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Статті в журналах з теми "Melting term"
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Zhou, Jian, Jing Li, Guoqiang Liu, Tao Yang, and Yongli Zhao. "Long-Term Performance and Deicing Effect of Sustained-Release Snow Melting Asphalt Mixture." Advances in Civil Engineering 2019 (June 11, 2019): 1–12. http://dx.doi.org/10.1155/2019/1940692.
Повний текст джерелаАнотація:
To accelerate snow and ice melting, traditional chloride-based salts are spreaded on asphalt pavement surface, causing serious environmental pollution and infrastructure corrosion. For sustained-release snow melting asphalt mixture, the snow melting agent of Mafilon is directly added to asphalt mixture by replacing partial mineral powder to develop a new type of functional asphalt mixture. In this paper, through the Marshall test, immersion Marshall test, rutting test, trabecular bending test, and Cantabro test, the effects of Mafilon addition on asphalt pavement performance is systematically analysed. Meanwhile, salt precipitation rate is measured by conductimetry to estimate effective deicing period of the pavement. Finally, a new experimental device is designed to quantitatively evaluate snow melting effect of sustained-release snow melting asphalt pavement. The experimental results show that replacing 70% of the mineral powder with Mafilon by volume can achieve satisfactory snow melting effect without affecting usability of asphalt pavement.
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Abdelaziz, Yasser A., F. M. Megahed, and M. M. Abdel-Aal. "LONG-TERM STABILITY OF Co-C AND Pd-C EUTECTIC FIXED POINTS FOR THERMOCOUPLES CALIBRATION." Measuring Equipment and Metrology 82, no. 1 (2021): 26–29. http://dx.doi.org/10.23939/istcmtm2021.01.026.
Повний текст джерелаАнотація:
Eutectic fixed points are close to becoming a reference for high temperatures calibration, especially as the new International Temperature Scale (ITS) approach to issue after the re-definition of the Kelvin unit. In this work the long-term stability of Co-C and Pd-C eutectic fixed points were investigated using NIS-Egypt facilities. The eutectic points were measured using Pt/Pd thermocouple. The total exposure to the Co-C and Pd-C melting temperature was about 200 h for the fixed-point cell and 150 h for the Pt/Pd thermocouple. The emfs of the thermocouple at the melting point were observed to drift by about 0.25 °C. Realization uncertainties were estimated to be ~ 0.446 ◦C for Co-C and ~0.742 for Pd-C (k = 2). Results show that Co-C and Pd-C eutectic cells can exhibit long term stability.
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Mira, Nadarajan, Liu, González-Benito, and Pritchard. "Lipid Thermal Fingerprints of Long-term Stored Seeds of Brassicaceae." Plants 8, no. 10 (October 14, 2019): 414. http://dx.doi.org/10.3390/plants8100414.
Повний текст джерелаАнотація:
Thermal fingerprints for seeds of 20 crop wild relatives of Brassicaceae stored for 8 to 44 years at the Plant Germplasm Bank—Universidad Politécnica de Madrid and the Royal Botanic Gardens, Kew’s Millennium Seed Bank—were generated using differential scanning calorimetry (DSC) and analyzed in relation to storage stability. Relatively poor storing oily seeds at −20 °C tended to have lipids with crystallization and melting transitions spread over a wide temperature range (c. 40 °C) that spanned the storage temperature, plus a melting end temperature of around 15 °C. We postulated that in dry storage, the variable longevity in Brassicaceae seeds could be associated with the presence of a metastable lipid phase at the temperature at which they are being stored. Consistent with that, when high-quality seed samples of various species were assessed after banking at −5 to −10 °C for c. 40 years, melting end temperatures were observed to be much lower (c. 0 to −30 °C) and multiple lipid phases did not occur at the storage temperature. We conclude that multiple features of the seed lipid thermal fingerprint could be used as biophysical markers to predict potential poor performance of oily seeds during long-term, decadal storage.
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Lysenko, N. O., O. O. Pedash, V. V. Klochykhin, and P. O. Kasai. "Influence of long-term soaking on the structure and properties of IN625 alloy samples made by selective laser melting." Paton Welding Journal 2022, no. 1 (January 28, 2022): 41–47. http://dx.doi.org/10.37434/tpwj2022.01.08.
Повний текст джерела
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Dolan, Brenda, Steven A. Rutledge, S. Lim, V. Chandrasekar, and M. Thurai. "A Robust C-Band Hydrometeor Identification Algorithm and Application to a Long-Term Polarimetric Radar Dataset." Journal of Applied Meteorology and Climatology 52, no. 9 (September 2013): 2162–86. http://dx.doi.org/10.1175/jamc-d-12-0275.1.
Повний текст джерелаАнотація:
AbstractA new 10-category, polarimetric-based hydrometeor identification algorithm (HID) for C band is developed from theoretical scattering simulations including wet snow, hail, and big drops/melting hail. The HID is applied to data from seven wet seasons in Darwin, Australia, using the polarimetric C-band (C-POL) radar, to investigate microphysical differences between monsoon and break periods. Scattering simulations reveal significant Mie effects with large hail (diameter > 1.5 cm), with reduced reflectivity and enhanced differential reflectivity Zdr and specific differential phase Kdp relative to those associated with S band. Wet snow is found to be associated with greatly depreciated correlation coefficient ρhv and moderate values of Zdr. It is noted that large oblate liquid drops can produce the same electromagnetic signatures at C band as melting hail falling quasi stably, resulting in some ambiguity in the HID retrievals. Application of the new HID to seven seasons of C-POL data reveals that hail and big drops/melting hail occur much more frequently during break periods than during monsoon periods. Break periods have a high frequency of vertically aligned ice above 12 km, suggesting the presence of strong electric fields. Reflectivity and mean drop diameter D0 statistics demonstrate that convective areas in both monsoon and break periods may have robust coalescence or melting precipitation ice processes, leading to enhanced reflectivity and broader distributions of D0. Conversely, for stratiform regions in both regimes, mean reflectivity decreases below the melting level, indicative of evaporative processes. Break periods also have larger ice water path fractions, indicating substantial mixed-phase precipitation generation as compared with monsoonal periods. In monsoon periods, a larger percentage of precipitation is produced through warm-rain processes.
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Winther, Jan-Gunnar. "Short- and Long-Term Variability of Snow Albedo." Hydrology Research 24, no. 2-3 (April 1, 1993): 199–212. http://dx.doi.org/10.2166/nh.1993.0022.
Повний текст джерелаАнотація:
The progress of snow albedo for the 1991 winter from Helligdagshaugen research site, Norway, is presented. The temporal reduction of albedo decreases as the snow undergoes a process of metamorphosis, as long as the snow depth is large enough to prevent absorption of solar radiation by the underlying terrain. Later, as the snow depth becomes less than about 10 cm and the area of bare patches grows, there is an increase in the temporal rate of reduction in albedo. An accumulated daily maximum temperature index is shown to be a good predictor of both the long-term development of the snow albedo and the daily mean albedo. The actual albedo deviates from the predicted long-term albedo due to variable meteorological conditions of which solar radiation is the most important one. Solar radiation and snow albedo are negatively correlated. Linear regression is performed for a winter period with no melting and for two distinct melting periods. Snow albedo was first determined as a function of temperature index alone. An improved accuracy of 2-6 per cent in estimated snow albedo was obtained when solar radiation was included. Very similar regression coefficients were found for two different periods.
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Karelin, V. A., and Vl V. Salomatov. "A review of modern numerical and analytical models of heat transfer in a dielectric layer during melting due to microwave radiation." Journal of Physics: Conference Series 2119, no. 1 (December 1, 2021): 012074. http://dx.doi.org/10.1088/1742-6596/2119/1/012074.
Повний текст джерелаАнотація:
Abstract In this work, numerical and analytical solutions of heat transfer in a dielectric layer during melting in the microwave field were considered. We considered solutions, where the source term was obtained based on the solution of Maxwell equation, as well as using the Lambert law. The conditions applicable for analytical solutions, allowing the parametric analysis, are determined. The areas of application of the technology of microwave melting of dielectrics, in particular with melting ice on water, defrosting products, etc., were also considered.
