A Matrix Inversion Normalized Least Mean Square (MI-NLMS) adaptive beamforming algorithm was developed for smart antenna application. The MI-NLMS which combined the individual good aspects of Sample Matrix Inversion (...A Matrix Inversion Normalized Least Mean Square (MI-NLMS) adaptive beamforming algorithm was developed for smart antenna application. The MI-NLMS which combined the individual good aspects of Sample Matrix Inversion (SMI) and the Normalized Least Mean Square (NLMS) algorithms is described. Simulation results showed that the less complexity MI-NLMS yields 15 dB improvements in interference suppression and 5 dB gain enhancement over LMS algorithm, converges from the initial iteration and achieves 24% BER improvements at cochannel interference equal to 5. For the case of 4-element uniform linear array antenna, MI-NLMS achieved 76% BER reduction over LMS algorithm.展开更多
Lassa hemorrhagic fever,caused by Lassa mammarenavirus(LASV)infection,accumulates up to 5000 deaths every year.Currently,there is no vaccine available to combat this disease.In this study,a library of 200 bioactive co...Lassa hemorrhagic fever,caused by Lassa mammarenavirus(LASV)infection,accumulates up to 5000 deaths every year.Currently,there is no vaccine available to combat this disease.In this study,a library of 200 bioactive compounds was virtually screened to study their drug-likeness with the capacity to block theα-dystroglycan(α-DG)receptor and prevent LASV influx.Following rigorous absorption,distribution,metabolism,and excretion(ADME)and quantitative structure-activity relationship(QSAR)profiling,molecular docking was conducted with the top ligands against theα-DG receptor.The compounds chrysin,reticuline,and 3-caffeoylshikimic acid emerged as the top three ligands in terms of binding affinity.Post-docking analysis revealed that interactions with Arg76,Asn224,Ser259,and Lys302 amino acid residues of the receptor protein were important for the optimum binding affinity of ligands.Molecular dynamics simulation was performed comprehensively to study the stability of the protein-ligand complexes.In-depth assessment of root-mean-square deviation(RMSD),root mean square fluctuation(RMSF),polar surface area(PSA),B-Factor,radius of gyration(Rg),solvent accessible surface area(SASA),and molecular surface area(MolSA)values of the protein-ligand complexes affirmed that the candidates with the best binding affinity formed the most stable protein-ligand complexes.To authenticate the potentialities of the ligands as target-specific drugs,an in vivo study is underway in real time as the continuation of the research.展开更多
In this paper,a unit cell of a single-negative metamaterial structure loaded with a meander line and defected ground structure(DGS)is investigated as the principle radiating element of an antenna.The unit cell antenna...In this paper,a unit cell of a single-negative metamaterial structure loaded with a meander line and defected ground structure(DGS)is investigated as the principle radiating element of an antenna.The unit cell antenna causes even or odd mode resonances similar to the unit cell structure depending on the orientation of the microstrip feed used to excite the unit cell.However,the orientation which gives low-frequency resonance is considered here.The unit cell antenna is then loaded with a meander line which is parallel to the split bearing side and connects the other two sides orthogonal to the split bearing side.This modified structure excites another mode of resonance at high frequency when a meander line defect is loaded on the metallic ground plane.Specific parameters of the meander line structure,the DGS shape,and the unit cell are optimized to place these two resonances at different frequencies with proper frequency intervals to enhance the bandwidth.Finally,the feed is placed in an offset position for better impedance matching without affecting the bandwidth The compact dimension of the antenna is 0.25λL×0.23λL×0.02λL,whereλL is the free space wavelength with respect to the center frequency of the impedance bandwidth.The proposed antenna is fabricated and measured.Experimental results reveal that the modified design gives monopole like radiation patterns which achieves a fractional operating bandwidth of 26.6%,from 3.26 to 4.26 GHz for|S11|<−10 dB and a pick gain of 1.26 dBi is realized.In addition,the simulated and measured crosspolarization levels are both less than−15 dB in the horizontal plane.展开更多
The paper proposes an Indoor Localization System(ILS)which uses only one fixed Base Station(BS)with simple non-reconfigurable antennas.The proposed algorithm measures Received Signal Strength(RSS)and maps it to the lo...The paper proposes an Indoor Localization System(ILS)which uses only one fixed Base Station(BS)with simple non-reconfigurable antennas.The proposed algorithm measures Received Signal Strength(RSS)and maps it to the location in the room by estimating signal strength of a direct line of sight(LOS)signal and signal of the first order reflection from the wall.The algorithm is evaluated through both simulations and empirical measurements in a furnished open space office,sampling 21 different locations in the room.It is demonstrated the system can identify user’s real-time location with a maximum estimation error below 0.7 m for 80%confidence Cumulative Distribution Function(CDF)user level,demonstrating the ability to accurately estimate the receiver’s location within the room.The system is intended as a cost-efficient indoor localization technique,offering simplicity and easy integration with existing wireless communication systems.Unlike comparable single base station localization techniques,the proposed system does not require beam scanning,offering stable communication capacity while performing the localization process.展开更多
