Relevant bibliographies by topics / Melt pool flow

Academic literature on the topic 'Melt pool flow'

Author: Grafiati
Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "Melt pool flow"

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Shuja, S. Z., and B. S. Yilbas. "Laser produced melt pool: Influence of laser intensity parameter on flow field in melt pool." Optics & Laser Technology 43, no. 4 (June 2011): 767–75. http://dx.doi.org/10.1016/j.optlastec.2010.12.003.

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Xu, Yixuan, Dongyun Zhang, Junyuan Deng, Xuping Wu, Lingshan Li, Yinkai Xie, Reinhart Poprawe, Johannes Henrich Schleifenbaum, and Stephan Ziegler. "Numerical Simulation in the Melt Pool Evolution of Laser Powder Bed Fusion Process for Ti6Al4V." Materials 15, no. 21 (October 28, 2022): 7585. http://dx.doi.org/10.3390/ma15217585.

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In order to track the free interface of the melt pool and understand the evolution of the melt pool, the flow of fluid, and the interface behavior of gas and liquid, a physical model is developed by using the VOF method in this paper. Its characteristics are a combined heat source model, including a parabolic rotation and a cylindrical distribution, and a powder bed stochastic distributed model with powder particle size. The unit interface between the metallic and gas phase in the laser–powder interaction zone can only be loaded by the heat source. Only the first and second laser scanning tracks are simulated to reduce the calculation time. The simulation results show that process parameters such as laser power and scanning speed have significant effects on the fluid flow and surface morphology in the melt pool, which are in good agreement with the experimental results. Compared with the first track, the second track has larger melt pool geometry, higher melt temperature, and faster fluid flow. The melt flows intensely at the initial position due to the high flow rate in the limited melt space. Because there is enough space for the metal flow, the second track can obtain smooth surface morphology more easily compared to the first track. The melt pool temperature at the laser beam center fluctuates during the laser scanning process. This depends on the effects of the interaction between heat conduction or heat accumulation or the interaction between heat accumulation and violent fluid flow. The temperature distribution and fluid flow in the melt pool benefit the analysis and understanding of the evolution mechanism of the melt pool geometry and surface topography and further allow regulation of the L-PBF process of Ti6Al4V.
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Peng, Jin, Liqun Li, Shangyang Lin, Furong Zhang, Qinglong Pan, and Seiji Katayama. "High-Speed X-Ray Transmission and Numerical Study of Melt Flows inside the Molten Pool during Laser Welding of Aluminum Alloy." Mathematical Problems in Engineering 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/1409872.

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By using the X-ray transmission imaging system, melt flows inside a molten pool were studied during laser welding of aluminum alloy at different welding speeds. Then, the correlation between temperature gradients along the direction of weld penetration and melt flows in the rear part of a molten pool was analyzed by using a three-dimensional numerical method. And the presented model was verified by experimental results. The corresponding investigation was carried out to further study the correlation between temperature gradient and melt flow behavior of the molten pool in the plate heated by preheating temperature. The results indicated that, in the rear part of the molten pool, the maximum flow velocity was located at the bottom of the molten pool. The melt metal in the rear molten pool caused by different welding speeds had significantly different flow trends. As the welding speed increased, the absorbed intensity on the keyhole front wall also increased as well as the recoil pressure that could maintain the keyhole opened. Consequently, the increase of the welding speed was more beneficial to improving the stability of the molten pool.
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Sun, Shou Jin, and Milan Brandt. "Investigation of Hastelloy C Laser Clad Melt Pool Size and its Effect on Clad Formation." Key Engineering Materials 384 (June 2008): 213–27. http://dx.doi.org/10.4028/www.scientific.net/kem.384.213.

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The melt pool size of a single-track clad in the laser cladding of Hastelloy C, a Nickel based alloy, on mild steel substrate has been investigated. The effect of laser processing parameters, such as laser power density, scan rate and powder mass flow rate on the melt pool size has been examined. It was found that the melt pool size is strictly controlled by the melt pool temperature which increases with laser power but decreases with increasing scan rate and powder mass flow rate. The melt pool size is critical for the clad formation in terms of clad height and dilution with the substrate. The clad height increases linearly with the ratio of melt pool size to powder stream diameter while the dilution is an exponential function of the ratio of melt pool size to laser spot size.
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Ur Rehman, Asif, Fatih Pitir, and Metin Uymaz Salamci. "Laser Powder Bed Fusion (LPBF) of In718 and the Impact of Pre-Heating at 500 and 1000 °C: Operando Study." Materials 14, no. 21 (November 5, 2021): 6683. http://dx.doi.org/10.3390/ma14216683.