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Ospennikova, O. G., P. G. Min, A. M. Rogalev, and V. E. Vadeev. "On the chemical composition, structure and mechanical properties of alloy EP648 fabricated by deformation, project die casting and selective laser melting." Voprosy Materialovedeniya, no. 1(101) (May 3, 2020): 44–54. http://dx.doi.org/10.22349/1994-6716-2020-101-1-44-54.
Повний текст джерелаАнотація:
The paper studies chemical composition, structure and mechanical properties of the heat-resistant nickel EP648 alloy obtained by deformation, die project casting and selective laser melting. It is shown that the deformed material is characterized by low porosity, high impact strength and ductility, the cast material has large grains, high long-term strength and low-cycle fatigue. The material obtained by selective laser melting is characterized by an increased content of oxygen and nitrogen, fine-grain structure with large variation in grain size strongly expressed and heredity, and also high short-term strength.
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Warner, Roland C., and W. Κ. Budd. "Modelling the long-term response of the Antarctic ice sheet to global warming." Annals of Glaciology 27 (1998): 161–68. http://dx.doi.org/10.3189/1998aog27-1-161-168.
Повний текст джерелаАнотація:
The primary effects of global warming on the Antarctic ice sheet can involve increases in surface melt for limited areas at lower elevations, increases in net accumulation, and increased basal melting under floating ice. For moderate global wanning, resulting in ocean temperature increases of a few °C, the large- increase in basal melting can become the dominant factor in the long-term response of the ice sheet. The results from ice-sheet modelling show that the increased basal melt rates lead to a reduction of the ice shelves, increased strain rates and flow at the grounding lines, then thinning and floating of the marine ice sheets, with consequential further basal melting. The mass loss from basal melting is counteracted to some extent by the increased accumulation, but in the long term the area of ice cover decreases, particularly in West Antarctica, and the mass loss can dominate. The ice-sheet ice-shelf model of Budd and others (1994) with 20 km resolution has been modified and used to carry out a number of sensitivity studies of the long-term response of the ice sheet to prescribed amounts of global warming. The changes in the ice sheet are computed out to near-equilibrium, but most of the changes take place with in the first lew thousand years. For a global mean temperature increase of 3°C with an ice-shelf basal melt rate of 5 m a−1 the ice shelves disappear with in the first few hundred years, and the marine-based parts of the ice sheet thin and retreat. By 2000 years the West Antarctic region is reduced to a number of small, isolated ice caps based on the bedrock regions which are near or above sea level. This allows the warmer surface ocean water to circulate through the archipelago in summer, causing a large change to the local climate of the region.
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Elgafy, Ahmed, Osama Mesalhy, and Khalid Lafdi. "Numerical and Experimental Investigations of Melting and Solidification Processes of High Melting Point PCM in a Cylindrical Enclosure." Journal of Heat Transfer 126, no. 5 (October 1, 2004): 869–75. http://dx.doi.org/10.1115/1.1800492.
Повний текст джерелаАнотація:
In the present work, a computational model is developed to investigate and predict the thermal performance of high melting point phase change material during its melting and solidification processes within a cylindrical enclosure. In this model the phases are assumed to be homogeneous and a source term, S, arises from melting or solidification process is considered as a function of the latent heat of fusion and the liquid phase fraction. The numerical model is verified with a test problem and an experiment is performed to assess the validity of the assumptions of it and an agreement between experimental and computational results is achieved. The findings show that utilizing of PCMs of high melting points is a promising technique especially in space applications.
Дисертації з теми "Melting term"
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Elkandari, Bader M. H. M. "Excimer laser surface melting treatment on 7075-T6 aluminium alloy for improved corrosion resistance." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/excimer-laser-surface-melting-treatment-on-7075t6-aluminium-alloy-for-improved-corrosion-resistance(c2da3b82-eeb5-4eae-a1dc-e4aefba18c62).html.
Повний текст джерелаАнотація:
High strength 7xxx aluminium alloys are used extensively in the aerospace industry because the alloys offer excellent mechanical properties. Unfortunately, the alloys can suffer localised corrosion due to the presence of large intermetallic particles at the alloy surface that are aligned in the rolling direction. Laser surface melting (LSM) techniques offer the potential to reduce and/or to eliminate the intermetallic phases from the surface of the alloy without affecting the alloy matrix.The present study concerns the application of LSM using an excimer laser to enhance the corrosion resistance of AA 7075-T6 aluminium alloy. The initial stage of the project was aimed at optimising the laser conditions for production of a uniform microstructure, with the increase in the corrosion resistance of the alloy being determined by potentiodynamic polarization measurements in sodium chloride solution. Low and high laser energy densities were used with a different number of pulses per unit area to treat the alloy surface, which were achieved by changing both the laser fluence and the pulse repetition frequency. A laser fluence of 3.3 J/cm2 with 80 pulses was subsequently selected as the optimum condition to treat the surface of the alloy. The composition and microstructure of the alloy before and after LSM treatment, and following corrosion tests, were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD).After the laser treatment, the surface and the cross-sections of the alloy showed a significant reduction in the number of large intermetallic particles and a relatively homogenous melted layer was generated that provided significant improvement in the resistance of the alloy against corrosion, as assessed by several corrosion test methods, including exfoliation corrosion (EXCO) tests. However, delamination of the melted layer was observed after extended testing in the EXCO solution which is possibly related to the formation of bands of fine magnesium and zinc-rich precipitates within the melted layer. Therefore, anodising in sulphuric acid was applied to the LSM alloy, in order to further increase the corrosion resistance and to protect the laser treated layer from delamination by generating a thin oxide film over the LSM layer. The results revealed that the anodic treatment increased the resistance of the alloy to exfoliation attack.
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Боянівський, Владислав Петрович. "Підвищення ефективності печей для переплавки алюмінієвого брухту". Master's thesis, Київ, 2018. https://ela.kpi.ua/handle/123456789/24376.
Повний текст джерелаАнотація:
Магістерська дисертація на тему «Підвищення ефективності печей для переплавки алюмінієвого брухту»: 104 с., 35 рис., 12 табл., 4 додатки, 15 джерел.
Об’єкт дослідження – піч для переплавки алюмінієвого брухту.
Мета роботи – підвищення енергетичної ефективності та удосконалення конструкції печей для переплавки алюмінієвого брухту.
Проаналізовані основні способи підвищення енергетичної ефективності.
Наведені результати розрахунків енергетичної ефективності печі місткістю 6 т, потужністю 600 кВт, для переплвки алюмінієвого брухту.
Показано, що за рахунок зменшення терміну відкриття форкамер знизилися витрати підведеної теплоти в печі на 45 %, а за рахунок зміни теплоізоляційних шарів - на 21 %.
Підібрані газоспалюючі пристрої – пальники типу ГПП-5 та наведена схема їх розміщення в боковій передній стінці печі.
Виконані розрахунки енергетичної та економічної ефективності переводу печі з електричного нагріву на газовий, при цьому для газового нагріву витрати підведеної теплоти зменшуються на 9 – 10 % порівняно з електричним.
Розрахунками визначено, що використання газового нагріву порівняно з електричним економічно більш ефективно, оскільки витрати на природний газ в циклі плавки для модернізованої печі потужністю 600 кВт зменшуються приблизно на 10 %.
Розроблена конструкція печі з нахиленим склепінням, для якої порівняно з традиційним зменшується термін плавки у середньому на 11 %, а ККД підвищується на 7 %.
Для утилізації теплоти димових газів обрано односторонньо-голчастий металевий рекуператор для підігріву дуттьового повітря з площею поверхні нагріву 12 м2.
В результаті встановлення рекуператора температура димових газів знижується від 800 °С до 390 °С, при цьому температура дуттьового повітря підвищується від 20 °С до 350 °С. Величина економії палива складає 16,9 %.