This paper presents a new Double-E-Triple-H-Shaped NRI(negative refractive index)metamaterial(MM)for dual-band microwave sensing applications.Here,a horizontal H-shaped metal structure is enclosed by two face-to-face ...This paper presents a new Double-E-Triple-H-Shaped NRI(negative refractive index)metamaterial(MM)for dual-band microwave sensing applications.Here,a horizontal H-shaped metal structure is enclosed by two face-to-face E-shaped metal structures.This double-E-H-shaped design is also encased by two vertical H-shaped structures along with some copper links.Thus,the Double-E-Triple-H-Shaped configuration is developed.Two popular substrate materials of Rogers RO 3010 and FR-4 were adopted for analyzing the characteristics of the unit cell.The proposed structure exhibits transmission resonance inside the S-band with NRI and ENG(Epsilon Negative)metamaterial properties,and inside the C-band with ENG and MNG(Mu Negative)metamaterial properties.A good effective medium ratio(EMR)of 8.06 indicates the compactness and effectiveness of the proposed design.Further analysis has been done by changing the thickness of the substrate material as well and a significant change in the effective medium ratio is found.The validity of the proposed structure is confirmed by an equivalent circuit model.The simulated result agrees well with the calculated result.For exploring microwave sensing applications of the proposed unit cell,permittivity and pressure sensitivity performance were investigated in different simulation arrangements.The compact size,effective parameters,high sensitivity and a good EMR represent the proposed metamaterial as a promising solution for S-band and C-band microwave sensing applications.展开更多
In this paper,the design and performance analysis of an Inkjetprinted metamaterial loaded monopole antenna is presented for wireless local area network(WLAN)and worldwide interoperability for microwave access(WiMAX)ap...In this paper,the design and performance analysis of an Inkjetprinted metamaterial loaded monopole antenna is presented for wireless local area network(WLAN)and worldwide interoperability for microwave access(WiMAX)applications.The proposed metamaterial structure consists of two layers,one is rectangular tuning fork-shaped antenna,and another layer is an inkjet-printed metamaterial superstate.The metamaterial layer is designed using four split-ring resonators(SRR)with an H-shaped inner structure to achieve negative-index metamaterial properties.The metamaterial structure is fabricated on low-cost photo paper substrate material using a conductive inkbased inkjet printing technique,which achieved dual negative refractive index bands of 2.25–4.25 GHz and 4.3–4.6 GHz.The antenna is designed using a rectangular tuning fork structure to operate at WLAN and WiMAX bands.The antenna is printed on 30×39×1.27 mm3 Rogers RO3010 substrate,which shows wide impedance bandwidth of 0.75 GHz(2.2 to 2.95 GHz)with 2 dB realized gain at 2.4 GHz.After integrating metamaterial structure,the impedance bandwidth becomes 1.25 GHz(2.33 to 3.58 GHz)with 2.6 dB realized gain at 2.4 GHz.The antenna bandwidth and gain have been increased using developed quad SRR based metasurface by 500 MHz and 0.6 dBi respectively.Moreover,the proposed quad SRR loaded antenna can be used for 2.4 GHz WLAN bands and 2.5 GHz WiMAX applications.The contribution of this work is to develop a cost-effective inject printed metamaterial to enhance the impedance bandwidth and realized the gain of a WLAN/WiMAX antenna.展开更多
First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different poly- morphs of BiVO4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the gen...First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different poly- morphs of BiVO4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the generalized gradient approximation （GGA） in the flame of density functional theory （DFT）. The calculated structural and electronic properties are consistent with the previous theoretical and experimental results. The electronic structures reveal that m-BiVO4, op- BiVO4, and st-BiVO4 have indirect band gaps, on the other hand, zt-BiVO4 has a direct band gap. From the DOS and Mulliken＇s charge analysis, it is observed that only m-BiVO4 has 6s2 Bi lone pair. Bond population analysis indicates that st-BiVO4 shows a more ionic nature and a similar result is obtained from the elastic properties. From the elastic prop- erties, it is observed that st-BiVO4 is more mechanically stable than the others, st-BiVO4 is more ductile and useful for high electro-optical and electro-mechanical coupling devices. Our calculated thermodynamic properties confirm the similar characteristics found from electronic and elastic properties, m-BiVO4 is useful as photocatalysts, solid state electrolyte, and electrode and other polymorphs are applicable in electronic device fabrications.展开更多
S aint Martin Island is the only coral island and one of the well-known tourist spots in Bangladesh.Because of its geographic location,electricity cannot be supplied from the mainland through the electricity grid.Dies...S aint Martin Island is the only coral island and one of the well-known tourist spots in Bangladesh.Because of its geographic location,electricity cannot be supplied from the mainland through the electricity grid.Diesel generators and solar power are the only means of electricity generation presently available there.Surrounded by the sea,Saint Martin Island has the ideal conditions for wave energy extraction.In this research,numerical models have been developed using the Delft3 D simulation software to determine the wave characteristics of different locations around Saint Martin Island.The results have been calibrated and validated against the data obtained from well-known data sources.The wave power densities have been calculated using the data obtained from the simulation models.The findings of the research show that the wave power density increases significantly from shallow water to deep water and a large amount of wave energy can be extracted during the summer and rainy monsoon seasons.The maximum hourly average value of wave power in 2016 has been determined to be6.90 kW/m at location with a water depth of 27.80 m.Wave energy resources are also observed to be sufficiently stable with the coefficients of variation of wave power density less than 0.62,except for December,January,and May of that particular year.Moreover,the annual effective energies have been determined to be within the range of 36.57 to 57.28 MWh/m,which will be sufficient to meet the electricity requirement of the island communities.展开更多