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The morphology of a melt pool has a critical role in laser powder bed fusion (LPBF). Nevertheless, directly characterizing the melt pool during LPBF is incredibly hard. Here, we present the melt pool flow of the entire melt pool in 3D using mesoscopic simulation models. The physical processes occurring within the melt pool are pinpointed. The flow patterns throughout the same are exposed and measured. Moreover, the impact of pre-heating at 500 and 1000 °C has been described. The study findings offer insights into LPBF. The findings presented here are critical for comprehending the LPBF and directing the establishment of improved metrics for process parameters optimization.
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Das, Saurabh, and Satya Prakash Kar. "Role of Marangoni Convection in a Repetitive Laser Melting Process." Materials Science Forum 978 (February 2020): 34–39. http://dx.doi.org/10.4028/www.scientific.net/msf.978.34.

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To effectively interpret the fluid flow dynamics in the molten metal pool, a numerical model was established. The moving repetitive Gaussian laser pulse is irradiated in the work piece. The consideration of laser scanning speed makes the transport phenomena complex. The continuity and momentum equations are solved to get the flow velocity of the molten metal in the melt pool. The energy equation is solved to know the temperature field in the work piece. The algebraic equations obtained after discretization of the governing equations by Finite Volume Method (FVM) are then solved by the Tri Diagonal Matrix Method. Enthalpy-porosity technique is used to capture the position of the melt front which determines the shape of the melt pool. Marangoni convection is considered to know its effect on the shape of the melt pool. The surface tension coefficient is taken as both positive and negative value while calculating the Marangoni force. The two possible cases will cause the Marangoni force to distort the flow dynamics in the melt pool . It's dominance over the buoyancy force in controlling the melt pool shape is focused in the present study. Further, the present model will present an insight to the consequences of laser scanning velocity over the melt pool dimensions and shape.
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Shuja, S. Z., and B. S. Yilbas. "Laser Heating and Flow Field Developed in the Melt Pool." Numerical Heat Transfer, Part A: Applications 59, no. 12 (June 15, 2011): 970–87. http://dx.doi.org/10.1080/10407782.2011.582418.

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Ebrahimi, Amin, Aravind Babu, Chris R. Kleijn, Marcel J. M. Hermans, and Ian M. Richardson. "The Effect of Groove Shape on Molten Metal Flow Behaviour in Gas Metal Arc Welding." Materials 14, no. 23 (December 4, 2021): 7444. http://dx.doi.org/10.3390/ma14237444.

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One of the challenges for development, qualification and optimisation of arc welding processes lies in characterising the complex melt-pool behaviour which exhibits highly non-linear responses to variations of process parameters. The present work presents a computational model to describe the melt-pool behaviour in root-pass gas metal arc welding (GMAW). Three-dimensional numerical simulations have been performed using an enhanced physics-based computational model to unravel the effect of groove shape on complex unsteady heat and fluid flow in GMAW. The influence of surface deformations on the magnitude and distribution of the heat input and the forces applied to the molten material were taken into account. Utilising this model, the complex thermal and fluid flow fields in melt pools were visualised and described for different groove shapes. Additionally, experiments were performed to validate the numerical predictions and the robustness of the present computational model is demonstrated. The model can be used to explore the physical effects of governing fluid flow and melt-pool stability during gas metal arc root welding.
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Shen, Hongyao, Jinwen Yan, and Xiaomiao Niu. "Thermo-Fluid-Dynamic Modeling of the Melt Pool during Selective Laser Melting for AZ91D Magnesium Alloy." Materials 13, no. 18 (September 18, 2020): 4157. http://dx.doi.org/10.3390/ma13184157.

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A three dimensional finite element model (FEM) was established to simulate the temperature distribution, flow activity, and deformation of the melt pool of selective laser melting (SLM) AZ91D magnesium alloy powder. The latent heat in phase transition, Marangoni effect, and the movement of laser beam power with a Gaussian energy distribution were taken into account. The influence of the applied linear laser power on temperature distribution, flow field, and the melt-pool dimensions and shape, as well as resultant densification activity, was investigated and is discussed in this paper. Large temperature gradients and high cooling rates were observed during the process. A violent flow occurred in the melt pool, and the divergent flow makes the melt pool wider and longer but shallower. With the increase of laser power, the melt pool’s size increases, but the shape becomes longer and narrower. The width of the melt pool in single-scan experiment is acquired, which is in good agreement with the results predicted by the simulation (with error of 1.49%). This FE model provides an intuitive understanding of the complex physical phenomena that occur during SLM process of AZ91D magnesium alloy. It can help to select the optimal parameters to improve the quality of final parts and reduce the cost of experimental research.
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LI, YOU-RONG, DONG-MING MO, LAN PENG, and SHUANG-YING WU. "NUMERICAL INVESTIGATION OF SILICON MELT FLOW IN A SHALLOW ANNULAR POOL UNDER AN AXIAL MAGNETIC FIELD." International Journal of Modern Physics B 21, no. 18n19 (July 30, 2007): 3486–88. http://dx.doi.org/10.1142/s0217979207044792.

