y. Cyrus. "Population Size and Early Development." In Population Dynamics. Oxford University Press, 1998. http://dx.doi.org/10.1093/oso/9780195121582.003.0019.
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The Malthusian theory hypothesizes that the natural environment imposes various capacity constraints on human population growth and that population size has been and will be checked by these constraints. In such a classical theory, which was presumably motivated by observations of the ancient world, population might be the most important dynamic variable, although its role is rather passive: population is a variable that would be affected by, but would not affect, the environment. Boserup (1981), however, sees the role of population in the development of human economy as more consequential. She gave many persuasive examples that showed that, at least for the period up to the mid-twentieth century, population size might be a variable which actively spurred technological progress. This is also the viewpoint held by Lee (1986) and Pryor and Maurer (1982). After the Industrial Revolution, the role of population in economic dynamics, along with the reduction of mortality fluctuations and the increasing control of female fertility, evidently became secondary. The key variable that dominates the analysis of economic dynamics in the neoclassical growth theory along the lines of Solow (1956) is capital (or per capita capital). In Solow’s growth model, the role of population is minimal in the steady state: neither the level nor the growth rate of the steady-state per capita consumption has anything to do with the size of a population; only the steady-state per capita income level will be affected by the population growth rate. The growth pattern in the latter half of the twentieth century is markedly different. A key feature of our recent growth experience is the rapid innovation of new technologies. Modern growth theory has embraced the concept of increasing returns to explain such a unique growth pattern. However, various versions of the theory of increasing returns turn out to be necessarily linked to population. The hypothesis of learning by doing implies that growth in productivity is an increasing function of aggregate production, which is itself positively related to the size of population.
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Gasser, Emily, Laura Arnold, and David Kamholz. "The languages of Halmahera and West New Guinea." In The Oxford Guide to the Malayo-Polynesian Languages of Southeast Asia. Oxford University PressOxford, 2024. http://dx.doi.org/10.1093/oso/9780198807353.003.0037.
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Abstract This chapter provides the first typological overview of the Austronesian languages spoken in Halmahera, Raja Ampat, and west New Guinea; together, the majority of these languages comprise the South Halmahera-West New Guinea (SHWNG) subbranch. The chapter covers topics in phonology, morphology, syntax, and lexicon. Basic constituent order is SVO in all languages, and most adpositions are prepositional; this generally head-initial profile, however, combines with widespread clause-final negation and aspect marking. Phonological inventories are generally straightforward (typically 10-15 consonants and 5-7 vowels). Stress tends to be penultimate, and several SHWNG languages have tone. Phonotactics are variable across the region: some languages have very simple syllable structure, while in others lengthy and unusual clusters are permitted. Noun phrases are head-initial, except for possessor NPs which precede the head. Most languages have an alienability distinction in possessive constructions. The languages are isolating to lightly agglutinating; productive inflectional morphology marking verbal subjects and possessors is common. True passive constructions are rare; several languages have productive applicative and/or causative morphology. Demonstrative systems generally make a three-way spatial contrast, and may be highly elaborated with directional demonstratives. Verb serialization is common, marking functions such as manner, cause-effect, direction of transfer, and purposive motion. The languages have either decimal or quinary-decimal numeral systems, with the numbers six through nine formed by addition. A repeating theme throughout this chapter is the role that contact with neighbouring non-Austronesian languages has played in the development of several features characteristic of the region.
Conference papers on the topic "Passage Feature Variables"
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Bapat, Siddhant, Siddharth Poreddy, Nicholas Vlajic, Richard Auhl, George Lesieutre, and Edward Smith. "Dynamic Behavior and Passive Vibration Control of a Flexible Tip-Loaded Support Arm System with Bracing Struts and Tailored Particle Impact Dampers." In Vertical Flight Society 80th Annual Forum & Technology Display. The Vertical Flight Society, 2024. http://dx.doi.org/10.4050/f-0080-2024-1361.
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Electric Vertical Takeoff Landing (eVTOL) aircraft feature heavy electric motors, battery packs, and rigid fixed-pitch rotors supported on flexible arms. Under substantial time-varying aerodynamic loads associated with variable rotor speeds and, with low intrinsic damping, such lightweight arms respond in bending and torsion at relatively high levels. In this paper, two methods of reducing vibration response in the operating frequency range are explored, one based on damping, the other on stiffness. A tailored particle impact damper system was evaluated experimentally to address near-periodic vibration over a range of frequencies. A forced torsional response test showed consistent 50% vibration reduction, with a 5% mass penalty. To stiffen the system, a cross-braced strut approach linked two arms such that the natural frequencies of their torsion modes would be increased beyond the rotor operating frequency range. A finite element model was developed and validated for a representative eVTOL configuration. Validation was conducted using a scale model aluminum beam set. The addition of a cross-braced strut efficiently stiffened the system, increasing its natural frequency by almost 120%, thus greatly reducing resonant torsional vibration within the operating range. Both approaches to vibration reduction for variable-speed eVTOL aircraft merit continued consideration and research.
