Gain-Enhanced Metamaterial Based Antenna for 5G Communication Standards

Metamaterial surfaces play a vital role to achieve the surface waves suppression and in-phase reflection,in order to improve the antenna performance.In this paper,the performance comparison of a fifth generation(5G)antenna design is analyzed and compared with a metamaterial-based antenna for 5G communication system applications.Metamaterial surface is utilized as a reflector due to its in-phase reflection characteristic and high-impedance nature to improve the gain of an antenna.As conventional conducting ground plane does not give enough surface waves suppression which affects the antenna performance in terms of efficiency and gain etc.These factors are well considered in this work and improved by using the metamaterial surface.The radiating element of the proposed metamaterial based antenna is made up of copper material which is backed by the substrate,i.e.,Rogers-4003 with a standard thickness,loss tangent and a relative permittivity of 1.524 mm,0.0027 and 3.55,correspondingly.The proposed antenna with and without metamaterial surface operates at the central frequency of 3.32 GHz and 3.60 GHz,correspondingly.The traditional antenna yields a boresight gain of 2.76 dB which is further improved to 6.26 dB,using the metamaterial surface.The radiation efficiency of the proposed metamaterial-based 5G antenna is above 85%at the desired central frequency.

Flexible impedance and capacitive tensile load sensor based on CNT composite

In this paper, the fabrication and investigation of flexible impedance and capacitive tensile load sensors based on carbon nanotube（CNT） composite are reported. On thin rubber substrates, CNTs are deposited from suspension in water and pressed at elevated temperature. It is found that the fabricated load cells are highly sensitive to the applied mechanical force with good repeatability. The increase in impedance of the cells is observed to be 2.0 times while the decrease in the capacitance is found to be 2.1 times as applied force increases up to 0.3 N. The average impedance and capacitive sensitivity of the cell are equal to 3.4 N^（-1） and 1.8 N^（-1）, respectively. Experimental results are compared with the simulated values,and they show that they are in reasonable agreement with each other.

Newtonian heating in stagnation point flow of Burgers fluid

The Newtonian heating effects in the stagnation point flow of a Burgers fluid are addressed in this paper. The boundary layer flow problems are stated in the spatial domain from zero to infinity. The solution expressions for the velocity and the temperature are obtained and examined for the influential variables. The tabulated values show comparison with the previous results. It is observed that the obtained results are in good agreement with the existing results in limiting sense.

Electrical Characteristics of A1/CNT/NiPc/PEPC/Ag Surface-Type Cell

The blend of nickel phthalocyanine （NiPc） （2 wt. %） poly-N-epoxypropylcarbazole （PEPC）, （1 wt. %） and carbon nano-tube （CNT） powder （2 wt. %） in benzole is deposited by drop-casting on glass substrates with pre-deposited metallic electrodes to fabricate Ag/CNT/NiPc/PEPC/A1 surface type cell. It is assumed that the high nonlinearity of the I — V characteristics is related to deep traps in the nano-scale depletion region in NiPc that is observed experimentally. The values of ideality factor and barrier height are determined from the I — V curve and they are found to be 8.4 and 1.05eV, respectively. The values of mobility and conductivity are calculated to be 7.94 × 10？8 cm/Vs and 3.5 × 10？6 Ω？1 cm？1. The values of ideality factor and series resistance are also calculated by using Cheung＇s functions, which are in good agreement with the values calculated from the I — V curve.

Recent advances and emerging trends of rare-earth-ion doped spectral conversion nanomaterials in perovskite solar cells

Organic-inorganic lead halide based perovskite solar cells(PSCs)have attracted unprecedented research interest over last decade.The high performance,combined with merits of low fabrication costs and ease of synthesis make PSCs promising alternate to state of the art silicon(Si)based solar cells.Howeve r,some inherent shortcomings of PSCs are hindering their market dominance over conventional photovoltaic technologies such as transmission loss of sub-bandgap photons,poor stability and hysteresis effects.Recently,use of rare earth(RE)ions doped nanomaterials in PSCs,has been identified as an effective means to address the aforementioned issues by expanding the range of absorption spectra minimizing the non-absorption loss of solar photons,enhancing light scattering and improving operational stability.This article reviews the recent progress in doping rare-earth(RE)ions in the building blocks of PSCs such as semiconductor electrodes and photoactive perovskite layers,and its use as a separate spectral conversion layer in PSCs.The effect of size,shape,constitution and concentration of RE-nanoparticles on the overall performance and device stability will be analyzed in detail.Moreover,we provide an outlook on the opportunities this newly developed field offers and the critical challenges faced in rationally and effectively using RE-ion-doped nanomaterials in PSCs for better operational stability and enhanced performance.