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In order to understand the effect of the magnetic field on surface patterns on semi-conducting silicon melt in industrial Czochralski furnaces, we conducted a series of unsteady three-dimensional numerical simulations of silicon melt flow in a shallow annular pool under the axial magnetic field for the magnetic field strength from 0 to 0.1T. The pool is heated from the outer cylindrical wall and cooled at the inner wall. Bottom and top surfaces are adiabatic. When the magnetic field is weak, the simulation can predict various three-dimensional oscillatory flows depending on the radial temperature difference. With the much larger magnetic field, three-dimensional flow becomes axisymmetric steady flow. Details of flow and temperature disturbances are discussed and the critical magnetic field strengths for the onset of axisymmetric steady flow are determined.
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Dissertations / Theses on the topic "Melt pool flow"

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Sherratt, Jo. "The effect of thermoplastics melt flow behaviour on the dynamics of fire growth." Thesis, University of Edinburgh, 2001. http://hdl.handle.net/1842/4788.

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The UK Health & Safety Executive are responsible for advising on ways to ensure the safety of employees within the workplace. One of the main areas of concern is the potential problem of unwanted fire, and it has been identified that within the area of large-scale storage in warehouses, there is an uncertainty posed by large quantities of thermoplastic. Some forms of thermoplastic exhibit melt-flow behaviour when heated, and a large vertical array exposed to a fire may melt and ignite forming a pool fire in addition to a wall fire. This project is largely experimental, and aimed at quantifying the effect of a growing pool fire fuelled by a melting wall on overall fire growth rate. The pool fire has been found to increase melting and burning rates, producing a much faster growing fire. It has also been found that - 80% of flowing and burning material will enter a potential pool fire, with only 20 - 25% of total mass loss actually burning from the original array. During the project 400+ small-scale tests and several medium-scale experiments have been undertaken at both Edinburgh University and the HSE's Fire & Explosion Laboratory, Buxton. The experiments have confirmed the main parameters governing pool fire development are molecular weight degradation rate and mechanism, which control flow viscosity. There have also been investigations into other influences, the most significant of which was found to be flooring substrate. These parameters then form the basis of a simple 1-D model. A semi-infinite heat transfer approximation is used to determine temperature profile through a thermoplastic exposed to its own flame flux, with extrapolated temperature dependant material properties. The derived profile is then inserted into a gravity driven flow model, to produce estimates of flow rate and quantity for plastics undergoing either random or end chain scission thermal degradation processes. The model identifies property data which are required to permit its use as a hazard assessment tool.
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Lee, Yousub. "Simulation of Laser Additive Manufacturing and its Applications." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440360229.

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Book chapters on the topic "Melt pool flow"

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Buchholz, Andreas, Benoît Commet, Gerd-Ulrich Grün, and Dag Mortensen. "Numerical Mass and Heat Flow Predictions in Aluminum DC Casting: A Comparison of Simulations with Melt Pool Measurements." In Continuous Casting, 121–30. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2006. http://dx.doi.org/10.1002/3527607331.ch18.

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Xiao, Xianfeng, Cong Lu, Yanshu Fu, Xiaojun Ye, and Lijun Song. "Progress on Experimental Study of Melt Pool Flow Dynamics in Laser Material Processing." In Liquid Metals [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97205.

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Laser material processing has becoming a rapid developing technology due to the flexibility of laser tool. Melt pool is the main product from the interaction between laser and material and its features has a great impact on the heat transfer, solidification behavior, and defects formation. Thus, understanding changes to melt pool flow is essential to obtain good fabricated product. This chapter presents a review of the experimental studies on melt pool flow dynamics for laser welding and laser additive manufacturing. The mechanisms of melt pool convection and its principal affecting factors are first presented. Researches on melt flow visualization using direct and indirect experimental methods are then reviewed and discussed.
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Fatoba, Olawale Samuel, Abimbola Patricia Idowu Popoola, Gabriel Ayokunle Farotade, and Sisa Lesley Pityana. "Computational Dynamics of Laser Alloyed Metallic Materials for Improved Corrosion Performance." In Advances in Civil and Industrial Engineering, 197–235. IGI Global, 2016. http://dx.doi.org/10.4018/978-1-5225-0329-3.ch008.

