The inerter: a retrospective

The paper provides an introduction and overview of the inerter concept and device. Careful attention is given to the distinction between the inerter as an ideal modelling element and devices that approximate the ideal behaviour. The background is given to the formal definition of the inerter as a mechanical one-port with terminal forces proportional to the relative acceleration between them. Four major methods of construction are described and modelled. The discussion focuses particularly on: the notion of terminals; the distinction between a device and an effect; sign reversals; back-driving in geared systems; the conceptual aspects of the modelling step for inerter embodiments; the problem of reverse engineering to discover a purpose. The paper includes an analysis and discussion of the rotational inerter. A brief review of the ideas of passive network synthesis that led to the inerter concept are provided. A discussion and analysis is given on several examples of integrated mechanical devices. The article concludes with an imaginary dialogue between the author and an interlocutor on the understanding and purpose of the inerter

Bounded Disturbance Amplification for Mass Chains with Passive Interconnection

This paper introduces the problem of passive control of a chain of N identical masses in which there is an identical passive connection between neighbouring masses and a similar connection to a movable point. The problem arises in the design of multi-storey buildings which are subjected to earthquake disturbances, but applies in other situations, for example vehicle platoons. The paper studies the scalar transfer functions from the disturbance to a given intermass displacement. It is shown that these transfer functions can be conveniently represented in the form of complex iterative maps and that these maps provide a method to establish boundedness in N of the H-infinity norm of these transfer functions for certain choices of interconnection impedance

Puccinellia : outstanding saltland grass

Puccinellia is a tussocky perennial grass with an outstanding ability to survive salty and waterlogged conditions. Considerable areas of saltland in Western Australia are suited to its growth. Seed is now available commercially and in this article the conditions to which the grass is suited are described and establishment and management methods are suggested

Bringing wheatbelt salt land back into production

INVESTIGATIONS carried out over many years on salt-affected land in the wheat- •*• belt of Western Australia have shown that it is often possible to return salt land to productivity. This article suggests how this may be done

Growing plants with salty water

LACK of good quality water in many parts of Western Australia often forces people to use salty water for irrigation and gardening. This article gives some hints on how to reduce salt damage to plants when salty water must be used for irrigation or gardening. It includes a table of plants which may be irrigated with water of varying degrees of salinity and lists precautions which should be taken for each group

The parallel projection operators of a nonlinear feedback system

The authors define and study a pair of nonlinear parallel projection operators associated with a nonlinear feedback system. The input-output L_2-stability of a feedback system is shown to be equivalent to a coordinating of the input and output spaces, which is also equivalent to the existence of a pair of nonlinear parallel projection operators onto the graph of the plant and the inverse graph of the controller. These projections have equal norms whenever one of the feedback elements is linear. A bound on this norm is given in the case of passive systems with unity negative feedback

Salt land survey, 1962 : report of a survey of soil salinity in the agricultural areas of Western Australia

IN Western Australia there are within the agricultural areas about one million acres of salt land, largely within the 14-25 inch rainfall area used for cereal and wool production. In March, 1962, farmers in 68 shires in the agricultural areas of Western Australia estimated that on their properties 305,270 acres of land previously cropped or sown to pasture had become salt affected. Of this total, 59,203 acres had gone salt in the seven years immediately before the survey

On a concept of genericity for RLC networks

A recent definition of genericity for resistor-inductor-capacitor (RLC) networks is that the realisability set of the network has dimension one more than the number of elements in the network. We prove that such networks are minimal in the sense that it is not possible to realise a set of dimension n with fewer than n-1 elements. We provide an easily testable necessary and sufficient condition for genericity in terms of the derivative of the mapping from element values to impedance parameters, which is illustrated by several examples. We show that the number of resistors in a generic RLC network cannot exceed k+1 where k is the order of the impedance. With an example, we show that an impedance function of lower order than the number of reactive elements in the network need not imply that the network is non-generic. We prove that a network with a non-generic subnetwork is itself non-generic. Finally we show that any positive-real impedance can be realised by a generic network. In particular we show that sub-networks that are used in the important Bott-Duffin synthesis method are in fact generic.A. Morelli was supported by the MathWorks studentship - a Cambridge University Trust fund

Marsupial chromosome DNA content and genome size assessed from flow karyotypes: invariable low autosomal GC content.

Extensive chromosome homologies revealed by cross-species chromosome painting between marsupials have suggested a high level of genome conservation during evolution. Surprisingly, it has been reported that marsupial genome sizes vary by more than 1.2 Gb between species. We have shown previously that individual chromosome sizes and GC content can be measured in flow karyotypes, and have applied this method to compare four marsupial species. Chromosome sizes and GC content were calculated for the grey short-tailed opossum (2n = 18), tammar wallaby (2n = 16), Tasmanian devil (2n = 14) and fat-tailed dunnart (2n = 14), resulting in genome sizes of 3.41, 3.31, 3.17 and 3.25 Gb, respectively. The findings under the same conditions allow a comparison between the four species, indicating that the genomes of these four species are 1-8% larger than human. We show that marsupial genomes are characterized by a low GC content invariable between autosomes and distinct from the higher GC content of the marsupial × chromosome