Forensic Assignment Stylometry

This chapter discusses the stylometry of portfolios of assignments submitted by individual students from the perspective of evidence gathering in cases of suspected contract cheating. It opens with a discussion of the properties of student-submitted assignments that distinguish those from “normal” texts as written by established authors and how those affect stylometry. Stylometry has evolved with a main focus on established writers writing in their individual styles, whereas students are learners developing their styles across a range of different types of assignments over their periods of study, often spanning several years. Any forensic stylometry of student assignments thus has to factor in such variabilities while discriminating documents written by students from those written by commissioned third parties. The second part of the chapter describes a novel stylometric approach based on information theory, still in development, that seeks to work around variabilities in student assignments. Initial evaluative case studies are presented

Radon as an anthropogenic indoor air pollutant as exemplified by radium dial watches and other uranium- and radium- containing artefacts

Radon is generally regarded as a naturally occurring radiological hazard but we report here measurements of significant, hazardous radon concentrations that arise from man-made sources, e.g. radium-dial watches. This study is an examination and assessment of health risks from radium and uranium found in historical artefacts, and the radon that emanates from them. This includes radium-dial watches, the main focus, plus clocks, aircraft instruments, and ornaments and artefacts made of uranium glass / uranium-glazed. Such objects were very popular in the 1930s and 1940s and are still readily available today. A collection of 30 radium-dial pocket and wrist watches was measured and shown to be capable of giving rise to radon concentrations two orders of magnitude greater than the UK Domestic Action Level of 200 Bq•m-3 in unventilated or poorly ventilated rooms. Furthermore, individual watches are capable of giving rise to radon concentrations in excess of the UK Domestic Action Level. We also highlight a gap in remediation protocols, which are focused on preventing radon entering buildings from outside, with regard to internally-generated radon hazards. Radon as arising from man-made objects such as radium-dial watches should be considered appropriately in radon protocols and guidelines

Monte-Carlo simulation of radon equilibrium under varying conditions

Preliminary results of a theoretical investigation into radon equilibrium under a variety of constraints will be presented, e.g. response to metallic daughter plate-out, response to modulation of radon ingress and phase relationship of alpha activity to cyclically modulated radon ingress. At the core of this investigation is the development of Monte-Carlo simulations of the radon (Rn-222) and thoron (Rn-220) decay chains. Currently, these simulations assume an hypothetical closed cubic metre of atmosphere and the simulations are time-stepped at constant interval. At each time-step, there is a radon or thoron ingress and each nuclei in the decay chains decays probabilistically, with nuclei and activity being aggregated and tabulated at the end of each time-step. Currently, the simulations have been coded in two open-source interpreted mathematical software packages; Scilab http://www.scilab.org) and Yorick (http://yorick.sourceforge.net). This has required that the decay chains are considered sequentially (in reverse order) within each time-step. However, once the simulations are finalised, these will be compiled to run on multi-core/CPU systems allowing the decay chain calculations to be paralleled at each time-step. This will allow much finer time resolution and generation of a larger statistical base from which to draw conclusions

Correlation and coherence analysis of paired time-series

Changes in radon and other soil-gas concentrations, and other parameters, before and after earthquakes have been widely reported. However, in the majority of such radon cases, changes in magnitude in single time-series have been reported, often large changes recorded using integrating detectors, and the majority of radon time-series analysis is reported for single time-series. With a single time-series, recorded at a single location, there is no measure of the spatial extent of any anomaly and, to a great extent, only anomalies in magnitude can be investigated. With two (or more) time-series from different locations, it is possible to investigate the spatial extent of anomalies and also investigate anomalies in time, i.e. frequency and phase components, as well as anomalies in magnitude. Techniques for investigating paired time-series for simultaneous similar anomalous features, developed and adapted from techniques more familiar in the field of signal analysis, will be presented. A paired radon time-series dataset is used to illuminate these techniques. This is not a restriction to radon time-series: it is simply that the investigation at the University of Northampton has been conducted on radon datasets. The particular time-series are characterised by weak, intermittent, out-of-phase 24-hour cycles. The correlation analysis (Crockett et al., 2006) reveals two anomalous short periods where the time-series correlate, these periods temporally corresponding to UK earthquakes. The coherence analysis (Crockett, 2012) reveals anomalous short periods where the time-series cohere at 24-hour and 12-hour cycles: two of these periods confirm the periods revealed by the correlation analysis but there is a third period which also temporally corresponds to a UK earthquak

Radon as a carcinogenic built-environmental pollutant

Radon (222Rn) has been highlighted by a number of authors as a significant public health concern. For example, it is the second most significant cause of lung cancer after tobacco smoking (ca. 1,000-2,000 and 21,000 deaths per year in the UK and USA respectively; US EPA, 2003; Darby et al., 2005; Dixon, 2006; HPA, 2009), yet a very high proportion of the general public appears to be unaware of the risk. This chapter deals with topical radon issues such as radon in the workplace; radon in homes; exposure to radon during leisure activities; radon and water; measurement and monitoring; seasonal correction; remediation; cancer risks; cost-benefit analysis and cost-effectiveness; mapping; future policies; and further research. This assessment of the state of radon research is focused on the UK as an example of a country where radon has been on the governmental agenda since the late 1970s, but also highlights radon issues throughout the world in, for example, the USA, Europe and Asia

