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Relevant bibliographies by topics / Highest weight modules

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Academic literature on the topic 'Highest weight modules'

Author: Grafiati

Published: 6 September 2023

Last updated: 7 September 2023

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Journal articles on the topic "Highest weight modules"

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Adams, Jeffrey. "Unitary highest weight modules." Advances in Mathematics 63, no. 2 (February 1987): 113–37. http://dx.doi.org/10.1016/0001-8708(87)90049-1.

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Matumoto, Hisayosi. "Whittaker modules associated with highest weight modules." Duke Mathematical Journal 60, no. 1 (February 1990): 59–113. http://dx.doi.org/10.1215/s0012-7094-90-06002-8.

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Dimitrov, I., and I. Penkov. "Partially integrable highest weight modules." Transformation Groups 3, no. 3 (September 1998): 241–53. http://dx.doi.org/10.1007/bf01236874.

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Chen, Guobo. "A Family of Non-weight Modules over the Virasoro Algebra." Algebra Colloquium 27, no. 04 (November 5, 2020): 807–20. http://dx.doi.org/10.1142/s100538672000067x.

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In this paper, we consider the tensor product modules of a class of non-weight modules and highest weight modules over the Virasoro algebra. We determine the necessary and sufficient conditions for such modules to be simple and the isomorphism classes among all these modules. Finally, we prove that these simple non-weight modules are new if the highest weight module over the Virasoro algebra is non-trivial.

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Grishkov, A. N., and F. Marko. "Description of costandard modules for Schur superalgebra S(2|2) in positive characteristic." Journal of Algebra and Its Applications 17, no. 02 (January 23, 2018): 1850038. http://dx.doi.org/10.1142/s021949881850038x.

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In this paper, we shall describe costandard modules [Formula: see text] of restricted highest weight [Formula: see text] for Schur superalgebra [Formula: see text] over an algebraically closed field [Formula: see text] of positive characteristic [Formula: see text]. Additionally, for a restricted highest weight [Formula: see text], we determine all composition factors of the costandard module [Formula: see text]; in particular we compute the decomposition numbers in the process of the modular reduction of a simple module with a restricted highest weight.

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Matumoto, Hisayosi. "Correction to Whittaker modules associated with highest weight modules." Duke Mathematical Journal 61, no. 3 (December 1990): 973. http://dx.doi.org/10.1215/s0012-7094-90-06137-x.

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Mazorchuk, Volodymyr, and Kaiming Zhao. "Characterization of Simple Highest Weight Modules." Canadian Mathematical Bulletin 56, no. 3 (September 1, 2013): 606–14. http://dx.doi.org/10.4153/cmb-2011-199-5.

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Abstract.We prove that for simple complex finite dimensional Lie algebras, affine Kac–Moody Lie algebras, the Virasoro algebra, and the Heisenberg–Virasoro algebra, simple highest weight modules are characterized by the property that all positive root elements act on these modules locally nilpotently. We also show that this is not the case for higher rank Virasoro algebras and for Heisenberg algebras.

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Boyallian, Carina, and Vanesa Meinardi. "Quasi-finite highest weight modules overWN∞." Journal of Physics A: Mathematical and Theoretical 44, no. 23 (May 6, 2011): 235201. http://dx.doi.org/10.1088/1751-8113/44/23/235201.

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Huang, Jing-Song, and Wei Xiao. "Dirac cohomology of highest weight modules." Selecta Mathematica 18, no. 4 (January 17, 2012): 803–24. http://dx.doi.org/10.1007/s00029-011-0085-8.

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Neeb, Karl-Hermann. "Square integrable highest weight representations." Glasgow Mathematical Journal 39, no. 3 (September 1997): 296–321. http://dx.doi.org/10.1017/s0017089500032237.

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If G is the group of holomorphic automorphisms of a bounded symmetric domain, then G has a distinguished class of irreducible unitary representations called the holomorphic discrete series of G. These representations have been studied by Harish-Chandra in [7]. On the Lie algebra level, the Harish-Chandra modules corresponding to the holomorphic discrete series representations are highest weight modules. Even for G as above, it turns out that not all the unitary highest weight modules belong to the holomorphic discrete series but there exists a condition on the highest weight which characterizes the holomorphic discrete series among the unitary highest weight representations. They can be defined as those unitary highest weight representations with square integrable matrix coefficients.

