Search results for "Shock"
showing 10 items of 1248 documents
A mixed H<inf>2</inf>/H<inf>&#x221E;</inf>-based semiactive control for vibration mitigation in flexible structures
2009
In this paper, we address this problem through the design of a semiactive controller based on the mixed H 2 /H ∞ control theory. The vibrations caused by the seismic motions are mitigated by a semiactive damper installed in the bottom of the structure. It is meant by semiactive damper, a device that absorbs but cannot inject energy into the system. Sufficient conditions for the design of a desired control are given in terms of linear matrix inequalities (LMIs). A controller that guarantees asymptotic stability and a mixed H 2 /H ∞ performance is then developed. An algorithm is proposed to handle the semiactive nature of the actuator. The performance of the controller is experimentally evalu…
Effects of double ground faults in Wind Farms collector cables
2015
Medium Voltage collector cables of Wind Farms have metal shields connected to the grounding systems of the towers and of the connection station. Thanks to this bonding, when a ground fault occurs, the fault current splits itself among all the grounding systems of the wind farm, this causing a reduction of the ground potential rise at the fault location. Nevertheless, in presence of double ground faults, very high ground potential rises occur at the two fault locations and safety against electric shock is not always assured. In order to study this issue, the paper presents a model for simulating in a simple way the effects of double ground faults occurring in Medium Voltage collectors of ext…
Mathematical modeling of vehicle frontal crash by a double spring-mass-damper model
2013
This paper presents development of a mathematical model to represent the real vehicle frontal crash scenario. The vehicle is modeled by a double spring-mass-damper system. The front mass m1 represents the chassi of the vehicle and rear mass m2 represents the passenger compartment. The physical parameters of the model (Stiffness and dampers) are estimated using Nonlinear least square method (Levenberg-Marquart algorithm) by curve fitting the response of a double spring-mass-damper system to the experimental displacement data from the real vehicle crash. The model is validated by comparing the results from the model with the experimental results from real crash tests available.
Current and Voltage Behaviour During a Fault in a HV/MV System: Methods and Measurements
2015
When a single line to ground fault happens on the MV side of a HV/MV system, only a small portion of the fault current is injected into the ground by the ground-grid of the faulty substation. In fact the fault current is distributed between grounding electrodes and MV cables sheaths. In systems with isolated neutral or with resonant earthing this may be sufficient to provide safety from electric shock. Experimental measurements were performed on a real MV distribution network: a real single line to ground fault was made and fault currents were measured in the faulty substation and in four neighbouring substations. In this paper the problem of fault current distribution is introduced, the te…
The Effect of Systemic Banking Crises on Entrepreneurship
2014
Economic crises have mixed effects on entrepreneurship. Through demand shocks, credit constraints, and unemployment, systemic banking crises affect the rate of start-up business creation, although the extent of their impact varies. Consequently, previous studies on the effect of crises on Entrepreneurship are inconclusive. The surge of global demand coupled with low credit availability reduces the prospects for new businesses. On the other hand, job losses caused by an economic crisis might lead many entrepreneurs to undertake new projects. These inconsistent conclusions highlight the need for more studies that explore the effect of systemic banking crises on entrepreneurship. This article …
A field methodology to study effects of UV radiation on fish larvae.
2003
There is a considerable lack of in situ specific information about the effects of UV-B radiation on limnic animals studied in the field. We exposed larval pike (Esox lucius L.) in two types of cuvettes (glass and quartz) placed at different depths (5 or 15 cm) to natural solar UV or to artificially enhanced UV-B (lamps on 3 h per day), simulating the scenarios for coming decades. Dose realism and comparability with earlier laboratory experiments was the main purpose, and therefore UV-B irradiances to the surface as well as underwater irradiances were directly measured. Result showed that UV-B dose rates in natural waters are low even though DOC concentration was low (4.8 mg/l) in our study …
Small heat shock proteins and the cytoskeleton: an essential interplay for cell integrity?
2012
Abstract The cytoskeleton is a highly complex network of three major intracellular filaments, microfilaments (MFs), microtubules (MTs) and intermediate filaments (IFs). This network plays a key role in the control of cell shape, division, functions and interactions in animal organs and tissues. Dysregulation of the network can contribute to numerous human diseases. Although small HSPs (sHSPs) and in particular HSP27 (HSPB1) or αB-crystallin (HSPB5) display a wide range of cellular properties, they are mostly known for their ability to protect cells under stress conditions. Mutations in some sHSPs have been found to affect their ability to interact with cytoskeleton proteins, leading to IF a…
Immigration, factor endowments and the productive structure of Spanish regions, 1996-2005.
2012
The participation of immigrants in the Spanish labour market has increased from less than 3% in 1996 to more than 13% in 2005. The factor proportion model of production was used to examine the impact of such a large labour supply shock on the industrial structure of Spanish regions. The results confirm that, first, labour endowment differences across regions help to explain the regional patterns of industry specialization. Second, immigrants and natives act as complementary factors in most industries. Third, the importance of immigration is relatively small compared with production technique changes and idiosyncratic industry changes in explaining the overall changes in industrial structure. …
Trading with Asymmetric Volatility Spillovers
2007
: We study the profitability of trading strategies based on volatility spillovers between large and small firms. By using the Volatility Impulse-Response Function of Lin (1997) and its extensions, we detect that any volatility shock coming from small companies is important to large companies, but the reverse is only true for negative shocks coming from large firms. To exploit these asymmetric patterns in volatility, different trading rules are designed based on the inverse relationship existing between expected return and volatility. We find that most strategies generate excess after-transaction cost profits, especially after very bad news and very good news coming from large or small firm…
Outgassing: Influence on speed of magma fragmentation
2013
[1] Predicting explosive eruptions remains an outstanding challenge. Knowledge of the controlling parameters and their relative importance is crucial to deepen our understanding of conduit flow dynamics and accurately model the processes involved. This experimental study sheds light on one important parameter—outgassing—and evaluates its influence on magma fragmentation behavior. We perform fragmentation experiments based on the shock tube theory at room temperature on natural pyroclastic material with a connected porosity ranging from 15% to 78%. For each sample series, we determine the initial pressure (P) required to initiate magma fragmentation (fragmentation threshold, Pth). Furthermor…