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Baykal, B. Aydin, Pelin B. Icer Baykal, and Preet M. Singh. "Modeling of Erosion-Corrosion in An Alkaline Environment by Machine Learning." In CORROSION 2019. NACE International, 2019. https://doi.org/10.5006/c2019-13450.
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Abstract Machine learning is a method that allows interpretations of new data using an established database of older data by referring to already-known results (known as “labels”) and extrapolating between them to estimate the label that would be assigned to a different experiment. This can be a powerful tool for corrosion prediction, because it makes it possible to estimate a range of corrosion rates for a certain family of materials in a specific range of environments without actually performing experiments. In this paper, the machine learning concept was applied to the erosion-corrosion of steels in white liquor, a strongly alkaline industrial chemical used for pulping wood chips. Previously obtained corrosion data in white liquor, which included different steel compositions, particle concentrations and sizes, temperatures and fluid properties such as viscosity were compiled and assigned labels based on previous assessments in the industry as passive, acceptable, marginal or unsuitable according to observed corrosion rate. Models using thirty selected variables were built based on this data using diverse machine learning methods, including support vector machines (SVM), decision trees, k-nearest neighbor methods (KNN). discriminant analysis etc. Feature selection was attempted for each model. The best accuracies for each method were compiled and assessed regarding their promise for predictive purposes in erosion-corrosion
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Chen, I.-Lun, Izzet Sahin, Lesley M. Wright, Je-Chin Han, and Robert Krewinkel. "Heat Transfer in a Rotating, Blade-Shaped, Two-Pass Cooling Channel With a Variable Aspect Ratio." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-59400.
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Abstract This study features a rotating, blade-shaped, two-pass cooling channel with a variable aspect ratio. Internal cooling passages of modern gas turbine blades closely follow the shape and contour of the airfoils. Therefore, the cross-section and the orientation with respect to rotation varies for each cooling channel. The effect of passage orientation on the heat transfer and pressure loss is investigated by comparing to a planar channel design with a similar geometry. Following the blade cross-section, the first pass of the serpentine channel is angled at 50° from the direction of rotation while the second pass has an orientation angle of 105°. The coolant flows radially outward in the first passage with an aspect ratio (AR) = 4:1. After a 180-degree tip turn, the coolant travels radially inward into the second passage with AR = 2:1. The copper plate method is applied to obtain the regionally-averaged heat transfer coefficients on all the interior walls of the cooling channel. In addition to the smooth surface case, 45° angled ribs with a profiled cross section are also placed on the leading and trailing surfaces in both the passages. The ribs are placed such that P/e = 10 and e/H = 0.16. The Reynolds number varies from 10,000 to 45,000 in the first passage and 16,000 to 73,000 in the second passage. The rotational speed ranges from 0 to 400 rpm, which corresponds to maximum rotation numbers of 0.38 and 0.15 in the first and second passes, respectively. The blade-shaped feature affects the heat transfer and pressure loss in the cooling channels. In the second passage, the heat transfer on the outer wall and trailing surface is higher than the inner wall and leading surface due to flow impingement and the swirling motion induced by the blade-shaped tip turn. The rotational effect on the heat transfer and pressure loss is lower in the blade-shaped design than the planar design due to the feature of angled rotation. The tip wall heat transfer is significantly enhanced by rotation in this study. The overall heat transfer and pressure loss in this study is higher than the planar geometry due to the blade-shaped feature. The heat transfer and pressure loss characteristics from this study provide important information for the gas turbine blade internal cooling designs.
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Arora, Ravi, Anna Lee Tonkovich, Mike J. Lamont, Thomas Yuschak, and Laura Silva. "Passive Heat Transfer Enhancement in Microchannels Using Wall Features." In ASME 2007 5th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2007. http://dx.doi.org/10.1115/icnmm2007-30104.
