2,222 research outputs found
Reconfigurable Antennas and their Applications
No full textOne of the biggest challenge in modern communication systems is to provide a single antenna for different applications. Existing antenna systems are limited to some applications. So it is important to design a single reconfigurable antenna for multiple applications.
Five different reconfigurable printed antennas for different applications are designed during the study of this thesis. In the first design an antenna for frequency reconfigurable applications is designed. The electrical length of the conductor is changed using PIN diodes and the resonance of antenna is shifted from 4.27 GHz to 3.56 GHz. Good agreement between simulated and measured results is observed. In the second and third designs, Ultra wideband (UWB) Multiple-Input Multiple-Output (MIMO) antennas with on-demand Wireless Local Area Network (WLAN) rejection are designed. The second design consists of two elements UWB-MIMO antenna and stubs are connected to the ground plane using PIN diodes. These stubs act as a stop-band filter and reject the band at 5.5 GHz center frequency. This design has a compact size of 23 x 39.8 mm2. The third design has almost same features as of second design but it has four elements. These elements are placed orthogonally to each other. The total size of this proposed design is 50 x 39.8 mm2. The ground plane is common and a band-stop design is placed between the ground planes. This band-stop design is connected with the ground plane using PIN diodes. When diodes are biased, the current is travelled to the nearly placed band-stop design and a notch is obtained around 5.5 GHz. In fourth design a reconfigurable array with a sensing circuit is designed. The array consists of four individual reconfigurable patches which are attached to the different conformal surfaces. These patches are reconfigured from 3.15 GHz to 2.43 GHz using PIN diodes. The correct phase at each element is provided using phase shifters. The sensing circuit is designed in such a way that only input voltage is changed to provide the correct phase on the switching frequency. The patterns of the array are recovered on both switching frequencies when array is attached to wedge or cylindrical surface. In the last design a series-fed array is designed. Composite Right/Left Handed Transmission Line (CRLH-TLs) are used instead of traditional meanderline microstrip lines to connect the array elements. These CRLH-TLs provided the zero phase at each connecting element, which resulted in broad side radiation patterns. To reconfigure the antenna to another frequency a small patch and second CRLH-TL is connected between array element
Economic analysis of DC power sources used in impressed current cathodic protection of underground pipelines
No full textObjective: The objective of this study is to calculate and analyze the economicparameters of three main DC power sources i.e. Thermoelectric Generator,Transformer Rectifier, and solar photovoltaic (PV) Solar System, which arewidely used in impressed current cathodic protection (ICCP) of undergroundpipelines. Methodology/Analysis : Initial or capital cost, operation andmaintenance costs of the afore-mentioned DC sources are computed, fora practical ICCP system of high transmission underground pipeline over aperiod. Present worth analysis technique of economic analysis with inflationadjustment using a spreadsheet is adopted to compute these values. Theanalysis period of 20 years is used for present worth calculations of these DCsources. Findings: The cost efficiency of DC power sources for an ICCP systemhave been discussed in very few research papers. The calculations are made foreither only one DC source at a time or the comparison is based on calculationwithout inflation adjustment. This study, in line with the currently adoptedmethodologies, provides a far easier and more comprehensive comparisonand analysis of the most economical DC source for the ICCP system ofunderground metallic pipelines. Novelty/ Improvement: DC power sourcesplay a pivotal role in an ICCP system that helps to mitigate the rate of corrosionin underground pipelines. This study contributes towards choosing the cost-effective DC Power source for an ICCP system of underground pipelines. Theresults are drawn using practical data. This subsequently helps in mitigatingthe rate of corrosion in these pipelines
3-18 GHz compact planar antenna for short-range radar imaging
No full textAn ultra-compact planar antenna aiming to be part of an imaging antenna array operating in the broad 3-18 GHz frequency range is presented. The antenna is made of two closely packed wide-band monopoles for simultaneous transmission and reception functionalities. A high isolation (> 20 dB) between the two patches is achieved through the insertion of a structured ground plane (decoupling structure). A prototype was fabricated on a Roger R4003c laminate measuring 58 mm2 x 33 mm2 and used in inverse synthetic array radar configuration for detecting a steel object with sub-centimetre spatial resolution
A Research Study of Lliterary Services of Nawab Muhammad Sharif Khan