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Laser alloying is a material processing method which utilizes the high power density available from defocused laser beam to melt both metal coatings and a part of the underlying substrate. Since melting occur solitary at the surface, large temperature gradients exist across the boundary between the melted surface region and underlying solid substrate, which results in rapid self-quenching and re-solidifications. Alloyed powders are deposited in a molten pool of the substrate material to improve the corrosion resistance of the substrate by producing corrosion resistant coatings. A 3D mathematical model is developed to obtain insights on the behaviour of laser melted pools subjected to various process parameters. Simulation with 3D model with different values of various significant processing parameters such as laser power, scanning speed and powder feed rate influences the geometry and dynamics of the melt pool, and cooling rates. It is expected that the melt pool flow, thermal and solidification characteristics will have a profound effect on the microstructure of the solidified region.
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Huber, Matthew S., Elizaveta Kovaleva, Martin D. Clark, and Stephen A. Prevec. "Inhomogeneous distribution of lithic clasts within the Daskop granophyre dike, Vredefort impact structure: Implications for emplacement of impact melt in large impact structures." In Large Meteorite Impacts and Planetary Evolution VI. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.2550(10).

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ABSTRACT The Vredefort granophyre dikes have long been recognized as being derived from the now-eroded Vredefort melt sheet. One dike, in particular, the Daskop granophyre dike, is notable for a high abundance of lithic clasts derived from various stratigraphic levels. In this study, we mapped the distribution of the clasts throughout the continuously exposed section of the dike using field mapping and aerial drone photography and attempted to constrain the emplacement mechanisms of the dike. We found that the clasts are not homogeneously spread but instead are distributed between clast-rich zones, which have up to 50% by area clasts, and clast-poor zones, which have 0–10% by area clasts. We examined three models to explain this distribution: gravitational settling of clasts, thermally driven local assimilation of clasts, and mechanical sorting of clasts due to turbulent flow. Of the three models, the gravitational settling cannot be supported based on our field and geophysical data. The assimilation of clasts and turbulent flow of clasts, however, can both potentially result in inhomogeneous clast distribution. Zones of fully assimilated clasts and nonassimilated clasts can occur from spatial temperature differences of 100 °C. Mechanical sorting driven by a turbulent flow can also generate zones of inhomogeneous clast distribution. Both local assimilation and mechanical sorting due to turbulent flow likely contributed to the observed distribution of clasts.
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Poel, Ibo van de. "Design for Sustainability." In Philosophy, Technology, and the Environment. The MIT Press, 2017. http://dx.doi.org/10.7551/mitpress/9780262035668.003.0008.

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Ibo van de Poel claims that there is substantial disagreement about the exact conception of sustainability even if there is general agreement on its desirability. We should see sustainability as a “compounded” value (not a mere technical issue) that consists of intergenerational justice, intragenerational justice, and care for nature. These values often conflict. The three most common ways of dealing with value conflicts are through life cycle analysis (which compares and aggregates multiple environmental impacts into one measure), respecification (which identifies higher-order and less controversial values to be specified into a design), or innovation (which develops new options that meet all design requirements). Usually value conflicts are can be handled by specifications of shared values or by new innovations. Van de Poel recommends a “values hierarchy” that organizes conflicting interpretations of a specific project in order to determine the available design options. He proposes “value dams” and “value flows” to manage conflicts among stakeholders, who might have different conceptions of sustainability. A value dam would prevent those design features that are strongly opposed by at least one or more stakeholders, and a value flow would promote design requirements that fit a number of different conceptions of sustainability.
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Singh, Anuj Kumar, Jayanta Kumar Pati, Shiva Kumar Patil, Wolf Uwe Reimold, Arun Kumar Rao, and Om Prakash Pandey. "Anisotropy of magnetic susceptibility (AMS) of impact melt breccia and target rocks from the Dhala impact structure, India." In Large Meteorite Impacts and Planetary Evolution VI. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.2550(14).