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Dissertations / Theses on the topic "Highest weight modules"

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Kac, Victor G., Minoru Wakimoto, and kac@math mit edu. "Integrable Highest Weight Modules over Affine Superalgebras and Appell's." ESI preprints, 2000. ftp://ftp.esi.ac.at/pub/Preprints/esi920.ps.

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Takemura, Koichi. "The decomposition of level-1 irreducible highest-weight modules with respect to the level-0 actions of the quantum affine algebra." 京都大学 (Kyoto University), 2000. http://hdl.handle.net/2433/181094.

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Krishna, Teja G. V. "Weights of highest weight modules over Kac-Moody algebras." Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5886.

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In this dissertation, broadly, we treat the weight-sets of arbitrary highest weight modules (uniformly) over all general complex Kac-Moody Lie algebras $\mathfrak{g}$, achieving the below. We obtain a uniform, explicit, cancellation-free and positive formula for the weight-sets of all highest weight modules $V$ (of all highest weights) over all Kac-Moody $\mathfrak{g}$. Interestingly, our formula for the weights of $V$ involves basic ingredients, namely the independent subsets in the Dynkin diagram of $\mathfrak{g}$ determined by $V$, and nothing else! Prior to our work, it seems that even for all (non-integrable) simple highest weight $\mathfrak{g}$-modules - despite these being treated for over a half century - their weight-formulas were not known until a few years ago. Namely, these were written-up in Khare [J. Alg. 2016] and Dhillon-Khare [Adv. Math. 2017 and J. Alg. 2022]; and our general formula recovers the formulas for simples in these papers. Leaving out general Kac-Moody or even general semisimple settings, given an arbitrary highest weight module $V$ over $\mathfrak{sl}_n(\mathbb{C})$ or in particular $\mathfrak{sl}_4(\mathbb{C})$, even in this case the weights of $V$ were not written down in the literature to the best of our knowledge. More importantly, our weight-formula naturally drives us to introduce and study a finite family of ``higher order Verma modules" $\mathbb{M}(\lambda,\mathcal{H})$ over Kac-Moody $\mathfrak{g}$, for every highest weight $\lambda\in \mathfrak{h}^*$ and (any) collection $\mathcal{H}$ of independent subsets in the Dynkin diagram of $\mathfrak{g}$. This family generalizes and includes: all Verma modules $M(\lambda)=\mathbb{M}(\lambda,\emptyset)$ at zeroth order level, and the parabolic Verma modules $M(\lambda,J)=\mathbb{M}(\lambda, \{ \{j\} \ |\ j\in J \})$ (which were introduced and studied by Lepowsky, Kumar, Mathieu,... to name but a few) at first order level. Importantly, our higher order Verma modules are crucial and universal for weight considerations: their weight-sets (which are finitely many when we fix their highest weight) are pairwise disjoint and exhaust the weight-sets of all highest weight $\mathfrak{g}$-modules. In this thesis, we also initiate the study of the characters of these universal modules, by computing them via BGG-type resolutions in certain cases. Next, a phenomenon in root systems which rewarded us with many applications on the weights side. First, recall the partial sum property for Kac-Moody root systems: every root of $\mathfrak{g}$ is an ordered sum of simple roots such that each partial sum is also a root. The course/journey to finding and proving our weight-formula mentioned above begins from proving a parabolic-generalization of this property, which we call as the parabolic partial sum property. Given a subset $S$ of simple roots, it allows one to write any (positive) root $\beta$ involving some simple roots from $S$ as: an ordered sum of roots, in which each root involves exactly one simple root from $S$ (unit $S$-height roots) and with each partial sum also being a root. The parabolic partial sum property has been devised in order to obtain a ``minimal" description for the weights of all (non-integrable) highest weight simples, which was posed by Khare. This thesis exhibits such minimal descriptions as an immediate application of the parabolic partial sum property; in fact we will more strongly show this property at the level of Lie words for any general Lie algebra graded over any free abelian semigroup. There is also another generalization of the partial sum property due to Khare and Kumar for highest weight simples in finite type, which we extend to the Kac-Moody setting in this thesis. There is another notable application of the parabolic partial sum property shown in this thesis. Chari and her coauthors [Adv. Math. 2009 and J. Geom. Phys. 2011] introduced and studied certain combinatorial subsets called weak faces and $(\{2\};\{1,2\})$-closed subsets of finite root systems. This is in order to construct Koszul algebras, study Kirillov-Reshetikhin modules over specializations of quantum affine algebras, and also to classify nilpotent ideals in the parabolic Lie subalgebras of finite type $\mathfrak{g}$, etc. These subsets (say subsets of a set $X$) are some discrete analogues/ generalizations of the faces for convex sets (the faces of the convex hull of $X$). In this thesis, we are concerned with such subsets of $X=$ a weight-set, generalizing the faces for convex hulls of weight-sets. Using the weak faces for weight-sets of finite-dimensional simples (in finite type) Khare extended the aforementioned results of Chari et al. Motivated by the applications of these two modern notions to representation theory, we completely classify the weak faces and $(\{2\};\{1,2\})$-closed subsets of weights of all highest weight modules (again uniformly) over all Kac-Moody $\mathfrak{g}$; extending and completing the partial classification results of Chari, Khare, and their co-authors from finite type. We more strongly show that both these notions are the same as the weights falling on the faces, for the convex hulls of these weight-sets. This shows the equivalence of these two notions, to the classical faces for the convex hulls of weights (which have been pursued from the 1960s).
NBHM Ph.D. Fellowship (Ref. No. 2/39(2)/2016/NBHM/R&D-II/11431) and by a Swarnajayanti Fellowship from the DST and SERB (Govt. of India).

