985 resultados para External Force
Resumo:
This paper offers a new insight into how organizations engage with external complexity. It applies a political action perspective that draws attention to the hitherto neglected question of how the relative power organizational leaders enjoy within their environments is significant for the actions they can take on behalf of their organizations when faced with external complexity. It identifies cognitive and relational complexity as two dimensions of the environment with which organizations have to engage. It proposes three modes whereby organizations may engage with environmental complexity that are conditioned by an organization's power within its environment. It also considers the intention associated with each mode, as well as the implications of these modes of engagement for how an organization can learn about its environment and for the use of rationality and intuition in its strategic decision-making. The closing discussion considers how this analysis integrates complexity and political action perspectives in a way that contributes to theoretical development and provides the basis for a dynamic political co-evolutionary approach. © The Author(s) 2011.
Resumo:
In this paper, a linear lightweight electric cylinder constructed using shape memory alloy (SMA) is proposed. Spring SMA is used as the actuator to control the position and force of the cylinder rod. The model predictive control algorithm is investigated to compensate SMA hysteresis phenomenon and control the cylinder. In the predictive algorithm, the future output of the cylinder is computed based on the cylinder model, and the control signal is computed to minimize the error and power criterion. The cylinder model parameters are estimated by an online identification algorithm. Experimental results show that the SMA cylinder is able to precisely control position and force by using the predictive control strategy though the hysteresis effect existing in the actuator. The performance of the proposed controller is compared with that of a conventional PID controller
Resumo:
Britain's labour force industrialised early. The industrial and service sectors already accounted for 40% of the labour force in 1381, and a substantial further shift of labour out of agriculture occurred between 1522 and 1700. From the early seventeenth century rising agricultural labour productivity underpinned steadily increasing employment in industry and services, so that by 1759 agriculture's share of the labour force had shrunk to 37% and industry's grown to 34%. Thereafter, industry's output acceleration during the Industrial Revolution owed more to gains in labour productivity consequent upon mechanisation than the expansion of employment.
Resumo:
We present a mechanism for cooling atoms by a laser beam reflected from a single mirror. The cooling relies on the dipole force and thus in principle applies to arbitrary refractive particles including atoms, molecules, or dielectric spheres. Friction and equilibrium temperatures are derived by an analytic perturbative approach. Finally, semiclassical Monte-Carlo simulations are performed to validate the analytic results.
Resumo:
The aim of this paper is to analyze the role of the pressure head, i.e., the difference of total pressure forces acting on the Indonesian seas waters from the western Pacific and the eastern Indian Ocean, in driving the Indonesian Throughflow (ITF) and in determining the total transport of the ITF. These questions have been discussed in the literature but no consensus has been reached. A regional model of the Indonesian seas circulation has been developed that properly resolves all major topographic features in the region. The results of model runs have been used to calculate all components of the overall momentum balance. The estimates disclose that the dynamical balance is primarily between the volume integrated Coriolis acceleration, pressure gradient and the area integral of local wind stress. It is shown that consideration of components of momentum balance in the direction of the outflow through the Indian Ocean port leads to the formulation of a diagnostic relation between total inflow transports due to the Mindanao and New Guinea Coastal Currents and the external pressure head, internal pressure head, bottom form stress, and area integrated wind stress. Based on this relation, it is concluded that the external pressure head is not the major driving force of the ITF, which is why there is no unique relation between the total transport of the ITF and the external pressure head. However, Wyrtki's suggestion to monitor the variability of the total transport of the ITF by measurement of the sea-surface-height difference between the western Pacific and the eastern Indian Ocean is validated.
Resumo:
OBJECTIVE: To assess the impedance cardiogram recorded by an automated external defibrillator during cardiac arrest to facilitate emergency care by lay persons. Lay persons are poor at emergency pulse checks (sensitivity 84%, specificity 36%); guidelines recommend they should not be performed. The impedance cardiogram (dZ/dt) is used to indicate stroke volume. Can an impedance cardiogram algorithm in a defibrillator determine rapidly circulatory arrest and facilitate prompt initiation of external cardiac massage?
DESIGN: Clinical study.
SETTING: University hospital.
PATIENTS: Phase 1 patients attended for myocardial perfusion imaging. Phase 2 patients were recruited during cardiac arrest. This group included nonarrest controls.
INTERVENTIONS: The impedance cardiogram was recorded through defibrillator/electrocardiographic pads oriented in the standard cardiac arrest position.
