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A Novel Flow-Balanced Friction Stir Channeling Technology: High rectangularity Design and Channel Formation Mechanisms

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ADVANCED ENGINEERING MATERIALS 2024年第22期26卷

作者： Huang, Yongxian Shan, Cheng Hu, Shengnan Wang, Shenglong Xie, Yuming Ma, Xiaotian Wang, Naijie Meng, Xiangchen Harbin Inst Technol State Key Lab Precis Welding & Joining Mat & Struc Harbin 150001 Peoples R China Harbin Inst Technol Zhengzhou Res Inst Zhengzhou 450046 Peoples R China Beijing Hangxing Machinery Mfg Co Ltd Beijing 100013 Peoples R China

Friction stir channeling (FSC) presents a promising approach for achieving continuous channels in heat exchangers, which are considered as leading candidates for high-efficiency thermal dissipation. However, the irregular cross-sectional shape of prepared channels induces stress concentration and compromises the load-bearing capacity and structural integrity. Herein, flow-balanced FSC (FB-FSC) technology is proposed to fabricate channels with enhanced rectangularity. This technique allows for precise control over the shape, path, position, and arrangement of the channels. The channel formation in FB-FSC is affected by material overflow-reflux behaviors and stick-slip conditions. Material overflows onto the shoulder due to shearing and extraction then refluxes under axial pressure to close the channel. The material stuck to the probe rotates accordingly and is pulled out into the channel cavity to form a deposition layer. By regulating channel formation mechanisms, channel rectangularity of 90.8%, continuous formation of 14 m, minimum spacing of 2 mm, variable arc radius, and gradient distribution are directly achieved via FB-FSC. The FB-FSC technology enables the efficient formation of cooling channels with high quality, which is significant for the design of heat exchangers to realize desired performances. Flow-balanced friction stir channeling is proposed for the fabrication of channels with high rectangularity. Balanced material overflow-reflux behaviors are achieved to get regular channels. Stick-slip condition guides the easing of material deposition behavior. High channel rectangularity achieves 90.8% with excellent processing *** (c) 2024 WILEY-VCH GmbH

关键词： channel formation mechanisms flow-balanced friction stir channeling material overflow-reflux behaviors rectangularity stick-slip condition

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A role of rectangularity in perceiving a 3D shape of an object

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VISION RESEARCH 2024年 221卷 108433页

作者： Dvoeglazova, Maria Sawada, Tadamasa HSE Univ Sch Psychol Moscow Russia Amer Univ Armenia Akian Coll Sci & Engn Yerevan Armenia Russian Armenian Slavon Univ Dept Psychol Yerevan Armenia European Univ Armenia Yerevan Armenia

rectangularity and perpendicularity of contours are important properties of 3D shape for the visual system and the visual system can use them as a priori constraints for perceiving shape veridically. The present article provides a comprehensive review of prior studies of the perception of rectangularity and perpendicularity and it discusses their effects on 3D shape perception from both theoretical and empirical approaches. It has been shown that the visual system is biased to perceive a rectangular 3D shape from a 2D image. We thought that this bias might be attributable to the likelihood of a rectangular interpretation but this hypothesis is not supported by the results of our psychophysical experiment. Note that the perception of a rectangular shape cannot be explained solely on the basis of geometry. A rectangular shape is perceived from an image that is inconsistent with a rectangular interpretation. To address this issue, we developed a computational model that can recover a rectangular shape from an image of a parallelopiped. The model allows the recovered shape to be slightly inconsistent so that the recovered shape satisfies the a priori constraints of maximum compactness and minimal surface area. This model captures some of the phenomena associated with the perception of the rectangular shape that were reported in prior studies. This finding suggests that rectangularity works for shape perception by incorporating it with some additional constraints.

关键词： rectangularity Perpendicularity 3D shape perception Manhattan world Carpenter world

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Robust Markov Decision Processes: Beyond rectangularity

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MATHEMATICS OF OPERATIONS RESEARCH 2023年第1期48卷 203-226页

作者： Goyal, Vineet Grand-Clement, Julien Columbia Univ Dept Ind Engn & Operat Res New York NY 10027 USA Ecole Hautes Etud Commerciales HEC Paris Dept Informat Syst & Operat Management F-78350 Jouy En Josas France