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ABSTRACT The ~11-km-wide, Paleoproterozoic Dhala impact structure in north-central India comprises voluminous exposures of impact melt breccia. These outcrops are discontinuously spread over a length of ~6 km in a semicircular pattern along the northern, inner limit of the monomict breccia ring around the central elevated area. This study of the magnetic fabrics of impact breccias and target rocks from the Dhala impact structure identified a weak preferred magnetic orientation for pre-impact crystalline target rocks. The pre- and synimpact rocks from Dhala have magnetite and ilmenite as common magnetic phases. The distributions of magnetic vectors are random for most impact melt breccia samples, but some do indicate a preferred orientation. Our anisotropy of magnetic susceptibility (AMS) data demonstrate that the shape of susceptibility ellipsoids for the target rocks varies from prolate to oblate, and most impact melt breccia samples display both shapes, with a slight bias toward the oblate geometry. The average value for the corrected degree of anisotropy of impact melt rock (P′ = 1.009) is lower than that for the target rocks (P′ = 1.091). The present study also shows that both impact melt breccia and target rock samples of the Dhala structure have undergone minor postimpact alteration, and have similar compositions in terms of magnetic phases and high viscosity. Fine-grained iron oxide or hydroxide is the main alteration phase in impact melt rocks. Impact melt rocks gave a narrow range of mean magnetic susceptibility (Km) and P′ values, in contrast to the target rock samples, which gave Km = 0.05–12.9 × 10−3 standard international units (SI) and P′ = 1.036–1.283. This suggests similar viscosity of the source magma, and limited difference in the degrees of recorded deformation. Between Pagra and Maniar villages, the Km value of impact melt breccias gradually decreases in a clockwise direction, with a maximum value observed near Pagra (Km = 1.67 × 10−3 SI). The poor grouping of magnetic fabrics for most impact melt rock samples implies local turbulence in rapidly cooled impact melt at the front of the melt flow immediately after the impact. The mean K1 for most impact melt samples suggests subhorizontal (<5°) flow in various directions. The average value of Km for the target rocks (4.41 × 10−3 SI) is much higher compared to the value for melt breccias (1.09 × 10−3 SI). The results of this study suggest that the melt breccias were likely part of a sheet-like body of sizeable extent. Our magnetic fabric data are also supported by earlier core drilling information from ~70 locations, with coring depths reaching to −500 m. Our extensive field observations combined with available widespread subsurface data imply that the impact melt sheet could have covered as much as 12 km2 in the Dhala structure, with an estimated minimum melt volume of ~2.4 km3.
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Sharma, Ram Chhavi. "Third Generation Solar Cells - Promising Devices to Meet the Future Energy Needs." In Photonic Materials: Recent Advances and Emerging Applications, 85–100. BENTHAM SCIENCE PUBLISHERS, 2023. http://dx.doi.org/10.2174/9789815049756123010008.

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Energy is the basic input for the improvement of the social status of human beings and the development of a nation. At present, we are observing a shift in the use of energy from non-renewable to the renewable energy due to exhausting natural resources of non-renewable energy and other environmental and climatic concerns. Solar energy resource is an inexhaustible source of energy. The development of first generation solar cells using silicon material in the middle of the nineteenth century introduced a new era in the renewable energy transformation process when the first solar cells were flown on the fourth satellite, the Vanguard-I in 1958. But despite abundant material resources, high stability and good performance, this technology could not fulfill the energy need except a fraction due to very long payback time. The second generation solar cells are also not very encouraging due to the scarcity of materials and their toxic nature. The third generation solar cells, due to extremely low energy payback time and unlimited availability of material are promising devices to contribute significantly in solar energy conversion, despite limitations of poor stability and low efficiency. The present chapter critically analyses the third generation solar cells, in regard to materials, production, fabrication process, energy payback time, efficiency and applications.
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Boyce, Gordon. "Introduction: Resource Flows and Maritime Infrastructures." In Resources and Infrastructures in the Maritime Economy, 1500-2000, 1–4. Liverpool University Press, 2002. http://dx.doi.org/10.5949/liverpool/9780973007329.003.0001.

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Resources and infrastructures represent two elements that interact in complex ways to support and shape economic activity. In the context of maritime endeavours, this interaction unfolds over relatively wide geographic areas and exhibits great complexity, since it is influenced by diverse and sometimes conflicting legal, social, cultural and institutional forces. Impacted in numerous ways by these variables, flows of resources, such as capital, goods, information, people and productive assets (even those that following their initial deployment become fixed) are coordinated with the aid of different kinds of infrastructures. Considering the latter from a maritime perspective immediately brings to mind physical infrastructures in particular ports. But intangible frameworks, including those networks of business contacts that constitute communication systems, social and cultural constructs that shape patterns of thought and behaviour, as well as formally constituted (legal) structures, exert a coordinating or mediating influence upon patterns of resource allocation. Both of these generic types of infrastructure – physical and intangible – develop sector-specific attributes: those employed to support maritime activities differ from those used for land-based purposes. Within these broad sectors, individual industries develop their own specialised infrastructures to meet their resource coordinating requirements. In the maritime context, the chapters below analyse both physical and intangible infrastructures. The former are examined directly by Elisabetta Tonizzi and James Reveley and Malcolm Tull, who evaluate ports and port policies in three different countries, while Michael Miller and Leos Müller and Jari Ojala consider non-physical forms – respectively, agency structures and consular networks. John Chircop explores a complex infrastructure consisting of social, cultural, economic and psychological ties. Hrefna Karlsdóttir examines a defective informal bargaining framework, and Carol Hill and Poul Holm refer to ports as well as intangible infrastructures that shaped capital and commodity flows....
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"Pacific Salmon: Ecology and Management of Western Alaska’s Populations." In Pacific Salmon: Ecology and Management of Western Alaska’s Populations, edited by John C. Linderman and Daniel J. Bergstrom. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781934874110.ch26.

