Distributed localization of a RF target in NLOS environments

We propose a novel distributed expectation maximization (EM) method for non-cooperative RF device localization using a wireless sensor network. We consider the scenario where few or no sensors receive line-of-sight signals from the target. In the case of non-line-of-sight signals, the signal path consists of a single reflection between the transmitter and receiver. Each sensor is able to measure the time difference of arrival of the target's signal with respect to a reference sensor, as well as the angle of arrival of the target's signal. We derive a distributed EM algorithm where each node makes use of its local information to compute summary statistics, and then shares these statistics with its neighbors to improve its estimate of the target localization. Since all the measurements need not be centralized at a single location, the spectrum usage can be significantly reduced. The distributed algorithm also allows for increased robustness of the sensor network in the case of node failures. We show that our distributed algorithm converges, and simulation results suggest that our method achieves an accuracy close to the centralized EM algorithm. We apply the distributed EM algorithm to a set of experimental measurements with a network of four nodes, which confirm that the algorithm is able to localize a RF target in a realistic non-line-of-sight scenario.Comment: 30 pages, 11 figure

Electric‐field dependence of interband transitions in In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As single quantum wells by room‐temperature electrotransmittance

Room‐temperature electrotransmittance has been used in order to investigate the interband excitonic transitions in a 250‐Å‐thick In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As single‐quantum‐well system as a function of an externally applied electric field. Parity forbidden transitions, involving conduction‐band states with quantum numbers up to n=5, which become more pronounced at high electric fields were observed. The ground‐state and the forbidden transitions showed a significant red shift due to the quantum confined Stark effect. A comparison with previously reported results on thinner InGaAs/InAlAs quantum wells indicated that the wide‐well sample exhibits the largest shift, as expected from theory. Despite the appreciable Stark shift, the rather large, field‐induced linewidth broadening and the relatively low electric field at which the ground‐state exciton is ionized poses limitations on using this wide‐quantum‐well system for electro‐optic applications

Observation of Droplet Size Oscillations in a Two-Phase Fluid under Shear Flow

Experimental observations of droplet size sustained oscillations are reported in a two-phase flow between a lamellar and a sponge phase. Under shear flow, this system presents two different steady states made of monodisperse multilamellar droplets, separated by a shear-thinning transition. At low and high shear rates, the droplet size results from a balance between surface tension and viscous stress whereas for intermediate shear rates, it becomes a periodic function of time. A possible mechanism for such kind of oscillations is discussed

Micro-evaporators for kinetic exploration of phase diagrams

We use pervaporation-based microfluidic devices to concentrate species in aqueous solutions with spatial and temporal control of the process. Using experiments and modelling, we quantitatively describe the advection-diffusion behavior of the concentration field of various solutions (electrolytes, colloids, etc) and demonstrate the potential of these devices as universal tools for the kinetic exploration of the phases and textures that form upon concentration

Risks associated with endotoxins in feed additives produced by fermentation

Acknowledgements We thank Jordi Tarrés Call, who recorded the discussions and offered advice about procedures, and Nicole Reisinger and Gerd Schatzmayr, who provided valuable information about endotoxins in animal feeds. The Rowett Institute of Nutrition and Health is funded by the Rural and Environment Science and Analytical Services Division (RESAS) of the Scottish Government.Peer reviewedPublisher PD

Patient and Public Involvement in the Development of Healthcare Guidance: An Overview of Current Methods and Future Challenges

Clinical guidelines and health technology assessments are valuable instruments to improve the quality of healthcare delivery and aim to integrate the best available evidence with real-world, expert context. The role of patient and public involvement in their development has grown in recent decades, and this article considers the international literature exploring aspects of this participation, including the integration of experiential and scientific knowledge, recruitment strategies, models of involvement, stages of involvement, and methods of evaluation. These developments have been underpinned by the parallel rise of public involvement and evidence-based medicine as important concepts in health policy. Improving the recruitment of guideline group chairs, widening evidence reviews to include patient preference studies, adapting guidance presentation to highlight patient preference points and providing clearer instructions on how patient organisations can submit their intelligence are emerging proposals that may further enhance patient and public involvement in their processes