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Ahmadi, Amir. "Axiomatic approach to cellular algebras." Thesis, 2020. http://hdl.handle.net/1866/23949.

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Les algèbres cellulaires furent introduite par J.J. Graham et G.I. Lehrer en 1996. Elles forment une famille d’algèbres associatives de dimension finie définies en termes de « données cellulaires » satisfaisant certains axiomes. Ces données cellulaires, lorsqu’elles sont identifiées pour une certaine algèbre, permettent une construction explicite de tous ses modules simples, à isomorphisme près, et de leurs couvertures projectives. Dans ce mémoire, nous définissons ces algèbres cellulaires en introduisant progressivement chacun des éléments constitutifs d’une façon axiomatique. Deux autres familles d’algèbres associatives sont discutées, à savoir les algèbres quasihéréditaires et celles dont les modules forment une catégorie de plus haut poids. Ces familles furent introduites durant la même période de temps, au tournant des années quatre-vingtdix. La relation entre ces deux familles ainsi que celle entre elles et les algèbres cellulaires sont prouvées.
Cellular algebras were introduced by J.J. Graham and G.I. Lehrer in 1996. They are a class of finite-dimensional associative algebras defined in terms of a “cellular datum” satisfying some axioms. This cellular datum, when made explicit for a given associative algebra, allows for the explicit construction of all its simple modules, up to isomorphism, and of their projective covers. In this work, we define these cellular algebras by introducing each building block of the cellular datum in a fairly axiomatic fashion. Two other families of associative algebras are discussed, namely the quasi-hereditary algebras and those whose modules form a highest weight category. These families were introduced at about the same period. The relationships between these two, and between them and the cellular ones, are made explicit.

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Tuček, Vít. "Invariantní differenciální operátory pro 1-gradované geometrie." Doctoral thesis, 2017. http://www.nusl.cz/ntk/nusl-368920.

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In this thesis we classify singular vectors in scalar parabolic Verma modules for those pairs (sl(n, C), p) of complex Lie algebras where the homogeneous space SL(n, C)/P is the Grassmannian of k-planes in Cn . We calculate cohomology of nilpotent radicals with values in certain unitarizable highest weight modules. According to [BH09] these modules have BGG resolutions with weights determined by this cohomology. Such resolutions induce complexes of invariant differential operators on sections of associated bundles over Hermitian symmetric spaces. We describe formal completions of unitarizable highest weight modules that one can use to modify method from [CD01] that constructs sequences of differential operators over any 1-graded (aka almost Hermitian) geometry. We suggest uniform description of octonionic planes that could serve as a basis for better understanding of the exceptional Hermitian symmetric space for group E6.