На базі програмного забезпечення Solid Works побудовані геометричні моделі багатошарових стінок печі та отримані результати розподілу температурних полів по товщині огороджувальних конструкцій. Наведені результати співставні з експериментальними даними отриманими на реальних печах.
Передбачені заходи з безпечної і комфортної роботи в приміщенні науково-дослідної лабораторії та заходи з пожежної безпеки та безпеки в надзвичайних ситуаціях.
Розроблено стартап-проект за шаблоном Business Model Canvas.Master's dissertation on "Improving the efficiency of furnaces for aluminum scrap remelting": 104 p., 35 f., 12 tables, 4 applications, 15 sources. The object of the study is an oven for aluminum scrap remelting. The purpose of the work is to increase energy efficiency and improve the design of furnaces for aluminum scrap remelting. Analyzed the main ways of improving energy efficiency. Presented the results of calculations of the energy efficiency of a 6-ton capacity kiln with a capacity of 600 kW for the remelting of aluminum scrap. It is shown that due to reduction of the opening time of the firebox, the cost of the supplied heat in the furnace decreased by 45% and due to the change of the thermal insulation layers - by 21%. Selected gas-fired devices - burners type GPP-5 and the scheme of their placement in the side of the front wall of the furnace. The calculations of the energy and economic efficiency of the furnace conversion from the electric heating to the gas have been performed, while for the gas heating the costs of the supplied heat are reduced by 9 - 10% in comparison with the electric one. Calculations have shown that the use of gas heating compared to electric is economically more efficient, since the cost of natural gas in the melt cycle for a 600 kV upgraded furnace decreases by about 10%. Developed the furnace design with an inclined vault for which the average melting time decreases by 11% compared to the traditional one, and the efficiency increases by 7%. For utilization of flue gases heat was chosen one-sided-needle metal recuperator for heating of blown air with the area of the heating surface 12 m2. As a result of the installation of the recuperator, the temperature of the flue gases is reduced from 800 °C to 390 °C, while the ambient air temperature rises from 20 ° C to 350 C. The amount of fuel savings is 16.9 %. Based on the Solid Works software, constructed geometric models of the multilayer walls of the furnace and obtained the results of the distribution of temperature fields along the thickness of the enclosing structures. The presented results are comparable to the experimental data obtained on real furnaces. Made provision for safe and comfortable work in the premises of a research laboratory and fire and safety measures in emergencies. A startup project based on the Business Model Canvas template has been developed.
Магистерская диссертация на тему «Повышение эффективности печей для переплавки алюминиевого лома» 104 с., 35 рис., 12 табл., 4 приложения, 15 источников. Объект исследования - печь для переплавки алюминиевого лома. Цель работы - повышение энергетической эффективности и совершенствование конструкции печей для переплавки алюминиевого лома. Проанализированы основные способы повышения энергетической эффективности. Приведены результаты расчетов энергетической эффективности печи вместимостью 6 т, мощностью 600 кВт, для переплавки алюминиевого лома. Показано, что за счет уменьшения срока открытия форкамер снизились расходы подведенной теплоты в печи на 45%, а за счет изменения теплоизоляционных слоев - на 21%. Выбраны газосжигающие устройства - горелки типа ГПП-5 и приведена схема их размещения в боковой передней стенке печи. Выполнены расчеты энергетической и экономической эффективности перевода печи с электрического нагрева на газовый, при этом для газового нагрева расходы подведенной теплоты уменьшаются на 9 - 10% по сравнению с электрическим. Расчетами установлено, что использование газового нагрева по сравнению с электрическим экономически более эффективно, поскольку затраты на природный газ в цикле плавки для модернизированной печи мощностью 600 кВт уменьшаются примерно на 10%. Разработана конструкция печи с наклонным сводом, для которой по сравнению с традиционным уменьшается срок плавки в среднем на 11%, а КПД повышается на 7%. Для утилизации теплоты дымовых газов выбран односторонне-игольчатый металлический рекуператор для подогрева дутьевого воздуха с площадью поверхности нагрева 12 м2. В результате установки рекуператора температура дымовых газов снижается от 800 °С до 390 °С, при этом температура дутьевого воздуха повышается от 20 °С до 350 °С. Величина экономии топлива составляет 16,9%. На базе программного обеспечения Solid Works построены геометрические модели многослойных стенок печи и получены результаты распределения температурных полей по толщине ограждающих конструкций. Приведены результаты сопоставимы с экспериментальными данными полученными на реальных печах. Предусмотрены меры по безопасной и комфортной работе в помещении научно-исследовательской лаборатории. Разработан стартап-проект по шаблону Business Model Canvas.
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Berlin, Katja. "In-situ transmission electron microscopy on high-temperature phase transitions of Ge-Sb-Te alloys." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19219.
Повний текст джерелаАнотація:
Das Hochtemperaturverhalten beeinflusst viele verschiedene Prozesse von der Materialherstellung bis hin zur technologischen Anwendung. In-situ Transmissionselektronenmikroskopie (TEM) bietet die Möglichkeit, die atomaren Prozesse während struktureller Phasenübergänge direkt und in Realzeit zu beobachten. In dieser Arbeit wurde in-situ TEM angewendet, um die Reversibilität des Schmelz- und Kristallisationsprozesses, sowie das anisotropen Sublimationsverhaltens von Ge-Sb-Te (GST) Dünnschichten zu untersuchen. Die gezielte Probenpräparation für die erfolgreiche Beobachtung der Hochtemperatur-Phasenübergänge wird hervorgehoben. Die notwendige Einkapselung für die Beobachtung der Flüssigphase unter Vakuumbedingungen und die erforderliche sauberer Oberfläche für den Sublimationsprozess werden detailliert beschrieben. Außerdem wird die Elektronenenergieverlustspektroskopie eingesetzt um die lokale chemische Zusammensetzung vor und nach den Übergängen zu bestimmen. Die Untersuchung der Grenzflächenstruktur und Dynamik sowohl beim Phasenübergang fest-flüssig als auch flüssig-fest zeigt Unterschiede zwischen den beiden Vorgängen. Die trigonale Phase von GST weist beim Schmelzen eine teilweise geordnete Übergangszone an der fest-flüssig-Grenzfläche auf, während ein solcher Zwischenzustand bei der Erstarrung nicht entsteht. Außerdem läuft der Schmelzvorgang zeitlich linear ab, während die Kristallisation durch eine Wurzelabhängigkeit von der Zeit mit überlagerter Start-Stopp-Bewegung beschrieben werden kann. Der Einfluss der Substrat-Grenzfläche wird diskutiert und die Oberflächenenergie von GST bestimmt. Die anisotrope Dynamik führt beim Phasenübergang fest-gasförmig der kubischen Phase von GST zur Ausbildung stabiler {111} Facetten. Dies erfolgt über die Bildung von Kinken und Stufen auf stabilen Terrassen. Die Keimbildungsrate und die bevorzugten Keimbildungsorte der Kinken wurden identifiziert und stimmen mit den Voraussagen des Terrassen-Stufen-Kinken Modells überein.High-temperature behavior influence many different processes ranging from material processing to device applications. In-situ transmission electron microscopy (TEM) provides the means for direct observation of atomic processes during structural phase transitions in real time. In this thesis, in-situ TEM is applied to investigate the reversibility of the melting and solidification processes as well as the anisotropic sublimation behavior of Ge-Sb-Te (GST) thin films. The purposeful sample preparation for the successful observation of the high-temperature phase transitions is emphasized. The required encapsulation for the observation of the liquid phase inside the vacuum conditions and the necessary clean surface for sublimation process are discussed in detail. Additionally electron energy-loss spectroscopy in the TEM is used to determine the local chemical composition before and after the phase transitions. The analysis of the interface structure and dynamic during the solid-to-liquid as well as the liquid-to-solid phase transition shows differences between both processes. The trigonal phase of GST exhibits a partially ordered transition zone at the solid-liquid interface during melting while such an intermediate state does not form during solidification. Additionally the melting process proceeds with linear dependence on time, whereas crystallization can be described as having a square-root time-dependency featuring a superimposed start-stop motion. The influence of the interface is addressed and the surface energies of GST are determined. The anisotropic dynamic of the solid-to-gas phase transition of the cubic GST phase leads to the formation of stable {111} facets. This happens via kink and step nucleation on stable terraces. The nucleation rates and the preferred kink nucleation sites are identified and are in accordance with the predictions of terrace-step-kink model.
