| 1. |
- Ahmad, Sarosh, et al.
(author)
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A Compact CPW-Fed Ultra-Wideband Multi-Input-Multi-Output (MIMO) Antenna for Wireless Communication Networks
- 2022
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In: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 10, s. 25278-25289
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Journal article (peer-reviewed)abstract
- In this article, a compact coplanar waveguide (CPW) technique based ultra-wideband multiple-input-multiple-output (MIMO) antenna is proposed. The design is characterized by a broad impedance bandwidth starting from 3 GHz to 11 GHz. The overall size of the MIMO design is 60 x 60 mm(2) (1.24 x 1.24 lambda(2)(g) @ 3 GHz) with a thickness of 1.6 mm. To make the design ultra-wideband, the proposed MIMO antenna design has four jug-shaped radiating elements. The design is printed on a FR-4 substrate (relative permittivity of epsilon(r) = 4.4 and loss tangent of tan delta = 0.025). The polarization diversity phenomenon is realized by placing four antenna elements orthogonally. This arrangement increases the isolation among the MIMO antenna elements. The simulated results of the ultra-wideband MIMO antenna are verified by measured results. The proposed MIMO antenna has a measured diversity gain greater than 9.98, envelope correlation coefficient (ECC) less than 0.02, and good MIMO performance where the isolation is more than -20dB between the elements. The group delay, channel capacity loss (CCL), and the total active reflection coefficient (TARC) multiplexing efficiency and mean effective gain results are also analyzed. The group delay is found to be less than 1.2ns, CCL values calculated to be less than 0.4 bits/sec/Hz, while the TARC is below -10dB for the whole operating spectrum. The proposed design is a perfect candidate for ultra-wideband wireless communication systems and portable devices.
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| 2. |
- Hussain, Muhammad Mahroz, et al.
(author)
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Arsenic biogeochemical cycling in paddy soil-rice system : Interaction with various factors, amendments and mineral nutrients
- 2021
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 773
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Journal article (peer-reviewed)abstract
- Arsenic (As) contamination is a well-recognized environmental and health issue, threatening over 200 million people worldwide with the prime cases in South and Southeast Asian and Latin American countries. Rice is mostly cultivated under flooded paddy soil conditions, where As speciation and accumulation by rice plants is controlled by various geo-environmental (biotic and abiotic) factors. In contrast to other food crops, As uptake in rice has been found to be substantially higher due to the prevalence of highly mobile and toxic As species, arsenile (As(Ill)), under paddy soil conditions. In this review, we discussed the biogeochemical cycling of As in paddy soil-rice system, described the influence of critical factors such as pH, iron oxides, organic matter, microbial species, and pathways affecting As transformation and accumulation by rice. Moreover, we elucidated As interaction with organic and inorganic amendments and mineral nutrients. The review also elaborates on As (im) mobilization processes and As uptake by rice under the influence of different mineral nutrients and amendments in paddy soil conditions, as well as their role in mitigating As transfer to rice grain. This review article provides critical information on As contamination in paddy soil-rice system, which is important to develop suitable strategies and mitigation programs for limiting As exposure via rice crop, and meet the UN's key Sustainable Development Goals (SDGs: 2 (zero hunger), 3 (good health and well-being), 12 (responsible consumption and production), and 13 (climate action)).
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| 3. |
- Khan, Owais, et al.
(author)
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A Novel Densely Packed 4 × 4 MIMO Antenna Design for UWB Wireless Applications
- 2023
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In: Sensors. - : MDPI AG. - 1424-8220. ; 23:21
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Journal article (peer-reviewed)abstract
- In this article, a compact 4-port UWB (Ultra-Wide Band) MIMO (Multiple Input Multiple Output) antenna is proposed. A low profile FR-4 substrate is used as a dielectric material with the dimensions of 58 × 58 mm2 (0.52λ × 0.52λ) at 2.8 GHz and a standard thickness of 1.6 mm. The proposed design characterizes an impedance bandwidth starting from 2.8 to 12.1 GHz (124.1%). Each of the four elements of the proposed MIMO antenna configuration consists of a monopole antenna with PG (partial ground) that has a slot at its center. The corner of each patch (radiator) and ground slot are rounded for impedance matching. Each unit cell is in an orthogonal orientation, forming a quad-port MIMO antenna system. For reference, the partial ground of each unit cell is connected meticulously with the others. The simulated results of the proposed quad-port MIMO antenna design were configured and validated by fabrication and testing. The proposed Quad-port MIMO design has a 6.57 dBi peak gain and 97% radiation efficiency. The proposed design has good isolation below 15 dB in the lower frequency range and below 20 dB in the higher frequency range. The design has a measured ECC (Envelop Correlation Co-efficient) of 0.03 and DG (Diversity Gain) of 10 dB. The value of TARC (Total Active Reflection Coefficient) over the entire operating band is less than 10 dB. Moreover, the design maintained CCL (Channel Capacity Loss) < 0.4 bits/sec/Hz and MEG (Mean Effective Gain) < 3 dB. Based on the obtained results, the proposed design is suitable for the intended high data rate UWB wireless communication portable devices.