This study proposed a new royal crown-shaped polarisation insensitive double negative triple band microwave range electromagnetic metamaterial absorber(MA).The primary purpose of this study is to utilise the exotic ch...This study proposed a new royal crown-shaped polarisation insensitive double negative triple band microwave range electromagnetic metamaterial absorber(MA).The primary purpose of this study is to utilise the exotic characteristics of this perfect metamaterial absorber(PMA)for microwave wireless communications.The fundamental unit cell of the proposed MA consists of two pentagonal-shaped resonators and two inverse C-shaped metallic components surrounded by a split ring resonator(SRR).The bottom thin copper deposit and upper metallic resonator surface are disjoined by an FR-4 dielectric substrate with 1.6 mm thickness.The CST MW studio,a high-frequency electromagnetic simulator has been deployed for numerical simula-tion of the unit cell in the frequency range of 4 to 14 GHz.In the TE mode,the offered MA structure demonstrated three different absorption peaks at 6.85 GHz(C-band),8.87 GHz(X-band),and 12.03 GHz(Ku-band),with 96.82%,99.24%,and 99.43%absorptivity,respectively.The electric field,magnetic field,and surface current distribution were analysed using Maxwell’s-Curl equations,whereas the angle sensitivity was investigated to comprehend the absorption mechanism of the proposed absorber.The numerical results were verified using the Ansys HFSS(high-frequency structure simulator)and ADS(advanced design system)for equivalent circuit models.Moreover,the proposed MA is polarisation and incident angle independent.Hence,the application of this MA can be extended to a great extent,including airborne radar applications,defence,and stealth-coating technology.展开更多
This paper reveals a new design of UHF CubeSat antenna based on a modified Planar Inverted F Antenna(PIFA)for CubeSat communication.The design utilizes a CubeSat face as the ground plane.There is a gap of 5 mm beneath...This paper reveals a new design of UHF CubeSat antenna based on a modified Planar Inverted F Antenna(PIFA)for CubeSat communication.The design utilizes a CubeSat face as the ground plane.There is a gap of 5 mm beneath the radiating element that facilitates the design providing with space for solar panels.The prototype is fabricated using Aluminum metal sheet and measured.The antenna achieved resonance at 419 MHz.Response of the antenna has been investigated after placing a solar panel.Lossy properties of solar panels made the resonance shift about 20 MHz.This design addresses the frequency shifting issue after placing the antenna with the CubeSat body.This phenomenon has been analyzed considering a typical 1U and 2U CubeSat body with the antenna.The antenna achieved a positive realized gain of 0.7 dB and approximately 78%of efficiency at the resonant frequency with providing 85%of open space for solar irradiance onto the solar panel.展开更多
Broadband response metamaterial absorber(MMA)remains a challenge among researchers.A nanostructured new zero-indexed metamaterial(ZIM)absorber is presented in this study,constructed with a hexagonal shape resonator fo...Broadband response metamaterial absorber(MMA)remains a challenge among researchers.A nanostructured new zero-indexed metamaterial(ZIM)absorber is presented in this study,constructed with a hexagonal shape resonator for optical region applications.The design consists of a resonator and dielectric layers made with tungsten and quartz(Fused).The proposed absorbent exhibits average absorption of more than 0.8972(89.72%)within the visible wavelength of 450–600 nm and nearly perfect absorption of 0.99(99%)at 461.61 nm.Based on computational analysis,the proposed absorber can be characterized as ZIM.The developments of ZIM absorbers have demonstrated plasmonic resonance characteristics and a perfect impedance match.The incidence obliquity in typically the range of 0◦–90◦both in TE and TM mode with maximum absorbance is more than 0.8972(∼89.72%),and up to 45◦angular stability is suitable for solar cell applications,like exploiting solar energy.The proposed structure prototype is designed and simulated by studying microwave technology numerical computer simulation(CST)tools.The finite integration technique(FIT)based simulator CST and finite element method(FEM)based simulator HFSS also helps validate the numerical data of the proposed ZIM absorber.The proposed MMA design is appropriate for substantial absorption,wide-angle stability,absolute invisible layers,magnetic resonance imaging(MRI),color images,and thermal imaging applications.展开更多
This paper presents a textile-based C-shaped split-ring resonators(SRR)metamaterial(MTM)unit cells with an electrical tunability function.The proposed MTM was composed of two symmetrical C-shaped SRR combined with a c...This paper presents a textile-based C-shaped split-ring resonators(SRR)metamaterial(MTM)unit cells with an electrical tunability function.The proposed MTM was composed of two symmetrical C-shaped SRR combined with a central diagonal metal bar,whereas the RF varactor diode is placed on the backside of the splitted ground plane.Stopband behavior of single and array MTM unit cells were analyzed while the achieved negative index physical characteristics were widely studies.Though four different MTM arrays(i.e.,1×1,1×2,2×1,and 2×2)were analyzed in simulation,a 2×2-unit cell array was chosen to fabricate,and it was further undergone experimental validation.This proposed tunable MTM exhibits double negative(DNG)/left-handed properties with an average bandwidth of more than 2.8 GHz.Furthermore,attainable negative permittivity and negative permeability are within 2.66 to 9.59 GHz and within 2.77 to 15 GHz,respectively,at the frequency of interest(between 1 and 15 GHz).Moreover,the proposed tunable MTM also showed tunable transmission coefficient characteristics.The proposed electrically tunable textile MTM might function in a dynamic mode,making it suitable for a variety of microwave-wearable applications.A satisfactory agreement between simulations and experiments were achieved,demonstrating that the proposed MTM can operate over a wide bandwidth.展开更多