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Simonelli, Marco. "Microstructure evolution and mechanical properties of selective laser melted Ti-6Al-4V." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/15070.
Повний текст джерелаАнотація:
Selective laser melting (SLM) has been shown to be an attractive manufacturing route for the production of ??/?? titanium alloys, and in particular Ti-6Al-4V. A thorough understanding of the relationship between the process, microstructure and mechanical properties of the components produced by this technology is however crucial for the establishment of SLM as an alternative manufacturing route. The purpose of the present study is thus to determine the microstructure evolution, crystallographic texture and the mechanical properties of SLM Ti-6Al-4V. The effect of several processing parameters on the density and the microstructure of the SLM samples were initially investigated. It was found that different sets of process parameters can be used to fabricate near fully dense components. It was found that the samples built using the optimised process window consist exclusively of ????? martensitic phase precipitated from prior ?? columnar grains. It was observed that the ?? grain solidification is influenced by the laser scan strategy and that the ?? phase has a strong <001> texture along its grain growth direction. The ????? martensitic laths that originate from the parent ?? grains precipitate according to the Burgers orientation relationship. It was found that ????? laths clusters from the same ?? grain have a specific misorientation that minimise the local shape strain. Texture inheritance across successive deposited layers was also observed and discussed in relation to various variant selection mechanisms. The mechanical properties of as-built and stress relieved SLM Ti-6Al-4V built using the same optimised process parameters were then investigated. It was found that the build orientation affects the tensile properties, and in particular the ductility of the samples. Samples built perpendicularly to the building direction showed higher ductility than those built in the vertical orientation. It was also observed that a stress relief heat treatment was beneficial to the mechanical properties of SLM Ti-6Al-4V. The ductility of the stress relieved samples was indeed higher than those found in the as-built condition. It was found that the predominant fracture mode during tensile testing is inter-granular. In terms of high-cycle fatigue, it was found that SLM Ti-6Al-4V is comparable to HIPed cast Ti-6Al-4V but it has a significantly lower fatigue resistance than that of wrought and annealed alloys. It was observed that porosity and the elongated prior ?? grain boundaries decrease substantially the fatigue life of the components. Cracks propagate either by fatigue striation or ductile tearing mechanisms. Using alternative laser scan strategies it was possible to control the microstructure of the as-built samples. It was observed that the laser scan vector length influences several microstructural features, such as the width of the prior ?? grains and the thickness of the ????? laths. It was found that re-melting the same layer has instead little effect on the microstructure. A novel laser scan strategy characterised by much lower laser power and scan speed than those typically used in SLM enabled finally to fabricate SLM Ti-6Al-4V with a microstructure close to that of conventionally manufactured Ti-6Al-4V. This study investigates for the first time the crystallographic texture evolution in Ti-6Al-4V manufactured by SLM. Further, this research presents for the first time the effect of the characteristic microstructure and crystallographic texture on the mechanical properties and fracture of SLM Ti-6Al-4V. Lastly, for the first time this research shows examples of microstructural control during the SLM fabrication of the same alloy using long laser dwell times.
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Wei, Lung-Chih, and 韋志龍. "Crystallization Kinetics and Melting Behavior of PEEK and Influence of Transcrystallinity on the Long-Term Tensile-Tensile Property of AS4/PEEK Composites." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/90490581219301463049.
Повний текст джерелаАнотація:
碩士國立中山大學
材料科學研究所
89
Crystallization kinetics and melting behavior of PEEK were studied by differential scanning calriometry (DSC) and modulated differential scanning calriometry (MDSC). The isothermal crystallization was performed in DSC between 290 and 320°C. The Avrami constants (n1, n2) and the level off time were determined from the Avrami analysis. The n1 values varied from 1.50 to 2.98, and the n2 values were between 0.52 and 1.37. The minimum induction time required for the occurrence of double melting peaks was obtained by increasing the isothermal crystallization time in a interval per minute. It was found that the minimum time was always longer than the level off time, which cannot be used as the delimitation for the occurrence of single or double melting peaks. To study the melting behavior and the mechanisms of double melting peaks, the samples after melting at 400°C for 15 min were crystallized isothermally between 200 and 320°C for 10 or 60 min, and then they were heated to 380°C at 10 or 2 °C/min, respectively. From the MDSC results of crystallization temperatures between 280 and 310°C, it is found that two different morphologies and melting-recrystallization phenomenon coexisted. As the isothermal crystallization temperature increased from 280 to 310°C, the contribution of melting-recrystallization to the upper melting peak gradually decreased. In the case of 320°C, the mechanisms of double melting peaks were dominated by two different morphologies only. Quasi-isotropic composites in the stacking sequence of [0/±45/90]2s were fabricated by a modified diaphragm forming apparatus. Three different processing conditions were used to prepare AS4/PEEK composites with the same crystallinity but different transcrystallinity. The morphology before and after the long-term tensile-tensile tests was observed by means of scanning electron microscope. The transcrystallinity has no significant effect on the short-term tensile test. This was due to the fibers in the 0° plies of [0/±45/90]2S laminates dominated the failure at high stress for the short-term tensile test. However, as the transcrystallinity increased, the failure cycles for the long-term tensile test became longer. This expressed that the delay of damage initiation in the 90° and ±45° plies of [0/±45/90]2s led to a longer failure cycles in the long-term tensile tests.
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Di, Pierro Michele. "Optimization of force fields for molecular dynamics." Thesis, 2014. http://hdl.handle.net/2152/28355.
Повний текст джерелаАнотація:
A technology for optimization of potential parameters from condensed phase simulations (POP) is discussed and illustrated. It is based on direct calculations of the derivatives of macroscopic observables with respect to the potential parameters. The derivatives are used in a local minimization scheme, comparing simulated and experimental data. In particular, we show that the Newton Trust-Region protocol allows for accurate and robust optimization. POP is illustrated for a toy problem of alanine dipeptide and is applied to folding of the peptide WAAAH. The helix fraction is highly sensitive to the potential parameters while the slope of the melting curve is not. The sensitivity variations make it difficult to satisfy both observations simultaneously. We conjecture that there is no set of parameters that reproduces experimental melting curves of short peptides that are modeled with the usual functional form of a force field. We then apply the newly developed technology to study the liquid mixture of tert-butanol and water. We are able to obtain, after 4 iterations, the correct phase behavior and accurately predict the value of the Kirkwood Buff (KB) integrals. We further illustrate that a potential that is determined solely by KB information, or the pair correlation function, is not necessarily unique.text
Книги з теми "Melting term"
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McElroy, Michael B. Energy and Climate. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780190490331.001.0001.
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The climate of our planet is changing at a rate unprecedented in recent human history. The energy absorbed from the sun exceeds what is returned to space. The planet as a whole is gaining energy. The heat content of the ocean is increasing; the surface and atmosphere are warming; mid-latitude glaciers are melting; sea level is rising. The Arctic Ocean is losing its ice cover. None of these assertions are based on theory but on hard scientific fact. Given the science-heavy nature of climate change, debates and discussions have not played as big a role in the public sphere as they should, and instead are relegated to often misinformed political discussions and inaccessible scientific conferences. Michael B. McElroy, an eminent Harvard scholar of environmental studies, combines both his research chops and pedagogical expertise to present a book that will appeal to the lay reader but still be grounded in scientific fact. In Energy and Climate: Vision for the Future, McElroy provides a broad and comprehensive introduction to the issue of energy and climate change intended to be accessible for the general reader. The book includes chapters on energy basics, a discussion of the contemporary energy systems of the US and China, and two chapters that engage the debate regarding climate change. The perspective is global but with a specific focus on the US and China recognizing the critical role these countries must play in addressing the challenge of global climate change. The book concludes with a discussion of initiatives now underway to at least reduce the rate of increase of greenhouse gas emissions, together with a vision for a low carbon energy future that could in principle minimize the long-term impact of energy systems on global climate.