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Books on the topic "Highest weight modules"

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1958-, Shelton Brad, ed. Categories of highest weight modules: Applications to classical Hermitian symmetric pairs. Providence, Rhode Island, USA: American Mathematical Society, 1987.

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Jakobsen, Hans Plesner. The full set of unitarizable highest weight modules of basic classical Lie superalgebras. Providence, RI: American Mathematical Society, 1994.

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Fermat's last theorem. Providence, Rhode Island: American Mathematical Society, 2013.

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Book chapters on the topic "Highest weight modules"

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Joseph, Anthony. "Highest Weight Modules." In Quantum Groups and Their Primitive Ideals, 96–130. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-78400-2_5.

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Humphreys, James. "Highest weight modules I." In Graduate Studies in Mathematics, 73–92. Providence, Rhode Island: American Mathematical Society, 2008. http://dx.doi.org/10.1090/gsm/094/05.

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Humphreys, James. "Highest weight modules II." In Graduate Studies in Mathematics, 93–106. Providence, Rhode Island: American Mathematical Society, 2008. http://dx.doi.org/10.1090/gsm/094/06.

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Alldridge, Alexander, and Zain Shaikh. "Superbosonisation, Riesz superdistributions, and highest weight modules." In Advances in Lie Superalgebras, 1–18. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-02952-8_1.

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Xu, Xiaoping. "Analogue of the Highest-Weight Theory." In Introduction to Vertex Operator Superalgebras and Their Modules, 203–34. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-015-9097-6_5.

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Kac, Victor G., and Minoru Wakimoto. "Integrable Highest Weight Modules over Affine Superalgebras and Number Theory." In Lie Theory and Geometry, 415–56. Boston, MA: Birkhäuser Boston, 1994. http://dx.doi.org/10.1007/978-1-4612-0261-5_15.

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Tanisaki, T. "Highest Weight Modules Associated to Parabolic Subgroups with Commutative Unipotent Radicals." In Algebraic Groups and their Representations, 73–90. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5308-9_5.

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Enright, Thomas J., Markus Hunziker, and W. Andrew Pruett. "Diagrams of Hermitian type, highest weight modules, and syzygies of determinantal varieties." In Symmetry: Representation Theory and Its Applications, 121–84. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4939-1590-3_6.

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García-Escudero, Juan, and Miguel Lorente. "Highest Weight Unitary Modules for Non-Compact Groups and Applications to Physical Problems." In Symmetries in Science V, 187–232. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4615-3696-3_10.

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Kac, Victor G., and Minoru Wakimoto. "On Characters of Irreducible Highest Weight Modules of Negative Integer Level over Affine Lie Algebras." In Lie Groups, Geometry, and Representation Theory, 235–52. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-02191-7_9.

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Conference papers on the topic "Highest weight modules"

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Bakhshi, Shashwat, Prahit Dubey, A. K. Srouji, and Zenan Wu. "Comparison of Different Liquid Cooling Configurations for Effective Thermal Management of Li-Ion Pouch Cell for Automotive Applications." In ASME 2020 Heat Transfer Summer Conference collocated with the ASME 2020 Fluids Engineering Division Summer Meeting and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/ht2020-9050.

