Indoor radio channel characterization and modeling for a 5.2-GHz bodyworn receiver

[Abstract]: Wireless local area network applications may include the use of bodyworn or handportable terminals. For the first time, this paper compares measurements and simulations of a narrowband 5.2-GHz radio channel incorporating a fixed transmitter and a mobile bodyworn receiver. Two indoor environments were considered, an 18-m long corridor and a 42-m2 office. The modeling technique was a site-specific ray-tracing simulator incorporating the radiation pattern of the bodyworn receiver. In the corridor, the measured body-shadowing effect was 5.4 dB, while it was 15.7 dB in the office. First- and second-order small-scale fading statistics for the measured and simulated results are presented and compared with theoretical Rayleigh and lognormal distributions. The root mean square error in the cumulative distributions for the simulated results was less than 0.74% for line-of-sight conditions and less than 1.4% for nonline-of-sight conditions

Propagation modelling and measurements in a populated indoor environment at 5.2 GHz

There are a number of significant radiowave propagation phenomena present in the populated indoor environment, including multipath fading and human body effects. The latter can be divided into shadowing and scattering caused by pedestrian movement, and antenna-body interaction with bodyworn or hand portable terminals [1]. Human occupants within indoor environments are not always stationary and their movement will lead to temporal channel variations that can strongly affect the quality of indoor wireless communication systems. Hence, populated environments remain a major challenge for wireless local area networks (WLAN) and other indoor communication systems. Therefore, it is important to develop an understanding of the potential and limitations of indoor radiowave propagation at key frequencies of interest, such as the 5.2 GHz band employed by commercial wireless LAN standards such as IEEE 802.11a and HiperLAN 2. Although several indoor wireless models have been proposed in the literature, these temporal variations have not yet been thoroughly investigated. Therefore, we have made an important contribution to the area by conducting a systematic study of the problem, including a propagation measurement campaign and statistical channel characterization of human body effects on line-of-sight indoor propagation at 5.2 GHz. Measurements were performed in the everyday environment of a 7.2 m wide University hallway to determine the statistical characteristics of the 5.2 GHz channel for a fixed, transverse line-of-sight (LOS) link perturbed by pedestrian movement. Data were acquired at hours of relatively high pedestrian activity, between 12.00 and 14.00. The location was chosen as a typical indoor wireless system environment that had sufficient channel variability to permit a valid statistical analysis. The paper compares the first and second order statistics of the empirical signals with the Gaussian-derived distributions commonly used in wireless communications. The analysis shows that, as the number of pedestrians within the measurement location increases, the Ricean K-factor that best fits the Cumulative Distribution Function (CDF) of the empirical data tends to decrease proportionally, ranging from K=7 with 1 pedestrian to K=0 with 4 pedestrians. These results are consistent with previous results obtained for controlled measurement scenarios using a fixed link at 5.2 GHz in [2], where the K factor reduced as the number of pedestrians within a controlled measurement area increased. Level crossing rate results were Rice distributed, considering a maximum Doppler frequency of 8.67 Hz. While average fade duration results were significantly higher than theoretically computed Rice and Rayleigh, due to the fades caused by pedestrians. A novel statistical model that accurately describes the 5.2 GHz channel in the considered indoor environment is proposed. For the first time, the received envelope CDF is explicitly described in terms of a quantitative measurement of pedestrian traffic within the indoor environment. The model provides an insight into the prediction of human body shadowing effects for indoor channels at 5.2 GHz

A DSMC investigation of gas flows in micro-channels with bends

Pressure-driven, implicit boundary conditions are implemented in an open source direct simulation Monte Carlo (DSMC) solver, and benchmarked against simple micro-channel flow cases found in the literature. DSMC simulations are then carried out of gas flows for varying degrees of rarefaction along micro-channels with both one and two ninety-degree bends. The results are compared to those from the equivalent straight micro-channel geometry. Away from the immediate bend regions, the pressure and Mach number profiles do not differ greatly from those in straight channels, indicating that there are no significant losses introduced when a bend is added to a micro-channel geometry. It is found that the inclusion of a bend in a micro-channel can increase the amount of mass that a channel can carry, and that adding a second bend produces a greater mass flux enhancement. This increase happens within a small range of Knudsen number (0.02 Knin 0.08). Velocity slip and shear stress profiles at the channel walls are presented for the Knudsen showing the largest mass flux enhancement