An Efficient Impersonation Attack Detection Method in Fog Computing

Fog computing paradigm extends computing,communication,storage,and network resources to the network’s edge.As the fog layer is located between cloud and end-users,it can provide more convenience and timely services to end-users.However,in fog computing(FC),attackers can behave as real fog nodes or end-users to provide malicious services in the network.The attacker acts as an impersonator to impersonate other legitimate users.Therefore,in this work,we present a detection technique to secure the FC environment.First,we model a physical layer key generation based on wireless channel characteristics.To generate the secret keys between the legitimate users and avoid impersonators,we then consider a Double Sarsa technique to identify the impersonators at the receiver end.We compare our proposed Double Sarsa technique with the other two methods to validate our work,i.e.,Sarsa and Q-learning.The simulation results demonstrate that the method based on Double Sarsa outperforms Sarsa and Q-learning approaches in terms of false alarm rate(FAR),miss detection rate(MDR),and average error rate(AER).

Sensitivity enhancement of OD-and OD-CNT-based humidity sensors by high gravity thin film deposition technique

The humidity sensing properties of the thin films of an organic semiconductor material orange dye （OD） and its composite with CNTs deposited at high gravity conditions have been reported. Impedance, phase angle, ca- pacitance and dissipation of the samples were measured at 1 kHz and room temperature conditions. The impedance decreases and capacitance increases with an increase in the humidity level. It was found that the sensitivity of the OD-based thin film samples deposited at high gravity condition is higher than the samples deposited at low gravity condition. The impedances and capacitance sensitivities of the of the samples deposited under high gravity condition are 6.1 times and 1.6 times higher than the films deposited under low gravity condition.

A Robust MPPT Control Based on Double Ended Forward Converter Architecture

In this paper,a stand-alone photovoltaic(PV)system based on a Double Ended Forward Converter(DEFC)is presented.The proposed converter is specified for 48 V,100Wapplications as most of the equipment used in telecommunication and aircraft fall in this range.The literature has limited potential application of DEFCin PV systems.The research work deals with an in-depth study of DEFCand proposes an improvedDEFCfor PV applications with battery backup.Besides,a bi-directional dc-dc converter for the battery is integrated to track theMaximumPower Point(MPP)of the PV generator.The converter is examined under variable irradiance and load conditions,and the analytical analysis of boundary conditions are implemented.The converter’s architecture also ensures built-in I-V curve tracing for the identification of MPP of PV generator.It offers low voltage stresses across switches and avoids sinking power supply and core resetting circuits.The topology’s behavior is analyzed based onMPP achievement and maintaining output under different conditions of battery backup availability,environmental,and load conditions.The PV system architecture is designed and analyzed theoretically and verified with simulations on the PSIM software.

Influence of Filler on the Microstructure, Mechanical Properties and Residual Stresses in TIG Weldments of Dissimilar Titanium Alloys

The influence of titanium alloy(Ti–5 Al–2.5 Sn) and commercially pure titanium(cp Ti) as fillers on dissimilar pulsed tungsten inert gas weldments of Ti–5 Al–2.5 Sn/cp Ti was investigated in terms of microstructure, mechanical/nano-mechanical properties, and residual stresses. A partial martensitic transformation was observed in the weldments for all the welding conditions due to high heat input. The microstructure evolved in the FZ/cp Ti interfacial region was observed to be the most sensitive to the proportion of α stabilizer in the filler alloy. Furthermore, the addition of filler alloy improved the tensile properties and nano-mechanical response of the weld joint owing to the increased volume of metal in the weld joint. As compared to the Ti–5 Al–2.5 Sn wire, the use of cp Ti filler wire proved to be better in terms of energy absorbed during tensile and impact tests, tensile strength and ductility of the dissimilar welds. An asymmetrical residual stresses profile was observed close to the weld centerline, with high compressive stresses on the Ti–5 Al–2.5 Sn side for both the weldments obtained with and without filler wires. This was attributed to mainly the low thermal conductivity of Ti–5 Al–2.5 Sn. The presence of residual stresses also influenced the nano-hardness profile across the weldments.

