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High Gain Beam Steering Antenna Arrays with Low Scan Loss for mmWave Applications
Get PDFIn millimeter-wave (mmWave) communications, the antenna gain is a crucial parameter to overcome path loss and atmospheric attenuation. This work presents the design of two cylindrical conformal antenna arrays, made of modified rectangular microstrip patch antenna as a radiating element, working at 28 GHz for mmWave applications providing high gain and beam steering capability. The microstrip patch antenna element uses Rogers RO4232 substrate with a thickness of 0.5 mm and surface area of 5.8 mm × 5.8 mm. The individual antenna element provides a gain of 6.9 dBi with return loss bandwidth of 5.12 GHz. The first antenna array, made by using five conformal antenna elements, achieves a uniform gain of approximately 12 dBi with minimal scan loss for extensive scan angles. In the second antenna array, a dielectric superstrate using Rogers TMM (10i) was used to modify the first antenna array. It enhanced the gain to approximately 16 dBi while still maintaining low scan loss for wide angles. The proposed array design method is very robust and can be applied to any conformal surface. The mathematical equations are also provided to derive the array design, and both array designs are verified by using full-wave simulations
Thermodynamic Investigation of a Modified Compression Ignition Engine Fueled by Diesel Biodiesel Ethanol Blends
Get PDFThe present study contrasts the thermodynamics analysis of modified diesel engines with traditional diesel engines. Thermodynamics study is done by the use of energy and exergy analysis for diesel, B20 (blend of 80 per cent diesel by volume with 20 per cent mahua biodiesel) and LHR modification and LTC 15 per cent EGR fuelled with B20 blend and 5 per cent ethanol with various loads ranging from no load to full load. Implemented two technologies for increasing engine efficiency. One of the primary techniques is the Low Heat Rejection (LHR) concept (or the so-called “Adiabatic” engine) applied. In the engine cylinder, a ceramic layer of Alumina (Al2O3) was used to modify the Low Heat Rejection (LHR). Another technique is Low-temperature combustion (LTC) modes are added by joining the inlet and exhaust pipes through valves to control the exhaust gas at an optimal rate of 15 per cent. The findings of energy and exergy distribution in the engine were compared using optimum alterations with fuel blends such as 20 per cent mahua biodiesel and 5 per cent ethanol. From energy distribution, best shaft power (QBP) (2.8kW) is transformed from heat input observed in the optimum altered engine at full load conditions compared to others. Due to modifications employed in the engine and fuels. Maximum unaccounted energy (QUN) loss in diesel (44 %). And highest thermal efficiency (31.2 %) is revealed in B20E5 (LHR+15 % LTC). From exergy distribution, it noticed that the same trend of energy distribution and at 100 per cent load condition, maximum (12.54kW) in diesel and minimum (8.45 kW) in B20E5 (LHR+15 % LTC) has obtained input availability (Ain).The maximum conversion rate of availability in brake power (Abp) (0.61 kW) in B20 (LHR). Compared to diesel, second law or exergetic efficiency more in B20E5 (LHR+15 % LTC). 