This study presents an Epsilon Mu near-zero(EMNZ)nanostructured metamaterial absorber(NMMA)for visible regime applications.The resonator and dielectric layers are made of tungsten(W)and quartz(fused),where the working...This study presents an Epsilon Mu near-zero(EMNZ)nanostructured metamaterial absorber(NMMA)for visible regime applications.The resonator and dielectric layers are made of tungsten(W)and quartz(fused),where the working band is expanded by changing the resonator layer’s design.Due to perfect impedance matching with plasmonic resonance characteristics,the proposed NMMA structure is achieved an excellent absorption of 99.99%at 571 THz,99.50%at 488.26 THz,and 99.32%at 598 THz frequencies.The absorption mechanism is demonstrated by the theory of impedance,electric field,and power loss density distributions,respectively.The geometric parameters are explored and analyzed to show the structure’s performance,and a near-field pattern is used to explain the absorption mechanism at the resonance frequency point.The numerical analysis method describes that the proposed structure exhibited more than 80%absorbability between 550 and 900 THz.The Computer Simulation Technology(CST Microwave Studio 2019)software is used to design the proposed structure.Furthermore,CSTHFSS interference is validated by the simulation data with the help of the finite element method(FEM).The proposed NMMA structure is also exhibits glucose concentration sensing capability as applications.So the proposed broadband absorber may have a potential application in THz sensing,imaging(MRI,thermal,color),solar energy harvesting,light modulators,and optoelectronic devices.展开更多
This work presents a dual band epsilon negative(ENG)metamaterial with a bilateral coupled split ring resonator(SRR)for use in C and X band wireless communication systems.The traditional split-ring resonator(SRR)has be...This work presents a dual band epsilon negative(ENG)metamaterial with a bilateral coupled split ring resonator(SRR)for use in C and X band wireless communication systems.The traditional split-ring resonator(SRR)has been amended with this engineered structure.The proposed metamaterial unit cell is realized on the 1.6 mm thick FR-4 printed media with a dimension of 10×10 mm2.The resonating patch built with a square split outer ring.Two interlinked inner rings are coupled vertically to the outer ring to extend its electrical length as well as to tune the resonance frequency.Numerical simulation is performed using CST studio suite 2019 to design and performance analysis.The transmission coefficient(S21)of the proposed unit cell and array configuration exhibits two resonances at 6.7 and 10.5 GHz with wide bandwidth extended from 4.86 to 8.06 GHz and 10.1 to 11.2 GHz,respectively.Negative permittivity is noted at frequencies between 6.76–9.5 GHz and 10.5–12 GHz,consecutively,with near-zero refractive index and permeability.The optimal EMR value depicts the compactness of the proposed structure.The 1×2,2×2 and 4×4 arrays are analyzed that shows similar response compared to the unit cell.Measured results of the 2×2 array shows the close similarity of S21 response as compared to simulation.The observed properties of the proposed unit cell ascertain its suitability for wireless communications by enhancing the gain and directivity of the antenna system.展开更多
Maize is an emerging important crop in Bangladesh because of its high yield potential and economic profitability compared to rice and wheat crops. There is a need to understand the growth and yield behavior of this cr...Maize is an emerging important crop in Bangladesh because of its high yield potential and economic profitability compared to rice and wheat crops. There is a need to understand the growth and yield behavior of this crop in varying production environments of Bangladesh. Crop model such as Decision Support System For Agro-technology Transfer (DSSAT) version 4.6 (DSSAT hereafter) can be utilized cost effectively to study the performances of maize under different production environments. It needs to calibrate and validate DSSAT model for commonly cultivated maize cultivars in Bangladesh and subsequently take the model to various applications, including inputs and agronomic management options and climate change that impacts analyses. So, the present study was undertaken to firstly calibrate DSSAT model for popular four hybrid maize cultivars (BARI Hybrid Maize-7, BARI Hybrid Maize-9, Pioneer 30B07 and NK-40). Subsequently, it proceeded with the validation with independent field data sets for evaluating their growth performances. The genetic coefficients for these cultivars were evaluated by using Genotype coefficient calculator (GENCALC) and Generalized likelihood uncertainty estimation (GLUE) module of DSSAT on the basis of first season experiment. The performance of the model was satisfactory and within the significant limits. After calibration, the model was tested for its performance through validation procedure by using second season data. The model performed satisfactorily through phenology, biomass, leaf area index (LAI) and grain yield. Phenology, as estimated through days to flower initiation and maturity, was in good agreement, although simulated results were slightly over predicted compared to observed values but within the statistical significance limit...when compared with observed values at specific growth stages of the crop. The final yield values (10.12 to 10.59 t·ha-1) were in close agreement with the observed values (10.16 to 10.94 t·ha-1), as the percentage error was within tolerable limit (0.39% 展开更多