We consider a robust approach to address uncertainty in model parameters in Markov decision processes (MDPs), which are widely used to model dynamic optimization in many applications. Most prior works consider the case in which the uncertainty on transitions related to different states is uncoupled and the adversary is allowed to select the worst possible realization for each state unrelated to others, potentially leading to highly conservative solutions. On the other hand, the case of general uncertainty sets is known to be intractable. We consider a factor model for probability transitions in which the transition probability is a linear function of a factor matrix that is uncertain and belongs to a factor matrix uncertainty set. This is a fairly general model of uncertainty in probability transitions, allowing the decision maker to model dependence between probability transitions across different states, and it is significantly less conservative than prior approaches. We show that under an underlying rectangularity assumption, we can efficiently compute an optimal robust policy under the factor matrix uncertainty model. Furthermore, we show that there is an optimal robust policy that is deterministic, which is of interest from an interpretability standpoint. We also introduce the robust counterpart of important structural results of classical MDPs, including the maximum principle and Blackwell optimality, and we provide a computational study to demonstrate the effectiveness of our approach in mitigating the conservativeness of robust policies.

关键词： Markov decision processes robust optimization rectangularity

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Dynamic consistency and rectangularity for the smooth ambiguity model

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JOURNAL OF ECONOMIC THEORY 2025年 225卷

作者： Savochkin, Andrei Shklyaev, Alexander Galatenko, Alexey Bocconi Univ Bocconi Italy Moscow State Univ Moscow Russia

We study the Smooth Ambiguity decision criterion in the dynamic setting to understand when it can satisfy the Dynamic Consistency and Consequentialism properties. These properties allow one to rewrite the decision criterion recursively and solve for optimal decisions by Dynamic Programming. Our result characterizes the possibility of having these properties through a condition that resembles Epstein and Schneider's (2003) rectangularity condition for the maxmin model. At the same time, we show that Dynamic Consistency and Consequentialism can be achieved for Smooth Ambiguity preferences in a narrower set of scenarios than one would hope for.

关键词： Smooth ambiguity Dynamic consistency Consequentialism rectangularity

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Variations in the morphometric characteristics of Fragilariopsis kerguelensis in the Southwest Pacific sector of the Southern Ocean over the past 40,000 years

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MARINE MICROPALEONTOLOGY 2025年 195卷

作者： Crosta, Xavier Sutre, Thibault Univ Bordeaux CNRS EPHE UMR 5805EPOC F-33405 Pessac France

High-throughput measurements demonstrated the presence of two morphotypes of Fragilariopsis kerguelensis in the Atlantic sector of the Southern Ocean, the proportions of which in downcore samples may be used to reconstruct past sea-surface temperatures quantitatively. We here measured the mean length, width, area, and rectangularity in core SO136-111 to assess variations in both morphotypes in the Polar Front Zone of the western Pacific sector of the Southern Ocean over the past 40,000 years. Mean length, width, and area increased rapidly at the end of the glacial period when the Polar Front migrated southward to reach the core site, ocean temperature increased, and sea ice was no longer present. In contrast, mean rectangularity decreased at the end of the glacial period, when the proportion of the cold-water, high-rectangularity morphotype declined as the ocean warmed at the core site. Downcore patterns and quantitative values of all morphometric characteristics in the southwest Pacific sector agree well with previous studies from the Atlantic sector, suggesting the presence of a similar population of F. kerguelensis in the open Southern Ocean. Nevertheless, rectangularity-based relationships can ultimately produce unrealistic estimates of sea-surface temperatures in core SO136-111 when the proportion of the high-rectangularity morphotype is too low, indicating that these approaches are now limited to temperatures below 3-4 degrees C.

关键词： Fragilariopsis kerguelensis Morphometrics rectangularity Biogeography Sea-surface temperature

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Distributionally robust modeling of optimal control

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OPERATIONS RESEARCH LETTERS 2022年第5期50卷 561-567页

作者： Shapiro, Alexander Georgia Inst Technol Sch Ind & Syst Engn Atlanta GA 30332 USA

The aim of this paper is to formulate several questions related to distributionally robust Stochastic Optimal Control modeling. As an example the distributionally robust counterpart of the classical inventory model is discussed in details. Finite and infinite horizon stationary settings are considered. (c) 2022 Elsevier B.V. All rights reserved.

关键词： Optimal control Distributional robustness Risk measures rectangularity Inventory model

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Conditional Distributionally Robust Functionals

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OPERATIONS RESEARCH 2024年第6期72卷 2745-2757页

作者： Shapiro, Alexander Pichler, Alois Georgia Inst Technol Sch Ind & Syst Engn Atlanta GA 30332 USA Univ Technol Fac Math D-09126 Chemnitz Germany

Many decisions, in particular decisions in a managerial context, are subject to uncertainty. Risk measures cope with uncertainty by involving more than one candidate probability. The corresponding risk averse decision takes all potential candidate probabilities into account and is robust with respect to all potential probabilities. This paper considers conditional robust decision making, where decisions are subject to additional prior knowledge or information. The literature discusses various definitions to characterize the corresponding conditional risk measure, which determines further the decision. The aim of this paper is to compare two different approaches for the construction of conditional functionals used in multistage distributionally robust optimization. As an application, we discuss conditional counterparts of a distance between probability measures.

