Coin Validation Research Articles

Numerical and experimental analysis of coin minting

This paper describes a numerical and experimental route for application and validation of finite elements in coin minting based on an industrial case study. The numerical work encompasses virtual prototyping of the dies from three-dimensional models prepared by the sculptor and finite element simulation of the coin minting process. The experimental work comprised independent determination of the stress–strain curve of the disk material by means of stack-compression tests, verification of the force values provided by the industrial coin minting press and validation of the numerical estimates of the progressive filling of the relief coin features and of the force vs. die stroke evolution. Results show that finite elements can be successfully applied to predict material flow and filling of the intricate relief coin features as well as to estimate the required coin minting forces before fabricating the actual dies.

Acoustic Spectrum Analysis of Genuine and Counterfeit Euro Coins

In this paper acoustic signal spectrum analysis using FFT and modal analysis based coin validation methods for authentic and counterfeit coins has been presented and investigated. For acoustical coin validation spectrum analysis has found to work well. Optimal parameters and methods for time-spectrum co-analysis has been estimated and discussed. In addition, the modal analysis for acoustic signals of coins has been implemented, the results of which has been presented and provide the authentication of the coin even with close acoustical signal spectrum. Proposed solutions has been implemented in Matlab and tested on real euro coins with denomination 50 cent, 1- and 2-euro, providing by first evaluations cost efficiency with high reasonable accuracy of described solutions. The counterfeited coins with domination of 2 euro have been tested with acoustical spectrum analysis and modal analysis evaluated in Matlab. The presented results provide the authentication of euro coins with high accuracy. DOI: http://dx.doi.org/10.5755/j01.eee.21.3.10384

Fast 3D-Vision System to Classify Metallic Coins by their Embossed Topography

This paper presents a security-related machine-vision solution for real-time classification of moving objects with highly reflective metallic surfaces and complex 3D-structures. As an application example of our so called Three-Color Selective Stereo Gradient Method (Three-Color SSGM) a classification system for three main coin denominations of Euro coins is presented. Such coins are quickly moving in a coin validation system. The objective is to decide only from comparison of specially measured and processed 3D-surface information with characteristic topographical data stored in a database whether a coin belongs to one of the reference classes or has to be rejected as a foreign or counterfeit coin. Under illumination from a three-color light emitting diode equipped ring a single image of the moving coin is captured by a digital color camera. Exploiting the spectral properties of the illumination sources, which correspond to the special spectral characteristics of the camera, three independent subimages can be extracted. Comparison between these subimages leads to a discrimination between a coin with real 3D-surface and a counterfeit coin based on a photographic image of a coin of the same type. After the coin has been located and segmented, grey value based rotation and translation invariant features are extracted froma normalized image. In combination with template matching methods, a coin can be classified. Classification results will be reported for the three main coin denominations of Euro coins.

An analysis of broken-layer characteristics in laser alloying for coinage applications

In laser surface alloying the distribution of alloying elements is mainly attributable to the convective behavior of the melt pool which is influenced by a number of factors including laser power density, size of the melt pool, interaction time, beam profile and the material physical properties. Any variation of the treatment conditions can change the flow pattern and the distribution of alloying elements in the melt pool. The laser alloying process reported in this article includes the steps of predeposition of multiple layers of different metals and subsequent alloying of these layers using a high power CO2 laser. A visible distinction between the alloyed and unalloyed regions or a difference in other physical properties is obtained. The work involves a study of the alloying types and the influence of the laser operating parameters and the thermal properties of the materials. It was found that properties such as the difference of the melting points between the coating layer and the substrate materials and thermal diffusivity (or thermal conductivity) of the substrate materials played an important role in the process. Laser control variables required for localized alloying for different substrates and coatings types were determined. The influence of both thermal properties and laser control variables on alloy types was investigated. A mathematical model was developed to establish an understanding of the process and the proper selection of the materials combinations required to achieve specific alloying types for coinage applications. Initial work on coin validation has shown promising results for automatic recognition of laser treated coins.

The focus and conduct of clinical trials

This paper discusses some issues regarding how putative stop-smoking treatments should be evaluated. Preliminary evaluations of treatments have used withdrawal symptoms as a surrogate for abstinence in an attempt to decide those treatments on which to carry out expensive full-scale clinical trials. However, withdrawal symptom severity has not been shown to relate to long-term abstinence in any prospective studies. Until a better understanding of the relationship between withdrawal symptoms and abstinence is obtained withdrawal symptoms cannot be considered an appropriate surrogate for abstinence. Research is needed into what pattern of short-term abstinence provides the best predictor of long-term abstinence. Evidence from carbon monoxide validation of short-term abstinence raises doubts about whether minor lapses back to smoking are likely to lead to full blown relapse. Further research into the use of expired-air CO in validation of claims of abstinence is required. Finally, the traditional clinical trials format is not well suited to evaluation of treatment programmes with a large behavioural component. An alternative based on the principles underlying biological evolution is proposed.