Geodynamic process as advection-convection of the Mid-Atlantic Ocean Ridge (MAR), that is exposed on land in Iceland is investigated. Advection is considered for the plate spreading velocity. Geodetic GPS data during ...Geodynamic process as advection-convection of the Mid-Atlantic Ocean Ridge (MAR), that is exposed on land in Iceland is investigated. Advection is considered for the plate spreading velocity. Geodetic GPS data during 2000-2010 is used to estimate plate spreading velocity along a profile in the Eastern Volcanic Zone (EVZ), Iceland striking N102。E, approximately parallel to the NUVEL-1A spreading direction between the Eurasian and North American plates. To predict subsurface mass flow patterns, temperature-dependent Newtonian rheology is considered in the finite-element models (FEM). All models are considered 2-D with steady-state, incompressible rheology whose viscosity depends on the subsurface temperature distribution. The thickness of lithosphere along the profile in the EVZ is identified by 700。C isotherm and 1022 Pa s iso-viscosity, those reach 50 ± 3 km depth at distance of 100 km from rift axis. Geodetic observation and model prediction results show the ~90% of spreading is accommodated within ~45 km of the rift axis in each direction. Model predicts ~8.5 mm.yr-1 subsidence at the surface of rift center when magmatic plumbing is inactive. The rift center (the highest magmatic influx is ~11 mm.yr-1) in model shifts ~10 - 20 km west to generate observed style surface deformation. The spreading velocity, isotherm and depth of isotherm are the driving forces resulting in the surface deformation. These three parameters have more or less equal weight. However, as the center of deformation in the EVZ shifts and most of the subsidence takes place in the volcanic system that is currently the active which is the located of plate axis.展开更多
基金Project supported by the IRPA Secretariat, Ministry of Science,Technology and Environment of Malaysia (No. 04-02-02-0029) andthe Zamalah Scheme
文摘A Matrix Inversion Normalized Least Mean Square (MI-NLMS) adaptive beamforming algorithm was developed for smart antenna application. The MI-NLMS which combined the individual good aspects of Sample Matrix Inversion (SMI) and the Normalized Least Mean Square (NLMS) algorithms is described. Simulation results showed that the less complexity MI-NLMS yields 15 dB improvements in interference suppression and 5 dB gain enhancement over LMS algorithm, converges from the initial iteration and achieves 24% BER improvements at cochannel interference equal to 5. For the case of 4-element uniform linear array antenna, MI-NLMS achieved 76% BER reduction over LMS algorithm.
文摘Lassa hemorrhagic fever,caused by Lassa mammarenavirus(LASV)infection,accumulates up to 5000 deaths every year.Currently,there is no vaccine available to combat this disease.In this study,a library of 200 bioactive compounds was virtually screened to study their drug-likeness with the capacity to block theα-dystroglycan(α-DG)receptor and prevent LASV influx.Following rigorous absorption,distribution,metabolism,and excretion(ADME)and quantitative structure-activity relationship(QSAR)profiling,molecular docking was conducted with the top ligands against theα-DG receptor.The compounds chrysin,reticuline,and 3-caffeoylshikimic acid emerged as the top three ligands in terms of binding affinity.Post-docking analysis revealed that interactions with Arg76,Asn224,Ser259,and Lys302 amino acid residues of the receptor protein were important for the optimum binding affinity of ligands.Molecular dynamics simulation was performed comprehensively to study the stability of the protein-ligand complexes.In-depth assessment of root-mean-square deviation(RMSD),root mean square fluctuation(RMSF),polar surface area(PSA),B-Factor,radius of gyration(Rg),solvent accessible surface area(SASA),and molecular surface area(MolSA)values of the protein-ligand complexes affirmed that the candidates with the best binding affinity formed the most stable protein-ligand complexes.To authenticate the potentialities of the ligands as target-specific drugs,an in vivo study is underway in real time as the continuation of the research.
文摘In this paper,a unit cell of a single-negative metamaterial structure loaded with a meander line and defected ground structure(DGS)is investigated as the principle radiating element of an antenna.The unit cell antenna causes even or odd mode resonances similar to the unit cell structure depending on the orientation of the microstrip feed used to excite the unit cell.However,the orientation which gives low-frequency resonance is considered here.The unit cell antenna is then loaded with a meander line which is parallel to the split bearing side and connects the other two sides orthogonal to the split bearing side.This modified structure excites another mode of resonance at high frequency when a meander line defect is loaded on the metallic ground plane.Specific parameters of the meander line structure,the DGS shape,and the unit cell are optimized to place these two resonances at different frequencies with proper frequency intervals to enhance the bandwidth.Finally,the feed is placed in an offset position for better impedance matching without affecting the bandwidth The compact dimension of the antenna is 0.25λL×0.23λL×0.02λL,whereλL is the free space wavelength with respect to the center frequency of the impedance bandwidth.The proposed antenna is fabricated and measured.Experimental results reveal that the modified design gives monopole like radiation patterns which achieves a fractional operating bandwidth of 26.6%,from 3.26 to 4.26 GHz for|S11|<−10 dB and a pick gain of 1.26 dBi is realized.In addition,the simulated and measured crosspolarization levels are both less than−15 dB in the horizontal plane.
基金This work is supported by Climate Change Institute,Universiti Kebangsaan Malaysia.
文摘The paper proposes an Indoor Localization System(ILS)which uses only one fixed Base Station(BS)with simple non-reconfigurable antennas.The proposed algorithm measures Received Signal Strength(RSS)and maps it to the location in the room by estimating signal strength of a direct line of sight(LOS)signal and signal of the first order reflection from the wall.The algorithm is evaluated through both simulations and empirical measurements in a furnished open space office,sampling 21 different locations in the room.It is demonstrated the system can identify user’s real-time location with a maximum estimation error below 0.7 m for 80%confidence Cumulative Distribution Function(CDF)user level,demonstrating the ability to accurately estimate the receiver’s location within the room.The system is intended as a cost-efficient indoor localization technique,offering simplicity and easy integration with existing wireless communication systems.Unlike comparable single base station localization techniques,the proposed system does not require beam scanning,offering stable communication capacity while performing the localization process.