Joint Deployment and Mobility Management of Energy Harvesting Small Cells in Heterogeneous Networks

Small heterogeneous cells have been introduced to improve the system capacity and provide the ubiquitous service requirements. In order to make flexible deployment and management of massive small cells, the utilization of self-powered small cell base stations with energy harvesting (EH-SCBSs) is becoming a promising solution due to low-cost expenditure. However, the deployment of static EH-SCBSs entails several intractable challenges in terms of the randomness of renewable energy arrival and dynamics of traffic load with spatio-temporal fluctuation. To tackle these challenges, we develop a tractable framework of the location deployment and mobility management of EH-SCBSs with various traffic load distributions an environmental energy models. In this paper, the joint optimization problem for location deployment and mobile management is investigated for maximizing the total system utility of both users and network operators. Since the formulated problem is a NP-hard problem, we propose a low-complex algorithm that decouples the joint optimization into the location updating approach and the association matching approach. A suboptimal solution for the optimization problem can be guaranteed using the iteration of two stage approaches. Performance evaluation shows that the proposed schemes can efficiently solve the target problems while striking a better overall system utility, compared with other traditional deployment and management strategies

Seismic Modeling and Incremental Dynamic Analysis of the Cold-Formed Steel Framed CFS-NEES Building

The objective of this paper is to present seismic modeling of a two-story cold-formed steel (CFS) framed building. The selected building, known as the CFSNEES building, was designed to current U.S. standards and then subjected to full-scale shake table tests under the U.S. National Science Foundation Network for Earthquake Engineering Simulation (NEES) program. Test results showed that the building’s stiffness and capacity was considerably higher than expected and the building suffered only non-structural damage and no permanent drift, even at maximum considered earthquake (per ASCE 7 and the selected California site) level. Past modeling, including that of the authors, largely focused on nonlinear hysteretic modeling of the shear walls. The test results indicate that additional building elements must be considered to develop an accurate characterization of the strength, stiffness, and ductility of the building. Advanced 3D models were developed in OpenSees to accurately depict the lateral response and included all structural and non-structural framing and sheathing, explicit diaphragm modeling, and nonlinear boundary conditions to capture bearing load paths. This paper details the modeling techniques adopted and typical results including comparison with experiments. The impact of the various modeling assumptions on the results is also explored to provide a measure of system sensitivity. In addition, incremental dynamic analysis was performed on the building model and the results post-processed consistent with the FEMA P695 protocol. For the CFS-NEES building, designed to current standards, results indicate that the advanced model predicts an acceptable collapse margin ratio. In the future, the modeling protocols established here provide a means to analyze a suite of CFS-framed archetype buildings and provide further insight on seismic response modification coefficients

Seismic Computational Analysis of CFS-NEES Building

The objective of this paper is to explore computational modeling of a coldformed steel framed building subjected to earthquake excitation. The selected two-story building will be subjected to full-scale motion on a shaking table in 2013 as part of the National Science Foundation funded Cold-Formed Steel – Network for Earthquake Engineering Simulation (CFS-NEES) project. The ledger-framed building employs load bearing cold-formed steel members throughout (wall, floors, and roofs) and employs OSB sheathed shear walls and an OSB sheathed diaphragm for the lateral force resisting system. Two- and three-dimensional analysis models capable of providing vibration, pushover, linear and nonlinear time history analysis are created in OpenSees. To date, the key nonlinearity investigated in the models is the characterization of the shear walls. The shear walls are either modeled as (a) elastic perfectly plastic, consistent with “state of the practice” level knowledge from AISI-S213 or (b) fully hysteretic with pinching and strength degradation based on shear walls tests conducted specifically for this building. The impact of the diaphragm stiffness is also investigated. Interaction of the lateral and gravity system, interaction of the joists, ledger, and walls, and the impact of openings on the diaphragm all remain for future work. The model is being employed to help determine the predicted experimental performance and develop key sensor targets in the response. In addition, the model will be used in incremental dynamic analysis to explore seismic performance-based design and sensitivity to model fidelity (2D, 3D, etc.) for cold-formed steel framed buildings