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The two important considerations in the design of a heat exchanger are — the total heat transfer rate and the allowable pressure drop. The allowable pressure drop defines the maximum flow rate through a single microchannel and economics drives the design towards this flow rate. Typically the flow rate in the microchannel is in laminar flow regime (Re < 2000) due to smaller hydraulic diameter. The laminar flow heat transfer in a smooth microchannel is limited by the boundary layer thickness. Commonly the heat transfer rate is enhanced by passively disrupting the laminar boundary layer using protrusions or depressions in the channel walls. More often these methods are best applicable at small range of Reynolds number where the heat transfer rate enhancement is more than the pressure drop increase and break down as the flow rate is changed outside the range. The benefit of a flow disruption method can be reaped only if it provides higher heat transfer enhancement than the increase in the pressure drop at the working flow rates in the microchannel. A heat transfer efficient microchannel design has been developed using wall features that create stable disrupted flow and break the laminar boundary layer in a microchannel over a wide range of flow rates. The paper experimentally investigates the developed design for the heat transfer enhancement and pressure drop increase compared to a smooth wall microchannel. A simple microchannel device was designed and fabricated with and without wall features. The experiments with single gas phase fluid showed promising results with the developed wall feature design as the heat transfer rate increase was 20% to 80% more than the pressure drop increase in the laminar regime. The wall feature design was an important variable to affect the magnitude of performance enhancement in different flow regime. A general criterion was developed to judge the efficacy of wall feature design that can be used during a microchannel heat exchanger design.
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Islam, Md Manjurul, Yuping He, and Timothy D. Webster. "Automated Design Synthesis of Articulated Heavy Vehicles With Active Trailer Steering Systems." In ASME 2010 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/detc2010-28160.
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This paper presents an automated design synthesis approach for articulated heavy vehicles (AHVs) with active trailer steering (ATS) systems. AHVs have poor maneuverability when traveling at low speeds. Moreover, AHVs exhibit unstable motion modes at high speeds. To address the problem of maneuverability, ‘passive’ trailer steering systems have been developed. These systems improve low-speed performance, but feature with low lateral stability at high speeds. Some ATS systems have been proposed to improve highspeed lateral stability. However, these systems typically degrade maneuverability when applied at low speeds. To tackle this conflicting design problem, a systematic method is proposed for the design of AHVs with ATS systems. This new design method has the following features: the optimal active design variables of the ATS systems and the optimal passive design variables of the vehicle are identified in a single design loop; in the design process, to evaluate the vehicle performance measures, a driver model is introduced and it ‘drives’ the vehicle model based on the well-defined testing specifications. Through the design optimization of an ATS system for an AHV with a tractor and a full trailer, this single design loop (SDL) method is compared against a published two design loop (TDL) method. The benchmark investigation shows that the former can determine better trade-off design solutions than those derived by the latter. This SDL method provides an effective approach to automatically implement the design synthesis of AHVs with ATS systems.
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Kamada, Yasunari, Kazuma Yamanaka, Takao Maeda, and Yukimaru Shimizu. "Feasibility Studies on a Small-Scale Wind Turbine for the Mountainous Area." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45358.
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In this study, a small-scale wind turbine for the mountainous area is developed. The technical features of this wind turbine are the high performance rotor with a blade tip-mounted Mie vane, the passive power control by a pitch-flap mechanism and a variable speed induction generator with inverter system. The test wind turbine is tested in Mie University wind turbine test field in a mountainous area. The output power performance, the passive power control in high wind speed, the performance improvement by the variable speed operation and the quality of power are discussed. As the results, it is demonstrated the power control by a passive pitch-flap mechanism, the suppressing effects for the fluctuating moments on the blade root and the characteristics of the variable speed generating system. Some flow patterns on the blade are shown.
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Jia, Xiuxian, Yu Du, and Kunmin Zhao. "Vibration Control of Variable Thickness Plates With Embedded Acoustic Black Holes and Dynamic Vibration Absorbers." In ASME 2015 Noise Control and Acoustics Division Conference at InterNoise 2015. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ncad2015-5914.
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In the past decade, plate-like structures embedded with one or more acoustic black hole (ABH) features have been developed as a promising passive approach for structural sound and vibration control. In this study, the concept of combining dynamic vibration absorbers (DVAs) and the ABH effect is proposed to further improve the vibration control effectiveness of a variable thickness plate. A finite element (FE) model is developed to analyze the vibration response of a plate embedded with both ABHs and DVAs under point force excitations. To demonstrate the effectiveness of different vibration control approaches, the vibration responses of plates of uniform thickness, variable thickness embedded with ABH features, variable thickness embedded with both ABH features and damping layers, and variable thickness embedded with both ABH features and DVAs are compared experimentally. It is shown that, in the frequency range considered in the current study which is up to 6.4 kHz, the uniform plate presents high average velocity response level. On the other hand, although 11.5% lighter, the variable thickness plate integrated with both ABH and DVA features results in the lowest response level. Results in this study demonstrate the potential of combing DVAs and ABHs together as an effective lightweight noise and vibration control approach.
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Vasper, Adam C., and Ingvild Bakke Fagereng. "Temperature Specifications for CCUS Completions Equipment: Steady-State and Transient Thermal Simulations." In SPE EuropEC - Europe Energy Conference featured at the 83rd EAGE Annual Conference & Exhibition. SPE, 2022. http://dx.doi.org/10.2118/209637-ms.