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Abstract An effective cooling mechanism is the backbone of a good automotive battery thermal management system (BTMS). In addition to prevention of extreme events such as thermal runaway, an automotive BTMS must be able to efficiently tackle aggressive environmental temperatures, and/or discharge and charge conditions during electric vehicle operation. Moreover, electrical performance and cycle life of the battery modules and packs are closely tied to the battery temperatures and thermal gradients, which increase with increase in C-Rates. In order to keep the battery temperatures to be under the operational temperature limit, it is crucial that the selected cooling mechanism provides efficient transport of the heat generated by the battery modules and packs to the cooling media under all discharge and charge conditions. Owing to its efficient thermal performance, liquid cooling is preferred by most electric vehicle manufacturers for battery thermal management. This usually incorporates battery modules exchanging heat with a flowing coolant via cold plate or cooling channels during operation. The current work aims to investigate different liquid cooling configurations and compare their relative thermal performance during operation of a high energy density Pouch Cell. The four configurations selected for this comparison are (1) Face cooling, (2) Single-Sided cooling, (3) Double-Sided cooling, and (4) a Hybrid cooling configuration. Test setups comprising of a commercially available 9 A-h NMC Pouch cell, cold plates, pump, heat exchanger, refrigeration cooling unit, and thermal sensors are built for the above four cooling configurations. During the tests, the selected cell is discharged at different discharge rates (C-Rates), i.e., 3C, 4C, and 5C. The overall cell temperatures and thermal gradient across the cell are measured using T-type thermocouples for the four cooling configurations. In order to capture the thermal gradient across the Pouch cell accurately, several thermocouples on the face of the cell are installed using a thermal interface material. Results show the superiority of Face cooling configuration in terms of overall thermal performance under all considered test conditions. Lowest cell temperatures and thermal gradients across the cell are observed for the Face cooling configuration, while highest temperatures and thermal gradients are observed for the Single-Sided cooling configuration. Much improved thermal performance is also observed in the case of the Hybrid cooling configuration as compared to the Single and Double-Sided cooling configurations. As implementation of the Face cooling configuration at the battery pack level may result in higher weight and cost of the battery pack, owing to its good thermal performance and straightforward scaling to battery pack level, the proposed hybrid liquid cooling mechanism provides a viable alternative to Face cooling for battery thermal management.

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Æsøy, Lene, Henry Piehl, and Ann Rigmor Nerheim. "System Simulation-Based Feasibility and Performance Study of Alternative Fuel Concepts for Aquaculture Wellboats." In ASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/omae2022-81106.

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Abstract Climate change and population growth are increasing the need for sustainable food production. The ocean covers around 70% of the earth’s surface area and there is a great potential in utilizing this for ocean farming. However, the maritime traffic needs to decrease the emissions per transported mass with 50% by 2030 to meet the Paris Agreement. With an increased ocean space utilization, the vessel fleet will increase due to operational demands. Hence, with increased energy consumption, the need for decarbonization will increase further. Wellboats are one of the main contributors to the CO2-emission related to traditional fish farming production of Atlantic Salmon, not counting the actual feed production. Within the well-boat the fuel system has the highest potential to reduce the carbon footprint. However, one of the major challenges with the renewable fuels are their low energy density compared to fossil fuels. New, promising energy concepts have emerged, but they lack a quantifiable performance evaluation within the complete aquaculture supply chain. Further, the choice of the vessel’s engine, generator and consumer modules affect each other. For example, changing to a fuel with lower energy density may lead to a larger fuel storage tank which then limits the available space for the fish tank. The main objective of this study is to use graphical system simulation to model and evaluate the performance of new concepts for low- and zero-carbon fuels. Based on these simulations, new fuel concepts can be compared with conventional marine diesel systems. The simulation model can be used to detect operational limitations with respect to range, transported mass (fish), vessel size, weight, and refueling possibilities. Further, it can also be used to identify bottlenecks in terms of size, weight, and voyage limitations. Based on the outcome of the wellboat system simulation model, the feasibility of fuel systems can be evaluated and used as recommendation for the design of new wellboats. The industry needs feasible solutions which are sustainable in terms of reliability and cost. The insights gained from using the simulation model aim to assist the industry to reach their emissions reduction goals by 2030, and to provide decision support for retrofitting the fuel and energy system of wellboats.

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Bischur, Enrico, and Norbert Schwesinger. "Plane PVDF-Foil Modules for Energy Harvesting of Dynamic Weight Forces." In ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2011. http://dx.doi.org/10.1115/smasis2011-5164.