Investigation on the Effect of Cable Length on Pulse Shape of High Voltage High Pulse Power Supply
Get PDFIn the present scenario of pulse power applications, transmission of high voltage pulses varies as per load condition. In the early days of its application, High Voltage High Pulse Power Supply (HVHPPS) design saw short distance between load and source, where the effect of cable length was not taken into account for design. This paper presents the effect of cable length on pulse shape of High Voltage High Pulse Power Supply. The load under observation is Klystron based high energy particle accelerator system. The performance of pulse power systems were observed continuously on a daily basis throughout the year and detailed analysis was carried out. This paper generates the model of pulse forming system and provides details of pattern distortion of the pulse shape due to various dynamic parameter changes i.e. impedance, Load Voltage, Load Current, Cavity Dimensional Changes (Microwave components) due to temperature variations and performance of the power supply. The results were analysed and validated with hardware results across a range of actual industrial loads
Unsteady CFD Studies for Gust Modeling in Store Separation
Get PDFAircraft and different store configurations must be certified before a flight. There is a small but finite probability of aircraft being hit by gust wind at the time of separation. Most store separation analyses from airborne platforms do not consider the gust phenomena because of the complexity and inadequate knowledge of its behavior. A dedicated task group was recently created to understand the gust-related phenomena in aircraft safety. Of the various gust cases, vertical gust is most severe and can cause instability leading to store collision. The situation is compounded in a long and heavy store due to its large projected area. No test procedures exist for simulation or practical tests of gust. A study was conducted to identify a test procedure for gust simulation using MIL standard data and Indian conditions. The current paper studies the emergency release condition where a vertical gust is hitting the aircraft to ascertain safe separation. A discrete gust with a 1-cosine shape and specified length and amplitude is imposed at the inflow boundary. The gust is allowed to sweep the computational domain containing the airborne platform and the store. The computed trajectory of the store, the miss distance, and its angular rates in the presence of gust are analysed in this work to study the safe separation of a store from an airborne platform. Simulations are also carried out to determine the effect of gust at the highest dynamic pressure in the flight envelope
An Experimental Investigation into Effect of Reinforcement Material on Mechanical Properties of Linear Low Density Polyethylene (LLDPE)
Get PDFThrough this paper an experimental investigation has been done. The composites of different reinforced material having significantly good strength and improved properties are prepared. A comparative study was performed among LLDPE with non-woven fabric, LLDPE and non-woven fabric reinforced with rice husk, LLDPE with non- woven fabric and ash of rice husk. Linear Low Density Polymer (LLDPE) is used as base material in this fabrication process. LLDPE is mixed with the non-woven fabric in different percentage composition by weight in addition to the other natural reinforcement material (rice husk). Further an experiment was performed to calculate the mechanical properties like tensile strength, Melt flow Index (MFI), flexural strength, hence a comparative study of composite with different types of reinforcement was done to investigate the effect of mixing of different reinforcement material. Results shows that LLDPE with non-woven fabric (15 %) have less strength as compared to LLDPE with non-woven fabric and rice husk (10 %) and LLDPE with non-woven fabric and ash of rice husk (5 %). Water absorption characteristics are studied following ASTMD 570, results shows that LLDPE absorbs 0.15 per cent water, followed by LLDPE with rice husk (0.03 %) and LLDPE with ash (0.038 %)
Optimal Step Size Technique for Frequency Domain and Partition Block Adaptive Filters for PEM based Acoustic Feedback Cancellation
Get PDFThe adaptive filtering approach has been commonly used to perform acoustic feedback cancellation (AFC) in digital hearing-aids due to its reliable performance and feasibility. Because the loudspeaker and microphone are close together in hearing aids, the corresponding signals are highly correlated, resulting in biased estimation if adaptive filters are used. This problem can be addressed with the help of the decorrelation prefilter by incorporating the Prediction Error Method (PEM) technique into AFC. Frequency-Domain Adaptive Filters (FDAF) are preferable over the time-domain implementation to achieve better performance in terms of convergence and computational complexity. In addition, Partition-Block Frequency-Domain Adaptive Filters (PBFDAF) offers low processing delay. However, because of their fixed step-size, there is a trade-off between initial convergence and steady-state misalignment in the widely used frequency-domain algorithms. While Variable Step-Size (VSS) algorithms can help with this issue, VSS techniques for frequency-domain algorithms have not been extensively studied in the context of PEM-AFC. Hence, in this paper, we presented an Optimal Step-Size (OSS) technique for both the FDAF-PEM_AFC and PBFDAF-PEM_AFC algorithms to simultaneously accomplish fast convergence and minimal steady-state error. A Feedback Path Change Detector (FPCD) was also incorporated into the proposed algorithms to address the problem of convergence in non-stationary feedback paths. The results of simulations show that the proposed algorithms are clearly superior, and they are encouraging
Reliability Analysis of Radiation Tolerant Low Voltage CCCII Circuit For Space Applications
