Sharif Digital Repository

This letter presents a new approach to low-power, low-latency, and frequency-selective wake-up receivers. A novel architecture is introduced to achieve frequency domain selectivity, including analog techniques, that enable data detection without the need for power-hungry digital processing. A two-mode duty cycling is also utilized, which helps reduce the power consumption of the receiver significantly with negligible latency. A prototype of the proposed receiver is fabricated and verified in a 180-nm CMOS process. The fabricated chipset achieves a sensitivity of-84.9 dBm with 4.32-ms wake-up latency and drains an average current of 12.2 μ text A}. Interference tests show an outstanding... 

Wake-up receivers (WuRX) have recently played a prominent role in many applications, such as the Internet of Things (1oT), Wireless Sensor Networks (WSN), and Wireless Body Area Networks (WBAN). In such systems, relying on limited battery energy for their functionality, the main receiver cannot run continuously because of its high power consumption. In most state-of-the-art WuRXs, the focus is on power consumption and sensitivity. in applications operating in dense environments such as the 915MHz1SM band, considering the congested activity of numerous radios, in-band frequency selectivity becomes imperative as well. Few state-of-theart WuRXs achieve a somehow considerable in-band... 

In this article, two optical-fibre probes used in displacement measurements are reported. In one arrangement, two optical fibres with protective buffer jackets are placed together, while in the second arrangement, the protective buffer jackets are removed and the two fibres are placed with the claddings in contact, with a concomitant smaller centrecentre distance. As the core and cladding diameters are the same in both probes, the effect of the centrecentre distance on double-fibre designs can be investigated. The reflected output powers are recorded for the probes as a function of the axial distance from a reflective surface. A theoretical model is also implemented, which considers the... 

In this study simulation results for three double-fiber optical designs for the reflection measurements are reported. Modeling is perused for three cases namely Equal Fibers (EF), transmitter fiber shorter (TS) and receiver fiber shorter (RS) designs. By proper modeling and written programs the operations of such symmetric double-fiber probes are simulated and the role of different crucial parameters such as fiber-to-fiber distance (t), fiber core radius (r) and fiber Numerical Aperture (NA) are investigated. In the second study simulation results for the transmitter fiber shorter and receiver fiber shorter designs are investigated for different fiber length differences (w). Finally... 

Design and operation of an opto-mechanical system for spectral analysis using a double fiber design for light delivery are reported in this study. A simple mechanical drive system is used, which is able to perform a fine course of angular motion for the scanning of the dispersive optical element. The presented system consists of a mechanical drive system, a dispersive element, a double fiber assembly and a photodetector. A source light, a digital multimeter and a PC are used to test the presented design. The first-order diffraction of the white light source is obtained by using a reflection diffraction grating in Littrow arrangement. By comparing the output reflection signals of the plane... 

This paper proposes an adaptive droop characteristic to enhance the superimposed droop frequency scheme for the control of DC microgrids. Conventional superimposed droop frequency scheme solves the poor current sharing and undesirable voltage regulation issues in DC microgrid. However, this method suffers from two main problems which are (i) instability in terms of load variation due to the limitation in transferrable reactive power, and (ii) poor voltage quality caused by the injected AC voltages in the DC system. In this paper, an adaptive droop characteristic is proposed to decrease the transferred reactive power and mitigate system overall voltage quality, and its performance is verified... 

Bladeless fan is a novel fan type that has no observable impeller, usually used for domestic applications. Numerical investigation of a Bladeless fan via Finite Volume Method was carried out in this study. The fan was placed in center of a 4×2×2m room and 473 Eppler airfoil profile was used as cross section of the fan. Performance and noise level of the fan by solving continuity and momentum equations as well as noise equations of Broadband Noise Source (BNS) and Ffowcs Williams and Hawkings (FW-H) in both steady state and unsteady conditions were studied. Flow increase ratio of the fan was captured. Furthermore, BNS method could find outlet slit of the air as the main source of the noise... 

Bladeless fan is a novel type of fan with an unusual geometry and unique characteristics. This type of fan has been recently developed for domestic applications in sizes typically up to 30cm diameter. In the present study, a Bladeless fan with a diameter of 60cm was designed and constructed, in order to investigate feasibility of its usage in various industries with large dimensions. Firstly, flow field passed through this fan was studied by 3D modeling. Aerodynamic and aeroacoustic performance of the fan were considered via solving the conservation of mass and momentum equations in their unsteady form. To validate the acoustic code, NACA 0012 airfoil was simulated in a two dimension domain... 

The large amplitude free vibration of an unsymmetrically laminated composite beam (LCB) on a nonlinear elastic foundation subjected to axial load has been studied. The equation of motion for the axial and transverse deformations of a geometrically nonlinear LCB is derived. Using the Ritz method, the governing equation is reduced to a time-dependent Duffing equation with quadratic and cubic nonlinearities. The homotopy analysis method (HAM) is used to obtain exact expressions for the dynamic response of the LCB. This study shows that the third-order approximation of the HAM leads to highly accurate solutions that are valid for a wide range of vibration amplitudes. The effects of different... 

In this research, we have investigated the three-dimensional elastic collision of two balls, based on friction in the tangential plane. Our aim is to offer analytical closed form relations for post collision parameters such as linear and angular velocities, collision time and tangential and normal impulse in three dimensions. To simplify the problem, stick regime is not considered. In other words, balls have a low tangential coefficient of restitution. Sliding, sliding then rolling, and rolling at the beginning of contact are three cases that can occur during impact which have been considered in our research. The normal interaction force is described by the Hertz contact force and... 

