Autonomous homing and docking tasks for an underwater vehicle

This paper briefly introduces a strategy for autonomous homing and docking tasks using an autonomous underwater vehicle. The control and guidance based path following for those tasks are described in this work. A standard sliding mode for controller design is briefly given. The method provides robust motion control efforts for an underwater vehicle’s decoupled system whilst minimising chattering effects. In a guidance system, the vector field based on a conventional artificial potential field method gives a desired trajectory with a use of existing information from sensors in the network. A well structured Line-of-Sight method is used for an AUV to follow the path. It provides guidance for an AUV to follow the predefined trajectory to a required position with the final desired orientation at the dock. Integration of a control and guidance system provides a complete system for this application. Simulation studies are illustrated in the paper

Some geometry and combinatorics for the S-invariant of ternary cubics

Given a real cubic form f(x,y,z), there is a pseudo-Riemannian metric given by its Hessian matrix, defined on the open subset of R^3 where the Hessian determinant h is non-zero. We determine the full curvature tensor of this metric in terms of h and the S-invariant of f, obtaining in the process various different characterizations of S. Motivated by the case of intersection forms associated with complete intersection threefolds in the product of three projective spaces, we then study ternary cubic forms which arise as follows: we choose positive integers d1, d2, d3, set r = d1 + d2 + d3 - 3, and consider the coefficient F(x,y,z) of H1^d1 H2^d2 H3^d3 in the product (x H1 + y H2 + z H3)^3 (a_1 H1 + b_1 H2 + c_1 H3) ... (a_r H1 + b_r H2 + c_r H3), the a_j, b_j and c_j denoting non-negative real numbers; we assume also that F is non-degenerate. Previous work of the author on sectional curvatures of Kahler moduli suggests a number of combinatorial conjectures concerning the invariants of F. It is proved here for instance that the Hessian determinant, considered as a polynomial in x,y,z and the a_j, b_j, c_j, has only positive coefficients. The same property is also conjectured to hold for the S-invariant; the evidence and background to this conjecture is explained in detail in the paper.Comment: 23 pages, plain Tex, updated and shortened, final versio

Look-up Tables to Link 1991 Population Statistics to the 1998 Local Government Areas

Between 1995 and 1998 the local authority structure and geography of the United Kingdom was substantially revised. The two-tier system of local government was abolished in Wales, Scotland, and in parts of non-metropolitan England, and replaced with a single-tier system. This involved the creation of a new set of local authority area boundaries which in many places cut across those of the old districts. In addition, many of the local authorities unaffected by the reorganisation nonetheless had experienced small - though demographically significant - boundary changes since the last census. By the time the final phase of the reorganisation came into effect on 1st April 1998 the local government map of the United Kingdom was very different from that of April 1991. There is a need therefore to provide demographic and other geographically based data for the new geography for years prior to 1998. This paper aims to fill a part of this requirement by focusing on two important issues. First, it describes a look-up table detailing exactly how the 1998 local government geography relates to 1991 Census areas, and second, it sets out methods for producing 1991 Census data and mid-1991 population estimates (including single year age detail) for the new geography. A selection of the results produced by the described methods is included in tables and population pyramids

'Face Up to the Truth': Helping Gay Men in Vietnam Protect Themselves from AIDS.

Appropriate AIDS prevention information is not available in Vietnam for men who have sex with men. Current AIDS prevention messages can be misunderstood with potentially dangerous results. We outline some features of gay culture in a provincial city in Vietnam. We describe the activities of a peer educator who made contact with a small group of young gay men during 1996 and 1997. All the young men were ill-informed about AIDS. Their attitudes and sexual practices made them vulnerable to AIDS. The peer educator provided clear information and emotional support. The peer education was done without government endorsement and on a very low budget

Corpus Analysis and Lexical Pragmatics: An Overview

Lexical pragmatics studies the processes by which lexically encoded meanings are modified in use; well-studied examples include lexical narrowing, approximation and metaphorical extension. Relevance theorists have been trying to develop a unitary account on which narrowing, approximation and metaphorical extension are all explained in the same way. While there have been several corpus-based studies of metaphor and a few of hyperbole or approximation, there has been no attempt so far to test the unitary account using corpus data. This paper reports the results of a corpus-based investigation of lexical-pragmatic processes, and discusses the theoretical issues and challenges it raises

A New Field Theoretic Approach to Criticality

A reorganized perturbation expansion with a propagator of soft infrared behavior is used to study the critical behavior of the mass gap. The condition of relativistic covariance fixes the form of the soft propagator. Finite approximants to the correlation critical exponent can be obtained in every order of the modified, soft perturbation expansion. Alternatively, a convergent series of exponents in large orders of the soft perturbation expansion is provided by the renormalization group in all spatial dimensions, $1\leq D\leq3$. The result of the $\epsilon$-expansion is recovered in the $D\rightarrow 3$ limit.Comment: 22 page