Search results for "Stability."

Kognitīvo uzdevumu ietekme uz stājas stabilitāti jauniem un veciem cilvēkiem

2017

Kopsavilkums Palielinoties cilvēka vecumam, palielinās kritienu un traumatisma riski. Tā kā Latvijā, kā arī Eiropā kopumā, palielinās populācijas novecošanās, kritienu un traumatisma riski pieaug, un to samazināšanai ir nepieciešami efektīvi profilaktiski pasākumi, kas uzlabotu īpaši gados veco cilvēku mobilitāti un novērstu kritienus. Pašreiz nav vienotu vadlīniju stājas stabilitātes pārbaužu metodikā un uzlabošanā, tādēļ ir nozīmīgi izprast faktorus, kas var ietekmēt posturālo kontroli. Tādejādi darbā tika izvirzīts mērķis noskaidrot kognitīvo procesu ietekmi uz stājas stabilitāti, kā arī izvērtēt antropometrisko parametru ietekmi uz līdzsvara saglabāšanu. Pētījumā piedalījās 60 izmeklēja…

Pseudospectrum of Reissner-Nordström black holes: Quasinormal mode instability and universality

2021

Black hole spectroscopy is a powerful tool to probe the Kerr nature of astrophysical compact objects and their environment. The observation of multiple ringdown modes in gravitational waveforms could soon lead to high-precision gravitational spectroscopy, so it is critical to understand if the quasinormal mode spectrum is stable against perturbations. It was recently shown that the pseudospectrum can shed light on the spectral stability of black hole quasinormal modes. We study the pseudospectrum of Reissner-Nordstr\"om spacetimes and we find a spectral instability of scalar and gravitoelectric quasinormal modes in subextremal and extremal black holes, extending similar findings for the Sch…

Indagine sperimentale sul comportamento di pareti sismiche in acciaio sottoposte a taglio

2005

The paper concerns the experimental results performed on steel (S 235) zinc plated panels having 1500 x 1150 x 1.5 mm dimensions, linked to hinged steel frame. In order to the slenderness of plates, considerable displacements out-of-plane are evident at loads significantly lower of ultimate load. Considering the steel constitutive curves obtained from tensile tests, the comparison of experimental and numerical (ADINA) results is proposed. The results show the excellent seismic behaviour of the system having stable hysteresis loops.

Progetto di Strutture in acciaio per le nuove costruzioni e per gli interventi di consolidamento. IV Edizione

2005

The book is a state of the art summary of recent development in the behavior, analysis and design of steel and composite structures. The book provides advanced students, researchers al professionals in civil and structural engineering with the basic principles upon which the modern codes are based. In the first part, the materials, the actions and the sectional behavior are analyzed on the base of the limit state theory. Then the connections (bolted and welded)and the stability effects are examined. In this way is possible speak about seismic performance, retrofitting an refurbishment of existing buildings, referring to the italian rules, to the european codes EC3, EC4 and to the AISC rules.

Stability of stochastic nonlinear systems with state-dependent switching

2013

In this paper, the problem of stability on stochastic systems with state-dependent switching is investigated. To analyze properties of the switched system by means of Itô’s formula and Dynkin’s formula, it is critical to show switching instants being stopping times. When the given active-region set can be replaced by its interior, the local solution of the switched system is constructed by defining a series of stopping times as switching instants, and the criteria on global existence and stability of solution are presented by Lyapunov approach. For the case where the active-region set can not be replaced by its interior, the switched systems do not necessarily have solutions, thereby quasi-…

Crystal structure and Hirshfeld surface analysis of [N(CH3)4][2,2′-Fe(1,7-closo-C2B9H11)2]

2017

Abstract This work investigates the meta -ferrabis(dicarbollide) anion that was isolated as salt of tetramethylammonium. The structure of the obtained crystal consisted of discrete [2,2′-Fe(1,7- closo -C 2 B 9 H 11 ) 2 ] − anions and disordered [N(CH 3 ) 4 ] + cations. The anion had a considerable chemical stability ensured by ionic and Van der Waals interactions. Thus, Hirshfeld surfaces and fingerprint plot were used to visualize, explore, and quantify intermolecular interactions in the crystal lattice of the title compound. This investigation proved that close contacts were dominated by H⋯H interactions.

Koeteltavien markkinoiden teoria ja tietokonevarausjärjestelmät : miksi teorian oletukset eivät toteudu Yhdysvaltain sisäisessä reittilentoliikentees…

1997

Copper-hydride nanoclusters with enhanced stability by N-heterocyclic carbenes

2021

AbstractCopper-hydrides have been intensively studied for a long time due to their utilization in a variety of technologically important chemical transformations. Nevertheless, poor stability of the species severely hinders its isolation, storage and operation, which is worse for nano-sized ones. We report here an unprecedented strategy to access to ultrastable copper-hydride nanoclusters (NCs), namely, using bidentate N-heterocyclic carbenes as stabilizing ligands in addition to thiolates. In this work, a simple synthetic protocol was developed to synthesize the first large copper-hydride nanoclusters (NCs) stabilized by N-heterocyclic carbenes (NHCs). The NC, with the formula of Cu31(RS)2…

Robust H<inf>∞</inf> control of Markovian jump systems with mixed time delays

2010

In this paper, the problem of stability analysis and control synthesis for Markovian jump linear systems with time delays and norm-bounded uncertainties is studied. The model under consideration consists of different time-invariant discrete, neutral and distributed delays. Delay-dependent sufficient conditions for the design of a mode-dependent delayed state feedback H ∞ control are given in terms of linear matrix inequalities (LMIs). A controller which guarantees stochastic stability and a prescribed level of H ∞ performance for the closed-loop system is then developed. A Lyapunov-Krasovskii functional (LKF) method underlies the control design. A numerical example with simulation results i…

Theoretical and Experimental Study of Polarization Modulation Instability in All-Normal Dispersion Photonic Crystal Fibers

2018

Experimental observation of polarization modulation instability in all-normal dispersion photonic crystal fibers is reported. Stokes and anti-Stokes sidebands with spectral shift of 40 nm were observed when the fiber was pumped at 1064 nm. Experimental results are baked by a vectorial four-wave mixing model.