Gender and transitional justice in Africa: Progress and prospects*

During the past few decades, different models of transitional justice (TJ) have developed throughout Africa to try to address the mass human rights abuses that have occurred during conflicts. These mechanisms, both judicial and nonjudicial, have often failed to adequately tackle the extensive gender-based violence that has been prevalent on the continent. This article examines the ways truth commissions, legal mechanisms, reparations, security sector reform efforts, and traditional mechanisms in Africa have dealt with gender-based human rights violations. While recent African TJ mechanisms have been innovative in developing means to address crimes against women, these mechanisms continue to fail victims. This is in large part because the current discourse on gender and transitional justice needs to be broadened to better address women’s experiences of conflict. Future TJ initiatives need to re-examine the types of violations prioritised, and recognise the continuum of violence that exists in pre-conflict and post-conflict societies. It is also important to challenge the transitional justicefield to stop reducing sexual-based violence to ‘women’s problems’, and explore how men are affected by the gendered dynamics of conflict.

Surfaxe: Systematic surface calculations

Surface science is key to understanding the properties of a wide range of materials for energy applications, from catalysts to solar cells to battery components. Computational modelling based on quantum mechanics is often used to calculate surface properties of materials, which in turn determine their stability and performance. The maturity of these “first-principles” methods, coupled with the huge amount of computational power accessible today, means they can now be used predictively in high-throughput screening workflows to suggest new materials for specific applications before they are synthesised. The surfaxe package provides a framework for such screening workflows, automating each stage of the process

Toward a feminist housing commons? Conceptualising care - (as) - work in collaborative housing

This article conceptualizes care-(as)-work in collaborative housing and addresses current debates on the potential of cohousing to embody a feminist commons. A focus on purpose-built cohousing projects in the UK enables us to focus on the values present in the initial phases of collective design and on the ongoing negotiations and mediation that take place through social interactions, resident-led self-management, and formal and informal mutual support. Our analysis is based on in-depth interviews and focus group discussions with two communities in England. Our contribution focuses on two aspects of care-(as)-work: how difficult emotions related to cohousing maintenance work are minimized for the good of the common and how such work is differentially embodied. Returning to cohousing’s transformational capacities as a feminist commons, we show that while boundaries of care in commoning are critical to residents, they are inherently blurry, performative and gendered

The key position: influence of staple location on constrained peptide conformation and binding

First published online 29 Sep 2016Constrained α-helical peptides are showing potential as biological probes and therapeutic agents that target protein-protein interactions. However, the factors that determine the optimal constraint locations are still largely unknown. Using the β-integrin/talin protein interaction as a model system, we examine the effect of constraint location on helical conformation, as well as binding affinity, using circular dichroism and NMR spectroscopy. Stapling increased the overall helical content of each integrin-based peptide tested. However, NMR analysis revealed that different regions within the peptide are stabilised, depending on constraint location, and that these differences correlate with the changes observed in talin binding mode and affinity. In addition, we show that examination of the atomic structure of the parent peptide provides insight into the appropriate placement of helical constraints.Kelly L. Keeling, Okki Cho, Denis B. Scanlon, Grant W. Booker, Andrew D. Abell and Kate L. Wegene

‘A Slow Build-Up of a History of Kindness’: Exploring the Potential of Community-Led Housing in Alleviating Loneliness

This article explores the potential of community-led housing (CLH) in combatting loneliness, and represents a mixed-methods research project carried out from just before the beginning of the pandemic, through 2020. Methods comprised a nationwide quantitative online survey of members of CLH groups (N = 221 respondents from England and Wales), followed by five case studies of communities representing a range of different CLH models. This qualitative element comprised participant observation, and semi-structured interviews at each group. The article also considers data from a smaller research project carried out by the same team in July 2020, that aimed to capture the experience of the pandemic for CLH groups, and comprising an online questionnaire followed by 18 semi-structured interviews. We conclude that members of CLH projects are measurably less lonely than those with comparable levels of social connection in wider society, and that such benefits are achieved through combinations of multiple different elements that include physical design, social design and through social processes. Notably, not all aspects of communities that contribute positively are a result of explicit intentionality, albeit the concept is considered key to at least one of the models