Wayne Read

Neural Network-based Handwritten Signature Verification

Handwritten signatures are considered as the most natural method of authenticating a person’s identity (compared to other biometric and cryptographic forms of authentication). The learning process inherent in Neural Networks (NN) can be applied to the process of verifying handwritten signatures that are electronically captured via a stylus. This paper presents a method for verifying handwritten signatures by using a NN architecture. Various static (e.g., height, slant, etc.) and dynamic (e.g., velocity, pen tip pressure, etc.) signature features are extracted and used to train the NN. Several Network topologies are tested and their accuracy is compared. The resulting system performs reasonably well with an overall error rate of 3:3% being reported for the best case.

Inflection Point Method to Estimate ch From Radial Consolidation Tests with Peripheral Drain

Horizontal coefficient of consolidation ch is a key parameter in the design of vertical drains and the following consolidation analysis of a soil layer. There are graphical and non-graphical methods available to estimate ch from laboratory radial consolidation tests with a central drain. Currently, the consolidation tests with peripheral drains have to be analysed through a curve fitting method for determining ch. In this technical note, a non-graphical inflection point method is proposed for determining ch for an oedometer test with peripheral drainage, based on the characteristic feature observed when the gradient of the theoretical Ur –log Tr relationship was plotted against Tr. The proposed method is validated through a series of consolidation tests on two reconstituted dredged clay specimens, tested in an oedometer subjected to radial drainage with peripheral drains. The consolidation settlements predicted from the proposed method, for the two different clays, were in excellent agreement with those measured in the oedometer. The proposed method will be a very valuable tool in the analysis of radial consolidation data when the drains are peripheral.

Series solutions for steady seepage through hillsides with arbitrary flow boundaries

Quantification of seepage through hillsides is important to the understanding of landscape hydrology, run-off generation, erosion processes, and the transport of solutes. For complicated flow domains, numerical solutions have the propensity to be computationally expensive and inaccurate. Analytical solutions are therefore inherently valuable; they also provide a means of checking the accuracy of numerical solutions and, because they provide continuous velocity fields, are extremely useful in generating descriptions of solute transport. This paper presents a method for obtaining analytical solutions for seepage in the saturated zone of homogeneous hillsides with arbitrary surface geometry, using a least squares method to determine the coefficients in a series expansion of the Laplace equation. It determines the (initially unknown) water table location and accommodates arbitrary shapes of the lower impermeable boundary. Flow solutions for a variety of flow domain geometries are provided, with the upper and lower boundaries expressed as cubic splines and piecewise linear polynomials.

Detecting Collusive Shill Bidding

Shill bidding is where spurious bids are introduced into an auction to drive up the final price for the seller, thereby defrauding legitimate bidders. Trevathan and Read presented an algorithm to detect the presence of shill bidding in online auctions. The algorithm observes bidding patterns over a series of auctions, and gives each bidder a shill score to indicate the likelihood that they are engaging in shill behaviour. While the algorithm is able to accurately identify those with suspicious behaviour, it is designed for the instance where there is only one shill bidder. However, there are situations where there may be two or more shill bidders working in collusion with each other. Colluding shill bidders are able to engage in more sophisticated strategies that are harder to detect. This paper proposes a method for detecting colluding shill bidders, which is referred to as the collusion score. The collusion score, either detects a colluding group, or forces the colluders to act individually like a single shill, in which case they are detected by the shill score algorithm. The collusion score has been tested on simulated auction data and is able to successfully identify colluding shill bidders

Errata to “series solutions for Laplace's equation with nonhomogeneous mixed boundary conditions and irregular boundaries”

Series solutions to Laplaces equation provide accurate analytical results for problems with regular boundary geometries. This paper develops the series approach, providing a solution methodology for problems with nonhomogeneous, mixed boundary conditions, defined on irregular boundaries. The series coefficients are obtained by first transforming to Poissons equation with some homogeneous boundary conditions, and then modifying the eigenfunction expansion theory to cater for irregular boundary geometry. The computational details for evaluating the series coefficients are given, and the method demonstrated by a practical example.

