Topologies of wireless mesh networks with inband backhauling

Proceedings of: PIMRC 2010: 21st Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications took place from 26-30 Sep. 2010 in Istanbul, TurkeyWireless mesh networks (WMNs) with in band backhauling use the same antennas for the backhaul as well as for the access. Therefore antennas of next hop neighbours need to be directed to each other. However, such a configuration is not possible in a three-sectorized hexagonal cell deployment. In this paper we derive several alternative topologies that are suitable for WMNs with in band backhauling. We show that a topology with four directional antennas per node and backhaul connectivity between indirect neighbours outperforms competing topologies in terms of handover rate, optimal maximum power, and system capacity.European Community's Seventh Framework ProgramPublicad

Investigation on iterative multiuser detection physical layer network coding in two-way relay free-space optical links with turbulences and pointing errors

Physical layer network coding (PNC) improves the throughput in wireless networks by enabling two nodes to exchange information using a minimum number of time slots. The PNC technique is proposed for two-way relay channel free space optical (TWR-FSO) communications with the aim of maximizing the utilization of network resources. The multipair TWR-FSO is considered in this paper, where a single antenna on each pair seeks to communicate via a common receiver aperture at the relay. Therefore, chip interleaving is adopted as a technique to separate the different transmitted signals at the relay node to perform PNC mapping. Accordingly, this scheme relies on the iterative multiuser technique for detection of users at the receiver. The bit error rate (BER) performance of the proposed system is examined under the combined influences of atmospheric loss, turbulence-induced channel fading, and pointing errors (PEs). By adopting the joint PNC mapping with interleaving and multiuser detection techniques, the BER results show that the proposed scheme can achieve a significant performance improvement against the degrading effects of turbulences and PEs. It is also demonstrated that a larger number of simultaneous users can be supported with this new scheme in establishing a communication link between multiple pairs of nodes in two time slots, thereby improving the channel capacity

Outage Performance of Free-Space OpticalCommunication Systems Over Turbulent Channels with Varying Atmospheric Visibilities

Free space optics is the technology where beams of light provideoptical connection using a line-of-sight path for communication as aform of video, voice, and data information between two points. A fewof the FSO system's limitations include atmospheric attenuationcaused by weather, which is the most difficult issue to solve because itseriously impairs system performance and results in poor signaltransmission. One of the important performance measures foranalyzing and enhancing FSO functionality for various fading statesassociated with different data rates is outage probability. This articleexamines FSO in terms of transmission optical power, feasible bitrates, and outage probability under clear, hazy, and moderate toheavy rainy conditions. The MATLAB simulation is implemented to dothe performance study. However, aperture diameters D = {20, 40, 80,100} mm and link distances L = {2.0, 3.5, 5.0} mm are seen to beessential characteristics for evaluating system performance. For allscenarios, the system's power consumption can be minimized byusing larger aperture diameters at lower bit rates, particularly in clearweather

Outage Performance of Free-Space OpticalCommunication Systems Over Turbulent Channels with Varying Atmospheric Visibilities

Free space optics is the technology where beams of light provideoptical connection using a line-of-sight path for communication as aform of video, voice, and data information between two points. A fewof the FSO system's limitations include atmospheric attenuationcaused by weather, which is the most difficult issue to solve because itseriously impairs system performance and results in poor signaltransmission. One of the important performance measures foranalyzing and enhancing FSO functionality for various fading statesassociated with different data rates is outage probability. This articleexamines FSO in terms of transmission optical power, feasible bitrates, and outage probability under clear, hazy, and moderate toheavy rainy conditions. The MATLAB simulation is implemented to dothe performance study. However, aperture diameters D = {20, 40, 80,100} mm and link distances L = {2.0, 3.5, 5.0} mm are seen to beessential characteristics for evaluating system performance. For allscenarios, the system's power consumption can be minimized byusing larger aperture diameters at lower bit rates, particularly in clearweather

Experimental and numerical Investigation of sudden expansion flow at sonic Mach number

The sudden expansion at the blunt base is a widespread phenomenon in the case of shells, rockets, and missiles. This study uses passive control in the form of ribs of various shapes and sizes in an abruptly expanded square cross-section duct at sonic Mach number. Three area ratios are examined in this study: 3.61, 5.76, and 7.84. In this study, passive control is employed at sonic Mach number in a suddenly expanded square cross-section duct. Three distinct rib sizes (6 mm, 8 mm, and 10 mm in diameter) at four locations inside the duct (1D, 2D, 3D, and 4D). The rib shapes considered for this study, rectangular, triangular, and semi-circular ribs, are investigated experimentally in the first stage. Experimental pressure data is used to compute base drag quantitatively. The outcomes of the simulation and the experiments agree reasonably well. The most efficient rib shape is a rectangular one with a diameter of 10 mm and an area ratio of 3.61. It raises the base pressure to almost three times that of the surrounding air. However, when the rib diameter is 6 mm, the control increases the base pressure, nearly equal to the ambient pressure. The outcomes of this study can be utilized to design an aerospace vehicle that meets the mission requirements. The passive control does not impact a higher area ratio despite the nozzle being under-expanded. The flow field inside the duct remains unchanged with and without control. Therefore, the passive control does not aggravate the duct’s flow field

