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This paper studies the problem of resilient dynamic output-feedback control schemes for continuous-time networked control systems (NCSs). A decentralized hybrid strategy is utilized while network imperfections, external disturbances, and noise are considered. Moreover, during data transmission, a practical denial-of-service (DoS) jamming attack, which periodically disturbs the network channels, is considered. To preserve the network resources, a decentralized event-triggered mechanism is employed to transmit only the sampled signals that are required. It is assumed that outputs and control inputs of each subsystem are transmitted to the corresponding decentralized controllers and actuators, respectively, over the different individual channels based on independent triggering mechanisms. At first, the NCS is modeled as a decentralized hybrid system with exogenous disturbance and noise. Then, sufficient conditions that guarantee the L 2 -stability of the NCS in the presence of external disturbances and noise, which is resilient to periodic DoS attacks, are provided in terms of the linear matrix inequalities. Finally, sufficient conditions are derived to deal with the time-varying delays. It has been demonstrated that the proposed technique can be effectively applied to a well-known continuous stirred tank reactor (CSTR) as a benchmark example. [ABSTRACT FROM AUTHOR]

The unique thermal energy storage system (TESS) as an auxiliary system of solar water heater has a critical part to demonstration in preserving and efficiently utilizing energy, resolving demand-supply mismatches, and boosting the efficiency of energy systems. In this research, a suitable Nano enhanced-Composite Phase Change Material (NCPCM) was prepared to utilize in two model of metal cylinders. First of all, an experimental test for determination of melting point has been investigated by temperature variation test (TVT) method for NCPCM based on paraffin component. Then, two nanomaterial types (TiO2 and CuO) mixed at 50%/50% with two concentrations (0.6% and 0.12%) were dispersed with slack paraffin to provide a total of four experiments to compare the average temperature evolution and exergy efficiency. A theoretical framework for exergy analysis give away that use of nano composites in PCMs will improve efficiency rather than a single nanomaterial. However, to assess capability of this system to integrate with solar water heater, if there is no solar radiation limitation, NCPCM with 1.2% wt. will be a better choice with higher cylinders diameter (HD-Cylinders). Neverthless, for climates with limited time in storage energy, NCPCM with 1.2% wt. and lower cylinders diameter (LD-Cylinders) is our best suggestion for maximum efficiency that can be used during the peak solar energy period. Therefore, by considering NCPCM and integrating this novel study with solar technologies as a reliable heat source, outline is an excellent way for saving energy consumption in buildings at any remote area. [ABSTRACT FROM AUTHOR]

Recently, due to the increasing demand for energy and the identification of fossil fuels and their pollution, the focus on renewable energy is increasing day by day, so the use of renewable energy and energy-saving techniques is very important. PCMs are one of the most effective means of thermal energy storage, whose task is to change phase with increasing temperature, store thermal energy, and release this energy with decreasing temperature. This is one of the applications of these materials in building walls. In this research, the aim is to analyze and investigate the use of phase change materials in addition to thermal insulation. For this purpose, optimization in terms of energy and thermal comfort of residents has been done by the response surface method. Four Iranian cities with different climates—Tehran, Bandar Abbas, Tabriz, and Rasht—have undergone this optimization. According to the results, it can be concluded that the best temperature for the heating thermostat is approximately 20 °C and for the cooling thermostat, approximately 28 °C and 25 °C. Also, the best thermal insulation and PCMs are polyurethane and BioPCMDSCM27Q21. The thickness of the thermal insulation in the range between 6.9 cm and 9.8 cm is chosen as optimal, and the thickness of the phase change material is approximately 5 cm optimal for all cities (except Tehran). Due to the optimization of thermal comfort between 25 and 60 %, heating electricity between 43 and 99 % and cooling electricity between 38 and 52 % have been improved. • This study deals with the use of PCM and thermal insulation in Iran, focusing on energy optimization and thermal comfort. • The best temperature for the heating thermostat is 20 °C and for the cooling thermostat 28 °C and 25 °C. • The best thermal insulation and phase change materials are polyurethane and BioPCMDSCM27Q21. • The optimal thickness of thermal insulation was obtained from 6.9 cm to 9.8 cm for all cities. • Thermal comfort 25-60 %, heating electricity 45-100 % and cooling electricity 40-53 % have been improved. [ABSTRACT FROM AUTHOR]