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Omstedt, Anders. The Development of Climate Science of the Baltic Sea Region. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.654.
Повний текст джерелаАнотація:
Dramatic climate changes have occurred in the Baltic Sea region caused by changes in orbital movement in the earth–sun system and the melting of the Fennoscandian Ice Sheet. Added to these longer-term changes, changes have occurred at all timescales, caused mainly by variations in large-scale atmospheric pressure systems due to competition between the meandering midlatitude low-pressure systems and high-pressure systems. Here we follow the development of climate science of the Baltic Sea from when observations began in the 18th century to the early 21st century. The question of why the water level is sinking around the Baltic Sea coasts could not be answered until the ideas of postglacial uplift and the thermal history of the earth were better understood in the 19th century and periodic behavior in climate related time series attracted scientific interest. Herring and sardine fishing successes and failures have led to investigations of fishery and climate change and to the realization that fisheries themselves have strongly negative effects on the marine environment, calling for international assessment efforts. Scientists later introduced the concept of regime shifts when interpreting their data, attributing these to various causes. The increasing amount of anoxic deep water in the Baltic Sea and eutrophication have prompted debate about what is natural and what is anthropogenic, and the scientific outcome of these debates now forms the basis of international management efforts to reduce nutrient leakage from land. The observed increase in atmospheric CO2 and its effects on global warming have focused the climate debate on trends and generated a series of international and regional assessments and research programs that have greatly improved our understanding of climate and environmental changes, bolstering the efforts of earth system science, in which both climate and environmental factors are analyzed together.Major achievements of past centuries have included developing and organizing regular observation and monitoring programs. The free availability of data sets has supported the development of more accurate forcing functions for Baltic Sea models and made it possible to better understand and model the Baltic Sea–North Sea system, including the development of coupled land–sea–atmosphere models. Most indirect and direct observations of the climate find great variability and stochastic behavior, so conclusions based on short time series are problematic, leading to qualifications about periodicity, trends, and regime shifts. Starting in the 1980s, systematic research into climate change has considerably improved our understanding of regional warming and multiple threats to the Baltic Sea. Several aspects of regional climate and environmental changes and how they interact are, however, unknown and merit future research.
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Vuorinen, Ilppo. Post-Glacial Baltic Sea Ecosystems. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.675.
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Post-glacial aquatic ecosystems in Eurasia and North America, such as the Baltic Sea, evolved in the freshwater, brackish, and marine environments that fringed the melting glaciers. Warming of the climate initiated sea level and land rise and subsequent changes in aquatic ecosystems. Seminal ideas on ancient developing ecosystems were based on findings in Swedish large lakes of species that had arrived there from adjacent glacial freshwater or marine environments and established populations which have survived up to the present day. An ecosystem of the first freshwater stage, the Baltic Ice Lake initially consisted of ice-associated biota. Subsequent aquatic environments, the Yoldia Sea, the Ancylus Lake, the Litorina Sea, and the Mya Sea, are all named after mollusc trace fossils. These often convey information on the geologic period in question and indicate some physical and chemical characteristics of their environment. The ecosystems of various Baltic Sea stages are regulated primarily by temperature and freshwater runoff (which affects directly and indirectly both salinity and nutrient concentrations). Key ecological environmental factors, such as temperature, salinity, and nutrient levels, not only change seasonally but are also subject to long-term changes (due to astronomical factors) and shorter disturbances, for example, a warm period that essentially formed the Yoldia Sea, and more recently the “Little Ice Age” (which terminated the Viking settlement in Iceland).There is no direct way to study the post-Holocene Baltic Sea stages, but findings in geological samples of ecological keystone species (which may form a physical environment for other species to dwell in and/or largely determine the function of an ecosystem) can indicate ancient large-scale ecosystem features and changes. Such changes have included, for example, development of an initially turbid glacial meltwater to clearer water with increasing primary production (enhanced also by warmer temperatures), eventually leading to self-shading and other consequences of anthropogenic eutrophication (nutrient-rich conditions). Furthermore, the development in the last century from oligotrophic (nutrient-poor) to eutrophic conditions also included shifts between the grazing chain (which include large predators, e.g., piscivorous fish, mammals, and birds at the top of the food chain) and the microbial loop (filtering top predators such as jellyfish). Another large-scale change has been a succession from low (freshwater glacier lake) biodiversity to increased (brackish and marine) biodiversity. The present-day Baltic Sea ecosystem is a direct descendant of the more marine Litorina Sea, which marks the beginning of the transition from a primeval ecosystem to one regulated by humans. The recent Baltic Sea is characterized by high concentrations of pollutants and nutrients, a shift from perennial to annual macrophytes (and more rapid nutrient cycling), and an increasing rate of invasion by non-native species. Thus, an increasing pace of anthropogenic ecological change has been a prominent trend in the Baltic Sea ecosystem since the Ancylus Lake.Future development is in the first place dependent on regional factors, such as salinity, which is regulated by sea and land level changes and the climate, and runoff, which controls both salinity and the leaching of nutrients to the sea. However, uncertainties abound, for example the future development of the Gulf Stream and its associated westerly winds, which support the sub-boreal ecosystems, both terrestrial and aquatic, in the Baltic Sea area. Thus, extensive sophisticated, cross-disciplinary modeling is needed to foresee whether the Baltic Sea will develop toward a freshwater or marine ecosystem, set in a sub-boreal, boreal, or arctic climate.
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Liu, Xiaodong, and Libin Yan. Elevation-Dependent Climate Change in the Tibetan Plateau. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.593.
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As a unique and high gigantic plateau, the Tibetan Plateau (TP) is sensitive and vulnerable to global climate change, and its climate change tendencies and the corresponding impact on regional ecosystems and water resources can provide an early alarm for global and mid-latitude climate changes. Growing evidence suggests that the TP has experienced more significant warming than its surrounding areas during past decades, especially at elevations higher than 4 km. Greater warming at higher elevations than at lower elevations has been reported in several major mountainous regions on earth, and this interesting phenomenon is known as elevation-dependent climate change, or elevation-dependent warming (EDW).At the beginning of the 21st century, Chinese scholars first noticed that the TP had experienced significant warming since the mid-1950s, especially in winter, and that the latest warming period in the TP occurred earlier than enhanced global warming since the 1970s. The Chinese also first reported that the warming rates increased with the elevation in the TP and its neighborhood, and the TP was one of the most sensitive areas to global climate change. Later, additional studies, using more and longer observations from meteorological stations and satellites, shed light on the detailed characteristics of EDW in terms of mean, minimum, and maximum temperatures and in different seasons. For example, it was found that the daily minimum temperature showed the most evident EDW in comparison to the mean and daily maximum temperatures, and EDW is more significant in winter than in other seasons. The mean daily minimum and maximum temperatures also maintained increasing trends in the context of EDW. Despite a global warming hiatus since the turn of the 21st century, the TP exhibited persistent warming from 2001 to 2012.Although EDW has been demonstrated by more and more observations and modeling studies, the underlying mechanisms for EDW are not entirely clear owing to sparse, discontinuous, and insufficient observations of climate change processes. Based on limited observations and model simulations, several factors and their combinations have been proposed to be responsible for EDW, including the snow-albedo feedback, cloud-radiation effects, water vapor and radiative fluxes, and aerosols forcing. At present, however, various explanations of the mechanisms for EDW are mainly derived from model-based research, lacking more solid observational evidence. Therefore, to comprehensively understand the mechanisms of EDW, a more extensive and multiple-perspective climate monitoring system is urgently needed in the areas of the TP with high elevations and complex terrains.High-elevation climate change may have resulted in a series of environmental consequences, such as vegetation changes, permafrost melting, and glacier shrinkage, in mountainous areas. In particular, the glacial retreat could alter the headwater environments on the TP and the hydrometeorological characteristics of several major rivers in Asia, threatening the water supply for the people living in the adjacent countries. Taking into account the climate-model projections that the warming trend will continue over the TP in the coming decades, this region’s climate change and the relevant environmental consequences should be of great concern to both scientists and the general public.