IoT-Based Indoor and Outdoor Self-Quarantine System for COVID-19 Patients

Even after two years since the declaration of the new virus Coronavirus Disease 19 (COVID-19), the reported cases are still considerably high in many countries, including Malaysia. The health authorities cannot monitor the health condition and track the location of every home-monitored patient at once due to many confirmed cases in a day. In order to overcome the shortage of manpower, an Internet of Things (IoT)-based self-quarantine system with Radio Frequency Identification (RFID) and Global Positioning System (GPS) tracking is proposed in this paper to monitor the health conditions of the Covid-19 patients and track their real-time location via mobile application. Biomedical sensors are used to measure health conditions such as temperature, pulse oximetry, and heart-rate monitor. In addition, the RFID readers are used to detect patients that intend to leave the quarantine area, and the GPS modules are used to track their actual geometrical location so that the authorities can take further action. The real-time data is automatically pushed to the cloud server for the authorities to remotely view the patient's health condition and location on the Google map using smart devices. Finally, a hardware prototype and a mobile application have been successfully developed in this project. The system is able to display the temperature, heartbeats, and blood oxygen saturation properly on a liquid crystal display (LCD) screen. All these measured values, together with the information from RFID detection and GPS location tracking, can be viewed on a smartphone

Output from VIP cells of the mammalian central clock regulates daily physiological rhythms

The suprachiasmatic nucleus (SCN) circadian clock is critical for optimising daily cycles in mammalian physiology and behaviour. The roles of the various SCN cell types in communicating timing information to downstream physiological systems remain incompletely understood, however. In particular, while vasoactive intestinal polypeptide (VIP) signalling is essential for SCN function and whole animal circadian rhythmicity, the specific contributions of VIP cell output to physiological control remains uncertain. Here we reveal a key role for SCN VIP cells in central clock output. Using multielectrode recording and optogenetic manipulations, we show that VIP neurons provide coordinated daily waves of GABAergic input to target cells across the paraventricular hypothalamus and ventral thalamus, supressing their activity during the mid to late day. Using chemogenetic manipulation, we further demonstrate specific roles for this circuitry in the daily control of heart rate and corticosterone secretion, collectively establishing SCN VIP cells as influential regulators of physiological timing

High-fidelity multimode fibre-based endoscopy for deep brain in vivo imaging

Progress in neuroscience constantly relies on the development of new techniques to investigate the complex dynamics of neuronal networks. An ongoing challenge is to achieve minimally-invasive and high-resolution observations of neuronal activity in vivo inside deep brain areas. A perspective strategy is to utilise holographic control of light propagation in complex media, which allows converting a hair-thin multimode optical fibre into an ultra-narrow imaging tool. Compared to current endoscopes based on GRIN lenses or fibre bundles, this concept offers a footprint reduction exceeding an order of magnitude, together with a significant enhancement in resolution. We designed a compact and high-speed system for fluorescent imaging at the tip of a fibre, achieving micron-scale resolution across a 50 um field of view, and yielding 7-kilopixel images at a rate of 3.5 frames/s. Furthermore, we demonstrate in vivo observations of cell bodies and processes of inhibitory neurons within deep layers of the visual cortex and hippocampus of anesthetised mice. This study forms the basis for several perspective techniques of modern microscopy to be delivered deep inside the tissue of living animal models while causing minimal impact on its structural and functional properties.Comment: 10 pages, 2 figures, Supplementary movie: https://drive.google.com/file/d/1Fm0G3TAIC49LVX6FaEiAtlefkWx1T2a5/vie

Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente

Thermodynamic, quantum efficiency, and photocatalytic properties of Cs2MZ6 (M = Ti, Zr, Hf; Z = Cl, I) double perovskites using DFT approach

Halide double perovskites have recently received considerable attention owing to their promising properties for a range of technological demands. Compounds Cs2MZ6 (M = Ti, Zr, Hf; Z = Cl, I) have been studied individually through experimental synthesis and computational modeling. Nevertheless, comprehensive comparative analyses of their optical characteristics, quantum efficiency, and photocatalytic potential for water splitting remain limited. In this study, the structural, electronic, optical, quantum efficiency, and photocatalytic properties for water splitting of Cs2MZ6 (M = Ti, Zr, Hf; Z = Cl, I) phases are systematically investigated via the full-potential linearized augmented plane wave plus local orbitals technique. The calculated band structures indicate a gradual decrease in the bandgap from Cl to I substitution, with most variants exhibiting indirect and relatively wide gaps. “The frequency-dependent optical properties, including the real and imaginary parts of the dielectric function, absorption coefficient, and optical conductivity, are systematically calculated up to 12 eV. The results reveal pronounced absorption peaks in the ultraviolet region, highlighting the potential of these compounds for high-frequency optoelectronic applications.” Thermodynamic stability was assessed via calculations of Gibbs free energy (kJ/mol) and entropy (S, J mol−1 K−1) as functions of temperature and pressure. The results consistently exhibit negative Gibbs free energies and rising entropy, indicating robust thermal stability. Furthermore, the computed band edge positions indicate potential for photocatalytic water splitting, with Cs2ZrI6 and Cs2HfI6 showing particularly favorable alignment for both hydrogen and oxygen evolution reactions under solar irradiation