Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 3
items per page: 25 50 75
Sort by:
Download PDF Download RIS Download Bibtex

Abstract

Hardly any sector has been hit as hard by the COVID-19 pandemic as the air transport industry. As lockdown measures are lifted, a recovery phase begins that will shape the global economic landscape for the years to come. In this context this paper raises the question of whether the pre-existing EU instruments for subsidizing air operations – Startup aid and the Public Service Obligation – none of which was designed with economic recovery in mind – can be adapted to the new circumstances after the current ad hoc measures under the Temporary Framework have dried up. The hypothesis which is taken as a starting point is that the existing state aid toolbox has built-in deficiencies which are hampering recovery efforts. This paper therefore attempts to determine whether alternatives can be sought within the confines of the EU state aid law, and if so what such alternatives might be.
Go to article

Authors and Affiliations

Jakub Kociubiński
1
ORCID: ORCID

  1. Associate professor (dr. hab.), Faculty of Law, Administration and Economics, University of Wrocław
Download PDF Download RIS Download Bibtex

Abstract

The paper presents a neutronic analysis of the battery-type 20 MWth high-temperature gas cooled reactor. The developed reactor model is based on the publicly available data being an ‘early design’ variant of the U-battery. The investigated core is a battery type small modular reactor, graphite moderated, uranium fueled, prismatic, helium cooled high-temperature gas cooled reactor with graphite reflector. The two core alternative designs were investigated. The first has a central reflector and 30×4 prismatic fuel blocks and the second has no central reflector and 37×4 blocks. The SERPENT Monte Carlo reactor physics computer code, with ENDF and JEFF nuclear data libraries, was applied. Several nuclear design static criticality calculations were performed and compared with available reference results. The analysis covered the single assembly models and full core simulations for two geometry models: homogenous and heterogenous (explicit). A sensitivity analysis of the reflector graphite density was performed. An acceptable agreement between calculations and reference design was obtained. All calculations were performed for the fresh core state.

Go to article

Authors and Affiliations

Marcin Grodzki
Piotr Darnowski
Grzegorz Niewiński
Download PDF Download RIS Download Bibtex

Abstract

An attempt is made in the current research to obtain the fundamental buckling torque and the associated buckled shape of an annular plate. The plate is subjected to a torque on its outer edge. An isotropic homogeneous plate is considered. The governing equations of the plate in polar coordinates are established with the aid of the Mindlin plate theory. Deformations and stresses of the plate prior to buckling are determined using the axisymmetric flatness conditions. Small perturbations are then applied to construct the linearised stability equations which govern the onset of buckling. To solve the highly coupled equations in terms of displacements and rotations, periodic auxiliary functions and the generalised differential quadrature method are applied. The coupled linear algebraic equations are a set of homogeneous equations dealing with the buckling state of the plate subjected to a unique torque. Benchmark results are given in tabular presentations for combinations of free, simply-supported, and clamped types of boundary conditions. It is shown that the critical buckling torque and its associated shape highly depend upon the combination of boundary conditions, radius ratio, and the thickness ratio.