基金This work was supported by the Universiti Kebangsaan Malaysia,Malaysia research grant code GUP-2019-005.
文摘This paper presents a new Double-E-Triple-H-Shaped NRI(negative refractive index)metamaterial(MM)for dual-band microwave sensing applications.Here,a horizontal H-shaped metal structure is enclosed by two face-to-face E-shaped metal structures.This double-E-H-shaped design is also encased by two vertical H-shaped structures along with some copper links.Thus,the Double-E-Triple-H-Shaped configuration is developed.Two popular substrate materials of Rogers RO 3010 and FR-4 were adopted for analyzing the characteristics of the unit cell.The proposed structure exhibits transmission resonance inside the S-band with NRI and ENG(Epsilon Negative)metamaterial properties,and inside the C-band with ENG and MNG(Mu Negative)metamaterial properties.A good effective medium ratio(EMR)of 8.06 indicates the compactness and effectiveness of the proposed design.Further analysis has been done by changing the thickness of the substrate material as well and a significant change in the effective medium ratio is found.The validity of the proposed structure is confirmed by an equivalent circuit model.The simulated result agrees well with the calculated result.For exploring microwave sensing applications of the proposed unit cell,permittivity and pressure sensitivity performance were investigated in different simulation arrangements.The compact size,effective parameters,high sensitivity and a good EMR represent the proposed metamaterial as a promising solution for S-band and C-band microwave sensing applications.
基金This work is supported by Universiti Kebangsaan Malaysia research Grant No:DIP-2020-010.
文摘In this paper,the design and performance analysis of an Inkjetprinted metamaterial loaded monopole antenna is presented for wireless local area network(WLAN)and worldwide interoperability for microwave access(WiMAX)applications.The proposed metamaterial structure consists of two layers,one is rectangular tuning fork-shaped antenna,and another layer is an inkjet-printed metamaterial superstate.The metamaterial layer is designed using four split-ring resonators(SRR)with an H-shaped inner structure to achieve negative-index metamaterial properties.The metamaterial structure is fabricated on low-cost photo paper substrate material using a conductive inkbased inkjet printing technique,which achieved dual negative refractive index bands of 2.25–4.25 GHz and 4.3–4.6 GHz.The antenna is designed using a rectangular tuning fork structure to operate at WLAN and WiMAX bands.The antenna is printed on 30×39×1.27 mm3 Rogers RO3010 substrate,which shows wide impedance bandwidth of 0.75 GHz(2.2 to 2.95 GHz)with 2 dB realized gain at 2.4 GHz.After integrating metamaterial structure,the impedance bandwidth becomes 1.25 GHz(2.33 to 3.58 GHz)with 2.6 dB realized gain at 2.4 GHz.The antenna bandwidth and gain have been increased using developed quad SRR based metasurface by 500 MHz and 0.6 dBi respectively.Moreover,the proposed quad SRR loaded antenna can be used for 2.4 GHz WLAN bands and 2.5 GHz WiMAX applications.The contribution of this work is to develop a cost-effective inject printed metamaterial to enhance the impedance bandwidth and realized the gain of a WLAN/WiMAX antenna.
文摘First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different poly- morphs of BiVO4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the generalized gradient approximation （GGA） in the flame of density functional theory （DFT）. The calculated structural and electronic properties are consistent with the previous theoretical and experimental results. The electronic structures reveal that m-BiVO4, op- BiVO4, and st-BiVO4 have indirect band gaps, on the other hand, zt-BiVO4 has a direct band gap. From the DOS and Mulliken＇s charge analysis, it is observed that only m-BiVO4 has 6s2 Bi lone pair. Bond population analysis indicates that st-BiVO4 shows a more ionic nature and a similar result is obtained from the elastic properties. From the elastic prop- erties, it is observed that st-BiVO4 is more mechanically stable than the others, st-BiVO4 is more ductile and useful for high electro-optical and electro-mechanical coupling devices. Our calculated thermodynamic properties confirm the similar characteristics found from electronic and elastic properties, m-BiVO4 is useful as photocatalysts, solid state electrolyte, and electrode and other polymorphs are applicable in electronic device fabrications.
文摘S aint Martin Island is the only coral island and one of the well-known tourist spots in Bangladesh.Because of its geographic location,electricity cannot be supplied from the mainland through the electricity grid.Diesel generators and solar power are the only means of electricity generation presently available there.Surrounded by the sea,Saint Martin Island has the ideal conditions for wave energy extraction.In this research,numerical models have been developed using the Delft3 D simulation software to determine the wave characteristics of different locations around Saint Martin Island.The results have been calibrated and validated against the data obtained from well-known data sources.The wave power densities have been calculated using the data obtained from the simulation models.The findings of the research show that the wave power density increases significantly from shallow water to deep water and a large amount of wave energy can be extracted during the summer and rainy monsoon seasons.The maximum hourly average value of wave power in 2016 has been determined to be6.90 kW/m at location with a water depth of 27.80 m.Wave energy resources are also observed to be sufficiently stable with the coefficients of variation of wave power density less than 0.62,except for December,January,and May of that particular year.Moreover,the annual effective energies have been determined to be within the range of 36.57 to 57.28 MWh/m,which will be sufficient to meet the electricity requirement of the island communities.
基金supported by Fundamental Research Grant Scheme(FRGS),MOE,Malaysia,Code:FRGS/1/2022/TK07/UKM/02/22.