Surface-type nonvolatile electric memory elements based on organic-on-organic CuPc-H_2Pc heterojunction

A novel surface-type nonvolatile electric memory elements based on organic semiconductors CuPc and H2Pc are fabricated by vacuum deposition of the CuPc and H2Pc films on preliminary deposited metallic （Ag and Cu） electrodes. The gap between Ag and Cu electrodes is 3040μm. For the current-voltage （I-V） characteristics the memory effect, switching effect, and negative differential resistance regions are observed. The switching mechanism is attributed to the electric-field-induced charge transfer. As a result the device switches from a low to a high-conductivity state and then back to a low conductivity state if the opposite polarity voltage is applied. The ratio of resistance at the high resistance state to that at the low resistance state is equal to 120-150. Under the switching condition, the electric current increases -- 80-100 times. A comparison between the forward and reverse I-V characteristics shows the presence of rectifying behavior.

Electromechanical Fields and Their Influence on the Internal Quantum Efficiency of GaN-Based Light-Emitting Diodes

The effect ofelectromechanical fields, i.e., polarization fields, on the efficiency droop of GaN-based light-emitting diodes is presented using both experimental and numerical analyses. The role of incorporating such polarization charge density in device performance is numerically investigated and further compared with the experimental results of internal quantum efficiency of three different devices in consideration.

Electrical characterization of the organic semiconductor Ag/CuPc/Au Schottky diode

This paper reports on the fabrication and investigation of a surface-type organic semiconductor copper phthalocyanine（CuPc） based diode.A thin film of CuPc of thickness 100 nm was thermally sublimed onto a glass substrate with preliminary deposited metallic electrodes to form a surface-type Ag/CuPc/Au Schottky diode.The current-voltage characteristics were measured at room temperature under dark conditions.The barrier height was calculated as 1.05 eV.The values of mobility and conductivity was found to be 1.74×10;cm;/（V·s） and 5.5×10;Ω;·cm;,respectively.At low voltages the device showed ohmic conduction and the space charge limited current conduction mechanisms were dominated at higher voltages.

Impact of Accelerated Ultraviolet Weathering on Polymeric Composite Insulators Under High Voltage DC Stress

This study investigates the weatherability of room temperature vulcanized(RTV)silicone rubber(SiR)and epoxybased material specimens with a composition of different nano and micro fillers against the collegial effects of high voltage DC,UV and temperature stresses.Bulk power transmission over long distances via HVDC is considered an economic option these days,so to ensure the system reliability,it is also critical to investigate these insulators under DC stress along with other environmental stresses(especially UV and temperature).For experimentation,composite samples i.e.neat epoxy(NE),epoxy with 15%micro SiO_(2)(EMS),epoxy with 5%nano SiO_(2)(ENS),neat SiR(NS),SiR with 15%micro SiO_(2)(SMS)and SiR with 5%nano SiO_(2)(SNS)are fabricated and subjected to accelerated aging in a weather chamber for 3,360 hours.Results reveal that SMS and SNS offer better hydrophobic behavior followed by EMS.However noticeable surface discoloration in the form of whitish shade with minor blackish spots is found in the case of SMS,while remaining samples also showed considerable color fading.Scanning electron microscopy(SEM)and Fourier Transform Infrared Spectroscopy(FTIR)results showed that SNS and SMS presented quite excellent resistance to the exposure of fillers.Hardness and weight of all specimens are evaluated throughout the experiment and particularly for the water immersion test.Moreover,leakage current analysis indicated that SNS and SMS revealed high leakage current suppression compare to other samples.Findings indicate that SNS and SMS showed enhanced resistance against UV weathering under high voltage direct current stress.