This paper mainly aims to obtain a minimum norm solution to the NP-hard absolute value equations (AVE) $$Ax-|x|=b$$Ax-|x|=b. In our proposed method, first we show that the AVE is equivalent to a bilinear programming problem and then we present a system tantamount to this problem. To find the minimum norm solution to the AVE, we solve a quadratic programming problem with quadratic and linear constraints. Eventually, we solve the obtained programming problem by Simulated Annealing algorithm. Numerical results support the efficiency of the proposed method and the high accuracy of calculation  

In the present study, a new swirling flow generator is studied which aims to enhance the convective heat transfer rate in a heat exchanger tube. This device has a four-point star cross section. The study mainly investigates the effect of swirl generator on heat transfer rate and pressure drop along the test tube which is under a constant and uniform heat flux. The working fluid in the experiments is the water–ethylene glycol mixtures with Prandtl numbers ranging from 5 to 150 at different Reynolds numbers from 12,000 to 27,000. The results clarify the potential of the applied swirl generator to make a significant enhancement in the heat transfer rate with a satisfactory rise in the pressure... 

We use the path integral optimization approach of Caputa, Kundu, Miyaji, Takayanagi, and Watanabe to find the time slice of geometries dual to vacuum, primary, and thermal states in the TT-deformed two-dimensional conformal field theories (CFTs). The obtained optimized geometries actually capture the entire bulk, which fits well with the integrability and expected UV completeness of TT-deformed CFTs. When the deformation parameter is positive, these optimized solutions can be reinterpreted as geometries at finite bulk radius, in agreement with a previous proposal by McGough, Mezei, and Verlinde. We also calculate the holographic entanglement entropy and quantum state complexity for these... 

The 3A zeolite is an excellent adsorbent for natural gas dehydration due to low energy requirement in regeneration step and easy operation. To perform a reliable modeling, a good equilibrium adsorption isotherm is mandatory. Accordingly, water, methane, methyl mercaptan (M-mercaptan) and CO2 adsorption isotherms and also the competitive adsorption loading versus temperature are described for the system using molecular simulation and mathematical models. It is found that CO2 competes with water for adsorption on 3A and lower temperature is required for selective removal of water. The mathematical model results showed that M-mercaptan and CO2 quickly adsorb on 3A and capacity of 3A for water... 

In the present study, a new swirling flow generator is studied which aims to enhance the convective heat transfer rate in a heat exchanger tube. This device has a four-point star cross section. The study mainly investigates the effect of swirl generator on heat transfer rate and pressure drop along the test tube which is under a constant and uniform heat flux. The working fluid in the experiments is the water–ethylene glycol mixtures with Prandtl numbers ranging from 5 to 150 at different Reynolds numbers from 12,000 to 27,000. The results clarify the potential of the applied swirl generator to make a significant enhancement in the heat transfer rate with a satisfactory rise in the pressure... 

Curved tunnels are more likely to have an accident and a fire source due to their physical characteristics. Using a 3D computational fluid dynamics tool with body-fitted grids, three different fire locations were investigated numerically in a series of curved tunnels with a turning radius of 50–1000 m and a heat release rate of 5–15 MW. Results showed that the critical velocity increased with increasing tunnel turning radius, and the straight tunnel had the highest critical velocity in all scenarios. For a tunnel with a 10 MW heat release rate, the critical velocity increased by 19 % from R = 50 to 1000 m. Furthermore, it was shown that the critical velocity was proportional to one-third... 

Two dimensional quantum materials possessing Dirac cones in their spectrum are fascinating due to their emergent low-energy Dirac fermions. In 8Pmmn borophene the Dirac cone is furthermore tilted, which is a proxy for spacetime geometry, since the future light-cone depends on the underlying metric. Therefore it is important to understand the microscopic origin of the tilt. Here, based on ab-initio calculations, we decipher the atomistic mechanism of the formation of tilt. First, nearest-neighbor hopping on a buckled honeycomb lattice forms an upright Dirac cone. Then, the difference in the renormalized anisotropic second-neighbor hopping, formed by virtual hoppings on one-dimensional chains... 

This paper presents the potential of acoustic emission (AE) technique to detect valve damage in internal combustion engines. The cylinder head of a spark-ignited engine was used as the experimental setup. The effect of three types of valve damage (clearance, semicrack, and notch) on valve leakage was investigated. The experimental results showed that AE is an effective method to detect damage and the type of damagein valves in both of the time and frequency domains. An artificial neural network was trained based on time domain analysis using AE parametric features (AErms, count, absolute AE energy, maximum signal amplitude, and average signal level). The network consisted of five, six, and... 

In this paper, a novel structure for MOSFET like CNTFETs (MOSCNTs) is proposed, combining the advantages of both high and low dielectrics to improve output characteristics. In this structure, the gate dielectric at the drain side is selected from a material with low dielectric constant to form smaller capacitances, while a material with high dielectric constant is selected at the source side to improve on current and reduce leakage current. The new structure is simulated based on the Schrödinger-Poisson formulation. Obtained results show that the proposed configuration has lower off and higher on current in comparison with low-k MOSCNTs. Also, using a two-dimensional model, a wide range of...