文摘This study proposed a new royal crown-shaped polarisation insensitive double negative triple band microwave range electromagnetic metamaterial absorber(MA).The primary purpose of this study is to utilise the exotic characteristics of this perfect metamaterial absorber(PMA)for microwave wireless communications.The fundamental unit cell of the proposed MA consists of two pentagonal-shaped resonators and two inverse C-shaped metallic components surrounded by a split ring resonator(SRR).The bottom thin copper deposit and upper metallic resonator surface are disjoined by an FR-4 dielectric substrate with 1.6 mm thickness.The CST MW studio,a high-frequency electromagnetic simulator has been deployed for numerical simula-tion of the unit cell in the frequency range of 4 to 14 GHz.In the TE mode,the offered MA structure demonstrated three different absorption peaks at 6.85 GHz(C-band),8.87 GHz(X-band),and 12.03 GHz(Ku-band),with 96.82%,99.24%,and 99.43%absorptivity,respectively.The electric field,magnetic field,and surface current distribution were analysed using Maxwell’s-Curl equations,whereas the angle sensitivity was investigated to comprehend the absorption mechanism of the proposed absorber.The numerical results were verified using the Ansys HFSS(high-frequency structure simulator)and ADS(advanced design system)for equivalent circuit models.Moreover,the proposed MA is polarisation and incident angle independent.Hence,the application of this MA can be extended to a great extent,including airborne radar applications,defence,and stealth-coating technology.
文摘This paper reveals a new design of UHF CubeSat antenna based on a modified Planar Inverted F Antenna(PIFA)for CubeSat communication.The design utilizes a CubeSat face as the ground plane.There is a gap of 5 mm beneath the radiating element that facilitates the design providing with space for solar panels.The prototype is fabricated using Aluminum metal sheet and measured.The antenna achieved resonance at 419 MHz.Response of the antenna has been investigated after placing a solar panel.Lossy properties of solar panels made the resonance shift about 20 MHz.This design addresses the frequency shifting issue after placing the antenna with the CubeSat body.This phenomenon has been analyzed considering a typical 1U and 2U CubeSat body with the antenna.The antenna achieved a positive realized gain of 0.7 dB and approximately 78%of efficiency at the resonant frequency with providing 85%of open space for solar irradiance onto the solar panel.
基金This work is supported by the Universiti Kebangsaan Malaysia research grant GUP-2020-074.
文摘Broadband response metamaterial absorber(MMA)remains a challenge among researchers.A nanostructured new zero-indexed metamaterial(ZIM)absorber is presented in this study,constructed with a hexagonal shape resonator for optical region applications.The design consists of a resonator and dielectric layers made with tungsten and quartz(Fused).The proposed absorbent exhibits average absorption of more than 0.8972(89.72%)within the visible wavelength of 450–600 nm and nearly perfect absorption of 0.99(99%)at 461.61 nm.Based on computational analysis,the proposed absorber can be characterized as ZIM.The developments of ZIM absorbers have demonstrated plasmonic resonance characteristics and a perfect impedance match.The incidence obliquity in typically the range of 0◦–90◦both in TE and TM mode with maximum absorbance is more than 0.8972(∼89.72%),and up to 45◦angular stability is suitable for solar cell applications,like exploiting solar energy.The proposed structure prototype is designed and simulated by studying microwave technology numerical computer simulation(CST)tools.The finite integration technique(FIT)based simulator CST and finite element method(FEM)based simulator HFSS also helps validate the numerical data of the proposed ZIM absorber.The proposed MMA design is appropriate for substantial absorption,wide-angle stability,absolute invisible layers,magnetic resonance imaging(MRI),color images,and thermal imaging applications.
基金This work is supported by the Universiti Kebangsaan Malaysia Research Grant under Grant Number.GUP-2020-017.
文摘This paper presents a textile-based C-shaped split-ring resonators(SRR)metamaterial(MTM)unit cells with an electrical tunability function.The proposed MTM was composed of two symmetrical C-shaped SRR combined with a central diagonal metal bar,whereas the RF varactor diode is placed on the backside of the splitted ground plane.Stopband behavior of single and array MTM unit cells were analyzed while the achieved negative index physical characteristics were widely studies.Though four different MTM arrays(i.e.,1×1,1×2,2×1,and 2×2)were analyzed in simulation,a 2×2-unit cell array was chosen to fabricate,and it was further undergone experimental validation.This proposed tunable MTM exhibits double negative(DNG)/left-handed properties with an average bandwidth of more than 2.8 GHz.Furthermore,attainable negative permittivity and negative permeability are within 2.66 to 9.59 GHz and within 2.77 to 15 GHz,respectively,at the frequency of interest(between 1 and 15 GHz).Moreover,the proposed tunable MTM also showed tunable transmission coefficient characteristics.The proposed electrically tunable textile MTM might function in a dynamic mode,making it suitable for a variety of microwave-wearable applications.A satisfactory agreement between simulations and experiments were achieved,demonstrating that the proposed MTM can operate over a wide bandwidth.
基金This work is supported by the Universiti Kebangsaan Malaysia research grant GGPM 2020-005.