MEASUREMENTS AND MAIN RESULTS: Phase 1: Stroke volumes from gated myocardial perfusion imaging scans were correlated with parameters from the impedance cardiogram system (dZ/dt(max) and the peak amplitude of the Fast Fourier Transform of dZ/dt between 1.5 Hz and 4.5 Hz). Multivariate analysis was performed to fit stroke volumes from gated myocardial perfusion imaging scans with linear and quadratic terms for dZ/dt(max) and the Fast Fourier Transform to identify significant parameters for incorporation into a cardiac arrest diagnostic algorithm. The square of the peak amplitude of the Fast Fourier Transform of dZ/dt was the best predictor of reduction in stroke volumes from gated myocardial perfusion imaging scans (range = 33-85 mL; p = .016). Having established that the two pad impedance cardiogram system could detect differences in stroke volumes from gated myocardial perfusion imaging scans, we assessed its performance in diagnosing cardiac arrest. Phase 2: The impedance cardiogram was recorded in 132 "cardiac arrest" patients (53 training, 79 validation) and 97 controls (47 training, 50 validation): the diagnostic algorithm indicated cardiac arrest with sensitivities and specificities (+/- exact 95% confidence intervals) of 89.1% (85.4-92.1) and 99.6% (99.4-99.7; training) and 81.1% (77.6-84.3) and 97% (96.7-97.4; validation).
CONCLUSIONS: The impedance cardiogram algorithm is a significant marker of circulatory collapse. Automated defibrillators with an integrated impedance cardiogram could improve emergency care by lay persons, enabling rapid and appropriate initiation of external cardiac massage.
Resumo:
This paper examines the relationship between class of origin, educational attainment, and class of entry to the labour force, in three cohorts of men in the Republic of Ireland using data collected in 1987. The three cohorts comprise men born (i) before 1937; (ii) between 1937 and 1949; and (iii) between 1950 and 1962. The paper assesses the degree of change over the three cohorts in respect of (a) the gross relationship between origins and entry class; (b) the partial effect (controlling for education) of origin class on entry class; (c) the partial effect of education (controlling for origins) on class of entry. In broad terms the liberal theory of industrialism would imply a movement, over the three cohorts, towards (a) increasing social fluidity; (b) a weakening of the partial effect of origin class; (c) a strengthening of the partial effect of education. These latter two trends should be particularly noticeable in the youngest cohort, which would, to some degree, have benefited from the introduction of free post-primary education in Ireland in 1967.
Our results provide almost no support for these hypotheses. We find that patterns of social fluidity in the origin/entry relationship remain unchanged over the cohorts. The partial effect of class remains relatively constant; and, while the partial effect of education on entry class changes over the cohorts, the most striking result in this area is the declining returns to higher levels of education. While the average level of educational attainment increased over the three cohorts, the advantages accruing to the possession of higher levels of education simultaneously diminished. Taken together our results suggest that, in Ireland, those classes that have historically enjoyed advantages in access to more desirable entry positions in the labour market have been remarkably adept at retaining their advantages during the course of industrialization and through the various educational and other labour market changes that have accompanied this process.
Resumo:
Key stakeholders in the UK charity sector have, in recent years, advocated greater accountability for charity performance. Part of that debate has focussed on the use of conversion ratios as indicators of efficiency, with importance to stakeholders being contrasted with charities’ apparent reluctance to report such measures. Whilst, before 2005, conversion ratios could have been computed from financial statements, changes in the UK charity SORP have radically altered the ability of users to do this. This article explores the impact on the visibility of such information through an analysis of the financial statements of large UK charities before and after the 2005 changes. Overall, the findings suggest that, despite the stated intention of increasing transparency in respect of charity costs, the application of the changes has resulted in charities ‘managing’ the numbers and limiting their disclosures, possibly to the detriment of external stakeholders.
Resumo:
Probing the functionality of materials locally by means of scanning probe microscopy (SPM) requires a reliable framework for identifying the target signal and separating it from the effects of surface morphology and instrument non-idealities, e.g. instrumental and topographical cross-talk. Here we develop a linear resolution theory framework in order to describe the cross-talk effects, and apply it for elucidation of frequency-dependent cross-talk mechanisms in piezoresponse force microscopy. The use of a band excitation method allows electromechanical/electrical and mechanical/topographic signals to be unambiguously separated. The applicability of a functional fit approach and multivariate statistical analysis methods for identification of data in band excitation SPM is explored.
Resumo:
Band excitation piezoresponse force microscopy enables local investigation of the nonlinear piezoelectric behavior of ferroelectric thin films. However, the presence of additional nonlinearity associated with the dynamic resonant response of the tip-surface junction can complicate the study of a material's nonlinearity. Here, the relative importance of the two nonlinearity sources was examined as a function of the excitation function. It was found that in order to minimize the effects of nonlinear tip-surface interactions but achieve good signal to noise level, an optimal excitation function must be used. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3593138]
Resumo:
Dynamic switching spectroscopy piezoresponse force microscopy is developed to separate thermodynamic and kinetic effects in local bias-induced phase transitions. The approaches for visualization and analysis of five-dimensional data are discussed. The spatial and voltage variability of relaxation behavior of the a-c domain lead zirconate-titanate surface suggest the interpretation in terms of surface charge dynamics. This approach is applicable to local studies of dynamic behavior in any system with reversible bias-induced phase transitions ranging from ferroelectrics and multiferroics to ionic systems such as batteries, fuel cells, and electroresistive materials. (C) 2011 American Institute of Physics. [doi:10.1063/1.3590919]