Частини книг з теми "Melting term"
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Ahbari, Abdellatif, Laila Stour, and Ali Agoumi. "Impacts of Climate Change on the Hydro-Climatology and Performances of Bin El Ouidane Reservoir: Morocco, Africa." In African Handbook of Climate Change Adaptation, 2363–86. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-45106-6_245.
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AbstractIn arid and humid contexts, dams’ reservoirs play a crucial role in water regulation and flood control. Under the projected climate change (CC) effects, even a preoptimized management approach (MA) of a reservoir needs to be assessed in this projected climate. This chapter aims to assess the impacts of CC on the Hydroclimatic (HC) variables of the basin upstream the reservoir of Bin El Ouidane (Morocco), and the effects on the performances of its preoptimized MA. The applied Top-Down assessment procedure included CORDEX climate projections, hydrological, siltation, evaporation, and management models. Concerning the HC variables, the results obtained concord with those reported in the literature in terms of trend, but not always in terms of intensity of change. On the other hand, the projections expected a decrease in the performances of the reservoir, except for criterion allocations’ standard deviation, calibrated during the optimization. Also, interesting conclusions have been found like: the change in precipitation dominant form, the accentuation of the pluvial hydrological regime, the advanced snow melting due to the temperature increase. This chapter presents a typical case study on how to use climate projections for reservoir MA adaptation, without being highly and negatively influenced by the climate model uncertainties.
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Johnson, Elizabeth Lominska, and Graham E. Johnson. "The Japanese Occupation, Recovery, and Transformation 1941–1970." In A Chinese Melting Pot, 72–83. Hong Kong University Press, 2019. http://dx.doi.org/10.5790/hongkong/9789888455898.003.0004.
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Kwan Mun Hau Village in Tsuen Wan includes the Yau, Chan, and Fan lineages. Some members also lived in nearby villages. Both reconstructed full genealogies and printed them for their members in the 1960s-70s, bringing them to the present and mentioning their halls, re-sited when Kwan Mun Hau moved in 1964. The Yau also preserved an important document, a will from 1837, dividing the property among the branches. Kwan Mun Hau has two protective shrines, one honouring nine long-term workers who died defending the village. Before the Japanese occupation, marriages were arranged, and sometimes made with small daughters-in-law. Women were expected to work hard for their husbands’ families. Children often did not survive, and families resorted to adoption.
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Johnson, Elizabeth Lominska, and Graham E. Johnson. "The Early Years of the Yau, Chan, and Fan Lineages in Tsuen Wan." In A Chinese Melting Pot, 43–71. Hong Kong University Press, 2019. http://dx.doi.org/10.5790/hongkong/9789888455898.003.0003.
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Tsuen Wan’s history as a Hakka district dates to the 18th century, after the lifting of the coastal expulsion order in the early Qing dynasty. It was poor and rugged, with some reclamation on the coast, and was famous for its pineapples, which could be taken by boat to Hong Kong Island. A daily coastal market developed, and connections to urban Hong Kong grew as industry developed. The district was self-governing through a body attached to the central Tianhou temple, and relatively peaceful, with many small lineages. Wealthier families often hired long-term workers to help with farming and business, but women were also known for their hard work in agriculture, and kin relationships through women helped in creating a tight-knit society. There also were strong bonds among women, expressed through their laments and mountain songs.
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Zocchi, Giovanni. "Statics of DNA Deformations." In Molecular Machines, 25–80. Princeton University Press, 2018. http://dx.doi.org/10.23943/princeton/9780691173863.003.0002.
Повний текст джерелаАнотація:
DNA is a deformable molecule. The term “deformable” implies phenomena rooted in the collective behavior of many atoms, and a description based on concepts of continuum and statistical mechanics. Long DNA molecules are an excellent experimental system to study the equilibrium conformations and dynamics of long, flexible molecules. This chapter discusses the following: DNA melting, the zipper model, experimental melting curves, base pairing and base stacking as separate, Hamiltonian formulation of the zipper model, 2 × 2 model, nearest neighbor model, connection to nonlinear dynamics, linear and nonlinear elasticity of DNA, bending modulus and persistence length, measurements of DNA elasticity (short and long molecules), the Euler instability, and the DNA yield transition.
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Eliasoph, Nina. "How to Learn Something in an Empowerment Project." In Making Volunteers. Princeton University Press, 2011. http://dx.doi.org/10.23943/princeton/9780691147093.003.0001.
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This chapter is an overview of “empowerment projects.” It shows how empowerment projects are supposed to blend different kinds of people and different kinds of organizations—civic association, state agency, nonprofit organization, family, and cultural tradition. Since funding is usually short-term, all of this blending has to happen flexibly, rapidly, and transparently, with documentation for multiple sources, each with a separate form. Organizers celebrate all this melting of stiff boundaries, finding it exciting and empowering. But the blending also produces tensions, as it is often hard to juggle this many different types of relationships all in one place, all at once.
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Mallon, Christopher, Shai Y. Waisman, and Ray C. Schrock. "Emergency Sales in the US and the UK." In The Law and Practice of Restructuring in the UK and US. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198755395.003.0002.
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Any business that relies on confidence in its financial position, its brand name or goodwill, talented (but mobile) employees, or short-term contracts with customers or counterparties will be particularly hard hit by suggestions that it is or may soon be experiencing financial distress. Businesses of this type have been likened to ‘melting ice cubes’—once exposed to the heat of potential insolvency, value in the business melts away rapidly as customers and counterparties look to terminate relationships, key employees look to exit, and the goodwill and brand name of the business become tarnished. The catastrophic and rapid collapse during 2008 of famous Wall Street and the City of London names illustrated this in dramatic fashion, but businesses of almost every type will suffer negative effects once financial difficulties become more widely known.
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Bianchi, Thomas S. "Effects of Sea-Level Rise and Subsidence on Deltas." In Deltas and Humans. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780199764174.003.0010.
Повний текст джерелаАнотація:
As I briefly mentioned in Chapter 3, the global mean sea level, as deduced from the accumulation of paleo-sea level, tide gauge, and satellite-altimeter data, rose by 0.19 m (range, 0.17–0.21 m) between 1901 and 2010 (see Figure 3.3). Global mean sea level represents the longer-term global changes in sea level, without the short-term variability, and is also commonly called eustatic sea-level change. On an annual basis, global mean sea-level change translates to around 1.5 to 2 mm. During the last century, global sea level rose by 10 to 25 cm. Projections of sea-level rise for the period from 2000 to 2081 indicate that global mean sea-level rise will likely be as high as 0.52 to 0.98 m, or 8 to 16 mm/ yr, depending on the greenhouse gas emission scenarios used in the models. Mean sea-level rise is primarily controlled by ocean thermal expansion. But there is also transfer of water from land to ocean via melting of land ice, primarily in Greenland and Antarctica. Model predictions indicate that thermal expansion will increase with global warming because the contribution from glaciers will decrease as their volume is lost over time. (Take a look at Figure 5.1 if you have doubts about glaciers melting.) And remember our discussion in Chapter 2 about the role of the oceans in absorbing carbon dioxide (CO2) and the resultant ocean acidification in recent years. The global ocean also absorbs about 90% of all the net energy increase from global warming as well, which is why the ocean temperature is increasing, which in turn results in thermal expansion and sea-level rise. To make things even more complicated, the expansion of water will vary with latitude because expansion of seawater is greater with increasing temperature. In any event, sea level is expected to rise by 1 to 3 m per degree of warming over the next few millennia.
