A novel method for mitigating the effects of dynamic coexistence on the operation of IEEE 802.15.4‐based mobile WSNs

Wireless networks dynamically coexist when their transmission ranges overlap as a result of mobility. Mobile wireless sensor networks (WSNs) may suffer from significant degradation of performance due to the interference caused by dynamic coexistence, which is particularly critical for health monitoring WSNs. In this paper, we propose a novel method to detect and mitigate the harmful effects of dynamic coexistence on the operation of IEEE 802.15.4‐based mobile health monitoring WSNs. IEEE 802.15.4 uses the guaranteed time slots (GTS) mechanism to eliminate contention; however, successful transmissions cannot be guaranteed for coexisting WSNs. We show that using limited clear channel assessments at the beginning of the GTS enables the mobile WSNs to avoid collisions with minimum overhead. This method can also be used in combination with the previously proposed mechanisms for coexistence management. We analytically investigate the effects of using this method on the performance of the dynamically coexisting WSNs. We use OPNET simulation to investigate the coexistence of health monitoring WSNs and also to validate the proposed method. Our results indicate that using the proposed mechanism, 2–10 coexisting mobile WSNs with relatively high transmission rates (20–30% of maximum throughput) can achieve 20–90% higher rates of successful transmissions, with less than 10% increase in power consumption. Copyright © 2014 John Wiley & Sons, Ltd.     

Roasted Sunflower Kernel Paste (Tahini) Stability: Storage Conditions and Particle Size Influence

Sunflower tahini faces quality problems due to the tendency of oil to exudate, causing accelerated rancidity and low marketability. In this study, the colloidal and oxidative stability of different trimodal particle size distributions of sunflower tahini (cumulative volume percentages of small, middle and large class populations of 9.61–16.67, 43.03–55.03 and 47.36–28.3) was evaluated during storage at three different temperatures. Decreasing sample particle size decreased the sunflower tahini colloidal stability. The coarsest prototype, being the most stable tahini in terms of oil separation, was included in the oxidative stability storage test together with a commercial tahini. The peroxide values of the studied sunflower tahini samples increased significantly (p < 0.05) with storage time, irrespective of storage temperature, while the p‐anisidine values showed an irregular pattern. Considering 30‐meq O₂/kg as a PV limit, the commercial tahini showed good oxidative stability as it was under this when stored 3 months at 4 °C, 2 months at room temperature and 1 month at 40 °C. The coarsest tahini sample was under the limit when stored 2 months at 4 °C, 1 month at room temperature and 2 weeks at 40 °C. Particle size was shown to be an essential parameter for controlling sunflower tahini's overall stability.     

The relationship between clients’ conformity to masculine norms and their perceptions of helpful therapist actions.

T. J. G. Tracey et al.’s (2003) common factors model derived from therapists and psychotherapy researchers has provided a parsimonious structure to inform research and practice. Accordingly, the current authors used the 14 common factor categories identified in Tracey et al.’s model as a guide to code clients’ perceptions of helpful therapist actions (e.g., intervention, way of being) in short-term psychotherapy. Next, they conducted a cluster analysis to establish meaningful subgroups of clients based on clients’ perceptions of helpful therapist actions. Finally, they explored if clients in these subgroups differed in their report of conformity to masculine norms. Clients (N = 161) from a university counseling center were recruited for the current study. Results revealed 3 clusters of clients based on their perceptions of helpful therapist actions: Insight (44%), Relationship (30%), and Information (26%). In contrast, Tracey et al. found 3 clusters: Bond (which includes Insight and Relationship), Information, and Structure of therapy (not found in the current study). Clients in the Insight and Relationship clusters reported more conformity to masculine norms as compared with clients in the Information cluster. There were no sex differences across clusters. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of a moving diffuser on a random electromagnetic beam

The effects of a moving diffuser on the spectrum, on the spectral degree of polarization, and on the spectral degree of coherence of a random electromagnetic beam are investigated. It is found that while the spectrum and the spectral degree of coherence change on transmission, the degree of polarization does not.     