文摘This study presents an Epsilon Mu near-zero(EMNZ)nanostructured metamaterial absorber(NMMA)for visible regime applications.The resonator and dielectric layers are made of tungsten(W)and quartz(fused),where the working band is expanded by changing the resonator layer’s design.Due to perfect impedance matching with plasmonic resonance characteristics,the proposed NMMA structure is achieved an excellent absorption of 99.99%at 571 THz,99.50%at 488.26 THz,and 99.32%at 598 THz frequencies.The absorption mechanism is demonstrated by the theory of impedance,electric field,and power loss density distributions,respectively.The geometric parameters are explored and analyzed to show the structure’s performance,and a near-field pattern is used to explain the absorption mechanism at the resonance frequency point.The numerical analysis method describes that the proposed structure exhibited more than 80%absorbability between 550 and 900 THz.The Computer Simulation Technology(CST Microwave Studio 2019)software is used to design the proposed structure.Furthermore,CSTHFSS interference is validated by the simulation data with the help of the finite element method(FEM).The proposed NMMA structure is also exhibits glucose concentration sensing capability as applications.So the proposed broadband absorber may have a potential application in THz sensing,imaging(MRI,thermal,color),solar energy harvesting,light modulators,and optoelectronic devices.
基金This work is supported by the Universiti Kebangsaan Malaysia Research grant code GUP-2020-074This research work is also supported by Bangabandhu Science and Technology Fellowship Trust,Ministry of Science and Technology,Bangladesh.
文摘This work presents a dual band epsilon negative(ENG)metamaterial with a bilateral coupled split ring resonator(SRR)for use in C and X band wireless communication systems.The traditional split-ring resonator(SRR)has been amended with this engineered structure.The proposed metamaterial unit cell is realized on the 1.6 mm thick FR-4 printed media with a dimension of 10×10 mm2.The resonating patch built with a square split outer ring.Two interlinked inner rings are coupled vertically to the outer ring to extend its electrical length as well as to tune the resonance frequency.Numerical simulation is performed using CST studio suite 2019 to design and performance analysis.The transmission coefficient(S21)of the proposed unit cell and array configuration exhibits two resonances at 6.7 and 10.5 GHz with wide bandwidth extended from 4.86 to 8.06 GHz and 10.1 to 11.2 GHz,respectively.Negative permittivity is noted at frequencies between 6.76–9.5 GHz and 10.5–12 GHz,consecutively,with near-zero refractive index and permeability.The optimal EMR value depicts the compactness of the proposed structure.The 1×2,2×2 and 4×4 arrays are analyzed that shows similar response compared to the unit cell.Measured results of the 2×2 array shows the close similarity of S21 response as compared to simulation.The observed properties of the proposed unit cell ascertain its suitability for wireless communications by enhancing the gain and directivity of the antenna system.
文摘Maize is an emerging important crop in Bangladesh because of its high yield potential and economic profitability compared to rice and wheat crops. There is a need to understand the growth and yield behavior of this crop in varying production environments of Bangladesh. Crop model such as Decision Support System For Agro-technology Transfer (DSSAT) version 4.6 (DSSAT hereafter) can be utilized cost effectively to study the performances of maize under different production environments. It needs to calibrate and validate DSSAT model for commonly cultivated maize cultivars in Bangladesh and subsequently take the model to various applications, including inputs and agronomic management options and climate change that impacts analyses. So, the present study was undertaken to firstly calibrate DSSAT model for popular four hybrid maize cultivars (BARI Hybrid Maize-7, BARI Hybrid Maize-9, Pioneer 30B07 and NK-40). Subsequently, it proceeded with the validation with independent field data sets for evaluating their growth performances. The genetic coefficients for these cultivars were evaluated by using Genotype coefficient calculator (GENCALC) and Generalized likelihood uncertainty estimation (GLUE) module of DSSAT on the basis of first season experiment. The performance of the model was satisfactory and within the significant limits. After calibration, the model was tested for its performance through validation procedure by using second season data. The model performed satisfactorily through phenology, biomass, leaf area index (LAI) and grain yield. Phenology, as estimated through days to flower initiation and maturity, was in good agreement, although simulated results were slightly over predicted compared to observed values but within the statistical significance limit...when compared with observed values at specific growth stages of the crop. The final yield values (10.12 to 10.59 t·ha-1) were in close agreement with the observed values (10.16 to 10.94 t·ha-1), as the percentage error was within tolerable limit (0.39%
文摘Geodynamic process as advection-convection of the Mid-Atlantic Ocean Ridge (MAR), that is exposed on land in Iceland is investigated. Advection is considered for the plate spreading velocity. Geodetic GPS data during 2000-2010 is used to estimate plate spreading velocity along a profile in the Eastern Volcanic Zone (EVZ), Iceland striking N102。E, approximately parallel to the NUVEL-1A spreading direction between the Eurasian and North American plates. To predict subsurface mass flow patterns, temperature-dependent Newtonian rheology is considered in the finite-element models (FEM). All models are considered 2-D with steady-state, incompressible rheology whose viscosity depends on the subsurface temperature distribution. The thickness of lithosphere along the profile in the EVZ is identified by 700。C isotherm and 1022 Pa s iso-viscosity, those reach 50 ± 3 km depth at distance of 100 km from rift axis. Geodetic observation and model prediction results show the ~90% of spreading is accommodated within ~45 km of the rift axis in each direction. Model predicts ~8.5 mm.yr-1 subsidence at the surface of rift center when magmatic plumbing is inactive. The rift center (the highest magmatic influx is ~11 mm.yr-1) in model shifts ~10 - 20 km west to generate observed style surface deformation. The spreading velocity, isotherm and depth of isotherm are the driving forces resulting in the surface deformation. These three parameters have more or less equal weight. However, as the center of deformation in the EVZ shifts and most of the subsidence takes place in the volcanic system that is currently the active which is the located of plate axis.
