Vehicular Traffic Intersecting Body-to-Body Communications Channels at 2.45 GHz

In this paper we investigate the effects of vehicular traffic on body-to-body (B2B) communications channels in an urban environment at 2.45 GHz. In particular, the impact of differing vehicle types passing in the vicinity of a B2B link are investigated for different body orientations relative to one another at the side of a busy urban street. Initial findings suggest that the average disturbance in a B2B channel can last for 2 seconds and depending on the vehicle size, fades in excess of 40 dB can occur. The body orientations are shown to be a significant factor on the effects of vehicular traffic on the B2B channel.

Simultaneous Measurements of the Channel Response for Multiple Eavesdroppers Operating in the Vicinity of a Body Area Network at 2.45 GHz

Channel randomness can be exploited to generate secret keys. However, to ensure secrecy, it is necessary that the channel response of any eavesdropping party remain sufficiently de-correlated with that of the legitimate users'. In this paper, we investigate whether such de-correlation occurs for a body area network (BAN) operating in an indoor environment at 2.45 GHz. The hypothetical BAN configuration consisted of two legitimate transceivers, one situated on the user's left wrist and the other on the user's waist. The eavesdroppers were positioned in either a co-located or distributed manner in the area surrounding the BAN user. Using the simultaneous channel response measured at the legitimate BAN nodes and the eavesdropper positions for stationary and mobile scenarios, we analyze the localized correlation coefficient. This allows us to determine if it is possible to generate secret keys in the presence of multiple eavesdroppers in an indoor environment. Our experimental results show that although channel reciprocity was observed for both the stationary and the mobile scenarios, a higher de-correlation between the legitimate users' channels was observed for the stationary case. This indicates that mobile scenarios are better suited for secret key generation.

Signal Reception Characteristics in the Proximity of Alice and Bob for Secure Indoor Peer-to-Peer Communications At 2.45 GHz

Mutual variation of the received signal which occurs as a consequence of the channel reciprocity property has recently been proposed as a viable method for secret key generation. However, this cannot be strictly maintained in practice as the property is applicable only in the absence of interference. To ensure the propagation defined key remains secret, one requirement is that there remain high degrees of uncertainty between the legitimate users channel response and that of any eavesdropper's. In this paper, we investigate whether such de-correlation occurs for an indoor point-to-point link at 2.45 GHz. This is achieved by computing the localized correlation coefficient between the simultaneous channel response measured by the legitimate users and that of multiple distributed eavesdroppers for static and dynamic scenarios.

Real-Time Channel Model Selection Using Windowed Received Signal Strength Measurements

This paper investigates the potential for using the windowed variance of the received signal strength to select from a set of predetermined channel models for a wireless ranging or localization system. An 868 MHz based measurement system was used to characterize the received signal strength (RSS) of the off-body link formed between two wireless nodes attached to either side of a human thorax and six base stations situated in the local surroundings.

Second-Order Statistics of κ−µ Shadowed Fading Channels

In this paper, novel closed-form expressions for the level crossing rate and average fade duration of κ − μ shadowed fading channels are derived. The new equations provide the capability of modeling the correlation between the time derivative of the shadowed dominant and multipath components of the κ − μ shadowed fading envelope. Verification of the new equations is performed by reduction to a number of known special cases. It is shown that as the shadowing of the resultant dominant component decreases, the signal crosses lower threshold levels at a reduced rate. Furthermore, the impact of increasing correlation between the slope of the shadowed dominant and multipath components similarly acts to reduce crossings at lower signal levels. The new expressions for the second-order statistics are also compared with field measurements obtained for cellular device-to-device and body-centric communication channels, which are known to be susceptible to shadowed fading.

