On the theory of electrostatic generators

A summary is given of the general quantitative theory of electrostatic generators in the final, simplified form, as progressively developed by the author in a number of previous papers. The method is illustrated by detailed application to (1) a four carrier, bisymmetric replenisher, (2) a six carrier, trisymmetric replenisher, (3) a four carrier, four symmetric, electrostatic alternator, and (4) a four carrier, bisymmetric, constant potential electrostatic generator. Various artifices for simplifying and shortening the labor of mathematical solution are given.     

Non-unilateral oscillations: Governor-controlled engine-driven generators

This paper has shown the nature of the oscillatory phenomena involved in the parallel operation of A.C. generators driven by governor-controlled prime movers to be either stable or unstable, depending on the magnitude of the various electrical and mechanical quantities in the system. Further, such systems are non-unilateral coupled systems, and thus classify themselves as systems capable of self-induced vibration, i.e. systems which, when once displaced from equilibrium, will oscillate with increasing amplitude. An analogous electric circuit, which permits of easy experimental solution of the more cumbersome actual case, was disclosed, involving vacuum tubes—no analogue being possible with ordinary inductance, capacity, or resistance coupling, because these latter always form unilateral systems, and never display instability. Further investigations concerning these phenomena in allied circumstances will form the basis for future publication.     

A further contribution to the modelling of multi-waveform generators

A method has been presented in recent papers for deriving precisely stabilized waveform generators by relating them to second-order conservative oscillators. The present paper suggests a method for considerably generalizing the previous class ofgenerator models. This should enable the development of a larger variety of waveform generators with ease and flexibility. The new method is analyzed and is shown to possess implications to theoretical biology and other fields.     

Copper acetate-facilitated transfer-free growth of high-quality graphene for hydrovoltaic generators

Direct synthesis of high-quality graphene on dielectric substrates without a transfer process is of vital importance for a variety of applications. Current strategies for boosting high-quality graphene growth, such as remote metal catalyzation, are limited by poor performance with respect to the release of metal catalysts and hence suffer from a problem with metal residues. Herein, we report an effective approach that utilizes a metal-containing species, copper acetate, to continuously supply copper clusters in a gaseous form to aid transfer-free growth of graphene over a wafer scale. The thus-derived graphene films were found to show reduced multilayer density and improved electrical performance and exhibited a carrier mobility of 8500 cm² V⁻¹ s⁻¹. Furthermore, droplet-based hydrovoltaic electricity generator devices based on directly grown graphene were found to exhibit robust voltage output and long cyclic stability, in stark contrast to their counterparts based on transferred graphene, demonstrating the potential for emerging energy harvesting applications. The work presented here offers a promising solution to organize the metal catalytic booster toward transfer-free synthesis of high-quality graphene and enable smart energy generation.     

Flatness-based adaptive fuzzy output tracking excitation control for power system generators

In this paper, a novel approach for the design of an indirect adaptive fuzzy output tracking excitation control of power system generators is proposed. The method is developed based on the concept of differentially flat systems through which the nonlinear system can be written in canonical form. The flatness-based adaptive fuzzy control methodology is used to design the excitation control signal of a single machine power system in order to track a reference trajectory for the generator angle. The considered power system can be written in the canonical form and the resulting excitation control signal is shown to be nonlinear. In case of unknown power system parameters due to abnormalities, the nonlinear functions appearing in the control signal are approximated using adaptive fuzzy systems. Simulation results show that the proposed controller can enhance the transient stability of the power system under a three-phase to ground fault occurring near the generator terminals.     

On fault detection of discrete-time switched systems via designing time-varying residual generators

This paper investigates the problem of fault detection (FD) for discrete-time switched systems. Under a dwell time constraint, a switching rule that depends on the measured output is constructed for the system. Time-varying residual generators are designed such that the switched system is asymptotically stable and also with the detection performance under this switching rule. The advantages of the proposed technique are threefold: 1) It has the advantages of both slow switching and fast switching. 2) It can extend the classic design of time-invariant residual generator. 3) It can guarantee the switched system still has the desired fault detection performance even if all subsystems are without it. This feature reduces the performance requirements for each subsystem. A numerical example illustrates the effectiveness of the proposed method.     

Business intelligence in magazine distribution

This case discusses the use of business intelligence systems in the running and optimisation of magazine distribution by a UK company. The company collects a wide range of data to help it monitor and optimise a supply chain involving subcontractors. The case study raises a number of issues which are discussed. It illustrates the variety of forces which are driving companies to adopt business intelligence systems. It demonstrates how business intelligence systems can help run business processes. It explores the problems and issues with sourcing, collecting and cleaning data. Issues around anonymisation and the concept of a ‘single version of the truth’ are discussed and ethical issues highlighted. It concludes that an understanding of the role of interpretation in data collection, collation and subsequent decision making is critical to business intelligence and calls for more research in this area.     

火焰形状对其热辐射通量的影响

在火灾中火焰的形状是不固定的,因此在工程计算中通常将其假定为特定的几何形状以简化热辐射通量计算。在计算中通常采用的几何形状有圆柱形、圆锥形、立方柱形、长板面形和点源。本文采用蒙特卡洛法计算五种火焰形状下的热辐射通量。通过比较得出火焰形状对其热辐射通量的影响因素。