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Plane PVDF-foil modules have been developed and successfully tested that generate electrical energy out of the mechanical energy of dynamic weight forces. For instance electrical energy can be generated, if people or vehicles pass such modules on a ground area. This method is based on the piezoelectric effect of stretched PVDF-foil. The energy conversion of the generator modules was investigated with regard to the remanent polarization of the PVDF material. Furthermore, the influence of the PVDF layer system was investigated on the energy conversion. The measured values are compared with values calculated analytically. It was found that a higher remanent polarization of the PVDF material lead to a better energy conversion. Even more electrical energy could be generated, if more PVDF layers were stacked above each other. If the values were normalized on the PVDF volume used in each case, the values of the electric energy were not constant. However, a maximum was observed at n = 21 layers. The measured energy values were higher than calculated values of the longitudinal piezoelectric effect. This could be caused by a simultaneous expansion of the PVDF film in a direction vertical to the direction of the mechanical load. These generator modules could be used as new energy source for emergency lighting, alarm systems, traffic sensors, etc.

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Yuruker, Sevket U., Raphael K. Mandel, Patrick McCluskey, Michael M. Ohadi, Shiladri Chakraborty, Yongwan Park, He Yun, Alireza Khaligh, Lauren Boteler, and Miguel Hinojosa. "Advanced Packaging and Thermal Management of High-Power DC-DC Converters." In ASME 2019 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ipack2019-6559.

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Abstract Thermal management of high-power electronics is often a major obstacle in achieving improved packaging density. Emergence of SiC devices allows higher voltage and temperature limits, but thermal management is still a bottleneck in achieving compact, reliable and high-performance systems. This study introduces the design of an advanced packaging configuration of a dual-active-bridge 10 kW DC-DC converter module with 97% efficiency and ∼1.5 × 104 kW/m3 power density based on preliminary modeling analysis. The proposed packaging scheme allows for significant volume reduction and considerably lighter weight at greater power levels than commercially available converter modules. We introduce an improved placement of high power/high frequency MOSFET switches on the board that enables double-sided cooling, where the dissipated heat is removed from both sides of the switches via manifold-microchannel cooler modules. The cooler modules are additively manufactured monolithic structures made out of a thermally and electrically conductive material, which in turn allows them to double function as electrical terminals for the switches. Their unique shape minimizes footprint utilization on the board while still providing significant area enhancement over the heat dissipating chips’ footprint. Moreover, thermal management of other components with significant heat flux, such as the transformer coils and magnetic core are also accomplished via dielectric liquid cooling with electrically insulating but thermally conductive 3D printed coolers. The overall circuit diagram, assembly configuration and flow routing within the system are demonstrated. The advantages of the proposed design over commercially available modules are discussed in detail.

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Fysikopoulos, Apostolos, Theocharis Alexopoulos, George Pastras, Panos Stavropoulos, and Georgios Chryssolouris. "On the Design of a Sustainable Production Line: The MetaCAM Tool." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-52960.

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Nowadays, manufacturing enterprises face enormous environmental challenges, due to complex and diverse economic trends, including shorter product life cycles, rapid advances in science and technology, increased diversity in customer demands and globalization of production activities. Consequently, the cost is highly affected by environmentally related factors. Energy efficiency is one of the main factors, which together with waste management, affect manufacturing decisions. The complexity and diversity of the factors that determine energy efficiency require intelligent systems for their optimization at each “manufacturing level”. Manufacturing decisions should be taken as fast as possible and with the highest possible accuracy. Artificial intelligence/machine learning tools have made significant progress during the last decade and are suitable for such applications. The main objective of the current study is that an architecture for the development of a networked, online, decision support tool, be provided towards achieving sustainable value chain management. The main idea behind the proposed design is that stakeholders be assisted in taking decisions towards improving the energy and eco-efficiency of the entire value chain or parts of it. This is suggested within the context of a multi-objective optimization procedure, taking into account other important decision making attributes, such as flexibility, quality and time for the final reduction in the overall cost. This architecture incorporates real time information modules that interact with online monitoring systems, using any available information within the value chain and the existing IT tools. A partial realization of the proposed idea is implemented in the form of a user friendly software tool (the MetaCAM tool). This based, decision support tool aiming to optimize a current production line or to propose alternatives for the manufacturing of a product. The tool performs optimization based on a set of predefined criteria, namely energy, waste, cost and time. For each of these criteria, the end-user selects the desired weight factor in order to drive the optimization procedure accordingly. The tool presents the characteristics of the setup of the proposed optimized line and maintains all used data and calculations in order to be reused when necessary. For the tool’s validation, three real case studies from different industrial sectors have been used. The first case study comes from the domestic appliances sector (refrigerator door panel), the second one from the automotive sector (a two seat bench for light commercial vehicles) and finally, the third case study derives from the aeronautics sector and deals with the production of the loading ramp hinge of a military aircraft.