In this study, a numerical model is developed to show the performance improvement of a cam–follower mechanism when using a roller type follower compared to the flat-faced follower. Nonconformal geometry besides the thermal effects due to the shearing of the lubricant film results in formation of a thin film in which the asperities contribute in carrying the load. The numerical model is developed in which the geometry, load, speed, lubricant properties, and the surface roughness profile is taken as input and the film thickness and friction coefficient as a function of cam angle are predicted. The asperities are assumed to have elastic, elasto-plastic, and plastic deformation. Simulation results indicated that the thermal effects cannot be neglected. Surface roughness is also a key parameter that affects the pressure distribution, film thickness, and friction coefficient. Finally, asperity and hydrodynamic pressure is reported and the performance of the two mechanisms is compared. Roller follower has a considerable preference in terms of friction coefficient compared to flat-faced follower. The minimum film thickness, however, is slightly larger in the flat follower. [ABSTRACT FROM AUTHOR]

Most industrial processes are characterized with large uncertainties. To deal with these kinds of processes and achieve fast and accurate control in a stable fashion, the multiple-model control methods have been demonstrated to be very effective. It is difficult to build the precise mathematic model of the object and to accurately control the object with the traditional control methods. This paper applies H-infinity robust control strategies to a 24-tray separating a mixture of methanol and water. The idea has favorable controls on control targets (rise time, settling time, overshoot and undershoot, the interaction between input and output) and help on stability of the system output. Then in order to show that the proposed controller affords a good robust performance consistently we have implemented four controllers.Performance analysis of the H-infinity robust controller, Model Predictive Control (MPC), conventional PID controller and also LQG/LTR has been done using MATLAB. The comparison of various time domain parameters was done to prove that the H-Infinity robust controller has best time characteristics and in face with uncertainties has better reacts as compared to other controllers. Beside this, MPC controller has satisfied result in robust stability. [ABSTRACT FROM AUTHOR]

A computationally efficient near-ground field prediction model is proposed to facilitate realistic wireless sensor network (WSN) simulations. In this model, using the principle of Fresnel zones, path loss is split into three segments. Certain propagation mechanisms dominate in each part. The distances that define the edges of each section are derived theoretically. The model is validated against several experimental datasets obtained in open and forested areas. It is noticed that the proposed model has higher accuracy compared to existing analytical near-ground propagation models. This enhancement is achieved by careful assessment of key features relevant to near-grazing propagation such as diffraction loss due to obstruction of the first Fresnel zone and higher order waves produced by terrain irregularities. Monte Carlo simulations are used to investigate the effects of antenna height, frequency of operation, polarization, and terrain dielectric and roughness properties on WSNs performance. It is realized that antenna height is by far the most influential geometric parameter to low-altitude WSNs connectivity and average number of neighbors. [ABSTRACT FROM PUBLISHER]

In this study, small perturbation method (SPM) and Kirchhoff approximation (KA) are incorporated into ray-tracing (RT) routines to model multiuser multi-input multi-output (MU-MIMO) channels formed on a rough dielectric terrain. The effect of surface roughness and correlation length, solid soil fractions, moisture content, link range, antenna height, polarization, radiation pattern, and carrier frequency are examined on received power, power delay and angular profiles, root mean square (RMS) delay and angular spread, coherence bandwidth, and coherence distance. Quantitative and qualitative analyses reveal that antenna directionality and terrain undulation and textural composition have significant impacts on the received signal power and channel multipath parameters and, hence, the performance of MU-MIMO terrain-based communication systems. [ABSTRACT FROM PUBLISHER]

One of the challenging problems of tribology is cam and follower elastohydrodynamic lubrication due to the simultaneous effect of various lubrication mechanisms. These mechanisms are transient, squeeze film, elastic deformation of contacting surfaces and variation of lubricant properties with pressure. In this paper, besides studying the mentioned factors, the effect of using a non-Newtonian lubricant such as grease is numerically investigated. The lubrication governing equations and Oswald's grease behavior equation have been discretized using finite difference technique. The system of equation has been solved via Multi-Grid method which is an advanced iterative method in solving system of partial differential equations. The results are shown for Newtonian oil compared to grease for different cam rotational speed. Also, different grease behaviors are investigated. The results are verified by comparison of the results obtained using the famous Newton-Raphson method. Findings show that the minimum lubricant thickness as well as the maximum pressure is lower when using grease compared to the case that a Newtonian lubricant is used. In the case of Newtonian lubricant, increasing the speed results in an increase in the lubricant film thickness but it is shown that, in the case of Non-Newtonian lubricant, speed does not affect the lubricant thickness. [ABSTRACT FROM AUTHOR]