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Corazza, Laura. "ICT and Interculture Opportunities Offered by the Web." In Encyclopedia of Information Communication Technology, 357–64. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-59904-845-1.ch047.
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In Italy, as in other European countries such as Germany and France, the words “multicultural” and “intercultural” have distinct meanings1. In some ways the passage the one from the other indicates the evolution of a concept that, when examined in detail, forces us to re-examine educational political, and cultural choices in a society. “In Italy, especially in the field of pedagogy, the term multicultural indicates a situation where cultures co-exist side by side but as yet, have not found a means of comparison and relating to each other . . The term intercultural, which originated in France and then spread to other European countries, on another hand, describes a situation of interaction between different cultures, often describing a prospect, a possible point of arrival or an objective to strive for; a situation in which the people of different cultures begin to open up to reciprocal relationships, thereby bringing about the possibility of integration, characterised by a political and cultural pluralism which aims at reciprocal respect and appreciation between the respective cultures”2. With Multiculturalism, people accept to live with those from other cultures with tolerance but without promoting forms of exchange and democratic co-existence. The form of social organization that derives from this is that of the “melting pot” which encourages the development of ghettos or “Little Italy” and “China towns”. However the Intercultural approach is reciprocal. It is for those who accept and listen, those who are tolerant, those who are not afraid of “contamination” but constantly seek to mediate between different points of view and backgrounds.
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Newnham, Robert E. "Thermoelectricity." In Properties of Materials. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780198520757.003.0023.
Повний текст джерелаАнотація:
When two different metals are connected together in a circuit and the two junctions are held at different temperatures, five physical phenomena take place simultaneously. Thermal and electric currents flow in the circuit, giving rise to Joule heating and thermal conduction. The driving forces for these currents are three interrelated thermoelectric phenomena: the Seebeck Effect, the Peltier Effect, and the Thomson Effect. For commonly used thermocouples, a voltage is developed when the junctions are held at different temperatures. In practice, one junction is held at a constant temperature (often the melting point of ice), and the open circuit voltage is measured as a function of the temperature of the second junction. If the reference temperature is 0◦C, then the thermocouple voltage can be expressed as a power series. . . . V = αT + βT2 + γ T3 +· · · , . . . where T is the temperature in ◦C and the coefficients depend on the choice of metals. Data for Cu–Ni and Cu–Fe thermocouples are presented in Fig. 21.2 along with the governing equations. If the cold junction is at a temperature other than 0◦C, it is only necessary to add a constant term. From this it follows that dV/dT at one junction is independent of the temperature of the second junction.
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Czebreszuk, Janusz. "Metallurgy in the Early Bronze defensive settlement in Bruszczewo, site 5, Śmigiel commune, Kościan district: One more step on the way to the synthesis." In Treasures of Time: Research of the Faculty of Archaeology of Adam Mickiewicz University in Poznań, 272–85. Adam Mickiewicz University Poznan, 2021. http://dx.doi.org/10.14746/wa.2021.15.978-83-946591-9-6.
Повний текст джерелаАнотація:
Long-term excavations carried out in the defensive settlement of the Únětice Culture in Bruszczewo (Śmigiel commune, Kościan district) have resulted in an abundant assemblage of artefacts related to metallurgy. These represent various ready-made products (i.e., ornaments, tools, and weapons), as well as some scrap prepared for smelting. Other finds included smelting by-products (metal prills/droplets) and unfinished and never used artefacts with preserved casting seams. Also, the artefact assemblage recorded at this site connected with metallurgy but made of other materials is unique in Europe. In this context, it is worth mentioning: tuyeres, melting pots, and clay footings, as well as a stone casting mould used for making open bracelets. This article presents an analysis and a description of these finds. The metal artefacts were analysed on the basis of the results of a metallurgical study, to which almost all metals recorded in Bruszczewo were subjected. Also, the applied chronological frame was based on the types of metal typical of the Únětice culture. The significant number of artefacts and their multi-aspect, archaeological and metallurgical analyses, place Bruszczewo among the key points on the map of knowledge of Early Bronze metallurgy on our continent. Moreover, this article indicates that the presented site offers great research potential that can be used in further studies into prehistoric metallurgical knowledge, including technological innovations.
Тези доповідей конференцій з теми "Melting term"
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Marzuki, H. Hashiguchi, M. Vonnisa, Harmadi, and Muzirwan. "Long-Term Change in Rainfall Rate and Melting Layer Height in Indonesia." In 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama). IEEE, 2018. http://dx.doi.org/10.23919/piers.2018.8597606.
Повний текст джерела
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Xiao, Yumin, R. S. Amano, E. K. Lee, Youn-Suk Choi, and Jianhui Xie. "A Non-Source Term Methodology in Simulation of Solidification." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33222.
Повний текст джерелаАнотація:
In this paper a non-source term method is developed to solve the energy equation. In this new method the discrete form of the energy equation remains the same and no extra source term is introduced. The mushy-zone is treated as a porous media during solidification. This method is incorporated into the existing finite volume based CFD code. Test cases analyzed in this paper include solidification of pure metal, pure metal solidification with natural convection due to the buoyancy, and binary alloy mushy flow problem with variable Cp. The calculated results are in good agreements with available published data. This method can be applied to simulate a wide range of melting/solidification processes.
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Li, Zheng, Mo Yang, and Yuwen Zhang. "Lattice Boltzmann Method Simulation of 3-D Melting Using Double MRT Model With Interfacial Tracking Method." In ASME 2016 Heat Transfer Summer Conference collocated with the ASME 2016 Fluids Engineering Division Summer Meeting and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/ht2016-7407.
Повний текст джерелаАнотація:
Three-dimensional melting problems are investigated numerically with Lattice Boltzmann method (LBM). Regarding algorithm’s accuracy and stability, Multiple-Relaxation-Time (MRT) models are employed to simplify the collision term in LBM. Temperature and velocity fields are solved with double distribution functions, respectively. 3-D melting problems are solved with double MRT models for the first time in this article. The key point for the numerical simulation of a melting problem is the methods to obtain the location of the melting front and this article uses interfacial tracking method. The interfacial tracking method combines advantages of both deforming and fixed grid approaches. The location of the melting front was obtained by calculating the energy balance at the solid-liquid interface. Various 3-D conduction controlled melting problems are solved firstly to verify the numerical method. Liquid fraction tendency and temperature distribution obtained from numerical methods agree with the analytical results well. The proposed double MRT model with interfacial tracking method is valid to solve 3-D melting problems. Different 3-D convection controlled melting problems are then solved with the proposed numerical method. Various locations of the heat surface have different melting front moving velocities, due to the natural convection effects. Rayleigh number’s effects to the 3-D melting process is discussed.
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ElGafy, Ahmed, Osama Mesalhy, Khalid Lafdi, and K. Bowman. "Mathematical Model to Describe Thermal Behavior of Phase Change Materials Contained in a Cylindrical Enclosure." In ASME 2003 Heat Transfer Summer Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/ht2003-47353.
Повний текст джерелаАнотація:
Heat transfer processes undergoing liquid-solid phase transformation have been of continuing interest for many researchers. Phase Change Materials, (PCMs); have received great consideration in electronic industry for cooling of electronics and in telecommunication equipment to control internal temperature under emergency operating conditions. High melting temperature materials have been proposed as thermal energy storage mediums in space applications because of their high melting temperatures and latent heat. In the present work, a numerical simulation is developed to predict the thermal performance of a phase change material of high melting point in a cylindrical enclosure. In this simulation the phases are assumed to be homogeneous and a source term, S, arises from melting and solidification processes is considered as a function of the latent heat of fusion and the liquid phase fraction. By introducing the thermo-physical properties of one of those materials, the thermal performance of it as a phase change material is predicted.
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Srinivasan, Vedanth. "Numerical Simulation of Melting/Solidification Phenomena Using a Multi–Fluid Modeling Approach." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-63841.