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| 4. |
- Khan, Umar Hasan, et al.
(author)
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Localization of Compact Circularly Polarized RFID Tag Using ToA Technique
- 2017
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In: Radioengineering. - : SPOLECNOST PRO RADIOELEKTRONICKE INZENYRSTVI. - 1210-2512 .- 1805-9600. ; 26:1, s. 147-153
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Journal article (peer-reviewed)abstract
- A compact, flexible crossed-dipole circularly polarized antenna using commercially available paper substrate is presented which caters North American frequency band. The crossed-dipoles have meandered lines for reduction of size as well as increased inductivity in the antenna. Dipoles have asymmetric T-shaped rectangular endings to provide the required compactness. Two semicircles are induced between the orthogonal dipoles and meandering matching structure to accomplish circular polarization excitation. Good impedance matching with the chip is achieved through a modified meander line matching structure. The proposed design dimensions are 32 x 32 x 0.4 mm(3). Systematic analysis revealed the results comprising circular polarization 3dB-AR bandwidth of 12 MHz (908-920 MHz) and power transmission coefficient bandwidth of 36 MHz (900-936 MHz). Time delay between interrogating signal and backscattered signal is measured and relative distance is calculated. Linear Least Square (LLS) method is applied to approximate the position of tag in interrogation area. The proposed tag is placed at known locations and its position is measured to analyze accuracy of the method by simulating the positioning algorithm code in MATLAB. Six valid tag positions 0.5-2 m read range and 0 degrees-150 degrees angular resolution has been investigated.
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| 5. |
- Khan, Umar Hasan, et al.
(author)
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Novel chipless displacement sensor circuit using spurline resonantor
- 2016
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In: IEICE Electronics Express. - : Institute of Electronics Information Communication Engineers. - 1349-2543. ; 13:23
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Journal article (peer-reviewed)abstract
- A novel uni-dimensional chipless displacement sensor circuit based on spurline resonators is presented. Sensor circuit design consists of two components: series of spurline resonators and a selector element. In response to displacement, the selector element slides over the spurline resonator slots that translating this movement into a corresponding change in the circuit's frequency response. The designed circuit offers a capacity of 16 bits in the 2-4.2 GHz frequency band. Half of the bits are designated as the sensory bits, while the other half are attributed as the ID bits. The formulated sensor has a dynamic range from 0-3.75 mm and a minimum resolution of 0.25 mm. The proposed sensor is a prime candidate for deployment in smart cities for ubiquitous infrastructural health monitoring.
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| 6. |
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| 7. |
- Shahid, Bilal, et al.
(author)
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Low-bandgap polymers with quinoid unit as π bridge for high-performance solar cells
- 2020
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In: Journal of Energy Chemistry. - : Elsevier BV. - 2095-4956. ; 40:2020, s. 180-187
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Journal article (peer-reviewed)abstract
- To construct efficient low band gap polymers, increasing the Quinone structure of the polymer backbone could be one desirable strategy. In this work, two D–Q–A–Q polymers P1 and P2 were designed and synthesized with thiophenopyrrole diketone (TPD) and benzothiadiazole (BT) unit as the core and ester linked thieno[3,4-b]thiophene (TT) segment as π-bridging, and the main focus is to make a comparative analysis of different cores in the influence of the optical, electrochemical, photochemical and morphological properties. Compared with the reported PBDTT EH –TBTT HD−i , P1 exhibited the decreased HOMO energy level of −5.38 eV and lower bandgap of 1.48 eV. Furthermore, when replaced with BT core, P2 showed a red-shifted absorption profile of polymer but with up-shifted HOMO energy level. When fabricated the photovoltaic devices in conventional structure, just as expected, the introduction of ester substituent made an obvious increase of V OC from 0.63 to 0.74 V for P1. Besides, due to the deep HOMO energy level, higher hole mobility and excellent phase separation with PC 71 BM, a superior photovoltaic performance (PCE = 7.13%) was obtained with a short-circuit current density (J SC ) of 14.9 mA/cm 2 , significantly higher than that of P2 (PCE = 2.23%). Generally, this study highlights that the strategy of inserting quinoid moieties into D–A polymers could be optional in LBG-polymers design and presents the importance and comparison of potentially competent core groups.
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