关键词： distributional robustness conditional risk measures strict monotonicity Wasserstein distance rectangularity

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Dynamically consistent objective and subjective rationality

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ECONOMIC THEORY 2022年第2期74卷 477-504页

作者： Bastianello, Lorenzo Faro, Jose Heleno Santos, Ana Univ Paris 2 Pantheon Assas LEMMA 4 Rue Blaise Desgoffe F-75006 Paris France Insper Rua Quata 300 BR-04546042 Sao Paulo Brazil

A group of experts, for instance climate scientists, is to advise a decision maker about the choice between two policies f and g. Consider the following decision rule. If all experts agree that the expected utility of f is higher than the expected utility of g, the unanimity rule applies, and f is chosen. Otherwise, the precautionary principle is implemented and the policy yielding the highest minimal expected utility is chosen. This decision rule may lead to time inconsistencies when adding an intermediate period of partial resolution of uncertainty. We show how to coherently reassess the initial set of experts' beliefs so that precautionary choices become dynamically consistent: new beliefs should be added until one obtains the smallest "rectangular set" that contains the original one. Our analysis offers a novel behavioral characterization of rectangularity and a prescriptive way to aggregate opinions in order to avoid sure regret.

关键词： Ambiguity Aversion Dynamic Consistency Objective Rationality Subjective Rationality Full Bayesian Updating rectangularity

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Revisiting the concept of squareness of engineering magnetic RE-Fe-B materials hysteresis curves

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JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 2024年 610卷

作者： Perigo, E. A. Fim, R. G. T. Faria, R. N. ABB US Corp Res Ctr 1021 Main Campus Dr Raleigh NC USA Alkimat Technol Sao Jose Brazil Univ Sao Paulo Nucl & Energy Res Inst Campus USP IPEN Sao Paulo Brazil

The hysteresis loop shape has been a topic of interest within the area of engineering magnetic materials ranging from nano to macro scales. The literature related to its terminology, quantification propositions, significance, and relationships among proposed methods is initially revisited, clarifying potential misconceptions and illustrating its relevance in the hard-magnetic materials area. Next, relationships of the shape of the second quadrant of permanent magnets related to crystallographic alignment, microstructural features/temperature, and chemical composition/processing are discussed focusing on rare-earth-based compounds.

关键词： Magnetic films Magnetic materials Permanent magnets rectangularity Squareness factor

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Factors controlling individual branch development during early growth of an experimental plantation ofEucalyptus pilularisin sub-tropical Australia

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TREES-STRUCTURE AND FUNCTION 2021年第2期35卷 395-405页

作者： West, P. W. Ratkowsky, D. A. Smith, R. G. B. Southern Cross Univ Forest Res Ctr Lismore NSW 2480 Australia Univ Tasmania Tasmanian Inst Agr Private Bag 98 Hobart Tas 7001 Australia

Key message Branch sizes and their vertical orientation increase progressively further up the lower stem to support a newly developing crown. Diameter at base, orientation, and height up the stem of live branches on the lower 5 m of tree stems were measured several times over 2.5-5.7 years of age in an experimental plantation of blackbutt (Eucalyptus pilularis) in sub-tropical eastern Australia. Stocking density at planting varied over 816-1667 stems ha(-1)and rectangularity of planting (ratio of distance between rows to distance between trees within rows) over 1-6. Tree stem diameters, heights and crown dimensions were also measured. The height above ground at which branches emerged from the stem was a primary factor determining their growth;the higher they were, the greater was their diameter and the more vertical their orientation. This was believed to reflect both a need for newer branches to grow larger than older branches, to support greater amounts of foliage as the crowns expanded towards full size, and for branches to be better oriented to seek sunlight as the crowns of surrounding trees also expanded. Secondary factors determining branch size were tree size and spacing between trees, factors that are likely to interact with each other. Larger trees tended to have larger branches, to support more leaf weight in larger crowns. The direction of emergence of branches from stems seemed little affected by tree or stand characteristics at these early stages of tree development. The results did not suggest any need to modify existing pruning regimes that have been developed for fast-growing eucalypt plantations in Australia.

关键词： Branching Eucalyptus Stocking density rectangularity Pruning

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