776 research outputs found
On the equilibrium problem and infinitesimal mechanisms of class theta tensegrity systems
No full textThis work presents a study on the equilibrium problem and the infinitesimal mechanisms of class θ= 1 tensegrity prisms. Local solutions of the self-equilibrium problem are numerically obtained through Newton-Raphson iterations. The presented results suggest that the analyzed structures can be usefully employed as building blocks of novel tensegrity metamaterials, due to their rich kinematic response and the considerably large number of infinitesimal mechanisms. © 2019 Author(s)
SIMOS feasibility report, task 4 : sign inventory management and ordering system
No full textThe Sign Inventory Management and Ordering System (SIMOS) design is a merger of existing manually maintained information management systems married to PennDOT's GIS and department-wide mainframe database to form a logical connection for enhanced sign management. To minimize the development costs, consideration was given to utilize existing hardware, software, communication channel and applications. The SIMOS project involved recommendations for reengineering the sign inventory/management procedures currently in place, and provides the technological solutions for effective statewide sign management
Numerical Analysis of Passively Mode-Locked Quantum-Dot Lasers With Absorber Section at the Low-Reflectivity Output Facet
No full textIn this paper, we present a theoretical study on the optimization of passively mode-locked quantum dot lasers based on an alternative cavity design. In particular, we investigate a geometry in which the saturable absorber is located near the low reflection facet of the chip (output facet). The investigation is carried out by means of a time-domain traveling wave numerical model for quantum-dot active medium for both the gain and absorbing sections. The analysis shows superior performance in terms of pulsewidth and peak power of devices based on the new geometry compared to devices based on the conventional geometry, where the saturable absorber is placed near the high reflectivity facet. The optimization relies on the enhanced bleaching of the saturable absorber when the latter is located near the output facet, which prevents the generation of colliding or self-colliding pulse effect
Goodness-of-fit tests in conditional duration models
No full textWe propose specification tests for the innovation distribution in conditional duration models. The new tests are based either on the cumulative distribution function, or on exponential transforms such as the Laplace transform and the characteristic function, or on characterizations of the innovation-distribution under test. We study the finite-sample performance of the proposed procedures in comparison with alternative tests which employ nonparametric density estimates as well as with tests based on entropy. A bootstrap version of the tests is utilized in order to study the small sample behavior of the procedures. A real-data example illustrates the applicability of our method and confirms conclusions drawn by earlier author
D -stability characterization problem can exhibit a polynomial computational complexity
No full textSince its appearance, the D-stability characterization problem was claimed to be NP-hard and actually it was solved efficiently for matrices of very low orders only. Recently, we introduced a new approach which makes this problem numerically feasible, since the related algorithm shows a practical computational complexity which reveals polynomial. After some remarks on computational complexity theory, here we provide details about the computational complexity of D-stability characterization problem and its historical improvement
LUP887793 Supplementary material - Supplemental material for Regional cerebral perfusion correlates with anxiety in neuropsychiatric SLE: evidence for a mechanism distinct from depression
No full textSupplemental material, LUP887793 Supplementary material for Regional cerebral perfusion correlates with anxiety in neuropsychiatric SLE: evidence for a mechanism distinct from depression by E Papadaki, E Kavroulakis, G Bertsias, A Fanouriakis, D Karageorgou, P Sidiropoulos, E Papastefanakis, D T Boumpas and P Simos in Lupus</p
On some conservation properties of the Trapezoidal Method applied to Hamiltonian systems
No full textThere is enough experimental and theoretical evidence that symmetric methods nearly preserve energy for long times when applied to several classes of Hamiltonian systems. In this paper we propose an interpretation of such good behaviour based on the definition of the discrete line integral
Energy and Quadratic Invariants Preserving Integrators of Gaussian Type
No full textRecently, a whole class of evergy-preserving integrators has been derived for the numerical solution of Hamiltonian
problems. In the mainstream of this research, we have defined a new family of symplectic integrators depending
on a real parameter α. For α = 0, the corresponding method in the family becomes the classical Gauss collocation formula
of order 2s, where s denotes the number of the internal stages. For any given non-null α, the corresponding method remains
symplectic and has order 2s − 2: hence it may be interpreted as a O(h
2s−2
) (symplectic) perturbation of the Gauss method.
Under suitable assumptions, it can be shown that the parameter α may be properly tuned, at each step of the integration
procedure, so as to guarantee energy conservation in the numerical solution. The resulting method shares the same order 2s
as the generating Gauss formula, and is able to preserve both energy and quadratic invariants
Full 3D CAD procedure for the speedy evaluation of the seismic vulnerability of masonry towers
No full textA very straightforward 3D CAD approach for the speedy evaluation of the seismic vulnerability of existing masonry towers is presented. The procedure requires only the detailed 3D geometric model of the structure and automatically calculates the collapse acceleration on a user defined failure mechanism. In this paper, few pre-assigned mechanisms are tested, as for instance vertical splitting, simple overturning at the base, rocking with inclined yield lines and combined rocking and vertical splitting. The restriction of the possible tower failure within such a few mechanisms grounds on previous numerical research in the field and post-earthquake surveys experience. In any case, any user can define his own mechanisms according to the specificity of the case-study under consideration, directly shaping distinct volumes inside the CAD software. The procedure is automatized and the direct application of the principle of virtual works-assuming that masonry behaves as a no-tension material-allows the immediate evaluation of the horizontal acceleration at collapse. The mechanism associated to the minimum acceleration, in agreement with the kinematic theorem of limit analysis, is that most probably would occur in reality during a seismic event. The approach allows a straightforward evaluation of the seismic vulnerability of a tower and can be used even by practitioners not familiar with advanced FE computations and limit analysis concepts, so adapting well to the heterogeneous community involved in cultural heritage preservation. The automatized procedure is applied in this paper to a historical tower located in central Italy, to show the capabilities of the approach. © 2019 Author(s)
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