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Abstract Different simulated injection scenarios can significantly cool carbon capture utilization and storage (CCUS)wells. Cases representing different scenarios were modeled to help determine appropriate temperature specifications for completions equipment in CCUS wells. Depleted reservoirs, in particular gas reservoirs, will not support a static column of liquid or dense-phase CO2 to surface at the initial reservoir pressure. During injection, unless there is significant friction or backpressure, the upper part of the well will be at low pressure, with CO2 in the gas phase. Injected, liquid CO2 will depressurize across the wellhead choke, or the upper tubing, resulting in significant cooling as the saturation curve is reached and the CO2 starts flashing. For steady-state injection across a narrow range of rates, a tapered or narrow completion string can be designed that provides sufficient friction pressure to keep the CO2 in the liquid phase. A portfolio or set of wells, potentially with different tubing sizes, will give more flexibility for managing injection rates. Transient scenarios such as injection startup or shutdown cause rapid changes in rate and can consequently induce severe thermal shocks. These cannot be completely prevented using only friction or passive downhole devices. Many completion options have been proposed to provide flexibility for injection rate changes and/or reservoir pressure increases. These include concentric or dual strings providing multiple flow paths with different flow areas and hence friction, downhole passive chokes, backpressure control valves, surface-operated downhole flow control valves, and various combinations of these and other technologies. Currently, the only methods to eliminate all the scenarios consideredmay be (active) backpressure control and surface-controlled downhole flow control valves. Whereas the transient effects are most severe in depleted reservoirs, they are also shown to occur in reservoirs approaching hydrostatic pressure. The most important component in the completion string is arguably the subsurface safety valve (SSSV). API 14B specifies a maximum leak rate for the closed SSSV. Following a blowout or depressurization event, a leak of high-pressure, liquid CO2 from below the SSSV to low-pressure, gas-phase CO2 above will cause localized cooling at the SSSV, in addition to that caused by the initial depressurization condition. Modeling included simulations of blowout and subsequent SSSV leakage phases for different periods of injection and hence reservoir cooldown. To quantify these effects, the work considered temperatures in the different radial sections of the well versus time and depth. Sensitivities on annulus fluid, reservoir properties including pressure and permeability, the rate of mass transfer between phases, and other variables were also investigated. Modeling was performed using a commercial dynamic multiphase flow simulator.
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Gershuni, A. N., A. P. Nishchik, E. N. Pis'mennyi, V. G. Razumovskiy, and I. L. Pioro. "On Features of Thermal Design of Passive Evaporation-and-Condensation Systems of Reactor Thermal Shielding." In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-30133.
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Further development of nuclear engineering is inseparably linked with the requirement of vast application of the passive systems of heat removal running without human intervention. Creation of such systems is impossible, if only conventional engineering solutions are used. As known, to prevent propagation of the fission products into the environment there are three safety barriers. To provide operation of the third safety barrier (containment shell), in particular, of the reactor cavities both in operational and emergency modes a passive evaporation-and-condensation (EC) system of heat removal is proposed. The features of thermal design of the EC systems for thermal shielding of the reactor cavities are considered. They make it possible to determine the optimal main design variables of the EC systems and prove reasonability and efficiency of their application. The performed study validates engineering feasibility of an efficient EC system for thermal shielding of the reactor equipment.
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Scott, James N., and Wilbur L. Hankey. "Navier-Stokes Solutions of Unsteady Flow in a Compressor Rotor." In ASME 1986 International Gas Turbine Conference and Exhibit. American Society of Mechanical Engineers, 1986. http://dx.doi.org/10.1115/86-gt-226.
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In order to achieve more accurate predictions of unsteady flow in a transonic compressor rotor an existing numerical approach has been modified by incorporating a turbulence model. The computations are performed by solving the complete time-dependent compressible Navier-Stokes equations using MacCormack’s explicit finite difference algorithm. These equations are solved for the flow through two adjacent rotor blades at a stream surface near the blade tip subjected to the wakes emitted from upstream stators. At this radial location the flow enters the blade passage at an absolute Mach number of 0.66. The high blade curvature at this radial location produces a large region of separated flow on the suction surface with laminar flow. To more accurately resolve the features of this flow separation the Baldwin-Lomax algebraic eddy-viscosity turbulence model is incorporated into the numerical procedure in regions, near the blade surface. The unsteady flow features are represented at the inflow boundary through the use of characteristic variables involving the upstream and downstream running Riemann invariants and the entropy variation expressed in terms of the total pressure profile. At the outflow boundary the concept of a “second throat” or choke point is implemented in conjunction with supersonic outflow conditions. The results are compared with numerical results obtained without the use of a turbulence model (laminar) for a single blade passage. Improved agreement with limited experimental data is also noted.