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<em>Abstract.</em>—The Kuskokwim Management Area supports subsistence, commercial, and sport fisheries for salmon. The area includes the Kuskokwim River, which is the second largest river system in Alaska, and the drainages that flow into Kuskokwim Bay, notably the Kanektok and Goodnews rivers. The salmon fisheries in the region are managed to achieve spawning escapement goals. When salmon abundance is projected to exceed these goals, managers allow harvest by the subsistence, commercial, and sport fisheries. If the harvestable surplus is limited, the subsistence fishery has a priority to access these salmon over the commercial and sport fisheries. This paper describes the status of salmon stocks, fisheries, and management practices used in the Kuskokwim River and Bay. Abundance of Kuskokwim area salmon stocks have been increasing during the 2000s since the poor runs that occurred from 1998 through 2000. Chinook <em>Oncorhynchus tshawytscha</em>, chum salmon <em>O. keta</em>, and sockeye <em>O. nerka </em>salmon stocks have achieved above average to record escapements since 2004. Although abundance of coho salmon <em>O. kisutch </em>has decreased in recent years, they achieved a record run in 2003. In most years, escapement goals have been met or exceeded. “Amounts necessary for subsistence” have been achieved for most species each year since 2001, with the exception of sockeye salmon in 2002. Although overall salmon abundance has increased in recent years, commercial fishery harvest has remained below historical averages, primarily because of poor salmon markets, low commercial fishing effort, and limited availability of commercial processing. Expanded escapement monitoring, the development of new escapement goals, estimation of total run sizes, effects of selective fishing, and improvement of commercial markets are all areas for future management and research focus.
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Lele, Uma, and Sambuddha Goswami. "Financing for Sustainable Structural Transformation." In Food for All, 394–496. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198755173.003.0008.

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Official development assistance (ODA) and domestic expenditures of developing countries on food and agriculture are often too small, relative to needs or for stimulating private investment. ODA and expenditures are suboptimally allocated mostly to subsidies, with little to public goods, such as agricultural education, research, and extension. Learning and evaluation of impacts need to improve and expand to meet complex challenges facing farmers. The multisectoral nature of agriculture means that agricultural financing must consist of multiple components, with resources that are public, private (household), and private (external to household), coming from six categories: public—domestic and international; private—domestic and international; and household—savings and remittances. Information on “traditional” ODA for agriculture is more available than for “nontraditional” ODA: for example, from emerging countries, including China’s growing involvement in Southern countries, private investments in value chains, land purchases, and private philanthropy. Aside from the Bill and Melinda Gates Foundation (BMGF), few philanthropists report aid to the Organisation for Economic Co-operation and Development–Development Assistance Committee (OECD–DAC). BMGF’s Aid Transparency Index (ATI) rating improved only from “very poor” (18.1 percent) in 2013 to “fair” (47.3 percent) in 2018. The 2020 ATI reported significant improvement in aid donors’ overall transparency, but less in impact of aid projects. New themes, including nutrition and the environment, pose challenges to estimating sources of resource flows in support of adaptation of agriculture. We show that, even though available aid has increased since 2020, resources are very small relative to needs and the extent of advocacy.
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Conference papers on the topic "Melt pool flow"

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Luo, Simin, Xin'an Wang, Yapei Zhang, Dalin Zhang, Suizheng Qiu, and Guanghui Su. "Numerical Research on Melt Pool Flow Characteristics Under Rolling Condition." In 2018 26th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icone26-81994.

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In-vessel-retention (IVR) has become an important subject of severe accident mitigation strategy. Up to now, many experimental and numerical investigations have been performed on the natural convection characteristics in melt pools with volumetric heating. But these studies are limited to the melt pools under static condition. As floating nuclear reactors become increasingly popular among both commercial and military ships, for successful application of IVR in this occasion, research should be done on the heat transfer characteristics of melt pool under moving conditions. Currently, the specially-designed facility is under construction in Xi'an China for the relevant experiment and numerical studies are performed beforehand. In this paper, a hemisphere with an inner radius of 0.5m, similar to LIVE experimental facility, is chosen to simulate the melt pool. Its flow behaviors under periodic rolling condition are simulated by means of CFD calculation. This work may cast a light on the melt pool characteristics under moving conditions and could be further evaluated by future experimental data.
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Li, Yourong, Nobuyuki Imaishi, Takeshi Azami, and Taketoshi Hibiya. "Thermocapillary flow in a thin annular pool of silicon melt." In International Symposium on Optical Science and Technology, edited by Ravindra B. Lal, Donald O. Frazier, and Narayanan Ramachandran. SPIE, 2002. http://dx.doi.org/10.1117/12.450139.