Go to article

Bibliography

[1] W.R. Dean. The elastic stability of an annular plate. Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, 106(737):268–284, 1924. doi: 10.1098/rspa.1924.0068.
[2] J. Tani and T. Nakamura. Dynamic stability of annular plates under pulsating torsion. Journal of Applied Mechanics, 47(3):595–600, 1980. doi: 10.1115/1.3153739.
[3] J. Tani. Dynamic stability of orthotropic annular plates under pulsating torsion. The Journal of the Acoustical Society of America, 69(6):1688–1694, 1981. doi: 10.1121/1.385948.
[4] D. Durban and Y. Stavsky. Elastic buckling of polar-orthotropic annular plates in shear. International Journal of Solids and Structures, 18(1):51–58, 1982. doi: 10.1016/0020-7683(82)90015-4.
[5] T. Irie, G. Yamada, and M. Tsujino. Vibration and stability of a variable thickness annular plate subjected to a torque. Journal of Sound and Vibration, 85(2):277–285, 1982. doi: 10.1016/0022-460X(82)90522-3.
[6] T. Irie, G. Yamada, and M. Tsujino. Buckling loads of annular plates subjected to a torque. Journal of Sound and Vibration, 86(1):145–146, 1983. doi: 10.1016/0022-460X(83)90951-3.
[7] J. Zajączkowski. Stability of transverse vibration of a circular plate subjected to a periodically varying torque. Journal of Sound and Vibration, 89(2):273–286, 1983. doi: 10.1016/0022-460X(83)90394-2.
[8] H. Doki and J. Tani. Buckling of polar orthotropic annular plates under internal radial load and torsion. International Journal of Mechanical Sciences, 27:429–437, 1985. doi: 10.1016/0020-7403(85)90033-5.
[9] M. Hamada and T. Harima. In-plane torsional buckling of an annular plate. Bulletin of JSME, 29(250):1089–1095, 1986. doi: 10.1299/jsme1958.29.1089.
[10] E. Ore and D. Durban. Elastoplastic buckling of annular plates in pure shear. Journal of Applied Mechanics, 56(3):644–651, 1989. doi: 10.1115/1.3176141.
[11] Chang-Jun Cheng and Xiao-an Lui. Buckling and post-buckling of annular plates in shearing, Part I: Buckling. Computer Methods in Applied Mechanics and Engineering, 92(2):157–172, 1991. doi: 10.1016/0045-7825(91)90237-Z.
[12] Chang-Jun Cheng and Xiao-an Lui. Buckling and post-buckling of annular plates in shearing, Part II: Post-buckling. Computer Methods in Applied Mechanics and Engineering, 92(2):173–191, 1991. doi: 10.1016/0045-7825(91)90238-2.
[13] P. Singhatanadgid and V. Ungbhakorn. Scaling laws for buckling of polar orthotropic annular plates subjected to compressive and torsional loading. Thin-Walled Structures, 43(7):1115–1129, 2005. doi: 10.1016/j.tws.2004.11.004.
[14] T.X. Wu. Analytical study on torsional vibration of circular and annular plate. Journal of Mechanical Engineering Science, 220(4):393–401, 2006. doi: 10.1243/09544062JMES167.
[15] R. Maretic, V. Glavardanov, and D. Radomirovic. Asymmetric vibrations and stability of a rotating annular plate loaded by a torque. Meccanica, 42(6):537–546, 2007. doi: 10.1007/s11012-007-9080-8.
[16] S.E. Ghiasian, Y. Kiani, M. Sadighi, and M.R. Eslami. Thermal buckling of shear deformable temperature dependent circular annular FGM plates. International Journal of Mechanical Sciences, 81:137–148, 2014. doi: 10.1016/j.ijmecsci.2014.02.007.
[17] H. Bagheri, Y. Kiani, and M.R. Eslami. Asymmetric thermal buckling of temperature dependent annular FGM plates on a partial elastic foundation. Computers & Mathematics with Applications, 75(5):1566–1581, 2018. doi: 10.1016/j.camwa.2017.11.021.
[18] H. Bagheri, Y. Kiani, and M.R. Eslami. Asymmetric compressive stability of rotating annular plates. European Journal of Computational Mechanics, 2019. doi: 10.1080/17797179.2018.1560989.
[19] J.N. Reddy. Mechanics of Laminated Composite Plates and Shells, Theory and Application. CRC Press, 2nd Edition, 2003.
[20] H. Bagheri, Y. Kiani, and M.R. Eslami. Asymmetric thermal buckling of annular plates on a partial elastic foundation. Journal of Thermal Stresses, 40(8):1015–1029, 2017. doi: 10.1080/01495739.2016.1265474.
[21] H. Bagheri, Y. Kiani, and M.R. Eslami. Asymmetric thermo-inertial buckling of annular plates. Acta Mechanica, 228(4):1493–1509, 2017. doi: 10.1007/s00707-016-1772-5.
[22] D.O. Brush and B.O. Almroth. Buckling of Bars, Plates, and Shells. McGraw-Hill, New York, 1975.
[23] M.R. Eslami. Thermo-Mechanical Buckling of Composite Plates and Shells. Amirkabir University Press, Tehran, 2010.
[24] Y. Kiani Y and M.R. Eslami. An exact solution for thermal buckling of annular FGM plates on an elastic medium. Composites Part B: Engineering, 45(1):101–110, 2013. doi: 10.1016/j.compositesb.2012.09.034.
[25] F. Tornabene, N. Fantuzzi F. Ubertini, and E. Viola. Strong formulation finite element method based on differential quadrature: a survey. Applied Mechanics Reviews, 67(2):020801-020801-55, 2015. doi: 10.1115/1.4028859.
Go to article

Authors and Affiliations

Hamed Bagheri
1
Yaser Kiani
2
Mohammad Reza Eslami
1

  1. Mechanical Engineering Department, Amirkabir University of Technology, Tehran, Iran.
  2. Faculty of Engineering, Shahrekord University, Shahrekord, Iran.

This page uses 'cookies'. Learn more