Low power arcjet performance

An experimental investigation was performed to evaluate arc jet operation at low power. A standard, 1 kW, constricted arc jet was run using nozzles with three different constrictor diameters. Each nozzle was run over a range of current and mass flow rates to explore stability and performance in the low power engine. A standard pulse-width modulated power processor was modified to accommodate the high operating voltages required under certain conditions. Stable, reliable operation at power levels below 0.5 kW was obtained at efficiencies between 30 and 40 percent. The operating range was found to be somewhat dependent on constrictor geometry at low mass flow rates. Quasi-periodic voltage fluctuations were observed at the low power end of the operating envelope, The nozzle insert geometry was found to have little effect on the performance of the device. The observed performance levels show that specific impulse levels above 350 seconds can be obtained at the 0.5 kW power level

MANAGERIAL POWER, STOCK-BASED COMPENSATION, AND FIRM PERFORMANCE: THEORY AND EVIDENCE

This paper studies theoretically and empirically the relation among CEO power, CEO compensation and firm performance. Our theoretical model follows the rent extraction view of CEO compensation put forward by the managerial power theory, and proxies CEO power by the bargaining power the CEO exercises in the determination of his compensation contract. We show (i) when there is no constraint on the CEO's salary, the CEO's stock-based compensation and the pay-performance sensitivity of CEO compensation are both independent of CEO power, although firm performance net of CEO compensation worsens as CEO power increases, and (ii) when the CEO's salary has a binding cap, the CEO's stock-based compensation and the pay-performance sensitivity of CEO compensation are both increasing in CEO power, resulting in better firm performance gross of CEO compensation, but worse firm performance net of CEO compensation. We test our theoretical findings using the sample of S&P1500 firms over the period of 2001-2005. The predicted relation between power and pay is largely supported. However, the relation between power and firm performance as predicted by theory has mixed support. This suggests that, while the managerial power theory has clear relevance in explaining the relation between power and pay, the scope of power needs to be broadened to have better understanding of how managerial power affects firm performance.Managerial power, agency theory, stock-based incentives, firm performance, pay-performance sensitivity.

Frequency and voltage partitioning in presence of renewable energy resources for power system (example: North Chile power network)

This paper investigates techniques for frequency and voltage partitioning of power network based on the graph-theory. These methods divide the power system into distinguished regions to avoid the spread of disturbances and to minimize the interaction between these regions for frequency and voltage control of power system. In case of required active and reactive power for improving the performance of the power system, control can be performed regionally instead of a centralized controller. In this paper, renewable energy sources are connected to the power network to verify the effect of these sources on the power systems partitioning and performance. The number of regions is found based on the frequency sensitivity for frequency partitioning and bus voltage for voltage partitioning to disturbances being applied to loads in each region. The methodology is applied to the north part of Chile power network. The results show the performance and ability of graph frequency and voltage partitioning algorithm to divide large scale power systems to smaller regions for applying decentralized controllers.Peer ReviewedPostprint (published version

Green communication via Type-I ARQ: Finite block-length analysis

This paper studies the effect of optimal power allocation on the performance of communication systems utilizing automatic repeat request (ARQ). Considering Type-I ARQ, the problem is cast as the minimization of the outage probability subject to an average power constraint. The analysis is based on some recent results on the achievable rates of finite-length codes and we investigate the effect of codewords length on the performance of ARQ-based systems. We show that the performance of ARQ protocols is (almost) insensitive to the length of the codewords, for codewords of length $\ge 50$ channel uses. Also, optimal power allocation improves the power efficiency of the ARQ-based systems substantially. For instance, consider a Rayleigh fading channel, codewords of rate 1 nats-per-channel-use and outage probability $10^{-3}.$ Then, with a maximum of 2 and 3 transmissions, the implementation of power-adaptive ARQ reduces the average power, compared to the open-loop communication setup, by 17 and 23 dB, respectively, a result which is (almost) independent of the codewords length. Also, optimal power allocation increases the diversity gain of the ARQ protocols considerably.Comment: Accepted for publication in GLOBECOM 201