SEMAT — The Next Generation of Inexpensive Marine Environmental Monitoring and Measurement Systems

There is an increasing need for environmental measurement systems to further science and thereby lead to improved policies for sustainable management. Marine environments are particularly hostile and extremely difficult for deploying sensitive measurement systems. As a consequence the need for data is greatest in marine environments, particularly in the developing economies/regions. Expense is typically the most significant limiting factor in the number of measurement systems that can be deployed, although technical complexity and the consequent high level of technical skill required for deployment and servicing runs a close second. This paper describes the Smart Environmental Monitoring and Analysis Technologies (SEMAT) project and the present development of the SEMAT technology. SEMAT is a “smart” wireless sensor network that uses a commodity-based approach for selecting technologies most appropriate to the scientifically driven marine research and monitoring domain/field. This approach allows for significantly cheaper environmental observation systems that cover a larger geographical area and can therefore collect more representative data. We describe SEMATs goals, which include: (1) The ability to adapt and evolve; (2) Underwater wireless communications; (3) Short-range wireless power transmission; (4) Plug and play components; (5) Minimal deployment expertise; (6) Near real-time analysis tools; and (7) Intelligent sensors. This paper illustrates how the capacity of the system has been improved over three iterations towards realising these goals. The result is an inexpensive and flexible system that is ideal for short-term deployments in shallow coastal and other aquatic environments.

An Anonymous and Secure Continuous Double Auction Scheme

A Continuous Double Auction (CDA) allows many buyers and sellers to continuously submit bids for the purchase and sale of a commodity (e.g., online share trading). Protocols protecting privacy in this type of powerful market mechanism are essential. However, until recently the security of CDAs has been given limited coverage. This paper describes a new scheme for conducting an anonymous and secure CDA. We show that any existing secure group signature scheme can be used to implement a CDA which has the following characteristics: unforgeability, anonymity, unlinkability, exculpability, coalitionresistance, verifiability, robustness and traceability. Furthermore, bidders can be added to and removed from the auction without affecting the process of the auction. Our scheme is more flexible than the only existing secure CDA scheme, which in contrast provides only a limited subset of these characteristics.

Measurement of the diffusion coefficient for salt in salt flat and mangrove soils

Excluded salt accumulated at mangrove roots must be transported away from the root zone by diffusive processes, due to the low permeability of most mangrove soils. The diffusion coefficient for salt in mangrove soils determines the rate of this diffusive transport but has not been determined experimentally before. In this work we used a 12-month long-time series of salt concentration profiles measured in a sediment core over which fresh water was continuously circulated, to determine the diffusion coefficient for salt in the soil. Salt concentrations were measured using an electrical conductivity probe that was developed for use in hypersaline (salt concentration up to and in excess of 120 g/l) conditions. A modified formula was experimentally determined to relate electrical conductivity to salt concentration and temperature, applicable up to a salt concentration of 200 g/l. This was done because standard formulae relating these variables do not apply in the hypersaline conditions often encountered in salt flat sediments. The salt concentration profiles were used in a simple mathematical model to determine a sediment diffusion coefficient for salt in a salt flat sediment. This value of D=(4.6±0.2) ×10−5 m2/day was approximately half that calculated theoretically.

A Simple Shill Bidding Agent

Shill bidding is where fake bids are introduced into an auction to drive up the final price for the seller, thereby defrauding legitimate bidders. Although shill bidding is strictly forbidden in online auctions such as eBay, it is still a major problem. This paper presents a software bidding agent that follows a shill bidding strategy. The malicious bidding agent was constructed to aid in developing shill detection techniques. The agent incrementally increases an auctions price, forcing legitimate bidders to submit higher bids in order to win the item. The agent ceases bidding when the desired profit from shilling has been attained, or in the case that it is too risky to continue bidding without winning the auction. The agents ability to inflate the price has been tested in a simulated marketplace and experimental results are presented. This is the first documented bidding agent that perpetrates auction fraud. We do not condone the use of the agent outside the scope of this research

RAS: a system for supporting research in online auctions

Online auctioning is unparalleled as rhe fastest growing exchange medium to emerge from electronic commerce technology. Buyers and sellers located around the world now auction various items from the latest DVD to rare collectibles. eBay and uBid are among the most successful and popular of the commercial online auctioneers. They use an auctioning process based on a type of auction referred to as an English auction. In an English auction. bidders outbid each other for an item. The winner is the bidder with the highest bid.