Characterization of vanadyl phthalocyanine based surface-type capacitive humidity sensors

This study presents the fabrication and characterization of novel surface-type capacitive humidity sensors using vanadyl phthalocyanine（VOPc） as the active material.The devices,which comprise three different thicknesses, have been fabricated using the thermal evaporation technique.A thin film of VOPc is deposited on thoroughly cleaned glass substrates with pre-patterned Ag electrodes.The capacitive effect of the samples under humidity has been investigated. Comparison of the samples with different thicknesses shows that the thinnest device seems more sensitive towards humidity.The humidity dependent capacitance properties of the sensor make it beneficial for use in commercial hygrometers.

Selection of suitable site in Pakistan for wind power plant installation using analytic hierarchy process(AHP)

Rise in environmental pollution is a critical problem faced by mankind today.Many interventions have been made to reduce the carbon emissions and other greenhouse gases.Interventions,such as the introduction of electric cars,and innovative techniques to harness energy from renewable sources have been implemented.Pakistan is also very focused on exploiting its renewable energy sources and many sources have been identified.Wind energy is considered to have a promising potential and numerous sites have been identified for installation of wind farms.In this paper,we have collected data for the sites with the capacity factor(key determinant of value of power plant)of 25%or above for 600 kW wind turbine and applied Multi-Criteria Decision Method to find the most suitable to least suitable site for the installation of wind farm with respect to different factors/criteria.Analytic Hierarchy Process is used to evaluate four potential sites based on the criteria of wind speed(m/s),wind power density(W/m^(2)),distance from grid station(km),capacity factor,transport cost and population density.Results show that the preference of site largely depends on the average annual wind speed and wind power density.Our study is helpful for government as they verify the findings of Pakistan Meteorological Department but with different approach.

Impedance hygrometer based on cellulose and CuPc

An investigation has been made on the properties of an impedance hygrometer fabricated using cellulose and copper phthalocyanine（Ag/cellulose/CuPc/Ag）.A 5wt%suspension of cellulose was prepared in water while the CuPc was dissolved in methanol.Cellulose film was deposited on glass substrates with preliminary deposited metallic electrodes followed by deposition of CuPc film.The resistances and capacitances of the samples were evaluated under the effect of humidity.The impedance was calculated from resistance and capacitance measurements.It was also measured during the experiment.It was observed that the capacitance of the sensor increases and resistance and impedance decrease with an increase in the relative humidity level.It was found that the impedance-humidity relationship showed more uniform changes in the interval of 31%—98%RH than the resistance-and capacitance-humidity relationships that showed visible changes in the humidity intervals of 31%-80%RH and 80%-98%RH respectively.The humidity-dependent impedance of the sample makes it attractive for use in impedance hygrometers.The impedance hygrometer may be used in instruments for the environmental monitoring of humidity.

Humidity sensitive organic field effect transistor

This paper reports the experimental results for the humidity dependent properties of an organic field effect transistor.The organic field effect transistor was fabricated on thoroughly cleaned glass substrate,in which the junction between the metal gate and the organic channel plays the role of gate dielectric.Thin films of organic semiconductor copper phthalocynanine（CuPc） and semitransparent Al were deposited in sequence by vacuum thermal evaporation on the glass substrate with preliminarily deposited Ag source and drain electrodes.The output and transfer characteristics of the fabricated device were performed.The effect of humidity on the drain current,drain current-drain voltage relationship, and threshold voltage was investigated.It was observed that humidity has a strong effect on the characteristics of the organic field effect transistor.

CuPc based organic-inorganic hetero-junction with Au electrodes

A hetero-junction of n-silicon（n-Si） and copper phthalocyanine（CuPc） has been fabricated.The current -voltage characteristics were investigated to explain the rectification and conduction mechanism.The effect of temperature and humidity on the electrical properties of n-Si/CuPc hetero-junction has also been investigated.The characteristics of the junction have been observed to be temperature and humidity dependent,so it is suggested that this junction can be used as a temperature and humidity sensor.