Most industrial processes are characterized with large uncertainties. To deal with these kinds of processes and achieve fast and accurate control in a stable fashion, the multiple-model control methods have been demonstrated to be very effective. It is difficult to build the precise mathematic model of the object and to accurately control the object with the traditional control methods. This paper applies H-infinity robust control strategies to a 24-tray separating a mixture of methanol and water. The idea has favorable controls on control targets (rise time, settling time, overshoot and undershoot, the interaction between input and output) and help on stability of the system output. Then in order to show that the proposed controller affords a good robust performance consistently we have implemented four controllers.Performance analysis of the H-infinity robust controller, Model Predictive Control (MPC), conventional PID controller and also LQG/LTR has been done using MATLAB. The comparison of various time domain parameters was done to prove that the H-Infinity robust controller has best time characteristics and in face with uncertainties has better reacts as compared to other controllers. Beside this, MPC controller has satisfied result in robust stability. [ABSTRACT FROM AUTHOR]

In this article, the design, simulation, and realization of an L-band axial-mode 1 × 2 short helical antenna array are presented. The antenna array has a compact size and is lightweight. To improve array performance, special attention is paid to important parameters, such as gain, impedance matching, axial ratio, and mutual coupling. Impedance matching is achieved by optimization of the helix wire radius and the feed length. Axial ratio is improved by adding the optimized incorrect turn at the end of the helix. Finally, to reduce the mutual coupling between the elements, split-ring resonators are designed and installed between the two antennas. [ABSTRACT FROM AUTHOR]

In this article, compact microstrip bandpass filters using dual-mode stub-loaded resonators and capacitive/inductive source-load coupling are presented to realize opposite asymmetric quasi-elliptic responses. Two transmission zeros are generated in each design to sharpen the cutoff slope at the two sides of the passband. Both the coupling matrix and the equivalent circuit approaches are adopted to investigate the operating mechanism of the proposed filters. Restrictions imposed on the individual coupling coefficients by the implementation of this type of filters are discussed in detail. The proposed bandpass filters are designed at the center frequency of 2.4 GHz with the bandwidth of 200 MHz. The simulated and measured results are presented. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26215 [ABSTRACT FROM AUTHOR]

Bilateral medial medullary stroke is a very rare type of stroke, with catastrophic consequences. Early diagnosis is crucial. Here, I present a young patient with acute vertigo, progressive generalized weakness, dysarthria, and respiratory failure, who initially was misdiagnosed with acute vestibular syndrome. Initial brain magnetic resonance imaging (MRI) that was done in the acute phase was read as normal. Other possibilities were excluded by lumbar puncture and MRI of cervical spine.MR of C-spine showed lesion at medial medulla; therefore a second MRI of brain was requested, showed characteristic "heart appearance" shape at diffusion weighted (DWI), and confirmed bilateral medial medullary stroke. Retrospectively, a vague-defined hyperintense linear DWI signal at midline was noted in the first brain MRI. Because of the symmetric and midline pattern of this abnormal signal and similarity to an artifact, some radiologists or neurologists may miss this type of stroke. Radiologists and neurologists must recognize clinical and MRI findings of this rare type of stroke, which early treatment could make a difference in patient outcome. The abnormal DWI signal in early stages of this type of stroke may not be a typical "heart appearance" shape, and other variants such as small dot or linear DWI signal at midline must be recognized as early signs of stroke. Also, MRI of cervical spine may be helpful if there is attention to brainstem as well. [ABSTRACT FROM AUTHOR]

A miniature harmonic-suppressed microstrip bandpass filter (BPF) with a new triple-mode stub-loaded resonator is presented in this letter. Four distinct mechanisms are utilized to create five transmission zeros (TZs), leading to sharp skirts and wide stopband. Both simulation and measurement results are presented. The simulated/measured minimum passband insertion loss is 0.66 dB/0.78 dB and the 20 dB rejection bandwidth is extended up to 4f0. The size of the filter is about 0.23\lambdag\times 0.17\lambdag, where \lambdag is the guided wavelength at the center frequency. [ABSTRACT FROM PUBLISHER]