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Ahuja, Suresh. "Effect of Interface and Depth on Hardness and Viscoelastic Modulus in Polycarbonate and Polyester Films." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42727.

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Hardness and modulus of a polymer is known to depend on its structure, molecular weight and number of segments between entanglements. Nano-indentation is used increasingly as a powerful tool to determine hardness and visco-elastic modulus of polymer surfaces linear, cross-linked or composites. Hysitron Nanoindenter was used in our investigation of contact deformation of surfaces of polyester and polycarbonate supported on an aluminum substrate. Bar coatings of polymer films were made from solutions and dried all at 110C for half an hour. The coatings were subjected to indentation including sinusoidal deformation at various contact depths and hardness as well as modulus is computed. The results show that hardness of surface of polycarbonate on polyester is higher than hardness of surface of polycarbonate, which in turn is higher than polyester surface. It appears that diffusion of polyester chains into compatible polycarbonate chains results in higher modulus of the surface than the modulus of either of the two polymers. Hardness and modulus of polycarbonate is found to decrease with contact depth and reaches a plateau around 600nm while that of polyester keeps on decreasing. Differences in contact deformation including the one arising from dynamic deformation between polycarbonate from that of polyester is analyzed in terms of morphology, molecular weight and entanglements.

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Tesch, Alrik, Martin Lange, Konrad Vogeler, Jens Ortmanns, Erik Johann, and Volker Gümmer. "An Experimental Investigation of a Tandem Stator Flow Characteristic in a Low Speed Axial Research Compressor." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-26104.

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A major goal in axial compressor development is to increase the efficiency and to reduce the weight of the module. In order to do so the power density has to be increased by raising the work per stage. Higher capability to do work can be achieved by increasing the circumferential velocity component of the fluid. Tandem stators might offer the ability to turn high swirling flow with lower losses compared to a single blade stator. In terms of higher aerodynamic loading the use of tandem vanes can be a key feature to allow the design of highly efficient and compact compressor modules. This paper presents the design and experimental validation of a single stage low speed axial compressor with a tandem outlet guide vane, representative for a modern jet engine high pressure compressor. Additionally to the overall compressor performance the 3D flow field of the tandem stator has been measured with a five hole probe at different operating points. The results will be discussed in comparison with numerical results. Furthermore, oil flow pictures are used to get a deeper insight into flow conditions inside the vane passage and to validate the numerically predicted secondary flow structures.

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Marotta, E. E., M. J. Ellsworth, J. Norley, and G. Getz. "The Development of a Bonded Fin Graphite/Epoxy Heat Sink for High Performance Servers." In ASME 2003 International Electronic Packaging Technical Conference and Exhibition. ASMEDC, 2003. http://dx.doi.org/10.1115/ipack2003-35060.

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IBM’s has recently introduced a high performance server that utilizes multichip modules that dissipate very high heat loads. Each multichip module consists of four microprocessor chips encased by a copper cap that serves to spread the heat load over an area of roughly 113 mm × 113 mm. The module is air cooled by a single aluminum alloy bonded-fin fan sink. For applications requiring the microprocessors to operate at higher frequencies, the aluminum heat sink, with its lower thermal conductivity, cannot provide sufficient cooling; therefore, a copper heat sink must be employed. However, copper alloys have the disadvantage of a significant weight penalty (density ∼ 8.9 g/cm3), being 3.3 times heavier than aluminum (density ∼ 2.7 g/cm3), and is significantly more costly to manufacture. A novel approach for an improved heat sink has been developed using a new natural graphite-based/epoxy composite material. This material has low density (∼1.9 g/cm3) and anisotropic thermal conductivity (∼370 W/m-K in two directions, ∼ 7 W/m-K in the third direction). Bonded fin manufacturing methods have been developed to produce a heat sink that exploits the material’s high thermal conductivity when used in combination with a copper spreader module, such as used in the IBM server. Convective heat sink thermal performance approaching that of copper (e.g. 0.030 °C/W) has been achieved at a fraction of copper’s weight. Therefore, additional hardware required to allow the copper heat sinks to withstand shock and vibration standards, was not necessary with the lightweight graphite solution. Mechanical issues involved with using the lower strength graphite materials in a metal retrofit situation had to be resolved. Solutions included the use of aluminum end plates to provide edge protection to the heat sink with metal stiffeners inserted into the base for extra structural integrity. A variety of mechanical attachment methods was evaluated to join the graphite to the copper heat spreader. Lapping procedures were developed for the graphite heat sink to provide the required flatness necessary to minimize the temperature drop across the interface.