Radon emissions from radium-dial watches

Preliminary research during the latter half of 2011 has indicated that significant and potentially hazardous radon concentrations can arise from radium-dial watches stored in the built environment. Radium (226Ra) decays via alpha-particle emission to radon (222Rn); in addition, mesothorium (228Ra) and radiothorium (228Th) were also used in such watches and decay to thoron (220Rn). In the main experiments conducted to date, a set of radium-dial watches representative of a small private collection, was placed in a controlled access room, of volume 67 m3, that is continuously ventilated to the external environment. Prior to placing the watches in the room, the radon level at the maximum ventilation rate was ca. 10 Bq/m3. This rose to ca. 190-230 Bq/m3 following the placing of the watches in the room, again under conditions of maximum ventilation. When the ventilation rate decreased to a ‘standby’ setting, the radon concentration increased rapidly to ca. 2-3 kBq/m3, then decreased rapidly to the lower concentration when the ventilation rate returned to maximum. Extrapolation of results of monitoring a single watch under zero-ventilation conditions indicates that the zero-ventilation equilibrium concentration in the room arising from the set of watches exceeds 5 kBq/m3 and Monte-Carlo simulation indicates this could exceed 10 kBq/m3, both of which are greatly in excess of the UK Action Levels. Observation of such levels is largely unreported in the literature and our preliminary conclusion is that whilst collectors might be aware of the radiation hazard that arises directly from the radioactive material content of such watches, they are probably not aware of the large radon (and thoron) hazard that can arise, particularly if the watches are kept in a poorly ventilated room in a private house

Enhancing BER performance limit of BCH and RS codes using multipath diversity

Modern wireless communication systems suffer from phase shifting and, more importantly, from interference caused by multipath propagation. Multipath propagation results in an antenna receiving two or more copies of the signal sequence sent from the same source but that has been delivered via different paths. Multipath components are treated as redundant copies of the original data sequence and are used to improve the performance of forward error correction (FEC) codes without extra redundancy, in order to improve data transmission reliability and increase the bit rate over the wireless communication channel. For a proof of concept Bose, Ray-Chaudhuri, and Hocquenghem (BCH) and Reed-Solomon (RS) codes have been used as FEC to compare their bit error rate (BER) performances. The results showed that the wireless multipath components significantly improve the performance of FEC. Furthermore, FEC codes with low error correction capability and employing the multipath phenomenon are enhanced to perform better than FEC codes which have a bit higher error correction capability and did not utilise the multipath. Consequently, the bit rate is increased, and communication reliability is improved without extra redundancy

Dynamic Bit Loading with the OGFDM Waveform Maximizes Bit Rate of Future Mobile Communications

A new Dynamic Bit Loading (DBL) scheme with the Orthogonal Generalized Frequency Division Multiplexing (OGFDM) is, for the first time, proposed, discussed and assessed. The key concept of this hybrid modulation format depends substantially on the adaptive distribution of the bit stream to be more compatible with the gained capacity of the realistic channel state. Due to the negative impact of employing the AQ1 fixed schemes of digital modulation on the performance of the conventional telecommunications systems, the influence of using the multi-level modulation system is investigated for the future applications of mobile communications. Utilising the DBL in the physical layer (PHY), a flexible range of modulation formats can be optimally assigned for each applied frequency sub-carrier in accordance with wireless channel circumstances. In addition, depending on the supportive features of the proposed modulation system, the performance in terms of channel capacity can be maximised at the acceptable limit of the Bit Error Rate (BER). As such, an extra enhancement can be achieved in the spectrum efficiency (SE) of the adaptively modulated wireless signal. Thus, an adjustable boost of the transmission range of used modulation formats can be reached with the introduced adaptation system. The performance of the DBL system through a wireless mobile channel under the Additive White Gaussian Noise (AWGN) is evaluated according to a various level of the Signal to Noise Ratio (SNR). Ultimately, regarding the numerical simulation, a MATLAB code is employed to simulate the performance (channel capacity & BER) of the proposed DBL that is fundamentally accommodated by the recent candidate waveform of future mobile technology (OGFDM)

Interpreting short and medium exposure etched-track radon measurements to determine whether an action level could be exceeded

Radon gas is naturally occurring, and can concentrate in the built environment. It is radioactive and high concentration levels within buildings, including homes, have been shown to increase the risk of lung cancer in the occupants. As a result, several methods have been developed to measure radon. The long-term average radon level determines the risk to occupants, but there is always pressure to complete measurements more quickly, particularly when buying and selling the home. For many years, the three-month exposure using etched-track detectors has been the de facto standard, but a decade ago, Phillips et al. (2003), in a DEFRA funded project, evaluated the use of 1-week and 1-month measurements. They found that the measurement methods were accurate, but the challenge lay in the wide variation in radon levels - with diurnal, seasonal, and other patterns due to climatic factors and room use. In the report on this work, and in subsequent papers, the group proposed methodologies for 1-week, 1-month and 3-month measurements and their interpretation. Other work, however, has suggested that 2-week exposures were preferable to 1-week ones. In practice, the radon remediation industry uses a range of exposure times, and further guidance is required to help interpret these results. This paper reviews the data from this study and a subsequent 4-year study of 4 houses, re-analysing the results and extending them to other exposures, particularly for 2-week and 2-month exposures, and provides comprehensive guidance for the use of etched-track detectors, the value and use of Seasonal Correction Factors (SCFs), the uncertainties in short and medium term exposures and the interpretation of results