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Noori Rahim Abadi, Seyyed Mohammad Ali, Yongcui Mi, Fredrik Sikström, and Isabelle Choquet. "Influence of Laser Beam Shaping on Melt Pool Thermocapillary Flow." In 6th World Congress on Mechanical, Chemical, and Material Engineering. Avestia Publishing, 2020. http://dx.doi.org/10.11159/htff20.125.

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4

Williams, K., William O'Neill, and William M. Steen. "Melt-pool and keyhole dynamics during thin-plate laser welding of steel." In Ninth International Symposium on Gas Flow and Chemical Lasers, edited by Costas Fotakis, Costas Kalpouzos, and Theodore G. Papazoglou. SPIE, 1993. http://dx.doi.org/10.1117/12.144555.

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Li, You-Rong, Lan Peng, Shuang-Ying Wu, Dan-Ling Zeng, and Nobuyuki Imaishi. "Three-Dimensional Flow of Silicon Melt in a Rotating Shallow Annular Pool." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-60640.

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In order to understand the mechanism of the surface patterns on silicon melt in Czochralski furnaces, we conducted a series of unsteady three-dimensional numerical simulations of silicon melt flow in a rotating shallow annular pool in the counter-clockwise direction under micro-gravity. The pool is heated from the outer cylindrical wall and cooled at the bottom of an inner cylinder. The temperature differences between the vertical outer wall and the inner wall are 16 K, 21 K, 26 K and 32 K. Bottom and top surfaces of the melt pool are adiabatic. When the rotation rate is very slow, the hydrothermal waves are dominant in the pool and propagate in a direction opposite to the pool rotation. When the rotation rate exceeds the first critical value, the phase velocity of the hydrothermal waves increases rapidly and its propagating direction becomes same as that of the pool rotation. With much larger rotation rate, the flow becomes an axisymmetric steady flow. Details of the flow and temperature disturbances are discussed and the critical rotation rates are determined.
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6

Ma, Chao, Madhu Vadali, Neil A. Duffie, Frank E. Pfefferkorn, and Xiaochun Li. "Melt Pool Flow and Surface Evolution During Pulsed Laser Micro Polishing of Ti6Al4V." In ASME 2013 International Manufacturing Science and Engineering Conference collocated with the 41st North American Manufacturing Research Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/msec2013-1117.

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Extensive experimental work has shown that pulsed laser micro polishing (PLμP) is effective for polishing micro metallic parts. However, the process physics have not been fully understood yet, especially with respect to the melt pool flow. A reliable physical model can be of significant assistance in understanding the fluid flow in the melt pool and its effect on PLμP. In this paper, a two-dimensional axisymmetric transient model that couples heat transfer and fluid flow is described that was constructed using the finite element method. The model not only provided the solutions to the temperature and velocity fields but also predicted the surface profile evolution on a free deformable surface. The simulated melt depth and resolidified surface profiles matched those obtained from optical images of PLμPed sample cross-sections. The model was also used to study the effect of laser pulse duration on the melt pool flow. The study suggests that longer pulses produce more significant fluid flows. The cut-off pulse duration below which minimal fluid flows should be expected was estimated to be 0.66 μs for Ti6Al4V, which also matched well with the experimental results. It is evident that the coupled model offers reliable predictions and thus can be extended for a more complex parametric study to provide further insights for PLμP.
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7

Zhou, Jun, Mohammad S. Davoud, and Hai-Lung Tsai. "Investigation of Transport Phenomena in Three-Dimensional Gas Metal Arc Welding of Thick Metals." In ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32686.

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Arc welding is generally used to join thick metals in many engineering applications. However, poor penetration often occurs due to arc heat diffusion into the base metal. Hence, arc welding of thick metals normally requires grooving and/or preheating of the base metal and sometimes requires multiple passes for very thick metals or metals with high conductivity, such as aluminum alloys. In gas metal arc welding of thick metals with grooves and preheating, complicated melt flow and heat transfer are caused by the combined effect of droplet impingement, gravity, electromagnetic force, surface tension, and plasma arc pressure. Understanding these complicated transport phenomena involved in the welding process is critical in improving the penetration depth and weld quality. In this study, mathematical models and associated numerical techniques have been developed to study the effects of grooves and preheating on melt flow, diffusion of species, and weld penetration in gas metal arc welding of thick metals. Complex melt flow, transient weld pool shape and distributions of temperature and species in the weld pool are calculated. The continuum formation is adopted to handle liquid region, mushy zone and solid region. VOF technique is used to handle transient deformed shape of weld pool surface. The preliminary results show both grooves and preheating have important effects on the melt flow in weld pool and the weld penetration. Computer animations showing the evolutions of temperature; melt flow; and the interaction between droplets and weld pool will be presented.
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8

Horvat, Andrej, Ivo Kljenak, and Jure Marn. "Dynamics of Heat Transfer in the Melt Pool at Nuclear Severe Accident Conditions." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0995.