Old Town Glasgow: Squalor, Agitation and City Improvements

In 1862, Glasgow Corporation initiated the first of a series of three legislative acts which would become known collectively as the City Improvements Acts. Despite having some influence on the nature of the built fabric on the expanding city as a whole, the most extensive consequences of these acts was reserved for one specific area of the city, the remnants of the medieval Old Town. As the city had expanded towards all points of the compass in a regular, grid-iron structure throughout the nineteenth century, the Old Town remained singularly as a densely wrought fabric of medieval wynds, vennels, oblique passageways and accelerated tenementalisation. Here, as the rest of the city began to assume the form of an ordered entity, visible and classifiable, one could still find and addresses such as ‘Bridgegate, No. 29, backland, stair first left, three up, right lobby, door facing’ (quoted in Pacione, 1995).

Unsurprisingly, this place, where proximity to the midden (dung-heap) was considered an enviable position, was seen by the authorities as a major health hazard and a source not only of cholera, but also of the more alarming typhoid epidemic of 1842. Accordingly, the demolitions which occurred in the backlands of the Old Town under the first of the acts, the Glasgow Police Act of 1862, were justified on health and medical grounds. But disease was not the only social problem thought to issue from this district. Reports from social reformers including Fredrick Engels suggested that the decay of the area’s physical fabric could be extended to the moral profile of its inhabitants. This was in such a state of degeneracy that there were calls for a nearby military barracks to be relocated to more salubrious climes because troops were routinely coming into contact ‘with the most dissolute and profligate portion of the population’ (Peter Clonston, Lord Provost, June 1861). Perhaps more worrying for the city fathers, however, was that the barracks’ arsenal was seen as a potential source of arms for the militant and often illegal cotton workers’ unions and organisations who inhabited the Old Town as well as the districts to the east. In fact, the Old Town and East End had been the site of numerous working class actions and riots since 1787, including a strike of 60,000 workers in 1820, 100,000 in 1838, and the so-called Bread Riots of 1848 where shouts of ‘Vive La Revolution’ were reported in the Gallowgate.

The events in Paris in 1848 precipitated Baron Hausmann’s interventions into that city. The boulevards were in turn visited by members of Glasgow Corporation and ultimately, it can be argued, provided an example for Old Town Glasgow. This paper suggests that the city improvement acts carried a similarly complex and pervasive agenda, one which embodied not only health, class conflict and sexual morality but also the more local condition of sectarianism. And, like in Paris, these were played out spatially in a extensive reconfiguration of the urban fabric of the Old Town which, through the creation of new streets and a railway yard, not only made it more amenable to large scale military manoeuvres but also, opened up the area to capitalist accumulation. By the end of the works, the medieval heritage of the Old Town had been almost completely razed, the working class and Catholic East End had, through the insertion of the railway yard, been isolated from the city centre and approximately 70,000 people had been made homeless.

Increase in microbial contamination risk with compression of the lid margin in eyes having cataract surgery

Purpose: To assess the bacterial contamination risk in cataract surgery associated with mechanical compression of the lid margin immediately after sterilization of the ocular surface.

Setting: Department of Cataract, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.

Design: Prospective randomized controlled double-masked trial.

Methods: Patients with age-related cataract were randomly assigned to 1 of 2 groups. In Group A (153 eyes), the lid margin was compressed and scrubbed for 360 degrees 5 times with a dry sterile cotton-tipped applicator immediately after ocular sterilization and before povidone-iodine irrigation of the conjunctival sac. Group B (153 eyes) had identical sterilization but no lid scrubbing. Samples from the lid margin, liquid in the collecting bag, and aqueous humor were collected for bacterial culture. Primary outcome measures included the rate of positive bacterial culture for the above samples. The species of bacteria isolated were recorded.

Results: Group A and Group B each comprised 153 eyes. The positive rate of lid margin cultures was 54.24%. The positive rate of cultures for liquid in the collecting bag was significantly higher in Group A (23.53%) than in Group B (9.80%) (P=.001).The bacterial species cultured from the collecting bag in Group B were the same as those from the lid margin in Group A. The positive culture rate of aqueous humor in both groups was 0%.