Reconstruction of Scattering Potentials from Incomplete Data

Abstract

In many situations encountered in physics and in other fields, one can frequently experimentally determine some but not all the Fourier components of a scattering potential. In this paper we present an integral equation which makes it possible to reconstruct any square-integrable function f(r) of finite support from the knowledge of its Fourier transform j (K) over any finite three-dimensional domain of K space. We illustrate the use of this integral equation by application to potential scattering at fixed energy and we show how it can be used to reconstruct details of the scattering potential beyond the usual resolution limit from measurements of the scattered field in the far zone of the scatterer.     

Invisible Bodies and Uniqueness of the Inverse Scattering Problem

Abstract

It is shown that within the accuracy of the first-order Born approximation there are no bodies that are invisible for all directions of incidence, i.e. that there are neither deterministic nor random non-scattering scatterers. An alternating orthogonal projections approach is also discussed for reconstructing the structure of deterministic scatterers from the knowledge of the scattered field in the far zone.     

Building Code Enforcement Burdens and Central City Decline

Since the enactment of Hammurabi's Code in ancient Babylon, building regulations have been relied upon to protect the public from the hazards of substandard building materials and slipshod construction techniques. Unnecessary building code requirements and strict enforcement practices, however, have been widely criticized for increasing the costs of new construction and rehabilitation, particularly within central cities. These burdens reduce the ability of central cities to compete successfully with surrounding suburban areas for population and economic development. In this article, we address the linkage between enforcement of building codes and construction activity. We show that central cities can capture a larger share of the market for single-family detached housing in their metropolitan areas and also spur commercial rehabilitation if they adopt more “business-friendly” approaches to building code enforcement. These gains can be achieved without reducing the degree of compliance with building regulations as long as enforcement efforts are strong. In short, one key to increasing economic development in central cities is to foster the right kind of enforcement, rather than having weak enforcement of building regulations.     

Novel 3D Wollastonite‐Based Scaffolds from Preceramic Polymers Containing Micro‐ and Nano‐Sized Reactive Particles

Wollastonite (CaSiO₃) ceramics are well known biomaterials which can be produced using many different techniques. The present paper illustrates an innovative processing method employing preceramic polymers (silicone resins) containing CaCO₃ micro‐ and nano‐sized particles, which act as reactive fillers. Silica from the decomposition of the silicone resins reacts at low temperature with the CaO deriving from the fillers, yielding wollastonite ceramics. Hydroxyapatite powders can also be added, to modify the biological response of the material. This approach enables the fabrication of 3D scaffolds via fused deposition or via conventional hot extrusion.     

Coherence filters and their uses. I. Basic theory and examples

Abstract

The phenomenon of correlation-induced spectral changes, discovered several years ago and extensively studied since then, is shown to offer the possibility of contructing novel types of spectral filter which have several properties that are not achievable with conventional filters. For example such filters can have different prescribed filtering properties in different directions of observation. In this paper the underlying theory is discussed and is illustrated by a few examples.     

Rapid determination of the fat content in packaged dairy products by unilateral NMR

BACKGROUND: Knowledge of the fat content in dairy products is important for both industry and consumers. A new procedure for rapid and non‐destructive determination of the fat content in dairy products using unilateral nuclear magnetic resonance (NMR) is proposed. The sample magnetisation is prepared using either T₁ suppression or diffusion editing, and read out via a Carr‐Purcell‐Meiboom‐Gill (CPMG) pulse sequence. RESULTS: A linear correlation between the measured NMR signal from the fat component and the declared fat content in the tested products validated both approaches as viable instrumental methods. The shortest measurement time was about 7 s. CONCLUSION: Advantages of the unilateral NMR method, including hardware simplicity and accommodation of commercially packaged products, make it attractive for routine use in industry. Copyright © 2008 Society of Chemical Industry