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Abstract Prediction of thermal loads on nuclear reactor vessel lower plenum after core melting and relocation during a severe accident requires knowledge about the core melt behavior, especially the circulation pattern. To analyze the heat transfer dynamics on the lower plenum walls, two-dimensional numerical simulations of a fluid flow with internal heat generation were performed for Rayleigh numbers 106, 107, 108, 109, 1011 and 1013 at Prandtl number 0.8. For subgrid motion modeling, a Large-Eddy Simulation Smagorinsky model was implemented. The minimum, time-average and maximum Nusselt numbers on the boundaries were calculated. The dynamics of fluid structures were analyzed to reveal the instability mechanisms and transition to turbulence. Results disclose Rayleigh-Taylor instabilities as a dominant mechanism for turbulence appearance, which occurs when the Rayleigh number is increased over 108. The structure dependence of fluid motion at high Rayleigh numbers makes the time-average of heat transfer hard to assess. The time-average values should be supplemented with probability distributions of related variables.
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Acharya, Ranadip, Rohan Bansal, Justin J. Gambone, and Suman Das. "Modeling of Solidification and Microstructure Evolution in the Scanning Laser Epitaxy (SLE) Process for Additive Manufacturing With Nickel-Base Superalloy Powders." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-66807.

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This paper investigates effects of natural and Marangoni convection on the resultant solidification microstructure in the scanning laser epitaxy (SLE) process. SLE is a laser-based additive manufacturing process that is being developed at the Georgia Institute of Technology for the additive manufacturing of nickel-base superalloys components with equiaxed, directionally-solidified or single-crystal microstructures through the laser melting of alloy powders onto superalloy substrates. A combined thermal and fluid flow model of the system simulates a heat source moving over a powder bed and dynamically adjusts the thermophysical property values. The geometrical and thermal parameters of the simulated laser melt pool are used to predict the solidification behavior of the alloy. The effects of natural and Marangoni convection on the resultant microstructure are evaluated through comparison with a pure conduction model. Inclusion of Marangoni effect produces shallower melt pools compared to a pure conduction model. A detailed flow analysis provides insights into the flow characteristics of the powder, the structure of rotational vortices created in the melt pool, and the solidification phenomena in the melt pool. The modeling results are compared with measurements and observation through real-time thermal imaging and video microscopy to understand the flow phenomenon. In contrast to the single weld-bead approach, the raster scan in SLE allows every position in melt pool to be visited twice by the solid-liquid interface as the scan source progresses. To properly address this situation, time tracking is incorporated into the model to correctly couple the microstructure prediction model. An optimization study is carried out to evaluate the critical values of the transition parameters that govern the columnar-to-equiaxed transition (CET) and the oriented-to-misoriented (OMT) transition. This work is sponsored by the Office of Naval Research through grant N00014-11-1-0670.
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Mujumdar, Soham S., Davide Curreli, Shiv G. Kapoor, and David Ruzic. "Modeling of Melt-Pool Formation and Material Removal in Micro Electro-Discharge Machining." In ASME 2014 International Manufacturing Science and Engineering Conference collocated with the JSME 2014 International Conference on Materials and Processing and the 42nd North American Manufacturing Research Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/msec2014-4108.

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This paper presents a μ – EDM melt-pool model to predict workpiece (anode) material removal from a single discharge μ – EDM process. To model the melt-pool heat transfer and fluid flow equations are solved in the domain containing dielectric and workpiece material. A level set method is used to identify solid and liquid fractions of the workpiece material when the material is molten by μ – EDM plasma heat flux. The plasma heat flux, plasma pressure and the radius of the plasma bubble have been estimated by a μ – EDM plasma model and serve as inputs to the melt-pool model to predict the volume of material removed from the surface of the workpiece. Experiments are carried out to study the effect of inter-electrode voltage and gap distance on the crater size. For inter-electrode voltage in the range of 100–150 V and gap distance of 0.5–2 μm, the model predicts crater diameter in the range of 150–165 μm and maximum crater depth of 25–35 μm for discharge duration of 5 μs. The crater sizes for most of experimental craters at higher gap distances show good agreement with the simulated crater shapes. However, at lower gaps, the model over-predicts the crater size.
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Reports on the topic "Melt pool flow"

1

McHugh, P. R., and J. D. Ramshaw. A computational model for viscous fluid flow, heat transfer, and melting in in situ vitrification melt pools. Office of Scientific and Technical Information (OSTI), November 1991. http://dx.doi.org/10.2172/10140275.

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2

McHugh, P. R., and J. D. Ramshaw. A computational model for viscous fluid flow, heat transfer, and melting in in situ vitrification melt pools. Office of Scientific and Technical Information (OSTI), November 1991. http://dx.doi.org/10.2172/5504904.

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