Get PDFIn this paper, the impact of radiation on the MOS devices is investigated on recently reported programmablesecond generation Current Controlled Conveyor (CCCII) wherein some updates are suggested to take Hot Carrier Injection, Bias Temperature Instability, and Time Dependent Dielectric Breakdown into account. As radiation is yet another important factor that causes change in threshold voltage, the transistors which are amenable to larger threshold shift and may lead to functional failure are identified first. Subsequently, three possibilities; uses of all thin oxide devices, all thick oxide devices, and mixed devices are being investigate and it is found that while using mixed devices, the circuit becomes functional at lower voltage without any effective increase in leakage current. Architecture is updated to enhance the performance of circuits under time-based ageing and radiation environment. The major challenge is to control dynamic leakage and radiative noise due to imposed radiation. All simulations are carried out using 28nm CMOS technology models in Cadence Virtuoso environment using ±1.0V supply voltage and results have been verified with post layout netlist. Proposed circuit can function at low voltage with the reduced degradation for 8 years at 25 °C consumes less area as compared to the existing CCCII circuit with 0.008 FIT value
Wideband Fabric Antenna for Ultra Wideband Applications using for Medical Applications
Get PDFTraditional cancer detection imaging techniques suffer high costs, high false negatives, high false positives,and pain. The microwave imaging techniques overcome the limitations, which depend primarily on antenna design. If an antenna is wearable and implantable, the imaging system gives better results with less pain and cost. A wide band fabric antenna that operates at the ultra-wideband frequency with a low specific absorption rate (SAR) on breast phantom is verified. The proposed design has Jeans material as a substrate and the copper patch as a radiating element. The patch is designed in a circular shape with an M-type slot to suppress the spurious modes. The designed antenna model is commonly used for monitoring microwave imaging and has dimensions of 28X30X1.6 mm3. The proposed antenna design covers 2.3-8 GHz frequency with a broadside radiation pattern. The gain over the operating frequency is about 2.3-4.5 dB, and the efficiency is 55 %–79 %. The antenna model was designed and simulated in CST microwave studio. The performance of an antenna is tested on breast cancer to detect the presence of tumor cells in the breast. The antenna analysis on the phantom was done by considering the tumor location and corresponding results are presented. By varying the sizes of the tumor the antenna performance is analysed. The simulated SAR values of the proposed antenna design on breast phantom are under the limits of FCC
Heat Transfer Modelling and Simulation of a 120 mm Smoothbore Gun Barrel During Interior Ballistics
Get PDFUnderstanding the heat transfer phenomenon during interior ballistics and consequently presenting a realistic model is very important to predict the temperature distribution inside the cannon barrel, which influences the gun wear and the cook-off. The objective of this work is to present a new detailed numerical model for the prediction of thermal behaviour of a cannon barrel by combining PRODAS interior ballistics simulation with COMSOL simulation. In this study, a numerical model has been proposed for the heating behaviour of a 120 mm smoothbore cannon barrel, taking into account the combustion equation of the JA-2 propellant. Temperature dependent thermophysical properties of product gases were used for the calculation of the convective heat transfer coefficient inside the barrel. Projectile position, velocity of the projectile, gas temperature inside the barrel, volume behind the projectile and mass fraction during interior ballistics have been obtained by PRODAS software and used in the numerical model performed by COMSOL multiphysics finite element modelling and simulation software. Temperature simulations show that maximum wall temperature inside the cannon barrel is observed after 3 ms from fire, when maximum value of the convective heat transfer coefficient inside the barrel is observed. The results reveal that the convective heat transfer coefficient of burned gases inside the gun has major effect than the burned gas temperature on the heat transfer phenomenon
Real Time Flow Control System for Precise Gas Feed in COIL
Get PDFThis paper reports development of a real time flow control system for precise, controlled and uniform gas feed to a flowing medium Chemical Oxygen Iodine Laser (COIL). The optimal operation of this prominent laser depends upon the desired supply of gas constituents such as nitrogen (N2), chlorine (Cl2) and iodine (I2) to achieve adequately mixed laser gas. The laser also demands real time variation of flow rates during gas constituent transitions in order to maintain stabilized pressures in critical subsystems. Diluent nitrogen utilized for singlet oxygen transport is termed as primary buffer gas and that for iodine transport is termed as secondary buffer gas (with main and bypass components). Also, nitrogen in precise flows is used for mirror blowing, nozzle curtain, cavity bleed and diffuser startup. A compact hybrid data acquisition system (Hybrid DAS) for precise flow control using LabVIEW 2014 platform has been developed. The supported flow ranges may vary from few mmole.s-1 to few hundred mmole.s-1. The estimated relative uncertainty in the largest gas component i.e. primary buffer gas feed is nearly 0.7%. The implementation of in-operation variation using flow ramp enables swift stabilization of singlet oxygen generator pressures critical for successful COIL operation. The performance of Hybrid DAS is at par with fully wired DAS providing the crucial benefit of remote field operation at distances of nearly 80m in line of sight and 35m with obstacle