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Tehrani, Mehran, Masoud Safdari, Scott W. Case, and Marwan S. Al-Haik. "Using Multiscale Carbon Fiber/Carbon Nanotubes Composites for Damping Applications." In ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2011. http://dx.doi.org/10.1115/smasis2011-5087.

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A novel technique to grow carbon nanotubes (CNTs) on the surface of carbon fibers in a controlled fashion using simple lab set up is developed. Growing CNTs on the surface of carbon fibers will eliminate the problem of dispersion of CNTs in polymeric matrices. The employed synthesis technique retains the attractive feature of uniform distribution of the grown CNTs, low temperature of CNTs’ formation, i.e. 550 °C, via cheap and safe synthesis setup and catalysts. A protective thermal shield of thin ceramic layer and subsequently nickel catalytic particles are deposited on the surface of the carbon fiber yarns using magnetron sputtering. A simple tube furnace setup utilizing nitrogen, hydrogen and ethylene (C2H4) were used to grow CNTs on the carbon fiber yarns. Scanning electron microscopy revealed a uniform areal growth over the carbon fibers where the catalytic particles had been sputtered. The structure of the grown multiwall carbon nanotubes was characterized with the aid of transmission electron microscopy (TEM). Dynamical mechanical analysis (DMA) was employed to measure the loss and storage moduli of the hybrid composite together with the reference raw carbon fiber composite and the composite for which only ceramic and nickel substrates had been deposited on. The DMA tests were conducted over a frequency range of 1–40 Hz. Although the storage modulus remained almost unchanged over the frequency range for all samples, the loss modulus showed a frequency dependent behavior. The hybrid composite obtained the highest loss modulus among other samples with an average increase of approximately 25% and 55% compared to composites of the raw and ceramic/nickel coated carbon fibers, respectively. This improvement occurred while the average storage modulus of the hybrid composite declined by almost 9% and 15% compared to the composites of reference and ceramic/nickel coated samples, respectively. The ultimate strength and elastic moduli of the samples were measured using standard ASTM tensile test. Results of this study show that while the addition of the ceramic layer protects the fibers from mechanical degradation it abolishes the mechanisms by which the composite dissipates energy. On the other hand, with almost no compromise in weight, the hybrid composites are good potential candidate for damping applications. Furthermore, the addition of CNTs could contribute to improving other mechanical, electrical and thermal properties of the hybrid composite.

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Ahuja, Suresh. "Effect of Additive on Hardness and Brittleness in Polycarbonate Films." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42728.

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Hardness and modulus of a polymer composite is known to depend on its structure, molecular weight, number of segments between entanglements and additives (filler). Nano-indentation is used increasingly as a powerful tool to determine hardness and visco-elastic modulus of polymer surfaces linear, cross-linked or composites. Hysitron Nanoindenter was used in our investigation of contact deformation of surfaces of filled polycarbonates supported on aluminum substrate. Bar coatings of polymer films were made from solution and dried all at 110C for half an hour. The results show that filled polycarbonate gives higher hardness than unfilled polycarbonate, which can give significantly different temperature dependence depending on molecular weight of the polycarbonate and structure of the filler. Depending on the type of filler and its concentration, the polycarbonate composite exhibits brittle-ductile transition at different strains. This behavior is analyzed in terms of chain mobility and free volume in the composite.

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