No full textNawab Muhammad Sharif Khan remained ruler of princely state of Dir. He had inclination towards literary activities as well. Some people may not agree with some of his political policies that he adopted during his reign but his contribution in literary field cannot be denied. They had love for learned and literary people due to which individuals with scholarly qualities were part of his court. In his era, he remained engaged in armed conflicts with internal and external forces. He had to cope with conspiracies and rebellion within the State. However, despite all these odds, he was able to contribute in the literary field as well. His endeavours in this regard are of great importance and it contributed towards promoting Pashtu language. In this research article, a review of the literary works is given that were written, translated and published with the support of Nawab Muhammad Sharif Khan. These literary services were “Manaqib Hazart Akhun Ilyas” by Muhammad Sharif Swati, “Shahana Ferdosi” (Pastu Translation) by Maulvi Muhammad Rafiq, “Tehzibul Islam alias Tuhfa Sharifia” by Qazi Irfan Uddin and “Sahifa Zareen” by Prag Narien Bhargo”. This study will reveal the personality traits of Nawab Sharif Khan, his administrative skills, generosity, love for knowledge and his literary taste
A New Urease Inhibitor from Viola betonicifolia
No full textUrease has attracted much attention, as it is directly involved in the formation of infection stones and contributes to the pathogenesis of urolithiasis, pyelonephritis, ammonia and hepatic encephalopathy, hepatic coma and urinary catheter encrustation. Moreover, urease is the major cause of pathologies induced by H. pylori, such as gastritis and peptic ulcer. In the present work, the new natural compound, 3-methoxydalbergione, was isolated from Viola betonicifolia. A mechanistic study of this compound as a natural urease inhibitor was performed by using enzyme kinetics and docking studies. 3-Methoxydalbergione could be considered as a lead molecule for drugs useful in the urease associated diseases
Racism and Islamophobia: A Personal Perspective
No full textThe article employs a subjective personal approach to show that new racisms are alive in the twenty-first century. Tracing my parents’ journey from India and Pakistan to Britain, it explores the political effects of the racism they and their children faced. Locating these reflections in a post-9/11 world, the article describes the turn my academic work has taken in response to media representations of Muslims, and calls for academic research on British Muslim identity to reflect the process of identity-making and its contingencies
Gene expression of thrombomodulin, TNF-α and NF-KB in coronary artery disease patients of Pakistan
No full textValuation of Environmental Management Standard ISO 14001: Evidence from an Emerging Market
No full textISO 14001 (Environmental Management Standard) helps corporations to build legitimacy and goodwill, and can be also viewed as an organizational response to institutional pressure to act proactively towards the environment. The purpose of this paper is to investigate how investors in the emerging country value voluntary environmental management standard ISO 14001 certification. The impact of voluntary environmental management standard ISO 14001 on market performance is still not clear. By using event study methodology, this study matched ISO-certified firms with non-certified ones based on three different matching principles that include return on assets, size, and industry. The findings indicated that investors negatively valued ISO 14001 in both the short and long run. The study recommended policy implications for managers, policy makers, and non-government organizations
A 4 element compact Ultra-Wideband MIMO antenna array
No full textIn this paper, a compact planar Ultra-Wideband (UWB) antenna array with 4 monopole radiators is presented. To enhance the isolation, polarization of nearly placed elements is exploited. The proposed MIMO antenna array is electrically small 50 × 39.8 mm2, printed on a low loss 1.524 mm thick Rogers TMM4 laminate with a dielectric constant of 4.5 and a loss tangent of 0.002. Simulation in HFSS and printed prototype results satisfy the return loss requirement of better than 10 dB and isolation better than 17 dB on the entire 2.5 to 12 GHz bandwidth. The calculated envelope correlation value of less than 0.03 and the compactness of the proposed antenna array makes it suitable for small portable handheld devices
Pattern and frequency reconfiguration of patch antenna using PIN diodes
No full textIn this article, an antenna with two patch elements is pattern and frequency reconfigured. One feed line is used to excite the two patch elements placed at any angle with respect to each other. The maximum rotation of each patch antenna element incorporated is 45°. For the impedance matching with 50 Ω, both elements are fed from the corner. The radiating elements are fed simultaneously using one feed line with the help of PIN diodes. When patch 1 is excited by biasing PIN diode 1, a broad side radiation pattern in the yz plane of the patch 1 is observed. Therefore, for the rotation angle by 7.5° the pattern rotation is about 5° Similarly, biasing PIN diode 2, resulted excitation of Patch 2. It is observed that pattern reconfiguration of 30° can be achieved by biasing PIN diode 1, whereas, up to −30° pattern reconfiguration can be achieved by exciting PIN diode 2, without compromising on the gain of the radiating elements. On the other hand, to achieve the frequency reconfiguration, two small radiating patches are added at 0.7 mm gap with the large radiating elements. PIN diodes are used between the small and large radiating elements. When diodes on the antenna elements are biased, patches resonate at 2.43 GHz otherwise the resonance occurred at 3.3 GHz. For the comparison with simulation results, a prototype is fabricated on low loss 1.524 mm thick Rogers TMM4 laminate (ɛr = 4.5, tanδ = 0.002). In the fabricated prototype, both the radiating elements are rotated at maximum angle and results are compared. A good agreement at both frequencies and radiation pattern reconfiguration is observed. The gain is almost 5.5 dBi for the reconfigured patterns at 3.3 GHz and 4.9 dBi at 2.43 GHZ. The antenna has maximum dimension of 58 × 100 mm2
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