Повний текст джерелаАнотація:
In this article, a fixed-grid finite volume approach to simulate the convection-dominated solidification/melting process is presented. An Eulerian multi–fluid modeling approach is employed to track the phase change interface by obtaining solutions to governing volume fraction, momentum and energy transport equations. The liquid-solid interfacial phase transfer effects are modeled using a novel mass transfer function incorporating the latent heat modification due to the phase change process. The alterations in the local phasic fractions and the resultant cellular latent heat is correctly realized using a source term approach within a homogeneous enthalpy modeling framework. The model fully implemented within the commercial CFD code AVL FIRE® V2010 is tested and validated using a (1) classical 1D Stefan’s problem (2) melting of gallium (3) tin solidification scenario. In addition to the mass, momentum and energy solutions, transport of species within multi-component liquids is made possible, thereby allowing means for efficient and accurate coupling between the temperature and concentration fields within the system. Description of the phase change fronts, the local velocity and temperature fields are discussed in detail. Results from the simulations are compared against experimental data wherever available. Discussions pertaining to the applicability of the model and its robustness are elaborated within the article.
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Jiang, J., and Y. X. Tao. "Interaction Coefficient Between Ice Particles in Convective Melting of Granular Packed Bed." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-1032.
Повний текст джерелаАнотація:
Abstract To numerically simulate the convective melting of packed bed it is necessary to determine the thermophysical properties or their constitutive equations. One of the most uncertain values among them is the solute interaction coefficient of solid particles, which represents the interaction force between solid particles and is equivalent to the viscosity term in Navier-Stokes equations if the dirty fluid model is applied. It was found from the previous study that the solute (solid particle) interaction coefficient, μs, characterizes the solubility such as the melting rate, the distribution of ice volume fraction, the velocity of ice particle, and the melting time. In this study, a parametric study based on the two-dimensional model for the convective melting of granular packed beds (Jiang et al. 1999) is conducted to determine the sensitivity of interaction coefficient to the model prediction. The packed bed considered here is collection of ice particles of various shapes. Warm water at a constant temperature enters horizontally the bed where melting takes place. Two cases are considered. One is to consider μs as constant, and the other is to consider it as a function of the ice volume fraction. The melting rate, fluid flow velocity and ice volume fraction distribution are discussed for different interaction coefficient values. An “optimal” interaction coefficient between ice particles is determined by comparing the simulation data with experimental data (Tao et al. 1998). It is found that the melting results are most sensitive to the value of constant interaction coefficient rather than to whether it is a constant or as a function of the ice volume fraction.
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Takase, Kazuyuki, Toshiharu Muramatsu, Takahisa Shobu, and Kazuyuki Tsukimori. "Computational Simulations on Melting Process of Fine Metal Powders With Laser Irradiation Welding." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-13219.
Повний текст джерелаАнотація:
At the commercial use stage in sodium-cooled fast breeder reactors, securing maintenance and repair better than an equal to that of present water-cooled reactors is needed. Especially a repair technology that secures the plant integrity for long-term operation period becomes indispensable in the heat exchanger tubes of the steam generator that form the boundary of sodium and water coolants. Then the present study focused on the standardization of welding technology with a laser. An experimental study regarding the welding of a stainless steel plate with the laser using fine metal powders is being performed. Moreover, a numerical study is performed to simulate the welding of the fine metal powder on the stainless steel plate. The fine metal powder is made of iron, and is heated by the laser beam, and then melts exceeding the melting temperature. This paper reports the computational results of the welding phenomenon of some metal powders which changes from solid to liquid and liquid to solid. The results were compared with the experimental results qualitatively.
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Prabhu, Vinit V., Ethan Languri, and Kashif Nawaz. "Experimental Validation of Mushy Zone Constant for Modeling of Solidification/Melting for Thermal Energy Storage Applications." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-24395.
Повний текст джерелаАнотація:
Abstract The thermal energy storage (TES) systems use phase change materials (PCM’s) for storage and release of thermal energy. A lot of research is being conducted in recent times for fast, efficient storage and release of thermal energy using phase change materials in order to utilize the vast amount of latent heat available at constant temperature during phase change process. The numerical modeling for solidification and melting of PCM is employed in various commercial software and applied for different applications which include the solidification or melting. In the numerical simulation of phase change process, the solidification and melting are modelled using enthalpy-porosity method developed some researchers previously. The mushy zone constant is an important factor in this method which is used in the governing equations as a source term to model the melt front. The aim of this study is to determine the role of mushy zone constant on the solidification/melting behavior of phase change material numerically and validate the results with the experiments. The melting behavior of PCM is studied in this paper. The experimental setup consisting of a cubical container of dimensions 3″ × 3″ × 3″ filled with PCM was considered. The box was heated from one side and insulated from other sides so that the heat supplied is transferred to the PCM to melt it completely. The melting behavior of PCM was observed by capturing images at specific time intervals with the help of a camera. The camera was placed in such a way with minimum parallax error. These results are validated with previous numerical study in which the mushy zone constant was varied from 104 to 106 to determine the optimum value. The PCM used in this study is a paraffin wax material having a melting point of 48 °C. The propagation of melt front is plotted at different time steps and validated with the numerical results. The propagation of melt front is observed to be different for each of the mushy zone constant values. It was observed that the melting for higher values of mushy zone constant is observed to be similar to the experiment for the initial part of melting. Also, the melting rate speeds up and is observed to be similar to melting in the lower values of mushy zone constant. This paper aims to be a starting point to determine the optimum mushy zone constant for different factors affecting the melting behavior such as different materials, temperature difference.
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Mani, Kasi B., Mohammad R. Hossan, and Prashanta Dutta. "Microwave Heating of Multi-Layered Composites for Bonding." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-85770.
Повний текст джерелаАнотація:
A detailed theoretical analysis has been carried out to study selective heating of multilayered dielectric composite under microwave heating by solving an unsteady energy equation with an electric field and frequency dependent heat source term. The source term is computed from simplified Maxwell’s equations under plane wave assumption. Analytical solution obtained from this study is used to understand the effect of layer thickness on temperature distribution in a thin layer of poly-aniline sandwiched between two polymer (PMMA) substrates. It is found that dielectric properties, sample thickness and processing time have significant influence on the microwave heating pattern. The highly dielectric poly-aniline absorbed more microwave power than that of PMMA and attained temperature above the melting point of PMMA in less than 2 minutes. These results show that localized melting of PMMA can be achieved using household microwave. This analytical investigation on multi-layered composites will provide a significant insight to understand and overcome the challenges of selective heating and localized bonding technique.
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Haidong, Ma, Wang Yungang, and Zhao Qinxin. "The Effect of Calcium-Bearing Mineral on Ash Melting Behavior During Zhundong Coal Combustion." In ASME 2017 Power Conference Joint With ICOPE-17 collocated with the ASME 2017 11th International Conference on Energy Sustainability, the ASME 2017 15th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2017 Nuclear Forum. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/power-icope2017-3221.
Повний текст джерелаАнотація:
Two typical pulverized Zhundong coal with different calcium oxide contents in ash were selected to use in this work. The liquid nitrogen was used to cool ash rapidly at different temperatures, in order to avoid changes in mineral condition. The ash melting behavior and mineral transition mechanism, especially calcium-bearing minerals was studied by ash melting point test platform, XRD, XRF, SEM and EDS. The results showed that the different states of calcium are the dominant reasons for different sintering behaviors of coal ash. The calcium-bearing minerals in ash, such as calcium oxide (CaO), calcium silicate (CaSiO3), gehlenite (2CaO·Al2O3·SiO2), and anorthite (CaO·Al2O3·2SiO2), etc., are the most important factors influencing the initial sintering behavior of coal ash in the temperature range from 1373K to 1473K under oxidizing atmosphere during coal combustion. That is the reason why ash starts to melt at relatively high temperature during ash melting behavior in laboratory, but has severe slagging and contamination characteristic at low temperature during coal combustion in boilers. The research achievments have important guiding significance for the design of partially or completely burning Zhundong coal boiler as well as its long-term safe and efficient operation. (CSPE)