Conclusion: Mechanical compression of the lid margin immediately before and during cataract surgery increased the risk for bacterial contamination of the surgical field, perhaps due to secretions from the lid margin glands.

Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

The κ− μ / Inverse Gamma Fading Model

Statistical distributions have been extensively used in modeling fading effects in conventional and modern wireless communications. In the present work, we propose a novel κ − µ composite shadowed fading model, which is based on the valid assumption that the mean signal power follows the inverse gamma distribution instead of the lognormal or commonly used gamma distributions. This distribution has a simple relationship with the gamma distribution, but most importantly, its semi heavy-tailed characteristics constitute it suitable for applications relating to modeling of shadowed fading. Furthermore, the derived probability density function of the κ − µ / inverse gamma composite distribution admits a rather simple algebraic representation that renders it convenient to handle both analytically and numerically. The validity and utility of this fading model are demonstrated by means of modeling the fading effects encountered in body centric communications channels, which have been known to be susceptible to the shadowing effect. To this end, extensive comparisons are provided between theoretical and respective real-time measurement results. It is shown that these comparisons exhibit accurate fitting of the new model for various measurement set ups that correspond to realistic communication scenarios.

The η − µ / Inverse Gamma Composite Fading Model

In this paper we propose a new composite fadingmodel which assumes that the mean signal power of an η−µ signalenvelope follows an inverse gamma distribution. The inversegamma distribution has a simple relationship with the gammadistribution and can be used to model shadowed fading due to itssemi heavy-tailed characteristics. To demonstrate the utility of thenew η−µ / inverse gamma composite fading model, we investigatethe characteristics of the shadowed fading behavior observed inbody centric communications channels which are known to besusceptible to shadowing effects, particularly generated by thehuman body. It is shown that the η−µ / inverse gamma compositefading model provided an excellent fit to the measurement data.Moreover, using Kullback-Leibler divergence, the η −µ / inversegamma composite fading model was found to provide a better fitto the measured data than the κ − µ / inverse gamma compositefading model, for the communication scenarios considered here.

Shadowed Fading in Indoor Off-Body Communications Channels: A Statistical Characterization using the κ – μ / Gamma Composite Fading Model

This paper investigates the characteristics of the shadowed fading observed in off-body communications channels at 5.8 GHz. This is realized with the aid of the $\kappa-\mu$ / gamma composite fading model which assumes that the transmitted signal undergoes $\kappa-\mu$ fading which is subject to \emph{multiplicative} shadowing. Based on this, the total power of the multipath components, including both the dominant and scattered components, is subject to non-negligible variations that follow the gamma distribution. For this model, we present an integral form of the probability density function (PDF) as well as important analytic expressions for the PDF, cumulative distribution function, moments and moment generating function. In the case of indoor off-body communications, the corresponding measurements were carried out in the context of four explicit individual scenarios namely: line of sight (LOS) and non-LOS (NLOS) walking, rotational and random movements. The measurements were repeated within three different indoor environments and considered three different hypothetical body worn node locations. With the aid of these results, the parameters for the $\kappa-\mu$ / gamma composite fading model were estimated and analyzed extensively. Interestingly, for the majority of the indoor environments and movement scenarios, the parameter estimates suggested that dominant signal components existed even when the direct signal path was obscured by the test subject's body. Additionally, it is shown that the $\kappa-\mu$ / gamma composite fading model provides an adequate fit to the fading effects involved in off-body communications channels. Using the Kullback-Leibler divergence, we have also compared our results with another recently proposed shadowed fading model, namely the $\kappa-\mu$ / lognormal LOS shadowed fading model. It was found that the $\kappa-\mu$ / gamma composite fading model provided a better fit for the majority of the scenarios considered in this study.

