Theoretical Analysis and General Characteristics for Nonlinear Vibration Energy Harvesters

In this paper, we present a systematic theoretical and numerical study of the output performance of nonlinear energy harvesters. The general analytical expression of output power for systems with different combinations of nonlinear stiffness and nonlinear damping, as well as symmetrical and asymmetrical systems, have been derived based on harmonic balance method, observing compliance with numerical results. We theoretically prove that there is a limit power for all nonlinear systems which is determined exclusively by the vibrator mass, excitation acceleration, and mechanical damping. The results also indicate that for symmetrical stiffness systems, the asymmetrical damping components have no effect on the output performance. Additionally, we derived semi-analytical solutions of the matching loads and numerically investigated the influence of nonlinear coefficients on the output power with matched load. When the load matches device parameters and is much larger than the internal resistance, the equivalent time-average damping is equal to the mechanical damping. Although the matching load and output power vary with the nonlinear coefficients, the normalized power and matching resistance ratio follow a power function, named matching power line, which is independent of the structural parameters. With the improvement of the equivalent time-average short-circuit damping in the vibration range, the normalized power moves to the right end of the matching power line, and the output power approach to the limit power. These conclusions provide general characteristics of nonlinear energy harvesters, which can be used to guide the design and optimization of energy harvesters.

The comparison of power capability between towed kite and horizontal axis fan

Airborne Wind Energy (AWE) mainly collects wind energy by tethered aircraft at a certain altitude. This paper discusses the recent development of AWE. The actuator disc theory is adopted to consider the influence of kites on wind flow obstruction. The difference of working mode between a horizontal-axis wind turbine (HAWT) and a crosswind kite power systems (CKPS) is compared, the power limit of HAWT and CKPS is calculated, and the reason of the limit power is analyzed. It is pointed out that CKPS has a wider range of flight and should be further analyzed and calculated rather than simply generalized by the system disk theory.

Alternative Criteria of Voltage Stability Margin for the Purpose of Load Shedding

Voltage instability takes on the form of a dramatic drop of transmission system voltages, which may lead to system disruption. During the past two decades it has become a major threat for the operation of many systems and, in the prevailing open access environment, it is a factor leading to limit power transfers. The objective of this paper is to present new method of under voltage protection with maximum utilization of system capabilities.

Ensuring the Continuity of Power Supply to the On-Board Auxiliary Devices of the Trolleybus through the Recuperation of Kinetic Energy

When a trolleybus travels through insulated sections of the overhead contact line, it experiences momentary power interruptions, which adversely affect the vehicle’s on-board auxiliary subassemblies. To reduce these negative effects, one can harness energy recovered via regenerative braking. A model power supply circuit diagram for structural systems of the trolleybus is proposed. Simulation tests were carried out to develop a method for analyzing power supply to trolleybus auxiliary devices and verify it in a real-life example. The results allow determination of the limit power that can be generated by the trolleybus drive system to feed auxiliary devices during interruptions in power supply from the overhead contact line. The possibility of powering the on-board auxiliary equipment of a trolleybus using energy from recuperation with a traction motor is presented.

(Words and) Images of power in Pier Paolo Pasolini's Petrolio

This contribution focuses on an unfinished novel, Petrólio by Pier Paolo Pasolini to reflect on nature and images of power, as interpreted by one of the greatest Italian post-war intellectuals. The central thesis is that while the peasant and fascist society was based on the male command, on the normative force of tradition, the contemporary consumer society is based on female persuasion, on the push to conform and not to differentiate. However, while patriarchal authoritarianism allowed emancipatory rebellion, consumerist homologation was able to prevent forms of resistance by disseminating power in an infinite network of relationships, whose plot cannot be dissolved. The reading of Petrólio invites the jurist not to focus exclusively on the rational aspects of the rules and procedures that limit power, but also to devote herself to reflecting on the two dimensions of power, the discursive and the aesthetic.

Kuwaiti opposition will fight attempts to limit power

Significance This comes ahead of by-elections on March 16 for two parliamentary seats vacated by opposition MPs after a court sentenced them to prison time for a crime of which they had previously been acquitted. Kuwait is the only Gulf state with a politically active parliament, and the cross-party opposition holds a narrow majority. However, the judiciary has become increasingly aligned with the interests of executive power, particularly following the protests of 2011, in its attempts to curtail the influence of the 65-member National Assembly. Impacts If voters choose loyalist candidates it will likely reflect a desire for stability at a time of perceived uncertainty elsewhere in the Gulf. The opposition bloc in parliament, even if reduced to a minority, will still attempt to obstruct the government by interpellating ministers. Legislation to replace the Constitutional Court with a more parliament-friendly body will probably fail.

Stepwise methods can limit power for hypothesis tests of cross-level interactions

In multilevel models, stepwise methods are commonly used to test cross-level interactions, where a cluster level variable explains differences in the effect of an observation level variable on the outcome.Researchers often wish to establish that there is between cluster variance in slopes before testing whether an observed cluster level variable explains between cluster variance in slopes.In the stepwise method, between cluster slope variance (i.e. random slopes) is required before a cross-level interaction is tested.We argue that this requirement unnecessarily reduces the power to detect true cross-level interactions, because it imposes an unnecessary constraint on the power to detect valid interactions.In short, the stepwise approach would only be valid if, in the same data, the stepwise approach always identifies true interactions that are also identified by a direct test of the interaction model. Using Monte Carlo simulations, we demonstrate that this is not the case.The power to detect a true interaction was especially low when the residual slope variance (i.e. variance unexplained by the interaction), the variance of the moderator, the number of observations per cluster, or the number of clusters was small.We recommend that researchers directly test interactions that are of interest, regardless of the presence of random slope variance.