Switched Diversity Techniques for Indoor Off-body Communications Channels: An Experimental Analysis and Modeling

This paper investigates the potential improvement in signal reliability for indoor off-body communications channels operating at 5.8 GHz using switched diversity techniques. In particular we investigate the performance of switch-and-stay combining (SSC), switch-and-examine combining (SEC) and switch-and-examine combining with post-examining selection (SECps) schemes which utilize multiple spatially separated antennas at the base station. During the measurements a test subject, wearing an antenna on his chest, performed a number of walking movements towards and then away from a uniform linear array. It was found that all of the considered diversity schemes provided a worthwhile signal improvement. However, the performance of the diversity systems varied according to the switching threshold that was adopted. To model the fading envelope observed at the output of each of the combiners, we have applied diversity specific equations developed under the assumption of Nakagami-$m$ fading. As a measure of the goodness-of-fit, the Kullback-Leibler divergence between the empirical and theoretical probability density functions (PDFs) was calculated and found to be close to 0. To assist with the interpretation of the goodness-of-fit achieved in this study, the standard deviation, $\sigma$, of a zero-mean, $\sigma^2$ variance Gaussian PDF used to approximate a zero-mean, unit variance Gaussian PDF is also presented. These were generally quite close to 1 indicating that the theoretical models provided an adequate fit to the measured data.

Life cycle assessment in the supply chain: a review and case study

The paper addresses the use of Life Cycle Assessment as a tool for analysing freight transport activity in product supply chains. Published works that have assessed freight transport energy use in supply chain operations are reviewed and their results summarized. A case study of the energy use in the supply chains for jeans sold in both the UK and France is presented. The results of this case study indicate that the location from which cotton is sourced can have a major impact on the total energy used in commercial transport in the jeans supply chain. However, overall, this has a limited impact on the total energy used in producing and supplying jeans. This is because the vast majority of total energy used in the supply chain is consumed during cotton cultivation, denim production and jeans manufacture. The work also demonstrates that the amount of energy used by consumers transporting jeans to their homes by car can be greater than the total commercial transport energy used in the supply chain (per kg of jeans transported).

Assessing energy consumption in supply chains

The paper addresses the transport activities and associated energy consumption involved in the production and supply of two products: jeans and yoghurt. In the case of jeans, the analysis is from the locations in which cotton is grown, to retail outlets in the UK; in the case of yoghurt, the analysis is from the supply of milk on farms, to retail outlets in France. The results show that the transport stages from the point of jeans manufacture to UK port are responsible for the greatest proportion of transport energy use per kilogram of jeans in the UK supply chain. In the case of the French yoghurt supply chains, the results indicate that each of the three transport stages from farm to third-party distribution centre consume approximately the same proportion of total freight transport energy. The energy used on the transport stage for yoghurt from third-party distribution centre to retail outlet varies depending on the type of retail outlet served. Far greater quantities of energy are used in transporting jeans than yoghurts from farm/field to retail outlet. This is explained by the distances involved in the respective supply chains. Both case studies demonstrate that the energy used by consumers transporting goods to their homes by car can be as great as total freight transport energy used in the supply chain from farm/field to retail outlet (per kilogram of product transported).

Roteiros e rotas portuguesas do oriente nos séculos XVI e XVII

Tese de doutoramento, História (História dos Descobrimentos e da Expansão), Universidade de Lisboa, Faculdade de Letras, 2016

Mathematical modelling of supercritical CO2 extraction of volatile oils from aromatic plants

The modelling of the experimental data of the extraction of the volatile oil from six aromatic plants (coriander, fennel, savoury, winter savoury, cotton lavender and thyme) was performed using five mathematical models, based on differential mass balances. In all cases the extraction was internal diffusion controlled and the internal mass transfer coefficienty (k(s)) have been found to change with pressure, temperature and particle size. For fennel, savoury and cotton lavender, the external mass transfer and the equilibrium phase also influenced the second extraction period, since k(s) changed with the tested flow rates. In general, the axial dispersion coefficient could be neglected for the conditions studied, since Peclet numbers were high. On the other hand, the solute-matrix interaction had to be considered in order to ensure a satisfactory description of the experimental data.